Malting, Brewing and Distilling Introduction relevant to the country of origin and the descrip- The essential process involved in brewing is tion of the product. Consequently, added enzymes the conversion of cereal starch into alcohol to may contribute different proportions of the enzyme make a palatable, intoxicating beverage Fermen- complement The alcohol content of the liquor produced by tation is mediated by yeasts appropriate to the fermentation is limited by the tolerance of the cereal or cereals involved. Most yeasts used belong to the species Saccharomyces cerevisiae. yeasts. Probably the most tolerant yeasts are used which now includes the ' bottom yeast'previ in sake production. They can survive alcohol ously classified as S. carlsbergensis(Reed ar contents of about 20% although the Nagodawithana, 1991) sold in a diluted form Two processes are involved: the starch has first Distillation allows the concentration of alcohol enzymes, and second, the sugars have to be character of which depends on flavours imparted fermented to alcohol by enzymes present in yeast. added flavours usually being extracts from other In the first process the enzymes may be producc plant sources. exogenously, in other organisms present. Alter For alcohol production from plant material, natively they may be added as extracts sugars must be present, as in fleshy fruits, or other substrates from which fermentable sugars are employed is known as malting. This comprises can be produced. Starch is such a substrate,so a controlled germination during which enzymes capable of catalyzing hydrolysis, not only of the West, the most commonly used cereal is starch,but also other components of the grain, barley but substantial quantities are derived from are produced. The most significant are the pro- maize(beer in central America), rye(kvass beer teases and the B-glucanases, as the products in the former U.S.S. R), rice(sake in Japan and resulting from their activities affect the qualiti shaoshinchu in China), sorghum(beer in Africa). of the beverage Triticale may be used as an adjunct in beers Other organisms are employed as a source of zymes in the production of sake -a beer produced from rice. Enzymes are added in solu- Malting tion, particularly when it is required to hydrolyze During malting, large molecular weight com- he starch etc. present in endosperm grits or ponents of the endosperm cell fours, themselves incapable of enzyme produc- proteins and the starch granules, are hydrolyzed tion. Such adjuncts may provide any proportion by enzymes rendering them more soluble in of the total starch, depending on legislation water
9 Malting, Brewing and Distilling Introduction The essential process involved in brewing is the conversion of cereal starch into alcohol to make a palatable, intoxicating beverage. Fermentation is mediated by yeasts appropriate to the cereal or cereals involved. Most yeasts used belong to the species Saccharomyces cerevisiae, which now includes the ‘bottom yeast’ previously classified as S. carlsbergensis (Reed and Nagodawithana, 1991). Two processes are involved: the starch has first to be converted to soluble sugars by amylolytic enzymes, and second, the sugars have to be fermented to alcohol by enzymes present in yeast. In the first process the enzymes may be produced in the grains themselves (endogenously) or exogenously, in other organisms present. Alternatively they may be added as extracts. The process in which the grain’s own enzymes are employed is known as malting. This comprises a controlled germination during which enzymes capable of catalyzing hydrolysis, not only of starch, but also other components of the grain, are produced. The most significant are the proteases and the P-glucanases, as the products resulting from their activities affect the qualities of the beverage. Other organisms are employed as a source of enzymes in the production of sake - a beer produced from rice. Enzymes are added in solution, particularly when it is required to hydrolyze the starch etc. present in endosperm grits or flours, themselves incapable of enzyme production. Such adjuncts may provide any proportion of the total starch, depending on legislation water. relevant to the country of origin and the description of the product. Consequently, added enzymes may contribute different proportions of the enzyme complement. The alcohol content of the liquor produced by fermentation is limited by the tolerance of the yeasts. Probably the most tolerant yeasts are used in sake production. They can survive alcohol contents of about 20% although the product is sold in a diluted form. Distillation allows the concentration of alcohol into drinks described as spirits, the special character of which depends on flavours imparted by the processing or added to a distillate, the added flavours usually being extracts from other plant sources. For alcohol production from plant material, sugars must be present, as in fleshy fruits, or other substrates from which fermentable sugars can be produced. Starch is such a substrate, so all cereals can be used for beer production. In the West, the most commonly used cereal is barley but substantial quantities are derived from maize (beer in central America), rye (kvass beer in the former U.S.S.R), rice (sake in Japan and shaoshinchu in China), sorghum (beer in Africa). Triticale may be used as an adjunct in beers. Malting During malting, large molecular weight components of the endosperm cell walls, the storage proteins and the starch granules, are hydrolyzed by enzymes, rendering them more soluble in 21 8
MALTING, BREWING AND DISTILLING 219 All cereals are capable of undergoing maltingmalting barley is 1. 5%; some 38% of this but barley is particularly suitable because the appears in the beer in the form of soluble adherent pales (lemma and palea -see Ch. 2) nitrogen compounds, the proportion of the provide protection for the developing plumule, or total nitrogen entering the beer being some- acrospire, against damage during the necessary what larger from two-row than from six-row handling of the germinating grains. Further, the husk(pales)provides an aid to filtration when the malt liquor is being removed from the residue of of barley lies in the firmness of the grain at high Dormancy insoluble grain components. A third advantage Harvest-ripe barley may not be capable of Both two-row and six-row barleys(see Ch. 2) germination immediately. While this is advan- are suitable: the former are generally used tageous in the field, protecting the crop against Europe the latter in North America. Distinct sprouting in the ear, it is clearly a problem in varieties were formerly grown for malting. They tion occurring. the mechanism of dormancy is feeding. Modern malting varieties have high a single cause is involved in all cases; in many yields and are thus suitable for the less demanding instances it has been shown that germination is alternative uses also inhibited by inability of the embryo to gain access The characteristics required of a malting barley to oxygen. a distinct phenomenon known as water sensitivity' can arise during steeping if a 1. High germination capacity and energy, with film of water is allowed to remain on the surface adequate enzymic activity 2. Capacity of grains modified by malting to oxygen to satisfy the needs of the developing produce a maximum of extract when mashed embryo and it acts as a barrier to the passage of prior to fermentation air. Dormancy declines with time and storage is 3. Low content of husk thus not just a means of holding sufficient stocks 4. High starch and low protein contents of gral during the storage of freshly harvested it is an essential part of the process of and handling as well as by genetic factors: loss which dormancy has declined sufficiently for of germination capacity can result from damage malting proper to commence. Bothdormancy to the embryo during threshing, or overheating and 'water sensitivity'are defined in relation to during drying or storage. the test performed In one test 100 grains are Provided that grains are ripe, free from fungal germinated on filter papers with 4 and 8ml of infestation and intact, the yield of malt extract water, the difference between viability and the should be directly related to starch content germination on 4 ml of water is called dormancy 1. Starch content is lower sensitivity. Factors involved in controlling and 2. Longer malting times are required breaking dormancy have been reviewed by Briggs 3. Modification never proceeds as far as in low.(1978) nitrogen barley 4. The greater quantities of soluble proteins lead Barley malting operations to haze formation and may provide nutrients for b of the The average nitrogen content of schematically in Fig, 9/ n malting are shown eping The practical steps
MALTING, BREWING AND DISTILLING 219 malting barley is 1.5%; some 38% of this appears in the beer in the form of soluble nitrogen compounds, the proportion of the total nitrogen entering the beer being somewhat larger from two-row than from six-row types. All cereals are capable of undergoing malting but barley is particularly suitable because the adherent pales (lemma and palea - see Ch. 2) provide protection for the developing plumule, or acrospire, against damage during the necessary handling of the germinating grains. Further, the husk (pales) provides an aid to filtration when the malt liquor is being removed from the residue of insoluble grain components. A third advantage of barley lies in the firmness of the grain at high moisture content. Both two-row and six-row barleys (see Ch. 2) are suitable: the former are generally used in Europe, the latter in North America. Distinct varieties were formerly grown for malting. They were lower yielding than varieties grown for feeding. Modern malting varieties have high yields and are thus suitable for the less demanding alternative uses also. The characteristics required of a malting barley are: Dormancy Harvest-ripe barley may not be capable of germination immediately. While this is advantageous in the field, protecting the crop against sprouting in the ear, it is clearly a problem in relation to malting, which depends on germination occurring. The mechanism of dormancy is not fully understood and indeed it is unlikely that a single cauSe is involved in all cases; in many instances it has been shown that germination is inhibited by inability of the embryo to gain access to oxygen. A distinct phenomenon known as ‘water sensitivity’ can arise during steeping if a film of water is allowed to remain on the Surface of grains. The water contains too little dissolved oxygen to Satisfy the needs of the developing embryo and it acts as a barrier to the passage of air. Dormancy declines with time and storage is thus not just a means of holding sufficient stocks of grain, it is an essential part of the process of malting. During the storage of freshly harvested barley tests are performed to detect the time at which dormancy has declined sufficiently for malting proper to commence. Both ‘dormancy’ and ‘water sensitivity’ are defined in relation to the test performed. In one test 100 grains are germinated on filter papers with 4 and 8 ml of water, the difference between viability and the germination on 4 ml of water is called dormancy while the difference bemeen the levels of gedation on the different volumes of water is the watersensitivity. Factors involved in controlling and breaking dormancy have been reviewed by Briggs (1978). 1. High germination capacity and energy, with adequate enzymic activity. 2. Capacity of grains modified by malting to produce a maximum of extract when mashed prior to fermentation. 3. Low content of husk. 4. High starch and low protein contents. The above qualities Can be affected by husbandry and handling as well as by genetic factors: loss of germination capacity can result from damage to the embryo during threshing, Or overheating during drying or storage. Rovided that grains are ripe, free from fungal infestation and intact, the yield of malt extract should be directly related to starch content. High-nitrogen barley is unsuitable for malting because: 1. Starch content is lower. 2. Longer malting times are required. 3. Modification never proceeds as far as in lownitrogen barleys. 4. The greater quantities of soluble proteins lead to haze formation and may provide nutrients for bacteria and impair the keeping quality The practical steps in malting are shown of the beer. The average nitrogen content of Barley malting operations schematically in Fig. 9.1
220 TECHNOLOGY OF CEREALS At intervals the grain is mixed and turned to Clean, graded barley grain rovide more uniform growth opportunities, and to prevent the roots from matting together. As the embryo grows it produces hormones including Steeping gibberellic acid, stimulating production of hydro lytic enzymes in the scutellum and aleurone layer, leading to 'modificationof the starchy endo- Chit malt perm. The malting process is regulated by the initial choice of barley, the duration of growth the temperature, the grain moisture content Germination changes in the steeping schedule, and by use of additives. When modification is sufficient it is stopped by kilning the 'green malt,, that is, by drying and cooking it in a current of hot dry air The dry, brittle culms are then separated and the finished malt is stored. Dry malt is stable storage and, unlike barley, it is readily crushe Kilning The conditions of kilning are critical in deter mining the character of the malt: it can cause a slight enhancement of the levels found in green Finished malt malt or completely destroy it. Malt contains relatively large quantities of soluble sugars and nitrogenous substances and, if it has been kilned Milling at low temperatures, it contains high levels of hydrolytic enzymes. When crushed malt is mixed with warm water the enzymes catalyze hydroly Ground malt of the starch, other polysaccharides, proteins and nucleic acids accessible to them whether from FIG 9. 1 Diagrammatic summary of the malting process the malt or from materials mixed with it. Malt also confers colour, aroma and flavour to the Selected barley is'steeped', usually by immer- product. The solution of the products of hydrolysis sion in water, for a period chosen to achieve a extracted from the malt is the wort'. It forms particular moisture level. The water is drained the feedstock for fermentation for brewing or from the grain, which germinates. Conditions are distillation(Briggs, 1978 regulated to keep the grain cool (generally below One of the benefits derived from the applica 18C)and to minimize water losses. as the grain tion of technology in malting has been the reduc- germinates the coleoptile(acrospire) grows beneath tion in time required to produce satisfactory the husk and pericarp while the 'chit(coleorhiza, malts. The amount of time saved can be inferred root sheath)appears at the base of the grain, and from the diagrams in Fig. 9. 3. It is clear that is split by the emerging rootlets. Fig. 9.2 most saving has occurred during the present FIG 9. 2 Diagrammatic longitudinal sections through barley grains in the early I imbibed grain, 2. rootlets emerged, 3. Rootlets and coleoptile emerged om Briggs(1978), Barley (Fig. 1. 11). Reproduced by courtesy of Chapman and Hall Ltd
220 TECHNOLOGY OF CEREALS Malting Clean, graded barley grains At intervals the grain is mixed and turned to provide more uniform growth opportunities, and to prevent the roots from matting together. As the embryo grows it produces hormones including gibberellic acid, stimulating production of hydrolytic enzymes in the scutellum and aleurone layer, leading to ‘modification’ of the starchy endosperm. The malting process is regulated by the initial choice of barley, the duration of growth, the temperature, the grain moisture content, changes in the steeping schedule,and by use of additives. When modification is sufficient it is stopped by kilning the ‘green malt’, that is, by drying and cooking it in a current of hot dry air. The dry, brittle culms are then separated and the finished malt is stored. Dry malt is stable on storage and, unlike barley, it is readily crushed. Kilning Sprouts The conditions of kilning are critical in determining the character of the malt: it can cause a slight enhancement of the levels found in green Finished malt malt or completely destroy it. Malt contains relatively large quantities of soluble sugars and nitrogenous substances and, if it has been kilned at low temperatures, it contains high levels of hydrolytic enzymes. When crushed malt is mixed with warm water the enzymes catalyze hydrolysis of the starch, other polysaccharides, proteins and nucleic acids accessible to them, whether from the malt or from materials mixed with it. Malt also confers colour, aroma and flavour to the product. The solution of the products of hydrolysis extracted from the malt is the ‘wort’. It forms the feedstock for fermentation for brewing or distillation (Briggs, 1978). One of the benefits derived from the application of technology in malting has been the reduction in time required to produce satisfactory malts. The amount of time saved can be inferred from the diagrams in Fig. 9.3. It is clear that most saving has occurred during the present 1 Steeping 7 “Chit malt” Germination 1 Green malt +-Ma1t + Milling Ground molt FIG 9.1 Diagrammatic summary of the malting process. Selected barley is ‘steeped’, usually by immersion in water, for a period chosen to achieve a particular moisture level. The water is drained from the grain, which germinates. Conditions are regulated to keep the grain cool (generally below lS°C) and to minimize water losses. As the grain germinates the coleoptile (acrospire) grows beneath the husk and pericarp while the ‘chit’ (coleorhiza, root sheath) appears at the base of the grain, and is split by the emerging rootlets. Fig. 9.2. 0 1 2 3 FIG 9.2 Diagrammatic longitudinal sections through barley grains in the early stages of germination. 1. imbibed grain, 2. rootlets emerged, 3. Rootlets and coleoptile emerged. From Briggs (1978), Barley (Fig. 1.11). Reproduced by courtesy of Chapman and Hall Ltd
MALTING, BREWING AND DISTILLING 221 6-8d o-35d 4-6d B863-7d 3-6d 3-6d 3 d IG9.3 Diagram showing the reduction, over three centuries, in periods needed for malting a nree stages involved in the process century, and that savings are made in all stages,(say 1.8% N), destined for a vinegar factory, although the greatest benefits have been achieved 46-49% m/c may be preferred. Higher moisture in the germination stage levels induce faster modification but greater losses are incurred(Briggs, 1978). Anaerobic condi tions are dangerous as they favour fermentation by micro-organisms present. The ethanol pro- Traditional malting included a ditch steep duced can harm the grain. On the other hand followed by germination in heaps on the floor. It excessive aeration leads to chitting under water was a labour-intensive proc he heaps or and, consequentially, an undue rise in moisture couches'required frequent turning. It was also content. time consuming It is desirable to replace steeping water with Current practice varies according to the size fresh, between 1 and 4 times, as phosphates of operation and the preference of the maltster and organic compounds, including alcohol, accu- but self-emptying steep tanks have replaced the mulate and the microbial population grows ditch steep Vessels may be fat-bottomed or During the first steep dissolved oxygen conical-bottomed tanks. They have facilities for depleted from steep-water at a rate of l mg/ water filling and emptying, and compressed air kg per hour but it rises 10-fold by the third blowers provide both aeration and 'rousing and steep Complete depletion is possible within one mixing during the steep. Together, these pro- hour. Temperature is controlled to a degree cesses combine to remove carbon dioxide which by the water temperature to between 10 and accumulates as a result of respiration of grains 16.C and micro-organisms associated with them vigo There are many variations in steeping practice rous aeration immediately after discharging the including steeping in running water(Bavarian barley into the steep tank also serves to raise and the ' flushing regime in which immersions dust, chaff and light grains to the surface for are frequent but cover the grains for only a few removal. These are accumulated and sold for minutes. Modern steep tanks are filled with barley to a depth of 1.2 m. This increases to Aeration, damping and temperature have to 1. 8 m when the grain is swollen. The uniform be carefully controlled in order that germina- depth of flat-bottomed tanks provides for more tion occurs at the required rate and to the uniform aeration and coz removal than in conical required degree, For poorly modified traditional bottomed vessels pale lager, European 2-rowed barley needs Following steeping, the grain is transferred to steeping to 41-43%m/c, while for a pale-ale malt germinating vessels. This may be by ' wet-casting 4345%is appropriate For a high nitrogen barley whereby it is pumped in water suspension or
1686 1886 Germinate Kiln IO-35d 4-6d Steep 6-8d - 3-7d 8-28 d 3-6 d -
222 TECHNOLOGY OF CEREALS Turner boom Exhaust oir Drive/ Rail Rotating spirals F Plenum FIG 9.4 Diagrammatic section through a circular germination vessel. Source: Gibson 1989. Reproduced by courtesy of Aberdeen University Press, Ltd dry-casting after draining. If additives are to be Temperature and humidity are controlled by added it is convenient to do so during transfer. humidifying and refrigerating or warming the air These may include gibberellic acid and potassium passing through. Air volumes passing are of bromate.The former hastens malting, especially the order of 0.15-0.2 m/sec/tonne of barley if bruised grains are present, and potassium Temperatures of 15-19oC are common. micro- bromate reduces respiration and hence the rise processor control of conditions is commonplace in temperature that accompanies it It is also said ( Gibson, 1989) to inhibit proteolysis and control colour develop The danger of microbial contamination is high malting loss by reducing root growth s reducing as air passing with high humidity is ideal for ment in the malting grain, as well as growth of bacteria and fungi and nutrients are plentiful. As well as introducing health hazards Germination microbes gain preferential access to oxygen, thus inhibiting the germination and modification of Early mechanical maltings had rectangular the barley for which the system is designed. In germination vessels, but this was followed in due some plants the germination and kilning are but is limited to about 100 tonnes and has a high advantage of the microbes being killed by ls course by the drum, which provided ideal control carried out in a single vessel and this has the unit cost. Later the circular germination vessel heat of kilning. Cleaning the dry residue is easier was developed and capacities rose to 500 tonnes. than complete removal of the wet remains of Features common to all mechanical maltings are germinating grai an automatic means of turning the germinating grains and a means of aeration. Turning may be performed by rotating spirals that are moved Kilning slowly through the grain mass. In the rectangular The objectives of kilning are to arrest botanical vessels they move end to end on booms while in growth and internal modification, to reduce he circular type vertical turners rotate on a boom moisture for grain storage, and to develop colour or alternatively they remain stationary while the and favour compounds in the malt. Kilning is grain is transported past on a rotating floor. It is responsible for 90% of the energy consumption usual for aeration to be provided by air passing of the entire malting process unless a heat recovery up(usually) or down, from or into a plenum' is in use, when the proportion may be reduced to beneath the floor which is constructed of slotted 75--80% steel plates. The layout of a circular germination For kilning, ambient air is heated by the pre vessel is shown in Fig. 9.4 ferred fuel and passed under positive or negative
222 TECHNOLOGY OF CEREALS Drive / Ra i I Rotating spirals I Perforated Humidificatibn system floor (plus refrigeration if required) FIG 9.4 Diagrammatic section through a circular germination vessel. Source: Gibson 1989. Reproduced by courtesy of Aberdeen University Press, Ltd. 'dry-casting' after draining. If additives are to be added it is convenient to do so during transfer. These may include gibberellic acid and potassium bromate. The former hastens malting, especially if bruised grains are present, and potassium bromate reduces respiration and hence the rise in temperature that accompanies it. It is also said to inhibit proteolysis and control colour development in the malting grain, as well as reducing malting loss by reducing root growth. Germination Early mechanical maltings had rectangular germination vessels, but this was followed in due course by the drum, which provided ideal control but is limited to about 100 tonnes and has a high unit cost. Later the circular germination vessel was developed and capacities rose to 500 tonnes. Features common to all mechanical maltings are an automatic means of turning the germinating grains and a means of aeration. Turning may be performed by rotating spirals that are moved slowly through the grain mass. In the rectangular The objectives of kilning are to arrest botanical vessels they move end to end on booms while in growth and internal modification, to reduce the circular type vertical turners rotate on a boom moisture for grain storage, and to develop colour or alternatively they remain stationary while the and flavour compounds in the malt. Kilning is grain is transported past on a rotating floor. It is responsible for 90% of the energy consumption usual for aeration to be provided by air passing of the entire malting process unless a heat recovery up (usually) or down, from or into a 'plenum' is in use, when the proportion may be reduced to beneath the floor which is constructed of slotted 75-80%. steel plates. The layout of a circular germination For kilning, ambient air is heated by the prevessel is shown in Fig. 9.4. ferred fuel and passed under positive or negative Temperature and humidity are controlled by humidifying and refrigerating or warming the air passing through. Air volumes passing are of the order of 0.15-0.2 m3/sec/tonne of barley. Temperatures of 15"-19"C are common. Microprocessor control of conditions is commonplace JGibSnn, 1989). The danger of microbial contamination is high as air passing with high humidity is ideal for growth of bacteria and fungi and nutrients are plentiful. As well as introducing health hazards microbes gain preferential access to oxygen, thus inhibiting the germination and modification of the barley for which the system is designed. In some plants the germination and kilning are carried out in a single vessel and this has the advantage of the microbes being killed by the heat of kilning. Cleaning the dry residue is easier than complete removal of the wet remains of germinating grain. Kilning
MALTING, BREWING AND DISTILLING 223 pressure through the bed of grains. a plenum compounds is favoured by the combination of high below the floor is provided as in the earlier stages temperatures with wet malts (Briggs, 1978). Small of the malting process. A recent innovation in contributions to malt colour may be caramelized kiln design is the double-deck version. In this sugars and oxidized polyphenols and other system green malt is loaded on to the upper deck contributions come from aldehydes, ketones, and transferred to the lower deck after partial alcohols, amines and miscellaneous other sub drying. Warmed air is passed first through the stances including sulphur-containing compounds drier, lower bed before passing, unsaturated, to and nitrogenous bases. These are discussed in the upper bed where it is capable of removing detail by briggs(1978)and Palmer(1989). Peated moisture from the green malt distillery malts, for Scotch whisky manufacture The depth of green malt in a modern kiln is take up many substances from the peat smoke 0.. 2 m. For maximum efficiency the bed and contain various alkanes, alkenes, aldehydes should be level and uniformly compacted, a alcohols, esters, fatty acids, aromatic and phenolic condition readily achieved by the automatic or substances, including phenol and cresols the use semi-automatic loading machinery available today. of peat as a fuel for kilning originated in cottage Conditions for kilning are determined by the industry enterprises in the crofts of the Scottish ature of the end product required. Variables Highlands where peat was the only available fuel include the extract potential, moisture content, for domestic heating In lowland distilleries peat colour and enzyme activity. Curing temperatures heating has now been superseded by a succession range from 80 to 100C. In modern kilns the of fuels, currently oil or gas. Direct heating by maltster is assisted in monitoring and controlling these fuels is not permitted as they can lead to conditions by control programmes incorporated introduction of nitrosamines into the product into automated systems Peatiness is a valued character of malt whiskies Enzymes survive high curing temperatures however and direct heating with peat is the rule best if the malt is relatively dry, but under these in their production conditions colour and flavour development are For production of brewing malts a major minimal. They develop mainly as a result of economic consideration is brewer's extract. This Maillard reactions occurring between the reducing is measured as hot water extract available as the roups of sugars and amino groups, mainly of soluble nitrogen required to maintain fermenta amino acids. Development of additional flavour tion and beer quality properties. An analysis of Table 9.1 Analytical Characteristics of Barley and Ale Malt Moisture content %o oluble nitrogen o nitrogen Minerals %o approx 2 olour EBC under 1.5 Hot water extract(1/kg) Dextrinizing unit(alpha-amylase) Endo B-glucanase(IRV units) under 100 of aberdeen unit
MALTING, BREWING AND DISTILLING 223 pressure through the bed of grains. A plenum compounds is favoured by the combination of high below the floor is provided as in the earlier stages temperatures with wet malts (Briggs, 1978). Small of the malting process. A recent innovation in contributions to malt colour may be caramelized kiln design is the double-deck version. In this sugars and oxidized polyphenols and other system green malt is loaded on to the upper deck contributions come from aldehydes, ketones, and transferred to the lower deck after partial alcohols, amines and miscellaneous other subdrying. Warmed air is passed first through the stances including sulphur-containing compounds drier, lower bed before passing, unsaturated, to and nitrogenous bases. These are discussed in the upper bed where it is capable of removing detail by Briggs (1978) and Palmer (1989). Peated moisture from the green malt. distillery malts, for Scotch whisky manufacture, The depth of green malt in a modern kiln is take up many substances from the peat smoke 0.85-1.2 m. For maximum efficiency the bed and contain various alkanes, alkenes, aldehydes, should be level and uniformly compacted, a alcohols, esters, fatty acids, aromatic and phenolic condition readily achieved by the automatic or substances, including phenol and cresols. The use semi-automatic loading machinery available today. of peat as a fuel for kilning originated in cottage Conditions for kilning are determined by the industry enterprises in the crofts of the Scottish nature of the end product required. Variables Highlands where peat was the only available fuel include the extract potential, moisture content, for domestic heating. In lowland distilleries peat colour and enzyme activity. Curing temperatures heating has now been superseded by a succession range from 80" to 100°C. In modern kilns the of fuels, currently oil or gas. Direct heating by maltster is assisted in monitoring and controlling these fuels is not permitted as they can lead to conditions by control programmes incorporated introduction of nitrosamines into the product. into automated systems. Peatiness is a valued character of malt whiskies Enzymes survive high curing temperatures however and direct heating with peat is the rule best if the malt is relatively dry, but under these in their production. conditions colour and flavour development are For production of brewing malts a major minimal. They develop mainly as a result of economic consideration is brewer's extract. This Maillard reactions occurring between the reducing is measured as hot water extract available as the groups of sugars and amino groups, mainly of soluble nitrogen required to maintain fermentaamino acids. Development of additional flavour tion and beer quality properties. An analysis of TABLE 9.1 Analytical Characteristics of Barley and Ale Malt Constituent Barley Ale malt Moisture content YO 15 4 Starch YO 65 60 0-D-glucan YO 3.5 0.5 Pentosans % 9.0 10.0 Lipid YO 3.5 3.1 Total nitrogen % 1.6 1.5 Total soluble nitrogen Oh 0.3 0.7 a-Amino nitrogen Oh 0.05 0.17 Sucrose o/o 1.0 2.0 Minerals Oh approx 2 approx 2 Colour "EBC under 1.5 5.0 Hot water extract (1"ikg) 150 305 Diastatic power (beta-amylase "L) 20 65 Dextrinizing unit (alpha-amylase) under 5 30 Endo P-glucanase (IRV units) under 100 500 Source: Palmer, 1989. Reproduced by courtesy of Aberdeen University Press
224 TECHNOLOGY OF CEREALS TABLE 9.2 fuel,25-30%; Characteristics of a selection of malts electricity, 15-20%: Malt type Extract Moisture Colour Final kiln wages,15-20%; (EBC) temperature repairs/maintenance, 10-20%; miscellaneous. 15-25% 44742 As with many wet processes of cereals the costs Crystal malt 100-30 00550 of water treatment before discharge are increasing as standards become more stringent. The Bio- Roasted malt logical Oxygen Demand (BOD)load from a Roasted barley 27 51000-1550230 30,000 tonnes per annum maltings is equivalent Of all the malts listed only ale and lager malts contain to a population of about 9000 people(Gibson enzymes 1989) Source: Palmer, 1989. Reproduced by courtesy of Aberdeen ale malt compared with that of barley is shown Malt pr。 duction in Table 9. 1. The characteristics of brewers malts Palmer(1989)reports that about 17 million of various types are given in Table 9.2 tonnes of barley are used annually, world-wide, to duce 12 million tonnes of malt and about 970 Ageing million hectolitres of beer. This represents about 10%of world barley production 6 Before use it is necessary to mill kilned malts it is customary to delay this process to permit By-products of malting moisture equilibration. Kilning effects drying rapidly and in individual grains a gradient exists The main by-product of malting is called 'malt from a higher inner to a lower outer(husk) sprouts. They are separated from kilned malt by moisture content. Differences in a malt of 3-5% passing the malt through revolving reels or a wire m.c.may be 4 or 5%(1-3% outside to 5-8% screen. They account for 3-5% of product and inside). Unless equilibrated, agglomeration of the they are incorporated into stock feeds. Typically damper parts can reduce extraction potential and they contain 25-34% N-compounds, 1. 6-2.2 undue fragmentation of dry husk leads to haze fat, 8.6-11.9% fibre, 6.0-7 1% ash and 35-44% in the extract(Pyler and Thomas, 1986). Storage N-free extract(Pomeranz, 1987 for up to 3 months may be used. As specifications become increasingly sensitive to moisture content Non-brewing uses of malt the conditions of storage progressively include humidity control(Palmer, 1989 Milled barley malt is used as a high diastatic supplement for bread flours which are low in Energy consumption and other costs natural diastatic activity, and as a favour supple ment in malt loaves. Malt extracts and syrups are The Energy Technology Support Unit published produced by concentrating worts by evaporation a report in 1985 of a survey of United Kingdom Malt is also used in the manufacture of malt maltsters. Specific energy consumed per tonne of vinegar malt ranged from 2. 48 to 6.81 G], with a weighted and electricity. Power costs comprised grain Adjuncts handling and process requirements Although malt derived from barley is generally Estimates of proportionate costs, including considered to be the superior feedstock for brewing these values are given by gibson(1989)as and distilling, it is common practice in many
224 TECHNOLOGY OF CEREALS TABLE 9.2 fuel, 25-30%; Characteristics of a Selection of Malts electricity, 15-20%; Malt type Extract Moisture Colour Final kilning wages, 15-20%; (“/kg) (Oh) (“EBC) temperature repairs/maintenance, 10-20%; (“C) miscellaneous, 15-25%. Ale* 305 4.0 5.0 100 As with many wet processes of cereals the costs Lager* 300 4.5 2.0 80 Cara pils 265 7.0 25-35 75 Crystal malt 268 4.0 100-300 75 of water treatment before discharge are increasing 70-80 150 as standards become more stringent. The Bio- Amber malt 280 2.0 Chocolate malt 268 1.5 900-1200 220 Roasted malt 265 1.5 1250-1500 230 logical Oxygen Demand (BOD) load from a Roasted barley 270 1.5 1000-1550 230 30,000 tonnes per annum maltings is equivalent * Of all the malts listed only ale and lager malts contain to a PoPulation of about 9000 People (Gibson, enzymes. 1989). Source: Palmer, 1989. Reproduced by courtesy of Aberdeen University Press. ale malt compared with that of barley is shown in Table 9.1. The characteristics of brewers malts of various types are given in Table 9.2. Ageing Before use it is necessary to mill kilned malts but it is customary to delay this process to permit moisture equilibration. Kilning effects drying rapidly and in individual grains a gradient exists from a higher inner to a lower outer (husk) moisture content. Differences in a malt of 3-5% m.c. may be 4 or 5% (1-3% outside to 5-8% inside). Unless equilibrated, agglomeration of the damper parts can reduce extraction potential and undue fragmentation of dry husk leads to haze in the extract (Pyler and Thomas, 1986). Storage for up to 3 months may be used. As specifications become increasingly sensitive to moisture content the conditions of storage progressively include humidity control (Palmer, 1989). Energy consumption and other costs The Energy Technology Support Unit published a report in 1985 of a survey of United Kingdom maltsters. Specific energy consumed per tonne of malt ranged from 2.48 to 6.81 GJ, with a weighted average of 3.74 GJ. Quoted costs included fuel and electricity. Power costs comprised grain handling and process requirements. Estimates of proportionate costs, including these values are given by Gibson (1989) as: Malt production Palmer (1989) reports that about 17 million tonnes of barley are used annually, world-wide , to produce 12 million tonnes of malt and about 970 million hectolitres of beer. This represents about 10% of world barley production. By-products of malting The main by-product of malting is called ‘malt sprouts’. They are separated from kilned malt by passing the malt through revolving reels or a wire screen. They account for 3-5% of product and they are incorporated into stock feeds. Typically they contain 25-34% N-compounds, 1.6-2.2% fat, 8.6-11.9% fibre, 6.0-7.1% ash and 3544% N-free extract (Pomeranz, 1987). Non-brewing uses of malt Milled barley malt is used as a high diastatic supplement for bread flours which are low in natural diastatic activity, and as a flavour supplement in malt loaves. Malt extracts and syrups are produced by concentrating worts by evaporation. Malt is also used in the manufacture of malt vinegar. Adjuncts Although malt derived from barley is generally considered to be the superior feedstock for brewing and distilling, it is common practice in many
MALTING, BREWING AND DISTILLING 225 countries to supplement malt with alternative Solubility of proteins is decreased and some sources of soluble sugars or starch capable of flavour may be introduced through their use if conversion to soluble sugars adequate treatment temperatures are used in The principal adjuncts, as such non-malt addi- processing them. Heat treated cereals can be tives are described, are rice, maize grits and added to malt before grinding; their extract yield cereal starches. Adjuncts contribute virtually no is increased if they are precooked before use enzymes to the wort so hydrolysis of their starch Investigations with extruded cereals gave poorer depends upon those enzymes present in the malt extract yields than traditional adjuncts( briggs et to which they are added. Use of adjuncts is al., 1986) common practice in the U.S. A. and this is one Sorghum was used more in the U.S. A. when reason for the preference there for the higher maize was in short supply during World War II, enzyme-containing six-row barleys. and it is used to a significant extent in mexico In the U.S. A. 38% of total materials used in today It has a lower fat and protein content and brewing(excluding hops) was reported to be a higher extract than maize and it thus has some contributed by adjuncts(Pyler and Thomas, merit 1986). Of this 46.5% was corn grits, 31. 4% rice Barley and wheat starch have a lower gelatinize- and 0.7% barley. Sugars and syrups accounted tion temperature than maize and rice starch for the remaining 21.4% hence digestion may occur at mash temperatures The form in which rice is added is the broken It is usual, however, to premash maize, rice grains that do not meet the requirements of milled wheat and barley etc. by cooking with a small rice. As the quality of the products of fermenta- amount of malt before adding them to the mash tion is little affected by the nature of the adjunct, Addition of barley provides a means of reducing the choice is usually made purely on economic the nitrogen content of the wort. It is disallowed grounds. This is not related only to the price per however, by the german beer law for the produc- tonne of the adjunct because the yield of extract tion of bottom-fermented beers in which only is not the same from each. Tests for extraction barley-malt, hops, yeast and water are allowed carried out in the laboratory generally give higher Top-fermented beers follow the same regulations values than those obtained in the commercial but wheat malt may be included(Narziss, 1984) practice. Pyler and Thomas quote 78% for rice For special beers, pure beet-cane-invert-sugar is and 74% for maize grits in the brewhouse and allowed 87-94%and 85-90% respectively in the laboratory (American Soc of Brewing Chemists procedure) Maize grits also contain higher levels of fat and Malts from other cereals protein than rice, both of which constituents are In Africa many malts are produced from considered undesirable sorghum and, to a lesser extent, from millets. In Other adjuncts used are: refined maize starch, the Republic of South Africa commercial produc- wheat and wheat starch, rye, oats, potatoes, tion is of the order of 1000 m litres annually tapioca, triticale, heat treated (torrefied or micro- and home brewing may be of the same order nized)cereals, cereal flakes. Micronization invol- (Novellie, 1977) ves heating grains to nearly 200oc by infrared Wheat malt is used in the production of wheat radiation while torrefication achieves similar malt beers. Examples of these and their character temperatures by use of hot air(Palmer, 1989). istics are shown in Table 9.3 In grains treated by either method the vapourized Malts made on a pilot scale from U. K.grown water produced disrupts the physical structure triticales were evaluated by Blanchflower and of the endosperm, denaturing protein and par- Briggs(1991). Viscosities of resulting worts were tially gelatinizing starch. Digestibility is thus high due to pentosans, particulaly arabinose and increased and these products are also used in xylose. Hot water extracts after five days germina- cattle feeds and whole-grain baked products. tion were 302-324 litre degree per kg. Filtered
MALTING, BREWING AND DISTILLING 225 countries to supplement malt with alternative Solubility of proteins is decreased and some sources of soluble sugars or starch capable of flavour may be introduced through their use if conversion to soluble sugars. adequate treatment temperatures are used in The principal adjuncts, as such non-malt addi- processing them. Heat treated cereals can be tives are described, are rice, maize grits and added to malt before grinding; their extract yield cereal starches. Adjuncts contribute virtually no is increased if they are precooked before use. enzymes to the wort so hydrolysis of their starch Investigations with extruded cereals gave poorer depends upon those enzymes present in the malt extract yields than traditional adjuncts (Briggs et to which they are added. Use of adjuncts is al., 1986). common practice in the U.S.A. and this is one Sorghum was used more in the U.S.A. when reason for the preference there for the higher maize was in short supply during World War 11, enzyme-containing six-row barleys. and it is used to a significant extent in Mexico In the U.S.A. 38% of total materials used in today. It has a lower fat and protein content and brewing (excluding hops) was reported to be a higher extract than maize and it thus has some contributed by adjuncts (Pyler and Thomas, merit. 1986). Of this 46.5% was corn grits, 31.4% rice Barley and wheat starch have a lower gelatinizaand 0.7% barley. Sugars and syrups accounted tion temperature than maize and rice starch, for the remaining 21.4%. hence digestion may occur at mash temperatures. The form in which rice is added is the broken It is usual, however, to premash maize, rice, grains that do not meet the requirements of milled wheat and barley etc. by cooking with a small rice. As the quality of the products of fermenta- amount of malt before adding them to the mash. tion is little affected by the nature of the adjunct, Addition of barley provides a means of reducing the choice is usually made purely on economic the nitrogen content of the wort. It is disallowed, grounds. This is not related only to the price per however, by the German beer law for the productonne of the adjunct because the yield of extract tion of bottom-fermented beers in which only is not the same from each. Tests for extraction barley-malt, hops, yeast and water are allowed. carried out in the laboratory generally give higher Top-fermented beers follow the same regulations values than those obtained in the commercial but wheat malt may be included (Narziss, 1984). practice. Pyler and Thomas quote 78% for rice For special beers, pure beet-cane-invert-sugar is and 74% for maize grits in the brewhouse and allowed. 87-94% and 85-90% respectively in the laboratory (American SOC of Brewing Chemists procedure). Malts from ot,er cereals Maize grits also contain higher levels of fat and protein than rice, both of which constituents are In Africa many malts are produced from considered undesirable. sorghum and, to a lesser extent, from millets. In Other adjuncts used are: refined maize starch, the Republic of South Africa commercial producwheat and wheat starch, rye, oats, potatoes, tion is of the order of 1000 m litres annually tapioca, triticale, heat treated (torrefied or micro- and home brewing may be of the same order nizec!) cereals, cereal flakes. Micronization invol- (Novellie , 1977). ves heating grains to nearly 200°C by infrared Wheat malt is used in the production of wheatradiation while torrefication achieves similar malt beers. Examples of these and their charactertemperatures by use of hot air (Palmer, 1989). istics are shown in Table 9.3. In grains treated by either method the vapourized Malts made on a pilot scale from U.K.-grown water produced disrupts the physical structure triticales were evaluated by Blanchflower and of the endosperm, denaturing protein and par- Briggs (1991). Viscosities of resulting worts were tially gelatinizing starch. Digestibility is thus high due to pentosans, particulaly arabinose and increased and these products are also used in xylose. Hot water extracts after five days germinacattle feeds and whole-grain baked products. tion were 302-324 litre degree per kg. Filtered
TECHNOLOGY OF CEREALS Beers Made from Wheat-Malt and their Characteristics T Character Origin Alcohol Flavour features Weizenbier Lager/Ale Bavar Full bodied, low hops Hoegards wit Full bodied bitter ource: Pomeranz, 1987, citing information from A. A. Leach of the Brewers' Society, U.K worts were turbid owing to proteinaceous materials. sugars. Hops are also added at this stage. As well Malt yields were between 87 and 90% as adding flavour they serve to sterilize the wort and participate in reactions that precipitate proteins Brewing responsible for haze when the wort is boiled Boiling may continue for 1.5-2h during boiling Beer the humulone or a-acids are isomerized to the bitter iso-a-acids. As the yield of bitter iso-a-acids Wort production extracted from the hops by boiling may be as lor as 30%, a modern procedure is to replace part of the The starting material for brewing may be pure raw hops by a pre- isomerized hop extract, which is (usually barley) malt, or a mixture of malt and added to the beer after fermentation. It is com- djunct. If solid adjuncts are to be included they mon for half the hops to be added at the beginning may be milled with the malt. The coarsely ground of the period and half at the end. The wort is material, on hydration with brewing liquor, cooled (to 15.5% C for British ales or to 4-7C produces a brewers'extract from the solubles, for pilsners and lagers), filtered and transferred to and a filter bed from the husk. The quality of pitching tanks where it is ' pitched with yeast (i.e the filter bed depends on the size of the husk yeast is added). Air is also passed into the hopped particles; they should not be too fine. The process wort to provide a supply of oxygen for the yeast is known as mashing and it is carried out in vessels which rapidly becomes active(added oxygen called mash tuns removes the lag phase that would otherwise occur) After an initial rest for hydration to be completed the temperature is raised above the gelatinization fermentation much more susceptible to digestion by amylase Yeasts vary in their behaviour during ferment enzymes, to produce soluble sugars. The process tion, some strains tend to flocculate, as a result of conversion, begun during malting, thus con- they trap CO2 and rise to the top Others, which tinues during this phase. do not flocculate. sink to the bottom. Several It is now necessary to separate the liquid wort styles of lagers are produced by bottom fermenta- from the solid remains of the malt and adjuncts, tion while many types of ales and stouts are and this is done by a process called lautering,. produced using top fermentation. Examples are The spent grains act as a filter bed when the given in table 9.4 mixture is transferred to a lauter tub, which has An efficient type of fermenter is a deep a perforated bottom. The spent grains accumulate cylindrical vessel with a conical base into which this and allow the liquid to pass through while the yeast eventually sediments. In such vessels retaining the fine solids. The sugary liquid is the liberation of carbon dioxide provides efficient known as the 'sweet wort' it is supplemented agitation, allowing cycles of filling, fermentation, with syrups at this stage if such adjuncts are to emptying and cleaning to be accomplished in 5 be used to increase the amount of fermentable days at 12 C or 2.5 days at 18C
226 TECHNOLOGY OF CEREALS TABLE 9.3 Beers Made From Wheat-Malt and their Characteristics Type Character Origin Alcohol Flavour features (Yo v/v) Weizenbeer LageriAle Bavaria 5-6 Full bodied, low hops Weisse Lager Berlin 2.5-3 Light flavoured Gueuze-Lambic Acid ale Brussels 5+ Acidic Hoegards wit Ale East of Brussels 5 Full bodied, bitter Source: Pomeranz, 1987, citing information from A. A. Leach of the Brewers' Society, U.K. worts were turbid owing to proteinaceous materials. Malt yields were between 87 and 90% sugars. Hops are also added at this stage. As well as adding flavour they serve to sterilize the wort and participate in reactions that precipitate proteins responsible for haze when the wort is boiled. Boiling may continue for 1.5-2 h. During boiling the humulones, or a-acids are isomerized to the bitter iso-a-acids. As the yield of bitter iso-a-acids Beer extracted from the hops by boiling may be as low Wort production as 30%, a modern procedure is to replace part of the The starting material for brewing may be pure raw hops by a pre-isomerized hop extract, which is (usually barley) malt, or a mixture of malt and added to the beer after fermentation. It is comadjunct. If solid adjuncts are to be included they mon for half the hops to be added at the beginning may be milled with the malt. The coarsely ground of the period and half at the end. The wort is material, on hydration with brewing liquor, cooled (to 15.5"-18"C for British ales or to 4"-7"C produces a brewers' extract from the solubles, for pilsners and lagers), filtered and transferred to and a filter bed from the husk. The quality of pitching tanks where it is 'pitched' with yeast (Le. the filter bed depends on the size of the husk yeast is added). Air is also passed into the hopped particles; they should not be too fine. The process wort to provide a supply of oxygen for the yeast is known as mashing and it is carried out in vessels which rapidly becomes active (added oxygen called mash tuns. removes the lag phase that would otherwise occur). After an initial rest for hydration to be completed Fermentation the temperature is raised above the gelatinization temperature of the starch. This renders the starch much more susceptible to digestion by amylase Yeasts vary in their behaviour during fermentaenzymes, to produce soluble sugars. The process tion, some strains tend to flocculate, as a result of conversion, begun during malting, thus con- they trap C02 and rise to the top. Others, which tinues during this phase. do not flocculate, sink to the bottom. Several It is now necessary to separate the liquid wort styles of lagers are produced by bottom fermentafrom the solid remains of the malt and adjuncts, tion while many types of ales and stouts are and this is done by a process called 'lautering'. produced using top fermentation. Examples are The spent grains act as a filter bed when the given in Table 9.4. mixture is transferred to a lauter tub, which has An efficient type of fermenter is a deep a perforated bottom. The spent grains accumulate cylindrical vessel with a conical base into which on this and allow the liquid to pass through while the yeast eventually sediments. In such vessels retaining the fine solids. The sugary liquid is the liberation of carbon dioxide provides efficient known as the 'sweet wort'; it is supplemented agitation, allowing cycles of filling, fermentation, with syrups at this stage if such adjuncts are to emptying and cleaning to be accomplished in 5 be used to increase the amount of fermentable days at 12°C or 2.5 days at 18°C. Brewing
MALTING, BREWING AND DISTILLING 227 TABLE 9. 4 Classical Beers of the World Classified According to Yeast Types Used in their Brewing Character Origin Alcohol Flavour features Malty, dry Lager/ Bavaria Light-bodied, light y Dusseldorf U.K. U.S. Can. Aus 2.5-5 Strong/old ale 68.4 ch, full, estery Stout(Mackeson weet, mild, lact. sour Porte London U. s, Can V. malty, Source: Pomeranz, 1987, using information from A. A. Leach of the Brewers'Society, U. K Fermentation continues for 7-9 days, producing Two thirds of the world's sake production takes ethanol and carbon dioxide. The gas may be place in Japan beer is bottled or casked. The reaction is the An essential difference between beer and sake collected for sale or for adding back whe exo- is that for sake the natural enzymes present in thermic and the temperature would rise unduly the grain are not employed in solubilizing the if not controlled. The yeast increases during starch, indeed they are expressly inactivated fermentation through asexual reproduction and before the saccharifying phase of sake brewing in consequence this constitutes an additional Enzymes are of course needed and these are by-product. During fermentation the ph drops derived from the fungus Aspergillus oryzae, they from 5.2 to 4.2 as a result of acetic and lactic acids synthesized by bacteria inevitably intro- are provided from a culture of that mould know oJl contains duced with the yeast. The green (jargon for including the alpha-and beta-amylases present young) beer is run off from the aggregated yeast cells and cooled to precipitate further haze in malt and an additional amylolytic en amyloglucosidase(see Fig. 3.12, p. 67), capable producing proteins and aged before filtering and of hydrolyzing starch polymers to glucose. The weeks( lagering before packaging into bottles balance of amylase to protease is inflenced by or kegs. An alternative treatment is for the green amylase production. The process is summarized beer to be run into casks, primed with sugars to permit secondary fermentation and with in Fig. 9.6 isinglass for sale as 'naturally conditioned beer; a The yeast used in sake production is a specialized product peculiar to the British Isles. ( TI train of Saccharomyces cereuisiae process is summarized schematically in Fig. 9.5. Unlike the husk of barley in the malting process, that of rice is not valued for its filtration Sake properties, nor indeed any other qualities. It is egree Sake production was reported to be 15 x 105 of polishing is severe; removing 25-30% of kl in 1985 the brown rice weight, in extreme cases 50%
MALTING, BREWING AND DISTILLING 227 TABLE 9.4 Classical Beers of the World Classified According to Yeast Types Used in their Brewing Type Character Origin Alcohol Flavour (Oh viv) features Bottom-fermented Munchener Lagedale Munich 4-4.8 Malty, dry, mod. bitter Vienna (Marzen) Lager Vienna 5.5 Full-bodied, hoppy Pilsner Lager Pilsen 4.5-5 Full-bodied, hoppy Dortmunder Lager Dortmund 5+ Light hops, dry, estery Bock Lager Bav., U.S., Can 6 Full-bodied Dopplebock Lageriale Bavaria 7-13 Full-bod., estery, winey Light beers Lager U.S. 4.2-5 Light-bodied, light hops Saissons Ale Belgium, France 5 Light, hoppy, estery Trappiste Ale Bel. Dutch Abbeys 68 Full-bodied, estery Kolsch Ale Cologne 4.4 Light, estery, hoppy Alt Ale Dusseldorf 4 Estery, bitter Provisie Ale Belgium 6 Sweet, ale-like Ales Ale U.K., U.S., Can., Aus 2.5-5 Hoppy, estery, bitter Strong/old ale Ale U.K. 68.4 Estery, heavy, hoppy Barley wine Ale/wine U.K. 8-12 Rich, full, estery Stout (Bitter) stout Ireland 4-7 Dry, bitter Stout (Mackeson) stout U.K. 3.7-4 Sweet, mild. lact. sour Porter stout London, U.S., Can 5-7.5 V. malty, rich Source: Pomeranz, 1987, using information from A. A. Leach of the Brewers’ Society, U.K. Fermentation continues for 7-9 days, producing ethanol and carbon dioxide. The gas may be collected for sale or for adding back when the beer is bottled or casked. The reaction is exothermic and the temperature would rise unduly if not controlled- The Yeast increases during fermentation through asexual reproduction and in consequence this constitutes an additional by-product- During fermentation the PH drops from 5.2 to 4.2 as a result of acetic and lactic acids synthesized by bacteria inevitably introTop-fermented Two thirds of the world’s sake production takes place in Japan. An essential difference between beer and sake is that for sake the natural enzymes present in the grain are not employed in solubilizing the starch, indeed they are expressly inactivated before the saccharifying phase of sake brewing. E~~~~~~ are of cOurSe needed and these are derived from the fungus Aspergillus 0 yzae, they are provided from a culture of that mould known as ‘koji7. Koji contains 50 different enzymes duced with the yeast. The green (jargon for young) beer is run Off from the aggregated yeast including the alpha- and bela-amylases present in malt and an additional amylolytic enzyme cells and cooled to precipitate further hazeproducing proteins and aged before filtering and carbonating. Lagers are stored at 0°C for some weeks (‘lagering’) before packaging into bottles amyloglucosidase (see Fig. 3.12, p. 67), capable of hydrolyzing starch polymers to glucose. The balance of amylase to protease is inflenced by or kegs. An alternative treatment is for the green beer to be run into casks, primed with sugars to cultural conditions, figher temperatures favouring amylase Production. The process is summarized permit secondary fermentation and ‘fined’ with isinglass for sale as ‘naturally conditioned’ beer; a product peculiar to the British Isles. (The brewing process is summarized schematically in Fig. 9.5.) Sake in Fig* 9*6. The Yeast used in sake Production is a specialized strain of Saccharomyces ce~visiae. Unlike the husk of barley in the malting process, that of rice is not valued for its filtration properties, nor indeed any other qualities. It is removed by milling (see Ch. 6). The degree Sake uroduction was reuorted to be 15 x lo5 of polishing is severe; removing 25-30% of
