Study On Photodegradation Of Chlorophyll In Green Prickleyash During Drying Process

High content of chlorophyll pigments in the peel of Green Prickleyash (Zanthoxylum schinifolium Sieb.et Zucc) leads to its green color. However, this visible green perishes quickly in the process of postharvest drying of green prickleyash, and the loss of green contributes to undesirable brown products which fetch at a very low price and thus have bad effect on the marketability of Green Prickleyash as well. Nowadays, investigations were carried out to study how chlorophyll degradation happened in postharvest fruits, especially for the enzymatic degradation pathway. However, few researchs on chlorophyll photodegradation were revealed. What’s more, few reseachers had studed the green loss of Green Prickleyash.In this paper, the fresh green prickleyashes were employed as experimental materials. Investigations were carried out to study how photochlorophyll degradation happened during drying. Through the different experimental designs and related result analyses, mechanisms of color change were scrutinized based on the process of chlorophyll degradation which may provide some references to the solutions dealing with Green Prickleyash and related theoretical researches. Meanwhile, this research may be helpful for the industry development of Green Prickleyash. The main results are as follows.1. To investigate effects of monochromatic light on chlorophyll breakdown in green prickleyashes,8kinds of monochromatic light were used. Among8kinds of monochromatic light, UV had the greatest effect on the green fading and the degradation of chlorophyll a, followed by blue light and yellow light. Meanwhile, UV had the greatest effect on the degradation chlorophyll b, followed by yellow light and blue light.2. To explore the mechanisms of chlorophyll photodegradation in the drying of Green Prickleyash, investigations using fresh green pricklyashes as raw materials with illumination of3kinds of monochromatic light and sunlight were carried out and changes in their peel colors and content of chlorophylls and derivatives were evaluated, research results were as follows: (1) The results showed the green of the peel color faded and chlorophylls underwent degradation. The peel color changed from brilliant green to brown and the content of chlorophylls decreased by57.94%with illumination of UV. However, the peel color remained green and the content of chlorophylls decreased less than that. Our results seemed to support that UV played an important role in chlorophyll degradation.(2) According to different drying modes, types, content and proportion of chlorophyll derivatives changed. The metabolization of some derivatives changed because of illumination, such as pheophorbide a and pyropheophorbide a. In addition, some chlorophyll derivatives came up with illumination of UV and sunlight, like pyropheophytin a, pyrochlorophyllide a and C132-OH-pheophytin a. Those brown derivatives might attribute to the deterioration of the color of peels. The content of brown derivatives consisted of nearly30%of total chlorophyll pigments in the dried green prickleyash with illumination of UV and that made18%of them with illumination of UV and sunlight. UV leaded to an accumulation of brown derivatives and fading of the green in the dried green prickleyash.(3) The results showed that illumination leaded to an accumulation of O2, H2O2and MDA, lower SOD activity and POD activity, and the reduction of ASA and GSH content. In addition, the proportion of memberane fatty acid composition of chloroplast in green prickleyashes changed to the accelerations of chlorophyll breakdown.This study was funded by the the National Natural Science Foundation of P.R. China (No.31071599) in the project of Mechanisms of Color Changes in Green Prickleyash during Natural Drying Proccesses.