ABSTRACT
Aims: A comparative study of fungi and bacteria fermentation of soybean (Glycine max) was carried out to determine the effect of fermentation on the nutritional composition of their fermented products: tempeh and ‘soy-iru’. Study Design: The experiment was carried out in the Department of Microbiology, Ekiti State University, Ado Ekiti, Nigeria, between August, 2017 and July 2018. Methodology: Soybean was processed into ‘soy-iru’ (bacterial fermentation) and tempeh (fungal fermentation) and the microbial load, physico-chemical properties, proximate composition, levels of anti-nutritional components (trypsin inhibitor and phytic acid), anti-oxidants (total phenol, total flavonoid and DPPH), in-vitro protein digestibility and vitamins (A, B, C, D, and E) were analyzed. Results: The microbial load, pH increased progressively during fermentation, while there was a decrease in the titratable acidity (TTA) of the two products. The protein(%), ash(%) and fat(%) contents of the Glycine max cotyledons increased from 29.56, 1.86 and 24.36 in unfermented substrate to 33.61, 2.21 and 26.90, respectively, after 24hrs of fermentation to produce tempeh. However, there was a reduction in the crude fibre(%) and carbohydrate(%) content from 2.94 and 41.29 in unfermented substrate to 2.53 and 32.57, respectively, after 24hrs of fermentation. Similar trends were observed during the production of ‘soy-iru’, however the change in proximate composition was not as significant as observed in tempeh. There was significant decrease in the trypsin inhibitor and phytic acid levels of the two products. The levels of anti-oxidants, vitamins B, D, E and protein digestibility increased significantly, in both bacterial and fungal-fermented products. Conclusion: This research has therefore shown that fungal fermentation of Glycine max seeds into tempeh may be a better alternative to ‘soy-iru’ which was obtained from bacterial fermentation, because of the significant lower level anti-nutritional factors in the former.
ABSTRACT
Aim: To select good strains of Bacillus subtilis for use as starter culture in the fermentation of Parkia biglobosa. Study Design: Fifteen (15) strains of Bacillus subtilis group obtained from commercial samples were used in starter-culture fermentation of Parkia biglobosa seeds to produce ‘iru’. Place and Duration of Study: Food Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC), Pahumthani, Thailand, between March to May 2010. Methodology: The quality of the starter culture-fermented products were compared on the bases of sensory evaluation, degree of hydrolysis (DH), level of ammonia nitrogen (NH3-N), pH and enzymatic activities. The 15 strains were also screened for haemolytic activity. Results: On the basis of the sensory scores of 5 parameters (color, odor, consistency, texture and over-all liking), particularly the over-all liking, 5 strains were rated the best (in descending order): BC4333 > 8B > 2B > 7A > 5A, amongst the 15 tested. There were good correlations between pH and DH (r= 0.926), DH and NH3-N (r=0.962) and between pH and NH3-N (r=0.945). The strain BC4333 produced the very soft variant of ‘iru’ (‘iru-pete’), without the addition of ‘kuuru’ (local potash). The quantity of extracellular enzymes (protease, amylase, pectinase, phytase and lipase) produced during fermentation varied significantly. None of the 5 strains was haemolytic on sheep blood agar. Conclusion: The 5 strains of Bacillus subtilis (BC4333, 8B, 2B, 7A, 5A) that showed potentials of being used as starter cultures for industrial production of ‘iru’, were nonhemolytic on blood agar.