The standard for allowing nitrite in milk is 0.2 mg / kg. Under normal circumstances, because the rumen microorganisms of the cattle have the function of decomposition and utilization, so nitrite does not appear to exceed the standard in milk. The reasons for exceeding the standard may be that raw milk
has been stored for a long time, and the feed and water eaten by cows contain nitrite. In addition, it is mainly due to the surface water contaminated by groundwater and a variety of agricultural and non-agricultural activities. , Such as the application of fertilizers, the decomposition of animal manure, nitrogen residues of crop residues, certain minerals, septic tanks, municipal waste, etc., which increase the content of nitrate and other substances in groundwater, once the amount exceeds the plant's ability to use, It can accumulate in the lower layer of soil or penetrate into the groundwater. Under the action of certain microorganisms in the environment, it will be converted into nitrite.
China mainly occurs in coastal sandy soils and low water wells. Therefore, the prevention of water wells is the first choice. The wells should not be too shallow. There should be well fences to keep away from manure pollution and prevent surface water from flowing into the wells. It is best not to use well water for dairy cows to drink and wash milk, and use tap water instead. Pay attention to environmental hygiene and reduce nitrate degradation caused by bacterial contamination. Some green materials will produce nitrite after they are piled up and heated, so the green materials purchased should be spread out in time to prevent the pile from heating up and deteriorating.