3.3.1.1 Tests in olive oil (migration cells)
Even though the preliminary test (for the new cellulose-based films with other coatings compared to Natureflex™N913 and N931) showed the suitability of olive oil to be used as a food simulant for migration tests, problems were encountered during the actual testing. Some films decomposed during the tests or the top layer (coating) of the film came loose during the migration tests, which could have influenced the migration. Furthermore, problems with the obtained chromatograms were encountered. No internal standard was detected for some samples (corresponding to the results obtained at Ghent University) or unreliable peaks were observed. It was not sure if the compounds represented by this peaks originated from the olive oil (possibly from the film as well). Furthermore, rather large variations between tests of the same film in the same simulant were observed, indicating that the results might not be reliable. These results, together with the results of the migration tests in olive oil performed at Ghent University, point out that olive oil, which is currently the most frequently used fatty food simulant for migration testing might not always be suitable for new biobased materials. Furthermore, the decomposition of the films and the large variations suggest that the composition of the film is not yet optimized.
3.3.1.2 Tests in other food simulants (total immersion)
The results of the overall migration tests in all 5 food simulants (95% ethanol as alternative for olive oil) at 40°C during 10 days and at 100°C during 2 hours of the five heat resistant cellulose- based films are shown in respectively figures 7.5 and 7.7 (test performed in April 2014, n=2) and 7.6 and 7.8 (tests performed in October 2014, n=4).
From figure 7.5 (n=2, test April 2014)) it can be seen that the overall migration limit (10 days – 40°C) is not exceeded for all cellulose-based films in 3% acetic acid and for some of the films in 10% ethanol (CelloTherm™T & Natureflex™NVR), in 20% ethanol (CelloTherm™T) and in 95% ethanol (Natureflex™NE and NK). These results indicate that the selection of one of these films as a packaging materials for a specific food products needs to be done carefully, since not all films seem suited for all types of food products. Figure 7.6 (n=4, test October 2014) shows that the migration limit (10 days – 40°C) is exceeded for all films in all different food
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simulants, except for the Natureflex™NVS in 3% acetic acid, which indicates that these films cannot be used as a packaging material. The results of the second test clearly differed from the results of the first test (figure 7.5). Furthermore, the results of the overall migration of the Natureflex™NK film in 10 and 95% ethanol presented in figure 7.3 (3.2.1.2) are clearly lower compared to the results presented in figures 7.5 and 7.6. This inconsistency in results of repeated measurements of the same material might be caused by an instability of the cellulose-based films (possible degradation or change in structure during storage). In Chapter 5, the instability of these films, probably caused by their hydrophilicity, was already noticed.
Figure 7.7 (n=2, April 2014) shows that the overall migration limit (2 hours – 100°C) was not exceeded for the CelloTherm™T and the Natureflex™NVS and NK films in 3% acetic acid and in 10%, 20% and 50% ethanol and for the Natureflex™NE film in 20% ethanol. For the Natureflex™NVR film the overall migration limit was exceeded in every food simulant. Furthermore, the overall migration limit was exceeded for every film in 95% ethanol. These results again indicate that the selection of one of these films as a packaging materials needs to be done carefully, since not all films seem suited for high heat applications (up to 121°C) for all types of food products. The results shown in figure 7.8 (n=4, October 2014) have an almost opposite outcome, with overall migration values within the legal limits for the Natureflex™NVR film in all food simulants, except 95% ethanol, for the Natureflex™NE and NK films in 3% acetic acid and 10% ethanol and for the CelloTherm™T film in 3% acetic acid. Migration limits were however also exceeded for every film in 95% ethanol. Therefore, these films are not suitable as a packaging material for lipophilic food products at high temperature use (up to 121°C). Also for the migration tests at 100°C, the results of the second test clearly differed from the results of the first test (figure 7.7). This inconsistency in results of repeated measurements of the same material, which was also found for the tests at 40°C, suggest that these cellulose-based films are not stable during storage. This confirms the findings described for the tests in olive oil (3.3.1.1), stating that the composition of the film is not yet optimized. The regular substitution of Natureflex™ films available on the market also point in this direction.
It must be noticed that for migration in 95% ethanol, it is possible that for some films, the migration limit is not exceeded, since for several food products, a simulant D2 reduction factor can be applied (table 2 ‘food category specific assignment of food simulants’ in regulation No. 10/2011).
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Furthermore, from all figures it is clear that in general overall migration increases with increasing apolarity of the test food simulant. This means more apolar (lipophilic) than polar (hydrophilic) compounds migrated from the films. The films consist out of a regenerated cellulose layer which is coated on both sides with a plastic layer. Since this coating is very thin, the high migration can be partly attributed to the middle cellulose layer. Cellulose is a polar (hydrophilic) compound, so the high migration is due to other film components (probably plasticizers). This increasing migration with increasing apolarity of the food simulant was also observed during migration testing by the film producer. But, in these tests, only the plastic layer (coating) was tested instead of the entire film, resulting in much lower migration values (<10 mg/dm2). Although legislation states that plastic-coated regenerated cellulose films should comply with the migration limits (point 14, page L172/72 of Commission directive 2007/42/EC relating to materials and articles made of regenerated cellulose film intended to come into contact with foodstuffs), in practice there is still a lot of confusion amongst companies in the food and packaging industry. Legislation is indeed ambiguous, since article 14 of Regulation 10/2011, which lays down rules for multi-material multi-layer materials (e.g. the Natureflex™ films) excludes plastic layers in multi-material multi-layer materials from the obligation to comply with both specific and overall migration limits (articles 11 and 12). This discrepancy in the legislation made the company decide to only perform migration tests on the plastic layer (coating) (according to Commission regulation EU 10/2011) without the cellulose layer (Commission directive 2007/42/EC).
Also, the migration at 40°C (OM2) is mostly higher compared to the migration at 100°C (OM5) (e.g. figure 7.6 and 7.8). This is not logic, since legislation (EU 10/2011) states that “test OM5 covers also food contact conditions described for OM1, OM2, OM3, OM4”. OM5 should represent the worst case scenario, but these results suggest that OM2 instead of OM5 represents the worst case condition.
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Figure 7.5: Results overall migration tests of CelloTherm™T, Natureflex™NVS, NVR, NE and NK in all 5 food simulants for 10 days at 40°C (n=2)
performed in April 2014 (--- = migration limit of 10 mg/dm²)
0 20 40 60 80 100 120 140 160 180 200
Ac. acid 3% EtOH 10% EtOH 20% EtOH 50% EtOH 95%
O M ( m g /d m ²)
Simulant (increasing apolarity)
OM at 40°C - 10 days
Cellotherm T NVS NVR NE NK
--- -
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Figure 7.6: Results overall migration tests of CelloTherm™T, Natureflex™NVS, NVR, NE and NK in all 5 food simulants for 10 days at 40°C (n=4)
performed in October 2014 (--- = migration limit of 10 mg/dm²).
0 20 40 60 80 100 120 140 160 180 200
Ac. acid 3% EtOH 10% EtOH 20% EtOH 50% EtOH 95%
O M ( m g /d m ²)
Simulant (increasing apolarity)
OM at 40°C - 10 days
Cellotherm T NVS NVR NE NK
--- -
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Figure 7.7: Results overall migration tests of CelloTherm™T, Natureflex™NVS, NVR, NE and NK in all 5 food simulants for 2 hours at 100°C (n=2)
performed in April 2014 (--- = migration limit of 10 mg/dm²)
0 20 40 60 80 100 120 140 160 180 200
Ac. acid 3% EtOH 10% EtOH 20% EtOH 50% EtOH 95%
O M ( m g /d m ²)
Simulant (increasing apolarity)
OM at 100°C - 2 hours
Cellotherm T NVS NVR NE NK
--- -