Effects of Natural and Inoculation Fermentation on the Antinutrient Composition of African Walnut Enriched with Carrot

Abstract

The effects of fermentation on the antinutrient composition of African walnut enriched with carrot and without carrot were carried out in this study. The submerged natural fermentation of non- enriched and carrot enriched (walnut 70%; carrot 30%)  African walnut was carried out and lasted for 5 days during which microorganisms were isolated and identified. Species of Lactobacillus and Bacillus that are most commonly used as probiotics in foods, drugs, and dietary supplements, which was isolated during the natural fermentation of African walnut, were then used singly and in consortium during inoculation fermentation. During the fermentation processes, the anti nutritional analysis was carried out on the fermented samples on a daily basis. Result revealed that the bacteria B. subtilis strain b17a and L. lactis SFL8 were the most predominant bacteria during the natural fermentation. Raw African walnut and carrot have tannin, saponins, Phytate and oxalate of  2.47± 0.10, 1.46 ± 0.10, 14.41 ± 0.10 , 3.29 ± .10  and 2.28 ± .08,  2.10 ± .10,11.50± .05, 0.37± .03 respectively. Raw walnut generally had a higher anti-nutrient composition than carrot except in saponins. Fermentation led to the reduction in antinutrient composition in the fermented sample. Natural fermented African walnut (NFW) and natural fermented African walnut enriched with carrot (NFWC) resulted in the highest reduction in antinutrient composition. NFW and NFWC had a reduction in tannin, saponins, Phytate and oxalate from (2.47±0.008b, 1.46±0.010a, 14.41±0.026d, 3.29±0.05c) to (0.98 ± 0.05a, 0.61±0.05a, 4.35±0.03a, 0.27±0.05a) and (0.91±0.005a, 0.45±0.005a, 3.61±0.03a, 0.17±0.005a) respectively. Inoculation fermentation in which a monoculture of L. lactis or B. subtillis was used as starter culture resulted in the least reduction in the antinutrient content. Carrot enrichment of fermented African walnut had a reducing effect on the antinutrient composition of African walnut as the fermentation enriched with carrot all had a reduced tannin, Phytate and oxalate composition compared to those that were not enriched. Hence, fermentation and enrichment with carrot can be employed in improving the nutritional quality of African walnut thereby helping in effectively utilising their potential as human food.