Terpenes and terpenoids

Terpenes are sourced from citrus peel, turpentine from pine trees, mint and other essential oils, or made synthetically from petrochemical or turpentine feedstocks. Besides flavour and fragrance, they serve as bio-based solvents and cleaning agents (d-limonene), as resin raw materials (pinenes), and as intermediates for vitamins and aroma chemicals.

Ask for the source (natural or synthetic), purity by GC, optical rotation for chiral terpenes, peroxide value for oxidisable materials such as limonene, and stabiliser content. Oxidised terpenes can become skin sensitisers, so storage under nitrogen and antioxidant addition are common. Several terpenes appear on fragrance allergen lists and must be declared on cosmetic labels above set levels.