INTRODUCTION Sorghum

INTRODUCTION
Sorghum ( sorghum bicolor) originated in Africa, and it adapts uniquely to Africa’s climate, being that it is drought resistant and also able to withstand periods of water-logging (Kimber, 2000). It is one of the most important cereal crops in the semi-arid tropics (SAT). Nigeria has been recorded as the largest producer of sorghum in West Africa, accounting for about 71% of the total regional sorghum output . The production of sorghum in Nigeria made up 35% of sorghum produce in Africa (Al-Rabadi et al., 2011).
About 90% of sorghum produced in the United States and India is used for animal feed, making Nigeria the world leading country in food grain sorghum utilization.(Catherine et.al., 2013). Also, it accounts for 50% of the of the cereal crop land area in west Africa and also as a food security crop known to survive adverse cultivating conditions,( Dicko et al., 2006. even with these sorghum will be elusive without continuous and significant improvement, not only in the production of sorghum but also in its uses as well
Though Sorghum is one of the underutilized crop species it plays an important role in the food security, income generation and food culture of the rural dwellers. It is the primary food crop in the northern part of Nigeria even though much attention has not been given to the traditional varieties of sorghum grown by the local farmers and their implicit value has been under-exploited even more-so underestimated. Even though sorghum has been identified as with these enormous benefits nevertheless it has been disregarded since it is perceived as food for the poor (Engle and Altoveros, 2000).
Legumes are promising in terms of nutrition, providing food security, agricultural development and in crop rotation in developing countries(Sridhar and Bhat 2007). Significant efforts been geared towards making legumes alternatives to expensive feed and also animal protein, especially in developing countries such as Nigeria. Research has been made on a wide variety of legumes, most of which are of limited relevance in human nutrition (Okomoda et al., 2016).The nutritional value of legumes is gaining massive interest globally because of the increasing demand of healthy diets. The utilization of legumes as protein source in the production of various formulated foods builds up on a daily basis, as legumes contains about 17-25% of protein. Yet even with the nutritive value of legumes, it is masked by incidents of anti-nutritional factors (ANFs), such as trypsin inhibitors, haemagglutinin, and saponin (Francis et al., 2001).
Cowpea (Vigna unguiculata L.) is an important source of plant protein in human diet. It a legume common to Africa. Cowpea provides a significant amount of dietary protein (18-35%) and lysine. Also in areas where protein rich food are in shortage it is known to provide nutritive value to human. (Khalid et.al.,2012). Cowpea-based food products can be used as weaning food, produced into flour for use in products such as infant formula, supplementary diet or diet for the convalescence or even into extruded products which offer variety of products such as snacks or breakfast cereal .
Bambara groundnut (Vigna subterranea) is extensively cultivated in Nigeria yet it is still considered one of the underutilized legume in Nigeria. . It is nutritionally superior to many legumes and is the preferred crop for many local people (Linnemann, 1990; Brough and Azam-Ali, 1992). Bambara is a rich source of protein (20-25%) It contains about 60% carbohydrate, its protein is reported to be higher in the essential amino acid methionine than other grain legumes (Stephens, 2003) . value has been placed on the nutritional and economic importance of bambara groundnut (Mkandawire, 2007).Despite its high and balanced protein content, Bambara remains under-utilised because it takes a long time to cook and contains anti-nutritional factors such as tannins and trypsin inhibitors, and it has poor milling characteristics, as it does not de-hull easily (Barimalaa and Anoghalu, 1997). Bambara has high nutrient value and in view of this it could be utilized in the development of more acceptable shelf stable food products such as extruded snacks.
Pigeon pea( Cajanus cajan) is cultivated in semi arid and semi humid tropics. Cajanus cajan is regarded as an important food for food security in regions with low or unreliable rainfall and droughts, because of its drought resistance (Crop Trust, 2014). The seeds of pigeon pea could be brown red black or green in colour ,they are most often hard coated ( Bekele-Tessema, 2007).. Pigeonpea is rich in starch, protein, calcium, manganese, crude fiber, fat, trace elements, and minerals. Besides its high nutritional value, pigeonpea is also used as traditional folk medicine in India, China, Philippines and some other nations. Pigeon peas has been recommended for a balanced diet with cereals and also to supplement for proteins in the rural and poor sector of developing countries (Saxena et.al., 2010) . Various factors contribute to the rather limited utilization of pigeon pea, one of which id the hardness of the seed. About 8-12 hours of cooking is required for cooking before it becomes soft. However de-hulling the seeds reduce the cooking time. (Fasoyiro et al.,2006), while milling these seeds into flour have provided a less tedious and well appreciated method of processing pigeon pea.
Extrusion technology has various advantages over traditional/conventional methods It is one of the most efficient processes currently used for solving world’s hunger and nutritional challenges (Hauck, 1981).
Extruders permit various production application and the production of many foods of nutritional importance. The ability of extruders to blend different ingredients in novel foods has been used in the development of functional foods. The Traditional snacks or breakfast cereals can be enhanced by the addition extra fibres or whole grain flour as ingredients during extrusion, transformed into palatable cereal-based products that also promote beneficial physiological effects. Functional ingredients that provide high antioxidant and bioactive compounds can be used in extrusion process to develop novel products with phytochemicals and other healthful food components. increasing their shelf-life and controlling the release of food ingredients at the right place and time.

PROBLEM STATEMENT
Consumption of a healthy breakfast ensures that the consumer gets adequate energy needed to go through a successful day. Sorghum, is an important cereal grain food, grown globally and rich in nutrients, dietary fibre, and bioactive components yet, it is considered an underutilized cereal and a less-value nutritional source to humans and often used as an animal feed. As the socioeconomic status of population grows daily, preferred cereals like wheat and rice are readily available, affordable, and in abundance thus decreasing the consumption of sorghum (Sheorain et al., 2000). One of the reasons for the underutilization of sorghum as human food have been the prevalent ‘misconceptions’ and lack of scientific data on the nutritional quality and also acceptability (or palatability) of sorghum-based products.
The deficiency of Protein-energy has been of concern and has been identified as the most ubiquitous form of malnutrition in regions where there is dependency on starch-based diets. Therefore legumes are daily explored for their nutritional advantages and supplementary benefits to cereal based products. Extruded breakfast cereals are produced from starch based products therefore fortification with macro and micro nutrient rich legumes giving much concern to underutilized legumes with desirable nutritional profile is of importance
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JUSTIFICATION OF STUDY
Cereal has been an important source of food across the globe . The awareness of the utilization of sorghum will definitely lead to increase in its demand and production. Sorghum grains has potentials in its use as food products because it is a less expensive alternative to other cereal ingredients such as corn and rice, Sorghum can also provide nutritional benefits related to lower digestibility of starch . An optimum mix ratio of legumes and cereals and the processing characteristics of extrusion will provide bio- available amino acid profile and palatable products .
In other to diversify and also improve on the utilization of sorghum, the fortification of sorghum with legumes given rise to cereal-legume based products. This is to compensate for the lacking nutrients and more-so supplement for the micro and macro nutrient lacking in cereals, while focusing on processing methods like extrusion which is efficient in the elimination or reduction of anti nutritional factors prevalent in cereal -legume based foods such as phytic acid, tannin, etc.
To meet consumers’ requirements, which presently is concerned with nutrition and consumption of healthy foods that promotes well-being and a positive life style, extrusion technology has been known to yield greater efficiency and higher productivity, increased throughput, ,thus enabling the production of numerous snacks and improving final product quality
Extrusion technique has gained various importance in the production of convenient foods and snacks. Research has shown that extrusion is a viable tool for enhancing protein digestibility which involves using controlled conditions of heat and moisture which lowers the formation of disulphide bonds in proteins.(Mahasukhnothachat et al., 2010)

OBJECTIVES
The general objective of this research was to optimize the blends of sorghum with Bambara, cowpea and guinea pea, and to optimize the effect of the different legumes, extrusion parameters on quality attributes as well as the in-vitro digestibility of extruded products from sorghum and Bambara, cowpea and pigeon pea.
Specific objectives;
Optimize the formulation ratio of sorghum and Bambara, cowpea and guinea pea composite flour using the mixture design methodology.
Characterize the different blends and formulation levels for their proximate composition and anti nutritional factor.
Optimize the effect of process parameters; feed moisture, barrel temperature, screw speed , extrusion type on the chemical, physical, functional, textural properties of the extruded product.
Assess the effect of extrusion process and parameters on the in-vitro starch and protein digestibility of the extruded products
Assess the effect of the process parameters on the sensory properties of the extruded products.

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