Optimization of the nutritional quality characteristics of cowpea-fortified nixtamalized maize using computer-generated response surface models Afoakwa E. O., Sefa-Dedeh, S., Cornelius B. & Sakyi-Dawson E. Department of Nutrition and Food Science University of Ghana, Legon, Ghana

INTRODUCTION  Nixtamalization -Defined -Nutritional significance  Cowpea fortification  Combined effects of nixtamalization, cowpea fortification and fermentation  Response surface methodology, an IT software program.

This refers to the alkaline cooking of corn (Zea mays). The process involves the cooking and steeping of corn in excess water containing calcium hydroxide (lime) solution. The process can be used to obtain products such as: Tortillas Tacos Tortillas chips Corn chips Other related productsNIXTAMALIZATION

 Decrease in tannin levels in high tannin grains  Increase in free calcium levels  Increase in bioavailability of iron and other related minerals  Faster release of amino acids  Increase in free nicotinic acid  Increase in availability of niacin (Hulse et al., 1980; Bharati and Vaidehi, 1989; Sefa-Dedeh et al., 2002) NUTRITIONAL SIGNIFICANCE:

As a means of resolving the problem of low energy density of cereal-based foods caused by high starch content of cereals, cowpea fortification has led to improvements of the protein quality and quantity of cereal-based foods (Afoakwa, 1996; Sefa-Dedeh et al., 2000; Sefa- Dedeh et al., 2001). COWPEA FORTIFICATION

The combination of nixtamalization, cowpea fortification and fermentation may prove a means of improving product functionality, protein nutrition and micro-nutrient availability in African traditional foods. These processes will help introduce variety to the traditional food base and as well improve food and nutrition security of Africans. COMBINED EFFECTS... COMBINED EFFECTS...

The study aimed at investigating the quality characteristics of cowpea-fortified nixtamalized maize using response surface models generated from STATGRAPHICS an IT software program. Main objective: Response surface methodology This is a statistical-mathematical method which uses quantitative data in an experimental design to determine and simultaneously solve multivariate equations, to optimize processes or products.

 Corn (Zea mays) – Accra market  Cowpea (Vigna unguiculata) – Crop Research Institute in Ghana  Lime (Calcium hydroxide) food grade – BDH Chemicals Ltd., Poole, England. MATERIALS AND METHODS:

A central composite rotatable design (CCRD) for K=3 was used with variables, Lime concentration (X 1 ), Moisture content (X 2 ) and Cowpea level (X 3 ) ; Process variables in CCRD for K=3. Variables Variable levels Lime concentration (%) Cowpea level (%) Moisture content (%) Experimental design

Flow diagram for the preparation of nixtamalized maize meal Whole grain Cook in lime(30 min) Steep in cooking liquor (18 hours) Cooked maize (Nixtamal) Wash Washed Nixtamal Mill Fresh Nixtamalized maize meal

ANALYTICAL METHODS:  Moisture and protein analyses – AOAC (1990)  pH and Titratable acidity – (Sefa-Dedeh et al, 2000)  Water absorption capacity (Yasumatsu et al., 1972)  Brabender cooked paste viscosity – AACC (1983)  Texture analysis – TA.XT2 Texture Analyzer

pH: The model equation used for the plot is: Y = X X 2 – X 1 2 – X 2 2 RESULTS

The model equation : Y = X X 1 X 2 Titratable acidity

Y = –0.5079X X 2 2 – X X 2 X 3 Protein content

Y = X X 3 2 – X 1 X X 2 X 3 Water absorption capacity

Y = X 1 – 6.011X 3 – X 1 2 – X 3 2 Cooked paste viscosity

CONCLUSIONS Lime and cowpea concentration significantly influence the titratable acidity, water absorption, protein content and cooked paste viscosity of fermented cowpea-fortified nixtamalized maize. Cowpea fortification in combination with fermentation can be employed to further improve the functionality, protein quality and quantity of energy dense nixtamalized maize.

CONCLUSIONS (Contd.) Alkaline cooking improves the protein content of nixtamalized maize products, which even become higher when fortified with cowpea. Nixtamalization, cowpea fortification and fermentation can be employed in the improvement of the nutritional quality of traditional foods made from maize. IT software programs can be used to optimize the nutritional quality of processed foods.

Acknowledgement This study was funded through the Bean-Cowpea (CRSP) Project by the USAID Grant No. DAN-1310-G-SS

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