Bixin

Bixin is a natural product found in the seeds of the achiote tree (Bixa orellana) that grows in Latin America, India, and East Africa. Like the carotenes, it contains nine conjugated double bonds, but with carboxyl groups rather than hexene rings at both ends.

Bixin is sometimes referred to as cis-bixin because of the lone (Z)-configuration of the second double bond from its ester terminus. When bixin is isolated, the thermodynamically unstable (Z)-bond isomerizes, coverting the molecule to all-trans-bixin.¹ Both bixins are insoluble in water; but base hydrolysis of either produces the water-soluble diacid norbixin.² All three molecules have vivid red-orange colors.

Indigenous peoples have long ground B. orellana seeds into a powder or paste called annatto, of which bixin is the principal ingredient. Annatto is used as a food colorant and flavoring agent; it is also extracted with hot water or oil to make liquids that are used for the same purposes. In modern times, annatto has become a commercial ingredient for coloring dairy products, margarine, baked goods, processed meats, and other foods.

Aqueous annatto extracts, which primarily contain norbixin, are frequently used to produce uniformly colored cheeses such as cheddars. Cheeses may have color inconsistencies from batch to batch because of multiple milk sources and seasonal variations in dairy-cow feed. January 20 is National Cheese Lovers Day, so as you slice your cheddar, be thankful for bixin and the achiote tree.

1. CAS Reg. No. 39937-23-0.
2. CAS Reg. No. 542-40-5.