The aim of this study was to investigate the antioxidant activity of Mentha pulegium leave extract that was performed by ultrasound probes and its effect on oxidative stability in soybean oil during storage. Various concentrations (300 to 800 ppm) of Mentha pulegium leave extract and TBHQ (100 ppm) were added to soybean oil and incubated at 65 ° C for 7 days. The total phenolic compounds of extracts were measured by Folin- Ciocalteu method and their antioxidant activity was performed using 1,1‐diphenyl‐2‐picryl hydrazyl (DPPH) radical scavenging (at 300 to 800 ppm) compared to TBHQ. Peroxide values (PVs) and thiobarbituric acid reacting substances (TBARS) levels were measured in each day up to day of seven in two concentrations of extracts (500 and 1000 ppm). statistical analysis showed that the highest antioxidant activity belonged to treat number 3(50 °^c,10 min) at 500 ppm, which did not show significant difference with TBHQ (p> 0.05). Also, PVs and TBARS levels in samples containing extracts were significantly lower than control sample (p <0.05). Based on the results, it can be concluded that Mentha pulegium leaf extract can be a suitable natural antioxidant as an alternative to synthetic antioxidants in the oil industry.
 

Keywords: Antioxidant, Ultrasound probes

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