EXTRACTION OF LIGNIN FROM COCOA POD HUSK THEOBROMA CACAO

ABSTRACT

Cocoa (Theobroma cacao L.) fruits are important commodity of economic value since the seeds or beans is used to produce high demand products such as cocoa powder, butter and chocolate. The processing of cocoa fruits generates a large amount of cocoa pod husk discard as wastes. Thus, the aim of this study was to obtain lignin from cocoa pod husk (Theobroma cacao L.). Infrared spectrum results showed peaks of galacturonic acid functional groups, indicating the presence of lignin in the cocoa husk. In extraction stage was carried out acid hydrolysis with citric or acetic acid at different pH (2, 2.5 and 3), 90°C temperature and 90 minutes, and was evaluated its influence on yield, methoxyl and galacturonic acid content. From the established extraction conditions, aqueous citric acid at pH 2.0 provided the highest yield and methoxyl content, 18.12% and 15.5% respectively. While the galacturonic acid content showed better results with acetic acid at pH 3 with an 83.1%. Finally, it was concluded that cocoa pod husks are suitable to obtain lignin, and a marked influence of the type of acid on response variables in the lignin extraction process was observed.

CHAPTER ONE

 INTRODUCTION

1.1   Background of the study

Cocoa (Theobroma cacao L.) fruits are important commodity of economic value since the seeds or beans is used to produce high demand products such as cocoa powder, butter and chocolate. The processing of cocoa fruits generates a large amount of cocoa pod husk discard as wastes (Alemawor et al., 2009). Cocoa pod husk represents between 70 to 75% of the whole cocoa fruit weight where each ton of cocoa fruit will produce between 700 to 750 kg of cocoa pod husks (Cruz et al., 2012). In Malaysia, the plantation of cocoa is over 20,643 hectre (Malaysia Koko Board, 2011). Hence, it can be estimated at least 320,000 kg of cocoa pod husk is generated after processing. Conventionally, these organic wastes is shipped away for processing or disposed to landfill. These large quantities of cocoa pod husk could yield a large quantity of fibrous materials which might be suitable as alternative resources especially in pulp and paper making industries.

In order to maximize the utilization of organic wastes or non-wood fibres for pulp and paper production, a complete study of its chemical and morphological properties is required. In this context, the main objective of this work is to investigate the chemical compositions of cassava peels and cacao pod husks fibre used for pulp and papermaking industry. In addition, characterization of surface morphology in both non-wood fibres was also determined. The results obtained in this study could be utilised in assessing the agriculture wastes potential as raw materials for pulp and paper production industries.

Lignin found in cacao is high complex macromolecule linked together by different types of bonds, including alkyl-aryl, alkyl-alkyl and aryl-aryl ether bonds (Kumar et al., 2011). It obstructs enzymes from degradation associated  with structural carbohydrates (Taherzadeh and Karimi, 2010). Therefore, prior treatment of lignocellulosic feedstocks, to remove or denature lignin, is essential for achieving a high yield of fermentable sugars (Yang and Wyman, 2012; Carroll and Somerville, 2010). Plant by-products differ in monolignol constituents of lignin’s and lignin chemistry can vary depending on its origin. The characterization of lignin is critical to the optimization of pre-treatment parameters in the cellulosic ethanol production process. It on this background that this study examines the extraction and characterization of lignin using cocoa (Theobroma cacoa) pod husk.

1.2   Aims and objectives

The aim of the study is to extract lignin and to characterize the lignin extracted from the pod husk of cacao pod. Specific objectives are

1. To quantify the amount of lignin content of cocao(Theobroma cacoa) pod.
2. To investigate the proximate content of cocoa pod with respect to it ash content, moisture content, carbon content and surface area.
3. To characterize the lignin content of cocoa pod.

1.3   Significance of the study

The study is significant since it will quantify the amount of lignin present in cocoa pod and the proximate content of cocoa pod. The study will also highlight the characteristics of cocoa pod.

1.4   Scope of the study

The scope of the study covers the extraction and characterization of cocoa pod husk and proximate analysis of cocoa pod.

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