Postharvest biochemical and textural characteristics of sh2 sweetcorn cobs

Abstract

The determination of storage conditions leading to optimum quality attributes and extended postharvest life of sweetcorn is essential. The increased consumption and consequently the need for greater consumer satisfaction have resulted in the introduction of supersweet sweetcorn. The present study, aimed to report on the effects of various postharvest factors on biochemical and texture-related characteristics of supersweet sweetcorn cultivars as current knowledge is still incomplete. Validation and optimisation of commonly used methods for the analysis of target compounds in sweetcorn was also an objective of the current work. The methods developed for the analysis of the target analytes (viz. ferulic acid, individual carotenoids, non-structural carbohydrates and vitamin C) were considered suitable. However, the Folin-Ciocalteu assay and the ferric ion reducing power assay, as methods for the determination of total phenolic content and total antioxidant capacity of sweetcorn, respectively, were shown as not appropriate for sweetcorn analysis. Documentation on firmness and biochemical compounds as affected by cooking and the interaction with various storage conditions is still limited. The current project was the first to extensively monitor quality changes in firmness, and other quality attributes under cooking conditions. Results revealed that increased cooking time resulted in greater ferulic acid content and a significant decline in firmness and qualityrelated target analytes such as L-ascorbic acid and carotenoids, yet no change in sugars was observed. The firmest kernels were reported to be those located in the central part of the cobs, which is also the preferred edible portion for consumers. Surprisingly, spatial sugar profiles indicated higher total sugar content in non-edible tissues (viz. core and shank), rather than kernels and the implications of this are discussed. Predictably, higher storage temperature and the longer storage period resulted in lower quality, yet genotype, controlled atmosphere and origin of the cobs were significant sources of variation for sugar content and firmness of kernels. The presence of husks (i.e. non-removal) on sweetcorn cobs promoted the retention of sugar content and colour over storage. Recommendations for improved methods for the measurement of target analytes leading to valid conclusions about optimum storage conditions are also included.