Phytochemical characterization of soybean oil with addition of Portulaca oleracea L. extract

ABSTRACT The main objective of the present work was to measure the total phenolic compound content and antioxidant activity of Portulaca oleracea L. extract, besides evaluating the oxidative stability and phytochemical compound retention present in soybean oil plus synthetic (TBHQ and BHT) and natural (Portulaca oleracea L. extract) antioxidants. The treatments soybean oil (SO), soybean oil plus 100 mg/kg TBHQ (TBHQ), soybean oil plus 100 mg/kg BHT (BHT), and soybean oil plus 100 mg/kg extract (Extract) were subjected to thermo-oxidation at 180 ºC/5 h. The extract presented 99.5 mg EAG/100 g of total phenolic compounds and 84.6, 35.5, and 1.8µM Trolox/100 g of antioxidant activity to DPPH, β-carotene/linoleic acid system, and FRAP, respectively. The oxidative stability for the Extract treatment was inferior to TBHQ, which showed the longest induction period (7.6 h). After heating, TBHQ and Extract treatments presented higher capacity of tocopherol and phytosterol retention, reaching values over 88 and 87%, respectively. Similar percentages of polyunsaturated fatty acids were found in SO and Extract treatments. The purslane extract in the 100 mg/kg concentration reduced the alterations suffered by soybean oil after heating and it can be used as a natural substitute for synthetic antioxidants.

摘要 本研究的核心目标为测定马齿苋（Portulaca oleracea L.）提取物的总酚类化合物含量与抗氧化活性，同时评估添加合成抗氧化剂特丁基对苯二酚（TBHQ）、二叔丁基对甲酚（BHT）及天然抗氧化剂马齿苋提取物的大豆油的氧化稳定性与植物化学物保留率。实验设置4组处理：大豆油（SO）组、添加100mg/kg TBHQ的大豆油（TBHQ组）、添加100mg/kg BHT的大豆油（BHT组）以及添加100mg/kg提取物的大豆油（提取物组），所有组别均于180℃下热氧化5小时。该提取物的总酚类化合物含量为99.5mg没食子酸当量（EAG）/100g，针对1,1-二苯基-2-三硝基苯肼（DPPH）、β-胡萝卜素/亚油酸体系以及铁还原抗氧化能力法（FRAP）的抗氧化活性分别为84.6、35.5及1.8μM Trolox/100g。提取物组的氧化稳定性劣于TBHQ组，后者的诱导期最长，达7.6小时。加热处理后，TBHQ组与提取物组的生育酚及植物甾醇保留能力更强，保留率分别超过88%与87%。大豆油组与提取物组的多不饱和脂肪酸占比相近。浓度为100mg/kg的马齿苋提取物可减轻大豆油经加热后发生的品质劣变，可作为合成抗氧化剂的天然替代物。