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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. | ||
The structures of proteins are somewhat delicate. At high temperature, protein molecules become "denatured"—they unfold, losing their shape and therefore their function. Protein function can also be damaged by [[shear | The structures of proteins are somewhat delicate. At high temperature, protein molecules become "denatured"—they unfold, losing their shape and therefore their function. Protein function can also be damaged by [[shear]] forces or inactivated by high or low [[pH testing|pH levels]]. Large proteins typically are either broken down by enzymes in the mash or they eventually precipitate (coagulate) during [[mashing]], [[boiling]], [[wort chilling|chilling]], or [[yeast|fermentation]]. Medium and small proteins, protein fragments, and amino acids are typically what pass to the final beer, affecting its sensory characteristics. However some malt proteins or modified products partly survive mashing and boiling and appear in the final beer relatively unchanged.<ref name=adb>Narziss L, Back W, Gastl M, Zarnkow M. [[Library|''Abriss der Bierbrauerei.'']] 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.</ref><ref name=bsp/> | ||
The words '''peptides''' or polypeptides refer to fragments of proteins consisting of smaller chains of amino acids, generally without a defined 3-dimensional structure.<ref name=fix/> | The words '''peptides''' or polypeptides refer to fragments of proteins consisting of smaller chains of amino acids, generally without a defined 3-dimensional structure.<ref name=fix/> | ||