Abstract

Escherichia coli, Salmonella enteritidis and Pseudomonas aeruginosa were subjected to pasteurization, ultra high temperature (UHT) treatment and sodium benzoate preservation to determine the effect of these treatments on lipopolysaccharide (LPS) structure. S. enteritidis was the only bacterium that showed an overall decrease in LPS liberation after subjection to the heat treatments. Pasteurization of E. coli resulted in changes in LPS composition, increased LPS liberation, abundance and allocation; while the same treatment applied to P. aeruginosa caused a decrease in the release of LPS from the outer membrane and noticeably influenced the component distribution measured in the supernatant of treated cells. Significant changes were evident in the lipid A, core and O-chain components of the LPS structure. Although no trends could be established, certain components like D- xylose (X), octadecanoic acid (C_18:0) and D-ribopyranose (RP) were subject to change in all three organisms tested and alteration in the distribution of D-fructopyranose (FP), L- leucine (L) and phenylalanine (PA) was unique to P. aeruginosa. These alterations occurred in the centres where endotoxicity, phylogenetic relationships and serotype classification are established.

Key words: Pasteurization, lipopolysaccharides, heat treatment, foodborne pathogens, gas chromatography-mass spectrometry.