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Fermentation Foods – Malt Beverages

Beer and ale are the most widely produced and consumed malt beverages in this country, and they will be explored here. They are constructed from ...

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MN Editors

Beer and ale are the most widely produced and consumed malt beverages in this country, and they will be explored here. They are constructed from malt, hops, yeasts, water, and malt adjuncts. Malt is produced from germinated and dried barley grains that have had their sprouts or germs removed. The dried blooms of the hop plant are known as hops. In addition to the malt’s carbs, starch- or sugar-containing components are added as adjuncts. The most commonly utilised starch adjuncts include corn and corn products, rice, wheat, barley, sorghum grain, soybeans, cassava, and potatoes. Sweet adjuncts consist of substances such as sugars and syrups.

Brewing of Beer 

As an illustration of the brewing process, beer production will be briefly described.

Malting

  • Barley grains are soaked or “steeped” at 10 to 15.6 degrees Celsius, germinated at 16 to 21 degrees Celsius for 5 to 7 days, and then kiln-dried.
  • Malt remains after the removal of the majority of sprouts or bacteria.
  • Before use, the malt, a source of amylases and proteinases, is crushed.

Mashing 

  • The objective of the mashing process is to make as much as possible of the important components of the malt and malt adjuncts soluble, and in particular to trigger the hydrolysis of starches and other polysaccharides, as well as proteins and their hydrolysis products.
  • First, the malt mash is created by combining ground malt with water between 38 and 50 degrees Celsius. After boiling or heating under steam pressure, the cooked, starchy malt adjuncts in water are added at a temperature of around 100 degrees Celsius.
  • This raises the temperature of the resulting cereal-malt mash to between 65 and 70 degrees Celsius, when saccharification (the creation of sugars from the starch) occurs rapidly.
  • The enzymes are deactivated by raising the temperature to around 75 degrees Celsius. The insoluble substances that settle to the bottom of the container act as a filter, ensuring that the wort, the resulting liquid, is clear.
  • This filtration may utilise a customised “lauter” tub. The filtering material’s rinsings are added to the wort.
  • Hops are then added to the wort to form the liquid that will be used to ferment the final wort.
  • In more advanced techniques, corn or barley-derived partially hydrolyzed syrups may be replaced for some mashing procedures and the mash itself.

Boiling the Wort with Hops 

  • After boiling the wort and hops mixture for approximately 2.5 hours, the liquid is filtered through the hop residues.
  • Hop solids and precipitated proteins are eliminated in this manner. The precipitate is washed with hot water to eliminate the majority of soluble material, and the washings are added to the initial filtrate.
  • Mash or wort is now ready for fermentation. The wort is boiled with hops for several reasons: (1) to concentrate it, (2) to sterilise it practically, (3) to inactivate enzymes, (4) to extract soluble substances from the hops, (5) to coagulate and precipitate proteins and other substances, (6) to caramelise the sugar slightly, and (7) to add antiseptic substances (primarily the alpha resins humulone, cohumulone, and adhumulone) to the wort and beer.
  • The effectiveness of these resins against gram-positive bacteria. Bitter acids and resins, which contribute to the flavour, stability, and head retention of beer, are extracted from hops, along with essential oil, which contributes a little flavour, and tannins, which are eliminated as much as possible since they may be responsible for poor flavours and haziness in beer.
  • Recent advancements include the substitution of the dried, entire hop flower with concentrated hop extracts or milled, vacuum-packed hops.

Fermentation 

  • For the inoculation or “pitching” of the cooled wort, a strain of Saccharomyces carlsbergensis is used as a specific beer yeast of the bottom type.
  • Typically, the pitching yeast is recovered from a previous fermentation. Approximately 1 pound of inoculum per barrel (31.5 gallons) of beer is utilised.
  • The temperature of the wort during fermentation varies among breweries, but is typically between 3.3 and 14 degrees Celsius.
  • Some brewers maintain the temperature between 3.3 and 4.4 degrees Celsius, while others begin with a low temperature and gradually increase it.
  • Within 8 to 14 days, usually 8 to 10 days, the fermentation process is complete. During fermentation, yeast turns most of the sugar in the wort into alcohol and carbon dioxide, as well as trace amounts of glycerol and acetic acid.
  • Proteins and fat derivatives generate trace amounts of higher alcohols and acids, which mix with organic acids and alcohols to produce aromatic esters.
  • As more carbon dioxide is produced, the foaming grows; when the fermentation is complete, the foaming disappears entirely.
  • Later on, the yeasts near the bottom “break,” or flocculate and settle. During the fermentation process and subsequent ageing of beer, bacterial development is undesirable.

Aging, or Maturing 

  • The immature, or “green,” beer is stored, or “lagered,” in vats at approximately 0 degrees Celsius for many weeks to months, during which time proteins, yeast, resin, and other unwanted components precipitate and the beer becomes clear and mellow or matured. Esters and other chemicals are generated to enhance the flavour and aroma, while the body becomes smoother.

Finishing 

  • After ageing, lager beer is carbonated to a CO2 level of between 0.45 and 0.52 percent, primarily by fermentation-collected gas.
  • After cooling, clarifying, or filtering, the beer is packed in bottles, cans, or barrels. The alcohol concentration is around 3.8% by weight.
  • Beer for cans or smaller bottles is temporarily pasteurised at 60 to 61 degrees Celsius or filtered via membranes or other materials to eliminate all yeasts.

Continuous Processes 

  • After the barley has been wetted and cleaned, a finely dispersed spray of aerated water is applied to the grain as part of the continuous malting process in order to hasten germination.
  • Continuous brewing utilises continuous mashing, boiling, and flowthrough fermentation. It is possible to bottle the beer without maturing.

Microbiology 

  • The brewing techniques have a significant impact on the ability of microorganisms to survive or thrive.
  • Although growth must occur during malting, in the main malt mash, and in the cereal-malt mash, little is known about the growth of organisms during malting, in the main malt mash, and in the cereal-malt mash.
  • However, boiling the wort and hops for 2.5 hours provides sufficient heat to kill all but the most resistant bacterial spores, such as those of some Bacillus or Clostridium species, and the combined action of heat and hop antiseptics may kill the majority of the remaining spores and inhibit their growth.
  • The yeast used for pitching should be a pure culture (although this is typically not the case) and should therefore not contribute any contaminating organisms.
  • Due to its low pH (between 3.7 and 4.5) and the presence of antiseptics produced from hops, the wort is hostile to certain organisms. During fermentation and ageing, low temperatures and anaerobic conditions are also present.
  • Additionally, the alcohol created may impede organisms. Due to its low pH, antiseptics in the form of alcohol and hop extracts (mostly resins or humulones), and low storage temperature, beer should inhibit the growth of microbes.
  • Additionally, conditions are anaerobic during production and storage, and the majority of retail beer has been pasteurised or filtered.
  • Despite all of these reasons why beer should be devoid of spoiling organisms, it is susceptible not only to physical and chemical faults, but also to “diseases” caused by bacteria.
  • Since the bacteria most responsible for beer infections are easily killed by temperatures below boiling, they must enter after the wort and hops have been boiled.

Beer Defects and “Diseases” 

  • The term faults will be used to describe undesired qualities with non-microbial sources, such as (1) turbidity caused by unstable protein, protein-tannin complexes. both starch and resin (2) off-flavors created by inferior substances or metal contact. and (3) inadequate physical attributes.
  • This topic will be limited to issues resulting from microbes, and will therefore be referred to as beer infections or beer disorders.
  • If the mash is stored for too long at temperatures favourable to these bacteria, it may undergo butyric acid fermentation by Clostridium spp. or lactic acid fermentation by lactics.
  • Such off-flavors may be transferred to the beer. It was mentioned that pitching yeast is typically infected with bacteria and wild yeasts and can serve as a source of spoiling organisms.
  • When yeasts and bacteria grow in beer, they cause turbidity, and beer yeasts that survived fermentation may be responsible for cloudiness. Similarly, wild yeasts, such as Saccharomyces pastorianus, can cloud beer.
  • Yeasts can be inhibited or excluded by excluding air, fermenting the majority of the sugar in the wort to make a “dry” beer, utilising good cultures of beer yeasts, and appropriately cleaning the facility.
  • Yeasts may also cause undesirable flavours and odours. Thus, S. pastorianus and Hansenula anomala may be responsible for bitterness and an ester-like taste, respectively.
  • The majority of yeasts produce fruity aromas, while others make hydrogen sulphide from the hop extract in beer. Potential spoiling organisms include yeasts able to exploit the dextrins in beer (e.g., Saccharomyces diastaticus).
  • Beer illnesses are typically caused by bacteria from the genera Pediococcus, Lactobacillus, Flavobacterium, and Acetobacter. Pediococcus cerevisiae is the cause of “Sarcina disease,” which is characterised by the sourness, turbidity, and stringiness of beer.
  • Because cocci frequently congregate in fours or tetrads, they were initially misidentified as sarcinae. Some lactobacilli can develop in beer because they are resistant to acid and hop antiseptics. Lactobacillus pastorianus* and L. diastaticus* are responsible for a sour flavour and a velvety turbidity.
  • From carbohydrates, these bacteria produce lactic, acetic, and formic acids as well as alcohol and carbon dioxide; they are especially detrimental in top fermentations, such as those used to produce ales.
  • Zymomonas anaerobium causes a silky turbidity and an odour evocative of hydrogen sulphide and apples when it grows in beer.
  • Carbon dioxide and alcohol are produced. It is easily killed by heat and is uncommon in beers that have been pasteurised.
  • Obesumbacterium proteus is responsible for the odour and flavour of parsnips in wort and beer. It cannot tolerate a pH as low as 4.2 and creates alcohol and acid.
  • It has been identified as a prevalent contaminant of yeast for pitching. Under aerobic conditions, species of Acetobacter and Gluconobacter that are resistant to acid and hop antiseptics can cause wort or beer to become sour.
  • Exposure to air can occur in worts that are stored too long, in empty beer barrels, and in pitching yeast.
  • Several species are responsible for sourness; Gluconobacter oxydans subsp. suboxydans* and G. oxydans subsp. industrius* may generate ropiness; and A. pasteurianus has been implicated for turbidity and sourness.
  • Other unidentified and incompletely characterised microbes have been attributed for beer illnesses. Species of Micrococcus*, Streptococcus, and Bacillus have been blamed of creating problems, however in some cases they were likely only present.
  • It has been reported that Streptococcus mucilaginosus, which is likely a pediococcus, causes ropiness.
  • It should be emphasised that all yeasts and bacteria that cause infections or diseases in wort and beer are killed by boiling the wort and hops and must enter thereafter from equipment, the air, the water, or the pitching yeast, and that aseptic and sanitary precautions will assist in preventing these issues.

Other Malt Beverages and Beer Types

Variations in malt drinks or beer kinds are typically attributable to (1) alcohol percentage, (2) malt and hops concentration, (3) time of ageing, (4) initial total solids (relative to fermentable carbohydrate present and left after fermentation), and (5) fermentation temperature.

  • Malt liquor: The alcohol concentration of malt liquor may be higher than that of normal beer.
  • Bock beer: Bock beer is a highly dark, alcoholic beer with a high alcohol level. Brewing requires the addition of more malt and hops, followed by a longer age period.
  • Pilsener: Pilsener is a light-colored, lager-style beer with few leftover fermentable carbohydrates.
  • Low-calorie, light, or no-carbohydrate: prehydrolyzed wort is used to produce low-calorie, light, or no-carbohydrate beers. Dextrin is hydrolyzed by fungal enzymes (glucoamylases and amylases) into maltose and glucose, which can be entirely fermented to alcohol; the net consequence is a decreased concentration of residual carbohydrates.
  • Ale: Ale is typically brewed with a top yeast, a strain of Saccharomyces cerevisiae, as opposed to the bottom yeast used to brew beer, but bottom yeast is occasionally utilised. The main fermentation occurs at a temperature range of 12.2 to 24.4 degrees Celsius, which is greater than that of beer. As a result, the fermentation is shorter, lasting only 5 to 7 days. The yeast at the top of the wort creates clumps that capture carbon dioxide gas and rise to the surface. Periodically, yeast scum is skimmed off. Ale contains more hops than beer, and some varieties have a greater alcohol content. Ale is often pale in colour and has a sour flavour.
  • Weiss beer, porter, and stout: Weiss beer, porter, and stout are ales since they are brewed with premium yeasts. Weiss beer is a light, sour ale primarily brewed with wheat. Porter and stout are luscious, dark, hefty ales.

Related Beverages 

  • Sake: Sake is a Japanese rice beer or wine with an alcohol concentration of approximately 14 to 17 percent. A starter, or koji, for sake is produced by cultivating Aspergillus oryzae on a rice mash that has been soaked and steamed until the highest production of enzymes is attained. This koji contains amylases that cause the hydrolysis of rice starch to sugars that are accessible to yeasts, as well as additional hydrolytic enzymes such as proteinases. The koji is combined with additional rice mash, the starch is transformed to sugar, and multiple species of Saccharomyces yeast carry out the alcoholic fermentation. After 10 to 14 days, the liquor filtered from the fermented material is called sake. Sonti is an Indian rice beer or wine. During fermentation, Rhizopus sonti and yeasts are active.
  • Pulque: Pulque is a beer-like beverage produced by the natural yeast fermentation of the juice of the agave or century plant. It contains about 6 percent alcohol.
  • Ginger beer: Ginger beer is a somewhat alcoholic, acidic beverage produced by the fermentation of a ginger-flavored sugar solution. The starter consists of yeast, Saccharomyces pyriformis, and a bacterium encapsulated in a capsule. Lactobacillus vermiformis* is surrounded by gelatinous capsular material.

Citation

APA

MN Editors. (November 27, 2022).Fermentation Foods – Malt Beverages. Retrieved from https://microbiologynote.com/fermentation-foods-malt-beverages/

MLA

MN Editors. "Fermentation Foods – Malt Beverages." Microbiology Note, Microbiologynote.com, November 27, 2022.

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