EFFECT OF PROCESSING ON THE STORAGE STABILITY AND FUNCTIONAL PROPERTIES OF COWPEA FLOUR IN THE PRODUCTION OF MOIN-MOIN AND AKARA

1.0 Introduction

1.1 Background of the Study

Vigna unguiculata, a legume commonly known as cowpea, is an important dietary staple in many developing nations because of its high nutritional value, low cost and availability (Boeh‐Ocansey 1989; Uzogara and Ofuya 1992; Prinyawiwatkul et al. 1996). Cowpeas are approximately 24% protein (with an amino acid content complementary to that found in cereals), 60% carbohydrates, are a good source of dietary fiber, and contain numerous vitamins and minerals (Bressani 1985; Phillips and McWatters 1991; Phillips 1993).

Akara is a traditional African product prepared by deep frying cowpea paste that has been whipped and seasoned with salt, chopped onions and either hot or bell peppers. The outer crust of akara is crisp and the interior is spongy and bread‐like. Akara is considered to be the most commonly consumed cowpea‐derived food in West Africa, and is made by individuals at home and sold fully prepared by vendors in marketplaces (Dovlo et al. 1976; Phillips and McWatters 1991). The traditional process for making akara is very time‐consuming and labor‐intensive, and requires the cowpeas be soaked, manually decorticated and wet‐milled. Microbial spoilage necessitates that the paste be used within several hours or be discarded, preventing the preparation of large amounts of paste that can be whipped and fried in small batches throughout the day (Bulgarelli et al. 1988).

To simplify akara preparation, easy‐to‐use readily hydratable cowpea meals and flours have been developed; however, akara prepared from commercially available meals and flours lacked the typical and desired fresh cowpea flavor and had a dense, dry texture disliked by consumers (Dovlo et al. 1976; McWatters 1983). An amalgam of growing, storage and processing conditions influence the functional properties of legume components ultimately determining the viability of a meal or flour as a starting material for akara (Phillips and McWatters 1991; Kaur and Singh 2005).

Past studies have been conducted with the aim of improving the functionality of cowpea meal and flour. Based on data from these past studies, it can be concluded that there are three keys to making acceptable akara from a processed meal or flour: cowpea proteins must maintain their structure in order to be functional; particle size distribution (PSD) of meal or flour must consist of at least 65% particles that fall in the medium size range, i.e., between 0.180 and 0.425 mm; and chunks of cell wall matrix must be present after processing (McWatters 1983, Ngoddy et al. 1986; Abbey and Ibeh 1988; Phillips et al. 1988; Henshaw et al.1996; Enwere et al. 1998; Kethireddipalli et al. 2002a,b; Singh et al. 2004). Although each of these factors is known to be core and it is assumed that they are confounding, the degree of importance of each factor is not well understood.

The hydration characteristics of the starting material, resulting flow characteristics and foaming of the paste influence the final appearance and texture (and hence the acceptability) of akara (McWatters and Brantley 1982). A starting material with a low level of hydration resulted in a dry dense product with a tough outer crust (McWatters 1983). Several researchers observed decreases in the functionality of plant fibers (i.e., water holding capacity) with decreasing particle size upon milling of plant material, and attributed this to the alteration of fiber structure and loss of the cell wall matrix as a result of shearing of the plant cells (Mongeau and Brassard 1982; Cadden 1987; Han and Khan 1990a,b; Auffret et al. 1994).

Although dry milling is preferable to wet milling because of economic and food safety issues (Phillips and McWatters 1991), the question of how to produce akara that matches the quality of product prepared from traditionally wet‐milled (WTM) peas using a dry‐milled starting material has been a challenge to researchers. Microscopic examination of hydrated cellular material from wet‐milled cowpea paste and pastes produced from dry‐milled cowpea meal and flour showed a difference in the amount of cell wall material (CWM) present and the condition of the CWM found (Kethireddipalli et al. 2002b). The researchers observed a significant amount of cell wall matrix forming networks in the WTM material, whereas cellular material from meal paste consisted of many intact cells. Finely milled flour also contained a significant amount of CWM; however, it lacked a network because of fine fragmentation during milling. The authors speculated that the wet milling of the cowpeas allowed for facile release of cell contents, including CWM, by easy rupture of turgid cells. The authors attributed the improved hydration and foaming characteristics and the superior texture of the akara made from the wet‐milled paste to the presence of the light and fluffy cell wall matrix.

For this study, it was decided to use a wet milling process to produce a cowpea paste, which was then freeze‐dried and ground into a meal to be compared with a dry‐milled meal and traditionally prepared cowpea paste. Initial quality tests indicated that control of thermal abuse and milling method alone did not ensure good functionality and thus, a high‐quality akara. Therefore, the freeze‐dried and hammer‐milled meals were fractionated by sieving with the particles recombined in order to control for PSD. Hence, the study was to identify the effect of processing on the storage stability and functional properties of cowpea flour in the production of moin-moin and akara.

1.2 Statement of the Problem

Cowpeas (Vigna unguiculata) are an important source of protein in developing countries especially in Nigeria. It is an example of grain legume which has found utilization in various ways in traditional and modern food processing in the world (Odedeji and Oyeleke, 2011). In countries such as Nigeria, and most of the sub-Sahara countries, animal products representing high concentration and quality of protein are either too expensive or simply unaffordable, thus increasing the dependence on cereal grains, roots and tuber crops. In Nigeria, cowpea is consumed in the form of bean pudding, bean cake, baked bean, fried bean, and bean soup amongst others. According to IITA (2009), cowpea grain contains about 25 % protein, and several vitamins and minerals. Most tropical countries are faced with Protein-Energy Malnutrition (PEM) as a result of increasing population and enhanced dependence on cereal and tuber based diet. It is estimated that about 800 million malnourished people exist in some of the least developed countries, mostly in sub-Sahara Africa.

Cereal and legume are known to complement each other when consumed together so as to provide adequate nutrients for the improvement of the nutritional well-being of the people (Chikwendu, 2007). Cowpea and maize, in spite of their great nutritional and economic importance are highly susceptible to many diseases and pests right from growing stage up to storage (Singh et al., 1997) and final consumption. Therefore, there is need to reduce post-harvest losses of these valuable grains via processing them into flour. There is limited information on the effect of processing on the storage stability and functional properties of cowpea flour in the production of moin-moin and akara, hence, the need to go into such research.

1.3 Aim and Objectives of the Study

The main aim of this study is to identify the effect of processing on the storage stability and functional properties of cowpea flour in the production of moin-moin and akara.

The specific objectives include;

1. To evaluate moin-moin samples from bambara and cowpea as functional properties of cowpea flour
2. To determine theproduction process of breadfruit flour using cowpea flour.
3. To find out basic Ingredients in ‘Moin-moin’ Preparation and Quality

1.4 Research Questions

The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:

• What are moin-moin samples from bambara and cowpea as functional properties of cowpea flour?
• What is the production process of breadfruit flour using cowpea flour?
• What are the basic Ingredients in ‘Moin-moin’ Preparation and Quality?

1.5 Significance of the Study

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.

1.6 Scope of the Study

This study is on the effect of processing on the storage stability and functional properties of cowpea flour in the production of moin-moin and ankara.

1.7 Limitations of the Study

The demanding schedule of respondents at work made it very difficult getting the respondents to participate in the survey. The researcher is a student and therefore has limited time as well as resources in covering extensive literature available in conducting this research. Information provided by the researcher may not hold true for all businesses or organizations but is restricted to the selected organization used as a study in this research especially in the locality where this study is being conducted.

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, questionnaire and interview).

Time constraint: The researcher will simultaneously engage in this study with other academic work. This consequently will cut down on the time devoted for the research work.

Finally, the researcher is restricted only to the evidence provided by the participants in the research and therefore cannot determine the reliability and accuracy of the information provided.

1.8 Definition of Terms

Cowpea: sprawling herb (Vigna unguiculata synonym V. sinensis) of the legume family related to the bean and widely cultivated in the southern U.S. for forage, green manure, and edible seeds also : its edible seed — called also black-eyed pea, field pea.

Stability: the quality, state, or degree of being stable: such as. (a) The strength to stand or endure: firmness. (b) The property of a body that causes it when disturbed from a condition of equilibrium or steady motion to develop forces or moments that restore the original condition.

Functional Properties: Functional properties describe how ingredients behave during preparation and cooking, how they affect the finished food product in terms of how it looks, tastes.

Storage: the state of being kept in a place when not being used : the state of being stored somewhere. : the act of putting something that is not being used in a place where it is available, where it can be kept safely, etc. : the act of storing something.

Moin-moin: Moimoi is a Nigerian steamed bean pudding made from a mixture of washed and peeled black-eyed beans, onions and fresh ground red peppers

Akara: akara (Nigeria) bean cake, fried black-eyed pea flour quotations: Àkàrà is a generic word meaning "bread" or "pastry", or the dish itself