Anethole

The sweet, liquorice-scented compound — chemically p-allylphenyl methyl ether, predominantly the trans isomer — that defines anise, fennel and star anise. It flavours confectionery, liqueurs such as ouzo, pastis and anisette, and many baked goods, and it causes the famous milky louche when water is added to anise spirits. Traditional medicine values it as a carminative and mild expectorant, and laboratory studies show antimicrobial activity. Food-grade anethole is used as a defined flavouring substance, but formulators respect dose: concentrated essential oils rich in anethole are far more potent than the culinary spices themselves.