Accelerated shelf-life testing for oxidative rancidity in foods-A review

Accelerated shelf-life test (ASLT) methods for processed foods are receiving greater attention. In this paper, current ASLT methodology for fatty foods is reviewed with particular emphasis on the testing of antioxidant effectiveness. In all the classical ASLT methods temperature is the dominant acceleration factor used. Its effect on the rate of lipid oxidation is best analysed in terms of the overall activation energy, E_A for liṕid oxidation. It is an inherent assumption in these tests that the E_A is the same in both the absence and the presence of antioxidants. An analysis of the rate equations for the uninhibited versus the inhibited oxidation indicates, however, that the E_A may be considerably higher in the latter case. ASLT data collected at 60-65°C bear this out and show that such tests lead to sizeable, but predictable, underestimation of the shelf-life extension by antioxidants for room temperature. In comparison, data collected at 98-100°C are much less predictable. At this higher temperature E_A-variations are generally smaller and both under- and overestimation of shelf-life is found. In addition, the use of such high temperatures for complex foods is ruled out because of secondary reactions of other food components. Other acceleration parameters for shelf-life used are the oxygen pressure, reactant contact and the addition of catalysts. The effect of these factors, although much less important than that of temperature, is discussed.