Alpha-tocopherol
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It has been found that yeast ethanol tolerance is significantly improved when accompanied by vitamin E administration (50-100ppm).[1]
Malt contains some fat-soluble vitamin precursors, of which the tocopherols (vitamin E) might be significant, but it is unclear if any of these reach the hopped wort.[2]
Vitamin E (α-tocopherol) is also a monophenolic compound present in barley and malt (Bamforth et al., 1993) which can quench free radicals. Their antioxidant activity is based mainly on the tocopherol-tocopheril quinone redox system (Randhir et al., 2008). The vitamin E content of cereal grains is influenced by plant genetics and is adversely affected by too much rain and humidity during harvest (Ball, 2006).[3] Content of vitamin E in barley ranged from 34.96 to 39.2 mg/kg dry weight and these results are in compliance to Hall (2001). The current research showed that vitamin E content increased during barley malting by 38% comparing to unprocessed barley.
Among cereal grains, barley contains relatively high levels of tocols. They are concentrated in the bran, and the level is not affected by malting. During mashing, most of the tocols are discarded with the spent grain.[4]
Vitamin E is one of the nonenzymatic antioxidant systems in living organisms. It is characterized by a “phytyl tail” (a C16H33 group) that enhances the solubility in lipid membranes but does not affect the antioxidant activity.[5]
Vitamin E (a-tocopherol) is also a monophenolic compound present in barley and malt 15 which can quench free radicals. Quenching of 1 O2 by tocopherol homologues decreases in the order a-�b->�->gtocopherol and depends on the free OH group at position 6 of the chromane ring.16 Their antioxidant activity was based mainly on the tocopherol±tocopheryl quinone redox system.3[6]
Tocopherols are monophenolic antioxidants known to stabilise most vegetables oils. The DPPH. method did not allow us to distinguish antioxidant activities of a-, d- and g-tocopherol. Only the inhibition of lipoxygenase activity allowed us to discriminate signi®cantly the three structures of tocopherol. gTocopherol appeared to be the most potent inhibitor, followed by d- and then a-tocopherol. Using the bcarotene linoleate model system, tocopherols were the most antioxidant structures among the pure compounds tested. A study by Dziezak37 showed that the antioxidant activity of tocopherols decreases from d- to a-tocopherol.[6]
Alpha-tocopherol is particularly effective as an antioxidant at higher temperatures.[7]
Vitamin E (a-tocopherol) can react with the lipid-peroxy radicals (Fig. 2) to produce radical forms of itself that are insufficiently reactive to abstract H• themselves. They are, therefore, highly efficient chain terminators. Vitamin E is fat-soluble and is thus inapplicable for use in beer, but this substance is a component of barley and malt (68) and may function in grain and during germination to suppress oxidative deterioration. It is also conceivable that related molecules, with similar effects, exist in barley (for example, resorcinolic lipids) (70). The vitamin E radical can be reduced back to vitamin E by ascorbate.[8]
Vitamin E is not useful as an additive after fermentation to help avoid oxidation, probably due to its low solubility.[9]
- Bamforth, C.W., Muller, R.E., Walker, M.D. (1993) Oxygen and oxygen radicals in malting and brewing: a review. Journal of the Science of Food and Agriculture, 51, pp. 79–88.
- Randhir, R., Kwon, Y.I., Shetty, K. (2008) Effect of thermal processing on phenolics, antioxidant activity and health-relevant functionality of selected grain sprouts and seedlings. Innovative Food Science and Emerging Technologies, 9, pp. 355–364.
- Ball G.F.M. (2006) Vitamins in Foods: analysis, bioavailability, and stability. In: Food science and technology. CRC Press, Taylor & Francis Group, USA, pp. 121–125.
- https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2007.tb00252.x antioxidant effects in beer
- http://phd.lib.uni-corvinus.hu/332/3/nagymate_emese_ten.pdf
- https://www.tandfonline.com/doi/abs/10.1080/00015128509435767
- https://www.researchgate.net/publication/226468368_Effects_of_Temperature_and_UV_Light_on_Degradation_of_-Tocopherol_in_Free_and_Dissolved_Form
- https://pubs.acs.org/doi/10.1021/ja01285a508
References[edit]
- ↑ Zhang, S., et al. "The influence of vitamin E supplementation on yeast fermentation." J. Inst. Brew. 2016; 122: 289–292.
- ↑ Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
- ↑ Dabina-Bicka I, Karklina D, Kruma Z. Polyphenols and vitamin E as potential antioxidants in barley and malt. Conference Proceedings of the 6th Baltic Conference on Food Science and Technology FOODBALT-2011; May 5–6, 2011; Jelgava, Latvia.
- ↑ https://www.cerealsgrains.org/publications/cc/backissues/1994/Documents/71_42.pdf
- ↑ Leopoldini M, Marino T, Russo N, Toscano M. Antioxidant properties of phenolic compounds: H-atom versus electron transfer mechanism. J Phys Chem A. 2004;108(22):4916–4922.
- ↑ a b Goupy P, Hugues M, Boivin P, Amiot MJ. Antioxidant composition and activity of barley (Hordeum vulgare) and malt extracts and of isolated phenolic compounds. J Sci Food Agric. 1999;79(12):1625–1634.
- ↑ Kikuzaki H, Hisamoto M, Hirose K, Akiyama K, Taniguchi H. Antioxidant properties of ferulic acid and its related compounds. J Agric Food Chem. 2002;50(7):2161–2168.
- ↑ Bamforth CW, Muller RE, Walker MD. Oxygen and oxygen radicals in malting and brewing: a review. J Am Soc Brew Chem. 1993;51(3):79–88.
- ↑ Brezová V, Polovka M, Staško A. The influence of additives on beer stability investigated by EPR spectroscopy. Spectrochimica Acta Part A. 2002;58(6):1279–1291.