MASTER BREWERS ASSOCIATION OF THE AMERICAS

1. MASTER BREWERS ASSOCIATION OF THE AMERICAS 43 MBAA Annual Conference October 13 – 15, 2011Hilton MinneapolisMinneapolis, MN The Use of Micro-oxygenation of Beer to Simulate Oak Barrel Maturation Molly Browning and John Stewart, New Holland Brewing Company, Holland, Michigan Abstract The taste panel ranked samples on a scale of 1-10 for body, astringency, global quality or roundedness, and wood character. Then the samples were ranked in order of which sample tasted most like it had been aged in a barrel. Conclusions It is becoming increasing popular for wineries to use micro-oxygenation machines on wine held in tanks to mimic the results of oak barrel maturation. The process of micro-oxygenation (Mox) involves a micro-oxygenation unit which takes sterile oxygen from a bulk tank or compressor and injects it into a liquid through a diffusion stone at a very low dosing rate, ranging from 0.5 ml/L/month to 2 ml/L/month. It is claimed that this process oxidizes tannins and creates a softer, more rounded wine similar to what is found after oak barrel aging. As an increasing number of breweries are now aging beer in oak barrels it was sought to determine if micro-oxygenation could be used to achieve similar results with beer. An oatmeal stout was aged under four different conditions including barrel aging and micro-oxygenation for a period of two months. A series of analysis of polyphenolic and ester compounds, as well as professional brewery taste panels were performed to compare these maturation techniques. The results from the analytical testing showed reduction in some polyphenolic compounds and an increase in others in the micro-oxidized sample; however there were no trends showing a direct correlation to barrel-aging. Both gallic acid equivalents and flavoniods showed similar trends between the base and the spirals and between the Mox and the barrel-aged samples. Mox and barrel-aged samples showed a reduction in flavoniod levels as well as an early increase then subsequent decrease in gallic acid equivalents. This is a similar result as seen in testing of tannic red wines. There was no overall difference in trend with total polyphenol testing. Regarding anthocyanins, the assay performed is one commonly used on fruit juices and wines, and was found not suitable for beer testing. Acetaldehyde levels were so low in all samples tested that no discernable difference was seen. From the taste panel results, the Mox sample was found to have a flavor profile that was closer to barrel-aging than only adding oak spirals to beer. Although the Mox sample ranked closer to a barrel-aged beer, the taste panel group consistently voted the barrel as being more like a barrel-aged beer over the Mox sample. The most noticeable difference between these two samples as reported by the taste panel was the variance in wood character. Micro-oxygenation could possibly be an application for pub brewers who are restricted on space for barrel-aging as well as an economical application for breweries with large-scale barrel-aging programs. Micro-oxygenation could give the flexibility of aging in tanks, thus allowing savings in labor and safety negating the need to rack beer to and from barrels. Another benefit is the much cheaper cost of wood alternatives versus barrels. It was apparent from the taste panel results that Mox brought the wood alternatives closer to barrel-aging flavor. We feel Mox is an important part in duplicating barrel-aging in stainless tanks with the proper wood alternative profile. We also feel there is potential for future testing regarding flavor compounds of barrel-aged beer and their relation to oxygenation. We believe this research could duplicate barrel-aging in a tank and potentially lead to faster aging times with the proper control of oxygenation levels and wood alternatives.. Results Introduction To see if using a micro-oxygenation unit on beer aged in a stainless vessel with wood alternatives would give similar results as barrel aging the following four aging conditions were tested: 1)Stout in a ½ bbl keg 2) Stout with oak spirals in a ½ bbl keg 3) 90 Gallons of Stout with oak spirals and micro-oxygenation unit in a 30 bbl fermenter 4) Stout aged in a previously used 55 gallon neutral wine barrel. The oak spirals were 1” X 8” American oak with a ratio of 10% heavy, 10% light and 80% medium toast levels used. Spirals were used at a rate of 1 spiral per 7.25 gallons per recommendation of the manufacturer. The micro-oxygenation unit was set to inject 2ml/L/month. Every two weeks during the two month aging period samples were taken from each vessel and tested for total polyphenols, flavonoids, total phenolics expressed as gallic acid equivalents and acetaldehyde. These tests were chosen based on there use in wine literature to show the “softening” of tannic red wines. Two taste panels were done once a month by a panel of nine brewery taste panel members. Taste Panel Ranking Results Most likely Barrel aged Least likely Barrel aged Barrel Mox Spirals Base Note: Testing results for both anthocyanins and acetaldehyde were inconclusive due to the testing methods used.