Some packaging adhesives can contaminate food - study

But the team from the University of Zaragoza stressed the Cramer method used to gather their results has drawbacks as it is not based on bioassays but a theoretical one used to estimate toxicity from a compound’s chemical structure.

The aim of the project was to highlight the need to study the composition of the substances with a view to aiding industry reformulation of them, scientists Marga Aznar and Elena Canellas told FoodProductionDaily.com. The research also sought to provide tools to help establish specific EU legislation on adhesives used in food packaging – as currently none exists, they added.

Methodology ​

The group studied four different acrylic adhesives and scrutinised 11 compounds contained in them. Some were solvents, while others were residual monomers or impurities remaining from manufacture. The research - Partition and diffusion of volatile compounds from acrylic adhesives used for food packaging multilayers manufacturing​ – was published in the Royal Society of Chemistry’s Journal of Materials Chemistry.

A layer containing the adhesive was placed on to a layer of packaging material (polymer or paper) that covered Tenax, a food stimulant. Analysis of the layers using mass spectrometry determined whether, and how far, any chemicals had diffused through. The reasons for migration into the food depended on factors such as the food itself, time, temperature and other structural properties, said the team.

Target for further studies​

The researchers categorised their findings into three toxicity classes: low, moderate and high. They found that 10 of the 11 compounds examined had low toxicity while the remaining compound - 2,4,7,9-tetramethyldec-5-yne-4,7-diol - belonged to the high category. The compound, which is used as a non-ionic surfactant, has high concentrations in some adhesives, said the researchers. This factor, together with its high toxicity, means it should be targeted for future studies, said team leader Cristina Nerín.

However, the researchers noted the compound is considered a moderate toxic by the USEPA (US Environmental Protection Agency), which means it has a lowest observed adverse effect level of 200 mg /kg/day.

"The estimation daily intake found in our studies was above the exposure value recommended by Cramer but below the USEPA value",​ said Aznar.

Four of the 11 compounds migrated into the Tenax. Two of these did so at higher toxicity levels recommended by the International Life Sciences Institute Europe, the body that investigates food safety and toxicology.

The group also said that "some of these compounds had a restriction or specification in the Commission Directive 2002/72/EC relating to plastic materials and articles intended to come into contact with foodstuffs".​ These were: 1-Hexanol-2-ethyl, which had a specific migration limit (SML) of 30 mg kg−1; 2-ethylhexyl acrylate which has a SML of 0.05 mg kg−1 and benzaldehyde, which had a risk of deteriorating the organoleptic characteristics of the food.

Significant breakthrough​

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Valérie Guillard, an expert in food technology and packaging at the University of Montpellier, France, said: "This work brings significant breakthroughs in the study of compliance with regulations of food contact materials."​ She believed the study showed that "migration of adhesive compounds is possible and at a level that could raise safety concerns".​

Aznar and Canellas said the work had demonstrated that some of the substances present in the adhesives could penetrate packaging and contaminate the food - adding it was necessary to control the composition of adhesives.

“It is necessary to know the quantity of the compound in the adhesive since toxicity depends on the compound but also on its daily intake,”​ they added. “Cramer rules help us to focus on the compounds that are expected to be more toxic and develop an analytical tool for its detection, but specific bioassays are needed to establish a lowest observed adverse effect level (maximum intake per person per day).”​

Partition and diffusion of volatile compounds from acrylic adhesives used for food packaging multilayers manufacturing​ by Elena Canellas, Margarita Aznar, Cristina Nerín and Peter Mercea

DOI : 10.1039/c0jm00514b

Source: Journal of Materials Chemistry.