In Latin, the word beer, bibere: meaning to drink. The beer-making process is known as brewing. The ancient Egyptians practiced beer brewing from barley as far back as 4,000 years ago. However, evidence indicates that Egyptians learned the craft from the Tigris and Euphrates tribes, where man’s culture is said to have originated. However, hops’ use is much more recent and can be traced back to a couple of centuries ago. 

Types of Beers :

It is possible to classify barley beers into two broad groups: top-fermented beers and bottom-fermented beers. This distinction is dependent on whether, at the end of fermentation, the yeast stays at the top of the brew (top-fermented beers) or the bottom of the sediment (bottom-fermented beers). 

Bottom-fermented beers 

Bottom-fermented beers are often referred to as lager beers because they have been processed for clarification and maturation or ‘lagered’ in cold cellars after fermentation. The strains of Saccharomyces uvarum (formerly Saccharomyces carlsbergensis) are yeast used in bottom-fermented beers. Most of the world’s lager beers are of the Pilsener kind (70 percent-80 percent). 

a. Pilsener beer: This is a medium hop, pale beer. 3.0-3.8 percent by weight is the alcohol content. It is traditionally lagered for two to three months. However, modern breweries dramatically reduced the lagering period that has been reduced in many breweries across the globe to about two weeks. The water is soft for the Pilsener brew, producing relatively few ions of calcium and magnesium. 

b. Dortmunder beer: a pale beer, but with fewer hops (and therefore less bitter) than Pilsener. It has a thicker body and taste, in any case. The alcohol level is also 3.0-3.8 percent and is slightly longer in a classical lager: 3-4 months. Brewing water, which contains significant quantities of carbonates, sulfates, and chlorides, is difficult. 

c. Munchner: This is a mildly sweet beer with a dark, aromatic, and full-bodied flavor since it is just mildly hopped. The alcohol content, ranging from 2 to 5% alcohol, may be very high. The water used for brewing is high in carbonates but low in other ions. 

d. Weiss (Weizen): Weiss beer from Germany made from wheat and steam beer from California, USA, are both highly effervescent bottom-fermented beers. 

Top-fermented beers 

Top-fermented beers with Saccharomyces cerevisiae strains are brewed. 

a. Ale: While it can be said that lager beer is of German or continental European origin, ale (Pale ale) is an English beer of its own. English ale is a pale, heavily hopped beer with a 4.0 to 5.0 percent (w / v) alcohol content, often as high as 8.0 percent. During and sometimes after fermentation, hops are added. Therefore, its high ester content is very bitter and has a sharp acid taste and wine aroma. The mild ale is sweeter since it hops less vigorously than the traditional pale ale. 

b. Porter: This is a medium-brown, heavy-bodied, highly foamed beer made of medium malts. It contains fewer hops than ale and is sweeter as a result. It has an alcohol content of approximately 5.0%. 

c. Stout: Stout is a heavy-bodied, very dark, vigorously hopped beer with a heavy aroma of malt. It is made from dark or caramelized malt; caramel can be added occasionally. It has a moderately high alcohol content, 5.0-6.5 percent (w / v), and is usually kept for up to six months, with fermentation in the bottle. Some stouts are less hopped than usual, which is sweet.

Raw Brewing Materials 

The raw materials are barley, malt, yeast, hops, water, and adjuncts. 

Malt from barley 

As a cereal for brewing, barley has the following benefits. Its husks are thick, hard to crush, and stick to the kernel. After mashing, this makes malting and filtration much more straightforward than for other cereals such as wheat. The second benefit is that during storage, the thick husk is protection against fungal attack. Third, the temperature of gelatinization (i.e., the temperature at which the starch is transformed into a water-soluble gel) is 52-59 ° C, far lower than the optimal temperature of barley malt alpha-amylase (70 ° C) as well as beta-amylase (65 ° C). 

Adjuncts :

Adjuncts are starchy materials that were initially introduced because a malt with higher diastatic power ( i.e., amylases) was developed by the six-row barley varieties needed to hydrolyze the starch in the malt. The definition now encompasses products other than those which are amylase hydrolyzed. For example, the word now contains added sugars (e.g., sucrose) to improve the beer’s alcoholic content. Starchy adjuncts, typically containing little protein, lead to fermentable sugars after their hydrolysis, which raises the alcoholic content. 

Hops :

Hops (varieties include: H. lupuloides, H. cordifolius, H. neomexicanus) are the dried cone-shaped female flowers of the hop-plant Humulus lupulus. 

(a) Hops, particularly against beer sarcina (Pediococcus damnosus) and other beer spoiling bacteria, have some antimicrobial effects. 

(b) They contribute to colloidal stability and foam head retention of beer because of the bitter substances’ colloidal origin. 

(c) During the wort’s boiling, the hops’ tannins help to precipitate proteins; if not extracted, these proteins create a low-temperature haze in the beer. 

Aquatic Water 

Water is so critical that the natural water available in the world’s great brewing centers has given beers unique to these centers a special character. As is the case, water with a vital calcium and bicarbonate ion content is ideal for developing darker, sweeter beers. 

(a) With the addition of calcium sulfate (gypsum), the water can be ‘brutalized.’ Gypsum addition neutralizes the carbonates’ alkalinity. 

(b) Acids: lactic acid, phosphoric acid, sulfuric acid, or hydrochloric acid can be added. CO2 is emitted, but there is an unwelcome risk that the resulting salt may remain. By gas stripping, the CO2 released is extracted. 

(c) Water may be decarbonated by the addition of lime calcium hydroxide or by boiling. 

(d) Water can be enhanced by ions’ exchange, eliminating all the ions if desired. 

One or more of the methods described above may be used simultaneously.

Brewer’s Yeasts :

Yeasts typically produce sugar alcohol under anaerobic conditions, although not all yeasts are inherently suitable for brewing purposes. In addition to alcohol production, brewing yeasts can generate a balanced proportion of wort sugars and proteins that generate esters, acids, higher alcohols, and ketones. The distinctive taste of beer contributes to these compounds. Several features differentiate the two kinds of brewers’ yeasts (i.e., the top and bottom-fermenting yeasts). 

(a) S. Uvarum typically occurs alone or in pairs (formerly S. carlsbergensis). S. Cerevisiae typically produces chains and even cross-chains sometimes. 

(b) S. Cerevisiae sporulates with greater ease than S. uvarum. 

(c) S. Cerevisiae can only ferment the fructose moiety; in other words, it lacks the enzyme system necessary to ferment the galactose and glucose-formed melibiose. 

(d) S. Cerevisiae strains have a more significant respiratory system than S. Uvarum, which is mirrored in the two groups’ various cytochrome spectra. 

After fermentation, yeasts have reused a variety of times, depending on the individual brewery tradition. In this practice, mutation and pollution are two risks.

Brewing Process: The brewing process involves the sequential events of malting, cleaning, mashing, operation, wort boiling treatment, fermentation, storage, and packaging.


Malting is intended to produce amylases and proteases in the grain. The germinated barley generates these enzymes to allow it to break down the carbohydrates and proteins in the grain to nourish the germinated seedling before its photosynthetic systems are sufficiently developed to support the plant. 

1. For brewing, not all barley strains are suitable. Barley grains are cleaned during malting; broken barley grains and foreign seeds, sand, metal bits are removed. 

2. At 10-15 ° C, the grains are then soaked in water. The grain absorbs water and ultimately increases in volume by about 4 percent. Embryo respiration begins as soon as the water is absorbed. 

3. Microorganisms develop in steep water, and the steep water is altered at 12-hour intervals until the grain’s moisture content is about 45 percent to allow grain deterioration. Steeping takes between two and three days. 

4. The grains are then drained from the moisture and moved for germination to a malting floor or a rotating drum. 

5. The heat produced by the sprouts hastens germination. Sometimes, moist, warm air is blown about 30 cm deep through the beds of germinating seedlings. Water on them may also be sprinkled. 

6. The starch granules in the endosperm are located inside the cells. Hemicellulose, which is broken down by hemicellulases before amylases can invade the starch, is composed of these cell walls. The grain also synthesizes alpha-amylase. Beta-amylase is already present but is bound to proteins and released by proteolytic enzymes and is not synthesized. Enzyme modification or development is completed in 4-5 days of seedling growth. 

Klining, which includes heating the green malt in an oven at a relatively mild temperature, prevents further reactions in the grain before the moisture content is reduced by around 40 percent to 6 percent. The heating temperature depends on the form of beer made. 

Klining takes 20-40 hours at 80-900C for the form of Pilsener. 

For Munich beers, drying at 100-1100CC takes up to 48 hours. 

Some alterations in the gross composition of the barley grain occur at the end of malting. As cattle feed, the rootlets are removed and used. At each point of malting, weight loss known as malting loss occurs, and the accumulated loss can be as high as 15 percent. Barley malt resembles swollen grains of unthreshed rice with its rich enzyme content and can be processed for significant periods before being used.

Malt cleaning and milling operations: 

1. The barley is carried to the upper part of the brewing tower. Subsequent processes take place on increasingly lower floors throughout the brewery process. 2. On the ground level floor, laggering and bottling usually are performed. 

3. Gravity is used in this way to transport the goods, and the pumping cost is removed. 

4. The barley malt is cleaned of dirt at the top of the brewing tower and passed over a magnet to remove pieces of metal, particularly iron, and then milled to expose malt particles to malt enzymes’ hydrolytic effects during the mixing process. 

The smaller the particles, the larger the malt extract would be. However, very fine particles hinder and unduly prolong filtration. Therefore, the brewer has to find a compromise particle size that will offer maximum extraction but allow a relatively quick filtration rate. The crushing is done regardless of the particle size, preserving the husks that contribute to filtration while reducing the endosperm to fine grits. 

Mashing : 

1. Mashing determines the nature of the wort. 

2. The mashing object is to extract as much as possible of the soluble portion of the malt and hydrolyze insoluble portions of the malt and adjuncts enzymatically. 

3. Mashing consists of combining the ground malt and adjuncts at temperatures suitable for the malt-derived amylases and proteases. 

4. Wort is known as the aqueous solution resulting from mashing. 

Starch (55%) and protein (10-12%) are the two largest grain’s dry weight components. The controlled breakdown of these two components affects the character of beer enormously. 

The degradation of starch during mashing : 

Around 55 percent of the dry weight of barley malt is produced by starch. 20-25 percent of the malt starch is composed of amylose. The alpha- and beta-amylases are the main enzymes in malt starch breakdown. 

Breakdown of proteins during mashing 

During malting, the breakdown of malt proteins, albumins, globulins, hordeins, and glutenins begins and continues during mashing through proteases that break down proteins into polypeptides and polypeptidases by peptones that break down polypeptides into amino acids. There is no pronounced optimum temperature of protein breakdown, but it occurs uniformly up to 60 ° C during mashing, above which temperature proteases and polypeptidases are greatly retarded. 

General environmental circumstances that affect mashing : 

A combination of temperature, pH, time, and concentration of the wort affects mashing progress. When the temperature is sustained for long periods at 60-65 ° C, a maltose-rich wort occurs because the beta-amylase activity is at its peak, and this enzyme mainly produces maltose. 

EnzymeOptimum TemperatureTemperature for destruction Optimum pH
Alpha- amylase70° C80° C5.8
Beta- amylase60-65° C75° C5.4

As shown in Table, the optimal pH for beta-amylase activity is approximately the same as that of proteolysis. The mash concentration is essential: the thinner the mash, the higher the maltose content and the extract.

Methods for mashing 

There are three main techniques for mashing: 

(a) Methods of decoction, where part of the mash is moved from mash tun to the mash kettle where it is boiled. 

(b) Methods of infusion, where the mash is never boiled, but the temperature rises steadily. 

(c) Form of double mash, where starchy adjuncts are boiled and added to the malt. 

Mash Separation : 

Husks and other insoluble materials are removed from the wort in two stages at the end of mashing. The wort is separated from the solids first. Second, by washing or sparring with hot water, the solids themselves are liberated from additional extractable content. 

1. The traditional way of separating the husks and other solids from the mash is to strain the mash in a lauter tun that is a vessel about 10 mm above the real bottom with a perforated false bottom, which the husks themselves form a bed in which filtration takes place. 

2. In recent times, the Nooter strain master has come into use in large breweries, particularly in the United States. 

3. Filtration, like the Lauter tun, is through a bed shaped by the husks, but straining is through a series of triangular perforated pipes positioned at various bed heights instead of a false bottom. 

4. Whereas the Lauter tub is cylindrical, the strain master itself is rectangular with a conical rim. Among others, its advantage is that it can accommodate more significant amounts than the Lauter pool. 

5. Cloth filters located in plate filters and scanning centrifuges are also used, and the Lauter tun and the strainmaster. 

The sparging (or hot water washing) of the mash’s solids is performed at about 80 ° C with water and continues until the extraction is complete. The material that is left is known as spent grain after sparging and is used as animal feed. The liquid is often extracted by centrifuging from the spent grain; the extract is used for cooking the adjuncts. 

Boiling Wort : 

The wort is boiled in a brew kettle used to be made of copper for 1–1.5 hours. It is applied when corn syrup or sucrose is used as an adjunct at the beginning of boiling. It also adds hops, some before and some at the end of the boiling process. The boiling objective is as follows: 

(a) Wort concentrate: 5-8 percent of the volume is lost during the boiling by evaporation. 

(b) To sterilize the wort before its entry into the fermenter to reduce its microbial load. 

(c) To inactivate some enzymes so that the composition of the wort does not alter. 

(d) To extract from hops soluble materials which not only aid in the removal of proteins but also help in the removal of proteins; 

The bitterness of hops was also added. 

(e) To precipitate proteins which, due to heat denaturation and complexing, form large flocks with tannins extracted from hops and malt husks. In beer, unprecipitated proteins form hazes, but too little protein contributes to the foam’s head’s inadequate formation. 

(f) To produce the beer color: some of the beer colors come from malting, but the bulk forms during the wort’s boiling. Color is produced by various chemical reactions, including sugar caramelization, phenolic compound oxidation, and amino acid and sugar reduction reactions. 

(g) Removal of volatile compounds: removal of volatile compounds such as fatty acids that may contribute to beer’s rancidity. 

The amount of precipitation and flock forming can be increased during the boiling, agitation, and circulation of the wort. 

Pre-fermentation treatment of wort: 

The hot wort is not sent to the fermentation tanks directly. If dried hops are used in a hop strainer, then they are typically removed. The proteins and tannins are precipitated during boiling while the liquid is still warm. When the wort has cooled to around 50 ° C, some more precipitation occurs. The warm precipitate is referred to as “trub” and consists of 50-60% protein, 16-20% hop resins, 20-30 percent polyphenols, and around 3% ash. The wort is oxygenated at approximately 8 mg/liter of wort during the fermenter transition to provide the yeast with the required oxygen for initial growth.

Fermentation :

The cooled wort is pumped into fermentation tanks or allowed to flow by gravity, and yeast generally collected from a previous brew is inoculated or ‘pitched in’ at a rate of 7-15 x 106 yeast cells/ml. 

Top Fermentation :

For the yeasts’ initial growth, the wort is applied via a fishtail mist so that it is aerated to the tune of 5-10 mg/liter of oxygen. At a temperature of 15–16 ° C, yeast is pitched in at the rate of 0.15 to 0.30 kg/hl. For about three days, the temperature is allowed to increase to 20 ° C steadily. At this stage, it is cooled to a constant temperature. It takes approximately six days for the whole primary fermentation. During this time, Yeasts float to the surface; they are scooped off and used for future pitching. The yeast transforms into a hard leathery coating in the last three days of fermentation, which is also skimmed off. Occasionally, the wort is moved after the first 24-36 hours to another vessel in the so-called dropping method. The switch assists in aerating the system and also allows the cold-break sediments to be discarded. It is also possible to achieve aeration by paddle circulation and using pumps. Nowadays, the conventional open tanks are being replaced by cylindrical vertical, closed tanks. 

Bottom Fermentation :

Wort is inoculated per ml of wort to the tune of 7-15 x 106 yeast cells. Over three to four days, the yeasts then expand four to five times in number. At 6-10 ° C, yeast is pitched in and is allowed to increase to 10-12 ° C, which takes about three to four days. At the end of fermentation, it is cooled to around 5 ° C. CO2 is released, and this produces a head called Krausen that starts to collapse as the yeasts begin to settle after four to five days. The total duration of fermentation can last for 7-12 days. 

Beer Components :

Anaerobic conditions predominate during wort fermentation in the top and bottom fermentation; the original oxygen is only necessary for cell growth. Fermentable sugars are converted by cooling to alcohol, CO2, and heat that must be extracted. There is no fermentation of Dextrins and Maltotetraoses. Amino acids produce higher alcohols (sometimes known as fusel oils), including propanol and isobutanol. Using the tricarboxylic acid cycle, organic acids such as acetic, lactic, pyruvic, citric, and malic are also derived from carbohydrates. 

Lagging : 

(a) Lagering: The beer, known as the ‘green’ beer, is harsh and bitter at the end of the primary fermentation above. It has a yeasty flavor because of higher alcohols and aldehydes, perhaps. It is stored at low temperatures (around 0 ° C) in closed vats for times that are used for as long as six months before maturing in some cases. 

There is secondary fermentation during lagering. Yeasts are often added, using some sugars in the green beer. Secondary fermentation saturates the beer with CO2, and the development of secondary fermentation is accompanied by the exhaust rate of CO2 from the safety valve. Active fermentation of wort or Krausen can be applied occasionally. CO2 may be chemically applied to the beer at some times. Evaporation during secondary fermentation reduces materials that can undesirably influence taste and are found in green beer, e.g., diacetyl, hydrogen sulfide, mercaptans, and acetaldehyde. There is an improvement in the desired beer ingredients, such as esters. During the lagering phase, any tannins, proteins, and hop resins that are still left are precipitated. 

Lagering gives the beer its final organoleptic characteristics that are attractive, but it is hazy due to protein-tannin complexes and yeast cells. To remove these, the beer is filtered through kieselguhr or membrane filters. 

(b) Beer Treatment: no extensive lagering of bottom-fermented beers occurs. In different ways, they are handled in casks or bottles. In specific procedures, at the end of fermentation, the beer is moved to casks with a load of 0.2–4.00 million yeast cells/ml. It is ‘primed’ by adding a small amount of sugar combined with caramel to enhance its taste and appearance. The yeast grows in the sugar, and the beer is carbonated. Hops at this point are also often added. At around 15 ° C, it is kept for seven days or less. The beer is ‘fined’ by the addition of Isinglass after ‘priming.’ Yeast cells, tannins, and protein-tannin complexes are precipitated by Isinglass, a gelatinous substance from the swimming bladder of fish. Following that, the beer is filtered or pasteurized and distributed. 

Packaging : 

Beer is moved to pressure tanks and then distributed to cans, bottles, and other containers. Beer cannot contact oxygen during the transfer; CO2 loss or contamination with microorganisms is also not permitted. Alcohol is applied to tanks under CO2 atmosphere, distilled under a CO2 counter-pressure, and all the equipment is routinely washed and disinfected to achieve these objectives. 

Before being filled, bottles are thoroughly washed with hot water and sodium hydroxide. A pasteurizer passes through the filled and crowned bottles, which heats the bottles for half an hour at 60 ° C. It takes about half an hour for the bottles to hit the pasteurizing temperature, stay in the pasteurizer for half an hour, and cool down for another half an hour. This pasteurization method often creates hazards that lead some larger breweries to carry out bulk pasteurization today and aseptically fill containers.

Schematic representation of industrial process of production of malt beverages.