Topic: Brewing Science

Acid Tolerance of Brewer’s Yeast

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In the last 15 years, American sour beer has grown from experiments tucked away in the sheds or corners of a handful of breweries, to dedicated producers and year-round offerings from the largest craft breweries. In some ways not much has changed: At their new Asheville, North Carolina brewery, Sierra Nevada positioned the tank for

Steeping & Soaking Grains


Steeping is the soaking of specialty malts, grains, and spices in water to extract flavors and aromas that we want to incorporate into our beer. It is, in essence, the making of

Evaluating Hop Oil Content

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There are no “Cascade” or “Saaz” aroma molecules, rather the relative proportions of hop oils drive their aroma contributions. The same four oils constitute 60-90% of the essential oils in every hop variety. Hop oils constitute less than 4% of a hop cone’s weight yet they provide most of the hop aroma, that combination of citrus,

Understanding Beer Spoilage

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Microorganisms can cause undesirable effects on beer in several ways, including undesirable changes in beer flavor and aroma. Growth of microorganisms on raw materials or in wort can produce changes that alter the normal fermentation pathways. Additionally, the growth of contaminants on raw materials or in wort can generate many different microbial metabolites that may

Maximize Your Mash: Understanding Impact of Equipment & Temperature

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There is an old saying that brewers make wort but yeast make beer. It is hard to argue against that fact, but the wort we feed the yeast will determine the final qualities in the beer. For example, the sugars available in the wort and its fermentability are critical parameters in determining how the beer

The Chemistry of Beer Flavor

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Beer is comprised of hundreds of different chemical compounds that contribute to the overall flavor and aroma perception of the beer. Different styles of beer have different flavor and aroma characteristics that vary depending upon the many factors associated with the production of the beer. The specific types and amounts of taste and aroma compounds

Theory and Practice of Lautering

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Lautering is the act of separating sweet wort from spent grains. The act of lautering wort is physically very similar to filtration. The flow of wort through a grain bed can be thought of physically as a type of filtration (liquid flowing through a “filter bed” of grain). The basic principles of filtration were established

Milling — Theory and Practical Consideration

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An all-grain brew day starts with heating the water and milling the grain. Learn the best ways to mill your malt.

Preventing Diacetyl

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Vicinal diketones (VDKs) are the products of normal beer fermentation within a brewery. The two VDKs that are of primary concern to brewers are 2,3-butanedione (diacetyl) and 2,3-pentanedione. Diacetyl in a finished beer creates a slickness on the palate at low concentrations, and has a characteristic flavor that is described as buttery or butterscotch at

Understanding Yeast Metabolism

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Yeast are microscopic, unicellular fungi that are capable of converting various types of sugar into ethanol and other byproducts. Yeast take in sugars and anaerobically (without oxygen) metabolize them to produce energy, additional yeast cells, ethanol, carbon dioxide and other metabolic byproducts: Sugar + Yeast → More Yeast + Ethanol + Carbon Dioxide + Metabolic

Quality Control & Testing Beer: Tips from Pros

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Behind many great brews are scientists testing and tasting beers in the lab. In fact, every beer — be it commercial or homebrew — can benefit from better quality control. Two beer lab experts share their advice. Brewer: Luke Chadwick, Bell’s Brewery in Kalamazoo, MI We run three testing programs at Bell’s: analytical, microbiological, and

Oxygenation of Wort

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Availability of dissolved oxygen to yeast during the initial stage of fermentation is very important. Yeast use oxygen to build cell membrane components that are essential to replication. Unsaturated fatty acids, sterols (both found in wort) and oxygen are all necessary for yeast to rapidly reproduce during the initial stage of fermentation. Without enough available

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