Dual Role of Lactic Acid Bacteria Cultures for Fermentation and Control of Pathogenic Bacteria in Fruit Enriched Fermented Milk

Abstract

The use of metabolites from lactic acid bacteria (LABs) to produce and extend the shelf life of dairy products is gaining interest worldwide. This research aimed at investigating the dual role of LABs for fermentation and control of pathogenic bacteria in fruit-enriched fermented milk. Lactic acid bacteria isolated from cheese whey were characterized and identified using standard biochemical tests. The LABs isolated were used to ferment powdered milk as single and combined starter culture for 4 hours under laboratory conditions, the products were enriched with fruit extracts and were subjected to physicochemical and organoleptic analysis. Crude bacteriocin extracted from the isolates were screened for antibacterial potency against Escherichia coli, Staphylococcus aureus, Salmonella enterica, Bacillus subtilis and Pseudomonas aeruginosa using agar well diffusion method. The isolates were identified as Lactobacillus sp. 1 and Lactobacillus sp. 2. The fermented milk had moisture content values that ranges from 72.28 to 72.42%, Ash content of 0.99 to 1.99%, total CHO of 22.26 to 22.56%, lipid content of 0.09 to 0.12%, crude protein of 3.92 to 4.21%, calorific value of 445.86 to 447.13kj/100g, while the titratable acidity (TTA) was from 7.21 to 7.23 mg/ml. The organoleptic score of the fermented milk products ranged from 66.00 to 85.00 %. The crude bacteriocins from the two isolates were effective against some of the test bacteria by producing growth inhibitory zones of similar diameters of 15.33, 14.66, and 13.33 mm against Escherichia coli, Staphylococcus aureus and Bacillus subtilis respectively. This research has demonstrated that the isolated LABs possess good fermentative potential and bacteriocinogenic activity and are promising for use in dairy industry.