Lipase Catalyzed Synthesis Of Fatty Acidstarch Esters From Vegetable Oil And Starch

Starch is a reproducible high polymer resource that is ubiquitous in life and has great biodegradability.However,there are a lot of disadvantage for the natural starch,such as processing difficulties,poor hydrophilic,poor mechanical properties and the tendency to form a gel.Natural starch can be modified by biological,chemical and physical methods,and the economic and practical value of natural starch can be improved by this process.Modified starch can be applied in various fields.Medium long chain fatty acid starch ester is a kind of modified starch with very special thermoplastic,emulsifying,hydrophobic and biodegradable.Medium long chain fatty acid starch ester was widely used in food,cosmetics,medicine,textile and other industries.In this study,by using commercially available vegetable oil and corn starch as raw materials natural pollution-free fatty acid starch ester was synthesized by Novozym435 lipase catalytic reaction.The pretreatment of corn starch with sodium hydroxide and urea mixed solution greatly improved the chemical reactivity of corn starch and vegetable oil,and the catalytic reaction conditions of lipase were optimized.The optimum conditions for fatty acid starch ester were obtained.The pretreated corn starch and synthetic fatty acid starch esters were analyzed by infrared spectroscopy and gas chromatography.The vegetable oil and the pretreated corn starch were used as the reaction substrates,and the lipase was used to catalyze synthesis of the vegetable oil corn starch ester in the microwave assisted and traditional heating respectively.The effects of reaction time,reaction temperature,the amount of vegetable oil,the reaction speed and the microwave power on the transesteriication reaction were investigated.The effects of reaction time,reaction temperature,vegetable oil addition amount,stirring rate and microwave power on the transesteriication reaction were investigated.On the basis of single factor,the optimum reaction conditions for traditional heating were as follows:reaction temperature 65? reaction time 20 h,vegetable oil addition amount 20 g,stirring rate 200 r·min^-1,degree of substitution was up to 0.0334;The optimum reaction conditions for microwave assisted heating were as follows:the reaction temperature was 60 ?,the reaction time was 3h,the dosage of vegetable oil was 20g,the microwave power was 240w,and the degree of substitution was 0.0362.Pretreated salt and salt mixture were placed in desiccator and set aside.Reaction system was pre-balanced for 5-7 days in desiccator and then put into microwave reactor to react.After reaction,10 mL 95%ethanol was added into reaction system to precipitate corn strach fatty acid ester and 65 ? ethanol was used to remove unreacted oil.Reaction system was dried at 70? to constant weight.And 80 mesh sieve was used to removed immobilized Novozym 435 lipase.The experimental results showed that the highest substitution degree of corn starch ester was 0.0413 when water activity?aw?was 0.57.