Cartonboards

Food and beverages can be very chemically aggressive milieux and may interact strongly with materials that they touch. Collectively, they are as good as many of the solvents used in a chemistry laboratory. For example, food acids can corrode metals, fats and oils can swell and leach plastics, and beverages can disintegrate unprotected paper and cartonboard. In fact, no food contact material is completely inert and so it is possible for their chemical constituents to... 

The inventory list of chemicals used to make plastics is comprehensive because plastics are of synthetic origin and their composition is known more or less completely (with the caveat about transformation products, see later). In contrast, paper as a natural material is less well defined and characterised and so any inventory list of chemicals used in paper-making will be only an incomplete list of chemicals that may be present in the paper or cartonboard packaging and that therefore may migrate. 

Case study 3 migration of benzophenone from printed cartonboard... 

When there was no benzophenone in the packaging there was none detected in the food. However, there was not a clear numerical correlation between levels of benzophenone in cartonboard and food. Differences in the composition of the foods tested may have been important in this respect, along with other factors such as the storage time, the storage temperature, the extent of any direct contact made between the food and the package, and the presence or absence of any barrier material between the printed cartonboard and the food. 

The results confirmed that benzophenone can migrate from printed cartonboard to food. The estimated intake of this substance was far less than the TDI of 0.01 mg/kg bw/day set by the SCF. Using a 97.5 percentile value for daily consumption for the foods that were tested (102 g), a mean value of bodyweight of 60 kg and a mean contaminant level, the intake was estimated at 0.001 mg/kg bw/day (one-tenth of the TDI) and no health effects would be expected in an individual s lifetime from the levels found in the survey. 

JOHNS s w, JiCKELLS s M, READ w A and CASTLE L, Studies on functional barriers to migration. 3. Migration of benzophenone and model ink components from cartonboard to food during frozen storage and microwave heating , Packag. Technol. Sci, 2000 13 99-104. 

Whilst there is considerable evidence to indicate that substances can volatilise from and/or transfer through packaging materials to the gas phase, there are very few studies on gas phase transfer to foods. Indirect evidence for gas phase transfer to foods was seen in studies by Anderson and Castle (2003) who measured levels of benzophenone in foodstuffs packaged in printed cartonboard materials. Benzophenone is a photoinitiator used in some UV cure inks for the printing of paper and board materials and has been shown to be present in printed paper and board materials indicating that it remains in the paperboard after printing (Johns et al 1995). 

The most extensive studies to date on transfer from secondary packaging to foods have been carried out by Jickells and co-workers (Jickells et al., 2005). These studies used combinations of food and packaging as would be used for retail sale. Cartonboard and corrugated board box were used in the study because they are used widely as secondary packaging materials. Model compounds (benzophenone, diheptyl phthalate, 2,6-diisopropylnaphthalene, 2,2-dimethoxyphenylacetophenone, 2-ethylnaphthalene and 2,4,6-... 

Metallised PP/PP laminate (outer PP film reverse-printed with nylon-based resin ink) bag PP film (fuUy printed on outer surface) heat-sealed single packs packed in PP film heat-sealed multipack (partially printed on outer surface) Cartonboard boxes in PP film overwrap (coated on both surfaces with VdC copolymer)... 

Cartonboard box fully printed on outer surface Cartonboard box fully printed on outer surface... 

Fig. 18.1 Food/packaging configurations for transfer studies from secondary packaging to foods (Jickells et al., 2005) (a) chocolate-coated cream wafer bars single- and multi-pack format in corrugated board box (b) milk chocolate-coated wafer biscuits in cartonboard boxes (c) chocolate-coated ice-cream bars in cartonboard box (d) oatcake biscuits in cartonboard boxes (e) savoury crackers in cartonboard boxes (f) wheat biscuit breakfast cereal in cartonboard boxes (g) crisps (potato chips) in corrugated board box.

Paper was shown to be a poor barrier to transfer where there was a relatively narrow air gap between the secondary packaging and the food, i.e., wheat breakfast cereal in a paper wrapper inside a cartonboard box. A PP wrapper in the same situation reduced transfer by between three to 19-fold (three-fold for trichloroanisole and 2-ethylnaphthalene, 7-fold for diisopropyhiaphthalene and 19-fold for diisopropylnaphthalene at 200 days). 

ANDERSON w A c and CASTLE L (2003), Benzophenone in cartonboard packaging materials , Food Addit Contam, 20, 607-618. 

Potato chips Polypropylene/aluminium/printing inks/polypropylene laminate Printed (external surface) polypropylene Polyethylene/aluminium/cartonboard container laminate printed on the external surface Polyethylene/aluminium/paper laminate with an uncoated metal base... 

Biscuits Polypropylene/aluminium/printing inks/polypropylene laminate Externally printed polyvinylidene chloride Polyethylene bag within a printed cartonboard box... 

Processed meat products Polyethylene bag within a printed cartonboard box Polyethylene/printing inks/polyester laminate Printed polyethylene to which a printed sticky label was applied Polypropylene container to which a printed sticky label was applied with a polystryrene lid... 

Fruit snacks Polyethylene/aluminium/printing inks/nitrocellulose coated laminate Polypropylene bag to which a printed sticky label was applied Cartonboard box printed on the external surface... 

The action of mechanically erecting, inserting primary pack, insertion of leaflet, then the closing of the carton is another world in which technical expertise may be required. The criteria on which the form of carton filling will be decided include, quantity per batch/lot/order, size and weight of the goods to be cartoned, cartonboard caliper, design of closure flaps, and what else, apart from the primary container, has to be inserted. 

The cartonboard caliper, particularly the consistency, is more critical than for hand cartoning as it affects the pre-break of the carton and once a machine is set to open pre-break there is little tolerance for variation. The faster and more sophisticated machines need tight tolerances. 

Creasability of boards BS 4818 1993 described the method of determining the creasing quality of cartonboard within the range of 300-1000 4m. This is important to the packaging line, since if the creases are not correct and do not assist the carton erection, the cartoning machine will not function correctly. 

With wines available in bag-in-box and in cartonboard structures, and with interest in the packaging of beer in plastics, there is considerable scope for similar active packaging systems with these products. 

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