Characteristic Properties of Derived Wort from Lactic Acid Bacteria (LAB) Challenged Sorghum Samples

Abstract

Aim: This study aimed at investigating lactic acid bacteria (LAB) as starter cultures for the improvement of alcoholic beverages. Methodology: Sorghum was obtained from Bodija market and also from the Institute of Agricultural Research and Training, Ibadan. LAB were isolated from spontaneously-fermenting sorghum.  The abilities of the LAB strains to produce antimicrobials and their antagonistic activity against known cereal pathogens were used to select the best three strains for further work. The selected strains were applied singly and in combination at inoculum concentration of 2.3 x 104 cells/mL for five days to challenge sorghum seeds prior to malting and wort production. Sorghum wort was fermented for five days with Saccharomyces carlsbergensis. Physiological and nutritional characteristics of the unchallenged and challenged sorghum, and fermentative characteristics of the wort were determined. Results: One hundred and twenty seven strains of LAB were isolated and identified as L. plantarum (32), L. brevis (31), L. fermentum (25), L. delbrueckii (8), L. casei (12) and L. acidophilus (19).  The pH reduced from 6.50+0.03 to 2.93+0.03. L. plantarum (WS) and L. casei (WS) also had the same total residual sugar content with value of 0.97+0.03% at day 5.  L. plantarum (WS) and L. casei (WS) produced the highest Total titratable acidity (TTA) with values of 4.77+0.03% while control (RS) had the least TTA with value of 3.97+0.09%.  Control (WS) had the highest protein content of 1.17+0.03%, L. casei (RS) had the least protein content with value of 0.93+0.03%. L. plantarum (WS) had the highest FAN content of 29.97+0.19mg/L while the least Free amino nitrogen (FAN) was produced by control (RS) with value of 19.37+0.07mg/L. Fermentation of the unchallenged wort with pH of 6.2 yielded ethanol content of 2.2 %. The subsequent fermentation produced 4.8 % ethanol. Conclusion: This study demonstrated the use of biological control methods, involving the use of LAB as starter cultures. It improved the quality of the end products in brewing. The use of LAB as starter cultures is an alternative treatment to chemical treatment which can be used to control microbial contamination during sorghum malting.