Water Absorption and Processing Characteristics of Dried Jujube under Different Temperatures Following Long-term Storage
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Abstract:
Jujube (Ziziphus jujuba Mill.) is a raw material used as both a medicine and food. It has attracted widespread interest concerning its health functions, storage and processing characteristics. The long-term storage of dried jujube can lead to severe dehydration, which causes the pulp to harden, the peel to darken, and its commodity value to decrease. Two types of Xinjiang jujube, Junzao and Huizao, that were stored for approximately 1 or 13 months, were selected as research samples to investigate the patterns of soaking and water absorption/rehydration and its effect on the processing properties of dried jujubes. Moisture content of Junzao and Huizao after 13 months of storage was reduced by approximately 50% compared with that of Junzao and Huizao after 1 month of storage. The duration of storage also affected fruit shape, pulp texture and composition, but the dried jujubes subjected to long-term storage retained good processing and utilization value. The water absorption curve of dried jujube was mostly logarithmic, and water absorption was affected by water temperature and the variety of dried jujube. Low-field magnetic resonance imaging demonstrated that water mainly infiltrated into the jujube fruit through the pedicle and surface. When the moisture content of Junzao and Huizao stored for about 13 months was 43.18 g/100 g on a dry mass basis (db) (T=40 ℃ ) and 41.06 g/100 g db (T=60 ℃ ), respectively, the jujubes underwent a slight softening, which was ideal for pitting and slicing. When the dry jujube was soaked until the moisture content, on a dry mass basis, was 129 g/100 g, it was fully softened and moisture was evenly distributed, which was ideal for beating and produced jujube pulp with good particle size and color.
