This study aims to investigate the influence of the different dosages of sulfur on the quality and the browning enzyme activity of Chrysanthemum morifolium cv. Boju. In this experiment,UV-spectrophotometry was used to determine the activities of browning enzymes,including polyphenol oxidase( PPO) and peroxidase( POD),in 7 different dosages of 0,4,8,16,50,150,200 g·kg~(-1)( weight ratio of sulfur/fresh chrysanthemum). A comprehensively comparison of the 7 chemical constituents of C. morifolium cv. Boju fumigated with 7 different dosage of sulfur was conducted by HPLC analysis. In this paper,the results showed that the activities of PPO and POD enzymes decreased significantly in chrysanthemum processed by sulfur fumigation. The activities of PPO and POD enzymes decreased gradually with the increase of sulfur dosage. When the sulfur dosage was higher than 4 g·kg~(-1),the PPO enzyme was significantly reduced. When the sulfur dosage was higher than 8 g·kg~(-1),the PPO enzyme was completely inactivated. The effect of different sulfur dosage s on the chemical composition was investigated. In comparison,it was found that when the sulfur dosage was 8 g·kg~(-1),the content of chlorogenic acid was higher than the 4 g·kg~(-1) and that of the sample without sulfur fumigation. Thereafter,with the increase of the sulfur dosage,the content of chlorogenic acid was unchanged. It was speculated that when harvesting,the tissue of fresh flower was destroyed,which caused the activation of browning enzymes. Afterwards,the sulfur fumigation could significantly reduce the activity of browning enzymes,which prevented the conversion of phenols in the reaction substrates( chlorogenic acid and 3,5-dicaffeoylquninic acid) into terpenoids,and better retained quinic acid components. However,when the sulfur dosage reached 8 g·kg~(-1) or16 g·kg~(-1),the content of quinic acid components were no longer changed,which indicated that the sulfur dosage had reached the saturated dosage. Similarly,when the sulfur dosage was increased,the contents of flavonoid aglycones showed a downward trend except for luteolin-7-O-glucoside. It was speculated that the sulfur fumigation inhibited the activity of hydrolase,which reduced the hydrolysis of flavonoid glycosides to aglycones. However,the reaction mechanism needed further verification. In conclusion,although sulfur fumigation could significantly inhibit browning,different dosages of sulfur had a significant effect on the chemical composition of C. morifolium cv. Boju,which could affect the consistency of quality and the stability of the therapeutic effect. Excessive use of sulfur was likely to cause a large amount of SO2 residues in C. morifolium cv. Boju,Therefore,different Sulphur dosages had a significant effect on the quality of chrysanthemum,which therefore was not recommended in production. A small dose of sulfur could be used to prevent enzymatic browning. When the dosage of sulfur increased to a certain extent or reached a saturation state,a small dose of sulfur is recommended in necessary. In this paper,the correlation between the sulfur dosage,the enzyme activity,and the main chemical constituents of chrysanthemum was clarified. The experimental research provided the guidance for regulating the harvesting processing of chrysanthemum and the harvesting processing,and improving the quality of chrysanthemum.
Keywords: Chrysanthemum morifolium cv.Boju; browning enzyme; chemical constituents; sulfur dosage.