Tempest in a K cup

K cupsA question came up about the risks of chemicals leaching out of those convenient coffee K cups. Yes, chemicals do leach out. That of course is the idea, you want to leach out the hundreds of compounds that contribute to coffee flavour and aroma and you also want a good shot of the stimulant caffeine. However, the likely reason for the question was concern about chemicals leaching out from the plastic. Yes, that happens too.

Anytime two surfaces come into contact, especially if one is a liquid, there will be transfer of chemicals. I don’t know exactly what plastic is used in these cups since the company maintains that this is proprietary information. By its texture, it seems the plastic is either polystyrene or polypropylene. It certainly is not polycarbonate which would be a source of bisphenol A (BPA). Traces of styrene, the compound from which polystyrene is made, may leach out. But styrene also occurs naturally in coffee beans, so all coffee will have some styrene. This is really not much of an issue because styrene is quickly metabolized and excreted.

If anyone has concerns about styrene, they had better stay away from cinnamon which can have as much as 39,000 ppb of styrene as opposed to the 5 ppb that may be leached out from polystyrene. They will also have to stay away from beer which has up to 25 ppb of naturally occurring styrene. If the K cup is made of polypropylene, there is no issue whatsoever. No compound of any consequence leaches out of this plastic. Basically what we have here is a tempest in a Kcup. If there is to be a concern, it centers in the environmental unfriendliness of these little cups which may pose a big problem in terms of where they end up.

Joe Schwarcz

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