Study On The Aqueous Enzymatic Extraction Technology Of "Double-low" Rapeseed Oil

Aqueous enzymatic extraction, a new and easy oil processing technology, has brought more and more people's attention due to mild extraction condition, non-use of organic solvents, and high quality. The final oil product with aqueous enzymatic extraction is a good food resource with non-toxic, low-denatured, and high biologic value. But this method has some issues because of complex processes, cost of enzymes, and so on. To optimize the aqueous enzymatic extraction, this thesis studied the selection of enzymes and the effect to oil yield of different pre-treatment methods in aqueous enzymatic extraction technology of rapeseed oil. The study results provide the theoretic basis for the application of aqueous enzymatic extraction of rapeseed oil.1. The pre-treatment of "double-low" rapeseed has a significant impact on oil yield. Comparing dry-heat and wet-heat process, with 120℃,2h for dry-heat and 110℃,10min for wet-heat,110℃, 10min. The result shows that the wet-heat is better than the dry-heat. Rapeseed treated with the wet-heat process requires less mechanical lapping time and has low emulsification rate, higher oil yield, and better oil flavor. After determining the pre-treatment method,3 factors, treatment temperature, treatment time, and grinding times, were selected to do a L9(34) orthogonal test. The result showed that the optimal conditions were 111℃as treatment temperature,10min as treatment time, and 6 times of grinding. The orthogonal experiment shows the primary factor to the secondary:grind times> temperature>time. With this optimal condition, the oil yield rate can be up to 84.83%.2. It was screened different types of enzymes, including cellulose, pectinase, neutral protease, and extracted enzyme (complex enzyme), used in the process of aqueous enzymatic extraction of rapeseed oil in the study. The results show that neutral protease has the highest oil extraction rate 83.51%, followed by cellulose with 80.3%. Based on the results, combinations of enzymes were also studied. The study indicates that the combination with neutral protease and cellulose has the best result with the oil extraction rate up to 83.91%. The oil extraction rate is increased by 0.4%, compared to using neutral protease alone. Due to cost considerations, neutral protease alone was selected for the enzyme kinetics study, which shows that the optimum condition is with temperature 50℃, pH 7.5,4 hours, enzyme usage 1.0‰, and substance concentration 1:4 (substance to water ratio). Under such a condition, the rapeseed oil extraction rate is up to 85%.3. Base on the kinetics of the enzyme, considering the impact of various factors to the oil extraction rate, temperature, time, substance to water ratio, and enzyme concentration were selected for a single-factorial experiment. The orthogonal experiment result shows that temperature and enzyme concentration have significant impact on oil production; substance to water ration has a relative impact, while time has no significant impact. Under the optimum condition of temperature 50℃, time 3.5-4h, substance to water ratio 1:4, and enzyme concentration 1.2%o, the oil yield can be up to 90.39%.4. The study of the quality of "double-low" rapeseed oil extracted by aqueous enzymatic method shows that there is a little change to the inherent properties of the rapeseed oil. For instance, iodine is 106.2g/100g, acid value 1.06mgKOH/g, peroxide 0.817mmol/kg, and saponification value 186.46mgKOH/g. These numbers indicate that the quality of rapeseed oil with aqueous enzymatic extraction is similar to that of the oil extracted by lixiviation process.