Brewing is among the oldest biotechnological processes, in which barley malt and—to a lesser extent—wheat malt are used as conventional raw materials. Other cereals as corn and sorghum could also be used in brewing.
1. Introduction
Brewing is a food process that began in the Middle East 10,000 years ago [1]. Today, at almost 200 billion liters a year, beer is one of the most commonly consumed low-alcohol beverages in the world—and, in terms of volume, after water and tea, the third most prevalent beverage in general [2][3][4][5][6]. Barley is the most used cereal for brewing; however, unconventional malted grains have been used successfully. For instance: rice is used in Asia, maize is used in America, and millet and sorghum are used in Africa [7][8][9]. This process of replacing barley malt in beer production is increasing, and several factors shown in Figure 1 have contributed to this.
Brewing is a food process that began in the Middle East 10,000 years ago [1]. Today, at almost 200 billion liters a year, beer is one of the most commonly consumed low-alcohol beverages in the world—and, in terms of volume, after water and tea, the third most prevalent beverage in general [2,3,4,5,6]. Barley is the most used cereal for brewing; however, unconventional malted grains have been used successfully. For instance: rice is used in Asia, maize is used in America, and millet and sorghum are used in Africa [12,13,14]. This process of replacing barley malt in beer production is increasing, and several factors shown in have contributed to this.
Figure 1.
Diversification factors of raw materials for obtaining beer.
Barley and maize are the most commonly used adjuvants in Europe as partial substitutes for malt [10][11][12]. Adjuvants are widely used in the beer industry (in variable proportions ranging from 10–50%) to provide additional sources of fermentable yeast carbohydrates, to improve foam stability, to change the color of beer, or to adjust the flavor of the finished product [13].
Barley and maize are the most commonly used adjuvants in Europe as partial substitutes for malt [15,16,17]. Adjuvants are widely used in the beer industry (in variable proportions ranging from 10–50%) to provide additional sources of fermentable yeast carbohydrates, to improve foam stability, to change the color of beer, or to adjust the flavor of the finished product [18].
2. Maize and Sorghum: Raw Materials for Brewing
2.1. Chemical Structure and Composition
The maize grain is 2.5–22 mm long and 3–8 mm wide. Depending on the variety and cultivation conditions, the weight of 1000 grains vary greatly (between 30 and 1200 g). Maize grains are constituted of endosperms (82–83%), germs (10–11%), pericarps (5–6%), and peaks (0.8–1.0%) [14]. Sorghum grains are rounded and sharp with a diameter of 4–8 mm. They vary in size, shape and color depending on the variety of sorghum. The weight of 1000 grains varies between 20 and 60 g. These grains are composed of endosperms (80–84.6%), embryos (7.8–12.1%), and shells (7.3–9.3%) [15].
For the beer industry, the chemical composition of raw materials is particularly important. Table 1 summarizes the physicochemical characteristics of the maize, sorghum, and barley.
The maize grain is 2.5–22 mm long and 3–8 mm wide. Depending on the variety and cultivation conditions, the weight of 1000 grains vary greatly (between 30 and 1200 g). Maize grains are constituted of endosperms (82–83%), germs (10–11%), pericarps (5–6%), and peaks (0.8–1.0%) [49]. Sorghum grains are rounded and sharp with a diameter of 4–8 mm. They vary in size, shape and color depending on the variety of sorghum. The weight of 1000 grains varies between 20 and 60 g. These grains are composed of endosperms (80–84.6%), embryos (7.8–12.1%), and shells (7.3–9.3%) [50].
For the beer industry, the chemical composition of raw materials is particularly important. summarizes the physicochemical characteristics of the maize, sorghum, and barley.
Physicochemical characteristics of maize, sorghum and barley.
* DM—dry matter.
Starch is the main component of cereals, and is the main substance that is later converted to fermentable carbohydrates in beer wort. The highest amount of starch is found in maize (62–80%), followed by sorghum (55.60–76.20%), and then barley (52.10–69.08%). The protein content varies between 8–15.25% for barley, 5.8–13.7% for maize, and 4.4–14.86% for sorghum. The fat content is 1.09–3% for barley and 2.2–5.91% for maize. Sorghum varies greatly, with a lipid content between 1.38–10.54%.
2.2. The Use in Brewing
2.2.1. Maize
Maize starch is widely applied (due to its high fermentability) as an adjuvant in the production of high-gravity beer [39]. Corn flakes or pre-gelatinized maize can be used to significantly reduce mashing time. Corn kernels produce a somewhat lower extract compared to other raw adjuvants (such as rice) due to the lower amount of dextrin in the wort after mashing. They also contain higher levels of lipids and proteins. It should be noted that the addition of corn derivatives has an important impact on the organoleptic properties of beer. In the future, it may be recommended that brewers/manufacturers use exogenous enzymes together with corn in order to enhance saccharification and amylolytic activity. Table 2 summarizes data from the literature on the production of beer assortments based on maize or maize derivatives.
2.2.2. Sorghum
Outside of Mexico and Niger, sorghum has not been widely used as an adjuvant, although its potential has been promoted. Sorghum semolina offers several advantages in beer brewing, including short boiling time, easy filtration, high extract content and highly nutritious wort [53]. The use of sorghum malt in beer manufacture has led to some difficulties, largely due its low amylolytic activity (which is insufficient for complete saccharification), high gelatinization temperature, and low content of free amino nitrogen. The use of sorghum malt in beer manufacture has led to some difficulties, largely due its low amylolytic activity (which is insufficient for complete saccharification), high gelatinization temperature, and low content of free amino nitrogen.
Table 3 summarizes data from the literature on obtaining beer assortments that use sorghum as a basic raw material.
| 57 |
| ] |
| [ | 110 | , | 111 | ,112,113] |
Tchapalo
(Coasta de Fildeș, Togo, Benin) |
Sorghum |
Lactic fermentation, alcoholic fermentation |
Non-alcoholic beer, turbid, shelf life 3 days |
[58][59][60][61][62] | [114,115,116,117,118] |
Bantu
(Africa de Sud) |
Sorghum |
Malting, grinding, mashing, lactic fermentation, alcoholic fermentation |
Turbid liquid, alcohol content 3–4% (v/v), sour taste, brown-pink color, rich in B vitamins |
[63][64][65][66] | [119,120,121,122] |
Dolo
(Burkina Faso, Benin, Rwanda) |
Sorghum |
Malting of red sorghum grains, crushing, mashing, cooking, lactic fermentation, filtration, boiling, alcoholic fermentation |
Turbid liquid, alcohol content 1–5% (v/v), sweet-sour taste, fruit flavor |
[67][68][69][70] | [123,124,125,126] |
Bili bili
(Ciad) |
Sorghum |
Malting, mashing, boiling, souring, and fermenting |
Turbid liquid, brown-pink color, sour taste, fruity, alcohol content 1–8% (v/v), low in carbohydrates and high in protein |
[71][72][73][74][75] | [104,127,128,129,130] |
Omalovu
(Namibia) |
Sorghum, millet |
Malting, drying, milling, souring, boiling, mashing, straining, alcoholic fermentation |
Unpasteurized beer, opaque, red-brown or cream color, pH = 3.06–4.34, alcohol content 0.18–4.05% (v/v) |
[71][76] | [104,131] |
4. Conclusions
The studies undertaken demonstrated the real potential benefits of using maize and sorghum in the brewing process, whether as simple adjuvants or via the brewing of beers made from 100% sorghum or maize malt.
Maize is a versatile money crop and is adaptable to various climatic conditions; globally, it is known as the queen of cereals. Sorghum is genetically close to corn, and is also called the camel plant due to its resistance to extreme drought conditions. Sorghum is also a vital staple food in many semi-arid areas of the developing world.
There are some limitations in the use of these two cereals: maize has bare grains and lacks a husk (which would act as an adjuvant for filtration). It also has a low level of enzymatic activity. The structure of the sorghum grain is similar to maize; it has no shell, and the aleurone layer inhibits the flow of enzymes. Moreover, the development of amylolytic enzymes during the germination of maize and sorghum is lower than in barley.
In countries around the world, craft and functional beer brewing has revived old varieties and created new ones. Specialist brewers have worked to advance novelty beers that exhibit a complete and rich taste through efficient processing. These new beverages are created using various ingredients, and often involve modifications of the brewing process.
In conclusion, industrial and scientific research can promote innovation by creating new assortments of beer using maize and sorghum. This, in turn, could have a significant impact on product quality improvements.
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