Compositional Characteristics of the Protein-form Amino Acid Composition of Plum Fruit Stored at High Temperature (30°C)

Abstract

The Alcohol Insoluble Solid (AIS) was prepared from'Sordum' plum (Prunus salicinaLindl.) during storage at 3, 20, and 30°C and the total nitrogen and protein-form amino acidcontent in the AIS and the free-amino acid content in the fruit were determined. 1) The AIScontents in plum fruit at the stage of firm mature were lower than those at thestage ofimmature and soft mature, whereas the total nitrogen content in the AIS increased with theprogress of harvest season. 2) A little change in the AIS content was observed duringstorage at 3, 20, and 30°C. The total nitrogen content in the AIS increased markedly at 20°C.The compositional ratio of free alanine and glutamate to the total free amino acid in thefruit stored at 20°C was about four times larger compared with that at harvest time. TheAIS content and compositional ratio of free alanine and glutamate increased slightly duringstorage at 3 and 30°C. 3) The AIS was composed of 18 kinds of protein-form aminoacids. The compositional ratio of glutamate was the highest among the all aminoacids, and that of cystine and methionine was the lowest. The amino acid composition of the AISat those three maturity stages was similar except hydroxyproline. The ratio of hydroxypro-line decreased during storage at 20°C and increased at 3 and 30°C, but the other protein-formamino acids containing alanine and glutamate changed slightly. From these results, thespecific increase of free alanine and glutamate in ‘Sordum' plum accompanied by deteriora-tion was not concerned in the changes of protein-form amino acid composition ofthe AIS inthe fruit.