Effect of Temperature on Survival of Yeast in 45° and 65° Brix Orange Concentrate

A study was conducted to determine the effect of cold-temperature storage on yeast survival in 45° and 65° Brix orange concentrate under simulated conditions of bulk storage. Suspensions were prepared from each of three strains of yeast which had been identified as to genus and species. Orange concentrates at 45° and 65° Brix were inoculated to contain approximately 1,000,000 organisms per ml. Inoculated samples were then stored at -17.8, -9.4, -1.1, and 4.4 C. Samples were analyzed for total viable yeast periodically during 15 months of storage. No yeast growth occured in either 45° or 65° Brix concentrate at temperatures below 4.4 C. Survival curves of one of the test organisms in both 45° and 65° Brix are presented. Yeast died faster in 45° Brix at -17.8 C than at -9.4 or -1.1 C, while in 65° Brix survival was greater at lower temperatures. Mold was detected in 45° Brix at -1.1 C and below after 7 or more months. In 65° Brix, mold was observed after 12 months at all temperatures above -17.8 C. Some samples showed a slight brown discoloration after extended periods of storage.