Effects of Probiotic Cells on the Mechanical and Antibacterial Properties of Sodium-Caseinate Films

Background and Objective: Food processing conditions such as heat, mechanical or osmotic stress can lead to considerable losses of probiotics' survival in food. Recently, the addition of probiotics into edible films has been proposed as an emerging technology for the delivery of probiotic cells. In this study, Lactobacillus acidophilus andLactobacilluscasei cells were incorporated into sodium caseinate matrix to develop a probiotic-based film which can improve food safety. Material and Methods: Probiotic cells were separately added to the film forming solutions andthe active films were prepared by casting method. The physical, optical and mechanical characteristics of the films were examined. Color properties were determined using a colorimeterand the mechanical properties of the films were evaluated by an Instron Universal Testing Machine. The viability of Lactobacillusacidophilus and Lactobacilluscaseiin the films was determined during a period of 12 days. The antibacterial activities of the films were also tested against Listeria monocytogeneson Trypticase Soy Agar medium at 4 degrees C. Results and Conclusion: Results demonstrated that lactic acid bacteria cells remained viable during a storage period of 12 days (> 4 Log CFU cm(-2)). The incorporation of lactic acid bacteria cells into the film polymer had no significant effect on tensile strength (p>0.05) whereas it significantly improves the appearance of films. Indeed, samples covered with the lactic acid bacteriafilm displayed higher antilisterial activity than the control group on day 6 of preservation (p <= 0.05). These findings show that the sodium caseinate film containing lactic acid bacteria cells can be used as a new effective packaging method for improving food safety.