Heat treatment to alleviation of woolliness of cold stored 'Dourado-2' peach

Abstract

The work was carried out with the objective to verify the effect of heat treatments on the incidence of woolliness in 'Dourado-2' peaches stored at 0^oC. Heat treatments were applied as conditioning temperature (50^oC during 2 hours or 20^oC during 48 hours) before cold storage. In intermittent warming, fruit treatments were warmed each five days at 25^oC during 24 hours or each ten days during 48 hours. Control fruit were continuously stored at 0^oC. The variables evaluated after 30 days at 0^oC (plus three days at room temperature) were: incidence of woolliness and decay, soluble solids content (SSC), acidity, ascorbic acid, skin color, firmness, respiratory rate, ethylene production and activity of polygalacturonase (PG) and pectinmethylesterase (PME). The intermittent warming with cycles of five or ten days and the conditioning temperature at 20^oC during 48 hours before cold storage was the most effective treatment to reduce incidence of woolliness. However, heat treatment hastened fruit softening. Ethylene production was higher in fruits intermittently warmed and this can be related to the higher activity of PG and PME and consequently to alleviation of woolliness of the fruit. Heat treatment caused little variations on SSC, acidity, ascorbic acid and skin color.