Fermentation of melon seeds for “Ogiri egusi” as affected by fermentation variables using Bacillus subtilis

• Main Authors: Ogueke, C. C., Okoli, A. I., Owuamanam, C. I., Ahaotu, I.
• Format: Article
• Language: English
• Published: Malaysian Society for Microbiology 2013-12-01
• Series: Malaysian Journal of Microbiology
• Subjects: toxicity; Ogiri egusi; fermentation variables; response surface; Bacillus subtilis; amino nitrogen
• Online Access: http://web.usm.my/mjm/issues/vol9no4/Research%201.pdf
• ISSN: 1823-8262; 2231-7538

Aims: Manipulation of fermentation variables during ‘Ogiri egusi’ production using Bacillus subtilis was studied with the view to improving the fermentation process and quality of product. The variables studied were relative humidity (RH), temperature and pore size of wrapping material. Methodology and results: Effect of variables on amino nitrogen, pH and peroxide value was determined on 24 h basis for 96 h. Attempt on optimization of process using response surface method was made. Amino nitrogen increased with fermentation time, the highest value (6.25 mg N/g) being obtained from sample fermented at 75% RH, temperature 35 °C and 90 µm pore size of wrapping material. Fermentation attained its peak at 48 h fermentation time. pH increased into the alkaline range within the period, the highest value (7.81) being from sample that gave the highest amount of amino nitrogen. Peroxide values obtained in all samples were far below the recommended value of 30 Meq/kg. However, the highest value (4.16 Keq/kg) was obtained in sample fermented at 85% RH, temperature 30 °C and 70 µm pore size of wrapper. Statistical analysis and response surface plots associated with analysis showed that the quadratic effect of variables was significant (p = 0.05). Effects of relative humidity and pore size of wrapping material were also significant and accounted for 99.56% of the amino nitrogen variation. Conclusion, significance and impact study: Manipulation of the fermentation variables significantly improved the process. Thus use of response surface method optimized the fermentation process especially the effects of relative humidity and pore size of wrapping materials. The suggested combination of variables for optimum fermentation is 75% RH, temperature 35 °C and 70 µm pore size of wrapper. This ultimately will improve product quality and reduce fermentation time.