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Story Index All-Grain Brewing Shortening an all-grain day, foam facts: Mr. Wizard
| Shortening an all-grain day, foam facts: Mr. Wizard |
| Ashton Lewis | |
| September 2007 | |
Taking a breather?In the March-April 2007 BYO, you described a mash technique while discussing the differences between commercial and homebrewers. You wrote of pub brewers who mash in and “take a short breather” and begin wort collection. I got the gist of it and tried it out on a recent batch. My short breather was 20 minutes before I did a recirculation and runoff. Yield was the same as when I previously rested my mash for 90 minutes. I definitely cut 70 minutes off my brew day just guessing at how to do this technique. Is it possible to get a full description as well as clarification of a “short breather”? Bob Haisen,
There are some brewing topics I address because I have been asked, and some subjects I opine about whether asked to or not. And there are some things I tend to avoid. Technique is heavily influenced by opinion and personal preference. Unless there is something really “wrong” with a particular technique, I tend to keep my mouth shut. Perhaps I have failed our readers by biting my tongue and I will attempt to redeem myself today! There are some techniques that many all-grain homebrewers practice that are at best a waste of time, and at worst may have a detrimental affect on beer flavor. One is mashing time. It seems that almost all recipes call for an infusion mash time ranging from 60-90 minutes and recipes using multi-temperature mashes are usually a bit longer. The truth is that malts these days are considerably different than malts from the past. Malt modification is usually very good, even with most European malt, and the enzymatic strength of certain barley malts (mainly 2-row varieties from North America) has increased over the past 30 years. This means that the goals of mashing can often times be accomplished in much shorter time periods when modern barley malts are used in brewing. When I say “modern” I am referring to malts made from new barley varieties that have been bred to address the requirements of the modern brewer. I have pointed out numerous times that Klages barley is no longer grown, yet brewers still equate U.S. 2-row barley with Klages. I remember in the early 1990’s going to annual barley crop reports given by Great Western Malting Company and hearing then how few acres were seeded with Klages. Things change with brewing raw materials and unless brewers remain up-to-date with current trends, brewing literature quickly becomes dated. Harrington, BA1202 and AC Metcalf are the varieties that really replaced Klages in the West. Most brewers want to accomplish a few primary goals during mashing. The first is to convert starch into fermentable and unfermentable sugars that end up giving beer the potential for alcohol and some residual carbohydrate that lends body and character to beer. The second goal is to yield as much of this extract as possible. Undermodified malt contains intact cell wall constituents (beta glucans and proteins) that make this secondary goal more difficult and is the reason that more intensive mashing methods are used when brewing with undermodified malt. The third goal, which is really an extension of extract yield, is to make extract recovery easy. When brewing with North American 2-row and 6-row barley malts the brewer can usually assume two truths. The first is that there are plenty of enzymes present in the malt to easily convert the starch in the malt plus additional starch from adjuncts (e.g., rice and corn). The second truth is that the malt is probably well modified. Assumptions are often times dangerous, but these two can usually be taken to the bank. The large brewers who buy and specify the majority of North American barley malt require high enzyme content and uniform modification and that’s what their suppliers produce. Assuming you are brewing with North American barley malt you have two basic options. You can choose to mash for 60–90 minutes because that’s what 95% or more of most brewing recipes dictate. Or you can mash for a shorter time period, for example, between 20–45 minutes, because that is all that is required for many beer styles. The long mash is safe and you are assured to have no conversion problems. The shorter mash times may cause problems if you get too aggressive on the low end, do not check for conversion using the iodine test and mash off at the end of the mash. But if you check for conversion, reduce your mash time gradually over time and do not mash off, you can successfully shorten your mash times with no problems. I’ll pause here and put some practical thoughts into this based on what you did with your recent brew. You mashed for 20 minutes and then recirculated the wort to clarify it before collection. I’ll assume this recirculation took 20 minutes. If you did not raise the mash temperature above about 158 ?F (70 ?C) you were actually mashing for 40 minutes. It just happens that you were mashing and recirculating during the same 20 minutes interval. The second comment you made about your experiment is that your yield did not change. Yield is one of the keys to mashing I list above and since the yield did not change from your 90 minute mashes you can logically conclude that 90 minutes is not required to achieve good yield (although the result from one trial is not enough data to draw any real conclusions). Many pub brewers who do not mash off use a mash duration similar to what you used and in some cases the “short breather” is as short as ten minutes. Again, it is important to understand from a biochemical view that the enzymes active in the mash do not recognize stages of mashing like “mash rest,” “recirculate” and “sparge.” Enzymatic reaction rates are primarily affected by temperature, pH and substrate/enzyme concentration. As long as the conditions for enzymatic reactions allow enzyme activity the mash continues. Even in mashes where the temperature is raised to mash off (usually around 168 °F/76 °C) after a relatively short conversion hold around 158 °F (70 °C) is complete, the extract yield is good and fermentable wort flows easily from the mash tun. In other words, the primary goals of mashing are accomplished. I stated earlier that, at best, long mashing is a waste of time and, at worst, long mashing can cause problems. I want to elaborate on this and briefly give two examples of problems stemming from long mashes. The first is that if you are using enzyme-rich malt you may end up producing wort that is more fermentable than you really want, resulting in a beer that has a thin character. One way to brew light beer is to use an extended mash between 145–150 °F (63–65 °C). The best selling beer in the United States — Bud Light — uses this method and their mashes last over three hours. If you want really fermentable wort, this method accomplishes your goals, but if you don’t want this type of wort, then the method is not a good fit for you and your beer. This is an extreme example, but illustrates how mashing time does far more than simply make for a negative iodine reaction. Mash time also influences the amount of flavor extracted from the malt during mashing. A few years ago we reduced the mash time used for our helles-style lager and immediately detected the absence of a subtle grainy off-flavor that we wanted to eliminate from this brew. At first we suspected that the change in mash schedule and beer flavor may have been related through a fluke, but repetition validated the relationship. Five months later, we bagged a gold medal at the GABF in the European-style Pilsener category. I’ll quickly finish with two more opinions about technique without much elaboration. Opinion #1: Many brewers recirculate their wort after mashing for an arbitrary time period that at times unnecessarily adds time to the brew day. You want to get the weak wort (weak because of water usually used to cover the false bottom) from the bottom of the mash tun back to the top of the mash before collecting wort and to get the wort reasonably clear. If you can do this in five minutes instead of 20, more time is not required to accomplish this brewing objective. Opinion #2: Many brewers collect their wort over a period of about 90 minutes because pundit-brewers state as fact that short wort collection times reduce yield. In contrasting fact, most commercial brewers try to collect their wort as quickly as possible because the lauter tun is the most expensive vessel in the brewhouse and is also the bottleneck to production speed. These brewers are keenly aware of extract yield and short wort collection time is usually limited by lauter tun design and not the ability to achieve good yields. When I was a brewing student at UC Davis, I brewed a lot of beer on a 5-gallon pilot brewhouse. Our wort collection times usually lasted between 30 and 45 minutes and yield was always quite good. This answer was rather long, but it’s possible the five to ten minutes it took to read may shave two hours from your all-grain brew day. Hopefully this was a good investment of time! Keeping your head upI’ve been trying to improve the head retention of my batches and have not had much luck. I recently brewed a dry stout with wheat malt and flaked oats, and I also increased the corn sugar amount for priming with visions of a thick, creamy, long-lasting head. But alas, it was not to be. When I pour the beer into my Murphy’s Irish Stout pint glass, I initially get a nice head, but this disappears within 30 seconds. After a minute or so, the beer actually appears completely flat. Is yeast presence a major head retention inhibitor? Also, I read Chris Colby’s piece “Balanced Recipe Formulation” (March-April 2007) where he states that adding wheat to a recipe in an effort to improve head retention should not be substituted for sound brewing practices. What exactly are those brewing practices and what are the things that would increase or decrease head retention? Chris Adams
Good foam is something that many brewers like on their brews for aesthetic and mouthfeel reasons. Foam looks appetizing on top of a pint of brew and also adds texture to the beer when drinking. Some draught beers have really creamy foams created by using nitrogen to froth up the beer. We use nitrogen for certan styles at Springfield Brewing Company and I love the effect on some beers, but getting great foam on a nitrogen-dispensed beer is much easier than from a carbonated beer. There are several things that can cause beer foam to be less than remarkable. Some of the real foam killers frequently seen in brewing are compounds that actively cause beer foam to collapse. Most of these substances have one thing in common and that is that they congregate on the surface of the beer and compete for space with beer foam at the gas-liquid interface. Lipids (fats and oils) and surface-active cleaners/sanitizers are two types of substances that really do damage to foam. While lipids usually do not come from brewing ingredients, they are frequently found on beer glasses that have either been soiled by lipstick or dirty dishwater. This is really more common than most people think when drinking beer at a bar. You can also transfer grease to a beer glass when you are munching on oily snacks — for example, peanuts or potato chips — while sipping a beer. Most soaps and sanitizers have surfactants to aid in their effectiveness and residuals of these compounds can cause foam problems. This is one reason that it is so important to rinse cleaners from brewing tools. If you use non-rinse sanitizers, it is very important to make sure that your sanitizer of choice does not damage beer foam. If you are not sure whether you’re using a sanitizer that damages foam you can do an easy test. Rinse one glass with water and one glass with sanitizer. Allow both glasses to drain upside down for 15–30 seconds so the surface is not completely dry. Pour a half bottle of beer from the same bottle in a similar fashion into both glasses to ensure foam formation and watch. If the foam in the glass rinsed with sanitizer crumbles like the Berlin Wall you’re using a wicked sanitizer! The beer itself has intrinsic properties that dictate the ability for good foam formation. In my experience with foam, the most important foam positive constituents of beer are proteinaceous compounds from the malt. Although the use of under-modified malt in brewing comes with a whole set of issues and is really hard to find, the breakdown of barley proteins during germination is limited and there is a relatively large amount of foam-positive protein in the malt. In contrast, well- and over-modified malts are fairly common and protein degradation in these malts is more extensive during malting (protein degradation is one of the key parameters used to gauge modification). The bottom line is that malt modification affects foam and most of the pale malt on the market today is well-modified and has less foam positive proteinaceous goodies than lesser modified malt. Some brewers have strong feelings about the importance of proteolytic activity during mashing; there are those who know it happens and how it affects beer and those who know that it really doesn’t happen and see it as a waste of time. Believers in proteolytic activity during mashing caution against a long rest around 122 °F (50 °C) because it can reduce the foam quality of the resulting beer. Adding some wheat malt to a brew can make up for the deficit in foam-positive proteins from barley malt because wheat malt contains much more foam positive compounds compared to barley malt. Although many recipes call for a small amount of wheat malt (about 5%) intended to improve foam, I have never found that this small amount does much for the beer. Our best seller is an unfiltered American-style wheat beer made using about 50% wheat malt and about 7% raw wheat. This beer has a very different foam appearance and stability compared to our all-barley malt beers. Our unfiltered wheat also contains yeast and I have never noticed much of a change in foam stability over time after bottling. Yeast can cause problems with beer foam over long storage periods because when yeast die and autolyze, enzymes spill into the beer. Proteolytic enzymes are included in this spilling and degrade foaming proteins in the beer. As you mention in your question, Belgian beers are known for really nice foam, and they are normally bottled conditioned. I do not think your foam problems come from yeast in the bottle. In addition to protein, hops are also considered foam positive because beers brewed with almost no hops have poorer foam stability compared to beers brewed with perceptible bitterness. This is more of a laboratory-type observation and most beers have enough hops to benefit from their foam positive nature. Adding more hops to improve foam affects flavor and while it is true that really hoppy beers often have good foam I cannot recommend using hops as a foam enhancer and a solution to bad foam in general. The gas content of beer, normally carbon dioxide, clearly influences foam because there would be no foam without gas evolution upon dispense. Carbon dioxide content primarily influences foam volume and not foam stability. So if you increase the carbon dioxide content of beer, you may have more foam initially but the rate of collapse will not be affected. Like adding more hops I don’t suggest adjusting your carbonation rate based on improving foam; the carbonation content affects flavor and you should shoot for a target in-line with the beer you are brewing. Some beer glasses contain little etched spots in the bottom that act as nucleation sites for bubbles to form. This causes the continual formation of foam while the beer sits in the glass and new foam formed replaces foam that has collapsed. Some people add a few pieces of coarse salt to the beer and these little chunks of salt do the same thing as the special etched spots. Samuel Adams (Boston Beer Company) recently came out with a special glass they developed to enhance the presentation of their beers and one of the design features is a little etched spot in the bottom. There are some ingredients used in certain brews that are believed to either be outright foam negative or at least have the potential to be foam negative. One common theme of such ingredients is the presence of lipids and examples include flaked oats, chocolate, coffee, vanilla, nuts and other nutty brewing ingredients. Although these ingredients contain more oil than malted barley (sometimes considerably), they do not necessarily cause foam problems. They can, however, and brewers need to look out for problems when using such ingredients. Your stout contains flaked oats and many brewers believe that oats cause foam problems. I think what Chris Colby meant when he stated that adding a bit of wheat malt should not be a substitute for sound brewing practice is that there is not a silver bullet to brewing beer with good foam. All the factors that affect foam must be considered to appease the foam gods. |
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