Control of E. coli growth and survival in Indian soft cheese (paneer) using multiple hurdles: Phytochemicals, temperature and vacuum

Microbial adaptations and growth at low temperatures impose challenge to safety of highly perishable food products like paneer. Survival of Escherichia coli under refrigeration necessitates investigations into additional hurdles. Use of phytochemicals offer a promising natural alternate for biocontrol of paneer and was investigated in this study. We demonstrated the antimicrobial activity of phytochemicals viz. Gallic acid, Quercetin, Piperine, Eugenol and Menthol against E. coli in vitro and in situ conditions within paneer. All phytochemicals killed E. coli in a concentration dependent manner exhibiting MIC similar to 100 mu g/mL wherein eugenol was most effective followed by quercetin, piperine, menthol and gallic acid respectively. We observed that vacuum alone was insufficient to abolish proliferation of E. coli within paneer, however low temperature storage reduced it. Gallic acid exhibited maximal reduction in E. coli count (3 logs) in situ paneer at 5 degrees C, followed by eugenol (1.9 log), quercetin (1.8 log), piperine (1.7 log) and menthol (0.9 log) respectively. Finally, sensory analysis established absence of off-flavors from eugenol, menthol and piperine containing paneer, but gallic acid and quercetin gave off-flavor and off-color respectively. This study established phytochemicals as alternate tools for inactivation of E. coli in paneer during refrigeration storage and impact safety of dairy foods.