Use of the Limulus test to determine the hygienic status of milk products as characterized by levels of Gram-negative bacterial lipopolysaccharide present

Abstract

SUMMARYThe Limulus test was used to investigate the occurrence of Gram-negative bacterial lipopolysaccharide (LPS) in milk and dairy products. This test specifically detects the extremely heat-resistant LPS, and so determines the total accumulated quantity of LPS in a product whether it has been heat-treated or not. A positive correlation between number of psychrotrophic bacteria and amount of LPS in fresh farm milk was found (r = 0·63). Fresh farm milk and freshly produced market milk contained on average < 1 ng LPS/ml. The Limulus test is considered highly suitable for use in the dairy industry, being a method which will characterize quickly and specifically the hygienic level of a product by the extent of the cumulative contamination by Gram-negative bacteria.