Starch degradation in buttercup squash (Cucurbita maxima)

Extractable activities of alpha-amylase, beta-amylase, and starch phosphory lase were investigated in order to understand the mechanism of starch degra dation in buttercup squash (Cucurbita maxima Duchesne ex Lam. 'Delica') wit h the ultimate goal of improving the conversion of starch into sweet sugars . During rapid starch synthesis (0 to 30 days after flowering), extractable activities of alpha-amylase and beta-amylase were low, but those of starch phosphorylase increased. After harvest, during ripening at 12 degrees C, o r in fruit left in the field, activities of alpha-amylase and beta-amylase increased. Starch contained 20 % to 25 % amylose soon after starch synthesi s was initiated and until 49 days after harvest irrespective of whether the crop remained in the field or in storage at 12 OC. Maltose concentrations were low prior to harvest, but levels increased during fruit ripening. Data suggest starch breakdown is hydrolytic in buttercup squash, with a-amylase being the primary enzyme responsible for initiating starch breakdown.