Mah Thung Hutth: Identifying Food Allergens

September 25, 2007 9:50 AM

Calling all food chemists: what do walnuts, spinach, and scallops have in common, composition-wise?

I have a mild food allergy to walnuts, spinach, and scallops. If I eat anything more than a few bites, my tongue feels a bit swolen and aches like a mofo for at least 20 minutes or more. The fact that my reaction to each of those items is identical makes me think it's one particular compound that's causing the trouble. While I obviously haven't sampled every edible thing on the planet, I can say I'm a fairly adventurous eater, and as far as I know I'm not allergic to any other fish, shellfish, mollusks, nuts, or greens commonly found in typically American / Western European meals.

I'm not looking to go on a Substance-X-free diet, especially since my reaction is hardly life-threatening; this question is really just academic, serving my own curiosity and love of useless bits of trivia than anything else.

posted by shiu mai baby to Science & Nature (7 answers total)

They don't have anything in common, probably.

Each foodstuff happens to contatin a different protein which sets your immune system off. The immune response feels the same to you each time, because it goes through the same routine, to X, to Y, and to Z.

That's the cartoon version. I'm curious to see what people who know what they're talking about have to say.
posted by sebastienbailard at 10:10 AM on September 25, 2007

IANAFC, but I was a fish dealer. One of the only things that you would find in a scallop that you wouldn't find in other shellfish is the chemical Sodium Tripolyphosphate. STP is used fairly often to swell the scallop with water weight before selling. It also has some preservative qualities. It's mostly found in frozen and lower priced scallops. STP can be an allergen to folks with phospate sensitivity.

I know nothing of spinach and walnuts.
posted by kuujjuarapik at 10:16 AM on September 25, 2007

The first two are pretty high in oxalic acid, which some people are sensitive to.

Have you tried scallops from a variety of sources? So-called "wet pack" scallops are preserved with sodium tripolyphosphate; I don't know that there are any common sensitivities to this additive, but it's worth trying "dry pack" scallops, which do not contain it.
posted by mr_roboto at 10:18 AM on September 25, 2007

Sounds like Oral Allergy Syndrome to me, although the scallops would be an outlier. I get something very similar whenever I eat walnuts, brazil nuts, carrots, certain apples .... feels like I ate hot peppers, combined with an itching sensation on the roof of my mouth and throat. It gradually subsides after 20 minutes or so. Oddly these effects did not come on until I was thirty years old or so, and it used to be just raw walnuts, then walnuts and brazil nuts, then a year or so later, carrots, I expect that more things will aggravate me as I age. The symptoms match the pains of seasonal allergies I also tend to get in the spring.
posted by chocolate_butch at 1:42 PM on September 25, 2007

Checked Harold McGee's On Food and Cooking for you, but can't find any notable component that they share. So that's a vote for the three-separate-allergies theory.
posted by eritain at 3:17 PM on September 25, 2007

From this previous thread, quoting in turn from somewhere else:

Foods that are edible, but that still contain significant concentrations of oxalic acid include - in decreasing order - star fruit (carambola), black pepper, parsley, poppy seed, rhubarb stalks, amaranth, spinach, chard, beets, cocoa, chocolate, most nuts, most berries, and beans. The gritty “mouth feel” one experiences when drinking milk with a rhubarb dessert is caused by precipitation of calcium oxalate. Thus even dilute amounts of oxalic acid can readily "crack" the casein found in various dairy products.

Do you get a reaction with any of those things?
posted by LobsterMitten at 6:14 PM on September 25, 2007

Re 'cracking the casein': It would be more accurate to say, 'cracking the micelles'. Calcium ions are not chelated in the casein or anything like that; they are in solution, but they wind up at the core of clusters of about 20 casein molecules, and at the core of micelles comprising a few hundred of these clusters. Anything that brings the local pH to 5.5 can undo the inter-micelle repulsion and disperse the protein clusters. I'm not sure whether, or why, oxalate would be special that way. This geeky digression was also brought to you by Harold McGee.
posted by eritain at 9:17 PM on September 25, 2007