Hard or Soft: A Brewer's Dilemma

Making great beer really comes down to having great ingredients. Most homebrewers put considerable time and energy into finding the right grains, hops, and type of yeast to use, but often overlook one of the most important ingredients, water. Water chemistry can have a large impact on the final outcome of the desired beer style. It’s not so much the water but the minerals and their associated ions that affect appearance and taste of beer. Now don’t misunderstand, you can make good beer with most municipal water supplies, but very hard or soft water can make it difficult to brew certain styles of beer.

“Soft” water contains low concentrations of dissolved salts, particularly salts of calcium. “Hard” water contains high concentrations of salts, mainly calcium bicarbonate or calcium sulfate. “Temporary hardness” is a term used to describe water content. It is caused primarily by calcium bicarbonate and gets its “temporary” name because if the water is boiled, bicarbonate is converted to carbonate which precipitates leaving the clarified water “softened”. In comparison, “permanent hardness” is mainly caused by calcium sulfate, and this remains in solution even after boiling. The distinction is important if the water is to be used for mashing and even more so for sparging.⁽¹⁾

Minerals and their associated ions can have an impact on flavor, aroma, color, head retention, alcohol, and stability of beer. In other words, just about every aspect of beer. The mineral content is largely influenced by its source, whether it is surface water (lakes and rivers) or from underground sources. Even cities from the same region can have dramatically different water profiles as seen in the table below (Table 1).

 

The primary ions important to brewers are calcium, sulfate, sodium, magnesium, and chloride, but there are some secondary ions that can influence brewing chemistry in large numbers. These secondary ions include Iron (Fe +1, +2), Copper (Cu +1), Zinc (Zn +2), and Manganese (Mn +2). Calcium ions (Ca2+) serve several important functions in brewing. They react with phosphates that are present in malt to acidify the mash. Acidification is an important step in creating an ideal environment for protein and starch reducing enzymes to work (See post on Mashing). The increased acidity can lighten the color of wort, increase hop utilization, and favors a reduction in astringent flavors. Calcium ions favor the formation of a good hot break (trub) and yeast flocculation, but they seem to have little effect on flavor^(1,2).

Sulfate ions (SO₄) are the major counter ions to calcium and magnesium ions in permanently hard water. They contribute to a drier, bitter flavor in beers that should be balanced by appropriate amounts of chloride ions. Yeast metabolize sulfates producing small amounts of hydrogen sulfide (H₂S), sulfur dioxide (SO₂), and other substances that contribute to the aromas of beers brewed with sulfate-rich water. The classic example is the `Burton nose' of the ales brewed at Burton-upon-Trent^(1,2).

Sodium ions (Na+) occur in some waters and the ion itself has no benefit in beermaking on its own. Sodium ions can impart sour/salty flavors at high concentrations (over about 150 mg/liter). Magnesium ions (Mg +2) are needed by many yeast enzymes, such as pyruvate decarboxylase (important enzyme in ethanol production). The effects of this ion often resemble those of the calcium ion, but the effects on pH from interactions with phosphates are less pronounced. The effects are often about half because this salt is more water soluble. Excess amounts can impart a sour or bitter flavor to beer^(1,2).

In Part 2 we’ll cover how you can adjust your water chemistry.

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1. Stevens, Roger, et al.; "Brewing: Science and Practice", Woodhead Publishing, 2004, ISBN 0-8493-2547-1
2. Papazian, Charlie (2003). The complete joy of homebrewing (3rd ed. ed.). New York: Collins. ISBN 0-06-053105-3.

Bama Beer Series: Cahaba Brewing Company

The Bama Beer Series will focus on the often overlooked breweries and brewpubs of Alabama. Alabama has a growing craft beer scene that has come into its own over the last few years and we will explore the beers of Alabama, some of which are the best in the south.

Cahaba Brewing Company, Downtown Birmingham, AL

Cahaba Brewing Company (CBC) was founded in the summer of 2011 by a group of friends united by their love of craft beer and home brewing, but officially opened its doors in September of 2012 (http://cahababrewing.com). Their brewery is on the outer edge of downtown Birmingham which features a small tap room with bar and picnic table seating. Best of all they have two skeeball machines and a skeeball league.

Cahaba Brewing’s namesake is the Cahaba River, a major tributary of the Alabama River and part of the larger Mobile River Basin. It is the longest free-flowing river in Alabama with 140 of its 191 miles undammed. It is among the most scenic and biologically diverse rivers in the United States. Many of CBC’s beers are named for the flora and fauna of the Cahaba River including, Oka Uba IPA, named after the Native American name for the river.

The brewery has four flagship beers on tap and nine specialty and seasonal offerings on a rotating basis. They also have a single hop series in which they brew an Extra Pale Ale that uses a single hop variety.

                                     

Below is a selection of some of the best they have to offer:

Oka Uba, IPA

COMMERCIAL DESCRIPTION

[Oka Uba IPA] has been described as liquid candy.  Weighing in at only 57 IBU’s (International Bittering Units), Oka Uba proves that hoppy IPA’s don’t have to be oppressively bitter.  Premium malts and lots of late hop additions will make this one of the most drinkable IPAs you’ve ever put in your mouth. 7.5% ABV

Nick

Draft. Light copper color with a small white head and nice lacing. Floral aroma with a resin and citrus hop flavor. Medium body with a medium bitter hop finish.

Taylor

Draft at the taproom. Pours copper with white frothy head. Aroma is grapefruit, caramel, nut, and pine resin. Nicely hoppy aroma. Taste is citrus, nut, bread, resin slight fruit.  medium body with a bitter finish. Really solid IPA.

India Pale Lager

COMMERCIAL DESCRIPTION

Who says ales should have all the hops?  Our passion for crafting excellent beers brings you India Pale Lager.  The lager yeast provides for a clean and dry base beer well suited for hopping!  The addition of bold American hops that showcase floral and citrus aromas give this lager the hoppy characteristics of an American IPA, wait American IPL. 6.6% ABV

Nick

Draft. Golden with thin white head. Aroma of pine hops and citrus (grapefruit). Light body with strong resinous hop bitterness upfront, some citrus notes, and a nice bitter finish.

Taylor

Draft pours clear light copper with frothy white head. Aroma of grapefruit, slight grain, floral, resin, very clean. Taste is hops up front, grapefruit, light fruit, nut, light grain. Light body with a very nice clean bitter finish. Very enjoyable beer.

Fraxinus Maximus, Double IPA

COMMERCIAL DESCRIPTION

In keeping with the Cahaba theme, Fraxinus is named after the Genus of the Ash tree which is a common species along our beautiful Cahaba River.  Fraxinus is an amazing Double IPA.  By using a technique called Hop Bursting, we are able to create a beer that has 120 calculated IBU’s.  However you’ll find it is anything but bitter, Fraxinus is a well balanced Double IPA with a solid malt backbone and complex hop aromas.  8.5% ABV

Nick

Draft. Copper color with medium white head and nice lacing. Citrus and pine hop aroma. Medium body with resin and citrus hop flavor with a bit of a soapy finish.-- Same overall score as before but more raspberries on the aroma and I didn’t get a soapy finish this time. A decent IPA

Taylor

Draft, pours clear copper with frothy white head. Aroma of caramel, grapefruit, nut, raspberry, hint of alcohol. Taste of caramel, cereal, grapefruit, medium body with bitter finish.

Liquidambar, American amber ale 

COMMERCIAL DESCRIPTION

Liquidambar is a crisp, malty beer with a beautiful caramel color.  This brew is finished with a healthy handful of palisade hops that impart an incredible balance between malt and hops.  This sessionable beer is made for drinking. 5.25% ABV

Nick

Draft at taproom. Light brown with small off white head. Aroma of malt sweetness and caramel. Medium/light body, malt, caramel, and some hop bitterness with a slightly sweet finish.

Taylor

Draft, burnt copper with a thin white heat.  Aroma of caramel, cereal, nut. Taste of earth and cereal, not much else. Light body with a slightly sweet finish.

Ryezome Rye Stout  

COMMERCIAL DESCRIPTION

People who don’t like stouts tell us they love Ryezome!  Ryezome is extremely crisp and finishes with pleasant aromatic hops and hints of coffee and chocolate.  With its light to medium body and refreshingly balanced profile you’ll find Ryezome quickly becoming your favorite stout. 5.8% ABV

Nick

Draft. Dark brown with a small tan head. Aroma of chocolate and roasted malts. Medium body with chocolate and malt notes and a slight hop bitterness.-- Much more sweetness both in the aroma and flavor. I prefer the less sweet version.

Taylor

Draft pours brown/black with tan head. Aroma of caramel, chocolate, raspberry, coffee. Taste of coffee, chocolate, burnt caramel. Bitter dry finish medium body.

Does Eating Yeast Really Mitigate Alcohol Intoxication?

Jim Koch of the Boston Beer Company recently stated in an interview with Esquire Magazine that his secret to drinking without the intoxicating side effect was to eat  a teaspoon of baker’s yeast (mixed with yogurt). He claims that the enzyme alcohol dehydrogenase (ADH) in the yeast supplements our own ADH breaking down some of the alcohol reducing the amount that is absorbed by our bodies. Sounds too good to be true right? Well, I have a sinking suspicion that it is, so let’s take a look at the science.

Alcohol dehydrogenase in humans is an enzyme that catalyzes the reaction of alcohol to acetaldehyde that is found in the liver. It helps to clear alcohol from the body in a form that can be excreted. In contrast to humans, baker’s yeast have three types of ADH enzymes: ADH1, ADH2, ADH3 (similar to ADH1)¹. This is where things start to get a little fishy.

ADH1 in yeast actually reduces acetaldehyde and NADH to ethanol (making more alcohol) to regenerate NAD⁺, an important part of glycolysis (the cycle used to create energy from glucose)². As luck would have it, the most active form of ADH in baker’s yeast (the kind that Koch is eating) is ADH1¹. So essentially, as you’re breaking down ethanol in your body, yeast could be converting it back into ethanol canceling out what your body is doing increasing the effect of that beer.

The second form of alcohol dehydrogenase (ADH2), does in fact catalyze alcohol into acetaldehyde. The only issue is that ADH2 production is inhibited by the presence of glucose (sugar) in the environment³. So, Koch’s recommendation of mixing the yeast with yogurt would effectively repress the transcription of ADH2 reducing its activity.

If you’re still not convinced, the optimum range for these enzymes is in the neutral to alkaline range ¹. Your stomach, as I’m sure you know, is acidic (low pH), and would decrease the activity of the enzymes (if it didn't completely destroy them). Not to mention the fact that there are many beers produced that remain unfiltered, containing live yeast cultures in the beer, and do not lose the amount of alcohol in them as they age.

Sadly, it seems like the only way to "drink" without getting drunk is to stick with non-alcoholic beer (e.g. O'Doul's) or you could just drink responsibly, know your limits, and have a designated driver. If you have any other tips to mitigate the effects of alcohol while drinking let us know, and we will check them out to see if they are scientifically sound! Happy brewing.

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1. Leskovac, V., Trivic, S., Pericin, D. 2002. The three zinc-containing aclohol dehydrogenases from baker's yeast, Saccharomyces cerevisiae. FEMS Yeast Research 2:481-494
2.  Bennetzen, J.L., Hall, B.D. 1982. The primary structure of Saccharomyces cerevisiae gene for Alcohol Dehydrogenase I. The Journal of Biological Chemistry 257:3018-3025
3. Vallari, R.C., Cook, J.W., Audino, D.C., Morgan, M.J., Jensen, D.E., Laudano, A.P., Denis, C.L. 1992. Glucose repression of the yeast ADH2 gene occurs through multiple mechanisms, including control of the protein synthesis of its transcriptional activator, ADR1. Molecular and Cellular Biology 12: 1663-1673

Cost of a Pint

Have you ever wondered what makes up the actual cost of your pint of craft beer? Me too.  I searched the interwebs for an answer to that question and to my surprise there was very little information about what actually makes up the cost of a pint. I guess that isn’t really surprising since most of the products we buy have hidden costs. Think about it. Do you know what the actual costs are for an oil filter, a loaf of sourdough bread, or an iPad? We know what we are willing to pay for these items, but do we really know the factors that make up the costs?

As for a craft beer, much of the costs come down to where your beer is brewed. Taxes, ingredient costs, labor, and whether the brewer owns their place of business can radically change the costs associated with producing a pint of beer. The size of the brewer’s setup can also have a large impact on the costs associated with production. A 100 barrel brew house may actually have higher ingredient and labor costs versus a 10,000 barrel brew house, but that aside, let’s speak in generalities. The following assumptions will be made on the basis of an average pint of beer costing $5 dollars.

Let’s say for the average brewery it costs about $50 per barrel (31 gallons) in ingredients to produce your average pale ale, but could go as high as $70 per barrel depending on the brewer’s setup and ingredient costs. If that barrel brings in revenue of $700 a barrel, between 6 to 8 percent of a pint of beer pays for the ingredients. To the average homebrewer that would mean your average 5 gallon batch of pale ale would cost less than $11 (wouldn’t that be nice).  Ingredient costs will also vary with the brewery’s location, shipping costs, and efficiency of their setup. Even a $0.06/lb difference in ingredient costs or a 3 percent difference in malt yield can have a large impact on the bottom line. ⁽¹⁾ If you were running a 10,000 barrel brewery and had a 3% decrease in efficiency that would increase your grain bill by about 15,500 pounds per year. For a million barrel facility that inefficiency would be an additional 1.55 million pounds of malt.⁽²⁾

Taxes are another part of the cost of a pint that will vary depending on the state you live in. Federal excise taxes vary depending on the brewery’s production rates with tax rates starting at $7 on the first 60,000 barrels for a brewer who produces less than 2 million barrels and $18 per barrel after the first 60,000 barrels. ⁽³⁾ That roughly works out to between 2 and 5 cents per 12oz can/bottle of beer. State beer taxes vary from state to state. Alabama has one of the highest beer tax rates with a 60 cent excise tax and 10% sales tax (45 cents) for onsite sales for each pint. That means the average Alabamian is paying 21% of their pint toward taxes versus 5.34% in Wisconsin.

Labor and equipment costs vary widely based on brewery size and equipment setup. Equipment setup can cost between $100,000 on the low side to millions of dollars on the high. Financing setups and paying employees can take a large chunk out of the remaining revenues that don’t go to ingredients and taxes. However, once equipment and/or the building are paid for, then a larger portion of the remaining revenue becomes profit. Of course the end result of more profits may lead the brewer to buy new equipment to make more beer. Whatever the costs that make up a pint, I am happy there are more and more craft brewers out there offering up some very tasty beers.

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1. Metzger, S. What Does Your Beer Really Cost. The New Brewer. Jan 2012. https://www.brewersassociation.org/attachments/0000/8424/JF_TNB12_Beer_Costing-1.pdf
2. Papazian, C., 1994. Home Brewer’s Companion. Avon Books.
3. Beer Tax Rates by State. Jan 2014. http://www.taxadmin.org/fta/rate/beer.pdf

YIC: Temperature-dependent Flavor Determination

*This is part three of the Yeast from the Iron City (YIC) series. For sampling, media, and plating information check out Part 1, and for Isolation Part 2.

Now that we had isolated our very own yeast strain, it was time to pray to the many gods of beer and hope that it would result in something drinkable. We wanted to use a fairly simple recipe to make sure the yeast would be the star player in terms of flavor. To determine the temperature that resulted in the best flavor profile (see ester post), the wort was split into three 1 gallon batches and placed under 3 different temperature regimes (Cold 45 °F, room temp 68 °F, warm 72 °F). The recipe is in the style of a Belgian pale ale and is as follows:

Fermentables
5.5 lb Light DME
.25 lb Caramel 40
.25 lb Caramunich
Hops
0.5 oz Galena       30 min
0.5 oz Hallertauer 15 min
.25 oz Chinook      5 min
Yeast
The Fringe
Estimated
OG: 1.050
FG: 1.018
ABV: 4.2%
IBU: 40

Starter:
A starter was made from the isolated yeast by going from a 100 ml starter to a 1 gal starter. The large starter was then allowed to ferment and settle. The liquid was decanted off until only approximately 2 L remained. I then swirled the solution to bring the yeast back into solution and filled 6 sanitized White Lab Vials. The remainder was then pitched into a 500 ml starter for this recipe.

Brew Day Notes:
The day went on without a hitch. Heated 4 gallons of water to 155 °F and steeped the grain for 30 minutes. The grain bag was then removed and the DME was then whisked in. The wort was then brought to a boil and the hops were added as is shows in the recipe. The wort was then cooled with the immersion chiller to 70 °F. The batch was poured into a bottling bucket for easy measuring and topped up to 3 gallons with filtered water. The batch was split between 3-1 gal jugs and 160ml of stater was added to each batch. The jugs were left at room temperature (68 °F) until fermentation had begun (about 12 hours). They were then placed at their respective temperatures (Warm, Room, and Cold temperatures).

It took approximately 2 weeks both the warm and room temperature batches to complete fermentation. The cold batch took about 3.5 weeks total. The vessel needed to be removed from the fridge for fermentation to begin again and then was placed back into the fridge. After fermentation seemed to slow the vessel was left at room temperature to finish fully and to clean up diacetyl.

Measured 
Vol: 3 1-gal
OG: 1.051
FG: (Warm-1.018; Room-1.017; Cold-1.018)
ABV:4.3%

Tasting:
1-28-14:
Warm (72 °F): Pours copper with frothy white head. Aroma of clove, spices, slight fruit, slightly dry. Taste is slightly sweet up front with a bitter finish. Slightly tart. Very clean taste compared to the aroma. Light body.

Room (68 °F): Same appearance. Aroma of slight fruit otherwise clean. Taste is light grain, sweeter front than the warm with a slight bitter finish. No noticeable tartness. Light body.

Cold (45 °F): Same appearance. Aroma of light fruit, grain, Belgian spices, caramel, it is the sweetest of the three. Slight banana notes. bitter sweet finish. Light body.

Overall: This style and recipe was not exceptionally great, but we expected this one to be very mild in flavor because of the very simple light grain bill. The yeast strangely seems to be quite clean producing slight Belgian notes but otherwise no funk or noticeable off flavors. Amazingly this seems to be the case across the entire range of temperatures. The only real noticeable effect of the temperature was a longer fermentation (obviously) and the beer ended at a slightly higher FG and lead to a slightly sweeter beer overall at cool fermentation temperatures. This was quite surprising to us to have a first attempt wild yeast that both attenuated relatively well (64%) at all three temperatures and did not impart any crazy off flavors. It would be interesting to pitch this yeast into a more complex Belgian style where the grain bill is more complex, like a Dubbel or a Quad, especially to see how it handles the higher levels of alcohol.

Currently, the yeast is being worked up in the lab to determine what genus and hopefully species it is so that we can better characterize it. Updates will follow!

Beer Consumption Transcends Demographics (mostly)

A recent trip to Europe got me thinking. Wait, wait, before you begin the eye rolls or the sighing, this is not yet another post on the wonders of European travel or a nose lifting espousing of European beer. It was my first trip to Europe and it got me thinking about beer consumption rates and how they compare to the United States and of course my science training took over. I wondered what factors could contribute to or go hand in hand with beer consumption rates? Could it be as simple as the number of breweries, the population per brewery, per capita income, or could it be seasonal temperatures? Obviously there are a multitude of factors at work in determining the impacts on beer consumption, but I was surprised by some of the results.

I started out with looking at the top ten per capita beer consumption countries. It was no surprise that the top ten looked like a line up for a 19^th century polo match, affluent (mostly), white (mostly), and European or former European colonies (Australia, Venezuela). I also looked at some countries with large production rates such as Belgium, Netherlands, and Canada as well as the bottom ten countries in the top 50 for per capita consumption. Some of these countries included Japan, Angola, Namibia, Mexico, and the Scandinavian countries. I hoped by adding some non-European countries that I might see some different trends, but again I was surprised with what I found.

When I began looking at some of the correlations (a mutual relationship or connection between two or more things), I was really surprised by some of the factors that I expected to have an impact on per capita beer consumption had no apparent relation. I was also surprised that production rates, including the number of breweries and population per brewery, had no correlation with per capita consumption rates. Total beer consumption was positively correlated to the number of breweries, total beer production, and summer temperatures. I would have thought winter temperatures may have had a positive correlation to consumption as I know I tend to feel like drinking more in winter.  Interestingly enough as beer consumption increased dairy consumption decreased, but I think this was largely due to countries at the bottom of the top 50 which had low dairy consumption rates (Angola, China, Namibia). When I looked at just the top 15 countries I didn’t see any correlation between dairy consumption and beer consumption rates, but again these were mostly European countries that have relatively the same dairy consumption rates.

The most surprising thing was that I didn't find any relationship between beer consumption rates and income. Studies have found a relationship between income and consumption rates ^(1,2) but those studies mainly looked at in-country numbers or regional comparisons. Even by looking at the bottom of the top 50 list, which has some relatively poor countries, I still didn’t see any correlation between income and beer consumption. Excise taxes also didn’t have any relation to beer consumption. Scandinavian countries have some of the highest excise taxes on alcohol but also have very high per capita consumption rates.

The only factor that seems to be a common thread is being associated with Europe. Most of the countries with the highest per capita consumption rates are European or were colonized by Western European countries. Beer may not have been invented in Europe but that is where it was perfected and has been brewed in its modern form since at least the Dark Ages. Some have made the argument that without beer (and wine) European civilization may not have been as successful as it was without safe drinking water (i.e. boiling/alcohol). Say what you will about European colonialism, but know that we have it to thank for the spread of beer globally. Prost! 

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1. Österberg, E.L. 2011. Alcohol tax changes and the use of alcohol in Europe. Drug and Alcohol Review. 30, 124–129.

2. Freeman, D.G. 2009. Beer in Good Times and Bad: A U.S. State-Level Analysis of Economic Conditions and Alcohol Consumption. Beeronomics Conference, Leuven, Belgium, May 2009

Data Sources

http://vegetarian.procon.org/view.resource.php?resourceID=004716

http://en.wikipedia.org/wiki/List_of_countries_by_milk_consumption_per_capita

http://www.st.nmfs.noaa.gov/st1/fus/fus11/08_percapita2011.pdf

http://bovbeers.wordpress.com/2011/07/02/number-of-breweries-worldwide/

http://www.brewersofeurope.org/docs/publications/2012/stats_2012_web.pdf

http://www.fin.gov.on.ca/en/tax/bwt/rates.html

http://www.caseysbeer.com.au/?page_id=97

http://chartsbin.com/view/1491

http://www.climatemps.com/countries-a.php

http://en.wikipedia.org/wiki/List_of_countries_by_GDP_(PPP)_per_capita

http://apps.who.int/gho/data/node.main.A1184?lang=en?showonly=GISAH

http://www.ttb.gov/tax_audit/atftaxes.shtml

Flavor Esters: An Introduction

Figure 1. Active flavor esters (adapted from Verstrepren et al., 2003)

Many of the fruity flavors (aromas) we perceive in a beer are in fact the products of yeast metabolism and not from the addition of fruits (Figure 1). Some of the esters produced by yeast are considered “off” or undesirable flavors, while others are appropriate at low levels. Some esters even give certain beers (e.g. hefeweizens) their characteristic taste.

To be perceived, the concentration of each ester must meet a specific threshold level; therefore, low levels of ester production will not impart any noticeable aroma. However, esters can have a synergistic effect on individual flavors, affecting overall beer flavor at concentrations well below their threshold⁽¹⁾.

Esters found in beer are synthesized from Acyl-CoA (a long chain fatty acid with Coenzyme A attached, which breaks down into Acetyl-CoA), and fusel alcohols by ester synthase enzymes (e.g. Alcohol acetyl transferase) found in yeast (Figure 2)⁽¹⁾. Beer is not the only place you will find esters; they can also be found naturally occurring in fruits and artificially in many of the candies we eat. In fact, the industry of flavor ester production is in high demand, producing esters for all of those artificially flavored foods and drinks we love to consume in addition to the cosmetics and pharmaceutical industries⁽²⁾.

Figure 2. Enzymatic ester synthesis (Verstrepren et al., 2003)

Unlike ester synthesis in beer, the majority of flavor esters for these industries are produced in labs by chemically synthesizing each compound (Figure 3)⁽²⁾. Recently, the growing trend for “natural foods” has generated a push against the consumption and use of products containing artificial ingredients. These industries have responded by turning to the noble yeast, albeit a different genus and species from those used for brewing, to enzymatically synthesize esters. Esters produced by this process can be labeled as “natural” quelling the fears of the chemically conscientious consumers⁽¹⁾.

Figure 3. Chemical ester synthesis

But I digress...Back to the important things in life, brewing! Temperature, specific-gravity, oxygen, fusel (German for “hooch”) alcohols, and fatty acids all have effects on the production of esters but they may vary depending on the yeast strain. There is a direct relationship between temperature, specific gravity, fusel alcohols, and activated fatty acids (Acyl-CoA, and Acetyl-CoA) with the production of esters⁽¹⁾. The manipulation of these factors is important when considering the style of beer you plan to brew. In general, ales contain higher levels of esters than lagers in part because of the yeast species used (read more) as well as the higher temperatures used during ale fermentation ( above 58°F) compared to those used to "lager" (32°F-56°F). In the next esters post I will talk about each about each factor in greater depth and the mechanism by which they modulate ester production. Until then, happy brewing!

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1. Verstrepren, K.J., Derdelinckx, G., Dufour, J.P., Winderickx, J., Thevelein, J.M., Pretorius, I.S., Delvaux, F.R. 2003. Review: Flavor-Active Esters: Adding Fruitiness to Beer. J Bioscience and Bioengineering 96(2): 110-118 
2. Larios, A., Garcia, H.A., Oliart, R.M., Valerio-Alfaro, G. 2004. Synthesis of Flavor and Fragrance esters using Candida antartica lipase. Appl Microbiol Biotechnol 65:373-376