The term “beer” is commonly used to refer to an alcoholic beverage produced by the saccharification of starch and fermentation of the resulting sugars. The starch and saccharification enzymes are often derived from malted cereal grains, most commonly malted barley. Most beer is also flavoured with hops, which add bitterness. The preparation of beer is called brewing. There are several steps in the traditional brewing process, which usually include malting, mashing, lautering, boiling, fermenting, conditioning, filtering, and packaging. Traditionally, brewing processes are conducted in a batch-wise fashion, However, continuous brewing processes are also known in the art.
Malting is the process where barley grain is made ready for brewing. Malting is broken down into three steps in order to help to release the starches in the barley. First, during steeping, the grain is added to a vat with water and allowed to soak for approximately 40 hours. During germination, the grain is spread out on the floor of the germination room for around 5 days. The final part of malting is kilning when the malt goes through a very high temperature drying in a kiln; with gradual temperature increase over several hours. When kilning is complete, the grains are now termed malt. The malt grains are milled or crushed to break apart the kernels and expose the cotyledon, which contains the majority of the carbohydrates and sugars; this makes it easier to extract the sugars during mashing.
Mashing converts the starches released during the malting stage into sugars that can be fermented. Mashing typically comprises mixing of the milled grain with hot water in a large vessel known as a mash tun. In this vessel, the grain and water are mixed together to create a cereal mash. During the mash, naturally occurring enzymes present in the malt convert the starches (long chain carbohydrates) in the grain into smaller molecules or simple sugars (mono-, di-, and tri-saccharides). This “conversion” is called saccharification. The result of the mashing process is a sugar rich liquid or “wort”, which is usually filtered over a mash filter or in a lauter tun using husks of the barley/malt as a natural filter aid in a process known as lautering. Prior to lautering, the mash temperature is usually raised to about 75-78° C. to deactivate enzymes. Additional water may be sprinkled on the grains to extract additional sugars (a process known as sparging).
The wort is usually moved into a large tank or kettle where it is boiled with hops and sometimes other ingredients such as herbs or sugars. The boiling process serves to terminate enzymatic processes, precipitate proteins, isomerize hop resins, and concentrate and sterilize the wort. Hops add flavour, aroma and bitterness to the beer. At the end of the boil, it is customary to clarify the hopped wort in a vessel called a “whirlpool”, where the more solid particles in the wort are separated out.
After the whirlpool, the wort is rapidly cooled via a heat exchanger to a temperature where yeast can be added. The cooled wort goes into a fermentation tank. Yeast is added, or “pitched”, to the fermentation tank. The fermenting process begins, where the sugars turn into alcohol, carbon dioxide and other components, including flavour substances. When the fermentation is complete the brewer may subject the beer to a “conditioning” treatment. Conditioning of the beer is the process in which the beer ages, the flavour becomes smoother, and flavours that are unwanted dissipate. After conditioning for a week to several months, the beer may be filtered and force carbonated for bottling, or fined in the cask.
The flavour (taste and smell) of beer is determined by flavour substances that originate from raw materials (malt, hop) as well as by flavour substances that are formed in the course of the brewing process, notably during heat treatments (mashing, wort boiling) and fermentation.
The relative concentration levels of these flavour substances in beer are affected by (bio)chemical reactions that lead to their formation as well as by bio(chemical) reactions that lead to their disappearance.
Beer contains a large number of different flavour substances, including volatile and non-volatile components. Important beer flavour substances include hydrophobic as well as hydrophilic compounds. The relative concentration levels in which these flavour substances occur in a beer determine the flavour character or flavour profile of the beer. A major challenge for every brewer is to ensure constant flavour quality, and especially to minimize batch-to-batch variations in flavour quality.
Since quality and composition of the natural raw materials used in beer brewing tend to vary and given that the flavour generation pathways responsible for the formation of flavour substances during brewing are affected by many different factors, it is evident that maintaining constant beer flavour quality is indeed a very difficult task.
Brewers are also continuously searching for ways to produce new types of beers with unique, appealing flavour profiles, preferably without resorting to the addition of flavourings or of other flavour contributing ingredients.
US 2002/0142410 describes a method of stabilizing the flavour of a fermented malt beverage comprising contacting said beverage with a reductase enzyme to inhibit, block, reduce, bind or inactivate Maillard reaction intermediates.
US 2011/0111086 describes a method for improving the flavour stability of a fermented beverage produced, the method comprising: adding an antioxidant (3,4-hydroxytryosol) prior to, or during an early stage of, fermentation.
US 2012/0015072 describes a method for producing a beer, comprising adding a catalase composition to the mash, the fermenting wort, the green beer and/or the fermented beer so as to improve the flavour and/or flavour stability of the finished beer.
US 2012/0207909 describes a method for producing an unfermented beer-flavoured malt beverage, comprising contacting a wort with activated carbon to reduce an unpleasant wort flavour.
US 2003/232108 describes a method for the production of a flavorless malt based solution by subjecting fermented intermediate beer to treatment with adsorption exchange resin to remove undesirable colors, odors and/or flavors.
EP-A 0 627 485 describes a method for the removal of unwanted components from beer, comprising: removing both undesirable and desirable components, separating the undesirable and desirable components and adding back the desirable components. Examples 1 and 2 describe the chromatographic isolation of beer flavour components from dialysis permeate from the production of alcohol-free beer (Example 1) and yeast sediment (Example 2). Example 3 describes the addition of the isolated flavour concentrates to alcohol-free beer.
US 2008/213568 describes a beaded polyether resin that can be used to scavenge undesirable compounds, notably carbonyl and/or sulfonyl compounds, from fermented products such as beer, cider or wine.
U.S. Pat. No. 5,308,631 describes a process for obtaining alcohol-free beer from a naturally alcoholic beer, consisting of:    a) bringing into contact an alcoholic beer with a solid adsorbent consisting of a hydrophobic zeolite to form an aqueous eluent phase and products adsorbed on said adsorbent;    b) separating the aqueous eluent phase from the adsorbent;    c) thermally desorbing said adsorbed products to form a desorbed phase;    d) recovering the desorbed phase;    e) separating the desorbed phase into an alcoholic phase and an aromatic aqueous phase; and    f) reconstituting an alcohol-free beer by mixing the aqueous phases recovered at the end of (b) and (e).
Polyvinylpolypyrrolidone (PVPP) particles are used by brewers to remove components that cause so called ‘chill haze’ in beer. Colloidal haze in beer arises from the formation of polyphenol-protein complexes during storage. Fresh beer contains acidic proteins and a variety of polyphenols. As these small polyphenols, termed flavanoids, polymerise and oxidise, they produce short chain (condensed) polyphenols termed tannoids. These tannoids are capable of bridging across a number of proteins through hydrogen bonding to form reversible chill haze. After further storage, stronger ionic and covalent bonds form between the tannoids and proteins resulting in irreversible permanent haze. Since the rate-determining factor in the development of haze is the change in the polyphenol fraction, reducing the levels of these haze precursors is a very efficient method of ensuring the colloidal stability of beer. PVPP is a cross-linked polymer that selectively complexes haze polyphenols, predominantly through very strong hydrogen bonding, with multiple attachment sides for haze polyphenols.
U.S. Pat. No. 4,766,000 describes a method for treating beer to prevent chill haze comprising contacting said beer with a combination of partially hydrophobic adsorbent and a silica gel, wherein the partially hydrophobic adsorbent is a precipitated silica reacted with up to 7% wt/wt of a silicone, wherein said silicone is dimethyl siloxane.
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