Antioxidant Activity of Green Tea Extract on Canola Oil Oxidation
Stability: Comparison of Free and Liposomal extract
Abstract
In the present study, green tea extract was encapsulated in liposomes
prepared by Mozafari method (without any organic solvents) and
characterized for its physicochemical properties e.g. encapsulation
efficiency, particle size and z- potential. The obtained results for
encapsulation efficiency, particles size and z- potential were 51.34,
419 nm and -57 mV, respectively. Total polyphenol content of green tea
was obtained 164.2 mg gallic acid /g extract. Free radical scavenging
activities of free and liposomal extract, with using DPPH method were
measured 90.6% and 93.37% respectively. Antioxidant activity of
ethanolic extract of green tea in free and liposomal form were measured
at concentration of 200, 600 and 1000 mg/L on the oxidative stability of
canola oil during 60°C temperature for 0, 4, 8, 12, 16, 20, 24, 28 and
32 days. The results compared with synthetic antioxidant butylated
hydroxytoluene at 200 mg/L. To evaluate antioxidant activity on canola
oil stability, peroxide value, Thiobarbitoric acid, anisidine value,
TOTOX and rancimat test measured. Results showed that liposomal green
tea extract acted more effective than free extracts. Also, 600 mg/L
concentration of green tea extract showed significant antioxidant
activity in compare to others. The increasing storage time and different
concentrations of ethanolic green tea extracts had significant effects
on canola oil stability (P≤0.05). The obtained results showed green tea
extract could act as an effective antioxidant. Green tea extract in free
and liposomal form at 600 mg/L concentration resulted stronger function
than butylated hydroxytoluene synthetic antioxidant.