Glycoproteins
Glycation is the non-enzymatic attachment of a sugar to a protein or lipid, occurring after the protein/lipid is made.[1][2][3] More specifically with regard to glycoproteins, glucose (or fructose) typically binds to a lysine or arginine amino acid residue on proteins.[4][1][5] Glycation occurs through a sequence of steps commonly known as a Maillard reaction, and is catalyzed by high temperatures.[2][4] Both Protein Z and LTP1 (the two major proteins in beer) are well documented to be glycated during the malting process.[2][5] Glycation has also been shown to occur to a smaller extent during the brewing process (e.g. during the mash or boil).[1]
Glycation influences the properties of proteins, particularly with regard to increasing their foam-promoting effects.[1][2][4][3][6][7] In fact, all proteins involved in beer foam (but also haze) formation are glycated to varying degrees.[1] Glycation also helps stabilize protein structure so that they do not precipitate during the brewing process.[4][8][9] Generally, glycoproteins are important for the formation of flavor and color of heated foods.[8]
Glycoproteins are broken down when mashing during longer rest periods in the range of 50–65°C (i.e. a "protein rest").[7] Conversely, a mash step in the range of 70–74°C increases the extraction of glycoproteins into the wort and they are no longer broken down at this temperature.[6][3][7][4]
See also[edit]
To review:
References[edit]
- ↑ a b c d e Steiner E, Gastl M, Becker T. Protein changes during malting and brewing with focus on haze and foam formation: a review. Eur Food Res Technol. 2011;232:191–204.
- ↑ a b c d Kerr ED, Fox GP, Schulz BL. Grass to glass: Better beer through proteomics. In: Cifuentes A, ed. Comprehensive Foodomics. Elsevier; 2020:407–416.
- ↑ a b c Fix G. Principles of Brewing Science. 2nd ed. Brewers Publications; 1999.
- ↑ a b c d e Jégou S, Douliez PJ, Mollé D, Boivin P, Marion D. Evidence of the glycation and denaturation of LTP1 malting and brewing process. J Agric Food Chem. 2001;49(10):4942–4949.
- ↑ a b Didier M, Bénédicte B. Soluble proteins of beer. In: Preedy VR, ed. Beer in Health and Disease Prevention. Academic Press; 2009:265–271.
- ↑ a b 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.
- ↑ a b c Narziss L, Back W, Gastl M, Zarnkow M. Abriss der Bierbrauerei. 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.
- ↑ a b Bobálová J, Petry-Podgórska I, Laštovičková M, Chmelík J. Monitoring of malting process by characterization of glycation of barley protein Z. Eur Food Res Technol. 2010;230(4):665–673.
- ↑ Stanislava G. Barley grain non-specific lipid-transfer proteins (ns-LTPs) in beer production and quality. J Inst Brew. 2007;113(3):310–324.