The combined effect of tocopherols, L-ascorbyl palmitate and L-ascorbic acid on the development of warmed-over flavour in cooked, minced turkey

The combined effect of a natural mixture of tocopherols (extracted from soybean oil), L-ascorbyl palmitate and L-ascorbic acid on oxidation of cooked, minced turkey meat, measured as 2-thiobarbituric acid reactive substances (TBARS) after reheating, was studied for three concentrations of each additive in a total of 19 combinations plus two control batches, each at two different oxygen pressures (21 and 1% O2), during 9 days of chilled storage (5 °C), and compared with an accelerated oxygen-bomb test at 90 °C. For initial screening of antioxidative activity, the latter test has been found to be a valuable analytical tool. The effect of the additives from the storage experiment could be measured by two parameters; (i) M, the maximal level of TBARS, and (ii) r, a first-order rate constant for development of TBARS. Tocopherols reduced M most significantly, L-ascorbyl palmitate to a lesser degree, and L-ascorbic acid increased M, in effect acting as a prooxidant. For 21% O2 packaging, the effect on M of the three additives and their concentrations was multiplicative and could be quantified by a protection factor, P(i-x,j-y,k-z), obtained by multiplication of the relative protection obtained by each additive at the lowest concentration used. In contrast to M, r was reduced more by L-ascorbyl palmitate than by tocopherols, while L-ascorbic acid had only a small effect on r. The combined use of tocopherols and L-ascorbyl palmitate in cooked, minced turkey meat products, optimises oxidative protection as a result of indirect synergism, i.e. tocopherols reduced mainly the maximum level of oxidation, while L-ascorbyl palmitate reduced the rate at which the maximum level of oxidation is approached.