A US firm has filed a patent to stop or at least reduce the amount of bisphenol A (BPA) that migrates from can coatings in food and beverage products.
The capture system is made of one or more materials which bind (capture) any BPA eluting from the BPA-containing coating.
It details using chitin or chitosan as some of the natural BPA-binding materials via electrospinning and molecular imprinting using varieties of cellulose as an example.
Electrospinning uses an electrical charge to draw fine fibres from a liquid and molecular imprinting is when functional monomers self-assemble around a template molecule.
Takahisa Kusuura and Fukiko Ozawa filed the patent on behalf of Empire Technology Development, Wilmington, US in November last year detailing the methods.
The aim of a polymer coating is to prevent contact between the interior surface of the can and the food or beverage, so the surface of the can does not get corroded and the contents are not contaminated.
The ratio of the BPA-binding material to BPA-containing polymer in the coating composition may range from about 5 weight percent (wt%) to about 80 wt%.
Electrospun binding material
The patent details how at least a portion of the interior surface of the can is covered with one or more of a first coating comprising BPA, and a second coating comprising an electrospun BPA binding material.
So the first coating is in contact with the interior surface and the second coating is at least partially layered over the first coating.
The second coating is configured to bind substantially all of the BPA leaching from the first coating.
The patent clarifies “substantially all of the bisphenol A" being binded as at least half.
Such naturally BPA-binding materials include chitin, chitosan, dextrin, fibroin, keratin and mixtures of any two or more.
This BPA-capture coating is formed by electrospinning the BPA-binding material to provide a microporous layer of nanofibers.
Due to the fact that the porous nanofiber layer is hydrophobic, the coating also prevents the food or beverage contents from contacting the BPA-containing coating.
The patent also states that the binding material of the second coating can be adapted to binding BPA by molecular imprinting using a BPA compound.
Such materials include cellulose, cellulose acetate, cellulose acetate butylate, lignocellulose, polyamine, N-alkyl acrylamide, N-vinyl pyrrolidone and a mixture of any two or more, they said.
Cellulosic polymers are particularly useful in the present technology as they are generally stable to heat and various solvents/liquids and are thus well-suited to the inner coating of food/beverage cans.
They also provide good strength to the molecular imprinted polymers (MIPs) when electrospun and are an abundant natural fiber that is inexpensive and easy to obtain and use, explains the patent.