Hot Air Treatment and its Effect on Nectarine Metabolism var. Big Top Stored at Different Temperatures
The effect of hot air treatment (35 °C / 36 h) on Big Top nectarines prior storage at 0 and 5 °C for 6, 18 and 27 days followed by 6 days at 20 °C (shelf life, sl) was evaluated. Respiratory activity was twice as much in fruits at 5 °C (24 mg CO2 kg-1h-1), compared to those kept at 0 °C during the respiratory peak. At 0 °C, the treated fruits showed between 2 and 5 % more respiratory activity. The total polyphenols were not affected by temperature or treatment (0.22 and 0.24 mg galic acid equivalent g-1 fw) but almost doubled in sl, especially in fruits from 0 °C. At some analysis moments, the total antioxidant capacity of untreated fruits stored at 0 °C (0.42 and 0.45 mg equivalent ascorbic acid g-1 fw) doubled the values of the treated ones, although this situation was reversed in sl. The superoxide dismutase activity was considerably higher in fruits treated and stored at 0 °C (15-30 units of activity mg-1 of protein), as opposed to the observed at 5 °C. The activity of polygalacturonase and pectinmethyl esterase, as well as the development of mealiness in sl and in untreated fruits from 5 °C, would indicate that the heat treatment had a protective effect reducing the occurrence of damage. However, the little or no response observed in other variables make it necessary to confirm the effect of heat treatment in future studies.
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