Vitamin effectiveness, heat stability

In the last 20 years much attention has been paid to the determination of vitamins in foodstuffs due to their nutritional implications and the need for an adequate quality control of food products. Vitamin analysis in these matrices is difficult due to the high variability in their composition and the great number of components, which implies the risk of interference and the low vitamin content. Additional problems are the existence of different chemical compounds with vitamin effects and their stability influenced by light, heat, oxygen, or pH conditions. The development of new analytical techniques has led in recent years to analytical methods that are more rapid, accurate, and sensitive. 

The occurrence of heat- and chemical-induced transformations of tryptophan and the nutritional and toxicologic consequences suggest a need for additional research to define possible approaches to prevent or minimize the formation of antinutritional and toxic tryptophan condensation and oxidation products in foods. The possible beneficial effects of antioxidants such as vitamins C and E, carotenes, flavonoids, indole derivatives, selenium compounds, and sulfur amino acids in enhancing the stability of tryptophan in foods need to be investigated. 

The relative merits of vitamin E supplementation for delaying warmed-over flavor (WOF) in muscle foods have been investigated. Webb et al. (1972) studied the effects of a-tocopheryl acetate supplementation on oxidative stability and flavor of broiler parts, which were pre-cooked, frozen and then re-heated. The supplementation of broilers with 11 or 22 lU a-tocopheryl acetate for 36 days resulted in pre-cooked meat with lower TEA values than that from non-supplemented birds. However, a sensory panel could not detect any treatment difference in flavor assessment. The panel did, however, corroborate a positive effect demonstrated... 

Stabilized whole rice bran is rich in protein, lipids, dietary fiber, vitamins, essential minerals, and important nutraceuticals such as phospholipids, choline, inositol, phytosterols, tocols, and tocotrienols. Tocols and tocotrienols are potent antioxidants that reduce the risk of cancers and CVD. The whole rice bran is stabUized in order to denature lipases that cause oxidative rancidity and to protect the intrinsic nutraceutical compounds. The stabilization of the rice bran is usually done by applying heat in an extrnder. The preservation of the oryzanol is of utmost importance because this compound is very effective in promoting cardiovascular health (Hoffpauer 2005). 

Vitamin A is soluble in oils and fats. The vitamin is not easily destroyed by heat but is readily oxidized. Preparations must, therefore, be protected from oxidation and are prepared in an atmosphere of carbon dioxide or nitrogen. In the absence of air, vitamin A is unaltered at moderate temperatures. The creams and lotions must therefore be free of oxidases, and perfumes must be free of peroxides. The addition of antioxidants is useful to maintain stability. Pure vitamin E is effective as an antioxidant in lipid solutions of vitamin A. 

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