Measuring Hordein (Gluten) in Beer - A Comparison of ELISA and Mass Spectrometry
News Mar 27, 2013
Subjects suffering from coeliac disease, gluten allergy/intolerance must adopt a lifelong avoidance of gluten. Beer contains trace levels of hordeins (gluten) which are too high to be safely consumed by most coeliacs. Accurate measurement of trace hordeins by ELISA is problematic.
We have compared hordein levels in sixty beers, by sandwich ELISA, with the level determined using multiple reaction monitoring mass spectrometry (MRM-MS).
Hordein levels measured by ELISA varied by four orders of magnitude, from zero (for known gluten-free beers) to 47,000 µg/mL (ppm; for a wheat-based beer). Half the commercial gluten-free beers were free of hordein by MS and ELISA. Two gluten-free and two low-gluten beers had zero ELISA readings, but contained significant hordein levels (p<0.05), or near average (60-140%) hordein levels, by MS, respectively. Six beers gave false negatives, with zero ELISA readings but near average hordein content by MS. Approximately 20% of commercial beers had ELISA readings less than 1 ppm, but a near average hordein content by MS. Several barley beers also contained undeclared wheat proteins.
ELISA results did not correlate with the relative content of hordein peptides determined by MS, with all barley based beers containing hordein. We suggest that mass spectrometry is more reliable than ELISA, as ELISA enumerates only the concentration of particular amino-acid epitopes; this may vary between different hordeins and may not be related to the absolute hordein concentration. MS quantification is undertaken using peptides that are specific and unique, enabling the quantification of individual hordein isoforms. This outlines the problem of relying solely on ELISA determination of gluten in beverages such as beer and highlights the need for the development of new sensitive and selective quantitative assay such as MS.
The article is published online in the journal PLoS ONE and is free to access.
Salmonella Cases No Longer Declining in the EUNews
The declining trend of salmonellosis cases in the EU has levelled off according to the annual report on zoonotic diseases. Cases of Salmonella Enteritidis acquired in the EU have increased in humans by 3% since 2014 and in laying hens, the prevalence increased from 0.7% to 1.21% over the same period.
New Rapid Test for Valley Fever Should Help Reduce Diagnosis DelaysNews
November saw a spike if cases of Valley fever. Fortunately, the recent—and timely—approval of a new rapid assay test for Valley fever should reduce delays in diagnosing the respiratory fungal infections—a frequent problem in treating the disease, which is caused by spores endemic to soils in the U.S. Southwest.READ MORE
Bringing ‘Avatar’-Like Glowing Plants to the Real WorldNews
The 2009 film “Avatar” created a lush imaginary world, illuminated by magical, glowing plants. Now researchers are starting to bring this spellbinding vision to life to help reduce our dependence on artificial lighting.READ MORE