Multiplex-Competitive ELISA for Detection and Characterization of Gluten during Yogurt Fermentation: Effects of Changes in Certain Fermentation Conditions on Gluten Protein Profiles and Method Reproducibility Assessment

Evaluation of Gluten Protein Profiles in Hydrolyzed Food Products by a Multiplex-Competitive Enzyme-Linked Immunosorbent Assay

The apparent gluten concentration profiles of 47 hydrolyzed foods (barley malt, sprouted grains, and hydrolyzed wheat proteins (HWP)) were evaluated using a multiplex-competitive ELISA that utilizes the G12, R5, 2D4, MIoBS, and Skerritt antibodies from commercial sources. Cluster analysis was conducted to evaluate similarities or differences in the gluten protein/peptide response profiles among the hydrolyzed foods and their similarities or differences with fermented foods analyzed previously by the ELISA. The gluten protein/peptide response profiles of the hydrolyzed foods mainly depended on the grain source (wheat, rye, or barley) of gluten. Some hydrolyzed foods presented profiles similar to those of certain fermented foods (e.g., barley malt and gluten reduced barley beers), whereas others presented unique profiles (e.g., HWP and sprouted wheat). Additional analysis using wheat gluten-incurred yogurts indicated that while not suitable for the barley- or rye-containing foods tested, a newly developed gluten-incurred yogurt calibrant shows promise for the possible use in the quantitation of several wheat-containing fermented and hydrolyzed foods.

A label-free aptamer-based colorimetric biosensor for rapid gliadin detection in foods: a focus on pasta, bread and cookies

Despite numerous advancements in gluten detection, a substantial need remains for innovative, cost-effective, in situ methods that can be employed without complex analytical instruments. Addressing this demand, this study introduces a pioneering label-free colorimetric biosensor for the in situ detection of gliadin, a major component of gluten, which is a prevalent trigger of food allergies. Our novel approach employs the strategic coating of gold nanoparticles (AuNP) with gliadin-specific aptamers. In the absence of gliadin, these aptamers stably disperse AuNP, preventing their aggregation. However, upon the introduction of gliadin and in the presence of sodium chloride, AuNP aggregate, yielding a measurable colorimetric signal that facilitates the precise quantification of gliadin. Under rigorously optimized conditions, this AuNP/aptamer-based colorimetric biosensor demonstrated exceptional sensitivity and selectivity, with a detection limit of 32.1 ng mL-1 and a linear response range of 0-300 ng mL-1. Critically, the sensor maintained reliable performance when applied to real-world food samples, including gluten-free bread, cookies, and pasta. Due to its simplicity, selectivity, speed, and cost-effectiveness, this assay represents a significant advancement over current gluten detection methods. Moreover, the developed AuNP/aptamer-based colorimetric biosensor design holds promising potential for adaptation to detect other food allergens or protein toxins through selective aptamer modifications.

Validated multiplex-competitive ELISA using gluten-incurred yogurt calibrant for the quantitation of wheat gluten in fermented dairy products

Currently, there are no available methods for accurate quantitation of gluten in fermented or hydrolyzed foods. In this study, gluten-incurred yogurt was used as a calibrant with a multiplex-competitive ELISA to quantitate gluten in fermented dairy products such as yogurt, kefir, and buttermilk, followed by a single-laboratory validation of the method. Four-parameter logistic calibration curves using five gluten-specific antibodies (R5, G12, 2D4, MIoBS, and Skerrit) were constructed, and averaging of the antibody responses was used as a strategy to get a single quantitative value. The lower limits of detection (LLOD) and quantitation (LLOQ) of the method were 1.9 and 5.5 µg/mL (ppm), respectively. Analysis of wheat gluten-incurred fermented dairy products (5, 8, 20, 100, and 500 µg/mL) prepared with multiple starter cultures and fermented for 24 or 48 h resulted in average gluten recoveries of 69-165%, 57-167%, and 54-148% for yogurt, kefir, and buttermilk, respectively. Only a few samples exceeded 150% recovery. The average coefficient of variation (CV) ranged from 10 to 34%, with the majority of the samples having a CV of < 30%. Experimental variations such as long-term refrigerated storage, spiking gluten after initial fermentation, using higher than recommended starter culture concentrations, or using wheat flour for contamination resulted in acceptable gluten recovery (50-150%) for the majority of the samples. Comparison of the performance of this method with a commercial competitive ELISA showed that the method has greater quantitative accuracy. This newly developed and validated method appears sufficiently sensitive and accurate to quantitate the amount of wheat gluten before fermentation, in select fermented dairy products.