Enhancing Potato Quality in Fries Production Using Ultrasonic Techniques

Abstract

This study explores the effects of ultrasonic treatment on the quality of potatoes processed into fries. Ultrasonic waves generate rapid pressure changes and cavitation effects, which can enhance seed vigor and growth. Over a three-year period (2015–2017) in east-central Poland, a field experiment was conducted using a randomized block design with split-plot divisions with three replications. The study compared two cultivation technologies: (a) with ultrasonic treatment of seed potatoes before planting, and (b) traditional technology. The second-order factor consisted of eight edible potato cultivars from all earliness groups (‘Denar’, ‘Lord’, ‘Owacja’, ‘Vineta’, ‘Satina’, ‘Tajfun’, ‘Syrena’, and ‘Zagłoba’). The sonication process was carried out using an ultrasonic bath with piezoelectric transducers. The results demonstrated significant impacts of the cultivation technology, potato variety, and weather conditions on the quality of fries. This research underscores the potential of ultrasonic treatment to improve the quality and consistency of potato products in the food industry. The use of ultrasound treatment on potato tubers before planting aligns with sustainable development by enhancing agricultural efficiency, reducing the environmental impact, and supporting socio-economic aspects of sustainable farming. It also aids in developing tools and methods for monitoring and quantifying sustainability efforts in potato processing, such as in the production of French fries. Future research should focus on optimizing ultrasonic parameters and exploring the long-term effects of sonication on potato storage and processing qualities.

1. Introduction

The growing demand for high-quality processed potato products, such as French fries, has led to the search for innovative methods to improve the sensory attributes and texture of these products. One such emerging technology involves the application of ultrasonic processing in agricultural practices [1,2]. Ultrasonic waves generate mechanical vibrations that cause cavitation effects that enhance seed vigor, plant growth, and yield by improving cell permeability and increasing nutrient absorption [3,4,5,6]. Recent studies have shown that ultrasonic processing can also affect the texture, color, and flavor of processed products, including French fries, by affecting the physicochemical properties of the raw material [4,5,6,7]. However, the potential of ultrasonic processing in potato cultivation remains under-explored. Most of the studies on the application of ultrasound in agricultural practices focus on its effect on seed germination, tuber germination, or water retention properties, leaving a gap in understanding its impact on the quality of the food. This study aims to fill that gap by investigating the effects of ultrasonic treatment of seed potatoes on the quality of a processed food product, such as French fries.

Ultrasonic processing involves the use of high-frequency sound waves (above 20 kHz), which in turn cause mechanical vibrations in the processed material (raw material). In the case of potato tubers, ultrasonic processing can affect its physical, chemical, and structural properties, which in the further processing stage can lead to an improvement in the quality of the final product, such as French fries or crisps. The mechanism of ultrasound action in relation to potatoes includes several important processes:

• The cavitation effect. Ultrasonic waves generate local pressure changes in the solution or medium surrounding the material, which leads to the formation and implosion of gas bubbles in the liquid (this process is called cavitation). The implosion of bubbles generates intense micro-streams and micro-impacts, which can as a result trigger the following:

  −

  Damage the cell walls of the potato, increasing the permeability of cell membranes and facilitating the exchange of nutrients and water;

  −

  Increase the exchange surface between potato cells and the environment, which accelerates the absorption of nutrients and enables more efficient transport of metabolites [3,5].

• Improved cell permeability. As a result of ultrasound, the structure of potato cells is slightly damaged, which leads to increased permeability of cell membranes. This results in, among other things, better water and nutrient uptake by tubers, which can consequently contribute to improved plant growth and increased tuber yields; -reduced cellular resistance to processes such as cooking or frying, which affects the consistency and texture of French fries [1,2,5,7].
• Changes in the chemical composition of potatoes. Ultrasound treatment can affect the physicochemical properties of the raw material, such as the dry matter, starch, soluble and reducing sugars, and proteins, which are crucial for the heat treatment process (e.g., frying French fries). For example, a reduced content of reducing sugars, which reduces the risk of excessive browning of French fries during frying, and thus improves their appearance and taste; an increased availability of starch, which can ultimately contribute to improving the texture of French fries, giving them a more desirable, crispy consistency after heat treatment [6].
• Increased enzymatic activity. Ultrasound can also affect the activity of enzymes present in potato tubers. Cavitation and the micro-streams generated as a result of this process can modify enzymes responsible for the ripening and storage of potatoes, which can -reduce the accumulation of reducing sugars during long-term storage of potato tubers, minimizing their negative impact on the quality of French fries; improve metabolic processes in tubers, promoting uniform ripening and a better quality of potatoes after the harvest.
• Increased efficiency of heat treatment: Thanks to increased cell permeability and changes in the chemical structure of potatoes, ultrasonic treatment can contribute to more uniform heat treatment (e.g., frying). Increased absorption of water and nutrients helps to shorten the frying time of French fries, which in turn reduces the risk of harmful substances such as acrylamides, formed as a result of long-term frying at high temperatures, or maintains the uniform structure of French fries, which in turn affects their final sensory quality—French fries become crispier on the outside and softer on the inside, by modulating factors such as texture and color [6,8].
• Impacts on water retention. Ultrasonic treatment can also affect water retention in potato tubers, which is crucial when frying French fries. Better water retention means less loss of French fries mass during frying, which leads to the production of French fries with a more desirable texture. As a result, the amount of fat absorbed by French fries during frying is reduced, which in turn affects their health and taste values.

All of the above processes indicate that ultrasonic treatment can significantly improve the quality of potatoes intended for French fries, positively affecting their chemical composition and consistency and the heat treatment process. By influencing the physiology and structure of potatoes, ultrasound offers potential benefits, both in agricultural cultivation and in subsequent processing, which can lead to fries with better organoleptic, sensory, and quality properties.

Research on the application of ultrasound treatment to potato tubers before planting can contribute to sustainable development on multiple levels:

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Increasing agricultural production efficiency: The use of ultrasound can improve the quality of tubers, enhance their germination capacity, and contribute to more efficient use of resources such as water, fertilizers, and crop protection products. More efficient production means reduced resource consumption while maintaining or increasing yields, supporting a sustainable approach to agriculture.

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Reduction in chemical crop protection products: The impact of ultrasound on tubers can reduce the need for chemical plant protection products, leading to lower environmental pollution and healthier agricultural products for consumers.

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Supporting biodiversity: Reducing chemical protection agents and optimizing cultivation methods can positively impact biodiversity in agricultural ecosystems, contributing to the protection of pollinating insects and beneficial organisms.

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Conservation of natural resources: Research on technologies like ultrasound supports a more precise approach to resource management, which is crucial in the context of climate change and the limited availability of water and arable land.

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Promoting scientific innovation: The application of ultrasound in agriculture exemplifies the integration of modern technologies with traditional farming practices. The development of such methods can lead to new tools for measuring, monitoring, and quantifying sustainable development in agriculture.

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Socio-economic benefits: Improving agricultural production efficiency and reducing costs associated with chemical crop protection products can result in better income for farmers, particularly in resource-constrained regions. Additionally, minimizing the negative environmental impact promotes the health and well-being of local communities.

Despite extensive research on ultrasound in the cultivation and processing of various agricultural crops, there is still a lack of comprehensive studies on the use of ultrasound in potato cultivation and processing. There are a limited number of studies on the effect of ultrasound on physiological processes in potato plants, such as germination, growth, and yield. Most studies to date have focused on early stages of production, such as germination stimulation or water retention properties, omitting long-term effects on crop quality. Although ultrasound has an effect on cellular structure, membrane permeability, and enzymatic activity, the mechanisms of these processes at the molecular level have not yet been fully explained. There is a lack of detailed studies in this area.

Moreover, there is a limited number of studies on ultrasonic processing on an industrial scale. In the research literature, the focus is most often on selected properties, such as the content of reducing sugars, starch, or dry matter. However, other features, such as organoleptic properties, storage stability, or the impact on minimizing food losses, are not analyzed in more detail. Therefore, the aim of this study was to assess the effect of ultrasonic treatment of seed potatoes on the quality of potato tubers intended for French fries. The focus was on the analysis of key tuber parameters, such as the dry matter content, starch ,and soluble sugars, which directly affect the sensory characteristics of French fries, such as taste, color, and texture. Particular attention was paid to reducing sugars, which participate in Maillard reactions during heat treatment, influencing the final appearance and taste of the product [8,9,10,11]. The conducted research aims to fill the gap in understanding the effect of ultrasonic treatment on potato processing, which can contribute to improving the quality of French fries and optimizing agricultural practices in the production of processed potatoes. Therefore, an alternative hypothesis (H1) was formulated, in relation to the null hypothesis (H0):

H0: 

Ultrasound treatment does not cause any changes in the quality of French fries.

H1: 

Ultrasound treatment of seed potatoes improves the quality of French fries, leading to beneficial changes in their sensory characteristics, such as color, taste, and texture, compared to French fries from traditionally grown potatoes.

In relation to the alternative hypothesis, this study aimed to demonstrate that the use of ultrasound in potato cultivation leads to significant differences in the quality of processed products (French fries) and their organoleptic characteristics.

2. Materials and Methods

Field and laboratory experiments were conducted in 2015–2017 at the Experimental Variety Evaluation Station in Uhnin (51°34′ N, 23°02′ E, altitude 155 m above sea level), in southeastern Poland. The field experiment was established using the randomized subblock method in a dependent design, split–split–plot, with three replications. The first-order factor was cultivation technology: (A) traditional without the use of ultrasound; (B) technology using ultrasound as a pre-planting treatment. The second-order factor was eight edible potato varieties from four earliness groups (very early: ‘Denar’ and ‘Lord’; early: ‘Owacja’ and ‘Vineta’; medium early: ‘Satina’ and ‘Tajfun’; medium late: ‘Syrena’ and ‘Zagłoba’).

2.1. Field Tests

The pre-crop for potato cultivation was spring barley. Phosphorus–potassium fertilization comprised 90 kg N, 90 kg P, and 135 kg K·ha⁻¹. In addition, compost was applied once in the crop rotation at a dose of 35 t·ha⁻¹.

Potato tubers were planted in the last ten days of April, at a spacing of 67.5 × 37 cm. In a 15 m² plot, 60 potato plants (2 rows of 30 plants each) were grown, with three replications under two cultivation technologies. Before emergence, mechanical protection methods were used, such as harrowing with a weeder and one-time ridging and covering. Just before plant emergence, Plateen 41.5 WG was applied at a dose of 2.0 kg·ha⁻¹, dissolved in 270 dm of water. After emergence, when the plants reached a height of 15–20 cm, the herbicide Leopard Extra 05 EC was sprayed at a dose of 3.0 dm ha⁻¹ to control monocotyledonous weeds. Plant protection treatments were performed in accordance with the thresholds of harmfulness of pests and the principles of good agricultural practice [12]. To control the Colorado potato beetle, the following preparations were used: Mospilan 20 SP (0.08 kg·ha⁻¹) and Coragen 200 SC (62.5 mL·ha⁻¹), with 300 L of water used to apply these insecticides, and the treatment performed with a sprayer with a current certificate. Potato blight was controlled using fungicides such as Infinito 687.5 SC (1.6 dm·ha⁻¹), Ekonom 72 WP (2.0 kg·ha⁻¹), and Pyton Consento 450 SC (2.0 dm·ha⁻¹), where a water dose of 300 dm·ha⁻¹ was used to apply these preparations. Decisions on the necessity and timing of chemical application were made based on our observations and announcements of the State Plant Protection and Seed Inspection. Potato tubers were harvested at the 99° stage on the 99° BBCH scale [13]. During harvesting, 20 tubers (10 pieces of sizes 51–60 mm and above 60 mm) were taken from each repetition of the field experiment, with a shape typical for a given variety, without visible external deformations and greening, intended for testing of fries [14]. In addition, 5.5 kg of tubers was collected from each plot during harvesting to determine the starch content, and 50 non-green, undamaged tubers were collected to analyze the content of dry matter and soluble and reducing sugars [15].

2.2. Experimental Methods for Preparing Seed Potato Tubers

In the experiment, two methods of potato crop management were applied:

Ultrasound Treatment: Before planting, potato tubers were subjected to ultrasound treatment in a water medium at a temperature of 18 °C for a duration previously determined in pilot studies (10 min). A longer exposure to ultrasound would have damaged the potato sprouts (Figure 1 and Figure 2).

Control Group: In the control group, the tubers were soaked in distilled water for 10 min before planting to create a similar environment to the ultrasound treatment and to eliminate the influence of water on the physiology of potato emergence.

The sonication of tubers was conducted in a bath device equipped with three piezoelectric ultrasonic transducers, attached under the bottom of a tank made of acid-resistant steel. The transducers generated ultrasound waves and were powered by an alternating current at a frequency of 50 Hz, with a power output of 200 W, in accordance with [16].

2.3. Laboratory Tests

2.3.1. Determination of Chemical Composition

The starch content was determined on an electronic hydrostatic balance according to Reimann–Parow in triplicate. The starch content in potato tubers was measured as follows: From a representative sample of tubers collected during harvesting, two samples were prepared—5 kg of dry tubers or 5.05 kg of wet tubers (weighed in air). The tubers were then weighed underwater, and the starch content was determined based on the weighing results. Before the measurement, the tubers were washed and cleaned of soil. The starch determination was carried out in clean water at a temperature of 17.5 °C [15]. The determination of dry matter content, as well as soluble and reducing sugar levels, was conducted using fresh potato tuber samples, with each analysis performed in triplicate. Dry matter content was measured using a two-step drying process. Initially, the sliced and crushed fresh tuber mass was dried at 60 °C for 20 h, followed by an additional drying phase at 105 °C for 2 h. The percentage of dry matter in the sample was calculated using the formula

$$\mathrm{DM}={\displaystyle \frac{(c-a)}{b}}\times 100\%,$$

(1)

where

DM—dry matter content (%);

a—initial weight of the empty container (g);

b—weight of the container with the fresh sample (g);

c—weight of the container with the dried sample (g).

The soluble and reducing sugar content was quantified using the Luff Schoorl iodometric method, a well-established approach for assessing sugar concentrations [17,18].

2.3.2. Quality Assessment of French Fries

Before making French fries, the tubers were washed, peeled manually, and mechanically cut into strips in a mechanical slicer, measuring 5 × 5 mm and at least 70 mm long. After rinsing the raw French fries with cold water to remove free starch, the strips were dried with filter paper and deep-fried in oil at 170 °C for 8 min to a moisture content of about 2%. The French fries were fried using a single-stage method, in rapeseed oil characterized by a high smoking point, above 235 °C, with high resistance to fat transformations during frying at high temperatures. This oil was characterized by a neutral taste and smell, emphasizing the natural character and aroma of the fried products. The proportions for one frying cycle were 100 g of raw French fries per 3 dm³ of oil. The frying time was selected by a trial method in order to obtain French fries with the same dry matter content. The frying process temperature was controlled using a CIE 307 temperature recorder equipped with a K-type thermocouple (MERA), with a measurement range of −40 ÷ +220 °C. Each sample was assessed immediately after frying in ten technological repetitions. The fried French fries were drained of excess fat on filter paper. The organoleptic assessment of the finished product was carried out at a consumption temperature of +65 °C. The flavor intensity profiles of the French fries and the visual and organoleptic values were determined by a 10-person trained team meeting formal requirements [19]. The sensory evaluation of French fries was conducted in the Laboratory of Commodity Science at the Faculty of Agrobioengineering, University of Life Sciences in Lublin. The evaluation team, consisting of laboratory staff and students, was previously familiarized with typical sensory profiles of French fries (e.g., ideal crispness, appropriate degree etc.). The sensory evaluation procedure was presented to the panelists as follows: The tasting was conducted in silence, free from external influences. Panelists rinsed their mouths with water or a neutralizing agent (e.g., non-carbonated water) between samples. The evaluation was carried out in a predetermined order under consistent conditions (lighting, temperature, sample quantity).

Each test was performed immediately after frying. The color and consistency of the fries were assessed on a 5-point Kirkpatrick’s scale, where 5—light gold color, very even; 4—light gold color, even; 3—light gold to dark gold color with brown edges, moderately even; 2—slightly dark color with brown spots, uneven; 1—dark color with brown spots, very uneven [20]. The consistency of the fries was also assessed on a 5° scale, where 5 means very crispy consistency and delicate flesh; 4—delicate, crumbled, brittle surface of the fries, very loose: 3—sufficiently crispy surface, slightly grainy or slightly bland flesh; 2—not very crispy surface, grainy or oily; 1—abnormal, abrasive, greasy surface [21]. The fat content in the French fries was determined by the Soxhlet extraction–gravimetric method [21]. The principle of this method is to separate fat from the crushed and dried substance by continuous extraction in a Soxhlet apparatus using petroleum or ethyl ether, evaporate the solvent from the extract, and determine the mass of the separated and dried fat at 105 °C by weighing. The moisture content of the French fries was measured by the gravimetric method [21]

In Figure 3a–e, the subsequent stages of raw material preparation for French fry production are shown. These include planting potato tubers in the field, observing full sprouting, allowing the vegetative growth phase of potato plants, peeling the tubers, and then cutting the potatoes into French fries. This cycle concludes with the frying process and sensory evaluation of the French fries.

2.3.3. Soil Sampling and Determination

Each year, before the experiment was established, 20 primary soil samples were taken, making up one general sample weighing approximately 0.5 kg [22]. The humus content in the topsoil was determined using the Tiurin method [23], the content of available P₂O₅ and K₂O was determined using the Egner–Riehm method [24,25], and the magnesium content in the soil was determined using the Schachtschabel method [22].

2.4. Soil Conditions

The tests were carried out on clayey soil developed from sandy clay; according to WRB [26], it is a podzolic soil.

Data on the macronutrient content, humus content, and pH in 2015–2017 indicate that this was soil of moderate fertility, with the following properties for macronutrients: Phosphorus was found at 9.3 mg 100 g⁻¹ soil, which suggests that the soil had moderate resources of this element. In 2017, an increase in available phosphorus in the soil was observed (10.6 mg 100 g⁻¹), which could have resulted from improved soil conditions or fertilization. The average potassium level (9.9 mg 100 g⁻¹) also indicated a moderate content of this macronutrient in the soil. Potassium is a key element affecting crop quality, including potato development. The average magnesium content (7.0 mg 100 g⁻¹) was within the range typical for soils with moderate levels of this element. Magnesium supports photosynthesis and is an important component of chlorophyll, which has a direct impact on plant health. The humus content averaged 1.02 g kg⁻¹, suggesting that the soil intended for the experiment contained moderate amounts of organic matter. Humus affects water retention, soil structure, and nutrient availability, which may affect potato growth and quality. Soil pH ranged from 5.8 to 6.6, meaning that the soil is slightly acidic to slightly neutral. Potatoes prefer a slightly acidic soil pH, which may promote the optimal growth and crop quality. In general, the soil was characterized by moderate macronutrient and organic matter resources. Its slightly acidic pH and relatively stable humus values indicated conditions favorable for potato cultivation, although it may require additional fertilization with phosphorus and magnesium to ensure optimal plant development (

Table 1. Soil characteristics before establishing the experiment.

Year of Research	Macronutrients [mg·100 g−1 soil]			Humus Content [g·kg−1]	pH [in KCL]
	P	K	Mg
2015	8.9	10.9	7.8	0.94	5.9
2016	8.3	9.1	7.0	1.06	5.8
2017	10.6	9.8	6.3	1.03	6.6
Mean	9.3	9.9	7.0	1.02	-

Source: The analysis was carried out at the Chemical-Agricultural Laboratory in Lublin.

).

2.5. Meteorological Conditions

Atmospheric conditions in the years of the study are illustrated in Figure 4 and Figure 5. The meteorological conditions presented in this manuscript are based on meteorological observations collected at the Variety Assessment Experimental Station in Uhnin, according to the applicable methodology [27]. During the potato vegetation period, a large variability in meteorological conditions was observed. In 2015, during the vegetation period, both the total rainfall and its distribution were not conducive to the potato yield. In the period from June to August, when intensive growth and accumulation of the tuber yield occur, there were significant water shortages in the soil. The Sielianinov hydrothermal coefficient, which takes into account both rainfall and air temperature, characterizes these months as dry or exceptionally dry. September rainfall improved the water balance, but it no longer had a significant effect on the yield of very early, early, and medium early potato varieties (Figure 4 and Figure 5).

2016 was characterized by the lowest rainfall, but with a favorable distribution in the potato growing season. In that year, the highest tuber yields were recorded. Only at the end of the growing season (August–September) was a rainfall deficit noted (Figure 4). The hydrothermal coefficient values describe these months as exceptionally dry and hot (Figure 5).

2017 was characterized by the most variable meteorological conditions. April was very humid, May turned out to be optimal in terms of water supply/rainfall, while in June, water deficits in the soil were already observed. The water balance improved humidity conditions in July. In August, a rainfall deficit was noted. The Sielianinov hydrothermal coefficient describes August as very dry.

September improved the water balance of that month, as 83.3 mm of water fell, but this had no effect on the tuber yield (Figure 5).

The equation for the trend of precipitation from 2015 to 2017 is given by

Y = 0.0186x³ − 0.6377x² + 6.3059xy

(2)

where y represents the predicted air temperatures, and x represents time (likely in years or months).

R² = 0.6955 is the coefficient of determination, indicating how well the model fits the data. The equation is a cubic polynomial, meaning it describes a curve with up to three changes in direction. This suggests that the trend in air temperatures over this period may show both increases and decreases, indicating some fluctuations. The R² value of 0.6955 means that approximately 69.55% of the variation in air temperatures can be explained by this model. This is a fairly good fit, but it leaves about 30% of the variation unexplained, suggesting some other factors may influence the trend. The positive coefficient for x³ indicates a steep increase at some points in time. The negative coefficient for x² suggests a decrease or slowdown at certain points. The positive coefficient for x indicates an overall upward trend during the time period.

In summary, the trend suggests variability in air temperatures over the years 2015–2017 with both increases and decreases, but an overall upward trend over time.

2.6. Statistical Calculations

The obtained research results were subjected to statistical analysis based on three-way analysis of variance (ANOVA) models, SAS 9.2 2008 [29]. A multiple t-Tukey test was also performed with a selected significance level of p = 0.05. The analysis of variance models included main effects and interactions between the studied factors, with particular emphasis on main effects and two-way interactions. The multiple t-Tukey comparative tests allowed for comprehensive comparative analyses of means, statistically identifying them into homogeneous groups of means by the least significant differences (LSDs). Subsequent letter indices (a, b, c) define groups of means in ascending order [30,31]. In addition, descriptive statistics of the studied features were generated using the SSPS program, and simple correlation was performed using the SAS 9.2 2008 program [29].

3. Results

3.1. Chemical Composition of Tubers

3.1.1. Dry Matter and Starch Content

The applied technologies increased the dry matter and starch content in tubers, but they did not have a significant effect on the values of these parameters. However, the varieties and years of research significantly modified the values of these parameters (

Table 2. The effect of technology, varieties, and years of cultivation on the content of starch, dry matter of tubers, and the sum of soluble and reducing sugars in % of the fresh mass of tubers.

Factors of the Experiment		Starch	Dry Matter	Total Soluble Sugars	Reducing Sugars
Technologies	Control object	14.3 a *	20.7 a	1.07 a	0.53 a
	Ultrasounds	14.5 a	21.0 a	1.03 a	0.52 a
	LSDp0.05	ns **	ns	ns	ns
Cultivars	‘Denar’ ‘Lord’ ‘Owacja’ ‘Vineta’ ‘Satina’ ‘Tajfun’ ‘Syrena’ ‘Zagłoba’	13.0 a 12.9 a 14.1 b 14.4 b 14.6 b 17.3 d 16.1 c 12.9 a	18.8 a 19.6 ba 20.4 bca 20.8 bc 21.4 dc 23.7 e 23.0 de 19.4 ba	1.17 de 1.07 db 1.22 de 0.9 ab 0.98 da 0.84 ab 0.74 a 1.45 e	0.64 cd 0.62 c 0.62 c 0.48 b 0.54 cb 0.29 a 0.31 a 0.74 d
	LSDp0.05	0.63	1.78	0.30	0.12
Years	2015 2016 2017	16.2 c 13.1 a 13.9 b	22.4 b 19.8 a 20.4 a	0.60 a 2.05 b 0.48 a	0.34 a 0.93 b 0.33 a
Mean		14.4	20.9	1.05	0.53
LSDp0.05		0.30	0.81	0.14	0.06

* Letter indices accompanying the means (significance groups) represent so-called homogeneous groups (statistically uniform groups). The occurrence of the same letter index for at least one of the means indicates no statistically significant difference between them. Consecutive letter indices a, b, c,… define groups of means in ascending order. ** not significant at p ≤ 0.05.

).

The genetic properties of the varieties significantly modified all the assessed chemical components. The first homogeneous group with the lowest starch content consisted of the following varieties: ‘Denar’, ‘Lord’, and ‘Zagłoba’, where the highest starch and dry matter content was noted in the ‘Tajfun’ variety. The high contents of the discussed components in the ‘Tajfun’ tuber allowed it to produce French fries with high utility parameters and, at the same time, fewer defects. Of the tested varieties, only the ‘Denar’ variety accumulated an insufficient amount of dry matter in the fresh mass of the tubers (18.8%), which should exclude this as a French fries variety (Table 2).

Variable weather conditions in the years of this study significantly modified the starch and dry mass content of the tubers. In the first year of the study (2015), the highest content of the discussed tuber components was recorded. During the growing season, a significant rainfall deficit was noted. The lowest starch and dry mass content was obtained in 2016, with an excess of rainfall during the growing season. The third year of the study with variable weather conditions did not favor the accumulation of dry mass of the tubers (Table 2).

All varieties, except ‘Denar’, responded positively to the use of ultrasound, but only three, ‘Satina‘, Tajfun’ and ‘Syrena’, responded with a significant increase in dry matter and starch content, compared to traditional technology (Figure 6).

3.1.2. Sugar Content

The use of sonication of tubers as a pre-planting procedure did not have a significant effect on the content of total soluble sugars or reducing sugars, although a positive trend was observed (Table 2).

However, varietal properties significantly modified the content of both total sugars and reducing sugars in the fresh mass of tubers. The ‘Syrena’ variety was characterized by the lowest content of soluble and reducing sugars, while the ‘Tajfun’ variety accumulated the least reducing sugars. The ‘Zagłoba’ variety had the highest content of soluble and reducing sugars (Table 2). Differences in the content of soluble and reducing sugars in individual potato varieties, such as ‘Syrena’, ‘Tajfun’, and ‘Zagłoba’, are of key importance for the quality of the produced French fries. Here is how these properties can affect the production process: in the case of the ‘Syrena’ variety—with the lowest content of soluble and reducing sugars, ‘Syrena’ is probably the most suitable for the production of French fries. The low content of reducing sugars minimizes the risk of Maillard reactions, which lead to excessive browning of the French fries and a bitter aftertaste. This can result in French fries with a lighter color and a more desirable flavor. In the case of the ‘Tajfun’ variety—with a low content of reducing sugars but a higher of total sugars, French fries from this variety can still show good quality in terms of color and flavor, although there may be some risk that the slightly higher content of soluble sugars will affect the texture or aftertaste of the French fries. The meteorological conditions varied significantly across the years of this study, leading to notable fluctuations in the levels of total sugars and reducing sugars in potato tubers. The lowest content of reducing and soluble sugars was obtained in the first and third years of the study, in which the growing seasons were characterized by a significant shortage of rainfall. The highest sugar contents were recorded in the wet year of 2016 (Table 2). This indicates that water deficiency limits the synthesis and accumulation of sugars, while excess water during the growing season can lead to their excessive accumulation.

3.2. French Fries Quality

3.2.1. French Fries Color

According to the results presented in

Table 3. Effect of technology, cultivars, and years on the advantages and disadvantages of French fries.

Factors of the Experiment		Assessment Parameters on the 5° Scale				Content of Fat (%)	Assessment Parameters on %
		Color	Visual Assessment	Consistency	Taste and Smell		Humidity	Dark Ends
Technologies	Traditional	3.98 a *	3.67 a	3.30 a	3.97 a	18.03 b	2.65 b	0.94 b
	With Ultrasound	4.18 b	3.84 b	3.66 b	4.22 b	17.84 a	2.51 a	0.56 a
	LSDp0.05	0.08	0.16	0.17	0.14	0.18	0.10	0.34
Cultivars	‘Denar’	3.65 b	3.19 b	2.67 a	4.11 b	18.30 b	2.81 cd	0.33 a
	‘Lord’	3.72 b	3.27 b	2.86 ab	3.92 b	18.22 b	2.64 bcd	1.0 ab
	‘Owacja’	4.20 c	3.22 b	3.22 b	3.92 b	17.98 b	2.61 abc	1.44 b
	‘Vineta’	4.53 d	4.56 d	4.36 d	4.75 c	17.96 b	2.44 abc	0.25 a
	‘Satina’	4.04 c	3.83 c	3.78 c	4.17 b	17.65 a	2.44 ab	1.72 b
	‘Tajfun’	4.83 e	4.72 d	4.25 cd	4.78 c	17.11 a	2.31 a	0.33 a
	‘Syrena’	4.85 e	4.92 d	4.31 cd	4.94 c	17.92 b	2.47 ab	0.00 a
	‘Zagłoba’	2.82 a	2.31 a	2.39 a	2.14 a	18.47 b	2.94 d	0.89 ab
	LSDp0.05	0.24	0.51	0.53	0.45	0.72	0.31	1.06
Years	2015	4.62 c	4.23 c	3.80 b	4.11 ab	17.65 a	3.22 b	0.10 a
	2016	3.44 a	3.09 a	2.81 a	3.93 a	18.18 b	2.30 a	1.84 b
	2017	4.17 b	3.93 b	3.82 b	4.23 b	17.96 b	2.23 a	0.29 a
Mean		4.08	3.75	3.48	4.09	17.93	2.58	0.75
LSDp0.05		0.11	0.24	0.25	0.21	0.27	0.14	0.50

* Letter indices accompanying the means (significance groups) represent so-called homogeneous groups (statistically uniform groups). The occurrence of the same letter index for at least one of the means indicates no statistically significant difference between them. Consecutive letter indices a, b, c … define groups of means in ascending order.

, the applied technology, cultivars, and years of study had a significant effect on the assessed features of French fries, including color. A significant positive effect of ultrasound was noted in the color assessment, where the French fries subjected to sonification obtained a significantly higher score, than those from the traditional technology. In the case of potato cultivars, the highest color score was obtained for the cultivars ‘Syrena’ and ‘Tajfun’, and the lowest for the cultivar ‘Zagłoba’. Years of research also significantly influenced the assessment of the color of French fries—the best results were obtained in 2015, and the lowest in 2016 (Table 3).

Figure 7 shows the effect of cultivation technology and varieties on the color of French fries. In the case of the varieties ‘Satina’ and ‘Zagłoba’, a significant effect of tuber sonification on the color of this product was found, compared to the traditional cultivation technology. In the variety ‘Denar’, on the other hand, an inverse relationship was noted: French fries obtained using the traditional technology were characterized by a nicer color than those obtained using the technology with ultrasound. In the remaining varieties, only an improvement in color was observed under the influence of ultrasound, but these relationships were not statistically confirmed (Figure 7).

Figure 8 shows the effect of the application of cultivation technology and the year of cultivation on the assessment of the color of French fries.

Interaction of cultivation technology and years: In the case of French fries from the control object, the highest assessment was obtained in 2017 and the lowest in 2015. French fries from tubers treated with ultrasound before planting obtained the highest assessments also in 2017 and the lowest in 2015. It should be noted that in all years, the results were higher compared to the control object. The differences in the assessments of the color of French fries between individual years were significant, both depending on the technology and the year of cultivation (Figure 8).

Thus, the use of ultrasound had a positive effect on the color of French fries in each year of this study, confirmed by the higher average assessments of this feature compared to the traditional technology in the control object. The differences in the assessments of the color of French fries between years were significant, which suggests that weather conditions may play an important role in shaping the quality of French fries in practice. The interaction of technology and years indicates that the effect of ultrasound was visible in all years, with only 2015 and 2017 showing a significant effect, and the greatest improvement in the color quality of French fries was observed in 2017 (Figure 8).

3.2.2. Visual Assessment of French Fries

French fries obtained from tubers grown in objects subjected to sonication obtained a higher visual assessment score compared to French fries produced using traditional technology (Table 3).

The genetic features of the tested varieties significantly differentiated this feature of French fries. The varieties ‘Syrena’, ‘Tajfun’, and ‘Vineta’ were in the same homogeneous group and obtained the highest assessment, while the lowest assessment of this feature was given to the variety ‘Zagłoba’ (Table 3).

Meteorological conditions in the years of this study also modified this feature. The visual assessment of French fries was the most favorable in the dry year of 2015 and the least favorable in the wet year of 2016 (Table 3).

An interaction between cultivation technology and conditions in the years of this study was also observed. French fries from tubers from the control object (without the use of ultrasound) obtained lower visual assessments compared to French fries obtained from tubers subjected to ultrasound. In the case of French fries from tubers treated with ultrasound, the scores were higher in each year, but only in 2015 and 2017 were these differences significant. In the subsequent years of this study, the visual score of the French fries systematically increased, which suggests that the years 2016 and 2017 could be characterized by more favorable growing conditions or other factors improving the appearance of the French fries (Figure 9). The differences between the technologies were significant, especially in 2017, which confirms that the technology with sonication has a positive effect on the visual quality of French fries, especially in more favorable years of cultivation (Figure 9).

3.2.3. Consistency of French Fries

The use of ultrasound improved the consistency of French fries compared to the product obtained using traditional technology. Genetic features differentiated this feature to a greater extent. The best consistency was characteristic of French fries produced from tubers of the ‘Vineta’ variety, while the lowest score was given to French fries obtained from tubers of the ‘Zagłoba’ and ‘Denar’ varieties. Years of cultivation also had a clear effect on the consistency of French fries. French fries obtained in 2015 and 2017 had the best consistency, and in 2016 the worst, which may be due to weather conditions or other cultivation factors (Table 3).

Figure 10 shows the effect of cultivation technology and years on the assessment of French fries consistency. French fries from traditional technology (without ultrasound) in 2015 obtained the highest consistency score. In the following years, the consistency scores decreased: 4.14 in 2016 and 3.51 in 2017. French fries from tubers grown from seed potatoes treated with ultrasound received a slightly lower score in 2015 compared to the traditional technology without the use of ultrasound. However, in 2016 and 2017, these scores were higher than in the case of French fries from the traditional technology. In summary, it should be stated that the use of ultrasound had a positive effect on the consistency of French fries, especially in 2016, where the difference between the two technologies was statistically significant. In other years, the effect of ultrasound was not statistically significant (Figure 10).

3.2.4. Taste and Smell of French Fries

The taste and smell rating was higher for French fries produced from tubers using the ultrasound technology compared to the technology without the use of ultrasound. The genetic features of the tested varieties significantly determined the fat and smell of the French fries. The varieties ‘Syrena’, ‘Tajfun’, and ‘Vineta’, belonging to the same homogeneous group, obtained the highest score, while the lowest score for this feature was given to the ‘Zagłoba’ variety (Table 3).

The years of research, regardless of the experimental factors, differentiated the value of this feature. 2017 was characterized by the highest score for taste and smell of French fries produced on the basis of the collected materials, while 2016 was characterized by the lowest score for the tested French fries. The differences in the ratings between the years suggest that the cultivation conditions in the individual years had a significant impact on the sensory quality of the French fries (Table 3).

Figure 11 shows the influence of cultivation technology (traditional, control, and with ultrasound) and years of cultivation on the assessment of taste and smell of French fries on a 5° scale. French fries from tubers that were subjected to ultrasound in each year obtained higher taste and smell assessments compared to French fries from control tubers; however, in 2015, the difference between both technologies was insignificant. In 2016, the difference was more significant, where French fries from the traditional technology obtained a significantly lower assessment than French fries from technology with ultrasound. In 2017, French fries with the use of ultrasound obtained a higher assessment compared to French fries from the control object (Figure 11). Thus, technology with the use of ultrasound had a positive effect on the taste and smell of French fries, especially in 2016 and 2017.

3.2.5. Fat Content in French Fries

French fries obtained from facilities where ultrasound was used on tubers before planting were characterized by a significantly lower fat content than French fries produced from tubers from traditional technology (Table 3). The genetic factor also had a significant effect on the value of this feature. Based on the value of the smallest difference, the tested varieties were grouped into two significantly different homogeneous groups. The first homogeneous group, in which the lowest fat content was recorded, included ‘Tajfun’ and ‘Satina’. The remaining varieties belonged to the second homogeneous group and did not differ significantly from each other. The years of research, regardless of the experimental factors, significantly modified the value of this parameter. French fries with the lowest fat content were obtained in 2015, with a significant rainfall deficit, and the remaining years of research did not differ significantly from each other (Table 3).

Virtually all varieties responded positively to the cultivation technology using ultrasound on tubers before planting, but a significant reduction in fat absorption by French fries occurred only in the case of three varieties: ‘Satina’, ‘Tajfun’, and ‘Zagłoba’. The remaining varieties were homogeneous in the value of this feature (Figure 12).

3.2.6. French Fries Defects

A positive effect of sonication of tubers was observed when analyzing the French fries in terms of their defects. The use of ultrasound significantly reduced the defects of French fries. These products prepared from tubers grown using traditional technology, as a control, had higher moisture and a significantly higher share of dark ends compared to French fries subjected to sonication before planting, which were characterized by lower moisture and a lower share of French fries with the defect of dark ends (Table 3).

French fries from traditional technology showed a significantly higher percentage of French fries with dark ends compared to the technology using ultrasound, which indicates a worse quality of French fries without the use of sonication (Table 3).

The genetic features of the tested potato varieties significantly differentiated the defects of this product, such as dark ends or moisture. French fries of the ‘Tajfun’ variety were characterized by the lowest moisture, while French fries produced from tubers of the ‘Zagłoba’ variety turned out to be the moistest of all the tested varieties. In the case of the varieties ‘Syrena’, ‘Vineta’, ‘Tajfun’, and ‘Denar’, the least dark ends were noted, so these varieties were placed in the same, homogenous group (Table 3).

Meteorological conditions in the years of this study significantly affected the defects of French fries. The most humid French fries were obtained in 2015, while French fries produced in 2016 and 2017 had similar, homogeneous moisture (Table 3).

Figure 13 shows the effect of cultivation technology (traditional and with ultrasound) and the interaction of cultivation years on the assessment of the moisture content of French fries. French fries from tubers that were subjected to ultrasound were significantly less humid in the first and third year of this study compared to French fries from control tubers. Only in 2016 was the difference between the two technologies insignificant. Therefore, the technology using ultrasound had a positive effect on the moisture content of the French fries (Figure 13).

Figure 14 illustrates the influence of cultivation technology (control object and application of ultrasound) and cultivation years on the defects of French fries, in particular, the percentage of dark ends. An interaction of cultivation technology and years was found on a serious defect of French fries, which is dark ends. The greatest number of dark ends was observed in 2016, and the years 2015 and 2017 did not differ significantly from each other in this respect (Figure 14).

The year 2015 was characterized by the highest average content of dark ends, both in the case of the control object and ultrasound. The heat and drought in that year created less favorable growing conditions. The year 2016 brought a significant improvement in the quality of French fries in terms of this trait, with values of 0.5% for the control object and 0.08% for French fries treated with ultrasound. This indicates more favorable growing conditions, as well as a clear effect of ultrasound technology on the reduction in defects. The year 2017 brought the lowest share of French fries with dark ends, both in the control object and in French fries treated with ultrasound. This suggests optimal growing conditions that year, which had a positive effect on the quality of French fries (Figure 14).

Therefore, the use of ultrasound in potato cultivation technology significantly improves the quality of French fries, by reducing the fat absorption by French fries and the share of dark ends, especially in years with less favorable conditions (2015 and 2016).

The years of cultivation had a significant impact on the quality of the French fries—in 2016 and 2017, a significantly lower share of French fries with dark ends was obtained than in 2015, which indicates better environmental conditions. The cultivation technology using ultrasound proved to be more effective in reducing the defects of French fries than traditional cultivation.

Summary: The use of ultrasound had a positive effect on most of the features of French fries, including color, visual assessment, consistency, taste and smell, fat content, and defects of this product (reduction in moisture and reduction in the share of French fries with dark ends). Potato varieties differed significantly in terms of the assessed features, with the ‘Zagłoba’ variety receiving the lowest scores in most categories. The years of this study had a varied effect on the assessed features of the French fries, with the best results obtained in 2015 for many parameters, while 2016 was the year with the worst results in the assessment of French fries, especially in the context of visual assessment and the presence of dark ends.

3.3. Descriptive Statistics of Tuber and French Fries Features

The mean indicates the average value for each variable in the table.

The standard error measures the precision of the sample mean, with lower values indicating greater precision. For example, the standard error for visual assessment (x2) is 0.10, while for moisture content (x4) it is 0.05, indicating fairly accurate estimates of the means for these variables (

Table 4. Descriptive statistics of the examined features of tubers and French fries.

Specification	x1	x2	x3	x4	x5	x6	x7	x8	x9	x10	x11
Mean	4.08	3.75	3.48	2.58	17.93	0.75	4.09	14.40	20.87	1.05	0.53
Standard error	0.08	0.10	0.10	0.05	0.06	0.13	0.09	0.18	0.19	0.06	0.03
Median	4.40	4.00	3.50	2.50	17.96	0.00	4.50	14.00	20.60	0.72	0.46
Standard deviation	0.96	1.25	1.19	0.61	0.73	0.77	1.08	2.19	2.30	0.76	0.33
Kurtosis	0.17	−0.34	−1.25	−0.92	2.42	3.17	0.65	−0.36	−0.50	−1.10	−1.08
Skewness	−1.06	−0.82	−0.11	0.15	−0.15	2.12	−1.15	0.51	0.27	0.65	0.48
Range	3.40	4.65	4.00	3.00	5.10	5.00	4.00	9.80	9.65	2.41	1.06
Minimum	1.60	0.35	1.00	1.00	14.60	0.00	1.00	10.00	16.00	0.18	0.09
Maximum	5.00	5.00	5.00	4.00	19.70	5.00	5.00	19.80	25.65	2.59	1.15
Coefficient of variation V	23.52	33.20	34.11	23.45	4.07	103.14	26.45	15.24	11.04	72.86	63.15

x1—color on a 5° scale, x2—visual evaluation on a 5° scale; x3—consistency on a 5° scale; x4—moisture in %; x5—fat in %, x6—dark ends in %, x7—taste and smell on a 5° scale, x8—starch in % of fresh mass, x9—dry mass in % of fresh mass; x10—soluble sugars in % of fresh mass; x11—reducing sugars in % of fresh mass.

).

The median indicates the middle value of the dataset. For example, the median fat content (x5) is 17.96%, while the median color score (x1) is 4.40, suggesting that the distribution of values for these variables is fairly central around the mean.

Standard deviation measures the spread or variability in a dataset. Higher values indicate greater variability. For example, the dark ends of French fries (x6) have a fairly large standard deviation, indicating significant variability in this attribute. In contrast, fat content (x5) has a lower standard deviation (0.73), suggesting less variability (Table 4).

Kurtosis measures the “tailenders” of the data distribution. Positive values indicate thicker tails, while negative values indicate thinner tails. For example, fat content (x5) had a high kurtosis of 2.42, indicating a distribution with thicker tails, which can signal extreme values. The dark ends (x6) also had high kurtosis (Table 4).

Skewness is a measure of the asymmetry of the data distribution. A negative skew indicates a longer left tail, while a positive skew indicates a longer right tail. For French fries color (x1), a negative skew of −1.06 was found, indicating that most observations were at the high end of the scale with a long tail to lower values. In contrast, the dark ends of French fries (x6) as a trait was positively skewed (2.12), indicating that the distribution was skewed toward the low end with a long right tail (Table 4).

The range is the difference between the maximum and minimum values in the dataset. For example, the range for fat content (x5) is 5.10%, as the fat content ranges from 14.60% to 19.70%. For the color of the French fries (x1), the range is 3.40, which covers values from 1.60 to 5.00.

The coefficient of variation (V) is the ratio of the standard deviation to the mean, expressed as a percentage. It is extremely useful for comparing the relative variability between variables. For example, dark ends (x6) had a high coefficient of variation (204.72%), indicating that the data were highly dispersed from the mean. In contrast, the fat content of the French fries (x5) had a very low coefficient of variation (4.07%), indicating that this variable was the most stable and least dispersed (Table 4).

3.4. Relationship Between French Fries Quality and Chemical Composition of Tubers

A positive correlation (values close to +1) means that as one variable increases, the other also tends to increase. A negative correlation (values close to −1) means that as one variable increases, the other tends to decrease. Values closer to 0 suggest little or no linear relationship between the variables (Figure 15).

Key correlations: Strong positive correlations were found between color (x1) and visual assessment of the product (x): (r = 0.85). Similarly, strong correlations were found between tuber dry matter (x9) and starch content (x8) (r = 0.88) and between soluble sugar content (x10) and reducing sugars (r = 0.94) (Figure 15).

Strong negative correlations were found between the color of the French fries (x1) and reducing sugars (r = −0.73), as well as between the dark ends of the French fries (x6) and their taste and smell (x7): (r = −0.31) (Figure 15).

The visual assessment (x2) strongly correlated with both color (x1) and consistency of the French fries (x3), suggesting a relationship between appearance and consistency of the product (Figure 15).

This analysis provides an overview of the relationships between sensory and compositional factors such as color, flavor, texture, and content (e.g., sugars, fat, starch) in the samples tested.

4. Discussion

The most up-to-date research on the quality of French fries and the influence of frying parameters indicates several key factors that determine their crispiness, fat content, and general sensory properties, as described herein.

Frying temperature—A high and stable frying temperature plays a key role in creating a crispy crust, as well as in limiting fat absorption. Numerous authors [8,32,33,34,35,36,37] confirm that rapid restoration of frying temperature after adding the raw material allows for obtaining French fries with a low fat content and better crispiness. This is consistent with the results of van de Loo [8], Grudzińska and Zgórska [9,33], Kita et al. [34], Sawicka and Barbaś [34], Pedreschi [36], and Pedreschi et al. [37], who emphasize the need to optimize frying technology to minimize temperature fluctuations.

Frying moisture and texture—The internal structure of the French fries, especially an even moisture content, is crucial for obtaining the desired texture of this product. As shown by van de Loon [8], excessive drying of the internal part of the French fries leads to a loss of texture, while proper management of the moisture level can significantly affect their crispiness.

Fat content—Recent studies have focused on reducing the fat content in French fries and minimizing the level of acrylamides, substances formed during frying. Pedreschi [36] and Pedreschi et al. [37] indicate that using a shorter frying time at higher temperatures allows for reducing the formation of acrylamide while maintaining good crispiness.

New technologies—It is emphasized in [2,36,38,39,40,41,42] that the use of innovative processing techniques, such as ultrasound, can improve the properties of French fries, especially in terms of uniformity of frying and texture of the final product. Ultrasonography is a promising technique supporting uniform evaporation of moisture and optimization of fat absorption.

4.1. The Effect of Ultrasound on the Quality of Raw Material and French Fries

The effect of technology on the chemical composition of tubers: The use of sonification (ultrasound) did not have a significant effect on the content of dry matter, starch, or soluble and reducing sugars in tubers. Although a positive trend was observed in some parameters, these differences were not statistically significant. This technology, despite the lack of significant differences, may be an interesting direction for further research in the context of optimizing potato cultivation. There are no data on this subject in the available literature.

The results of our own research on French fries produced using seed potato technology subjected to ultrasonic processing confirm the positive effect of this technology in improving the sensory quality of food products (Table 4). Our research indicates a significantly better color, consistency, taste, and smell of French fries from tubers subjected to sonication, which is consistent with observations from other studies.

According to Teixeira da Silva et al. [2], the problem with the use of ultrasound is that it causes heating depending on how long the plants are subjected to this treatment and its intensity. Under the influence of long-term application of ultrasound, the number of proteins, such as heat shock proteins, increases in the treated plants. Some heating may also occur as a side effect of the application of ultrasound. A little later, in the case of PE-US treatment, an increase in the level of heat shock proteins was detected. Therefore, the plant material should be kept at a constant temperature (25 °C) to avoid the side effect of heating. In the case of AB-US, the treatment conditions may not be suitable for maintaining a constant temperature of the plant material (i.e., direct cooling of the plant material was not possible).

There are increasingly frequent reports in the literature on the effectiveness of ultrasound in improving the quality of processed food. Our own studies indicate that ultrasonic treatment affects the texture and color of potatoes by reducing the water content, which improves the crispiness of fried products. Similarly, studies conducted by [2,40] suggest that ultrasound leads to a reduction in water content in fried products, which has a beneficial effect on their consistency and improves stability during frying, which is crucial in the production of French fries.

The use of ultrasound in potato processing also has a beneficial effect on the processes related to oil reduction during frying, which is consistent with the observations of [2]. Their research results suggest that sonication can lead to a more uniform heat distribution and better water retention in products, which promotes a higher quality French fries [38]. In summary, the use of ultrasound in the processing of potato tubers has great potential in improving the sensory properties of French fries, especially in terms of their color, crispiness, and consistency, which makes this technology a promising alternative in modern food production.

4.2. Genetic Features and Quality of French Fries

The genetic properties of the tested varieties had a significant impact on all assessed chemical parameters of the tubers (starch, dry matter, sugars). The ‘Tajfun’ variety was distinguished by the highest content of dry matter and starch, which makes it ideal for the production of French fries with high utility values and fewer defects. In turn, the ‘Denar’ variety, due to its insufficient dry matter content, is not suitable for the production of French fries. Significant differences between the varieties in the content of soluble and reducing sugars indicate their potential to obtain French fries of different qualities, especially in terms of color and taste (Table 4).

Frying French fries, especially the final stage, has a key impact on the quality of the final product. During this process, drastic changes in the water and oil content occur, as well as significant modifications to the microstructure of the French fries. Frying at a high temperature causes rapid evaporation of water from the surface of the French fries, which leads to the formation of a crispy crust, while the interior of the French fries remains soft. The use of oil with a high oleic acid content, such as sunflower oil, additionally improves the consistency of the French fries, positively affecting the texture and taste of the final product [8,33,34]. The quality of the French fries depends largely on the genetic characteristics of the potato varieties and their chemical composition, especially the content of dry matter, starch, and sugars. Varieties with a higher content of dry matter and starch, such as ‘Tajfun’ and ‘Syrena’, were characterized by a better structure during frying, which translated into higher-quality French fries. Such varieties absorb less fat during frying, which is crucial for obtaining a crispy texture and the right taste [34,37]. A higher starch content in the tubers also limits the formation of a dark color resulting from the Maillard reaction, which improves the overall visual appeal of the product. Potato varieties that contain fewer reducing sugars, such as glucose and fructose, have a lower risk of excessive browning during frying, which is desirable for the production of light-colored French fries [36]. In turn, varieties such as ‘Zagłoba’, characterized by a higher content of reducing sugars, are more susceptible to excessive browning and a poorer structure of the French fries, resulting in a lower organoleptic quality.

The content of dry matter, starch, and soluble sugars, including reducing sugars, is a key indicator of the quality of potatoes intended for the production of French fries and crisps. The appropriate proportions of these components in the tubers affect not only their sensory properties, such as taste, consistency, and color, but also the stability of the heat treatment of the final product [34,41]. Optimizing these parameters can increase the quality of the final product by minimizing undesirable effects during frying or baking. In the case of French fries production, the content of total sugars, including sucrose, glucose, and fructose, is of particular importance. Too high a level of total soluble sugars, exceeding 1% in the fresh mass of tubers, leads to deterioration of the organoleptic properties of fried products, including French fries, which is manifested by their sweet aftertaste [34,42]. However, reducing sugars—glucose and fructose—play a key role in supporting the quality of the final product in potato processing. Their increased content in tubers increases the risk of unfavorable changes during heat treatment [11]. During heat treatment at high temperature (above 140 °C), reducing sugars take part in Maillard reactions with amino acids, which determines the final color, taste, and smell of French fries. An increased content of reducing sugars in potatoes results in excessive browning and a bitter aftertaste, which significantly reduces their quality [7,9]. Studies show that the content of reducing sugars in potatoes may vary depending on the variety and growing conditions, which emphasizes the need to monitor these parameters [43].

A long-term storage of potatoes before processing can also increase the content of reducing sugars, which in turn leads to an increase in the intensity of the Maillard reaction, contributing to the formation of an undesirable dark color in French fries [10]. Therefore, control of the level of reducing sugars and appropriate storage and processing conditions are crucial to ensure the desired sensory quality of French fries, including their color, taste, and aroma.

Therefore, the selection of the appropriate potato variety with the optimal chemical composition, taking into account the content of dry matter, starch, and sugars, is crucial to obtain French fries of high visual and taste quality. In recent studies, attention is drawn to the increasing role of genetics and tuber chemistry in the optimization of processing processes.

In the case of French fries production, the content of total sugars, including sucrose, glucose, and fructose, is of particular importance. Too high a level of total soluble sugars, exceeding 1% in the fresh mass of tubers, leads to deterioration of the organoleptic properties of fried products, including French fries, which is manifested by their sweet aftertaste [34,42]. However, reducing sugars—glucose and fructose—play a key role in supporting the quality of the final product in potato processing. Their increased content in tubers increases the risk of unfavorable changes during heat treatment [11].

4.3. Reaction of Varieties to Ultrasound

The reaction of potato varieties to ultrasound may vary depending on their genotype and physicochemical properties. In the case of the varieties tested in this experiment, such as ‘Syrena’, ‘Vineta’, and ‘Tajfun’, the use of sonication brought better results in terms of the quality of the French fries—a better color and consistency and fewer dark ends are the key benefits. Meanwhile, the ‘Denar’ variety showed less improvement, which suggests that the response to ultrasound may be strongly dependent on varietal characteristics.

There are few reports in the literature on the different response of varieties to ultrasonic treatment. Duan et al. [44] suggest that differences in the response of varieties to ultrasound may be due to the starch structure and sugar content in different varieties, which affects the efficiency of ultrasonic treatment and the final quality of the French fries. Varieties with a higher dry matter content, e.g., ‘Tajfun’, may respond better to sonication, because the water content in the tubers is crucial for the ultrasonic process. Also, studies by Pedreschi et al. [37] show that the effect of ultrasound on potato tubers can significantly improve the texture and reduce fat absorption during frying, which contributes to better final quality of French fries. The response of varieties with different moisture levels, e.g., our variety ‘Denar’, may be less favorable, which requires further research on adapting the processing parameters to the specific characteristics of individual varieties. Thus, sonification has shown clear benefits for some potato varieties, especially those with favorable traits such as high starch and low moisture, which improve frying efficiency and French fries quality. However, further research is needed to fully understand these interactions and optimize processes for different varieties.

The use of ultrasound in the production of French fries is currently being investigated for improving the quality and efficiency of processing. High-frequency ultrasound is being used as an emerging technology for differentiating plant proteins. Van den Wouwer et al. [45] found that the use of temperature-controlled ultrasound during protein extraction from potato peels significantly increased the protein yield (up to 91%) compared to conventional methods (33%). Ultrasound improved cell decomposition and protein recovery without compromising foaming properties, although long-term treatment affected adsorption kinetics due to protein aggregation. Ultrasound can therefore serve as a pre-treatment technology that reduces oil consumption, improves texture, and shortens the frying time. This research is part of a broader review of ultrasound technologies that also includes other sectors of the food industry. The use of ultrasound is currently being intensively developed in the context of reducing the fat content of fried products such as crisps and French fries, which may affect the health properties of these products. The ultrasonically-assisted frying system (UAFS) significantly reduces oil absorption in potato chips, with two-step ultrasound treatment creating pores that minimize oil uptake. The optimal method (USB73-US) lowers the oil content by over 32%, while also reducing enzyme activity and color changes of this product during frying [46]. This technology is relatively new and requires further research, but recently there has been growing interest in its potential application.

Research on the effects of sonification on different potato varieties is limited, but some studies indicate that the effects of sonification may depend on specific varietal characteristics, such as starch structure or sugar content [44]. Therefore, further research is needed to better understand these interactions.

Due to the increasing use of potatoes for food processing and high consumer requirements when purchasing edible potatoes, varieties with a regular shape should be sought, generating the least possible losses during peeling and processing [39].

4.4. The Influence of the Environment on the Quality of Raw Material and French Fries

Weather conditions in the years of this study had a significant impact on the content of starch, dry matter, and sugars in tubers. The year 2015, characterized by a shortage of rainfall, favored the accumulation of starch and dry matter, while the excess rainfall in 2016 led to their lower content. The variability in weather conditions also had an impact on the content of sugars—excess water favored their accumulation, while the deficiency of rainfall limited the synthesis and accumulation of sugars, which emphasizes the importance of hydrological conditions in the growing season (Table 3). Water shortages, which occurred primarily in 2015, but also in 2017, can lead to a decrease in the content of dry matter and starch in potato tubers. Water stress limits the processes of photosynthesis and the transport of photosynthetic products, such as sugars, to tubers, which results in lower starch accumulation [47]. In the opposite conditions, when water availability is high, potatoes can accumulate more dry matter, but excessive moisture can lead to a decrease in starch content in favor of other substances, such as soluble sugars.

High temperatures during plant growth can limit starch accumulation in tubers. Potatoes accumulate starch best at moderate temperatures, and excessive heat can lead to thermal stress, which slows down the metabolic processes responsible for starch synthesis. Too-low temperatures can also negatively affect dry matter accumulation, as potatoes can accumulate more water, which reduces their technological value for processing [42].

Soil resources and fertilization: The content of nutrients in the soil, especially nitrogen, phosphorus, and potassium, directly affects the synthesis and accumulation of dry matter and starch. Excess nitrogen can lead to an increase in plant mass at the expense of tubers, which in turn can reduce starch accumulation. In turn, an appropriate potassium content supports starch synthesis and increases its concentration in tubers.

Weather conditions during the growing season, especially the length and intensity of sunlight, can significantly affect the dry matter and starch content of tubers. A longer sunny period promotes the production of assimilates (photosynthetic products), which are converted into starch. In turn, short periods of sunlight and frequent rains can limit the accumulation of dry matter and starch. The variability in the content of soluble and reducing sugars in potato tubers under the influence of meteorological conditions, proven in our studies, and especially the lack of water availability, can be interpreted in the context of plant physiology and their response to water stress.

Rainfall deficiencies (first and third year of study): Drought stress caused potato plants to direct their energy towards survival, limiting processes such as photosynthesis and sugar accumulation. In such conditions, the plant focuses on protecting water resources, which can lead to lower synthesis and transport of sugars in tubers. Reduced enzymatic activity and limited photosynthetic development may explain the reduced sugar content in years with low humidity.

In the humid year 2016, where there were conditions of high water availability, plants had better conditions for active growth, which stimulated metabolic processes, including the synthesis and accumulation of sugars. Higher sugar contents in tubers in years with high humidity may result from greater photosynthetic activity and better transport of assimilates (photosynthesis products) to tubers, where they are stored as sugars.

Thus, water deficiency limits the synthesis and accumulation of sugars, while excess water in the growing season leads to their excessive accumulation in tubers. This results from the natural response of plants to the availability of resources—in water stress, survival is the priority, while in humid conditions conducive to growth, plants store more sugars in tubers. For the production of French fries, a lower sugar content in dry years may be more beneficial, because it reduces the risk of excessive browning during frying. In humid years, a high sugar content, especially reducing sugar, increases the risk of deterioration in the quality of French fries. This is confirmed by research results [33,34,35].

These findings highlight the importance of monitoring potato growing conditions and the potential need to modify them to obtain the optimum quality of the processed product.

Environmental conditions, such as temperature, precipitation, and soil moisture, have a significant impact on potato tuber quality and, consequently, on the characteristics of processed products such as French fries. In particular, years with lower precipitation and moderate temperatures, such as 2015, are conducive to a better tuber quality, which translates into more favorable sensory properties of French fries. Optimal water and thermal conditions support the accumulation of an appropriate amount of starch and dry matter, which is conducive to obtaining a good texture and flavor in the finished product.

Soil conditions can significantly affect the properties of potato tubers and, consequently, the quality of potato products such as French fries [48]. High soil moisture and low temperatures during potato plant growth can lead to a poorer tuber quality. The year 2015 was the most favorable for most of the analyzed characteristics, which may be related to more favorable meteorological conditions during this period, such as temperature and humidity. The year 2016 was the most unfavorable, which was particularly visible in the higher moisture content of French fries and the greater share of French fries with dark ends.

However, high soil moisture, as in 2016, can lead to a poorer quality of French fries due to the excessive content of reducing sugars and higher moisture content of tubers, which affects the unfavorable Maillard reactions during frying, leading to darkening of the French fries and their sweeter, undesirable taste. Studies by Pedreschi et al. [37] confirm that excessive soil moisture can also lead to the development of diseases, which additionally reduces the quality of tubers and increases the share of French fries with dark ends [49].

The use of ultrasound technology before planting potatoes, as shown in several studies [3,4,5,6], can mitigate some of the negative effects of unfavorable environmental conditions, improving the permeability of the cell membranes of the tubers and increasing their growth potential and the quality of the processed product. Recent studies have shown that the use of innovative agricultural technologies, such as ultrasound, combined with the control of environmental conditions, can be crucial for optimizing potato production in variable climatic conditions [48]. By using precise agrotechnical methods, such as monitoring hydration and temperature [48], it is possible to reduce the risk of excessive accumulation of reducing sugars, which improves the quality of the final product, French fries.

4.5. French Fries Quality and Chemical Composition of Tubers

Analysis of the relationship between the chemical composition of potato tubers and the quality of French fries showed significant correlations between compositional components, such as starch content, total soluble sugars, and reducing sugars, and sensory features, such as color, taste, or texture of French fries. A strong positive correlation between color (x1) and visual assessment (x2) (r = 0.85) suggests that a visually attractive product has a greater chance of being positively assessed by the consumer. Interestingly, a high content of reducing sugars was negatively correlated with the color quality of French fries (r = −0.73) (Table 4, which confirms that a higher concentration of reducing sugars can lead to undesirable browning and, consequently, to a deterioration in sensory quality. In turn, the strong positive correlation between dry matter content and starch (x8) (r = 0.88) indicates that potato varieties with a higher dry matter content are more suitable for the production of French fries, because they can better retain their structure during frying, which improves their texture and taste. This is confirmed by previous studies, which indicate that a higher starch content in tubers leads to lower fat absorption and better product consistency [8,37].

Recent studies confirm and extend established correlations between the chemical composition of potato tubers and the sensory properties of French fries. Reducing sugars such as glucose and fructose were found to play a major role in the Maillard reaction, causing browning of French fries during frying. The study by Zhang et al. [46] emphasizes that higher levels of reducing sugars can induce excessive browning, affecting both the appearance and flavor of French fries. This is consistent with the negative correlation (r = −0.73) between reducing sugars and color mentioned in our study. Furthermore, new studies on starch content and its effect on texture are supported by ongoing studies on how starch and dry matter contribute to oil absorption during frying. According to the 2024 study by Acurio et al. [50], a higher starch content reduces oil absorption and results in a more desirable texture of French fries. Furthermore, the use of advanced frying technologies such as ultrasonic-assisted frying has also shown promising results in improving texture and reducing oil absorption because it improves water removal from French fries while maintaining their structure [51] These findings underscore the importance of selecting potato varieties with optimal starch and simple and reducing sugar contents in order to improve both the nutritional and sensory properties of French fries. Recent studies confirm and expand on the established correlations between the chemical composition of potato tubers and the sensory qualities of French fries. It has been found that reducing sugars, such as glucose and fructose, play a key role in the Maillard reaction, leading to browning during frying. The study by Zhang et al. highlights that higher levels of reducing sugars can indeed cause excessive browning, impacting both the appearance and taste of French fries [46]. This aligns with the negative correlation (r = −0.73) between reducing sugars and color quality mentioned in our research.

4.6. Practical Implications

The use of ultrasound in potato processing has promising practical implications. This technology can be used to improve the quality of French fries, especially in terms of their color, consistency, and overall sensory evaluation. For the processing industry, where the quality of French fries is a key factor, sonication can be an effective method for improving the final product, especially in the case of varieties that respond well to this technology. The results indicate that varieties such as ‘Syrena’, due to the lowest content of reducing sugars, may be the most suitable for producing French fries with a lighter color and better taste, avoiding the Maillard reaction. The ‘Tajfun’ variety, although also with a low level of reducing sugars, may in some cases affect the texture quality of the French fries due to the higher content of soluble sugars. The ‘Zagłoba’ variety, with the highest sugar content, may generate French fries with an undesirable color and taste.

It is important to adapt this technology to the specific potato varieties and the environmental conditions in which they are grown to obtain the best results. Furthermore, it is possible to use ultrasound in other stages of production, which can improve the efficiency of processing and reduce waste.

Therefore, both the variety selection and the climatic conditions play a key role in supporting the quality of potato tubers and their suitability for processing, in particular, for the production of French fries.

4.7. Limitations of Ultrasound Technology

Despite promising results, there are some limitations to ultrasound technology in French fries processing. Not all potato varieties respond equally well to sonication, which means that the technology may require further optimization depending on the specific genetic characteristics of the tubers. Additionally, the costs of implementing sonication on a large scale can be high, which is a significant barrier for smaller producers.

Limitations that may arise when using ultrasound in potato processing for fries include the following:

• Technological limitations:

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  Equipment cost: Ultrasound-generating devices can be expensive to purchase and maintain, which can be an economic barrier, especially for small and medium-sized enterprises.

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  Process scalability: The effectiveness of ultrasound on a small laboratory scale may not be fully translated to an industrial scale. Further research is needed to scale up the technology.

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  Precise parameter settings: The effectiveness of ultrasound depends on the precise selection of parameters such as frequency, intensity, and duration of operation. Incorrect settings can lead to damage to the potato structure or insufficient effects.

• Raw material limitations:

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  Differences in potato varieties: Individual potato varieties differ in starch content, moisture content, or texture, which can impact the effectiveness of ultrasound.

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  Seasonality and raw material quality: Potatoes stored for a long time may have a changed structure (e.g., increased content of reducing sugars), which may affect the interaction with ultrasound.

• Potential product quality issues:

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  Impact on structure and texture: Excessive exposure to ultrasound may lead to the destruction of the cellular structure of potatoes, which may negatively affect the texture of the fries after frying.

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  Sensory changes: Some ultrasound parameters may cause changes in the taste, smell, or color of the fries, which could reduce their acceptance by consumers.

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  Uneven effect: On a large industrial scale, ultrasound may not act evenly on the entire raw material, resulting in variable quality of the final product.

• Health and regulatory constraints:

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  Process safety: Ultrasound technology must be carefully assessed for food safety. Potential changes in chemical structure may require further studies on the impact on consumer health.

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  Regulatory compliance: In some countries, the use of ultrasound in food processing may require additional certifications or compliance with specific regulations.

• Environmental constraints:

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  Energy consumption: Ultrasound-based processes can require significant amounts of electrical energy, which can increase operating costs and the environmental burden.

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  Waste generation: Ultrasound can cause increased cell sap secretion, leading to additional production of liquid waste requiring disposal.

• Need for further research:

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  Lack of sufficient data: Ultrasound technology in potato processing for French fries is new, and therefore there is limited research on its long-term effects and optimal parameters.

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  Unpredictable effects: The introduction of ultrasound can lead to unexpected physicochemical interactions that need to be thoroughly investigated.

Another limitation is that the impact of ultrasound on other aspects of potato processing, such as their nutritional value or shelf life, has not yet been sufficiently studied. This requires further research to ensure that the technology does not negatively affect other important aspects of the final product. In summary, although ultrasound offers potentially innovative solutions for potato processing, further research is needed on its efficiency, cost-effectiveness, and impact on product quality and the environment.

5. Conclusions

The use of ultrasound in potato processing technology before planting significantly improved the quality of French fries: Sonification of potato tubers allowed us to obtain French fries with a lighter color, better consistency, and higher sensory evaluation in terms of taste and smell. Additionally, the reduction in moisture content and the reduction in the share of French fries with dark ends confirm the effectiveness of this technology in improving the quality of the final product.

The effect of the potato variety on the effectiveness of ultrasound: The reaction of potato tubers to the use of ultrasound varied depending on the variety. This variability results from genetic traits, such as the dry matter content, starch, and the sum of sugars and reducing sugars. Optimization of sonification technology should take into account the selection of varieties that best respond to this innovative solution.

The quality of French fries largely depended on the chemical composition of potato tubers: A higher starch and dry matter content favored the production of French fries with a better consistency and a lower share of French fries with dark ends. On the other hand, excess reducing sugars led to undesirable browning and deterioration of sensory quality. Selection of appropriate varieties and control of the chemical composition of potato tubers before processing were crucial for obtaining high-quality products.

Importance of environmental conditions and crop management: Variability in the dry matter and starch content in potatoes resulted from the interaction of environmental conditions (e.g., water availability, temperature) and cultivation techniques. Limited water availability in the soil during vegetation has a beneficial effect in reducing the sugar content, which improves the quality of French fries, while excess water promoted sugar accumulation and deteriorated sensory characteristics.

Application of ultrasound as an innovative solution for changing climate conditions: The technology of potato tuber sonification can be particularly useful in changing climate conditions, where variability in precipitation and temperature affects potato quality. Sonification supported us to obtain high-quality French fries even in years with unfavorable weather conditions, which suggests increased production stability and quality in the processing industry.

Support for sustainable development: Ultrasound technology reduces production losses by improving the quality of French fries and reducing waste. It can be used in the framework of policies supporting innovative and sustainable solutions in agriculture and the food industry. Its implementation on an industrial scale supports production efficiency and responds to the growing demand for high-quality products.

Recommendations for the processing industry: Ultrasound technology before potato planting is recommended for implementation in the commercial production of French fries. Its use not only improves the sensory and technological quality of French fries but also helps to achieve better economic results in food processing.