PROXIMATE AND SENSORY PROPERTIES OF AKARA PRODUCED FROM DIFFERENT BLENDS OF AFRICAN YAM BEAN AND COWPEA

1.1 Introduction

Cowpea (Vigna unguiculata) is popularly grain legume referred to as ‘beans’ in West Africa. It is nutritious and provides protein, vitamins, and minerals. Cowpea grain contains about 25% protein, making it extremely valuable where many people can’t afford proteins from animal sources such as meat and fish (Oumarou et al., 2014 and Appiah et al., 2011). Cowpea flour has been used as a nutritious ingredient in fried and baked products, as well as comminuted meat products, such as chicken nuggets and meatballs (Agnes et al., 2007 and Ombogo, 2017). African Yam Bean (AYB) (Sphenostylisstenocarpa) is one of the less utilised legumes that are gradually going into extinction (Klu et al., 2001); this may be due to the long cooking time it requires and its taste. However, it can be used in preparation of other food products.

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, Research hypothesis and questions, Limitations of the Study and Definition of technical terms.

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1.2 Background of Study

Cowpea is an important food crop in West Africa. It is often called as “poor man’s meat” in this region where people cannot afford expensive animal protein. Cowpea is often recommended for pregnant and nursing mothers due to its high nutritional values. The ripe seed on average contains 22.0% protein, 1.4% fat, 59.1% carbohydrate, and 3.7% ash. The energy value is 1,420 k (340 kcal) per 100 g. Cowpea is the preferred pulse in large parts of Africa. The mature seeds are cooked and eaten alone or together with vegetable, spices, and often palm oil, to produce a thick bean soup which accompanies the staple food (cassava, yam plantain) (Vanderborght et al., 2001).

Cowpea can be grown under rain-fed conditions as well as by using irrigation or residual moisture along river or lake flood plains during the dry season, provided that the range of minimum and maximum temperatures is between 28 and 30°C (night and day) during the growing season. Cowpea performs well in agro-ecological zones where the rainfall range is between 500 and 1200 mm/year.

According to Adewale et al., (2010), the vast genetic and economic potentials of AYB have been recognized; especially in reducing malnutrition among Africans and the crop has not received adequate research attention. Up till now, it is classified as a neglected underutilised species (NUS) (Bioversity, 2009). Its intended use in improving nutritional quality of cowpea-based snacks will add value to these cowpea-based snacks as well as provide more utilisation for the legume.

African yam bean (AYB) is an herbaceous leguminous plant occurring throughout tropical Africa (United States Department of Agriculture (USDA), 2007). It is grown as a minor crop in association with yam and cassava. AYB serves as security crop; it has the potential to meet year round protein requirements if grown on a large scale (World Health Organization (WHO), 2002). African yam bean (AYB) is highly nutritious with high protein, mineral and fibre content. Its protein content is reported to be similar to that of some major and commonly consumed legumes. Its amino acid profile is comparable if not better than those of cowpea, soy bean and pigeon pea (Obizoba & Souzey, 1989; Ene-Obong & Carnovale, 1992; Uguru & Madukaife, 2001).

The potential role of AYB in the management of many aging and chronic non- communicable diseases has been reported (Enwere, 1998; Nwachi, 2007; Alozie, Udofia, Lawal & Ani, 2009). In Ghana, the water drained after boiling may be drunk by lactating mothers to increase their milk production (Klu, Amoatey, Bansa & Kumaga, 2001). The economic potential of AYB has been recognized, especially in reducing malnutrition among Africans (Adewale, 2010). Use of better quality cowpea, enrichment with African yam bean as well as use of response surface methodology for standardisation of the processing methods and storage studies of the cowpea-based snacks will suggest the appropriate processing and storage conditions. This will result in improved sensory, nutritional and storage properties of this Nigerian cowpeabased snacks (Akara).

Therefore, in Nigeria where the research was carried out, the activities that was conducted is to know the Proximate and Sensory Properties of Akara Produced from Different Blends of African Yam Bean and Cowpea.

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1.3 Statement of Problems

Investigation reveals that inspite of the good attributes of AYB, it is underutilized and rarely consumed in urban and rural areas in Nigeria. Its current status as a minor crop means that its potential is largely unexploited. It faces the danger of extinction (Klu et al., 2001). The use of AYB may be limited by the beany flavour and long cooking time. These limitations can be overcome by processing like fermentation, soaking, roasting among others (Nnam, 1994; Ene-Obong & Obiziba, 1995; Nnam, 1999; Fasoyiro, Ajibade, Omole, Adeniyan & Farinde, 2006; Adewumi and Odunfa, 2009).

Some studies have been carried out on the nutrient, anti nutrient and toxic substance composition of AYB and some of its products and processing methods to improve the food use (Ene-Obong & Obizoba, 1995; Nnam, 1997; Nnam, 2003; Omeire & Ogbonna, 2006; Onyechi and Nwachi, 2008). Little has been done on the effect of 24h fermentation with and without lim e, 48h fermentation in lime water and roasting to address the beany flavour. Little has equally been done on the effects of these processing methods on nutrient, anti nutrients, toxic substances, anti physiological factors and other organoleptic characteristic of AYB flour and gruel.

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1.4 Aim and Objectives of Study

The aim of the study is to determine the Proximate and Sensory Properties of Akara Produced from Different Blends of African Yam Bean and Cowpea. In achieving this aim, the following specific objectives were laid out as follows:

1. To determine the properties of selected cowpea and African yam bean seeds cultivars for processing suitability,
2. To determine the storage properties and adsorption isotherm characteristics of the products, and
3. To assess the consumers‟ acceptability of the products developed.
4. To evaluate the effect of some processing parameters (frying temperature, frying time and quantity of AYB flour) on the physico-chemical, functional, nutritional and sensory properties of the flour blends and the cowpea-based snacks.

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1.5 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 the properties of selected cowpea and African yam bean seeds cultivars for processing suitability?
• What is the effect of some processing parameters (frying temperature, frying time and quantity of AYB flour) on the physico-chemical, functional, nutritional and sensory properties of the flour blends and the cowpea-based snacks?
• What is the storage properties and adsorption isotherm characteristics of the products?

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1.6 Significance of Study

There is little information on the utilization of African yam bean seed, a nutrient dense but neglected underutilized species (NUS) of legume) to enrich cowpea snacks. The development of these cowpea-based snacks through value-added processes will establish appropriate and optimum conditions for improving the product quality. It will offer wider utilisation to AYB, leading to job creation both at farm and industrial level. Also, the crude, nonstandardised processing operations associated with this Nigerian snack will be upgraded as a way of improving its nutritional, sensory and storage properties. This research work is in line with national policies of food security and upgrading traditional food processing techniques, thus adding value to Nigerian snacks.

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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1.7 Scope of Study

The study focuses on the Proximate and Sensory Properties of Akara Produced from Different Blends of African Yam Bean and Cowpea.

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1.8 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).