Sunday, 5 October 2014

The Detection of Gluten in Oats

Oats come from a different taxononomic family to wheat, barley and rye and their main storage
proteins are avenins.  Although ELISA tests can detect wheat gliadins, rye secalins, and to a lesser extent barley hordeins, they do not detect oat avenins.  Avenins have some of the same amino acid sequences (which contribute to the whole protein) as gliadins, as discussed in Section 4.1, and it is thought that these sequences may induce a response experienced by someone with Coeliac disease who has consumed oats.   As it is not conclusive as to which part of the oat protein (if any) triggers a reaction in Coeliac patients, there is still no simple, low cost test that measures the amino acid sequences or peptides from oats that may be deleterious to individuals with Coeliac disease. 
Although ELISA tests do not measure oat avenins, High Performance Liquid Chromatography (HPLC) is one technique that will measure oat avenins when present.  HPLC involves a two-stage process to detect oat avenins: an initial extraction of protein; and then subsequent quantitation of avenins if they are present.  The method that is used by the New Zealand Institute for Crop and Food Research is Reverse Phase High Performance Liquid Chromatography (RP-HPLC) (Lookhart & Peterson, 1994).  Unlike ELISA tests which react to a specific amino acid sequence, HPLC separates out each avenin and measures the actual amount of each avenin present, the physical quantity, which may be expressed as a percentage or a weight ratio (e.g. ug/g).  As different HPLC techniques vary in sensitivity, an estimate of the level of detection of avenins using HPLC is 50 ppm (5 mg/100 g) (Simmons, personal communication).  Given that HPLC is a more complex process that relies on the use of specific analytical equipment rather than a testing kit that can be purchased, it may be more expensive and not as readily accessible to food manufacturers as commercially available test kits such as the ELISA test.  
Excerpt from the Food Standards

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