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 本研究的主要目的是测定马齿苋（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、二丁基羟基甲苯BHT）与天然抗氧化剂（马齿苋提取物）的大豆油的氧化稳定性及植物化学成分保留率。本研究设置四组处理：纯大豆油（SO）、添加100 mg/kg TBHQ的大豆油（TBHQ组）、添加100 mg/kg BHT的大豆油（BHT组）以及添加100 mg/kg提取物的大豆油（提取物组），所有样品均在180℃条件下进行5小时的热氧化处理。该提取物的总酚类化合物含量为99.5 mg没食子酸当量（EAG）/100 g；在1,1-二苯基-2-苦基肼自由基（DPPH）清除法、β-胡萝卜素/亚油酸体系以及铁还原抗氧化能力（FRAP）法三种检测体系中，其抗氧化活性分别为84.6、35.5及1.8 μM Trolox/100 g。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。经热氧化处理后，TBHQ组与提取物组的生育酚与植物甾醇保留率更高，分别可达88%与87%以上。纯大豆油组与提取物组的多不饱和脂肪酸保留率相近。浓度为100 mg/kg的马齿苋提取物可减轻大豆油经热氧化后发生的品质劣变，可作为合成抗氧化剂的天然替代品。