IMMUNOCHEMICAL ANALYTICAL METHODS FOR THE DETERMINATION OF PEANUT PROTEIN IN FOODS

Authors: Whitaker, Thomas; Slate, Andrew; WILLIAMS, KRISTINA - FDA; TRUCKSESS, MARY - FDA

Submitted to: Journal of the Association of Official Analytical Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2005
Publication Date: 3/5/2005
Citation: Whitaker, T.B., Slate, A.B., Williams, K.M., Trucksess, M.W. 2005. Immunochemical analytical methods for the determination of peanut protein in foods. Journal of the Association of Official Analytical Chemists. 88:161-174.

Interpretive Summary: Contamination of foods with peanut proteins can cause severe allergenic reactions that can result in shock and death. The determination of peanut proteins in foods at various stages of the manufacturing process by analytical methods can reduce the risk of serious reactions in highly sensitized individual by removing contaminated foods from the market system. The U.S. Food and Drug Administration (FDA) is developing an inspection program to randomly test foods for unintentional peanut contamination using commercially available test kits. The efficiency of detecting and removing contaminated foods depends on the performance of the test kits used to quantify peanut proteins in foods. A study was conducted to evaluate the performance (accuracy and precision) associated with four commercially available test kits at detecting peanut proteins in four different foods. The performance of the test kits will be used to help field inspectors minimize the errors associated with not detecting contaminated lots. Minimization of false negatives will make the food supply safer for individuals allergic to peanut proteins.

Technical Abstract: Peanut proteins can cause allergenic reactions that can result in respiratory and circulatory effects in the body sometimes leading to shock and death. The determination of peanut proteins in foods at various stages of the manufacturing process by analytical methods can reduce the risk of serious reactions in the highly sensitized individual. The method performance of four commercially available enzyme-linked immunosorbent assay (ELISA) kits for the detection of peanut proteins in milk chocolate, ice cream, cookies and breakfast cereals was evaluated. The four test kits were evaluated for accuracy (recovery) and precision using known concentrations of peanut or peanut proteins in the four food matrices. Two different techniques, called incurred and spiked, were used to prepare samples with four known concentration of peanut protein. Defatted peanut flour was added in the incurred samples and water-soluble peanut proteins were added in the spiked samples. The incurred levels were 0.0, 10, 20, and 100 g whole peanut per g of food, while the spiked levels were 0.0, 5, 10, and 20 g peanut protein per g of food. Performance varied by test kit, protein concentration, and food matrix. The Veratox kit had the best accuracy or lowest percent difference between measured and incurred levels of 15.7% when averaged across all incurred levels and food matrices. Recoveries associated with the Veratox kit varied from 93 to 115 % for all food matrices except cookies. Recoveries for all kits were about 50% for cookies. The analytical precision, as measured by the variance, was found to increase with an increase in protein concentration. However, the coefficient of variation (CV) was stable across the four incurred protein levels and averaged 7.0% when averaged across the four food matrices and analytical kits. The r-Biopharm test kit had the best precision or a CV of 4.2% when averaged across all incurred levels and food matrices. Since measured protein values varied by test kit and food matrix, a method was developed to normalize or transform measured protein concentrations to an adjusted protein value that was equal to the known protein concentration. The normalization method adjusts measured protein values to equal the true protein value regardless of the type test kit or type food matrix.