1. Scope and operational definitions

In technical language it is essential to separate three concepts that are often confused:

1. Gluten hydrolysis/proteolysis
→ fragmentation of proteins (gliadins and glutenins) into smaller peptides.

2. Reduction of immunogenic peptides/epitopes for celiac disease→ degradation of specific sequences rich in proline and glutamine (e.g. “Pro-rich” peptides) that resist digestion and activate immune responses in celiac patients.

3. “Elimination” of gluten→ a much more ambitious objective, achievable only under controlled technological conditions (selected strains, often enzymatic co-adjuvants, long fermentation times), and not equivalent to normal baking with traditional sourdough.

2. Evidence: what studies show

2.1 Fermentation with selected lactic acid bacteria: targeted degradation of immunogenic peptides

Di Cagno et al., 2004 (Applied and Environmental Microbiology) demonstrate that the use of selected lactobacilli with specialized peptidases is able to hydrolyze proline-rich peptides, including peptides with high immunogenicity (the work explicitly discusses the hydrolysis of “Pro-rich” peptides and the application to an experimental baked product).
The study also includes an acute clinical challenge test in subjects with celiac disease within the described experimental protocol. (PubMed)

Key technical points (what is “demonstrated”)

• The ability to degrade prolamin fractions critically depends on strain selection (it is not an automatic effect of any sourdough). (PubMed)

• Degradation involves peptides known to resist gastrointestinal digestion thanks to enzymatic systems (peptidases) not typical of baker’s yeast alone. (PubMed)

Immediate applicative limit

The protocol is not “generic sourdough”: it is a biotechnology using selected strains and defined conditions; it is not automatically transferable to any artisanal process. (PubMed)

2.2 “Enhanced” fermentation: selected lactobacilli + fungal proteases (extensive detoxification)

Rizzello et al., 2007 (Applied and Environmental Microbiology) show an even more “engineered” approach: a mixture of selected lactobacilli + fungal proteases during prolonged fermentation.

The study uses several analytical techniques (immunological and instrumental) to estimate residual gluten and the persistence of different protein fractions. (PubMed)

Key technical points

• Complete hydrolysis of gliadins and other soluble fractions reported in the experimental process; partial persistence of a fraction of glutenins (not all structural fractions are necessarily “eliminated”). (PubMed)

• Measurement of residual gluten through immunological tests (R5-ELISA) and confirmation through proteomic/spectrometric analyses in the protocol. (PubMed)

• Biological evaluation of immunoreactivity (tests on immune cell lines) to estimate the “toxicity” of the pepsin-trypsin digest of the fermented product. (PubMed)

Applicative limit

This scenario requires enzymatic co-adjuvants (fungal proteases) and a controlled setup: it is an industrial/biotechnological process, not the equivalent of standard sourdough management in a bakery. (PubMed)

2.3 Selected lactic fermentation on different cereals: role of pH and endogenous enzymes

De Angelis et al., 2006 (Journal of Cereal Science) study the fermentation of rye flours with selected lactic acid bacteria, showing extensive hydrolysis of ethanol-soluble polypeptides and a reduction of immunochemical detectability (R5-Western), also discussing the role of pH in activating hydrolysis through endogenous flour enzymes. (ScienceDirect)

Key technical points

The observed degradation results from a combination of:

• microbial proteolytic activity (selected strains)

• pH-dependent hydrolysis (activation of endogenous cereal enzyme systems) (ScienceDirect)

The work supports the “biotechnological” logic of controlled fermentation as a tool to reduce contamination/reactivity risk in specific contexts (in experimental terms). (ScienceDirect)

Applicative limit

Again: selected strains + defined process conditions; this is not an automatic generalization for “any sourdough.” (ScienceDirect)

3. Where baker’s yeast and “traditional” sourdough fit

3.1 Baker’s yeast (Saccharomyces cerevisiae)

Within the framework of the above studies, the effect of baker’s yeast is mainly:

• fermentative kinetics (CO₂, volumetric development)

• indirect influence on maturation (time/temperature)

but not a proteolytic activity comparable to that of selected lactic bacteria and/or added proteases.

In other words: with baker’s yeast the “improved digestive management” (when observed) is more related to maturation time and transformations of the starch-protein matrix, not to extensive degradation of immunogenic gluten sequences (in the terms used in the cited studies).

(This is a conclusion derived by comparing the mechanisms reported in studies on selected LAB and proteases.) (PubMed)

3.2 “Non-selected” sourdough (spontaneous sourdough starter)

Spontaneous sourdough can determine:

• acidification

• partial proteolysis

• rheological modifications

However, the literature showing “almost total” degradation or marked reduction of immunogenic epitopes typically uses:

• selected lactic strains with specific peptidases (PubMed)

and/or

• fungal proteases in combination (PubMed)

Therefore, at a manualistic level, the correct formulation is:

Fermentation with sourdough can increase gluten proteolysis; extensive degradation of immunogenic sequences requires controlled biotechnological protocols (selected strains and, in some cases, enzymatic co-adjuvants).

4. Applicative limits

Protocols aiming to drastically reduce the immunogenic fraction of gluten do not coincide with the standard production of sourdough bread/pizza. (PubMed)

The result depends on:

• microbial species/strains used (selection) (PubMed)

• fermentation time

• acidity/pH (and relative enzymatic activation) (ScienceDirect)

• possible use of technological proteases (PubMed)

Even when very extensive degradation is observed, some studies report possible persistence of certain fractions (e.g. part of the glutenins) depending on the protocol. (PubMed)

5. Cited studies

Di Cagno, R. et al. (2004). Sourdough bread made from wheat and nontoxic flours and started with selected lactobacilli is tolerated in celiac sprue patients. Applied and Environmental Microbiology, 70(2), 1088–1096. DOI: 10.1128/AEM.70.2.1088-1096.2004 (PubMed)

Rizzello, C.G. et al. (2007). Highly efficient gluten degradation by lactobacilli and fungal proteases during food processing: new perspectives for celiac disease. Applied and Environmental Microbiology, 73(14), 4499–4507. DOI: 10.1128/AEM.00260-07 (PubMed)

De Angelis, M. et al. (2006). Fermentation by selected sourdough lactic acid bacteria to decrease coeliac intolerance to rye flour. Journal of Cereal Science, 43(3), 301–314. DOI: 10.1016/j.jcs.2005.12.008 (ScienceDirect)

In-depth analysis

Effects of sourdough and/or yeast use in gluten fermentation: scientific evidence

Primary studies (main evidence)

1. Effects of LAB + yeast co-fermentation on gluten degradation

Title: Effects of Co-Fermentation with Lactic Acid Bacteria and Yeast on Gliadin Degradation in Whole-Wheat Sourdough

Summary: The study evaluates how selected strains of Lactic Acid Bacteria (LAB) and baker’s yeast (Saccharomyces cerevisiae) co-ferment gluten in whole-wheat sourdough. The combined fermentation leads to significant degradation of gliadin and glutenin fractions, with reduction of gluten content. Strains such as Lactobacillus brevis and Pediococcus pentosaceus show high proteolytic activity. (MDPI)

2. Reduction of gluten allergenicity in fermented products

Title: From gluten structure to immunogenicity: Investigating the effects of lactic acid bacteria and yeast co-fermentation on wheat allergenicity in steamed buns

Summary: LAB + baker’s yeast co-fermentation induces depolymerization of gluten macromolecules and reduces total immunoreactivity compared with non-fermented controls. Significant decreases in α/γ-gliadins and glutenins associated with celiac disease are observed. (PubMed)

3. Immunogenic peptides and sourdough

Title: A Case Study of the Response of Immunogenic Gluten Peptides to Sourdough Proteolysis

Summary: Fermentation with sourdough modifies gluten structure and the release profile of immunogenic peptides during in vitro digestion, without necessarily eliminating them completely. Comparative study between sourdough bread and rapid-leavened bread. (PubMed)

4. Bacillus spp. isolated from sourdough and gluten hydrolysis

Title: Gluten hydrolyzing activity of Bacillus spp isolated from sourdough

Summary: Bacillus strains isolated from sourdough degrade the immunogenic 33-mer peptide and gliadin sequences, reducing gluten below 110 mg/kg. Potential application in reduced-gluten products. (SpringerLink)

5. Pilot clinical study on fermented products

Title: Gluten-free sourdough wheat baked goods appear safe for young celiac patients: a pilot study

Summary: Fermentation with selected lactobacilli and fungal proteases reduces gluten below 10 ppm. Products tested on children with celiac disease in remission show good clinical tolerability. (PubMed)

6. Recent review on the role of fermentation (2025)

Title: Sourdough Fermentation and Gluten Reduction: A Biotechnological Approach for Gluten-Related Disorders

Summary: LAB fermentation contributes to the reduction of gluten peptides but is not sufficient alone to eliminate all immunogenic sequences. Combined processes with exogenous proteases are more effective. (MDPI)

Previously cited studies, with greater detail

A. Bacillus spp isolated from sourdough
DOI: 10.1186/s12934-020-01388-z

Further detail: The study demonstrates the high proteolytic activity of Bacillus strains against gliadin substrates and the 33-mer peptide. Extensive hydrolysis leads to gluten levels <110 mg/kg in fermented sourdough.

B. Label-free quantitative proteomics and sourdough fermentation
DOI: 10.1016/j.foodchem.2023.137037

Further detail: Proteomic analysis identifies 85 allergenic proteins modulated by fermentation. Some microbial combinations show reduction of gliadins containing immunogenic sequences, suggesting a selective effect of fermentation on the wheat protein fraction.

C. Yeast–bacteria interactions and immunogenicity
DOI: 10.1016/j.ifset.2023.103281

Further detail: Co-cultures of yeasts (Saccharomyces, Torulaspora) with Pediococcus acidilactici show greater gluten depolymerization and reduced immunogenicity compared with single-yeast fermentations.

General conclusions

Sourdough fermentation can partially degrade gluten and reduce specific immunogenic peptides. The reduction does not equal complete elimination: without exogenous proteases, residual gluten often remains. Effectiveness strongly depends on microbial strains and fermentation conditions.

What does all this mean for those seeking gluten-light products?

Products made with sourdough (sourdough fermentation) generally present technological and biochemical characteristics superior to products obtained with rapid leavening, especially regarding tolerability and overall quality.

In particular:

Partial gluten degradation

Prolonged fermentation promotes hydrolysis of some gliadin and glutenin fractions, reducing protein complexity compared with non-fermented doughs.

Modified peptide profile

Even when gluten is not eliminated, its structure changes, with a potential reduction of specific immunogenic peptides.

Perceived improved digestibility

Many non-celiac consumers report better gastrointestinal tolerance compared with industrial baked products produced with rapid fermentation.

Reduction of other critical factors

Sourdough fermentation also contributes to decreasing FODMAPs and some antinutritional compounds.

⚠️ Important note: gluten-light products are not automatically safe for people with celiac disease. Traditional fermentation improves quality and tolerability, but only controlled and validated processes can lead to gluten levels compatible with a gluten-free diet.

For those who are not celiac but seek products that are more digestible, less stressful for the intestine and based on natural fermentation processes, sourdough currently represents one of the most interesting solutions supported by scientific literature.

The Science Behind Bread and Pizza

Chapter I – Gliadins and Glutenins: the essential building blocks
Chapter II – Fermentation in professional baking and pizzeria production
Chapter III – Gluten degradation during fermentation
Chapter IV – Scientific evidence and application limits

Fermentation, Proteolysis and Potential Modulation of Mucosal Stimuli

1. Technical premise

Physiological evidence shows that some protein peptides resistant to digestion can:

• modulate paracellular permeability

• activate innate immunity pathways

• interact with the intestinal microbial ecosystem

In the context of professional baking, the technological interest is not clinical but biochemical and structural: reducing the fraction of peptides relatively resistant to enzymatic digestion and modifying digestive kinetics through appropriately designed fermentation.

It should be emphasized that the primary function of protein digestion is the hydrolysis of dietary proteins — including gluten — into free amino acids and small peptides (mainly di- and tripeptides), which can cross the intestinal epithelium via specific transport systems and be used as metabolic substrates for the various metabolic functions of the body.

The peptide fraction that is not completely hydrolyzed, consisting of larger peptides, nor absorbed at the level of the small intestine, reaches the colon where it is partially metabolized by the intestinal microbiota through fermentative processes; the unused portion is eliminated with feces.

Enzymatic hydrolysis therefore represents the key step for making proteins nutritionally available and limiting the presence of peptide fractions relatively resistant to digestion.

2. How fermentation can act on resistant peptides

2.1 Acidification and enzymatic activation

Sourdough fermentation leads to:

• pH reduction (≈ 3.8–4.8 depending on the system)

• activation/modulation of endogenous flour proteases

• production of microbial peptidases

Resulting effect:

• reduction of the average molecular weight of protein fractions

• increase in the pool of short peptides and free amino acids

• remodeling of the peptide profile

This does not correspond to “elimination of gluten,” but to modification of the distribution of protein fragments (greater quantity of short peptides).

2.2 Depolymerization of the gluten network

Prolonged fermentation can:

• reduce the gluten macropolymer

• modify the secondary structure of proteins

• make the network less compact and more accessible to digestive enzymes

Potential physiological consequence:

• improved accessibility to gastric/pancreatic proteolysis

• reduction of the fraction of persistent long peptides

2.3 Time as a critical variable

The maturation time is determinant:

In professional practice, fermentations of 24–72 h at controlled temperature increase the probability of significant but structurally controlled proteolysis.

3. Baker’s yeast vs sourdough

Baker’s yeast (Saccharomyces cerevisiae)

• limited proteolytic activity

• mainly indirect effect (time, hydration, activation of flour enzymes)

• reduction of resistant peptides mainly dependent on maturation time

Sourdough (LAB + yeasts)

• direct peptidase activity

• structuring acidification

• greater protein remodeling at equal time

4. Interaction with microbiota and intestinal barrier

In light of physiological and experimental evidence, there is in vitro and murine model evidence suggesting a possible systemic impact of gluten on intestinal permeability and inflammatory balance, particularly in subjects with genetic predisposition, immunological vulnerability or pre-existing clinical conditions.

In this context, long and resistant peptides derived from gluten may interact with the intestinal barrier and innate immunity, influencing their functionality. Such interaction may translate into modifications of intestinal permeability, variations in microbiota composition and modulation of immune responses.

Therefore, a criterion of nutritional prudence does not represent excessive caution but rather an act of preventive responsibility.

In healthy individuals there are currently no solid and conclusive clinical data demonstrating a significant systemic impact of gluten on intestinal permeability or inflammatory balance.

The real effect also depends on:

• the state of the intestinal mucosa

• the composition of the microbiota

• the overall composition of the meal

• stress level and lifestyle

• exposure to environmental contaminants

* By “possible impact” it is meant that the interaction between gluten and the organism is closely related to the state of the subject and to their overall biological context. Numerous factors — diet, stress, lifestyle habits and environment — may influence the outcome.

** Finally, it must be specified that by “healthy subject” we do not simply mean an individual without clinically manifest diseases, but a person without ongoing pathologies and without a state of chronic low-grade inflammation. This distinction is fundamental, since in clinical practice the term “healthy” is often used in a limited sense, coinciding only with the absence of formal diagnoses.

5. Digestibility as a property of the food matrix

It is essential to reiterate:

Digestibility is not a property of the protein or starch fraction alone, but of the entire food matrix.

Factors influencing the real digestion of the finished product include:

• fibers (bran, arabinoxylans)

• lipids

• final hydration

• alveolar structure

• protein–starch interaction

• baking method

The presence of fibers, for example, modifies the digestive kinetics of starch and proteins much more than a simple variation in protein content would.

6. Practical implications for the professional

If the goal is to obtain a product with:

• high biochemical maturation

• more evolved protein profile

• lower fraction of peptides relatively resistant to digestion

the design levers are:

1. reduction of yeast dosage

2. controlled extension of fermentation

3. use of well-managed sourdough

4. control of temperature and pH

5. balance between proteolysis and structural stability

7. Technical conclusion

In traditional baking:

Prolonged fermentation and controlled acidification can remodel the peptide profile of gluten. This remodeling may reduce the fraction of protein fragments relatively resistant to digestion. Physiological evidence shows that such fragments, in experimental models, can modulate barrier function and innate immunity. Direct transfer of these results to healthy humans requires interpretative caution.

Chapter IV – Scientific Evidence and Applicative Limits

1. Scope and operational definitions

In technical language it is essential to separate three concepts that are often confused:

1. Gluten hydrolysis/proteolysis
→ fragmentation of proteins (gliadins and glutenins) into smaller peptides.

2. Reduction of immunogenic peptides/epitopes for celiac disease→ degradation of specific sequences rich in proline and glutamine (e.g. “Pro-rich” peptides) that resist digestion and activate immune responses in celiac patients.

3. “Elimination” of gluten→ a much more ambitious objective, achievable only under controlled technological conditions (selected strains, often enzymatic co-adjuvants, long fermentation times), and not equivalent to normal baking with traditional sourdough.

2. Evidence: what studies show

2.1 Fermentation with selected lactic acid bacteria: targeted degradation of immunogenic peptides

Di Cagno et al., 2004 (Applied and Environmental Microbiology) demonstrate that the use of selected lactobacilli with specialized peptidases is able to hydrolyze proline-rich peptides, including peptides with high immunogenicity (the work explicitly discusses the hydrolysis of “Pro-rich” peptides and the application to an experimental baked product).
The study also includes an acute clinical challenge test in subjects with celiac disease within the described experimental protocol. (PubMed)

Key technical points (what is “demonstrated”)

• The ability to degrade prolamin fractions critically depends on strain selection (it is not an automatic effect of any sourdough). (PubMed)

• Degradation involves peptides known to resist gastrointestinal digestion thanks to enzymatic systems (peptidases) not typical of baker’s yeast alone. (PubMed)

Immediate applicative limit

The protocol is not “generic sourdough”: it is a biotechnology using selected strains and defined conditions; it is not automatically transferable to any artisanal process. (PubMed)

2.2 “Enhanced” fermentation: selected lactobacilli + fungal proteases (extensive detoxification)

Rizzello et al., 2007 (Applied and Environmental Microbiology) show an even more “engineered” approach: a mixture of selected lactobacilli + fungal proteases during prolonged fermentation.

The study uses several analytical techniques (immunological and instrumental) to estimate residual gluten and the persistence of different protein fractions. (PubMed)

Key technical points

• Complete hydrolysis of gliadins and other soluble fractions reported in the experimental process; partial persistence of a fraction of glutenins (not all structural fractions are necessarily “eliminated”). (PubMed)

• Measurement of residual gluten through immunological tests (R5-ELISA) and confirmation through proteomic/spectrometric analyses in the protocol. (PubMed)

• Biological evaluation of immunoreactivity (tests on immune cell lines) to estimate the “toxicity” of the pepsin-trypsin digest of the fermented product. (PubMed)

Applicative limit

This scenario requires enzymatic co-adjuvants (fungal proteases) and a controlled setup: it is an industrial/biotechnological process, not the equivalent of standard sourdough management in a bakery. (PubMed)

2.3 Selected lactic fermentation on different cereals: role of pH and endogenous enzymes

De Angelis et al., 2006 (Journal of Cereal Science) study the fermentation of rye flours with selected lactic acid bacteria, showing extensive hydrolysis of ethanol-soluble polypeptides and a reduction of immunochemical detectability (R5-Western), also discussing the role of pH in activating hydrolysis through endogenous flour enzymes. (ScienceDirect)

Key technical points

The observed degradation results from a combination of:

• microbial proteolytic activity (selected strains)

• pH-dependent hydrolysis (activation of endogenous cereal enzyme systems) (ScienceDirect)

The work supports the “biotechnological” logic of controlled fermentation as a tool to reduce contamination/reactivity risk in specific contexts (in experimental terms). (ScienceDirect)

Applicative limit

Again: selected strains + defined process conditions; this is not an automatic generalization for “any sourdough.” (ScienceDirect)

3. Where baker’s yeast and “traditional” sourdough fit

3.1 Baker’s yeast (Saccharomyces cerevisiae)

Within the framework of the above studies, the effect of baker’s yeast is mainly:

• fermentative kinetics (CO₂, volumetric development)

• indirect influence on maturation (time/temperature)

but not a proteolytic activity comparable to that of selected lactic bacteria and/or added proteases.

In other words: with baker’s yeast the “improved digestive management” (when observed) is more related to maturation time and transformations of the starch-protein matrix, not to extensive degradation of immunogenic gluten sequences (in the terms used in the cited studies).

(This is a conclusion derived by comparing the mechanisms reported in studies on selected LAB and proteases.) (PubMed)

3.2 “Non-selected” sourdough (spontaneous sourdough starter)

Spontaneous sourdough can determine:

• acidification

• partial proteolysis

• rheological modifications

However, the literature showing “almost total” degradation or marked reduction of immunogenic epitopes typically uses:

• selected lactic strains with specific peptidases (PubMed)

and/or

• fungal proteases in combination (PubMed)

Therefore, at a manualistic level, the correct formulation is:

Fermentation with sourdough can increase gluten proteolysis; extensive degradation of immunogenic sequences requires controlled biotechnological protocols (selected strains and, in some cases, enzymatic co-adjuvants).

4. Applicative limits

Protocols aiming to drastically reduce the immunogenic fraction of gluten do not coincide with the standard production of sourdough bread/pizza. (PubMed)

The result depends on:

• microbial species/strains used (selection) (PubMed)

• fermentation time

• acidity/pH (and relative enzymatic activation) (ScienceDirect)

• possible use of technological proteases (PubMed)

Even when very extensive degradation is observed, some studies report possible persistence of certain fractions (e.g. part of the glutenins) depending on the protocol. (PubMed)

5. Cited studies

Di Cagno, R. et al. (2004). Sourdough bread made from wheat and nontoxic flours and started with selected lactobacilli is tolerated in celiac sprue patients. Applied and Environmental Microbiology, 70(2), 1088–1096. DOI: 10.1128/AEM.70.2.1088-1096.2004 (PubMed)

Rizzello, C.G. et al. (2007). Highly efficient gluten degradation by lactobacilli and fungal proteases during food processing: new perspectives for celiac disease. Applied and Environmental Microbiology, 73(14), 4499–4507. DOI: 10.1128/AEM.00260-07 (PubMed)

De Angelis, M. et al. (2006). Fermentation by selected sourdough lactic acid bacteria to decrease coeliac intolerance to rye flour. Journal of Cereal Science, 43(3), 301–314. DOI: 10.1016/j.jcs.2005.12.008 (ScienceDirect)

In-depth analysis

Effects of sourdough and/or yeast use in gluten fermentation: scientific evidence

Primary studies (main evidence)

1. Effects of LAB + yeast co-fermentation on gluten degradation

Title: Effects of Co-Fermentation with Lactic Acid Bacteria and Yeast on Gliadin Degradation in Whole-Wheat Sourdough

Summary: The study evaluates how selected strains of Lactic Acid Bacteria (LAB) and baker’s yeast (Saccharomyces cerevisiae) co-ferment gluten in whole-wheat sourdough. The combined fermentation leads to significant degradation of gliadin and glutenin fractions, with reduction of gluten content. Strains such as Lactobacillus brevis and Pediococcus pentosaceus show high proteolytic activity. (MDPI)

2. Reduction of gluten allergenicity in fermented products

Title: From gluten structure to immunogenicity: Investigating the effects of lactic acid bacteria and yeast co-fermentation on wheat allergenicity in steamed buns

Summary: LAB + baker’s yeast co-fermentation induces depolymerization of gluten macromolecules and reduces total immunoreactivity compared with non-fermented controls. Significant decreases in α/γ-gliadins and glutenins associated with celiac disease are observed. (PubMed)

3. Immunogenic peptides and sourdough

Title: A Case Study of the Response of Immunogenic Gluten Peptides to Sourdough Proteolysis

Summary: Fermentation with sourdough modifies gluten structure and the release profile of immunogenic peptides during in vitro digestion, without necessarily eliminating them completely. Comparative study between sourdough bread and rapid-leavened bread. (PubMed)

4. Bacillus spp. isolated from sourdough and gluten hydrolysis

Title: Gluten hydrolyzing activity of Bacillus spp isolated from sourdough

Summary: Bacillus strains isolated from sourdough degrade the immunogenic 33-mer peptide and gliadin sequences, reducing gluten below 110 mg/kg. Potential application in reduced-gluten products. (SpringerLink)

5. Pilot clinical study on fermented products

Title: Gluten-free sourdough wheat baked goods appear safe for young celiac patients: a pilot study

Summary: Fermentation with selected lactobacilli and fungal proteases reduces gluten below 10 ppm. Products tested on children with celiac disease in remission show good clinical tolerability. (PubMed)

6. Recent review on the role of fermentation (2025)

Title: Sourdough Fermentation and Gluten Reduction: A Biotechnological Approach for Gluten-Related Disorders

Summary: LAB fermentation contributes to the reduction of gluten peptides but is not sufficient alone to eliminate all immunogenic sequences. Combined processes with exogenous proteases are more effective. (MDPI)

Previously cited studies, with greater detail

A. Bacillus spp isolated from sourdough
DOI: 10.1186/s12934-020-01388-z

Further detail: The study demonstrates the high proteolytic activity of Bacillus strains against gliadin substrates and the 33-mer peptide. Extensive hydrolysis leads to gluten levels <110 mg/kg in fermented sourdough.

B. Label-free quantitative proteomics and sourdough fermentation
DOI: 10.1016/j.foodchem.2023.137037

Further detail: Proteomic analysis identifies 85 allergenic proteins modulated by fermentation. Some microbial combinations show reduction of gliadins containing immunogenic sequences, suggesting a selective effect of fermentation on the wheat protein fraction.

C. Yeast–bacteria interactions and immunogenicity
DOI: 10.1016/j.ifset.2023.103281

Further detail: Co-cultures of yeasts (Saccharomyces, Torulaspora) with Pediococcus acidilactici show greater gluten depolymerization and reduced immunogenicity compared with single-yeast fermentations.

General conclusions

Sourdough fermentation can partially degrade gluten and reduce specific immunogenic peptides. The reduction does not equal complete elimination: without exogenous proteases, residual gluten often remains. Effectiveness strongly depends on microbial strains and fermentation conditions.

What does all this mean for those seeking gluten-light products?

Products made with sourdough (sourdough fermentation) generally present technological and biochemical characteristics superior to products obtained with rapid leavening, especially regarding tolerability and overall quality.

In particular:

Partial gluten degradation

Prolonged fermentation promotes hydrolysis of some gliadin and glutenin fractions, reducing protein complexity compared with non-fermented doughs.

Modified peptide profile

Even when gluten is not eliminated, its structure changes, with a potential reduction of specific immunogenic peptides.

Perceived improved digestibility

Many non-celiac consumers report better gastrointestinal tolerance compared with industrial baked products produced with rapid fermentation.

Reduction of other critical factors

Sourdough fermentation also contributes to decreasing FODMAPs and some antinutritional compounds.

⚠️ Important note: gluten-light products are not automatically safe for people with celiac disease. Traditional fermentation improves quality and tolerability, but only controlled and validated processes can lead to gluten levels compatible with a gluten-free diet.

For those who are not celiac but seek products that are more digestible, less stressful for the intestine and based on natural fermentation processes, sourdough currently represents one of the most interesting solutions supported by scientific literature.

The Science Behind Bread and Pizza

Chapter I – Gliadins and Glutenins: the essential building blocks
Chapter II – Fermentation in professional baking and pizzeria production
Chapter III – Gluten degradation during fermentation
Chapter IV – Scientific evidence and application limits

sangiorgio.l@libero.it

Biochemistry, Rheology and Microbiology of Fermentation and the Starch–Protein Matrix

The present text analyzes the biochemical, rheological and microbiological foundations underlying the production of bread and pizza. The role of gluten proteins (gliadins and glutenins), fermentative systems (baker’s yeast and sourdough), dosage and time variables, and direct and indirect dough-making methods are examined. The approach adopted is technological-functional, with particular attention to the structural, aromatic, digestive and shelf-life implications of the finished product.

Chapter I – Protein Architecture of Dough: Gliadins, Glutenins and the Gluten Network

When we mix flour and water, we are not simply combining ingredients: we are activating a complex protein system that determines structure, consistency and the final result.
At the base of everything is gluten, a three-dimensional network created by the interaction between two families of wheat proteins: gliadins and glutenins. Understanding their balance means understanding why a pizza dough stretches easily while bread dough must sustain a tall, aerated structure.

1️⃣ The Gluten Network: A Dynamic Balance

Gluten does not exist “already formed” in flour. It is created when:

Glutenin + Gliadin + Water + Mixing = Gluten network

Water hydrates the proteins, the mechanical energy of mixing makes them interact, and an elastic network capable of trapping fermentation gases is formed. But the two proteins perform different and complementary roles.

2️⃣ The Role of Glutenins: Strength and Elasticity

Glutenins – Structural Effects

Glutenins provide:

Elasticity (ability to return to the original shape)
Tenacity (resistance to deformation)
Structure

A dough rich in glutenins:

Is more resistant
Retains gases better
Develops vertical volume

If excessive:

Too tenacious
Difficult to stretch
“Spring-back” effect

3️⃣ The Role of Gliadins: Extensibility and Viscosity

Gliadins are responsible for:

Extensibility (ability to stretch without tearing)
Malleability
Viscosity

Thanks to gliadins, the dough:

Stretches easily
Does not tear during handling
Maintains good workability

If they dominate excessively, however, the dough:

Becomes soft
“Spreads”
Struggles to maintain shape

4️⃣ Pizza: Extensibility Is Required

In the case of pizza, the goal is to obtain a thin disk that:

Stretches easily
Does not tear
Does not retract during shaping

Extensibility is therefore fundamental. A dough too rich in glutenins would be “rubbery” and difficult to open.

For this reason, pizza flours (often soft wheat) are designed to have:

A good balance between strength and extensibility
A P/L ratio (tenacity/extensibility) balanced or slightly shifted toward extensibility

If the dough is too tenacious, it is possible to intervene with:

Longer maturation (longer resting time)
Increased hydration
Choosing a flour with a lower P/L ratio

In summary: more extensibility = easy stretching and good alveolation.

5️⃣ Bread: Structural Strength Is Required

Why does bread need more glutenins?

Bread has a different goal: to develop vertically and sustain an internal structure rich in alveoli.

Here the following come into play:

Elasticity
Structural strength
Capacity to retain fermentation gases

Bread dough therefore requires a stronger gluten network, with a higher glutenin component.

If gliadins dominate too much:

The dough becomes weak
It spreads instead of rising
The bread results low and poorly structured

In summary: more glutenins = more strength and vertical development.

6️⃣ Balance Is the Key

The fundamental point is not “which protein is better”, but their ratio.

Too much glutenin → tenacious dough, hard to stretch
Too much gliadin → soft and unstable dough
Correct balance → elastic and extensible structure

The difference between pizza and bread lies precisely in this balance:

7️⃣ Conclusion

Pizza → more extensibility (gliadins)
Bread → more strength and elasticity (glutenins)

The quality of a dough does not depend only on the quantity of proteins, but on their interaction, processing, hydration and maturation time. Every time we stretch a pizza or shape a loaf of bread, we are working with a delicate molecular balance: a true protein architecture that transforms flour and water into a living, elastic and extensible structure.

Chapter II – Fermentation in Professional Baking and Pizzeria Production

Role of baker’s yeast and sourdough, quantities, time and dough-making methods

1. Introduction

Fermentation represents the biological and technological core of professional baking and pizza production. It is not limited to the production of gas for dough volume increase, but profoundly determines:

Mechanical structure
Extensibility
Alveolation
Aromatic profile
Digestibility
Shelf life

The professional does not simply manage a “leavening”, but a complex biochemical process in which interact:

Microorganisms
Endogenous flour enzymes
Gluten proteins
Starches
Time
Temperature

This chapter systematically analyzes the role of baker’s yeast and sourdough, the influence of dosage and fermentation time, and the impact of processing methods (direct dough and indirect dough with biga) on the finished product.

2. The Role of Baker’s Yeast

2.1 Microbiological Nature

Baker’s yeast consists predominantly of Saccharomyces cerevisiae, a unicellular microorganism capable of metabolizing simple sugars present in dough.

Alcoholic fermentation produces:

Carbon dioxide (CO₂)
Ethanol
Secondary metabolites (esters, higher alcohols, aldehydes)

CO₂ is retained by the gluten network and generates the increase in volume.

2.2 Technological Effects

Baker’s yeast:

Provides gas for structural development
Indirectly stimulates enzymatic activity
Influences fermentation rate
Determines part of the aromatic profile

It does not significantly modify dough pH (limited acidity), therefore the effect on the protein structure is mainly mechanical and fermentative, not acidifying.

3. The Role of Sourdough

3.1 Microbiological Nature

Sourdough is an ecosystem composed of:

Wild yeasts
Lactic acid bacteria (homo- and hetero-fermentative)

These microorganisms produce:

CO₂
Lactic acid
Acetic acid
Proteolytic enzymes
Complex aromatic compounds

3.2 Technological Effects

The combined activity of yeasts and bacteria

The combined activity of yeasts and bacteria determines

The controlled acidity of yeasts and bacteria directly influences

Progressive acidification (pH reduction)
Elasticity
Modification of gluten structure
Extensibility
Activation of proteases
Shelf life
Improved microbiological stability
Aromatic depth

4. Quantity and Time: General Principles

4.1 Relationship Between Dosage and Speed

The quantity of fermenting agent regulates:

CO₂ production speed
Metabolic intensity
Process duration

Fundamental principle:

More yeast → rapid fermentation
Less yeast → slow fermentation

However, speed does not coincide with maturation.

4.2 Time as a Key Variable

Time allows:

Enzymatic degradation of starches (amylases)
Partial protein hydrolysis
Reorganization of the gluten network
Formation of aromatic metabolites

A short fermentation may produce volume, but not necessarily structural and biochemical maturation.

5. Effects on Digestibility

5.1 Technical Definition

Digestibility refers to:

Reduction of intestinal fermentable load
Partial pre-digestion of starches and proteins
Better structural organization of the crumb

It does not imply absence of gluten, but a more advanced biochemical transformation.

5.2 Baker’s Yeast

Baker’s Yeast Dosage

High dosage + short time
Low dosage + long time

Limited maturation
Greater maturation

Lower enzymatic activity
Better enzymatic degradation

Higher presence of residual sugars
Biochemically evolved dough

Possible sensation of heaviness
Greater sensation of lightness

5.3 Sourdough

Fermentation with sourdough determines:

Progressive reduction of pH (controlled acidification)
Increase of proteolytic activity (endogenous enzymes + microbial activity)
Partial hydrolysis of gluten proteins
Greater degradation of fermentable sugars
Modification of the rheological properties of the gluten network

Measurable technological and physiological effects

Prolonged sourdough fermentations involve:

Reduction of residual fermentable carbohydrates
Partial protein pre-digestion
Better structural organization of the crumb
Slower glycemic response compared to short fermentations
Greater microbiological stability of the product

The combination of these factors may determine:

Reduction of intestinal fermentative load
Lower intestinal gas production compared to rapidly fermented doughs

Individual physiological response may vary depending on personal conditions, but the biochemical mechanisms described above are objectively measurable.

6. Effects on Pizza and Bread

6.1 Pizza

Structural objectives

High extensibility
Absence of “spring-back” effect
Aerated cornicione
Melt-in-the-mouth texture

Typical strategy

Very low yeast dosage
Long maturation (24–72 hours)
Temperature control

Results

Greater extensibility
More complex aroma
Lower sensation of bloating

6.2 Bread

Structural objectives

Vertical development
Crumb stability
Shelf life

Objectives with baker’s yeast

Regular structure
Delicate aroma

Objectives with sourdough

Irregular alveolation
Thick crust
Deep aroma
Longer shelf life

7. Dough-Making Methods

7.1 Direct Dough

7.1.1 Definition

All ingredients are mixed in a single phase.

7.1.2 Fermentation Dynamics

Immediate complete hydration
Single fermentation
Structure progressively built

7.1.3 Effects on the Product

Effects on the product

Texture
Homogeneous crumb
Regular alveolation

Aroma
Linear profile
Lower complexity

Digestibility
Good if accompanied by long fermentation times
Lower if fermentation is short

Shelf life
Faster staling
Lower protective acidification

7.2 Indirect Dough with Biga

7.2.1 Definition

Solid preferment (45–50% hydration) with:

Flour
Water
Small quantity of yeast

Fermentation 16–24 hours before the final dough.

7.2.2 Biochemical Dynamics

During biga maturation:

Early enzymatic activation
Production of light organic acids
Pre-maturation of gluten
Development of aromatic precursors

7.2.3 Effects on the Product

Effects on the product

Texture
Large and irregular alveolation
Greater lightness
Crispier crust

Aroma
Greater complexity
Light lactic aromas
Intensification of toasted notes

Digestibility
Dough already partially matured
Lower residual fermentable load

Shelf life
Better moisture retention
Slower staling
Greater aromatic persistence

8. Systemic Comparison

9. Integrated Design Principle

In professional contexts, dough design simultaneously considers:

Type of fermenting agent
Dosage
Time
Temperature
Method (direct or indirect)

There is no universally superior solution, but rather a balance consistent with:

Product identity
Sensory objectives
Desired structure
Production organization

10. Conclusion

Fermentation is not an accessory step, but a process of structural and biochemical transformation. The quantity of yeast, the choice between baker’s yeast and sourdough, the maturation time and the adopted method (direct or biga) constitute tools of applied food engineering. The professional does not simply “let a dough rise”: they design the behavior of matter over time in order to obtain a structural, aromatic and functional result consistent with the identity of the final product.

Essential Bibliography

Gluten, Protein Structure and Rheology

1. Wieser, H. (2007).
   Chemistry of gluten proteins.
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   DOI: 10.1016/j.fm.2006.07.004

2. Shewry, P. R., & Tatham, A. S. (1997).
   Disulphide bonds in wheat gluten proteins.
   Journal of Cereal Science, 25(3), 207–227.
   DOI: 10.1006/jcrs.1996.0100

3. Belton, P. S. (1999).
   On the elasticity of wheat gluten.
   Journal of Cereal Science, 29(2), 103–107.
   DOI: 10.1006/jcrs.1998.0233

4. Dobraszczyk, B. J., & Morgenstern, M. P. (2003).
   Rheology and the breadmaking process.
   Journal of Cereal Science, 38(3), 229–245.
   DOI: 10.1016/S0733-5210(03)00059-6

Baker’s Yeast and Alcoholic Fermentation

5. Fleet, G. H. (2007).
   Yeasts in foods and beverages: impact on product quality and safety.
   Food Microbiology, 24(2), 103–112.
   DOI: 10.1016/j.fm.2006.07.002

6. Walker, G. M. (1998).
   Yeast Physiology and Biotechnology.
   John Wiley & Sons.
   ISBN: 978-0471964467

Sourdough and Sourdough Microbiology

7. De Vuyst, L., & Neysens, P. (2005).
   The sourdough microflora: biodiversity and metabolic interactions.
   Trends in Food Science & Technology, 16(1–3), 43–56.
   DOI: 10.1016/j.tifs.2004.02.012

8. Gobbetti, M., De Angelis, M., Di Cagno, R., Calasso, M., & Archetti, G. (2019).
   Novel insights on the functional/nutritional features of sourdough fermentation.
   International Journal of Food Microbiology, 302, 103–113.
   DOI: 10.1016/j.ijfoodmicro.2018.05.018

9. Poutanen, K., Flander, L., & Katina, K. (2009).
   Sourdough and cereal fermentation in a nutritional perspective.
   Food Microbiology, 26(7), 693–699.
   DOI: 10.1016/j.fm.2009.07.011

10. Hammes, W. P., & Gänzle, M. G. (1998).
    Sourdough breads and related products.
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Focus on Digestibility

1️⃣ Arendt et al., 2007

Impact of sourdough on the texture of bread
Food Microbiology, 24(2), 165–174.

Study Objective

Analyze the effect of sourdough fermentation on:

Crumb structure
Texture
Starch retrogradation
Shelf life

Key Points Relevant to Digestibility

1. Controlled acidification

Reduction of pH
Influence on starch gelatinization and retrogradation

2. Modification of starch structure

Acidity slows retrogradation
Better water retention
Greater crumb stability

3. Gluten–starch interaction

Acid fermentation modifies the protein matrix
Better starch distribution within the gluten network

Implications for Digestibility

Digestibility is influenced through:

Greater enzymatic accessibility to starch
Less compact and less collapsed structure
More modulated carbohydrate release

In technical terms: acid fermentation modifies the microstructure of the starch–protein matrix, influencing digestive kinetics.

2️⃣ Liljeberg & Björck, 1998

Delayed gastric emptying rate may explain improved glycaemia…
European Journal of Clinical Nutrition, 52(5), 368–371.

Study Objective

Evaluate the effect of food acidity on post-prandial glycemic response.

Key Points

1. Reduction of meal pH

Slows gastric emptying

2. More gradual glycemic response

Lower glycemic peak
Better control of glucose absorption

3. Physiological mechanism

A more acidic environment modifies digestion and absorption rate.

Implications for Bread and Pizza

In sourdough bread:

Lower pH
Presence of organic acids

may contribute to:

Slowing digestive kinetics
Reducing the rate of glucose release

Digestibility does not mean “fewer calories”, but a more modulated metabolic release.

3️⃣ Katina et al., 2006

Effects of sourdough and enzymes on staling of high-fibre wheat bread
LWT – Food Science and Technology, 39(5), 479–491.

Study Objective

Analyze the effect of:

Sourdough
Enzymatic activity
Fiber structure

on:

Staling
Retrogradation
Texture

Key Points

1. Prolonged enzymatic activity

Greater degradation of starches
Partial hydrolysis of polysaccharide structures

2. Slower retrogradation

Better crumb stability over time

3. Enzyme–structure interaction

Greater modification of the structural matrix

Implications for Digestibility

Partially modified starch → different digestive enzymatic response
Greater enzymatic availability
Reduction of residual fermentable substrates

Long fermentation alters carbohydrate structure before baking.

What Is Scientifically Meant by “Digestibility” in Long-Fermented Bread and Pizza

Based on the three studies, it can be defined as:

1️⃣ Structural modification of the matrix

Gluten–starch reorganization
Greater accessibility to digestive enzymes

2️⃣ Reduction of residual fermentable load

Lower presence of rapidly fermentable sugars

3️⃣ Modulation of glycemic response

Slower glucose release
Buffering effect of acidity

4️⃣ Influence on gastric emptying

Lower pH → slower emptying
More gradual absorption

Final Technical Synthesis

Digestibility in long-fermented bread and pizza is obtained through:

Time (enzymatic maturation)
Acidification (sourdough)
Structural modification of starch and proteins
Reduction of residual fermentable load
Modulation of glycemic response

It is a structural biochemical effect, not a merely “perceived” property.

Enzymatic and microbial transformations do not concern only starch and aromas: under specific conditions, they also involve the protein fraction of gluten, reshaping its peptide profile. This topic is addressed in Chapter III.

The Science Behind Bread and Pizza

Chapter I – Protein Architecture of Dough: Gliadins, Glutenins and the Gluten Network
Chapter II – Fermentation in professional baking and pizzeria production
Chapter III – Gluten degradation during fermentation
Chapter IV – Scientific evidence and application limits