UK develops screening techniques for printing ink ‘set off’
The Food Standards Agency (FSA) has unveiled the results of a project to develop screening tests for so-called ‘set-off’.
The body defines set off as “the unintentional transfer of substances used in printing inks from the printed (outer) surface of materials and articles intended for food packaging to the inner food contact surface”.
The agency said it commissioned the research after the ink producers supplying into the packaging industry began widespread introducing polymeric photoinitiators - used in printing inks to speed up the drying process of the ink using ultra violet light - and synergists, which take part in the photoinitiator reaction.
This process came about in the after the discovery of the chemical 2-Isopropylthioxanthone (ITX) in milk and beverages packaged in multi-layer cartons around eight years ago caused concern. Set off was pinpointed as a likely cause.
The FSA noted the scarcity of published data on the extent of transfer of these new compounds to food contact surfaces via set off and their subsequent migration into food.
Safety tool
The research project, carried out by Pira International over a two and a half year period, had three chief aims. The first was to develop screening techniques with the ability to measure the amount of set-off from the replacement substances and other ink components on food contact surfaces of packaging visible to the naked eye.
The agency said it was successful in developing the scanner to measure visible set off in food contact surfaces in packaging that was suitable for regulators and industry players.
It also successfully developed exposure techniques and analytical methods to quantify individual ink components on food contact surfaces to allow for the measurement of non-visible set off.
This led to the creation of a list of commonly used photoinitiators and synergists to enable the identification and measurement of the relevant compounds.
This method also included techniques for non-visible elements. The research said it was satisfied this was valid despite challenges in replicating exactly ‘set off’ patterns found as a result of commercial storage pressures on packaging.
“[The] results tended to demonstrate that set off is not a food safety issue because of the low levels of printing ink components found to set off from the prepared films,” concluded the agency.
Method development key
The final target was to assess the migration of ink components from specially prepared films in a variety of foods.
These films contained known ink compositions at levels higher than would be expected in commercial applications.
The clear objective was to promote set off to test the developed method and allow comparison of data and did not involve the testing of food packaging.
The method can be carried out within one working day to help laboratories identify photoinitiators and synergists on unused packaging and estimate worst case migration for shelf life applications of six months or longer at room temperature.
The FSA said it plans to discuss the methodology with industry players and used it to inform future work on food packaging where set off could occur.
“The project will enable laboratories to identify printing ink components on unused food packaging, estimate worst case migration and thereby assist in the prevention of packaging transferring components to foods at undesirable levels,” said the agency.
To view the full research report and appendices click HERE
