Studies on the quality of ice cream

The quality of ice cream was investigated by taking samples from retail outlets on two occasions; summer 1979 and summer 1980. Bacteriological, chemical, physical and organoleptic tests were carried out on 50 samples of thirteen brands from the first sampling. A limited number of bacteriological and physical and chemical tests were carried out on twelve replicates of four brands in the second sampling. No pathogenic microorganisms were detected in ice cream and the lack of residual phosphatase suggested that pasteurization had been adequate. Low numbers of thermoduric bacteria but variable numbers of coliform bacteria and mesophilic bacteria were found in the ice cream samples suggesting some post-pasteurization contamination. Examination of isolates on plates poured with violet red bile agar showed that many of the colonies that could be considered typical of coliform bacteria were more closely related to Pseudomonas aeruginosa than to Enterobacteriaceae. Brands differed in their chemical properties but the variation between brands was not marked. Little difference between brands was found from organoleptic tests on the ice cream samples studied