Determination The Glycemic Indices Of Yam Flour With Bambara Nut And Sorghum Fibre.

CHAPTER ONE

INTRODUCTION

• Background of Study

Yam is a starchy vegetable which serves as a staple food in regions like West Africa, Southeast Asia, and the Caribbean (Liu et al., 2007). In these regions, notably West Africa and New Guinea, yam is a primary agricultural commodity and the focal point of elaborate rituals (Encyclopaedia Britannica, 2018). Yam is usually eaten boiled, roasted, or fried (Mohankumar et al., 2000). It can also be processed into flour and baked or made into dough. Yam provides high calories in the diet and has a low glycemic index. However, yam flour has a higher glycemic index than whole yam.

Glycemic index is a value assigned to foods or used to measure how slowly or quickly the foods increase the blood glucose levels. There are certain factors that affect the GI of foods. They include processing/preparation methods, ripeness, food meal combination, and starch structure and form. The GI of foods affect the health conditions of consumers, and it has been shown that it the blood sugar levels as well as influences weight loss. The glycemic index of foods is also affected by the dietary fibre and protein content of the food.

Dietary fibres are plant-based carbohydrates that move through the gastrointestinal tract with little to no digestion. It also reduces the rate of conversion and absorption of carbohydrates and sugar respectively, adds bulk to the stool thereby preventing constipation (Veronese et al., 2018). Dietary fibres consist of non-starch polysaccharides and other plant components such as cellulose, resistant starch, resistant dextrins, inulin, lignins, chitins (IMFNB, 2005). Regular intake of soluble fibres, such as beta-glucans from oats or barley, has been established to lower blood levels of LDL cholesterol, a risk factor for cardiovascular diseases (Veronese et al., 2018).

There are indigenous foods of Nigeria and other developing countries rich in dietary fibre which are underutilized by locals in reducing/balancing the glycemic index of their meals. This is either due to ignorance or lack of knowledge of good processing techniques for maximum yield.

Proteins are macronutrients that are essential to building muscle mass. They are commonly found in animal products, though they are also present in other sources, such as nuts and legumes (Szalay, 2015). They are made of long chains of amino acid residues. Proteins perform a variety of functions, and the chief characteristic that allows this is their ability to bind with other molecules specifically and tightly. This ability thereby helps to reduce the conversion of carbohydrates to sugar when bound with protein.

Sorghum is a cereal grain plant of the grass species cultivated for its grain, which is used for food for humans, animal feed, and ethanol production. It originated in Africa, but is now cultivated widely in tropical and subtropical regions (Dillon et al., 2007). Sorghum grain contains gluten free, high in resistant starch and more abundant and diverse phenolic compounds compared to other major cereal crops (Awika and Rooney, 2004). The dietary fibre content of sorghum is high and thus good for control blood sugar levels.

Bambara nut is a grain legume grown mainly by subsistence farmers in sub-Saharan Africa. It is cultivated for its subterranean pods, is extremely hardy and produces reasonable yields even under conditions of drought and low soil fertility (FAO, 2021). They can be eaten fresh or boiled after drying, and can be ground either fresh or dry to make puddings (Wikipedia, 2021). It is a sustainable, low-cost source of complex carbohydrates, plant-based protein, unsaturated fatty acids, and essential minerals (magnesium, iron, zinc, and potassium), especially for those living in arid and semi-arid regions (Azman et al., 2019).

• Statement of Problem

The demand for yam flour has risen over the years with technology and advancement taking over the world. This has however raised concerns over the health complications of this development. Yam flour has a relatively moderate to high GI than the whole yam, and this increases the chances of increased blood sugar levels in consumers and could lead to increase in diabetes. In light of the above, this project work is tailored to produce a composite yam flour with Bambara nut and sorghum fibre, yielding a product with increased protein and dietary fibre content improving blood sugar levels thus reducing risks of coronary heart diseases and diabetes.

• Objective of Study

Overall Objective

• To produce a composite yam flour with Bambara nut and sorghum fibre.

Specific Objectives

• To produce whole yam flour
• To produce sorghum fibre
• To produce Bambara nut flour
• To mix the composite flour
• To determine the proximate composition of Bambara nut flour and sorghum fibre.
• To determine their functional properties
• To determine the anti-nutritional factors
• To determine their sensory properties
• To determine the glycemic indices of the formulated composite flours
• Justification of Study
• The composite yam flour will increase satiety levels hence reducing quantity of food consumed, also save cost and possible risk of health complications.
• The composite flour will also encourage the consumption of yam flour by diabetics, obese and elderly persons.
• The results obtained will also contribute to further and future study on the impact of protein and fibre on glycemic indices of high carbohydrate foods.
• Scope of Study

The scope of this project study is to process bambara nut into flour and sorghum into fibre. The flour and fibre will then be mixed with processed yam flour in proportions to give a composite flour. The proximate composition, functional and sensory properties of the flours will then be analysed using generally accepted methods and standards. The glycemic indices of the flours are also measured by feeding to subjects and readings taken and recorded