| Summary: | 碩士 === 輔仁大學 === 食品營養學系 === 88 === People have concerned about biological properties of radish (Raphanus sativus L.) increasingly. However, development of radish juice or canned radish soup would be convenient for household users and application on food industry. Three cultivars radish, Mei-Hua-Chyun、Chei-Yeh-Meei-Nong-Tzao-Sheng and Gan-Tzae-I, were used in this experiment. The heat stability of myrosinase which is relevant to biological activity of radish was studied. Then the optimum blanching condition was determined by heat stability of peroxidase and polyphenol oxidase combined with the results of various blanching conditions’ effect on enzymes activities and physiochemical characteristics of radish juice. To obtain the optimum condition for radish juice or canned radish soup, sterilization and concentration effects on physiochemical characteristics and sensory evaluation of radish juice were also compared.
The results showed that enzymes activities and general physiochemical characteristics varied by cultivar, among them fresh Gan-Tzae-I had higher enzyme activity in myrosinase and peroxidase. Ascorbic acid、 sugar content and free amino acids were higher in Mei-Hua-Chyun. The optimum blanching condition was 90 degree C water for 5 minutes. It is advantageous on operational convenience and high juice yield. Comparing with radish juice from non-blanching, the soluble solids、titratable acidity and formol nitrogen were decreased after blanching, but pH value and color were not significantly different from non-blanching.
Sterilization lowered pH、titratable acidity、formol nitrogen、sugar content and free amino acids of radish juice. UHT treatment gave better appearance. L value of canned radish juice was significantly lower than UHT because of browning. The results of sensory evaluation on color and overall likeness indicated that the extent of consumer preference for UHT product was significantly higher than canned（p<0.05）.
The pH、titratable acidity、formol nitrogen、sugar content、 free amino acids and color of the reconstituted radish juice were affected by concentration methods. Generally, radish juice concentrated by vacuum evaporation had higher quality, especially on color. The L value of vacuum evaporation was significantly different from evaporation（p<0.05）. But sensory evaluation did not show similar results, it could be caused by the likeness difference between pannels. This research recommended that after blanching, further radish juice was sterilized by UHT or concentrated by vacuum evaporation. It would be the optimum condition for manufacture of radish juice.
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