Hamam Fayez, Shahidi Fereidoon
Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3X9.
J Agric Food Chem. 2006 Jun 14;54(12):4390-6. doi: 10.1021/jf052540r.
The ability of different lipases to incorporate omega3 fatty acids, namely, eicosapentaenoic acid (EPA, C20:5n-3), docosapentaenoic acid (DPA, C22:5n-3), and docosahexaenoic acid (DHA, C22:6n-3), into a high-laurate canola oil, known as Laurical 35, was studied. Lipases from Mucor miehei (Lipozyme-IM), Pseudomonas sp. (PS-30), and Candida rugosa (AY-30) catalyzed optimum incorporation of EPA, DPA, and DHA into Laurical 35, respectively. Other lipases used were Candida anatrctica (Novozyme-435) and Aspergillus niger (AP-12). Response surface methodology (RSM) was used to obtain a maximum incorporation of EPA, DPA, and DHA into high-laurate canola oil. The process variables studied were the amount of enzyme (2-6%), reaction temperature (35-55 degrees C), and incubation time (12-36 h). The amount of water added and mole ratio of substrates (oil to n-3 fatty acids) were kept at 2% and 1:3, respectively. The maximum incorporation of EPA (62.2%) into Laurical 35 was predicted at 4.36% of enzyme load and 43.2 degrees C over 23.9 h. Under optimum conditions (5.41% enzyme; 38.7 degrees C; 33.5 h), the incorporation of DPA into high-laurate canola oil was 50.8%. The corresponding maximum incorporation of DHA (34.1%) into Laurical 35 was obtained using 5.25% enzyme, at 43.7 degrees C, over 44.7 h. Thus, the number of double bonds and the chain length of fatty acids had a marked effect on the incorporation omega3 fatty acids into Laurical 35. EPA and DHA were mainly esterified to the sn-1,3 positions of the modified oils, whereas DPA was randomly distributed over the three positions of the triacylglycerol molecules. Meanwhile, lauric acid remained esterified mainly to the sn-1 and sn-3 positions of the modified oils. Enzymatically modified Laurical 35 with EPA, DPA, or DHA had higher conjugated diene (CD) and thiobarbituric acid reactive substance (TBARS) values than their unmodified counterpart. Thus, enzymatically modified oils were more susceptible to oxidation than their unmodified counterparts, when both CD and TBARS values were considered.
研究了不同脂肪酶将ω-3脂肪酸，即二十碳五烯酸（EPA，C20:5n-3）、二十二碳五烯酸（DPA，C22:5n-3）和二十二碳六烯酸（DHA，C22:6n-3），掺入一种名为Laurical 35的高月桂酸油菜籽油中的能力。来自米黑根毛霉（Lipozyme-IM）、假单胞菌属（PS-30）和皱褶假丝酵母（AY-30）的脂肪酶分别催化EPA、DPA和DHA最佳掺入Laurical 35中。使用的其他脂肪酶是南极假丝酵母（Novozyme-435）和黑曲霉（AP-12）。采用响应面法（RSM）以实现EPA、DPA和DHA最大程度地掺入高月桂酸油菜籽油中。研究的工艺变量包括酶量（2%-6%）、反应温度（35-55℃）和孵育时间（12-36小时）。添加的水量和底物摩尔比（油与n-3脂肪酸）分别保持在2%和1:3。预测在酶负载量为4.36%、43.2℃下反应23.9小时时，EPA掺入Laurical 35的最大量为62.2%。在最佳条件下（酶量5.41%；38.7℃；33.5小时），DPA掺入高月桂酸油菜籽油中的量为50.8%。在酶量5.25%、43.7℃下反应44.7小时时，DHA掺入Laurical 35的相应最大量为34.1%。因此，脂肪酸的双键数量和链长对ω-3脂肪酸掺入Laurical 35有显著影响。EPA和DHA主要酯化为改性油的sn-1,3位，而DPA随机分布在三酰甘油分子的三个位置上。同时，月桂酸主要仍酯化为改性油的sn-1和sn-3位。用EPA、DPA或DHA酶法改性的Laurical 35的共轭二烯（CD）值和硫代巴比妥酸反应性物质（TBARS）值高于未改性的对应物。因此，当同时考虑CD和TBARS值时，酶法改性油比未改性油更易氧化。
