To investigate the cause of the sugar increase, starch contents were determined for OPT samples whose sap was squeezed for the sugar analysis (Fig. 7). At Day 0, the average
starch content was 3.5% of dried solid OPT disc and it decreased sharply from the beginning of the storage. Starch content dropped to 0.5% at Day 30 and became negligible after 60 days. Assuming that the moisture content is 70%, the solid is 30 g and the sap is 70 ml when the whole OPT sample is