Fresh-Cut Kiwifruit Structure and Firmness as Affected by Heat Pre-treatments and Post-cut Calcium Dips

The effect of heat pre-treatment (45 A degrees C/25 min), applied to whole fruit, and post-cut calcium dips in 1 and 2 g/L CaCl2 solutions on respiration rate and texture preservation of kiwifruit slices was studied. During a 9-day period, packages' atmosphere composition, slices' firmness, pectin content and sensory scores were evaluated. Histological observations of samples were also performed. Neither heat pre-treatment nor calcium dips alone were effective in diminishing respiration rate of the slices but the application of both treatments revealed a synergistic effect on respiration rate reduction. Calcium-dipped fruit slices showed better firmness preservation. Post-cut calcium dips, alone or combined with heat pre-treatments, yielded slices presenting higher insoluble/total galacturonic acid ratio, indicating formation of calcium pectates. Slices from heat-pre-treated fruits, even in the absence of calcium, also revealed insoluble/total galacturonic acid ratio similar to calcium-treated slices, supporting, despite the lower firmness value, a more structured tissue, as observed in SEM microphotographs. Sensory and physical-chemical parameters obtained were correlated. The effectiveness of calcium treatment was equally observed for both tested concentrations during a 9-day shelf life period.