Study on migration of hydrocarbon contaminants from food contact materials in food

Food packaging is a rapidly evolving field. Packaging keep food safe and retains its nutritional properties and sensory characteristics; furthermore, it provides additional features that are important for consumers. Packaging system, as well as other food contact materials (FCM) such as adhesives and printing inks, are the main sources of chemicals in food products and beverages. Human exposure to chemicals from food contact materials may occur as a result of migration, a mass transfer phenomenon resulting from a tendency to balance all chemical potential within a system from the packaging into foodstuff. There are several parameters affecting migration, which are related to food, to packaging and to chemicals that are involved. The food packaging legislation establishes an overall migration limit (OML), which measures the inertness of the materials and that regards all chemicals in a packaging, and a specific migration limit (SML) for specific substances that may be dangerous for human health. An important tool to evaluate the compliance of FCM with the limits are the migration tests. Food simulants as well as temperature, time and contact conditions for migration testing are regulated for plastic materials, but not for paperboard material, so that contact condition are derived at least partially from plastic legislation. A very important class of contaminants involved in migration from packaging into food are hydrocarbons, in particular mineral oil hydrocarbons (MOHs) consisting of MOSH (mineral oil saturated hydrocarbons) and MOAH (mineral oil aromatic hydrocarbons), and polycyclic aromatic hydrocarbons (PAHs). The MOSH fraction may include polyolefin oligomeric saturated hydrocarbons (POSH), oligomers of polyolefin, which can migrate from plastic bags, heat-sealable layers and other laminates as well as adhesives and plasticizers. Different studies have demonstrated that MOHs, POSH and PAHs migrate from packaging into food and contaminate it with negative effects for human health. In the first part of this PhD work a rapid migration test, using simple and cheap commercially glass weighing bottles was developed to assess the migration of mineral oil from cardboard. At the end of the test, mineral oil was extracted from cardboard and from Tenax® and the entity of migration was calculated both in terms of direct migration (amount of MOHs found in simulant) and in terms of indirect migration (contamination lost by cardboard). The two measures were in good agreement demonstrating the mass balance in the cell. The migration test performed was subsequently used to evaluate the efficiency of a new sequential polymer treatment of paperboard to develop a barrier against the migration of mineral oil. The material consisted of two layer deposited on the cardboard. The first, poly (methyl methacrylate) protective layer, gave hydrophobicity to cardboard, while the second, cyclic olefin copolymer, filled the open pores of the material surface and reduced the mineral oil hydrocarbon migration. Subsequently, the developed migration tests was also used to study the migration of MOHs from recycled cardboard into dry semolina and egg pasta under accelerated condition (40°C 10days) to determine the influence of some parameters on migration process. Amount of pasta, type of contact pasta/cardboard, food size and head space volume, were studied parameter that showed a great effect on MOHs migration from cardboard. They influenced the entity of the migration, but also the molecular weight range of hydrocarbons that can migrate into the pasta. The study of these parameters pointed out that the migration tests suggested to evaluate the compliance of the packaging material, do not always reflect the real mechanisms involved in migration in real food. Semolina and egg pasta behaved very differently: egg pasta tends to have a higher absorbing effect than semolina pasta, especially when low amount of pasta are in contact with the cardboard. This is not only attributable to the fat content but also at structure and porosity of the matrix. A correlation with data obtained from migration test with Tenax® was finally carried out. Tenax® tended to overestimate the migration in semolina pasta and, at the opposite, to underestimate the migration in egg pasta. Another part of this work regarded the investigation on the presence of selected hydrocarbon contaminants (mineral oil and polycyclic aromatic hydrocarbons) in pizza boxes collected in different areas of Italy. From the analysis of cardboards, three sources of contamination were clearly identified: illegal presence of recycled paper, printing ink containing alkylbenzenes, and refined paraffin (food-grade mineral oil used in the waterproofing of paper). All of the cardboard boxes showed low level of PAHs. The potential of these contaminants to migrate from cardboard into the pizza was demonstrated carring out migration tests using Tenax® as simulant. The per capita daily intake from “take away” pizza was calculated both for MOHs and for PAH8, showing a negligible (0.005%) global diet intake contribution for PAHs, but not for mineral oils, for which, the average contribution ranged between 7.3% and 12.8%. Regarding plastic materials, a study on the presence of POHs in ready-to-eat vegetable soup, packaged in polypropylene container, was conduct. The analysis of food before and after microwave heating demonstrated that a part of POHs contamination was from the production of the soup and another part migrated from PP container. The migration depends on fat content of the soup, on original amount of POHs in the container and on heating conditions. Different simulant were tested to assess the migration of the POH from containers and their performance was compared with those in real food. Vegetable olive oil as simulant tends to overestimate the contamination, also when fat reduction factor was applied. Instead, the ethanol 95% seems to be the best choice for the migration test. Finally, the last part of the work a simple method based on a liquid–liquid partition step to eliminate the bulk of the saturated hydrocarbons, followed by DI-SPME using a Carbopack Z/PDMS fiber, was employed for selective uptake and concentration of BaP (Benzo(a)pyrene) in the analysis of microcrystalline waxes. A preliminary step using liquid-liquid partition was necessary to remove the bulk of saturated hydrocarbons. Wax sample was dissolved in cyclohexane, and BaP was extracted with dimethyl formammide (DMF)/water 9/1 (v/v). A mixture of water and hexane were added to the residual DMF/water in order to change the coefficient partition of BaP and extract it in hexane. The latter was the most suitable solvent to carry out the final enrichment step by direct-immersion solid phase microextraction (SPME). The method showed good performances of repeatability and recovery. Characterization of gas chromatographic profile of waxes was also evaluated. They show different profiles of distribution ranging from n-C20 to n-C60. All of the samples presented less than 5% of hydrocarbons below n-C25 In addition, artificial saliva from chewing tests was collected and analyzed in order to evaluate possible release of hydrocarbon particularly BaP from waxes, gum bases and chewing gums during their contact with human saliva in the mouth. No detectable amount of contaminants were found in samples.