I recently switched to 10-gallon (38-L), electric brew-in-a-bag (BIAB) batches, from 10-gallon (38-L), three-vessel batches, and my beer quality has dropped to a depressing level. The first brew was a lightweight hoppy beer that came out very flabby. No real personality, just sort of blah. The next was a darker beer with lots of flaked oats in the grist. It did not attenuate and is so worty as to be undrinkable.
These batches have me questioning the mash chemistry as it relates to such a loose mix. I am using full pre-boil volumes to mash, then draining the basket and putting the heat to it. With about 20 pounds (9.1 kg) of grain and 17 gallons (64 L) of water, am I diluting the mash so much as to make a water adjustment (or pH adjustment) necessary?
The first thing I do when discussing mash thickness is to calculate the liquor-to-grist ratio (water weight divided by grain weight) because this ratio is the basis for discussion related to thickness. Infusion mashes typically range from 2.5–3.0 L/kg (1.2–1.5 qts./lb.) and stirred mashes usually range from 3.0–5.0 L/kg (1.5–2.4 qts./lb.), with 5.0 L/kg (2.4 qts./lb.) being a very thin mash. Your mash has a liquor-to-grist ratio of 7.1 L/kg (3.4 qts./lb.), which is extremely thin. So what is the significance of mash thickness?
In the view of many brewers, mash thickness mainly relates to functionality. If you are doing a single-temperature, infusion mash, a thick mash is usually desired because the first wort gravity is nice and high, the mash bed floats atop the high-gravity wort, and the low ratio of water to malt keeps the concentration of mash enzymes and their starchy substrates high. The latter point is important to enzyme kinetics as the rate of enzymatic reactions is directly related to the concentrations of substrates and enzymes. An enzyme is also less prone to thermal denaturation when attached to its substrate; this is one reason why the optimal temperatures for a given enzyme are over a temperature range, as opposed to a single value.
If brewers could use thick mashes for stirred mashing, many would because a thick mash yields a high first wort gravity. But when a mash is stirred and then pumped to a lauter tun, or pumped to a decoction kettle, a thinner mash is simply easier to handle (I am referring to commercial equipment here). This is why many recipes for lagers use thinner mashes. I believe, and present as an argument in this answer, that commercial brewers choose to thin their mashes out for a combination of reasons that include: Ease of mash handling, improved extract yield, reduced sparge water volume, influence on wort fermentability, and influence on beer flavor. As long as mash pH and the concentration of calcium ions are kept in the ideal range (keep reading), an extremely thin mash should not be the root cause of brewing failure.
The BIAB method employs thin mashes for the same basic reasons other brewing technologies use thin mashes: Functionality. The primary distinction between the BIAB method and other brewing methods, aside from the simple equipment, is the lack of sparging. Brewers using a brewhouse with a mash tun or lauter tun can, of course, do the same using their brewing set-ups. Kirin Ichiban, anyone? The thin mash used in the BIAB method allows brewers to produce a full volume of wort without messing around with sparging or adding any water after beginning the mash. But with this thin mash comes a dilution of the buffering systems that control mash pH, and a dilution of calcium ion concentration.
Without knowing more about your brews, it is impossible to know the cause of the failures, but focusing on your water is important, especially given your location. Indianapolis water comes from limestone aquifers and contains a lot of carbonate. This type of water often results in a mash pH that is outside of the ideal pH range of 5.2–5.5. And since thin mashes contain more water minerals and less mash buffers, mainly amino acids and phosphates, than thick mashes, high carbonate water is more problematic in these thin mashes. Your water contains plenty of calcium, but if you were using water with a low calcium content, for example reverse osmosis (RO) water, you would want to make sure that you have at least 50 mg/L of calcium in the mash water because calcium thermally stabilizes alpha-amylase.
I am a big fan of using RO water for brewing because it makes water adjustment easier. But there are many brewers who prefer using their local water. No problem with doing this, but more attention is required. At a bare minimum, a pH meter should be used to monitor mash and wort pH. The mash pH should fall between 5.2–5.5. This pH range is important for enzyme activity; if the pH is too high or too low, starch conversion, wort fermentability, and wort separation can all be negatively influenced. Wort pH during sparging (obviously, not for BIAB brewers) should also be monitored when using water high in carbonates because wort pH increases as gravity drops, and with this can come more tannins; it is normal for brewers to stop collecting wort when the gravity is less than 2 ˚Plato/1.008 or when the pH rises above 5.8–6.0. Although mash pH, and the wort pH that flows from the mash during wort collection for brewers using mash tuns, can be adjusted by adding different salts to the mash system, it is easier to adjust mash pH using either lactic or phosphoric acid.
In the summary of your problems, you mention that your first brew seemed “flabby.” This is a wine term used to describe wines lacking acidity; a flabby wine lacks structure and is appropriately labeled by this funny term. Although this moniker is sometimes used for beer, it is not something that most brewers have in their lexicon . . . maybe your question will result in a spike of this quirky term! The useful thing about this descriptor is that it has a direct connection to process. A flabby beer can be converted into a crisp beer by keeping the pH of the mash, and especially the wort, on the low end of the ideal range. This is best done when brewing, as opposed to attempting to tone the body of a flabby beer by adding acid. One very effective brewing technique is to adjust wort pH at kettle-fill, before the boil begins. This method makes for a cleaner hop bitterness, and really helps to make a crisp beer when brewing styles like Pilsner and Kölsch.
Don’t hang up your mash bag too quickly! I was a skeptic of this method when it first came on the scene because it is so different from other mashing methods, but tasting great beers made from the BIAB technique has changed my opinion. It may take you several more batches to exorcise the demons from your BIAB brews, but you should be able to dial this method in to help you reap its benefits of reducing brewing time and using less equipment.
Measure Ph Correctly (Sidebar)
Mash pH is one of those brewing topics that is commonly discussed, but surprisingly little is written in the brewing literature about how to measure mash pH. I guess the reason for this is that measuring mash pH is really pretty simple. You take a pH meter, plunge the probe into the sample, and note the pH on the meter’s digital display. Oh yeah, make sure to calibrate the meter with standards before using. The mash pH should ideally be between 5.2 and 5.5.
But pH is affected by temperature. When a mash sample is cooled to room temperature, the pH increases by approximately 0.35. Many owners of pH meters don’t worry about this because most of the pH meters on the market have built-in temperature compensation, so even this detail has been taken care of by modern convenience. So it seems that pH measurement really is as easy as 1-2-3 . . . yet it is not so easy.
There is a catch; what do the pH references in literature really mean? Does mash pH 5.2 refer to the actual pH of the hot mash, or does it refer to the pH of the cooled sample that is measured at room temperature (the norm for older lab methods before temperature compensation became common)? Oddly enough, most of the references to pH in brewing textbooks and in the brewing research literature do not provide a reference temperature, or even a method, about the pH measurement. Scientific papers typically provide excellent detail to the most mundane of measurements, but for some reason pH is often cited with nothing more than a value. The millivolt output of a pH electrode varies with sample temperature, and there are tables that can be easily found showing the effect of temperature on the pH probe. Temperature also affects the dissociation of buffer systems, like a brewer’s mash, the effect becomes compounded, and tables are not available for all permutations.
The rule of thumb pH range of 5.2–5.5 is the pH of the actual hot mash, not the cooled sample. This means that the temperature-corrected pH is about 0.35 units higher, or pH 5.55–5.85. It is really best to use pH meters without automatic temperature compensation (ATC) because the ATC only accounts for the difference in how the electrode output voltage is affected by temperature and if you use the output from a temperature-corrected pH the result is confusing to compare to data published in the brewing literature.
How do hops affect the final gravity of a beer? I recently brewed a New England IPA with 12 ounces of hops for 5 gallons (19 L). The final gravity was 1.018 and I expected 1.014 with the GigaYeast Vermont IPA yeast. So to me it tastes stronger than the 5.5% ABV that I calculated, and I don’t understand why the hop content doesn’t make the hydrometer float higher.
Barrington, Rhode Island
Hops do not have a significant impact on wort or beer density because the concentration of hop soluble compounds is simply too low to make much of an impact on density. In order to increase the density of 1 liter of wort by 1 ˚Plato, 0.01 kg or 10,000 mg of soluble solids must be added. A beer that contains 100 mg of iso-alpha-acids per liter of beer (100 IBUs) adds sufficient “extract” to boost the gravity by 0.1 ˚Plato, which is within the error range of the typical brewery hydrometer. Hops do lend compounds to beer other than iso-alpha-acids, such as non-isomerized alpha acids, beta acids, and hop oils, but these are minor players in comparison to the iso-alpha-acids. Furthermore, hop oils are not brought into solution by dissolution and do not affect gravity like dissolved solids. When miscible liquids are added to an aqueous solution, the effect on density is a weighted average of densities. For example, if you mix 100 mL of water (density = 1.000 g/mL) with 100 mL ethanol (density = 0.789 g/mL) you end up with a 50% (volume/volume) ethanol solution with a density of 0.895 g/mL.
So let’s dig a bit deeper into what you observed. For starters, you ended up with a gravity that was higher than what you expected. I take a pretty cynical view about expected finish gravities (FG). Is the expected FG based upon what the recipe states? Is it based on the yeast strain used for fermentation? Is the expectation based on the malts used in the mash? Has the mash profile been factored into the predicted outcome? Or is the expectation based on a forced fermentation of the wort using the same yeast strain as the actual brew? The only thing that really matters is the latter; all the other questions just give information to help formulate an educated guess. Kind of like a brewer’s parlor trick borrowed from magicians who can intuit so much from basic observations. So if your expectation of 1.014 was based on any method other than a forced fermentation, I would argue that your expectation, not the finished beer gravity, seems off! I am going to come back to this subject.
You also think the beer tastes stronger than your calculated strength. This is one of those observations that can be a warning flag. Not all alcohols have the same perception of strength, and not all beers containing the same concentration of alcohols are perceived the same. When I taste a beer with a higher-than-expected FG that seems stronger than expected, my first thought is a fermentation problem that resulted in the production of more high-molecular weight alcohols (fusels). The primary factors that tend to increase higher alcohol production during fermentation include high fermentation temperature, low pitching rate, increased cell growth, increased wort amino nitrogen, yeast strain, and higher-than-normal wort aeration levels. In your particular case, you may be associating higher strength with higher levels of higher alcohols.
The corollary to the strength discussion is two beers that seem to be different in strength, yet have the same alcohol composition. In this case, a drier beer with lower background flavor intensity usually seems stronger than a beer with more flavor and bigger body. Not what you observed, but something that may be perceived. A contemporary example of this is how many craft beer drinkers are surprised by the strength of an IPA because the flavor intensity masks the strength.
Now it is time for a variant on the topic; how can a brewer actively influence the final gravity of a beer? The basic answer to the beginning of this detour is that the wort fermentability is pushed in the desired direction. The first thing that brewers need to keep in mind is that many of the classic brewing textbooks are becoming out-of-date with respect to current trends in barley and malt. Today’s malt tends to contain a more potent enzyme package in comparison to malts that were common when some of these books were written. Today’s malts, even those made in Europe, tend to be very well modified, and much of the discussions about using mashing to compensate for undermodified malt is not relevant to most of the malt being produced around the brewing world.
One strategy to control fermentability is to either preserve or actively reduce the potency of the enzyme package that comes in with malt. This is not something that many brewers consider because enzymes are invisible, they cannot be tasted in malt, and they don’t have an obvious effect on finished beer flavor. Since enzyme concentration is directly related to reaction rate, more enzymes means less time required for mashing. But look at contemporary brewing recipes and begin looking back in time. You will probably discover that mash times and temperatures cited in recipes have not changed over the last 30 years. During this same 30-year period malts most certainly have changed.
One idea is to figure out how to give the modern mash a chill pill. Shortening the mash is one way to harness these very “hot” (highly enzymatic) modern malts. A related idea, and one that I did not pursue with my answer to Dave Allen’s BIAB question, is to use mash thickness to cool off these hot malts. Since enzymes are more prone to thermal denaturation when not latched onto their substrates, thinning the mash out makes mash enzymes more sensitive to temperature. Diluting the enzyme package with unmalted grains (adjuncts) is another possibility. Brewers can also source malts that are lower in enzymes, but this is not so easy these days.
The use of special malts is another way to exert control over finished beer gravity. Crystal and roasted malts are changed in the process such that malt enzymes are not able to convert much, if any, of the extract from these malts into fermentable sugars. So using more or less of these ingredients is yet another tool in the brewer’s tool box that can be used to influence beer.
Yeast selection can also be used to influence FG. Some strains are able to ferment a wider array of carbohydrates than others, specifically some strains can ferment maltotriose (a polysaccharide containing three glucose monomers) while others cannot. And some yeast strains tend to exit the scene early and leave residual extract in the beer. I am not a big fan of the latter method of FG “control” because it is not exactly precise, and leaves the beer prone to uncontrolled re-fermentation in the bottle. Then there are the yeasts that secrete enzymes, so-called diastatic yeast strains that will finish off what was left unconverted in the mash. Brettanomyces and some saison yeasts are known to be diastatic; these critters need to be used with care because they will continue fermenting high FG beers in the bottle.
The take home message here is that the world of brewing is constantly changing. Bumping present materials and methods against older references is a useful and head-scratching exercise. Many a brewer has solved a brewing problem by noting the differences in the beer-time continuum. Brew long and prosper!