Technical Session 06: Quality Considerations Session
Hisao Koizumi, Asahi Breweries,Ltd.,Suita Brewery,Japan
Co-author(s): Yuichi Nakamura, Asahi Breweries, Ltd., Suita Brewery, Japan
ABSTRACT: In our breweries, large vessels with a capacity of several thousand hectoliters are used to brew beer. For reasons of cost-effectiveness, sanitary conditions, and appropriate cleaning, only one sampling device is usually installed on the large vessels, and no assurance is given that the sampled liquid taken from the device represents the whole beer in the large vessel. Therefore, we developed equipment to directly sample the beer in the large vessel from several positions at different heights. This paper reports on the application of the equipment to the 5,000 hL fermentation vessel, which is filled with four batches of wort prepared as 1,250 hL each for fermentation. Four perfluoro alkoxyl alkane resin tubes were extended from the vessel bottom to the intermediate heights between the liquid levels, where four batches of 1,250 hL wort reached, respectively, and the fermenting beer was sampled from each layer. The bottommost layer (3.8 m above the vessel bottom) was designated sample #1, the 9.2 m high position was sample #2, the 12.5 m was sample #3, and the topmost layer (15.8 m high) was sample #4, and the fermenting beer and yeast were analyzed. We used the equipment to compare the uniform pitching method, where the same amount of yeast and air were pitched into the first to fourth batches of wort, and the early pitching method, where the same amount of yeast and air were pitched into the first to third batches of wort, while neither yeast nor air was injected into the fourth batch of wort. Under the uniform pitching condition, the temperature, number of yeast cells, specific gravity, and amino nitrogen level during fermentation were almost the same at all of the four positions in the fermentation vessel. However, in the case of the early pitching method, the bottommost layer and the upper three layers were not blended, and fermentation started as each layer was kept independent. After around 50–60 hr from initiation of fermentation, convection was generated, and the 5,000 hL of fermenting beer became uniform. According to the sensory tests, the beer brewed by the early pitching method had a higher rating with smaller variations. The sampling equipment we developed for this enabled us to sample fermenting beer and yeast from an arbitrary height at any time and evaluate the distribution and uniformity of the fermenting beer components, temperature, and yeast cells, which was applicable to improvement of beer flavor in practical brewing processes.
Hisao Koizumi received an M.S. degree in biotechnology from Hiroshima University, Japan. He began employment with Asahi Breweries, Ltd., in April 2001. After working as a researcher in the laboratory, he was transferred to the brewing section of the Suita brewery.