酶法催化制备含有中链及中长链脂肪酸的甘油二酯及性质表征

Enzymatic preparation and characterization of medium chain diacylglycerols and medium-and long-chain diacylglycerols

采用富含棕榈酸和硬脂酸的分子蒸馏单甘酯(MAG)和癸酸为原料,以Novozyme 435酶为催化剂,通过酯化反应制备富含中链脂肪酸及中长链脂肪酸的甘油二酯(DAG)(含有中链脂肪酸甘油二酯(MCD)和中长链脂肪酸甘油二酯(MLCD))。通过单因素试验探究了底物摩尔比(癸酸与MAG摩尔比)、反应温度、反应时间、加酶量对产品中DAG含量的影响,利用气相色谱仪(GC)、差示扫描量热仪(DSC)、脉冲核磁共振仪(p-NMR)、X-射线衍射仪(XRD)和偏振光显微镜(PLM)分析手段,研究DAG产品的脂肪酸与甘油酯组成、热力学性质、固体脂肪含量、结晶特性等。最终所选工艺条件为:底物摩尔比1∶1,反应温度65℃,反应时间35 min,加酶量5%。在所选择的工艺条件下,DAG含量为(37.3±0.1)%,其中MCD含量和MLCD含量分别为(7.28±0.1)%和(30.02±0.1)%,DAG和甘油三酯(TAG)的含量比为9.8∶1;固体脂肪含量表明产品具有一定的可塑性,通过晶型和晶体微观形态分析,DAG主要为β晶型。研究结果可为后续相关产品的开发提供基础理论依据。

Medium chain diacylglycerols （MCD） and medium- and long- chain diacylglycerols （MLCD） were prepared via the enzymatic esterification of molecular distillated monoacylglycerols （MAG） rich in palmitic acid and stearic acid and capric acid catalyzed by Novozyme 435. The effects of substrate molar ratio, reaction temperature, reaction time and enzyme dosage on the content of DAG inthe product were studied by single factor experiment, and the obtained DAG were charact- erized by differential scanning calorimeter （DSC）, pulsed nuclear magnetic resonance （p - NMR）, X -ray diffractometer （XRD） and polarized light microscope （PLM） to study its compositions of fatty acids and glyceride, thermodynamics proper- ties, solid fat content and crystallization property.The results showed that the optimal conditions were obtained as follows： molar ratio of capric acid to MAG 1： 1, enzyme dosage 5%, reaction temperature 65 ℃ and reaction time 35 min. Under these condi- tions, the content of DAG was （37.3 ± 0. 1 ） %, which consisted of （7.28 ±0. 1 ） % of MCD and （30. 02 ±0.1）% of MLCD, and the content ratio of DAG to TAG was 9.8：1 in the crude products. Sol- id fat content profiles demonstrated that the products had potential use in plastic fats after purification. XRD spectra reflected that β form was the dominant crystal form in the final system. The results could provide theoretical basis for the development of further products.