For most consumers, bread is ‘flour, yeast, salt’. Professionals know better: between 50 – 60% of a bread dough, by mass, is water.
By Dimitrios Argyriou, Food Scientist, Managing Director, GRAINAR
Water is not just a neutral carrier. It is a reactive, structured, and highly dynamic component that influences dough rheology, fermentation behavior, baking performance, product volume, texture, flavor development, and shelf life. In other words, if you do not understand your water, you do not fully understand your product.
This article looks at water from a baking-science perspective: its quality, its behavior in dough, its transformations in the oven, and its central role in freshness and safety.
1. What ‘water’ really means in a bakery
Chemically, water is H2O. In practice, the water that flows into a bakery is never just pure H2O:
+ It contains dissolved minerals (calcium, magnesium, bicarbonates, sulphates, etc.).
+ It may carry trace organic substances and gases.
+ It is involved in three physical states during processing:
o ice (frozen dough),
o liquid water (mixing, fermentation, baking),
o and vapor (oven spring, crust formation, drying).
Inside dough or batter, water is also not all the same:
+ Bound water is strongly associated with molecules such as proteins, starch, sugars and salts. It no longer behaves like ‘free’ water and has a much lower mobility.
+ Loosely bound and free water form the continuous phase where solutes are dissolved, reactions occur, and microbes can grow.
Bakers never see these distinctions, but they are behind critical phenomena such as gluten development, starch gelatinization, stickiness, crumb softness, and staling.
2. Water quality: more than just ‘potable’
In most industrial bakeries, incoming water is municipal ‘drinking water’. It is already treated and monitored for safety. However, the fact that water is potable does not mean it is optimal for baking.
We can think of water quality in four dimensions:
Microbiological
Water used in food production must be free from pathogens. Disinfection (usually by chlorination, ozonation, or UV) is standard in municipal systems.
For bakers, microbiological safety is normally covered by local authorities. Problems arise mainly when:
+ The bakery uses its own well or a local source,
+ Or when maintenance fails – e.g., contamination of storage tanks or pipes.
In such cases, the bakery itself becomes responsible for regular testing (indicator organisms like coliforms and E. coli) and appropriate treatment.
Chemical composition and hardness
From a baking perspective, this is often the most important aspect. Hard water contains significant amounts of calcium and magnesium salts, while soft water contains very little of these ions.
Their impact:
+ Moderate hardness (approx. 50–100 ppm as CaCO3) is generally favorable for breadmaking.
+ Ca²+ and Mg²+ ions strengthen gluten, help gas retention, and support yeast nutrition.
+ Very soft water may lead to weak, sticky dough and poor gas retention.
+ Very hard water may over-strengthen the gluten network and slow down fermentation, producing a tight crumb and reduced volume.
Water softening technologies (ion exchange, reverse osmosis) solve scaling and equipment problems, but they may strip water of minerals essential for optimal dough performance. In such cases, bakers may need to:
+ Adjust formulations (e.g., salt and improver dosage),
+ Or re-introduce specific ions (e.g., via mineral blends or yeast foods).
Taste and off-flavors
Chlorine, some organic contaminants, or extreme mineral profiles can impart noticeable off-tastes. In most products, the flavour impact is subtle; in high-hydration doughs and long-fermented products such as sourdough, or focaccia, it becomes more evident.
Regulatory framework
Globally, drinking water is controlled through national laws and guided by organizations such as the WHO. For bakers, the practical takeaway is simple:
+ Use only water that meets local drinking-water standards.
+ If a bakery operates using its own water source, it must be treated and monitored as if it were a small ‘water utility’ for the bakery.
“Water activity is, conceptually, the ‘effective’ water available for reactions and microbial growth.”
Dimitris Agryriou, Food Scientist, Managing Director, Grainar
3. Water as a structural ingredient in dough
Once water meets the flour, its role becomes structural, not just functional.
Hydration of starch and pentosans
Wheat flour starch granules and pentosans (arabinoxylans) are strongly hydrophilic:
+ Starch granules slowly absorb water, swelling as water penetrates the granule structure.
+ Pentosans bind multiple times their own weight in water, strongly affecting dough viscosity and water absorption.
This early hydration stage determines dough consistency – one of the core ‘levers’ bakers use to tune dough machinability and final crumb structure.
Gluten formation and protein functionality
Proteins in wheat flour (gliadins and glutenins) require water to:
+ Hydrate and unfold,
+ Move and interact,
+ Form a continuous gluten network that traps gas.
The balance is delicate: too little water will lead to under-hydrated proteins, a tight dough, and, respectively a poor volume. Conversely, adding too much water will weaken the structure, resulting in sticky dough, with a risk of collapsing.
Minerals (Ca²+, Mg²+), pH, and mixing energy all interact with hydration to define the final gluten network. Water is the medium that allows these interactions to occur.
Water, solutes and osmotic effects
In dough, water dissolves:
+ Sugars (for yeast and Maillard reactions),
+ Salts (NaCl, baking soda, etc.),
+ Organic acids (sourdough, improvers),
+ Small proteins and peptides.
The resulting solution has a certain osmotic pressure. High osmotic pressure – usually found in sweet doughs, due to a high concentration of sugar and salt, for instance – slows water influx into yeast cells and can stress them, reducing fermentation speed. The control of water and solute concentration is therefore directly linked to fermentation performance.
Hydrophilic, hydrophobic and emulsifiers
Water does not mix with fats on its own. This is where emulsifiers and amphiphilic molecules, such as lecithin in egg yolk or mono- and diglycerides, come into play, where the hydrophilic part interacts with water, while the hydrophobic part interacts with fats.
These molecules:
+ Help disperse fats in the dough,
+ Stabilize gas bubbles,
+ Interact with starch to retard retrogradation and delay staling.
Again, the functionality is mediated by water. Without water, the hydrophilic region of these molecules cannot organize and do its job.
4. What happens to water in the oven?
When dough enters the oven, the behavior of the water it contains drives almost every major transformation during the baking proces.
From liquid to vapor: oven spring and crust
As the temperature rises:
1. Water in the dough heats up and approaches 100°C.
2. The vapor pressure inside gas cells increases sharply.
3. Steam expansion contributes to oven spring, together with expanding CO2.
4. Near the surface, water evaporates faster than it can be replaced from the interior. As a result, a dry crust forms.
The rate at which water is driven off the surface – influenced by oven temperature, air flow, humidity and steam injection – determines:
+ Crust thickness and color,
+ Shine and blistering,
+ The balance between crispness and chewiness.
Starch gelatinization and protein denaturation
Two key temperature ranges are critical:
+ Starch gelatinization (~60–80°C in dough, depending on water and solutes):
Starch granules absorb water, swell, and lose their crystalline structure, forming a gel that sets the crumb structure.
+ Protein denaturation and gluten setting (~80–95°C):
Gluten proteins lose their native conformation and form a more rigid network.
Both transitions depend on the availability and mobility of water. Limited water (as in cookies) can prevent extensive gelatinization, producing a short, crumbly texture. High water availability (high-hydration breads) allows full gelatinization, giving open, elastic crumbs.
Water in alternative baking technologies
In microwave baking, the energy couples mainly with water molecules:
+ Water heats first, resulting in rapid internal heating.
+ Surface temperatures often remain below those achieved in conventional ovens, meaning there will be poor browning, limited flavour development, and different moisture gradients.
Understanding how water absorbs and redistributes microwave energy is key to developing formulations and processes that can deliver acceptable quality under these condition
5. Water activity: controlling safety and shelf life
Total water content is only part of the story. For microbial stability and texture, water activity (av) is more important.
Water activity is, conceptually, the ‘effective’ water available for reactions and microbial growth. It is related to the vapor pressure of water in a product relative to pure water at the same temperature.
Typical ranges:
+ Fresh bread, with a high av (>0.94), is microbiologically perishable and requires short shelf life or protective packaging.
+ Semi-moist cakes and pastries have an intermediate av , which makes mold growth possible; preservatives, packaging and hygiene are critical in this case.
+ Dry crackers, biscuits, crispbreads, with a low av (<0.6), are microbiologically stable, but extremely sensitive to moisture uptake from the environment (loss of crispness).
Bakers manage water activity by combining:
+ Formulation (sugars, salts, polyols, humectants),
+ Baking profile (how much moisture is driven off),
+ Cooling and packaging (how quickly products are sealed, permeability of films),
+ Storage conditions (temperature and ambient humidity).
Along the moisture sorption isotherm, the same product composition can behave differently during drying (desorption) and moisture uptake (adsorption). This hysteresis explains why a biscuit once softened by poor packaging rarely returns to its original crispness, even if re-dried.
6. Practical implications for bakers
For a bakery technologist or production manager, the science of water translates into a series of practical control points:
1. Know your water source:
+ Monitor hardness periodically.
+ Be cautious when changing site, drilling new wells, or installing softeners/reverse osmosis.
+ Record water temperature; seasonal changes may require process adjustments.
2. Match water hardness to product style:
+ For bread and rolls, moderately hard water usually gives the best balance of gluten strength and fermentation behavior.
+ Very soft or very hard water may require recipe or process corrections (salt, improvers, fermentation time).
3. Control water temperature and addition:
+ Use water temperature as a key parameter to achieve consistent dough temperature across seasons.
+ Keep accurate records of water absorption for each flour lot; small changes can significantly affect dough handling and volume.
4. Think ‘bound’ vs ‘free’ water when troubleshooting:
+ Sticky doughs, poor mixing tolerance, inconsistent proofing, or unexpected staling often relate to how water is being distributed among starch, proteins, pentosans, sugars, and fats – not just how much water you added.
5. Use water activity as a design too:
+ Target specific av ranges for bread, cake, biscuit, and filled products.
+ Combine process (baking time/temperature, cooling) and packaging choices to hit that target reliably.
6. Integrate water into your quality system.
+ Include water checks (hardness, temperature, conductivity, microbiology if relevant) in your HACCP and quality plans.
+ Train teams to understand water as an ingredient with specification – not just ‘what comes from the tap.’
Conclusion
Water is often treated as a background condition in baking – something to adjust until the dough ‘feels right’. Modern baking science shows that it deserves a much more central place.
From molecular interactions with starch and proteins, through phase transitions in the oven, to water activity and shelf life, water is the invisible driver of structure, flavor, and freshness. For bakeries facing ever-tighter specifications, longer distribution chains, and pressure to reduce waste, treating water as a strategic ingredient – not a commodity – is no longer optional. It is a competitive advantage.
References
1. Cauvain, S.P. & Young, L.S. (2007). Technology of Breadmaking (2nd ed.). Springer. A comprehensive treatment of water’s roles in mixing, fermentation, baking, and product quality.
2. Pyler, E.J. & Gorton, L.A. (2010). Baking Science & Technology (4th ed.). Sosland Publishing. Classic industry reference; includes practical guidance on water hardness and dough performance.
3. Sluimer, P. (2005). Principles of Breadmaking: Functionality of Raw Materials and Process Steps. AACC International. Focused explanations of how water interacts with flour components and process steps.
4. Mondal, A. & Datta, A.K. (2008). Bread baking—A review. Journal of Food Engineering, 86(4), 465–474. Integrates heat/mass transfer with structure setting; extensively discusses water’s role in baking dynamics.
5. Wagner, M.J., Lucas, T., et al. (2007). Water transport in bread during baking. Journal of Food Engineering, 78(4), 1087–1096. Foundational on moisture migration, vapour pressure, and crumb setting.
6. FDA (2014). Water Activity (aw) in Foods (Inspection Technical Guide). U.S. Food & Drug Administration. Clear definitions and regulatory context for a_w thresholds.
7. Barbosa-Cánovas, G.V., Fontana, A.J., Schmidt, S.J., & Labuza, T.P. (Eds.). (2007/2020). Water Activity in Foods: Fundamentals and Applications (1st/2nd ed.). Wiley/IFT Press. Definitive handbook on a_w, isotherms, and shelf-life design.
8. WHO (2022). Guidelines for Drinking-water Quality (4th ed., updated). World Health Organization. Global benchmark for potable water used in food production.
9. Courtin, C.M. & Delcour, J.A. (2002). Arabinoxylans and endoxylanases in wheat flour bread-making. Journal of Cereal Science, 35(3), 225–243. Explains how AX and xylanases influence water distribution, dough handling, and loaf volume.
10. Zhou, W. (Ed.). (2014). Chapters “Water” and “Baking” in Bakery Products Science and Technology (2nd ed.). Wiley-Blackwell. Up-to-date textbook chapters linking water properties to product structure and processing.