Stabilisation of frying oils with natural antioxidative components

Abstract

Deep-fat frying is a complex, thermal chemical process that produces fried foods with desirable colour, appearance, flavour, and texture. Normally, less stable liquid oils are hydrogenated to enhance their oxidative stability for deep-fat frying purposes. However, considerable amounts of trans and positional isomer fatty acids are formed during hydrogenation, which are nutritionally undesirable. The stability of frying oils is sometimes increased by careful blending of polyunsaturated oils with more saturated oils. The natural way of improving oxidative and flavour stability of frying oils and fats is by adding natural antioxidative components and precursors present in the plant kingdom, such as 'virgin' olive oil, sesame seed oil (SSO) and rice bran oil (RBO). A variety of natural antioxidative components, present in these oils, comprise tocopherols and tocotrienols, special sterols e.g. Δ5-avenasterol and sterol esters, squalene, sesamolin, sesamol, sesaminol and related compounds, polyphenols, etc. Various antioxidative components present in SSO and RBO are largely retained in Good-Fry® Constituents (GFC), manufactured according to European patent as well as USA and worldwide patent applications pending (Silkeberg and Kochhar, 2000) Generally, palm olein, palm oil, partly hydrogenated rapeseed oil/soybean oil and/or their blends are mainly used by the frying industry for the production of a variety of snack products and pre-fried convenience foods. Several new frying oils with good oxidative stability, which do not require hydrogenation, are now commercially available on the European market, for example high-oleic sunflower seed oil stabilised with GFC. The results showed that the addition of 6% GFC to unhydrogenated rapeseed provided crisps, produced on industrial scale, with stability similar to those fried in palm olein without GFC. Shelf life of crisps fried in soybean oil, iodine value 130, was substantially increased by addition of 5% GFC. The Good-Fry® Constituents can also be added, with advantages of flavour stability of fried snacks, to oils such as palm oil or palm olein at lower levels of 2%. It is forecasted, to meet an ever-growing consumer demand of 'healthier' snack products, the usage of natural antioxidative components in stabilising frying oils rich in monounsaturated fatty acids (MUFAs) will grow tremendously.