Tjahjadi, C.
Department Industrial Food Technology Universitas Padjadjaran E-mail : [email protected]
Abstract
In Indonesia grain sorghum was known since 1925 and cultivated in the semi-arid regions of Java and Nusa Tenggara islands. Production is still low, hardly any statistics are available. In 2008 central Java produced about 1.483 tons from 1.291 ha. Renewed interest in sorghum in West Java began in 1999 as cattle feed, mainly due to its resistance to drought. Demand for wheat flour in Indonesia is rising continuously as a consequence of population increase and changes in way of living particulary in urban areas. Dependencany on few crops such as rice and wheat flour may be solved by food diversification to ensure national food security.
Various commodities suggested are root-crops (cassava, sweet potato and arrowroot) and minor cereal crops (sorghum, job’s tears, millet). There are three types of grain sorghum based on tannin content, respectively type I (non-pigmented testa), type II (low-pigmented testa) and type III (pigmented testa and pericarp). Decortication produces sorghum-rice, which is more palatable and acceptable, because it is removes both pericarp and the testa to various degrees to yield sorghum-rice of yellowish white to greenish white color.
Decortication may be done by traditional, mechanical and chemical methods. The overall quality of the decorticated product depends on inherent characteristics of the grains and the method of decortications employed, but good results for all three types of sorghum could only be obtained by abrasive decortication. Sorghum-rice could be used to manufacture sorghum flour. Sorghum-rice and flour are versatile food materials. Sorghum flour is free of gluten and can be added to a variety of food as they are almost taste and scent free and naturaly has a color ranging from creamy to pinkish or reddish brown depending on the sorghum cultivar and hulling efficiency of the sorghum-rice. Sorghum-rice and flour doesn’t have good binding properties, which may be solved by applying specific prosessing or cooking methods such as cooking to induce gelatinition, pressure cooking or adding various food additives such as hydrocolloids, starches, food protein, sugar and mixing with other flours including wheat flour. Attempts have been done to manufacture food based on sorghum-rice respectively ‘kerupuk’, ‘keripik’, ‘opak’, ‘rengginang’ (rice-crispis), puff sorghum, snack based on puffed sorghum and food based on flour respectively bread, sweet rolls, cake, noodle and various cookies.
Introduction
Grain sorghum (Sorghum bicolor L. Moench) is native to tropical Africa. It is a leading cereal grain in both Africa and India, and now ranks fifth among the world’s most important grains, respectively rice, wheat, corn and barley. The world’s largest producers of grain sorghum are USA, India, Nigeria and Mexico, while the leading exporters are the USA, Australia and Argentina (US-Grain Council, 2008)
In Indonesia grain sorghum was known since 1925 and cultivated in the semi-arid regions of Java and Nusa Tenggara islands. Production is still low, hardly any statistics are available. In
2008 Central Java produced about 1.483 tons of sorghum grains from a total area of 1.291 ha (Anonymous, 2006).
Sorghum is inherently a very efficient crop, it emerges quickly and produces a rapid ground cover; it is efficient at using limited amounts of water and nutrients and has a high growth rate. It may be cultivated in various cropping systems repectively inter-cropping, sequential-cropping, relay-sequential-cropping, ratoon-cropping and rotational-cropping (Gruben and Partohardjono, 1996). Consequently cultivation of sorghum has great prospect especially for regions depending on rainfall for irrigation (Sihono, 2008; Sirappa, 2003).
Renewed interest in sorghum cultivation in West Java began in 1999, when some of Unpad’s researchers got involved in an Agribisnis development project to use sorghum plants as cattle feed, mainly due to it resistance to drought. However, farmers involved in this project insisted besides feed the crop should also produce grains that can be sold for additional income. Since then research were carried out involving plant breeding, crop cultivation, postharvest handling and processing of sorghum grains. Recently plans have been made by the BPPT and The Indonesian National Reseach Institute (LIPI) to carry more advanced research on sorghum. Sorghum generally posseses seeds of bronze, brown to brownish red color due to high tannin contents. Pericarp and tannin must be removed to make the grains edible and acceptable. On the other hand a high tannin content makes the crop more birdproof and disease resistant. Nutritionally, however tannins react with proteins causing indigesbility of these proteins. Moreover tannins also cause sorghum products to be astringent and reddish of color (Rooney and Sullines, 1977 vide Sirappa, 2003).
Sorghum grains may serve as substitute for rice as well as wheat flour. Sorghum contains 70 – 90% carbohydrates, 7.4 – 14.2 % protein, 2.4 – 6.5 % fat, 1.2 – 3.4 % ash, containing iron, phosphor and calcium. Tannin content range beween 0.4 – 3.6 %. Tannins are present mainly in the pericarp and testa (Plessis, 1998).
Decortication of sorghum grains removes both the pericarp and testa from the endosperm (Sinuseng and Prabowo, 1999). The pericarp have a tendency to adhere firmly to the kernel depending on thickness. Both pericarp and testa contain pigments, while the sorghum endosperm is either white or yellowish white. Degree of decortication could be measured by hulling efficiency (FAO, 2004).
Sorghum-rice (decorticated sorghum) could be used as a substitute for rice and rice-based food products. It can also be milled to yield sorghum flour which may be used to substitute wheat flour either partially or totally. Demand for wheat flour in Indonesia is rising continuously as a consequence of population increase and change in way of living particulary in urban areas. Most urban citizens consume fast food and snacks which are mostly based on wheat flour.
Dependencany on few crops such as rice and wheat flour may be solved by food diversification. Various commodities suggested include employing root-crops (cassava, sweet potato and arrowroot) and minor cereal crops (sorghum, job’s tears, millet). In this way Indonesian food security problems might be solved.
Types of Seed Sorghum and Decortications of Sorghum Grains Types of Seed Sorghum
The sorghum seed consists of pericarp (bran) 6.0 – 9.3%, embryo (7.0 – 12.1%) and endosperm 80.0 – 84.6 % (Rooney and Miller, 1982; Wall and Ross, 1970). Grain sorghum maybe classified into 3 categories based on tannin content (Figure 1), respectively type I (non-pigmented testa), type II (low-pigmented testa) and type III (pigmented testa and pericarp) (Hagerman et al., 1988 vide Waniska, 2000).
Various breeding programs to obtain sorghum types adapted to Indonesian conditions have been done. The result are UPCA-S1, UPCA-S2, Katengu, Feterita (Mudjisihono and Suprapto, 1987), B-100, B-95, B-72 and B-68 (Soeranto, 2004) and Unpad 1.1 a white sorghum type (Anas, 2009).
tannin sorghum white sorghum tannin sorghum (Local cultivar) (Genotype 1.1.) (Genotype B-100)
Figure 1. Types of Grain Sorghum Decortication of Sorghum Grains
Decortication of grain sorghum produces sorghum-rice, which is more palatable and acceptable because it is removes both pericarp and the testa to various degrees to yield sorghum-rice of yellowish white to greenish white color. Low tannin and tannin sorghum yield sorghum-rice of yellowish white color with reddish specks at the hyllum. Structure of sorghum grain is presented in Figure2.
Aleuron layer Peripheral layer Test
a
Scutelum Radicle
Hilum Pericar p
Germ Stylar
Figure 2. Sorghum Seed Structure (Rooney and Miller, 1981)
Decortication may be done by traditional, mechanical and chemical methods. The overall quality of the decorticated product depends on inherent characteristics of the grains and the method of decortication employed. White sorghum could be decorticated by the three pearling methods with satisfactory result. Low tannin and tannin sorghum grains could not be pearled with satisfactory result by the alkali debranning and traditional method (using mortar and pestle), but good results for all three types of sorghum could be obtained by abrasive decortication (Figure3).
White sorghum Low tannin Tannin sorghum
(Unpad 1.1) (genotype B-100) (indigenous cultivar) Figure 3. Sorghum-rice Decorticated by Mortar and Pestle Methods
Degree of abrasive decortication of sorghum could be measured by hulling efficiency (HE) (FAO, 1994). Sorghum-rice of the Unpad 1.1. and indigenous cultivar pearled to various hulling efficiency are presented in Figure4.
Indigenous Cultivar
(0’) (1‘) (1,5‘) (2‘) (2,5‘) White sorghum (Unpad 1.1)
HE: 100% HE: 39,36% HE: 30,33% HE: 24,25%
(0’) (5’) (7,5‘) (10‘)
Figure 4. Sorghum-rice with Various Hulling Efficiency (Mardawati, et al., 2009) Sorghum Flour Milling
Sorghum grains can not be stored more than two months due to pest and disease infestation, but sorghum flour may be stored for more than six months (Dogget, 1988).
Flour production involves grinding and refining cereal grains by a process called milling.
Table 1. Wholemeal and Sorghum Flour Fractions of to Two Sorghum Cultivar
Flour Fraction (Mesh) Indigenous Unpad 1.1
> 120
pinkish yellow with a small amount of brownish red specks
bright creamy
101 – 120
pinkish yellow bright creamy with some dark specks
81 – 100
pinkish yellow bright creamy
61 – 80
pinkish yellow with a small amount of brownish red specks
bright creamy with a large dark specks
41 – 60
pinkish yellow with a small amount of
brownish red specks bright creamy with some dark specks
21 – 40
pinkish yellow with a small amount of brownish red specks
bright creamy
> 80
pinkish yellow with a small amount of brownish red specks
bright creamy with some dark specks
Wholemeal
pinkish yellow with a small amount of brownish red specks
bright creamy
Usually before milling the grains are subjected to a brief conditioning treatment (2–3 hours) to remove pericarp in large pieces and efficient separation of the desirable products (Gani, 2011). Small scale milling is done by hammer mill or disc mill and than fractionated by sieving. Generally cereal flour posseses a particle size more than 80 mesh. Yields of sorghum wholemeal was about 91-93% but sorghum flour more than 80 mesh was about 35%. The cultivar Unpad 1.1 yields bright creamy flour with some dark specks and the indigenous type yields pinkish yellow flour with a large amount of brownish red specks (Table 1). Sorghum flour has more advantages than sorghum-rice, it is more practical and can be enriched and mixed to yield composite flour suitable for producing various food products.
Food Products Based on Sorghum-rice and –Flour Sorghum-rice Based Food Products
Sorghum-rice cooked by traditional method respectively boiling or steamming are has a sandy texture, due to the germ and embrionic disc. This can be removed by sieving or cooking in pressure cooker. The last method is more practical and has been used for manufacturing of food products such as crackers and other snacks (‘kerupuk’, ‘opak’,
‘keripik’).
Sorghum-rice cooked by traditional method and pressure cooking have a loose non- sticky texture. Therefore to produce ‘opak’ or ‘keripik’ a binder is needed such as tapioca.
However in “kerupuk’ manufacture the tapioca starch has to be pre-gelatinized and gelatinized. Type and concentration of binding agent for manufacturing various snack food based on cooked sorghum-rice is shown in Table 2. Moreover sorghum-rice still has reddish brown specks (except the white cultivar), that give specific coloring to the food product (Fig 5).
Table 2. Type and Concentration of Binding Agent for Manufacturing Various Snack Food Based on Cooked Sorghum-rice
Food Product Type and Concentration of Binding Agent
Sorghum-rice Cultivar
Keripik 7.5% tapioca Unpad 1.1
Keripik 7.5% tapioca Indigenous
Kerupuk Gelatinize 40% tapioca Unpad 1.1
Kerupuk Gelatinize 60% tapioca Zh-30
Opak 40% tapioca Unpad 1.1
indigenous Keripik Unpad 1.1 keripik Unpad 1.1 Opak Zh-30 kerupuk stick
Figure 5. Snack Products Based on Sorghum-rice
Sorghum Flour Based Food Products
Sorghum flour is gluten free and contain a small amount of phenolic compounds. Gluten free flour may be used to produce food for people alergic to gluten, such as celiac deseases patients and autistic children. Tannin content of the sorghum flour causes a pinkish or brownish color, but also have antioxidant properties (US Grain Council, 2008). Sorghum flour color may be covered up by using food colors, cinnamon, cocoa powder, etc. Sorghum flour doesn’t have good binding properties, which may be solved by applying specific prosessing or cooking methods such as cooking to induce gelatinization, pressure cooking or adding various food additives such as hydrocolloids, starches, food protein, sugar and mixing sorghum flour with other flours including wheat flour (composite flour). Substitution of sorghum flour in the production of various food products are shown in Table 3 and Figure6
Table 3. Percentage Sorghum Flour in Various Food Products Food Product Percentage
Sorghum Flour Binding Agent Sorghum Flour Cultivar
Bread 20% 80% Wheat flour B 100
Sweet rolls 30% 70% Wheat flour + sugar Unpad 1.1
Cookies 100% 38% sugar Unpad 1.1
Pound Cake 1 70% 30% Corn starch Indigenous
Pound Cake 2 70% 30% Corn starch + 2% xanthan gom
Indigenous
Figure 6. Product Based on Sorghum Flour
Conclusions
There are three types grain sorghum based on tannin content, respectively type I (non-pigmented testa), type II (low-(non-pigmented testa) and type III ((non-pigmented testa and pericarp).Decortication produces sorghum-rice, which is more palatable and acceptable.
Sorghum-rice and flour are versatile food materials. Sorghum flour is free of gluten and almost taste and scent free with a color ranging from creamy to pinkish or reddish brown.
Attempts have been done to manufacture food based on sorghum-rice respectively
‘kerupuk’, ‘keripik’, ‘opak’, ‘rengginang’ (rice-crispies), puffed sorghum, snacks based on puffed sorghum and flour respectively bread, sweet rolls, cake, noodles and various cookies.
Acknowledgment
We thank the Universitas Padjadjaranthrough the Andalan project 2009-2010 for providing research fundings
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