Study On The Application Of Ultrasound Wave Technology For Reverse Osmosis Membrane Preparing Technology In Green Tea Infusion

Membrane tea juice concentrating processing technology can solve a lot of problems of the traditional hot concentration such as wasted great energy and damaging the quality by oxidation of heat-sensitive material-polymerization, as well as causing poor cold solubility, plain flavor and bad aroma.however, the processing technology could cause some problems such as resources waste,lower concentration degree of tea juice,low efficiency etc. In this study, with Zhejiang Green broken tea as the material, ultrafiltration combined reverse osmosis concentrating as the process, we applied ultrasonic technique to the extraction of green tea, ultrafiltration clarification and reverse osmosis concentrating.1. Using temperature of 50℃assisted with ultrasonic extraction method to compare with the conventional extraction method (water temperature of 90℃and 10 min), we compared the ingredient extraction rate, the content of catechins and the color changes of green tea extracts. And the results showed that:In the former condition, the dry component, tea polyphenols, amino acids, caffeine extraction rates and catechins, especially EGCG content could meet or exceed the conventional extraction method after extract for 15 minutes; The brightness and yellow-green degree of juice extracted from green tea were significantly better than conventional extraction method. This shows that, the green tea extraction rate were good, the color quality and the health care function were better than green tea juice in the extraction method with ultrasonic assisted low temperature (50℃).2. The use of membrane separation applied CA 20000,50000,100000 molecular weight membrane. We studied the effects of ultrasonic ultrafiltration on the green tea juice membrane flux, chemical composition, catechin and color. the results showed that the membrane flux increased by 28%～33% of 100000 molecular weight,40%-250% of 50000 molecular weight,2 times of 20000 molecular weight; the contents of tea polyphenols, caffeine, amino acids, catechins and other effective chemical composition had been improved, but the contents of macromolecules such as protein, pectin, and chromatic aberration had not been affected after ultrasonic treatment. This showed that ultrasound can destroy the macromolecular polymer in green tea juice to some extent, separate and release more effective substances, reduce the attachment probability of macromolecules in the ultrafiltration membrane and increase flux.3. Using the membrane separation to study the effects of ultrasonic to membrane flux, concentration and components of concentrated Green tea juice by reverse osmosis membrane under three conditions as 0.4,0.6,0.8 Mpa. The results showed that reverse osmosis average membrane flux were improved, under 0.4,0.6 and 0.8 Mpa conditions, the concentration time is cut by 29.6%,31.2%,24.7%; The concentration of juice increased by 13.2%,18.8%t,18.7%. This shows that ultrasonic cavitation and mechanical effects can reduce the adhesion of Juice green tea in reverse osmosis membrane and defer the concentration polarization of membrane ends, so as to reduce the pollution to reverse osmosis, increase the membrane flux, raise the concentration of Green tea concentrated juice and content of inclusions, and improve concentration efficiency.4. According to the process of reverse osmosis concentration of green tea juice, we selected the 100000 molecular weight membrane and the 0.8Mpa pressure of reverse osmosis and set 8 treatments. With all the above, we analyzed the application of ultrasonic to the technique of reverse osmosis of green tea juice concentration. The results showed that:With the processing of ultrasonic on ultrafiltration and reverse osmosis, the membrane flux has increased by 33.9% and 34.5%; and the total flux increased about 33.4%; The density of green tea juice,the contents of inclusions and the utilization of green tea have been improved after ultrasonic concentration; The brightness and greeness of juice extracted from green tea obtained by ultrasonic extraction have both improved. The results illustrated that, using ultrasound to the process of reverse osmosis membrane could accelerate the speed of the process while increase the density of green tea juice, the contents of inclusions and the utilization of green tea and improve the color of concentrate.