超高温処理法が牛乳のビタミンに及ぼす影響について : (I)ビタミンCの破壊

概要

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The destruction of ascorbic acid in milk treated by the U.H.T. process (two seconds at 135℃) was compared with that of milk treated by holder pasteurization (15 minutes at 75℃). Ascorbic acid was determined spectrophotometrically by the 2,4-dinitrophenylhydrazine method. In the U.H.T. process 31.5% of the original ascorbic acid was lost during the heat treatment. In case of holder pasteurization, however, the percentage of ascorbic acid destruction in average was as high as 64.8%. Immediately after the heat treatments, nearly all of the ascorbic acid remained was present as reduced form, especially in U.H.T. treated milk. The percentage of ascorbic acid destruction proved to be as low as 11.9% in U.H.T. treated milk when stored at 7℃ for 24 hours, whereas a loss of 22.4% was found during the storage of pasteurized milk.