Effects of Pretreatment and Drying Methods on Quality and Antioxidant Activities of Dried Jujube (Zizyphus jujuba) Fruit
2013
Kim, J.W., Catholic University of Daegu, Gyeongbuk, Republic of Korea | Lee, S.H., Catholic University of Daegu, Gyeongbuk, Republic of Korea | No, H.K., Catholic University of Daegu, Gyeongbuk, Republic of Korea | Hong, J.H., Catholic University of Daegu, Gyeongbuk, Republic of Korea | Park, C.S., Catholic University of Daegu, Gyeongbuk, Republic of Korea | Youn, K.S., Catholic University of Daegu, Gyeongbuk, Republic of Korea
This study was performed to determine the effects of pretreatment (NT: non-treatment, BTS: boiling treatment with 3% sodium chloride, DTG: dipping treatment in glycerol) and drying methods (sun drying, hot air drying, and cold air drying) on the physicochemical properties and antioxidant activities of dried jujube (Zizyphus jujuba Mill.) fruits. Our results show that moisture content is lower (P0.05) with DTG, and that moisture content is lower with hot air drying compared to other drying methods. The bulk density was highest with BTS. The soluble solids content was highest with DTG. Additionally, the soluble solids content were highest in the following order: hot air drying cold air drying sun drying. The titratable acidity of hot air drying was highest of all the drying methods. The titratable acidity was higher with NT and DTG, and the brix and acid ratio of sun drying was higher than other drying methods. Among the drying methods, BTS showed the best browning-retarding effect, whereas boiling treatment affected quality and color. The total polyphenol content from hot air drying and NT or DTG treatment was relatively higher than the content from BTS. The flavonoid content was highest with BTS, and all dried jujube showed relatively high antioxidant activities. The sensory evaluation results indicated that the organoleptic scores for overall preference were higher in the NT and DTG treatment groups. These results suggest that pretreatment and drying methods affect the quality of dried jujube fruit, and show that glycerol treatment with hot air drying can be applied to the production of high quality dried jujube.
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