Enzymes
Please check back later for additional changes
An enzyme is a protein that catalyzes a chemical reaction, greatly speeding it up. Enzymes are active even in very low concentrations. Enzymes play an important role in every fermented beverage, and all life processes.
With many enzymes, the catalytic action is tied to the action of an additional non-protein component (coenzyme) that binds with the enzyme structure. Bivalent metal ions, such as iron, magnesium, or calcium are often involvedbas coenzymes, for example.
For beer production, grain is malted in order to increase the amount of enzymes. Enzymes active during the mash include α- and β-amylase, proteases, peptidases, β- (1,3)(1,4)-glucanases and lipases.[1] The most important action of these enzymes is that during the mash they break down the starches in the grain into fermentable sugars. Brewers may sometimes add extra enzymes such as glucoamylase in order to further break down the complex sugars (dextrins). Hops also have enzymes that can break down dextrins.
During the mash, enzymes break down components in the malt (i.e. proteins and starch). This activity depends on various factors, but most importantly on the temperature. Each enzyme has its own optimal temperature. At higher temperatures, the enzymes denature, which is the unfolding of the enzymes' three-dimensional structure, making them inactive. Enzyme activity is also affected by pH. Enzyme activity is also affected by pH, and activity decreases at pH values higher or lower than each enzyme's respective optimal value, although the effect of pH is not as large as the effect of temperature. Enzyme activity lasts longer in thicker mashes than in thinner mashes.[2]
Alpha amylase, beta amylase, and limit dextrinase, see Saccharification.
α-Amylase randomly hydrolyses the α-1,4-D-glucosidic linkages in both amylose and amylopectin (Fig. 1), while β-amylase facilitates the successive exohydrolysis of the penultimate 1,4-α-D-glucosidic linkage at the non-reducing end of chains. The ongoing action of α-amylase provides a continuously increasing availability of sites for hydrolysis by β-amylase.[3]
Limit dextrinase is capable of hydrolysing the 1,6-α-D-glucosidic linkages found in amylopectin. This enzyme has only restricted activity under normal mashing conditions, because its optimal temperature for activity is much lower than those encountered during a typical mashing procedure.[3] Much more importantly, however, at normal mashing pHs (5.2–5.5), limit dextrinase is inhibited to a large extent by its proteinaceous inhibitor.[3]
Beta-glucan solubilase, endo-beta-glucanases, see Mashing.
The beta-amylase can be damaged at values below 5.4.[2]
Proteolytic enzymes in the mash and their optimal temperatures:[2]
- Endopeptidases (45-50°C)
- Carboxypeptidase (50°C)
- Aminopeptidase (45°C)
- Dipeptidases (45°C)
Phosphatases...
Lipoxygenases, lipases, peroxidase, polyphenoloxidase are all bad news...
Lipoxygenases (LOX) oxidize fatty acids to hydroxy fatty acids, which are precursors to staling compounds. These enzymes are formed during malting and activated during milling and mashing. LOX activity is enhanced with a low dough-in temperature and pH closer to 6.0.[2] Much of the LOX is destroyed during kilning, moreso in darker malts. Things that reduce LOX activity:
- Selecting a more kilned malt
- LOX does not require oxygen, however it is inhibited by preventing oxygen (air) from contacting the milled grain
- High dough-in temperature, high mash temperature, and short mash duration
- A more coarse crush
- Milling temperature?
- Low pH value
The most commonly used group of enzymes in brewing for the hydrolysis of the wort mainly consists of alpha-amylase, beta-amylase, endo-beta-1,3:1,4-glucanases and other enzymes (e.g. proteinase, carboxypeptidases, lipoxyiganase). These enzymes convert polymeric substances such as starch, proteins, starch cell walls, etc. to low molecular weight materials influencing mainly the fermentation of wort sugars and hence the quality of the final product.[4]
A family of enzymes, working in concert, is required for efficient starch hydrolysis during mashing. The enzymes present in malt are mainly alpha-amylase, beta-amylase, alpha-glucosidase, and debranching enzyme. They have an important role during malting and also in the wort production process. In particular, alpha-amylase and beta-amylase degrade starch granules (made of different structures of amylose and amylopectin) produce sugars that the brewers’ yeast can ferment. The hydrolysis of starch will directly determine the success of the fermentation and will contribute significantly to the flavor, color, and stability ofthe final beer.[5]
In wine production, a group of enzymes known as pectinase is commonly added to improve clarity and extraction.
Microbes use a large variety of enzymes in order to grow, survive, and conduct fermentation. (See Fermentation.) In fact, all life processes in living organisms are controlled by enzymes.[2]
Some enzymes can have a negative impact (such as polyphenol oxidase in fruit) and we can take steps to inhibit their undesirable effects.
The action of enzymes is influenced by pH, temperature, and other factors. High temperatures will permanently disable enzymes because the protein structure becomes irreversibly distorted, preventing them from functioning.
- https://www.researchgate.net/profile/David_Evan_Evans/publication/230559002_Assessing_the_impact_of_the_level_of_diastatic_power_enzymes_and_their_thermostability_on_the_hydrolysis_of_starch_during_wort_production_to_predict_malt_fermentability/links/5789973608ae5c86c99ae90f.pdf
- https://www.researchgate.net/profile/David_Evan_Evans/publication/226691242_The_Properties_and_Genetics_of_Barley_Malt_Starch_Degrading_Enzymes/links/578f1cf408ae81b4466ed501/The-Properties-and-Genetics-of-Barley-Malt-Starch-Degrading-Enzymes.pdf
- http://lowoxygenbrewing.com/forum/viewtopic.php?f=11&t=1821
- "Enzymes in Brewing."
- "Barley malt limit dextrinase: Varietal, environmental, and malting effects"
- "The proteinaceous inhibitor of limit dextrinase in barley and malt"
References
- ↑ Szwajgier, D. "Dry and Wet Milling of Malt. A Preliminary Study Comparing Fermentable Sugar, Total Protein, Total Phenolics and the Ferulic Acid Content in Non-Hopped Worts." J. Inst. Brew. vol. 117, no. 4, 2011, pp. 569–577.
- ↑ a b c d e Kunze, Wolfgang. "3.2 Mashing." Technology Brewing & Malting. Edited by Olaf Hendel, 6th English Edition ed., VBL Berlin, 2019. p. 230.
- ↑ a b c https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2010.tb00425.x
- ↑ Mousia, Z., et al. "The effect of milling parameters on starch hydrolysis of milled malt in the brewing process." Process Biochemistry, Vol. 39, No. 12, 2004, pp. 2213-2219.
- ↑ Warpala, IWS, and Pandiella, SS. "Grist Fractionation and Starch Modification During the Milling of Malt." Food and Bioproducts Processing, Vol. 78, No. 2, 2000, pp. 85-89.