Biological acidification of a mash containing 20% barley using Lactobacillus amylovorus FST 1.1:: Its effects on Wort and beer quality

This study evaluates the influence of biological mash and wort acidification using a thermophilic proteolytic/amylolytic active Lactobacillus amylovorus on brews containing 20% (wt/wt) unmalted barley in laboratory-scale trials as well as 10-hL pilot-scale brews. The biologically acidified mash was compared with a chemically acidified mash, 100% malt mash unacidified, and 80% malt (wt/wt)/20% (wt/wt) barley unacidified mash. Characteristics such as pH, extract, color, viscosity, total soluble nitrogen (TSN), free amino nitrogen (FAN), apparent fermentability, P-glucan, sugar, and amino acid profiles of the resultant worts were determined. In the pilot-scale brews, foam stability, accelerated shelf life, and sensory evaluation of the beer was determined. It was clearly shown that biological acidification (BA) could compensate for a lower enzymatic activity level of grists containing 20% (wt/wt) barley. Increased levels of extract, fermentability, TSN, and FAN were observed in the laboratory-mash trials along with a sharp decrease in P-glucan levels when BA was applied. Cast-out wort showed a considerable increase in nitrogenous fractions. Viscosity was decreased by acidification of mashes but did not correlate with P-glucan levels. The final biologically acidified beer showed a lighter color, improved foam stability, and a more well-rounded taste with increased shelf life in comparison with the chemically and the nonacidified beer.