Improving Gluten-Free Rice Bread Using Sourdough Bacteria

Greg Howard
25th July, 2025

Improving Gluten-Free Rice Bread Using Sourdough Bacteria

Increasing the concentration of sourdough fermented with either Lactobacillus fermentum or Lactobacillus plantarum progressively lowered the pH of the rice-based gluten-free bread, a key factor contributing to the overall improvement in bread quality and shelf-life.

Image adapted from: Seyedahmadi et al. / CC BY (Source)

Key Findings

  • Research from Tabriz, Iran, found that adding sourdough to gluten-free rice bread significantly improved its overall quality and shelf life
  • Sourdough, particularly at higher concentrations, made the bread more acidic, which helped prevent mold and yeast growth, keeping it fresh longer
  • The most preferred gluten-free rice bread, based on taste and texture, was made with 20% sourdough, balancing benefits with consumer acceptance
The increasing prevalence of conditions like celiac disease, gluten intolerance, and wheat allergy means that approximately 1 in every 14 Americans requires or chooses to avoid gluten. Beyond medical necessity, many individuals are also adopting gluten-free (GF) diets due to a perception of improved health. This trend has fueled significant growth in the global GF market, which reached 4.63 billion USD in 2017 and was projected to hit 6.47 billion USD by 2023[2]. While various grains and pseudocereals like millet, corn, amaranth, and quinoa serve as foundations for GF products, a major challenge lies in achieving a quality that matches traditional gluten-containing foods. Often, this requires the addition of processing aids such as starches, gums, and enzymes, which can sometimes lead to an imbalance in nutrients[2]. Addressing these challenges, recent research from the Tabriz Higher Education Institute of Rab-Rashid[1] explored how sourdough fermentation could enhance the quality of gluten-free rice flour bread. Sourdough fermentation is a traditional biotechnology known to profoundly affect the rheology (how dough flows and deforms), sensory characteristics (flavor and aroma), and shelf life of baked goods[3]. This study specifically investigated the impact of using two distinct bacterial strains, Lactobacillus fermentum and Lactobacillus plantarum, in sourdough, along with varying dough yields and sourdough concentrations in the final bread. The study aimed to improve GF bread by leveraging the natural processes of sourdough. The researchers prepared sourdough using either Lactobacillus fermentum or Lactobacillus plantarum as starter cultures, at two different dough yields: 200% and 300%. These sourdoughs were then analyzed for characteristics such as pH (a measure of acidity), lactic acid concentration, and the count of lactic acid bacteria present. Following this, the prepared sourdoughs were incorporated into rice-based gluten-free bread at concentrations of 10%, 20%, and 30%. The resulting breads were evaluated for their physicochemical properties, including pH, moisture content, color (measured by L, a, and b indices, which indicate lightness, red/green, and yellow/blue respectively), and microbial stability, specifically mold and yeast counts over time. Sensory acceptance was also assessed to determine consumer preference. The findings demonstrated that the specific bacterial strain and dough yield significantly influenced sourdough characteristics. For instance, sourdoughs made with L. fermentum at both 200% and 300% yield showed the highest pH levels (4.53 and 4.60, respectively), indicating less acidity. Conversely, sourdough prepared with L. plantarum at a 200% yield had the highest lactic acid content (620.33 mg/100g dry basis), suggesting a more pronounced sour flavor. When these sourdoughs were incorporated into bread, the results were notable. Increasing the sourdough content in the bread formula led to a lower pH in the final product, meaning it was more acidic. This increased acidity is a key factor in extending shelf life, as it inhibits the growth of spoilage microorganisms. Indeed, the study found that higher sourdough content resulted in lower mold and yeast counts, indicating better preservation. For example, control bread, without sourdough, had the highest mold and yeast counts (7.95 log cfu/g, where log cfu/g is a logarithmic measure of colony-forming units per gram, indicating microbial population) after four days, while bread with 30% sourdough at a 200% dough yield had significantly lower counts (0.72 log cfu/g) on the first day. This aligns with earlier research highlighting sourdough fermentation's deep effects on the shelf life attributes of baked goods[3], and specifically, how Lacticaseibacillus paracasei SP5 sourdough improved resistance against mold and rope spoilage[4]. Furthermore, the study observed changes in bread color: higher sourdough content led to lower a and b color indices (less red/green and yellow/blue hues) but a higher L color index (lighter bread). An increase in dough yield, from 200% to 300%, generally resulted in higher pH, greater baking loss, and increased mold and yeast counts, suggesting that a 200% dough yield was more favorable for overall quality and preservation in this context. Crucially, the sensory evaluation revealed that consumer acceptance peaked and then declined with sourdough levels up to 20%. The optimal bread, based on sensory preferences, was made with 20% sourdough using either L. fermentum or L. plantarum at a 200% dough yield. This indicates that while sourdough offers benefits, there is an optimal concentration for taste and texture. This finding supports the broader understanding that sourdough fermentation profoundly affects the sensory features of baked goods[3], and specific strains can lead to a higher concentration of volatile compounds that contribute to flavor[4]. This study builds upon and complements previous scientific work on sourdough and gluten-free foods. It directly addresses the "quality departure" challenge in GF products[2] by demonstrating a natural, fermentation-based approach to improve texture, flavor, and shelf life, rather than relying solely on processing aids. While previous studies have shown that sourdough can decrease gluten content and increase mineral bioavailability[3], this research focuses on its application to inherently gluten-free flours like rice, showing how specific Lactobacillus strains, which are common in sourdoughs[5], can be harnessed to overcome the inherent limitations of GF ingredients. The findings provide scientific support for using specific sourdough concentrations and bacterial strains to produce high-quality, palatable, and longer-lasting gluten-free rice bread, offering a significant step forward for the growing GF market.

NutritionHealthBiotech

References

Main Study

1) Enhancing the quality of rice-based gluten-free bread using sourdoughs fermented with Lactobacillus fermentum and Lactobacillus plantarum

Published 22nd July, 2025

https://doi.org/10.1038/s41598-025-11872-4

Related Studies

2) Current applications of gluten-free grains - a review.

https://doi.org/10.1080/10408398.2020.1713724

3) Novel insights on the functional/nutritional features of the sourdough fermentation.

https://doi.org/10.1016/j.ijfoodmicro.2018.05.018

4) Quality Characteristics of Novel Sourdough Breads Made with Functional Lacticaseibacillus paracasei SP5 and Prebiotic Food Matrices.

https://doi.org/10.3390/foods11203226

5) Evolution of sourdough microbiota in spontaneous sourdoughs started with different plant materials.

https://doi.org/10.1016/j.ijfoodmicro.2016.05.025


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