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COMPARATIVE STUDY ON THE PRODUCTION OF OXIDIZED STARCH FROM SORGHUM USING SODIUM HYPOCHLORITE AND POTASSIUM PERMANGANATE
ABSTRACT
This project is the production of oxidized starch from sorghum starch using sodium hypochlorite and potassium permanganate. After the analysis Table 1 shows that; the starch oxidized with NaOCl has the lowest percentage yield of (88%) as compare with KMn04 (91 %). And Table 2 shows the effect of sodium hypochlorite concentration on starch viscosity. Increase in concentration lead to the decrease in starch viscosity. The sample produced by treatment with chlorine at 5.0% this effect was more pronounced (at 67.2.2oC the torque 4% was at 29.7), for a high concentration starch slurry (20%). This starch also presented cold swelling, with detectable viscosity (around 20% of torque) at the beginning of the analysis (50oC), these results are in agreement with those of that found lower pasting temperature for different corn starches when oxidized, mainly at the concentration 5.0% of NaOCl related with structural weakening of the starch granules.
CHAPTER ONE
1.0 INTRODUCTION
Oxidized starch is widely used in food and non-food industries where film formation and adhesion properties are desired. The major application of oxidized starch is as a surface sizing agent and as a coating binder in paper industry. Native starch paste is often not used in such applications because of the low solubility and high viscosity of the pastes. Aqueous solutions of native starch are more prone to retrogradation than those of oxidized starch.
Based on the behavioral diversities of native starches such as being biodegradable, the presence of functional groups and its macroscopic granular structure, the starch chemist by selection of raw material followed by application of selected modification techniques can devise products with a broad range of functional characteristics.
Oxidized starch is produced by reaction of starch with oxidizing agent. During the course of the reaction several reactions occur which leads to the introduction of carbonyl and carboxyl groups and degradation of starch molecules. Hence oxidized starch exhibits low viscosity due to depolymerisation and improved stability of starch dispersion from the presence of functional groups. (Maurer, 1999).
Starch can be oxidized with oxidizing agent namely periodate, dichromate, permanganate, persulphate, hypochlorite and hydrogen peroxide. Depending on the starch source, it has been established that the property of oxidized starch produced is influenced by the concentration of the oxidizing agent and the rate of addition, time, temperature and pH.in the commercial practice, alkaline hypochlorite is the common used oxidizing agent. The other known oxidizing agents are rarely used. The reason for this preference is not clear and seems to be based on mere convention. (Miller, 1995).
Also compared to other cereals sorghum starch is not commonly utilized m industrial applications though its grain composition is very much similar to the most popularly used cereal corn. (Watson, 1984). Sorghum is also readily available and cheap.
1.1 SORGHUM
Sorghum is a genus of plants and grass family. Most species are native to Australia with some extending to Africa, Asia, Mesoamerica and certain islands in Indian and pacific oceans. (FAO, 1995).
One of the specie is grown for grain while many others are used as fodder plants either intentionally cultivated or allowed to grow naturally in pasture lands. The plants are cultivated in warm climates world-wide and naturalized in many places. (FAO, 1995). Other names include durra, Egyptian millet, guinea corn; milo etc. sorghum for centuries has been one of the most important staple foods for millions of poor rural people in the semiarid tropics of Asia and Africa. For some impoverished region of the world, sorghum remains a principal source of energy, proteins, vitamins and minerals. Sorghum grows in harsh environments where other crops do not grow well such as cassava.
Grain sorghum is the third most important cereal crop grown in the United States and the fifth most important cereal crop grown in the world. In 2010, Nigeria was the world’s largest producer of grain sorghum followed by the US and India.
1.2 ORIGIN
Rich finds of sorghum bicolor have been recovered from Qasribrim in Egyptian Nubia, the wild example have been dated back to circa 800-600BCE and the domesticated one no earlier than CE 100. Most cultivated varieties of sorghum can be traced back to Africa where they grow on savannah lands. Sorghum was planted extensively in parts of the Middle East, No11h Africa and Europe (Wayne and Richard, 2005). the name sorghum comes from Italian sorgo in turn from latinsyricum(granum) meaning grain of Syria.
Sorghum is well adapted to growth m hot, arid or semi-arid areas. The many subspecies are divided into four groups grain Sorghums such as milo, grass sorghum(for paste and hay),sweet sorghums formerly called guinea corn used to produce sorghum syrups and broom corn for brooms and brushes.
The FAO reports that 440000 square kilometres were devoted worldwide to the production in 2004.In the US sorghum is used primarily as a maize com substitute for livestock feed because their nutritional values are very similar. Some hybrids commonly grown for feed have been developed to deter birds and therefore contain a high concentration of tannins and phenolic compounds which causes the need for additional processing to allow the grain to be digested. (FAO, 2010).
1.3 CULTIVATION
Sorghum requires an average temperature of at least 25°C to produce maximum grain yields in a given year. Maximum photosynthesis is achieved at daytime temperatures of at least 30°C. Night time temperature below 13°C for more than a few days can severely reduce the plants potential grain production. Sorghum cannot be planted until soil temperatures have reaches l 7°C. the Jong growing season usually 90-120 days, causes yields to be severely decreased if plants are not in the ground early enough sorghum in general is a very competitive crop and does well in competition with weeds in narrow rows. Sorghum produces a chemical compound called sorgoleone, which the plant uses to combat weeds. The chemical is so effective in preventing the growth of weeds it sometime prohibits the growth of other crops harvested on the same field (F AO, 1995).
Sorghum’s growth habit is similar to that of maize but with more side shouts and a more extensively branched root system. The root system is fibrous and can extend to a depth of up to l .2m. The plant finds 75% of its water in the top metre of soil and because of this, in dry areas; the plan’s production can be severely affected by the water holding capacity of the soil. The plant require up to 70- 100mm of moisture every 10 days in early stages of growth, and as sorghum progresses through growth stages and the roots penetrate more deeply in to the soil to tap into hidden water reserves, the plants need progressively less water. By the time the seeds heads are filling optimum water conditions are down to about 50mm every 10 days. (Wayne and Smith, 2005).
1.4 SCIENTIFIC CLASSIFICATION
Kingdom: Plantae
Order: Poales
Family: Poaceae
Subfamily: Panicoideae
Tribe: Andropogoneae
Genus: Sorghum
1.5 COMPOSITION
The structure and composition of the sorghum kernel is quite similar to that of corn. The kernels are flattened spheres measuring about 4.0mm long, 3.5mm wide and 2.5mm thick. The weight of individual kernels ranges from 8 to 50mg with an average of 28mg. colors of the prehybrid varieties range from white through pale orange, tan and red to dark red- brown. Most grain in commercial channels is a brownish red colour because one or both parents of the best hybrids have that colour. (Martin,2007).
The structure of the sorghum germ is identical to that of corn germ. The endosperm differs from that of the corn only in the relative proportions floury and horny endosperm entirely surrounds the floury region. The dense peripheral endosperm layer comprises a larger portion of the kernel than in corn and results in much greater problems in much greater problems during starch purification. (Watson et al, 2005).
The pericarp of grain sorghums show the most differences from corn.it is covered with a thick layer of wax. (Seckinger et al, 1996) most varieties have a thick mesocarp layer in the pericarp layer containing very small unrecoverable starch granules; some varieties have a thick orange pigmented testa layer (Sanders, 1995) which shatters during wet milling and adds coloured particles to the starch. The epidermis layer of pericarp of some varieties contains water- soluble, flavone-type pigments ranging in colour from red to orange. In some varieties, a purple flavonoid contained in the glume which surrounds each seed leaches into the seed and gives a gray cast to isolated starch.
1.6 CHEMICAL COMPOSITION
Proximate Analysis of Grain Sorghum.
| Range % dry basis | Average % dry basis | |
| Water(% wet basis) | 8-20 | 15.5 |
| Starch | 60- 77 | 74.1 |
| Protein (Nx6.25) | 6.6-16 | 11.1 |
| Fat (CCl4) | 1.4 – 6. 1 | 3.7 |
| Ash | 1.2 – 7.1 | 1.5 |
| Crude fiber | 0.4-13.4 | 2.6 |
(Miller, 1995} ..
The chemical composition of commercial grain sorghum based on proximate analysis is shown above. The grain sorghum differs from corn in minor ways. Moisture content is generally lower because the grain dries more in the field before harvest compared with corn; starch and protein contents are 1-2% higher, while total fat is always lower because the germ constitutes a smaller proportion of the kernel than it does in corn. Furthermore the pericarp wax amounts to about 8% of the total fat and must be removed in refining crude oil. (Hubbard et al, 2005). Analysis of the wax indicates that it is comprised of saturated fattyacids, aldehydes and alcohols of 27-30 carbons atoms. (Bianchi et al, 1997). All sorghum varieties contains tannins but dark- brown, bird resistant varieties contain tannin levels so high as so reduce digestibility when fed. (Maxon and Rooney, 2002).
1.7 STARCH
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined by glycosidic bonds (a covalent bond that joins a carbohydrate molecule to another group which may or may not be another carbohydrate). This polysaccharide is produced by most green plants as an energy store. It is the most common carbohydratein human diets and is contained in large amounts in such staple foods as potatoes, wheat, maize, rice and cassava.
Pure starch is a white, tasteless and odourless powder that is insoluble in cold water and alcohol. It consist of two types of molecules the linear and helical amylase and the branched amylopectin. Depending on the plant, starch generally contains 20 to 25% amylase and 75 to 85% amylopectin by weight. (Brown and Poon, 2005).
Structure of Amylose molecule
Structure of Amylopectin molecule
1. 7.1 AMYLOSE CONTENT OF VARIOUS STARCHES
| Starch source | % Amylose |
| Waxy rice | 0 |
| High amylose corn | 70 |
| Corn | 28 |
| Cassava | 17 |
| Waxy sorghum | 0 |
| Wheat | 26 |
| Sweet potato | 18 |
| Arrow root | 21 |
| Sago | 26 |
| Potato | 20 |
(FAO, 1995).
1. 7.2 AMYLOPECTIN CONTENT OF VARIOUS STARCHES
| Starch source | % amylopectin |
| Waxy rice | 100 |
| High amylose corn | 30 |
| Corn | 70-72 |
| Cassava | 83 |
| Waxy sorghum | 100 |
| Wheat | 74 |
| Sweet potato | 82 |
| Arrow root | 79 |
| Sago | 74 |
| Potato | 80 |
(FAO, 1995)
Starch-possess properties such as high viscosity, insolubility, low dispersion rate and stability which makes its application unsuitable for use in food products as thickening agent, stabilizer or emulsifier; in pharmaceuticals as a disintegrant; in construction; oil exploration; textile and as a binder in paper industry. It is as a result of this, that starch is modified to allow it function properly under conditions frequently encountered during processing or storage so as to increase their stability against excessive heat, acid, shear, time, cooling or freezing; to change their texture; to decrease or increase their viscosity; to lengthen or shorten gelatinization time; or to increase their visco-stability. (Smith et. al, 2005).
1.8 STARCH MODIFICATION
Starch has various applications in industry. And to obtain or effect its use in any of this industry its modification is required. In general the susceptibility of starch modification is determined primarily by the fact that the material is biodegradable, its macroscopic granular structure and by the presence of certain functional groups. Moreover depending on the location of the hydroxyl group and the bond type (alpha (l-4) glycosidic versus alpha (1-6)-glycosidic), starch reveals different properties when chemical modification is concerned.
Hydroxyl group at carbon C-6 is primarily alcohol while at C-2 and C-3 carbons it is secondary alcohols. (Bemiller et al 2009).
It is the presence of the three (3) hydroxyl groups in glucose that makes it susceptible to substitution reactions and enables the number of possible modification of starch.
The grain size of the starch also affects the reactivity. The larger the grains are, the
higher the modification susceptibility is as external factors have easier access to the larger grains. (Lewandowicz and Maczynski, 2000).
1.8.1 GRANULE SIZE DISTRIBUTION OF VARIOUS STARCHES
| Starch species | Grain size range (µm) | Average size (µm) |
| Waxy rice | 2-13 | 5.5 |
| High amylase starch | 4-22 | 9.8 |
| Corn | 5-25 | 14.3 |
| Cassava | 3-28 | 14 |
| Sorghum | 3-27 | 16 |
| Wheat | 3-34 | 19.5 |
| Sweet potato | 4-40 | 18.5 |
| Arrow root | 9-40 | 23 |
| Sago | 15-50 | 33 |
| Potato | 10-70 | 36 |
Starch is modified according to the modification process utilized and is divided into three (3) main groups;
1.9 PHYSICAL PROPERTIES OF OXIDIZED STARCH
- Oxidized starch is whiter than the native starch and the degree of whiteness increases with the extent of treatment. (Hall et al, 2011).
- They are sensitive to heat, tending to yellow or brown when exposed to high temperature. This yellowing tendency during drying has been related to the aldehyde content. With increasing aldehyde content, the oxidized starch becomes increasingly yellow on storage., (Walton, 2010).
- Oxidized starches gelatinize at a lower temperature than native starches.
- They produce aqueous dispersions of greater clarity and lower viscosity. These dispersions have fewer tendencies to set back or gel, (Anne, 2004).
1.10 WHY STARCH IS OXIDIZED.
- Obtain low viscosity
- Obtain high-solid dispersions and resistance to viscosity increases or gelling in aqueous dispersion.
- Cause depolymerisation which results in a lower viscosity dispersion.
- Introduce a carbonyl and carboxyl groups which minimize retrogradation of amylase thus giving viscosity stability.
- Improve whiteness and reduce microbial content, (Maurer, 1999).
1.11 APPLICATIONS OF OXIDIZED STARCH
- PAPER INDUSTRY: About 80-85% of Oxidized starch is used primarily in paper industry as a paper coating binder where it’s high fluidity and good binding and adhesive properties make it effective in high solids pigmented coating colours. (Lucas and Fletcher, 2012). Oxidized starches were also used for paper and paperboard surface sizing to seal pores, tie down loose surface fibers, improve surface strength, and provide hold out of printing inks. Viscosity stability of oxidized starch dispersions as well as the range of viscosities available made them particularly suitable. (Zuderveld and Stoutjesdijk, 2005).
- TEXTILE INDUSTRY: Starch has a long history in the manufacture of textiles; it is used primarily as warp sizing but also in finishing and printing (Radley, 1998). The high fluidity, stable viscosity, and flow properties at high solids of oxidized starch allows for greater add• on to the yarn and provides good abrasion protection. Such starches are readily soluble and can be desized from the woven cloth. Oxidized starches may be used in back- filling where a mixture of starch and filler such as clay is applied to the back of a fabric to fill the interstices of the weave and impart opacity and stiffness. The lower oxidized starch penetrates fabric to a greater extent than do higher viscosity starches. (Moore, 2012).
- CONSTRUCTION INDUSTRY: Oxidized starches are also used in the fabrication of construction materials such as insulation and wall boards and acoustic tiles to provide adhesive, binding and sizing properties.
- FOOD INDUSTRY: In food industry, slightly oxidized starches have been used in batters and beading’s for foodstuffs such as fried fish where it is claimed to give good adhesion to the food. It is used as stabilizers in ice-cream and milk pudding production. Oxidized starch can also replace Arabic gum due to its excellent stability leading to a clear food product.
- LAUNDRY: Oxidized starch is used in laundry finishing, sometimes in aerosol cans for home use. (Antinori and Rutenberg, 2000).
1.12 JUSTIFICATION OF THE WORK
The application of starch in the paper, food and textile industry is very important as it has numerous advantages. Native starch has high viscosity and other functional properties which makes its application unsuitable (Gollieb and Capelle, 2005). It is as a result that starch is modified to allow it function properly.
The study is expected to provide information on how to produce oxidized starch using the suitable oxidizing agent and to study the effect of concentration on starch. This information will serve to clear our doubt on why alkaline hypochlorite is mostly used for the oxidation of starch.
1.13 SCOPE OF THE WORK
The study will be based on the oxidation of sorghum starch using two oxidizing agent viz; NaOCI and KMnO4 at different concentration. Also the viscosity and viscosity stability will be determined.
1.14 LIMITATION OF THE STUDY
In any research there must be some short falls and this research is not an exception since sodium bisulphite (NaHSO3) is the most used reducing agent its lack of availability lead to the use of sodium thiosulpbate (Na2S2O3). Also lack of basic equipment apparatus such as temperature controlled water bath, rheometer lead to the use of other modified method.
1.15 AIM AND OBJECTIVES
- Oxidizing sorghum starch using two oxidizing agents viz; Sodium hypochlorite (NaOCl) and Potassium permanganate (KMnO4).
- To establish the oxidizing agent suitable for the oxidation of starch.
- To determine the effect of different concentration on physicochemical properties of sorghum starch which could provide information used to improve the manufacturing process as well as the product properties for some certain application
SOLD BY: Enems Project| ATTRIBUTES: Title, Abstract, Chapter 1-5 and Appendices|FORMAT: Microsoft Word| PRICE: N2000| BUY NOW |DELIVERY TIME: Within 24hrs
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