World Journal of Microbiology and Biotechnology 8, 509-511
Sorghum brewing using sweet potato enzymic flour to increase saccharification M.U. Etim and O.U. EtokAkpan* The diastatic activity of three sweet potato varieties was principally due to ~-amylase. Substitution of sorghum malt with sweet potato at 20% (w/v) gave a higher activity than an all-sorghum malt. Maltose in the sorghum/potato wort was $0 mg/ml, similar to that in barley malt. The free alpha amino nitrogen of the sorghmn/potato worts was lower than that of the all-sorghum malt but was still within the range needed for yeast growth. Incubation of the potato enzymic extract with isolated sorghum endosperm cell walls and viscosity tests demonstrated the presence of (1 -~ 3,1 --* 4)-~-glucanase (limiting in sorghum) in the sweet potato. Key words: fl-Amylase, saccharification, sorghum, sweet potato
A recent innovation in Nigerian brewing is the utilization of locally-grown cereals as raw materials for the production of beer (Adejemilua 1989). Sorghum remains the preferred grain (because of climate), though it contains low activities of fl-amylase, the enzyme which controls, to a large extent, saccharification during mashing (Aniche & Palmer 1990; EtokAkpan & Palmer 1990a). Sorghum malts, therefore, produce poor fermentable worts with high levels of dextrins, which can cause filtration problems and haze in the beer (Glennie & Wright 1986; Aisien & Muts 1987), and low maltose. Preliminary studies have shown that fl-amylase is present in the grains of many cereals and to a significant degree in the sweet potato (Murty 1940). The amylase of the sweet potato appears to contain no alpha component and it degrades starch in a pattern similar to that of barley malt fi-amylase (Robyt & Whelan 1968). As sweet potato grows abundantly in Nigeria, this study explores the possibility of using sweet potato fl-amylolytic flour to complement that of sorghum during mashing.
Materials and Methods Samples
Brown sorghum, SK5912, and Proctor barley were from the Seed Production Unit of the Institute of Agricultural Research, Zaria, M.U. Etim and O.U. EtokAkpan are with the Department of Brewing Science & Technology, University of Uyo, P. M. B. 1017, Uyo, Akwa Ibom State, Nigeria. * Corresponding author.
Nigeria. The sweet potato varieties (brown, yellow and white) were harvested locally at Uyo in Nigeria. The sorghum and barley both had germinative energy above 97%. They were steeped in water (250 g grains/500 m[) for 24 h, drained for 4 h and then germinated at 25~ for 6 days. Kilning was done at 55~ for 24 h. The potatoes were peeled, washed and cut into slices. These were kilned as the grains before grinding into flour. Detection of the Amylases and (I --* 3,I --~ 4)-•-Glucanase
a-Amylase activity and total reducing power (diastatic power) were determined in aliquots of buffered extracts of malts and potato flours (10 mg sample/ml), as described earlier (EtokAkpan & Palmer I990a), fl-amylolytic activity being selectively inhibited by HgCl2. fl-Amylolytic activity was deduced from the difference between total and a-amylase reducing powers. 0c-Amylaseactivity was also estimated using amylose Azure Blue dye {EtokAkpan & Palmer 1990a). The assay of (1 ~ 3,I ~ 4)-fl-glucanase was done viscometrically using fl-glucan, extracted from barley with water at 40~ activity was calculated as the amount of enzyme required to produce a i0% reduction in initial viscosity in 100 min (Scott 1972; EtokAkpan & Palmer 1990b). The presence of (1--* 3,1 ~ 4)-flglucanase was further validated by isolating sorghum endosperm cell walls by the method of Palmer (1975) and incubating I0 mg of these walls with 2.5 ml of extraction buffer and 2.,5 ml of dialysed (sugar-free) enzyme extracts for 8 h at 37~ Sugars resulting from hydrolysis of the sorghum walls were analysed by high performance liquid chromatography (HPLC). Hot-Water Extract and Fermentable Sugars
The preparation of a hot-water extract of barley and estimation of free a-amino nitrogen of worts were carried out as recommended by the Institute of Brewing (Anon. 1986). The all sorghum and sorghum/potato extracts were obtained from a modified mashing procedure in which the extracted enzymic wort was decanted and added back to the starchy mash residue after it had been boiled
1992 Rapid Communications of Oxford Ltd
Worm Journalof Microbiologyand BiotechnoIogy,Vol 8. 19012
~09
M . U . Etim and O.U. EtokAkpan
Table 1. AcUvitles of amylases in sweet potatoes, sorghum and barley. Sample
Total reducing power*
~-Amylase reducing power*
c(-Amylase activity (with amylose Azure)t
IS-Amylase reducing power*
1.3 1.9 1.7 1.0 1.8
1.11 0.48 0.52 0.45 0.48
0.46 0.22 0.25 0.21 0.22
0.25 1.41 1.20 0.55 1.32
Sorghum (SK5912) Proctor barley Brown potato White potato Yellow potato
* mg glucose equivalent/ml/5 min. 1 Activity as increase in absorbance at 565 nm.
Table 2. Hot-water extracts and free alpha amino nitrogen (FAN) of worts. Wort samples
Extract (l~
Extract contribution by potato (%)
FAN (mgll)
--6.7 15.6 23.2
152 136 147 136 128
100% sorghum 350 100% barley 301 10% potato/90% sorghum 373 20% potato/80% sorghum 405 30% potato/70% sorghum 431
and cooled (EtokAkpan 1988; Palmer et al. 1989). Wort sugars were analysed by HPLC. All estimations were done in triplicate and the expressedresults are means of determinations which varied by not more than 4%.
Results and Discussion The reducing power (diastatic power) is a measure of the potential of an extract to produce sugars from solubilized starch. In barley, this activity is principally from r-amylase (Meredith 1965). The results in Table 1 show that brown and yellow sweet potatoes have higher reducing power than either white sweet potato or sorghum. The bulk of the reducing power of yellow and brown potatoes comes from the activity of ]J-amylase (as in barley). In contrast, the reducing power of sorghum comes principally from c~-amylolytic activity. Earlier speculation that potato tubers may be devoid of 0r activity (Robyt & Whelan
Table 3. Activity of (1 ~ 3, 1 --, 4)-is-glucanase in sweet potato, sorghum and barley. Sample
Sorghum (SK5912) Brown potato Proctor barley
Activity (units/mg sample)
Glucose released from sorghum cell walls"
11 91 140
0 12 17
* Glucose released from isolated sorghum cell walls by extracts of samples (% cell wall weight).
5 10
WorldJournalof Microbiologyand Biotechnology,Vol 8, 1992
1968), is not supported by this study; Table 1 shows the presence (though at a low level compared with that in sorghum) of ~-amylolytic activity in the potatoes, demonstrated in assays using the amylose Azure Blue dye, which is specific for c~-amylase (Klein et al. 1969). An 'extract' comprises the dissolved materials (mostly sugars and free amino acids) present in wort and derived from the grist. Rapid sugar (maltose) production from starch is principally from the action of the saccharifying enzyme (r-amylase). The results of the present study (Table 2) show that, whereas all-sorghum malt had an extract of 350 l~ substitution with potato at 20% (w/v) raised it to 404 l~ The trend was that of an increasing extract with increased potato substitution. The American double-mashing procedure is based on the principle that a high percentage of cereal adjuncts (sorghum or wheat) can be used because of the high ~- and r-amylase activities of six-row barley malts. Adjuncts also dilute the nitrogenous compounds in the mash/wort (Hahn 1966; Briggs et al. 1981). Table 2 also shows that substitution of the sorghum malt with potato at all ratios (10 to 30%) leads to dilution of wort-free, amino nitrogen. Apparently, the various proteases that produce free amino nitrogen from the proteins are at a low level in the sweet potato. Fortunately, the level of free amino nitrogen after dilution with the substituted potato flours was within the range of 100 to 150 mg/1 which is the limit adequate for yeast growth during fermentation of sorghum and barley worts (Pickerell 1986). The endosperm cell walls of sorghum (consisting most of the grains' fl-glucan) are not degraded during malting as happens in barley (Glennie 1984). Consequently, passage of the hydrolytic enzymes which modify the contents of the endosperm cells is impaired. This explains, in part, the poor modification of the sorghum grain during malting (Palmer et al. 1989). Also, during mashing, the valuable starch and proteins enclosed in those endosperm cells which are not disrupted by milling are lost. The non-degradation of the sorghum endosperm cell walls has been linked (in part) to the apparent absence of fl-glucan degrading (1 ~ 3,1 ~ 4)fl-glucanase in sorghums (EtokAkpan 1988; EtokAkpan & Palmer 1990b). Against this background, the detection of some (i ~ 3,1 ~ 4)-fl-glucanase activity (Table 3) in the
Sorghum brewing with sweet potato Table 4. Sugar profile of sorghum worts. Wort sample 100% sorghum 20% potato/80% sorghum
Glucose (mg/ml)
Maltose (mglml)
Maltotriose (mg/ml)
6 6
13 50
13 12
sweet potato is viewed with keen interest. This could function in the mash to disrupt endosperm cell walls not disrupted by milling, thereby releasing the enclosed starch and proteins into the mash for hydrolysis by the amylases and proteases, respectively. That this is probably so is seen in the results of Table 3; sorghum malt extract was unable to hydrolyse isolated sorghum endosperm cell walls to release glucose, unlike extracts of brown potato and Proctor barley. Barley, unlike sorghum, has a full array of the fl-glucanases--(1 --~ 3,1 --* 4)-fl-, (1 --* 3)-fl-, (1 --* 4)-fl-glucanases and the fl-glucosidases (Manners & Marshall 1969; Bamforth et al. 1979). The fermentable sugars of wort are glucose, maltose and maltotriose. Though the extract of the sorghum supplemented with brown potato at 20% was higher than that of barley, the profile of fermentable sugars may not necessarily be comparable. The measurement of extract is based on specific gravity, which in turn depends on dissolved solids such as the fermentable sugars, free amino acids, oligosaccharides, peptides and the like. The level of maltose in the sorghum/20% potato wort was 50 mg/ml (Table 4), which is comparable with the value of 52 mg/ml reported for an all-barley malt wort (Macleod 1977). This indicates a significant improvement over the sugar (maltose) profile of the 100% sorghum wort. Although the increase in extract by the substitution with potato (at 20%) was only 16% (Table 1), that of maltose was four-fold higher. This was possibly the result of the high fl-amylolytic activity of the potato flour, since d-amylase is low in sorghum. Mashing with brown potato flour may therefore be the answer to the saccharification problem of sorghum.
Conclusion For the efficient brewing of sorghum beer brown sweet potato could be used in place of extraneous enzymes, at a low cost, since it grows abundantly in Nigeria. More research, however, would be needed to establish the flavour of the final beer produced from this approach. Mash separation equipment, such as the traditional lauter tun, may have to be changed and high pressure mash filters used for speedy wort recovery.
Aisien, A.O. & Muts, G.CJ. 1987 Microscale malting and brewing studies of some sorghum varieties. Journal of the Institute of Brewing 93, 328-331. Aniche, G.N. & Palmer, G.H. 1990 Development of amylolytic activities in sorghum malt and barley malt. Journal of the Institute of Brewing 96, 377-379. Anon. I986 Institute of Brewing Recommended Methods of Analysis. London: Institute of Brewing. Bamforth, C.W., Martin, H.L. & Wainwright, T. 1979 A role for carboxypeptidase in the solubilization of barley fl-glucan.Journal of the Institute of Brewing 85, 334-338. Briggs, D.E., Hough, J.S., Stevens, R. & Young, T.W. 1981 Malting and Brewing Science. Vol. I, Malt and Sweet Wort. London: Chapman and Hail. EtokAkpan, O.U. 1988 Biochemical Studies of the Malting of Sorghum and Barley. PhD Thesis. Heriot-Watt University, Edinburgh. EtokAkpan, O.U. & Palmer, G.H. 1990a A simple Diamylase procedure for the estimation of o-amylase and diastatic activity. Journal of the Institute of Brewing 96, 89-9I. EtokAkpan, O.U. & Palmer, G.H. 1990b Comparative studies of the development of endosperm-degrading enzymes in malting sorghum and barley. World Journal of Microbiology and Biotechnology 6, 408-417. Glennie, C.W. 1984 Endosperm cell wall modification in sorghum grains during germination. Cereal Chemistry 61, 285-289. Glennie, C.W. & Wright, A.W. 1986 Dextrins in Sorghum beer. Journal of the Institute of Brewing 92, 384-386. Hahn, R.R. i956 Sorghum as brewing adjunct. Brewers" Digest 41, 7O-76. Klein, B., Foreman, J.A. & Searcby, R.L. 1969 The synthesis and utilization of Cibachron Blue-Amylose: A new chromogenic substrate for determination of amylase activity. Analytical Biochemistry 31, 412-425. Macleod, A.M. 1977 Beer. In Economic Microbiology. Vol. I. Alcoholic Beverages, ed Rose, A.H. pp. 43-137. London: Academic Press. Manners, D.J. & Marshall, J.J. I969 Studies on carbohydrate metabolizing enzymes. Part XXIII. The fl-glucanase system of malted barley. Journal of the Institute of Brewing 75, 550-561. Meredith, W.O.S. 1965 Combined action of alpha and beta amylases in saccharification. Proceedings of the American Society of Brewing Chemists 5, 5-10. Murty, K.S. 1940 Amylase; its occurrence ill sweet potato tuber and seeds. Indian Chemistry Society 17, 578-583. Palmer, G.H. 1975 Influence of endosperm structure on extract development. American Society of Brewing Chemists Proceedings 33, 174-180. Palmer, G.H., EtokAkpan, O.U. & Igyor, M.A. 1989 Review: Sorghum as brewing material. MIRCEN Journal of Applied Microbiology and Biotechnology 5, 265-275. Pickereli, A.T.W. 1986 The influence of free alpha amino nitrogen in sorghum beer fermentations. Journal of the Institute of Brewing 92, 568-571. Robyt, J.F. & Whelan, W.J. 1968 The Amylases. In Starch and its Derivatives, ed Radley, J.A. pp. 432-438. London: Chapman and Hall. Scott, R. 1972 Solubilization of fl-glucan during mashing. Journal of the Institute of Brewing 78, 411-412.
References
Adejemilua, F. I989 The Nigerian Brewing Experience. Beverage World International 2, 36--40.
(Received in revised form 18 March 1992; accepted 1I April 1992)
World Journal of Microbiology and Bio~ecflnology, Vol 8, 1992
.~ 1 1
Sorghum brewing using sweet potato enzymic flour to increase saccharification M.U. Etim and O.U. EtokAkpan* The diastatic activity of three sweet potato varieties was principally due to ~-amylase. Substitution of sorghum malt with sweet potato at 20% (w/v) gave a higher activity than an all-sorghum malt. Maltose in the sorghum/potato wort was $0 mg/ml, similar to that in barley malt. The free alpha amino nitrogen of the sorghmn/potato worts was lower than that of the all-sorghum malt but was still within the range needed for yeast growth. Incubation of the potato enzymic extract with isolated sorghum endosperm cell walls and viscosity tests demonstrated the presence of (1 -~ 3,1 --* 4)-~-glucanase (limiting in sorghum) in the sweet potato. Key words: fl-Amylase, saccharification, sorghum, sweet potato
A recent innovation in Nigerian brewing is the utilization of locally-grown cereals as raw materials for the production of beer (Adejemilua 1989). Sorghum remains the preferred grain (because of climate), though it contains low activities of fl-amylase, the enzyme which controls, to a large extent, saccharification during mashing (Aniche & Palmer 1990; EtokAkpan & Palmer 1990a). Sorghum malts, therefore, produce poor fermentable worts with high levels of dextrins, which can cause filtration problems and haze in the beer (Glennie & Wright 1986; Aisien & Muts 1987), and low maltose. Preliminary studies have shown that fl-amylase is present in the grains of many cereals and to a significant degree in the sweet potato (Murty 1940). The amylase of the sweet potato appears to contain no alpha component and it degrades starch in a pattern similar to that of barley malt fi-amylase (Robyt & Whelan 1968). As sweet potato grows abundantly in Nigeria, this study explores the possibility of using sweet potato fl-amylolytic flour to complement that of sorghum during mashing.
Materials and Methods Samples
Brown sorghum, SK5912, and Proctor barley were from the Seed Production Unit of the Institute of Agricultural Research, Zaria, M.U. Etim and O.U. EtokAkpan are with the Department of Brewing Science & Technology, University of Uyo, P. M. B. 1017, Uyo, Akwa Ibom State, Nigeria. * Corresponding author.
Nigeria. The sweet potato varieties (brown, yellow and white) were harvested locally at Uyo in Nigeria. The sorghum and barley both had germinative energy above 97%. They were steeped in water (250 g grains/500 m[) for 24 h, drained for 4 h and then germinated at 25~ for 6 days. Kilning was done at 55~ for 24 h. The potatoes were peeled, washed and cut into slices. These were kilned as the grains before grinding into flour. Detection of the Amylases and (I --* 3,I --~ 4)-•-Glucanase
a-Amylase activity and total reducing power (diastatic power) were determined in aliquots of buffered extracts of malts and potato flours (10 mg sample/ml), as described earlier (EtokAkpan & Palmer I990a), fl-amylolytic activity being selectively inhibited by HgCl2. fl-Amylolytic activity was deduced from the difference between total and a-amylase reducing powers. 0c-Amylaseactivity was also estimated using amylose Azure Blue dye {EtokAkpan & Palmer 1990a). The assay of (1 ~ 3,I ~ 4)-fl-glucanase was done viscometrically using fl-glucan, extracted from barley with water at 40~ activity was calculated as the amount of enzyme required to produce a i0% reduction in initial viscosity in 100 min (Scott 1972; EtokAkpan & Palmer 1990b). The presence of (1--* 3,1 ~ 4)-flglucanase was further validated by isolating sorghum endosperm cell walls by the method of Palmer (1975) and incubating I0 mg of these walls with 2.5 ml of extraction buffer and 2.,5 ml of dialysed (sugar-free) enzyme extracts for 8 h at 37~ Sugars resulting from hydrolysis of the sorghum walls were analysed by high performance liquid chromatography (HPLC). Hot-Water Extract and Fermentable Sugars
The preparation of a hot-water extract of barley and estimation of free a-amino nitrogen of worts were carried out as recommended by the Institute of Brewing (Anon. 1986). The all sorghum and sorghum/potato extracts were obtained from a modified mashing procedure in which the extracted enzymic wort was decanted and added back to the starchy mash residue after it had been boiled
1992 Rapid Communications of Oxford Ltd
Worm Journalof Microbiologyand BiotechnoIogy,Vol 8. 19012
~09
M . U . Etim and O.U. EtokAkpan
Table 1. AcUvitles of amylases in sweet potatoes, sorghum and barley. Sample
Total reducing power*
~-Amylase reducing power*
c(-Amylase activity (with amylose Azure)t
IS-Amylase reducing power*
1.3 1.9 1.7 1.0 1.8
1.11 0.48 0.52 0.45 0.48
0.46 0.22 0.25 0.21 0.22
0.25 1.41 1.20 0.55 1.32
Sorghum (SK5912) Proctor barley Brown potato White potato Yellow potato
* mg glucose equivalent/ml/5 min. 1 Activity as increase in absorbance at 565 nm.
Table 2. Hot-water extracts and free alpha amino nitrogen (FAN) of worts. Wort samples
Extract (l~
Extract contribution by potato (%)
FAN (mgll)
--6.7 15.6 23.2
152 136 147 136 128
100% sorghum 350 100% barley 301 10% potato/90% sorghum 373 20% potato/80% sorghum 405 30% potato/70% sorghum 431
and cooled (EtokAkpan 1988; Palmer et al. 1989). Wort sugars were analysed by HPLC. All estimations were done in triplicate and the expressedresults are means of determinations which varied by not more than 4%.
Results and Discussion The reducing power (diastatic power) is a measure of the potential of an extract to produce sugars from solubilized starch. In barley, this activity is principally from r-amylase (Meredith 1965). The results in Table 1 show that brown and yellow sweet potatoes have higher reducing power than either white sweet potato or sorghum. The bulk of the reducing power of yellow and brown potatoes comes from the activity of ]J-amylase (as in barley). In contrast, the reducing power of sorghum comes principally from c~-amylolytic activity. Earlier speculation that potato tubers may be devoid of 0r activity (Robyt & Whelan
Table 3. Activity of (1 ~ 3, 1 --, 4)-is-glucanase in sweet potato, sorghum and barley. Sample
Sorghum (SK5912) Brown potato Proctor barley
Activity (units/mg sample)
Glucose released from sorghum cell walls"
11 91 140
0 12 17
* Glucose released from isolated sorghum cell walls by extracts of samples (% cell wall weight).
5 10
WorldJournalof Microbiologyand Biotechnology,Vol 8, 1992
1968), is not supported by this study; Table 1 shows the presence (though at a low level compared with that in sorghum) of ~-amylolytic activity in the potatoes, demonstrated in assays using the amylose Azure Blue dye, which is specific for c~-amylase (Klein et al. 1969). An 'extract' comprises the dissolved materials (mostly sugars and free amino acids) present in wort and derived from the grist. Rapid sugar (maltose) production from starch is principally from the action of the saccharifying enzyme (r-amylase). The results of the present study (Table 2) show that, whereas all-sorghum malt had an extract of 350 l~ substitution with potato at 20% (w/v) raised it to 404 l~ The trend was that of an increasing extract with increased potato substitution. The American double-mashing procedure is based on the principle that a high percentage of cereal adjuncts (sorghum or wheat) can be used because of the high ~- and r-amylase activities of six-row barley malts. Adjuncts also dilute the nitrogenous compounds in the mash/wort (Hahn 1966; Briggs et al. 1981). Table 2 also shows that substitution of the sorghum malt with potato at all ratios (10 to 30%) leads to dilution of wort-free, amino nitrogen. Apparently, the various proteases that produce free amino nitrogen from the proteins are at a low level in the sweet potato. Fortunately, the level of free amino nitrogen after dilution with the substituted potato flours was within the range of 100 to 150 mg/1 which is the limit adequate for yeast growth during fermentation of sorghum and barley worts (Pickerell 1986). The endosperm cell walls of sorghum (consisting most of the grains' fl-glucan) are not degraded during malting as happens in barley (Glennie 1984). Consequently, passage of the hydrolytic enzymes which modify the contents of the endosperm cells is impaired. This explains, in part, the poor modification of the sorghum grain during malting (Palmer et al. 1989). Also, during mashing, the valuable starch and proteins enclosed in those endosperm cells which are not disrupted by milling are lost. The non-degradation of the sorghum endosperm cell walls has been linked (in part) to the apparent absence of fl-glucan degrading (1 ~ 3,1 ~ 4)fl-glucanase in sorghums (EtokAkpan 1988; EtokAkpan & Palmer 1990b). Against this background, the detection of some (i ~ 3,1 ~ 4)-fl-glucanase activity (Table 3) in the
Sorghum brewing with sweet potato Table 4. Sugar profile of sorghum worts. Wort sample 100% sorghum 20% potato/80% sorghum
Glucose (mg/ml)
Maltose (mglml)
Maltotriose (mg/ml)
6 6
13 50
13 12
sweet potato is viewed with keen interest. This could function in the mash to disrupt endosperm cell walls not disrupted by milling, thereby releasing the enclosed starch and proteins into the mash for hydrolysis by the amylases and proteases, respectively. That this is probably so is seen in the results of Table 3; sorghum malt extract was unable to hydrolyse isolated sorghum endosperm cell walls to release glucose, unlike extracts of brown potato and Proctor barley. Barley, unlike sorghum, has a full array of the fl-glucanases--(1 --~ 3,1 --* 4)-fl-, (1 --* 3)-fl-, (1 --* 4)-fl-glucanases and the fl-glucosidases (Manners & Marshall 1969; Bamforth et al. 1979). The fermentable sugars of wort are glucose, maltose and maltotriose. Though the extract of the sorghum supplemented with brown potato at 20% was higher than that of barley, the profile of fermentable sugars may not necessarily be comparable. The measurement of extract is based on specific gravity, which in turn depends on dissolved solids such as the fermentable sugars, free amino acids, oligosaccharides, peptides and the like. The level of maltose in the sorghum/20% potato wort was 50 mg/ml (Table 4), which is comparable with the value of 52 mg/ml reported for an all-barley malt wort (Macleod 1977). This indicates a significant improvement over the sugar (maltose) profile of the 100% sorghum wort. Although the increase in extract by the substitution with potato (at 20%) was only 16% (Table 1), that of maltose was four-fold higher. This was possibly the result of the high fl-amylolytic activity of the potato flour, since d-amylase is low in sorghum. Mashing with brown potato flour may therefore be the answer to the saccharification problem of sorghum.
Conclusion For the efficient brewing of sorghum beer brown sweet potato could be used in place of extraneous enzymes, at a low cost, since it grows abundantly in Nigeria. More research, however, would be needed to establish the flavour of the final beer produced from this approach. Mash separation equipment, such as the traditional lauter tun, may have to be changed and high pressure mash filters used for speedy wort recovery.
Aisien, A.O. & Muts, G.CJ. 1987 Microscale malting and brewing studies of some sorghum varieties. Journal of the Institute of Brewing 93, 328-331. Aniche, G.N. & Palmer, G.H. 1990 Development of amylolytic activities in sorghum malt and barley malt. Journal of the Institute of Brewing 96, 377-379. Anon. I986 Institute of Brewing Recommended Methods of Analysis. London: Institute of Brewing. Bamforth, C.W., Martin, H.L. & Wainwright, T. 1979 A role for carboxypeptidase in the solubilization of barley fl-glucan.Journal of the Institute of Brewing 85, 334-338. Briggs, D.E., Hough, J.S., Stevens, R. & Young, T.W. 1981 Malting and Brewing Science. Vol. I, Malt and Sweet Wort. London: Chapman and Hail. EtokAkpan, O.U. 1988 Biochemical Studies of the Malting of Sorghum and Barley. PhD Thesis. Heriot-Watt University, Edinburgh. EtokAkpan, O.U. & Palmer, G.H. 1990a A simple Diamylase procedure for the estimation of o-amylase and diastatic activity. Journal of the Institute of Brewing 96, 89-9I. EtokAkpan, O.U. & Palmer, G.H. 1990b Comparative studies of the development of endosperm-degrading enzymes in malting sorghum and barley. World Journal of Microbiology and Biotechnology 6, 408-417. Glennie, C.W. 1984 Endosperm cell wall modification in sorghum grains during germination. Cereal Chemistry 61, 285-289. Glennie, C.W. & Wright, A.W. 1986 Dextrins in Sorghum beer. Journal of the Institute of Brewing 92, 384-386. Hahn, R.R. i956 Sorghum as brewing adjunct. Brewers" Digest 41, 7O-76. Klein, B., Foreman, J.A. & Searcby, R.L. 1969 The synthesis and utilization of Cibachron Blue-Amylose: A new chromogenic substrate for determination of amylase activity. Analytical Biochemistry 31, 412-425. Macleod, A.M. 1977 Beer. In Economic Microbiology. Vol. I. Alcoholic Beverages, ed Rose, A.H. pp. 43-137. London: Academic Press. Manners, D.J. & Marshall, J.J. I969 Studies on carbohydrate metabolizing enzymes. Part XXIII. The fl-glucanase system of malted barley. Journal of the Institute of Brewing 75, 550-561. Meredith, W.O.S. 1965 Combined action of alpha and beta amylases in saccharification. Proceedings of the American Society of Brewing Chemists 5, 5-10. Murty, K.S. 1940 Amylase; its occurrence ill sweet potato tuber and seeds. Indian Chemistry Society 17, 578-583. Palmer, G.H. 1975 Influence of endosperm structure on extract development. American Society of Brewing Chemists Proceedings 33, 174-180. Palmer, G.H., EtokAkpan, O.U. & Igyor, M.A. 1989 Review: Sorghum as brewing material. MIRCEN Journal of Applied Microbiology and Biotechnology 5, 265-275. Pickereli, A.T.W. 1986 The influence of free alpha amino nitrogen in sorghum beer fermentations. Journal of the Institute of Brewing 92, 568-571. Robyt, J.F. & Whelan, W.J. 1968 The Amylases. In Starch and its Derivatives, ed Radley, J.A. pp. 432-438. London: Chapman and Hall. Scott, R. 1972 Solubilization of fl-glucan during mashing. Journal of the Institute of Brewing 78, 411-412.
References
Adejemilua, F. I989 The Nigerian Brewing Experience. Beverage World International 2, 36--40.
(Received in revised form 18 March 1992; accepted 1I April 1992)
World Journal of Microbiology and Bio~ecflnology, Vol 8, 1992
.~ 1 1
