Inhibition of psychrotrophic bacterial growth in refrigerated milk by addition of carbon dioxide.

R. F. Roberts, South Dakota State University
G. S. Torrey



Treatment of refrigerated milk with 20 to 30 mM CO2 was evaluated as a method for extending storage-life by inhibiting growth of psychrotrophic bacteria. Generation times for each of five psychrotrophic pseudomonads were significantly longer when grown at 7°C in sterile milk treated with CO2 than when the same bacteria were grown in ungassed sterile milk.

When raw milks were stored at 7°C and treated with CO2, the time required for aerobic plate counts to increase 10-fold was at least 24 h longer than in the same milks left untreated. Numbers of coliforms, psychrotrophs, and anaerobes (facultative and obligate) were significantly lower in raw milks treated with CO2 than in untreated milks incubated at 7°C for 6 d.