Good foam or bad foam?

February 18, 2011 9:23 PM

Is a green foam on steel cut oats normal?

I'm cooking a batch of steel cut oats (just simmering with water) and they have a bright green foam on the top (the foam doesn't completely cover the surface, but most of it). I searched on Google and have found that the foam is either a mold and I should throw the oats away or a protein, and should just stir it and eat. Can someone tell me which is correct?
(They're bulk oats from the local co-op.)

posted by queseyo to food & drink (19 answers total)

Steel cut oats ought to be close to nature, but not bright green. I'd err on the side of caution,& ditch the batch, as much as I love oatmeal.
posted by MidSouthern Mouth at 9:38 PM on February 18, 2011

I'm with MidSouthern Mouth. When I cook steel cut oats, a foam definitely forms. But it's a creamy white/off-white foam. Green is weird. I'd be more concerned that it was some kind of chemical residue or some substance that leaked into the container, though - I don't think mold foams up like that when you cook it. Either way, throw it out, definitely.
posted by Sara C. at 9:47 PM on February 18, 2011 [1 favorite]

Mold. Stick your nose in there and smell. Does it smell like something you want to eat? Throw it out.
posted by at the crossroads at 9:48 PM on February 18, 2011

Bad foam.
posted by mhoye at 9:52 PM on February 18, 2011

Sounds like mold; on the other hand, boiling water may kill the spores. I say eat!
posted by dfriedman at 9:55 PM on February 18, 2011

It's actually probably fine -- likely it's just a reaction with your tap water. This has happened to me more than once, for some reason usually when I let the oats boil too long and the foam built up. It was tasty and fine :).
posted by susanvance at 10:07 PM on February 18, 2011

Here's a study about the oats themselves turning green: The green oat story: possible mechanisms of green color formation in oat products during cooking; they say it's due to water chemistry and will happen more with water from a well, but can be avoided if you let the well water sit for a few hours before cooking with it.

Not sure if this is the same as your green scum. But when I searched Google for this, I entered "steel cut oats g" and it completed to "steel cut oats green scum" - so it seems to be a more common thing than one might expect.
posted by LobsterMitten at 10:11 PM on February 18, 2011 [4 favorites]

Rereading your question just now, I should point out that what I'm talking about is a light, gray-green tinge. If it's really "bright" green, I'd toss it.
posted by susanvance at 10:13 PM on February 18, 2011

My parents occasionally have this problem with their well water and their love of steel cut oats. After a mild amount of freaking out and some water testing that indicated no problems, they've come to accept it.
posted by mandymanwasregistered at 11:56 PM on February 18, 2011

I don't know about the well water angle, but I cook steel-cut oats all the time, and have never seen this. I wouldn't eat it.

(And killing mold doesn't help you if the mold has already excreted harmful chemicals into the food. It's not the microorganism that gets you; it's the poison.)
posted by ixohoxi at 4:43 AM on February 19, 2011

While a doctor I know recommend other green breakfast foods (eggs, ham); he doesn't say anything about oatmeal. I would be wary.
posted by jellywerker at 7:08 AM on February 19, 2011 [6 favorites]

Why don't you cook another (small) batch of oats with bottled or distilled water? You'll then know if it's a water chemistry issue.
posted by prenominal at 7:57 AM on February 19, 2011 [2 favorites]

Do the oats look or smell moldy? Aflatoxin is a real thing, and not heat motile, but if the foam is uniformly green, it's probably as per lobstermitten's article.

According to the link, depending on how the oats were processed, you might still get this effect with distilled water. Acidifying (I'd use a little white vinegar) and then boiling your water and then cooking the oats in it should make the effect go away but if you're too heavy handed with the vinegar your oats are going to taste pretty weird.
posted by Kid Charlemagne at 11:16 AM on February 19, 2011 [1 favorite]

The oats didn't smell bad, and the foam was white-ish in spots, pale green in others, with wisps of bright green (like Easter grass green). In the first batch there was a scummy bright green ring all around the side, plus the splotchy green and white foam on top, which freaked me out enough to toss the whole thing out and start again. When the second batch also produced green foam, though less than the first, I checked the internet and posted this question.

I'm assuming it's the water, even though I've made oats before and not had this problem. When I called the co-op to ask if they had any info, they actually cooked a small batch themselves, and it came out normal. I will try some of the suggestions about the water and see if it helps. (Kid Charlemagne, is adding vinegar meant to counter the mineral content of the hard water, or to kill the aflotoxin? Chemistry is not one of my strengths.)
posted by queseyo at 2:07 PM on February 19, 2011

oats are cheap...even the kind that come in highly artsied up tins. Health is expensive.

Toss the oats, or return them if you're brave.
posted by hal_c_on at 5:48 PM on February 19, 2011

Acetic acid (vinegar) in unlikely to take out most food toxins - at least not in concentrations you want around your food.

What they are saying in that abstract is that when you boil water containing sodium bicarbonate, you drive off CO2, leaving sodium hydroxide (aka Lye) in the water, but they also point out that if the bicarbonate (or trace amounts of lye*) may come in with the oats so my idea of boiling the water with vinegar before adding the oats may put you back where you started.

In retrospect, I'd add the vinegar and oats to the water, let them soak a few minutes and then boil so if the base is coming in with the oats, it would still get neutralized. If it were me playing around with this, I'd use hydrochloric acid and add it to my water until it just barely tasted sour (we're talking a couple drops here, assuming the grade you get at the hardware store 32%) then add my some oats and cook after letting them soak for a few minutes. (If I were doing this with 32% HCl, I'd also wear safety glasses, not add those few drops of acid to the water in my kitchen, wash my hands afterward, and then not eat that batch of oats since it's likely to taste funky and the HCl you get at the hardware store is probably not particularly pure.)

*Strong bases are very good for cleaning out the plumbing for beer making (and other food processing equipment) but you have to rinse thoroughly! If you don't, the remaining lye isn't likely to be concentrated enough to cause you any harm, but your beer will taste soapy.
posted by Kid Charlemagne at 5:55 PM on February 19, 2011

This happened to me! It was a weird green ring around the edge of the pan, it didn't look anything like mold, and I had been afraid to eat steel-cut oats since then. This is with regular Montreal tap water.
posted by OLechat at 7:56 PM on February 19, 2011

My oat foam is always blue, but I've eaten the oats happily and lived to tell the tale. Our town water is terrible. I don't know if this information helps you.
posted by TrarNoir at 11:36 AM on February 20, 2011

I'm dying to know - did the water bottle experiment work? Are you now happily eating tasty steelcut oats?
posted by stoneweaver at 5:46 PM on February 25, 2011 [1 favorite]