Antimicrobial Effect of Organic Acids Produced by Selected Strains of Lactic Acid Bacteria during Storage of Ugba (Fermented African Oilbean Seeds)

Abstract

The antimicrobial effect of organic acids produced by selected strains of lactic acid bacteria during storage of ugba were examined. The objective was to determine changes in pH, titratable acidity, organic-acid profiles and microbiological quality in starter-culture-fermented ugba compared with spontaneously fermented product. The African oil bean seeds (Pentaclethra macrophylla Benth) and the Alchornea laxiflora Benth leaves (Akwukwo ugba – the popular leaves for wrapping ugba) were purchased from Urbani main Market, Umuahia - Nigeria. The seeds were identified, sorted, graded and washed in order to remove spoilt seeds, dust and extraneous materials from wholesome seeds prior to processing. The control and LAB inoculated samples were prepared in the laboratory using the traditional and experimental procedures. The ugba produced using LAB starter cultures and uninoculated samples were subjected to physicochemical and microbiological analysis during storage. Results show that the LAB inoculated and uninoculated ugba samples were significantly different (P<0.05) in hydrogen ion concentration (pH) and total titratable acidity (TTA) during storage. The temperature range recorded (28-36oC) favoured the growth of lactic acid bacteria. The pH of the inoculated ugba samples decreased towards acidity and the uninoculated counterpart increased slightly towards alkalinity, ranging within 3.42 – 7.32, while the total titratable acidity decreased, falling within the range of 0.033 – 0.085 as the storage days progressed. Result of organic acid content showed that; formic, acetic, lactic and butyric acids significantly (P<0.05) increased as storage period progressed. The microbial quality of ugba samples inoculated with LAB starter cultures showed less microbial load with improved keeping qualities than their uninoculated counterparts during storage.