Influence of Ultrasound and the Conditions of Convective Drying with Dehumidified Air on the Course of the Process and Selected Properties of Apple Tissue.

Aleksandra Matys,Artur Wiktor,Magdalena Dadan,Dorota Witrowa-Rajchert

doi:10.3390/foods10081840

Aleksandra Matys, Artur Wiktor + Show 2 more

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https://doi.org/10.3390/foods10081840

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Abstract

The conditions of convective drying induce a negative effect on the quality of the dried products, and thus, innovative solutions, such as the utilization of ultrasound and dehumidified air are gaining importance. Therefore, the aim of this study was to evaluate the impact of ultrasound pretreatment and variable air temperature on the kinetics of convective drying with dehumidified air and the quality of dried apples. Apples were dried with dehumidified and non-dehumidified air at 55, 70 and 85 °C. Preliminary ultrasound treatment was conducted by immersion for 60 min. The effect of both ultrasound and dehumidified air utilization was more prominent in the terms of drying time reduction, when lower drying temperatures were used. Drying of apples with dehumidified air, preceded by ultrasound pretreatment, resulted in a greater rehydration capacity of the products, and limited the browning process. Dehumidified air increased the lightness of the dried products, while sonication darkened them. The use of ultrasound before drying coupled with a drying with dehumidified medium at a temperature of 70 °C reduced the exposure of the product to a high temperature and oxygen. Products treated before dehumidified air drying with ultrasounds were characterized by high total phenolic content and the greatest antioxidant activity. This was because such technological treatment reduced exposure of the product to a high temperature and oxygen.

Highlights

IntroductionConvective drying (hot air drying) is traditional method used frequently for dehydration of different food materials [1] by hot air
Convective drying is traditional method used frequently for dehydration of different food materials [1] by hot air
The aim of this study was to determine the kinetics of the ultrasound-pretreated apples dried by the means of convective drying with dehumidified air carried out at variable air temperature, as well as to compare selected quality properties of the obtained products

Summary

Introduction

Convective drying (hot air drying) is traditional method used frequently for dehydration of different food materials [1] by hot air. More than 90% of dried food is obtained by convective drying [5] This method consumes over 25% of the energy used by the industry in developed countries [6,7]. A significant energy consumption [9,10], a low thermal efficiency, and long drying times can be mentioned, resulting in an unsatisfactory quality of the obtained products [1]. The long exposure of the product to a high temperature and oxygen leads to numerous adverse physical changes in the product [2] It induces a destructive effect on the labile bioactive compounds, significantly reducing nutritional and sensory quality of dried material [11]. An interesting solution is modification of a convective dryer to combine it with an air dehumidifier

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