All about truffle oil.
The white truffle (tuber magnatum pico) is a parasitical fungus with a cult following. Devotees, drawn by a taste that's woodsy, earthy, penetrating, and a scent somewhere between garlic and sex, hungrily await the season for this wild delicacy (late October through December), eager to slice truffles wafer-thin over pasta, risotto, and egg dishes.
The French use pigs to find truffles, but Italians employ trained dogs (which would you prefer in the back of your car?). Gastronomes swear that the most intense white truffles come from around the towns of Alba and Asti in Piemonte, but truffles are found in many Italian regions.
I've eaten an unfair share of truffles over the years, so naturally I was intrigued when "truffle oil" began appearing on American menus in the mid '80s. I'd seen truffle paste (smashed up truffles with a bit of aroma added) used in Italy, but never truffle oil, which made me suspicious. So I dug around like a truffle hound, and here's what I found:
The oil is infused with an aroma that is synthesized. Urbani, the largest packager of truffle products, uses a "natural" scent distilled from white truffle scraps, but I find it an exaggeration. You just can't extract the genuine aroma out of a truffle - period. Less scrupulous producers are said to odorize their oils with petroleum products. Urbani also sells oil with a pasteurized crumble of white truffle in the bottle (they patented a process to prevent fermentation and are therefore the only producers to include the genuine thing in their oil), but for me it really doesn't have any flavor.
Other truffled options? Truffle flour (sometimes called "truffle powder") is simply perfumed white flour. Truffle butter contains specks of less intense summer truffles, plus aroma. Tinned or jarred truffles lose over 50 percent of their aroma in processing; frozen ones lose around 30 percent.
Of course, your best choice is to visit Piemonte in the late fall and taste fresh truffles (around $25 per serving or $900 per pound). You can bring one back through U.S. customs if it's entirely free of dirt.
But, please, don't buy the oil.