|Im, Hanna - UNIVERSITY OF WISCONSIN|
Submitted to: Journal of American Society of Brewing Chemists
Publication Type: Abstract Only
Publication Acceptance Date: February 5, 1996
Publication Date: N/A
Technical Abstract: Highly purified alpha-glucosidases from germinated barley seeds were previously shown to be heat labile as determined by a 50 percent loss of activity after a 10 min incubation at 47 and 39 degree C for the high and low pI isoforms, respectively. The objectives of the work presented here were to determine the effects of kilning and mashing temperatures on the activity of alpha-glucosidases in malt extracts, and to evaluate the contribution of alpha-glucosidases to the production of glucose in the final wort. About 66 percent of the maltase and 88 percent of the p-nitrophenol alpha-glucosidase activities survived kilning when the maximal temperature reached was 85 degree C. During mashing, almost all alpha-glucosidase activity was retained until temperatures reached 55 degree C. Incubation at 72 degree C for starch conversion rapidly inactivated alpha-glucosidases. A modified mashing schedule was developed that extended the time alpha-glucosidase was active; this resulted in an increased production of fermentable sugars. The inclusion of conduritol B epoxide, a specific inhibitor of alpha-glucosidases, during mashing reduced glucose production. It was concluded that alpha-glucosidases significantly contribute to the production of fermentable sugars from starch during mashing.