Advantages of Liquid Nitrogen Spraying Quick-freezing on the Quality Preservation of Bayberry
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Abstract:
In order to find an optimal freezing method and provide technical and theoretical support for improving frozen quality characteristics of Bayberry, liquid nitrogen spraying quick-freezing (NF-20,-40,-60,-80,-100 ℃) was adopted with immersion freezing (IF) and refrigerator freezing (RF) as comparison. The frozen time, maximum ice crystal zone time (ti), thawing loss rate, total phenol, anthocyanin, total sugar, hardness, vitamin C, oxygen radical absorbance capacity, polyphenol oxidase changes of frozen bayberries were investigated. The results showed that the ti of NF-100 ℃ treatment was only 6.44% of that of IF, and was 1.34% of that of RF. The significant advantages of NF-100 ℃ were also shown on the quality proprieties, the nutrients(total sugar, vitamin C, total phenol and anthocyanin content were 29.22 mg/g, 27.98 mg/g, 1.52 mg/g and 0.89 mg/g, respectively) could be kept more than 80% of the fresh bayberry; compared with immersion freezing and refrigerator freezing, the thawing loss rate was lowered by 58.91% and 63.39% respectively; the hardness was enhanced by 15.15% and 34.75% respectively. In conclusion, Liquid nitrogen sparying quick-freezing is an optimal way to freeze bayberry, and -100 ℃ of NF is the appropriate frozen temperature to maintain the quality of bayberry in the temperature range of -20 ℃~-100 ℃.
