Abstract
Long-term storage of Japanese chestnut (Castanea crenata Siebold & Zucc.) fruit using a polyethylene bag was carried out between October 2004 to September 2005. In order to create different O2/CO2 compositions in the bags, we used 1, 2, or 5 layers of polyethylene bags. The concentrations of soluble sugars and starch and the microstructure of cotyledonary parenchyma cells were investigated as fruit quality factors. The rate of sound fruits was decreased for all treatments at 2 months of storage. When 5 layers of polyethylene bag were used, all fruits lost their commercial quality at 10 months of storage. At 3 months of storage, there were large differences in gas composition among the treatments. The higher number of polyethylene films facilitated a decrease in the O2 content and increase in the CO2 content. Scanning electron microscopic observation of cotyledonary parenchyma cells demonstrated that the degree of starch breakdown in each treatment was also different at 3 months of storage. Starch breakdown was extensive when 1 or 2 layers of polyethylene bag were used but was decreased when 5 layers of polyethylene bag were used. These morphological differences indicate that gas composition in the bags affects fruit respiration and reserves mobilization. The amyloplast density and starch concentration in sound fruits were relatively high at 11 months of storage when 1 and 2 layers of polyethylene bag were used. At this stage, although the sound fruits rate was low (approx. 50%), a high amount of storage reserves was retained in these fruits. These findings suggest that the amount of storage reserves in chestnut fruit at harvest affects fruit storability; in other words, well-matured fruits have a good potential for long-term storage.
