Effects Of Artificial Light Sources Such As Ultraviolet On Chemical Properties And Quality Of Withered Leaves

In this paper,the short-term and long-term artificial wilting of tea leaves in vitro were carried out by using artificial light sources such as UV.The changes of flavor components of withered leaves under different wilting modes were analyzed to explore the dynamic changes and differences between chemical components and sensory quality of withered leaves under different artificial light sources.In addition,the effect of water loss rate and temperature on the irradiation effect of UV was studied.The main research results are as follows:(1)Three UV light sources,UV-A,UV-B and UV-C,were set up to wither the fresh tea leaves for 5 hours in a short time with the aid of the wilting trough,and the conventional wilting which ultraviolet radiation intensity was 0 was used as the control.The difference between UV-A and UV-B is the biggest,followed by UV-B and UV-C,and the difference between UV-A and UV-C is the smallest.The effect of different UV wave band on the content of different substances in withered leaves is different.For example,UV-B treatment can increase the content of water extract,catechins,polyphenols,EGCG and reduce the content of alkaloids,UV-A,UV-C treatment can reduce the content of catechins,polyphenols and other substances.(2)Four kinds of artificial light sources(UV-B,UV-A,UV-A with UV-B,UVB with far-infrared)were set up to use the long-term withering of the fresh tea leaves.The water content of the withered leaves was reduced to 15%-20%,and the indoor natural withering was used as the control.Compared with the indoor natural withering,four kinds of artificial light source can promote the fresh leaf water loss and the transformation of biochemical components in the leaves,accelerate the withering process,and facilitate the formation of sensory quality of withered leaves.Under four kinds of UV withering modes,the effect of UV-A withering is better than that of UVB withering;the effect of UV-A with UV-B combination light withering is better than that of UV-A or UV-B single light source withering;the effect of UV-B with far-infrared combination light withering is better than that of UV-B single light source withering.(3)Different water loss rate(rapid water loss,slow water loss,water conservation)had a great influence on the UV-A wilting effect,and the sensory quality and taste components of tea samples were significantly different.UV-A wilting was the most beneficial to the formation of tea taste quality,followed by rapid water loss treatment and slow water loss treatment.Different temperature treatments(room temperature 27 ?,medium temperature 35 ?,high temperature 45 ?)had some influence on the effect of UV-A wilting,but it was not as significant as water loss rate treatment.The effect of medium and high temperature treatment is better than that of normal temperature treatment,but there is no significant difference between them.