Synthesis of titanium dioxide thin films and its application in reducing microbial load of milk

Milk has rich nutritional content packed with fats, proteins and water. It also contains beneficiary and non-beneficiary microbes which account for its short shelf life. Currently cold storage, pasteurization, ultra-high temperature, microfiltration and addition of lactose peroxidase are the methods of choice to control milk spoilage and prolong its shelf life. Their limitations include high energy consumption and loss of variable proportion of heat sensitive nutrients. Titanium dioxide (TiO2) nanoparticle coated thin film was used in food packaging industry for its antimicrobial property. TiO2 thin films were synthesized by sol gel process; it was characterized with scanning electron microscopy which showed pore size as 5 m and Fourier transform infrared spectroscopy which showed metal present in sample is TiO2, zinc and silver. Exposure of raw milk at room temperature to TiO2 thin films doped with zinc or copper for a couple of hours showed zone of inhibition in disc diffusion technique, reduction in acid production. It also showed reduction in optical density indicating inhibition of growth in growth curve analysis, increase in the time required for methylene blue reduction and a five log folds decrease in bacterial count estimated using serial dilution plate count. The present studies were carried out under room temperature and pressure which is an added advantage in terms of energy as well as retention of nutrients. Though TiO2 is insoluble in water one needs to address it toxicity issues and adverse effects if any on the nutritional quality of milk before scaling up the process.