Ask the Alchemist #86


Unbeknownst to me, I had made my own brewing cocoa recently, calling it "chocolatea" and shared it with my office-mates. (I used a 1/12" sieve prior to winnowing to remove the fines. I brewed the fines in my tea brewing basket.) It was really tasty!! However, I threw it away after having a discussion with a chocolate maker. He mentioned that he heard most beans coming into the country get sprayed for bugs at the port of entry and that I should use caution. I didn't want to accidentally slow-poison my coworkers. What can you tell me about beans being spray at US ports of entry? Is this stuff actually safe to drink?

First and foremost, yes it is safe to drink. Now for the why.

If a bean is not labeled Organic, it is indeed 'sprayed'. That is in quotes as technically it is not sprayed. It is gassed. Usually by methyl bromide. And although that is rather toxic (it's why they are using it after all), it is also very, very, very volatile (it boils away at 3.6 C and has a very low vapor pressure) and goes away with no detectable residue.

In my prior life I was an organic analytical chemist and methyl bromide is something I analyzed for. I tested beans I knew had been gassed and could never find any. And that is down to 5 mg/kg. That was in raw beans. After roasting at 300-400 F it is simply not going to be there. It has no way to be there. Methyl bromide does not stick to surfaces as it is a gas a room temperature. While trying to look up toxicity data, I kept running into the issue that there is only inhalation data. Why? Because it is that volatile and it just does not apply to solids. Even in water, where it is regulated, the toxicity level is so much above the solubility level that in reality, it is a moot point.

This should give you an idea how much this stuff does not want to stay around. In order to analyze for a compound, you need something to compare against. A Standard. My Methyl Bromide Standard was in methanol, which it is pretty soluble in (unlike water). I kept it in a sealed vial, at -20 C, opening it 1 or 2 times a week. And never letting it get above -10 C. With that limited and careful handling the methyl bromide would be gone within a month. From a sealed, sub-frozen vial!!

I hope that convinces you there is simply no residue or danger from this gassing.

So fear not. You can use cocoa beans that have been gassed and not poison yourself in the least.

Comment