The relationships between the alcohol yield obtainable from different malts and some readily measurable parameters have been investigated. Gel filtration studies clearly show that melanoidintype condensation products, which were previously suggested as a cause of low fermentability, are not produced in significant amounts in highly modified malts. These studies also show im portant details relating to the hydrolysis of dextrins in distillers' worts and washes. Measurement of the limit dextrinase activity of a range of distillers' malts has indicated that this enzyme is not a limiting factor in determining wort fermentability and its concentration does not correlate with the overall spirit yield. There may be a relationship between the whole amylase complex, as ex pressed by the diastatic power and wort fermentability. From a study of the reducing sugar con tents of worts, it was confirmed that the major factor controlling fermentable extract in malt is the relative amounts of starch-derived sugars in the wort. It now appears possible to determine the fermentability of distilling wort by the standard extract and the reducing power of the wort obtained by the standard I.O.B. extraction.Key words: malt extract, fermeittahility, spirits, enzymie activity, carbohydrate. IntroductionIn most published research aimed al maximizing I he yield or extract from malt, (">.2«.*»»s) little attention has been paid lo the proportion of the extract which is available for conversion to alcohol [i.e. the potential spirit yield). This is probably due to the influence of the Brewing Industry where there is more interest in the total maximum extract, but less emphasis on the maximization of alcohol production. In direct contrast to this, distillers arc primarily concerned with obtaining the maximum 'fermentable' extract in unboiled worts.a Indeed, it is possible to produce malts with very high extracts but whose spirit yields arc lower than some comparatively under modified malts."-11 In an earlier investigation it was found that, under standard production conditions, the fcrmcniability of distillers' wort (i.e. unboiled) is inversely linked with the levels of cold water extract and of soluble nitrogen in the malt." The present collaborative study was initiated to determine Ihe underlying reasons for such relationships.It was suggested, as one possibility, that lower fermentabilitics in highly modified malts may be caused by the removal of potentially fermentable reducing sugars by condensation with amino acids. Such condensation products have been proposed as melanoidin precursors but have only been de tected in trace amounts in malts.3" A second possible factor in determining fcrmcntabilily is the relative amount of catabolic enzymes in (he malt. Since it is possible for enzyme levels in highly modified malts to diminish12 or to be destroyed by proteolysis,2 it was decided that amylasc and limit dextrinasc activities should be monitored. For this purpose, a scries of malts of high and low fermentability, which had been kilned under ...