酶促酯交换制备富含植物甾醇酯与甘油二酯食用油Preparation of edible oil rich in phytosterol esters and diacylglycerol by enzymatic transesterification

旨在为新型功能油脂的制备提供参考，以植物甾醇和大豆油为原料，采用“一步法”酶促酯交换反应制备富含植物甾醇酯与甘油二酯（DAG）的食用油。以植物甾醇转化率为指标，在筛选脂肪酶及溶剂基础上，对反应条件进行优化，并对产物的组成、理化指标及产物中植物甾醇酯和DAG脂肪酸组成进行测定。结果表明：脂肪酶AK “Amano”在酶促酯交换反应中表现出最高的反应活性，适宜的反应溶剂为正己烷；酶促酯交换的最佳条件为植物甾醇与大豆油物质的量比1∶ 2、脂肪酶添加量12%（以植物甾醇与大豆油的总质量计）、植物甾醇浓度100 mmol/L、反应物水分活度0.529、反应温度50 ℃、反应时间24 h，在此条件下植物甾醇转化率为54.9%，产物中植物甾醇酯含量达到21.59%，DAG含量为7.84%，二者总含量达29.43%，酸值（KOH）为0.90 mg/g，过氧化值为1.84 mmol/kg，符合食用油脂的国家标准；产物中植物甾醇酯与DAG的脂肪酸组成与大豆油的脂肪酸组成高度重合。综上，可利用“一步法”酶促酯交换制备富含植物甾醇酯和DAG的食用油。 To provide reference for the preparation of novel functional oil, edible oil rich in phytosterol esters and diacylglycerol (DAG) was prepared via a one-step enzymatic transesterification process using phytosterol and soybean oil as raw materials. The conversion rate of phytosterols served as the key evaluation index, following the screening of lipases and solvents, reaction conditions were systematically optimized. The composition, physicochemical indicators of products and fatty acid composition of phytosterol esters and DAG in the products were analyzed.The results indicated that lipase AK "Amano" exhibited the highest catalytic activity for the transesterification, with n-hexane being the optimal solvent. The optimal reaction conditions were determined as follows: molar ratio of phytosterol to soybean oil 1∶ 2, lipase dosage 12% (based on the total mass of phytosterol and soybean oil), phytosterol concentration 100 mmol/L, water activity 0.529,reaction temperature 50 ℃, and reaction time 24 h. Under these conditions, the phytosterol conversion rate reached 549%. The final product contained 2159% phytosterol esters and 7.84% DAG, resulting in a combined content of 29.43%. The product exhibited an acid value of 0.90 mgKOH/g and a peroxide value of 1.84 mmol/kg, complying with national standards for edible oils. Fatty acid composition analysis revealed that the composition of the phytosterol esters and DAG in the final product closely resembled those of the original soybean oil. In conclusion, the one-step enzymatic transesterification method can be used to preparae edible oil rich in phytosterol esters and DAG.