Assessment of precooling technologies for sweet corn

Sweet corn is classified among highly perishable horticultural commodities. Thus, it can be deteriorated rapidly after harvest resulting in high loss and poorer produce quality. Sweet corn's sugar loss is about four times higher at 10°C compared to 0°C. Precooling, immediately after harvest, has shown to be an effective method to maintain the quality for a wide range of fresh fruits and vegetables during storage. Further, this method leads to reduction in metabolism and respiration rate of the produce, retardation of its senescence, and inhibition of growth of pathogens. In addition to diminishing postharvest losses of the produce, efficient precooling is required for increasing the length of duration of marketing time for better profitability.Precooling of sweet corn was accomplished by three main methods including forced-air, water and vacuum cooling. Operating parameters such as temperature, pressure, orientation of corn cobs, air flow rate and water flow pattern were defined and studied for optimization. The assessment and comparison of the performance of precooling systems was achieved by determining the effect of these parameters on half cooling time and quality of the produce during storage for 7 and 21 days at 1°C and 90-95% RH. In addition, room cooling method was also tested and compared to the three precooling systems. The use of three sweet corn cultivars was important to compare their quality response to different cooling methods.Experiments were performed on a lab-scale vacuum cooler and modified forced-air and water cooler systems. The results showed that changing the cob orientation perpendicular to the direction of flow medium, using higher air flow rate in forced-air cooling and immersed water flow pattern in water cooling, can significantly reduce the half cooling time of the produce. Finally, the best method to be recommended for precooling sweet corn is by using hydrocooling which results in superior quality produce and minimum time