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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:

Product	Dominant characteristic	Protein ratio
Pizza	Extensibility	Good presence of gliadins
Bread	Strength and elasticity	Greater glutenin component

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

Variable	Direct	Biga
Structure	Regular	Airy and light
Aroma	Linear	Complex
Digestibility	Depends on time	Generally higher
Shelf life	Medium	Higher
Management complexity	Low	Medium/High

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.
   Food Microbiology, 24(2), 115–119.
   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.
    Food Microbiology, 15(5), 487–495.
    DOI: 10.1006/fmic.1998.0191

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