The properties and genetics of barley malt starch degrading enzymes

Abstract

The main uses of the world barley crop are for animal feed, human food and malting for brewing. The average annual crop between 2003-07 was 145 million tonnes/pa, of which 68% was used for feed, 6% for food and 18% for malting (http://www.e-malt.com). The level and quality of barley starch degrading enzymes has little bearing on its use for animal feed or food however these are critical parameters for malting quality. Thus this chapter will concentrate on the brewing implications of starch degradation by barley starch degrading enzymes. The properties and quality of barley malt starch degrading enzymes are of primary importance to the efficiency and profitability of brewing (beer and whiskey), and the bio-fuel (bio-ethanol) industries. The barley starch degrading enzymes hydrolyse starch into fermentable sugars that yeast convert into alcohol. This process is key for the alcohol producing industries as the starch substrate makes up approximately 60% of grain weight (Chapter 4, Holtekjolen et al., 2006). Malted barley is the main source of the diastase or diastatic power (DP) enzymes that hydrolyse starch.