The Effect of Steeping Time on the Final Malt Quality of Buckwheat

Transcription

1 The Effect of Steeping Time on the Final Malt Quality of Buckwheat H.H. Wijngaard 1,2, H.M. Ulmer 1,2, M. Neumann 3 and E.K. Arendt 1,4 ABSTRACT J. Inst. Brew. 111(3), , 2005 To determine the effect of steeping time on final buckwheat malt quality, buckwheat was steeped for three different times resulting in three different out-of-steep moisture contents: 7 h steeping (35%), 13 h steeping (40%) and 80 h steeping (45%). An increased steeping time increased malting losses, total betaamylase activity and Kolbach index. On the contrary total nitrogen, friability and viscosity of consequent congress worts were decreased. A maximum alpha-amylase activity was found in buckwheat malted with an out-of-steep moisture content of 45%. Beta-amylase existed in a soluble and latent form in buckwheat. The latent form was solubilised during malting. In addition extra beta-amylase was produced. In general the optimum out-of-steep moisture content for buckwheat is between 35 to 40%, which is a compromise between attaining the desired malt quality and minimising malting loss. Key words: Buckwheat, enzyme activity, malting, malt quality, moisture content, steeping time. INTRODUCTION Buckwheat is a traditional crop grown in Central and Eastern Europe and Asia. China was the biggest producer of buckwheat in 2003, followed by Russia and the Ukraine 13. Nevertheless it is possible to grow buckwheat in other parts of the world as it is a short-duration crop and requires a moist and temperate climate to grow 27. Buckwheat (Fagopyrum) has similarities with cereals such as barley. The buckwheat achenes (fruits) consist predominantly of starch 4, they are edible and they have a starchy endosperm and a non-starchy aleurone layer 3. Buckwheat does not belong to the grass family (Poaceae) as cereals do and therefore it is called a pseudo-cereal and differences exist in the structure of the grain. In recent years buckwheat has regained interest as an alternative crop for organic cultivation and as a health food 32. Buckwheat has considerable health benefits, such as protein of high biological value due to the relative high amino acid 1 Department of Food and Nutritional Sciences, National University of Ireland, University College Cork, College Road, Cork, Ireland. 2 National Food and Biotechnology Centre, National University of Ireland, University College Cork, College Road, Cork, Ireland. 3 University of Applied Sciences, Marquardstraße 35, Fulda, Germany. 4 Corresponding author. e.arendt@ucc.ie Publication no. G The Institute of Brewing & Distilling scores and high levels of lysine, when compared to cereals. In addition buckwheat contains several antioxidants such as rutin, which has a hypotensive effect and is claimed to strengthen capillary blood vessels 36. It also contains fagopyrins, which are claimed to reduce diabetes II 23. In addition, buckwheat is regarded as gluten-free, which means that buckwheat does not contain gluteninlike proteins, which are toxic for people suffering from coeliac disease 1,14. The incidence of coeliac sufferers worldwide has been predicted to increase over the next years due to a heightened awareness of the disease and improved diagnostic procedures 12. This will lead to an increased demand by the consumer for gluten-free products, such as gluten-free beers. In micro-brewing, buckwheat is one of the main grains used for the production of glutenfree beers and is added mainly as an unmalted adjunct 24. The objective of this work is to optimise the malting process of buckwheat, in order to get malt of high enzymatic content. Barley malt is produced by modifying barley as efficiently as possible and the buckwheat malting process must be adapted due to structural differences between barley and buckwheat grain. Barley is a monocotyledonic plant and buckwheat is a dicotyledonic plant. This entails that triangular buckwheat fruit contains two cotyledons instead of one cotyledon (called the scutellum in barley) 20. Due to this botanical difference, enzyme production and therefore the malting process will differ between buckwheat and barley. In previous studies the importance of optimising the germination temperature during buckwheat malting was determined to get optimum malt quality 37. In this paper the effect of steeping time on final buckwheat malt quality was examined. Three different steeping durations and consequent out-of-steep moisture contents (SMC) were used. The obtained results were compared to barley controls. It is known that the barley grain should have reached a SMC of 43 46% to reach a sufficient modification during malting 8. To define the optimum SMC for buckwheat, steeping characteristics of buckwheat were determined first. From these trials three different SMC s were selected and the effects of these three SMC s on buckwheat malt quality were evaluated. MATERIALS AND METHODS Materials Unmalted buckwheat. Common buckwheat (Fagopyrum esculentum) was used in the malting trials. The buckwheat samples were grown in Eastern Europe and harvested in The buckwheat was received from Trouw VOL. 111, NO. 3,

2 Table I. Characteristics of unmalted BH and unmalted and malted barley. Unmalted BH Unmalted barley Malted barley Moisture content (%) TN (%) Size (mm) Shape three-edged symmetrical symmetrical Germinative energy 4 ml (%) n.a. Germinative energy 8 ml (%) n.a. Alpha-amylase activity (international units g 1 wet wt.) Total beta-amylase activity (units g 1 wet wt.) Protease activity (mg leucine h 1 g 1 wet wt.) n.a. = not applicable B.V. (Rotterdam, The Netherlands). The characteristics of buckwheat with remaining hull (BH) are shown in Table I. Unmalted and malted barley. Unmalted and malted barley (variety Optic, grown in Ireland in 2002) were obtained from the Malting Company of Ireland (Cork, Ireland). They were used as controls in all malt quality analyses. The characteristics of the unmalted and malted barley samples are shown in Table I. Procedures Water uptake rate. BH was continuously soaked in water at 10 C for up to 87 h in a micro-malting machine (Joe White Malting Systems, Perth, Australia). Pouches (n = 2) with 25g BH were soaked for 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 13, 32, 39, 59, 63, 80 and 87 h. The samples were centrifuged at 300 g for 5 min to remove surface water. To determine moisture contents, the samples were predried for 24 h at 50 C, after which EBC-method 4.2 was followed 10. Malting trials. The malting trials were carried out in duplicate (n = 2). In every trial 3 different steeping times were applied, which resulted in 3 different moisture percentages at the end of steeping. Steeping: 7 h resulted in 35% moisture (B35), 13 h in 40% moisture (B40) and 80 h in 45% moisture (B45). The steeping temperature, germinating and kilning conditions were kept constant: steeping temperature (10 C); germination conditions (15 C/4 days) and kilning conditions (45 C/5 h and 50 C/12 h). Analyses Rootlet length of green malt. The single rootlet length of the buckwheat samples was determined by measuring the rootlet of 100 seeds with a ruler and calculating the means, after 12 h of steeping and 24, 48 and 58 h of germination. Germinative energy. Germinative energy was determined by using EBC-method Malting loss. Six pouches with 50 g of BH were placed in the malting machine at the start of the malting process. After kilning the samples were weighed and polished with a vortex cleaner, which removed rootlets. Malting losses (%) were calculated using the difference in weight divided by the initial weight, multiplied by 100. Friability. Friability was determined by following EBC-method Alpha-amylase activity. To measure alpha-amylase activity ICC standard method was followed using an enzyme kit (Megazyme, Bray, Ireland). Alpha-amylase activity was calculated according to manual instructions. Total and soluble beta-amylase activity. Total and soluble beta-amylase activity was determined following the method described in the beta-amylase Megazyme enzyme-kit. A dilution factor of 250 times was used. Betaamylase activity was calculated according to manual instructions. Mashing. All malt samples were mashed according to EBC-method Extract (%) of resulting wort was measured using a SCABA (Tecator AB, Höganäs, Sweden). Viscosity. Viscosity of congress worts was measured using a falling ball viscometer (Haake Gmbh, Karlsruhe, Germany) according to EBC-method Total nitrogen (TN). Total nitrogen of unmalted and malted buckwheat were analysed according to EBC-methods (barley section) and (malt section), respectively 10. Total soluble nitrogen (TSN) and Kolbach Index (KI). Total soluble nitrogen was determined following EBC-method (malt section) 10. Kolbach Index (KI) can be calculated with the formula: KI = (TSN/TN) * 100%. Free amino nitrogen (FAN). FAN contents of all worts were determined following EBC-method 8.10 (wort section) 10. RESULTS AND DISCUSSION Water uptake rates Many factors influence the water uptake of kernels including size, nitrogenous content and initial moisture content of the grains 8. Since buckwheat has a different shape, size, nitrogenous content and moisture content compared to barley (Table I), it is likely that water uptake rates differ and parameters of the steeping process are influenced. In two-row barley the water uptake up to a moisture content of 24%, was extremely rapid. At this early stage of water uptake, mainly physical absorption of water occurred into the embryo of the barley kernel. Thereafter, the water uptake rate became very slow but continued at a linear rate until it reached its saturation point. During this stage water diffused slowly into the endosperm of the barley kernel 19. In general, when grain is soaked in water the moisture content increases rapidly at first but progres- 276 JOURNAL OF THE INSTITUTE OF BREWING

3 sively slows down 6,25. To determine the water uptake rate of buckwheat and the effect of steeping time on the moisture content of buckwheat, BH was soaked continuously for 87 h. Buckwheat showed a rapid increase of moisture first, which slowed down gradually as is found in other grains (Fig. 1). In contrast to barley, buckwheat reached a higher moisture content during the stage of rapid moisture uptake. The moisture content of BH increased during 13 h steeping, from 11.73% to 40.02%. At this point water uptake slowed and after 87 h of steeping BH reached a moisture content of 45.48%. Barley reached a moisture content of approximately 45% after 120 h when soaked at 14.4 C 6, while buckwheat reached 45% moisture after 80 h of soaking. It has been reported that smaller grain size increases water uptake in grains 15. Buckwheat with an achene size of 4 6 mm is smaller compared to barley grains (6 12 mm). This is probably the main reason for the difference in water uptake rate. Steeping losses are mainly due to three factors: displacement of dust, dissolving of materials from the grain by leaching and metabolic activity of the grain, releasing CO 2 and small amounts of ethanol. The steeping loss of barley has been reported to fall within the range of % of the initial dry weight of the grain 5. Buckwheat showed higher steeping losses. At a final moisture content of 46%, the steeping loss of BH was 1.45%. Fig. 1 shows that BH reached a moisture content of 35% after 7 h (B35), 40% after 13 h and 45% after 80 h. These steeping times and relating moisture contents were used in the malting trials. Malting trials Rootlet length. As mentioned before barley is monocotyledonic and buckwheat is dicotyledonic, which means buckwheat, contains not only one but two cotyledons. In monocotyledons the cotyledon acts as an absorptive tissue during germination, transferring endosperm nutrients to the embryo. In barley and other grasses the cotyledon is synonymous to the scutellum. In the mature seed the endosperm is still present. In buckwheat and other dicotyledonic plants the cotyledons store nutrients, which are used during and after germination. During the development of the embryo, the cotyledons become thick and filled with starch or protein, while the endosperm shrinks, due to the supply of nutrients. After germination the cotyledons are large and the endosperm may be completely used up 26. This illustrates one of the main differences between barley and buckwheat. Another difference is that the tested buckwheat samples were not water-sensitive in comparison to barley samples. Water-sensitivity is defined by the difference between germinative energies determined in the 4-ml and 8-ml test 6. Buckwheat samples germinated well in both water volumes, whereas barley samples germinated better in 4 ml water than in 8 ml water. Therefore the barley sample (variety Optic) was classified as water-sensitive (Table I). Buckwheat germinates with just a single rootlet and not as barley with several rootlets and acrospire. In the present study, the length of the single rootlet of germinating buckwheat was measured and it was observed that the rootlet length increased with increasing SMC (Fig. 2). After 60 h germination, the mean root lengths of B35, B40 and B45 were 13.4 mm, 17.2 mm and 29.4 mm respectively (Table II). The increase in rootlet length can be explained by increased malting time. When sufficient oxygen is present and the grain is not water-sensitive, grains can already start to chit during steeping. Since B45 was steeped 67 h longer than B40, during steeping of B45, chitting had probably already started. After 12 h germination 90.35% of B45 showed rootlet growth, while neither B35 or B40 showed rootlet growth. Malting loss. Malting losses result from a number of factors: a) leaching of compounds from grain during steeping, b) respiration of the grain and fermentative processes and c) the removal of rootlets 5. Smart et al 33 found that as the SMC increased, the malting losses in barley increased. In buckwheat a similar trend was observed. B45 was found to have the highest malting losses, followed by B40 and B35, which revealed the lowest malting losses (Table II). This can be explained by the following: (i) a higher steeping loss was determined with increased SMC; (ii) a higher rootlet length was observed with increased SMC (see previous results). Since rootlets are removed during malt cleaning, malts with longer rootlets will result in higher malting losses. Fig. 1. Means of moisture percentages (%) of BH against soaking time (h). Fig. 2. Buckwheat kernels of B35, B40 and B45 after 60 h of germination. VOL. 111, NO. 3,

4 Table II. Average values of trial I and II of characteristics of B35, B40, B45 and control barley malt. Parameter B35 B40 B45 Barley malt Rootlet length after 60 h germination (mm) n.a. Malting loss (%) n.a. Moisture percentage kilned and cleaned malt (%) TN (%) Wort viscosity (mpas) Friability (%) Alpha-amylase activity (international units g 1 wet wt.) Filterability poor poor poor good Extract d.w. (%) Fermentability (%) TSN (% m /m) Kolbach Index (%) FAN (mg L 1 ) n.a. = not applicable In general, malting losses of barley are recorded between 6.5% and 10.5% 5. When these limits are applied to malting buckwheat, the malting loss of B45 (10.74%) is at the upper limit of this range. Lower malting losses were determined in B35 and B40, 7.43% and 7.89%, respectively. Total Nitrogen (TN). In barley, besides protein many other nitrogenous compounds are present, such as amino acids and nucleic acids. Apart from substances leached from the grain during steeping, there is no loss of nitrogen from the barley grain during malting and the respiratory loss of dry matter tends to raise the TN of the grain. However, nitrogenous compounds move into the rootlets during malting and the removal of rootlets after malting leads to a significant loss of TN in the finished malt 6. TN of buckwheat malt decreased with increasing SMC (Table II). This can be explained by the fact that at higher SMC s more nitrogenous compounds were used for rootlet growth. It is assumed that a similar mechanism occurs in buckwheat as in barley and nitrogenous compounds are moving into the rootlets during germination. Since the rootlets of the buckwheat malts were removed, more TN was removed with the longer rootlets. Viscosity. During barley malt brewing 1,3 1,4-mixed -glucans are particularly important because these -glucans can: i) reduce extract yields in the brewhouse; ii) participate in haze formation in wort and beer and iii) cause high wort and beer apparent viscosities 18. These high apparent viscosities can lead to lautering and beer filtration problems 17. The 1,3 1,4-mixed -glucan is mainly found in the endosperm cell walls that surround barley starch granules. Like barley starch granules, buckwheat starch granules are located in cells in the endosperm and are surrounded by relatively thin cell walls 29. In contrast to barley, these cell walls do not contain 1,3 1,4-mixed -glucan 37. Nevertheless, the viscosity of buckwheat congress worts was significantly higher than congress worts produced with barley malt. This could indicate the presence of a polysaccharide other than 1,3 1,4-mixed -glucan in buckwheat wort. Asano et al 2 have identified a polysaccharide in the buckwheat grain that consisted of xylose, mannose, galactose and glucuronic acid. Although the proportion of soluble fibre was relatively small (2.9%) 32, these soluble fibre compounds cause high viscosities and are therefore very significant for the brewing process. Table II shows the viscosity of congress worts produced from buckwheat malts steeped at different moisture contents. It is clearly seen that with increased SMC, wort viscosity decreased. This could be explained by the fact that polysaccharides might be degraded to a higher extent in worts derived from buckwheat malts with higher SMC s. When malting barley, a reduction in -glucan content of worts was reported when malting with higher SMC s. The authors found a significant relation between -glucan contents and viscosities of worts 33. Friability. When malting barley, the degree of physical modification can be measured with a friabilimeter. With high homogeneity of the barley malt, friability correlates with other malt quality parameters such as enzymatic activity and fermentability of congress worts 21. Smart et al 33 found, that friability of barley malts was enhanced when higher SMC s were applied. They reported that friability increased from 69% with a SMC of 41%, to a friability of 88% when the moisture content was raised to 49%. Additionally the increase in friability in barley malt correlated with lower viscosities and lower -glucan levels of consequent worts. In contrast to barley, the friability of buckwheat malt decreased with increasing SMC (Table II). The friability values of malted buckwheat samples were much higher (91.22% to 96.95%) than values reported for barley. A possible explanation can be found in the structure of the buckwheat grain. As in barley, a proteinaceous matrix surrounds the starch granules in buckwheat 29. But in buckwheat only 35% of the total protein is located in the endosperm 3. Dunaevsky and Belozersky 9 reported that the majority of storage protein in monocotyledons (barley) is hydrolysed in the endosperm during seedling growth. In dicotyledons (buckwheat), storage proteins are firstly hydrolysed in the cotyledons. Radovic et al 31 characterised seed storage proteins in buckwheat seeds and identified 13S globulin as the major storage protein. Besides 13S globulin that was found only in cotyledons, minor class storage proteins that resided both in endosperm and cotyledons existed. During embryo development, the cotyledons in dicotyledonic plants become thick and fill with starch or protein, while the endosperm shrinks since it supplies the nutrients 26. This might explain why in barley a positive correlation and in buckwheat a negative correlation between protein modification and friability was 278 JOURNAL OF THE INSTITUTE OF BREWING

5 Fig. 3. Averages of trial I and II of soluble ( ) and total ( ) beta-amylase activity (U g 1 (wet wt.)) of BH, B35, B40 and B45. found 11. The dicotyledonic opposed to a monocotyledonic structure of the grain could affect friability and more structural research has to be carried out to confirm this. Alpha-amylase activity. Alpha-amylase is an endoenzyme, which randomly acts on -1-4 links of starch releasing small dextrins and fermentable sugars 22. In Table II alpha-amylase activities of B35, B40, B45 and the control barley malt are shown. No difference was found between alpha-amylase activity in B35 (steeping time of 7 h) and B40 (steeping time of 13 h). B45, which corresponds with a steeping time of 80 h, showed the highest alpha-amylase activity ( IU g 1 (wet wt.). Hence it seems that alpha-amylase activity is enhanced with a steeping time higher than 13 h. Alpha-amylase activity of the control barley malt was more than twice as high ( IU/g) than the maximum amount of alphaamylase found in buckwheat malt. Possibly a buckwheat seed does not require a higher level of alpha-amylase activity due to differences in the starch structure. Buckwheat starch granules have a much smaller size (4 6 µm) than barley (6 12 µm); therefore enzymes have a large total surface area to act upon 3. The amylose:amylopectin ratio is lower 38, which should have consequences for the enzymatic degradation. Most evidence presented in literature leads to the conclusion that amylopectin is more readily degraded than amylose 6. Finally buckwheat starch is more easily degraded by porcine pancreatic alpha-amylase than corn and wheat starch 30. This could imply that a lower amylolytic enzyme activity is needed to degrade buckwheat starch. Total and soluble beta-amylase activity. Beta-amylase is an exo-enzyme that releases maltose molecules from the non-reducing ends of amylose and amylopectin 22. In unmalted barley, beta-amylase exists in a latent form, bound by disulphide bondages and a soluble form. During malting the latent form is transformed to the soluble form. Proteolytic enzymes or agents can reduce disulphide linkages and release the bonds of the latent enzyme 7. In this study cysteine was used to free the bound enzyme. By using a buffer with and without added cysteine, total as well as soluble beta-amylase activity, were determined. Fig. 3 shows soluble and total beta-amylase activity in unmalted and malted buckwheat. The differences between soluble and total beta-amylase activity suggest that buckwheat has a latent form of beta-amylase such as found in barley 34. In addition it can be seen in Fig. 3 that a total beta-amylase activity of units g 1 (wet wt.) was observed in unmalted buckwheat. During malting total beta-amylase activity was increased to a maximum of units g 1 (wet wt.) in B45. Since all malted buckwheat samples showed a higher total betaamylase activity than unmalted buckwheat, it can be concluded that beta-amylase was synthesized during malting. This is in contrast to barley, in which total beta-amylase activity is not (or very little) increased by the malting process 35. Total beta-amylase activity was increased with an increase in steeping time (Fig. 3). In buckwheat, soluble beta-amylase activities were not influenced by different SMC s (Fig. 3). Soluble beta-amylase activity is regarded as beta-amylase active in the grain, and is therefore more important than total beta-amylase activity. The maximum level of soluble beta-amylase activity detected in buckwheat was units g 1 (wet wt.), which is significantly lower than what is found in barley ( units g 1 (wet wt.); control malt). Similar low levels of beta-amylase were found in finger millet and sorghum 28. Applying air rest stages during steeping or optimising kilning procedures could probably optimise malting procedures and hence enzyme activities. Congress mashing. All congress mashes of B35, B40 and B45 were dark blue, when coloured with iodine after 1 h at 70 C, which indicated that all mashes were still starch positive. Wijngaard et al 37 reported that gelatinisation temperatures of buckwheat malts ranged from C. Therefore it is more likely that starch positive mashes were due to relatively low amylolytic activities of buckwheat malt compared to barley malt. In addition all congress mashes of B35, B40 and B45 showed a poor filterability. In future research, obtaining a starch free mash should be emphasised, by optimising germination, kilning and mashing procedures. Extract and fermentability. In previous studies a relation between alpha-amylase activity and extract content of buckwheat malt was found 37. B45 showed an increase of VOL. 111, NO. 3,

6 alpha-amylase activity of 15% compared to B35 and B40 and therefore B45 was expected to have a maximum extract percentage. In contrast, a maximum extract was found in wort obtained from B40 (Table II) and no correlations between alpha-amylase activity and extract percentages were found (results not shown). In addition a minimum fermentability was determined in B45 (Table II). Total Soluble Nitrogen (TSN), Kolbach Index (KI) and Free Amino Nitrogen (FAN). Nitrogenous compounds that are derived from the malt by proteolysis and extraction can affect fermentation, foam, mouth feel, the tendency to form hazes in the final beer and mash filtration 5. Protein hydrolysis differs in monocotyledons and dicotyledons. In monocotyledonic seeds (barley and sorghum), gibberellic acid is formed in the embryo or aleurone layer in response to a factor diffusing from the embryo. In the aleurone layer, gibberellic acid stimulates synthesis of hydrolytic enzymes, which are then secreted into the endosperm and hydrolyse storage proteins. In dicotyledonic seeds (buckwheat) the case is much more complex. The embryonic axis serves most probably, as a site of efflux of the products of protein hydrolysis in the cotyledons during seedling growth and thus regulates the course of proteolysis. The enzyme responsible for the first stage of proteolysis was already present in dry buckwheat grain. Earlier results confirm the fact that proteolytic activity was already present in unmalted buckwheat 37. It was assumed that the second stage of storage protein hydrolysis in buckwheat cotyledons is regulated by concentrations of amino acids and peptides accumulating at the site of hydrolysis, possibly by feedback inhibition 9. As a result of this complex proteolysis in buckwheat, the only significant difference between the different buckwheat malts was found in KI s of the tested worts. KI increased with increasing SMC (Table II). This could be due to higher proteolytic activity in buckwheat malts with higher SMC s. No significant differences were found in FAN contents of the different worts and no relation was found between FAN and TN, FAN and TSN, and FAN and KI of each wort. The FAN-levels of congress worts ranged from to mg l 1, while the FAN level of the control barley malt congress wort was determined at mg l 1. Although the level of FAN in barley malt was higher than in buckwheat malt, the FAN level will probably be sufficient to ensure a healthy fermentation, once the mashing program is optimised. Barley malt wort should certainly not contain a FAN-level less than 100 mg l 1 to ensure a healthy fermentation 6. CONCLUSIONS The objectives of this study were to determine: i) the effect of steeping time on the moisture content of unhulled buckwheat and ii) the impact of out-of-steep moisture content (SMC) on the quality of buckwheat malt. In the first part of the study buckwheat was continuously soaked in water for 87 h. BH showed a similar water uptake curve to other grains, which means moisture uptake increases rapidly to a certain point, after which moisture uptake slows down. BH showed a faster water uptake than barley, probably due to the fact that buckwheat does not contain husk layers and is smaller in size. In the second part of the study the effect of three different SMC s on buckwheat malt quality were assessed. The three SMC s that were used and their relating steeping times were: 35%/7 h steeping (B35), 40%/13 h steeping (B40) and 45%/80 h steeping (B45). In general an increased SMC increased malting losses, total beta-amylase activity and KI and decreased TN, viscosity and friability. The SMC should be a compromise between attaining the desired malt quality and keeping the malting losses to a minimum. B35 and B40 showed a malting loss of 7.43% and 7.89%, respectively. B45 showed a maximum malting loss of 10.74%. Hence the malting loss of B45 exceeded the acceptable range for malted barley, which lies between 6.5 and 10.5%. This higher malting loss of B45 was caused by a higher steeping loss and longer rootlets. The longer rootlets also explain a decrease in TN, since it is assumed that degraded proteinaceous compounds move into the rootlets during germination and rootlets are removed during malt cleaning. Since TN was decreased with an increased SMC, it was expected that the protein matrix in buckwheat was broken down further and the friability would be increased, but the opposite was found and the friability decreased with an increasing SMC. Alpha-amylase activities and especially beta-amylase activities were low in all buckwheat malts, which led to starch positive mashes. It was observed that beta-amylase exists in a soluble and latent form in buckwheat. During buckwheat malting beta-amylase was solubilised, which is similar to what is observed during barley malting. The difference between buckwheat and barley malting is that in buckwheat additional beta-amylase is produced. From this study it can be concluded that the optimum SMC for the production of buckwheat malt lies between 35 and 40%. At these moisture levels the malting loss falls within the acceptable range and malt quality is optimised. 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