Quantification of Barley Contaminants in Gluten-Free Oats by Four Gluten ELISA Kits

Abstract

Pure oats are generally accepted to be safe for most celiac patients, and consumption of oats provides advantageous dietary fibers. However, oats can be contaminated by gluten proteins from wheat, barley, and/or rye. The analytical challenge lies in the reliability of the quantification method and how to maintain the contamination level under a gluten-free food threshold of 20 mg/kg. In this study, we investigated barley-spiked oat flour samples at four levels using four gluten ELISA kits. The largest recovery variance was with the R5 kit that gave 5–6 times overestimation; the G12 kit cross-reacted with oat proteins and gave 4–5 times overestimation at all spiked levels. The Total Gluten and Morinaga kits gave satisfactory recoveries. Total barley hordeins were isolated and characterized to be used as a common calibrator in all four kits aiming at harmonizing the results and to test the kits’ performance. Immunoblotting of total hordein isolate revealed that Total Gluten and Morinaga antibodies provided an overall detection, while R5 and G12 antibodies recognized specific hordein groups leading to a larger difference when wheat and barley were used as the calibrant. Calibration with total hordein isolate corrected the overestimation problem and decreased the variability between the four gluten kits.

IoT System for Gluten Prediction in Flour Samples Using NIRS Technology, Deep and Machine Learning Techniques

“…In fact, AOAC Official Method has validated one of these kits to measure gluten in various types and forms of food [14]. Although some authors have detected limitations and variations of 20 ppm among results using ELISA commercial kits for gluten quantification on heated and processed food [12,13,15], others have noticed some improvements when applying the methods to dairy products [16] and plant seeds [17], with results that allow quantification until 5.5 ppm. The ELISA method is quicker and easier to perform than instrumental techniques, however, it takes time (from 30 min to 2.5 h [13]) and laboratory equipment is necessary.…”