Evaluation of temperature, microbial load, and water activity on storage stability of heat processed sweet sorghum juice

Fresh expressed sorghum juice contains several types of microorganisms such as nonfecal bacteria, yeasts, and molds. The juice is usually contaminated during harvesting of the cane and during handling the juice before processing to a finished syrup. Spoilage of sorghum juice can occur within 5 hours after its expression from the cane due to the high level of microorganisms.

This study evaluated a preservation technique for sorghum juice by heat processing the juice to 30° to 45° Brix semi-syrups. The heat processing of the juice to a boil kills all vegetative cells and the less heat resistant microorganisms and concentrates the juice to a semi-syrup by evaporation of water. Sorghum juice processed to 35° Brix or higher and stored at 13°C or lower could be held for at least 21 days without any detectable spoilage. Also, juice processed to 35° Brix or higher and stored at 20°C would require processing with an extreme care to prevent recontamination in order for it to be stored for up to 21 days. Processing the sorghum juice to a semi-syrup of at least 45° Brix (sugar level) will prevent the growth of surviving heat resistant microorganisms present in the juice. At this sugar level, the semi-syrup can be held for at least 21 days at a minimum temperature of 13°C without any detectable spoilage.