P-4

Application of biological acidification to improve the quality, flavour and processability of beer produced with twenty percent raw barley.
Reinhold M. Barta (1), Karl Bayer (1), DECLAN L. GOODE (2), and Elke K. Arendt (2), (1) Institute of Applied Microbiology, University of Agricultural Sciences, Vienna, Austria; (2) Department of Food Science, Food Technology and Nutrition, National University of Ireland, Cork, Ireland.

Traditionally the use of unmalted barley in brewing has been associated with problems such as poor yield of extract, mash filtration difficulties, negative effects on total soluble nitrogen and free amino nitrogen, lower fermentability, reduced zinc content, increased levels of beta glucans (increased viscosity) and flavour problems. The objective of this work was to evaluate the influence of biological mash and wort acidification on brews containing 20% unmalted barley using both laboratory scale trials as well as 10 hl pilot scale brews. The following mash compositions were studied; (a) 100% malted barley mash not acidified, (b) 80% malted barley and 20% unmalted barley not acidified, (c) 80% malted barley and 20% unmalted barley acidified with lactic acid, (d) 80% malted barley and 20% unmalted barley acidified with Lactobacillus amylovorus. A slightly modified Congress mashing program was used when working at a laboratory scale. A decoction mashing programme was applied to the pilot scale brews. Characteristics of the laboratory scale mashes and the pilot scale brews examined included mash pH, extract, colour, filterability, viscosity, total soluble nitrogen (TSN), free amino nitrogen (FAN), high molecular weight nitrogen (HMWN), fermentability, beta glucan, zinc, foam stability and sugar and amino-acid profiles. A full process and beer analysis including sensory evaluation was in addition carried out on the 10 hl brews. The results of these studies showed that for nearly all of the parameters analysed the biological acidification of mash using Lactobacillus amylovorus enhanced the quality of beer and improved the processability of mashes containing 20% unmalted barley. With regard to the Nitrogen-analysis (TSN, FAN, HMWN), viscosity, foam stability and bitter units there was no significant difference between beer (a), (c) and (d). The sensory results as well could not show any significant differences between these brews. However, there was an increase of beta glucan in all brews with 20% barley, up to a level of 250 mg/l, but without negative effects on lautering or beer filtration. From this work it was clearly shown that biological acidification could compensate for reduced quality and flavour loss generated by the use of 20% unmalted barley as an adjunct for brewing.

Declan Goode received a Bachelor of Science Degree in Food Technology from The National University of Ireland, Cork, Ireland in 1998. He is currently in the final stages of completing a Master of Science Degree in the area of Brewing at The National University of Ireland, Cork. His thesis is entitled 'Brewing with unmalted sorghum and commercial enzymes'. He was recently appointed head brewer at the newly developed pilot scale brewing research facilities at The National University of Ireland, Cork, Ireland.