A simple rapid method was developed using gold nanorods for the colorimetric detection of lipopolysaccharide extracted from the generic strain, E. coli K12, which was used as a surrogate for the pathogenic strain, E. coli O157:H7. The principle is based on the aggregation of the cetyltrimethylammonium bromide-capped gold nanorods in the presence of lipopolysaccharide dispersed in phosphate buffer (pH 7.2). The interaction of the gold nanorods caused a rapid colour change from blue to black, which was visible through naked eye. The colour change was accompanied by a decrease in the absorbance of the longitudinal surface plasmon resonance (691 nm) of gold nanorods in the UV-visible spectra. The transmission electron microscopy confirmed the interaction of the gold nanorods with lipopolysaccharide. A good linearity (correlation coefficient R2 = 0.9725) was obtained between the concentration of lipopolysaccharide and absorbance ratio A/A0 of gold nanorods for the lipopolysaccharide concentration ranging from 200 ng/ml to 5 ng/ml. The limit of detection of the developed probe was found to be 1.11 ng/ml. Further, the developed probe was successfully employed in the detection of lipopolysaccharide spiked in food products like apple juice, mango juice, liquid milk, milk powder, and raw milk, and a good recovery percentage of 97%-106% was observed. © 2016 American Scientific Publishers.