ABSTRACT
In this study, sunflower, corn, peanut and hazelnut oils were investigated according to their oxidative stability and antioxidant activity parameters. The related vegetable oils were treated with gallic acid, rutin and carotenoid. Olive leaf extract having a large variety of phytochemical was also valorized. After the leaf samples were extracted through a homogenizer, they were added into the vegetable oils, respectively. Moreover, synthetic antioxidants were also dissolved into the oils for control reasons. Stability of the vegetable oils against the oxidation was evaluated via Rancimat by measuring induction time. The quality parameters of treated and untreated oil samples were compared depending on phenolic and carotenoid contents, antioxidant activity and induction time.
ABSTRACT
Sideritis montana L. endemic of Turkey was screened for its polyphenols content and antioxidant activity. Factor analysis and experimental design have been applied to understand the structure of the separation process, to determine the effective parameters, and to accomplish the performance improvement. Face-centred composite design (FCD) of response surface methodology (RSM) was applied to evaluate the influences of solvent concentration, solvent amount, extraction time, and stirring speed of homogenizer-assisted extraction (HAE) as well as to model and to optimize the HAE. Quadratic models were highly significant (pâ¯<â¯0.0001) for the responses studied with high coefficients of determination (R2) of 0.9440, 0.9415 and 0.9521. The result of the study suggests that 15.02â¯mL of 22.69% EtOH solution (v/v), 70.16â¯s, and 9524.52â¯rpm of mixing speed are the optimal conditions to obtain the highest yield of total polyphenols (TPC) and flavonoids (TFC), and the best antioxidant activity (AA). Rosmarinic acid was identified as the most abundant component.
