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.     

Characterizing the migration of antioxidants from polypropylene into fatty food simulants

The migration (diffusion and equilibrium) processes of antioxidants (AOs) from polypropylene (PP) films of different thicknesses into n-heptane and 95% ethanol as fatty food simulants were analysed at 20, 37 and 60°C. Heptane fully extracted the AOs from the polymer while a partition equilibrium described the migration to ethanol. The kinetics of migration were also studied via the diffusion coefficients. As expected, diffusion was found to be faster when the polymer was in contact with heptane, due to polymer swelling by the solvent. The kinetics of the process in ethanol was described by different theoretical expressions which are discussed. Equations disregarding partition equilibrium failed to describe the process and the diffusion coefficient values obtained through them were much smaller than the actual ones and dependent on film thickness. The results also showed the significance of food simulant selection in the analysis of food-packaging interactions and migration variability with thickness.     

Experimental and theoretical study of LDPE versus different concentrations of Irganox 1076 and different thickness

This work presents a theoretical and experimental study on the specific migration process, describing the mass transfer of a model migrant Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (I-1076), an antioxidant commonly used in the polyolefins processing. Film samples (LDPE), with initial concentration of Irganox between 1000 and 6000 (mg/kg), and thickness of 50-190 ??m, were placed in contact with fatty (EtOH 95%) and aqueous (EtOH 10%) food simulants at 40 °C for 20 days, in order to obtain the concentration evolution in the food simulant which was measured by HPLC. On the other hand, a phenomenological model based on a resistances-in-series approach was developed considering the diffusion through the polymer film, natural convection in the food simulant and the thermodynamic equilibrium between the polymer and the liquid simulant phase. For the thickest films, the diffusion coefficient of I-1076 through the polymer phase was estimated varying between 1.95·10^− 13 (m² s^− 1) and 2.0·10^− 13 (m² s^− 1) at 40 ºC. On the contrary, the thinnest one shows a significant decrease of the diffusion coefficient value, which was evaluated in 1.0·10^− 14 (m² s^− 1). This modification can be explained by means of a crystal distribution and size in the thinnest polymer film prepared by CAST extrusion. The mathematical model developed is a tool for prediction and analysis which can be used to facilitate the characterization of polymers, and it could predict the response as packaging for food in a specific application.     

Influence of flavour absorption on oxygen permeation through LDPE, PP, PC and PET plastics food packaging

The effect of flavour absorption on the oxygen permeability of low-density polyethylene (LDPE), polypropylene (PP), polycarbonate (PC) and polyethylene terephthalate (PET) was studied using an isostatic continuous flow system. Polymer samples were exposed to a model solution containing limonene, hexyl acetate, nonanone and decanal at 40°C. After exposure, one part of each sample was analysed for absorbed flavour compounds using a Large Volume Injection GC Ultrasonic 'in vial' extraction method, and from the other part, oxygen permeability was measured in a permeation cell at 25°C. After 8h of exposure, LDPE and PP samples showed a significant linear (R² = 0.82 and 0.99) increase in oxygen permeability of 21 and 130%, respectively. Owing to swelling of the polymer samples resulting from flavour absorption, the structure of the polymeric network changed (i.e. opened) and consequently increased oxygen permeability. The oxygen permeability of exposed PC showed a significant linear (R² = 0.78) decrease of 11% after 21 days. PC obviously did not swell like LDPE or PP. Therefore, it was suggested that absorbed flavour compounds occupied or blocked 'microcavities' through which normally oxygen is transported. Absorption of flavour compounds by PET did not affect the oxygen permeability of PET significantly.     

Simple models for assessing migration from food-packaging films

Owing to their simplicity, two migration models based on Fick's Second Law have been frequently used for the assessment of migration of additives and contaminants from food-packaging films. While the two models are known to provide accurate estimates of diffusion coefficients for complete migration, they could generate considerable estimation errors for significantly partitioned migration. In this paper, the applicability of the two models to partitioned migration is defined by examining the assumptions and derivations of the two models as well as their errors in estimating diffusion coefficients. Furthermore, a simple migration model, based on more realistic assumptions than the two models, is proposed. The proposed model can provide far better estimates of diffusion coefficients for partitioned migration than the two models.     

Modelling of simultaneous two-sided migration into water and olive oil from nylon food packaging

Nylon 6 and nylon 12 food packaging materials used as sausage casings are typically exposed to fatty food on one side and boiling water on the other during the cooking process. To simulate the migration behaviour under these conditions, a special migration cell was constructed and filled with olive oil on one side of the polymer and water on the other to find out what amounts of the migrants will transfer to either side and phase at 100 °C. Results show that when a nylon 6 film is exposed to the conditions as described above, total mass transfer of the monomer—caprolactam—into the water phase occurs after 2 h at 100 °C. Nylon 12 sausage casings release similar amounts of their monomer—laurolactam—into both the aqueous and oil phase. An existing computer migration model was adapted to simulate the situation of simultaneous two-sided migration applying previously determined diffusion and partitioning coefficients. The suitability of the model was confirmed by experimental data.     

Study of diffusion through LDPE film of Di-n-butyl phthalate

The apparent diffusion coefficients (D) across a PE-LD film of Di-n-butyl phthalate (DnBP) dissolved in isooctaneand ethanol,werecalculated indifferentways and compared. DnBP, a common plasticizer of plastics and printing inks, may be a possible contaminant of flexible packaging and PE-LD is the most common food-contacting polymer. To perform diffusion measurements, small plastic sachets filled with solutions of the contaminant were used at three different temperatures. The D coefficients of the two solvents and dissolved DnBP were calculated using the lag time method, a formula taking into account the molar weight and absolute temperature,and an equation based on the initial concentration and the amounts migrated after subsequent times. The results demonstrated great solvent interference in the plasticizer diffusion across polyethylene; in particular as far as isooctane is concerned, a remarkable co-diffusion of both the plasticizer and the non-polar solvent must be assumed. Isooctane quickly penetrates PE-LD but ethanol also diffuses across PE-LD, although at a greatly reduced speed. These facts must be considered for realistic prediction of migration or effectiveness of the functional barrier.     

Migration of additives from polymers into food simulants: numerical solution of a mathematical model taking into account food and polymer interactions

The principle of a computing program describing precisely the migration of additives from a polymer into a food simulant is presented. As six parameters are used to fit the simulant sorption and additive extraction kinetics, the parameters have been determined by independent experiments. Owing to the complicated coupling between the liquid and additive diffusion processes, migration kinetics cannot be obtained by a mathematical resolution of kinetic equations, but they must be calculated by numerical analysis. The method is applied to a UV absorber in polypropylene migrating into glyceryl tripelargonate, a pure triglyceride, of which behaviour and average molecular weight are similar to official fatty food simulants. Properly designed experiments validate the model used to fit the migration kinetics. The possibility of erasing any parameters is also discussed.     

Determination of bisphenol A in, and its migration from, PVC stretch film used for food packaging

Bisphenol A (BPA) is used as an additive in polyvinyl chloride (PVC) products, including stretch films used for food packaging. The BPA contents were investigated of several brands of stretch film bought locally but marketed internationally or throughout Spain and which were presumably produced at different manufacturing plants. Their major components were identified by FTIR (Fourier Transform Infrared Spectrometry) and horizontal attenuated total reflectance, and the migration of BPA from these materials into the standard European Union food simulants was determined by high-performance liquid chromatography (HPLC) using both fluorescence (FL) and ultraviolet (UV) detection, the identity of the analyte being confirmed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). The two HPLC detection methods had different detection limits (30 μg l^-1 for UV, 3 μg l^-1 for FL), but afforded virtually identical BPA determinations for the samples tested. BPA contents ranging from 40 to 100 mg kg^-1 were found in three of the five PVC-based films analysed, and a content of 500 mg kg^-1 was found in a fourth; for these determinations, extraction into acetonitrile was used. In standard tests of migration into water, 3% acetic acid and olive oil over 10 days at 40°C, migration from a given film was in all cases greatest into olive oil. Migration from the films with non-zero BPA contents ranged from 3 to 31 μg dm^-2, values higher than those reported for many other food-contact materials, but lower than the European Union specific migration limit for BPA. PVC stretch film nevertheless may make a significant contribution to contamination of foodstuffs by BPA, and should be taken into account in estimating BPA intake or exposure to this substance.     

Prediction of worst case migration: presentation of a rigorous methodology

An improvement of the Piringer model, allowing the prediction of a worst case migration from packaging to food is presented here. The authors are proposing other constants for the calculation of the upperbound value of the diffusion coefficient, using experimental data determined by a film to film method. Considering the plasticizing effects of food simulants, a model involving the variation of the diffusion coefficient versus space and time must be used. Future fields of investigation are discussed: the relationship between diffusion coefficients and the volume of the migrant (instead of molar mass), and the variation of diffusion coefficient activation energy with temperature.     

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.     

Evaluating the migration of ingredients from active packaging and development of dedicated methods: a study of two iron-based oxygen absorbers

The behaviour of two commercial oxygen-scavenging products with respect to migration of active ingredients into foodstuffs was investigated. Migrants were identified, and by using appropriate analytical methods, migration was determined in a variety of liquid, solid or gelled food simulants and foods. Simulants were chosen to cover a range of water activities and viscosities. Foods and the gelled food simulant agar were packed with and without vacuum, and with the oxygen scavenger in various locations relative to the packed food. The main migrants, as identified by X-ray fluorescence spectrometry, infrared spectroscopy and scanning electron microscopy with energy-dispersive spectrometry were Na + and Cl - in non-acidic aqueous simulants, and Na + , Cl - and Fe 2+ in 3% acetic acid. Migration into aqueous simulants exceeded the current European Union limit for total migration from plastic materials (assumed to be currently applicable to these systems) and was probably excessive by any reasonable standard. However, neither oxygen scavenger appeared to release significant quantities of migrants into solid foods when the scavenger was properly located in the package and the packing process does not favour the contents becoming wet by water released from the food.     

Influence of flavour absorption by food-packaging materials (low-density polyethylene, polycarbonate and polyethylene terephthalate) on taste perception of a model solution and orange juice

The influence of flavour absorption by low-density polyethylene (LDPE), polycarbonate (PC) and polyethylene terephthalate (PET) on taste perception of a model solution containing seven flavour compounds and orange juice in glass bottles was studied with and without pieces of the respective plastic films after dark storage at 20°C. Owing to absorption, the amount of flavour compounds in the model solution exposed to LDPE decreased substantially. From the model flavour solution valencene was almost completely absorbed by LDPE, followed to a lesser extent by decanal, hexyl acetate, octanal and nonanone. Less flavour compounds were absorbed from the model solution by PC and PET. In contrast to LDPE, valencene was absorbed in the lowest amounts and decanal in the highest. Limonene was readily absorbed from orange juice by LDPE, while myrcene, valencene, pinene and decanal were absorbed in smaller quantities. Only three flavour compounds were absorbed from orange juice by PC and PET in very small amounts: limonene, myrcene and decanal. Although the flavour content between controls and polymer-treated samples differed substantially, the loss of flavour compounds due to absorption by LDPE, PC and PET did not influence taste perception of a model solution and orange juice significantly up to 29 days of dark storage at 20°C as determined by triangular taste panel tests.     

Polymer additive migration to foods-a direct comparison of experimental data and values calculated from migration models for polypropylene

To reduce the amount of compliance testing for food contact polymers the use of migration modelling is under discussion and being evaluated by an EU Commission funded project (Evaluation of Migration Models No. SMT4-CT98-7513). The work reported in this paper was exclusively funded by industry to provide data for the independent evaluation of a diffusion based model using eight different samples of polypropylene (PP) covering the range of polymers specification and five commonly used plastics additives. One hundred and fifty experimental migration data have been obtained in triplicate and used to evaluate a Fickian-based migration model in the prediction of specific migration of five additives into olive oil. All tests were conducted using olive oil, representing the most severe case for fatty foods, with test conditions of 2h at 121 ° C, 2h at 70 ° C and 10 days at 40 ° C, representing short term exposures at high temperatures and room temperature storage. Predicted migration values were calculated using the Piringer 'Migratest Lite' model by entering the measured initial concentration of additive in the polymers(C_p,0) in to the equations together with known variables such as additive molecular weight, temperature and exposure time. Where necessary the data generated in this study have been used to update the model. The results indicate the Piringer migration model, using the 'exact' calculations of the Migratest Lite program, predicted migration values into olive oil close to, or in excess of, the experimental results for > 97% of the migration values generated in this study. For all measurements, the predicted migration from the Migratest Lite program was greater than 70% of the observed value. This study has identified the possibility that random co-polymers of propylene and ethylene give higher migration than other grades of polypropylenes and could be treated as a separate case. However, further work on more samples of random co-polymers is required to confirm this finding.     

Polymer additive migration to foods - a direct comparison of experimental data and values calculated from migration models for high density polyethylene (HDPE)

To reduce the amount of compliance testing for food contact polymers the use of migration modelling has been proposed. This study was conducted to provide valid data for the independent evaluation of two such diffusion-based models using a range of different high density polyethylene (HDPE) polymers and plastics additives. Seventy-two experimental migration data have been obtained in triplicate and used to evaluate two Fickian-based migration models in the prediction of specific migration of four HDPE additives into olive oil. All tests were conducted using olive oil, representing the most severe case for fatty foods with test conditions of 2h at 70oC, 6h at 70oC, 10 days at 40oC representing short term exposures at high temperatures and room temperature storage. Predicted migration values were calculated by inserting the measured initial concentration of additive in the polymers (Cp,0) into the equations together with known variables such as additive molecular weight, temperature and exposure time. The results indicate that both models predict migration values into olive oil close to, or in excess of, the experimental results. The Piringer migration model, using the 'exact' calculations of the Migratest Lite program, gave an overestimation for 83% of the migration values generated in this study. The highest overestimation was 3.7 times the measured value. For all measurements, the predicted migration from the Migratest Lite program was greater than 50% of the observed value. The FDA model was found more accurately to predict migration in most situations but underestimated migration more frequently. Differences in the polymer specification had little effect on specific migration of the additives investigated.     

Effect of ionizing radiation on the physicochemical and mechanical properties of commercial monolayer flexible plastics packaging materials

The effect of γ-radiation doses (5, 10, 30 kGy) on the mechanical properties, gas and water vapour permeability, infrared (IR) spectra, and overall migration into aqueous and alternative fatty food simulants of commercial monolayer flexible packaging films ethylene vinyl acetate (EVA), high-density polyethylene (HDPE), polystyrene (PS), bi-axially oriented polypropylene (BOPP), low-density polyethylene (LDPE) and Ionomer was studied. For comparison purposes, respective non-irradiated (control) films were also studied. The results showed that radiation doses of 5, 10 and 30 kGy did not induce any statistically significant changes in the permeability of all studied films to gases (oxygen and carbon dioxide) and water vapour. Likewise, IR spectra of all studied films showed no significant differences after all absorbed doses. The mechanical properties (tensile strength, percentage elongation at break and Young's modulus) of all studied films remained unaffected after absorbed doses of 5 and 10 kGy. In contrast, the tensile strength of HDPE, BOPP and Ionomer films irradiated at a dose of 30kGy decreased. In addition, the percentage elongation at break of LDPE and Ionomer films irradiated at a dose of 30 kGy decreased while Young's modulus of all samples remained unaffected. All mechanical properties of PS and EVA films remained unaffected after radiation at 30 kGy. Radiation (all absorbed doses) resulted in no statistically significant differences in overall migration values into distilled water for all studied films. For 3% aqueous acetic acid, absorbed doses of 5 and 10 kGy did not affect overall migration values of all investigated samples with the exception of the Ionomer film, for which the overall migration value decreased at 10 kGy. An absorbed dose of 30 kGy caused an increase in BOPP overall migration values and a decrease in Ionomer overall migration values. In contrast, a dose of 30 kGy induced no changes in overall migration values of EVA, HDPE, LDPE and PS films into the same simulant. There were no statistically significant differences in overall migration values of EVA, PS and LDPE films into iso-octane for all absorbed doses. In contrast, a dose of 30 kGy resulted in an increase in overall migration values of BOPP and a respective decrease in HDPE and Ionomer films.     

A study on the migration of organic pollutants from recycled paperboard packaging materials to solid food matrices

Paper and board are widely used as food packaging materials, mainly for disposable products. As public interest in conservation of natural resources has accelerated in the past several years, the use of recycled paper and board has increased. Recycled fiber materials can be used in certain limits as food contact materials. The safety of recycled fiber-based materials for food contact applications is largely dictated by the ability of post-consumer contaminants to be absorbed into recycled materials and later released by the packaging material and trapped on the food. The present work was undertaken with the aim of investigating the physicochemical behavior of selected model contaminants on paper and board, in contact with foodstuffs thus producing a fundamental set of data about their mobility from recycled paper and board into foods. More specifically, the kinetics of migration of selected model contaminants (surrogates) from contaminated recycled paper packaging samples into dry foodstuffs with different fat content was studied using a method based on solvent extraction and GC-FID quantification. Results showed the ability of selected contaminants of various types and various volatilities to potentially transfer to dry foods. The proportion of substances migrated to food was strongly dependent on the nature of the paper samples, fat content of the food, chemical nature and volatility of the migrant. The highest level of migration of organic pollutants was observed for the substrate with the highest fat content. Furthermore, it is shown that contact time and temperature have a significant effect on migration of model contaminants into foods.     

Potential migration of Diisopropyl naphthalenes from recycled paperboard packaging into dry foods

The results of a study of the potential migration of diisopropyl naphthalenes (DIPN) from recycled paperboard packaging into some types of dry solid foodstuffs are reported. Paperboard diskettes containing different DIPN concentrations were prepared and put into contact with four types of dry solid foodstuffs, having high specific surface areas and different lipid contents. At regular intervals the DIPN content in the foods was determined. Two migration mechanisms have been proposed and verified. The first one relates to the direct contact existing between paperboard and foodstuff. The second one refers to the indirect contact between paperboard and food, controlled by an air space created above the paperboard into which the DIPN has diffused. Both mechanisms occurred and the migration depended on different factors: the contact time, the characteristics of the foodstuffs and the DIPN content in the cellulose-based matrix. However, only very low levels of contamination in the foodstuffs occurred in migration. As a consequence, this report also considers possible limitations which could be applied to the content of carbonless copy paper in packaging paperboard formulations.     

Investigation of migration from paper and board into food-development of methods for rapid testing

A range of paper and board materials including carton board, corrugated board, napkins and paper towels intended for contact with food have been solvent extracted and substances present at the highest levels identified and quantified by GC/MS. Dibutyl phthalate, and diisopropylnaphthalene (DIPN) were selected to study migration to food and potential food simulants with the aim of developing a simple quick test that will give an equivalent or higher result. Tenax was found to be a suitable food simulant for dry foods and dry 'fatty foods' such as pastry and cake and was also found to be a suitable simulant for pizza base tested at higher temperatures for short contact times. The percentage migration values from corrugated and carton boards were generally in the range 15-40%, with the highest percentage being 49% for rice using conditions representing ambient storage. Quick tests were developed using Tenax under accelerated conditions of 4h at 80°C to cover room temperature storage with dry foods and fatty dry foods. These tests are suitable for compliance testing of paperboard samples if migration limits are applied in future legislation. Migration from tissues, napkins and paper towels was found to be at very low or not detectable levels, even when the levels of DIPN and DBP were significant. It is strongly suspected that this finding is due to a combination of short contact time, low grammage and the fact that the tissues absorb fat and moisture from foods, thus minimizing extraction from the paper. In all cases, the results from migration experiments into food and Tenax indicate that for the substances found at highest concentrations in the paper, currently accepted safety limits were not exceeded where they exist in EU legislation or in working documents applying to plastics.     

Effect of pectinase on the oil solvent extraction from different genotypes of sunflower (Helianthus annuus L.)

Pectinase-assisted solvent extraction of oil and total tocopherol from sunflower hybrids with different structural characteristics was studied by means of laboratory tests carried out in a stirred batch extractor at 50 °C. From the oil yield results obtained for the two hybrids studied, black-hull (P20) and striped-hull hybrids (ACA 884), it could be observed that oil was extracted at different rates in both hybrids. Analyzing the performance data versus time in the control samples, ACA 884 oil was released more easily and remained invariant with time, whereas for P20 the extraction was slower and the maximum value was reached at 60 min. The fiber wall structure collapsed by the enzymatic action, improving oil release and allowing a faster extraction. The efficiency of the treatment was measured in terms of the percentage of increase in oil yield compared with the control samples. It was observed that in hybrid ACA 884 the mean increases were not significantly different (p = 0.9295) over time (4.12% d.b.). Hybrid P20 showed a significant increase in the percentage of oil yield (p = 0.0001) at 10 min (10.85% d.b.), and then it remained virtually constant over time (4.89% d.b.). The black-hull hybrid (P20) presented significant differences in fatty acid composition due to the enzymatic action. Pectinase treatment was highly effective in the tocopherol extraction from hybrid P20 (p < 0.001), obtaining a 32.3% increase on average. The maximum values were 662 and 220 μg g dried ground seed⁻¹ at 60 and 120 min for black-hull and striped-hull hybrids, respectively. The enzymatic treatment effectively produced an increase in oil and tocopherol yields for the black-hull hybrid.