EFFECTS OF FERMENTATION ON THE NUTRITIONAL COMPOSITIONS AND TOXICOLOGICAL PROPERTIES OF WALNUT (TETRACARPIDIUM CONOPHORUM LINN.) ENRICHED WITH CARROT.

Abstract

Despite the nutritive and medicinal values of African walnut, the crop is still included in the list of lesser known crops in Nigeria. The effects of fermentation on the nutritional compositions and toxicological properties of African walnut enriched with carrot and without carrot were carried out in this study. The natural fermentation of African walnut enriched with carrot and African walnut without carrot was carried out 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, that was isolated during the natural fermentation of African walnut, were then used singly and in consortium in the control fermentation. During the natural and control fermentation processes, proximate, anti-nutritional, mineral and antimicrobial analyses were determined on the fermented samples on daily basis for 5 days using standard methods. The immunostimulatory properties of fermented walnut was studied in an apparently healthy albino rats while the therapeutic and prophylactic properties of fermented walnut were studied in Shigella dysentariae infected albino rats by checking for the physical appearance, haematological parameters and histopathological effect on vital organs. Bacteria namely; Bacillus subtilis, Lactobacillus lactis, Micrococcus luteus, Lactobacillus plantarum, Lactobacillus casei and fungi; Penicillium notatum, Rhizopus oryzae, Penicillium chrysogenum, Candida albicans and Rhizopus stolonifer were isolated during the fermentation of African walnut among which B. subtilis was the most predominant. Fermentation reduced the antinutrient compositions of African walnut and the highest reduction was in the naturally fermented walnut that was enriched with carrot (NFWC) in which tannin, saponins, phytate and oxalate reduced from 2.47, 1.46, 14.41 and 3.29 to 0.91, 0.45, 3.61 and 0.17 respectively. Fermentation improved the protein content of Africa walnut (23.5% to 35.3). Fermentation of Africa walnut with B. subtilis had the highest protein content (35.3%) on Day 3, and among the fermented samples, NFWC had the highest crude fibre content (7.46%) on the fifth day of fermentation. Fermentation reduced all the minerals determined except potassium in walnut enriched with carrot and fermented with L. lactis where fermentation led to 4.5% increase. The antimicrobial assay showed that unfermented African walnut had the highest zones of inhibition on all the test bacteria except Pseudomonas aeruginosa and B. cereus. Among the test bacteria used in the in-vitro assay, S. dysenteriae was the most susceptible bacteria to the fermented broth cultures. The In-vivo therapeutic assay revealed that the groups of rat orogastrically dosed with S. dysenteriae showed signs of infection after 24hours. Following treatment, all the groups infected and treated on the fourth day had recovered except the groups treated with unfermented walnut, walnut fermented with B. subtilis and walnut fermented with L. lactis. Furthermore, the white blood cell (WBC) of group treated with unfermented walnut (12.47 ×109/L) was within the normal range (7 – 13 ×109/L) of WBC for an apparently healthy rat but was higher when compared with the groups treated with fermented samples. The result of the liver and kidney histopathology revealed that all the infected animals showed various degree of deformity ranging from karyolysis to dilation of sinusoids for liver and destruction of glomerular tuft to disappearances of glomerular room for kidney. Prophylactic efficacy of fermented samples prolonged the onset of infection for 48 hours; however, the negative control group (the unfed and the infected rats) showed various symptoms of shigellosis after infection. An immunostimulatory effect was observed among apparently healthy rats fed with fermented samples after 7 days of administration with fermented samples when compare to the control group (unfed group), with group fed with NFWC having the best immunostimulatory effect with packed cell volume, WBC, lymphocyte and neutrophil count of 49.5, 9.5, 46.5, and 54.5 respectively. However, feeding with unfermented walnut had a suppressive effect on the immune system with PCV, WBC, lymphocyte and neutrophil count of 39.7, 4.7, 39.5 and 40.0 respectively. Administration of fermented samples had no toxicology effect on the liver and kidney of apparently healthy rat, but the group fed with unfermented African walnut showed liver and kidney with histological defects. Therefore, fermentation of African walnut and enrichment of walnut with carrot can be employed in improving the nutritional quality and reducing the toxicological effect of African walnut, thereby helping in effectively utilizing their potential as drug and human food.