Impact of Microwaving on the Protein Content and Microbial Levels of Whole Wheat Flour for Use in Oral Immunotherapy

Rationale: Food products used in Oral Immunotherapy studies conducted under INDs have to meet specific criteria for allergen content and bioburden. We studied the effect of microwaving on the protein content and bioburden of whole wheat flour proteins (Tri a 19 and Tri a 37).

Methods: SDS-PAGE analysis coupled with densitometric scanning was conducted on whole wheat flour subjected to microwaving at 1000 Watts for increasing lengths of time (0min, 1min, 2min, 4min, 7min and 10min) to determine the effect of microwaving on protein content. Thermally processed and unprocessed whole wheat flour was tested for the presence of Escherichia coli, Salmonella, aerobic bacteria, mold and yeast levels.

Results: Microwaving wheat flour for varying times resulted in <10% variance in the content of Tri a 19 and Tri a 37 proteins as revealed by SDS-PAGE and densitometry analysis. Bioburden testing revealed a significant decrease in aerobic plate count (>2500cfu/g at 0min to 470cfu/g at 10min), yeast (>2500cfu/g at 0min to <10cfu/g at 10min), mold (150cfu/g at 0min to <10cfu/g at 10min), Escherichia coli and Salmonella levels (Presumptive/10g at 0min to Negative/10g at 10min) with microwaving. Importantly, the levels of these microbes after 10 minutes of microwaving met criteria established by USDA for an orally delivered drug product.

Conclusions: Microwaving of whole wheat flour leads to a significant decrease of bioburden levels without significantly altering the protein content. Future studies will determine the effect of microwaving on the allergenicity of wheat proteins using Western blotting, ELISA and basophil activation testing.