Process and Quality Control Procedures
8 Microbial Testing
Routine cheese microbial analyses should include yeast and molds, Salmonella sp., Staphylococcus aeureus, Listeria sp. and Escherichia coli. Raw milk cheese of some varieties should be considered higher risk and in some cases cheese made from heat treated but not pasteurized milk must also be considered higher risk. Microbial analyses should be performed near the time of retail sale and, preferably also at the time of manufacture. A positive test for any species of Listeria should be followed up with specific tests for Listeria monocytogenes. Similarly, substantial numbers of E. coli or Staphylococcus aureus should be followed up with tests for enterophathogenic E. Coli or coagulase positive Staphylococcus aureus, respectively. Cheese whey should be monitored for the presence of bacteriophage specific for the culture currently in use.
Table 8.1. List of Standards for Dairy Products. Fluid cow's milk products, except creams, shall have a freezing point of -0.508°C or lower.
| Product | Bacteria | n | c | m | M |
|---|---|---|---|---|---|
| Cheese (pasteurized milk) | S. aureus E. coli |
5 | 2 | 100 | 10,000 (/g) 1,000 (/g) |
| Cheese (unpasteurized milk) | S. aureus E. coli |
5 | 2 | 100 | 10,000 (/g) 1,000 (/g) |
| Cheese (pasteurized) without ripening, including fresh cheeses, lactic curd with a minimum of 50% moisture | Coliform | 5 | 2 | 100 | 100 (/g) |
| Fermented dairy products (e.g. buttermilk, yogourt, sour cream) | Coliform | 5 | 2 | 100 | 100 (/g ou ml) |
| Pasteurized milk, cream and other non-fermented dairy products | Mesophilic aerobic bacteria (32°C) Coliform |
5 5 |
2 2 |
10,000 1 |
25,000 (/ml) 10 (/ml) |
| Frozen dairy products | Mesophilic aerobic bacteria (32°C) Coliform |
5 5 |
2 2 |
10,000 10 |
50,000 (/ml) 100 (/ml) |
| Butter | Mesophilic aerobic bacteria (32°C) Coliform |
5 5 |
2 2 |
10,000 10 |
50,000 (/g) 100 (/g) |
| Milk powders and other dairy product powders | Mesophilic aerobic bacteria (32°C) Coliform |
5 5 |
2 2 |
10,000 10 |
50,000 (/g) 100 (/g) |
| Evaporated, sweetened and condensed milk | Shall be commercially sterile |
Adapted from the Canadian Dairy Information Centre (1997), amended July 2005.
n=number of sample units (subsamples) to be examined per lot
c=maximum number of sample units (subsamples) per lot that may have a bacterial concentration higher than the value for “m” without violation of the Regulations.
m=maximum number of bacteria per g or ml of product that is of no concern (acceptable level of contamination)
M=maximum number of bacteria per g or ml of product, that if exceeded by any one sample unit (subsamples) renders the lot in violation of the Regulations
The Canadian Food And Drug Act and Regulations defines acceptable limits for several pathogens in cheese made from pasteurized milk and for cheese made from raw or unpasteurized milk. The limits for cheese made from pasteurized milk per g of cheese are: 500 coliform bacteria, 100 Escherichia coli, and 100 coagulase positive Staphylococcus aureus. The permitted numbers per gram of raw milk cheese are 5,000 coliforms, 500 E. coli, and 1,000 coagulase positive S. aureus. The tolerance for Listeria monocytogenes in cheese and any other ready to eat product is zero.
Table 8.2. Microbiological Limits for Dairy-Cheese, Hard. Ex. Parmesan, aw<0.95 and pH<5.6. All cheeses are made with pasteurized milk.
| Criteria & EMP Target Microorganism |
Microbiological Limit | Recommended Action if Limit is Exceeded | Comments | |
|---|---|---|---|---|
| Routine | Non-Routine | |||
| Coliforms | <100/g | Investigate, implement corrective action | ||
| E. coli (generic) | <10/g | Investigate, implement corrective action; if >100/g, reject lot | ||
| Listeria spp. (EMP) | Negative for Zone 2 or 3 | Investigate, consider Zone 1 and finished product testing, implement corrective action | ||
| Listeria spp. (product) | Negative in 25 g | Reject lot | May be in-process vat sample due to the aging process for natural cheese | |
| Salmonella | Negative in 275 g | Reject lot | May be in-process vat sample due to the aging process for natural cheese | |
| S. aureus | 100/g | Investigate | Test for toxin if slow acid development; if positive for toxin, destroy product | |
Adapted from Wisconsin Association for Food Protection (WAFP) (2018).
Table 8.3. Microbiological Limits for Dairy-Cheese, Soft, Semi-Soft, Surface-Ripened. Ex. Brie, Fresh Mozzarella, aw>0.95 and pH>5.4. All cheeses are made with pasteurized milk.
| Criteria & EMP Target Microorganism |
Microbiological Limit | Recommended Action if Limit is Exceeded | Comments | |
|---|---|---|---|---|
| Routine | Non-Routine | |||
| Coliforms | <100/g | Investigate, implement corrective action | ||
| E. coli (generic) | <10/g | Investigate, implement corrective action; if >100/g, reject lot | ||
| Listeria spp. (EMP) | Negative for Zone 2 or 3 | Investigate, consider Zone 1 and finished product testing, implement corrective action | ||
| Listeria spp. (product) | Negative in 125 g | Reject lot | 125-g analytical unit composed of 5 x 25-g samples | |
| Salmonella | Negative in 375 g | Reject lot | ||
| S. aureus | 100/g | Investigate, implement corrective action. If ≥10^4 /g, reject lot due to potential for enterotoxin production |
Test for toxin if slow acid development; if positive for toxin, destroy product | |
Adapted from Wisconsin Association for Food Protection (WAFP) (2018).
Virus of the bacterial culture for the cheese.
