Changes of Qualities of Onion Flakes During Storage Period Using Different Temperatures

This study was undertaken to find the changes in the water activity, color, browning index, pH, Brix, and microorganisms of onion flakes during 70 days. The onion flakes were stored for 70 days at a relative humidity of 90% and different storage temperatures (20oC, 30oC, 40oC). Results revealed that water activity continued to increase during storage. Samples stored at 40oC increased faster than samples stored at 20oC and 30oC. L-value was decreased at all storage temperatures. The a-value and b-value were decreased at samples stored at 40oC. Also, Lvalue and b-value showed a tendency to decrease as the storage temperature increased. Browning index increased during storage; moreover, pH value and Brix were decreased over the storage period and more rapidly at higher temperatures. Aerobic bacteria were 1.54 log CFU/mL of onion flakes stored at 20oC, 1.4 log CFU/mL at 30oC, and 2.0 log CFU/mL at 40oC on the 14th day of storage. After that, it was not detected at 40oC and continued to increase when stored at 20oC and 30oC. Also, levels of Escherichia coli and Staphylococcus aureus were not detected during storage. Thus, to maintain the quality of onion flakes, it is necessary to control storage temperature and relative humidity.