# Maize and Sorghum as Raw Materials for Brewing, a Review
## 2 Maize and Sorghum: Raw Materials for Brewing
### Chemical Structure and Composition  
Barley, maize and sorghum are part of the _Poaceae_ family, all of which are monocotyledonous herbaceous plants with fasciculate roots and stems--formed by nodes and internodes--with spike-shaped inflorescence (Figure 2) [47]. The grains are caryopses; barley grains have a straw-like, sticky coating, which protects the germs during the malting process, while maize and sorghum are bare grains, devoid of this coating. The average dimensions of barley grains are generally between 8-12 mm long, 3-5 mm wide and 2-4.5 mm thick. Depending on the variety and cultivation conditions, the weight of 1000 grains can vary between 37-45 g [48]. Barley grains are composed of endosperm (80-90%), embryos (2-5%), and shells (8-15%). 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. Table 1 summarizes the physicochemical characteristics of the maize, sorghum, and barley. The composition of cereals (shown in Table 1) varies according to seed maturity, date of harvest, variety/species, soil and climatic conditions, crop management, storage, and drying conditions applied after harvest. Starch is the main component of cereals, and is the main substance that is later converted to fermentable carbohydrates in beer word. Therefore, one can determine the brewing qualities of a raw material by examining the starch content. This is important for the alcohol industry. 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%. Figure 2: Plants of maize and sorghum. According to the chemical composition of maize grains, carbohydrates and proteins are its key components play a significant role in the process of obtaining beer. The major chemical component of the maize kernel is starch, concentrated in the endosperm. The composition of maize starch is genetically controlled. Amyloidectin and amylose are the main components of starch. Normal corn usually contains 25-30% amylose and 70-75% amylope. Nevertheless, maize types with amylose contents as high as 85% (amylomaize) and as low as 1% or even less (waxy maize) have been reported. In maize grains, starch can be found in granular forms which vary in size and shape depending on the type of maize. Normal maize starch has a bimodal particle size distribution, with granules <10 \(\upmu\)m and >10 \(\upmu\)m in relative percentages of 10.2% and 89.8%, respectively. A cell's walls contain proteins, phenolic acids and nonstarch polysaccharides such as \(\beta\)-glucan and arabinylan [39]. A second component of maize kernels is protein. Maize varieties have different levels of protein content. Waxy corn grains have higher protein content (11.03%) than normal corn (8.05-8.62%) and flint corn (8.5-8.7%). Zein represents about 60% of the total protein in corn. Zein contains very low lysine and tryptophan percentages. Zein is comprised of 21.4% glutamine, 19.3% leucine, 9.0% proline, 8.3% alanine, 6.8% phenylalanine, 6.2% isoleucine, 5.7% serine, and 5.1% tyrosine. Depending on the type of maize, the grain can contain lipids up to 5.91%. Even though the lipid percentage can be high, the fat content of the endosperm can be relatively low (approximately 1%).