Study of the activity of lactic acid strains isolated from cheese cultures

Rogelj, I.; Slanovec, T.; Godic, K.; Perko, B. . VTOZD za zivinorejo, Institut za mlekarstvo

Study of the activity of lactic acid strains isolated from cheese cultures

1987

Rogelj, I. | Slanovec, T. | Godic, K. | Perko, B. (Biotehniska fakulteta, Ljubljana (Yugoslavia). VTOZD za zivinorejo, Institut za mlekarstvo)

We were studying the proteolytic and acidification characteristics of lacticacid microorganisms belonging into two species: Streptococcus thermophilus and Lactobacillus helveticus. These strains were isolated from pure cheese cultures. The inoculum into sterile nonfat dry milk was 1 % and the incubation temperature was 43'C. The time of coagulation depended on the strain and it was in the range from 5 hours to 9 hours 30 minutes. The highest titration acidity which was reached with the specius Str. thermophilus after 24 hours of incubation was 40,96'SH/100 ml. pH value at this time was 4.31. When the strains Lbc. helveticus were tested, the highest value of the titration acidity after 24 hours was 87.04'SH/100 ml and pH was 3.53. Low proteolitic activity was characteristic for all strains of the Str. thermophilus species and the values after 24 hours were even lower as after 6 hours of incubation. The average was 9.8 mg of tyrosin in 1 ml of milk.

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