Texture and the cell wall polysaccharides of buttercup squash ‘Delica’ (Cucurbita maxima)

Abstract

Texture of buttercup squash ‘Delica’ (Cucurbita maxima D.) during storage, and the effect of cooking on the texture, have been investigated using a penetrometer and an Instron Universal Testing Machine. Firmness (measured by penetrometer) of uncooked and cooked squash increased during the first 2 months of storage (P < 0.001). The Texture Profile parameters of hardness, fracturability, and gumminess tended to decrease during storage, whereas cohesiveness, chewiness, and springiness remained unchanged. A procedure for isolating cell walls in tissues containing high levels of starch has been developed. An initial extraction of the tissues with HEPES buffer‐containing mercaptoethanol was followed by grinding the residue in a ball mill and a second HEPES buffer extraction. Any remaining starch was gelatinised and then removed by α‐amy‐lase treatment. Sequential fractionation of the cell wall polysaccharides was done. The cell walls of buttercup squash at harvest were composed of 34% pectin, 26% hemicelluloses, and 39% cellulose by dry weight.

Key words:

• buttercup squash
• Cucurbita maxima
• cell wall
• cell wall polysaccharides
• texture
• fruit firmness
• postharvest