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

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.

Application of pulsed electric field prior to vacuum drying: Effect on drying time and quality of apple tissue

“…Thus, in most variants, an increase in the TPC was observed after drying the materials. During drying, browning products are formed, which may have reacted with the Folin's reagent used in this assay (Wiktor et al 2020;Matys et al 2021). This may explain the increased content of these compounds in the dried apples.…”

“…During the drying, the weight of the apples was continuously (without any interruption in the drying process, using the same sample throughout the entire process) recorded every 10 min, which served to determine the drying time (time to achieve MR = 0.02 by dried apples) (Sacilik and Elicin 2006;Piotrowski et al 2007;Schultz et al 2007;Beigi 2016). The MR (moisture ratio) was calculated according to Equation (4) (Matys et al 2021…”

“…Among all the drying methods, convective drying is the most used method of food preservation in the food industry. The use of hot air in this process, thereby causing the long-term exposure of the material to oxygen and high temperatures, conduces the formation of adverse changes in the physical and chemical properties of the treated material (Matys et al 2021). The quality of the obtained dried material can be improved by drying under a vacuum.…”

The Effect of Processing Methods on Food Quality and Human Health: Latest Advances and Prospects

“…These additives are known to be prejudicial to human health, and are associated with a variety of health problems. This collection includes four reviews and six original research articles [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. The review on high-pressure processing (HPP) technology is focused on fruit and vegetable products [ 1 ].…”

“…Power ultrasound is another technology that can be used alone or to improve the efficiency of traditional food processes. Apples were sonicated before drying, which sped up the drying process and improved the product quality [ 2 ]. One other study presented results of the effect of ultrasound processing of tomato vinegar on its bioactive compounds.…”