| The content of polyphenols in summer and autumn green tea is relatively high,while the amino acids,vitamins and aromatic substances are low.Compared with spring tea,summer and autumn tea is bitter and tastes poor,and its quality is far inferior to that of spring tea.In addition,summer and autumn tea has large yield,high nutritional value and low utilization rate.In this study,the double-screw extruder was used to process summer and autumn green tea powder(GTP),and the effect of extrusion on summer and autumn green tea was analyzed.A certain proportion of summer and autumn green tea powder was added to the corn flour(CF)for extrusion processing to study the extrusion characteristics.A kind of instant powder product with high nutritional value and easy to be absorbed and convenient brewing was developed,in order to expand the comprehensive utilization of summer and autumn green tea.The main results are as follows:1)The twin-screw extruder was used to extrude the summer and autumn green tea powder(GTP),and the changes of the leaching functional components and microstructure of the summer and autumn teas before and after puffing were analyzed.The results showed that the content of tea polyphenols and crude fiber in GTP decreased,but soluble total sugar increased after extrusion processing.After the expansion of summer and autumn green tea,the surface structure was observed to be smooth under scanning electron microscope.2)A certain proportion of GTP was added to the corn flour(CF),and then study the effect of the amount of GTP on the extrusion properties.The results showed that the content of tea polyphenols,crude protein,crude fiber and crude fat in the extruded samples increased after adding GTP.Meanwhile,their content increased with the increase of GTP.The increase of GTP content has a significant effect on the color of extruded samples.With the increase of the content of GTP,the puffing degree of extruded samples decreased,the bulk density increased,but the value of WAI value and WSI decreased,and the gelatinization degree also decreased.The microstructure results showed that the pore sizeof the extruded sample was gradually reduced,and bubbles were reduced and become finer with the increase of the content of GTP.The results of infrared spectroscopy showed that the structure of the absorption peaks of corn flour and summer and autumn green tea compound corn flour samples were similar,without obvious changes,but the absorption peaks of the two samples changed after extrusion.The X-ray diffraction results showed that the corn flour has a typical A crystal structure.After extrusion,the extruded samples showed a pronounced V crystal structure,and the crystal area was reduced.Similar results were observed for the summer and autumn green tea compound corn flour extruded samples.The diffraction curve did not change significantly,but the characteristic peak of the diffraction intensity weakened.3)Summer and autumn green tea compound corn reconstitute powder had been prepared.The proportion of GTP was 10%.The summer and autumn green tea compound corn flour was extruded,meanwhile the effect of three factors such as particle size,water temperature and water quantity on the effect of hedging were studied.The results showed that the optimum brewing process: the powder particle size of 80-100 mesh,water temperature of 80℃,and the ratio of powder with water for 1:5.The extruded summer and autumn green tea compound corn flour was used as the main ingredient in the experiment,and adding xylitol,maltodextrin and salt,using sensory evaluation as index,orthogonal experiment was applied to obtain the best formula: raw material 10 g,xylitol 5g,malt dextrin 2.5g,salt 0.05 g.The product had good taste and contained higher functional ingredients of tea polyphenols. |
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