关键词: 京郊, 蔬菜, 产品器官, 硝酸盐, 亚硝酸盐, 维生素C

Abstract: Recent years, nitrate content in vegetables has gained extensive attention. The contents of nitrate, nitrite and vitamin C in 52 kinds of vegetables from Beijing suburb were determined. Results indicated that a difference in nitrate accumulation was observed among different species, cultivars and parts of some vegetables. The contents of nitrate in different vegetable species calculated on the basis of fresh weight declined in the following order: root vegetables (420.66 mg/kg), leafy vegetables (281.24 mg/kg), stem vegetables (279.54 mg/kg), fruit vegetables (176.54 mg/kg) and flower vegetables (157.93 mg/kg). The contents of nitrate in different cultivars from one species exhibited 1.13－5.48 fold difference. Meanwhile, the content of nitrate in different leaf parts of Chinese cabbage and cabbage revealed a gradual decrease trend in following sequence: rossette leaf, middle head leaf and inner head leaf. The content of nitrate in cucumber also exhibited a gradual decrease trend in top part, basal part and middle part. Moreover, a decrease trend for the content of nitrate in cucumber was also observed in fruit mesocarp, exocarp fruit endocarp, placenta and seeds. The content of nitrate exhibited a declined trend in root periderm, secondary phloem in radish, secondary and primary xylem of the root. The contents of nitrite in the majority of vegetables were under 1 mg/kg although some vegetable species such as garland chrysanthemum could reach up to 6.74 mg/kg. Nitrite accumulations less significantly differed among different cultivars, species or parts as compared to nitrate accumulation. The content of vitamin C in fruit, leafy and flower vegetables was generally higher than that in other species although pepper could reach up to 146.56 mg/100 g. However, no significant difference in vitamin C content among different cultivars was observed. It is suggested that consumers scientifically and reasonably vegetables for health, although the majority of vegetables from Beijing suburb have the contents of nitrite and nitrate within their safety ranges.

Key words: Beijing suburb, vegetable, edible part, nitrate, nitrite, vitamin C