It is time to try your first bottle of that (hopefully) great beer you have just brewed. You pop the cap, nice hiss, good carbonation. You pour your beer and admire its creamy head, good color, and sparkling clarity. The aroma is a fragrant bouquet with some fruity esters and a nice balance of malt and hops. Your first taste reveals some maltiness and then notes of hop spiciness. On your second taste you turn your attention to the body, or mouthfeel. It should be firm and smooth — but wait, something is wrong. The beer is thin and somewhat watery. Not to worry.
A variety of steps cause the body to be different than intended. A good understanding of the techniques and processes that influence body will aid the homebrewer in making that special beer.
Body is the sensation of palate fullness, the viscosity and feel of beer in the mouth. It is a characteristic of beer that reflects its ending density and refers to the mouth-filling and thickness properties that a given sample contains.
Protein, unfermentable sugars (dextrins), beta-glucans, carbon dioxide and, sometimes as in Guinness, nitrogen, nuetral alcohols, and foam, which really depends on most of these factors, make up beer’s body. The terms mouthfeel and body may be interchangeable.
Mouthfeel qualities are distinctly different from flavor. This concept is often misunderstood. The Beer Judge Certification Program (BJCP) and the American Homebrewers Association (AHA) on their beer competition score sheet have five major categories that include appearance, bouquet/aroma, flavor, body, and drinkability. Body accounts for five points out of a possible 50 points, or 10 percent of the score.
Body is rated as thin (light) to full (heavy), with many other descriptors applying. These include sweet, neutral, dry, bland, vinous, firm, smooth, rough, watery, and proper or improper for the style.
There are two other characteristics often associated with mouthfeel. Astringency is a dry, puckering sensation that is more mouthfeel than flavor. Although “alcoholic” is sometimes considered a taste, its warming sensation caused by ethanol and higher alcohols is also considered a characteristic of body.
The description of a beer as thin or full bodied can be appropriate for certain styles of beer. American lagers are classified as light bodied, while at the other end of the spectrum are full-bodied beers such as bock beers and imperial stouts. Barleywines are classified as very full bodied.
The Significance of Protein
Of the prominent factors contributing to body in beer, protein is considered most significant.
Protein is an enormously complex organic compound containing nitrogen derived from amino acids. In the brewing process it is an essential compound whose role is often misunderstood for good reason.
Almost all of the protein encountered in brewing comes from grain. The vast majority of nitrogen is supplied by the protein, which averages 16 percent nitrogen. A strong, healthy fermentation must have sufficient nitrogen derived from protein.
Proteins are similar to carbohydrates in that they are very long chains of complex molecules that are elementary building blocks linked together in specific ways. Complex proteins are formed by long chains of amino acids linked together by peptide bonds.
Protein in the proper form and amounts contributes to mouthfeel or body of beer, promotes head retention, and provides essential nutrients for yeast to promote strong, healthy fermentation. The wrong amount of protein contributes to myriad problems including turbidity, flavor instability, poor head retention, and sluggish or stuck fermentation.
The majority of protein molecules in raw, unmalted grain are extremely large and must be broken down. This starts with the malting process, in which whole, unmalted barley is germinated to a certain degree and then dried to make malted barley. The most significant action that occurs is the development of enzymes that act directly to degrade or modify the complex chains of nitrogen-based proteins into smaller chains of amino acids correctly termed polypeptides, not proteins, and into single amino acids. Also, small amounts of dextrins and fermentable sugars are developed and some insoluble starch is made soluble.
Long chains of high-molecular-weight protein are undesirable, and at least 50 percent of these long chains should be broken down into medium and small chains or removed to enhance body and heighten flavor stability, head retention, attenuation, and clarity and to provide a strong, healthy fermentation.
Enzymes are perhaps the most important class of protein in the brewing process. At least eight enzymes in malt can break down or degrade proteins, but each plays a highly specific role.
Enzymes Do What?
The enzymes most critical to contributing body to beer are proteases, or proteolytic enzymes, which break down proteins into polypeptides and amino acids, and beta-glucanases which reduce the size of beta-glucans into smaller and less viscous, hence less mouthfeel, beta-glucan molecules. The bulk of these enzymatic changes occur during malting.
During germination the barley seed synthesizes these enzymes, along with many others such as amylases, to allow the seed to grow. The barley seed grows by dissolving large organic molecules found in the barley's starch endosperm to give the growing seed sugar. The endosperm is a complex structure of starch granules, sought after by brewers, embedded in a protein matrix and encased by cell walls made of beta-glucans.
Beta-glucanases dissolve the endosperm cell walls and allow the proteases to begin breaking down the matrix surrounding starch granules, which in turn allows the amylases to convert barley starch into sugars needed by the growing embryo. The maltster and brewer want the cell walls and protein matrix to be degraded but want to retain as much starch as possible. When the embryo uses sugars for energy, carbon dioxide and water are formed that are lost from the malt. This is called malting loss and must be controlled by the maltster.
Malts with low losses during malting are usually undermodified, which means they retain a lot of barley-like qualities, such as intact cell walls and undegraded proteins. Beers made from these malts typically have good mouthfeel qualities. Traditional lager malts tend to be less well modified than traditional ale malts.
Malts with higher losses are usually overmodified and contain few intact cell walls and a high proportion of small polypeptide fragments. Beers made from these malts may suffer from poor mouthfeel qualities, especially if the malts are excessively
The conventional wisdom concerning this whole process of protein breakdown was that a lot of it occurred in malting and that more occurred in mashing during the "protein rest." The idea held that undermodified malts require a protein rest to increase the levels of wort amino acids and to reduce the size of the protein that, if left undegraded, would cause problems in lautering. The problem with this idea is that almost all malt proteases are destroyed during kilning.
This view is no longer held by many brewing scientists, however. The research conducted by a group led by brewing science professor Michael Lewis, Ph.D, at the University of California, Davis, in the 1980s indicates that the protein rest merely dissolves protein, which is then later precipitated at higher temperatures but does not have a proteolytic component. This idea has more recently been confirmed by research groups at John Labatt Ltd. and Miller Brewing Co.
Some beta-glucanases that survive kilning can further reduce beta-glucan size, and hence wort viscosity, at temperatures between 100° and 130° F. The activity of these enzymes tends to reduce mouthfeel but reduces the problems in lautering associated with undermodified malts.
Other enzymes that the homebrewer can significantly control are alpha- and beta-amylase, which both degrade starch. These enzymes convert the long, complex chains of starch molecules into dextrins and fermentable sugars. Dextrins give beer fuller body and aid in head retention.
Saccharification is the process of converting large, complex molecules of starch into fermentable sugars such as glucose, maltose, and maltotriose, and larger, unfermentable dextrin chains (dextrins have four or more glucose molecules in their chain). Saccharification is due to the action of alpha-amylase and beta-amylase. Alpha-amylase randomly breaks the starch into smaller pieces. Beta-amylase attacks the non-reducing end of starch (of which there are very many) and the products of alpha-amylase to yield maltose.
Long chains of the simple sugar glucose make up starch, which is not fermentable in these attached chains. Double glucose molecules comprise very fermentable maltose, and four or more glucose molecules resulting from the incomplete breakdown of starch are unfermentable sugars that are tasteless and add body or mouthfeel to beer.
Because starch contains many branch points in its structure and beta-amylase cannot attack these branches, the random action of alpha-amylase enables beta-amylase to be more effective at producing maltose. Beta-amylase is most active between 140° and 149° F and alpha-amylase is most active around 158° F. Thus, lower temperatures and/or slower temperature increases from say 140° F to 158° F will result in more maltose; these worts are very fermentable and may suffer from poor mouthfeel. Higher temperatures will tend to produce worts with a higher proportion of dextrins. This means less alcohol but more of the compounds associated with body.
The extract brewer needs to pay attention to the type of extract used. Some extracts are more fermentable than others. Two extracts that have lower fermentability resulting in fuller-bodied beers are Laaglander and John Bull of England. Two extracts with relatively high fermentability are Alexander’s light malt extract and Munton’s light malt extract. Ask your local homebrew supply shop about malt’s fermentability, and keep detailed notes on the brands with which you have experimented.
There are many raw materials that have high proportions of body-building compounds that are commonly used to increase the mouthfeel of beer. These include dextrin malt, malto dextrin, crystal malt, flaked barley, and flaked oats.
Dextrin malt. Dextrin malt is made from malted barley and is a type of crystal malt. Also known as cara-pils or cara-crystal, dextrin malt contributes body to beer, aids in foam retention and beer stability, and gives the beer additional smoothness and sometimes a sense of sweetness. All this is accomplished without affecting the color or flavor of the beer.
Dextrin malt is stewed at higher temperatures than crystal malt, resulting in the creation of a larger proportion of dextrins. Then it is kilned at very low temperatures to avoid darkening, rendering it tasteless and relatively colorless. Therefore, it may be used on both pale and dark beers. Use dextrin malts for 5 percent to 20 percent of total grist to achieve full advantage for light-colored beer and 2 percent to 10 percent of total grist in dark beers. Because dextrin malt has been enzymatically degraded during processing, it does not need to be mashed with enzymatic grains and can be used in partial grain mashes.
For the extract brewer dextrin powder or malto-dextrin adds another dimension to brewing. Most malt extracts are designed for a standard ratio of fermentability. The use of dextrin powder allows a fuller brew. Dextrin powder is added to the boiling wort. Check the dextrin content of the powder to see if any portion consists of fermentable sugar. If so, adjust accordingly.
Crystal malt. Crystal malt, also know as caramel malt, like dextrin malt will add body and head retention to beer. Unlike dextrin malt, it will also add sweetness and enrich the color of beer. It comes in a variety of colors from light to dark. It can also be used in partial grain mashes.
Lactose. Lactose is unfermentable milk sugar, which may be used to increase body and mouthfeel, especially in sweet stouts. It may be added directly to the boil.
Flaked barley and oats. Unmalted, flaked grains, especially barley and oats, are rich in large beta-glucan gums from undegraded cell walls and contain a lot of undegraded proteins. Both classes of compounds are associated with mouthfeel, especially undegraded beta-glucans. In fact much of the protein contributed by these products never makes it into the wort because it is lost during mashing and boiling. This is not the same with polypeptides from malted grains. The beta-glucans, however, do survive and give wort and beer added viscosity. It is for this reason that lautering and filtration can be significantly affected by unmalted and undermodified grains. In practice these products should not exceed 15 percent of the total grist bill.
Notable examples of beers that use flaked grains for mouthfeel purposes are Guinness Stout, which uses flaked barley, and Samuel Smith's and Young's oatmeal stouts, obviously using oatmeal.
Some features of fermentation and finishing (maturation and clarification) can have a pronounced effect on mouthfeel because they can alter the amount of body-building compounds found in beer. The selection of yeast and the use of clarifying agents and filtration methods are important for this reason.
Attenuation. Another factor that can play a role in body and mouthfeel is attenuation. A high-attenuating yeast will ferment out, further providing a lower final gravity with a thinner-tasting beer. Such a beer is usually drier and less malty. The strain of yeast used is important, and with some styles of beer, the body will need to be compensated for in brewing to offset high-attenuating yeast. Remember, the medium-length proteins can be increased or the dextrin in the beer can be enhanced to provide for a smoother, more full-bodied beer.
Clarifying agents. There are several other factors that the homebrewer needs to be aware of that affect body. Haze can be a problem in brewing, and one of the causes of haze is large protein molecules in the finished beer. Clarifying agents such as Irish moss, gelatin, isinglass, and Polyclar help bond haze molecules together and drop them out of suspension. Care must be taken not to overuse clarifying agents, because they can remove not only the large haze-producing protein molecules but also the medium-chained proteins that promote body and mouthfeel.
Filtering. Filtering beer to reduce or eliminate chill haze can also strip out body, flavor, and head retention. Do not use a micron filter that is too fine. The heavier, more full-bodied beers can be affected most by filtering the beer.
Ron Bach is an award-winning homebrewer, certified beer judge, competition organizer, and president of the Central Florida Homebrewers club.