ウメ果実の貯蔵と低温障害に関する研究 (第1報)

Abstract

Japanese apricot (mume) fruits are usually harvested in the mature-green stage and processed as umeboshi (a kind of pickle) or used for liquer production before the fruits ripen. While yellowed and softened ripe fruits lose salability and the fruits are quite perishable, a storage method has not yet been developed. The purpose of the present study is to clarify the requirements for proper handling and storage of mume fruits, and to investigate the mechanism of mume fruit chilling injury which has unique characteristics at low temperature. This paper describes the general aspects of external and internal changes occurring in storage at various temperatures. Five cultivars of mume fruits were picked at the ordinary mature-green stage and packed with perforated polyethylene bags.The fruits ripened with a sharp increase of both carbon dioxide and ethylene production at 15°C, while shelf-life varied markedly among cultivars ranging from 6 days to over a month. At 10°C, ripening was delayed markedly, the production of ethylene and carbon dioxide dropped noticiably and the climacteric pattern was obscure. At 5°C and 1°C, ripening was suppressed and occurrence of chilling injury or decay limited the shelf-life. Unlike other commodities, chilling injury of mume fruits developed much sooner at 5-6°C than at 1°C, while the time of occurrence and the degree of incidence varied markedly with cultivars and other factors.Pulp slices of healthy-appearing fruits which had been stored at various temperatures for various periods were prepared, and oxygen uptake and carbon dioxide output were determined at 30°C. Respiratory quotients for slices prepared from 10°C- and 15°C-stored fruits did not change notably, but the RQ for 1°C-stored fruits showed a striking increment during storage, reaching a peak as high as 3 or more. At the period when RQ increased abnormally, sugar content and ethylene production also increased considerably, suggesting the existence of physiological turning even in the healthy fruits stored at low temperature. Similar but less marked changes were found in the fruits stored at 5°C.