Volatile Compounds Determination by GC-MS and Identification of Dominant Microorganism at Varying Fermentation Period of Ogi Slurry

Volatile compounds (VOCs) and associated microbes of ogi at varying soaking and fermentation periods were detected with the aid of Gas Chromatography-Mass Spectrometry (GC-MS) and cultural methods, respectively. Thirty-five (35) VOCs were identified and classified into Carbonyl, Alcohol, Aldehydes, Esters and Organic acid. The average amount of volatile compounds of Ogi produced at varying period (16 and 24 h) varies significantly. Twelve (12) of the detected VOCs had higher concentration and the principal components analysis (PCA) revealed that few of the identified VOCs contributed significantly to the characteristic attributes of Ogi. The first principal components (PC1) had Eigen values of 15.33 (43.80%) and 17.84 (51%) while the second principal components (PC2) had Eigen values of 12.57 (35.90%) and 9.67 (27.60%), respectively. Presence of different species of Candida and Lactic Acid Bacteria (LAB) isolates at different fermentation levels (0 to 48 h) of Ogi     was established.  The population of LAB and yeast increased with rate of fermentation from 0 to 24 h but remained constant at 36 and 48th h of fermentation. The isolated LAB include Pedicoccus spp, Leuconostoc spp, Lactobacillus acidophilus, Lactococcus spp and other Lactobacillus spp. while the Candida spp present in the Ogi samples include; Candida krusei, Candida glabrata, Candida parasilosis, Candida albicans, Candida tropicalis and Candida kefyr. Candida spps exhibited a varying temperature for growth while growth of LAB ceased at temperature above 45oC but not below 15oC. Molecular identification further revealed the following LAB; Lactobacillus pentosus strains, Lactobacillus fermentum strains, Pediococcus pentosaceus strains and Weissella confusa strains, while dominant yeast were Candida tropicalis strains, Candida auris isolate, Candida glabrata strain, Pichia kudriavzevii culture, Candida albicans strain and Issatchenkia orientalis strain. This study revealed that LAB and Yeast are actively involved in the fermentation of ogi. The fermentation condition and the identified microorganism evidently contributed to the amount and types of VOCs detected. Practical Applications : The consumers' acceptance of Ogi slurry is predominantly hinged on the aroma, flavour and taste. Sensory acceptability is indirectly or directly connected to the concentration of volatile compounds of the product. The processing conditions (fermentation periods) stand the chance of playing very important role in the types and concentration of these volatile compounds. The knowledge of the volatile compounds will be useful in monitoring Ogi's freshness and quality and subsequently may be of commercial interest, most especially with the identified Lactic Acid Bacteria and yeast and the detected volatile compounds. This information may be of commercial interest if the predominant volatile compounds detected in Ogi are to be synthesized artificially.