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Studies in the Preservation of Dehydrated Oncom
Thesis Abstract:
An experiment was conducted to determine the effect of sodium chloride (4-8%), sorbic acid (0.2-2.0%), sorbitol (0.2-2.0%), propylene glycol (0.8-6.0%), and mixture of sodium chloride (10%) with other humectants on the storage characteristics of oven dried (50ºC) oncom. The chemical and microbial changes were studied throughout the storage period.
Both sodium chloride and sorbic acid inhibited the microbial growth in the system. Even at high concentralion, propylene glycol (6%) and sorbitol (0.2-2.0%) did not affect bacterial growth and mold and bacterial growth, respectively.
Increasing the concentration of each humectant decreased water activity and microbial population. Prolonged drying at 50ºC reduced the moisture content and microbial population of the product. The increase in amino nitrogen content and the decrease in reducing sugar content during drying (50ºC) of oncom did not kill all microorganisms present nor did it stop enzymatic reactions.
However, during storage of dried oncom, moisture content increased and the microbial load influenced the amino nitrogen formation, pH, and use or reducing sugar. With mixed humectants, the increase on amino nitrogen content and decrease in reducing sugar content were lower than those containing single humectant.
In general, a high moisture level before storage gave poorer quality products that were acceptable up to 60 days of storage. A low moisture level of dried oncom resulted through a longer oven drying period and gave more stable product that Iasted for more than 60 days. Oncom containing mixed humectants could be stored longer than those treated with single humectant.
