Sorghum
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Sorghum malts differ from barley malts in their high gelatinization temperatures and reduced diastatic power, which can be attributed to lower beta-amylase activities, while alpha-amylase activity at least equals that of barley malt (see Enzymes and Mashing).[1] Sorghum requires a mash with exogenous enzymes.[2] Sorghum malt also has very low protein, however FAN levels are in the normal range from the resulting wort (see Yeast).[3] Lastly, sorghum has higher levels of pentosans, increasing viscosity.
Sorghum starch gelatinization temperature: 68°C to 76°C[4]
Sorghum grains are huskless. The grains are variously pigmented, having red, white, brown, yellow, or pink coloration.[4] Some cultivars of sorghum have moderate levels of β-amylase, while many others contain low β-amylase levels.
Nitrogen solubilization, starch extract development, wort separation, and beer filtration are more limited when beer is produced from sorghum malt rather than from barley malt.[4] Irrespective of commercial enzyme addition, sorghum malts, mashed at 65ºC, produce low extracts. It has been suggested that increased α-amylase stability can result from calcium ion addition and enhanced extract development in sorghum mashes will occur. In contrast to barley malt worts, sorghum worts usually contain high percentages of dextrins. The lower wort maltose concentration (approximately 15%) of some sorghum worts reflects the reduced β-amylase activity (diastatic power) and fermentation extract of some sorghum malts.
Sorghum is important as a malt surrogate, especially in Africa. Only varieties with lower tannins and lower polyphenols are suitable for these beers. The mashing process for sorghum proceeds as follows: It is mashed at 50 ° C, with proteases, β-glucanases and heat-stable α-amylases being added immediately. The latter are added again after the protein rest for about 40 minutes. It is heated to 80 ° C. in approx. 20 min and to 90 ° C. after a rest period of 10 min and held there for approx. 60 min. It is then cooled to 66 ° C. in a mash cooler, adjusted to pH 5.5 with acid and another dose of enzyme with protease, β-glucanase, heat-stable α-amylase and even amyloglucosidase is added. The rest takes about 40 minutes. The mash, reheated to 78 ° C, is then lautered through a mash filter.[5]
As well as economic reasons, sorghum offers an interesting potential as raw material for brewing due to its high starch content and the absence of gluten, what makes it suitable for the elaboration of gluten-free beers for celiac people. Nevertheless, there are some inherent problems associated with sorghum that must be solved to better compete with barley in the elaboration of European-type beer. A major disadvantage for the use of malted sorghum in brewing is the usual low DP and amylolytic activity during mashing. Although alpha-amylase isoenzymes are de novo synthesized during sorghum germination, very low or even total absence of beta-amylase levels are detected, causing incomplete saccharification of starch and low levels of maltose in comparison to barley wort. In addition, the higher gelatinization temperature of sorghum starch with regard to barley increases thermal deactivation of the enzymes.[6]
Beers produced from a combination of barley malt and sorghum are known to age much faster than an all-barley malt lager.[7] In sorghum grains where the fat content is higher, then the potential danger of staling arising from fat deterioration is higher. Although the fat content of these cereals falls within brewing specification, the nature and quality of the fat can exert considerable influence on its susceptibility to oxidative changes during processing of the raw materials. In addition, prolonged storage of these raw materials under conditions of high ambient temperature and humidity can accelerate fat degradation resulting in rancidity (Aidoo 1993; Simpson 1996; Gardner 1988). The level of fats reported in sorghum ranges from 4.0–4.5%.
Increasing the barley percentage in the mash leads to better trub formation and therefore better flavor stability.[7]
Like barley, sorghum contains substantial amounts of phenolic compounds, although the level varies widely between different types of sorghum.[8]
References[edit]
- ↑ Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
- ↑ Krottenthaler M, Back W, Zarnkow M. Wort production. In: Esslinger HM, ed. Handbook of Brewing: Processes, Technology, Markets. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2009.
- ↑ Meussdoerffer F, Zarnkow M. Starchy raw materials. In: Esslinger HM, ed. Handbook of Brewing: Processes, Technology, Markets. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2009.
- ↑ a b c Stewart GG. Adjuncts. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
- ↑ Narziss L, Back W, Gastl M, Zarnkow M. Abriss der Bierbrauerei. 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.
- ↑ Guerra NP, Torrado-Agrasar A, López-Macías C, et al. Use of Amylolytic Enzymes in Brewing. In: Preedy VR, ed. Beer in Health and Disease Prevention. Academic Press; 2009:113–126.
- ↑ a b EtokAkpan OU. Preliminary study of fat oxidation in sorghum and maize brewing. World J Microbiol Biotechnol. 2004;20:569–573.
- ↑ Shen S, Huang R, Li C, Wu W, Chen H, Shi J, Chen S, Ye X. Phenolic compositions and antioxidant activities differ significantly among sorghum grains with different applications. Molecules. 2018; 23(5):1203.