New Zealand Journal of Crop and Horticultural Science abstracts

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Heat treatments increase sweetness and flesh colour of buttercup squash

BRUCE L. BYCROFT
VIRGINIA K. CORRIGAN
DONALD E. IRVING^*

Food Industry Science Centre
New Zealand Institute for Crop & Food
 Research Ltd
Private Bag 11 600
Palmerston North, New Zealand

^*Present address: School of Land and Food,  University of Queensland, Gatton, Qld 4345,  Australia. email: d.irving@mailbox.uq.edu.au

Abstract  Buttercup squash (Cucurbita maxima Duchesne `Delica') fruit were heated to 30 or 33deg.C in air for up to 7 days, then stored at 12deg.C for up to 7 weeks. Control fruit remained at 12deg.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 12deg.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 [[alpha]]-amylase, [[beta]]-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.

Keywords  buttercup squash; Cucurbita maxima; flesh colour; starch degradation; sucrose; taste

H98055
Received 19 November 1998; accepted 6 August 1999

PDF file of entire paper: medium quality (587K); (scanned from paper original: notes about this process)

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