Selected excerpts from poster session, Master Brewers Assoc. of the Americas convention; Milwaukee, WI, October 4-7, 2003

Modern Brewery Age, Oct 6, 2003

Select Poster Presentations follow:

P-4: A Comparison of Monitoring Yeast Fermentations by RF Impedance with Traditional Methods of Biomass Estimation

John Carvell, Aber Instruments Ltd., Science Park, Aberystwyth, U.K.; Coauthor: R. Todd

On-line radio frequency measurements have traditionally been used in brewing to monitor the live cell concentrations being pitched into a fermenter or recovered during cone cropping at the end of fermentation. The method can, however, provide both valuable quantitative and qualitative information on the yeast biomass during fermentation. In this paper, we present a comparison for a range of pilot plant fermentations between using radio-frequency to provide a measurement of viable yeast biovolume and alternative traditional methods for estimating biomass, including dry weight, microscopic counting incorporating a correction for cell viability, and the Coulter Counter. Data are also presented from production brewery fermenters using an on-line radio-frequency biomass probe to track the viable cell biovolume throughout all the stages of seeding, cell growth, and flocculation. The radio-frequency profiles reveal unique, information at certain critical stages of the fermentation that cannot be detected by using traditional methods. We also reveal how additional real-time information on the quality of the yeast cell can be extracted in the future by using radio-frequency probes.

P-5: Servomyces-A Biological Nutrient. Tobias Fischborn, Lallemand Inc., Montreal, QC, Canada; Coauthors: J. McLaren, E. Geiger, F. Briem, and K. Glas

Zinc deficiency in brewer's wort is a known and accepted problem in the brewing industry. Zinc is an essential mineral micronutrient for yeast which influences the stabilization of yeast proteins and membrane, activates enzymes, accelerates riboflavin synthesis, and stimulates sugar uptake. The most common practice to compensate for zinc deficiency in brewer's wort is the addition of mineral zinc. In this study, we compare the addition of Servomyces, a yeast-based nutrient, to mineral zinc and inactivated yeast with respect to their effect on fermentation kinetics, fermentation efficiency, and flavor profile. Lab fermentations have been conducted at Weihenstephan and Doemens and industrial fermentations have been conducted in commercial breweries. The results demonstrate that Servomyces shortens fermentation time and increases alcohol yield and biomass production significantly compared to a control or to mineral zinc addition. The profile of fermentation by-products determined by gas chromatography was only slightly different from the control, but the beers treated with Servomyces were described as cleaner and better balanced. Servomyces is a biological alternative to mineral zinc additions.

P-7: The Effect of a Simulated Kilning Regime on the Profile and Antioxidant Activity of the Free Phenolics Extracted from Green Malt. Elizabeth Inns, University of Reading, Whiteknights, Reading U.K.; Coauthors: J. M. Ames, H. E. Nusten, and L. Buggey

This study evaluated the effect of a simulated kilning regime on the profile and antioxidant activity of free phenolics extracted from green malt. The free phenolics were subjected to a simulated killing regime involving heating from 25 to 200[degrees]C over 27 h. Samples were taken at intervals throughout heating and assessed for antioxidant activity and color. Where possible, phenolics were identified and quantified. Individual peak areas, attributed to specific phenolics, changed with progressive heating during simulated kilning, as monitored by HPLC. Although there was a fall in the level of phenolics at the beginning, overall there was an increase as heating increased from 80 to 100[degrees]C. Similarly, the antioxidant activity of the free phenolics decreased overall during heating, but there was an increase in activity as heating was increased from 80 to 100[degrees]C. The reasons for this temperature effect are currently being investigated.

P-9: The Importance of Free Amino Nitrogen in Wort and Beer

Christoforos Lekkas, Heriot-Watt University, Riccarton, Edinburgh, U.K.; Coauthors: G. G. Stewart, A. Hill, B. Taidi, and J. Hodgson

There is a lack of knowledge as to how wort nitrogenous materials affect different yeast strains and their fermentation performance and on what levels are needed to produce high-quality beer. FAN and individual amino acid composition were examined and differences were observed between normal and various high-gravity worts, with and without adjuncts. The EBC-ninhydrin and gradient elution HPLC methods were used for measuring FAN and amino acids, respectively. For ammonia determination, a spectrophotometric assay was utilized. Different yeast strains exhibited different amino acid absorption rates and preferences. In anaerobic fermentations, adequate amino acid consumption occurred. It was determined that yeast amino acid uptake depends on an immense variety of factors, including percentage of total assimilable nitrogen, individual amino acid concentration, quality and absorption rate, amino acid competitive inhibition, yeast strain and generation, and yeast growth phase. It was also determined that FAN affects a great range of other fermentation factors such as cell growth, biomass, viability, pH, and attenuation rate. This information can be used to design a more meaningful malt specification and to adjust process parameters in the brewhouse.