New edition: NMKL 192 Gram-negative bacteria in pasteurized milk and cream. Detection of recontamination.
NMKL 192 Ed. 2 2024. Gram-negative bacteria in pasteurized milk and cream. Detection of recontamination.
This is a qualitative screening method. Gram-negative bacteria do not survive high temperature short time (HTST) pasteurization (i.e. a minimum heat treatment at 72 °C for 15 seconds). The presence of Gram-negative bacteria in pasteurized milk and cream therefore indicates post pasteurization contamination. Although the level of contamination is very low, even a few bacteria/l, growth of Gram- negative bacteria may limit the shelf life. A method that is intended to detect recontamination by Gram-negative bacteria in milk and cream is described. Generally, Pseudomonas spp. dominate. This method has been developed for Gram-negative bacteria in milk and cream but could be applicable to other heat-treated food matrices.
This NMKL method has not been validated in an interlaboratory study.
