ABSTRACT
Aim: This study investigated the microbiological, physicochemical and antinutritional properties of three varieties of fermenting melon seeds namely: Citrullus vulgaris (Schrad), Citrullus colocynthis (L) and Cucumeropsis mannii (Naud) for ogiri production. Methodology: Ogiri was produced from these three varieties of melon seeds following the traditional fermentation process while online monitoring was used to evaluate microbial hazards using standard microbiological techniques. Physicochemical and antinutritional properties were determined using standard methods. Results: Bacterial counts ranged from 7.0 x 103 cfu/g to 2.4 x 104 cfu/g for Citrullus vulgaris, 3.2 x 105 cfu/g to 3.7 x105 cfu/g for Citrullus colocynthis and 8.7 x 106 cfu/g to 9.1 x 106 cfu/g for Cucumeropsis mannii. Some of the isolated microorganisms from the fermenting melon seeds include Lactobacillus species, Bacillus species, Aerococcus viridans, Staphylococcus aureus, Micrococcus luteus, Aspergillus niger, Penicillium species and Fusarium eguseti. Cucumeropsis mannii had the highest crude fibre and protein (12.7 and 38.5 mg/g) but lowest values for fat and ash while Citrullus vulgaris recorded the highest values of 35.3 and 3.4 mg/g There were no significant differences in values obtained for sodium, Cucumeropsis mannii had highest values for potassium and phosphorus (0.36 and 0.29 mg/kg). Citrullus vulgaris was outstanding in mineral content for magnesium with the highest value of 0.27 mg/kg and lowest for calcium (0.29 mg/kg) compared to 0.30 and 0.34 for Cucumeropsis mannii and Citrullus colocynthis respectively. Anti-nutrients were highest in Citrullus vulgaris and lowest in Cucumeropsis mannii. Acidic pH of 5.78 was recorded in Citrullus colocynthis but increased to 8.91 and 8.69 in Citrullus vulgaris and Cucumeropsis mannii indicating that Citrullus colocynthis may not be appropriate for ogiri production. Conclusion: Cucumeropsis mannii compares favourably with traditionally used Citrullus vulgaris resulting in higher fibre, protein, mineral contents with lower values of anti-nutrients and therefore recommended as a good substitute for ogiri production.
ABSTRACT
Aims: This Bacillus subtilis has been identified to be the main fermenting bacterium during indigenous production of “ogiri egusi”; a traditional soup flavouring rich in protein. Evaluation of the use of starter and broth cultures of this bacterium in the production of ‘ogiri egusi’ was therefore undertaken with the view to improve the fermentation process and quality of product. Methodology and Results: Cowpea granules in association with Bacillus subtilis cells were developed as starter cultures for the fermentation. Results obtained showed that the starter cultures resulted in an increase in the aminonitrogen from 1.67±0.02 to 19.96±0.05 mg N/100 g dry matter in 48 h while the broth cultures increased the aminonitrogen from 1.63±0.03 to 16.54±0.05 mg N/100 g dry matter in 72 h. There was also a corresponding increase in the protease activity of the fermentation conducted with the starter cultures from 2.69±0.03 to 54.98±0.04 mg N/min in 48 h. The broth cultures produced an increase from 2.65±0.02 to 47.61±0.06 mg N/min in 72 h. Changes in these parameters for the natural process were gradual and reached their peaks at 120 h with values of 9.89±0.13 mg N/100g dry matter and 31.92±0.03 mg N/min respectively. Peroxide values for the fermentation processes increased throughout the period; however the starter cultures produced the lowest value (10.20±0.10 meq/kg) showing that rancidity may not occur in the product fermented by the starter culture. Conclusion, significance and impact of study: The starter cultures significantly reduced fermentation time from 96 – 120 h in the natural process to 48 h. Thus use of starter cultures optimized the process of fermentation and will eliminate chances of contamination of product with pathogens and spoilage organisms. This ultimately will improve product quality.