ESTIMATION OF MICROBIOLOGICAL QUALITY OF EGG USING CHROMOGENIC LIMULUS AMOEBOCYTE LYSATE ENDPOINT ASSAY

Abstract

ABSTRACT Gram‐negative microorganisms, including Pseudomonas and Aeromonas, are widely implicated in the spoilage of liquid egg products. The ratio of gram‐negative to gram‐positive organisms in egg is essentially constant, and the aerobic plate count (APC) gives a good indication of the overall microbiological quality of egg. However, this method requires 5 days to complete, which limits its practical application. Our objective was to determine whether the rapid chromogenic Limulus amoebocyte lysate (LAL) assay could be applied to assess the microbiological quality of eggs. A modified LAL (BioWhittaker, Inc., Walkersville, MD) procedure was compared with the APC. LAL values were plotted against conventional plate counts, and a strong correlation (R2 = 0.93; n = 40) was observed. Subsequent experiments showed that LAL values allow an accurate prediction of APC (R2 = 0.81; n = 50). These results indicate that the LAL assay is a viable alternative to APC for the estimation of the microbial load in egg, requiring just 16 min to complete.