Octyl sinapate as a new antioxidant to improve oxidative stability and antioxidant activity of rapeseed oil during accelerated storage

Abstract

The effect of the addition of a novel lipophilic antioxidant—octyl sinapate to refined rapeseed oil on its oxidative stability and antioxidant activity—was evaluated using the accelerated shelf-life test. The oxidation processes of rapeseed oils without and with octyl sinapate were analyzed as amounts of primary (peroxide values, conjugated diene) and secondary (anisidine values, conjugated triene) oxidation products and total oxidation (TOTOX) index. The synthesized antioxidant strongly inhibited the generation of secondary oxidation products during accelerated storage of rapeseed oil up to 4 weeks at 40 ± 1 °C under light (power of luminous flux = 385 lm). Moreover, antioxidant activity of rapeseed oil after enrichment with new antioxidant determined by four spectrophotometric methods: 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid, 2,2-diphenyl-1-picrylhydrazyl, ferric reducing antioxidant power, and Folin–Ciocolteu were about 14, 14, 7, and 27 times higher in comparison with the refined oil without octyl sinapate. Antioxidant activity of the enriched rapeseed oil was reduced by about 20–40% during the accelerated storage period, while significantly higher decrease (55–70%) in antioxidant capacity of the refined rapeseed oil took place under these conditions. The addition of new lipophilic antioxidant to rapeseed oil effectively delayed secondary lipid oxidation processes and significantly increased its antioxidant activity under the accelerated conditions, which mimic the autoxidation process upon real storage conditions.