Analysis and identification of the volatile compounds in melon-bitter leaf soup

Melon-bitter leaf soup is one of the most widely consumed soup delicacies across West Africa, owing to its unique and distinct flavour. The aim of this study therefore was to identify volatile compounds in this soup, thus establishing a critical baseline for further work. Melon-bitter leaf soup was prepared according to standard method. Functional groups of chemical moieties in the soup were obtained using Fourier Transform Infra-red Spectroscopy (FT-IR). Analysis and identification of the volatile compounds in the soup was by Headspace micro-extraction at 40°C coupled with gas chromatography/mass-spectroscopy (GC/MS) using helium as carrier gas at a constant flow rate of 1 ml/min and an injection volume of 0.5 µl (split ratio of 10:1). Amines, esters, acids, benzenes, alkanes, pyrazines and terpenes were established and authenticated. Major aroma contributors to the soup flavour were found to be acetic acid (22.31%), 3-methylbutanoic acid (13.38%), 2-methylbutanoic acid (6.38%), 2-methylpropanoic acid (4.69%), tetramethylpyrazine (4.45%), butanoic acid (2.51%), propanoic acid (2.09%), trimethylpyrazine (1.55%), methylpyrazine (1.10%), furfural (1.10%), hexanoic acid (0.64%), linalool (0.38%), 1,8-cineole (eucalyptol) (0.35%) and 2,5 dimethylpyrazine (0.29%), all characterized with distinct peaks on the chromatogram. Volatile flavor compounds associated with melon bitter leaf soup were isolated and identified. Acetic acid was the major flavorant.