Heat treatments increase sweetness and flesh colour of buttercup squash

Abstract

Buttercup squash (Cucurbita maxima Duchesne ‘Delica') fruit were heated to 30 or 33°C in air for up to 7 days, then stored at 12°C for up to 7 weeks. Control fruit remained at 12°C throughout. Sucrose and starch concentrations were measured in edible portions of raw squash, and the perceived sweetness of the cooked fruit was evaluated using a trained sensory panel. Enzymes of starch degradation and sucrose metabolism were also extracted and assayed. Sucrose content, on a dry weight basis, was as much as 250% higher in heat‐treated fruit than in fruit kept at 12°C. Sucrose accumulated with increasing length of treatment and continued to accumulate during subsequent storage. There was a strong correlation between sucrose content and panel sweetness rating. Heat treatments also increased the red/ yellow colour of the flesh. Both increased sucrose concentration and redder flesh colour appear to increase the acceptability of buttercup squash to consumers. In a subsequent experiment, we found that extractable activities of α‐amylase, β‐amylase, starch phosphorylase, D‐enzyme, sucrose synthase, sucrose phosphate synthase, maltase, and maltose phosphorylase did not differ in samples taken from heat‐treated or non‐heat‐treated squash.

Key words:

• buttercup squash
• Cucurbita maxima
• flesh colour
• starch degradation
• sucrose
• taste