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 alpha- and beta-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 degrees C, 62 degrees C and 72 degrees C with intermediate heating by 1 degrees C/min. Thermal inactivation kinetics parameters determined for alpha- and beta-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 alpha-amylase, but not beta-amylase inactivation in real mashing conditions, suggesting that beta-amylase stability is enhanced during mashing by components present or formed in the mash.

Automated summary

The study investigated the activity and inactivation kinetics of α-amylase and β-amylase during barley malt mashing, finding that temperature had an impact on the activity differences among different varieties, but these differences were not reflected in the resulting wort composition after mashing in the actual process.