Combined single-stage tempering and microwave vacuum drying of the edible mushroom Agrocybe chaxingu: Effects on drying characteristics and physical-chemical qualities

Abstract To reduce the moisture content gradient during drying, a single-stage tempering treatment based on parameters including intermediate moisture content (M), tempering temperature, tempering time and relative humidity was used to assist microwave vacuum drying (MVD) of the edible mushroom Agrocybe chaxingu. The influences of these parameters on product quality were analyzed by response surface methodology. The tempering treatments led to the increased effective moisture diffusivity and shortened effective drying time when compared with continuous MVD. Analysis of variance results showed M has the most significant impact on the quality parameters of A. chaxingu including the rehydration ratio, polysaccharide content, free amino acid content (FAA), and color, while the other three parameters only had a small but significant effect on some of those characteristics. Compared to continuous MVD, the total FAA content of tempering treatments enhanced by 10.81%–32.08%, especially aspartic, glutamic acid, isoleucine, leucine and valine. Overall, tempering-assisted MVD was found to be a potential drying of A. chaxingu, as it offers a more efficient drying process with better quality.