Most tea enthusiasts are very familiar with the term infusion. The word decoction, on the other hand, is a bit more alien. What's the difference?
The word infuse means to steep in liquid, usually to extract flavor and other soluble ingredients. Infusion is the method used to prepare most herbal teas. Usually, in the case of most tea and herbal teas, the water is hot. Cold-brewed iced tea is one exception to the usual pattern of hot water. The temperature can also vary considerably, such as with more delicate green teas, but the general idea is the same.
Usually, tea is prepared by making a covered infusion, ensuring that the more fleeting aromas do not escape to the air and can be enjoyed while drinking the cup.
The word decoct, on the other hand, means to extract the flavor or essence of something by continued boiling. Decoction differs from infusion with boiling water in that it involves a continuing heat source, keeping the water boiling. Even when you start with boiling water, the water stays below the boiling point during the whole infusion process (and quickly cools further). Decoction is often a longer process than infusion, because it involves extraction of substances that infusion is unable to fully bring out.
The term "decoction" is rarely used in the context of beverages. Some beverages, however, do involve continuous boiling in their preparation, but the term is less commonly used even in these cases.
What effect does decoction vs. infusion have?
Decoction allows for extraction of more substances from whatever plant is being decocted or infused. However, it also allows for more aromas to escape into the air, especially when compared to making a covered infusion.
Decoction is more often used for roots, for extracting chemicals that diffuse slower and are less likely to escape into the air. It tends to be used when the medicinal properties or biological activity of the plant are more important than the flavor or aroma. Decoction is the preferred way of preparing kava, for instance. It is also frequently used in herbal medicine, especially for roots.
Do you use decoction for preparing anything?
I sometimes use decoction as a method of preparing certain herbal teas. One example would be making ginger tea from fresh ginger root: fresh ginger root infuses slowly and you can produce a much more powerful herbal tea by decocting (boiling continuously) the ginger than you can by infusing it, even if you have thinly sliced the root.
Do you ever use decoction for preparing any tea, herbal tea, or blends?