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Organisation: Sorghum Institute of LAAS
Author: Jianqiu Zou & Yuxue Shi
Edited by AGSI/FAO: Danilo Mejia (Technical), Beverly Lewis (Language&Style), Carolin Bothe (HTML transfer)

CHAPTER VIII: Industrial use of sorghum


1.3 Primary product

1.4 Secondary and derived product


1. Introduction

Sorghum (Sorghum bicolor (L) Moench) is a globally cultivated cereal that is called a `Life Saver' in some areas. It is a major crop grown in the semi-arid and arid regions of Africa and Asia where it is used as a staple food. In China, sorghum or kaoliang, is one of the earliest cultivated crops growing mainly in Northeast, Northwest and North China temperate zones.

Chinese sorghum production is based on grain sorghum, to sugar-refining sorghum, forage sorghum and craft sorghum. It is a unique due to its tolerance to drought, waterlodging, saline-alkali, infertile soil and high temperatures. Sorghum can obtain a consistent high yield even in certain semi-arid and arid areas where rice, wheat and corn are not well adapted. Sorghum plays an important role in crop rotation systems. Sorghum is a C4 species with high photosynthesis efficiency. It can achieve higher yields with a lower input of resources in compared to other crops.

Most grain sorghum in China is used as food to make various breads, cakes, dumplings and noodles. But sorghum is commonly called "coarse food "because of its amino acids imbalance and high tannin content (Table 1).

Table 1. The Composition of Chinese Sorghum Resources and Hybrids

Starch %

Protein %

Lysine %
Tannin %

Chinese sorghum resources

the highest

16.30

0.43

1.29

 

the lowest

6.62

0.10

0.04

mean

11.46

Hybrids

the highest

15.20
0.41
2.64

the lowest
6.50
0.07
0.03

In recent years, Chinese sorghum researchers have directed their attention to improving sorghum quality by breeding and processing. Obvious improvements have been gained (14). Sorghum kernels provide good concentrated feed similar to corn in nutritional value. Sorghum stalks and leaves can be used as green fodder, ensilage or hay.

In China, making strong liquors from sorghum kernels represents a long history and high technological level. The world famous Maotai and Fen liquors are made from sorghum. Its by-product of distillers' grain can be used as high quality feed. Sorghum grains produce starch, starch noodles and vinegar.

Chinese Kaoliang is a special sorghum group in the world. There are about 17 thousand sorghums cultivars in China, the representatives of them are: Guandong Qing, Luyi Waitou, Shanchishan, Wawa kaoliang, Bakecha, Xiaongyue 253, Fenzhi Dahongsui, Xiang Kaoliang, Zhuyeqing, Hongke Nian, Waibo Zhang and etc. (7, 11).

Chinese sorghums have great variety of panicles (Fig. 1) (4), growing periods, plant heights, head lengths, and 1,000-kernel weights (Table 2) (2). Typically they are high dark red soft glum, white vein and dry pith.

Figure 1: The Sketch Map of Chinese Kaoliang Spike THE SKETCH MAP OF CHINESE KAOLIANG SPIKE

Table 2. Structural Features of Chinese Sorghum

 

Growing period day

Plant height
cm

head length
cm

length 1,000 kernel weight
g

Max.

166

435

50

39

Min.

88

92

11

12

Mean

115-125

250-300

22-33

21-26

1.3 Primary product

Milling is very important in China, because many sorghum foods are made of decorticated sorghum and sorghum flour. Milled sorghum is usually decorticated to remove the pericarp, followed by crushing of the decorticated grains into flour.

Milling machines can be divided into three types: friction milling (pressure system), grinding milling (speed system) and mixed milling.

Friction milling decorticates grains depending on the friction between components and grains or between grains. The method suits the corneous endosperm variety. Peeled grains from this method are smooth, even, with less breakage and higher milling yields.

Relying on its hard, concentrated and sharp edges, the emery roller in grinding milling cuts pericarps repeatedly by relative motion at a set speed, so the pericarps are removed. The method is suited to floury endosperm varieties. The decorticated grains derived from this method are rough and uneven with poor colour.

Mixed milling was invented by China combining the advantages of grinding milling with friction milling, with stress on the former. It is a good milling method with a great future.

There are two kinds of dry flour milling methods: whole grain flour milling and decorticated grains flour milling. Making flour from whole grains can yield 90 percentage, but digestibility is low at 18.55 percentage with poor flavour. Making flour from peeled sorghum grain can produce high quality flour with good digestibility, but yields 8.5 percentage.

The wet flour milling method is better than dry milling. Flour produced by this method is good quality with white, fine grains and 5 percentage higher digestibility than dry milling. The flour is easy to store. The procedure of wet flour milling is described in Figure 2. (4).

Unprocessed grains -> Cleaning -> Washing -> Heating -> Making flour -> Drying -> Packaging

Figure 2: Processing Method of Wet Flour Milling

Traditional sorghum foods

Sorghum is a staple food crop in China, especially in North China. People there can make many kinds of rich and colourful sorghum foods which have different flavours. According to Shukun Zhao (12,13), there are about 40 kinds of sorghum foods. Table 8 summarises some different sorghum foods.

Table 8 Classification of Sorghum Foods

Type

 

Name of representative

decorticated
grain foods

cooked produces

porridge

gan mifan, lao mifan, shui mifan, er mifan
dou mifan
chazi zhou, doumi zhou, ermi zhou, Jianmi zhou, naibuzi.

flour foods

steamed products

boiled products

baked products
parched products
glutinous products

YuYu, baocha, wowo, tiaotiao, jiaozi, dundun, boboye, fagao
hele, miantiao, mianpian, gangsimian, miangedatang, daoxuemian, suantangzi
jianbing, famianbing, dabingzi
chao mian, youchamian
niangao, niandoubao, nianhuoshao, nianbing, suhaozi

Popping foods

 

penghuasu, baomihua, chaomibua

1.4 Secondary and derived product

In China, almost every part of sorghum can be used (Table 9 and Figure 3).

Table 9 Utilisation of Sorghum By-Product

Sorghum component

Utilisation

root

fuel

stalk

fuel, mat, hat, building materials,
frame materials, barrier

peduncle

cover

threshed spike

broom, potscouring brush

Figure 3: Articles Made of Sorghum By-products ARTICLES MADE OF SORGHUM BY_PRODUCTS

Making sorghum liquor using sorghum grains

Sorghum liquor is a unique Chinese alcoholic drink with a history of about 1500 years. It is one of six kinds of world famous distillation liquor. There are many kinds of sorghum liquor in China. The characteristics of Chinese sorghum liquor are:

a. Strictly selected materials;

b. Meticulous processing;

c. Excellent quality;

d. Special flavour;

e. Very strong.

The traditional ingredient of alcoholic drinks in China is sorghum. "Good liquor is always connected with sorghum" is a well-known adage. China is the first country to make distillation liquor with sorghum. Famous and precious sorghum liquors of China include (4,9,15):

Maotai: It was produced in Guizhou province, in 1704. In the International Fair of Panama between 1915 and 1916, Maotai gained the second prize in the competition and was elected World Famous Liquor. It is the most famous liquor in China served at state banquets. The key ingredient of Maotai is local high quality sorghum.

Fen Liquor: It is manufactured in Shanxi province, China. It has the longest brewing history (about 1500 years). In the International Fair of Panama of 1915, it won the First Class Gold Medal.

Wuliangye: It is made in Sichuan province of China. It was awarded the Gold Medal in the International Fair of Panama in 1915. It uses five kinds of crops as materials (Sorghum, glutinous rice, rice, corn and wheat). 60 percentage of Wuliangye is sorghum.

Jiannanchun: It is also made in Sichuan province of China. It begun to be produced 300 years ago in Qing dynasty. Its materials are five crops: Sorghum, rice, corn, wheat and glutinous rice, Sorghum accounts for 40 percentage of the recipe.

Xi Feng: It is produced in Shanxi province. It won second prize in Southeast Asia Competition of 1909. It is made exclusively from sorghum.

Luzhoutequ: It is produced in Sichuan province of China. It has about a 300-year history. It won the Gold Medal and Certificate of Merit in the International Fair of Panama in 1919.

Sorghum and corn have very similar composition, but for making liquor, sorghum is better than corn. First, sorghum has a lower protein and lipids content than corn. During the fermentation, protein is hydrolysed for amino acids, and then the amino acids are changed into senior alcohol. These senior alcohols are the main source of the liquor flavour. If the protein content is too high, too much mixed alcohol will be produced, and the high mixed alcohol content in the liquor will produce white sediment in lower temperatures. Similarly, if the lipid is too high, a lot of fatty acid is produced causing a bad smell and white precipitate. So, suitable protein content will benefit distillation. Second, and most important, sorghum has a small tannin content (about 0.5~2.0 percentage). Tannin inhibits harmful micro-organisms and increases liquor-making productivity. Tannins also produce some aromatics which give sorghum liquors their special flavour. The general method of making sorghum liquor is described in Figure 4.

Figure 4: Flow Diagram of Sorghum Liquor Making Process FLOW DIAGRAM OF SORGHUM LIQUOR MAKING PROCESS

Making liquor using sweet sorghum stalk and waste residue from sugar refining

Sweet sorghum stalks have a high sugar content good for making liquor. Usually, 4.5-5.0 kg 62 percentage liquor can be distilled using 50-kg sweet sorghum stalks. The method is similar to using sorghum grain (Figure 5). The advantages of processing sweet sorghum stalks on the spot are that the residue can be used to produce methane, feed or manure. Moreover, the waste residue of refining sugar also contains some sugar, which can be fermented for sorghum liquor. About 1.5-2.5 kg 50 percentage sorghum liquor will be produced from 50-kg waste residue (4).

Figure 5: Processing Method of Liquor Using Sweet Sorghum Stalk PROCESSING METHOD OF LIQUOR USING SWEET SORGHUM STALK

Making liquor using sweet sorghum stalk

Here the juice of stalks is directly fermented and then filtered (Figure 6).

Figure 6: The Processing Method of Making Keller Liquor THE PROCESSING METHOD OF MAKING KELLER LIQUOR

Making Liquor By Sorghum Bran

Sorghum bran is a by-product of milling sorghum where generally, more than 20 percentage sorghum bran will be derived. The composition of sorghum bran is 40~ 60 percentage starch, 11~ 15 percentage raw protein, 4~ 10 percentage raw lipids and higher tannin content. Because the high content of lipids in sorghum bran cause too much acid, the temperature of cellar should be lower to guarantee the quality of the liquor (4).

Brewing beer

Traditional brewing ingredients of beer are barley and rice. Along with the development of the beer industry, there were insufficient resources. Sorghum is a new potential substitute for barley or rice, which can not only resolve the ingredient problem, but also raise economic benefits (10).

Although there is a traditional sorghum beer in Africa, it is an acid type of beer quite different from traditional beer in Europe. Chinese sorghum beer is similar to European beer. Its colour, flavour and quality are similar to barley beer. The brewing method is as follows (Figure 7).

Figure 7: Brewing Method of Sorghum Beer BREWING METHOD OF SORGHUM BEER

Refining sugar

Making syrup from sweet sorghum stalks has a long history in China, but the production of crystalline sugar is only several decades old. There are three end products in sugar refining--yellow granulated sugar, brown granulated sugar and syrup. Their quality was up to standard. The total sugar in crystalline sugar can generally reach about 92 percentage (82.09 percentage sucrose+10.5 percentage reducing sugar), and water content is about 7 percentage (4).

The sugar extracting productivity with sweet sorghum stalks is about 4 percentage (1). Figure 8 gives the details of sugar refining.

Making vinegar

Vinegar with its acid flavour can whet the appetite, help digestion, or assist medicine. A large amount of high-quality vinegars in North China are made from sorghum grains.

Sorghum vinegars are thick quality, mellow flavour and full of delicate fragrance. Shanxi Old Mature Vinegar is one of the most famous Chinese sorghum vinegars.

To make vinegar get ethanol from the starch by fermenting. Ethanol becomes vinegar by oxidisation. So, its processing method is similar to making sorghum liquor. Besides sorghum grains, many kinds of residues from sugar extraction, such as sediment foam, also can be used to manufacture vinegar. About 1.3-1.5 kg vinegar can be distilled from 1-kg sediment. Its quality is the same as vinegar made from grain.

Figure 8: The Processing Method of Sugar THE PROCESSING METHOD OF SUGAR

Making monosodium glutamate

Monosodium glutamate (MSG, C5H8O4NNa.H2O) is the reactant of glutamic acid and sodium carbonate, and glutamic acid is fermenting product of glucose (C6H12O6).

2C6H12O6+2NH3+ +3O2 2C5H9O4N +2CO2+6H2O

In China, the raw component to make monosodium glutamate is starch, such as rice, corn and sorghum. If we use sweet sorghum stalks to make MSG, it should be very convenient, because the process from starch to sugar can be omitted. What we need to do is transform sucrose to glucose. If the yield of sweet sorghum stalk is 75,000 kg/ha, grain yield is 4,500 kg/ha, the output of MSG will be 243.8+80.4=324 kg. It is 2.5 times more than rice which is a considerable economic benefit.

Making Sorghum Sweetmeat

In ancient China, people made malt sugar as a food; its other name is water malt sugar. Any kind of starch can be used make maltose. Because maltose has very strong hygroscopicity and gentle sweet taste, it is one of the necessary constituents in candy, cake and jam. Sorghum sweetmeat, a kind of maltose made of sorghum starch, is a famous special local product from the Shandong province. The main composition of sorghum sweetmeat is maltose (about 50~65 percentage) and dextrin (about 20~25 percentage). It also contains some moisture and a small amount of protein, starch, and ash (4).

Making paper

The leaves and stalks are the materials of the grass family paper making, which can be used to make writing paper (rough straw paper), wrapping paper, and other products. In addition, the residue which from sugar refining of sweet sorghum stalks is also used for papermaking. Comparing other papermaking materials, sorghum leaves and stalks are easy to convert into pulp Size chemical pulp use only a small amount of chemicals to fabricate paper products that are homogeneous and smooth. However, the paper made from sorghum stalks and leaves show strong transparency and brittleness plus poor folding and bursting. The process of making paper is described as Figure 9 (4).

Figure 9: The Method of Making Paper Using Sorghum Leaves and Stalks THE METHOD OF MAKING PAPER USING SORGHUM LEAVES AND STALKS

Making plywood using sorghum stalks

The cellulose content in sorghum stalk is very high, at about 48 percentage of dry weight (4). Sorghum stalks are not only light, but also pliable and hard. Sorghum stalks can be used to produce sorghum plywood. Comparing shaving board and fibreboard, sorghum plywood has many advantages.

A. Light with high strength;

B. Better insulation capability;

C. Highly durable;

D. The size, thickness and specific gravity of board are suitable for multi-function applications;

E. The holding power of nails and screws is generally lower than that of wood board;

F. Tropical rainforests for wood making materials are conserved.

The material used for sorghum plywood is from sorghum stalks. Sorghum is an annual plant with great deal planted all over the world making it simple to get raw materials for plywood. On the other hand, sorghum stalks are by-products of sorghum. By using sorghum stalks to make plywood, farmers can earn 3000 yuan/ha more than before. Because sorghum plywood is a substitute for woodboard, it can reduce the use of wood materials to conserve acres of forests.

Shenyang Xinyang Sorghum Plywood Company Ltd., which is a joint venture of China and Japan, can produce about 60,000-m3 plywood each year. Their processing method is described in Figure 10. The sorghum plywood can be used to construct tables, doors, furniture and decorative materials (Figure 11).

Figure 10: The processing method of sorghum plywood THE PROCESSING METHOD OF SORGHUM PLYWOOD

Figure 11: The Furniture and Ornament Made of Sorghum Plywood (the picture is kindly provided by Shenyang Xinyang Sorghum Plywood Company Ltd.) FURNITURE AND ORNAMENT MADE OF SORGHUM PLYWOOD

Making alcohol

The oil crisis is a world-wide problem, creating urgency to seek new replaceable energy source with no delay. Alcohol can partly replace oil. So the challenge is how to get enormous volumes of alcohol? Sorghum is an efficient material in making alcohol.

Making alcohol using sorghum grains

In China, the main method to make alcohol is fermenting starchy materials. (Figure. 12). Because of its high starch content, sorghum grains are an important material of making alcohol. Normally, 1,000-kg sorghum grains can produce 390-L alcohol (9).

Figure 12: Flow Figure of Making Alcohol FLOW FIGURE OF MAKING ALCOHOL

Making alcohol using sweet sorghum stalks

Sweet sorghum is similar to sugarcane as its sugar storage organ is stalk. Sweet sorghum stalk contains considerable sugar and rich fibre. Compared to sugarcane, the advantages of sweet sorghum are:

A: it reproduces with seeds, do not use stalk as seedling;

B: growth period is only half of sugar cane.

Figure 13 is flowing diagram of using sweet sorghum stalks to make alcohol (4)

Figure 13: Flowing Diagram of Making Alcohol by Using Sweet Sorghum Stalks FLOWING DIAGRAM OF MAKING ALCOHOL BY USING SWEET SORGHUM STALKS

In this procedure, the process of converting starch into sugar is eliminated shortening the producing time. The stalks can be utilised comprehensively. For example, the juice of the stalks cane used to produce alcohol and nitrogenous fertiliser which can satisfy the need of crops or herbage, leaves and residue may be used as feed, waste is used to produce methane used to generate electricity. So, the main products of pastureland are not only livestock products, but also liquid fuel. It takes about 18.2 tons sorghum stalks to produce one ton alcohol, the net income is 300-yuan (1).

Extracting pigments from sorghum glume

Most of sorghum pericarps and glumes are coloured, According to variety, their colour can be dark to light, such as brown, red, yellow, and white. Sorghum pigments belong to isoxanthoketone galactoside which has many kinds of components. In ancient China, people found glume pigment sorghum to be very stable useful to dye woollens, cotton, linen, and other textiles. However, most of sorghum glumes are either discarded or used as fertiliser, because no suitable pigment extracting method. In recent years, researchers in Sorghum Institute of Liaoning Academy of Agricultural Science have done a great deal of research work about pigments on its physiochemical properties, extracting methods and applications. They successfully extracted pigments from sorghum glumes, named Sorghum Red Pigment (Figure 14) (3). After the pigments extracted, sorghum glumes can be reused. For example, if one can use sorghum glumes as material for making vinegar and extracting glue, or as fillings to produce mushrooms. When it encounters light and heat, the pigments keep stable colouring and excellent function. Along with improvement of people's living standards, edible pigments are evolving from synthetic pigments to natural pigment. It is because synthetic pigments are harmful to human's health. People are more and more interested in natural pigments. Based on Chinese Law, synthetic pigments are not permitted to be used in food and cosmetics. Extracting pigments from sorghum glumes provides a good way for people to get treasures from waste.

Sorghum Red Pigment is dark red powder with natural soft colour, containing no poison or no special odour, which is able to be used in foods, meat products, beverage, cosmetics, medicine and textiles.

The main components of sorghum red pigment are 5,4'-dihydroxy-7-0-isoxanthoketone galactoside (molecular formula: C21H20O10, molecular weight: 432.37) and 5,4'-dihydroxy-6, 8-dimethoxy-7-0-isoxanthoketone galactoside (molecular formula, C23H24O12 , molecular weight, 492.42), Their structural formulae are described as Figure15 (2).

Material (sorghum glumes) Cleaning Washing Extracting Filtering

Concentrating Centrifuging Drying Sterilising Inspecting Packing

Products

Figure 14: The General Extracting Method of Sorghum Red Pigment THE GENERAL EXTRACTING METHOD OF SORGHUM RED PIGMENT

(1) 5,4'-dihydroxy-7-O-isoxanthoketone galactoside

(2) 5,4'-dihydroxy-6, 8-dimethoxy-7-O-isoxanthoketone galactoside

Figure 15: The Structural Formulae of Sorghum Red Pigments

In 1992, The Extracting Technology of Sorghum Red Pigment declared their invention patent. In 1995, Liaoning Keguang Natural Pigment Company Ltd. was established, which is a joint venture of Liaoning Academy of Agricultural Sciences, China and Koyo Shangyo Company Ltd., Japan. Their products fall into two series: alcohol soluble (A) and water soluble (W), produced through 6 technological processes. A-100, A-200,W-300,W-400, W-500, etc. are the main varieties sold at home and abroad. Annual output of natural Sorghum Red Pigment is more than 20 tons. Both economic performance and social effects are good. Following is some applications of Sorghum Red Pigment (6).

Meat products

Between August and November 1992, Shenjin Meat products Factory of Shenyang used Sorghum Red Pigment researched by Sorghum Institute, Liaoning Academy of Agricultural. Science as an additive for ham, (The dosage was 0.34 g Sorghum Red Pigment in one kilogram ham.) roasted 400 kg ham at 3000C, which expresses soft nature tone and reality.

Cosmetics

Baita Daily Chemical Product Factory successfully used Sorghum Red Pigment on lipstick and shampoo. The Products has soft and bright colour, therefore natural Sorghum Red Pigment is thought to be a substitute of synthetic pigment in cosmetics.

Medicine: Using as colouring agent of sugar-coated tablets and capsules

In November 1992, Shenyang Pharmaceutical College successfully used Sorghum Red Pigment as colouring agent of sugar-coated pills. In March 1994, Tiexi Capsule Plant of Shenyang, added 4.6 g Sorghum Red Pigment per kilogram Capsule, got ideal results. The product is dark red, smooth, with no unpleasant door, no gaps or shapelessness. When inspected, every target adheres to national standards.

Using as Colouring Agent of Traditional Chinese Patent Medicine

Xinmin Hongqi Pharmaceutical Factory used Sorghum Red Pigment as colouring agent of traditional Chinese patent medicine. The problem has been resolved for the colour tone match of traditional Chinese patent medicine to pharmaceutical requirements.

Candy

In April 1993, Shenyang Bakery successfully made 10 kg fruit candy using Sorghum Red Pigment with the dosage of 0.025 g. The candy had stable colour with no unpleasant odor. The results were satisfactory.

Another confectionery manufacturer, Shenyang Dayi Manufactory, used Sorghum Red Pigment as a colouring agent of health-care candy, and got positive results. Moreover, Sorghum Red Pigment also can be used in colouring of beverage, jellies, cakes, and textiles.

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