Can't overnight vegetables be eaten like arsenic?
On the evening of July 27 and the morning of July 28, the reporter of Legal Evening News made three self-made reference samples and one salad, ordered two reference samples from the hotel (the fried samples on July 27 were stored in the refrigerator), and sent the fried samples of six control groups to the Beijing Zhiyunda Food Safety Testing Center for testing.
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Experimental steps
Sample Source: Self-made fried vegetable control sample 3 groups, Salad salad group, Hotel ordered control sample 2 groups.
On the afternoon of July 27 and the morning of July 28, self-made stir-fried vegetables: spinach scrambled eggs, shrimp skinned cabbage scrambled vermicelli, vegetarian fried potato shreds, self-made salad
Order Hotel takeout on the afternoon of July 27 and the morning of July 28: Gongbao Chicken Ding and Oyster Oil Lettuce
Note: All samples on July 27 are stored in fresh-keeping boxes in refrigerators.
Testing items: Nitrite content in stir-fried and salad overnight vegetables and newly prepared samples
Limit standard: Because the national standard does not regulate the content of related substances in food of catering industry, there is no "national standard" for stir-fried vegetables. In this test, GB2760-2014 and GB2762-2012 were used as references. The nitrite residues in cooked meat products were not more than 30 mg/kg, and the nitrite content in pickled vegetables was not more than 20 mg/kg. The original national standard GB15198 stipulated that the nitrite content in fresh vegetables should not exceed 4mg/kg, which is now discarded.
Samples No.1 and No.2 Gongbao Chicken Ding
Raw materials: chicken, peanut, onion
The results showed that the color of overnight vegetable samples and new vegetable samples did not change, and the nitrite content of the two samples was almost zero.
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Sample No.3 and No.4 Oyster Oil Lettuce
Raw material: lettuce
The results showed that the color of overnight vegetable samples and new vegetable samples did not change, and the nitrite content of the two samples was almost zero.
Sample salad No.5 and No.6
Raw materials: cucumber, corn kernels, starchless ham
The results showed that the color of overnight vegetable samples and new vegetable samples did not change, and the nitrite content of the two samples was almost zero.
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Samples 7 and 8: Spinach scrambled eggs
Raw materials: spinach, eggs
The results showed that the color of overnight vegetable samples and new vegetable samples did not change, and the nitrite content of the two samples was almost zero.
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Samples No.9 and No.10 Shrimp Skin Cabbage Fried Fans
Raw materials: shrimp skin, cabbage, vermicelli
The results showed that the color of overnight vegetable samples and new vegetable samples did not change, and the nitrite content of the two samples was almost zero.
Sample No.11 and No.12 Fried Potato Shreds
Raw materials: potatoes, red and yellow peppers
The results showed that the color of overnight vegetable samples and new vegetable samples did not change, and the nitrite content of the two samples was almost zero.
(Note: odd number is new, even number is overnight)
detection result
The results showed that the nitrite content of six overnight vegetable samples had little change.
Yang Yusi, an inspector at the Consumer Experience Center for Food Safety Inspection of Beijing Zhiyunda Science and Technology Co., Ltd., told the Legal Evening News that the nitrite content of overnight vegetables had risen sharply, and it was rumored that eating for a long time could cause cancer.
The results of this experiment showed that the nitrite content of overnight vegetable samples and ready-made vegetable samples in the six control groups did not change significantly, and the nitrite content of the six groups of samples could be neglected, which was far lower than the minimum nitrite content of vegetable in the original national standard, i.e. 4mg/kg.
Zhang Yuping, technical manager of CEC Experience Center and postdoctoral student of Agriculture, China Agricultural University, said that the nitrite content of overnight vegetables did not increase significantly from the test results, which showed that netizens worried that "the nitrite content of overnight vegetables has increased dramatically, and long-term consumption is prone to cancer" is a rumor.
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Expert opinion: overnight vegetable can be safely stored
Zhang Yuping said that nitrite in overnight vegetables is usually converted from nitrate in vegetables, and nitrate in vegetables mostly comes from nitrogen in the environment, especially nitrogen fertilizer. Nitro reductase can be found in plants, which will reduce nitrate to nitrite. Therefore, nitrate and nitrite are commonly found in vegetables. However, vegetable species, planting methods and nitrogen fertilizer levels all affect the amount of nitrate and nitrite. Nitrite content in vegetables such as beans, cucumbers and onions is very low, while that in leafy vegetables such as spinach is relatively high. However, compared with the national standard that nitrite content in pickled vegetables does not exceed 20 mg/kg, the nitrite content in fresh vegetables is very small.
Zhang Yuping said that in the cooking process, the reductase in vegetables has been destroyed, and some bacteria will also have nitroreductase, so the main determinants of nitrite content in leftovers are bacterial contamination and storage conditions of leftovers, long exposure to bacteria, and no refrigeration.