Effect of Dissolved Carbon Dioxide on the Growth of Psychrotrophic Organisms in Cottage Cheese

Abstract

The effect of dissolved CO2 on the growth of psychrotrophic spoilage bacteria in 2% fat creamed cottage cheese was investigated. Cottage cheese was inoculated with 103 cfu/g of a mixture of three Gram-negative psychrotrophic spoilage bacteria and stored in sealed glass containers at 4 and 7°C for 80 d. Carbon dioxide was added by dissolution into the cream dressing prior to the addition of curd. No growth, including yeasts and molds, was detected in the cheese containing CO2 during 70 d of storage at 4°C or 30 d at 7°C. Fresh appearance of the cheese containing CO2 was maintained for 80 d at 4°C or 60 d at 7°C. During the first 10 d of storage at 7°C or 17 d at 4°C, cottage cheese packaged without dissolved CO2 had 104-fold more colony-forming units (predominantly Gram-negative psychrotrophs) than that packaged with dissolved CO2. Gram-negative organisms made up a smaller proportion of the total bacterial counts in CO2-treated cheese than in the control product. These data indicate that dissolved CO2 can effectively inhibit the growth of Gram-negative bacteria in creamed cottage cheese packaged in high barrier containers.