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Paul Bolin, 1Paul B. Schwarz, 3Berne L. Jones, and 2Richard D. Horsley1
Department of Cereal Science and 2Department of Crops and Weed SciencesThe soluble proteins (SP) released during the malting of barley effects many aspects of brewing and beer quality. The effects of SP on beer quality are variable, both positive and negative. A long-term goal is to reduce the levels of SP in malt and stabilize concentrations among malt pieces. The objective of this research was to determine the effects of variety (Stander and Robust), location of growth (Hettinger, Williston and Dickinson, ND), growth year (1996 and 1997), steep moisture content (42%, 45% and 48%), green malt germination temperature (15o and 18o) and germination time (0, 2, 3 and 5 days) on protease activity. Protease activity was measured directly in malted samples using an in solution protease activity assay. The experiment was arranged as a randomized complete block design, 3 replications, and results statistically analyzed using SAS procedures. A significant increase in protease activity was observed with increasing germination time and germination temperature. Significant 2-way interactions were observed on protease activity: 1) between variety and germination time and; 2) between germination time and germination temperature. A delay in the onset of proteolytic activity by a specific group of protease enzymes was found by: 1) decreasing the germination temperature and; 2) in Robust compared to Stander. Lowering germination temperature and shortening germination time can reduce protease activity. Reduced protease activity would lead to lower SP and higher quality malt.