ABSTRACT
A three-factor three level Response surface methodology central composite retortable design (CCRD) was adopted to study the effect of feed composition (X1), feed moisture content (X2) and screw speed (X3) on proximate compositin, amino acid and sensory evaluation during extrusion of pearl millet and cowpea flour mixtures for the purpose of fura production. The mean observed value of protein for the fura extrudates ranged from 11.2 – 16.8%. Analysis of variance indicates that linear and quadratic effects significantly (P<0.05) affected the protein content of fura extrudates as expected. The mean value of lysine for the extrudates ranged from 5.1 - 6.6g/100g protein and the methionine content ranged from 1.3 - 3.8g /100g protein. The regression models fitted to the experimental data showed high coefficients of determinants with R2 = 0.96, 0.94, 0.94, 0.85 and 0.80 for protein (CHON), carbohydrate (CHO), fat (FAT), ash (ASH) and water (HOH) respectively. The R2 = were 0.90, 0.85, 0.86, 0.92, 0.88, 0.85 and 0.93 for lysine, i/leucine, leucine, valine, methionine – cystine, threonine and tryptophan respectively. The coefficients shows good fit. The importance of process variables on system parameters and physical properties could be ranked in the following order: Feed Composition (X1)>Feed Moisture (X2)>Screw Speed (X3). The optimum values obtained for feed composition, feed moisture and screw speed are 36.5% cowpea level, 22.3% feed moisture content and 186.7 rpm respectively. The corresponding optimum values of lysine, protein content, expansion ratio and bulk density are 6.6g/100g protein, 16.6%, 2.8 and 0.52 Kgm-3 respectively. The data obtained from the study could be used for control of product characteristics and possible projection for the commercial production of fura or any enriched protein based food from the blends pearl millet and cowpea.
ABSTRACT
Millet grains were steeped in 1% sodium metabisulphite (1:2w/v) for 5min and subsequently washed and wet milled; the cereal paste was gelatinized with boiling water (1:1w/v, 76±2oC) and immediately hydrolyzed separately either with α+β-amylases, α+amyloglucosidase or rice malt. The hydrolyzed cereal starch was inoculated with a 12h starter culture (2%v/w) of Lactobacillus plantarum, L. fermentum, and Lactococcus lactis and fermented for 6h. Chemical (pH, titratable acidity), physical (viscosity, S.G., total soluble solids) and sensory quality of the hydrolyzed cereal slurry and the fermented product were determined. The results obtained in this study show that the pH of the products decreased with concomitant increases in titratable acidity (% lactic acid) during production; however, the decrease in pH was more prominent in the ‘kunun-zaki’ produced from the cereal starch treated with α+β-amylases and this, differed from the other products (p<0.05). There was an increase in viscosity with a corresponding decrease in the total soluble solids (TSS) in all the samples throughout production; the decrease in TSS is an indication of an increase in the activity of the fermenting LABs. Furthermore, the sensory quality attributes of the three products were generally acceptable by the taste panelist in all the parameters evaluated (appearance, aroma, taste), however, the ‘kunun-zaki’ produced using the cereal starch treated with rice malt was preferred in taste and this was significantly different (p<0.05) from the other products. This study has shown that ‘kunun-zaki’ of acceptable quality could be produced within 7h, the marked reduction in the processing time of ‘kunun-zaki’ from 12-7h could encourage large-scale production of this popular drink.