Written by : Léa Ribet, Scientific Affairs Research Associate, Lesaffre Institute of Science & Technology

Bread is a staple food consumed by millions of people worldwide every day. It belongs to the category of fermented foods, defined by a simple combination of ingredients: flour, water, salt, yeasts, and occasionally, bacteria (the latter being optional).

While the dough rises naturally through yeast fermentation, bacteria play a role in its acidification. Together, bacteria and yeasts form the ferments, whose influence extends far beyond the technological aspects of breadmaking. They also act on the nutrients contained in the flour, sometimes pre-digesting them, which makes these nutrients more accessible and digestible when the bread is consumed.

The nutritional characteristics of bread

These primarily stem from the type of flour used to make it. The less processed and more whole the flour, the richer it is in beneficial fibres and micronutrients, such as vitamins and minerals, which are valuable for meeting our daily nutritional needs.

The choice of cereal variety is also important, influencing the breadmaking method, taste and overall nutritional profile. For example, wholemeal rye bread is a valuable source of fibre and minerals such as iron, zinc, magnesium and manganese.

In general, the cereals used for breadmaking share common nutrients of interest, such as complex carbohydrates (starch), vegetable proteins (mainly gluten), and relatively low levels of fat and simple sugars. These nutrients contribute to long-term health as part of a balanced diet.

It is important to note that the nutritional value of final product depends on the recipe: a sandwich bread, for example, does not have the same nutritional composition as a wholemeal crusty bread. In addition, bread is usually eaten with other foods and toppings so nutritional intake must be considered holistically.

The role of microorganisms and fermentation on the digestibility of bread.

While the nutrients in bread primarily come from cereals, the role of microorganisms and fermentation should not be overlooked. The fermentation process, mediated by yeasts and lactic acid bacteria, not only makes bread edible but may also have an impact on its digestibility, especially for individuals with food sensitivities.

Digestibility of bread in relation to food sensitivity

During fermentation, bacteria and yeast produce enzymes – specialised molecules that act as catalysts, speeding up chemical reactions in the body and in various processes, such as fermentation. For instance, specific enzymes named peptidases, produced by lactic acid bacteria, can break down proteins of flours, in particular, the immunogenic peptides (gliadins) of gluten. This natural hydrolysis releases smaller peptides and amino acids.

Some studies have indicated that specific sourdough breads could be more comfortably digested by people experiencing sensitivity to wheat, likely due to the degradation of these gluten components.1,2

However, the effect of sourdough fermentation on gluten content and resulting sensitivity can vary depending on the specific strains of ferments used, fermentation conditions (such as time, pH and temperature), and the flours and cereals employed.3

It’s important to note that people with coeliac disease are intolerant to gluten and must completely exclude it from their diet, though gluten-free breads made from alternative grains such as corn or rice exist as an alternative.

Digestive discomfort is often attributed to gluten, however, science points to other possible components in cereals.

In parallel, enzymes like inulinase and invertase, naturally produced by certain yeasts and bacteria during fermentation, can help reduce the levels of fermentable sugars known as FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) in bread, particularly fructans.

FODMAPs have been associated with digestive discomfort in individuals with sensitivity, such as those with irritable bowel syndrome (IBS).3,4

Finally, recent studies reveal another potential benefit of fermentation on molecules called ATIs (amylase trypsin inhibitors), also suspected of playing a role in the discomfort of those with digestive sensitivity.5

Mineral Bioavailability

Fermentation could enhance the bioavailability of certain minerals, such as iron, calcium, magnesium and zinc. Indeed, during the breadmaking process, phytic acid – a well-known antinutrient particularly present in wholegrain flours – is broken down. Phytic acid can bind to such minerals, reducing their accessibility.

Sourdough fermentation, by increasing the acidity of bread, amplifies the degradation of phytic acid, making minerals potentially more accessible to the body.6

This biological phenomenon is a concrete illustration of how fermentation can reveal all the nutritional benefits of wholegrain flours.

More potential benefits

Some scientific studies have suggested that sourdough fermentation, under very specific conditions, could lead to a reduction in the glycemic index and an increase in the feeling of satiety.7 Bread consumption could also influence gut microbiota composition and activity, particularly in relation to the production of short chain fatty acids.8

Additionally, fermentation may result in the synthesis of beneficial biomolecules, such as polyols with antioxidant effects or exopolysaccharides with prebiotic properties. However, these effects have only been demonstrated in specific cases and should not be generalised to include all types of fermentation and conditions.3

Fermentation, the diversity of ferments and the creation of new products

The diversity of ferments and cereals used in breadmaking presents infinite possibilities for developing new breads with unique characteristics. By combining flours rich in essential nutrients with ferments that have specific properties, it is possible to naturally develop breads that cater to local or niche trends and preferences in nutrition and wellbeing, while maintaining their typical taste and accessibility.

Conclusion

Fermentation is a natural process that has been used for centuries to make tasty foods and preserve them. As scientific understanding of this process continues to grow, new discoveries are revealing the many benefits of fermentation. We can already say with some certainty that fermentation is not just a matter of taste and texture, it also represents a powerful tool for the nutritional enhancement of bread products.

However, we are also conscious that consumers are invested in the traditional and comforting imagery associated with bread. This highlights the importance of innovating in the nutrition field while maintaining the familiar characteristics that make bread a staple in the daily diets of millions of people.9

For more information-

Zoé Henneguier

E: z.henneguier@lesaffre.com

77 rue de Menin, 59520

Marquette-lez-Lille, France

References

1. Di Cagno R, De Angelis M, Lavermicocca P, De Vincenzi M, Giovannini C, Faccia M, Gobbetti M. Proteolysis by sourdough lactic acid bacteria: effects on wheat flour protein fractions and gliadin peptides involved in human cereal intolerance. Appl Environ Microbiol. 2002 Feb;68(2):623-33.

2. De Angelis M, Cassone A, Rizzello CG, Gagliardi F, Minervini F, Calasso M, Di Cagno R, Francavilla R, Gobbetti M. Mechanism of degradation of immunogenic gluten epitopes from Triticum turgidum L. var. durum by sourdough lactobacilli and fungal proteases. Appl Environ Microbiol 2010;76(2):508–18.

3. Ribet L, Dessalles R, Lesens C, Brusselaers N, Durand-Dubief M. Nutritional benefits of sourdoughs: A systematic review. Adv Nutr. 2023 Jan;14(1):22-29.

4. Fraberger V, Call LM, Domig KJ, D’Amico S. Applicability of yeast fermentation to reduce fructans and other FODMAPs. Nutrients 2018;10(9):1247.

5. Huang X, Schuppan D, Rojas Tovar LE, et al. Sourdough fermentation degrades wheat alpha amylase/ trypsin inhibitor (ATI) and reduces pro-inflammatory activity. Foods 2020;9(7):943.

6. García-Mantrana I., Monedero V., Haros M. Myo-inositol hexakisphosphate degradation by Bifidobacterium pseudocatenulatum ATCC 27919 improves mineral availability of high fibre rye-wheat sour bread. Food Chem. 2015;178:267–275.

7. Chatonidi G, Pradal I, De Vuyst L, Courtin CM, Verbeke K. Effect of lactic acid-rich sourdough bread on appetite regulation: A randomized, double-blind controlled trial. Curr Res Food Sci. 2024 Dec 16;10:100956.

8. Martinez Tuppia, C.; Rezaei, M.N.; Machuron, F.; Duysburgh, C.; Ghyselinck, J.; Marzorati, M.; Koper, J.E.B.; Monnet, C.; Bosco, N. In Vitro Human Gastrointestinal Digestibility and Colonic Fermentation of Wheat Sourdough and Yeast Breads. Foods 2024, 13, 3014.

9. NielsenIQ-GfK & Brainvalue / Lesaffre Market survey 2024©