What infusion means
An infusion is both the process of steeping ingredients in a liquid or fat to extract their flavour, and the flavoured liquid that is produced. The ingredients, such as leaves, flowers, herbs, spices, seeds or fruit, are soaked in the liquid, which draws out their flavour compounds, aromatic oils and sometimes colour. The best-known infusion is a cup of tea, made by steeping tea leaves in hot water. Herbal teas, made from plants such as mint, chamomile or lemon verbena, are often called herbal infusions or tisanes.
In cooking, infusions are used constantly, even if the word is not always mentioned. Vanilla, bay or citrus peel are infused into milk and cream for custards and sauces. Saffron is infused in warm water or stock to release its colour. Herbs, spices and chillies are infused into oils, butters, vinegars and syrups, and spirits are infused with fruit, as in sloe gin.
Heat speeds up an infusion, while cold infusions, such as cold brew coffee, are slower but gentler. An infusion differs from a decoction, in which tougher ingredients such as roots, bark and seeds are boiled or simmered to extract their flavour. You will see the word infusion in recipes for drinks, sauces and desserts, and in food science explanations.