Kvasny Prum. 1997; 43(9): 233-236 | DOI: 10.18832/kp1997017

Formation of Aldehydes by Controlled Oxidation of Amino Acids of Beer.Peer-reviewed article

J. ŠAVEL, D. ZDVIHALOVÁ, M. PROKOPOVÁ

Amino acids dissolved in distilled water or unhopped wort were oxidized with peroxo (di) sulfate, permanganate and potassium dichromate under a simultaneous steam distillation. During oxidation of amino acids with ammonium peroxo (di) sulfate in water were obtained volatile products with a different nature of off-flavours and a positive reaction with thiobarbituric acid and Schiff s agent and 2, 4 - dinitrophenylhydrazine. Phenylalanine f.e. has provided a floral flavour and methionine a putrefaction of cabbage. During oxidation of amino acids in unhopped wort has only a pungent cardboard flavour arisen and the quantity of volatile substances has decreased. An unhopped wort is supposed to contain substances partly blocking the oxidation of some amono acids. The presence of melanoidins and ethanol has influenced the nature and intensity of off-flavours. After the oxidation of amino acids with potassium dichromate and potassium permanganate mostly hard to define musty off-flavour has arisen, while methionine has again a putrefaction of cabbage provided. There are discussed possibilities of the formation of volatile carbonyl compounds from amino acids in the presence of active form of oxygen and a simultaneous action of antioxidative substances from malt. For the measurement of ability of substances to undergo oxidation in the presence of further substances the test with tetramethyl-p-phenylenediamine and ammonium persulfate has been suggested. The supposed mechanism of the formation of significant compounds during the ageing of beer includes the oxidation of amino acids, melanoidins and alcohols by active form of oxygen.(In Czech, English summary only)

Keywords: beer, amino acids, oxidation, aldehydes, analysis

Published: September 1, 1997