EFFECT OF HEAT TREATMENT IN CONTROL OF Penicillium digitatum (Sacc.) ON ORANGE FRUITS (Citrus sinensis Osbeck)

Abstract

The effectiveness of postharvest treatments with hot air and steam to control green mold growth and keeping quality were studied on orange fruits. Wholesome oranges were artificially inoculated with Penicillium digitatum. The inoculated oranges were divided into treatment portions, labeled according to treatment and treated by exposing to hot air at 46°C for 15, 30, 60, 120 and 240 minutes; 75°C for 2, 4, 8, 16 and 32 minutes. Other lots were treated by steaming separately at 50°C and 55°C for 150 seconds, 5, 10, 20 and 40minutes respectively. The controls were not treated with heat. Ten replicates were set up for each treatment and stored at 28°C±2°C and relative humidity (RH) of 95%. The parameters measured indicated that fruits rot, weight loss, freshness, heat damage, internal damage, total soluble solids, titratable acidity, mycelia growth and viability of fungi spores were affected by the heat treatments. This study has, therefore, demonstrated that interaction occur between temperature and time of treatment to influence pathological damage by Penicillium digitatum to fruits. This study has shown that, it is practicably feasible to preserve orange fruits for fifty-four days by heat treatment without losing its quality attributes. Pre-storage steam treatment at 550C for 150 seconds offered the best treatment for prolonging the storage life and quality of the fruits.