Written by Steve Cannon

Spent Grain & Dregs

Brewing by-products are “spent grain” and the sediment (or “dregs”) from the filtration process which may be dried and resold as “brewers dried yeast” for poultry feed or made into yeast extract which is used in brands such as Vegemite and Marmite. The process of turning the yeast sediment into edible yeast extract was discovered by German scientist Justus von Liebig.

Recycling

Brewer’s spent grain (also called spent grain, brewer’s grain or draff) is the main by-product of the brewing process; it consists of the residue of malt and grain which remains in the lauter tun after the lautering process. It consists primarily of grain husks, pericarp, and fragments of endosperm. As it mainly consists of carbohydrates and proteins and is readily consumed by animals, spent grain is used in animal feed. Spent grains can also be used as fertilizer, whole grains in bread as well as in the production of flour and biogas. Spent grain is also an ideal medium for growing mushrooms, such as shiitake, and already some breweries are either growing their own mushrooms or supplying spent grain to mushroom farms. Spent grains can be used in the production of red bricks, to improve the open porosity and reduce thermal

Written by Steve Cannon

Intro

Filtering stabilises the flavour of beer, holding it at a point acceptable to the brewer, and preventing further development from the yeast, which under poor conditions can release negative components and flavours Filtering also removes haze, clearing the beer, and so giving it a “polished shine and brilliance”. Beer with a clear appearance has been commercially desirable for brewers since the development of glass vessels for storing and drinking beer, along with the commercial success of pale lager, which – due to the lagering process in which haze and particles settle to the bottom of the tank and so the beer “drops bright” (clears) – has a natural bright appearance and shine

There are several forms of filters; they may be in the form of sheets or “candles”, or they may be a fine powder such as diatomaceous earth (also called kieselguhr) which is added to the beer to form a filtration bed which allows liquid to pass but holds onto suspended particles such as yeast. Filters range from rough filters that remove much of the yeast and any solids (e.g., hops, grain particles) left in the beer to filters tight enough to strain colour and body from the beer. Filtration ratings are divided into rough, fine, and sterile. Rough filtration leaves some cloudiness in the beer, but it is noticeably clearer than unfiltered beer. Fine filtration removes almost all cloudiness. Sterile filtration removes almost all microorganisms.

Sheet (Pad) Filters

These filters use sheets that allow only particles smaller than a given size to pass through. The sheets are placed into a filtering frame, sanitized (with boiling water, for example) and then used to filter the beer. The sheets can be flushed if the filter becomes blocked. The sheets are usually disposable and are replaced between filtration sessions. Often the sheets contain powdered filtration media to aid in filtration.

Pre-made filters have two sides. One with loose holes, and the other with tight holes. Flow goes from the side with loose holes to the side with the tight holes, with the intent that large particles get stuck in the large holes while leaving enough room around the particles and filter medium for smaller particles to go through and get stuck in tighter holes.
Sheets are sold in nominal ratings, and typically 90% of particles larger than the nominal rating are caught by the sheet.

Kieselguhr Filters

Filters that use a powder medium are considerably more complicated to operate but can filter much more beer before regeneration. Common media include diatomaceous earth and perlite.

Written by Steve Cannon

Intro

After an initial or primary fermentation, beer is conditioned, matured, or aged in one of several ways which can take from 2 to 4 weeks, several months, or several years, depending on the brewer’s intention for the beer. The beer is usually transferred into a second container, so that it is no longer exposed to the dead yeast and other debris (also known as “trub”) that have settled to the bottom of the primary fermenter. This prevents the formation of unwanted flavours and harmful compounds such as acetaldehyde

Kräusening

Kräusening is a conditioning method in which fermenting wort is added to the finished beer. The active yeast will restart fermentation in the finished beer, and so introduce fresh carbon dioxide; the conditioning tank will be then sealed so that the carbon dioxide is dissolved into the beer producing a lively “condition” or level of carbonation. The kräusening method may also be used to condition bottled beer

Lagering

Lagers are stored at cellar temperature or below for 1–6 months while still on the yeast The process of storing, or conditioning, or maturing, or aging a beer at a low temperature for a long period is called “lagering”, and while it is associated with lagers, the process may also be done with ales, with the same result – that of cleaning up various chemicals, acids, and compounds
Secondary fermentation
During secondary fermentation, most of the remaining yeast will settle to the bottom of the second fermenter, yielding a less hazy product.

Bottle Fermentation

Some beers undergo an additional fermentation in the bottle giving natural carbonation This may be a second and/or third fermentation. They are bottled with a viable yeast population in suspension. If there is no residual fermentable sugar left, sugar, or wort or both may be added in a process known as priming. The resulting fermentation generates CO2 that is trapped in the bottle, remaining in solution, and providing natural carbonation. Bottle-conditioned beers may be either filled unfiltered direct from the fermentation or conditioning tank, or filtered and then reseeded with yeast

Cask conditioning

Cask ale (or cask-conditioned beer) is unfiltered, unpasteurised beer that is conditioned by a secondary fermentation in a metal, plastic, or wooden cask. It is dispensed from the cask by being either poured from a tap by gravity, or pumped up from a cellar via a beer engine (hand pump) Sometimes a cask breather is used to keep the beer fresh by allowing carbon dioxide to replace oxygen as the beer is drawn off the cask Until 2018, the Campaign for Real Ale (CAMRA) defined real ale as beer “served without the use of extraneous carbon dioxide”, which would disallow the use of a cask breather a policy which was reversed in April 2018 to allow beer served with the use of cask breathers to meet its definition of real a

Barrel-ageing

Barrel-ageing (US: Barrel aging) is the process of ageing beer in wooden barrels to achieve a variety of effects in the final product. Sour beers such as lambics are fully fermented in wood, while other beers are aged in barrels which were previously used for maturing wines or spirits. In 2016 “Craft Beer and Brewing” wrote: “Barrel-aged beers are so trendy that nearly every taphouse and beer store have a section of them

Written by Steve Cannon

Intro

Fermentation takes place in fermentation vessels which come in various forms, from enormous cylindroconical vessels, through open stone vessels, to wooden vats. After the wort is cooled and aerated – usually with sterile air – yeast is added to it, and it begins to ferment. It is during this stage that sugars won from the malt are converted into alcohol and carbon dioxide, and the product can be called beer for the first time.

Most breweries today use cylindroconical vessels, or CCVs, which have a conical bottom and a cylindrical top. The cone’s angle is typically around 60°, an angle that will allow the yeast to flow towards the cone’s apex but is not so steep as to take up too much vertical space. CCVs can handle both fermenting and conditioning in the same tank. At the end of fermentation, the yeast and other solids which have fallen to the cone’s apex can be simply flushed out of a port at the apex. Open fermentation vessels are also used, often for show in brewpubs, and in Europe in wheat beer fermentation. These vessels have no tops, which makes harvesting top-fermenting yeasts very easy. The open tops of the vessels make the risk of infection greater, but with proper cleaning procedures and careful protocol about who enters fermentation chambers, the risk can be well controlled. Fermentation tanks are typically made of stainless steel. If they are simple cylindrical tanks with bevelled ends, they are arranged vertically, as opposed to conditioning tanks which are usually laid out horizontally. Only a very few breweries still use wooden vats for fermentation as wood is difficult to keep clean and infection-free and must be repitched yearly.

Brewing yeasts are traditionally classed as “top-cropping” (or “top-fermenting”) and “bottom-cropping” (or “bottom-fermenting”); the yeasts classed as top-fermenting are generally used in warm fermentations, where they ferment quickly, and the yeasts classed as bottom-fermenting are used in cooler fermentations where they ferment more slowly. Yeast was termed top or bottom cropping because the yeast was collected from the top or bottom of the fermenting wort to be reused for the next brew. This terminology is somewhat inappropriate in the modern era; after the widespread application of brewing mycology, it was discovered that the two separate collecting methods involved two different yeast species that favoured different temperature regimes, namely Saccharomyces cerevisiae in top-cropping at warmer temperatures and Saccharomyces pastorianus in bottom-cropping at cooler temperatures. As brewing methods changed in the 20th century, cylindro-conical fermenting vessels became the norm and the collection of yeast for both Saccharomyces species is done from the bottom of the fermenter. Thus, the method of collection no longer implies a species association. There are a few remaining breweries who collect yeast in the top-cropping method, such as Samuel Smiths brewery in Yorkshire, Marstons in Staffordshire and several German hefeweizen producers.

For both types, yeast is fully distributed through the beer while it is fermenting, and both equally flocculate (clump together and precipitate to the bottom of the vessel) when fermentation is finished. By no means do all top-cropping yeasts demonstrate this behaviour, but it features strongly in many English yeasts that may also exhibit chain forming (the failure of budded cells to break from the mother cell), which is in the technical sense different from true flocculation. The most common top-cropping brewer’s yeast, Saccharomyces cerevisiae, is the same species as the common baking yeast. However, baking, and brewing yeasts typically belong to different strains, cultivated to favour different characteristics: baking yeast strains are more aggressive, to carbonate dough in the shortest amount of time; brewing yeast strains act slower, but tend to tolerate higher alcohol concentrations (normally 12–15% abv is the maximum, though under special treatment some ethanol-tolerant strains can be coaxed up to around 20%). Modern quantitative genomics has revealed the complexity of Saccharomyces species to the extent that yeasts involved in beer and wine production commonly involve hybrids of so-called pure species. As such, the yeasts involved in what has been typically called top-cropping or top-fermenting ale may be both Saccharomyces cerevisiae and complex hybrids of Saccharomyces cerevisiae and Saccharomyces kudriavzevii. Three notable ales, Chimay, Orval and Westmalle, are fermented with these hybrid strains, which are identical to wine yeasts from Switzerland.

There are three main fermentation methods, warm, cool, and wild or spontaneous. Fermentation may take place in open or closed vessels. There may be a secondary fermentation which can take place in the brewery, in the cask or in the bottle.

Warm Fermentation

In general, yeasts such as Saccharomyces cerevisiae are fermented at warm temperatures between 15 and 20 °C (59 and 68 °F), occasionally as high as 24 °C (75 °F), [ while the yeast used by Brasserie Dupont for saison ferments even higher at 29 to 35 °C (84 to 95 °F). They generally form a foam on the surface of the fermenting beer, which is called barm, as during the fermentation process its hydrophobic surface causes the flocs to adhere to CO2 and rise; because of this, they are often referred to as “top-cropping” or “top-fermenting”– though this distinction is less clear in modern brewing with the use of cylindro-conical tanks. Generally, warm-fermented beers, which are usually termed ale, are ready to drink within three weeks after the beginning of fermentation, although some brewers will condition or mature them for several months.

Cool Fermentation

When a beer has been brewed using a cool fermentation of around 10 °C (50 °F), compared to typical warm fermentation temperatures of 18 °C (64 °F), then stored (or lagered) for typically several weeks (or months) at temperatures close to freezing point, it is termed a “lager”. During the lagering or storage phase several flavour components developed during fermentation dissipate, resulting in a “cleaner” flavour. Though it is the slow, cool fermentation and cold conditioning (or lagering) that defines the character of lager, the main technical difference is with the yeast generally used, which is Saccharomyces pastorianus Technical differences include the ability of lager yeast to metabolize melibiose and the tendency to settle at the bottom of the fermenter (though ales yeasts can also become bottom settling by selection) though these technical differences are not considered by scientists to be influential in the character or flavour of the finished beer, brewers feel otherwise – sometimes cultivating their own yeast strains which may suit their brewing equipment or for a particular purpose, such as brewing beers with a high abv.

Brewers in Bavaria had for centuries been selecting cold-fermenting yeasts by storing (“lagern”) their beers in cold alpine caves. The process of natural selection meant that the wild yeasts that were most cold tolerant would be the ones that would remain actively fermenting in the beer that was stored in the caves. A sample of these Bavarian yeasts was sent from the Spaten brewery in Munich to the Carlsberg brewery in Copenhagen in 1845 who began brewing with it. In 1883 Emile Hansen completed a study on pure yeast culture isolation and the pure strain obtained from Spaten went into industrial production in 1884 as Carlsberg yeast No 1. Another specialized pure yeast production plant was installed at the Heineken Brewery in Rotterdam the following year and together they began the supply of pure cultured yeast to brewers across Europe. This yeast strain was originally classified as Saccharomyces carlsbergensis, a now defunct species name which has been superseded by the currently accepted taxonomic classification Saccharomyces pastorianus.

Spontaneous Fermentation

Lambic beers are historically brewed in Brussels and the nearby Pajottenland region of Belgium without any yeast inoculation. The wort is cooled in open vats (called “coolships”), where the yeasts and microbiota present in the brewery (such as Brettanomyces) are allowed to settle to create a spontaneous fermentation and are then conditioned or matured in oak barrels for typically one to three years.