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New Insights into Drying Technologies in Food Processing
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New Insights into Drying Technologies in Food Processing

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

Deadline for manuscript submissions: closed (20 October 2023) | Viewed by 5047

Special Issue Editors

Prof. Dr. Shaojin Wang

E-Mail Website
Guest Editor
1.College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China
2. Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA
Interests: drying, disinfestation, and pasteurization of foods using RF energy
Special Issues, Collections and Topics in MDPI journals
Dr. Bo Ling

E-Mail Website
Guest Editor
College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling District, Xianyang 712100, China
Interests: food processing using different physical fields, especially for RF energy

Special Issue Information

Dear Colleagues,

Drying, as an effective food preservation method, extends the shelf-life of food and reduces storage, packaging, and transportation costs. However, drying methods used for food dehydration must not only be efficient and economic, but also provide high-quality products based on various quality attributes. Although hot air dryers are most commonly used in the food industry, this conventional technique has serious flaws, such as high energy consumption, long process time, and low efficiency, negatively impacting food quality. Hence, many emerging thermal and combination methods have been effectively studied. This Special Issue aims to focus on recent developments and applications of emerging thermal (radio frequency, microwave, ohmic, infrared, etc.), non-thermal (vacuum, ultrasound, pulsed electric field, etc.), and combination methods in drying food and agricultural products.

This issue will provide major emerging methods, research strategies, and optimized protocols used in developing environmentally friendly drying processes based on different cutting-edge technologies.

Prof. Dr. Shaojin Wang
Dr. Bo Ling
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Foods is an international peer-reviewed open access semimonthly journal published by MDPI.

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

  • microwave heating
  • radio frequency heating
  • ohmic heating
  • infrared heating
  • ultrasound
  • pulsed electric field
  • emerging thermal and non-thermal technologies

Published Papers (4 papers)

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Research

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13 pages, 1964 KiB  
Article
Hot-Air-Assisted Radiofrequency Drying of Olive Pomace and Its Effect on the Quality of Olive Pomace Oil
by Sinem Turan, Aysel Elik Demir, Fahrettin Göğüş and Derya Koçak Yanık
Foods 2023, 12(18), 3515; https://doi.org/10.3390/foods12183515 - 21 Sep 2023
Cited by 1 | Viewed by 882
Abstract
In this study, the drying of olive pomace in a hot-air-assisted radio frequency system (HA–RF) was conducted, and its effects on crude olive pomace oil quality were investigated. In this respect, the effects of radiofrequency electrode distance (90, 105 and 120 mm), sample [...] Read more.
In this study, the drying of olive pomace in a hot-air-assisted radio frequency system (HA–RF) was conducted, and its effects on crude olive pomace oil quality were investigated. In this respect, the effects of radiofrequency electrode distance (90, 105 and 120 mm), sample thickness (2.5, 5, 7.5 and 10 cm) and compaction density (~0.45, ~0.60 and ~0.82 g/cm3) on drying rate have been evaluated. The best drying, with a higher drying efficiency, was obtained with 1 kg of sample weight and a 10 cm product thickness, ~0.45 g/cm3 compaction density and 105 mm electrode distance. Moreover, the results showed that the compaction density significantly affects the drying rate. The drying time was prolonged by approximately four times by increasing the compaction density from ~0.45 to ~0.82 g/cm3. The drying rate of olive pomace in HA–RF drying was compared with drying performed using hot air (HA) and radiofrequency (RF). The results revealed that HA–RF application reduced the drying time by almost 1.7 times compared to hot air drying and by about 2.7 times compared to radiofrequency. The peroxide value, free fatty acid content, p-anisidine value, polyaromatic hydrocarbon content, L*, a*, b*, chlorophyll and total carotenoid content of the oil extracted from the olive pomace dried under the best drying conditions were 1.09%, 12.2 meq O2/kg oil, 3.01, <1 ppb, 38.6, 7.5, 62.56, 105.25 mg pheophytin a/kg oil, 2.85 mg/kg oil, respectively. The drying of olive pomace in a hot-air-assisted radio frequency system could be an alternative way to ensure the safe and rapid drying of olive pomace. Full article
(This article belongs to the Special Issue New Insights into Drying Technologies in Food Processing)
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13 pages, 7106 KiB  
Article
Heat Flux Analysis and Assessment of Drying Kinetics during Lyophilization of Fruits in a Pilot-Scale Freeze Dryer
by Ivan Sedmak, Matic Može, Gorazd Kambič and Iztok Golobič
Foods 2023, 12(18), 3399; https://doi.org/10.3390/foods12183399 - 11 Sep 2023
Viewed by 796
Abstract
Vacuum freeze-drying as a process for achieving high product quality has attracted increasing attention in the last decade. Particularly in the pharmaceutical field and food processing industries, lyophilization can produce high-quality products compared to samples dried by conventional methods. Despite its benefits, lyophilization [...] Read more.
Vacuum freeze-drying as a process for achieving high product quality has attracted increasing attention in the last decade. Particularly in the pharmaceutical field and food processing industries, lyophilization can produce high-quality products compared to samples dried by conventional methods. Despite its benefits, lyophilization is a time-consuming and costly process that requires optimization of a number of process parameters, including shelf temperature, chamber pressure, freezing rate, and process time. This paper reports on the implementation of heat flux measurements that allow noninvasive real-time determination of the endpoint of the primary drying stage as an essential parameter for the effective optimization of the overall drying time. Quantitative analysis of the drying kinetics of five fruits (kiwifruit, avocado, Asian pear, persimmon, and passion fruit) was assessed by comparing the heat flux and temperature profiles of samples during the lyophilization process. For a 24 h lyophilization cycle, average heat fluxes in the primary drying phase ranged from 250 to 570 W/m2. A significant correlation was found between the temperature and heat flux distributions at the estimated endpoint of the sublimation process and the corresponding transition into the secondary drying stage. Furthermore, good agreement was also found for the freezing phase. The use of real-time heat flux measurements proved to be a cost-effective experimental method to better understand the process variables in order to reduce the lyophilization cycle time and overall energy consumption. Full article
(This article belongs to the Special Issue New Insights into Drying Technologies in Food Processing)
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17 pages, 4189 KiB  
Article
Insight into the Effects of Drying Methods on Lanzhou Lily Rehydration
by Xinyu Zhang, Lu Xue, Zijian Wu, Wen Zhang, Han Zhang, Cuiyu Zhao and Dandan Liu
Foods 2023, 12(9), 1817; https://doi.org/10.3390/foods12091817 - 27 Apr 2023
Cited by 1 | Viewed by 1263
Abstract
This study investigated the effects of drying methods (hot air drying (HAD), microwave vacuum drying (MVD), and vacuum freeze drying (VFD)) on the rehydration performance (RP) of dried Lanzhou lily scales (LLS). Rehydration rate and water migration showed that MVD had the best [...] Read more.
This study investigated the effects of drying methods (hot air drying (HAD), microwave vacuum drying (MVD), and vacuum freeze drying (VFD)) on the rehydration performance (RP) of dried Lanzhou lily scales (LLS). Rehydration rate and water migration showed that MVD had the best RP, followed by VFD, while HAD had the worst. The results of additional morphology observation using scanning electron microscopy (SEM) and micro X-ray computed tomography (CT) imaging showed that both MVD and VFD created more channels in more porous structures, which facilitated their better RP than that by HAD. The results also revealed the spatial structure diversity (including pores, channels size, and internal network) of each dried Lanzhou lily scale group. In addition, studies analyzed how drying techniques affected the physiochemical properties of lily starch, including its water solubility, pasting profiles, and starch particle morphology. The findings indicated that when MVD was in operation, partial gelatinization in lily starch was brought about by thermal effects, allowing MVDS crystals to change from B-type to V-type and causing MVDS to have better water absorption ability. Consequently, despite the fact that MVD’s desiccated lilies have a lower porous structure and thinner channels than VFD’s, MVD has a higher RP than VFD. Full article
(This article belongs to the Special Issue New Insights into Drying Technologies in Food Processing)
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Review

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27 pages, 2038 KiB  
Review
Novel Efficient Physical Technologies for Enhancing Freeze Drying of Fruits and Vegetables: A Review
by Jianhua Yao, Wenjuan Chen and Kai Fan
Foods 2023, 12(23), 4321; https://doi.org/10.3390/foods12234321 - 29 Nov 2023
Cited by 2 | Viewed by 1690
Abstract
Drying is the main technical means of fruit and vegetable processing and storage; freeze drying is one of the best dehydration processes for fruit and vegetables, and the quality of the final product obtained is the highest. The process is carried out under [...] Read more.
Drying is the main technical means of fruit and vegetable processing and storage; freeze drying is one of the best dehydration processes for fruit and vegetables, and the quality of the final product obtained is the highest. The process is carried out under vacuum and at low temperatures, which inhibits enzymatic activity and the growth and multiplication of micro-organisms, and better preserves the nutrient content and flavor of the product. Despite its many advantages, freeze drying consumes approximately four to ten times more energy than hot-air drying, and is more costly, so freeze drying can be assisted by means of highly efficient physical fields. This paper reviews the definition, principles and steps of freeze drying, and introduces the application mechanisms of several efficient physical fields such as ultrasonic, microwave, infrared radiation and pulsed electric fields, as well as the application of efficient physical fields in the freeze drying of fruits and vegetables. The application of high efficiency physical fields with freeze drying can improve drying kinetics, increase drying rates and maintain maximum product quality, providing benefits in terms of energy, time and cost. Efficient physical field and freeze drying technologies can be well linked to sustainable deep processing of fruit and vegetables and have a wide range of development prospects. Full article
(This article belongs to the Special Issue New Insights into Drying Technologies in Food Processing)
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