| Tea plant(Camellia oleifera Abel)is our unique edible woody oil and economic crops in the south of China,which contained oil as high as 40%or more,was known as one of the four major woody oil crops with the other three(palm,olive,coconut)in the world.In recent years,due to the increasingly serious environmental pollution and enzyme cost decreasing,the aqueous enzymatic extraction process has the attracted much attention,which has advantages of simple equipment,mild conditions,good quality and so on.But the formation of emulsion in the process and the problem of demulsification difficulty restricted the further development of aqueous enzymatic extraction process,so it has not been realized industrialization.Camellia oleifera seed as the research object,firstly,this paper optimized the aqueous enzymatic extraction process and akaline demulsification process.Further,the mechanism of demulsification,the quality of oil,the oxidative stability of tea oil were studied.The specific research contents and results were as follows:First of all,with the total oil extraction rate as the study index,Pectinase NCB-PE40+cellulase AE80(2:1)was proved to be the best at broken wall effect through several broken wall enzyme screening.Its enzymolysis conditions were optimized by response surface method on the basis of single factor experiment.The results showed that under the optimized conditions(enzyme addition 1.00%,enzymolysis temperature 50?,the ratio of material and liquid 1:6,enzymolysis time 3 h,enzymolysis pH4.5),the total oil extraction rate can reach 95.13%.After digestion,macromolecule material such as free protein connected oil and water to form a large number of oil-in-water emulsion(the cream).In order to further improve the free oil yield,demulsification must be done.The principle of alkaline demulsification was to creating alkaline environment for the emulsion system so that the charges of the proteins on the surface of the oil droplet would increase and the electrostatic repulsive power among the protein molecules was enhanced and then they were easily desorbed from the surface,thus the membrane would become thin which was in favor of the protein hydrolysis and the aggregation of oil droplets,ultimately demulsification.In allusion to emulsion formed in the above method of extraction,alkaline demulsification was studied.Firstly alkaline protease Alcalase 2.4 L hydrolysis conditions were optimized according to the single factor experiment:enzyme addition 1.50%,enzymolysis temperature 60?,time 100 min,pH9.0;secondly main alkaline treatment conditions were optimized with response surface experiment:pH=9.0,temperature 60?,time 45min.Under the above optimal conditions,demulsification ratio was up to 90.15%.In order to explaining the inner mechanism of alkaline demulsification from the molecular level and the micro perspective,the change of oil drops before and after alkaline processing were observed through fluorescence microscopy:the oil droplets in the original emulsion were small and numerous,but after alkaline processing,the oil droplets turned to be large and decrease.Besides,the enzymolysis process of emulsion was also studied through laser particle size analyzer:as the enzymolysis time increased,small oil drops of the emulsion reduced and large oil drops increased gradually,the total number of oil drops decreased and the average diameter of those increased gradually.For further verifying the feasibility of alkaline demulsification and evaluating the quality of demulsified oil,the physicochemical indexs of demulsified oil and fatty acid composition were determined.The results indicated that compared with freezing-thawing and heating ways of demulsification,the alkaline demulsification had a largest influence on the peroxide value and acid value,but little influence on the other index:the peroxide and acid value of alkaline demulsified oil was the smallest;freezing-thawing secondly,heating largest;in addition,the physicochemical property and the fatty acid composition of several demulsification oil were relatively stable,thus alkaline demulsification process was feasible.In order to improve the oxidative stability and extend storage time of tea seed oil,this paper used the "the rotary unitized design principles" to optimize the antioxidants combination of TBHQ,PG and BHT.The results indicated that adding 0.02%TBHQ,0.009%PG and 0.012%BHT as multiple antioxidants,0.02%VC as synergist to the camellia oleifera seed oil could effectively inhibit oxidation,displaying a marked improving effect on antioxidation performance.In the above conditions,the period of the camellia oleifera seed oil could be prolonged from 4d to 30d in 60?,and the assurance period from 2 months to 16 months in 20?. |
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