Malt

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Malt is made from germinated cereals such as barley, wheat, oats, rye, sorghum, millet, rice, maize (corn), and pseudo-cereals such as buckwheat and quinoa. However, barley remains the main cereal used for the production of beverages such as standard beer, craft beer, and malt whiskey.[1]

Special malt is the term used to describe malt which is used to contribute specific color or flavor attributes to beer. Malts used primarily for extract like pale ale and pilsner are termed white malts (UK) or base malts (US).[2]

When selecting a malt, it is wise to maintain a healthy cynicism claims made about the properties of each product and what they will do to your beer, because they are all variations on a theme so are not likely to differ markedly to a competitor's analogue. The information provided is primarily there to sell you the grain.[2]

Munich and Vienna malts are in effect darker versions of white (base) malts. It is argued by some that they are not actually special malts as their final processing is not carried out in a roasting drum. They contribute a greater amount of color and flavor but retain diastatic power. Their method of production encourages the formation of highly colored/flavored compounds through non-enzymatic browning. Munich comes in dark and light variants ranging from 15 to 35 EBC. Because of the way they are produced they have high potential for picking up color in the kettle by activation of color precursors. They are produced by germinating high nitrogen barleys until they are well modified but not over-modified and then kilning at elevated moisture levels and slightly higher kilning temperature. The result is a more richly aromatic grain than pale ale malt. Vienna malt is the lighter cousin of Munich made with well modified rather than highly modified barley and is kilned at a lower temperature.[2]

Cara is an abbreviation of caramel. This is a bit misleading because caramelization isn’t responsible for the flavor and color properties of any malt, let alone cara malt, although arguably they do have caramel-like properties. Cara malts are produced by allowing the endosperm of the malt to convert extensively to produce reducing sugars and amino acids and then kilning/roasting moist, at 150�180 °C to facilitate non-enzymatic browning. A range of cara malts are available from various suppliers which give different characteristics but all variations on the sweet, rich, malty and full-bodied theme. Because the endosperm has been heated at elevated moisture levels the enzymes of conversion are denatured and cara malts will not contribute any enzymatic power to the mash.[2]

Crystal malts take the caramelization of the endosperm to the next level. The term crystal refers to the crystalline appearance of the endosperm of the malt. Crystal malts are produced from high nitrogen barleys which are then over-modified and roasted at very high moisture levels. The result is a stewing of the grain and extensive production of colored and flavored compounds through non-enzymatic browning. When the liquified endosperm is dried it sets into a glasslike (crystalline � hence the name) mass. As with cara malts, crystal malts range in color from golden to deep red. There is some crossover between high color cara malts and low color crystals. Crystal malt is thought to contribute to head retention and aid the action of finings. High percentages of crystal malts in grists (grain bills) can give rise to problems with sterile cartridge filters.[2]

Black malts are prepared by roasting a standard malt to high temperature. The high degree of heating causing burning and burnt flavor. Dehusked malts are sold as less bitter and astringent than their standard counterparts. Although it sits comfortably within this style of grain, roasted barley isn’t actually a malt as the grains are not germinated before roasting.[2]

There are breeding programs in all the main barley growing areas of the world which develop new varieties through breeding and selection and unless you start brewing with a heritage variety like Maris Otter or Golden Promise the chances are after a few years the variety you buy will change. This is a good justification for using these premium price varieties. The impact of variety on flavor is however quite a contentious issue amongst brewers. As yet there is little scientific proof that valued/heritage varieties do confer superior flavor and even less showing they provide better brewhouse performance. Most experienced brewers would attest to the fact that the malting company making the malt certainly does have an impact on the quality of the flavor from the malt. One aspect which should not be forgotten in any discussion about the flavor from a particular variety, is that unless the grain processes consistently well in the brewhouse and provides the necessary nutrients to give effective fermentations any innate flavor quality in the grain becomes fairly insignificant.[2]

See also acidulated malt

Malted cereals other than barley are classed by many jurisdictions as adjuncts. They are produced in relatively small amounts. Some are used in brewing European-style beers; others are used in the manufacture of opaque beers, distilled products, foodstuffs, and confectionary. These malts are made from temperate-zone cereals (wheat, rye, triticale, and oats) and also from tropical cereals (sorghum, corn [maize] and rice). Only barley and oat grains in the temperate-zone cereals are husked. Wheat, rye, and triticale are huskless, and this can give rise to malt house problems.[3]

Malt types can influence the flavor and color of beer. Dark malts are important to the production of certain beer types. These characteristics in dark malt are the result of a Maillard reaction that is initiated due to the killing temperatures used in the production of such malts.[4]

Unmalted barley is an unsuitable material for making beer by itself. It lacks the necessary enzymes for brewing, it is not easily friable for milling, and it produces a highly viscous extract that is defcient in amino acids and lacks the color and flavor required for making a good quality product. During malting, selected and prepared barley is steeped in cold aerated water for 40-50 hours, followed by 3-5 days of cool aerated germination. During this time the shoot and rootlet grow and important enzymes form and act. The grain is then dried by kilning with warm air that fixes the properties of the malt and imbues malt with its unique flavor.[5]

  • Base malts such as Pilsner, lager malt, and pale ale malt are produced by germination at 15-17°C (59-63°F) and dried in a cool airflow to about 8% moisture. These malts are kilned at low temperatures of 50-70°C (122-158°F) before curing at a final temperature of 70-85°C (158-185°F). Pale ale malts are typically given kilning temperatures of 60-90°C (140-194°F) and are cured at up to 105°C (221°F) to develop higher color (3-5 SRM) and more flavor. The flavors expressed are lightly grainy with hints of toast and warmth. Note that these temperatures are ranges of typical conditions that maltsters might choose at their discretion—there are no standardized recipes for specific types of malt.
  • Highly-kilned malts are base malts (or base malts that have not been fully cured) that have been kilned to a higher color, such as pale ale, Vienna, Munich, and aromatic malts. The highly kilned malts are heated dry (3-10% moisture) at low temperatures (120-160°F/50-70°C) to retain their diastatic enzymes. Aromatic and Munich malt are kilned at higher temperatures than base malts (195-220°F/90-105°C) to produce richly malty and bready flavors. Only Maillard reactions are involved; caramelization reactions occur at higher temperatures. The congress mash pH of these malts drops by a couple tenths from that of the base malt. The higher curing temperature reduces or eliminates acid-producing microflora.
  • Caramel malts are produced by roasting green malt, i.e., malt that was not dried by kilning after germination. These malts are put into a roaster and stewed at the saccharification range of 150-158°F (65-70°C) until starch conversion takes place inside the husk. Afterwards, these malts are roasted at higher temperatures of 220-320°F (105-160°C), depending on the degree of color wanted. Heating at these temperatures causes both caramelization and Maillard reactions. The maximum color achievable is about 150 SRM or 300 EBC.
  • Roasted malts include amber, brown, chocolate, and black malt. These malts start out green like the caramel malts above, but are kilned to a lower percentage of moisture (5-15%) before roasting. Amber malts are produced by roasting fully kilned pale ale malt at temperatures up to 335°F (170°C). These temperatures give the malt its characteristic toasty, biscuity (cookie), and nutty flavors. Brown malts are roasted longer than amber malts, but at lower temperatures, and achieve a very dry, dark toast flavor, with color equal to that of the caramel malts.
  • Chocolate malt starts out with more moisture before roasting than brown malt, but less than caramel. The roasting process begins at about 165°F (75°C) and is steadily increased to over 420°F (215°C), where the malt develops chocolaty flavors. Some degree of caramelization occurs, but the majority of the flavors are from Maillard reactions and some degree of pyrolysis (controlled charring). Black (Patent) malts are roasted to slightly higher temperatures of 428-437°F (220-225°C) producing coffee-like flavors. Roast barley is produced in a similar manner but the difference is that it is never malted to begin with. Again, the majority of flavors come from Maillard reactions and pyrolysis.[6]

Specialty malts can be divided into two basic categories, those that are simply heated, and those that go through a special process to caramelize the sugar (crystal AKA caramel malts).[7] In each group there is a wide variety of colors available. These malts are used for the color and character that they provide. Unlike pale malts, dark malts should be used as fresh as possible in order to retain their aromas. These special malts do not have emailing activity due to the high processing temperature.

Crystal malts are believed to improve beer stability.[7]

Malt analyses available do not reliably predict a malt's brewhouse performance, and brewers have yet to agree on what set of analyses should be used to specifically define a malt.[7]

Coloured and special malts' flavours change and decline with age and so these materials should be used fresh and their lab worts should be tasted and smelled to see that they are `normal'. Although chemical `marker' substances, such heterocyclic, nitrogen-containing Maillard products, have been sought, to allow flavour to be quantified indirectly by chemical analyses, this approach has had little success.[7]

Traditional analyses of malt do not always reflect potential brewhouse performance.[1]

There are many special malting barley varieties from the past that are being used to make specialty malts today, such as Klages, Golden Promise, and Maris Otter.[1]

It's long been a consensus that the traditional malt analysis specifics provide limited information about brewhouse behavior, and the usefulness provided for determining the effect of the malt on wort or beer quality is virtually non-existent.[8] These days, a malt analysis is very much like a risk management tool—it is used to give some idea about how much a particular batch of malt may vary from previous batches. In other words, the use of the specification is to minimize variation rather than predict brewhouse performance. It is a point of reference to compare different suppliers, different crop years, and new varieties and to match raw materials purchasing to customer requirements. As such, it is a well-established benchmark. However, in some ways the malt analysis directs the brewer in how to avoid process difficulties by adjustment of the grist or mashing conditions based on the variance. A malt analysis doesn't necessarily help with selecting a malt because malts with apparently the same analytical specification can have widely different performance in brewing practice.

A traditional malt analysis can be subdivided into five key groups: starch conversion, carbohydrate conversion, carbohydrate extract, color, and enzyme potential.[8]

When setting a specification for a colored malt, it is not advisable simply to increase the color in the hope that you can then use less in the grist. For example, lower color crystal malts are sweet and fruity, whereas higher color crystal malts are treacly and more bitter.[8]

There is clearly much to be gained by understanding malt flavor in more detail. The low-tech grinding and wetted-porridge method allows the more obvious differences in flavors to be appreciated by almost anyone with a reasonable ability in sensory analysis and with improved levels of training and description some very elegant profiles and troubleshooting are possible.[8]

See The Handbook of Craft Brewing chapter 1 for a discussion of how to read a malt analysis.


Malt that has not been adequately modified during the malting process may benefit from a 113–126°F (45–52°C) protein and beta-glucan rest; see Mashing.[7] This rest increases degradation of beta-glucan and protein so that the starch can be accessed. The protein rest therefore helps increase yield and attenuation. However, such a low mash-in creates problems such as poor head retention due to the excessive protein degradation. Therefore a "protein rest" should be reserved only for poorly modified malts. The increased amino acids (FAN) from a "protein rest" is generally unnecessary since the FAN is usually adequate without it.[9][10][11]

Unfortunately, simply adding a protein rest may have little to no effect, because after initial degradation by the β-glucanases at lower temperatures, many more high molecular weight β-glucans are liberated during the maltose rest at 62–65 °C. These can no longer be broken down, because the β-glucanases have already been denatured due to the increase in temperature. A reliable and almost complete degradation of β-glucans can be achieved, however, if the β-glucan solubilase activity is initiated in the mash before the β-glucanase rest occurs. The temperature optima of both enzymes (endo-β-1,4-glucanase: T opt. approx. 45 °C; β-glucan solubilase: T opt. approx. 62 °C) make infusion impossible. Therefore, an ample sized portion of the mash needs to be separated from the main mash, and the insoluble β-glucans must be liberated at an elevated temperature; see Decoction mash. Due to its considerable volume, this portion of the mash must be cooled with cold liquor prior to being returned to the main mash. Afterwards, β-glucan degradation occurs once the entire mash is allowed to rest in the mash tun at a lower temperature.[12] This process should be considered a salvage technique for malt otherwise giving very poor extract, and it should rarely if ever be needed.

Only the activity of beta-amylase correlates well with the determination of diastatic power, DP, as it is usually determined.[7]

Isoenzymes of β-amylase from different barleys have different temperature sensitivities. Barleys with the more stable enzyme give malts which yield the most fermentable worts.[7]

Many hundreds of potentially active flavour substances are derived from malts or adjuncts and include aldehydes, ketones, amines, thiols and other sulphur-containing substances, heterocyclic oxygen-, nitrogen- and sulphur-containing substances and phenols.[7]

Diastatic power, the total activity of starch degrading enzymes in barley malt, is considered to be an important quality characteristic for malting and brewing.[13] Several hydrolytic enzymes contribute to diastatic power, however, including alpha-amylase, beta-amylase (main contributor), limit dextrinase and alpha-glucosidase. Of these enzymes, beta-amylase is laid down during grain filling and alpha-amylase, alpha-glucosidase and limit dextrinase are synthesized during germination, predominantly in the scutellum and aleurone layers. Diastatic power, like other quality attributes in barley, has been reported to be determined by a complex interaction of genetic and environmental factors.

The activity of mainly alpha-amylase, beta-amylase, and limit dextrinase is collectively called "diastatic power" (DP). In the brewing industry, DP is a key parameter of malting quality since it is an estimate of the capacity of the malt to degrade starch into fermentable sugars. Methods for estimating the diastatic activity of malt are generally based on its ability to generate reducing sugars. The main units and criteria used to measure the DP of a malted cereal are:[14]

  • Degrees Lintner (°L), defined by the JECFA (the Joint FAO/WHO Expert Committee on Food Additives) and the IoB (Institute of Brewing) as follows: "A malt has a diastatic power of 100°L if 0.1 ml of a clear 5% infusion of the malt, acting on 100 ml of a 2% starch solution at 20°C for 1 h, produces suffi cient reducing sugars to reduce completely 5 ml of Fehling's solution." For a complete description of the method see http://www.fao.org/ag/agn/jecfa-additives/specs/Monograph1/Additive-270.pdf . The DP is around 35–40 for standard barley malts, but it can be as high as 100–125 for lager malts, and over 160 for some high-protein North American malts which have far more enzymatic power than they require to hydrolyze the starch from the malt. Therefore, they enable the brewer to use these malts as an amylases source in the case of unmalted starch adjuncts addition.
  • Degrees Windisch–Kolbach (°WK), used by the EBC (European Brewery Convention), which can be converted to Lintner units as follows:
    DPL = ( °WK + 16 ) ÷ 3.5
  • Sorghum diastatic units (SDU), used by the SABS (South African Bureau of Standards) especially for sorghum, and not easily comparable to ºL and ºWK.


Diastatic power highly correlates with the level of beta-amylase, however the actual efficiency of starch degradation is also influenced by the levels of other starch-degrading enzymes. Therefore higher diastatic power does not necessarily produce wort with higher levels of fermentable sugars in the mash.[15]

Beta amylase is considered the principal enzyme responsible for diastatic power.[16]

The quality of barley malt is determined by its extract and the degree of fermentability of that extract (apparent attenuation limit [AAL]). For the commercial malt trading, diastatic power (DP) is often used as an approximation for AAL since DP is more simply and quantitatively measured, particularly because there is a significant impact of yeast strain or source on alcohol yield.[17] DP is a measure of starch hydrolyzing enzymes that are the combined activity levels of β-amylase, α-amylase, limit dextrinase, and α-glucosidase.

Although the DP specification generally gives an indication of potential malt starch degrading capacity, brewers are increasingly losing confidence in the value of the DP parameter. To illustrate brewers concerns, a series of commercial case studies were presented in Evans et al., (2007) which provides examples of where the DP specification was of questionable value or in some cases downright misleading.[18]

  • Evans, D.E., Li, C. and Eglinton, J.K., (2007) A superior prediction of malt attenuation. In Eur. Brew. Conv. Cong. Proc. Venice Vol. 31:54-66.

A low protein, high starch grain will have a flourier (softer) endosperm which is a result of more amylose, with large granules. Grain hardness is a physical measure and is positively related to traits such as high malt friability, higher wort extract and higher wort fermentability and variation in fermentable sugars where a softer grain is better for these traits. Low protein and low hordein is positively related to higher grain hydration rates, higher friability, and improved malt modification. However, the up-side increase in protein content is an increase in β-amylase as there is a portion bound up in the hordein while some beta-amylase is free. An increase in β-amylase should also result in an increase in wort maltose, but the amount of extract is negatively related protein content, so less starch will be available in the mash.[19]

Diastatic power does not always accurately estimate the level of fermentable sugars generated during mashing or the subsequent wort fermentability. The developing trend is for the brewer to measure individual malt diastatic power enzymes (DPE) levels to more accurately predict and evaluate the starch degrading capacity and potential wort fermentability in order to assess malt quality.[20]

For poorly modified, malt Narziß and Litzenburger found maximal extract concentration at 60°C for isothermal mashing.[21]

The degree of protein modification affects bready flavor and palatefulness, extensive modification of proteins is a cause of empty beer taste.[22]

Aside from determining the ratio between soluble and total protein amount (“Kolbach” index), the breakdown of the network of barley storage proteins dictates the accessibility to starchy reservoirs that will then provide the fermentable carbohydrates. In effect, the Kolbach index is a reliable predictor of the potential degree of starch conversion. Hordeins are known to affect the diastatic power of malt wherein the total hordein grain content negatively correlates with the malting quality (Smith and Simpson, 1983). However, the total hordein content alone is a poor indicator of malting properties, because the composition of cultivar-specific hordeins is unquestionably relevant to the technological parameters. Overall, the relationships between the content of total or individual protein classes and malting traits are conflicting, as brewing is a highly intricate process, difficult to reproduce in simple model systems (Gupta et al., 2010).[23]


Potential sources

References

  1. ↑ a b c Palmer GH. Barley and malt. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
  2. ↑ a b c d e f g Howe S. Raw materials. In: Smart C, ed. The Craft Brewing Handbook. Woodhead Publishing; 2019.
  3. ↑ Stewart GG. Adjuncts. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
  4. ↑ Ferreira, Inês M., and Guido, Luís F. "Impact of Wort Amino Acids on Beer Flavour: A Review." Fermentation. 2018, 4, 23.
  5. ↑ Warpala IWS, Pandiella SS. Grist fractionation and starch modification during the milling of malt. Food and Bioproducts Processing. 2000;78(2):85–89.
  6. ↑ Palmer J, Kaminski C. Water: A Comprehensive Guide for Brewers. Brewers Publications; 2013.
  7. ↑ a b c d e f g h Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
  8. ↑ a b c d Davies N. Malts. In: Bamforth CW, ed. Brewing Materials and Processes: A Practical Approach to Beer Excellence. Academic Press; 2016.
  9. ↑ Kunze W. Hendel O, ed. Technology Brewing & Malting. 6th ed. VBL Berlin; 2019.
  10. ↑ Fix G. Principles of Brewing Science. 2nd ed. Brewers Publications; 1999.
  11. ↑ Visser MJ. Evaluation of malted barley with different degrees of fermentability using the Rapid Visco Analyser (RVA). University of Stellenbosch. 2011.
  12. ↑ Sacher B, Becker T, Narziss L. Some reflections on mashing – Part 2. Brauwelt International. 2016;6:392-397.
  13. ↑ Arends AM, Fox GP, Henry RJ, Marschke RJ, Symons MH. Genetic and Environmental Variation in the Diastatic Power of Australian Barley. J Cereal Sci. 1995;21:63–70.
  14. ↑ Guerra NP, Torrado-Agrasar A, López-Macías C, et al. Use of Amylolytic Enzymes in Brewing. In: Preedy VR, ed. Beer in Health and Disease Prevention. Academic Press; 2009:113–126.
  15. ↑ MacGregor AW, Bazin SL, Macri LJ, Babb JC. Modelling the contribution of alpha-amylase, beta-amylase and limit dextrinase to starch degradation during mashing. J Cereal Sci. 1999;29(2):161–169.
  16. ↑ Yin C, Zhang GP, Wang JM, Chen JX. Variation of beta-amylase activity in barley as affected by cultivar and environment and its relation to protein content and grain weight. J Cereal Sci. 2002;36(3):307–312.
  17. ↑ Evans DE, Collins H, Eglinton J, Wihelmson A. Assessing the impact of the level of diastatic power enzymes and their thermostability on the hydrolysis of starch during wort production to predict malt fermentability. J Am Soc Brew Chem. 2005;63(4):185–198.
  18. ↑ Evans DE, Li C, Eglinton JK. The properties and genetics of barley malt starch degrading enzymes. In: Zhang G, Li C, eds. Genetics and Improvement of Barley Malt Quality. New York: Zhejiang University Press, Hangzhou and Springer Verlag; 2009:143–189.
  19. ↑ Bamforth CW, Fox GP. Critical aspects of starch in brewing. BrewingScience. 2020;73(9/10):126–139.
  20. ↑ Hu S, Dong J, Fan W, et al. The influence of proteolytic and cytolytic enzymes on starch degradation during mashing. J Inst Brew. 2014;120(4):379–384.
  21. ↑ Kühbeck F, Dickel T, Krottenthaler M, et al. Effects of mashing parameters on mash β-glucan, FAN and soluble extract levels. J Inst Brew. 2005;111(3):316–327.
  22. ↑ Benešová K, Běláková S, Mikulíková R, Svoboda Z. Activity of proteolytic enzymes during malting and brewing. Kvasný Prům. 2017;63(1):2–7.
  23. ↑ Picariello G, Mamone G, Nitride C, Ferranti P. Proteomic analysis of beer. In: Colgrave ML, ed. Proteomics in Food Science. 2017:383–403.
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