[Presence of nitrates and nitrites in raw milk as subject to the system of milk purchasing]. / Wystepowanie azotanów i azotynów w mleku surowym w zaleznosci od systemu jego skupu.

The content of nitrates and nitrites was determined in raw milk supplied to dairy works in the purchasing system: producer--milk collecting basin--dairy. In all, 480 milk samples were analysed. Most samples contained nitrates in amounts not exceeding 2 mg of NO3-/kg, while nitrites were present in trace amounts or were not detected at all. In comparison with milk taken immediately after milking the level of nitrates in milk in collecting basin was nearly twice as high. The source of these nitrates was probably water incompletely removed after washing and rinsing of collector containers.