Starch hydrolysis during mashing: A study of the activity and thermal inactivation kinetics of barley malt α-amylase and β-amylase

Hydrolysis of starch is key in several industrial processes, including brewing. Here, the activity and inactivation kinetics of amylases throughout barley malt mashing are investigated, as a prerequisite for rational optimisation of this process. Varietal differences were observed in the activity of α- and β-amylases as a function of temperature for six barley and malt varieties. These differences were not reflected in the resulting wort composition after mashing, using three isothermal phases of 30 min at 45 °C, 62 °C and 72 °C with intermediate heating by 1 °C/min. Thermal inactivation kinetics parameters determined for α- and β-amylases of an industrially relevant malt variety in a diluted system showed that enzymes were inactivated at lower temperatures than expected. The obtained kinetic parameters could predict α-amylase, but not β-amylase inactivation in real mashing conditions, suggesting that β-amylase stability is enhanced during mashing by components present or formed in the mash.