The principles of malting and the biochemical and structural changes in the barley grain during the malting process are described. One problem, particularly with pale malts, is that the desirable processes (endosperm modification, development of enzymes required for mash conversion, etc.) are generally accompanied by the formation of various substances capable of producing off flavours in beer, together with precursors of other such substances and enzymes involved in off flavour formation. The effects of changes in malting technology and of the methods of producing different malt types on the composition of the finished malt and the flavour stability of the resulting beer are discussed. New developments in brewing technology (fractionated milling, mash separation systems capable of functioning without husks, and immobilized yeast fermentation systems), together with the demand for a longer shelf life for nationally and internationally marketed products and the prospect of compulsory ingredient labelling conferring marketing advantages on brewers using products derived from malt to replace established additives and processing aids, are likely to impose new demands on the malting industry. Possible solutions to some of the problems described are presented, including improved post harvest conditioning of the barley, the control of the microorganisms responsible for many of the undesirable enzymes and other unwanted constituents by encouraging the growth of beneficial microorganisms (e.g. lactic acid bacteria) during steeping and germination, and investigating the roles of potentially undesirable endogenous barley enzymes in the physiological processes within the germinating grain so as to be able to minimize their unwanted effects. It may also be possible to breed new barley varieties less susceptible to these problems.
Keywords : barley biochemistry composition enzymic activity germination kilning malting off flavour physiology quality