Use of Sinapic Acid Alkyl Esters as Antioxidants in Microencapsulated Flaxseed Oil

Enzymatically synthesized hexyl (C6) and palmitoyl (C16) esters of sinapic acid were incorporated into microencapsulated flaxseed oil as antioxidants. The antioxidant activity and lipid oxidation retarding effect of the sinapic acid esters were tested during storage using different methods. Sinapate-enriched microencapsulated flaxseed oils were found to be more stable against oxidation during storage compared to microencapsulated and free oil. In addition, the results of antioxidant analyses and lipid oxidation measurements revealed the superiority of palmitoyl sinapate (longer alkyl side chain) over hexyl sinapate. The polarity of the analysis medium provides information on the antioxidant properties and stability of the added sinapic acid esters since sinapic acid alkyl esters gave different results when tested directly in the analysis medium. The results showed that lipophilic esters of sinapic acid, especially palmitoyl sinapate, can be successfully used as antioxidants to stabilize microencapsulated flaxseed oil.