Flavour Qualities of Frozen Sweetcorn are Affected by Genotype and Blanching

Abstract

Peroxidase activity is used by the food processing industry as an indi- cator of adequacy of the blanching process and to predict off-flavour develop- ment in frozen food. Research reported herein showed that total peroxidase activity did not parallel flavour changes in frozen unblanched supersweet (sh2) or sugary enhanced (sullse) sweet corn genotypes. Frozen corn-on-the-cob of 'Florida Staysweet' (sh2), 'Merit' (standard sweet-sul) and 'Bodacious' (sullse), blanched and unblanched, was subjected to sensory evaluation and peroxidase analysis following frozen storage up to 12 months. Trained taste panellists rated the unblanched sh2 and sullse corn as acceptable up to 8 months of frozen storage. Kernels were cut from cobs after 0 and 12 months of storage. Proteins were extracted from acetone powders of kernels and separated by isoelectric focusing and native PAGE. Banding patterns differed according to genotype and storage duration. These results suggested molecular differences in peroxidase iso- zymes among the sweet corn genotypes which could be involved in off-flavour development. All genotypes contained a peroxidase isozyme having a molecular mass of 80 kDa and PI of 4-5. The sullse and sh2 genotypes produced an addi- tional peroxidase band of 13.8 kDa. An additional peroxidase isozyme (PI 5.4) appeared in extracts from the sul genotype after 12 months storage. Although changes in total peroxidase activity may not predict flavour changes in all geno- types, the presence or absence of certain peroxidase isozymes may be useful in predicting off-flavour development in sul frozen corn.