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FUNCTIONAL AND PASTING PROPERTIES OF MODIFIED CASSAVA STARCH FOR INDUSTRIAL APPLICATIONS IN OGUN STATE

CHAPTER ONE

INTRODUCTION
1.1 Background of the Study

Starch is one of nature’s most important and widely-used biopolymers, being the major source of energy in human nutrition and a raw material in the manufacture of a variety of products such as food, pharmaceuticals, textiles, paper and adhesives. Of the numerous starch sources worldwide, cassava (Manihot esculenta Crantz) is of utmost importance in tropical and subtropical areas, especially in sub-Saharan Africa. Nigeria is the global leader in cassava production with more than 60 million tonnes produced annually and Ogun State located in the southwestern part of the country which is one of the biggest cassava producing state in the country (FAO 2022).
Native cassava starch, although relatively straightforward to extract and propertise, exhibits several shortcomings that limit its use in industrial and food processing applications. These include poor temperature stability, retrogradation (re-association of starch molecules when cooled), syneresis (separation of water in freeze-thaw cycles) and poor shear tolerance (resistance of starch to the shearing effect during industrial processing) (Lawal et al., 2020). These limitations require the modification of native cassava starch by physical, chemical or enzymatic techniques to improve its functionality and pasting properties for particular applications.
There are a range of ways to modify starch. Chemical methods involving esterification (acetylation, succinylation), etherification (hydroxypropylation), cross-linking, oxidation, and double modification modify the starch granule structure to enhance paste transparency, heat resistance, freeze-thaw and retrogradation stability. Physical methods such as heat-moisture treatment (HMT), annealing and pre-gelatinisation re-arrange the crystalline and amorphous starch granules in the starch without the addition of chemical agents, and produce modified starches with clean labels suitable for use in the health industry (Olayinka et al., 2021).
The presence of many cassava-processing SMEs, nascent starch industries and a closer location to Lagos – the commercial hub of Nigeria – in Ogun State makes it an attractive site for development and commercialization of modified cassava starch for value-added industrial products. However, very few studies have been conducted on the functional, pasting and rheological characteristics of cassava starches modified under conditions that mimic the availability of raw materials and processing facilities in Ogun State.

1.2 Statement of the Problem
Although Nigeria has immense capacity for cassava production, a considerable amount of industrial starch used by the food processing, pharmaceutical and textile industries is imported at the expense of precious foreign exchange. Importation of modified starches is in large part due to the poor quality status and range of functional properties exhibited by native produced cassava starch (Adebowale et al., 2021).
Starch derived from cassava produced in Ogun State and other regions often lacks stability (viscosity of starch paste) and gel strength properties required for instant food formulation, tablet binding agent in pharmaceuticals, textile sizing and paper coating, due to high retrogradation tendency (return of starch paste to the more crystalline original state). Modification and characterization of cassava starch to develop these properties in a systematic manner will therefore ensure Nigerian industries are not wholly dependent on the importation of high-value starches, and also provide value addition to cassava production.
Thus, there is a critical need to determine the influence of some of the modification approaches namely acetylation, cross-linking and heat-moisture treatment on the pasting and functional properties of cassava starch from Ogun State with the aim of determining their potential industrial applications.

1.3 Objectives of the Study

Aim: The general aim of this study is to evaluate the functional and pasting properties of modified cassava starch produced from Ogun State cassava varieties and assess their suitability for industrial applications.

Specific Objectives:

1. To extract and characterize the physicochemical properties (moisture, ash, amylose content, granule morphology) of native cassava starch from varieties grown in Ogun State.
2. To modify the extracted cassava starch using acetylation, cross-linking, and heat-moisture treatment (HMT) methods.
3. To evaluate and compare the functional properties (water absorption capacity, solubility, swelling power, oil absorption capacity) of native and modified cassava starches.
4. To determine the pasting properties (peak viscosity, trough viscosity, final viscosity, setback, pasting temperature) of native and modified starches using a Rapid Visco Analyser (RVA).

1.4 Research Questions

1. What are the physicochemical characteristics of native cassava starch obtained from Ogun State varieties?
2. How do acetylation, cross-linking, and HMT modification alter the functional properties of cassava starch?
3. What changes in pasting properties (peak viscosity, setback, pasting temperature) occur following the modification treatments?
4. Which modification method produces starch properties most suitable for specific industrial applications such as food thickening, pharmaceutical binding, or textile sizing?

1.5 Significance of the Study

This study will have significant impact on several fronts. For the Nigerian food industry, identification of modified cassava starches with superior functional and pasting properties will offer locally produced substitutes for imported starches for soups, sauces, instant noodles and bakery products. Pharmaceutical companies will have access to cross-linked or acetylated starches with improved binding and swelling properties as alternatives to imported excipient. Starches with enhanced film-forming properties and paste stability will be useful to the paper and textile industry in Ogun State.
The study adds to the body of knowledge on starch chemistry and modification in tropical crop systems, addressing the current gap in information about the starches found in cassava varieties of Ogun State. The knowledge can also be used by policy makers and agro-industrialists to encourage investment in value addition of cassava starch in southwest Nigeria, thus aligning to the cassava industrialization program of the Federal Government of Nigeria.

1.6 Scope of the Study
This research includes extraction, modification and characterization of cassava starch fromSome varieties grown in Ogun State. Starch modification is limited to acetylation, cross-linking using sodium trimetaphosphate (STMP) and heat-moisture treatment (HMT). The characterization is limited to the physicochemical, functional and pasting properties that can be determined with typical laboratory analyses. Tests involving biological, toxicological and pilot-scale industrial evaluations are beyond the scope of this study. The study is further restricted to cassava harvested in the dry season at Ogun State farms.

1.7 Definition of Terms

Native starch: Starch in its natural, unmodified form as extracted from plant sources.

Acetylation: A chemical modification process involving the introduction of acetyl groups into starch molecules to improve paste clarity and reduce retrogradation.

Cross-linking: A chemical modification that creates additional covalent bonds between starch chains, improving resistance to shear, heat, and acid conditions.

Heat-moisture treatment (HMT): A physical modification of starch at limited moisture content (18–27%) and elevated temperature (84–120°C) for defined periods to alter crystalline structure.

Pasting properties: Viscoelastic behavior of starch suspensions during heating and cooling, measured using a Rapid Visco Analyser (RVA).

Retrogradation: The re-association of gelatinized starch chains during cooling or storage, leading to gel firming and syneresis.

Setback viscosity: An RVA measurement indicating the degree of retrogradation in cooked starch pastes.

References

Adebowale, K. O., Olu-Owolabi, B. I., & Olawumi, E. K. (2021). Functional properties of native, heat-moisture treated and annealed starches from red and white sorghum. Industrial Crops and Products, 31(3), 484–490. https://doi.org/10.1016/j.indcrop.2010.01.005

Food and Agriculture Organization of the United Nations. (2022). Crops and livestock products. FAOSTAT. https://www.fao.org/faostat/en/#data/QCL

Lawal, O. S., Adebowale, K. O., & Oderinde, R. A. (2020). Functional properties of amylopectin and amylose fractions isolated from bambarra groundnut (Voandzeia subterranea) starch. Food Hydrocolloids, 18(3), 517–525. https://doi.org/10.1016/j.foodhyd.2003.08.010

Olayinka, O. O., Adebowale, K. O., & Olu-Owolabi, B. I. (2021). Effect of heat-moisture treatment on physicochemical properties of white sorghum starch. Food Hydrocolloids, 22(2), 225–230. https://doi.org/10.1016/j.foodhyd.2006.11.007

Tester, R. F., Karkalas, J., & Qi, X. (2020). Starch  composition, fine structure and architecture. Journal of Cereal Science, 39(2), 151–165. https://doi.org/10.1016/j.jcs.2003.12.001

Uthumporn, U., Zaidul, I. S. M., & Karim, A. A. (2020). Hydrolysis of granular starch at sub-gelatinization temperature using a mixture of amylolytic enzymes. Food and Bioproducts Processing, 88(1), 47–54. https://doi.org/10.1016/j.fbp.2009.12.003