ABSTRACT

 The biopreservative effect of lactic acid bacteria on certain quality attributes of ugba (fermented African oil bean seeds) were studied. The pure culture of lactic acid bacteria (Lactobacillus plantarum) isolated from ugba samples produced by traditional method, were successively screened and used (in single) to ferment African oil bean slices. The samples (ugba produced by spontaneous fermentation with that produced by LAB starter cultures) were subjected to shelflife study and microbiological analysis as well as proximate, antinutritional, minerals and sensory attributes, and the mean values statistically analysed using a one-way Analysis of Variance at P < 0.05. Sample B inoculated with LAB starter culture was able to store for more than 7 days with less microbial load showing improved keeping qualities than those products processed locally that were purchased from the market that started spoiling from day 4. The results also showed that the following bacterial isolates were involved in the fermentation: Bacillus spp., Lactobacillus spp., Streptococcus spp., Micrococcus spp., and spoilage of ugba: Proteus spp., Staphylococcus spp., Pseudomonas spp., Escherichia coli. Fungal contaminants: Penicillium spp., Aspergillus spp and Rhizopus spp., were also observed. The use of LAB starter culture in Sample B shortened the fermentation period from 72 h to 48 h with a significant reduction in pH (7.32 — 6.44) and increase in titratable acidity (0.068 — 0.097) as the fermentation time progressed, showing a favourable temperature (3 7°C) for the activities of lactic acid bacteria. There were significant differences (P<0.05) among all the samples in the pH and titratable acidity. The proximate composition of all the ugba samples had different levels of protein content (14.27%, 14.20%, 14.17%, 14.03%, 12.76%) respectively. Fat content (10.23% - 15.75%), moisture content (41.22% - 54.23%), ash content (0.67% - 2.89%), fibre content (7.07% - 9.03%) and carbohydrate content (10.79% - 25.73%), with Sample B (ugba produced by LAB starter culture) having the highest values in protein, fat and ash contents. There were significant differences (P><0.05) among all the samples in the proximate compositions. The antinutritional factors of ugba produced by LAB starter culture had a significant reduction at the end of the fermentation process: tannins were reduced by >68%; oxalates were reduced by >90%; cyanide was reduced by >31% and phytic acid was reduced by >62% respectively. There were significant differences (P

<0.05) among all the samples in the antinutritional factors. The samples had different levels of mineral content: magnesium (162.05 — 189.06 mg/bOg), calcium (270.10 — 298.19 mg/bOg), sodium (11.35 — 20.65 mg/100g), potassium (16.80 — 24.73 mg/l0og) and phosphorous (209.10 — 214.16 mg/l0Og), with Sample B (ugba produced by LAB starter culture) having the highest values in magnesium, calcium, potassium and phosphorous contents. There were significant differences (P><0.05) among all the samples in the mineral contents. Sample B (ugba produced by LAB starter culture) had good sensory attributes especially in appearance and texture while Sample D (salted market ugba) was rated best in taste and aroma (flavour). However, sample B and C were more preferred. >