Analysis of quality changes and hot air drying characteristics of Xinjiang jujube (Zizyphus jujuba cv. Junzao) by hang on trees drying

Abstract The purpose of this study was to explore the changes in quality indicators and hot air drying characteristics of jujube during the natural hang on trees drying stage, and to determine the optimal picking period for Xinjiang jujube suitable to drying and processing, samples were collected six times in a 7-day cycle, respectively denoted as S1-S6, research the effects of different picking stages on the nutrient content, color, hot air drying kinetics and drying quality of Xinjiang jujube during hang on trees drying. The results showed that the water content of jujube gradually decreased; the percentage of soluble solids, total and reducing sugars increased, but the total mass of those in a single jujube decreased, and the percentage of ascorbic acid and total mass decreased during the natural drying process. The hot air drying time is different at different picking stages. The highest ascorbic acid content after hot air drying is 87.14 mg/100 g for jujube at stage S4. with a decreasing trend in cracking rate after drying from S1 to S6 and an increasing trend in rehydration. Used AHP to evaluate the quality comprehensively, found that jujube picked at S4 were more suitable for drying and processing.