Fruit responses to postharvest heat treatment time: characterisation of heat-treated strawberry (Fragaria x ananassa) cv. 'Candonga' fruits

Strawberries cv. 'Candonga' were heat-treated in an air oven (45°C) for 0.2 and 4 h, and then stored at 0°C for 2 days. One-way ANOVA revealed significant differences in terms of physical and chemical quality properties due to heat treatment time (P=0.000). In particular, as treatment time increased, strawberries showed a significant decrease of weight, firmness, redness (a*), yellowness (b*) and colour saturation (chroma). Additionally, the fruits were darker (lower L* value) after 2 h of treatment and lighter after 4 h (higher L* value). Among chemical quality properties, ph and soluble solids content (SSC) increased during treatments, whereas vitamin C content (TAA) decreased. After 4 h of treatment, total anthocyanins and total soluble phenolics (TSP) significantly decreased and increased, respectively. Principal component analysis (PCA) was executed on the correlation matrix of significant variables. Two principal components were extracted, explaining the 73.38% of the data variance. PC1 (60.15% variance) was associated with most of the physical and chemical variables, whereas PC2 (13.23% variance) was associated with fruit lightness. PCA was found to be of value in obtaining a visual representation of fruit samples based on heat treatment time.