Drying kinetics and quality attributes of jujube (Zizyphus jujuba Miller) slices dried by hot-air and short- and medium-wave infrared radiation

Abstract

As representatives of the traditional and innovative drying method, hot-air (HA) and short- and medium-wave infrared radiation (SMIR) drying were chosen to conduct comparative study, respectively. In the present study, drying kinetics of jujube slices during HA and SMIR drying at 60, 70, 80 and 90 °C were investigated, quality attributes such as color, vitamin C (VC), total flavonoids content (TFC) and cyclic adenosine monophosphate (cAMP) content of dried jujube slices were evaluated. Both HA and SMIR drying process occurred mainly in the falling rate period. Drying time used in SMIR drying was 33∼83% of that in HA drying. Logarithmic model and Two-term model were the best in describing the drying process in HA and SMIR drying, respectively. Deff values of jujube slices were varied from 1.43 × 10−8 to 2.28 × 10−7 m2/s. Values of Deff in SMIR drying were two times higher than HA drying. Jujube slices dried by SMIR revealed better color, higher retentions of VC, TFC and cAMP content than HA drying. Compared with HA drying, SMIR drying showed shorter drying time, higher drying efficiency and better quality of products, indicating SMIR drying was a more promising drying method for jujube processing.