When one writes about cyanide in a food column, it gets people's attention.
In my column of Dec. 8, I wrote that apple, peach and apricot seeds contain amygdalin, a glycoside (a kind of carbohydrate) that hydrolyzes, or reacts with an enzyme in the digestive system, to produce hydrogen cyanide. The specter of poisoned apples apparently induced a sort of Danse Macabre.
Relax. While apples have suffered more than their share of notoriety from Eve to Snow White, I also stated that it would be difficult to eat enough of the seeds to accumulate a lethal dose. Nevertheless, several readers responded with anxious e-mails. Here are some excerpts from their electronic angst:
I have been eating the entire apple since fifth grade, when we were given one government surplus apple every day and I didn't want to get up to throw the core in the wastebasket. That was about 50 years ago, and apples are one of my favorite fruits to eat while I read, so I've eaten a lot of them. Of course, I didn't chew the seeds, nor do I now. So aren't they just traveling through my system whole? Why would this be toxic?
I can't help wondering whether you swallowed the core in unchewed chunks, seeds and all.
The apple's seed coat is tough and largely impervious to digestive juices, so it would indeed pass harmlessly through your body. If the seed were chewed, however, the amygdalin would be released and could produce hydrogen cyanide. Still no problem, however, because the body has an enzyme that can detoxify small amounts of cyanide. Just don't chew and swallow the seeds from a dozen apples at a time. An apple a day may keep the doctor away, but a dozen a day would summon him quickly.
The same fretful reader continues:
A spokeswoman for the National Dietetic Association was quoted on TV a couple of weeks ago as saying that there are antioxidant properties in grape seeds, and so we should eat the seeds for maximum benefit. Again, grape seeds (which I also eat but don't chew) must be going through me whole, so how would I get any antioxidant benefits from them?
Chew 'em. There's no amygdalin in grape seeds.
On the same date [as your column appeared], the Food section's "On the Fridge" feature showed a bottle of apricot kernel oil, touted as having a nutty flavor and being able to take high heat. Wouldn't this oil be poisonous?
It's true that apricot pits contain rather hefty amounts of amygdalin and hence, of potential hydrogen cyanide. In order of decreasing amounts, the seeds of all the following fruits contain amygdalin: apricot, peach, plum, apple, almond and quince.
But there's little danger of anyone's having the chutzpah (not to mention the teeth) to crack and eat very many apricot seeds. I do have a cousin who as a kid used to eat peach pits regularly, and he's still alive at 79, though a bit weird. (Just kidding, Albert.) Apricot kernel oil is obtained from the pits by cracking them open and separating the shells from the kernels (or "nuts") by flotation in brine. The kernels are then pressed to extract the oil. Because amygdalin dissolves in water but not in oil, the oil is amygdalin-free and perfectly harmless.
I remember, growing up in Lebanon, that there were two kinds of apricot seeds. One we called "almond-apricot" because the white seed inside the hard shell was sweet and almondlike with barely a hint of bitterness. The other kind had a very bitter seed, and families for ages soaked those seeds in many changes of water to remove the bitterness and used them in both sweet and savory dishes. Is it just that no one ate a large-enough quantity of these seeds to die of poisoning? Or are there other factors at play here?
I'm sure that way back in history some people did indeed eat enough to die, which is how their survivors decided there must be a better way.
There are at least 50 known varieties of apricots, ranging in size from marbles to baseballs and in color from white to dark purple. One may assume that the bitter apricots are likely a variety that contains enough bitter-tasting amygdalin to be dangerous, and people learned quite early that water removed both the bitterness and the dangerous but water-soluble amygdalin.
Terminology, Take 2: In my Dec. 22 column, I wrote about peeling citrus fruits as if our objective were to separate the outermost, colored layer (the flavedo or zest) from the white pith layer (the albedo) just beneath it. I should have said that we want to separate the whole "peel," that is, the flavedo and albedo layers together, from the juicy pulp. My apologies.
Robert L. Wolke(www.professorscience.com) is professor emeritus of chemistry at the University of Pittsburgh. His book, "What Einstein Told His Cook-2: Further Adventures in Kitchen Science," will be published in April. He can be reached at email@example.com.
Perspicacious reader Natalie Aronsohn of north Bethesda noted a Giant Food weekly special advertised as "Large raw white shrimp (26-32 per pound) and Extra Large cooked shrimp (31-40 per pound)." Let's see, now. Those "large" 40-per- pound shrimp must be bigger than the "extra-large" 32-per- pound shrimp, right?
Have you noticed any silly things on food labels? Send your Labelingo contributions, along with your name and town, to Food 101, Food Section, The Washington Post, 1150 15th Street NW, Washington, D.C., 20071 or to the e-mail address at the end of my column.