Friend or foe? Study monitors the helpful plasticizers that rub off on our food

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  • Published: Oct 15, 2016
  • Author: Ryan De Vooght-Johnson
  • Channels: HPLC
thumbnail image: Friend or foe? Study monitors the helpful plasticizers that rub off on our food

Last word

Since the beginning of time we have faced a battle against invisible microbes. Using reconnaissance gathered during the eighteen and nineteenth centuries, foodstuffs are often vacuum sealed with thanks to plasticizers. But can too much of a good thing be bad?

“Gentleman,” the father of Microbiology, Louis Pasteur, once admonished, “it is the microbes who will have the last word.” How eerily correct he was.

Today, the Germ Theory of Disease—meticulously revised over the years by the likes of John Snow, Pasteur himself, and Robert Koch—is the orthodox. Refuse to adhere to its tenets at your peril.

Disciples spreading the word preach of Pasteur’s ingenious experiment of the 1860s involving a swan-neck flask. Through this crude bit of apparatus, Pasteur disproved the critics of Lazazaro Spallanzani—who showed a century earlier that bacteria could be killed through boiling and secondly that sterilised broth would remain so as long as it was sealed from the outside.

“There is no known circumstance in which it can be confirmed that microscopic beings came into the world without germs,” Pasteur concluded. Fast forward to the twenty-first century, food is religiously sterilised and sealed in a vacuum, before being shipped to your local convenience store.

‘Pop’

Venture into your local grocery store, and you will come across aisle upon aisle of glass jars. These glass jars, much like Pasteur’s S-curved glassware, prevent microbes from reaching and spoiling their contents. But in contrast to Pasteur’s paraphernalia, glass jars are airtight—springing to life with a characteristic ‘pop’ when their contents are re-introduced to the atmosphere.

This impenetrable seal is not formed between the glass and metal lid, but by some form of plastisol—most frequently of polyvinyl chloride (PVC)—that coats the screw thread. What’s more, a quarter-to-a-half of this plastisol is made up of a plasticizer. Typically based on esters of polycarboxylic acids with straight or branched aliphatic alcohols protruding outwards, these plasticizers bestow the otherwise rigid metal-and-glass surfaces the malleability to form the airtight seal.

But there’s a slight snag. ‘Plasticizers and additives, being incorporated in PVC gasket seal, have the potential for migration into the food mainly during packaging and sterilization procedure,’ writes Francesca Lambertini from Barilla foods of Parma, Italy, first author of a recently published study on plasticizers in foods.

The ‘migration could continue due to occasional contact during transportation and storage,’ she adds. In response, the EU has imposed ‘migration’ limits, which require plasticizers to transfer no more than 60 mg per 1 kg of food.

HPLC-MS/MS

Writing in the Journal of Mass Spectrometry, Lambertini and colleagues set out to devise the tools able to police conformity to the levels of common plasticizers in both packaging and foods.

Taking the PVCs precipitated from three different gasket seals with tetrahydrofuran and ethanol, Lambertini resolved the constituent plasticizers using an HPLC system equipped with a C18 column and configured to a 55-minute gradient comprising three buffers. Resolved plasticizers then underwent atmospheric pressure chemical ionisation (electrospray ionisation was trialled, but was inferior in many outcomes) and were then mass analysed as they fragmented using both targeted (i.e. MRM/SIM) and non-targeted approaches (i.e. full scan).

Lambertini’s HPLC-MS/MS assay was trained to follow the reactions of 16 plasticizers and in some instances could detect as low as 3.0 μg/kg and quantitate down to 7.3 μg/kg. Admittedly, precision when quantitating at levels lower than 100 μg/kg became an issue, albeit not for plasticizers of ~2.5 mg/kg.

With the newly developed method in hand, Lambertini and colleagues purchased Bolognese sauce at local markets and produced an oily basil pesto at pilot plants, then packaged these within glass jars sealed with three different gaskets of known compositions. They then quantitated the levels of three plasticizers in the sauces after 3, 6 and 11 months of ‘poor’ storage conditions —upside down, at room temperature, and thoroughly shaken every month.

‘The advantage of overcoming relevant analytical issues concerning the handling of food matrixes, in particular oily sauces,’ the Italian researchers conclude, ‘makes the present method suitable for rapid and high throughput analysis for migration studies at relative effective costs.’

Related Links

J. Mass Spectrom., 2016, 51, 805–813. Lambertini et al. Multiresidual LC–MS analysis of plasticizers used in PVC gaskets of lids and assessment of their migration into food sauces.

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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