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What are the main process parameters for instant flower tea?

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(1) Countercurrent extraction: green tea and deionized water are subjected to countercurrent extraction at a tea-to-water ratio of 1:15 for 15 min, with the extraction water temperature at 90°C. In commonly used instant tea production processes, the extraction operation is carried out intermittently, making it difficult to complete the tasks of discharging and separating the tea liquor from the tea residue within 15 min, which causes the tea leaves to remain too long in the high-temperature tea liquor, resulting in large aroma loss, a heavily bitter and astringent tea liquor with a strong stewed, over-cooked taste, and greatly reduced instant tea quality. The developed horizontal continuous countercurrent extractor, in order to reduce axial mixing of tea and water within the extractor and weaken back-mixing, adopts three horizontal extractors connected in series, achieving effective isolation of inter-stage back-mixing. The tea liquor and tea residue are continuously discharged from both ends of the extraction system, and the countercurrent extraction time can be controlled at about 15 min by adjusting the flow rates of tea and water. Compared with intermittent extraction, aroma loss is small and the taste of the tea liquor is noticeably improved.

(1) Countercurrent extraction: green tea and deionized water are subjected to countercurrent extraction at a tea-to-water ratio of 1:15 for 15 min, with the extraction water temperature at 90°C. In commonly used instant tea production processes, the extraction operation is carried out intermittently, making it difficult to complete the tasks of discharging and separating the tea liquor from the tea residue within 15 min, which causes the tea leaves to remain too long in the high-temperature tea liquor, resulting in large aroma loss, a heavily bitter and astringent tea liquor with a strong stewed, over-cooked taste, and greatly reduced instant tea quality. The developed horizontal continuous countercurrent extractor, in order to reduce axial mixing of tea and water within the extractor and weaken back-mixing, adopts three horizontal extractors connected in series, achieving effective isolation of inter-stage back-mixing. The tea liquor and tea residue are continuously discharged from both ends of the extraction system, and the countercurrent extraction time can be controlled at about 15 min by adjusting the flow rates of tea and water. Compared with intermittent extraction, aroma loss is small and the taste of the tea liquor is noticeably improved.

(2) Separation and impurity removal: after coarse filtration, the extracted tea liquor is rapidly cooled to about 25°C through a heat exchanger, then fed by a beverage pump into a disc centrifuge. For further gravity sedimentation, to ensure the clarity of the instant tea when brewed, the separation factor of the centrifuge should be greater than 10000, and the feed flow rate should be properly adjusted according to the centrifuge's production capacity.

(3) Vacuum thin-film concentration: the centrifugally clarified tea liquor is fed into a vacuum thin-film centrifugal evaporator for concentration. The evaporation temperature is adjusted to 55°C and the vacuum degree to 0.9×103Pa. Under the action of centrifugal force, the tea liquor rapidly forms a thin film of about 0.1mm in the evaporation chamber, and evaporation and concentration are completed within 1 to 2S. A single concentration can reach the suitable concentration for spray drying (15oBx).

(4) Preparation of dried flower extract: the dried flower extract is prepared by pressure extraction. The amounts of dried flowers used, based on the mass ratio of tea to dried flowers, are respectively: chrysanthemum to tea 10:1, jasmine to tea 14:1, magnolia to tea 20:1. The flower-to-water ratios for extraction are respectively: chrysanthemum and jasmine 1:5; magnolia 1:6. The extraction pressure is 0.8Mpa and the extraction temperature is 80°C. The extraction time for chrysanthemum and jasmine is 15min, and for magnolia 20min. After extraction ends, the temperature is lowered to about 15°C and then reduced to normal pressure, and the flower residue is separated by pressing. The flower residue is sent to the tea extraction stage for a second extraction, and the extract is clarified by high-speed centrifugation and then sent to a mixer to be mixed with the concentrated tea liquor.

(5) Mixing and spray drying: the concentrated tea liquor and the flower extract obtained by pressing and separation are sent to a mixer for mixing, then sent to a spray drying tower for drying. The inlet temperature of the drying tower is 190°C and the outlet temperature is 75°C.

Standard used for the product: QB2499-2000

Key equipment: food machinery horizontal countercurrent extractor, heat exchanger, high-speed disc centrifugal separator, pressure extraction tank, juicer, mixing tank, centrifugal spray drying tower.

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