EFFECT OF FERMENTATION TIME AND ADDITION OF CITRIC ACID ON THE QUALITY CHARACTERISTICS OF CASSAVA FLOUR

1.1 Introduction

Cassava (Manihot esulenta crantz) constitutes one of the main staple foods in many sub-Saharan countries in Africa. Cassava is a significant source of calories for more than 500 million people worldwide (cook 1985). It plays a food security role in providing a stable food base in areas prone to drought and famine. One main disadvantage of cassava is its rapid microbiogical determination occurrence (Sanni 1992). This cassava is processed into flour (cassava flour) and preserved.

Cassava flour is a fraction of cassava obtained from the roots. It is a good source of carbohydrates but a poor source of protein. Cassava flour differs from tapioca four in that tapioca is made from the cassava staunch of the cassava plant where cassava flour is the ground root. It is naturally glutten free. It is a good for bread, other baked food and celiac diet. Cassava flour is a good substitute for wheat flour. As a side note; insects will not eat cassava flour not even cockroach. Cassava flour may be fermented or unfermented.

Quality characteristics of cassava describes the properties and nutritional qualities/chemical characteristics of cassava flour which include the moisture content, protein content, fibre content, starch quality, cynagenic compounds present etc varying amount of these elements mentioned have been said to significantly reduce when the cassava flour is subjected to fermentation process.

Fermentation derived from the latin word feven meaning to be boiling. The best known example is the degradation of sugars in alcohol by yeast as exemplified in the spontaneous transformation of fruit juice into wine or cider with vigorous evolution of carbon (iv) oxide given the impression of boiling. The term is now used generally to describe metabolic process in which chemical changes are effected, not only on sugars but in many organic substrates by micro organism or derived enzymes.

In food processing, fermentation is typically the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria or a combination of the two. Food fermentation has been said to serve five main purpose which include the enrichment of diet through development of a diversity of flavours, aromas and textures in food substrate, preservation of substantial amount of food through lactic acid, alcohol acetric acid and alkaline fermentations, biological enrichment of foods substrates with protein, essential amino acids, essential fatty acids and vitamins, elimination of antinutrients and a decrease in cooking time and fuel requirement.

Natural fermentation proceeds human history. Since ancient times, however, humans control fermentation process. Fermentation time describes the period allowed for the fermentation to take place. That is, the time allotted for fermentation to occur in a given food substrate.

As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Limitations of the Study and Definition of technical terms.

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1.2 Background of Study

Cassava flour production till date is carried out at local levels mostly by local women who do so to enhance household food security (Fapojuwe, 2008), and according to Nweke et al. (2002), production of cassava flour remains labour-intensive. Large scale production of cassava flour in Nigeria failed probably due to the limited information on processing variables that promote detoxification in cassava, and fermentation to produce unique flavor characteristics associated with cassava flour (Achinewu and Owuamanam, 2001; Nweke et al., 2002).

Fresh cassava root contains a toxic compound (hydrogen cyanide), which is harmful for human consumption and apparently detrimental for the use of cassava in food industries (Iglesias et al., 2002). However, research have shown that processing techniques such as peeling, fermentation, soaking and drying can detoxify and reduce the cyanide content, improve palatability and add value to the root (Cardoso et al., 2005; Burns et al., 2012). Converting cassava root into food forms and raw materials such as fufu, cassava flour, tapioca, flour, chips and pellets can extend the shelf-life, facilitate trade and promote industrial use (Taiwo, 2006; Fadeyibi, 2012).

Globally, there is a notable increase in demand and price of cereals, especially wheat, which consequently influences the price of cereal-based products (FAO, 2013). The rising cost of importing wheat flour for food in many developing countries such as Nigeria has spurred the need for research to develop suitable flour from local agricultural materials such as cassava, which are cheaper but also possesses suitable quality attributes and functional properties. Furthermore, wheat flour contains gluten which causes celiac disease especially to gluten intolerant persons (Briani et al., 2008). Studies have recommended gluten-free diet as a suitable treatment for patients with celiac disease, gluten intolerance and wheat allergic reactions (Gaesser & Angadi, 2012; Alvarez & Boye, 2014). Therefore, non-wheat gluten-free flour developed from root and tuber crops such as sweet potato (Ipomoea batatas), cassava (Manihot esculenta), potato (Solamum tuberosum), yam (Dioscorea spp) and cocoyam (Xanthosoma sagitifolium) offer the potential to alleviate the double burden of rising cereal prices and gluten intolerance (Aryee et al., 2006; Ammar et al., 2009; Sanful & Darko, 2010). In particular, the use of gluten-free flour from high quality cassava root as composite flour in highly sought after foods such as bread has gained popularity in many developing countries (Eddy et al., 2007).

High quality cassava flour is white or creamy, unfermented and gluten-free flour obtained from cassava root and it is used in the food industry for the production of pasta and confectionery (Taiwo, 2006; Shittu et al., 2008). When wheat was substituted by up to 20% in bread, Eddy et al. (2007) found that cassava flour added no foreign odour or taste to the product formed and no significant changes were observed in other bread characteristics. The physicochemical properties of cassava flour offer the benefit of good functionality as raw material for the manufacturing of various food products. For instance, the high starch content of cassava flour contributes to crispy texture of processed products (Falade & Akingbala, 2010), while its low fat content is an excellent attribute for controlling rancidity and enhancing shelf-life stability of the product (Charles et al., 2005; Eleazu et al., 2011). Flour and other materials used in manufacturing food products need to be packaged and stored properly prior to utilisation to ensure the quality, safety and storage stability. To realise the full potential of cassava flour in food processing, either alone or in combination with other raw materials such as wheat flour, knowledge of the effects of package types and storage conditions on quality and shelf-life stability of cassava flour is important.

Therefore, in Nigeria where the research was carried out, the activities that was conducted is to know the Effect of Fermentation Time and Addition of Citric Acid on the Quality Characteristics of Cassava Flour.

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1.3 Statement of Problems

Traditional processing of cassava by fermentation is centered on reduction of cyanide in the resultant product through extended period of fermentation for up to 7days as important strategy for the safety of product (Sanni, 2005). However, the traditionally processed cassava flour contain varied amount of residual cyanide because of the tendency by local processors to shorten the duration of fermentation in order to meet growing market demand (Nweke et al., 2002).

It is difficult to understand how cassava and cassava products such as cassava flour can be promoted without giving proper consideration to the fact that it contains cyanogens (linamarin) that liberates poisonous cyanide in the body. Consumption of cassava and its products containing amounts of cyanide can cause acute intoxication, with symptoms of dizziness, headache, nausea, vomiting, stomach pains, diarrhea and sometimes death (Oluwole et al., 2003). Since lethal dose is proportional to body weight, children tend to be more susceptible to outright poisoning than adults. In regions where there is iodine deficiency, which causes goiter and cretinism, cyanide intake from cassava exacerbates these conditions (Delange et al., 1994). In west Africa particularly Nigeria, there is a disease called tropical ataxic neuropathy (TAN), which generally occurs in older people who have consumed a monotonous cassava diet over years. TAN is progressive and causes unsteady walking, produces loss of sensation in hands, loss of vision, deafness and weakness (Dulcer et al., 2008). Until recently, long term cyanogenic intake was linked with the occurrence of TAN but recent work has shown that the situation may be more complex. Also, when cassava and its products are eaten, most of the ingested cyanide is converted into thiocyanate, a reaction catalyzed by the enzyme rhodanese, which uses up part of the pool of S-containing essential amino acids, methionine and cystein (Cardoso et al., 2004). These amino acids are essential in the diet because they can only be obtained from the food consumed. A shortfall of this S-containing amino acid would limit protein synthesis and could cause stunting in growing children, as was found in a study of children in DRC (Dulcer et al ., 2008).

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1.4 Aim and Objectives of Study

The main aim of the study is to determine the effect of fermentation time and addition of citric acid on the quality characteristics of cassava flour. In achieving this aim, the following specific objectives were laid out as follows:

1. To investigate how different fermentation times influence the quality characteristics of cassava flour.
2. To produce cassava flour at controlled conditions of temperature, relative humidity and time.
3. To monitor the fermentation time for breakdown and removal of cyanogenic compounds and cyanide.
4. To determine the proximate composition, functional and pasting properties of the final products.
5. To determine the sensory attributes of the products.

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1.5 Significance / Justification of Study

There is need to optimize the local cassava flour processing methods as well as its industrialization especially by reducing the fermentation time and achieving the elimination of cyanide while maintaining cassava flour quality.

This present study considered the variability in the environment and fermentation conditions (temperature, relative humidity and duration of fermentation) during fermentation of cassava mash as they affect quality characteristics of cassava flour and reduction of cyanide.

This study will be of immense benefit to other researchers who intend to know more on this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for other study.

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1.6 Scope of Study

The study focuses on the determination of the Effect of Fermentation Time and Addition of Citric Acid on the Quality Characteristics of Cassava Flour. The samples were analyzed for pH, TTA and HCN. Thereafter, the samples were toasted to obtain the final product (cassava flour) which was analyzed for proximate, chemical, functional, pasting and sensory properties.

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1.7 Limitations of the Study

During the course of this study, many things militated against its completion, some of which are:

1. Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
2. Research material: availability of research material is a major setback to the scope of the study.
3. Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
4. Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).