ANALYSIS OF MECHANISM OF DECOMPOSING PROCESS CONTAMINATED WITH FILM-FORMING YEASTS IN UME-ZUKE, SALTED UME-PROCESSED PRODUCT

'Ume-zuke', a salted ume-processed product which is manufactured from ume fruit (Japanese Apricot, Prunus mume Sieb. et Zucc. var. microcarp a Makino) by salting with sodium chloride, is one of the traditional f ood produced in Japan. There is a serious problem about deterioration of 'Ume-zuke by film-forming yeast in recent trend of reducing salt co ncentration in food products. In present study, to clarify the mechani sm in evolution of contamination with film-forming yeast in 'Ume-zuke: isolation, identification, and characterization of yeast, the surveyi ng on the time course of changes in yeast flora, and some constituents in the decomposed 'Ume-zuke' sample during salting process were perfo rmed. All isolates were identified on the basis of standard biochemica l and morphological tests as Kloeckera apiculata (17 isolates), Pichia anomala (37 isolates), Candida guilliermondii (14 isolates), Debaryom yces hansenii (29 isolates) and other un-identified Candida sp. (8 iso lates). As a result of surveying of changes in yeast flora, K. apicula ta from ume fruit was the dominant species at initial stage, but decre ased progressively. On the other hand, with the salting period progres s, strains of P. anomala, C. guilliermondii and D. hansenii increased subsequently. At the last stage of salting period, strains of D. hanse nii were only detected after the rise of the pH of 'Ume-zuke'. And, su ccessive decrease of organic acid content and the pH rise in 'Ume-zuke ' caused by assimilation of P. anomala was observed. In conclusion, th ese results support the following mechanism. P. anomala which showed r apid growth and strong assimilation ability of organic acids in 'Ume-z uke' was the main film-forming yeast species together with C. guillier mondii promoting yeast contamination by pH rise in 'Ume-zuke'. And, D. hansenii and other yeasts increased because of pH rise, and its growt h spread the yeast contamination.