Microbiological assessment of maize ogi cofermented with pigeon pea.

Maize was cofermented with pigeon pea for ogi production and evaluated for microbiological qualities. White maize and pigeon pea were mixed at ratios of 90:10, 80:20, 70:30, 60:40, and 50:50, respectively, with 100:0 serving as the control. Mixtures were cofermented for 96 h at 27 ± 2°C, and microbiological and sensory qualities analyzed were carried out using analysis of variance. Values were significant at p ≤ .05. Results showed that there was a gradual decrease in the pH and increase in total titratable acidity (TTA), respectively, during fermentation in all the samples. At the end of fermentation, pH ranged from 3.47 to 4.27 and TTA ranged from 0.47% to 0.54%, respectively. Total heterotrophic count (THPC) ranged from 5.76 to 5.90 log cfu/g; lactic acid bacteria (LAB) from 6.15 to 5.98 log cfu/g; and yeasts from 5.51 to 5.79 log cfu/g. Microorganisms isolated were lactic acid bacteria (Lactobacillus buchneri, L. casei, L. pentosus, Pediococcus pentosaceus), yeasts (Saccharomyces cerevisiae, Candida kefyr, C. krusei, C. tropicalis), molds (Aspergillus niger, A. flavus, Penicillium oxalicum, Mucor racemosus and Rhizopus stolonifer) and other aerobic bacteria (Klebsiella oxytoca, Enterobacter amnigenus, Staphylococcus xylosus, Bacillus subtilis, B. firmus, Corynebacterium kutscheri, C. striatum, and C. afermentans). In conclusion, the total heterotrophic plate count (THPC) in fortified maize: pigeon pea products was very high. This could constitute health hazards to infants as weaning foods. However, the microbial loads could be reduced through heat treatment as ogi is usually boiled or treated with boiled water before consumption and it can therefore be concluded that the fortified maize: pigeon pea products could be used as weaning foods.

Production of citric acid by Aspergillus niger immobilized in Detarium microcarpum matrix

Aims: This study investigated the potential use of Detarium microcarpum as a support matrix for the immobilization of fungal cell and its subsequent use in the production of citric acid. Methodology and results: Conidia of Aspergillus niger were immobilized on Detarium microcarpum matrix crosslinked with glutaraldehyde (2.5% v/v). Effects of various immobilized conditions on citric acid yield were determined. Citric acid production was optimum at 9% gel concentration, 5.0 mm bead size and 400 mg spore load. Higher citric acid yield (82g/L) was obtained by immobilized cells while free cells gave (61 g/L). Immobilized gels were stable for 15 days in the fermentation medium and retained about 75% of initial yield after five repeated cycles. Conclusion, significance and impact of study: This study therefore shows that D. microcarpum is a novel matrix for cell immobilization and will enhance production of citric acid in batch system.

Assessment of the antimicrobial activity of lactic acid bacteria isolated from two fermented maize products - ogi and kunnu-zaki

The lactic acid bacteria (LAB) used in this study were isolated from two traditional fermented maize products- ogi and kunnu-zaki. The antimicrobial activities of the isolated LAB against some indicator organisms (Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia, Proteus mirabilis and Bacillus cereus) was investigated. The LAB population in the ogi samples ranged from 5.39 log cfu/g to 6.40 log cfu/g while that of kunnu-zaki ranged from 6.11 log cfu/g to 6.70 log cfu/g. The lactic acid bacteria isolated were identified as Lactobacillus plantarum, L. fermentum, L. lactis, L. acidophilus, L. mesenteroides, L. casei, and Streptococcus thermophilus. Cell free supernatant of the LAB was able to inhibit the growth of the indicator organism used. The largest zone of inhibition was 11 mm produced by L. plantarum against Klebsiella pnuemoniae while the least zone of inhibition was 3 mm produced by L. acidophilus against E. coli. The LAB tested also produced various antimicrobial compounds such as lactic acid, diacetyl and hydrogen peroxide and quantitative estimation of these antimicrobial compounds was carried out. The highest yield of lactic acid was 2.18 g/L produced by S. thermophilus, highest yield of diacetyl was 2.5 g/L produced by L. plantarum while the highest yield of hydrogen peroxide was 0.006 g/L produced by L. plantarum.