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Brewing with Gluconases

 

  Difficulties associated with the use of barley as an adjunct are,as mentioned,linked with the avaibility of β-glucan for extraction.To account for transformation of β-glucanduring malting;(1)in analogy to protopectinase, release of insoluble hemicellulosic β-glucan by an unknown heat-stable enzyme system,(2)partial degradation of this glucan by endo  β-1,3-glucanase,and (3)degradation of all these smaller water soluble gums by endo-barley β-glucanase.Apparently this as yet undemonstrated enzyme system releases the sluble β-glucans from barley but there is not enough glucanase activity in the remaining malt to degrade them during the mashing.The inability of the existing barley enzymes to do so has been usually attributed to their inactivation during heating in relation to the amount of glucan which is extracted.

Some effort has been made to the potentiate the action of these glucanases before they are heat-inactivated during the programmed heating that takes place during the mashing.More recently isolated an endo-β-1,3-glucanase from unkilned,germinated barley which possessed considerable heat stability,at least more than had been previously observed for the activity referred to as ‘’barley β-glucan endo-hydrolase.’’However,while stable at the early stage of mashing it was fairly unstable at 60°C in the puer state,rapidly inactivated at 65°C and almost instantaneously destroyed at the higher tempratures employed when bacterial amylase is used.