Emulsification Mechanism of Natural Components in the Process of Aqueous Extraction of Camellia Oil and Oil Extraction Technology

Author:Yang Jian Yuan

Supervisor:yin yu long deng ze yuan


Degree Year:2019





Camellia oil is one of the four major woody edible oils in the world,and known as―eastern olive oil‖because of its high oleic acids and reasonable fatty acid composition.Camellia oil also exhibits a wide range of pharmaceutical and medical functions,such as lowering blood lipid,lowering blood pressure,softening blood vessels,antibacterial,anti-inflammatory,antioxidant,anti-tumor and enhancing human immunity.Aqueous extraction of oil from oilseeds is a novel method due to its nutrition,safety and economy,but the severe emulsification in the process of aqueous extraction of camellia oil is a barrier to its industrialized application.To explore the formation mechanism of this emulsion during aqueous extraction of camellia oil,and solve the problem of demulsification.In this study,we analyzed the main composition of emulsions formed during aqueous extraction of camellia oil.The main natural emulsifiable components in emulsions were separated,purified and identified.Moreover,the emulsions were reconstructed with the main components or their compounds,and their emulsifying properties were analyzed and compared.A novel extraction method of camellia oil by emulsified oil-frozen/thawed was investigated.The main research results are shown as follows:1.The emulsions formed during aqueous extraction of camellia oil was mainly composed of crude fat(67.83±0.55%),moisture(28.23±0.80%),protein(0.83±0.02%),polysaccharide(1.03±0.08%),tea saponin(1.26±0.05%),phospholipids(0.82 mg/g)and crude fiber(0.05±0.00%).The composition of emulsifiable solids in emulsion accounted for only 3.25%.2.The alcohol-insoluble emulsifiable crude proteins of Camellia oleifera Abel.seeds(CSEP)were obtained from the emulsion formed during aqueous extraction of camellia oil,and two major protein fractions(CSEP-A and CSEP-B)were isolated and purified from CSEP.CSEP-A was composed of seven major proteins/subunits with a molecular weight ranging from 13 to 35 kDa and a few polysaccharides.CSEP-B was a protein mixture with a molecular weight range of 13-15 kDa.At pH7.0,CSEP-A had higher intrinsic fluorescence intensity and surface hydrophobicity,compared to CSEP-B.Both CSEP-A and CSEP-B were rich in Glu,Arg and Asp.However,hydrophobic amino acids contents in CSEP-A(33.47±2.35%)was significantly higher than that of CSEP-B(18.70±0.03%).CSEP-A had a significantly higher emulsifying activity index(EAI),lower creaming index(CI)and similar emulsion stability index(ESI)than CSEP-B,therefore,the emulsion droplets formed with CSEP-A showed better stability.Oleosins were found to be major emulsifiable proteins in CSEP-A.3.The alcohol-soluble components were obtained from the emulsions formed during aqueous extraction of camellia oil.A strongly emulsifiable complex was separated and purified using chromatography technique.The tea saponin,carbohydrate and protein complex(TCPC),with excellent emulsifying properties,were confirmed by the Fourier Transform Infrared(FTIR)and thermogravimetric analysis(TGA).The emulsion formed with TCPC and oil was remarkably stable at a wide range of pH values(5-11),ionic strength(0-200 mM NaCl),thermal treatment(60-90℃;30 min),and even after 14 days storage at room temperature(10-25℃).However,the TCPC emulsion showed particles aggregation at pH 3.0,and flocculation occurred at 300 mM NaCl ionic strength,and demulsification during frozen/thawed cycle.Therefore,TCPC could be reasonably regarded as one key emulsifiable compound during aqueous extraction of camellia oil.4.Comparing the emulsifying characteristics of emulsion formed by CSEP,TCPC and CSEP+TCPC,the emulsifying activity index(EAI)of CSEP(96.73 m~2/g)was much higher than that of TCPC(74.76 m~2/g)and CSEP+TCPC(76.41 m~2/g),while the emulsion stability index(ESI)of CSEP(174.50 min)was much lower than that of TCPC(323.97 min)and CSEP+TCPC(275.99 min);The particles of each emulsion sample showed normal distribution and good particle uniformity,and the average particle size and particle size distribution of each emulsion showed no significant change even after 14 days of storage.However,the average particle size of CSEP emulsion(389.43 nm)was much larger than that of CSEP+TCPC(262.40 nm)and TCPC(264.97 nm)emulsion.The observation of the microstructure of emulsion was consistent with the particle size measurement.At the same time,theζ-potential of CSEP emulsion was lower than that of TCPC and CSEP+TCPC emulsion,and the flocculate and float appeared in CSEP emulsion.The rheological property showed that each CSEP,TCPC and CSEP+TCPC emulsion sample had obvious pseudoplastic fluid characteristics and shear thinning.In the angular frequency scanning range of 0.1-100.0 rad/s,both storage modulus(G′)and loss modulus(G″)of emulsion showed as follows:CSEP+TCPC emulsion>TCPC emulsion>CSEP emulsion.It indicated that the gel strength of CSEP+TCPC emulsion sample was the highest,and the combination of CSEP and TCPC may synergistically enhance the gel strength of emulsion.5.A novel aqueous extraction of camellia oil by emulsified oil–frozen/thawed was investigated.The emulsified oil was collected,frozen and thawed,and the free oil was obtained(AEEF).The optimal processing conditions were three times as much water as powder of camellia seed(m/V),grinding at 70℃ for 6 min,repeating2 circles to collect the emulsified oil;then the emulsified oil was frozen(?20 ~oC)/thawed(50℃)for 2 cycles.The yield of camellia oil was 89.37±0.51%,which was significant higher than that of microwave-assisted aqueous enzymatic extraction(MAAEE,83.05±1.14%),and was similar to that of press extraction,and solvent extraction based refining processes.Additionally,the total oxidation value(TOTOX)of the free oil extracted using AEEF(AEEF-Oil,6.82±0.12%)was significantly lower than those of MAAEE,CEP or SE.The content of benzo(a)pyrene(0.48 g/kg)was lower than SE-Oil,which was much lower the group standard of extra oil-tea camellia seed oil(T/LYCY001-2018).In comparison to SE-Oil and CEP-Oil,AEEF-Oil had higher contents ofα-tocopherol and squalene,and owned more favorable natural volatile compounds.The results indicated that the novel AEEF may be a promising aqueous extraction method.Therefore,in this study,we investigated a novel method to solve the problem of emulsification,which was based on elucidating the formation mechanism of this emulsion during aqueous extraction of camellia oil.