夏蜜柑果汁製造に関する基礎的研究 (第21報) : アスコルビン酸の褐変化反応下での分解

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The Natsudaidai juice stored at room temperature deteriorates in flavor much more rapidly than the other juices. The deterioration in flavor is accompanied by the loss of ascorbic acid and the darkening of juice. Accordingly, it is recognized that ascorbic acid and its decomposition products play an important part on the darkening.Ascorbic acid in the presence of an acid yields furfural with the evolution of cabon dioxide. It is presumable that, furfural formed during the decomposition of ascorbic acid turns brown by polymerizing itself or with amino acids. Some furfurals were detected in browned Natsudaidai juice stored at room temperature.The juice was allowed to stand in contact with air, in which case the ascorbic acid was oxidized fairly rapidly. The primary product of oxidation of ascorbic acid is dehvdroascorbic acid, which is not colored. Surgical catgut immeresed in an alcoholic solution of ascorbic acid slowly turns red in the presence of air, as found by BLOCH. A similar reaction may occur in orange juice but it would be much slower. It is probable that the dehydroascorbic acid is hydrolyzed to 2,3-diketogulonic acid. 2,3-diketogulonic acid was also detected in an aged orange juice.Concentrated orange juice stored at room temperature gives rise to carbon dioxide without any sign of fermentation. The source of the carbon dioxide in this reaction is 2,3-diketogulonic acid, which is decarboxylated after its formation by the hydrolytic cleavage of the lactone ring of dehyfroascorbic acid.According to some investigations on natural juice, reductones other than ascorbic acid were not present in fresh juice, but they were found in stored juice. The author consideres the hydrolytic scission product of furfural as one of the unknown reductones. The chemistry of that reductone will be discussed in the next report.From this experiment, the mechanism of furfural formation from ascorbic acid in the browning reaction was suggested as follows : Ascorbic acid→Dehydroascorbic acid→2,3-Diketogulonic acid→Reductone (HOCH=CH-CH=COH-CHO)⇌Furfural
公益社団法人日本生物工学会の論文
1956-07-15

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野村男次
山口大学農学部

夏蜜柑果汁製造に関する基礎的研究 (第21報) : アスコルビン酸の褐変化反応下での分解

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