The Research Of Aqueous Enzymatic Extraction Of Walnut Oil And Enrichment Of Polyunsaturated Fatty Acid

For the issues of few profound processing products and low value-added of Xinjiang walnut, extractwalnut oil usually by pressing, walnut meal can’t be fully utilized because of protein denaturation, a systemof aqueous enzymatic used in extraction of walnut oil and aolecular distillation used in enrichmentpolyunsaturated fatty acids of walnut oil was studied in the present paper. There are different steps of oilextraction on different oil seeds, and this paper studied appropriate process route of aqueous enzymaticmethod for walnut. Pretreatment-parameters, enzymatic-parameters, quality of oil, condition ofdemulsification, ethyl ester-parameters of molecular distillation process were studied at the same time.Conclusions including five parts are as follows:（1）Pre-treatment technology which impacted aqueous enzymatic method used in extraction ofwalnut oil was studied in this paper. Based on the results of single-factor tests, adopted the software design（by Design-Expert7.1.6Trial）response surface optimization experiment. The optimal process parameterswere determined: thermal annealing time was19min, temperature controlled by53℃, pulping time was8min, in this case, the rate of walnut oil extraction was54.83%.（2）The influence of some factors（single-enzyme, double-enzymes, binary-enzymes a andbinary-enzymes b） on extraction ratio of walnut oil were studied. The extraction rates were62.66%,67.89%,62.74%,62.70%. Based on the results of single-factor tests, adopted the software design（byDesign-Expert7.1.6Trial）response surface optimization experiment, the optimal process parameters weredetermined: enzymolysis temperature was60℃, amount of enzymewas3.5%(the amount of cellulase was70U/g, the amount of papain was3360U/g), rate of soild to liquid was1:8, enzyme digestion time was4h,in this case, the rate of walnut oil extraction was76.91%.（3）The effects of demulsification process were studied. This paper, with orthogonality designing theexperiment and finding the parameters through optimizing method as well, the sequence of every factor forthe rate of walnut oil extraction was: ultracentrifugation speed>ultracentrifugation time>pH. The optimumprocess parameters of demulsification were determined: ultracentrifugation speed was12000r/min,ultracentrifugation time was25min, pH was4.5. In this case, the rate of walnut oil extraction was84.01%,residual oil rate was6.92%. We got the walnut oil which the rate of refining was97.84%from the oil whichwas deacidified. And this paper also determined the physical and chemical characteristics of walnut oil.（4）Pre-treatment technology（esterification of walnut）of concentrated poly-unsaturated fatty acidswas studied. With orthogonality designing the experiment, we found the parameters through optimizingmethod as well. The sequence of every factor for the rate of walnut oil extraction was: reaction temperature>catalyst concentration>alcohol-oil ratio>reaction time. The optimum process parameters of esterificationwere determined: reaction temperature was75℃，reaction time was150min, alcohol-oil ratio was8:1,concentration of catalyst was0.8%, in this case, commutative law of ester was94.74%.（5）In this paper, molecular distillation was studied. Based on the results of single-factor tests,adopted the software design（by Design-Expert7.1.6Trial）, response surface optimization experiment. Theprocess parameters were determined: operating pressure was3Pa, distillation temperature was109℃,scraper speed was380r/min. In this case, PUFAs content was92.87%.