ArticlePublisher preview available

Drying of peaches by a combination of convective and microwave methods

February 2023
Journal of Food Process Engineering 46(4)

DOI:10.1111/jfpe.14296

Authors:

Kyriakos Kaderides

Aristotle University of Thessaloniki

Athanasia M. Goula

Aristotle University of Thessaloniki

The aim of this work is to study a method to extend the storage life of peaches reducing energy and time consumption and ensuring food quality. The conventional method of hot air dying presents many drawbacks, whereas the microwave drying usually leads to overheating and textural damage. Thus, in this work, a combination of convective and microwave methods, more specifically a two‐stage drying process with an initial convective air drying followed by a microwave drying (microwave finishing), was studied for the drying of peaches. Peaches dried at 70°C for various times, 200, 278, 355, 433, and 510 min, were then dried in a microwave oven at powers of 300, 500, and 800 W. Drying rates were examined, whereas dry peaches were characterized for their color, antioxidant capacity, shrinkage, and rehydration ability under optimized conditions for the situations with and without pretreatment with ascorbic acid. Mass transfer of water was described by nine empirical models and by the diffusional approach. The shrinkage of peach tissue during microwave finishing was evaluated and diffusion coefficients were assessed with shrinkage considered. The microwave finishing reduced the drying time by 89 ± 40%, while a smaller shrinkage was observed, with better rehydration characteristics. Practical applications Peaches are important commodities in terms of global agricultural production. As peach is a perishable product with a short shelf‐life, the food industry has been forced to find methods, such as drying, that extend its storage life by months. The conventional method of hot air dying presents many disadvantages. Last decades, microwave drying proposed an alternative way to improve the quality of dehydrated products. However, microwave is rarely used alone as a drying method and is usually combined with other drying techniques. The main goal of this work is to study an innovative method to extend the storage life of peaches reducing energy and time consumption and ensuring food quality.

Drying curve (a) and drying rate curve (b) for drying of peaches by the conventional hot air drying method at 70°C.

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Drying curve (a) and drying rate curve (b) for drying of peaches by microwaves at 300, 500, and 800 W.

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Drying curve (a) and drying rate curve (b) for drying of peaches by microwave finishing with power of 500 W and microwave introduction time of 355 min.

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Drying curve (a) and drying rate curve (b) for drying of peaches by microwave finishing with powers of 300, 500, and 800 W and microwave introduction time of 433 min.

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Experimental and predicted values of moisture ratio change for the modified Page model at microwave finishing with power of 300, 500, and 800 W and microwave introduction time of 433 min.

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ORIGINAL ARTICLE

Drying of peaches by a combination of convective and

microwave methods

Theodora Chatzilia | Kyriakos Kaderides | Athanasia M. Goula

Department of Food Science and Technology,

School of Agriculture, Forestry and Natural

Environment, Aristotle University,

Thessaloniki, Greece

Correspondence

Athanasia M. Goula, Department of Food

Science and Technology, School of Agriculture,

Forestry and Natural Environment, Aristotle

University, 541 24 Thessaloniki, Greece.

Email: athgou@agro.auth.gr

Abstract

The aim of this work is to study a method to extend the storage life of peaches

reducing energy and time consumption and ensuring food quality. The conventional

method of hot air dying presents many drawbacks, whereas the microwave drying

usually leads to overheating and textural damage. Thus, in this work, a combination

of convective and microwave methods, more specifically a two-stage drying process

with an initial convective air drying followed by a microwave drying (microwave fin-

ishing), was studied for the drying of peaches. Peaches dried at 70C for various

times, 200, 278, 355, 433, and 510 min, were then dried in a microwave oven at

powers of 300, 500, and 800 W. Drying rates were examined, whereas dry peaches

were characterized for their color, antioxidant capacity, shrinkage, and rehydration

ability under optimized conditions for the situations with and without pretreatment

with ascorbic acid. Mass transfer of water was described by nine empirical models

and by the diffusional approach. The shrinkage of peach tissue during microwave fin-

ishing was evaluated and diffusion coefficients were assessed with shrinkage consid-

ered. The microwave finishing reduced the drying time by 89 ± 40%, while a smaller

shrinkage was observed, with better rehydration characteristics.

Practical applications

Peaches are important commodities in terms of global agricultural production. As

peach is a perishable product with a short shelf-life, the food industry has been

forced to find methods, such as drying, that extend its storage life by months. The

conventional method of hot air dying presents many disadvantages. Last decades,

microwave drying proposed an alternative way to improve the quality of dehydrated

products. However, microwave is rarely used alone as a drying method and is usually

combined with other drying techniques. The main goal of this work is to study an

innovative method to extend the storage life of peaches reducing energy and time

consumption and ensuring food quality.

KEYWORDS

diffusion coefficient, drying, microwave, peach, rehydration, shrinkage

1|INTRODUCTION

Peach (Prunus persica) is a member of the Rosaceae family and is char-

acterized as “stone fruit”due to the fact that its seeds are found in a

hard endocarp. It is one of the most nutritionally fruits worldwide with

a significant amount of various polyphenols, carotenoids, vitamins

(provitamin A and vitamin C), fibers, and minerals (potassium) (Saidani

et al., 2017). Peaches are important products as far as their global

Received: 9 November 2022 Revised: 14 January 2023 Accepted: 28 January 2023

DOI: 10.1111/jfpe.14296

https://doi.org/10.1111/jfpe.14296

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