Study On Enzymatic Interesterification Of Lard And Rape Oil And Fatliquoring Performance Of Its Oxidized-Sulfited Products

In order to solve the oil spot problem of lard fatliquor throughly, the raw oil with similar freezing point and iodine value compared with natural neat’s foot oil was synthesized through enzymatic interesterification of lard and diverse source rape oil. Meanwhile, with the new oil material oxidized-sulfited, the reaction rules of oxidation-sulfitation and fatliquoring performance of its products were studied emphatically. The study widened the application of lard in fatliquor and developed a new leather-used raw oil with potential application prospect. The contents and results of the study were stated below:The appropriate reactive conditions in enzymatic interesterification of lard and rape oil were optimized by single factor experiment method and orthogonal experiment method in which the solid fat content and freezing point of product were used as indexes. The results showed that mass ratio of reactants was 50:50, time was 4h, dosage of lipase Lipozyme TILM was 4%, temperature was 90℃, and compared with natural neat’s foot oil, the raw oil with similar freezing point and iodine value was synthesized and the solid fat content, freezing point and iodine value of the product were zero,4℃ and 79, respectively.The oxidation reaction rules of enzymatic interesterification oil were studied by experiments in which the rising rate and the maximum of peroxide value (POV) were used as indexes. The results showed that the rising rate and the maximum of POV increased within the range of 80-90℃, and they remained the same within the range of 90-95℃; with the dosage of self-restraint supported organic catalyst increasing, the rising rate of POV increased and the maximum remained the same; with ventilation quantity changing from 0.5L/min to 1.0L/min and 1.5L/min gradually, the rising rate of POV increased first and decreased later, and the maximum remained the same; with the holes in air distributor increasing from single-hole to multiple-holes, the experiments showed that the rising rate of POV increased and the maximum remained the same; Within the oxidation time range of 0-6h, acid value, carbonyl value and viscosity of oxidized oil increased slightly, and after 6h they increased significantly; with the time increasing, refractive index of oxidized oil kept on increasing steadily. Compared with mixed lard and rape oil, the POV of enzymatic interesterification of lard and rape oil was always higher in the oxidation process. The FT-IR study for oxidized oil showed that the oxidized oil had chemical group-OOH in 3466cm-1, which verified the oxidation mechanism.The appropriate sulfitation conditions were optimized by single factor experiment method in which the transparent time during the process of sulfitation, the content of combinative sulfonate, the reaction rate of sodium pyrosulfite, the appearance of products, the emulsion stability of products 1:9 were used as indexes. The results showed that the dosage of OS-15 was 3%, the dosage of sodium pyrosulfite was 6%, the temperature was 75℃, the time was 4h. The effects of oxidized oil POV on products were analysed in which the indexes mentioned above, the content of remaining sodium pyrosulfite and average emulsion particle diameter of the products were used as indexes. The results showed that with the rising oxidized oil POV of 250-450mmol/kg, the transparent time during the process of sulfitation shortened to around 90min, the content of combinative sulfonate rised to 3.38%, the reaction rate of sodium pyrosulfite increased to 91.94%, the content of remaining sodium pyrosulfite decreased to 1.90mgSO2/g, the appearance of products changed from turbidity to transparency; meanwhile, with the rising POV of oxidized oil, average emulsion particle diameter of products reduced from 93.92nm to 82.66nm in turn. In addition, the static emulsion stability of products was also studied from micromechanism perspective. The results showed that with the rising POV of oxidized oil, the static emulsion stability of products was better. Compared with oxidized-sulfited enzymatic interesterification oil, oxidized-sulfited mixed oil and its emulsion was unstable, and showed lower content of combinative sulfonate of 3.10%, lower reaction rate of sodium pyrosulfite of 85.05%, and higher content of remaining sodium pyrosulfite of 3.59mgSO2/g. At last, The FT-IR study for sulfited oil showed that the sulfited product had characteristic peak of sulfonate in 3466cm-1, which verified the sulfition mechanism.The products with different POV were applied in leather fatliquoring of shaved bovine wet blues. According to the study on the rate of emulsion absorption and cleaning rate during the process of fatliquoring, oil section distribution of fatliquoring leather, sense properties of fatliquoring leather, air permeability, static water absorption, physical and mechanical properties and SEM, the results indicated that with rising POV, fatliquoring leather had better rate of emulsion absorption and cleaning rate, oil section distribution, sense properties, air permeability, static water absorption, physical and mechanical properties and fiber dispersion. The fatliquoring experiment for oxidized-sulfited enzymatic interesterification oil and oxidized-sulfited mixed oil showed that the former had better comprehensive fatliquoring performance than the latter. In addition, fatliquoring leather of the former had no oil spots as time goes by.