1. Introduction
Packaging in addition to basic protective function, serves increasingly as an information and marketing tool. This is achieved by a multi printing of the packaging (fig. 1). Paper and paperboard are not sufficient barriers to stop migration of harmful substances into food product which is packed in [1, 2, 3]. Development of a sorption layer between cellulose packaging and food product (fig. 2) was the goal of the SoLaPack research project realized in the framework of the CORNET [4]. Barrier coatings are made of various substances approved for contact with food, such as starch granules, cyclodextrins, latex, bentonites etc. As a critical substances for testing were selected benzophenone (BP), bisphenol A (BPA), mineral oils (MO) and phthalates (Ph), which may be present in packaging from recycled cellulose. Barrier properties were tested using migration chamber with a Tenax as a food simulant (4.0g/dm2) [5]. Determination of benzophenone and phthalates migration was carried out using gas chromatography and mass spectrometry (GC/MS) [6,7]. Mineral oils were determined by gas chromatography with FID detector (GC-FID) [8] and bisphenol A was determined by liquid chromatography with fluorescence detector (HPLC-FLD) [9].
Samples for migration studies properties where prepared by our Partners from Center of Bioimmobilisation and Innovative Packaging Materials (CBIMO), Centre de Recherche et de Contrôle agro-alimentaire, emballage, environnement et textile (CELABOR), Centre de Ressources Technologiques en Chimie (CERTECH) and Papiertechnische Stiftung (PTS).
Compositions of sorption coatings contained: zeolite – ABS DEO1000, acrylate binder (Acronal), styrene-butadiene binder (Styronal), starch and γ-cyclodextrin in different combinations. A list of functionalized paper samples along with information on the composition of the applied protective layer is in the tab. 1.
2. Experimental
2.1. Migration
All experiments were carried out with the use of migration cell (model FABES MC60). Where 1 gram of critical substance was placed on bottom of the migration cell (fig. 3). Then functionalized paper disc (0.32 dm2) was placed in the middle (with coating layer down). And after placing of 1.28g of Tenax on opposite side of paper, tighten cells were thermostated in temp. 40°C for BP, 70°C for MO and Ph and 100°C for BPA. Extraction of Tenax was carried out with methanol (80 mL) and 1 mL was taken for gas chromatographic analysis. For mineral oils mixture of ethanol-hexane was used as extraction solvent.
In the case of BPA migration studies, before HPLC analysis methanol solution was concentrated to 1 mL and filtered through a 0.2 μm filter.
3. Chromatographic analysis
3.1. Benzophenone and phthalates
The GC/MS analysis of benzophenone and phthalates was carried out with the chromatograph HP 5890 series II coupled with detector HP 5972 on HP-FFAP capillary column (30 m,
0.25mm, 25μµm). The temperature program was as follows:
1 min. at 100°C, programmed at 6°C/min. to 240°C and 5 min. at 240°C. Carrier gas helium flow was 0.95 ml/min. The temperatures of injector and detector were 240°C. Benzophenone retention time under these conditions is 19.5 min. Mass spectra detector was operating in SIM mode. Molecular ion m/z = 182 was used as quantitation ion.
3.2. Mineral oils
The GC-FID analysis of mineral oils was carried out with the HP 5890 series II Plus chromatograph on ZEBRON ZB5 capillary column (15 m, 0.25mm, 25μµm). The temperature program was as follows: 9 min. at 60°C, programmed at 22°C/min. to 240°C then programmed at 30°C/min. to 380°C and kept in this temperature for 12 min. The temperatures of injector was 280°C and FID detector was 365°C.
3.3. Bisphenol A
HPLC separation of bisphenol A was performed with Agilent Technologies 1100 coupled with fluorescence detector (excitation 335 nm, emission 317 nm) on Spherisorb ODS2 Waters column (250 x 4.6 mm, 5 µm) thermostated at temp. of 30˚C and with isocratic elution: 20% water – 80% methanol. The flow rate of the mobile phase was 0.5 ml/min. Sample injection volume was 10 µl. BPA retention time under these conditions is 6.7 min.
4. Results
Parallel with the functionalized papers was performed testing of reference paper containing no sorption layer. All samples were analyzed under identical conditions. Absorption properties were calculated by comparison of integrated peaks of critical substances with reference sample peak (fig. 4). Table 1 presents the results of effectiveness of the sorption layers in retaining critical substances from the migration into Tenax® as a food simulant, expressed as the percentage with respect to the reference sample. In three cases (marked with asterisk) for bisphenol A was very low, which was caused by instability of coating sorption (micro-cracks) under experiment conditions (100˚C) necessary for the application due to the low volatility of BPA.
5. Conclusion
Chromatographic studies (GC/MS, GC/FID or HPLC) of specific migration of benzophenone, phthalates, mineral oils and bisphenol A to Tenax through the packaging material with a protective layer, allowed for predicting materials with the best barrier properties and to choose the best coated papers for further technological and industrial testing [10]. These materials with sorption layers are stopping migration of critical substances while are not a barrier where condensation in the packaging can occur.
This research was financially supported by the NCBiR – project CORNET /1/12/11/2012
Sources
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