PHYSIOLOGICAL, BIOCHEMICAL AND GENETIC REGULATION OF CARBOHYDRATE METABOLISM IN CEREAL TISSUES
Location: Cereal Crops Research
Title: Diastatic power
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: December 22, 2010
Publication Date: September 28, 2011
Citation: Duke, S.H., Henson, C.A. 2011. Diastatic power. In: Oliver, G., editor. The Oxford Companion to Beer. First edition. New York, NY: Oxford University Press. p. 288.
Interpretive Summary: This layman’s guide to beer includes information on essentially all aspects of the production and commerce of beers throughout the world. The most important traits of different styles of beer and their different methods of production are both of historical and current value as are the descriptions of the various measures of quality that define the commercial value of the malts used to produce beer. One of the two most important measures of quality is that known as ‘diastatic power’, DP, which is reported on in this section of the guide. DP has been used for over 175 years as the primary indicator of a malt’s ability to produce the sugars that are used by yeast in the generation of fermented malt-based beverages. The impact of this published work will be a user-friendly text that educates readers on the history, production and commerce of beers throughout the world.
diastatic power: Diastatic power, abbreviated DP, is the total activity of malt starch degrading enzymes that hydrolyze starch to fermentable sugars. The starch degrading enzymes contributing to this process are a-amylase, ß-amylase, limit dextrinase, and a-glucosidase. The driving force for DP appears to be ß-amylase which usually correlates better with DP than the other starch degrading enzymes and has the highest activity of all starch degrading enzymes in malt. Behind malt extract, DP is usually considered the second most important malt quality measurement. For complete conversion of starch to sugars, high levels of barley malt DP are especially important when adding substantial amounts of unmalted adjunct to the mashing tun during brewing. Mashing converts malt starch into fermentable sugars; however, ß-amylase and other starch degrading enzymes are inactivated as the temperature during mashing, and DP disappears. There is a dilemma in this phenomenon in that as temperatures rise, starch becomes gelatinized and is a better substrate for starch degrading enzymes. The term DP had its origins with the discovery of diastase in barley malt by two French chemists, Anselme Payen and Jean-François Persoz, which was published in 1833. They precipitated diastase from an aqueous mixture of milled barley, and found that small amounts could liquefy starch to form sugars, and that it was unstable at high temperatures. This was one of the first reports of the properties of an enzyme. The suffix –ase, commonly used for naming enzymes, was derived from the name diastase. In the late nineteenth and early twentieth centuries, methodologies for measuring malt DP were developed.