P1-82 ELISA Detection of Gluten in Traditionally Brewed Soy Sauce Samples Obtained during Manufacture

Monday, August 1, 2016
America's Center - St. Louis
Wanying Cao, Illinois Institute of Technology/IFSH, Bedford Park, IL
Mikio Bakke, Kikkoman USA R&D Laboratory, Madison, WI
Binaifer Bedford, U.S. Food and Drug Administration, Bedford Park, IL
Eric Garber, U.S. Food and Drug Administration, College Park, MD
Lauren Jackson, U.S. Food and Drug Administration-CFSAN, Bedford Park, IL
Introduction: Analytical methods are needed to detect and quantify gluten in ingredients, finished foods and food processing environments. However, detection of gluten in hydrolyzed and fermented foods presents an analytical challenge.

Purpose: This study tracked changes in gluten detection in traditionally brewed soy sauce samples obtained at different stages of production using five commercial gluten ELISA kits.

Methods: Traditionally brewed tamari soy sauces formulated without wheat were produced in a pilot plant and spiked with 0 μg/g, 7.2 μg/g and 72 μg/g gluten at the moromi mash stage of production. Traditionally brewed regular soy sauce formulated with wheat was produced in a pilot plant. Tamari and regular soy sauce samples were collected during various stages of production and analyzed in triplicate using five commercial gluten ELISA kits.

Results: Gluten concentrations in the tamari moromi mash spiked with 72 μg/g gluten were 19 (4% CV) – 31 (3% CV)  μg/g, as measured with the Ridascreen sandwich, Ridascreen competitive, AgraQuant G12 sandwich, Aller-Tek sandwich, and Morinaga sandwich ELISA kits. The high sensitivity of the Morinaga ELISA (LOQ, 0.27 μg/g) enabled the lowest detection of gluten in the tamari moromi mash spiked with 7.2 μg/g gluten, while other kits were unable to detect gluten in this sample.  Gluten concentrations in tamari sauces after 1-6 months of fermentation were <LOQ values for all ELISA kits.  Analyses of regular soy sauce samples indicated the presence of 5,600 (5% CV) – 32,000 (6% CV) μg/g gluten in koji, and 2,100 (0.1% CV) - 18,000 (4% CV) μg/g in the moromi mash. Gluten levels in regular soy sauce after 1-6 months of fermentation were <LOQ values of the ELISA kits.

Significance: This study demonstrates that reliable detection and accurate quantification of gluten, subjected to the fermentation process used in the production of soy sauce, is not possible using available ELISA technology.