Oxidative stability of conjugated linoleic acid-rich soy oil.

摘要

A conjugated linoleic acid (CLA) rich soy oil (CLARSO) has been produced by photo-isomerization of linoleic acid with an iodine catalyst, but the oxidation of CLARSO has not been reported. The objective of this study was to determine the effects of CLA and iodine on the oxidation of CLARSO. A control of commercial soy oil (CSO) and 3 oils containing 0.35% iodine and either 0%, 8%, and 15% CLA were stored in dark for 10 days at 50°C in 10 mL vials. Headspace oxygen depletion (OD), peroxide value (PV), change in weight (CW), and p-anisidine value (PAV) were measured daily. All treatments had significantly greater OD than CSO (p0.05), but CLA effect was not significant. Iodine interfered in PV reaction, therefore results were inconclusive. CLA level had significant effect on CW (p0.05); with increasing CLA concentration there was an oxidation increase. PAV was low for all treatments. The effect of iodine on oxidation was unresolved. The study was repeated with control CSO, and 8 treatment combinations of 0%, 0.175%, and 0.35% iodine, and 0%, 10%, and 20% commercial CLA added to soybean oil. These were stored under same conditions but at 65°C, and only OD and CW were measured. Iodine level had significant effect on OD and CW. Increasing iodine concentration resulted in greater oxidation. CLA level had a significant effect on CW, but did not affect OD. Volatile oxidation products of CSO, CLARSO, and oils with added 0.35% iodine, 20% CLA, and CLA + iodine were determined. CLA promoted an increase in volatile production, but iodine did not. Iodine and CLA cause an increase in oxidation, and may be pro-oxidants. The effect of CLA and iodine together on oxidation is not yet clear.