Microbiological, Physicochemical and Enzymatic Changes in Fermented African Locust Bean ( Parkia biglobosa ) Seeds Using Bacillus subtilis and Additives

Abstract

Traditional fermentation of dried seeds of Parkia biglobosa is used to produce a local product called ‘iru’. It is a condiment consumed mostly in Western Nigeria. In this study, the effect of Bacillus subtilis BC4333 starter cultures and different additives, such as local softening agents called ‘kuuru’, Hibiscus sabdariffa seed cotyledon and ash from cashew (Anacardium occidentalis) plants on the microbiological, physicochemical, and enzymatic properties of fermented Parkia biglobosa seeds were investigated. The dried seeds of Parkia biglobosa were processed by boiling the cotyledons with Hibiscus sabdariffa, ‘kuuru’ and Anacardium occidentalis (cashew plant) ash using natural fermentation and Bacillus subtilis strain BC4333 as a starter culture. The fermentations were carried out at 35 0 C for 36 hrs. Commercially fermented Parkia biglobosa seed (called ‘iru-pete’) was used as control. All the samples were analyzed for microbial, physicochemical and enzymatic properties using standard biochemical techniques. ‘Iru’ produced using ‘kuuru’ (IFK) had the highest microbial count of 7.88 log CFU/g, while the microbial count of íru’ produced with ash (IFA) and ‘iru’ produced with dried seeds of Hibscus sabdariffa (IFH) were 7.69 log CFU/g and 7.75 log CFU/g respectively. The pH of the fermented products ranged between 7.06 and 7.91, while the unfermented sample (UFS) had pH 6.68. The unfermented sample had the highest total titratable acidity (TTA) of 2.6×10 -2 N while the ‘iru’ samples produced using ‘kuuru’ (IFK) had the least TTA of 1.0×10 -2 N. Fermentation significantly (P<0.05) increased the moisture content of the products. Starter culture fermented ‘iru’ (F14) had the highest protease, amylase and phytase activity of 232.3UPR, 0.41UAM and 71.85UPH respectively. Findings from this study suggest that ‘iru’ produced by addition of Bacillus subtilis strain BC4333 had the best desirable biochemical qualities when compared to the other tested additives and thus recommended for commercial scale.