Lipolytic and proteolytic screening techniques were applied to cultures isolated from young Cheddar cheese manufactured in 10 Iowa cheese plants. Twenty-one cultures were selected for study. These included 16 enterococci and 5 lactic group streptococci. These strains were examined for lipolytic activity when grown in skimmilk, cream, and skimmilk containing tributyrin; changes in proteolysis index, plate counts, and pH in skimmilk incubated at 7, 15, 21, and 32 C also were determined, And, combinations of enterococci and lactic streptococci were studied.

One-half of the Streptococcus durans strains frequently produced as much as 10 times more acetic acid than the others; the five strains of lactic streptococci consistently produced the lowest quantities of acetic acid. Compared with enterococci, except for Streptococcus faecalis var. liquefaciens, the lactic streptococci were more proteolytic, produced lower pH values, and had less viability at 15, 21, and 32 C. Enterococci other than S. faecalis var. liquefaciens were not proteolytic. All cultures showed tributyrinase activity; enterococci were the most active. Combining enterococci and lactic streptococci produced anomalous results.

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Author notes

1Journal Paper No. J-6544 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1188.

2Present address: Escuela de Lecheria, Colonia Suiza, Uruguay.