Douglas McNeill examines the optimum solution for the use of paper and paperboard packaging for fatty products.
Paper and paperboard offer particular advantages as packaging materials. Of particular importance is: high rigidity; excellent possibilities as graphic media; they are produced from renewable resources; they are generally easy to recycle.
To be used in direct contact packaging of fatty food products such as bakery products like pastries and biscuits and fast food products like burgers, however, some form of grease barrier treatment has to be applied to prevent penetration of grease into the paper and staining of the package.
Two treatment methods are two commonly used:
€ Application of a thin coating of a plastic such as polyethylene.
€ Application of a fluorochemical surface treatment.
Until recently, for a barrier purely to grease, fluorochemical treatments appeared to offer significant advantages. Production costs were low as the treatment could be applied during the manufacture of the paper or board.
The paper or board produced in this way could be printed, glued and recycled in much the same way as untreated grades. In Europe, usage of fluorochemically treated materials for food packaging was particularly high in the UK.
By contrast, the production costs for plastic coated paper and board are higher as the coating has to be applied in a separate conversion process. These materials are also perceived to be more difficult to recycle due to the difficulty in separating the plastic content.
degradation
The whole picture changed in 2000 when 3M Co took their Scotchban range of fluorochemical grease-proofing agents off the market.
Immediately prior to this Scotchban had had an estimated 90 per cent share of the paper and board fluorochemical treatment market. It was subsequently disclosed that perfluoro-octyl sulfonate (PFOS), which was both an intermediate in the electrochemical fluorination process used by 3M and a result of degradation from the end-products, had been identified as a persistent bio-accumulative toxic (PBT) hazard ie it had been found to have an affinity for animal and human tissue and, due to its exceptional stability, had the potential to accumulate to toxic levels.
In the United States, the Environmental Protection Agency (EPA) applied strict controls over the use of PFOS materials in 2001 which effectively limited the use of PFOS chemicals to specialised, low volume, well contained, process applications in the aerospace and electronics industries.
After further investigation these controls were extended to cover a closely related class of perfluoro-octanoic acid (PFOA) compounds and telomers which may metabolise or degrade to PFOA.
On 14th April 2003 EPA released a preliminary risk assessment for the chemical PFOA and is starting a public process to identify and generate additional information to streangthen risk assessement.
Studies have indicated that PFOA causes developmental toxity and other effects in laboratory animals. EPA's prelinimary assessment indicates potential exposure of US general population also to PFOA at very low levels
How has this affected European food packaging practice? While plastic coatings have increased their market share, there is still a significant part of the market which, being highly cost-driven, continues to use fluorochemical treatments. The PFOS chemicals have, however, largely given way to fluorotelomers which do have official clearance for food contact application at present.
For the future, however, there is a strong case for plastic coatings to completely replace fluorochemical treatments. This case rests on the following:
€ Plastic coatings provide a lower risk solution. The plastics used ie low and high density polyethylene, polypropylene have been comprehensively studied and found to satisfy all food contact requirements.
€ Recycling of plastic coated paper and board is becoming increasingly easier as waste paper mills upgrade their stock preparation systems and improve existing plastic separation facilities.
€ Plastic coatings do not just give a barrier to grease, oils and fats. They also protect against water and moisture vapour and they impart heat sealing properties.
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DouglasMcNeill is development manager at Walki Wisa Ltd, Garstang, Lancashire, UK. www.walkiwisa.com or www.epa.gov/oppt
