Alterações bioquímicas e fisiológicas durante a maturação e o armazenamento de graviola sob refrigeração associada a 1-metilciclopropeno e cera

Abstract

Four experiments with soursop were conducted aiming to evaluate: 1. changes that affect fruit quality during ripening, under ambient temperature; 2. physical, physico-chemical and chemical changes during ripening under ambient temperature, and their relationship with respiratory rate (RR) and ethylene production (EP); 3. effects of dosages of 1-methylcyclopropene (1-MCP) on the fruit ripening, under ambient temperature, and 4. effect of postharvest treatments with wax coating and 1-MCP for fruit conservation under refrigerated storage. For experiment 1, fruits were evaluated at 1, 2, 3, 4 and 5 days after harvest, under 26.3 ± 0.6°C and 87.6 ± 12.2% RH. Total titratable acidity (TTA) increased 8 times in relation to the et day, while the total soluble solids (TSS) doubled. Polyphenol oxidase activity increased until the 4th day, while peroxidase activity decreased from the 2nd day. Pectin methylesterase increased steadily and the polygalacturonase (PG) reached its peak in the 3rd day, decreasing coincidentally with the decrease of total pectin content. The increase of cell wall J3- galactosidase associated with the PG was expected with the fruit softening progress. Besides, the decrease of starch content coincided with the increase of amylase activity. For experiment 2, fruits were evaluated at 0, 1, 2, 3, 4 and 6 days after harvest under 23.4 ± 1.1°C and 81.8 ± 10.6% RH. Pulp firmness (FP) decreased from 60 N to 0.9 N. Such decrease was perceivable even before the EP had been detected. In ripe fruits the TSS content was 14.4°Brix and the TTA was equivalent to 0.92% of malic acid. For experiment 3, fruits were kept at 0, 200, 400 and 600 ppb of 1-MCP and stored for 0, 2, 4, 6 and 8 days under 24.0 ± 1.0°C and 90.8 ± 7.3 RH. The 1-MCP delayed the time of occurrence and reduced the peak intensity of RR as well as of EP. The weight loss (WL) was 13 to 24% lower in treated fruits. The 1-MCP also delayed the reduction of PF, with 200 ppb as the most efficient dosage. For experiment 4, the following postharvest treatments were evaluated: control, 1-MCP 200 ppb, wax coating and wax coating + 1- MCP 200 ppb, together with storage periods of 0, 4, 8, 11,13 and 15 days, under 15.4 ± 1.1°C and 86.0 ± 7.3% RH. Postharvest treatments delayed the period and the intensity of RR and EP, besides being retentive of PF. The wax coating was the most efficient treatment in reducing the WL and allowing fruits with best appearance until 13 days.