Study On Selecting And Optimizing Technological Conditions Of Producing Concentrated Tea Juice With High Concentration And No Sediment

In this paper, by using oolong tea as experimental material, we studied the technological process and technological parameters of producing concentrated tea juice, which was of high concentration and no sediment. We studied the technology and parameters of extracting tea and the adding quantities of entrapment agent and antioxidant by way of orthogonal experiments, and we researched the effects of different conditions of ultra-filtration, nano-filtration and reverse-osmosis on flux and main ingredients in tea juice, by which we acquired the technologies and parameters of ultra-filtrating and concentrating tea juice. The technological process of producing concentrated tea juice with high concentration and no sediment was made sure, which provided the reliable data and can be applied expand production after test successfully. The detailed conclusions as follows:1. The relative extracting rate of tea polyphenol. caffeine and amino acid respectively was 89.36%, 75.44%, 95.72% at 60℃ for 60 minutes with 0.04% cellulase and 140 times weight water. There was no obvious difference between the extracting effect with cellulase at low temperature and that with conditional extracting technology at high temperature (90℃, 12.5min, 1:100), the extracting rate of amino acid even higher;2. Not only high flux could be obtained, but also high retainable rate of tea polyphenol, caffeine and amino acid by ultra-filtration with working pressure of ultra-filtration membrane ranging from 0.1Mpa to 0.12Mpa and suitable temperature for tea juice ranging from 35℃ to 40℃. The retainable rate of tea polyphenol. caffeine and amino acid respectively was 80.17%, 80.98% and 90.77%. The tea juice was much clearer and,brighter than that before ultra-filtration;3. The working pressure of nano-filtration membrane is 0.6 ~0.7Mpa, suitable temperature for tea juice is 20℃. The working pressure of reverse-osmosis membrane is 0.5 ~ 0.6Mpa, suitable temperature for tea juice is 35 ~ 45 ℃. We could choose reverse-osmosis alone or connecting reverse-osmosis with nano-filtration as concentrating technology according to different demand.The retainable rate of tea polyphenol. caffeine and ammo acid respectively was 98.23%, 87.45% and 85.28% by concentrating connecting reverse-osmosis with nano-filtration;4.β -cyclodextrin was chosen as entrapment agent with 1.5%. Ascorbic acid was chosen as antioxidant with 0.04%;5. The technological process of producing concentrated tea juice with high concentration and no sediment was: tea → crushed and through sieve (size in the range of 40-60 mesh) → extracting with cellulase at low temperature - filtering at low pressure → ultra-filtration → the first concentrating (reverse-osmosis) → the second concentrating (nano-filtration or reverse-osmosis)→ adding entrapment agent and antioxidant → UTH sterilization - aseptic filling→ products;6.The concentration of concentrated tea juice could reach 20% (Brix) with no sediment, and it kept the original flavor of oolong tea.