43-4 |
Antioxidant capacity of bottle-conditioned (containing live yeast) beer |
N. MORRIS and M. A. Daeschel. Food Science and Technology, Oregon State University, 100 Wiegand Hall, Corvallis, OR 97331 Natural antioxidants prevent uncontrolled oxidative reactions by decreasing molecular oxygen levels, scavenging chain-initiating and chain-propagating free radicals, chelating metals, or decomposing peroxides. Beer is rich in antioxidants, derived both from malt and hops, which are believed to be important for flavor stability. Yeasts may be viewed as antioxidants because of their ability to scavenge oxygen and their enzymatic and non-enzymatic defenses against oxygen radicals. Our objective was to determine whether bottle-conditioned beer (which contains live yeast) has a higher antioxidant activity compared to that of conventional beer. Beer wort was prepared, brewers yeast added, and allowed to complete primary fermentation. The beer was bottle-conditioned (naturally carbonated) by the addition of a second yeast and sugar. Treatments consisted of using three different yeasts. Controls consisted of artificially carbonating the beer. Antioxidant capacities were determined using FRAP analysis. Results indicated that there was a slight, but measurable, increase in the level of antioxidant capacities between the three bottle-conditioned beers compared to the control. These results suggest it’s likely the malt and hops components that play the major role in the antioxidant capacity of beer. Consequently, the flavor stability and antioxidant health benefits from beer would be determined more from the concentration of these compounds in the recipe and brewing process, rather than from yeast fermentation and bottle-conditioning. However, it’s well known that bottle-conditioned beer has a longer shelf life. This is likely due to the ability of yeast to metabolize any free oxygen present, rather than any innate antioxidant ability. Alterations in the brewing formulation to increase levels of antioxidants from malt and hops will likely have a significant impact on the antioxidant activity of the finished beer, thus increasing shelf stability and health benefits.
Session 43, Food Microbiology: Food mycology
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