Alpha-tocopherol is the principal free radical scavenger in biological membranes, and the tocopherol isomer with the greatest vitamin E activity. The naturally-occurring isomer of a-tocopherol is d-a-tocopherol, which is found only in the lipophilic portions of green plants and oilseeds. Synthetic vitamin E is a mixture of eight isomers of a-tocopherol, and is the most common form of supplemental vitamin E in animal diets. A variety of reproductive and muscular diseases occur when animals are vitamin E-deficient. Levels of supplemental vitamin E required to alleviate these symptoms are relatively low.
Fresh product color and product flavor are important components of meat quality. The desired color for fresh beef, lamb and pork is a reddish hue, which is due to the oxygenated form of the primary fresh meat pigment, myoglobin. Myoglobin is a heme protein, which means that a portion of this molecule contains an iron molecule. The iron molecule, which is normally in the ferrous state, can become oxidized to the ferric state. When this occurs, myoglobin exists as metmyoglobin and undesirable brown and gray hues are observed. Consumers avoid purchasing products which are discolored in this manner.
Fatty acids are principal contributors to product flavor. Undesirable flavors are caused by oxidized fatty acids, and those fatty acids which possess double bonds are susceptible to oxidation. Fatty acids with multiple double bonds are commonly found as components of biological membranes.
It had been known that fatty acid oxidation in meat products derived from nonruminant species could be delayed by dietary supplementation of vitamin E. Also, it was known that there is a positive correlation between fatty acid oxidation and myoglobin oxidation, but a dietary strategy for delaying myoglobin oxidation was not recognized.
The key to extending color display life and delaying fatty acid oxidation in fresh beef products is long-term dietary supplementation of vitamin E at an elevated level. The benefits of vitamin E supplementation are not as marked in fresh lamb and pork as in beef. Dose and duration effects of vitamin E supplementation on quality of fresh, frozen and cooked beef will be discussed. A proposed mechanism of action, market economic implications, and current implementation of this technology will be reviewed.