|photo courtesy of Vermont Pub & Brewery|
"(W)hen we began brewing at Vermont Pub and Brewery 18 years ago, our water was very soft. However, in the intervening time our own “great lake” Champlain has been invaded by zebra mussels. When the little suckers die, their shells disintegrate into calcium carbonate. Our water supply has become much more carbonate, and therefor (sic) more alkaline. As Jim Koch of Sam Adams pointed out to me years ago, alkalinity produces dull-flavored beers." - from "Brewing Water: Tips from the Pros" in Brew Your Own Magazine, Sept. 2006
|photo courtesy of Wikimedia commons|
So zebra mussels affect beer brewing? There is another link between aquatic critters and beer other than isinglass? As a home brewer and an aquatic ecologist, I was intrigued by this notion. I had also been putting off any real effort toward understanding water chemistry despite these personal interests. I decided to investigate this idea that an invasive mussel might affect how beer is made locally and perhaps learn something along the way.
First lets clarify what Greg Noonan was saying regarding water softness and alkalinity. To do this well, we need to understand a bit about the chemistry of water. Most of us know that water is made up of two hydrogen molecules attached to one oxygen molecule (ie. H two O). These three molecules arrange themselves in space in a way that more electrons hang out near the oxygen atom, leaving fewer electrons near the two hydrogen atoms. This means that a molecule of water has a slight negative charge near oxygen and a slight positive charge near the two hydrogens. This property allows water to react with a wide variety of charged particles (called ions), including other water molecules. When other substances are added to water, like when water flows through the Basin's watershed or when a brewer combines malted barley with warm water, reactions between those substances and water will change where electrons spend their time and the numbers of positively and negatively charged ions in the liquid. Scientists have developed the pH scale to describe the amount of certain positively-charged ions in a liquid. When there are equal numbers of positively and negatively charged parts of water (like in distilled water) the pH is 7. When positively charged parts of water out-number the negative the liquid is acidic, pH drops below 7 (with a minimum of 0); when negatively charged parts of water out-number the positive the liquid is alkaline and the pH rises above 7 (with a maximum of 14). Typically, the pH of Lake Champlain's water is around 7.8 to 8.
Water hardness is a measure of two particular minerals in water: calcium and magnesium. Soft water has low concentrations of these minerals and hard water has high concentrations of them. These minerals typically exist as mineral salts, with positively-charged mineral ions bonded to negatively-charged ions like carbonate and sulfate. When added to water, these ions separate from one another and react with other charged ions and with the oppositely-charged areas of the water molecules. In aquatic environments, water can react with rocks like limestone (calcium carbonate) or gypsum (calcium sulfate). Lake Champlain's Basin has very little of these minerals in the rocks themselves, but has some calcium carbonate in the form of mussel and snail shells. When the negatively-charged carbonate ions are in abundance in water, the pH is higher than 7 and is alkaline.
In the statement above, Greg attributed the changes in the water at his brewery to the infestation of zebra mussels, with the death of older zebra mussels adding carbonate and alkalinity to his brewing water. Aha! An ecological hypothesis in disguise!
Did the arrival and subsequent infestation of zebra mussels in Lake Champlain cause a change in levels of carbonate ions? Although zebra mussels and other freshwater mussels do have shells composed almost entirely of calcium carbonate, the animals themselves grow their own shells by taking in calcium from their aquatic environment and binding it with carbonate. In fact, the earliest life stages of mussels have no shells at all and swim in the water column. Current research suggests that in most cases, lakes have to have enough dissolved calcium (8-20 milligrams per Liter) to support an infestation of zebra mussels. Therefore, the overall amount of calcium carbonate in Lake Champlain likely hasn't changed because zebra mussels have to have the component parts in their environment to create calcium carbonate. Efforts by the Vermont Department of Environmental Conservation's Lake Champlain Monitoring team to detect any changes in calcium concentrations caused by zebra mussels confirm this.
However, it is possible that zebra mussels have altered how much calcium carbonate is dissolved in the water (rather than bound up in shells) of Lake Champlain at any given time. Like most organisms in the lake, they likely grow fastest in the warmer months and cease growing (with older ones dying) in the colder water temperatures of winter. So it is possible that calcium carbonate levels rise in winter when zebra mussels are no longer taking it up from the water. Unfortunately the publicly available data (here) collected by the VT DEC is collected only three times each year which makes it unsuitable to answer this question.
|A home-brewed German altbier|
photo courtesy of B. Swisher
Water is the single-most largest ingredient in beer. Even before brewers ever understood the complexity of water chemistry in the ways that Mr. Noonan alludes to, the local sources of water shaped the variety of beer styles across the globe. With the scientific understanding of water and brewing chemistry we now have, anyone can replicate the chemistry of water from well-known brewing centers as Munich, Pilzen, Dublin, London, and Burton-on-Trent.
Want to find out more about the flavors and origins of beer? Come join us in sampling the beer styles of Germany at ECHO's FeBREWary Beer Event on February 14. More information here.
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