Ryegrass is well known as a major problem weed in Australian cropping, but new evidence is showing that is potentially not the end of its nuisance value.
Research has found it may also be a damaging contaminant in gluten-free crops, such as pulses, millet, buckwheat and sorghum.
Gluten-like proteins have been identified in ryegrass varieties that could have the potential to cause adverse reactions for those with gluten intolerance or coeliac disease when mixed in with gluten-free products.
Sophia Escobar-Correas, a researcher based at Edith Cowan University and working in conjunction with CSIRO, said that while scientifically only proteins in wheat could be called gluten, the proteins identified in the ryegrass seemed to be similar to those in wheat.
She said researchers were keen to test whether consumers have adverse reactions similar to those they experience with gluten.
It presents a potential problem for farmers growing crops for use in the gluten-free food industry as ryegrass has a very small seed and can be difficult to keep out of a sample when harvesting.
While ryegrass is not a major crop in sorghum producing regions in northern Australia, it is the single most costly weed in the south, where there is a significant pulse industry including popular human consumption crops such as lentils and faba beans.
Increasing awareness of gluten intolerance and coeliac disease has in turn created demand for gluten-free grains, while pulses are benefiting from the hunt for sources of plant protein, meaning new opportunities for Australian grain growers, however this will be jeopardised if the product ends up causing an intolerance due to the presence of ryegrass.
Work led by ECU and CSIRO found that gluten-like proteins found in ryegrass could be mixing with crops commonly used as gluten-free products or wheat replacements and could cause a reaction among people with coeliac disease or gluten intolerance.
Dr Escobar-Correas said up to 30 per cent of people with coeliac disease said they had symptoms even when they were adhering to a gluten-free diet.
"We want to help them with this and check whether there are potentially small amounts of a gluten like substance in very small amounts in their food making a difference or whether we can rule that out," she said.
She said although further work needed to be done the major concern was trace amounts of ryegrass in the harvested crop, rather than contamination once the grain entered the food processing system.
The research identified the problematic proteins in 10 cultivars of ryegrass, with Dr Escobar-Correas saying there were 19 different proteins identified altogether.
"While these proteins aren't gluten in a scientific sense, they have the potential to trigger reactions for people who are coeliac and those with a gluten intolerance," Dr Escobar-Correas said.
Dr Escobar-Correas said the next step is to undertake clinical studies to investigate whether these proteins trigger a coeliac response.
"If these proteins cause a reaction for people with gluten intolerance, then it's important that we develop tests to detect their presence in food products which are otherwise gluten-free," Dr Escobar-Correas said.
Michelle Colgrave from ECU and CSIRO was a co-author on the research and said it has identified an important potential challenge for gluten-free products
"In 2019, the global market for gluten-free foods was worth around $6.3 billion and its growth shows no sign of slowing," Professor Colgrave said.
"This research will help give consumers and producers confidence that products labelled as gluten-free are free from other proteins which may trigger reactions resulting from agricultural co-mingling," she said.
Ryegrass species are widely spread across Australia, along with its use as a livestock feed and in the turf industry it is also a widespread weed in cropping systems, in particular in southern Australia.
The full report: 'Perennial ryegrass contains gluten-like proteins that could contaminate cereal crops' has been published in the journal Frontiers in Nutrition and can be accessed on the journal's webpage.