Ascorbic acid

From Brewing Forward
This page is in progress
Please check back later for additional changes
Ascorbic acid molecular structure
Molecular structure of ascorbic acid

Ascorbic acid (AA), also called Vitamin C, is an organic acid that is known for its effect as an antioxidant.[1]

Sources of ascorbic acid[edit]

  • Malt - Malt contains trace amounts of ascorbic acid, around 3.5 mg/kg.[2] While not present in barley, it's formed during malting, and only partly survives kilning.[3][4]
  • Additive - Ascorbic acid powder can be used as an additive to help prevent oxidation.

Products:
Ascorbic acid powder (MoreBeer) - 1 oz, 2 oz, 1 lb, 5 lb, 55 lb
Pure (via Amazon) - 1 lb food grade

Effects[edit]

Ascorbic acid is well-known to have antioxidant effects.[5] It retards browning in dough at 1.5 g/kg barley.

AA (1 mM) helps prevent barley lipid oxidation.[6]

Vitamin C (ascorbic acid) is a well-known antioxidant. The main function of vitamin C as a radical producer is to provide the regenerating system for tocopherol (Dewick, 2006). Ascorbic acid can act as a synergist with tocopherol by regenerating or restoring their antioxidant properties. (Niki, 1987). Ascorbic acid and its esterified derivatives may also function as oxygen scavengers. Vitamin C declines in the heating process (Pokorny, 2001).[2]

Best known of the nonenzymatic protectants is ascorbic acid, which undergoes the redox interchanges shown in Figure 3. The electrons are lost in oxidation of the ascorbate, providing reducing equivalents that can make ascorbate a powerful antioxidant in food systems. Semidehydroascorbic acid, for the most part, disproportionates (eq. 16) as follows: 2 semidehydroascorbate -> ascorbate +.dehydroascorbate (16). Ascorbate reacts rapidly with superoxide and perhydroxyl and even more rapidly with hydroxyl to yield the semialdehyde. The redox chemistry of ascorbic acid is highly complex. Thus, copper-induced oxidation of ascorbate produces peroxide and hydroxyl and ascorbic-copper mixtures inactivate many enzymes. For example, papain will be inactivated by this couple if the palliatives are introduced into beer simultaneously (28). Ascorbate can reduce Fe(III) to Fe(II) and, in the presence of H2O2, will actually stimulate the formation of hydroxyl (36). Ascorbate is a natural component of barley and malt (71). In various plant tissues (though not yet in barley seeds), the enzyme dehydroascorbate reductase has been shown to restore ascorbate to its reduced form with the intermediacy of glutathione (GSH), the latter being oxidized to its dithiol state (GSSG) (eq. 17).[7]

ascorbic acid remarkably protects tannoids from oxidation (tested 50mg ascorbate + 2.5g malt + 50mL H2O), even with high-oxygen brewing at that concentration.[8]

AA help prevent loss of phenolic compounds in wort by preventing their oxidation.[9]

Several phenolic compounds in wort and beer are more potent antioxidants than ascorbic acid (vitamin C).[10][11]

The reversibly oxidized form of ascorbic acid (called dehydroascorbic acid) undergoes an irreversible change in aqueous solution above pH 4 at ordinary temperatures. The product of this change (diketogulonic acid?) is a stronger acid than dehydroascorbic acid, and is a more powerful reducing agent than ascorbic acid itself. The rates of appearance of all of these manifestations of the irreversible change in dehydroascorbic acid exhibit the same dependence on the hydrogen ion concentration. They are also all independent of the presence of air or oxidizing agents. The irreversible change is therefore not an oxidation. It is also independent of the oxidizing agent used to form dehydroascorbic acid.[12]

Ascorbic acid can be made to take up the equivalent of at least 3 atoms of oxygen in the course of its oxidation, in three separate steps, depending on pH.[12]

Ascorbic acid has been described to prevent caffeic acid oxidation at pH 7.0 (Cilliers & Singleton, 1990) and to regenerate caffeic acid from phenoxyl radical.[13] The presence of ascorbic acid (1%) either alone or together with EDTA completely prevented caffeic acid degradation during alkaline hydrolysis of bound phenolics with NaOH. the loss of chlorogenic acid during homogenization in the absence of ascorbic acid and EDTA is unlikely to be due to spontaneous autoxidation. More likely, the loss is due to enzymatic oxidation, occurring in fresh fruits by the action of polyphenol oxidase (Coseteng & Lee, 1987; Matheis, 1987). The ability of ascorbic acid to reduce back the phenoxyl radical intermediate produced during oxidation of phenolic compounds is probably responsible for the observed effect. Such a mechanism has been already demonstrated for the phenoxyl radical intermediate derived from caffeic acid oxidation, which is reduced back to caffeic acid by ascorbate.

Adding AA had little impact on the specific gravity of the recovered wort. Although the pH of the mash was lowered by AA initially, it rose progressively during mashing. The pH of the control mash decreased. The addition of AA led to markedly higher levels of polyphenol and thiols being measurable in the wort. This result is consistent with reports of AA functioning: AAO consumed oxygen, which was used to oxidize polyphenols and thiols. There is generally also a lower color observed in small‐scale laboratory mashes (with the exception of the 60 min measurement, which was perhaps a spuriously high value). This result is regarded as consistent with less polyphenol oxidation in the mashes in view of the extremely high affinity of AAO II for AA and oxygen, coupled with its thermotolerance. There are some consequences to oxygen ingress in a mash, including possibilities of oxidation of unsaturated fatty acids, cross‐linking of thiol‐rich proteins, and oxidation of polyphenols with the production of color [12]. The addition of AA to mashes is expected to engender diminution in such effects. Bamforth et al. [4] anticipated increased measurable levels of such groups in mashes containing AA. An increased level of polyphenol surviving into wort and a decrease in the amount of color produced would be expected.[4] In short: Addition of ascorbic acid to mashes results in the survival of higher levels of polyphenol and thiols into wort and reduced color in that wort, commensurate with AAO preferentially consuming oxygen. Consequently, in adding ascorbic acid, oxygen is less available for other reactions, such as thiol oxidation and polyphenol oxidation in mashes.

Ascorbic acid used as a beer additive can help compensate for some level of oxidation, but can also catalyze oxidation reactions if the amount is insufficient, making things worse instead of better.[14]

Ascorbic acid has a dual role in coloration reactions (protective vs. enhancing).[15]

It is important to note that sulfur dioxide additions do not bind the oxygen and, therefore, do not prevent the first step in this coupled oxidation. Some winemakers use ascorbic acid, or vitamin C, as an antioxidant. Ascorbic acid sometimes protects the fruit and acts as an antioxidant, while at other times it can act as a proto-oxidant, or oxidative promoter.[16]

The two roles of ascorbic acid are mainly the result of concentration and the presence of adequate sulfur dioxide. As illustrated below, when ascorbic acid is added to wine, it binds oxygen rapidly to form two reaction products, dehydroascorbate and hydrogen peroxide. If there is not enough ascorbic acid maintained to react with the oxygen, oxidative degradation, including coupled oxidation, can occur. If there is not adequate sulfur dioxide maintained to bind with the hydrogen peroxide formed by the ascorbic acid, wine oxidation can occur.[16]

Therefore, the keys to optimizing the performance of ascorbic acid as an antioxidant are to maintain a concentration of about 50 mg/L, and to have adequate sulfur dioxide. The use of ascorbic acid involves the following considerations:[16]

  • Reaction between ascorbic acid and oxygen much more rapid than SO2
  • SO2 does not directly react with oxygen, but mainly with reaction products, such as H2O2
  • Optimum levels of ascorbic acid (50 mg/L or more) and more SO2 can prolong the antioxidant phase of ascorbic acid.
  • For example: If 100 mg/L ascorbic acid in wine reacts completely with oxygen, 62 mg/L SO2 is required to react with the ascorbic acid oxidation product

The possible use of ascorbic acid should be determined based on the assessment of white wine longevity and oxidation potential. This addition compound may have a place in the production of some delicate, low phenol white wines.

ASC participates in the initiation of the radical reactions in the beer samples, and so ascorbic acid works as a prooxidant in the degradation of the beer. Consequently, adding ascorbic acid to conventionally-brewed beer may not be desired.[17]

Addition of sodium ascorbate accelerated the rate of formation of spin adducts, which demonstrates that it acts as a prooxidant during the oxidation of (conventionally-brewed and filtered) beer[18]

Ascorbic acid can increase the potential for wine oxidation if adequate sulfite is not present.[19]

Reducing agents must be coupled to the oxidation process in beer in order to recycle the transition metal ions through their lower, oxygen-active redox states. Ascorbic acid has the ability to perform this role during the Fe-catalyzed oxidation of ethanol in model reactions.[20]

Other effects:

  • Inhibition of beta-amylase - The structure of ascorbic acid (in its reduced form) strongly inhibits the action of malt beta-amylase,[21] which could possibly adversely affect starch degradation during mashing. This is due to its dienol structure and not its antioxidant properties. The inhibition is greatly increased in the presence of copper. It's possible that sulfite prevents the inhibition by an unknown mechanism.
  • Inhibition of alpha-amylase - The oxidized form of ascorbic acid inhibits the action of alpha amylase,[22] which could possibly have a negative effect on starch degradation during mashing.
  • Chlorine neutralization - AA can be used to remove chlorine compounds from municipal tap water, but it is not the best option for this purpose because the result of the reaction is oxidized ascorbic acid, which is a powerful oxidant and can potentially damage the wort.[23]
  • Removal of volatile sulfur compounds (VSCs) - AA helps to remove hydrogen sulfide and other VSCs (especially the stubborn disulfide compounds),[12] facilitating reactions with copper. See Hydrogen sulfide.
  • Sulfite testing interference - AA can cause falsely elevated sulfite measurements for certain methods of SO2 testing, because it reacts with iodine.[citation needed]
  • Stainless steel corrosion - At low concentration, ascorbic acid helps prevent corrosion of stainless steel, but at higher concentration it causes corrosion.[24][25][26]

Usage for beer production[edit]

Ascorbic acid added during mashing can reduce lautering time due to its antioxidant effect.[27]

We can demonstrate the very real benefit of ascorbate additions to a mash in terms of protecting against oxidation[28] Cites . Kanauchi, M.; Simon, K.J. and Bamforth, C.W.: Ascorbic acid oxidase in barley and malt and its possible role during mashing. Journal of the American Society of Brewing Chemists, 72 (2014), pp. 30-35.

The addition of ascorbate to mashes can preferentially scavenge the oxygen and make for less thiol oxidation, less colour and higher polyphenol levels in the wort.[29]

Often sulfur dioxide is used in combination with ascorbic acid, since the latter can efficiently scavenge oxygen before reaction of oxygen with phenolic compounds.[15] If ascorbic acid is used without sulfur dioxide then the hydrogen peroxide and dehydroascorbic acid degradation products can lead to the formation of spoilage pigments upon the near depletion of ascorbic acid.

AA may be added at packaging of beer or wine in combination with sulfite.[30] Suggested dosage is 0.02-0.08 mg/L (ppm).

The shelf life of AA is generally at least 1-2 years.[31][32]

See also[edit]

Potential sources[edit]

References[edit]

  1. ↑ White, C. https://www.jstrack.org/brewing/Yeast_nutrition_article.pdf
  2. ↑ a b Dabina-Bicka I, Karklina D, Rakcejeva T, Sniedzane R, Kviesis J. The dynamics of vitamins C and E in barley products during malting. Proceeding of the Annual 16th International Scientific Conference. 2010:111–115.
  3. ↑ Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
  4. ↑ a b Kanauchi M. Oxidative enzyme effects in malt for brewing. In: Kanauchi M, ed. Brewing Technology. IntechOpen. 2017:29–47.
  5. ↑ Quinde-Axtell Z, Powers J. Baik BK. Retardation of discoloration in barley flour gel and dough. Cereal Chem. 2006;83(4):385–390.
  6. ↑ Baxter ED. Lipoxidases in malting and mashing. J Inst Brew. 1982;88(6):390–396.
  7. ↑ 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.
  8. ↑ Chapon L, Chemardin M. The dissolving and oxidation of malt tannoids on mashing-in. Proceedings from the Annual meeting of American Society of Brewing Chemists. 1964;22(1):244–258.
  9. ↑ McFarlane WD, Sword PT. Determination of anthocyanogens: III. Analysis of barley and malt. J Inst Brew. 1962;68(4):344–350.
  10. ↑ Callemien D, Collin S. Structure, organoleptic properties, quantification methods, and stability of phenolic compounds in beer—a review. Food Rev Int. 2009;26(1):1–84.
  11. ↑ Liégeois C, Lermusieau G, Collin S. Measuring antioxidant efficiency of wort, malt, and hops against the 2,2'-azobis (2-amidinopropane) dihydrochloride-induced oxidation of an aqueous dispersion of linoleic acid. J Agric Food Chem. 2000;48(4):1129–1134.
  12. ↑ a b c Borsook, H., et al. "The Oxidation of Ascorbic Acid and its Reduction in vitro and in vivo*" J. Biol. Chem. 1937. 117:237-279.
  13. ↑ Nardini M, Cirillo E, Natella F, Mencarelli D, Comisso A, Scaccini C. Detection of bound phenolic acids: prevention by ascorbic acid and ethylenediaminetetraacetic acid of degradation of phenolic acids during alkaline hydrolysis. Food Chem. 2002;79(1):119–124.
  14. ↑ Nielsen H. The control of oxygen in beer processing. J Inst Brew. 1973;79(2):147–154.
  15. ↑ a b Sonni F, Clark AC, Prenzler PD, Riponi C, Scollary GR. Antioxidant action of glutathione and the ascorbic acid/glutathione pair in a model white wine. J Agric Food Chem. 2011;59(8):3940–3949.
  16. ↑ a b c Zoecklein B. Enology Notes #133. Virginia Tech website. 2007. Accessed online March 2024.
  17. ↑ 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.
  18. ↑ Andersen ML, Outtrup H, Skibsted LH. Potential antioxidants in beer assessed by ESR spin trapping. J Agric Food Chem. 2000;48(8):3106–3111.
  19. ↑ Mansfield, AK. "Kicking up a Stink: Treatment for Sulfur Off-Odors." Cellar Dweller. Cornell University. Apr 2010.
  20. ↑ Irwin, AJ, et al. "The Role of Copper, Oxygen, and Polyphenols in Beer Flavor Instability." Journal of the American Society of Brewing Chemists, vol. 49, no. 3, 1991, pp. 140–149.
  21. ↑ Hanes CS. The reversible inhibition of β-malt-amylase by ascorbic acid and related compounds. Biochemical Journal. 1935;29(11):2588.
  22. ↑ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1253306/pdf/biochemj01102-0394.pdf
  23. ↑ deLange AJ. Campden tablets (sulfites) and brewing water. Homebrew Talk website. 2012. Accessed March 2024.
  24. ↑ Hong MS, Kim SH, Im SY, Kim JG. Effect of ascorbic acid on the pitting resistance of 316L stainless steel in synthetic tap water. Met Mater Int. 2016;22(4):621–629.
  25. ↑ Fuchs-Godec R, Pavlovic MG, Tomic MV. The inhibitive effect of vitamin-C on the corrosive performance of steel in HCl solutions. Int J Electrochem Sci. 2013;8(1):1511–1519.
  26. ↑ Irwan, Fuadi A, Suhendrayatna. Investigation of ascorbic acid as environment-friendly corrosion inhibitor of low carbon steel in marine environment. In: IOP Conf Ser: Mater Sci Eng. 2019;536(1):012108.
  27. ↑ Karabín M, Hanko V, Nešpor J, Jelínek L, Dostálek P. Hop tannin extract: a promising tool for acceleration of lautering. J Inst Brew. 2018;124(4):374–380.
  28. ↑ Kanauchi M, Bamforth CW. A Challenge in the study of flavour instability. Brew Sci. 2018;71(Sept/Oct):82–84.
  29. ↑ https://onlinelibrary.wiley.com/doi/full/10.1002/jib.594
  30. ↑ Kunze, Wolfgang. Technology Brewing & Malting. Edited by Olaf Hendel, 6th Engligh Edition ed., VLB Berlin, 2019. p. 509.
  31. ↑ https://www.dudadiesel.com/choose_item.php?id=asc8c
  32. ↑ https://www.intralabs.co.uk/ascorbic-acid/100g-ascorbic-acid-powder.html
Retrieved from "https://brewingforward.com/index.php?title=Ascorbic_acid&oldid=12942"