Lipid oxidation causes off- and rancid flavors that are serious problems during storage of fresh meat and precooked meat products. The cooking processing causes development of characteristic flavor of cooked meat from the Maillard reaction and the degradation of lipids (Mottram, 1998). Tims and Watts (1958) were the first researchers to describe warmed-over flavor (WOF) as the undesirable flavor of cooked meat during short-term refrigerated storage. The WOF is highly related to lipid oxidation (Love, 1983), and is one of the primary off-flavors in precooked stored beef that is a nitrite-free meat product. WOF makes it difficult to introduce precooked beef products as convenience foods into the market place.
Recently, many researchers have indicated a lot of reactions, including lipid oxidation, involved in the development of undesirable flavor in meat (Spanier et al., 1988; St. Angelo et al., 1988). Meat flavor deterioration (MFD) is currently used to describe this undesirable flavor (Spanier et al., 1988). However, autoxidation, which is a continuous free radical chain reaction (Pearson et al., 1983), is still hypothesized as the major reaction responsible for WOF of precooked roast beef.
A lot of processes damage the structure of meat products that would contribute to lipid oxidation and WOF in precooked beef. The ES causes contraction of muscle and improves the tenderization process. Dutson et al. (1980) summarized the possible mechanisms of ES to improve meat tenderness as accelerating postmortem glycolysis and rigor mortis, reducing pH conditions, increasing glycolytic activity, and promoting release of lysosomal enzymes. Disruption of muscle structures could promote lipid oxidation and increase the off-flavor problem in meat. However, there is little research regarding the relationship of electrical stimulation and lipid oxidation or off-flavor problems of precooked meat products.
The major purposes of this study were to evaluate the rate of lipid oxidation or warmed-over flavor that could be affected by electrical stimulation of precooked roast beef after refrigerated storage and to seek the optimum quality of precooked roast beef from the lipid oxidation and warmed-over flavor standpoint.