Explain how minimum internal cooking temperatures are established.

Minimum internal cooking temperatures are based on a number of factors. These include: (1) the anticipated level of pathogenic bacteria in the raw product, (2) the initial temperature of the food, and (3) the food's bulk, which affects the time to achieve the needed internal product temperature. Other factors to be considered include post-cooking heat rise and the time the food must be held at a specified internal temperature.

To kill pathogens, food must be held at a sufficient temperature for the specified time. There are a variety of time/temperature combinations for specific foods that can be equally effective. For example, when cooking a beef roast, the microbial lethality achieved at 112 minutes after it has reached 130°F is the same lethality attained as if it were cooked for 4 minutes after it has reached 145°F. The microbial lethality using these criteria will eliminate over 99.9999% of the Salmonella that is on the product.

Cooking requirements are based in part on the biology of pathogens. The thermal destruction of a microorganism is determined by its ability to survive heat. Different species of microorganisms have different susceptibilities to heat. Also, the growing stage of a species, such as the vegetative cell of bacteria, is less resistant than is the spore form of a bacterium.

Food characteristics also affect the lethality of cooking temperatures. Heat penetrates into different foods at different rates. High fat content in food reduces the effective lethality of heat. High humidity within the cooking vessel as well as the moisture content of food aid thermal destruction.

Heating a large roast too quickly with a high oven temperature may char or dry the outside, creating a layer of insulation that shields the inside from efficient heat penetration. To kill all pathogens in food, cooking must bring all parts of the food up to the required temperatures for the correct length of time.