Survey of lysinoalanine level in some pasteurized and sterilized milk samples on the Iranian market

Pasteurization and sterilization processes will increase the safety of milk and milk products, but they might produce harmful substances which will lower the nutritional quality of the heated milk. The aim of this study was to determine the level of lysinoalanine (LAL) in pasteurized and sterilized milk that are common on the Iranian market. Protein content of milk was determined by the Kjeldahl method. The proteins were hydrolyzed by hydrochloric acid (6N) in oven. Protein hydrolysate was dissolved in distilled water and the pH was adjusted by adding sodium hydroxide. Amino acids in samples were derivatized by dansyl chloride and lysinoalanine was determined by high performance-liquid chromatography. Lysinoalanine was present in raw, pasteurized and sterilized milk at the levels of 0-5 mg/kg, 35-86 mg/kg and 110-233 mg/kg, respectively that was much higher compared to reported levels in other studies. In order to reduce the level of LAL in foods, it is suggested that heat processing of proteinous foods, especially milk and milk products should be controlled.

کلیدواژه ها:

HPLC ، milk ، lysinoalanine ، pasteurization ، sterilization ، protein