Investigating the influence of wort amino acid composition on fermentability using a model solution

Yeast and Fermentation Session
Blanca Gómez G., Laboratorio Tecnológico del Uruguay (LATU)
Co-author(s): Aaron MacLeod, Grain Research Laboratory, Canadian Grain Commission, Canada; Tania De León, Laboratorio Tecnológico del Uruguay (LATU), Uruguay; Michael J. Edney, Grain Research Laboratory, Canadian Grain Commission, Canada

ABSTRACT: Fermentability is an important malt quality parameter as it predicts potential beer production. The most important process in brewing fermentation is the assimilation of carbohydrates and nitrogenous compounds by yeast. An adequate level of free amino acids in wort ensures efficient yeast growth and, hence, appropriate fermentation performance. Wort is a very complex medium containing a range of nutrients, and this complicates research on relationships of fermentability with micronutrients. To study the relationship between individual amino acid profiles and fermentability, a controlled medium (broth) was created with high maltose syrup and pure amino acids. The broth simulates a standard wort (12°P), and pure amino acids were added to the solution at concentrations similar to what is expected in a standard 12°P malt wort. Four amino acids (glutamine, asparagine, arginine, and lysine) were studied in depth by varying their concentration in the broth while maintaining the same total amino acid content. Each amino acid was studied separately by preparing three model solutions. The first contained the standard concentrations for all amino acids; the second increased the proportion of the one amino acid being studied; and the third contained a decrease in the proportion of the one amino acid being studied. Each solution was fermented using three different yeast strains (lager, ale, and Fleischman). Results showed a significant effect of yeast strains on fermentability level. Furthermore, changes in lysine and glutamine concentrations showed a significant effect on fermentability for some of the yeast strains, but asparagine and arginine presented no significant effect on fermentability for any of the yeasts. Similar significant reductions in pH during fermentations were also found. It was concluded that individual yeast strains have varying requirements for amino acids, and these requirements are not the same for each essential amino acid.

Blanca Gómez received a B.S. degree in biochemistry from Universidad de la República in Montevideo, Uruguay. She began employment with Laboratorio Tecnológico del Uruguay (LATU) in 1998 as a chemist in the analytical laboratory of the Malting Barley Unit. She worked in quality assurance and became a quality manager for ÖVQ. In 2009 Blanca received an M.S. degree in food science from the University of Manitoba and is working on her research project at the Grain Research Laboratory, Canadian Grain Commission, in Winnipeg, MB. Since 2009 she has functioned as a scientist in the Cereals Department of LATU and is in charge of research projects. She belongs to the Uruguayan Barley Board, serving as executive secretary from 2010 to 2011.