Dough: NIRS tests low-gluten wheat

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  • Published: Apr 1, 2016
  • Author: David Bradley
  • Channels: Infrared Spectroscopy
thumbnail image: Dough: NIRS tests low-gluten wheat

Better wheat for coeliac disease

Near-infrared spectroscopy (NIRS) can be used to distinguish between strains of wheat of low gliadin content that have been produced by RNA interference (RNAi), from non-transgenic wheat lines and so might be a suitable food for people with coeliac disease. (Wheat field photo by David Bradley)

Near-infrared spectroscopy (NIRS) can be used to distinguish between strains of wheat of low gliadin content that have been produced by RNA interference (RNAi), from non-transgenic wheat lines and so might be a suitable food for people with coeliac disease.

Coeliac (celiac) disease is an autoimmune disorder that detrimentally affects the function of the small intestine in people with a genetic predisposition to the condition. The most common symptoms include chronic diarrhoea, abdominal distention, malabsorption, loss of appetite, anaemia and in children a failure to develop normally. The trigger for symptoms is ingestion of any of a number of wheat proteins known generally as gluten. These proteins are also found in other cereal crops, including rye and barley. The immune system offers an inflammatory response to the presence of gluten in the gut leading to the common symptoms, although other problems are known and not all sufferers experience the same symptoms.

María Dolores García-Molina, Francisco Barro of the Department of Plant Breeding, at the Institute for Sustainable Agriculture (IAS), part of Spain's Higher Council for Scientific Research (CSIC) in Córdoba, and Juan García-Olmo of the NIR/MIR Spectroscopy Unit at the University of Córdoba, explain how wheat is the most widely cultivated cereal food crops. Wheat proteins represent just 9 to 15 percent of the mass with starch (carbohydrates) representing between 60 and 75 percent of the grain. Gluten proteins represent 80 to 85% percent of the protein mass and almost a third of that is gliadins, with half being glutenins. The monomeric gliadins are essential to a good dough for bread making. Unfortunately, about 1 in 100 people worldwide have the enteropathic sensitivity to gluten we know as celiac disease. There is, however, some evidence that the numbers may be greater and that coeliac disease is under-diagnosed and perhaps more common than current statistics would suggest.

Gliadins

People with coeliac disease are advised to follow a gluten-free diet for life and in some cases must avoid any contact with the allergenic glutens that trigger their symptoms. As such, there is much effort to develop strains of wheat that retain the useful properties of gluten for bread making but without the health problems for people with coeliac disease. "The development of new cereal varieties, and specially wheats, with reduced immunogenic gluten content would be extremely significant," the team writes in the journal PLoS One, "both to improve the diet and to reduce the incidence of disease, as it has been shown that disease initiation is associated with the amount and duration of gluten exposure." There has been a rather "fashionable" move towards gluten-free products even for people without coeliac disease who may or may not have a different kind of intolerance to these proteins. Unfortunately, many of these manufacturer products are less nutritious and often highly processed. There is a market for healthier low-gluten products for both those who perceive of wheat as a "bad" foodstuff and for those who have a serious medical condition. "One promising approach for reducing gluten toxicity and, therefore, the incidence of gluten-related intolerances from cereals is the down-regulation of immunodominant gluten peptides by RNA interference (RNAi)," the team reports.

NIRS assessment

As such, the team has now scanned low-gliadin wheat samples using a Foss-NIR Systems 6500 System II instrument. They then developed discrimination models for the entire spectral range, 400 to 2500 nanometres and for the ranges 400-780, 800-1098 and 1100-2500 nm, with a subsequent partial least square (PLS) analysis. They also carried out two external validations on samples from the years 2013 and 2014 and demonstrated a minimum accuracy of 99% for flour samples and 96% for the classification of whole grain samples. The transgenic sample set included 409 samples for whole grain sorting and 414 samples for flour experiments, while the non-transgenic set consisted of 126 and 156 samples for whole grain and flour, respectively, the team writes.

Low-gluten and gluten-free products are important, but it is important to sustain the nutritional quality of the wheat from which they are derived. Traceability is critical and to ensure that products aimed at people with coeliac disease and non-coeliac gluten sensitivity (NCGS) can rely on the food they eat not being contaminated with the proteins that cause them harm, straightforward quality control tools are needed. Those same tools can also be used to assess and help develop suitable wheat strains in the first place.

Related Links

PLoS One 2016, online: "Effective Identification of Low-Gliadin Wheat Lines by Near Infrared Spectroscopy (NIRS): Implications for the Development and Analysis of Foodstuffs Suitable for Celiac Patients"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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