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 ...

This paper encompasses a re‐evaluation of published literature and data regarding wort attenuation in malt distilleries raising questions and discussing how the conventional wisdom has changed over time and what questions still need to be answered. Current knowledge is summarized in the following four points: (a) Under normal malting conditions, starch granules are partially degraded by a combination of α‐amylase and α‐glucosidase. This complex can open up the granule at specific sites on the surface and create characteristic ‘pin‐hole’ lesions, which may be widened by secondary hydrolysis by α‐ and β‐amylase, limit dextrinase and α‐glucosidase (maltase). (b) All of these diastatic enzymes can survive mild kilning, probably by forming heat stable complexes on and within the starch granules and can continue a complete degradation of starch when mashed at ambient temperatures with glucose as the end product. (c) At normal mashing temperatures, starch granules gelatinize and dissolve with a concomitant rapid degradation to glucose, maltose, maltotriose and dextrins ranging from degree of polymerization (DP) 4 to > DP20. If there is immediate wort boiling after run‐off, this is the final composition of starch derived carbohydrates according to the conventional paradigm. (d) All malt worts also contain a small amount of panose, isopanose as well as glucosyl maltodextrins, based on a core of 62‐α‐glucosyl maltose (panose) or 6‐α‐maltosyl glucose (isopanose), which are remnants of the α‐amylase/glucosidase degradation of granular starch. These dextrins are resistant to the action of debranching enzymes and their concentration may vary between 4 and 8% of the malt extract, depending on the degree of modification of the host starch granules. They may be created at the active sites of this enzyme complex when the granule is gelatinized. In a conventional mash of unboiled distilling wort, the spectrum of wort dextrins produced from gelatinized starch is reduced to true ‘limit’ dextrins of DP4–8 by continued α‐amylolysis during early fermentation. These dextrins will contain side chains of either maltose or maltotriose residues surrounding the α‐1,6‐glucosidic linkage and can be debranched by limit dextrinase during late fermentation, leaving only the above glucosyl maltodextrins dextrins in the spent wash. Copyright © 2016 The Institute of Brewing & Distilling

Barley starch exists in two clearly defined populations of large (ca. 25 μ diameter) and small (ca. 5, μ diameter) granules, whilst in wheat there is a range of granule sizes with no similar bimodal distribution. The small granules of barley represent about 90% of the total starch granules by number, but account for only about 10% of the total starch in weight. Fractions containing only large or only small granules have been isolated from both barley and wheat. The small granules from barley have a higher amylose content than the large granules, a higher gelatinisation temperature, and are usually associated with more protein. In contrast, large and small granules from wheat differ only slightly in their respective amylose contents but, like barley differ in gelatinisation temperatures and amounts of associated protein. It is proposed that starch synthesis in the small starch granules of barley is under different genetic control from that in the large granules.

The jS-glucan extracted from ungerminated barley with water at 40°C has a much lower specific viscosity than the corresponding material isolated from a wort prepared at 65°C from a two-day germinated barley malt.Both glucans are similar in that they are polymers of /3-D-glucose, with approximately 74% of the linkages in the £-1,4 configuration and 26% in the £-1,3 configuration. However, the two glucans are not hydrolysed to the same extent either by a partially purified bacterial endo-)9-1,3-glucanase or by a homogeneous endo-/?-1,3-glucanase from malted barley.The malt giucan is readily hydrolysed, causing a rapid decrease in specific viscosity but with no measurable increase in reducing power, whereas barley giucan undergoes only limited hydrolysis under similar conditions. Thus, different jS-glucan preparations from barley or malt may be identical in the proportion of /J-1,3 to /M,4-linkages but the overall arrangement of linkages, and hence susceptibility to enzyme attack, differs according to the source and the method of extraction of the giucan. The molecular weights of both jS-glucan preparations and the products of their enzyme hydrolysis have been determined by agarose gel permeation chromatography. A simple model which illustrates the underlying structural relation ships of the /J-glucans from barley and malt is suggested.

Dextrins from a sweet wort, prepared by infusion mashing, were fractionated by paper chromatography according to their molecular weights and further into linear and branched dextrins. Each fraction was treated with j9-amylase and with the debranching enzyme, pullulanase. The products of this enzymic hydrolysis were identified by paper chromatography. From the pattern of oligosaccharides so obtained, structures have been postulated for the dextrins with a degree of polymer ization of 4 to 8 glucose units. The linear dextrins, maltotetraose, maltopentaose, maltohexaose, maltoheptaose, and malto-octaose, were shown to be present in wort. In addition, at least eleven branched dextrins were found: 6a-ec-maltosylmaltose, 6-a-glucosyl-maltotriose, two branched pentasaccharides, two branched hexasaccharides, two branched heptasaccharides and three branched octasaccharides. T the detailed structures (i.e., the structures of Introduction^moiecular-weight-isomers) of the indi-