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Protein: Difference between revisions
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[[File:2xfr b amylase.png|thumb|3D representation of β-amylase enzyme structure]] | [[File:2xfr b amylase.png|thumb|3D representation of β-amylase enzyme structure]] | ||
Proteins are a versatile substance required for all forms of life. They consist of long chains built from an assortment of different [[amino acids]] joined by "peptide links". When a protein is being built, the chain is folded into a particular 3-dimensional structure, and this structure is the basis for its function. Examples of function include building, degrading, or modifying other molecules (i.e. [[enzymes]]), maintaining cellular structure, or transporting molecules across the cell membrane. Proteins may be combined with various other molecules, such as [[sugars]] in the case of [[glycoproteins]], or various other groups (such as [[iron]]) in the cases of some enzymes.<ref name=bsp/> | Proteins are a versatile substance required for all forms of life. They consist of long chains built from an assortment of different [[amino acids]] joined by "peptide links". When a protein is being built, the chain is folded into a particular 3-dimensional structure, and this structure is the basis for its function. Examples of function include building, degrading, or modifying other molecules (i.e. [[enzymes]]), maintaining cellular structure, or transporting molecules across the cell membrane. Proteins may be combined with various other molecules, such as [[sugars]] in the case of [[glycoproteins]], or various other groups (such as [[iron]]) in the cases of some enzymes.<ref name=bsp>Briggs DE, Boulton CA, Brookes PA, Stevens R. [[Library|''Brewing Science and Practice.'']] Woodhead Publishing Limited and CRC Press LLC; 2004.</ref> | ||
The cereal [[grain]]s used in [[brewing]] contain a substantial amount of protein, second only to [[starch]].<ref name=yu>Yu W, Zhai H, Xia G, et al. [https://www.sciencedirect.com/science/article/abs/pii/S0924224420306002 Starch fine molecular structures as a significant controller of the malting, mashing, and fermentation performance during beer production.] ''Trends Food Sci Technol.'' 2020;105:296–307.</ref> Thousands of different proteins have been detected in wort, and these proteins and their degradation products are important factors in beer quality. They are influenced, modified, and aggregated throughout the whole [[malting]] and brewing process.<ref name=steiner/><ref name=kerr/> Arguably the most important proteins in the [[malt]] are the [[enzymes]] responsible for various functions during [[mashing]]. Some of the malt protein is broken down by proteolytic enzymes, and the protein degradation products are responsible for beer [[foam]] and mouthfeel while others are utilized by the [[yeast]] as a source of nitrogen (to build their own proteins).<ref name=bsp/><ref name=kunze>Kunze W, Hendel O, eds. [[Library|''Technology Brewing & Malting.'']] 6th ed. VLB Berlin; 2019.</ref><ref name=fix/> Indirectly, the proportions of protein components affect the flavors produced by yeast during fermentation. The color of the beer is influenced by [[Maillard reaction]]s between the sugars and protein components during the [[boiling|boil]], which give rise to color and flavor compounds. Proteins also serve as a natural layer of protection against [[oxidation]]. Not all proteins are beneficial however; some enzymes cause unwanted effects, other proteins may contribute to beer [[haze]] (in combination with [[phenolic compounds]]), some may cause [[lautering]] problems, and some proteins can have negative health effects on certain beer drinkers (e.g. hordein, a "[[gluten-free beer|gluten]]" protein from barley). Stemming from protein degradation, the nitrogen level in the final beer can also affect its susceptibility to the growth of contaminating organisms. | The cereal [[grain]]s used in [[brewing]] contain a substantial amount of protein, second only to [[starch]].<ref name=yu>Yu W, Zhai H, Xia G, et al. [https://www.sciencedirect.com/science/article/abs/pii/S0924224420306002 Starch fine molecular structures as a significant controller of the malting, mashing, and fermentation performance during beer production.] ''Trends Food Sci Technol.'' 2020;105:296–307.</ref> Thousands of different proteins have been detected in wort, and these proteins and their degradation products are important factors in beer quality. They are influenced, modified, and aggregated throughout the whole [[malting]] and brewing process.<ref name=steiner/><ref name=kerr/> Arguably the most important proteins in the [[malt]] are the [[enzymes]] responsible for various functions during [[mashing]]. Some of the malt protein is broken down by proteolytic enzymes, and the protein degradation products are responsible for beer [[foam]] and mouthfeel while others are utilized by the [[yeast]] as a source of nitrogen (to build their own proteins).<ref name=bsp/><ref name=kunze>Kunze W, Hendel O, eds. [[Library|''Technology Brewing & Malting.'']] 6th ed. VLB Berlin; 2019.</ref><ref name=fix/> Indirectly, the proportions of protein components affect the flavors produced by yeast during fermentation. The color of the beer is influenced by [[Maillard reaction]]s between the sugars and protein components during the [[boiling|boil]], which give rise to color and flavor compounds. Proteins also serve as a natural layer of protection against [[oxidation]]. Not all proteins are beneficial however; some enzymes cause unwanted effects, other proteins may contribute to beer [[haze]] (in combination with [[phenolic compounds]]), some may cause [[lautering]] problems, and some proteins can have negative health effects on certain beer drinkers (e.g. hordein, a "[[gluten-free beer|gluten]]" protein from barley). Stemming from protein degradation, the nitrogen level in the final beer can also affect its susceptibility to the growth of contaminating organisms. | ||
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===Wort nitrogen levels=== | ===Wort nitrogen levels=== | ||
Nitrogen is present in many forms in wort. All-malt wort contains about 650–1000 mg/L nitrogen, of which about 20% is proteins, 30–40% is polypeptides, 30–40% is free amino acids, and 10% is nucleotides and other nitrogenous compounds.<ref name=lei>Lei H, Zheng L, Wang C, Zhao H, Zhao M. [https://www.sciencedirect.com/science/article/abs/pii/S0168160512006150 Effects of worts treated with proteases on the assimilation of free amino acids and fermentation performance of lager yeast.] ''Int J Food Microbiol.'' 2013;161(2):76–83.</ref> | Nitrogen is present in many forms in wort. All-malt wort contains about 650–1000 mg/L nitrogen, of which about 20% is proteins, 30–40% is polypeptides, 30–40% is free [[amino acids]], and 10% is nucleotides and other nitrogenous compounds.<ref name=lei>Lei H, Zheng L, Wang C, Zhao H, Zhao M. [https://www.sciencedirect.com/science/article/abs/pii/S0168160512006150 Effects of worts treated with proteases on the assimilation of free amino acids and fermentation performance of lager yeast.] ''Int J Food Microbiol.'' 2013;161(2):76–83.</ref> See [[Free amino nitrogen]] for more information regarding amino acid content of wort. | ||
Free amino nitrogen | |||
==Proteins in the boil== | ==Proteins in the boil== | ||