Esther Sakyi-Dawson

Response Surface Methodology for Studying the Effects of Feed Moisture and Ingredient Variations on the Chemical Composition and Appearance of Extruded Sorghum-Groundnut-Cowpea Blends

Studies were conducted to evaluate the effects of feed moisture and ingredient variations on the chemical composition and appearance of extruded sorghum-groundnut-cowpea blends using response surface methodology. Central composite rotatable design for k = 3 was used to study the combined effect of feed moisture (12 to 44 percent), groundnut concentration (zero to 10 percent) and cowpea level (zero to 20 percent) on the chemical composition and appearance of extruded ready-to-eat sorghum-legume blends in a single screw extruder. Product moisture, crude protein, crude fat, ash (minerals), crude fibre, carbohydrate and colour (L, a and b-values) were determined on the products using standard analytical methods. The results showed that irrespective of the feed moisture level, the extrusion process could reduce the product moisture to levels between six to 10 percent and low enough to extend the shelf life of the derived products. Increasing additions of cowpea and groundnut resulted in significant increases in protein, fat and ash (minerals - calcium, iron, and phosphorus) contents of the sorghum-legume extrudates. Increasing addition of cowpea decreased the redness of the sorghum extrudates, while no changes were noted with groundnut additions. Contrary, increasing groundnut addition generally increased the yellowness at all cowpea concentrations, while only minimal changes were noted with cowpea additions. The lightness of the sorghum extrudates decreased with increasing cowpea and groundnut concentrations, and this was more pronounced at higher cowpea concentrations and with increasing groundnut levels. The level of feed moisture showed no effect. Models developed for the indices gave R2-values ranging from 67.04 percent (for a-value) to 87.83 percent (for fat content), with insignificant lack of fits indicating the adequacy of the model in explaining the data. The optimal conditions likely to produce ready-to-eat puffed snack with enhanced nutritive value and appearance from sorghum-groundnut-cowpea blend extrudates was at low feed moisture (10 to 14 percent), cowpea level (18 to 20 percent) and groundnut level (six to eight percent).

Utilization of cowpeas for human food

Abstract This paper reviews the research and outreach accomplishments of the cowpea utilization project sponsored by the United States Agency for International Development-funded Bean/Cowpea Collaborative Research Support Program. Research has examined a limited number of cultivars and has taken as its starting point mature, dry seeds. A broad spectrum of food quality issues have been studied, including: • safety concerns and physiological effects associated with consuming legume seeds and products made from them; • chemical composition and nutritional quality of the seeds and products; • physical and functional behavior of seeds and products; and • socioeconomic aspects including sensory quality of seeds and products, consumer acceptance, and costs and impacts of technology adoption. Research foci have included: • The effect of pretreatment and storage on cowpea food quality; • processing whole seeds to improve food quality; • conversion of legume seeds into food ingredients, principally flours and meals; • processing seeds and ingredients to improve food quality; and • improvement of traditional foods and development of new foods from bean and cowpea-based ingredients.

Yeasts in the traditional brewing of pito in Ghana

Yeasts from pito, a cereal-based traditional alcoholic beverage were isolated and characterized using biochemical and physiological tests. A total of 21 strains belonging to 8 genera were identified as Saccharomyces cerevisiae (8), Candida tropicalis (4), Kloeckera apiculata (2), Hansenula anomala (2), Torulaspora delbrueckii (3), Schizosaccharomyces pombe (1) and Kluvyeromyces africanus (1). Various diluents used for a 2 h holding period shows that 0.1% malt extract and peptone gave 20% decrease in cell viability for all the isolates, while phosphate buffer least supported the survival of the yeast cells with about 90% decrease in cell viability obtained for S. pombe at the end of the 2 h holding period. The effect of pH and temperature on the growth of the isolates revealed that at relatively low temperatures, growth increased with increasing pH, but a decrease was observed with increasing pH at high temperatures for S. cerevisiae and Candida tropicalis. All the isolates demonstrated good growth (102 to 106 c.f.u./ml) at 10% ethanol concentration over a period of 8 days incubation. However, growth of K. africanus was completely inhibited after 4 days incubation period. The quality indices of the beverage produced using S. cerevisiae as a single-starter organism compared favourably with the traditional brew. The paper suggests ways of scientifically regulating the production of fermented foods in sub-Saharan Africa.

Campylobacter, Salmonella, Shigella and Escherichia coli in live and dressed poultry from metropolitan Accra

This study on the microbiology of chicken assessed a total of 97 live birds from three selected farms and 87 carcasses/chicken parts from two supermarkets, two open markets and one wholesale outlet (cold store) in the Accra metropolis. Campylobacter spp. were isolated from 14 (14.4%) gut contents of live birds from three farms. None of the frozen birds were positive for Campylobacter spp. These isolates were sensitive to most common antibiotics but not to ampicillin and tetracyclines. Salmonella spp. were isolated from 7 (7.2%) gut contents and 13 (6.8%) carcasses and were resistant to erythromycin. cefotiam, penicillin, ampicillin and cefadroxil. Samonella spp. had varied susceptibilities to nalidixic acid, chloramphenicol and minocyclin. No Shigella spp. was isolated from any of the live birds but 6 (6.9%) of imported chicken samples from the cold store and two markets were positive. Fosfomycin and chloramphenicol were the only antibiotics effective against these isolates. Twelve different Escherichia coli serovars were identified from the total of 21 positive samples. These, in order of magnitude isolated, are E. coli 0158 (14.3%), 0125 (14.3%), 025 (9.5%), 028ac (9.5%), 0159 (9.5%). 015 (9.5%), 0126 (9.5%), 063 (4.8%), 0143 (4.8%), 026 (4.8%), 078 (4.8%), 0164 (4.8%). Cefadroxil, ampicillin, penicillin, cefotiam, tetracycline and erythromycin were ineffective against all strains of E. coli isolated. Minocyclin was effective against all strains with the exception of E. coli 0159, 025, 0164 and 063, which were moderately susceptible. All strains with exception of E. coli 0164 were susceptible to fosfomycin. Nalidixic acid, chloramphenicol, kanamaycin, ceftrioxone and amoxycillin all showed varied effectiveness against the strains isolated. It is concluded that imported and locally produced chicken is a potential source of multiple-antibiotic-resistant enteropathogenic bacteria. Measures to improve the microbial quality of chicken are discussed.

Application of response surface methodology for studying the product characteristics of extruded rice-cowpea-groundnut blends

Response surface methodology (with central composite rotatable design for k=3) was used to investigate the product properties of extruded rice–cowpea–groundnut blends in a single screw extruder. The combined effect of cowpea (0–20%), groundnut (0–10%), and feed moisture (14–48%) levels were used for formulation of the products. The product moisture, expansion ratio, bulk density and total colour change were studied using standard analytical methods. Well-expanded rice–legume blend extrudates of less bulk density and lower moisture content were produced at low feed moisture. Increasing legume addition affected the various shades of colour in the product. Models developed for the indices gave R2 values ranging from 52.8% (for the b-value) to 86.5% (for bulk density). The models developed suggested that the optimal process variables for the production of a puffed snack with an enhanced nutrition and spongy structure from a rice–cowpea–groundnut blend are low feed moisture of 14–20% and maximum additions of 20% cowpea and 10% groundnut. A lack-of-fit test showed no significance, indicating that the models adequately fitted the data.

Antimicrobial interactions of microbial species involved in the fermentation of cassava dough into agbelima with particular reference to the inhibitory effect of lactic acid bacteria on enteric pathogens

Lactic acid bacteria, Bacillus species and yeasts are involved in the fermentation of cassava dough into agbelima. Microbial interactions within and between these groups of microorganisms were investigated in addition to the survival of five enteric pathogens inoculated into agbelima under various conditions. Nine out of 10 cultures of lactic acid bacteria isolated at the end of agbelima fermentation showed inhibitory effect against 10 cultures of lactic acid bacteria isolated at the start of fermentation. Only 3 out of 10 isolates of Bacillus subtilis were inhibited by 10 isolates of lactic acid bacteria tested. No interactions were observed between yeasts and the lactic acid bacteria, whereas three of the Bacillus isolates showed inhibitory effects against the yeasts. Twelve isolates of Lactobacillus plantarum tested inhibited the growth of an isolate each of Lactobacillus fermentum and Lactobacillus brevis but none tested positive for bacteriocin production. The antimicrobial effect of the lactic acid bacteria was attributed to acid production. In fermenting cassava dough, enteric pathogens survived to different extents depending on pH and their sensitivity to acids. Vibrio cholerae C-230, Salmonella typhimurium 9 and Salmonella enteritidis 226 were not detectable in 10 g of sample after 4 h when inoculated into the 48-h fermented product, agbelima, whereas Shigella dysenteriae 2357T and Escherichia coli D2188 were detectable up to 8 h in the product.

The microflora of fermented nixtamalized corn

Nixtamalization is a traditional process that improves the nutritional quality of corn. To provide a means of utilizing the nutritional benefits of nixtamalized corn and improve product acceptability, lactic acid fermentation was applied. The objective of the study was to study the microbial profile and establish the important lactobacilli of fermenting nixtamalized corn dough. Two batches of cleaned whole corn were subjected to the process of nixtamalization, using two concentrations of lime (0.5 or 1.0%), milled, made into a dough (50% moisture) and fermented spontaneously for 72 h. A control sample was prepared without alkaline treatment. pH and titratable acidity of the dough were measured. Aerobic mesophiles, lactic acid bacteria, yeasts and molds were enumerated on Plate Count Agar (PCA), deMan, Rogossa and Sharpe (MRS) Agar and Malt Extract Agar (MEA), respectively. The identity of lactobacilli present was established at the species level using API 50 CHL. The pH of all the fermenting systems decreased with fermentation time with concomitant increase in titratable acidity. Lactic acid bacteria in numbers of 1.6 x 10(9), 2.3 x 10(9) and 1.8 x 10(9) cfu/g, respectively yeasts and molds, and numbers of 8.0 x 10(7), 5.0 x 10(5) and 1.7 x 10(5) cfu/g, respectively were observed in the control and the two nixtamalized (0.5% and 1.0% lime) samples after 48 h of fermentation. Lactobacilli identified in the fermenting nixtamalized corn dough were Lactobacillus plantarum, Lactobacillus fermentum and Lactobacillus cellobiosus as well as Pediococcus spp. The study demonstrates that nixtamalized corn though alkaline in nature can be subjected to spontaneous fermentation to produce a sour product.

Application of response surface methodology for studying the quality characteristics of cowpea-fortified nixtamalized maize

Studies were conducted on the chemical and functional properties of fermented cowpea-fortified nixtamalized maize using response surface methodology. The central composite rotatable design for Ks3 was used to study the combined effect of lime concentration (0–1%), moisture content (55–65%) and cowpea level (0–30%) on pH, titratable acidity, water absorption, protein and viscosity of fermented nixtamalized maize. Regression models were developed to predict the variables. The presence of lime and cowpea influenced the pH, titratable acidity, water absorption, protein content and the cooked paste viscosity of the fermented cowpea-fortified maize. The presence of lime during fermentation generally decreased titratable acidity, water absorption and cooked paste viscosity while the addition of cowpea increased most of the studied indices. Cowpea fortification can therefore be used to increase the nutritive value of nixtamalized maize with acceptable product quality characteristics. 2002 Elsevier Science Ltd. All rights reserved.

Microbiological evaluation of ghanaian maize dough co-fermented with cowpea

Fermented maize dough meals form a large proportion of peoples diet in Ghana. To enhance the nutritive value of these carbohydrate-rich foods, protein complementation was introduced. In this study, microbial ecology of fermenting maize dough fortified with 20% cowpea was investigated. A total of 106 microbial strains were isolated from different batches of the fermenting dough at periodic intervals. Ten genera of microorganisms namely Lactobacillus, Leuconostoc, Saccharomyces, Debaryomyces, Candida, Bacillus, Micrococcus, Klebsiella, Escherichia and Aspergillus were identified, with lactic acid bacteria species being predominant. A lactic count of log 9.9 cfu/g was obtained at the end of 72 h fermentation relative to log 6.6 cfu/g recorded for aerobic mesophiles. At the 12 h fermentation period, the population of yeasts was less than log 1.0 cfu/g, but gradually rose to log 5.36 cfu/g by 48 h followed a slight decline at the end of 72 h fermentation period (log 4.08 cfu/g). Enteric microorganisms that were isolated from the raw cowpea were less than log 1.0 cfu/g at 12 h of fermentation, while the Aspergillus species were isolated from the raw maize and the dough subjected to drying treatment. The growth of inoculated enteropathogenic E. coli and S. typhimurium was inhibited in the cooked, fermented maize-cowpea dough, and at 72 h, they were not within detectable limit. The study concluded that addition of cowpea at 20% level did not affect the natural fermentation characteristics of the maize dough.

Optimisation of chocolate formulation using dehydrated peanut-cowpea milk to replace dairy milk.

BACKGROUND The rheological properties of chocolate, based upon its acceptability by consumers, are determined largely by the ingredients and their proportions used in the formulations. Milk chocolates are very popular because milk provides flavour and smooth texture to the product. This study aimed to determine the optimal ingredient formulation for vegetable milk chocolate using peanut-cowpea milk as a substitute for dairy milk. The study followed a four-component constrained mixture design, with cocoa liquor, vegetable milk, cocoa butter and sugar as the components. Lecithin and vanillin were added at a constant amount to all formulations. Critical attributes of the chocolates were evaluated using descriptive sensory tests and instrumental techniques. RESULTS Regression models were fitted to the data, and the optimum ingredient formulation for acceptable vegetable milk chocolate was determined. The vegetable milk had significant (P = 0.05) influence on flavour, mouth feel, hardness and after taste of chocolates. CONCLUSIONS The optimum ingredient formulation for acceptable vegetable milk chocolates was determined to be cocoa liquor (18.00%), sugar (30.75%), peanut-cowpea milk (28.93%), and cocoa butter (22.32%). The results demonstrate that it is feasible to use vegetable source milk for chocolate. The findings also provide clues for scale-up criteria for large-scale production of vegetable milk chocolate.