| Summary: | 碩士 === 國立嘉義大學 === 食品科學系研究所 === 101 === The purpose of this study was to investigate the antioxidative activity and antioxidative components (including phenolics content and flavonoids content) of waste lemon peels (Citrus limon) extracts with different solvent extractions. Results showed that the optimal extraction conditions of lemon peels were: solvent ratio of 15/1 (v/w), extraction temperature of 40℃ and extraction time of 60 min. The order of extraction yield was methanol > water > ethanol. In this study, the extracts of different groups including lemon peels methanol extract (ME), lemon peels ethanol extract (EE), lemon peels water extract (WE) and the acidification lemon peels methanol extract (AcME) were used for the analysis of antioxidative activity. The ME had the hightest total phenolics content and the total flavonoids content which was 70.52 ± 0.77 GAE mg/g dm and 65.51 ± 0.08 QE mg/g dm, respectively. On the other hand, when the sample concentration was at 2000 ppm, the AcME showed the highest antioxidative activity. The reducing power, trolox equivalent antioxidant capacity and ferric reducing antioxidant power of AcME was OD700nm = 2.64, 58.96% and OD593nm = 1.114, respectively. The DPPH radical scavenging activity of AcME was similar to BHA at 500 ppm, but the ferrous ion chelating capacity was lower than that of EE. The lemon peels were rich in antioxidative components. Nevertheless, when lemon peels treated with heating and acidification then extraction by methanol, the highest antioxidative activity of extract was found. Therefore, AcME may be used as a natural antioxidants. The major phenolics compounds of lemon peels extract were hesperetin, naringin, p-coumaric acid and ferulic acid. Moreover, the major polymethoxylflavones of lemon peels extracts were nobiletin, sinensetin and tangeretin. Lemon peels treated with acidification indeed could increase the content of 5-OH nobiletin. In addition, the AcME was added in soybean oils with different concentrations, and store at room temperature for six months. This test was investigated the feasibility of AcME as a natural antioxidants. The oxidation stability of oils was determined by acid value (AV), peroxide value (POV), carbonyl value (CV), dielectric constant, color value and fatty acid compositions. Results showed that the AcME (2000 ppm) group has a good oxidation stability. The antioxidative activity of AcME (2000 ppm) group was similar to BHA at 200 ppm. Therefore, this study suggested that AcME may be used as a natural antioxidant added in edible oils.
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