The Evolution of Mechanical Properties and Cellular Structure of Apples During Freeze Drying Combined with Hot Air Drying (FD-HAD) Process

Apples are one of the most popular fruits in the world and have a significant share in domestic and international fruit production. Drying is a common method used to extend the shelf life of apples. However, it also induces irregular morphological changes in apples, which are essential to maintainin...

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Main Authors: Lili Li, Mengmeng Yang, Lewen Zhu, Wenchao Liu, Linlin Li, Weiwei Cao, Junliang Chen, Linlin Zhao, Chung Lim Law, Tongxiang Yang, Guangyue Ren, Xu Duan
Format: Article
Language:English
Published: MDPI AG 2024-12-01
Series:Foods
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Online Access:https://www.mdpi.com/2304-8158/13/23/3951
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author Lili Li
Mengmeng Yang
Lewen Zhu
Wenchao Liu
Linlin Li
Weiwei Cao
Junliang Chen
Linlin Zhao
Chung Lim Law
Tongxiang Yang
Guangyue Ren
Xu Duan
author_facet Lili Li
Mengmeng Yang
Lewen Zhu
Wenchao Liu
Linlin Li
Weiwei Cao
Junliang Chen
Linlin Zhao
Chung Lim Law
Tongxiang Yang
Guangyue Ren
Xu Duan
author_sort Lili Li
collection DOAJ
description Apples are one of the most popular fruits in the world and have a significant share in domestic and international fruit production. Drying is a common method used to extend the shelf life of apples. However, it also induces irregular morphological changes in apples, which are essential to maintaining the structural integrity of the material. Therefore, it is necessary to understand the effect of cellular changes at the microscopic level on the macroscopic deformation of the material during drying. In this paper, the evolution of cell wall pectin fractions and viscoelastic properties of apples during freeze drying combined with hot air drying was investigated. The findings indicated that during the HAD stage, a decrease in the relaxation modulus (<i>E</i><sub>1</sub>) of the samples was observed in the compression tests when the sample temperature was significantly higher than the glass transition temperature (<i>T</i><sub>g</sub>). As the difference between the two decreased, the samples exhibited increased stiffness and higher <i>E</i><sub>1</sub>. The results of the pectin content analysis showed that the HAD process accelerated the loss and degradation of water-soluble pectin in the samples with high moisture content at the transition point. Simultaneously, the esterification degree of chelator-soluble pectin increased, leading to a reduction in the support provided to the cellular structure of the samples, which consequently affected their mechanical properties. These findings may provide valuable information for the application of freeze drying combined with hot air drying in the efficient processing of dried fruit and vegetable products.
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spelling doaj-art-8d7a0de0279a4da9a088d3c9a6e59a212025-08-20T01:55:45ZengMDPI AGFoods2304-81582024-12-011323395110.3390/foods13233951The Evolution of Mechanical Properties and Cellular Structure of Apples During Freeze Drying Combined with Hot Air Drying (FD-HAD) ProcessLili Li0Mengmeng Yang1Lewen Zhu2Wenchao Liu3Linlin Li4Weiwei Cao5Junliang Chen6Linlin Zhao7Chung Lim Law8Tongxiang Yang9Guangyue Ren10Xu Duan11College of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471000, ChinaCollege of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471000, ChinaCollege of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471000, ChinaCollege of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471000, ChinaCollege of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471000, ChinaCollege of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471000, ChinaCollege of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471000, ChinaCollege of Tourism and Culinary Science, Yangzhou University, Yangzhou 225127, ChinaDepartment of Chemical and Environmental Engineering, Malaysia Campus, University of Nottingham, Semenyih 43500, Selangor, MalaysiaCollege of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471000, ChinaCollege of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471000, ChinaCollege of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471000, ChinaApples are one of the most popular fruits in the world and have a significant share in domestic and international fruit production. Drying is a common method used to extend the shelf life of apples. However, it also induces irregular morphological changes in apples, which are essential to maintaining the structural integrity of the material. Therefore, it is necessary to understand the effect of cellular changes at the microscopic level on the macroscopic deformation of the material during drying. In this paper, the evolution of cell wall pectin fractions and viscoelastic properties of apples during freeze drying combined with hot air drying was investigated. The findings indicated that during the HAD stage, a decrease in the relaxation modulus (<i>E</i><sub>1</sub>) of the samples was observed in the compression tests when the sample temperature was significantly higher than the glass transition temperature (<i>T</i><sub>g</sub>). As the difference between the two decreased, the samples exhibited increased stiffness and higher <i>E</i><sub>1</sub>. The results of the pectin content analysis showed that the HAD process accelerated the loss and degradation of water-soluble pectin in the samples with high moisture content at the transition point. Simultaneously, the esterification degree of chelator-soluble pectin increased, leading to a reduction in the support provided to the cellular structure of the samples, which consequently affected their mechanical properties. These findings may provide valuable information for the application of freeze drying combined with hot air drying in the efficient processing of dried fruit and vegetable products.https://www.mdpi.com/2304-8158/13/23/3951freeze dryinghot air dryingglass transition temperatureviscoelastic characteristicspectin contentpectin esterification degree
spellingShingle Lili Li
Mengmeng Yang
Lewen Zhu
Wenchao Liu
Linlin Li
Weiwei Cao
Junliang Chen
Linlin Zhao
Chung Lim Law
Tongxiang Yang
Guangyue Ren
Xu Duan
The Evolution of Mechanical Properties and Cellular Structure of Apples During Freeze Drying Combined with Hot Air Drying (FD-HAD) Process
Foods
freeze drying
hot air drying
glass transition temperature
viscoelastic characteristics
pectin content
pectin esterification degree
title The Evolution of Mechanical Properties and Cellular Structure of Apples During Freeze Drying Combined with Hot Air Drying (FD-HAD) Process
title_full The Evolution of Mechanical Properties and Cellular Structure of Apples During Freeze Drying Combined with Hot Air Drying (FD-HAD) Process
title_fullStr The Evolution of Mechanical Properties and Cellular Structure of Apples During Freeze Drying Combined with Hot Air Drying (FD-HAD) Process
title_full_unstemmed The Evolution of Mechanical Properties and Cellular Structure of Apples During Freeze Drying Combined with Hot Air Drying (FD-HAD) Process
title_short The Evolution of Mechanical Properties and Cellular Structure of Apples During Freeze Drying Combined with Hot Air Drying (FD-HAD) Process
title_sort evolution of mechanical properties and cellular structure of apples during freeze drying combined with hot air drying fd had process
topic freeze drying
hot air drying
glass transition temperature
viscoelastic characteristics
pectin content
pectin esterification degree
url https://www.mdpi.com/2304-8158/13/23/3951
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