Red Potato Pulp and Cherry Pomace for Pasta Enrichment: Health-Promoting Compounds, Physical Properties and Quality

Featured Application

Featured Application: Common by-products of plant origin could be used to fortify pasta with health-promoting compounds.

Abstract

Cherry pomace and red potato pulp were examined as a source of nutritional and health-promoting compounds in pasta products, which could gain popularity among consumers. An attempt was made to obtain such pasta with the help of low-temperature extrusion (50 °C). The purpose of the study was to demonstrate which additive and in what quantity would have a more favorable effect on the nutritional, pro-health and physical quality of pasta. It was found that all pasta samples obtained with cherry pomace had a higher content of fat (10%), ash (3%), fiber (2 times) and polyphenols (22%), together with α tocopherols, than pasta with red potato pulp. Nonetheless, it had a lower water-binding capacity (20%) and higher optimum cooking time. Pasta with cherry pomace was characterized by a good taste and an attractive smell, so this additive should be recommended to obtain products with better nutritional and pro-health value and quality, especially at 30%.

1. Introduction

One of the significant global challenges today is food spoilage. Development goals for the Agenda 2030 cover the sustainability of food consumption and production. It is mentioned to reduce per capita food waste by 50% worldwide and decrease food waste throughout the entire production and distribution process. This problem is largely exacerbated by globalization and lack of access to adequate infrastructure [1]. According to Sagar et al. [1], each year, around 30% of the food that is still edible goes to waste instead of being consumed worldwide, with 1.3 billion tons of food thrown away annually. The vast majority of waste from the food industry comes from fruits and vegetables, which contain large amounts of organic residues. The significant losses occur because the raw material has a very short shelf life and is prone to quality deterioration during transportation and/or exposure in retail settings. According to FAOSTAT, waste associated with fruit and vegetable processing accounted for 22% in 2019. They include solid and liquid materials that typically have no further use. Failure to appropriately process them can lead to increased pollution of the soil, surface water and groundwater [2,3,4,5].

Starch production is a technology that generates large quantities of by-products potentially hazardous to the environment. The isolation of starch from potatoes produces three types of organic waste: potato pulp, potato juice and juice water. The production of every ton of isolated starch leads to 1.36 tons of potato pulp, 0.14 cubic meters of potato juice and 3.66 tons of juice water being generated [6]. Potato pulp is formed after washing out starch from disintegrated cells of potato tubers. Besides starch residues inside intact cells, it contains some minerals (Ca, Cl, Na, P and Mg) and insoluble non-starch compounds, including polyphenols contained in fiber. Potato pulp is virtually free of toxic glycoalkaloids present in raw potatoes: solanine and chaconine (typically only 0.006% of the potato’s fresh weight), because they are water-soluble and thus washed away with water during the processing [6,7].

The sour cherry (Prunus cerasus L.) is a valuable fruit that can be effectively processed into such products as jams, juices, nectars and soft drinks. The annual harvest of sour cherries in Poland is high, leading to the production of large quantities of pomace. Cherry pomace can be a valuable source of anthocyanins; hydroxycinnamic acids; procyanidins; quercetin and kempferol, as well as vitamins; minerals and dietary fiber (pectin, cellulose and hemicellulose) [8,9,10].

Waste from the fruit industry, such as fruit pomace, and from the starch industry, such as potato pulp, contain about 70% water, which promotes the rapid multiplication of microorganisms. Thus, such wastes are microbiologically unstable and can be used as post-production raw materials only after appropriate processing, such as airflow or freeze-drying. Such treatment could be profitable, because by-products of plant origin could be a source of many components, such as proteins, fats, aldehydes, alcohols, pectin, organic acids, vitamins, minerals and dietary fiber [11]. The change of wastes, which can contribute to environmental pollution, into valuable post-production raw materials rich in nutrients and health-promoting components for further processing fits perfectly into the implementation of zero waste technology, meeting 1 of the 17 goals of sustainable development. Fruit pomace, for example, from cherries, as well as red potato pulp, can therefore be used for the production of food products such as bread, muffins, cakes and pasta [8,9,10,11,12,13].

Pasta is among the most popular cereal products in the world that are cheap and very easy to prepare, which is why it has gained great popularity among different age groups. Pasta can be prepared from semolina but also from other types of wheat flour, with some optional ingredients, such as eggs [14,15,16]. Due to the fact that the basic recipe for pasta is very simple, the product is rich in carbohydrates and protein and low in fat but also poor in micronutrients vitamins or dietary fiber if we use refined flour. Therefore, very often, pasta is fortified with raw materials of vegetable origin, such as bran, flax seeds and milled pomace, to increase the nutritional and functional value of the product [13,14,15,16]. This study also aimed to determine the effect of different levels of freeze-dried additives (cherry pomace and red potato pulp) on the nutritional composition of pasta (protein, fat, ash and carbohydrate content); the amount of pro-health substances (dietary fiber of soluble and insoluble fractions, total polyphenols and tocopherols) and the functional and physical properties of these pastas, i.e., water absorbance, as well as texture and color. In addition, the sensory characteristics were determined using e-nose and e-tongue tools. An additional objective of the study was to identify which of the above-mentioned post-production raw materials would most favorably affect the content of nutritional and health-promoting compounds, as well as the functional and physical characteristics of pasta.

2. Materials and Methods

2.1. Materials

The material for the study was pasta (chifferi rigati and elbows, Figure 1) with different percentages (10, 20 and 30%) of freeze-dried red potato pulp or freeze-dried cherry pomace (freeze-drying provides the microbiological stability of the material). The cherry pomace came from HORTINO Zakład Przetwórstwa Owocowo-Warzywnego Leżajsk Sp. z o.o. (Lezajsk, Poland), while red potato pulp was obtained as a waste product after laboratory isolation of red potato starch of the Magenta Love variety (from the Institute of Environmental Protection and Organic Farming in Spisska Bela, Slovakia, collected 2021), according to the methodology of Vischmann et al. [17]. Pulp and pomace samples were frozen (−20 °C, overnight) and lyophilized in a Labconco FreeZone 6 freeze-dryer (USA) at −47 °C under 37 Pa for 24 h. The freeze-dried samples were stored at room temperature and ground using a Labconco 3100 grinder (Perten Instruments, Springfield, IL, USA).

2.2. Pasta Formulation

Pasta with secondary raw materials of plant origin, i.e., cherry pomace and red potato pulp (10, 20 and 30%), were obtained by mixing the ingredients (flour, water, eggs, salt and additive derived from secondary vegetable raw materials,

Table 1. Pasta formulations.

Type of Pasta	Wheat Flour, Type 450 (g)	RPP 1 (g)	CP 1 (g)	Water (g)	Egg Mass (g)	Salt (g)
Control	500	0	0	150	56	5
RPP-10 1	450	50	0	160	56	5
RPP-20	400	100	0	170	56	5
RPP-30	350	150	0	210	56	5
CP-10 1	450	0	50	160	56	5
CP-20	400	0	100	170	56	5
CP-30	350	0	150	210	56	5

¹ Enrichment with by-products: RPP—red potato pulp; CP—cherry pomace and 10, 20 and 30—a share of a by-product in formulation.

) in a laboratory spiral mixer SP 12 (Diosna, Osnabrück, Germany) for 15 min at low speed. The pasta was made using a Gina low pressure extruder (Ostoni, Cormano, Italy), with a screw length of 30 cm and a diameter of 5.5 cm, and the forming nozzle had a diameter of 1.7 mm. The pressure during extrusion was about 3.4 × 10⁵ Pa, and the temperature was 50 °C. The pasta that was expelled from the extruder was then subjected to a drying process as a single layer for 30 h at 40 °C at a moisture content of up to 12.5% in a chamber air flow dryer.

The prepared pasta (approx. 110 g) was cooked in 1000 mL of distilled water for, at most, 8 min. After cooling, the sample was frozen (−20 °C) and then lyophilized for 24 h in a Labconco FreeZone 6 freeze-dryer at −47 °C under 37 Pa. The pasta that had undergone freeze-drying was kept at ambient temperature and ground using a Labconco 3100 grinder prior to the analyses.

2.3. Methods

The following compounds and parameters were determined in the samples (freeze-dried red potato pulp, cherry pomace and pasta with the above ingredients).

2.3.1. Chemical Composition

The Kjeldahl method (AOAC method No. 920.87) using the Kjeltec 2200 extraction unit (Foss, Hillerød, Denmark) was used for protein determination (N × 5.7), fat was evaluated according to the Soxhlet method (AOAC method No. 953.38) using Soxtec Avanti 2055 (Foss, Denmark) and the ash content according to the AOAC (2006) method [18]. Available carbohydrates were calculated by difference: 100—fat—protein—ash—water—dietary fiber. The contents of the total dietary fiber (TDF) and its soluble (SDF) and insoluble (IDF) fractions were determined using method 32-07 AACCI. TDF was calculated as the sum of the soluble and insoluble fractions. The aforementioned determinations were made in at least 2 replicates.

2.3.2. Content of Polyphenols

The ethanol extracts used for antioxidant evaluation were prepared by dissolving 0.6 g of the sample in 30 mL of 80 g/100 g ethanol, shaking it in the dark for 120 min (electric shaker: type WB22, Memmert, Schwabach, Germany) and centrifuging (15 min, 4500 rpm. 1050× g) in a centrifuge (type MPW-350, MPW MED. Instruments, Warsaw, Poland). The supernatant for further analyses was stored at −20 °C. The total polyphenol content (TPC) was measured using Folin–Ciocalteu reagent (F–C reagent), in accordance with the spectrophotometric method of Singleton et al. [19]. Then, 5 mL of the extract was diluted to a volume of 50 mL with distilled water, and 5 mL of it was combined with 0.25 mL of F–C reagent (combined 1:1 v/v with distilled water) and 0.5 mL of 7% Na₂CO₃. The contents were vortexed (WF2, Janke & Kunkel, Staufen, Germany) and stored for 30 min in a dark place. The absorbance at the wavelength λ = 760 nm was measured using a Helios Gamma 100–240 (Thermo Fisher Scientific, Runcorn, UK). The results were expressed in mg catechin/g DM.

2.3.3. Texture Analysis

The maximum cutting force and energy (as the integral of the force vs. distance curve) for freshly cooked pasta were determined using the TAXT2 plus texture analyzer (Stable Micro Systems, Godalming, UK) using a HDP/BS flat knife for cutting the sample (throughout the whole diameter, the distance was set to 22 mm, while the samples were less than 20 mm) at a speed of 3 mm/s (registering 200 points per second). Data collection was conducted using Exponent v.4.0.13.0 software. The measurements were performed in seven repeated trials, disregarding two outlier results.

2.3.4. Water Absorption of Pasta

The water absorption of the pasta was measured following the earlier established methodology [20]. In summary, 10 g of dry pasta was cooked in 500 mL of water (optimum cooking time 7–8.5 min at boiling water), then drained and reweighed. This process was repeated three times. The water absorption (WA) of the pasta was calculated using the provided formula: (a − b)/a, where a—mass of pasta before cooking; b—mass of pasta after cooking.

2.3.5. Optimum Cooking Time (OCT)

According to the method of Bouacida et al. [21], the optimum cooking time can be determined by observing the point at which the inner core of the pasta vanishes after using a razor blade to make a crosscut or by compressing the pasta between two glass slides for 30-s intervals.

2.3.6. Analysis of Volatile Compounds Using an Electronic Nose

Analysis of volatile compounds in the pasta samples was carried out using the HERACLES II electronic nose (Alpha MOS, Toulouse, France) according to the procedure described by Kowalski et al. [22].

2.3.7. Taste Analysis Using an Electronic Tongue

Instrumental taste analysis of the pasta samples was performed using an Alpha MOS ASTREE II electronic tongue (Alpha MOS., Toulouse, France) with seven liquid sensors according to Kowalski et al. [22].

2.3.8. Color Analysis

Past color was evaluated using the CM-3500d spectrophotometer (Konica Minolta Inc., Tokyo, Japan) with reference to illuminant D₆₅ and a visual angle of 10°. The results collected in five replicates for each sample were expressed using the CIE (L*a*b*) system [23], with the coordinates L* (lightness, 0—black and 100—white), a* redness (+) and greenness (−) and b* yellowness (+) and blueness (−). Color differences (ΔE*) between samples, according to the CIE formula, were calculated as follows:

ΔE* = [(ΔL*)² + (Δa*)² + (Δb*)²]^½

as the distance between two points in a three-dimensional color space.

It is assumed that a standard observer notices the color difference as follows:

0 < ΔE < 1—no difference,

1 < ΔE < 2—the difference could be noticed only by an experienced observer,

2 < ΔE < 3.5—the difference could be noticed by inexperienced observer,

3.5 < ΔE < 5—clear color difference,

5 < ΔE—two different colors.

2.3.9. Determination of Tocopherols by Gas Chromatography [24]

Preparation of Samples for Analysis

A sample of 1 g was weighed to the nearest 0.0001 g into a 100 mL Erlenmeyer flask; then, 20 mL of freshly prepared saponification reagent consisting of 18 mL of 2 M KOH solution in methanol and 2 mL of 10% ascorbic acid was added. The flask was tightly closed and incubated for 40 min at 85 °C, then cooled to room temperature. After cooling, the contents of the flask were shaken and mixed with 10 mL of hexane, followed by 10 mL of saturated NaCl solution. The upper hexane top layer was placed in 20 mL vials and evaporated in a stream of nitrogen, and 2 mL of hexane was added to the dried samples and mixed in an ultrasonic bath for 10 s. If necessary, the samples were filtered through a syringe nylon filter with a pore size of 0.2–0.45 µm. The samples were analyzed by GC-FID.

GC-FID chromatographic analysis conditions:

• Column: SH-5MS Shimadzu capillary column (30 m × 0.25 mm × 0.25 μm).
• Temperature program: column operating temperature: initial 285 °C for 5 min, then an increase in temperature at a rate of 5 °C/min to 290 °C and holding at this temperature for 19 min. Time of the whole analysis is 25 min.
• Dispenser temperature: 280 °C
• Carrier gas: helium, flow rate 0.92 mL/min
• Split: 1:10

FID detector parameters:

• detector temperature: 310 °C
• hydrogen: 40 mL/min
• air: 400 mL/min
• make-up: 30 mL/min

Injection volume: 1 µL.

2.3.10. Statistical Analysis

One-way analysis of variance and Duncan’s post hoc test at the 0.05 level of significance were used to determine the significance of differences. Calculations were performed using Statistica 11.0 software (StatSoft Inc., Tulsa, OK, USA).

3. Results and Discussion

3.1. Characteristics of Freeze-Dried Red Potato Pulp and Cherry Pomace

Comparing the content of protein, fat, ash and dietary fiber in freeze-dried red potato pulp and freeze-dried cherry pomace, it was observed that the amount of protein was 32% lower in freeze-dried cherry pomace than in freeze-dried red potato pulp, while the fat content of the pulp was 38% lower than the cherry pomace (

Table 2. Chemical composition (g/100 g DM) of the applied secondary raw materials of plant origin.

Compounds		Red Potato Pulp	Cherry Pomace
		Chemical composition
Protein		11.32 ± 0.03 b 1	7.75 ± 0.02 a
Fat		0.55 ± 0.01 a	0.89 ± 0.03 b
Ash		4.78 ± 0.01 b	1.66 ± 0.01 a
Dietary fiber		5.48 ± 0.08 a	24.89 ± 0.12 b
of which:	soluble	3.62 ± 0.03 a	15.36 ± 0.02 b
	insoluble	1.86 ± 0.05 a	9.53 ± 0.1 b
Carbohydrates		76.00 ± 0.98 b	64.07 ± 0.1 a
		Bioactive compounds
Polyphenols 2		1394 ± 108 a	1636 ± 115 b
α-tocopherol 3		0.17 ± 0.02 a	0.28± 0.01 b
β-tocopherol 3		0.32 ± −0.01 b	0.17 ± 0.03 a
γ-tocopherol 3		1.20 ± 0.01 b	0.37 ± 0.01 a
δ-tocopherol 3		1.09 ± 0.01 a	1.31 ± 0.04 b

¹ Different letters in rows indicate significant differences between individual samples (p ≤ 0.05); data are presented as a mean ± SD; ² in mg catechin equivalent/100 g of DM; ³ in mg /100 g of DM.

). In the case of ash, freeze-dried red potato pulp was characterized by a three times higher mineral content compared to the cherry pomace (Table 2). The opposite trend was observed for dietary fiber, as a higher content of its insoluble fraction, soluble fraction and total dietary fiber was observed in freeze-dried cherry pomace compared to freeze-dried red potato pulp by four times, five times and five times, respectively. Taking into account the content of polyphenols and available carbohydrates, it should be noted that the content of polyphenols in freeze-dried cherry pomace was 17% higher compared to freeze-dried red potato pulp (Table 2). As for available carbohydrates, a higher content of 18% was determined in freeze-dried red potato pulp than in freeze-dried cherry pomace (Table 2), which is a natural consequence of the fact that potato pulp contains bound starch, which constitutes about 30% of its dry weight and, therefore, is a richer source of digestible carbohydrates. The α-tocopherol content was twice as high in red potato pulp (RPP) compared to cherry pomace (CP) in contrast to β-tocopherol. The γ-tocopherol content was three times higher in the RPP than in the CP, and the amount of δ-tocopherol was about 20% higher in CP than in RPP (Table 2).

3.2. Effect of Freeze-Dried Red Potato Pulp and Cherry Pomace on the Nutritional Value and Health-Promoting Content of Wheat Pasta

The control wheat pasta contained 13.81% protein. The effect of introducing freeze-dried red potato pulp into wheat pasta was to increase the protein content by 0.7% relative to the control, when 30% Magenta Love pulp was introduced. The pasta with 10 and 20% Magenta Love pulp had identical protein contents compared to the control (

Table 3. Chemical composition (g/100 g) of pasta samples.

	Protein	Fat	Ash	Carbohydrates
Control	13.81± 0.04 d 1	2.76 ± 0.03 c	0.87 ± 0.01 a	67.99 ± 0.43 g
RPP-10	13.83 ± 0.04 d	2.48 ± 0.04 b	0.88 ± 0.01 a	67.48 ± 0.01 f
RPP-20	13.88 ± 0.04 d	2.43 ± 0.01 a	1.12 ± 0.03 c	66.32 ± 0.01 e
RPP-30	13.91 ± 0.03 e	2.40 ± 0.02 a	1.27 ± 0.01 d	65.80 ± 0.23 d
CP-10	13.67 ± 0.03 c	2.70 ± 0.02 c	1.02 ± 0.01 b	64.83 ± 1.07 c
CP-20	13.45 ± 0.1 b	2.64 ± 0.12 c	1.09 ± 0.01 c	63.12 ± 0.08 b
CP-30	13.38 ± 0.03 a	2.72 ± 0.07 c	1.08 ± 0.01 c	60.01 ± 1.32 a

¹ Different letters in columns indicate significant differences between individual samples (p ≤ 0.05); data are presented as the mean ± SD.

). In the case of freeze-dried cherry pomace, there was a marked decrease in the protein content (by 2.3% on average) in relation to the control pasta. It can be noted that this reduction in the protein content is due to a partial replacement of wheat flour, which is a rich source of protein (9.3%), with freeze-dried pomace, which had lower level of this nutrient (7.75%). Additionally, an observed decrease may be caused by the cooking process, which could wash out part of the protein [25]. In contrast, the stable protein content of pasta with freeze-dried red potato pulp is most likely due to the fact that the freeze-dried potato pulp itself has a fairly high protein content of 11.32% (Table 3). Such a high protein content of 13% and above is, according to many authors, an indicator of good quality pasta [26,27,28]. Oak et al. [29] reported that the high protein content of pasta has the following effects: reducing the susceptibility to overcooking, reducing dry matter loss during cooking, improving firmness and reducing the stickiness of the surface of the products after cooking. It should also be noted that the introduction of freeze-dried potato pulp into pasta increases the nutritional value of the final products, because potato protein has a high biological and nutritional value because it contains all the essential amino acids (such as lysine, lecithin, phenylalanine and tyrosine). The biological value of potato protein is comparable to that of chicken egg protein (chemical score (CS) is in the range of 57–69%) [30] and other animal proteins and is significantly higher than the biological value of pea, wheat and rice proteins. In addition, potato protein is the richest lysine source in the plant world [31].

In the case of lipids, it was observed that the highest fat content was in the control sample (2.76%), and as the proportion of freeze-dried red potato pulp increased, the amount of this component decreased in the range of 3 to 13% compared to the control (Table 3). The pasta with 20 and 30% of freeze-dried potato pulp contained the least fat (Table 3). The main source of fat in the produced pasta was egg yolk, the content of which was the same in each type of pasta. The addition of eggs not only enriches the nutritional value of the obtained pasta but also improves the cooking properties and sensory evaluation. Potato pulp contains less fat (0.55%, Table 2) than wheat flour (about 1.2%), which is being replaced by it. It is likely that the gluten present in wheat flour bound the fat from the egg mass better than the pulp (it increased the amount of bound fat in favor of free fat), so it may have been partially washed out during the cooking process [26]. When freeze-dried cherry pomace was used in the wheat pasta recipe, the fat content was identical to that of the control, regardless of the level of freeze-dried pomace addition used (Table 3). Based on information from a number of sources, the extent to which fat is bound depends on the characteristics of the raw material (two types of raw materials were introduced: potato pulp and cherry pomace) and the process parameters used during production [32]; hence, a decrease or stabilization of the amount of fat in the final product may result (Table 3).

Taking into account the minerals, it was observed that the lowest content of ash was recorded in the control sample (0.87%), and as the proportion of freeze-dried red potato pulp in the pasta increased, the amount of this component increased in the range from 26% to 45% compared to the control. Pasta with the highest proportion of freeze-dried red potato pulp contained the highest amount of ash. Cherry pomace contributed to an increase in ash by 23% in pasta, with its addition compared to the control (Table 3). It should be emphasized that the increase in the amount of ash in pasta supplemented with the above-mentioned additives was due to the large amount of ash in these additives (in relation to wheat flour—0.7% ash), because the amount of ash in freeze-dried red potato pulp was three times greater than in cherry pomace, hence such a large increase in this component in pasta with the share of pulp in relation to the control and pasta with the share of cherry pomace (Table 2 and Table 3).

In the case of available carbohydrates, their content was highest in the control pasta and then decreased due to the replacement of flour, which is rich in carbohydrates (about 74%), with freeze-dried potato pulp or cherry pomace, which had a much lower content of carbohydrates but a high content of fiber and polyphenols (Table 2 and Table 3).

The polyphenol content increased after both the introduction and freeze-dried red potato pulp, as well as freeze-dried cherry pomace in the pasta, compared to the control. A higher content of polyphenols was recorded in pasta with cherry pomace compared to pasta with freeze-dried red potato pulp (

Table 4. Dietary fiber fractions (g/100 g DM) and polyphenols (mg catechin equivalent/100 g of DM) in pasta samples.

		Dietary Fiber		Polyphenols
	Soluble	Insoluble	Total
Control	1.72 ± 0.03 a 1	0.84 ± 0.06 a	2.56 ± 0.03 a	57 ± 14 a
RPP-10	2.21 ± 0.02 b	1.12 ± 0.01 b	3.33 ± 0.01 b	104 ± 1 b
RPP-20	2.75 ± 0.04 c	1.51 ± 0.04 c	4.26 ± 0.08 c	152 ± 6 c
RPP-30	2.95 ± 0.04 d	1.67 ± 0.02 d	4.62 ± 0.02 d	234 ± 2 e
CP-10	3.69 ± 0.02 e	2.09 ± 0.01 e	5.78 ± 0.01 e	146 ± 1 c
CP-20	4.29 ±0.04 f	2.81 ± 0.08 f	7.70 ± 0.04 f	178 ± 5 d
CP-30	6.84 ± 0.04 g	3.97 ± 0.04 g	10.82 ± 0.07 g	275 ± 0.03 f

¹ Different letters in columns indicate significant differences between individual samples (p ≤ 0.05); data are presented as the mean ± SD.

), which is a consequence of the significantly higher polyphenol content of freeze-dried cherry pomace than freeze-dried red potato pulp (Table 2). After the enrichment of pasta with orange by-product fiber, Crizel et al. [33] observed an increase in the polyphenol content in the range of 23 to 43% in comparison to the control, while, in the study of Baigts-Allende et al. [34], concerning the use of Hibiscus sabdarifa by-product in pasta, the observed increase in polyphenols was more than tenfold.

Pasta containing both freeze-dried potato pulp and freeze-dried cherry pomace had significantly higher contents of soluble and insoluble fiber fractions and total dietary fiber relative to the control (Table 4). For the insoluble fiber fraction, samples with freeze-dried red potato pulp showed a higher content of this fraction ranging from 28% to 71% compared to the control. In the case of freeze-dried cherry pomace incorporated into pasta, the increase in this fiber fraction was two to four times that of the control (Table 4). Freeze-dried potato pulp contributed to an increase in the soluble fraction from 33 to 98% in relation to the control. For fruit pomace, the increase in the soluble fiber fraction was two to four and a half times in comparison to the control (Table 4). Similarly, a greater increase in the total dietary fiber was observed in pasta with cherry pomace two to four times greater than in pasta with freeze-dried red potato pulp (an increase of 30 to 80%) relative to the control (Table 4). This is most likely due to the content of fiber fractions in the cherry pomace itself, which is four times higher (insoluble fraction) or five times higher (soluble fraction and total fiber) relative to the corresponding fiber fractions in freeze-dried red potato pulp (Table 2). Such a large increase in fiber content, especially in the case of cherry pomace, will affect the nutritional value of this type of pasta, because dietary fiber has anticancerogenic, hypoglycemic and hypercholesteremic properties. At the same time, it was found that the increase in fiber fractions, as well as total fiber, was proportional to the amount of added pomace and potato, and the largest increase was observed at the 30% addition level of the above-mentioned components in pasta.

In the research of Aijla et al. (2010) [35] concerning the influence of powdered mango skin on the contents of dietary fiber fractions and increase in their level was between 24% and 57% (soluble fraction), 87% and 144% (insoluble fraction) and 61% and 107% (total fiber) in pasta containing the above-mentioned additive in comparison to the control. According to Aranibar et al. [36], in which pasta was enriched with chia seeds (2.5% to 10% addition level), an increasing tendency in the total dietary fiber (from 58% to 217%) could also be observed. Also, Bchir et al. [37] noticed that date, apple and pear by-products as functional ingredients of pasta lead to a rise in the fiber level parallel to the level of their addition (2.5–10%); the observed effects ranged between 30 and 325% in comparison to the control pasta. The pastas enriched with tomato by-products were characterized by an elevated level of the soluble fiber fraction (22 to 43%) and insoluble one (35 to 59%), corresponding to the 31 to 54% change in total fiber in comparison to the control [38]. Crizel et al. [33] showed that the enrichment of pasta with orange by-product fiber could result in an augmentation of the soluble dietary fiber level between 19 and 43%, while the respective change in the insoluble fraction could even be threefold, which corresponds to the increase in total fiber up to two times in comparison to the control.

The increase in total dietary fiber reported by Baigts-Allende et al. [34] after using Hibiscus sabdarifa by-product (10–20%) to enhance the nutritional quality of pasta was even ninefold in the case of the soluble fraction, while the levels of total and insoluble fiber were approximately double those found for the control when 20% of addition was applied in the pasta formulation.

In the study of Kultys and Moczkowska-Wyrwisz [14] on the effect of using carrot pomace and beetroot-apple pomace on dietary fiber in pasta, the highest applied of the additives (30%) resulted in the largest increase of soluble, insoluble and total fibers (3.5-fold, 2.5-fold and 3-fold, respectively) in comparison to the control. All the above-mentioned authors [14,33,34,35,36,37,38] showed that the content of the soluble and insoluble fiber fractions, as well as total dietary fiber, increased successively with the increase in the level of the applied addition, which was also noted in this work (Table 4).

Similar patterns could be found referring to the nutrient content of pasta enriched with various by-products. Fares and Menga [23] observed the successive increase in the protein content of pasta after adding chickpea flour (in the range between 5 and 19%). The change was explained by the high level of protein in chickpea (23.40 g/100 g DM) in the raw material. Similar results were reported by Bashir et al. [39], who enriched pasta by chickpea flour and defatted soy flour. The changes observed by the authors were not only concerning protein (up to 51% increase) but also fat (64%) and ash (42%). At the same time, the authors reported a 12% decrease in the carbohydrate content in comparison to the control. The inclusion of oat flakes and spirulina in the pasta formulation also caused the increase in the contents of protein (21%), fat (89%) and ash (160%), with a decrease in carbohydrates, compared to the control [40].

In the study of Bchir et al. [37] concerning the use of apple, date and pear by-products as functional ingredients in pasta, it was observed that the protein content was not changed in comparison to the control, but the fat content increased in the range between 3 and 16% and the ash content in the range from 45 to 90% in comparison to the control. In the research of Padalino et al. [38], pasta was enriched with tomato by-products, which resulted in a drop in the protein content by 30% in comparison to the control, similar to the observations of Crizel et al. [33], who found a 7% drop in the protein content after enriching pasta with orange by-product fiber. In the latter study, a significant increase in the fat content was also observed in the range from 42 to 71% and a parallel elevation of the ash content from 3 to 18% as compared to the control. Baigts-Allende et al. [34], who used Hibiscus sabdarifa by-product (10–20%) for pasta enrichment, reported a 10% drop in the protein content and an increase in the ash level between 61 and 95%, accompanied by a rising fat content (by 6% on average), in comparison to the control pasta. Aranibar et al. [36], who supplemented pasta with chia seeds (2.5% to 10%), observed an increase in the protein content (in the range between 2% and 15%) and ash (in the range between 3% and 14%) in comparison to the control, which was also parallel to the level of supplementation.

3.3. Effect of Freeze-Dried Red Potato Pulp and Cherry Pomace on the Cooking and Physical Characteristics of Wheat Pasta

An important factor in determining the pasta quality is the cooking performance. It should be characterized by retention of its form after cooking, durability and expandability of the product at the least possible weight loss. Pasta that possesses favorable qualities should exhibit a high ability to absorb water and the appropriate texture [15]. The hydrothermal treatment of pasta brings out its culinary traits, which are primarily influenced by the pasta recipe and processing techniques employed. Taking into account the fact that the addition of new ingredients that enrich the basic pasta formulation can cause some disruption in the microstructure of the starch–gluten network and, therefore, can lead to modifications in the sensory and culinary properties of the finished product [14,26], it is necessary to study the effect of freeze-dried red potato pulp and cherry pomace on the culinary characteristics of wheat pasta.

Analyzing the water absorption of the pasta, it should be noted that the control was characterized by the lowest value of this parameter, and the introduction of freeze-dried red potato pulp and cherry pomace increased this parameter (

Table 5. Technological parameters of the pasta samples.

	Water Absorption	Optimum Cooking Time	Shear Force [N]	Shear Work [J]
Control	109.52 ± 1.2 a 1	8.5 ± 0	2.74 ± 0.62 b	3.33 ± 0.70
RPP-10	130.97 ± 2.31 d	8.0 ± 0	2.37 ± 0.83 a	4.12 ± 0.84
RPP-20	156.36 ± 1.08 e	8.0 ± 0	1.95 ± 0.34 a	3.29 ±1.04
RPP-30	158.27 ± 0 f	7.5 ± 0	1.98 ± 0.30 a	3.18 ± 0.57
CP-10	118.18 ± 2.13 b	7.5 ± 0	2.47 ± 0.38 ab	3.78 ± 0.80
CP-20	124.53 ± 1.56 c	7.0 ± 0	2.82 ± 0.42 b	4.39 ± 1.22
CP-30	127.26 ± 1.28 d	7.0 ± 0	2.76 ± 0.60 b	4.34 ± 1.33

¹ Different letters in columns indicate significant differences between individual samples (p ≤ 0.05); data are presented as the mean ± SD.

). The effect of enriching the pasta with freeze-dried red potato pulp was an increase in water absorption ranging from 19 to 45%, while, in the case of cherry pomace, it ranged from 8 to 16% relative to the control. Many authors have indicated that dietary fiber derived from vegetables contains many hydrophilic groups that can form bonds with water molecules [15]. In addition, the proportion of the dietary fiber fraction in the added ingredient can have an important impact, as such raw material contains a significant amount of the soluble fiber fraction, which contributes to the faster and better binding of water in the product than the insoluble fiber [41]. Water absorption is influenced not only by the content of fiber and its fractions but also by the amount of starch and pectin, which, among other things, have hydrophilic properties [42]. The factors are also the starch internal structure, number and location of hydroxyl groups in pectin, their methylation degree, interactions between polymers and the presence of polyphenols. All of these factors affect the interactions between the product’s components and water and ultimately determine the water absorption [43]. The results of the study presented in this work clearly confirm such relations. Although freeze-dried cherry pomace contains a higher amount of dietary fiber and both its fractions compared to freeze-dried potato pulp, as well as the pasta obtained with its participation, contain significantly more fiber and its soluble and insoluble fractions compared to pasta with potato pulp, the water absorption of such pasta is lower. It should be noted that the structure of the fiber is very important, because the higher content of pectin in the finished products affects their increased water absorption. This indicates that the methylation degree of pectins could be decisive for the results, as its high values result in more hydrophobic properties of pectins, which strongly affects the water-binding properties [43]. Additionally, according to Sivam et al. [44], polyphenols (Table 2), which are abundant in cherry pomace, could form hydrogen bonds with protein, starch and polysaccharides, changing the interactions between those constituents and water and, thus, modifying water absorption. This may be the reason for the lower water absorption of pasta with cherry pomace than pasta with potato pulp (Table 5). Mineral components, which were also introduced with the addition of cherry pomace and, above all, potato pulp (three times higher ash content than in cherry pomace) could also affect the water absorption of finished products [45]. The presence of a significant amount of ash in pasta samples with 10, 20 and 30% potato pulp, which caused an increase in water absorption in these final products in the range of 19 to 45% relative to the control (Table 5), confirms this observation. Xu et al. [46] observed a slight increase in water absorption by the product (4%) compared to the control after the introduction of apple pomace in pasta. In the study of Tolve et al. [47], on the enrichment of pasta with grape pomace, it was shown that the rising level of this additive may result in a decrease of the water absorption of pasta. The study of Kultys and Moczkowska-Wyrwisz [14] clearly showed that the water absorption of pasta depends on the formulation and type of the additive. In the study, the authors used the same level of two additives (10–30%): beet-apple pomace and carrot pomace, claiming an increase in the water absorption of pasta compared to the control when carrot pomace was used but no change when beet-apple pomace was applied.

Based on the results obtained, it can be observed that increasing the proportion of cherry pomace or potato pulp reduces the cooking time of pasta (Table 5). This may be related to an increase in the content of dietary fiber contained in vegetables or fruits. Dietary fiber contains many hydrophilic groups in its structure, so it binds water faster, reducing cooking time [15]. Also, in the study of Bchir et al. [37] on the application of date, apple and pear by-products as functional ingredients in pasta, a decrease in the optimum cooking time was observed in comparison to the control. Padalino et al. [38] reported 1 min shorter optimum cooking time in comparison to the control after including tomato by-product in the pasta formulation; also, in the study of Kultys and Moczkowska-Wyrwisz [14] on the effect of using beetroot-apple pomace and carrot pomace on the physical properties of pasta, a shorter optimum cooking time was caused by the change in the pasta formulation. The above-mentioned authors explained the reduction of the optimum cooking time with the introduction of a dietary supplement by the increase in the content of fiber. The increase in the fiber fractions content of pasta (Table 4) was connected with a decrease in the optimum cooking time (Table 5). Most probably, the fiber interfered with the development of the protein–starch matrix during the mixing of the pasta ingredients and the lamination of the dough. The reason for this may be the competition between those constituents and soluble fiber for the water necessary to transform the protein structure and thus to embed the starch granules in the gluten network [48].

The texture parameters determined for the pasta samples indicate that the maximum shearing force is a more suitable parameter than the total shear work because of a significant dependence of the latter value on the overall shape of the pasta sample. High variations in pasta geometry result in significant values of the standard error and, consequently, a lack of significant differences between shear work for the analyzed samples. On the other hand, the values of the shearing force seem to distinguish the sample with both types of additives, being higher for the pasta with a share of cherry pomace and lower for the samples with the addition of red potato pulp. The reason may be an increased water absorption caused by the addition of cherry pomace, which is much higher in comparison to the control sample. The level of the applied addition was not significant in this case, with the exception of the pasta with 10% addition of cherry pomace exhibiting intermediate values of shearing force.

Color is among the most important visual parameters for the evaluation of product quality and its organoleptic score [49]. It is also the main indicator in the evaluation of the suitability of the product for consumption and its consumer appeal [14]. With the introduction of freeze-dried red potato pulp and cherry pomace to pasta, a decrease in the parameter L* was observed compared to the control (

Table 6. Color parameters of the pasta samples.

	L*	a*	b*	ΔE*
Control	71.58 ± 1.12 f 1	0.51 ± 0 a	17.53 ± 0.5 e	-
RPP-10	48.59 ± 0.5 e	4.95 ± 0.12 b	13.8 ± 0.5 d	23.70 ± 0.56 a
RPP-20	45.53 ± 0.76 cd	5.57 ± 0.17 c	13.32 ± 1.12 d	26.81 ± 0.82 c
RPP-30	41.84 ± 0.13 a	6.16 ± 0 d	13.08 ± 0.53 d	30.85 ± 0.32 d
CP-10	48.46 ± 1.15 e	6.98 ± 0.1 e	7.4 ± 0.47 c	25.94 ± 0.15 b
CP-20	44.87 ± 0.98 c	9.16 ± 0 f	5.73 ± 0.13 a	30.70 ± 0.75 d
CP-30	43.12 ± 0.12 b	10.79 ± 0 g	6.09 ± 0.12 b	31.06 ± 0.17 d

¹ Different letters in columns indicate significant differences between individual samples (p ≤ 0.05); data are presented as the mean ± SD.

). The reason for this trend is that the two types of additives introduced are pink in color and so will affect the brightness of the final product. Also, the formation of Maillard reaction products, for example, during the drying process, could have a significant influence on this parameter. The non-enzymatic browning observed during pasta drying could be caused, among other things, by high temperature. The Maillard reaction is a complex chemical reaction between reducing sugars and amino acids [15]. In the case of the color parameter a*, it was observed that the value of this parameter increased in pasta with freeze-dried red potato pulp, and at the 30% share of this additive, the value of this parameter was 6.16 higher in relation to the control. Also, in the case of pasta with freeze-dried cherry pomace, an increase in the value of a* was observed. In the case of the highest share of freeze-dried cherry pomace, the value of the a* parameter was 10.79 times higher than in the control (Table 6). It should be noticed that a* increased successively in relation to the percentage of both additives used to enrich the pasta, but it was definitely higher when freeze-dried cherry pomace was used. This parameter is created by the group of polyphenols (anthocyanins) present in both additives used to enrich pasta. In addition, it was observed that the value of the b* parameter decreased when both cherry pomace and freeze-dried red potato pulp were added to the pasta, with a greater decrease noted for the cherry pomace (Table 6). Kultys and Moczkowska-Wyrwisz [14] also observed a decrease in L* after enrichment of pasta with carrot and beet-apple pomace compared to the control. Similarly, Crizel et al. [33] and Baigts-Allende et al. [34] reported darkening of the pasta after adding orange by-product fiber and Hibiscus sabdarifa, respectively. According to these authors, this is a natural consequence of the introduction of a color additive to pasta. The indices a* and b* were shaped differently depending on the color of the additive and, in particular, on the presence of polyphenols, carotenoids or other colorants such as chlorophyll in this additive.

Taking into account the overall differences in color (ΔE*) between the two samples, as experienced by a standard observer, it can be concluded that, in the case of pasta with red potato pulp, a large color difference was observed between the pasta samples with increasing proportions of potato pulp. On the other hand, in the case of pasta with cherry pomace, a clear difference could be observed only between pasta with 10% pomace and samples with higher levels of this additive. In the case of pasta with a 20% and 30% share, no difference in the color of these products was observed.

3.4. Effect of Freeze-Dried Red Potato Pulp and Cherry Pomace on the Volatile Compound Profile of Wheat Pasta

Table 7. Contents of the volatile compounds (%) in pasta samples.

Volatile Compound	Control	RPP-10	RPP-20	RPP-30	CP-10	CP-20	CP-30
Aldehydes
2-Methylpropanal	11.97 ± 0.09 g	9.84 ± 0.07 f	8.99 ± 0.05 e	8.14 ± 0.04 c	8.39 ± 0.06 d	6.93 ± 0.07 b	5.53 ± 0.05 a
3-Methylbutanal	nd	2.91 ± 0.02 d	3.25 ± 0.03 e	3.59 ± 0.03 f	1.98 ± 0.04 c	1.82 ± 0.03 b	1.67 ± 0.02 a
Acetaldehyde	27.79 ± 0.16 f	23.40 ± 0.14 e	19.38 ± 0.11 d	15.34 ± 0.12 b	14.83 ± 0.13 a	15.22 ± 0.11 b	15.59 ± 0.09 c
Benzaldehyde	8.73 ± 0.06 f	6.85 ± 0.05 b	7.76 ± 0.07 d	8.67 ± 0.08 f	8.46 ± 0.05 e	7.11 ± 0.04 c	5.81 ± 0.06 a
Hexanal	4.90 ± 0.07 d	1.00 ± 0.04 a	2.74 ± 0.05 b	4.49 ± 0.06 c	4.34 ± 0.06 c	3.49 ± 0.07 c	2.68 ± 0.05 b
Octanal	nd	nd	nd	nd	nd	0.12 ± 0.01 a	0.23 ± 0.02 b
Ketones
2,3-Pentanedione	0.94 ± 0.03 a	4.05 ± 0.09 e	2.89 ± 0.05 d	1.73 ± 0.04 b	2.23 ± 0.03 c	3.96 ± 0.06 e	5.62 ± 0.07 f
3-Heptanone	0.80 ± 0.02 d	3.58 ± 0.05 f	2.22 ± 0.04 e	0.85 ± 0.01 d	0.69 ± 0.02 c	0.61 ± 0.03 b	0.53 ± 0.02 a
Butan-2-one	3.13 ± 0.07 f	2.91 ± 0.05 e	2.85 ± 0.07 d,e	2.79 ± 0.06 d	2.35 ± 0.04 c	2.25 ± 0.05 b	2.15 ± 0.08 a
Pentan-2-one	1.31 ± 0.03 b	2.91 ± 0.04 e	4.70 ± 0.07 f	6.51 ± 0.06 g	1.79 ± 0.05 d	1.46 ± 0.04 c	1.14 ± 0.03 a
Alcohols
1-Octanol	nd	0.53 ± 0.02 c	0.52 ± 0.03 c	0.50 ± 0.02 c	0.48 ± 0.03 c	0.41 ± 0.01 b	0.34 ± 0.02 a
2-Phenylethanol	1.64 ± 0.03 c	6.47 ± 0.08 f	4.20 ± 0.08 e	1.92 ± 0.07 d	1.62 ± 0.04 c	1.25 ± 0.05 b	0.89 ± 0.03 a
Ethanol	6.87 ± 0.08 b	5.77 ± 0.07 a	6.98 ± 0.08 b	8.19 ± 0.09 c	14.95 ± 0.14 d	16.58 ± 0.13 e	18.14 ± 0.11 f
Esters
2-Phenyl ethyl anthranilate	1.97 ± 0.06 f	1.23 ± 0.03 e	1.09 ± 0.05 d	0.95 ± 0.04 c	1.05 ± 0.05 d	0.79 ± 0.04 b	0.55 ± 0.03 a
2-Phenylethyl butanoate	2.96 ± 0.08 e	2.98 ± 0.05 e	2.85 ± 0.04 e	2.73 ± 0.07 d	2.38 ± 0.05 c	1.95 ± 0.06 b	1.55 ± 0.04 a
2-Phenylethyl phenyl acetate	1.21 ± 0.06 d	1.18 ± 0.05 d	0.59 ± 0.04 c	nd	0.38 ± 0.01 a	0.48 ± 0.02 b	0.57 ± 0.03 c
Benzyl phenyl acetate	1.15 ± 0.05 e	nd	0.51 ± 0.02 a	1.03 ± 0.04 d	1.00 ± 0.03 d	0.88 ± 0.06 c	0.77 ± 0.05 b
Butyl acetate	2.40 ± 0.05 b	0.59 ± 0.03 a	2.45 ± 0.08 b	4.32 ± 0.07 c	10.27 ± 0.09 d	14.94 ± 0.14 e	19.42 ± 0.13 f
Ethyl acetate	2.67 ± 0.04 c	4.60 ± 0.05 e	5.81 ± 0.06 f	7.02 ± 0.08 g	2.85 ± 0.06 d	2.44 ± 0.04 b	2.05 ± 0.05 a
Ethyl dodecanoate	0.72 ± 0.03 e	nd	0.23 ± 0.01 a	0.46 ± 0.02 c	0.72 ± 0.02 e	0.54 ± 0.03 d	0.37 ± 0.01 b
Ethyl isobutyrate	nd	nd	nd	nd	0.41 ± 0.02 a	1.28 ± 0.05 b	2.11 ± 0.04 c
Ethyl tetradecanoate	1.90 ± 0.06 g	1.41 ± 0.02 f	1.35 ± 0.04 e	1.29 ± 0.02 d	1.25 ± 0.03 c	1.09 ± 0.02 b	0.95 ± 0.03 a
Lactones
δ-decalactone	2.95 ± 0.03 d	2.85 ± 0.05 c	3.04 ± 0.06 e	3.23 ± 0.07 f	2.94 ± 0.06 d	2.44 ± 0.05 b	1.97 ± 0.03 a
γ-nonalactone	0.55 ± 0.03 c	2.03 ± 0.06 f	1.40 ± 0.07 e	0.77 ± 0.05 d	0.58 ± 0.04 c	0.46 ± 0.03 b	0.34 ± 0.02 a
γ-Butyrolactone	5.29 ± 0.08 d	5.22 ± 0.09 d	5.43 ± 0.10 e	5.64 ± 0.11 f	4.97 ± 0.08 c	4.28 ± 0.09 b	3.62 ± 0.07 a
γ-Methyl-γ-ethylbutyrolactone	1.67 ± 0.05 a	2.85 ± 0.06 f	2.70 ± 0.04 e	2.54 ± 0.07 d	2.55 ± 0.06 d	2.19 ± 0.04 c	1.84 ± 0.06 b
Pyranones
Ethyl maltol	1.02 ± 0.05 e	0.53 ± 0.03 b	0.77 ± 0.04 d	1.01 ± 0.06 e	0.79 ± 0.05 d	0.63 ± 0.05 c	0.47 ± 0.04 a
Maltol	nd	0.64 ± 0.03 c	0.78 ± 0.04 d	0.92 ± 0.03 e	0.52 ± 0.02 b	0.25 ± 0.01 a	nd
Phenols
4-Ethylguaiacol	4.29 ± 0.09 f	2.52 ± 0.07 b	3.37 ± 0.06 d	4.23 ± 0.08 f	3.99 ± 0.07 e	3.17 ± 0.06 c	2.38 ± 0.05 a
Guaiol	1.18 ± 0.03 c	1.15 ± 0.02 c	1.15 ± 0.03 c	1.14 ± 0.02 c	1.26 ± 0.05 d	0.98 ± 0.03 b	0.71 ± 0.01 a

nd—not detected; different letters in rows indicate significant differences between individual samples (p ≤ 0.05); data are presented as the mean ± SD.

and Figure 2 and Figure 3 show the results of the evaluation of aroma compounds in the control and fortified pasta. The predominant fraction of volatile compounds in both the control and enriched pasta was aldehydes, mainly acetaldehyde and 2-methylpropanal. Similarly, other authors have indicated that aldehydes are the predominant fraction of the volatile compounds of pasta [50,51]. However, the content of these compounds decreased progressively in relation to the percentage of both additives used to enrich the pasta, particularly with the use of freeze-dried cherry pomace. Pasta with both freeze-dried potato pulp and freeze-dried cherry pomace had significantly higher contents of alcohols, esters and ketones but lower aldehydes compared to the control. It should be noted that the content of alcohols and esters increased successively in relation to the percentage of both additives used to enrich the pasta but was significantly higher when freeze-dried cherry pomace was used. Similarly, the levels of ketones and lactones increased gradually with the percentage of both additives used to fortify the pasta but were significantly higher when freeze-dried potato pulp was used. However, in the case of pasta enriched with potato pulp, aldehydes (i.e., acetaldehyde, followed by 2-methylpropanal, 3-methylbutanal and benzaldehyde) were still the predominant volatile compounds. Significant amounts of ketones (2,3-kentanedione, 3-heptanone, butan-2-one and pentan-2-one) were also present, followed by 2-phenylethanol and ethanol, ethyl acetate, 4-ethylguaiacol and γ-butyrolactone. The main volatile compounds identified in pasta enriched with freeze-dried cherry pomace were ethanol and butyl acetate. The concentration of these compounds increased with increasing the cherry pomace addition, which may influence the perception of a pleasant, sweet, fruity and slightly spicy taste. In addition, pasta enriched with freeze-dried cherry pomace was characterized by a high content of acetaldehyde, 2-methylpropanal, benzaldehyde, γ-butyrolactone and 4-ethylguaiacol. Most of these compounds are degradation products of the relevant amino acids and sugars [51,52].

3.5. Effect of Freeze-Dried Red Potato Pulp and Cherry Pomace on the Taste of Wheat Pasta

The effect of different freeze-dried additives on the taste of the pasta was analyzed using an electronic tongue equipped with seven sensors (i.e., SRS-sour, STS-salty, UMS-umami, SWS-sweet, BRS-bitter, GPS-metallic and SPS-spicy). It was shown that pasta enriched with both freeze-dried potato pulp and freeze-dried cherry pomace had higher sweet, sour, bitter, salty and umami tastes compared to the control sample (Figure 4A). The intensity of these tastes progressively increased as the percentage of both additives used to fortify the pasta increased. Interestingly, the enriched pastas showed some similarities in their taste profiles. For the sweet taste of the fortified pasta, the highest and lowest scores were observed for the pasta with the highest addition of freeze-dried cherry pomace and the lowest addition of freeze-dried red freeze-dried potato pulp. A similar trend was observed for sour, salty and umami tastes. It is interesting to note that, in the case of bitter taste, its intensity was similar in the pasta with the two additives.

3.6. Effect of Freeze-Dried Red Potato Pulp and Cherry Pomace on the Tocopherol Content of Wheat Pasta

Considering vitamin E, and especially the tocopherol isomers α, β, γ and δ, it can be concluded that, in the case of α tocopherol, a decrease in the value of this isomer was clearly observed regardless of the 10% addition of red potato pulp or cherry pomace to the pasta (

Table 8. Content of tocopherols in pasta enriched in by-products.

	α-Tocopherol (mg/100 g)	β-Tocopherol (mg/100 g)	γ-Tocopherol (mg/100 g)	δ-Tocopherol (mg/100 g)
Control	0.13 ± 0.01 b 1	0.78 ± 0.03 d	0.17 ± 0.01 b	0.32 ± 0.01 c
RPP-10	0.06 ± 0.01 a	0.24 ± 0.03 c	0.30 ± 0.01 c	0.23 ± 0.01 b
RPP-20	0.11 ± 0.01 b	0.13 ± 0.01 b	0.32 ± 0.02 c	0.20 ± 0.01 b
RPP-30	0.12 ± 0.01 b	0.10 ± 0.01 b	0.40 ± 0.01 d	0.23 ± 0.01 b
CP-10	0.08 ± 0.02 a	0.04 ± 0.01 a	0.12 ± 0.01 a	0.47 ± 0.10 d
CP-20	0.21 ± 0.01 c	0.07 ± 0.02 a	0.14 ± ±0.02 a	0.15 ± 0.01 a
CP-30	0.22 ± 0.01 c	0.11 ± 0.01 b	0.18 ± 0.01 ab	0.14 ± 0.01 a

¹ Different letters in columns indicate significant differences between individual samples (p ≤ 0.05); data are presented as the mean ± SD.

). At the remaining addition levels in the case of red potato pulp, there was an identical α-tocopherol content in pasta with red potato pulp and the control, while pasta with 20 and 30% cherry pomace contents had a 60% increase in α tocopherol compared to the control. The amount of β-tocopherol was highest in the control. In contrast, the additions of both red potato pulp and cherry pomace caused a drastic decrease in the β-tocopherol content of the pasta, with a greater decrease observed in the sample with cherry pomace than the one with red potato pomace. The amount of γ-tocopherol was lower in pasta with 10 and 20% cherry pomace compared to the control, while the same amount of this isomer was observed in pasta with 30% cherry pomace compared to the control.

In contrast, the introduction of red potato pulp resulted in an increase in the γ-tocopherol content of about 88% with 10 and 20% addition of this pulp to pasta and about 135% with the 30% share of red potato pulp in pasta compared to the control. The amount of δ-tocopherol in the control oscillated around 0.32. The amount of δ-tocopherol decreased in pasta with the share of red potato pulp by 30% compared to the control. Cherry pomace caused an increase in δ-tocopherol only when the 10% share of the pomace was used for pasta production, reaching 47% relative to the control. The other additives (20 and 30%) unfortunately caused a decrease in δ-tocopherol in the pasta relative to the control.

In summary, cherry pomace contributed to an increase in α-tocopherol but a decrease in γ, δ and β-tocopherol, with the exception of pasta with 10% cherry pomace, in which δ-tocopherol increased in comparison to the control. In the case of red potato pulp, it can be said that it caused a reduction in β- and δ-tocopherol and increased γ-tocopherol relative to the control. The amount of α-tocopherol was almost identical to the control when 20 and 30% shares of red potato pulp were used, while the exception was the 10% share.

4. Conclusions

Both red potato pulp and cherry pomace are sources of nutritional compounds and health-promoting compounds (fiber and polyphenols), with the amount of the latter being greater in cherry pomace than red potato pulp. It was shown that both these waste products, in the form of freeze-dried powders, can be used for the fortification of food products (in this case, pasta). The addition of potato pulp and cherry pomace resulted in a decrease or maintenance of the protein and fat and reduction of carbohydrates in the pasta samples as compared to the control. In contrast, their presence caused an increase in ash, fiber and polyphenols. It was found that the cherry pomace pasta (irrespective of the addition level) had significantly higher fat (approx. 10% on average), ash (3%), fiber (two times) and polyphenols (approx. 22%) than the red potato pulp pasta. Red potato pulp addition resulted in an increase in α and γ-tocopherols, while cherry pomace caused an increase in only α and δ-tocopherols (with a 10% share of pomace in the pasta). The water-binding capacity of pasta with cherry pomace was lower than of pasta with potato pulp (approx. 20%), despite the higher fiber content in the latter samples. The water-binding capacity could therefore be influenced by the amounts of polyphenols and ash and their interactions. It was found that, with the increase in by-products added to the pasta formulation, there is a reduction in the optimum cooking time due to the introduction of dietary fiber with this additive. Additions of by-products reduced the L* color value, while the parameters a* and b* were modified depending on the level of anthocyanins in the analyzed material. Pasta samples with the addition of by-products were characterized by a significantly higher content of alcohols and esters in the case of cherry pomace and ketones in the case of potato pulp but a significantly lower content of aldehydes compared to the control. With an elevated addition of by-products, the amount of these compounds in the pasta samples increased. The sweetness of the pasta was related to the addition of cherry pomace, but sour, salty, umami and bitter taste descriptors were similar in the case of pasta made from both cherry pomace and red potato pulp. Among all the analyzed pasta, the sample with 30% cherry pomace should be recommended as a product with improved nutritional value, quality and, especially, pro-health properties.