What is Vat Pasteurization?
Pasteurization is the destruction of all disease producing bacteria, as well as 90-99 percent of all other bacteria that may affect product quality. Because of this, pasteurization is the most important function of a milk plant. Vat pasteurization, also known as batch pasteurization or the holding method, heats every particle of milk or cream in properly designed and operated equipment, at 145°F (63°C) for 30 minutes*. If the fat content of the milk product is 10 percent or greater, or a total solids of 18% or greater, or if it contains added sweeteners, the specified temperature shall be increased by 5°F (3°C).
How Does Vat Pasteurization Work?
In vat pasteurization, it is necessary to heat the milk product to 145°F in the vat. The presence of both butter granules and cream plug are possible in milk and cream. Agitation is necessary to achieve the proper consistency and texture as well as rapid, even heating. Incorrect agitation will cause churning.
Finding the right balance of heating and agitation is important to efficiently operate a vat pasteurizer. If the heating temperatures are too low, the milk product temperature will not raise quick enough. If heating temperatures are too high, the milk product may “cook on” the heating surface. The speed of heating is affected by the ability of your agitator to keep the product moving to, and away from, the heating surface. However, simply speeding up your agitator will not necessarily give you the desired result. Agitators are designed for certain speeds and highly efficient agitators may require high heating water temperatures. Failure to balance the heating surface with your agitation type and speed can result in improper pasteurization.
During the holding period, the vat must remain closed to prevent cooling from occurring during pasteurization. Vats should have an airspace heater to keep the air above the product at or above 145°F. Airspace heaters also ensure the pasteurization of milk droplets that are splashed on the sides of the vat and condensate on the inside of the vat cover. The bottom and sides of the vat must be insulated or jacketed to maintain proper temperatures during the holding period.
Do I Need Vat Pasteurization?
Processing plants that handle less than 1000 gallons daily may use the pasteurizing vat as the storage tank. Standardization and the adding of vitamin concentrates can be done in the vat pasteurizer before heating.
Vat pasteurization has to be done at a high temperature for a long period of time. It is also the lowest cost option for pasteurization. Because of the temperature, time and cost, it is often used in smaller plants or for smaller batches.
*Standards from the Grade “A” Pasteurized Milk Ordinance 2013, provided by the U.S. Department of Health and Human Services, Public Health Service and Food and Drug Administration.