Since bitter almonds are difficult or impossible to obtain in the United States, home cooks, professional chefs and industrial users have long resorted to alternative sources for intense almond flavor.
Apricot and peach kernels, easy enough to obtain from fresh fruits by cracking open the pits (put them in a kitchen towel and hit them with a hammer), can substitute for bitter almonds, though they have less amygdalin and thus less flavor. Generations of home canners have used one or two kernels to add a heightened flavor when cooking peach, apricot and cherry jam.
"The flavors are close enough," says Tim Woods of Echo restaurant in Fresno. "I prefer bitter almonds, however, because the apricot kernels often have a musty taste."
China exports bitter nuts which are often called almonds but are botanically apricot kernels. The fruits, closely related to almonds, are grown primarily for their seeds, not for their flesh. To complicate matters, China and Central Asian countries also produce sweet apricot kernels, which can be eaten like normal almonds. Chinese bitter apricot kernels are available at some ethnic markets in the United States (often without warnings of their toxicity, in violation of state and federal regulations), but before buying it's important to ask whether the kernels are bitter or sweet. The bitter kernels are often called "north" almonds, and the sweet kernels, "south" almonds. All bitter nuts, of course, must be cooked to remove the cyanide.
Peach leaves macerated in hot water may also be used for bitter almond flavor.
The most common sources of bitter almond taste, however, are almond extracts, which are distilled to be free of cyanide. "Pure" almond extract should contain natural oil of bitter almond, a colorless fluid, along with water and alcohol. "Natural" extract usually is flavored with benzaldehyde made from cassia, a relative of cinnamon. "Imitation" extract uses synthetic benzaldehyde, which is manufactured from a petrochemical.
Although oil of bitter almond can be pressed from bitter almonds, apricot kernels and other fruit kernels containing amygdalin (such as those from peaches, plums or cherries), true bitter almonds almost never are used. Apricot kernels yield more oil and, being byproducts of the fruit industry, are cheaper.
It takes 100 pounds of kernels to make 1.7 ounces of bitter almond oil, so the natural product is very expensive compared to the synthetic benzaldehyde in "imitation" almond extract. Many cooks say that pure and natural almond extracts have a more rounded taste than the imitation product, but the flavoring in all three forms consists almost entirely of benzaldehyde, and chemists must use sophisticated analytical tests to tell the difference.
There is thus considerable incentive for manufacturers to substitute the cheaper products, and several industry sources claim that most of what is sold as oil of bitter almond in the United States is actually from cassia or even synthetic.
"I'd question whether there's any of the real stuff around any more," said Kim Bleimann, president of Berje Inc., an importer of essential oils based in Bloomfield, N.J.
In response, Laurie Harrsen, a spokeswoman for McCormick, the nation's leading extract manufacturer, said: "The oil of bitter almond in McCormick's pure almond extract is derived from apricot kernels, in accordance with FDA regulations."