We mentioned vanilla as an example of extraction by soaking in a cold solvent, but this is not always the best way of extracting the flavored and scented substances found in the fruits, seeds, leaves, bark or roots of plants. The list of methods below is not exhaustive, but does cover the methods that you can safely use at home.
• Cold soaking at room temperature in a solvent such as water or ethanol.
• Hot soaking by subjecting the plant material to a hot liquid solvent.
• Boiling the plant material in a solvent, or passing hot vapor through the material to vaporize the substances required. Note: we only recommend steam for this method.
• Expression, or squeezing to extract under pressure.
• Infusion into a solid or semi-solid "carrier" material such as fats or oils, followed by extraction. Cold Infusion
Cold infusion (soaking) is the simplest technique, and has the advantage of not using heat. Many large organic molecules break down when heated, with considerable changes in their flavor and aroma. Jasmine is an example of a plant material that cannot be successfully extracted with hot solvents or steam. Cold soaking is a great way to start extracting botanicals, because the only equipment you need is a large jar or bottle.
Cold soaking is used widely in Europe to prepare some excellent liqueurs. In Germany, the "Rumtopf" or "Rum Pot" is a Christmas tradition. Early in the year, about a kilogram (2.2 pounds) of the first berry fruits are put in the bottom of a big ceramic pot together with a kilogram of sugar. A bottle of rum is poured on top and a close-fitting lid put on the pot to prevent evaporation. As different fruits come into season throughout the year, they are added, along with more sugar and rum as needed. When Christmas arrives, the pot is opened to yield a rich, ruby red fruit liqueur (without a hint of rum flavor), and a superb supply of fruit for desserts.
Other familiar products produced this way are the herbal and flower-flavored oils and vinegars that are now widely available and easily made.
Here is a recipe for the vanilla essence that we mentioned earlier: Cut several vanilla pods into small pieces about I cm (V2 inch) long, place them in a small screw-top jar, and fill it with 95% ethanol. Allow it to soak for at least two weeks. The longer this is kept, the better it gets.
If you can't make your own 95%, it is sold in the U.S. as "Everclear", and in Europe as "Polish Spirit". Just make sure that any strong ethanol you buy is intended for beverage use and does not contain denaturants!
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