EFFECT OF DIFFERENT FERMENTATION METHODS ON THE NUTRIENT AND ANTINUTRIENT CONTENTS OF KERSTING’S GROUNDNUT (Macrotyloma geocarpum)

Abstract

Kersting’s groundnut (Macrotyloma geocarpum) was subjected to liquid and solid state fermentation. The raw and fermented samples were analyzed for microbial load, proximate composition, mineral content, antinutrient, and amino acid contents. The microorganisms isolated and identified were: Bacillus licheniformis, Bacillus subtilis, Bacillus megaterium, Bacillus polymyxa, Bacillus coagulans, Lactobacillus plantarum, Staphylococccus aureus, Aspergillus niger, Rhodotorula spp, Aspergillus parasiticus, Rhizopus stolonifer, and Saccharomyces cerevisae. All the five species of Bacillus were found in both fermentation methods, with Bacillus subtilis as the predominant organism all through the fermentation period. Total bacterial count (TBC) during liquid fermentation ranged from 5.33x103cfu/g to 9.67x103cfu/g, while TBC during solid fermentation ranged from 5.33x103cfu/g to 8.00x103cfu/g. Total fungal count was observed to increase from 1.33x103sfu/g to 5.67x103sfu/g in solid fermentation and from 1.33x103sfu/g to 3.33x103sfu/g after 72 hours of liquid fermentation. The result of proximate analysis shows that liquid state fermentation increased the protein content from 18.11 to 22.95% of the nut while solid state fermentation increased protein content from 18.11 to 19.07%. Both fermentation methods reduced crude fibre and increased fat content respectively, while soluble carbohydrate decreased in liquid state. Mineral analysis revealed potassium as the most abundant mineral followed by magnesium and calcium. A total of 17 amino acids were analyzed in Kersting’s groundnut subjected to different fermentation methods. The amino acid analysis showed leucine as the most abundant essential amino acid and glutamic acid as the most abundant non-essential amino acid. The total essential amino acid (TEAA) ranges between 46.39% to 46.85% of the total amino acid (%TAA). The value of all the essential amino acids increased after 24 hours of liquid and 48 hours of solid fermentation, but later decreased as fermentation time increased. Anti-nutrient contents decreased more in liquid state fermentation than the solid state. The overall result obtained from this study revealed that liquid fermentation for 24 hours and solid fermentation for 48 hours are the suitable fermentation methods and time that may enhance the proximate composition and amino acids quality of Kersting’s groundnut.