An Investigation of the Effects of Drying Methods and Conditions on Drying Characteristics and Quality Attributes of Agricultural Products during Hot Air and Hot Air/Microwave-Assisted Dehydration

Abstract

Hot air and microwave-assisted hot air drying of apples (Golden delicious), strawberries (Fragaria vesca cv. Elsanta), tomatoes (Lycopersicon esculentom var. Roma), and mushrooms (A. bisporus) were performed in a commercial microwave oven that had been modified to incorporate a hot air dryer. The same microwave power intensity was used in all experiments. We investigated the effect of the above-stated methods on the structural, optical, mechanical, and rehydration characteristics of dried samples. Scanning electron microscopy (SEM) was used to evaluate the structural damage associated with two drying methods. The drying rate was significantly affected by microwave energy; therefore, drying time was reduced by 80, 70, 74, and 66%, respectively for apples, strawberries, tomatoes, and mushrooms, respectively. Specific volume, particle density, and porosity variation were estimated using models proposed in the literature. Some structural damage occurred, as observed in SEM micrographs. Optical, mechanical, and rehydration parameters were enhanced by microwave treatment for apples, strawberries, and tomatoes. However, negative effects were observed in the case of mushrooms.