Research On The Effects Of Different Storing Methods On Green-leaf Vegetables Nitrite And Nitrosamine Contents And The Inhibition Of Vitamin E On The Contents In Vitro

The latest report about the incidence of Chinese malignant tumors in 2014 was issued by National Cancer Center. In the report, digestive cancer ranked on the top list of morbidity and mortality of malignant tumors, and the prevalence of gastric and liver cancer listed on the top. The cause of this situation was associated with long-time intake of foods containing N-nitroso compounds according to long-time investigations. As is known to all, nitrosamines is one of the highly damaging compounds and their toxicity and carcinogenicity is extremely strong, which has drawn great attention. Nitrosamines are synthesized by the combination of nitrite and amine in the body through chemical or biological pathways. Nitrite is mainly derived from vegetables and amine mainly exists in meat, cured meat and smoked fish. Nitrite is often used as antibacterial agent or coloring agent added into food like sausage. Traditional Chinese diets are based on plant food, of which cereal are the staple food and vegetables combined with small amount of meat are assistant food. Previous studies have shown that exogenous intake of nitrite is from plant food, especially vegetables. Nitrite formation in vegetables is affected by transportation and storage conditions, meanwhile, a large amount of vitamins in fresh vegetables can also affect the transformation process in the body. Thus reducing the intake of nitrite and amine can effectively prevent and reduce the risk of digestive cancer, greatly improving people’s health.Recently, because of the high price in second-tier cities, many office workers generally bring overnight meal and heat it for lunch in order to save the cost of living. Nutritionists and media have different opinions on whether nitrite content of overnight meal is exceeding the national standard and harmful to human body. It was reported in many researches that various kinds of antioxidants, which is rich in fruits, vegetables and natural plants, have effects on nitrite and nitrosamine production. However, there exists great limitation because indirect determination methods are used in many researches. Furthermore, the effect of vitamin E on nitrite and nitrosamine contents of vegetables processed is not clear.The object of our research is to explore the effect of different storing ways on green-leaf vegetables nitrite and nitrosamine contents and the inhibition of vitamin E on the contents in vitro.The first part: the change of nitrite content in several kinds of leafy vegetable after different storageObjective:We planned to study the effect of different storing ways and utilization modes on nitrite content of green-leaf vegetables.Methods: Taking spinach, rape and water spinach as materials, we investigated the effects of four different storing ways(25℃, 25℃ bagged, 4 ℃, 4 ℃ bagged) on nitrite content of fresh and stir-fried vegetables.Results : The content of nitrite increased at first and decreased later in four different storing ways of fresh vegetables, and the change of four types of storages ranged as follows: 25 ℃ bagged > 25 ℃ > 4 ℃> 4 ℃ bagged; after being stir-fried, nitrite content of these vegetables in four storing ways rose as time went on. It reached the peak after 24 hours and the content of vegetables bagged in 25 ℃was the highest.Conclusion : Trying to choose fresh vegetables when you buy and consume vegetables, and processed vegetables should be kept bagged in cold storage and edible within 12 hours.The second part: the inhibition of vitamin E on nitrite production under the condition of simulated gastric acidObjective: To research the inhibition of vitamin E on nitrite generation under the condition of simulated gastric acid. Methods: We chose spinach as materials, and after being stir-fried, vegetables of four groups(the control group, vitamin E oil group, vitamin E group and vitamin C group) were stored bagged at 25 ℃. Then nitrite content was detected at different time point(0 h, 6 h, 12 h, 24 h, 48 h), and we also investigated the inhibition of vitamin E on nitrite generation under the condition of simulated gastric acid. Results: Vitamin E and vitamin C had inhibitory effect on nitrite generation under the condition of simulated gastric acid. Nitrite content of processed vegetables which were stored within 12 hours had no significant difference compared with control group(P > 0.05), however, the difference was statistically significant after 12 hours.(P < 0.05). Conclusion: Vitamin E has the inhibitory effect on nitrite generation under the condition of simulated gastric acid.The third part: vitamin E blocked nitrosamine synthesis of processed vegetables in vitroObjective: Exploring the blocking effect of vitamin E on nitrosamine synthesis of processed vegetables in vitro. Method: Spinach and cabbage were chosen for materials, then after being stir-fried, these vegetables were divided into two groups(control group, experimental group) and stored at room temperature. The NDMA content of stir-fried vegetables was detected at 0 h, 6 h, 12 h, 24 h and 48 h using SD-GC-MS.Results: Vitamin E could strongly blocked NDMA synthesis in stir-fried vegetables, NDMA content of stir-fried vegetables stored within 6 hours had no significant difference compared with control group(P > 0.05), but after 12 hours, it was statistically different(P < 0.05), and at 24 h, vitamin E had the strongest inhibition of NDMA synthesis in processed vegetables.Conclusion: Vitamin E could partly blocked NDMA synthesis of processed vegetables under the condition of hydrochloric acid in gastric; as a common health product, vitamin E played a positive role on removing nitrosamines.