P-14
Control of oxidation during mashing by an added antioxidant—Influence on lipid composition and flavor stability
Presenter: Saara Poyri, VTT Biotechnology, Espoo, Finland
Co-Authors: Anu Kaukovirta-Norja and Hannele Virtanen, VTT Biotechnology, Espoo, Finland; Pekka Lehtinen, Helsinki University of Technology, Espoo, Finland; Peter Hartwall, Hartwall Ltd, Helsinki, Finland; Pekka Reinikainen, Polttimo Companies/ LP Research Centre, Lahti, Finland; Johanna Siirila, Sinebrychoff Ltd, Kerava, Finland; and Silja Home, VTT Biotechnology, Espoo, Finland

Oxidation during beer processing has a considerable influence on beer flavor and flavor stability. Much effort is used these days to control and decrease the oxygen levels during down-stream processing. However, less is known about the amount of available oxygen and its impact and reactions during mashing. Earlier results show that it is possible to control oxidation during mashing by introducing special gas atmosphere into the mash kettle. Furthermore, the addition/use of antioxidants is an attractive approach to control oxidation during mashing. In the present study, the influence of oxidative conditions and the use of a common food antioxidant, ascorbic acid, on mashing and wort parameters and on beer quality was studied. The addition of ascorbic acid to mashing liquor diminished the oxidation during mashing to almost nonexistent. The indicator time test (ITT) used to measure the reduction power, i.e., antioxidativity of wort and beer, showed that ascorbic acid survived the process and was still active in the final beer. The addition of ascorbic acid diminished also the total amount of carbonyl compounds, but the amount of hexanal, a lipid-originating carbonyl, increased. The beers were stored for 6 to 12 weeks in room temperature or cold room, and the flavor deterioration was evaluated by a trained tasting panel. The effect of ascorbic acid on beer flavor stability was contadictory. Regardless of the measured, powerful antioxidative effect during the whole beer-making process, ascorbic acid seemed not to have the ability to improve beer flavor stability. These results support the observations that antioxidative compounds may have a pro-oxidative nature depending on food matrix, antioxidant concentration, and processing conditions.

Saara Poyri graduated from Helsinki University of Technology in 1996 with an M.Sc. (chem. eng.). Since 1998, she has been working as a Ph.D. student at VTT Biotechnology, studying the effect of proteins and oxidation in the brewing process.