Antioxidants may be divided into true antioxidants, which slow the rate of oxidation of certain beer components or reduce the undesirable effects thereof, and oxygen scavengers, which exert their effect by removing molecular oxygen from beer. Twentynine potential antioxidants were tested in pilot brews and classified on the following system. If the experimental beer, treated with potential antioxidant, exhibits better colloidal and flavour stability than the control beer (as judged by chill stability measurements and taste panel evaluation) and its oxygen uptake is greater than the oxygen uptake by the control beer (as measured by gas chromatography), then the agent acts as an oxygen scavenger. If the rate of oxidation is reduced by means other than oxygen removal, then the agent acts as a true antioxidant. Ten of the compounds tested (A 1 to A 10) are the subject of the authors' patent - Canadian patent 110,541 (1971). Four of these, A 1, A 3, A 4 and A 5, are recommended for use in beer (10 to 100 ppm) as strong antioxidants. Another, A 6 (10 to 100 ppm) are recommended as weak antioxidants. All are of the phenolic type. The mechanism by which these compounds act varies with temperature, concentration, and the level of air included in the bottle (beers were bottled with low air and with 2 ml of added air). Thus, A 1 behaved as an oxygen scavenger at 0 degrees C but as a true antioxidant at 20 degrees C both with low and high air content. A 6 (10 ppm) was an oxygen scavenger with low air but a true antioxidant with high air. At higher concentration (50 ppm) the roles were reversed. Rutin and humic acid acted as oxygen scavengers under all the conditions tested.
Keywords: antioxidant beer brewing chillproof haze polyphenol precipitation tannin