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Protein: Difference between revisions
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Flavor stability is the ability of the beverage to resist changes to flavor due to oxidation and other problematic forces). It is significantly influenced by the proteins present in the beer. | Flavor stability is the ability of the beverage to resist changes to flavor due to oxidation and other problematic forces). It is significantly influenced by the proteins present in the beer. | ||
Protein thiols, which are derived from cysteine residues in proteins (as discussed above), possess antioxidative capacity in beer and wort.<ref name=lund>Lund MN, Lametsch R, Sørensen MB. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/jib.155 Increased protein–thiol solubilization in sweet wort by addition of proteases during mashing.] ''J Inst Brew.'' 2014;120(4):467–473.</ref> The | Protein thiols, which are derived from cysteine residues in proteins (as discussed above), possess antioxidative capacity in beer and wort.<ref name=lund>Lund MN, Lametsch R, Sørensen MB. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/jib.155 Increased protein–thiol solubilization in sweet wort by addition of proteases during mashing.] ''J Inst Brew.'' 2014;120(4):467–473.</ref> The concentration of free thiols correlates with the oxidative stability of beer because thiols remove reactive oxygen species (ROS).<ref name=lundm>Lund MN, Petersen MA, Andersen ML, Lunde C. [https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-2015-0602-01 Effect of protease treatment during mashing on protein-derived thiol content and flavor stability of beer during storage.] ''J Am Soc Brew Chem.'' 2015;73(3):287–295.</ref> The major contribution to the protein thiol concentration in beer is believed to be mainly from LTP1 because it is rich in cysteine and is a major component of beer protein.<ref name=lund/><ref name=lundm/> A number of other proteins have also been identified in beer that contain several cysteine residues, so they could also contribute significantly to the thiol concentration in the beer.<ref name=lund/> In fact, beer LTP1 has been shown to scavenge one of the dominating radical compounds in beer, the 1-hydroxyethyl radical, at a rate similar to other reactive compounds in beer such as hop bitter acids.<ref name=lundm/> The free thiol concentration diminishes as the beer or wort is exposed to oxygen.<ref name=lund/> As discussed above, thiols can serve as antioxidants during mashing. However, even if the wort is oxidized during mashing, the disulfides are reduced during fermentation, thus converting them to active antioxidants in the beer.<ref name=lund/> Of course, oxygen-limited packaging is also extremely important to prevent degradation of beer flavor. | ||
Beer LTP1 has been shown to scavenge one of the dominating radical compounds in beer, the 1-hydroxyethyl radical, at a rate similar to other reactive compounds in beer such as hop bitter acids. LTP1 only serves as an antioxidant when its disulfide bonds are reduced to free thiols.<ref name=lundm/> Disulfide bonds are reducible by different chemical reagents, as well as by compounds produced by the yeast such as SO2 and thioredoxin. LTP1 has been found in its reduced form in fresh beer, which suggests that LTP1 is reduced during the brewing process, possibly during wort boiling or during fermentation by compounds produced by the yeast, and that it has the potential to act as an antioxidant in beer. Therefore, even if the wort is oxidized during mashing, the disulfides are reduced during fermentation, converting them to active antioxidants in the beer.<ref name=lund/> Of course, oxygen-limited packaging is still extremely important to prevent degradation of beer flavor. | Beer LTP1 has been shown to scavenge one of the dominating radical compounds in beer, the 1-hydroxyethyl radical, at a rate similar to other reactive compounds in beer such as hop bitter acids. LTP1 only serves as an antioxidant when its disulfide bonds are reduced to free thiols.<ref name=lundm/> Disulfide bonds are reducible by different chemical reagents, as well as by compounds produced by the yeast such as SO2 and thioredoxin. LTP1 has been found in its reduced form in fresh beer, which suggests that LTP1 is reduced during the brewing process, possibly during wort boiling or during fermentation by compounds produced by the yeast, and that it has the potential to act as an antioxidant in beer. Therefore, even if the wort is oxidized during mashing, the disulfides are reduced during fermentation, converting them to active antioxidants in the beer.<ref name=lund/> Of course, oxygen-limited packaging is still extremely important to prevent degradation of beer flavor. | ||