Web Summary Oxidation of lipids, fat-soluble vitamins and carotenoid pigments not only lowers the nutritive value of feed, it also creates off-flavors and off-odors and affects the perception of feed quality. This article explains how antioxidants can be effectively used to minimize oxidation in feeds. Stating that it is almost impossible to oxidation as raw materials are necessarily exposed to air anyway, the author outlines ways to to slow down the process. The first, and most important, is the removal of free radicals and the second is to remove metal ions. The removal of free radicals is accomplished by the use of antioxidants. The most effective antioxidants are organic compounds which possess a labile hydrogen atom which they can donate to the molecule at risk of autoxidation, thereby breaking the reaction chain. The most prevalent compounds available as antioxidants available to industry are: butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tertbutylhydroquinone (TBHQ), esters of gallic acid (e.g. propyl gallate, PG, dodecyl gallate, DG) and ethoxyquin (EQ). All of these compounds possess the labile H atom associated with a benzene ring. Tricarboxylic acids, such as citric or phosphoric acids essentially take the metal ions out of circulation. They work during the initiation stage of free radical development. However, it is virtually impossible to remove metal ions totally as susceptible raw materials are stored, pumped, conveyed, etc, through copper, steel or zinc-plated equipment. Citric acid and citrates are the best options as they are naturally-occurring, less corrosive and, therefore, safer to handle than phosphoric acid. While it is clear that some single antioxidants are more effective at preventing peroxide formation than others (BHA is better than BHT, which in turn appears better than EQ), synergism exists between the commonly available antioxidants. It is proven that a blend of various antioxidants offer much better control of the free radical generation than any single antioxidant at the same concentration, i.e. 1 + 1 = 3! This is utilized very effectively in the formulation of what are referred to as ‘cocktails’ of antioxidants available to the feed industry. Antioxidants of choice are the ‘cocktail’ blends which contain a safe chelating agent, (citric acid is the only one currently available). Such preparations accommodate for protection of a wider range of raw materials and variables than a single or ‘straight’ antioxidant compound. The formulation of antioxidants is not merely a random blending of component antioxidants but a careful balance borne out of experience. The rates of use are again a question of experience handling the susceptible materials concerned, their history and their autoxidation status. It must be re-iterated, that once autoxidation has begun it continues but can be brought under control and abated by efficient antioxidants. The earlier the treatment is applied the better the control. The article has 3 figures. Full Paper
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