Preservation of raw milk by the addition of carbon dioxide

Abstract

SUMMARY The effects of concentrations of 10–30 mM/1 of CO 2 on the growth of psychrotrophic milk spoilage organisms were examined, both in untreated whole milk and in pure cultures of Pseudomonas fluorescens growing in skim-milk and broth. Spoilage of refrigerated untreated whole milk was found to be inhibited by the addition of CO 2 and the effect was enhanced with increasing concentrations of CO 2 and decreasing storage temperature. Experiments with pure cultures of Ps. fluorescens showed that the inhibitory effects of CO 2 were not due to increased acidity or to displacement of dissolved O 2 , but to the presence of CO 2 per se which induced an increase in the duration of the lag phase of growth and had only a small effect on the logarithmic phase.