Scott J. Eilert Excel Corporation

Publish Date: June 3, 2006

Postmortem metabolism of porcine muscle is more rapid than beef or lamb (Marsh et al. 1972). Metabolism of intramuscular glycogen plays the primary role in the conversion of muscle to meat and the expression of different quality attributes of fresh pork. The two most common quality concerns with fresh pork are pale, soft, and exudative (PSE) and dark, firm, and dry (DFD) lean, with PSE being much more economically important than DFD. Both are a result of postmortem glycogen metabolism. The level and extent of postmortem pH decline is glycogen dependent as anaerobic conversion of glycogen to lactic acid results in the achievement of an acceptable (or unacceptable) meat pH. The PSE condition occurs when intramuscular lactic acid (localized lactidosis) accumulates very rapidly (<1h) while the carcass temperature is still high. The initiation of glycolysis could be attributed to many things: 1) genetic predisposition (porcine stress syndrome); 2) elevated metabolism or if a pig is prone to a high excitability (Grandin, 1994); 3) pre-slaughter stress; and/or 4) combinations of all of these. Activation of the glycolytic system just prior to exsanguination leads to the production of heat which will elevate the pigs body temperature. Pearson (1987) wrote that the ultimate condition of pork muscle is influenced by skeletal muscle pH drop as a function of time, in vivo temperature patterns, carcass chilling rate, and the conditions at the onset of rigor mortis. The rate of postmortem pH decline is approximately three times faster in carcasses that ultimately produce PSE meat, regardless of presence or absence of the stress gene (Mitchell and Heffron, 1982). This rapid pH drop while the carcass temperature is above 37C leads to denaturation of myofibrillar proteins that bind water (Penny, 1969).

Publish Date: June 3, 2006

Enhanced pork is the process of adding non-meat ingredients to fresh pork to improve the eating quality of the final product where eating quality is defined as the juiciness, tenderness and flavor of pork. In adding these ingredients, the color and the shelf-life of the final product may be impacted either negatively or positively. Shelf-life of pork can be affected either by the microbial levels in the final product or by color or flavor deterioration and the addition of non-meat ingredients may influence different aspects of shelf-life. The major ingredients used in enhanced pork are water, sodium phosphates, salt, sodium lactate, potassium lactate, sodium diacetate and varying flavoring agents of which lemon juice has been singled out for use in some products. What do these non-meat ingredients do for or in the final product? A summary of each ingredients functionality is presented below. However, when some ingredients are used together, the combined effects may provide greater positive or negative effects for different quality attributes. These effects are discussed in the paper, but are not identified below.