Performance of Husked, Acid Dehusked and Hull-less Barley and Malt in Relation to Alcohol Production R. C. Agu1,2, T. A. Bringhurst1 and J. M. Brosnan1 ABSTRACT J. Inst. Brew. 114(1), 62–68, 2008 Studies carried out on normal husked barley, normal hull-less (naked) barley, acid dehusked barley and acid dehusked hull-less barley, as well as the malts derived from them, showed that when acid dehusked barley samples (obtained from either husked or hull-less barley), were processed using commercial enzyme preparations, they produced more alcohol when compared with the alcohol yield obtained from the barley samples from which the acid dehusked samples were derived. When the husked (Optic) control, acid dehusked and hull-less barley samples were malted, Optic control barley produced malt that gave higher dextrinising units (DU) and diastatic power (DP), whilst acid dehusked Optic and hull-less barley produced malts that gave similar DU results on day 5 of the germination time. When mashed, acid dehusked (Optic) barley malt produced wort that filtered faster than the wort obtained from the malt made from hull-less barley. This observation is very important because it shows that the husk of the barley is not the only factor that determines the filtration performance of the malted barley, since both the malt samples made from husked and acid dehusked barley had similar filtration rates on day 5 of the germination time. The slow filtration rate observed for the wort made from hull-less barley suggests that other factors play some role during the filtration of the mash made from hull-less barley malt. Although hull-less malt appeared to develop lower DU and DP enzyme activities, when compared with the values obtained for the Optic control, hull-less barley malted faster and produced optimum predicted spirit yield (PSY) at day 4 of the germination time. In contrast, the control husked Optic barley malt that had higher DU and DP produced equivalent (optimum) predicted spirit yield one day later at 5 days germination time. This is an advantage for hull-less barley, both in terms of time and energy saving during the malting of barley. Although the acid dehusked Optic barley produced more alcohol than the husked control when commercial enzyme preparation was used to process barley, it was surprising that when the derived malt was assessed, it gave a lower predicted spirit yield than the husked control, even though it produced a higher amount of hot water extract (HWE). The higher extract yield and lower predicted spirit yield obtained from the malt made from acid dehusked malt confirmed that high extract yield is not necessarily associated with high fermentable extract. Key words: Alcohol yield, acid de-husked barley, barley, diastatic power, dextrinising unit, filtration rate, hull-less barley. 1 The Scotch Whisky Research Institute, Research North Avenue, Riccarton, EH14 4AP, Scotland, United Kingdom. 2 Corresponding author: E-mail: Reginald.agu@swri.co.uk Publication no. G-2008-0303-533 © 2008 The Institute of Brewing & Distilling 62 JOURNAL OF THE INSTITUTE OF BREWING INTRODUCTION One major reason why extensive research work is still being carried out on barley is the central role barley plays in many industrial processes such as brewing, distilling and beverage industries. Also, development of different varieties of barley by plant breeders, aimed at producing barley varieties of improved quality has sustained research into barley. One of the most significant advances in the use of barley was the development of hull-less barley types which might be suitable for use in the production of Scotch whisky. Some studies carried out on hull-less barleys appear to suggest that they contain important brewing qualities, especially with regard to high extract recovery from the malt5,13. Also, previous work at the Scotch Whisky Research Institute (SWRI), looking at an early type of hull-less barley, has shown that the use of malt from this type of barley can provide substantially higher alcohol yields, compared with conventional barley malt. Although hull-less barley will malt faster than conventional barley5, one of the problems identified was that the absence of a suitable filter bed, normally provided by the husk component of conventional barley, would lead to problems with drainage, particularly in relation to malt distillery applications12. It was, however, considered that this material would most likely be applicable in malt distilleries using a wort filter, rather than a mash tun. Studies also showed that hull-less barley appeared to have higher levels of β-glucan than husked barley5,13. If a suitable enzyme-rich hull-less malt could be produced, this could potentially find an application in the grain distillery, and the intrinsic high alcohol yield from the malt would enhance distillery yield. At the time it was known that the early types of hull-less barley had not been optimised either for malting or for distilling, and it was necessary to wait until more suitable malting quality varieties became available before continuing with work in this area. A new variety of hull-less spring barley (Penthouse), supplied by a plant breeder, became available from the harvest of 2005. Although only available in very limited quantities, the SWRI has been carrying out some work looking at the suitability of this variety for distilling. Initial work was carried out on this batch of hull-less barley at SWRI (unpublished data) and elsewhere5 looking at its malting characteristics. Since the quantity of hull-less barley provided by the plant breeder for this study was limited, it was necessary to prepare our own micro-maltings to provide sufficient sample to undertake our studies on this material. With our current state of knowledge, it was considered that it might be possible to apply hull-less barley malt in the production of malt whisky, if we could improve mash tun drainage performance by adding hull-less malt as part of the grist of high quality pot-still malt. The processing property of mixed grist of control, hull-less and acid dehusked barley, and individual malt grists of control, hull-less and acid dehusked barley using the SWRI wheat cook procedure3 is presented in this paper. MATERIALS AND METHODS Germination energy (4 mL test) Germination tests were carried out as described in Method 1.7 of the Recommended Methods of the Institute of Brewing19. Total nitrogen content of barley Total nitrogen was determined on whole grains by NIR using a Foss Infratech 1241 NIR instrument, using a factor of 6.25 for total protein. Acid de-husking of the cereal samples The hull-less barley samples (Penthouse – low nitrogen, TN = 1.56%; high nitrogen, TN = 2.03% dry weight basis) used in this study were grown in the United Kingdom and were supplied by a plant breeder (Syngenta Seeds). Husked Optic barley (obtained from Scotch Whisky Research Institute – SWRI) was used as the control barley. The Optic control barley was dehusked using 50% sulphuric acid (H2SO4) as described in previous work7. Hull-less barley or normal wheat (Istabraq) was also dehusked in a similar way. Although hull-less barley or wheat has no husk, acid de-husking will also remove the pericarp5. Micro-malting of barley Laboratory micro-malting of barley was carried out as described in previous work4. Barley samples were steeped at 16°C by immersion in water for 8 h, followed by 16 h air-rest, followed by 24 h of immersion in water. Steeped samples were micro-malted at Heriot-Watt University using the Custom Laboratory Products micro-malting equipment (Keith, Banffshire). Grain was germinated at 16°C for 4 or 5 days. After germination, samples were kilned at 50°C (Seeger Kiln, Seeger Machinenfabrik, Fellback, Germany) for 16 h, and de-rooted by hand to give the finished malt. Malt dextrinising unit (DU) and diastatic power (DP) Malt DU and DP analyses were carried out by a commercial maltster using standard industry methods. Rapid visco-analysis (RVA) of Optic, hull-less and acid de-husked barley Studies of the viscosity properties of Optic control, hull-less and acid de-husked samples derived from these barley samples were carried out using a Newport Scientific Rapid Visco Analyser® (RVA) instrument supplied by Calibre Control (Asher Court, Lyncastleway, Appleton, Warrington, UK), using standard programmes for unmalted cereals and malted barley as described previously3,4,16. Alcohol yield analysis Mashing, filtration studies and alcohol yield from malted cereals. The commercial malt sample used in the filtration experiment was obtained from a distilling company. In order to study the effect of husk on filtration performance of hull-less barley malt, different proportions (50% commercial malt: 50% hull-less malt, or 25% commercial malt: 75% hull-less malt) of commercial malt were mixed with hull-less malt. The predicted spirit yield (PSY) was determined essentially as described for the fermentability of unboiled worts in Method 2.16 of the Recommended Methods of Analysis of the Institute of Brewing11,18. Malted samples were mashed for 1 h using the LB 8 Electronic (Funke-Gerber Instrument, Germany). After mashing, filtration of the mashed samples was carried out using Ederol 12 folded filter papers (32 cm) (H. Rudebeck and Co. Ltd, UK). During filtration, the time taken to collect different volumes of wort was recorded. In order to study the effect of husk on filtration rate of malt, a husked control malt was mixed with hull-less malt as reported above and then mashed at 65°C, and the wort obtained was filtered and timed as described earlier. Hot water extract (HWE) of wort was determined from the original gravity, measured using a Paar DMA 5000 density meter (Anton Paar Ltd, UK). Worts were pitched with distiller’s yeast, “M” type, supplied by Kerry Bio-Science (Menstrie, Clackmannanshire, UK) at a pitching rate of 1.25 g yeast to 250 g of wort. Fermentation was carried out in a thermostatted water bath at 33°C for at least 44 h. The final gravity of the fermented wash was measured using an Anton Paar 5000 density meter. Alcohol yield from un-malted cereals. The method was based on that of Brosnan et al.12 and was described in detail in a previous publication in this Journal3. In this method a commercially produced bacterial α-amylase enzyme preparation (Termamyl 120L), supplied by Novozyme, France S.A., was used during the pre-cooking stage of the process. This enzyme acts as a processing aid to facilitate the laboratory scale handling of the cereals. RESULTS AND DISCUSSION Properties of the barley samples studied The results in Table I show some of the properties of the barley samples studied. The barley samples had the acceptable germination energy necessary for malting barTable I. Some properties of the barley samples studied. Parameters Moisture (%) Germination energy (4 mL ) % Total nitrogen (%) dry weight Protein (%) N × 6.25 Optic control barley Acid dehusked Optic Hull-less barley 10.7 98 12.5 99 11.1 98 1.49 1.48 1.56 9.3 9.3 9.8 VOL. 114, NO. 1, 2008 63 ley, especially for the hull-less barley whose embryo is prone to damage as a result of a lack of protective husk during harvesting in the field. The results in Table I further show that both the Optic control barley and the acid dehusked barley derived from the Optic control barley had similar nitrogen content. Malting performance of Optic, acid de-husked Optic and normal hull-less barley Results shown in Fig. 1 and Fig. 2 give a visual indication of the progress of malting after 96 h. Fig. 1 shows a visual comparison of (unsieved) Optic barley and acid dehusked Optic barley after 96 h of germination. The results show that the Optic control barley germinated normally under the micro-malting conditions that were used, with normal rootlet and acrospire growth. On the other hand, with the hull-less barley, there was extensive acrospire growth, although this was not as great as with acid dehusked Optic barley. These results further confirm that a Fig. 1. Visual comparison of germination progress for samples of unsieved hull-less barley, Optic control barley and acid dehusked Optic barley after 96 h. A) Unsieved hull-less barley after 96 h germination. B) Optic control after 96 h germination. C) De-husked Optic after 96 h germination. 64 JOURNAL OF THE INSTITUTE OF BREWING shorter malting cycle would be required for malting either acid dehusked or hull-less barley5, which was clearly seen in the results of germination test (4 mL test) where acid dehusked barley achieved maximum germination in 48 h rather than 72 h. In this regard, if germination is not controlled carefully, this would lead to a significantly higher malting loss. Fig. 2 compares the germination progress of hull-less barley that has been separated into small (<2.5 mm) and normal/large corn fractions (>2.2 mm), after 96 h under the same conditions. While both fractions show extensive acrospire growth, there was much more acrospire development in the small corn fraction. This is further evidence that corns of different sizes will malt at different rates4. Malt analyses: DU and DP The results of the DU and DP of the malt samples (Table II) indicate that the enzyme levels from the husked Optic control were on the whole higher than for the hullless or acid dehusked samples on both day 4 and day 5. It is important to observe that the DU and DP of hull-less or acid dehusked barley were similar on day 5 germination, but were significantly lower than those of the husked control Optic. It is also important to note from the results in Table II that whilst Optic control barley developed higher diastatic enzyme (DU and DP) levels, the malt made from acid dehusked Optic barley or hull-less barley developed similar levels of these enzymes, especially on day 5 of the germination period, despite the fact that the acid dehusked Fig. 2. Visual comparison of the germination progress of hullless barley fractions. A) <2.5 mm hull-less barley (small corns) after 96 h germination. B) >2.2 mm hull-less barley (normal/ large corns) after 96 h germination. Table II. Malt analyses – amylolytic enzyme activity. Germination time (days) Sample Day 4 malt Optic control malt Acid dehusked Optic malt Hull-less barley malt Optic control malt Acid dehusked Optic malt Hull-less barley malt Day 5 malt Dextrinising unit (DU) Diastatic power (DP) °L 48 30 23 51 32 33 133 85 80 125 89 83 Table III. Filtration experiment – time (min) to collect wort from Optic and hull-less malts. Germination time (days) Sample Day 4 malt Optic control malt Acid dehusked Optic malt Hull-less barley malt Optic control malt Acid dehusked Optic malt Hull-less barley malt Day 5 malt barley was derived from the husked Optic control. The presence of husk may have played some role in differences observed in the modification rate of the barley samples by not only protecting the embryo from damage during malting, the husk will also help to retain more moisture required for continued modification during malting10. Barley with a damaged embryo will not germinate, and un-germinated barley will not contribute to enzyme development during malting5. It is important to mention that the hull-less barley used in this study was in perfect condition and therefore detrimental effects on malting performance of hull-less barley caused by damaged embryos were avoided5. However, the full role that the husks of barley play during the malting and processing of malted barley is not fully understood at present, and our observation during processing of these malted barley samples is discussed later in this paper. The higher enzyme levels observed for Optic control barley, when compared with lower enzyme levels observed for the hull-less barley suggest that higher nitrogen content of hull-less barley is not associated with the development of these enzymes1,9. Processing properties of malts of barley, acid de-husked and hull-less barley Filtration properties of the barley malts. Table III shows the filtration performance of the malted barley samples following mashing and wort collection. Clearly, the results in Table III show that the filtration rates for the hull-less micro-malts were much slower than for the conventional control malt (Optic), taking about double the time to collect the same quantity of wort. Interestingly, the acid dehusked Optic (day 5 germinated malt) malt gave similar filtration rates to the husked control, rather than the hull-less malt. Since the wort obtained from Optic control or acid dehusked Optic malt (day 5 germinated malt) had similar filtration rates, the husk of barley may not be solely responsible for the fast filtration rate of the wort of malted barley. This suggests that other factors controlling the filtration rate are intrinsic to the grain itself rather than simply a function of the presence or absence of husk as was originally thought. In this regard, acid dehusked barley has no husk but, its wort filtered at almost double the rate of wort obtained from hull-less barley malt, confirming that while the husks of barley play impor- 50 mL 100 mL 150 mL 3.2 4.8 7.0 3.8 5.4 8.3 9.7 13.3 22.0 10.0 14.8 23.2 26.2 30.2 60.0 34.8 36.8 60.0 Table IV. Filtration experiment – time (min) to collect wort from different malts. Time taken to collect 150 mL of wort Sample Optic control malt Acid dehusked Optic malt Commercial malt (C-malt)* Hull-less barley malt (TN = 1.56%) Hull-less barley malt (TN = 2.03%) Hull-less malt (50%): C-malt (50%) Hull-less malt (75%): C-malt (25%) *C-malt Day 4 malt Day 5 malt 26 30 34 60 63 42 47 35 37 34 60 69 48 55 = Commercial (SWRI) malt tant roles during filtration of wort of malted barley, other factors also play an important part during the filtration of the wort of malted barley. This may be linked to beta-glucan content of hull-less barley and malt5,13. Extended filtration studies. In order to further investigate the filtration performance of hull-less barley malt, hull-less barley malt was mixed with “normal” malt in different proportions shown in the Methods Section and then mashed. Filtration rates were then assessed. Samples of the high nitrogen hull-less micro-malted malt was used in this second experiment because it had a higher filtration rate (Table IV). This was compared with a grist containing 100% of the commercial control malt and Optic control micro-malt. The results obtained are shown in Table IV. It can be seen that both the Optic control micro-malt (day 5 malt) and commercial malt samples produced wort that filtered at the same rate because similar time was taken to collect equivalent volumes of wort made from both malts. When hull-less barley malt was mixed with an equal amount of commercial malt (50/50) and mashed in a similar way, the filtration results improved significantly by approximately 30%. In contrast, when the proportion of hull-less malt to commercial malt was adjusted to 75% hull-less malt and 25%, only a 20% improvement in filtration rate was achieved. The results of this experiment were however, very positive and showed clearly that the inclusion of conventional, commercial malt in the grist gave a significant improvement in filtration rate for hullless malt. The improved filtration times were still slower than the commercial malt on its own, but the experiments VOL. 114, NO. 1, 2008 65 Table V. Fermentability assessment of the malt samples. Germination time (days) Sample Day 4 Optic control malt Acid dehusked Optic malt Hull-less barley malt Optic control malt Acid dehusked Optic malt Hull-less barley malt Day 5 HWE (%) dry Fermentable extract (%) PSY (LA/tonne) dry 74.2 82.3 79.6 76.3 81.4 78.9 64.6 57.8 66.9 66.5 57.1 66.4 418.3 374.3 433.1 433.8 371.2 434.1 Table VI. Alcohol yield of barley and wheat processed using SWRI cook method. Alcohol yield from barley (LA/tonne) Sample Optic barley Hull-less barley Wheat Wheat Original barley Acid de-husked barley Alcohol yield difference (LA/tonne) % Alcohol yield difference 419.0 447.8 456.6 442.4 461.5 469.7 475.6 461.9 42.5 21.9 19.0 19.5 10.0 4.9 4.2 4.4 showed that there is scope for optimisation and that the use of hull-less malt would be feasible, but an optimal combination of hull-less malt and commercial malt has yet to be determined. Predicted spirit yield from malt of control, acid dehusked and hull-less malts. Although the hull-less barley malt appeared to develop lower amyloytic enzymes (DU and DP), and produced wort that filtered more slowly when compared with the malt made from Optic control, some advantages can be ascribed to the performance of malt made from hull-less barley. This is because when the malt samples were mashed and the wort fermented to determine the predicted alcohol yield (PSY), hull-less malt achieved maximum hot water extract (HWE) and PSY on day 4 germination because it malted faster (Table V). In contrast, the Optic control required 5 days to achieve a similar level of HWE and PSY. These results therefore confirm that although the DU and DP levels of hull-less malt appeared to be “low”, they produced similar levels of HWE and PSY as control Optic malt that appeared to develop “higher” DU and DP levels. These results further confirm that amylolytic enzymes of malted barley should be set as a range and not as single values as reported previously6. The results for the acid dehusked Optic malt were interesting. Whilst acid dehusked malt gave wort that filtered faster than hull-less malt, it had similar DU and DP values as hull-less malt, and produced wort with high HWE5,13, and the resulting PSY was unacceptably low. This is a huge disadvantage for the acid dehusked barley. The poor PSY result obtained for acid dehusked barley was probably a result of enzyme damage, or structural changes in the endosperm materials during the acid dehusking process (discussed later in this paper). The latter is the most probable reason, because both the acid dehusked and hull-less barley produced similar levels of DU and DP enzymes during malting (see Table II), but hullless barley malt produced significantly higher PSY results. The acid dehusked malt gave a poor fermentability (ca 70%; data not shown), as well as lower fermentable extract (Table V). Again, this highlights a very important observation, which was not reported in previous studies5,13, that HWE is not a reliable index of potential fermentability. 66 JOURNAL OF THE INSTITUTE OF BREWING Acid dehusking of barley. Originally, in the context of these experiments, a batch of acid dehusked barley (Optic) was prepared (see Methods section). This was intended as an additional control to provide an additional basis for comparison between hull-less and conventional barley. However, this material gave some interesting results, which are worth reporting and which will help to elucidate some trends that were found. While dehusked barley is similar to hull-less barley in that there is no husk, the dehusking process also has the effect of removing the pericarp5,7, which will influence grain properties. To study this more closely, a sample of hull-less barley was also subjected to the acid dehusking process, which would effectively remove the pericarp from the hull-less grain. The acid dehusked hull-less barley was then compared with the acid dehusked Optic for alcohol production using the SWRI method, which is used for wheat and other un-malted cereals3. Alcohol yield of barley and acid de-husked barley. When the barley samples were processed for alcohol yield potential as used in grain distilling for wheat reported in our earlier communication3 (see Methods section), the results of the alcohol yield obtained are shown in Table VI. It is interesting to note that the alcohol yield obtained from the acid dehusked Optic barley was 43 LA/tonne (10%) more than the alcohol yield obtained from husked Optic control barley. Similarly, acid dehusked hull-less barley also produced more alcohol (21 LA/tonne) than the normal hull-less barley. A possible interpretation of these results with regard to higher alcohol yield obtained from acid dehusked Optic barley (Table II), would be to conclude that the higher alcohol yield obtained from acid dehusked barley was caused by using more grains during the processing of the acid dehusked barley because the husk of barley has been reported to contribute about 10% of barley composition17. However, the higher alcohol result (21 LA/tonne or ~5%) also obtained from acid dehusked hull-less barley (which has no husk), strongly suggests that other unknown factors are responsible for the higher alcohol yield obtained from acid dehusked barley of both types of barley. In order to further confirm whether acid dehusking will produce more alcohol than from normal cereal, wheat (which has no husk) was dehusked and processed in a similar way. The results obtained are also shown in Table VI. It can be seen from the results presented in Table VI that acid dehusked wheat samples also produced more alcohol (over 19 LA/tonne or ~4%) than the original normal wheat samples. It is therefore possible that acid dehusking results in modification or degradation or hydrolysis, of cell wall materials or other non-starch polysaccharides (NSP) such as cellulose and hemicellulose materials14,15 of barley, resulting not only in easier access to starch, but also better extraction of fermentable sugars (such as glucose) deriving from endosperm and the non-starch polysaccharides of these cell wall components2, resulting in the higher alcohol yield obtained from these cereals. These results, however, confirm that dehusking cereal grains will yield samples that will produce more alcohol than the original cereal. Agu et al.2 also reported the production of ethanol from other cellulose and hemicellulose materials derived from other materials by combined heat and sulphuric acid treatment. The glucose sugars released from non-starch cellulose materials from acid dehusked cereals during processing might have contributed to a higher alcohol yield obtained from acid dehusked barley and wheat when the acid dehusked barley or wheat was processed. RVA analysis. These results were interesting and it was decided to look more closely at the acid dehusked and hull-less barley using the Rapid Visco Analyser (RVA). The samples were analysed using the RVA method for unmalted cereal as described previously3,16 and the RVA profiles are shown in Fig. 3 and Fig. 4. The RVA profiles of the acid dehusked samples were both different from the original hulled and hull-less barley. In Fig. 3, the dehusked Optic gave a similar profile to the original untreated sample, but had a significantly higher peak viscosity. In both cases the breakdown viscosity was the same, indicating that the starch composition was similar for both the untreated and dehusked Optic barley. The set back viscosity of the dehusked sample shows an unusually steep slope at about 10 min for unknown reasons. This perhaps indicates increased retrogradation, of a more linear (amylose-like) starch fraction or as a result of the solubilisation of viscous cell wall material. This contrasts with the viscosity profiles of the hull-less and acid dehusked hull-less samples, shown in Fig. 4. These gave a higher viscosity than either the conventional or dehusked Optic barley. The viscosity of the acid dehusked hull-less barley was much higher than its untreated equivalent, giving a peak viscosity, which was more than double that of the normal hull-less barley. Although the viscosity of the acid dehusked hull-less barley was much higher, the shape of the profile was almost identical to that of the acid dehusked Optic sample, indicating that the acid dehusking treatment has had the same effect on both samples. The RVA and alcohol yield results agree with our previous report3, where it was shown that a high RVA peak and final viscosity resulted in a higher alcohol yield. The higher RVA peak and final viscosity obtained from the acid dehusked barley, in contrast to the lower RVA peak and final viscosity obtained from the original barley was a result of a higher viscous load of the cereal3, rather than the influence of microbial enzyme activity associated with the grains8. Al- though, amylase activity will have some effect in reducing the RVA pasting profiles of cereal grains, this was not the case in this study because the effect of enzymes (from malt and/or microbial preparations) on RVA pasting characteristics of different cereals, and especially wheat, has been investigated extensively at SWRI (data not published). Therefore the higher viscous load present in the cereal resulted in the higher alcohol yield obtained from the acid dehusked barley3. The results of acid dehusking showed that the limitation of alcohol yield in cereals could be, in part, due to the presence of some cellulosic materials which are not hydrolysable during the normal cooking process, but which were hydrolysed by the acid dehusking process. It is also very likely that the similar pattern of elevated set back viscosity observed in the later stages of the RVA analysis, for both the dehusked samples of Optic and hull-less barley were caused by the same factor(s), but these trends are not fully understood. It is also very likely that hydrolysis products of these non-starch polysaccharides might have contributed to the hump observed towards the final viscosities in the RVA profiles of the acid dehusked samples of barley reported in Fig. 3 and Fig. 4, and may also have contributed not only to the higher RVA profiles of the acid dehusked samples, but also to the higher alcohol yields3. Fig. 3. RVA pasting properties of Optic control and acid dehusked Optic barley. Fig. 4. RVA pasting properties of normal hull-less and acid dehusked normal hull-less barley. VOL. 114, NO. 1, 2008 67 CONCLUSIONS The results have shown that although the malting properties of hull-less barley are very different from a conventional spring barley variety such as Optic, with suitable care it should be feasible to produce suitable malt from hull-less barley. One major advantage with malting hull-less barley is that water uptake would be very rapid during the steeping cycle, and it would therefore malt faster. While diastatic enzyme levels (DU/DP) for the micro-malts derived from hull-less barley variety appeared to be relatively low compared with husked Optic barley malt, hull-less malt produced malt that gave optimum predicted spirit yield earlier than the predicted spirit yield obtained from husked Optic control malt. This suggests that the hull-less malt is capable of developing sufficient enzymes at earlier stages of malting and will save costs and energy. The filtration properties associated with hull-less malt were due to some intrinsic property of the cereal itself, rather than simply a result of the lack of husk to form a filter bed. Other studies5,13 have shown that the beta glucan levels in hull-less barley and malt are quite high and may affect the filtration rate in hull-less malt. However, when used as part of a mixture with conventional malt, even at a high hull-less malt inclusion rate of up to 75 percent, there was an improvement in filtration performance. With the current samples, an inclusion rate of 50 percent was sufficient to give a significant improvement in filtration times. This shows that once a suitable hull-less distilling barley is identified, it should be possible to optimise its performance in the mash tun. Acid dehusked barley was prepared to provide an ‘artificial’ Optic counterpart for the hull-less barley, and while not central to the work which has been described above, this has provided some additional information which will help to further elucidate the processing properties of barley. Clearly while the dehusking process can result in higher alcohol yields, by providing easier access to the starch, there would be no advantage to using this process in alcohol production (i.e. in a non-Scotch whisky context) since it has other serious negative effects which can inhibit alcohol yield. This process may however, be useful in bio-ethanol production. Further studies will be carried out with more suitable hull-less barley varieties as they become available from barley breeders. Savings in time and energy should also encourage further studies of the alcohol producing potential of hull-less barleys. ACKNOWLEDGEMENTS The authors would like to thank the Directors of the Scotch Whisky Research Institute for permission to publish this paper. The authors would also like to thank Syngenta Seeds for providing the hull-less barley used in this study, and Mark Patterson (SWRI) for his technical assistance. 68 JOURNAL OF THE INSTITUTE OF BREWING REFERENCES 1. Agu, R. C., Quality assessment and performance of malted barley for food processing. Tech. Q. Master Brew. Assoc. Am., 2005, 42, 199-203. 2. Agu, R. C., Amadife, A. E., Ude, C. M., Onyia, A., Ogu, E. O., Okafor, M. and Ezejiofor, E., Combined heat treatment and acid hydrolysis of cassava grate waste (CGW) biomass for ethanol production. Waste Management, 1997, 17, 91-96. 3. Agu, R. A., Bringhurst, T. A. and Brosnan, J. M., Production of grain whisky and ethanol from wheat, maize and other cereals. J. Inst. Brew., 2006, 112, 314-323. 4. Agu, R. A., Brosnan, J. M., Bringhurst, T. A., Palmer, G. H. and Jack, F. 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