Increase your attenuation education and brew with Attenuzyme® Pro
Increase your attenuation education and brew with Attenuzyme® Pro
Simply put, attenuation is a measure of reduction in value. For the average brewer, this equates to a metabolism of sugar content in wort. In traditional brewing, we measure the extract (sugar) from raw materials, and then compare that to the residual sugar content left, after metabolic activity has stopped (terminal gravity). The difference, or reduction quantity, is called attenuation.
When measured via tools such as a hydrometer, we are not measuring the alcohol content of beer, but rather the amount of sugar dissolved in water. Since alcohol is lighter than water, we refer to the measurements as “apparent attenuation” as opposed to “real degree of fermentation”. Our reference point is water, measured at 1.000, and ethanol is approximately 21% lighter than water, so we must account for this in some way. Real degree of fermentation is the percentage of extract that was fermented, a more “real” measure of our attenuation.
Hydrometer set – A precision set of hydrometers is a great way to measure attenuation. Plato is the common measurement for brewers, however specific gravity offers a greater degree of accuracy.
An all-barley wort will, on average, contain about 45% maltose, 15% maltotriose, 15% monosaccharides, and 25% higher-chained saccharides. An all-barley wort will, on average, contain about 45% maltose, 15% maltotriose, 15% monosaccharides, and 25% higher-chained saccharides. Monosaccharides are easily adsorbed by most yeast, however maltose presents brief resistance and maltotriose is a bit more finicky. Both sugars are simple chains of glucose molecules, two and three units respectively, but they must be cleaved into single units to be ultimately utilized by the yeast. Maltase present in the yeast cell is primarily responsible for the break-down into consumable units. Although maltase is present in germinated barley, and essential for successful brewing, it often does not play a large role in the mashing process. Optimal temperature range of maltase is 95-104°F, meaning it does not see favorable conditions in most mashes, and is often denatured before saccharification is complete.
Enzyme denature/renature - Most enzymes are denatured under high heat. Bonds are broken and the special shape that makes catalyzing reactions possible is lost.
Generally, a lager yeast strain is selected for beers where metabolism of maltotriose is desired because lager strains are apt to metabolize maltotriose much more quickly than ale strains under similar circumstances. Despite popular belief, maltose and maltotriose are both fermentable by ale and lager strains, technically. The variation in maltotriose metabolism between lager and ale strains is due to transporting molecules across the plasma membrane. Once in contact with maltase, free glucose will be cleaved and metabolized as normal.
In highly attenuated wort, fewer limit dextrins remain. This is due to efficient cleaving of single, double, and triple glucose chains. As more units are lost to yeast metabolism, the highly branched remnants are left behind providing flavor and body. Targeting your desired attenuation level is a very important step in recipe building. Brewers should work to achieve a balance between extract efficiency and flavor profile. High attenuation can improve overall production efficiency, but it is important to understand where that efficiency comes from. Nothing is free, and any improvement in attenuation comes at the cost of residual sugar. Many brewers are familiar with adding dextrin malt to improve mouthfeel or wheat to increase foam stability, but these same principles can be applied to wort extract composition. Adding higher percentages of limit dextrin malts will leave more highly branched remnants, compensating for glucose body/mouthfeel “lost” to fermentation, but only to a point.
Polysaccharides - Due to its highly bonded structure cellulose is insoluble in wort. Amylose is efficiently cleaved due to its linear structure. After hydrolyzation, enzymes are able to “fit” into place and break linkages along the chain. Amylopectin is similarly hydrolyzed and cleaved by enzymes until only the stumpy remnants remain. The remnants, called limit dextrins provide much of the residual character.
A very traditional beer style can be accentuated with unconventional brewing techniques, as in the case of Hefeweizen. Some brewers will remove (or decoct) a portion of mash to favor maltase action and increase the overall fermentability of wort. As free glucose is increased in wort, so is the potential for esterification. If a “banana bomb” is the goal, resting in a low range (95-104°F) for extended periods will help. On the other hand, if clove is the signature you seek, a ferulic acid rest at 122°F may be just the ticket. The higher temperature will decrease the effectiveness of maltase, but will increase the activity of ferulic acid decarboxylases. To balance, a stop at each temperature for a short rest is ideal.
In the past, adjunct percentages were limited by the diastatic power of the remaining malt in a given grist, so brewers often tried to incorporate 6-row barley to boost enzymatic activity. Six row barley generates kernels that are slightly smaller and contain less starch reserve, as compared to 2-row barley. Their advantage comes from an increased percentage of outer kernel layer (aleurone), which contains the majority of enzymes in the barley kernel. Increasing the enzyme content and rest period of the grist/mash was necessary to ensure full conversion of adjunct starch sources.
Enzyme Activity – In order to target effective mashing, align as many factors as possible. Temperature is often the most influential, however supplemental enzymes can offer forgiveness in this area. Be sure to buffer pH according to your enzyme complex, and provide enough water for full hydrolyzation. Increasing overall enzyme content can reduce rest times significantly.
When exploring a low-calorie light-lager or Brut IPA, supplemental enzymes are the bees’ knees. Both these styles have a commonality not evident in their names, and that is a signature dry finish. When measured with an average hydrometer, final specific gravity readings can be sub-1.000 due to the complete conversion and metabolism of all starch components. This is due to the density of the lighter alcohol compounds created during fermentation, giving an apparent attenuation of 100% or more!
Supplemental enzymes such as Attenuzyme® can provide unique advantages when making your Brut IPA or Low-Cal Lager. Pullulanase and glucoamylase work together to free virtually all available sugar for fermentation. Dosing at higher levels, perhaps 2ml per pound of grist, accelerates the hydrolysis of amylopectin and amylose to maximum levels, leaving them available for further enzymatic action. Pullulans are chains of maltotriose units that are bound by glycosidic linkages and pullulanases work to break those bonds, freeing maltotriose units for fermentation or further enzymatic breakdown. This one of the keys to unlocking full fermentation potential.
As we mentioned earlier, lager yeast is capable of metabolizing maltotriose. However, ale strains see more resistance in transferring the plasma membrane. An easy way around this resistance, regardless of yeast strain used, is to reduce the maltotriose even further to maltose, or glucose. Glucoamylase, sometimes referred to as amyloglucosidase (AMG), works throughout the mashing and fermentation processes, cleaving single glucose molecules along the way. Supplementing this reaction quickly reduces the quantity of maltotriose into the smaller units of maltose and glucose. From here, yeast can finally complete the starch to alcohol conversion with the least amount of energy expended. Glucoamylase is not specific to maltotriose, so it will free glucose from amylose and amylopectin directly as well.
Plasma Membrane & Yeast Cell – Breaking down starch to its simplest form, glucose, is Ideal for transporting across the plasma membrane. Once inside the plasma membrane yeast can metabolize the sugar into alcohol.
Balance is dependent on product perimeters, so consider all aspects in targeting attenuation goals. Rich, bold beers do not have to send good money down the drain, and high ABV beers do not have to pour excessive money into the mash tun. A small touch of enzymes can encourage consistency between normal mashes, especially if there is a fluctuation in raw material quality, or large quantities of adjuncts. Targeting usage in the mash allows for optimal results without adding enzymes into the active fermentation process. Heating at mash-out or in the kettle will fully denature the activity, “stabilizing” the wort composition for further processing. When enzymes are added to in active fermentation, they may remain active for extended periods, unless further action is taken. Pasteurization is one way to ensure the majority of enzymatic action has ceased, regardless of exo- or endo-genus origin.
The main takeaway: attenuation is central to the development of any fermented beverage. Single handedly, it can make your product exquisite, or it can make it undrinkable. Sweet syrup-like body might be great for a maple porter, but a low-cal lager should be just the opposite, thinner than water. When exploring the use of supplemental enzymes, dose according to your intended purpose. Often it is best to start low and increase until a desirable balance is achieved, but when looking to reach 100% attenuation - best cut to the chase. Remember the basic principles. Residual sugar is flavor, body, and mouthfeel; but also calories, cost, and a reduction in alcohol. Aim for less waste and more money in your pocket, try something different!
