Experimental Research Of Extrusion On Green Tea-leaves

Since the beginning of the21th centery, with the rapidly development and growth of the teaprocessing industry in China. There are also gradually increase of various types of tea-leaves as a result.However, China’s current comprehensive utilization of tea-leaves is still in the preliminary stages.Every year there are a lot of tea-leaves not been adequately utilized. The discard of these tea-leaves willnot only seriously pollute the environment, but also is a huge waste of resources. Therefore, improvingthe utilization level of these tea resources will have a high economic value and social value.In this paper the reserarcher extruded green tea-leaves with DS30-III twin-screw extruder.According to single factor investigation, the mathematical models respectively with the content ofGallic acid, free amino acids and crude fiber as the responses to moisture content of material, feedingspeed, rotational speed of screw and processing temperature were established by using response surfacedesign. It was followed by response surface analysis. Through research, there are following conclusions:1. Optimized the formulas by Statistics method, the optimal extrusion parameters of high contentof Gallic acid in green tea–leaves were that moisture content of material was70%, feeding speedrotational was58r/min, speed of screw was60r/min and processing temperature was60℃. Thesignificance of parameters on the content of Gallic acid in green tea-leaves was decreased according tothe ranking of moisture content of material＞rotational speed of screw＞processing temperature＞feeding speed. The content of Gallic acid in the tea-leaves taht is dealt with optimalextrusion parameters is3.57mg/g, which is4.06times than the raw materials before extrusion.2. During the research it was found that the significance of extrusion parameters on the content offree amino acids in green tea-leaves was decreased according to the ranking of moisture content ofmaterial＞rotational speed of screw＞processing temperature＞feeding speed. The optimal extrusionparameters of high content of free amino acids in green tea–leaves were that moisture content ofmaterial was70%, feeding speed rotational was106r/min, speed of screw was120r/min and processingtemperature was20℃. The content of free amino acids in the tea-leaves that is dealt with optimalextrusion parameters is1.98%, which is2.3times than the raw materials before extrusion.3. The results showed that the significance of extrusion parameters on the content of Crude fiber ingreen tea-leaves was decreased according to the ranking of rotational speed of screw＞processingtemperature＞feeding speed＞moisture content of material. The extrusion optimal parameters of lowcontent of Crude fiber in green tea-leaves were that moisture content of material was70%, feedingspeed rotational was90r/min, speed of screw was90r/min and processing temperature was50℃.At thispoint, the content of Crude fiber in the tea-leaves is15.12%, which is83.26%of the raw materialsbefore extrusion.