Evaluation of electron donating ability of b-carotene by using soybean oil and 2,2-diphenyl-1-picrylhydrazyl(DPPH) in acetone system
B. OZCELIK1, J. Lee2, and D. B. Min2. (1) Food Engineering Department, Istanbul Technical University, Maslak-Istanbul 80626, Istanbul, 80626, Turkey, (2) Department of Food Science and Technology, The Ohio State University, 2015 Fyffe Court, columbus, OH 43210-1007
b-Carotene is an excellent singlet oxygen quencher and has free radical scavenging activity due to the possible electron or hydrogen donation. The carotene is considered as antioxidant in free radical oxidation due to its radical scavenging activity.
To determine the free radical scavenging mechanism of b-carotene in DPPH in acetone and to study the effects of b-carotene in soybean oil oxidation.
Ten mL of 0.05 mM DPPH containing 0, 0.05, 0.1, 0.2, or 0.5 mM b-carotene in acetone were prepared triplicate in 30 mL bottles. The concentration of DPPH was measured at 517 nm every 30 minutes for 5 hours at 25oC. The headspace oxygen contents of 10 mL soybean oil in 30 mL bottles containing 200 ppm b-carotene, BHA, BHT and TBHQ under dark at 55oC for 2 weeks were analyzed by gas chromatography.
As the concentrations of b-carotene increased from 0 to 0.5 mM in acetone, the concentration of DPPH decreased from 15% to 75% for 5 hours. The b- carotene cation radical was determined at 938 nm, which indicated that b-carotene donated electrons to DPPH. The headspace oxygen contents of soybean oil with 200 ppm BHA, BHT, and TBHQ were 14, 16, and 20%, respectively, when control sample was 12%, but the 200 ppm b-carotene has only 10% (p<0.05). b-Carotene was not hydrogen donating antioxidant but acted as a pro-oxidant by being cation radical in soybean oil.
The electron donating ability of b-carotene was shown by the formation of b-carotene cation radical in acetone system and the pro-oxidant effect on soybean oil. b-Carotene donated electron to free radicals and the b-carotene cation radical accelerated lipid oxidation.
Session 30A, Food Chemistry: Lipids