**5. Fortification of traditional delicacy (pounded yam) meal with soybean flour**

Yam, a member of the genus "*Dioscorea*" is an important staple in Nigeria and other West African countries (Cliff *et al.,* 2007). Yam is the perennial herbaceous vine cultivated for the consumption of their starchy tubers in Africa, Asia, latin America and oceanic. Due to their abundance and consequently, their importance to survival, yam was highly regarded in Nigeria ceremonial culture and even worshipped

Before the introduction of cereals and grains in West Africa, yam was the major source of carbohydrate. Ukpabi (1992), reports that yam is considered a man's crop and has ritual and socio-cultural significance. Today, yams are grown widely throughout the tropics. In 2005 48.7million tones of yam were produce world wide. Besides their importance as food source, yam also play a significant role in the socio-culture of some producing regions like the celebrated New Yam festivals in West Africa

The greater part of the worlds yam is kept and eventually consumed in the fresh state. Nevertheless, as a result of the combination of high degree of perishability, bulkiness, distance from production area to the consuming centre and the seasonal nature of production, attention has therefore been drawn to the processing of tubers into flour which depend on some vital functional properties of yam varieties.

Holford (1998) reported that, yams are high in vitamin C, dietary fiber, vitamin B6, potassium and manganese, while being low in saturated fat and sodium. Further more, yam products are high in potassium – sodium balance in the human body and so protect against osteoporosis and heart disease.

Yam products generally have a lower glycemic index than potato products which means that they will provide a more sustained form of energy and give better protection against obesity and diabetes (Schlitz, 1993).According to Rickard (1978) and Igbeka, (1985) harvested tubers are frequently attacked by several viruses, bacteria, fungi and insects. Also rodent feed on some of the harvested tubers stored in the barns, therefore there is need for processing

#### **5.1 Processing and utilization of yam flour**

Processing will greatly increase the utilization of root crops, the flour can be use as a component of multi mix baby foods and in composite flour for making bread .

The Food and Agricultural Organization (1987) have reported that, processing of yam involves peeling the root then cutting into slices, blanching, and dried. Peeling can be effected by immersion in 10% lye solution or by steaming at high temperature (150oC) for short period. Dried product require less storage space and have a longer shelf life. They can be quickly reconstituted into pounded yam and prepared for eating.

According to Bourdoux *et al*., (1983), composite flour incorporating yam has been used in extruded products such has noodles and macaroni, similar processes could be used in production of flour products from other root crops.

Raw yam flour has also found increasing uses in bakery as dough conditioners in bread making and as stabilizers in ice-cream and as thickener in soups . Pregelatinized flour is also used for making instant pounded yam which brings succor to pounded yam lovers as the drudgery of pounding is eliminated (Adeyemi and Oke, 1991).

Production of Yam flour and subsequent reconstitution leads to a dumping lacking in firmness, texture and rigidity of the conventional pounded yam. This witling down of the conventional pounded yam consistency makes many not to accept reconstituted yam flour meal as pounded yam.

**5. Fortification of traditional delicacy (pounded yam) meal with soybean flour**  Yam, a member of the genus "*Dioscorea*" is an important staple in Nigeria and other West African countries (Cliff *et al.,* 2007). Yam is the perennial herbaceous vine cultivated for the consumption of their starchy tubers in Africa, Asia, latin America and oceanic. Due to their abundance and consequently, their importance to survival, yam was highly regarded in

Before the introduction of cereals and grains in West Africa, yam was the major source of carbohydrate. Ukpabi (1992), reports that yam is considered a man's crop and has ritual and socio-cultural significance. Today, yams are grown widely throughout the tropics. In 2005 48.7million tones of yam were produce world wide. Besides their importance as food source, yam also play a significant role in the socio-culture of some producing regions like the

The greater part of the worlds yam is kept and eventually consumed in the fresh state. Nevertheless, as a result of the combination of high degree of perishability, bulkiness, distance from production area to the consuming centre and the seasonal nature of production, attention has therefore been drawn to the processing of tubers into flour which

Holford (1998) reported that, yams are high in vitamin C, dietary fiber, vitamin B6, potassium and manganese, while being low in saturated fat and sodium. Further more, yam products are high in potassium – sodium balance in the human body and so protect against

Yam products generally have a lower glycemic index than potato products which means that they will provide a more sustained form of energy and give better protection against obesity and diabetes (Schlitz, 1993).According to Rickard (1978) and Igbeka, (1985) harvested tubers are frequently attacked by several viruses, bacteria, fungi and insects. Also rodent feed on

Processing will greatly increase the utilization of root crops, the flour can be use as a

The Food and Agricultural Organization (1987) have reported that, processing of yam involves peeling the root then cutting into slices, blanching, and dried. Peeling can be effected by immersion in 10% lye solution or by steaming at high temperature (150oC) for short period. Dried product require less storage space and have a longer shelf life. They can

According to Bourdoux *et al*., (1983), composite flour incorporating yam has been used in extruded products such has noodles and macaroni, similar processes could be used in

Raw yam flour has also found increasing uses in bakery as dough conditioners in bread making and as stabilizers in ice-cream and as thickener in soups . Pregelatinized flour is also used for making instant pounded yam which brings succor to pounded yam lovers as the

Production of Yam flour and subsequent reconstitution leads to a dumping lacking in firmness, texture and rigidity of the conventional pounded yam. This witling down of the conventional pounded yam consistency makes many not to accept reconstituted yam flour

some of the harvested tubers stored in the barns, therefore there is need for processing

component of multi mix baby foods and in composite flour for making bread .

be quickly reconstituted into pounded yam and prepared for eating.

drudgery of pounding is eliminated (Adeyemi and Oke, 1991).

Nigeria ceremonial culture and even worshipped

celebrated New Yam festivals in West Africa

**5.1 Processing and utilization of yam flour** 

production of flour products from other root crops.

osteoporosis and heart disease.

meal as pounded yam.

depend on some vital functional properties of yam varieties.

This meal which reduces drudgery of pounding, faces limited local, ethnic and regional acceptance. It becomes necessary therefore to fortify yam flour with locally available firming agents to reconstitute a yam flour meal close to the conventional pounded yam. Addition of soybean to such fortified yam flour would increase the nutritional status and also its functionality. This was accomplished by firming-up yam flour with cassava starch.

Cassava "*Manihot escullenta*" is a staple food consumed in both rural and urban areas of Nigeria.

Starch is one of the most important plant product to man (Landry and Moreax, 1982). It is an essential component of food providing a large proportion of the daily colorific in take (Scott *et al.,* 2000). Cassava starch is recommended for use in extruded snacks for improved expansion (Senthiikumar and Subburam, 2001). It is also used as a thickener in foods that are not subjected to rigorous processing conditions (Okezie and Kosikowki, 1982).

Cassava starch, which is very bland in flavour is used in processed baby foods as a filler materials and bonding agent in confectionary and biscuit industries (Fregene *et al.,* 2003) Cassava starch can perform most of the function where maize, rice and wheat starch are currently used.

A technology of adding cassava starch to yam flour (Figure4) with 25% levels of cassava starch was developed(Fig5).The yam flour (Figure 5) strengthened with cassava starch was then fortified with soybean flour up to 30% levels of substitution(Figure 6).


Fig. 4. Flow diagram for Traditional Yam flour Preparation

Fig. 5. Flow process for Improved Yam flour Preparation (FIIRO,2003)

Pre enrichment of yam tuber flours with native cassava starch up to 25% produced very firm gels close to the traditionally pounded yam meals(Table13). Sensory evaluation (Table 14) showed that yam flour fortified with cassava starch as gelling agent was generally more acceptable in appearance colour, taste, consistency and overall acceptability than those fortified with corn starch(Table14). Addition of 10% soybean flour enhanced the protein content of the meal as well as had no noticeable rheological problems on the firmness or moudability. Addition of 10% soybean flour brought the rheological characteristics of the sample to nearly the same with conventional pounded yam. This improvement is as a result of the increased stability of the yam starch due to added cassava starch. This increased stability is reflected in the high sensorial scores of the fortified meals(Table15). With the high sensorial rating obtained for samples at 10% levels of substitution it is concluded that firming yam flour with 25% cassava starch and fortifying with soybean will produce a dumpling in the mould of conventional pounded yam. Adoption of this technology would lead to greater utilization of cassava produced maximally in this part of the world



PV=Pasting Viscosity TR=Trough BD=Break down FV=Final Viscosity SB=Set Back Viscosity PT= Time at Peak Viscosity PT=Temperature at Peak Viscosity

A=Conventional Pounded Yam B=Pounded Yam with 25% cassava starch C= Pounded Yam with 25% corn starch D= Pounded Yam with 5% cassava starch

Table 13. Pasting Characteristics of Yam /Cassava or corn Starch flour for Pounded Yam Preparation


A=Conventional Pounded Yam

B=Pounded Yam with 25% cassava starch

C= Pounded Yam with 25% corn starch

D= Pounded Yam with 5% cassava starch

Table 14. Acceptability of Reconstituted Yam Flour/ Firmed Cassava /Corn Starch


A=Conventional Pounded Yam

222 Soybean Physiology and Biochemistry

firming yam flour with 25% cassava starch and fortifying with soybean will produce a dumpling in the mould of conventional pounded yam. Adoption of this technology would

Fig. 6. Process Flow Diagram for production of Firmed Yam /Soybean flour for pounded

 PV (RVU TR (RVU) BDU) FV (RVU) SB (RVU) PT (mins) PT (oC) A 90.83 80.16 10.66 140.96 60.79 6.96 61.85 B 126.00 114.0 12.00 158.08 44.08 6.70 61.65 C 120.4 105.75 14.79 192.04 86.29 6.96 61.92 D 100.08 88.33 11.75 153.46 65.12 7.00 61.87

PV=Pasting Viscosity TR=Trough BD=Break down FV=Final Viscosity SB=Set Back Viscosity PT= Time

A=Conventional Pounded Yam B=Pounded Yam with 25% cassava starch C= Pounded Yam with 25%

Table 13. Pasting Characteristics of Yam /Cassava or corn Starch flour for Pounded Yam

Samples Appearance Colour Taste Consistency Overall

A 5.40 5.60 6.70 4.70 7.10 B 7.20 6.80 6.60 6.50 6.20 C 3.50 3.00 3.00 3.20 2.90 D 8.80 8.30 8.90 8.90 8.60

Table 14. Acceptability of Reconstituted Yam Flour/ Firmed Cassava /Corn Starch

Acceptability

Yam Preparation

**Samples Pasting**

Preparation

A=Conventional Pounded Yam

B=Pounded Yam with 25% cassava starch C= Pounded Yam with 25% corn starch D= Pounded Yam with 5% cassava starch

**Parameters**

at Peak Viscosity PT=Temperature at Peak Viscosity

corn starch D= Pounded Yam with 5% cassava starch

lead to greater utilization of cassava produced maximally in this part of the world

B=Reconstituted Fortified Pounded Yam Flour with 10% Soybean flour

C= Reconstituted Fortified Pounded Yam Flour with 15% Soybean flour

D= Reconstituted Pounded Yam Flour with 20% Soybean flour

E= Reconstituted Pounded Yam Flour with 30% Soybean flour

Table 15. Sensory Evaluation of Reconstituted Yam/Soybean Flour enriched with Cassava Starch


PV=Pasting Viscosity TR=Trough BD=Break down FV=Final Viscosity SB=Set Back Viscosity PT= Time at Peak Viscosity PT=Temperature at Peak Viscosity

A=Conventional Pounded Yam

B=Fortified Pounded Yam Flour with 10% Soybean flour

C=Fortified Pounded Yam Flour with 15% Soybean flour

D= Pounded Yam Flour with 20% Soybean flour

E= Pounded Yam Flour with 30% Soybean flour

Table 16. Pasting Characteristics of Yam flour for Pounded Yam Preparation
