parisa abdolsattari

Due to the fact that the use of biodegradable films helps to protect the environment, in this study, the physical, mechanical, antioxidant and thermal properties of polylactic acid films containing polypyrrole, ‌ polyaniline and copper oxide were investigated. The results showed that due to the addition of oxidant nanoparticles, the thickness of the films increased and their water vapor permeability decreased significantly. The solubility of the films also decreased significantly with increasing the amount of copper oxide nanoparticles. The resulting films showed less flexibility due to the addition of polyaniline and polypyrrole, while their resistance to failure showed a relative increase. Antioxidant activity of polylactic acid films containing polypyrrole / CuO and polyaniline / CuO showed a significant increase compared to pure polylactic acid (p<0.05). Pure polylactic acid film did not show any electrical conductivity, If the addition of polypyrrole and polyaniline increased the electrical conductivity of the films, the copper oxide nanoparticles also had no significant effect on the electrical conductivity. These films can be used as biosensors in food packaging due to their conductivity and suitable thermal, mechanical and water vapor permeability properties.

Iranian white Cheese is a traditional type of cheese in Iran which is popular and widely consumed because of its pleasant organoleptic properties. To manufacture this cheese, raw milk is heated below pasteurization temperature, therefore, pathogenic and spoilage bacteria remain and cause several diseases in public health. In this research three kinds of nanocomposite films based on LDPE incorporated 1) Ag, CuO, ZnO, 2) Cloisite 15A, Cloisite 20A, Cloisite 30B that produced by extrusion method were used for packaging of the cheese and kept in 4°C during 28 days. Data analysis carried out using SPSS statistical software based on a completely randomized design. The results showed the nanocomposite films incorporated with metal nanoparticles had a significant decrease in the growth of Staphylococcus aureus, coliform, mold and yeast after 28 days, while, the growth of lactic acid bacteria decreased but less than control film. Sensory properties of cheese samples packed in active films were not significantly changed. However, physicochemical characteristics such as pH and moisture content were affected significantly by active films. Overall migration of packaging active films in food simulants were within amounts allowed by national and international legislations.