Development of a direct sampling method for verifying the cleanliness of equipment shared with peanut products

A direct sampling method was developed to verify the cleanliness of stainless steel equipment used to produce peanut products. The protocol consisted of sampling the product-contact area with two Critical Swab® flat zapped-head foam swabs pre-moistened with 20 mM phosphate, pH 7.2 (PBS), mixing each swab in PBS for 1 h, and analyzing the extract for peanut residues. Quantitation of peanut residues was accomplished with a non-specific assay while SDS–PAGE was used to ensure the recovery of the allergen, Ara h 1. This sampling approach was able to recover 90–95% of the peanut proteins at sub-microgram levels and Ara h 1 at low nanogram levels directly from a stainless steel surface.