Research On Migration Of Food-contact-nanomaterials

In this paper, we reviewed the development trends and safety researches of food contact nano-materials. Research methods of nano-materials and food contact materials were combined to investigate migration of food contact nano-materials. In order to study migration characteristics of nano-materials in the food contact materials under various conditions, two commercially available nano-silver food packaging materials-nano silver PP (Ag-PP) food container made in Korea and nano-silver polyethylene (Ag-HDPE) storage bag made in Japan, were chosen. The shape, size and content of nano silver products were investigated. Migration experiments were carried out under 25℃,40℃, and 50℃, and the results were analyzed by AAS. Additionally, the effect of simulated liquid food types, soaking temperature, soaking time and etc on the migration of nano-silver was discussed. Finally, the values of experimentally measured diffusion coefficient and the prediction diffusion coefficient of general Pringer model were compared. The results will be helpful in understanding theoretical and experimental researches.Firstly, the shape, size and content of nano silver product determination. The plastic products were treated by direct calcination and microwave digestion, then, XFS, SEM-EDS, and AAS were used to characterize the samples. The results show that the morphologies of nano silver in both products are spherical granules, in which the content of nano silver in PP food container is approximate 38μg/g plastic, with grain sizes ranging from 20 nm to 1μm, while the content of nano silver in polyethylene storage bag is approximate 102.5μg/g plastic, with grain size of about 25μm.Secondly, migration experiments via immersion method. Four food simulating solutions including water, acids, alcohol and oil with temperatures of 25℃,40℃and 50℃, and immersion time of 3,6,9,12 and 15 days, respectively, were employed to study the migration. The results show that a same migration manner was found in the two nano packing materials:nanoparticles migrate in water, acids, alcohol, and oil food simulating solutions, the maximum migration is in oil solution, then in acidic solution; in a particular simulating solution, the migration of nano silver increases with increasing immersion time, and increases with increasing immersion temperature. Compared with the present results, the grain size is smaller and the amount of migration is more of migrated nano silver in polyethylene storage bag than those of PP food container, respectively. Moreover, the migration of nano silver in different simulating solutions of the two products is higher than the safety value 0.1 ppb.Thirdly, migration analytical model values of chemicals in polymers were discussed. Using the prediction diffusion coefficient of general Pringer model, the predictive values of diffusion coefficient were calculated. Compared with the values of experiments and prediction, the experimental values are far lower than that of predictive values that is several orders of magnitude difference. It is suggested that the present general diffusion coefficient model is not suitable to evaluate the safety of nano-materials, further improvements should be perfected.Finally, we summarize the present researches and give some suggestions on the future works.