Using ELISA to detect allergens in salad dressing

Tuesday, 07 July 2009 22:43

Certain food matrices and processing conditions are known to affect the detection of protein residues using the ELISA method. The detectability of proteins in mustard, egg, milk, and gluten in salad dressing was investigated by Dr Steve Taylor and his colleagues at the Food Allergy Research and Resource Program (FARRP) in Nebraska.

In initial recovery experiments, salad dressing was formulated with 0 to 1000 ppm mustard flour, with the mean percent recovery only 7.7%± 1.6%. Adjusting the pH to 7 prior to spiking with mustard improved recovery to 94.1%± 7.6%. However, if the pH was neutralised after spiking, the recovery was only 11.1%± 1.7.

Vinegar was spiked with mustard flour at pH 3, 3.5, and 4, and detectability of mustard was found to be lowest at pH 3. The authors mentioned this was probably because of acid precipitation of mustard proteins that renders them insoluble and nonextractable.

In the same study, commercial salad dressings containing 100 ppm (mg/kg) of egg, milk, or gluten were analyzed  every 2 to 4 days for 90 days using 3 commercially available ELISA kits. A decrease in the detection of the egg, milk, and gluten in the salad dressing upon storage was observed.

Conclusions drawn from the study included the importance of understanding the differences in ELISA test kits for certain food matrices, and the impact of product storage on extraction of detectable proteins.

Reference: Lee et al. 2009. Journal of Food Science. Vol 74(5). pp. T46-T50(1).