Study On The Aqueous Extraction Of Oil And Starch From Tea Seed

China is the hometown of tea and the tea plant resources are very rich. Tea seed, as a sideline product in tea cultivation, is rich in fat, starch,protein and so on.Every year in the past,almost all of the tea seed was thrown away,resulting in a tremendous waste.Therefore,there is a bright prospect in studying and developing the main components of tea seed.Taking tea seed as raw material, its chemical composition was researched in this paper. Aqueous extraction with ultrasonic technology was used to extract tea seed oil and starch and its optimal process parameters were gained through optimization of the extraction conditions by orthogonal experiment on the basis of the single-factor test. The effects of heating, organic solvent extraction and freezing and thawing altogether three demulsification methods were compared and the tea seed starch was purified by applying thin alkali method. With tea seed oil produced by ether extraction and commercial maize starch as control group, some quality indicators for tea seed oil produced by aqueous extraction and physical and chemical properties of the tea seed starch after purification were investigated.The main conclusions are as follows:The contents of fat, starch and protein in tea seed are 28.86%,19.75%,11.16%,and the differences in content of each component are not sinnificant. So, developing tea seed comprehensively is valuable.The optimum process conditions of aqueous extraction with ultrasonic technology for tea seed oil and starch were: raw material comminution degree of 60 to 80 meshes,mixed water pH6,ratio of liquid to material 4: 1(mL/g), extraction temperature 70℃, extraction time 4 h,ultrasonic time 30 min.Under these conditions, the oil extraction rate was 70.79%,the by-product (starch) extraction rate was 56.13%. After drying, the color of starch was yellowish.Heating, organic solvent extraction and freezing and thawing all affected demulsification , but their demulsification extents were different. The demulsification effect of freezing and thawing was the best,followed by heating,organic solvent extraction in turn.Freezing and thawing was chosen as the demulsification method in the experiment and its optimum process parameters were : freezing time 24h , thawing temperature 60℃,thawing time 2h.Under these conditions,the oil yield was over 70%.The tea seed oil produced by aqueous extraction was clear and transparent, with natural smell and taste of tea seed oil, no peculiar smell. Compared with the tea seed oil produced by ether extraction, the tea seed oil produced by aqueous extraction had higher saponification value and iodine value, lower acid value and peroxide value and other similar quality indicators. So, its overall quality was better.Thin alkali method was used better to remove protein from the tea seed starch and improve purity of the starch. After soaking the starch for 3 times, protein residues was 0.55%.The tea seed starch after purification had good apparent quality. In addition to higher content of crude fat, its other indicators were in line with the requirements of the second grade of national industrial and edible maize starch.Particles of the tea seed starch with smooth surface are oval or round,giving an diameter of 4 to 11μm;not easy to gelatinize because of its high pasting temperature; solubility and swelling strength increase gently with temperature rise ; compared with maize starch , the transparency and freeze-thaw stability are inferior , but the anti-retrogradation is a little superior and the viscosity is also higher.