| Natural cocoa butter is the main component of chocolate.It contains about 80% of double saturated symmetrical triglycerides,namely,1,3-dipalmitoyl-2-oleoylglycerol(POP),1-palmitoyl-2-oleoyl-3-stearoyl glycerol(POS),1,3-distearoyl-2-oleoylglycerol(SOS)and βcrystal,which gives chocolate the melting property in the mouth.However,natural cocoa butter has some problems,such as limited production,regional restrictions,and easy softening in tropical areas.Therefore,the synthesis of two kinds of structured lipids(POP and SOS)by enzymatic transesterification was studied,then POP and SOS were used as the base oil to prepare cocoa butter equivalent.The main properties of the structural esters and the prepared cocoa butter were analyzed,which was to provide a new base oil for the production of cocoa butter equivalent,and provide a research basis for the high value utilization of peanut oil with high oleic acid.Firstly,using peanut oil with high oleic acid and ethyl palmitate(self-made)as raw materials,POP was synthesized by transesterification under the catalysis of Novozym 40086.The optimal reaction conditions were obtained through a single factor experiment: the reaction time 5 h,the molar ratio of ethyl palmitate to high oleic peanut oil 9:1,the dosage of enzyme2% and the reaction temperature 50℃.On this basis,the response surface optimization was carried out,and the optimal process conditions were determined by taking POP content,acyl migration and the relative content of sn-2 oleic acid as response values: reaction time 3 h,molar ratio of ethyl palmitate to high oleic acid peanut oil 11:1,dosage of enzyme 3%(based on the total substrate mass),and reaction temperature 50℃.The content of POP was 86.48%,the acyl migration was 3.25%,and the relative content of sn-2 oleic acid was 72.88%.The crude POP product was refined by physical distillation and solvent extraction.The triglyceride content in the final product was 96.16%,the diacylglycerol content was 2.22% and the monoacylglycerol content was 1.28%,which could be used as the base oil for the next preparation of cocoa butter equivalent.Secondly,SOS was synthesized by transesterification using peanut oil with high oleic acid and ethyl stearate(self-made)as raw materials under the catalysis of Novozym 40086.The optimal reaction conditions were obtained through single factor experiment: the reaction time 7 h,the molar ratio of ethyl stearate to peanut oil with high oleic acid 9:1,the dosage of enzyme 3%(based on the total mass of substrate),and the reaction temperature 60℃.On this basis,the response surface optimization was carried out by taking SOS content,acyl shift and the relative content of sn-2 oleic acid as response values to determine the optimal process conditions: the reaction time 5 h,the molar ratio of ethyl stearate to high oleic acid peanut oil11:1,the dosage of enzyme 3.80%(based on the total mass of substrate),and the reaction temperature was 56℃.The SOS content was 85.45%,the acyl migration was 6.18%,and the relative content of sn-2 oleic acid was 78.43%.The crude SOS product was refined by physical distillation and solvent extraction.The triglyceride content in the final product was 95.92%,the diacylglycerol content was 2.32% and the monoacylglycerol content was 1.39%,which could be used as the base oil for the next preparation of cocoa butter equivalent.Finally,POP structure ester,SOS structure ester and laboratory made mixed structure ester(POP: 12.92%,POS: 47.60%,SOS: 25.68%)were the base oil,and eight kinds of cocoa butter products were prepared.By studying the properties of different content structure esters and eight kinds of cocoa butter products(CBE-1 to CBE-8),and comparing and analyzing the performance differences between similar cocoa butter products and natural cocoa butter,the following conclusions were found: the higher the content of saturated fatty acid and high melting point triglyceride in the structural ester,the higher the SFC value at the same temperature,the heat absorption peak and heat release peak will move to the high temperature region,and the crystal type will change.The structural ester POP(86.48%)had similar SFC variation trend to the middle distillate of palm oil,and could be used as the cocoa butter base oil.The structural ester SOS(85.45%)had similar crystallization melting characteristics to the extract stearin of mango kernel oil,and had the potential to be used as the cocoa butter amendment to solve the softening problem of natural cocoa butter in tropical areas.For CBE-1 to CBE-4 products,the fatty acid and triglyceride composition and the change trend of SFC were basically similar to that of natural cocoa butter,but the solid fat content was lower at 25℃(about 24%)and higher at 35℃(about 9%).The crystallization melting characteristics and crystal patterns of the four types of cocoa butter products were similar to those of natural cocoa butter,but there was a small exothermic peak at 25℃,which is related to the triglyceride with a higher melting point.In addition,compared with natural cocoa butter,CBE-5 to CBE-8showed great differences in the composition of fatty acids and triglycerides,crystallization and melting characteristics,and contained higher POP or SOS.Although the higher proportion of POP or SOS increased the solid fat content of CBE-5 to CBE-8 at 25℃(36%-45%),it was still lower than that of natural cocoa butter. |
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