Difference between revisions of "Grain"
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Microbial communities found on barley are very diverse and change significantly throughout the malting process, with more diversity occurring further along in the malting process. In the barley fields, Gram-negative bacteria (especially ''Erwinia herbicola'') are abundant. Climate is said to have the most impact on which species grow in barley fields. For example ''Fusarium'' species are encouraged by high humidity, and are associated with mycotoxins and gushing problems in beer. During dry storage of barley, spore forming bacteria tend to survive. Xerophilic fungi (fungi that doesn't need much water) also survive on dry barley during storage <ref name="Lievens1">[https://lirias.kuleuven.be/bitstream/123456789/323403/2/Just%C3%A9%20et%20al.%202011_Microflora%20during%20Malting%20of%20Barley%20Overview%20and%20Impact%20on%20Malt%20Quality.%20Brewing%20Science%2064,%2022-31..pdf Microfl ora during Malting of Barley: Overview and Impact on Malt Quality. A. Justé, S. Malfl iet, M. Lenaerts, L. de Cooman, G. Aerts, K. A. Willems and B. Lievens. 2011.]</ref>. | Microbial communities found on barley are very diverse and change significantly throughout the malting process, with more diversity occurring further along in the malting process. In the barley fields, Gram-negative bacteria (especially ''Erwinia herbicola'') are abundant. Climate is said to have the most impact on which species grow in barley fields. For example ''Fusarium'' species are encouraged by high humidity, and are associated with mycotoxins and gushing problems in beer. During dry storage of barley, spore forming bacteria tend to survive. Xerophilic fungi (fungi that doesn't need much water) also survive on dry barley during storage <ref name="Lievens1">[https://lirias.kuleuven.be/bitstream/123456789/323403/2/Just%C3%A9%20et%20al.%202011_Microflora%20during%20Malting%20of%20Barley%20Overview%20and%20Impact%20on%20Malt%20Quality.%20Brewing%20Science%2064,%2022-31..pdf Microfl ora during Malting of Barley: Overview and Impact on Malt Quality. A. Justé, S. Malfl iet, M. Lenaerts, L. de Cooman, G. Aerts, K. A. Willems and B. Lievens. 2011.]</ref>. | ||
Revision as of 14:41, 14 October 2015
For a general overview of grain in brewing, see Homebrew Talk Wiki page on Grain.
Contents
Microbial Populations on Barley
Malting Process
Microbial communities found on barley are very diverse and change significantly throughout the malting process, with more diversity occurring further along in the malting process. In the barley fields, Gram-negative bacteria (especially Erwinia herbicola) are abundant. Climate is said to have the most impact on which species grow in barley fields. For example Fusarium species are encouraged by high humidity, and are associated with mycotoxins and gushing problems in beer. During dry storage of barley, spore forming bacteria tend to survive. Xerophilic fungi (fungi that doesn't need much water) also survive on dry barley during storage [1].
Microbial communities change quite a bit during the malting process. It is thought that the factors affecting this are the initial microbe populations, interactions between species, the variances in the malted barley characteristics/processes, and additives. Different malting houses are likely to form "in-house" microflora populations. The first step in malting, which is steeping, sees the first large change in microbial populations. The steeping process favors lactic acid bacteria (LAB), which are seen in extremely small numbers before steeping. Particularly these are Leuconostoc species. In the case of yeasts, Basidiomycota fungi grow, as wellas Fusarium [1].
The second step of malting, which is germination, sees starches converted to sugars, which causes microbial populations to increase once again. Where Leuconostoc species of bacteria were dominate during steeping, the germination process is where Lactobacillus species begin to dominate the microbial community. A greater diversity of species also occurs during this step in malting. As far as fungi, Ascomycetous yeasts begin to dominate, where as Alternaria and Cladosporium decline [1].
During kilning, microbial populations are reduced by a factor of 10-100, but are still higher than that of field barley. The high degree of variability is dependent on the kilning temperature and procedure. Heat resistant microbes, perhaps by forming biofilms, can survive the hot temperatures. These include Rhizopus and Mucor species [1].
Malted Barley
(In Progress)