Influence of starter culture of lactic acid bacteria on the shelf life of agidi, an indigenous fermented cereal product
A total of eight lactic acid bacteria were isolated from various fermented cereal gruels (ogi). They were identified as Lactobacillus plantarum, Lactobacillus casei, Leuconostoc mesenteroides, Lactobacillus brevis, Lactobacillus fermentum, Lactobacillus delbrueckii, Lactobacillus acidophilus and Pediococcus acidilactici. P. acidilactici in OG3 produced the highest quantity (12.0 g/l) of lactic acid after 48 h, while L. acidophilus in OG3 produced the least (3.6 g/l). All the tested isolates produced hydrogen peroxide with L. mesenetroides, OG2 having the highest yield of 54 mg/l after 36 h. Diacetly was also produced by all the test organism with L. fermentum, OG2 having the highest yield of 6.5 g/l, while the lowest producer was L. casei with 3.2 g/l. Bacteriocin production was observed in cell free supernatant of all the test organisms except L. fermentum in OG2, L. casei in OG3 and L. brevis in OG4. The bacteriocin produced by L. plantarum in OG3 and L. casei in OG3 had the highest antagonistic activity against Aspergillus flavus and Aspergillus niger used as indicator organisms. Agidi was produced using both bacteriocin producing (BP) L. plantarum OG3 and L. casei ogi made from white sorghum (OG1) and non bacteriocin producing (NBP) L. fermentum OG2 and L. brevis.OG4 The study showed that agidi produced with BP mixed starter cultures had a better shelf life of 6 days before spoilage occurred, relative to 4 days observed for agidi produced using non-bacteriocin producing starter culture and 2 days for the traditionally produced agidi.
Keywords: Lactic acid bacteria, bacteriocin, fermentation, agidi, shelf life