Kinetics of the thermal degradation of phenolic compounds from achiote leaves (Bixa orellana L.) and its effect on the antioxidant activity

Abstract This work evaluates the effect of temperature and soluble solids on the degradation rate of phenolic compounds, and antioxidant activity of extracts from Bixa orellana L. leaves. The temperatures were studied in the range of typical food processes (70-90 °C) and food storage (−20-37 °C). The results showed that the thermal degradation of the phenolic compounds follows first-order kinetics, in which the degradation rate depends on the temperature, the amount of soluble solids, and the pH. The loss of antioxidant activity also follows first-order kinetics. Under different storage conditions, the half-life times of the total phenols were in the range 40.72-202.47 days, while for the antioxidant activity, the half-times were from 55.87-68.83 days for the ABTS and from 57.85-107.03 days for the FRAP method. The antioxidant activity of the extracts follows the same pattern of thermal degradation as the phenolic compounds. Therefore, we conclude that antioxidant activity is due to its phenolic compounds.

摘要 本研究评估了温度与可溶性固形物对胭脂树（Bixa orellana L.）叶片提取物中酚类化合物降解速率及抗氧化活性的影响。本次研究的温度覆盖了典型食品加工温度区间（70~90℃）与食品储藏温度区间（-20~37℃）。结果表明，酚类化合物的热降解遵循一级动力学规律，其降解速率受温度、可溶性固形物含量及pH值共同影响；抗氧化活性的损失同样符合一级动力学模型。在不同储藏条件下，总酚类物质的半衰期介于40.72~202.47天之间；而就抗氧化活性而言，2,2'-联氮-双(3-乙基苯并噻唑啉-6-磺酸)（ABTS）法测得的半衰期为55.87~68.83天，铁还原抗氧化能力（FRAP）法测得的半衰期为57.85~107.03天。该提取物的抗氧化活性与酚类化合物的热降解规律保持一致，因此本研究得出结论：该提取物的抗氧化活性源自其所含的酚类化合物。