Harold McGee's excellent piece on the alliums this morning, as usual in anything he explores, told me things I didn't know about garlic and onions. McGee takes much of it from Garlic and Other Alliums: The Lore and the Science, a new book by Eric Block, who has spent his life studying the volatile, sulfur-containing compounds in onions and garlic that make some people very happy and others run. (Here's a link to English Amazon; it's published by the Royal Society of Chemistry, though Block is Forest Hills-bred and works at SUNY Albany.) The people who run (often including me, if it's strong garlic—though perhaps I'm running from my grandmother, who was incapable of cooking without it) are obeying the signal the plants evolved to drive away predators.
In addition to tips for avoiding garlic breath—raw kiwi, eggplant (isn't that a dangerous nightshade?), and mushrooms—McGee, summarizing Block, sorts out the alliums by which compounds they contain/emit when attacked, a.k.a. crushed or sliced:
Garlic cloves produce a chemical called allicin, which is responsible for their strong pungency and aroma. It's a relatively large molecule and acts mainly on direct contact with the eater, the plant world's version of hand-to-hand combat.
The flat-leafed allium known as Chinese or garlic chives produces a small amount of garlicky allicin, but much more of a different weapon that has a milder, cabbage-like aroma.
Onions, shallots, scallions and leeks share a special stockpiled chemical and a second defensive enzyme. They produce a sulfur molecule that's small and light enough to launch itself from the damaged tissue, fly through the air and attack our eyes and nasal passages. This long-distance weapon is called the lachrymatory factor because it makes people's eyes water.
Worth remembering, along with numerous other tips. But what stuck out was the injunction never to feed any allium to your pet, as allicin is dangerous. I thought immediately of Marion Nestle's new book, Feed Your Pet Right, which I've been meaning to write about. Like everything she writes—and this is her first book with Malden C. Nesheim, professor emeritus of nutritional sciences at Cornell University—this is a model of clarity and good sense. And all-inclusive, at least all you'd need to know to care for your pet. And she and Nesheim even wade into the Great Raw Debate, which I gather is the current hot topic among pet-lovers. (Isn't there always one?)
I couldn't imagine they would omit such a critical piece of information—think of all those leftover stews, mysteriously and invaluably enhanced by long-cooked alliums, as McGee says braised meat dishes particularly are! Think of everything my grandmother ever cooked! So I looked in the index, and of course there were two entries. After presenting the conflicting current opinions on the matter and trying to extrapolate the amounts that could be considered dangerous from a 2008 National Research Council report, they typically come down with judicious, succinct advice:
Althought it is difficult for us to believe that one clove of garlic could do much harm, pets don't need onions and garlic, so why take a chance?
If I ever want good sense, I turn to Nestle. When we get that dog we've been dreaming about, we'll turn to Nestle and Nesheim.