牛乳中の遊離アミノ酸類とその加熱による変化

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1. Free amino acids and related compounds of 15 mixed herd milks, collected in Tokyo and Kushiro area, were analyzed by means of ion exchange column chromatography. Seventeen free amino acids, phosphoserine, glycerophosphoethanolamine, phosphoethanolamine, ethanolamine, urea, taurine, ammonia, methioninesulfoxide and citrulline were chromatographically identified and their concentrarions were determined. The main constituents of total ninhydrin reactive compounds were urea (64%), the most predominant, phosphatides (17%) and free amino acids (15%).The concentration of total free amino acids was 60 micro moles per 100ml. The most concentrated one was glutamic acid, 25 micro moles per 100ml. Glycine, lysine, alanine and proline were also relatively concentrated. Though the milk samples were collected at different area in different seasons of the year, the variations of analytical data among them were observed small. The coefficient of variation of free amino acids concentration was calculated as 13%.2. Effect of heat upon the composition of free amino acids and related compounds was investigated. At 63°C beating, even after 90 minutes, only little changes were observed. By various heat treatments from 75°C, 15 minutes to 120°C, 10 minutes, decrease in the concentration of free amino acids and increase of ammonia were found. Increase of retaining free amino acids and marked increase of ammonia in the milk heated at 120°C for 20 minutes were probably due to the heat decomposition of proteins. Manufacturing pasteurization (85°C HTST) and sterilization (115°C and 140°C UHT or 150°C steam injection), on the other hand, caused less changes.
社団法人日本畜産学会の論文

牛乳中の遊離アミノ酸類とその加熱による変化

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