Milk - Grading

Grading

In the United States, there are two grades of milk, with Grade A primarily used for direct sales and consumption in stores, and Grade B used for indirect consumption, such as in cheese making or other processing.

The differences between the two grades are defined in the Wisconsin administrative code for Agriculture, Trade, and Consumer Protection, chapter 60. Grade B generally refers to milk that is cooled in milk cans, which are immersed in a bath of cold flowing water that typically is drawn up from an underground water well rather than using mechanical refrigeration.

• Grade A farms are inspected every six months, while Grade B farms are inspected every two years {WI-ATCP 60.24.2}
• Both types of farms are required to have two cleaning vats in the milk house for washing and rinsing of equipment {WI-ATCP 60.07.2(g)}. A farm also must have an additional separate sink and faucet provided for hand washing {WI-ATCP 60.07.2(h)}, unless the bulk tank was installed before Jan 1, 1979, or the farm uses milk cans.
• Grade A milk stored in a bulk tank is cooled to 45 °F (7 °C) within two hours of milking. Grade A milk in a tank may only rise to 50°F if milk from additional milking sessions is added to the tank (potentially requiring a plate cooler to reduce the temperature of a large volume influx quickly enough) and must be cooled back to 45°F within two hours. {WI-ATCP 60.2.4(b)}
• Grade B milk in milk cans is cooled to 50 °F (10 °C) within two hours of milking. Grade B farms cannot mix milk into cans from previous milking. {WI-ATCP 60.2.4(c)}
• The somatic cell count (SCC) of Grade A or B cow or sheep milk may not exceed 750,000 cells per mL, and the SCC of Grade A or B goat milk may not exceed 1,000,000 cells per mL. {WI-ATCP 60.15.4}
• The bacterial plate or loop count of Grade A milk may not exceed 100,000 per mL, while Grade B milk may not exceed 300,000 per mL. {WI-ATCP 60.15.2}
• A bacterial plate count test is required at least once a month. {WI-ATCP 60.18.3} If the bacterial count exceeds 100,000 per mL for Grade A or 300,000 per mL for grade B in 3 out of 5 tests, the license to sell milk is suspended. The license will be revoked immediately if the bacterial count ever exceeds 750,000 per mL. {WI-ATCP 60.18.6}