Biopreservative potential of Lactobacillus strains in yoghurt dessert

The effects of Lactobacillus fermentum, L. helveticus, L. reuteri and L. rhamnosus on radical scavenging activity (DPPH and ABTS), lactate concentration and antibacterial potential (against E. coli, P. aeruginosa, S. sonnei, S. aureus and B. cereus) of yoghurt dessert were investigated during fermentation (37 °C for 24 h). The amount of protein carbonyls and the peroxide and anisidine values were also examined during cold storage period (5 °C for 10 days) in order to evaluate the oxidative stability of produced samples. During the fermentation period, L. helveticus had the greatest effect on increasing the antioxidant activity (DPPH and ABTS) of samples, while the highest lactic acid concentration (22.1 g/kg) and strains viability (9.5 log CFU/g) were related to the samples fermented by L. fermentum. Lactobacillus fermentum was the most effective antipathogen strain, while the lowest antibacterial activity observed for L. rhamnosus strain. Moreover, P. aeruginosa and S. sonnei exhibited the highest and B. cereus the lowest resistance to Lactobacillus strains, respectively. During the cold storage, the viability of LAB showed an increasing trend until the fourth day and then gradually decreased by 7–11%. The oxidative stability of all fermented samples was significantly (p ≤ 0.05) higher than that of control during the cold storage. The yoghurt dessert fermented by L. helveticus exhibited the lowest peroxide and anisidine values and the protein carbonyls concentration during the cold storage which it can be attributed to the higher antioxidant activity of this strain compared to others. It can be concluded that the Lactobacillus strains have the potential to be used as an effective biopreservation tool in yoghurt dessert production.