Volatile Compound Profiling of Fermented Locust Beans (Parkia biglobosa) from Different Fermentation Conditions in Oyo State

Fermented locust bean, locally known as iru in South West Nigeria, is a widely used food condiment produced by spontaneous fermentation of the seeds of Parkia biglobosa. The fermentation process generates characteristic flavour volatiles that define the sensory profile of the product and have potential bioactive properties, yet the comprehensive volatile compound profiles of iru produced under different traditional fermentation conditions in Oyo State have not been systematically investigated. This study profiled volatile organic compounds in iru produced under five fermentation conditions varying temperature, duration, seed treatment, and container type. Samples were prepared by solid-phase microextraction headspace sampling with a divinylbenzene-carboxen-polydimethylsiloxane fibre, and volatile compounds were identified and quantified by gas chromatography-mass spectrometry using retention index matching and spectral library comparison. Over 120 volatile compounds were identified across the five fermentation conditions, comprising aldehydes, ketones, pyrazines, alcohols, furans, sulphur compounds, esters, and organic acids. Pyrazines, responsible for nutty and roasted aromas, were significantly more abundant in samples fermented at higher temperatures above 40 degrees Celsius. Acetic acid and 3-methylbutyric acid, contributing to the pungent character, were present in highest concentrations in samples fermented for longer than 72 hours. Sulphur compounds, including dimethyl disulphide, were prominent markers of advanced fermentation. This study provides the most comprehensive volatile compound characterisation of iru from Oyo State to date and forms a foundation for process standardisation and industrial production of this culturally significant condiment.

Keywords: fermented locust beans, Parkia biglobosa, volatile compounds, SPME-GC-MS, fermentation conditions