Lipid peroxidation is the cause of rancidity in oils and fatty foods are therefore prone to rancidity. Lipid peroxidation occurs when the fatty acids in food are chemically oxidised through loss of electrons, and this can often cause the generation of free radical chain reactions that induce further lipid peroxidation. This process is chemically similar to the oxidation that occurs to lipid components in the tissues of living organisms. Living systems use antioxidants to protect from the damaging effects of lipid peroxidation, and the addition of antioxidants to foods has a similar protective effect. The use of antioxidants in foods manufacture is therefore an effective way to increase shelf times and to maintain the freshness of foods that contain components that are prone to oxidation, particularly lipids. Fish contains a high proportion of long chain highly polyunsaturated fatty acids, and these are particularly prone to oxidation. Deterioration of fish, even if frozen is therefore a problem that prevents the long term storage of fatty fish.
The use of antioxidants as food preservatives is not a recent phenomenon. Artificial antioxidants such as butylated hydroxytoluene (BHT) is a relatively tried and tested means of food preservation. However, more recently interest in the use of foods as antioxidant preservatives has increased. One such antioxidant, green tea, has shown promise as a useful food preservative in the protection of long chain polyunsaturated fatty acids in fish. For example in one study1. researchers investigated the effects of green tea as a preservative in mackerel fillets. The fillets were frozen in commercial freezers with and without green tea extracts, with mackerel frozen at -80 °C acting as a control. The results of the study showed that the green tea extract was effective at preventing lipid peroxidation in the fish at 250 ppm, but was less effective at the higher concentration of 500 ppm. Green tea may therefore hold useful properties as an antioxidant in food preservation, but dosage appears to play a role in determining effectiveness.
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