Microbial Standards for Milk

Microbial Standards for Raw and Pasteurized Milk

New York State milk standards (New York Ag and Markets, 2006) are based on those defined in the FDA Pasteurized Milk Ordinance (PMO, 2009). Dairy regulations vary from state to state, and some states may have different standards.

Milk Test Maximum Limit
Prepasteurized milk for Grade A use Total bacteria Individual producer not to exceed 100,000/mL1
    Commingled not to exceed 300,000/mL2
  Somatic cell count Individual producer not to exceed 750,000/mL
  Drugs No positive test on drug residue detection
Grade A pasteurized milk Total Bacteria 20,000/mL
  Coliforms Not to exceed 10/mL
Raw milk3 Total bacteria 30,000/mL
  Somatic cell count Not to exceed 750,000/mL
  Drugs No positive test on drug residue detection

1Individual producer milk is milk that is still on the farm.

2Commingled milk is milk that has left the farm and has been mixed with other individual producer milk in a tank, either during shipment or at the processing plant.

3New York State regulations for raw milk intended to be consumed as raw milk.

Microbial Tests for Raw and Pasteurized Milk

For more information on microbial and other tests performed on milk see the literature references by Cornell University (1998) and Wehr and Frank (2004).

Bacteria Count

The total bacteria count is the number of bacteria in a sample that can grow and form countable colonies on Standard Methods Agar after being held at 32°C (90°F) for 48 hours.

Coliform Count

The coliform count is the number of colonies in a sample that grow and form distinctive countable colonies on Violet Red Bile Agar after being held at 32°C (90°F) for 24 hours. Coliforms are generally only present in food that have been fecally or environmentally contaminated.

Somatic Cell Count

Somatic cells are blood cells that fight infection and occur naturally in milk. The presence of mastitis (an infection of the mammary gland) in the cow will increase the somatic cell count. The somatic cell count can be determined by direct microscopic examination or by electronic instruments designed to count somatic cells.