Words by: Simon Difford
Alcohols ability to draw out flavoursome substances from herbs and spices by infusion and then preserve those flavours has been used since the Middle Ages – originally by monks to produce potions with perceived health benefits – water of life. Today infusion/maceration is used to flavour spirits.
Infusion simply involves immersing herbs, spices, nuts or fruit in alcohol and leaving to soak until the desired flavours have leached out. The same applies to macerating, but as the name implies, in this case the botanicals being infused are first broken up/sliced/diced to expose a larger surface area, so allowing the alcohol to leach flavour from more of the botanical's cells.
Motion, heat and pressure can be used to increase the rate of extraction. Motion can be as simple as shaking a bottle in which something is being infused every few hours, or in commercial applications infusion often takes place in revolving tanks. Heating, (leaving in a warm place), helps break open the botanical's cells, so allowing the alcohol to more easily extract flavour while pressure forces the alcohol into the botanical being infused.
Beware of the speed and degree of extraction. A common mistake is to allow over extraction by adding too much of the flavouring substance or leaving it in the alcohol for too long. Tea, for example, infuses very quickly and starts releasing unwanted bitter tannins after just five minutes while vanilla pods can be left for days and hard substances such as nuts left for weeks.