The Research Of Liquid State Process Of Lard

Lard is a kind of abundant aniamal fat resources.It is welcomed for the peculiar odour while the melting point is too high to be solid at room temperature.The oil which can keep the smell of lard as well as can be used as the vegetable oil is expected by the consumers. In this paper,the effect of different influencing factors to the process of dry fractionation was researched.Meanwhile,the process was Optimized.The crystallization properties and the technology of the dry fractionation shorten was studied. The enzyme of Lipozyme TL I was used to perpare the liquid state lard in the paper.The banlance temperature,crystallization temperature,cooling rate and the crystal growing time were studied in the paper by single factor and orthogonal test.The optimum conditions of first-step dry fractionation were banlance temperature 70℃,crystallizaiton temperature 21℃,cooling rate 2℃/h,growing time 14h.The optimum conditons of second-step dry fraction were banlance temperature 60℃, crystallization temperature 16℃,cooling rate 0.5℃/h,growing time 30h. The test showed that the yield of first-step olein was 81.59% and the second-step olein can be 87.5%.The yeild of the first-step olein could be 87.5%,the lowest melting point was 22.3℃.The second-step olein can be 79.93%,the melting point was 11.5℃. Olein fraction by second dry fractionation can be in liquid state at 15℃for 24h.It was clear and smell good.Other Fctors to the dry fractionation were studied,such as mixing manners,cooling way.As the result of the experiment,the dealing way of striing was better than high speed shearing.The meltting point of the former was 21.9℃while the latter was 27.9℃.In addition.the slow cooling way was better than fast cooling way.The crystallization, thermal, physical, structural,chemical properties of the product of dry fractionation, including the raw material lard,first-step olein,first-step stearin,second-step olein,second-step stearin were investigated using differential scanningcalorimetry(DSC),pulsed nuclear magnetic resonance (NMR), Texture Analyser(TPA) and gas chromatography (GC). The lard was fractionated into various stearin and olein fractions by means of a dry fractionation process. On the basis of the SFC result,the SFC of the first-step stearin was 59.24% at 10℃. While the SFC of the raw material lard, second-step stearin, first-step olein and second-step olein was 41.73%,32.32%,29.48% and 11.13%.Then the SFC of the second-step olein was 0.67%,0 at 25℃.The physical properties of fractions, such as slip melting point, iodine values,cloud point,and solid fat content were dependent on the crystallization temperatures,cooling rate and growing time.The orders of the hardness and gumminess of the samples was first-step stearin> raw material lard>second-step stearin>first-step olein> second-step olein. Particularly,the SFC of first-step stearin and second-step stearin decreased linearity as the increased of temperature which can be explained for the varieties of the triglycerides in the stearins were sole.As the result of fatty acid analysis,the fatty acid of C20:1 could not be detected in the two kinds of oleins.There were not the fatty acid of C18:3,C20:0 and C20:l.The content of unsaturated fatty acid was higher in the oleins than in the stearins and there was the highest unsaturated fatty acid content in the second-step olein.The thermal properties of the samples were studied.The cooling curve and the melting curve were getted and the relation of the heat flow and the temperature was studied by the method of DSC.The result of the analysis of colour showed that the second-step olein was most bright.The technology of the dry fractionation shorten was studied.There were three kinds of phases cooling technologies. Generally,The period was reduced from 30 h-50h to 15 h.The yield of the olein can be 56.90% and the meltting point was 12.0℃.The enzyme of Lipozyme TL IM was used to peipare the liquid state lard. The enzymeload,organicsolvent, substrateratio, reaction time and reaction temperature were studied. The results showed that the optimum conditions were as follows:Hexane was the reaction medium; enzyme load was 15%(Wt% of substrates); mole ratio of substrateswas1:2 (lard:caprylicacid);reaction time was 24h and the reaction temperature were 55℃.The lowest melting point of the product can be 11.5℃.Therefore,the feasibility of the method and the edible quality should be researched in the future studies.