ARS | Publication request: A Comparison Of Barley Malt Amylolytic Enzyme Thermostabilities As Indicators Of Malt Sugar Concentrations

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 27, 2009
Publication Date: June 6, 2009
Citation: Henson, C.A., Duke, S.H. 2009. A Comparison of Barley Malt Amylolytic Enzyme Thermostabilities as Indicators of Malt Sugar Concentrations. Meeting Abstract. ASBC Newsletter. 69:28.

Technical Abstract: This study was conducted to test the hypothesis that barley malt amylolytic enzyme thermostabilities would correlate negatively with malt sugar concentrations. Seeds of four two-row and four six-row North American elite barley cultivars were steeped and germinated in a micromalter for 6 days. At 24h intervals throughout germination, green malt was removed and kilned. Malts were assayed for individual amylolytic enzyme thermostabilities and malt sugars were extracted at the same temperature that thermostabilities were tested (70°C for 30 min). Malt alpha-amylase activity was enhanced by treatment at 70°C at day 1 of germination and to a lesser extent from days 3 through 6 of germination. Malt beta-amylase and limit dextrinase activities were the least thermolabile at day 1 of germination than on subsequent days of germination, suggesting that seedling developmental influences thermostability of these amylolytic enzymes. For all cultivars combined, over all days of germination, malt beta-amylase and limit dextrinase thermostabilities correlated negatively and highly significantly with total and malt sugars and individual malt sugars with degrees of polymerization less than DP4 (r=-0.656, P<0.0001, r=-0.767, P<0.0001, respectively). Malt alpha-amylase thermostability at 70°C did not correlate significantly with malt sugars. Maltodextrins with increasing degrees of polymerization from maltotetraose to maltoheptaose correlated positively and highly significantly with beta-amylase and limit dextrinase activities. Six-row cultivars beta-amylase and limit dextrinase thermostabilities correlated slightly better than two-row cultivar thermostabilities with total and individual malt sugar concentrations. These data suggest that with a short period of heat treatment at 70°C starch degradation in a malt extract is significantly limited by the thermostabilities of beta-amylase and limit dextrinase.