Jaroslav Dobiáš

Changes of properties of polymer packaging films during high pressure treatment

Abstract The effect of high pressure on the polymer packaging materials was studied. Seven single material films as well as seven laminates suitable for high pressure preservation of food or commonly used as food contact layer were pressurized using the pressure 600 MPa for 60 min. The effect of pressure treatment on the change of following film parameters were evaluated: mechanical properties (tensile strength and seal strength), transparency (absorbance at 450 and 600 nm), water vapour permeability, global migration characteristics into fat food simulants (95% ethanol and isooctane) and the transfer of food simulants (water and olive oil) into packaging materials. The obtained results confirmed the influence of high pressure treatment on functional properties of tested films, in some cases in rather significant level (loss of heat sealability, changes of migration levels, etc.). The obtained results need further confirmation by tests done in closer cooperation with packaging materials producers, which enables better understanding of film changes.

Resistance of vegetative cells and ascospores of heat resistant mould Talaromyces avellaneus to the high pressure treatment in apple juice

Thermoresistant moulds including Talaromyces avellaneus are frequent microbial contamination of fruit juices and purees, which are supposed as food products suitable for pressure pasteurisation. The effect of high pressure treatment on survival of vegetative cells and ascospores of T. avellaneus was studied. The vegetative cells T. avellaneus were very sensitive to high pressure, the sufficient pressure treatment for the reduction by six orders was 200 MPa at 17 °C for 60 min or 300 MPa at 17 °C for 5 min. In apple juice the ascospores of T. avellaneus were relatively resistant to the high pressure treatment, the treatment of 600 MPa at 17 or 25 °C for 60 min reduced their concentration by two or three orders, respectively. Sufficient inactivation rate was obtained when the combination of pressurisation and gentle heating was used, the total reduction (by six orders) was reached at 600 MPa and 60 °C after 60 min.

Properties of polyethylene films with incorporated benzoic anhydride and/or ethyl and propyl esters of 4-hydroxybenzoic acid and their suitability for food packaging.

Benzoic anhydride and ethyl and propyl esters of 4-hydroxybenzoic acid (ETP and PRP, respectively, also termed parabens) incorporated into low density polyethylene (LDPE) film were studied with regard to migration into food and food simulants at 6°C and 25°C, and changes in selected properties of the film were investigated. Antimicrobials were incorporated into polymer film in concentrations of 5g/kg and 10g/kg. The addition of parabens into the polymer was more difficult than benzoic anhydride due to their volatility. For benzoic anhydride, 30–40% and 10–20% of the added amount was found to leach from the film into aqueous and olive oil food simulants, respectively. The migration into both water and olive oil followed a very similar course in the case of parabens. Migration levels over 90% and in the range of 70% to 80%, relative to the amount of agent in the film, were determined for ETP and PRP respectively. The incorporation of antimicrobials into the film significantly changed the functional characteristics of the packaging material, i.e. permeability of oxygen, carbon dioxide and water vapour, tensile strength, coefficient of friction, sealing strength and transparency. Shelf life tests with packaged cheese and toasted bread demonstrated the efficiency of the film containing 10g/kg of BA against mould growth on the food surface during storage at 6°C.

Development of antimicrobial packaging materials with immobilized glucose oxidase and lysozyme

AbstractPackaging based on immobilization of antimicrobial enzymes provides a promising form of active packaging systems applicable in food processing. Glucose oxidase and lysozyme were immobilized by the Ugi reaction with cyclohexyl isocyanide and glutaraldehyde on polyamide and ionomer films partially hydrolysed by hydrochloric acid. The immobilization of the enzymes on the surface of films was confirmed by FT-IR spectroscopy and the films were characterized by the specific activity of the immobilized enzymes. The enzyme migration into model solutions and the effect of pH, temperature and storage time on the activity of immobilized enzyme were also evaluated. Immobilization of lysozyme onto polyamide and ionomer films resulted in the loss of enzyme activity. The polyamide and ionomer films with immobilized glucose oxidase inhibited the growth of bacteria Escherichia coli CNCTC 6859, Pseudomonas fluorescens CNCTC 5793, Lactobacillus helveticus CH-1, Listeria ivanovii CCM 5884 and Listeria innocua CCM 4030 on agar media.

Occurrence of extractable ink residuals in packaging materials used in the Czech Republic

Residues of printing ink components were determined in 94 samples of packaging materials commercially used in the Czech Republic for food packaging. The samples tested included printed polyethylene and polypropylene films, co-extruded and laminated films, paperboard beverages boxes, foils for thermo sealing of polystyrene cups, and polypropylene cups. Printing ink components were extracted with diethylether, then separated and determined using gas chromatography-mass spectrometry (GC/MS). Fifty compounds potentially originating from printing were isolated, identified and quantified. No acute health risk for consumers were identified, even though several findings of high levels of photo-initiators (e.g. in polyethylene terephthalate (PET) films for thermo sealing of polystyrene cups) as well as plasticizers (acetyl tributyl citrate, tributyl aconitate, 2-butoxyethyl oleate and 2-ethylhexyl diphenyl phosphate in co-extruded films) indicate that their real migration into food and/or food simulants needs to be undertaken for a proper safety evaluation.

Occurrence of 2-phenylphenol in food paper packages

AbstractTwenty three paper based packaging materials commercially used for food packaging in the Czech Republic were analysed with regard to 2-phenylphenol (OPP) content using HPLC technique with fluorimetric detection. The HPLC method was modified with the aim to increase its sensitivity. OPP was detected in quantities ranging from 10 mg kg−1 to 527 mg kg−1 in twenty tested samples. The level of OPP in packaging materials was in close correlation to the content of recycled pulp in used paper material. The migration of OPP from two packaging materials comprised of paperboard coated with low density polyethylene (LDPE) into food simulants was determined at 40°C for 10 days. The levels of migration into 3% acetic acid, 10% ethanol and olive oil were below the limit of detection of used analytical procedure. In the case of 95% ethanol, 13% and 21% of OPP present in tested samples were transferred into simulant. The found occurrence of OPP in paper packages does not pose any significant safety risk for food consumer, but OPP could be considered as wide spread contaminant in paper materials.

Testing the influence of various conditions on the migration of epoxidised soybean oil from polyvinylchloride gaskets

Epoxidised soybean oil (ESBO) is widely used as a plasticiser and stabiliser mainly in food contact materials on the base of polyvinylchloride (PVC), especially in the gaskets of jar lids. PVC gaskets containing 10–37% of ESBO were prepared by the baking of PVC plastisols at various process temperatures (180–240°C) in the laboratory. ESBO migration into olive oil and 3% acetic acid was studied at various temperatures (4°C, 25°C, 40°C and 60°C) during a storage time up to 12 months. ESBO released into food simulants was transmethylated, derivatised and analysed by gas chromatography-mass spectrometry (GC/MS). The effect of food processing, i.e. pasteurisation (80°C and 100°C) and sterilisation (125°C) on ESBO migration was also evaluated. The results were critically assessed with respect to the test conditions of specific migration in accordance with the current European Union legislation (Regulation (EU) No. 10/2011). The levels of ESBO migration found confirmed that the test conditions (i.e. 40°C or 60°C, 10 days) representing contact in the worst foreseeable use scenario seem to be insufficient for the simulation of ESBO migration during long-term storage and thus do not provide satisfactory objective results.

Determination of imazalil by on-line coupled capillary isotachophoresis with capillary zone electrophoresis

A simple, rapid and reproducible capillary isotachophoretic on-line coupled with capillary zone electrophoresis (CITP-CZE) method for the determination of IMz in food packaging extracts and its residues in apples is described. A good separation of the IMZ from other sample constituents was achieved within 15 minutes without any sample clean up. Method characteristics (linearity, accuracy, intra-assay and detection limit) were determined. Less amount of time involved, sufficient sensitivity and low running cost are the important attributes of CITP-CZE method.

HPLC determination of thiol-containing anti-browning additives in fruit and vegetable products

The HPLC determination of residual thiol-containing anti-browning additives (cysteine, N-acetyl-cysteine and reduced glutathione) in treated fruit and vegetable products using the Ellmans reagent (5,5′-dithiobis(2-nitrobenzoic acid); DTNB) is described. The thiols were isolated by extraction with solvent containing NaF, EDTA, acetic and ascorbic acids and derivatized with the Ellmans reagent in an aqueous medium at pH 8.0. The resulting disulphides were determined by reverse phase HPLC with mobile phase consisting of methanol and phosphate buffer pH 7.5. The UV-detection at 330 nm was used. The optimal extraction and derivatization conditions were found and the method was used to determine the residual concentrations of thiols in potato, avocado, apple and banana purees, sliced mushrooms and frozen basil treated with cysteine.

Migration of epoxidised soybean oil from PVC gaskets of commercial lids: simulation of migration under various conditions and screening of food products from Czech markets

Previous studies have shown that a large number of polyvinylchloride (PVC) lid gaskets exceed the existing migration limits for epoxidised soybean oil (ESBO) and correct prediction of ESBO release into food therefore appears to be a difficult issue. ESBO migration from PVC gaskets of metal closures into food simulants and food products from the Czech market is evaluated during a survey in 2009 and subsequently one in 2012 to assess progress in lid manufacturing and official testing conditions. ESBO migration from lids into various food simulants was studied at various temperatures (25, 40 and 60°C) during storage times up to 12 months. ESBO released into food simulants or food products was transmethylated, derivatised and analysed by GC-MS. The levels of ESBO migration in foodstuffs in 2012 exceeded the specific migration limit (SML) in fewer products in comparison with the previous survey. However, most of the products were analysed at a time far from the expiry date and exceedance of the SML at the end of the product shelf life is not therefore excluded. More severe test conditions (60°C for 10 days) for specific migration given by the current European Union legislation (Regulation (EU) No. 10/2011) still seem to be insufficient for the simulation of ESBO migration during long-term storage.