Characteristics of Organisms Contributing to Spoilage in Cottage Cheese

Abstract

The effect of incubation temperature, pH, sodium chloride, heat, chlorine, quaternary compounds, iodophor, and sorbic acid on the growth of 17 organisms isolated from spoiled cottage cheese was determined. None of the organisms showed growth in trypticase soy broth after incubation for 3 days at 3[degree]C. Fifteen of the 17 organisms showed growth ranging from slight to profuse, after incubation for 7 days at 10[degree]C. Most of the organisms thrived in the pH range of 6.7 to 7.4 and, with the exception of Torulopsis Candida, growth was retarded at pH 5.4 to 5.2 and below. Fourteen of the 17 organisms grew in 5% NaCl, whereas only 4 grew in 7% NaCl. Pasteurization at 61.7[degree]C for 30 minutes destroyed all organisms tested. Sixteen of the cultures survived 48.9[degree]C for 15 minutes in skim-milk, whereas, only one survived the above temperature and holding time in whey at pH 4.55. Under the conditions of this study, hypochlorite was the most effective germicide employed, followed by the iodophor and quaternary compounds. The concentrations of sorbic acid used were not effective in completely destroying the organisms, when the pH was not reduced.