Sterile reconstituted nonfat dry milk containing 0.1% (v/v) each of 19 cleaning or sanitizing compounds intended for use on dairy farms or in milk factories was inoculated with Streptococcus lactis 4175, Streptococcus cremoris C-13, Streptococcus thermophilus ST4 or Lactobacillus bulgaricus. Milk then was incubated at 32°C for 12 h and pH and titratable acid were determined. Five products (alkaline inflation cleaner, hypochlorite sanitizer-farm use, isopropanol udder wash, ammonium chloride detergent-factory use, alkaline cleaner A-factory use) were inhibitory to at least three of the four lactic acid bacteria at the 0.1% concentration. These were then tested at 0.050, 0.025, 0.012 and 0.006% concentrations. Of the five products, only the isopropanol udder wash (at all four concentrations) inhibited S. lactis and S. cremoris. The isopropanol udder wash at all four concentrations and the ammonium chloride cleaner at 0.050% inhibited L. bulgaricus. S. thermophilus was inhibited by the isopropanol udder wash at 0.050%, whereas the alkaline cleaner A-factory use, at 0.050 and 0.025%, may have been mildly stimulatory to acid production by this bacterium.
MODELLING OF LACTIC ACID PRODUCTION BY STREPTOCOCCUS CREMORIS HP
