Construction,Characterization And Application Of Tea Nano-selenium Stabled By Tea Nano-aggregates

Because of its high efficiency and low toxicity properties,nano-selenium has gradually become a research hotspot in the field of selenium supplement,but which also extremely unstable and easy to gather into black selenium to lose activity.In order to improve the stability of nano-selenium,the researchers constructed nano-selenium with protein,polysaccharide and EGCG by combining with nano-selenium.Tea nano-aggregates are rich in tea extract protein,tea polyphenols and soluble sugar,which possess the chemical foundation of nano-selenium template.The study firstly used green tea nano-aggregates as template,used the redox reaction of ascorbic acid?Vc?and sodium selenite?Na₂SeO₃?,studied the influence of reactant ratio,template content,reaction time and reaction temperature on the formation of nano-selenium,established a preparation method of green tea nano-aggregates nano-selenium.On this basis,comparing stable function of nano-selenium stabled by tea extract,nano-aggregates and supernatant of Camellia ptilophylla black and green tea,oolong tea,white tea,yellow tea and pu-er tea et al,discussed the chemical mechanism of tea nano-aggregates nano-selenium.Then,analyzed its basic morphology and combination feature with dynamic light scattering,electron microscope,x-ray diffraction,x-ray photoelectron spectroscopy,infrared spectroscopy and other technologies,evaluated its antioxidation and anticancer activity with chemical and in vito cell method,and preliminary studied the influences of some factors like pH on nano-selenium stability.Finally,pu-er tea extract nano-selenium with high stability and activity was used as functional strengthening component combined with pu-er tea instant powder as stabilizer to build a antioxidant pickering emulsion,which was further used to load curcumin,studied the effects of the stability of curcumin and the slow release of gastric and intestinal juice.The main results are as follows:?1?Construction method and characteristics properties of green tea nano-aggregates nano-seleniumPreparation condition of green tea nano-aggregates nano-selenium:Vc:Na₂SeO₃reaction ratio was 8:1,green tea nano-aggregates content was 500 mg/L,the reaction time was 1 h and the reaction temperature was 40?,constructed nano-selenium present spherical,of which particle size was about 25⁷5 nm,Zeta potential value was highly 41.5mV,and possessed high static stability.?2?Construction of nano-selenium stabled by Camellia ptilophylla black and green tea and other five kinds of teaThe nano-selenium stabled by tea extract,nano-aggregates and supernatant of Camellia ptilophylla black and green tea and other five kinds of tea all were spherical,however,it was best to use pu-er tea extract,nano-aggregates and supernatant stable nano-selenium,among them,the stable effect of tea nano-aggregates was better than that of the original tea extract,the stable effect of the supernatant was worst.?3?Characteristics and functional activity of tea nano-seleniumNano-selenium stabled by green tea nano-aggregates,pu-er tea extract,pu-er tea nano-aggregates and pu-er tea supernatant all were amorphous zero-valent,the surface elements in nano-selenium including Se,C and O,selenium content were all above 85%.Each template may be combined with nano-selenium with a non-covalent bonds through its tea polyphenols,proteins,alkaloids,polysaccharides and amino acids,which prevent further accumulation and precipitation.The above tea nano-selenium had a significant antioxidant activity and a dose-dependent effect.It's anticancer activity was selective to the cancer cell line,which had the strongest inhibitory effect on the proliferation of HCT 116 cells and had the weakest effect on the proliferation of HepG2 cells.And there still was good stability after digestion of simulated gastrointestinal tract.?4?Stability of tea nano-seleniumNano-selenium had a certain tolerance to the change of pH within 5¹1 range,the average diameter of the system was not significantly changed,and the Zeta potential value of the system was higher than 30 mV,and the static stability was higher.The addition of metal salt would reduce the stability of tea nano-selenium,morever,nano-selenium was more sensitive to bivalent metal ion Ca²⁺and Mg²⁺than metal ion Na⁺,and the capacity induced nano-selenium coagulation of Mg²⁺was also stronger than Ca²⁺.Tea nano-selenium show high static stability under 60?,80?and 95?,which could adapt to heat treatment in normal food processing process.Nano-selenium had certain tolerance to storage temperature,and the proper increase of storage temperature was beneficial to the dispersion of particles.Nano-selenium stored 25?for 40 days,the particles in the system were dynamically combined,the Zeta potential value was kept above30 mV,and the nano-selenium sol was stable.?5?The stability mechanism of tea nano-selenium The nano-selenium were constructed by theabrownin,Pu'er Tea extract dialyzate,Pu'er tea instant powder,theaflavin,EGCG,caffeine,theophylline,80%catechin extrac and gallic acid respectively.The result showed that the theabrownin nano-selenium and the Pu'er Tea extract dialyzate nano-selenium had the highest stability,which had the clarified appearance.EGCG plays a synergistic role in constructing of nano-selenium by green tea nano-aggregates.?6?Construction and stability properties of pickering emulsion of pu-er tea extract nano-selenium and Pu'er tea instant powder?1?The dilution rate of Pu'er tea extract nano-selenium was 20 times,Pu'er tea instant powder adding amount was 2%,oil-water ratio was 4:6,aqueous dispersion of pH 7,prepared pickering emulsion was highly stable and the emulsion droplet size were small.?2?The stability of pickering emulsion at the initial pH was the highest,changing pH could reduce the stability of emulsion.The emulsion prone to flocculate and aggregate and the stability of emulsion decreased after adding electrolytes,the effect of divalent metal ion Ca²⁺was stronger than that of metal ion Na⁺.When stored under normal temperature,with the increase of storage time,the size of emulsion droplet increased significantly,the aggregation stability of emulsion droplets decreased,and flocculation and condensation between droplets occurred.?3?The emulsion had high static stability and stable emulsion.However,Pickering emulsion of pu'er tea was better than that of pu'er tea,and the stability of Pickering emulsion was the worst.?7?Pu'er tea extract nano-selenium combined with pu-er tea instant powder Pickering emulsion load curcumin and its slow release.The retention rate of curcumin was highly to 98.45%,and the retention rate of curcumin was greatly Improved:Under natural light conditions,and stored at room temperature for 20 days,the retention rate of curcumin was as high as 37.28%,which was16 times that of oil-soluble curcumin.avoid light and stored at 4°C for 20 days,the retention rate of curcumin was as high as 91.47%,which was 2.7 times that of avoid light,and stored at 4°C for 20 days.At the same time,emulsion embedding can improve the stability of curcumin in simulated gastric juice and its release in simulated intestinal juice.The maximum release of curcumin in simulated intestinal fluid could reach 7.51%after 1 h.