2 Rapid method to determine post-pasteurization contamination and shelf life of milk and liquid milk products

摘要

PURPOSE: A method for the quick decision in secondary pollution of liquid milk product is provided which uses a preliminary culture method for the selective culture of a gram negative bacillus, and a resazurin pigment reduction method for the detection of the gram negative bacillus. CONSTITUTION: A method for the quick decision in secondary pollution and storage of liquid milk product comprises: (1) treating sterilization liquid milk product; (2) adding the selective reagent of a gram negative bacillus such as sodium deoxycholate and cetrimide, or the bacillus contained the same reagent; (3) preliminary culturing at 18-25C and 30C for 18 hours; (4) adding resazurin; (5) culturing at 30C; and (6) checking the change of the color from blue color to violet every 30min or 1hour. The change of a color of liquid milk product indicates its pollution.