Effect of mash pH on flavor profile

Importance of mash pH

In a previous article on the mash, I mentioned that high pH can have adverse effects on the beer. Here is a write up of an experiment that tries to qualify the difference between two beers with different mash pH's.

What does a high pH do to my beer?

pH is a measure of the concentration of hydrogen ions in a solution. In explicit terms, the pH is -log[H+], where [H+] is the concentration of hydrogen ions in moles/L. A consequence of the -log function is that as the concentration of the hydrogen ion increases, the pH goes down. The most common range of pH is between 0-14, but it can be higher or lower and even a negative number (though a pH outside that range is very rare outside of a lab).

pH affects your beer in two ways. First, each enzyme in the mash has an optimal range of function in terms of temperature and pH. The enzymes responsible for converting the starches to sugars function most efficiently between a pH of 5.3 and 5.8. As the pH during the saccrification rest increases above 6.0, the enzymes will yield a wort that is less attenuative.

The pH also affects the flavor of the beer. The husks of the grain are full of tannins that can be extracted during the mash and sparge. The reaction pathway of how these chemicals dissolve into the beer is simple. The tannins are a weak acid and, like all acids, have a tendency to donate a hydrogen ion into solution. However being a weak acid, this donation only occurs when the concentration of hydrogen ions is relatively low (as is the case when the pH is too high).

If the concentration of hydrogen ions in solution is low enough, a hydrogen ion will dissociate from the tannin, leaving behind a negatively charged molecule. This negatively charged molecule can more easily dissolve into solution due to water's polar nature. This is why it is important to keep the pH in check: the free hydrogen ions will prevent the tannins from dissolving into the solution.

Most online sources give a pH threshold of 5.8 to 6.0 to prevent tannin extraction. This experiment was conducted to determine qualitatively where the tannin extraction starts in terms of pH.

Experimental Design

Two batches of beer were brewed identically except the water of one was not treated with phosphoric acid to reduce the pH. The two batches of beers are identified as B#160 and B#171. The mash pH of B#160 was 6.0, while the mash pH of B#171 was 5.8. Again, the aim of this experiment was to show how small changes in the mash pH can result in a completely different beer.

A survey was completed with nine participates to rate different aspects of the beer on a scale of 0-6, with 0 being not present and 6 being overpowering. The aspects are Aroma, Carbonation, Body, Hop Character, Fruity/Estery, Malty/Grainy, Roasted, Caramel, Aftertaste, Bitterness, Diacetyl, and Astringency. In addition to these specific categories, each participate rated their overall impression of the beer on a scale from -4 to +4; -4 is awful, 0 is average, and +4 is awesome. The ratings for each category were averaged and used to develop some sort of description of the beer.

Results

Table 1 - Batch parameters

There were some differences between the two beers other than the mash pH, which are tabulated in table 1. The "Final Runnings" is the last portion of the liquid that is run off from the lauter and into the boil kettle. The pH of this will be close to the mash pH at the beginning of the run off and will climb to neutral as the grain is sparged. The gravities are reported in degrees Plato. Ideally, the gravity of the final runnings should not drop below 3.0degP, and the pH should not be above 6.

The differences between the brews that led to interesting results in the surveys are the starting and final gravities. B#160 had a slightly higher starting gravity and a much higher final gravity. This is reflected in the lower % Attenuation, and can be interpreted as B#160 having more residual sugars. Both batches had accurate pitch rates, and were fermented with a low generation of yeast.

Survey Results

Table 2 - Survey Results

Table 2 shows the survey results in tabular form, while Figure 1 shows the results in a spider graph. The major differences are the overall rating and the astringency. B#160 had a significantly (with a 95% higher confidence) higher astringency and lower rating, while the other difference fell within the error of the experiment. B#171 was very well received by the taste panel who reported its astringency as barely recognizable.

The ratings for the caramel/roasted character are interesting if you consider the starting and final gravities of each batch. B#171 counter-intuitively rated higher in both caramel and roasted than B#160 in spire of a lower final gravity. This result might be attributed to the astringency of B#160 masking the caramel/roasted character of the beer.

Figure 1 - Spider graph of survey results

The other differences between the two batches were in the carbonation and the bitterness. The carbonation is reflected in the volumes of CO2 in the beer at the time of packaging. Bitterness is easily mistaken for astringency. This may explain why B#171 was rated as having less bitterness, in spite of having the same hop bill.

Conclusions and Take-away

This experiment shows that a 0.2 difference in the mash pH can lead to astringency that will be a detriment to a beer's flavor.

There are several options available to homebrewers for adjusting the mash pH. Using food grade phosphoric acid isn't an option, as it can only be purchased in gallons (enough for tens of thousands of gallons of beer). The most economical is to add 1-2% by weight acidified malt. This malt is coated in lactic acid, which will bring the pH of your mash down. However at high concentrations, the lactic acid can lead to off flavors. I've heard that many homebrew stores sell a buffer solution that you can add to your mash, but I have no experience with them.

This experiment highlights the importance of monitoring the pH of the mash to ensure it is in the range of 5.3 to 5.8. Litmus paper can be used to get an idea of the pH, but is no substitution for a digital meter. If you are serious about making good beer, a digital pH meter should be a priority investment. They are relatively cheap from amazon, and can cost less than a batch of beer.


NOTE:I am an amazon affiliate, and will only recommend products I have experience with. Below is the most reliable pH meter, as long as you take proper care of it.

Rise and Fall of US Barley

Sorry for the delay in getting this out (memorial day weekend), but craft beer is killing the US barley industry.

About Barley

There are two types of barley: two-row and six-row. Two-row barley is used in the majority (if not all) of European beers. In fact, this has led to the perception that two-row is superior than six-row when it comes to brewing. Compounding this perception is the fact that 6-row is used to feed animals in Europe. The Columbian Exchange brought goods and ideas indigenous in Europe to the Americas for the first time, among which goods was barley. In most parts of the Americas only six-row is suited to grow, leading to a stranglehold on the American beer market that has lasted for over 300 years. However, in the northern regions of America (i.e Canada), two-row can thrive.

The primary states that grow barley are largely in the mid- and north-west of the United States. Cargill (a malt company) does have contracts in Virginia and Pennsylvania, but these are few and far between. The production of barley has been tracked by the UN since the early 60s, and show an interesting trend for the US. Their in-depth analysis on the wide-wide industry can be found online here. This article has more about the international barley market than you could ever need. But let's focus on the United States.

Figure 1 - United States Barley Produced  / Imported

Figure 1 was generated from the FAO statistics database and shows that American barley production (blue trace, axis on the left) has been on the decline since the beginning of the 90s. We are producing half the amount of barley as we were in 1995. Up until the 90s we were importing minimal barley, at less than 20,000 tonnes per year. However, imports (red trace with axis on right) rose dramatically in the beginning of the 90s.

NOTE: The two trances have different scales and the United States has produced more barley than we have imported since these statistics were being recorded. Including in 1994, where the imported trace is higher than the produced trace.

The statistics from the UN Food an Agriculture database show that the overwhelming majority of US barley import comes from Canada, which almost exclusively produces two-row. These trends have been driven by the craft beer explosion.

To understand why, we must first examine the difference between barley types.

Two-Row versus Six-Row

Physical

Figure 2 - Types of barley

The most obvious difference lies in the structure of the kernels along the ear of the plant. The two- or six-row denotes the number of columns around the ear. Figure 2 shows the differences between the two types. The sprout in the middle is two-row, while the sprout on the right is 6-row.

A direct implication of the arrangement of barley kernels is on the size of each individual. Because there are more kernels packed into 6-row, they tend to be smaller. Being smaller gives them a higher surface area to volume ratio, making them better suited for american lagers (more on that later). However, two-row have a better yield in terms of weight of kernels per acreage of crop, though not by much.

Figure 3 - Chemical differences in barley types

The differences go past the obvious physical features and also deal with the chemical contents of the kernels. Figure 3 contains an analysis performed on two different batches of barley, one being two-row and the other being four-row. The table is taken from this article, and it displays the differences in the malt types. The article was written by Paul Schwartz and Richard Horsley and explains the differences between the barley types.

Chemical

The chemical differences between the malts come into play during the mash stage of brewing. Two-row has more starches (given in the table as extract) and less protein, while six-row has more proteins and less starches. The differences may seem minute, but they become substantial when you are using thousands of pounds of malt to create a single batch of beer.

Each of the parameters given in figure 3 will be addressed in a future post. The table shows that six-row has more proteins as a whole, but less a-amylase. This means that beta-amylase is more plentiful with respect to alpha-amylase, leading to a more efficient mash (see this post on the mash for differences between alpha and beta amylase). A trade off for this more efficient mash is less starch with which to work.

Why 6-row in American Lagers?

Besides the fact that 6-row is always been better suited for the climate and soil conditions in America, the physical and chemical differences of the individual kernel make it the more appropriate type of barley for American lagers. Due to the high adjunct levels in american lagers, the increased capacity for conversion (called diastatic power) is desirable, while the limited starch content is moot. A highly portion of the sugar in american lagers come from corn/rice. The high surface area to volume ratio means there will be more husks in the mash that will aid in preventing the adjunct cereals from clogging the grain bed during the sparge.

So back to the original point.

The craft brewing market in the US is killing its barley industry. Figure 1 shows the production of american barley drop off in the 90s, while our imports temporarily spike. While our imports have made their way down to what they were for most of the 60s-80s, barley production in the US is the lowest it has been since the UN has started recording these statistics.

The demand for american 6-row barley is collapsing. The standard american light lager that once had a stranglehold on the american beer market is losing popularity and people are instead drinking brews that derive their sugar from 2-row barley instead of corn/rice. This shift in demand put stress on the supply of barley, and the US was forced to increase its imports (mostly from Canada). Maltsters have been forced to divert thousands of acres from 6-row barley to keep up with the demand. It will only be a matter of time before maltsters develop a variety of 2-row that will grew well in the US.

While this economic pressure has stunted the US production of barley, it has led to the coming of age of the US beer culture. 30 years ago, it would be difficult to find an ale made in america at a super market. Instead, consumers had a choice of 15 different takes on a single style. Now any corner store will have a variety of styles from several different local breweries. While the craft beer has stunted the barley industry, it has rejuvenated the American beer culture.