Abstract:
Postharvest loss of big onion is considerable and one of major issues which adversely
affects food security in Sri Lanka. One of major reasons is improper storage conditions
where, mainly due to harvesting coincides with rainy season or harvest just before
rainy season. Hence, storage of harvested onion is critical in rainy weather where high
relative humidity prevails during second inter-monsoon and Maha seasons.
Temperature (T) and relative humidity (RH) should be controlled to reduce
postharvest loss of big onion during storage period. Therefore, this experiment was
conducted to evaluate the effect of controlled temperature and relative humidity on
postharvest loss of big onion during storage period. Ambient storage (AS) (partially
rainy day: 30.05±1.48 °C, 79.31±3.76% RH; Sunny day: 33.99±1.86 °C, 57.06±8.88%
RH) and controlled storage (CS) (27.15±0.41°C, 70.57±7.3% RH) were used as
treatments with complete randomized design with three replicates (150 kg each).
Onions were harvested from selected fields in Anuradhapura district, Sri Lanka and
subjected for shade curing. Physiological weight loss (PWL), Rotten percentage (RP),
Sprouted percentage (SP), Total soluble solids (TSS), Total color difference (TCD) and
Total postharvest loss (TPL) were recorded for six weeks period. No significant
differences (p >0.05) were observed for PWL and TCD between treatments. PWL of
onions in AS and CS were 9.32±1.38 and 9.16±0.94% respectively. However, there
were significant differences (p <0.05) observed for TSS, SP and for RP between
treatments. RP of onions were 8.09±0.19 and 5.46±0.17% in AS and CS respectively.
There was significant difference (P <0.05) observed for TPL after the storage period
where, 24.85±1.04 and 19.45±0.92% in AS and CS respectively. It can be concluded
that the control storage conditions (27.15±0.41°C, 70.57±7.3% RH) could be used to
reduce the postharvest losses of big onion during storage. However, temperature and
relative humidity should be optimized with further experiments.
