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Effects of Vacuum Freeze-Drying and Hot-Air Drying on the Quality of Blueberry Fruits

XU Qing-qing, CHEN Hang-jun, GAO Hai-yan, SONG Li-li, MU Hong-lei   

  1. 1. College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, China;
    2. Key Laboratory of Fruits and Vegetables Postharvest and Processing Technology Research of Zhejiang Province,
    Food Science Institute, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
  • Online:2014-03-15 Published:2014-04-04

Abstract:

The effects of vacuum freeze-drying and hot-air-drying on the quality of blueberry fruit were investigated in thisstudy. The eutectic point and consolute point of blueberry were determined using the resistance method to analyze freezedryingcurve. Ultrastructure, rehydration rate and the contents of vitamin C (VC) and anthocyanin of hot-air and vacuumfreeze dried blueberry fruits were also investigated. The results showed that the eutectic and co-melting temperatures ofblueberry were -33 and -30 ℃, respectively. Compared with hot-air drying treatment, vacuum freeze-drying maintaineda higher rehydration capacity. The contents of VC, anthocyanin and total phenolic in vacuum freeze dried blueberry were5.52 mg/100 g, 1.55 mg/g and 3.55 mg/g, respectively. Therefore, vacuum freeze-drying has the advantages over hot-airdrying in maintaining the rehydration characteristics, sensory quality and active ingredients of dried blueberry fruit.

Key words: blueberry, vacuum freeze drying, freeze-drying curve, eutectic point, consolute point