Anne-Marie Riquet

Food and packaging interactions: determination of the kinetic parameters of olive oil diffusion in polypropylene using concentration profiles

The penetration of olive oil into polypropylene was studied in order to allow a complete modellization of food and packaging interactions. Oil concentration profiles through polypropylene food trays were determined by FTIR-microscopy measurements along the thickness at various times. Calculations of the relevant parameters characterizing Fickian diffusion, namely constant diffusivity, coefficient of convective mass transport on the surface and concentration at equilibrium were carried out. This way of working has proven to be considerably shorter and more accurate than the method consisting of recording the global absorbance of the substance absorbed, especially when the amount of diffusing fat is low. Major conclusions are: that absorption of olive oil is strongly influenced by convection; the diffusion coefficient of olive oil in polypropylene is constant. Possible consequences to simplify global migration testing are discussed.

Safety evaluation of an ionized multilayer plastic film used for vacuum cooking and meat preservation

The main concern in safety evaluation of ionized plastic food packaging materials is the possible formation of unsuspected potential migrants. Solvent extracts and migrates of a polypropylene-based multilayer film, beta-irradiated at 80 kGy and widely used for vacuum cooking of packaged meat were studied, using complementary analytical techniques. 1H-NMR and HPLC showed that 96% of the initial phenolic stabilizer was not found after irradiation. A phosphite stabilizer and its reaction products, identified by GC-MS, accounted for 35% of the initial amount. The sum of all potential migrants derived from the additives accounted for less than 1% of global migration. This global migration was mainly due to oligomers. By comparison our results with literature work done with the same film, but at lower doses, it was suggested that larger electron beam doses reduce the possibility of migration and enhance the consumers safety.

Identification of potential migrants from a vinylic organosol varnish by gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry

The inner coating of food cans may include epoxy resins, using bisphenol A diglycidyl ether (BADGE) as crosslinking agent. Unreacted BADGE and various derivatives may migrate into foodstuffs. As a prerequisite to migration studies, it is essential to identify all potential migrants in solvent extracts of the coating. In this study the chemical structures of substances extracted from a vinylic organosol are determined by gas and liquid chromatography, coupled to mass spectrometry, on the basis of mass fragmentation patterns and/or comparison with authentic samples. Two classes of substances are found: BADGE, the corresponding monoethers and HCl adducts on one hand, and bisphenol F diglycidyl ether isomers and derivatives on the other hand. The possible origin of these compounds is discussed.

Food and packaging interactions: Tailoring fatty food simulants

Migration of paramagnetic probes from rigid PVC within 24 h at 50 degrees C depends on the simulant to a considerable extent. With a strongly swelling simulant like tert.butyl acetate, the rate of diffusion is governed by the rate of penetration of the medium into the polymeric network. Isooctane has a very weak interaction with rigid PVC. With a mixture of tert.butyl acetate and isooctane it is possible to adjust the aggressivity of the medium and to tailor an alternative simulant that interacts with the polymer in the same fashion as the EUs official fatty food simulants. Particular responses of polar probes underline the importance of the interaction between simulant and additives in the choice of alternative fatty food simulants for rigid PVC.

Quick methods to control compliance of plastic materials with food packaging regulations

A general strategy is presented, aiming to provide plastics manufacturers, food industries and enforcement laboratories with quick methods to check whether migration from materials for food contact will be acceptable during the time of use. The strategy involves several steps, with increasing time demand and cost. Monitoring extraction kinetics allows both the optimization of the extraction time, and the selection of conditions where extraction is more severe than migration. The influence of the extracting solvent is discussed. It may give rise to specific non-extraction of some migrants, which may change the conclusions when the solvent is used in replacement of a fatty food simulant. Factors ruling this effect at a given temperature are identified: the affinity to the solvent with the migrant (selectivity), its ability to reach molecules entangled in the polymeric network (accessibility) and its interaction with the polymer (penetration). The kinetic parameters of the penetration of olive oil into polypropylene have been determined by the determination of profiles of concentration.

CONSEQUENCES OF POLYPROPYLENE FILM IONISATION ON THE FOOD/PACKAGING INTERACTIONS

The influence of ionising treatment on plastic packaging is dealt with in the context of food safety. Various samples of polypropylene (PP) were investigated by Electron Spin Resonance (ESR) following irradiation with an accelerated electron beam. In the presence of air, alkyl radicals (P·) formed by ionisation under vacuum are quickly oxidised into peroxyl radicals (POO·), whose stability varies with their location. Reaction derivatives of the aminoxyl type (>NO·) have been detected after ionisation of films doped with amine light stabilisers (of the HALS or hydroxyphenylbenzotriazole type). Control and irradiated samples of PP were then immersed in liquid food simulating fatty acid esters. After contact with films doped with light stabilisers, >NO* derivatives were detected in the contact media. Two types of contamination were demonstrated: either by reaction of the stabiliser in the packaging before migration, or by migration followed by reaction with hydroperoxides present in the contact medium.

INTERACTIONS BETWEEN PVC AND SIMULATOR MEDIA USING PARAMAGNETIC PROBES

Media simulating lipid foodstuffs that are recognised in the official texts of the EEC are all triglycerides such as olive or sunflower oils or synthetic mixtures of triglycerides such as HB307. The testing of possible migration in such media implies long and demanding analytical protocols for the food industry, particularly because of the need to assay triglycerides adsorbed by packaging. Analysts responsible for testing the quality of plastics would therefore like the regulatory authorities to replace lipid simulators by volatile substances, which could provide quick tests with simple analytical protocols. Work carried out in this field in the last twenty years has been unable to identify the criteria for selecting simulator media for lipid foodstuffs 11-61. The divergent results obtained could be related to the diversity of additive behaviours. The degree of branching of the migrant, its shape, its functional groups, dipolar or hydrogen bonding type reactions that it can form with the polymer or with other additives all seem to play an equally important role as the molecular volume. Other criteria must also be taken into account in order to define the equivalence between fats and volatile liquids, including

The consequences of physical post-treatments (microwave and electron-beam) on food/packaging interactions: A physicochemical and toxicological approach.

The safety of microwave and electron-beam treatments has been demonstrated, in regards to the formation of reaction products that could endanger human health. An integrated approach was used combining the potential toxicity of all the substances likely to migrate to their chemical characterizations. This approach was applied to polypropylene (PP) films prepared with a selection of additives. Components were identified by liquid and gas chromatography using a mass selective detector system. Their potential toxicity was assessed using three in vitro short-term bioassays and their migrations were carried out using a standards-based approach. After the electron-beam treatment some additives decomposed and there was a significant increase in the polyolefin oligomeric saturated hydrocarbons concentration. PP prepared with Irgafos 168 led to a significantly strong cytotoxic effect and PP prepared with Irganox 1076 induced a dose-dependant estrogenic effect in vitro. Migration values were low and below the detection limit of the analytical method applied.

Tailoring fatty food simulants made from solvent mixtures (2): determining the equivalent migration behaviour of olive oil and of solvents in the case of polyolefins

It is suggested that solvent mixtures consisting of an ester and of an inert solvent can be used as fatty food simulants capable of having the same migration behaviour as olive oil with plastics. Migration tests carried out with low-density polyethylene for 20 and 48h in an 8 and 5% mixture of tert-butyl acetate in ethanol respectively gave results equivalent to those obtained with olive oil after 10 days at 40°C. The use of solvent mixtures facilitated the analysis and improved detection limits, giving good repeatability. Furthermore, the more rapid migration in solvent mixtures can be particularly useful for industrial controls as alternative test methods.

Tailoring fatty food simulants made from solvent mixtures (1): comparison of methanol, ethanol and isopropanol behaviour with polystyrene.

To investigate the use of solvent mixtures as test media replacing olive oil in migration tests, the interaction of polystyrene with mixtures composed of various amounts of tert.butyl acetate (mimicking the ester functions of oil) and of a low molecular weight alcohol (methanol, ethanol and isopropanol as inert co-solvent) was studied, using FTIR. Isopropanol, which has a lesser tendency to form hydrogen bonds in the plastic, can be used as main component of alternative fatty test media, its aggressiveness to polystyrene being tailored by adjusting the concentration of tert.butyl acetate. Concentrations below 20% seem useful on the basis of the mechanism of displacement of the alcohols.