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Recent Developments in High-Quality Drying Technology of Vegetables and Fruits...
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Recent Developments in High-Quality Drying Technology of Vegetables and Fruits Products

A special issue of Foods (ISSN 2304-8158). This special issue belongs to the section "Food Engineering and Technology".

Deadline for manuscript submissions: closed (15 December 2022) | Viewed by 15746

Special Issue Editor

Prof. Dr. Karim Allaf

E-Mail Website
Guest Editor
Laboratory of Engineering Science for Environment LaSIE-UMR-CNRS 7356, University of La Rochelle, 17042 La Rochelle, France
Interests: process engineering; process simulation; modeling; optimization; chemical reaction engineering; extraction; environmental pollution
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Recently, food drying operations have undergone significant development to improve product quality (microbiological, nutritional, textural, sensory, functional, etc.), reduce the energy consumption and processing time, and improve the suitability of equipment. The world’s population needs a great hygienic and nutritional improvement of the final product. The dried product often does not reach a level capable of effectively eliminating bacteria, insects, and fungi responsible for producing mycotoxins. The preservation of most nutrients such as vitamins, fatty acids, proteins, micronutrients, and antioxidants is of particular interest for the health of the consumer. However, drying operations lend themselves differently depending on plants (seeds, vegetables, fruits, etc.), biochemical composition, morphological characteristics, food applications, and functional quality. In this Special Issue, the objective is to highlight the different innovative processes, energy consumption considerations, and drying kinetics. It is to engage different modeling methods involving empirical, kinematic, phenomenological, and physical analyses. The Special Issue should also study the scaling up of innovative processes in a beneficial way to allow a wide industrial exploitation of the still underutilized processes.

Prof. Dr. Karim Allaf
Guest Editor

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • solar and sun drying
  • osmosis drying 
  • super-heated steam drying
  • convective drying processes 
  • instant controlled pressure-drop DIC 
  • swell-drying
  • microwave drying
  • ultrasonic drying
  • dehydrofreezing
  • intermittent drying
  • drying by successive intervals
  • infra-red drying
  • empirical analysis and phenomenological and mathematical modeling

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Published Papers (6 papers)

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Research

15 pages, 655 KiB  
Article
Fluidized Bed Drying of Wheatgrass: Effect of Temperature on Drying Kinetics, Proximate Composition, Functional Properties, and Antioxidant Activity
by Ranjika Chakraborty, Piyush Kashyap, Ram Kaduji Gadhave, Navdeep Jindal, Shiv Kumar, Raquel P. F. Guiné, Rahul Mehra and Harish Kumar
Foods 2023, 12(8), 1576; https://doi.org/10.3390/foods12081576 - 7 Apr 2023
Cited by 4 | Viewed by 2274
Abstract
Wheatgrass is a valuable source of nutrients and phytochemicals with therapeutic properties. However, its shorter life span makes it unavailable for use. So, storage-stable products must be developed through processing in order to enhance its availability. Drying is a very important part of [...] Read more.
Wheatgrass is a valuable source of nutrients and phytochemicals with therapeutic properties. However, its shorter life span makes it unavailable for use. So, storage-stable products must be developed through processing in order to enhance its availability. Drying is a very important part of the processing of wheatgrass. Thus, in this study, the effect of fluidized bed drying on the proximate, antioxidant, and functional properties of wheatgrass was investigated. The wheatgrass was dried in a fluidized bed drier at different temperatures (50, 55, 60, 65, 70 °C) using a constant air velocity of 1 m/s. With increasing temperature, the moisture content was reduced at a faster rate, and all drying processes took place during the falling rate period. Eight mathematical models under thin layer drying were fitted into the moisture data and were evaluated. The Page model was the most effective in explaining the drying kinetics of wheatgrass, followed by the Logarithmic model. The R2, chi-square, and root mean squared value for Page model was 0.995465–0.999292, 0.000136–0.0002, and 0.013215–0.015058, respectively. The range of effective moisture diffusivity was 1.23–2.81 × 10−10 m2/s, and the activation energy was 34.53 kJ/mol. There was no significant difference in the proximate composition of was seen at different temperatures. The total phenolic content (117.16 ± 0.41–128.53 ± 0.55 mgGAE/g), antioxidant activity (33.56 ± 0.08–37.48 ± 0.08% (DPPH), and FRAP (1.372 ± 0.001–1.617 ± 0.001 mgAAE/g) increased with the rise in temperature. A significant increase was observed in functional properties, except for the rehydration ratio, which decreased with rising temperature. The current study suggests that fluidized bed drying improves the nutritional retention of wheatgrass with good antioxidant activity and functional properties that can be used to make functional foods. Full article
(This article belongs to the Special Issue Recent Developments in High-Quality Drying Technology of Vegetables and Fruits Products)
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15 pages, 2672 KiB  
Article
Design of a Greenhouse Solar-Assisted Heat Pump Dryer for Kelp (Laminaria japonica): System Performance and Drying Kinetics
by Huanyu Kang, Guochen Zhang, Gang Mu, Cheng Zhao, Haolin Huang, Chengxiang Kang, Xiuchen Li and Qian Zhang
Foods 2022, 11(21), 3509; https://doi.org/10.3390/foods11213509 - 4 Nov 2022
Cited by 8 | Viewed by 2341
Abstract
In order to solve a series of problems with kelp drying including long drying time, high energy consumption, low drying efficiency, and poor quality of dried kelp, this work proposes the design of a novel greenhouse double-evaporator solar-assisted heat pump drying system. Experiments [...] Read more.
In order to solve a series of problems with kelp drying including long drying time, high energy consumption, low drying efficiency, and poor quality of dried kelp, this work proposes the design of a novel greenhouse double-evaporator solar-assisted heat pump drying system. Experiments on kelp solar-assisted heat pump drying (S−HP) and heat pump drying (HP) under the condition of irradiance of 100−700 W/m2 and a temperature of 30, 40, or 50 °C were conducted and their results were compared in terms of system performance, drying kinetics, and quality impact. The drying time was reduced with increasing irradiance or temperature. The coefficient of performance (COP) and specific moisture extraction rate (SMER) of S−HP were 3.590−6.810, and 1.660−3.725 kg/kW·h, respectively, roughly double those of HP when the temperatures are identical. The Deff of S-HP and HP were 5.431 × 10−11~11.316 × 10−11 m2/s, and 1.037 × 10−11~1.432 × 10−11 m2/s, respectively; additionally, solar radiation greatly improves Deff. The Page model almost perfectly described the changes in the moisture ratio of kelp by S−HP and HP with an inaccuracy of less than 5%. When the temperature was 40 °C and the irradiance was above 400 W/m2, the drying time of S−HP was only 3 h, and the dried kelp maintained the green color with a strong flavor and richness in mannitol. Meanwhile, the coefficient of performance was 6.810, the specific moisture extraction rate was 3.725 kg/kWh, and the energy consumption was 45.2%, lower than that of HP. It can be concluded that S−HP is highly efficient and energy-saving for macroalgae drying and can serve as an alternate technique for the drying of other aquatic products. Full article
(This article belongs to the Special Issue Recent Developments in High-Quality Drying Technology of Vegetables and Fruits Products)
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17 pages, 2765 KiB  
Article
Effect of Swell-Drying on Mango (Mangifera indica) Drying Kinetics
by Luis Alberto Casaverde-Pacherrez, Carmen Téllez-Pérez, Colette Besombes, Daniel Marcelo-Aldana, Karim Allaf and Edilberto Vásquez-Díaz
Foods 2022, 11(15), 2220; https://doi.org/10.3390/foods11152220 - 26 Jul 2022
Cited by 3 | Viewed by 2742
Abstract
Swell-Drying operation (SD) was applied on mangoes to evaluate its effect on drying kinetics: starting accessibility (δW), apparent drying coefficient (Dapp), and time to obtain a final moisture content of 20% d.b (tf = 20% d.b). Swell-drying [...] Read more.
Swell-Drying operation (SD) was applied on mangoes to evaluate its effect on drying kinetics: starting accessibility (δW), apparent drying coefficient (Dapp), and time to obtain a final moisture content of 20% d.b (tf = 20% d.b). Swell-drying consisted of (1) submitting fresh mangoes to a first pre-drying stage under Convective Air Drying (CAD) until a moisture content of 37% d.b; (2) applying Instant Controlled Pressure Drop (DIC) treatments on pre-dried mangoes by following a central composite rotatable design (steam pressure: 0.2–0.6 MPa and treatment time: 5 and 55 s); and (3) apply post-drying of mangoes under CAD. In both cases, CAD was performed at 60 °C and airflow of 1 m/s. Results showed that both the treatment time and the steam pressure impacted the Dapp and the δW. By comparing to the control, SD (0.54 MPa and 48 s) increased the Dapp and δW to 12.2 and 2.7 times, respectively. Moreover, SD triggers a significant reduction in post-drying time (tf = 20% d.b), being this of 2.4 h vs. 30.8 h. These results could be linked to the expansion of the internal pores of mangoes generated by the instant autovaporization of residual water triggered by DIC treatment. Full article
(This article belongs to the Special Issue Recent Developments in High-Quality Drying Technology of Vegetables and Fruits Products)
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21 pages, 3097 KiB  
Article
A Preliminary Study on the Effect of the Instant Controlled Pressure Drop Technology (DIC) on Drying and Rehydration Kinetics of Maize Kernels (Zea mays L.)
by Anaberta Cardador-Martínez, Juan Leopoldo Pech-Almeida, Karim Allaf, Natalia Palacios-Rojas, Maritza Alonzo-Macías and Carmen Téllez-Pérez
Foods 2022, 11(14), 2151; https://doi.org/10.3390/foods11142151 - 20 Jul 2022
Cited by 7 | Viewed by 2090
Abstract
Maize is one of the three worldwide cereal crops with the most outstanding production; however, its postharvest losses range from 2 to 40% due to inadequate harvesting, drying, and storage technologies. This study focuses on the Instant Controlled Pressure Drop technology (DIC) effect [...] Read more.
Maize is one of the three worldwide cereal crops with the most outstanding production; however, its postharvest losses range from 2 to 40% due to inadequate harvesting, drying, and storage technologies. This study focuses on the Instant Controlled Pressure Drop technology (DIC) effect on maize kernels’ drying and rehydration kinetics. In total, 19 different DIC treatments were carried out on maize kernels (~25% d.b.). The DIC parameters studied were steam pressure (0.1 to 0.4 MPa) and treatment time (10 to 90 s). After DIC treatment, drying kinetics were carried out by Convective Air Drying (CAD) at 50 °C and 0.4 ms−1 airflow. Rehydration kinetics and Water Holding Capacity (WHC) were evaluated at 20 °C. In comparison to CAD samples, DIC (0.4 MPa and 90 s) reduced the drying time from 180 min to ~108 min. Additionally, regarding the rehydration and WHC results, DIC achieved the same moisture content in only 3.5 min that controls achieved after 1 h of rehydration (0.40 g H2O/g dry matter). Moreover, DIC (0.4 MPa and nine cycles of 10 s) increased the WHC 2.3 times compared to the control. In this way, DIC could be a postharvest technology to improve maize kernels’ drying operations and functional properties. Full article
(This article belongs to the Special Issue Recent Developments in High-Quality Drying Technology of Vegetables and Fruits Products)
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14 pages, 957 KiB  
Article
Effect of Osmotic Dehydration Pretreatment on the Drying Characteristics and Quality Properties of Semi-Dried (Intermediate) Kumquat (Citrus japonica) Slices by Vacuum Dryer
by Azime Özkan-Karabacak, Gülşah Özcan-Sinir, Ali Eren Çopur and Murat Bayizit
Foods 2022, 11(14), 2139; https://doi.org/10.3390/foods11142139 - 19 Jul 2022
Cited by 16 | Viewed by 2497
Abstract
The effect of osmotic dehydration (OD) pretreatments at different temperatures and immersion times on drying characteristics, total phenolic content (TPC), total antioxidant activity (TAA) (DPPH and CUPRAC methods), and color of kumquat slices dried under vacuum conditions (70 °C-100 mbar) was investigated. The [...] Read more.
The effect of osmotic dehydration (OD) pretreatments at different temperatures and immersion times on drying characteristics, total phenolic content (TPC), total antioxidant activity (TAA) (DPPH and CUPRAC methods), and color of kumquat slices dried under vacuum conditions (70 °C-100 mbar) was investigated. The OD pretreatment was performed in a sucrose solution (45 °Bx) at the temperatures of 40 and 50 °C and immersed at times of 30, 60, and 90 min. OD before vacuum drying decreased the total required drying time by up to 70 min compared to the control non-pretreated samples. Page, Modified Page, Henderson Pabis, and Two Terms Exponential models were found to satisfactorily describe the drying behavior of thin layer dried kumquat slices. The minimum and maximum values of effective moisture diffusivity (Deff) for semi-dried kumquat slices were 5.04 × 10−8 to 7.19 × 10−8, respectively. OD treatments induced a decline in TPC (5.30–33.92%) and TAA (23.63–59.34% and 4.17–31.67% for DPPH and CUPRAC assays, respectively) of kumquat slices. It was observed that OD pre-treatment can decrease the gross drying time, and make the color and sensorial attributes of dried kumquats better. Full article
(This article belongs to the Special Issue Recent Developments in High-Quality Drying Technology of Vegetables and Fruits Products)
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20 pages, 4894 KiB  
Article
Experimental and Numerical Study of a Turbulent Air-Drying Process for an Ellipsoidal Fruit with Volume Changes
by Carlos E. Zambra, Luis Puente-Díaz, Kong Ah-Hen, Carlos Rosales, Diógenes Hernandez and Roberto Lemus-Mondaca
Foods 2022, 11(13), 1880; https://doi.org/10.3390/foods11131880 - 25 Jun 2022
Cited by 3 | Viewed by 2157
Abstract
It is common in the numerical simulations for drying of food to suppose that the food does not experience a change of volume. The few numerical studies that include volume changes assume that the shrinkage occurs symmetrically in all directions. Therefore, this effect [...] Read more.
It is common in the numerical simulations for drying of food to suppose that the food does not experience a change of volume. The few numerical studies that include volume changes assume that the shrinkage occurs symmetrically in all directions. Therefore, this effect has not been fully studied, and it is known that not considering it can be detrimental for the accuracy of these simulations. The present study aims to develop a three-dimensional model for the simulation of fruits that includes the volume changes but also takes into consideration the asymmetry of the shrinkage. Physalis peruviana is taken as the subject of study to conduct experiments and imaging analyses that provided data about the drying kinetics and asymmetric shrinkage mode. The effective diffusion coefficient is found to be between 10−12 m2 s−1 and 1.75 × 10−9 m2 s−1. The shrinkage occurs essentially in only one direction, with an average velocity of 8.3 × 10−5 m/min. A numerical modelling scheme is developed that allows including the shrinkage effect in computer simulations. The performance of the model is evaluated by comparison with experimental data, showing that the proposed model decreases more than 4 times the relative error with respect to simulations that do not include volume changes. The proposed model proves to be a useful method that can contribute to more accurate modeling of drying processes. Full article
(This article belongs to the Special Issue Recent Developments in High-Quality Drying Technology of Vegetables and Fruits Products)
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