The adsorption and desorption of phytochemicalfrom lemon peel extract by the graphene oxide and its application as antioxidant in frying oil

In this study, the graphene oxide was used as adsorbent for the separation (adsorption and desorption) of flavonoids from lemon peel. Properties of desorption extract (total phenolic content, total flavonoid content, scavenging ability of DPPH free radicals) were determined. Antioxidant activity of desorption extract at three levels of 250, 500 and 1000 ppm and BHT synthetic antioxidant at 200 ppm in antioxidant-free frying oil were evaluated by measuring peroxide value, thiobarbituric acid test, conjugated DN and color index. Each gram of lemon peel extract contained 19767.20 μg phenolic compounds and 33.552 μg flavonoids on dry matter. Each gram of desorption extract contained 5861.56 μg phenolic compounds and 3.446 μg flavonoids on dry matter. Peroxide value, thiobarbituric acid, conjugated DN and color index of oil increased with increasing heating time and the highest increase was observed in the control treatment without antioxidants. Treatments containing desorption extract at 500 and 1000 ppm, can compete with BHT antioxidant. The results of this study indicated that desorption extract can be used as a replacement for synthetic antioxidants in oil.