Rancimat Test
The results of rancimat is visible in Figure 1. The lowest and highest
stability belonged to control and green tea extract liposome in 1000
mg/L level. Oil samples containing green tea extract liposome had higher
oxidative stability than free green tea. Green tea extract, in 1000 mg/L
concentration, in the rancimat test, had the best oxidative stability,
with induction period 9.5 h, while in oven test showed the lower
stability. The reason was that in the oven and rancimat test are used of
60 ⸰C and 120ºC, respectively. In the high temperatures such as rancimat
test, lipids oxidation mechanism significantly changes while in oven
test, side reactions including polymerization and cyclization were in
its minimum amount. The rate of oxidation depends to oxygen
concentration and oxygen solubility, in the high temperatures, decreases
(Frankel., 1993). Yin et al. studied the effect of green tea extract
green tea (catechin at 0.25, 0.5 and 1 µmol/g oil on the sunflower oil
stability by rancimat test. Oil samples induction period had upward
trend by increasing antioxidant concentration. Induction period for
control and oils containing green tea extract in 0.25, 0.5 and 1 µmol/g
oil concentrations was about 1.9, 4.8, 7.5 and 11.8, respectively (Yin
et al., 2012). Gramza et al. evaluated the effect of antioxidant
properties aqueous and ethanol green tea extracts at 200, 500 and 1000
mg/L on the sunflower stability in the rancimat test. They stated oil
samples containing green tea ethanolic extracts at 1000 mg/L during 6.45
h induction period had the longest oxidative stability (Gramza et al.,
2006).