Essential Properties and Treatment of Water in Food Processing

Water is one of the most heavily used resources in any food processing facility. It serves as an ingredient, a cleaning agent, a heat transfer medium, and much more. Yet, the quality of that water can make or break the safety, taste, appearance, and shelf life of your final product. Understanding the essential properties of processing water – and how to treat it – is foundational knowledge for anyone involved in food manufacturing.

Why water quality matters in food processing 🔗

In a food plant, water does far more than just flow through pipes. It is used for blending, mixing, washing raw materials, generating steam, cooling, rinsing equipment, and even as a direct ingredient in products like beverages, soups, and sauces. According to Oklahoma State University’s food industry fact sheet, when water is used as a food ingredient, its impurities can directly affect the texture, shelf stability, appearance, aroma, and flavour of the finished product. As a processing aid, the purity of water influences how well it performs tasks like dissolving ingredients or transferring heat.

This is exactly why food processing water must meet strict potable water standards – meaning it must be safe for human consumption. But potability alone is not always enough. Depending on the application, processing water may also need to be low in dissolved minerals, free from off-flavours and off-odours, and chemically neutral to avoid interfering with the product.

Key properties of ideal processing water 🔗

Not all potable water is equally suitable for food processing. A municipal water supply that is perfectly safe to drink may still contain minerals, gases, or organic compounds that cause problems in a manufacturing setting. Here are the critical properties that food-grade processing water must possess.

Chemical purity 🔗

Processing water should be free from excessive dissolved chemicals, including heavy metals, pesticide residues, and industrial contaminants. Even trace levels of certain metals like iron and copper can catalyse oxidation reactions in food, leading to rancidity, vitamin degradation, and undesirable colour changes. As noted by ScienceDirect’s overview on sequestrants, trace metals naturally present in water can cause discolouration and off-flavours in processed foods. Chemical purity ensures that the water does not introduce any unwanted reactive elements into the product.

Low mineral salt content 🔗

Dissolved mineral salts – particularly calcium, magnesium, iron, and manganese – are one of the biggest concerns for food processors. High mineral content can cause cloudiness or turbidity in beverages, alter the colour of canned vegetables, toughen legumes during cooking, and change the taste profile of finished products. For instance, research published on ScienceDirect explains that hard water can alter bread dough consistency, produce firmer and denser bread, and even weaken the surface of pasta noodles. Keeping mineral salts low is essential for consistent product quality.

Absence of turbidity 🔗

Turbidity refers to the cloudiness caused by suspended particles such as silt, clay, organic matter, or microorganisms. In food processing, turbid water is unacceptable because it can introduce contaminants, interfere with disinfection, and make final products appear unappealing. Surface water sources – rivers, lakes, and reservoirs – tend to have higher levels of suspended materials and turbidity compared to groundwater. Proper filtration and settling treatments are necessary to bring turbidity down to acceptable levels before the water enters the production line.

No off-colours and off-flavours 🔗

Water that has a noticeable taste or colour can directly transfer those characteristics to food products. Iron in water, for example, can impart a metallic taste and cause discolouration in light-coloured foods. Chlorine, while essential for disinfection, can leave a detectable flavour if present in excess. Hydrogen sulphide gives water a characteristic rotten-egg smell. For products where water is a primary ingredient – such as beverages, broths, or reconstituted foods – even subtle off-flavours become immediately noticeable to consumers. Activated carbon filtration is one of the most commonly used methods to remove odour and flavour-causing compounds from water.

Microbiological safety 🔗

Processing water must be free from pathogenic microorganisms including bacteria, viruses, and parasites. The U.S. FDA requires that any water coming into contact with food or food-contact surfaces must be safe and of adequate sanitary quality. Contaminated water can introduce pathogens like E. coli, Salmonella, and Cryptosporidium into the food supply, potentially causing widespread foodborne illness. Chlorination, UV radiation, and ozonation are standard disinfection methods used to ensure microbiological safety.

Appropriate pH 🔗

The pH of processing water affects everything from the effectiveness of cleaning chemicals to the taste and stability of the final product. Most food processing operations require water with a near-neutral pH, typically between 6.5 and 8.5. Water that is too acidic can corrode equipment and pipes, while highly alkaline water can affect product flavour and interfere with certain processing steps.

Understanding water hardness 🔗

Water hardness is one of the most commonly discussed water quality issues in food processing. It refers to the concentration of dissolved calcium (Ca²⁺) and magnesium (Mg²⁺) ions in water. These minerals enter the water naturally as it flows through limestone, chalk, and other geological formations.

Temporary vs. permanent hardness 🔗

Water hardness is classified into two types based on the kind of mineral compounds present:

Temporary hardness is caused by dissolved calcium and magnesium bicarbonates. It is called “temporary” because it can be removed simply by boiling the water. When heated, bicarbonates decompose into insoluble carbonates, carbon dioxide gas, and water. The carbonates precipitate out and can be filtered away. This is the white, chalky scale you often see inside kettles.

Permanent hardness is caused by calcium and magnesium sulphates and chlorides. Unlike temporary hardness, it cannot be removed by boiling. Chemical treatment methods such as ion exchange or the addition of soda ash (sodium carbonate) are required to deal with permanent hardness.

The total hardness of water is the sum of both temporary and permanent hardness, and it is typically expressed in milligrams per litre (mg/L) of calcium carbonate (CaCO₃) equivalent. Water with less than 60 mg/L is considered soft, while water exceeding 120 mg/L is classified as hard.

How hard water affects food processing 🔗

Hard water creates several problems in a food manufacturing environment:

Scale formation on equipment: When hard water is heated, dissolved minerals precipitate out and form a hard, chalky deposit known as scale. This scale builds up inside boilers, heat exchangers, pipes, and nozzles. Scale acts as an insulator, reducing the efficiency of heat transfer equipment and increasing energy consumption. Over time, it can clog pipes and lead to equipment failure.

Reduced cleaning efficiency: Hard water reacts with soaps and detergents to form insoluble compounds (commonly known as soap scum), which reduces their cleaning effectiveness. According to Food Safety Magazine, water hardness profoundly affects cleaning chemical performance and may cause the formation of films, scale, or precipitates on equipment surfaces. Food processors who switch to softened water often see a significant reduction in chemical usage.

Impact on product quality: In baking, high calcium and magnesium levels can toughen gluten, making dough less elastic and bread denser. In canning, hard water can cause cloudiness in brines and syrups. In beverages, it affects taste, mouthfeel, and clarity. Hard water can also interfere with the dissolution and dispersion of food ingredients during processing.

Water treatment methods for food processing 🔗

Since raw water – whether from municipal supplies, wells, rivers, or reservoirs – rarely meets all the quality requirements for food processing without some form of treatment, food plants rely on a combination of treatment methods. Here are the most important ones.

Boiling 🔗

Boiling is the simplest method to remove temporary hardness. When water is heated to its boiling point, calcium and magnesium bicarbonates decompose and precipitate as carbonates. These solids can then be removed by filtration. However, boiling is energy-intensive and impractical for large-scale industrial operations. It is mainly useful for small volumes or as a quick fix.

Ion exchange 🔗

Ion exchange is one of the most widely used water softening methods in the food industry. In this process, hard water passes through a resin bed containing sodium or potassium ions. As explained by the University of Nebraska-Lincoln’s water resources programme, calcium and magnesium ions in the water attach to the resin beads while sodium ions are released into the water in exchange. Once the resin is saturated, it is regenerated by flushing with a salt brine solution, which replaces the captured calcium and magnesium with fresh sodium ions. Ion exchange systems are efficient, scalable, and widely adopted in food processing facilities for both softening and demineralisation.

Reverse osmosis 🔗

Reverse osmosis (RO) forces water through a semi-permeable membrane under pressure, removing dissolved minerals, salts, and other impurities. RO produces very high-purity water and is particularly useful for applications where even low mineral content is unacceptable – such as in beverage manufacturing or boiler feed water. The downside is that RO systems are more expensive to install and maintain, and they produce a significant amount of wastewater (the reject stream).

Chemical softening 🔗

Chemical softening involves adding reagents like lime (calcium hydroxide) and soda ash (sodium carbonate) to hard water. These chemicals react with dissolved calcium and magnesium to form insoluble precipitates that can be removed through sedimentation and filtration. This method – known as lime-soda softening – is effective for treating large volumes of water and is commonly used in industrial water treatment plants. It can address both temporary and permanent hardness, though it requires careful dosing and generates sludge that must be disposed of properly.

Use of sequestering (chelating) agents 🔗

Rather than physically removing hardness minerals from water, sequestering agents work by binding to calcium and magnesium ions and holding them in a soluble, stable complex. This prevents the minerals from reacting with other substances or precipitating out as scale. Common sequestering agents used in the food industry include EDTA (ethylenediaminetetraacetic acid), citric acid, and polyphosphates.

According to ScienceDirect, EDTA and polyphosphates can be used in canned seafood to prevent the formation of glassy struvite crystals by binding magnesium, and in fruits and vegetables to prevent discolouration. Citric acid, a naturally occurring chelating agent, is widely used in the soft drink industry for both flavouring and metal ion sequestration. The World Health Organization and the FAO/Codex Alimentarius guidelines recommend that water treatment decisions be based on hazard analysis of the source water and intended use.

Filtration 🔗

Filtration removes suspended solids, sediment, and particulate matter from water. It ranges from simple sand or multimedia filters for removing larger particles to microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) membranes for progressively finer separation. Activated carbon filtration is specifically used to remove chlorine, organic compounds, and taste- and odour-causing substances. Filtration is typically a preliminary step that precedes other treatments like ion exchange or reverse osmosis.

Disinfection 🔗

Disinfection ensures the microbiological safety of processing water. The most common methods include chlorination, ozonation, and ultraviolet (UV) irradiation. Chlorination is inexpensive and provides a residual disinfectant that continues to protect water in the distribution system. Ozone is a powerful oxidiser that kills pathogens without leaving a residual taste but dissipates quickly. UV treatment is effective against bacteria, viruses, and protozoa without adding any chemicals to the water. Many food plants use a combination of these methods for robust microbiological control.

Matching water quality to its intended use 🔗

Not every application in a food plant requires the same level of water purity. A well-designed water management plan matches treatment intensity to the specific use case:

Water as a food ingredient demands the highest quality. It must be free from off-flavours, odours, colour, excessive minerals, and microorganisms. Treatments typically include activated carbon filtration, softening, disinfection, and sometimes reverse osmosis.

Washing and rinsing water needs to be clean and preferably soft. Hard water wastes cleaning chemicals and leaves residues on surfaces. According to Oklahoma State University, soaps, cleaners, and sanitisers perform much better in softened water, and many processors see a dramatic reduction in chemical usage after installing softening systems.

Boiler feed water for culinary (sanitary) steam requires thorough treatment to prevent scale formation, corrosion, and carryover of impurities into the steam. Corrosive components like dissolved oxygen and carbon dioxide may need to be removed by deaeration, and pH should be maintained around 8.5.

Cooling water has somewhat less stringent purity requirements but still needs to be managed to prevent microbial growth, scale, and corrosion within cooling systems.

The bigger picture: water safety and regulatory compliance 🔗

Water safety in food processing is not optional – it is a regulatory requirement. Under the U.S. FDA’s Good Manufacturing Practices (21 CFR Part 110), any water that contacts food or food-contact surfaces must be safe and of adequate sanitary quality. Similarly, the European Union mandates that food businesses use water that meets drinking water standards for any food production activity.

A comprehensive water management plan involves regular testing of physical, chemical, and microbiological parameters; maintaining treatment equipment; mapping the entire water and plumbing system within the facility; and keeping detailed records. The Food Safety Magazine recommends that companies consult credible water treatment experts to determine the best treatment programme for their specific needs, as there is no one-size-fits-all solution.

Food processors should also have contingency plans for water supply disruptions – such as boil-water advisories – that outline how to handle production, quarantine affected products, and resume normal operations safely.

What do you think? How does the quality of water in your region affect the food products you consume daily? If you were setting up a small-scale food processing unit, which water treatment method would you prioritise first – and why?

References

1. https://extension.okstate.edu/fact-sheets/water-use-in-the-food-industry.html
2. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/sequestrant
3. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/water-hardness
4. https://www.fda.gov/regulatory-information/search-fda-guidance-documents/guidance-industry-use-water-food-manufacturers-areas-subject-boil-water-advisory
5. https://www.food-safety.com/articles/4624-assuring-water-quality-and-safety-in-food-processing
6. https://water.unl.edu/managing-hard-water/
7. https://www.who.int/publications/i/item/9789241516402
8. https://www.fao.org/fao-who-codexalimentarius/sh-proxy/jp/?lnk=1&url=https://workspace.fao.org/sites/codex/Standards/CXG+100-2023/CXG_100e.pdf
9. https://www.food-safety.com/articles/10294-dynamics-of-water-quality-for-food-and-beverage-processing