Figure 3.1. Culture Activity Test
This section is adapted from two reports prepared by: Mark Mitchell (1995), Ontario Ministry of Agriculture, Food and Rural Affairs, Guelph, Ontario
Figure 3.1. Culture activity test: example.
Culture Lactococcus lactis subsp. lactis
Lactococcus lactis subsp. cremoris
Temperature 37 C
Inoculum 2% of mother culture prepared with 10% reconstituted skim milk powder.
Test media 1 10% skim milk powder, low heat, antibiotic free.
Test media 2 Same as one with 1% cheese whey.
Titratable acidity after 4 hours:
Treatment 1 0.34%
Treatment 2 0.25%
pH versus time
|Skim with whey||6.61||6.57||6.5||6.42||6.35||6.31||6.3||6.3||6.29||6.29|
- Test media 1 shows normal growth. 0.34% acidity after 4 h with a 2% inoculum is adequate for most types of cheese. pH versus time plot is typical, reaching pH 5.2 between 6 and 7 hours.
- Test media 2, containing cheese whey, shows inadequate acid development, indicating the probable presence of bacteriophage in the cheese plant.