‘Novel and competitive’ starter cultures identified for gluten-free sourdoughs

By Stephen Daniells

- Last updated on GMT

Related tags: Lactic acid bacteria, Lactobacillus

Scientists in Ireland have identified ‘novel and competitive’ starter cultures for gluten-free sourdoughs, a result that may enable the industrial scale production of the cereal products.

The production of teff or buckwheat sourdoughs yielded lactic acid bacterial strains and yeasts not present in the commercial starter cultures, which may see industrial-scale gluten-free sourdough production become a reality, according to findings published in the International Journal of Food Microbiology​.

“The results of our study show that not all lactic acid bacteria and yeast strains present in commercial starters are suitable for the fermentation of buckwheat and teff sourdoughs, developed by continuous back-slopping,” ​wrote the researchers, led by Professor Elke Arendt from the School of Food and Nutritional Sciences, University College Cork.

“In these complex ecosystems, the flour was not only a source of spontaneous species, which either outcompeted or co-dominated with the starters lactic acid bacteria and yeasts, but it also exerted a key role in driving the selection of the dominant strains.

“Gluten-free flours represent thus an important reservoir for the selection of competitive starters for the production of gluten-free sourdough bread,”​ they added.

Great hopes for sourdough

Sourdough has already been identified as an ideal gluten-free food. Only recently, Professor Arendt co-authored a review in the journal Food Microbiology​ on the how sourdough could help solve the gluten-free issue.

Prof Arendt told FoodNavigator recently: “Sourdough has a lot of potential, particularly from a flavour and structure perspective. The strains used are also anti-fungal and that can extend the shelf-life of bread without the need of chemical preservatives.”

But employing sourdoughs requires a detailed knowledge of the strains and starter cultures for each grain. Sorghum sourdough would need a specific strain, like Lactobacillus reuteri​ or Lactobacillus fermentum​, while buckwheat flour would require other starter cultures.

“I have great hopes for sourdough in gluten-free bread,”​ said Prof Arendt.

And with global market reported to be worth $2.6bn by 2012, up from $1.56bn last year, according to Packaged Facts, there is clearly the financial incentive to produce new foods for this category.

The new study takes a step forward in the large scale production of gluten-free sourdoughs. By using selected lactic acid bacteria (LAB) and yeasts starter cultures the researchers sought to obtain consistent sourdough quality.

Selection of the strains is important, said the researchers, and can be done according to the strains’ technological properties, such as rate of acidification, aroma and/or antifungal compounds. “If such starters are developed, the industrial production of gluten-free sourdough bread on a large scale is likely to become a reality in the food market,”​ wrote Prof Arendt and her co-workers.

Study details

The Cork-based researchers prepared four laboratory-scale sourdoughs using buckwheat or teff flour. Two different starter cultures were used to initiate the fermentation of the dough.

Analysis of the final sourdough showed that both products contained “unique and complex lactic acid and yeasts communities […], comprising strains which originated from the flours”​, said the researchers.

Commenting on the actual strains present, Prof Arendt and her co-workers stated: “Among the lactic acid bacteria present in both starter culture A and starter culture B, ​L. helveticus and ​L. paracasei strains did not persist in buckwheat or teff sourdoughs. ​Lc. argentinum was competitive only in buckwheat sourdoughs, whereas ​L. reuteri persisted only in teff sourdough.

​L. fermentum and ​L. helveticus present in both starters dominated only the sourdoughs fermented at the higher temperature,” ​they added.

Two yeast strains - Kazachstania barnetti​ and Saccharomyces cerevisiae​ – outcompeted the starter yeasts in teff sourdoughs, a result the researchers described as ‘remarkable’.

“The isolation of autochthonous LAB and yeasts from the stable teff and buckwheat sourdoughs indicates that both flours represent an important reservoir for the isolation of novel and competitive starters for the production of gluten free sourdough bread,”​ they concluded.

Source: International Journal of Food Microbiology
​Volume 142, Issues 1-2, Pages 142-148
“Development of buckwheat and teff sourdoughs with the use of commercial starters”
Authors: A.V. Moroni, E.K. Arendt, J.P. Morrissey, F. Dal Bello

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