| Medium-and long-chain triglycerides (MLCT) comprised of both medium-chain fattyacids (MCFA) and long-chain fatty acids (LCFA) in the same glycerol backbone werewidely used in clinical nutrition support, infant foods and low-calorie foods. Bothenzymatic and chemical catalyst were used for the esterification MCFA and LCFA withglycerol for the preparations of MLCT, the influence of different factors towards TG yield,esterification degree (ED) and residual fatty acids content were studied in the esterificationprocess for the production of MLCT. Through the process, the optimum reaction conditionsof the production of MLCT were obtained finally.The catalysis effect of five commercial lipases were studied in solvent-free system,Novozyme435and Lipozyme RM IM had relative higher of catalysis activity than threeother lipases of Lipase A “Amanoâ€6, Lipozyme TL IM, Porcine Pancreas lipase whichwerenot fit for using in this system. The recycle of Novozyme435and Lipozyme RM IMwere also studied and these two lipases had the same catalysis activity. Due to the relativelong reaction time of Lipozyme RM IM-catalyzed esterification for the production ofMLCT which was3times longer than that of Novozym435and too many papers publishedby foreign scholar, so the research of Novozym435-catalyzed esterification for thesysthesis of MLCT in this paper was further carried out. The optimum conditions ofone-factor and response surface methodology study of Novozym435were as follows:reaction temperature90oC,4.0wt%enzyme load (relative to the weight of total substrates),substrate molar ratio (fatty acids/glycerol) of3.0:1,12.37h, agitation rate of120r/min,MLCF and LCFA molar ratio of1.1:1and water content of0.75%. Under the optimumconditions, the yield of TG, MLCT, and the residual FFA content were93.54%,72.19%,and4.21%, respectively. After the produre of separation and purification, the yield of TG,MLCT, and the residual FFA content were97.44%,77.11%, and0.21%, respectively.TheMLCT content (77%) of the product was similar to that (75%) of FE73403(Pharmacia AB,Sweden), which was broadly used in parenteral or enteral nutrition support. The content ofcaprylic acid, capric acid, and long-chain fatty acids of TG were24%,10%, and66%,respectively. The thermodynamics study was also carried out in this paper and good linearrelationship between lnV0and1/T was obtained (R2=0.988). The value of Eacalculatedaccording to the Arrhenius law was slightly lower than other Eavalues reported bylipase-catalyzed esterification process and this indicted the reaction happened easily.The absorption peak of crystallization of purification product was relative single andwide temperature range detected by DSC, which indicted the triglycerides content of thesimilar crystal in the product was relative high and their had good compatibility. Theabsorption peak of melt in the purification product was relative broad and complex, whichhad one big peak and a little of impure peaks, this may be caused by the rapid melting oflow melt point triglycerides and residual fatty acids.The optimum conditions of chemical catalyst-catalyzed esterification for the syntheisiof MLCT through one-factor study as follows: reaction temperature150oC,0.4wt%enzymeload (relative to the weight of total substrates), substrate molar ratio (fatty acids/glycerol) of3.0:1,60min, agitation rate of800r/min, MLCF and LCFA molar ratio of1.11:1. Underabove-mentioned conditions, the yield of TG was almost90%, and after the purificationprocess, the yield of TG was up to96%and the content of caprylic acid, capric acid, andlong-chain fatty acids of TG were24%,11%, and65%, respectively, which was similar tothat of FE73403(Pharmacia AB, Sweden), which was broadly used in parenteral or enteralnutrition support. |
