COMPARISON OF WHITE YAM (Dioscorea Rotundata) AND AERIAL YAM (Dioscorea Bulbifera)
CHAPTER ONE
1.0                     INTRODUCTION
1.1    Yam as an Edible Tuber
    Yam is the common name for some plant species in the genus Dioscorea (family Dioscoreacea) that form edible tubers.  Yams are perennial beerbaceceous vines cultivated for consumption of their starchy tuber in many temperate and sub-tropical world regions.  The tubers themselves are also called “Yam” having numerous cultivars and related specie (Ajanaku et al, 2002).
    In this study, we will be concerned with White Yam (Dioscorea Rotundata) and Aerial Yam (Dioscorea Bulbifera) (Shantha Kumari, et al, 2008).  Aerial yam Dioscorea Bulbifera is popularly known in Igbo land as Edu, known in Yoruba as Idacha and Hausa known as Ambaligenasis.  Aerial yam is a tropical old world; “Yam”, having auxiliary potatoes like tubers, some of which are edible after cooking.  It is a weed in the tropics and Florida (kouakou, et al, 2010).
    Aerial yam is also known as air potatoe, bitter yam or potatoe yam.  It is a perennial crop and it has pale green for female crop and it has white aging to purple for male crop.  It can be boiled and eaten with palm oil and also processed into flour (Baah, 2009), while white yam (Dioscerea Rotundata) is a subspecies of yam native to Africa.  It is one of the most important cultivated yams.  White yam can be cooked and eaten with palm oil, stew or sauce.  It can also be eaten fried or can as well turn into flour for “fufu” production (Adebowale, et al, 2008).

1.2    Flours from Roots and Tubers
    Roots and tubers can be processed into flours and reconstituted into “fufu” though generally some specie like water yam (Dioscorea Alata) contains less sugar and has an extended shelf life (Otoo and Aseidu, 2008) which ensures availability in times of scarcity.  It is also known for its high nutritional content.
    Yam flour is powered starch widely used in food preparation.  Typically, white yam flour is commonly used in Africa dishes, such as “Amala”, “Fufu”, etc.  It may be used in many other recipes if desired as well.  It is prepared by grinding dried yam until they reach a powdered consistency (Jaya Kody, et al, 2007).  White yam tuber (Dioscerea Rotundata) can be processed by washing, peeling, slicing, blanching, drying and milling into instant yam flour.  This flour contains about 940 calories which 88% is carbohydrates, 0.5% protein, 4.1% fiber, 11% ash, 1.1% fat, minerals 5%, vitamins 6.7% (Deh, 2002).
    Aerial yam tubers can be processed into flour as well by peeling, slicing, blanching, drying, and milling.  This flour can be reconstituted into “fufu” and eaten with soup.  Aerial yam flour is also rich in calories and it contains a number of flavonoids and is flavonoids.  It has a chemical composition of 4.5% crude protein, 1.9% crude lipid, 87.5%, nitrogen free extract, 0.86% potassium, 0..14% magnesium, 0.12% phosphorus, 67.46% moisture content, 3% vitamins, 6% minerals.

1.3    Justification of Study
    Due to the popularity and demand of white (Dioscerea Rotundata) which contributes to poor utilization of Aerial yam and this leads to its wastage and post harvest losses.  Aerial yam is a tuber and a good source of carbohydrates, hence it is necessary to compare it white yam in the basis of its yield, chemicals and functional properties; thus, increasing the utilization of aerial yam.
1.4    Objectives of the Study
    The objective of this study is to compare the yield and to determine the chemicals and functional properties of white yam flour and aerial yam flour.
The Specific Objectives
1.    To compare the yield of white yam and aerial yam flour.
2.    To determine the chemicals and functional properties of aerial yam and white yam flour.
3.    To produce “fufu” from both flours.