Purpose: This study examined how the brewing process and the addition of a prolyl endopeptidase enzyme (Brewers Clarex®) affected gluten detection in beer brewed with barley malt using gluten-specific ELISA and lateral flow devices (LFDs).
Methods: Beer (55 L) was brewed from barley malt in a pilot plant, and Clarex®was added at varying dosages [0 (control), 0.017, 0.034, 0.068 ml/liter] to equal volumes (13 L) of beer before fermentation. Beer samples were collected until 8.5 weeks fermentation/aging. Five ELISA tests (Ridascreen Gliadin sandwich, Ridascreen Gliadin Competitive, Aller-Tek Gluten, Morinaga Wheat/Gluten, AgraQuant G12) and four LFD kits (AgraStrip G12, ELISA Systems sandwich, ELISA Systems competitive, Morinaga Gluten/Gliadin IIR) were used to detect gluten in samples. Pilot plant trials and analytical tests were completed in triplicate.
Results: Gluten concentrations in unfermented beer ranged from 96 to 191 ppm gluten across three trials as measured with the AgraQuant G12 ELISA [LOQ, 4 ppm]. After 8.5 weeks fermentation/aging, control beer had <LOQ 10 ppm gluten, while the Clarex®-treated beer (0.017, 0.034, 0.068 ml/liter) had 4 to 21 ppm gluten, <LOQ 35 ppm gluten, and <LOQ 23 ppm gluten, respectively (≤6% CV for all samples). Control beer fermented/aged for 8.5 weeks and subjected to a filtration treatment had up to seven ppm gluten, while comparable Clarex®-treated beer had gluten levels <LOQ of the AgraQuant ELISA. While the AgraStrip LFD tests gave positive results for all unfiltered beer samples, only the control treatment gave positive results for filtered beers.
Significance: Variability exists when determining gluten content in hydrolyzed and fermented foods. Complementary methods, such as mass spectrometry, are needed to detect gluten in fermented and hydrolyzed foods.