Effect of heat treatment on the quality of onions during long‐term tropical storage

Abstract

SummaryOnion bulbs (cv. Nasik red) were exposed to hot air currents prior to storage to curtail storage losses. Treatments at 80°C for 30min or 60°C for 1 h resulted in heat damage while temperatures of 60°C for 30min or 50°C for 3h or 40°C for 48 h did not cause any heat damage to the bulbs.A commercial lot treated at 47, 50 or 53°C for 3h and another commercial lot treated at 47 or 50°C for 2‐5 h, were stored for 4 or 5 months in ventilated polyethylene bags at (1) ambient conditions 20‐30°C, RH 50‐80%, and (2) 21 ± 1°C, RH 60‐65%. In general the treated lots had more marketable bulbs, with less incidence of Aspergillus niger infection than untreated controls. Factorial experiments using temperatures 47, 50, and 53°C with durations of treatment between 2 and 5 h revealed that the temperature and duration of heat treatment had a significant effect on the yield of good bulbs and reduction in microbial spoilage during storage. Treatment at a temperature from 47 and 50°C for a duration between 2 and 4 h gave best results when stored at 21 ± 1°C. the effect of treatment lasted up to 3 months in storage.