Strain breakthrough points to gluten-free sourdough

Writing in the International Journal of Food Microbiology​, researchers from the University of Hohenheim report that Lactobacillus plantarum​ RTa12 and Pediococcus pentosaceus ​RTa11 allowed stable fermentation.

Yasemin Sterr, Agnes Weiss, and Herbert Schmidt suggest that the strains could be used individually or in combination and “may be considered as candidates for amaranth sourdough starter cultures”​.

Great hopes for sourdough​

Sourdough has already been identified as an ideal gluten-free food. Only recently, Professor Elke Arendt from the Department of Food and Nutritional Science at University College Cork 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 a 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 identification of strains to produce amaranth sourdough as a gluten-free alternative.

Sterr, Weiss, and Schmidt prepared spontaneous fermented sourdoughs from five amaranth flours. The doughs were fermented on a laboratory scale at 30 degrees Celsius for 10 days.

At the end of this time, the acidity of all the doughs had increased, from pH6.0 to about pH 4.0. P. pentosaceus​ was identified as the dominant species in all sourdoughs, while the strains L. plantarum​ RTa12, and L. sakei ​RTa14 were also identified as potential started cultures.

Sourdoughs using both L. plantarum​ RTa12 and P. pentosaceus​ RTa11 were characterized further and both strains were found to lead to fast pH declines and stable fermentation at the different temperatures studied.

“The scheme proposed in this study yielded two promising strains, ​L. plantarum RTa12 and ​P. pentosaceus RTa11, which pose interesting opportunities, both as single cultures or in combination,”​ wrote the researchers.

“Technological applicability and sensoric quality of amaranth sourdoughs prepared with these strains will be in the focus of future research,”​ they concluded.

The study was supported by the German Ministry of Economics and Technology

Alternative or ancient grains​

The potential of alternative or ancient grains, such as amaranth, buckwheat, quinoa, brown rice, sorghum, and teff to offer gluten-free alternatives to wheat-based favourites is nothing new. Last month, scientists from the Celiac Disease Center at Columbia University in New York reported that the use of such alternative flour sources could improve intakes of protein, iron, calcium and fibre (Journal of Human Nutrition and Dietetics​).

Source: International Journal of Food Microbiology​
Published online ahead of print, doi: 10.1016/j.ijfoodmicro.2009.09.006
"Evaluation of lactic acid bacteria for sourdough fermentation of amaranth"​
Authors: Y. Sterr, A. Weiss, H. Schmidt