Maltose Effects on Barley Malt β-Amylase Activity and Thermostability at Low Isothermal Mashing Temperatures

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Maltose increases the activity and thermostability of barley β-amylase at high mashing temperatures. Here we examined the effects of maltose on malt β-amylase activity and thermostability at reduced mashing temperatures. The β-amylase activity was relatively thermostable at both 52 and 58 °C with or without added maltose. At 52 °C, only 500 mM maltose significantly increased (P = 0.0004 to P < 0.0001) Harrington β-amylase activity over mashes without maltose (controls) from 30 to 90 min of mashing. With Morex, at 52 °C, 50 to 500 mM maltose significantly increased β-amylase activity (P = 0.0004 to P < 0.0001) compared to controls at 60 and 120 min. At 58 °C, Harrington β-amylase activity was significantly increased (P = 0.017) only at 120 min with additions of 200 to 500 mM maltose. In contrast, maltose additions to Morex mashes at 58 °C significantly increased β-amylase activities at 30 min (400 and 500 mM), at 60 and 90 min (50 to 500 mM), and at 120 min (100 to 500 mM). This suggests that genotypes with a Morex-like β-amylase phenotype could benefit from low initial mashing temperatures. Incubations with 0 to 500 mM mannitol at 52 and 58 °C were compared with incubations containing maltose and in general mannitol had fewer effects than maltose.