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Activation of soluble-inactive limit dextrinase and its application
Huang, X.

Most limit dextrinase exists usually in the inhibited form following malting. We explored the transformation of this inhibited enzyme to the free and uninhibited enzyme by the control of aeration in germination, and compared the results to those of malt that was aerobically germinated and that was stored before beer making. It was shown that there was potential to improve the utilization level of soluble-inactive limit dextrinase and to receive other benefits as well. Limit dextrinase (EC3.2.1.4) is commercially important because there is evidence that conditions during mashing which promote activation of this enzyme lead to an alteration of carbohydrate composition that increases fermentability (1); the free enzyme hydrolyzes a-1,6 glucosidic linkages in amylopectin and branched dextrins, leading to an increase in fermentable carbohydrates in wort. The activity of limit dextrinase is minimal in mature barley grains, but during germination its activity slowly increases after an initial lag period (2). In germinating stage, limit dextrinase exists in three forms: free (soluble-active), latent (soluble-inactive) and bound (3). Our aim was to explore the activation of soluble-inactive limit dextrinase during malting in order to maximize its potential activity during mashing. The latent limit dextrinase should be active particularly during the early stages of mashing because there is evidence that malt extract protects the enzyme (4).The activation is very important because 90% of the extract in wort are carbohydrates consisting of 75% of fermentable sugars and 20% of non-fermentable dextrins (5). Greater limit dextrinase activity will decrease the non-fermentable proportion of the carbohydrate and obviously shorten malt storage period before beer making. The specific aims laid down in this paper were to determine

Descriptors: Lsliche-inaktive Grenzdextrinase, Aktivierung, Keimung

Monatsschrift fr Brauwissenschaft 56, Nr. 7/8, S. 132-133, 2003