The chromogenicLimulusamoebocyte lysate (LAL) assay may be used to distinguish between ultra high temperature (UHT) and in‐container sterilized (ICS) milks, when applied to samples which have received an additional heat treatment of 100°C for 10 minutes. This heat treatment resulted in a significant increase (p<0.001) in the availability of lipopolysaccharides in ICS milks which did not occur in UHT milk samples. This method for distinguishing between these milk types is, however, limited to samples whose sera require extensive dilution prior to testing. This possibly reflects the calcium levels prese