By Erwin Waters
The final internal temperature of a meat product, whether it be a sausage, ham or any processed meat, will determine the cooking loss, shelf life and the palatability of the product. All of these factors relate to profit and quality.
Final internal temperatures of 161.6 degrees F to 172.4 degrees F are recommended. The importance of getting all of the product to these recommended temperatures is evident. One undercooked frankfurter in a package can spoil the others, and overcooking will result in additional cooking losses.
Avoiding variations
To avoid variations in the internal temperatures, the following rules must be observed:
-- Variations in product dimensions.
The dimensions of the product will have a major effect on the variations in internal temperatures.
Products must be assorted prior to cooking. Hams in cooking containers of the same height and width, or products in casings of the same diameter, no matter how long, can be cooked at the same time. The product's length has no effect on the heat transfer to its center.
Solid muscle pieces, which are difficult to assort into exact dimensional sizes, need to be separated into sizes where the shortest dimension does not vary more than 1 inch (2.5 centimeters) at the thickest portion of the muscle.
To insure that all of the products in the batch attain the desired internal temperature with minimum variations, the water temperature (in a water bath system or the wet bulb temperature in an oven system) should not be more than 41 degrees F higher than the desired final core temperature in the last cooking cycle.
A holding period of 10 minutes to 30 minutes, depending on the dimension of the product (at a water or wet bulb temperature not exceeding 35.6 degrees F more than the internal temperature), is recommended.
-- Insertion of temperature probes.
Incorrect insertion of the temperature probe, which controls or indicates the internal temperature of the product, can result in undercooked batches, and large variations of internal temperatures. For all products-whether hams in cooking molds, products in casings or solid muscle items-the probe needs to be inserted into the center of the product parallel to the long diminution of the product.
Only the tip of the probe measured the temperature, and it is difficult to determine if the tip of the probe is in the center when inserting the probe into the side of a product.
-- Loading of product in the cooking equipment.
The energy contained in the cooking medium, whether water, air or steam, must make contact with total surfaces of the product.
Under no circumstance should products touch.
Even loading patterns, with sufficient space between products, is of the utmost importance in avoiding variations in internal temperatures.
In a water-cooking system, all of the products must be below the surface of the water.
-- Circulation of heating medium. Even if the aforementioned requirements are observed, the heating medium must have a sufficient flow force to properly circulate around all of the surfaces of the products.
Circulation a must
Poor circulation will result in stratification and stagnation of the cooking medium, resulting in differing temperatures at different points inside the cooking equipment.
The velocity of the heating medium passing over the surfaces of the product will determine the amount of energy that the heating medium is able to transfer to the product. The higher the velocity, the greater the energy transfer. In water-cooking systems, bubbling compressed air or steam through the water in the tank is not the answer.
The air or steam bubbles breaking through the surface carry away energy, and make it appear as if the water is in circulation.
In actuality, inside the tank that water is not moving. The only positive method is with the use of a pumped water circulation system.
In ovens, the hot air or steam must have sufficient velocity to force itself through the spaces between the products and be evenly distributed inside the oven chamber.
The design and process functions of the oven must conform to these requirements.
It is much easier to move moist, hot air or steam than dry, hot air. This is one of the reasons that a steam finishing cycle at the end of a processing program should be used.
Erwin Waters is senior consultant with Cook and Thurber LLC Food Industry Consultant Management Group. He can be reached at 407/391-2290 or 608/831-6958. His fax numbers are 407/391-1840 and 608/831-7101.