Most foods have some inherent oxidation resistance due to the presence of naturally occurring antioxidant compounds, however this resistance will eventually diminish and the role of antioxidants as additives to enhance shelf life becomes clear.
The time till the onset of oxidation will vary with the degree of unsaturation of the fat, temperature, light, degree of exposure to oxygen during processing and packaging and the presence of copper and zinc which catalyse the process of oxidative rancidity.
The objective of antioxidant performance testing is to
- Benchmark the performance of different antioxidants at different dose rates to compare efficacy with due consideration to the cost of the protection system.
- Ultimately provide an indication of shelf life at “in use” or ambient storage conditions.
There are a variety of techniques we have available at Vitablend to measure performance. Many of these techniques rely on elevated temperatures so that results may be obtained within a reasonable time frame. Results obtained from studies carried out at elevated temperatures do in fact tend to underestimate real life performance, so some careful interpretation is required. This is because at higher temperatures alternative reaction pathways with higher activation energies may come into play, phase changes may occur in the sample and in addition, thermal degradation and volatile loss of the antioxidant itself is a possibility.
Of course rarely can we afford the luxury of letting a sample sit on the shelf for 6-12 months so these methods do prove extremely useful despite their limitations.
Links to:
Rancimat
Oxipres
Classical Test