Sodium Hydroxide Uses in Food Industry: How Caustic Soda Is Used in Food

Caustic soda, also known as sodium hydroxide (NaOH), has several uses in the food industry. Food manufacturers use it in different stages of production, including fruit and vegetable peeling, olive processing, pretzel baking, cocoa treatment, edible oil refining, and equipment cleaning.

In food processing, caustic soda helps manufacturers prepare raw materials, control certain production steps, and maintain clean equipment. Its use depends on the type of food, the production method, and the required result.

Sodium hydroxide is also known as E524 in the European food additive system and INS 524 in the Codex system. However, its use in food production is subject to specific rules. The product must meet the required quality standards, and manufacturers must follow the correct handling and processing procedures.

This guide covers the main uses of caustic soda in food production, explains why manufacturers use it, and highlights what buyers should know about the product.

Where Is Caustic Soda Used in the Food Industry?

Caustic soda is used in several food production processes. Its main role is to help manufacturers prepare ingredients, adjust certain properties, or clean production equipment.

The following table summarizes its main applications.

Application	Main purpose
Fruit and vegetable peeling	Removes skins before further processing
Olive processing	Reduces bitterness in olives
Pretzel production	Creates the typical dark and glossy crust
Cocoa processing	Adjusts acidity and changes cocoa colour
Edible oil refining	Removes free fatty acids from crude oil
Food plant cleaning	Removes grease, fats, and protein residues

The amount and concentration of caustic soda depend on the process. Food manufacturers select the product and prepare the solution according to their production requirements.

Beyond food production, caustic soda has many other industrial applications. These include paper manufacturing, textiles, detergents, and chemical production. Read more about caustic soda applications in different industries.

1. Fruit and Vegetable Peeling

One of the common uses of caustic soda in food processing is chemical peeling. Food manufacturers use this method to remove the outer skin of fruits and vegetables before canning or other production steps.

Products such as tomatoes, potatoes, peaches, pears, apricots, and carrots can be processed using this method.

During chemical peeling, fruits or vegetables pass through a sodium hydroxide solution. The solution loosens the skin and makes it easier to remove. Water jets or mechanical equipment then separate the skin from the product.

The process usually includes three main steps:

1. Treatment: The product comes into contact with a caustic soda solution.
2. Peeling: The loosened skin is removed using water or mechanical equipment.
3. Rinsing: The product is washed to remove remaining caustic soda from its surface.

The concentration, temperature, and treatment time affect the peeling result. Manufacturers adjust these conditions according to the type and condition of the product.

For example, tomatoes may be treated with solutions containing around 8% to 25% sodium hydroxide for a short period. These values are reported in published processing studies. They are not universal operating instructions.

Caustic soda helps food manufacturers process large quantities of produce in a relatively short time. However, the process also creates alkaline wastewater that requires proper treatment.

Manufacturers can prepare the required solution using either solid caustic soda or concentrated liquid caustic soda. The choice depends on their equipment, storage facilities, and production needs.

Learn more about solid and liquid caustic soda types.

2. Olive Processing and Bitterness Removal

Caustic soda also plays an important role in the processing of table olives.

Fresh olives naturally contain a bitter compound called oleuropein. This compound gives raw olives their strong bitter taste. Before olives can be prepared for many commercial markets, manufacturers need to reduce this bitterness.

One common method uses a sodium hydroxide solution.

In the Spanish-style olive processing method, green olives are treated with a diluted caustic soda solution. The solution helps break down oleuropein and reduces the bitterness of the fruit.

The treatment must be controlled carefully. Manufacturers consider several factors, including:

• Olive variety and ripeness
• Caustic soda concentration
• Treatment temperature
• Processing time

After the treatment, olives are washed several times to remove the remaining solution. They are then placed in brine, where fermentation and further flavour development take place.

The amount of caustic soda used depends on the processing method and the condition of the olives. The treatment must also be controlled to prevent excessive softening or changes in colour.

For commercial olive producers, consistent product quality and controlled processing are important. This makes the quality and correct preparation of the processing chemicals relevant to the production process.

3. Pretzel Production and Baking

Caustic soda is also used in the production of traditional pretzels.

The dark colour and glossy surface of pretzels are partly the result of an alkaline treatment before baking. For this purpose, manufacturers dip the dough into a diluted sodium hydroxide solution or apply the solution to its surface.

This treatment changes the surface conditions of the dough and helps create the typical brown colour during baking.

The process generally includes:

1. Preparing the dough.
2. Applying a diluted caustic soda solution.
3. Baking the treated dough.
4. Allowing the pretzels to cool before packing.

The concentration of the solution varies according to the recipe and production method. Some industrial processes use lower concentrations, while certain bakery methods use stronger solutions.

During baking, sodium hydroxide reacts with carbon dioxide and changes into sodium carbonate. This is why the final baked product is different from the dough before baking.

Although this application uses a diluted solution, handling caustic soda still requires proper protective equipment and safety procedures. The chemical is corrosive and can cause serious skin and eye injuries.

4. Cocoa and Chocolate Processing

Sodium hydroxide is one of several alkaline substances used in cocoa processing.

This process is commonly known as alkalisation or Dutch processing. Its purpose is to change some of the natural properties of cocoa powder.

Natural cocoa is slightly acidic. During alkalisation, manufacturers treat cocoa with an alkaline solution to increase its pH.

This process can produce several changes:

• A darker cocoa colour
• A milder and less acidic taste
• Better dispersion in certain liquid products

The final result depends on the cocoa beans, the selected alkaline substance, and the processing conditions.

Potassium carbonate is commonly used for cocoa alkalisation. Sodium hydroxide is another alkaline substance that may be used in permitted applications.

For manufacturers, the choice of alkali depends on the desired product characteristics and the applicable food regulations.

5. Caramel Colour Production

Caustic soda can also be used in the production of caramel colour.

Caramel colour is a food colouring made by heating carbohydrates under controlled conditions. Manufacturers use it to give different food and beverage products a brown colour.

It is used in products such as:

• Soft drinks
• Sauces
• Bakery products
• Some confectionery products

During production, different processing conditions and ingredients create different types of caramel colour.

Sodium hydroxide is one of the alkaline substances that may be used in certain caramel production processes. Its role is related to controlling the reaction conditions during manufacturing.

The type of caramel colour and the production method determine which processing materials are suitable.

6. Edible Oil Refining

Another industrial use of caustic soda is edible oil refining.

Crude vegetable oils may contain free fatty acids and other unwanted materials. These substances can affect the quality, stability, and final characteristics of the oil.

One of the refining methods uses sodium hydroxide to neutralise free fatty acids.

During this process, caustic soda reacts with free fatty acids and forms soap. This material is known as soapstock and can then be separated from the oil.

The main stages include:

1. Preparing the crude oil.
2. Adding a controlled amount of caustic soda.
3. Allowing the reaction to take place.
4. Separating the soapstock from the oil.
5. Washing and drying the refined oil.

The amount of caustic soda required depends on the free fatty acid content and the quality of the crude oil.

This is why concentration and product consistency are important for oil refining facilities. Manufacturers need to control chemical dosing to achieve the required refining result.

7. Cleaning Food Production Equipment (CIP)

Caustic soda is widely used for cleaning equipment in food manufacturing facilities.

Food production equipment can collect fats, proteins, oils, and other residues during operation. If these materials are not removed properly, they can affect hygiene and production quality.

Many food plants use a system called Cleaning in Place (CIP). This method cleans tanks, pipes, pumps, and other equipment without taking the entire system apart.

Caustic soda is commonly used in the alkaline cleaning stage of CIP.

It helps break down and remove organic residues, especially fats and proteins. The cleaning solution is circulated through the equipment and then removed through rinsing.

A typical CIP process includes:

1. Pre-rinse: Water removes loose product residues.
2. Alkaline cleaning: A caustic soda solution removes fats and proteins.
3. Intermediate rinse: Water removes the alkaline solution.
4. Acid cleaning: An acid solution helps remove mineral deposits.
5. Final rinse: The equipment is rinsed before production starts again.

The concentration and temperature of the cleaning solution depend on the equipment and the type of contamination.

Caustic soda is often supplied to industrial facilities in concentrated liquid form. The plant then dilutes it to the required concentration.

Since cleaning is repeated regularly, a consistent product and a reliable supply are important for food manufacturers.

For more information about safe storage and handling, see our guide to caustic soda handling, storage and safety.

Is Caustic Soda Safe in Food?

Caustic soda is a highly corrosive chemical. Concentrated sodium hydroxide must never be consumed or handled without proper protection.

However, it can be used in food production under approved conditions.

In some processes, manufacturers rinse the product after treatment. In others, sodium hydroxide reacts during processing and changes into other substances.

The important point is that its use must follow the applicable food safety requirements. The presence of an approved food processing application does not mean that concentrated caustic soda is safe to eat.

Sodium hydroxide has different regulatory references in different markets:

• United States: Sodium hydroxide is listed under FDA regulation 21 CFR 184.1763 for use under good manufacturing practice.
• European Union: Sodium hydroxide is listed as food additive E524.
• Codex Alimentarius: It is identified as INS 524.

These references do not remove the need to check the rules for each food category and market.

Food manufacturers must also use suitable product quality, follow approved processing methods, and maintain proper cleaning and rinsing procedures.

Food-Grade Caustic Soda: What Should Buyers Know?

Not all caustic soda products are suitable for food-related applications.

Food manufacturers must select a product that meets the quality requirements of their process and the relevant food regulations.

Food-grade caustic soda is supplied with specific quality requirements and supporting documentation. Buyers should check these details before placing an order.

Some important points include:

1. Product quality

Check the sodium hydroxide content and the limits for impurities. Requirements may differ according to the applicable standard and intended use.

2. Certificate of Analysis (CoA)

A batch-specific Certificate of Analysis provides information about the tested product. It helps buyers compare the delivered material with the agreed specifications.

3. Safety Data Sheet (SDS)

The SDS provides important information about chemical hazards, storage, handling, and emergency measures.

4. Product form

Caustic soda is available in different forms, including flakes, pearls, and liquid. The right choice depends on the buyer's production equipment and handling requirements.

5. Packaging and transportation

Packaging should suit the product form, storage conditions, and transportation method. Buyers should also consider the required export documents and destination-country regulations.

For more information, see our guides to caustic soda types and caustic soda packing.

Frequently Asked Questions

Is caustic soda used in food production?

Yes. Caustic soda is used in several food processing applications, including fruit peeling, olive processing, pretzel production, cocoa alkalisation, and edible oil refining. It is also widely used for cleaning food production equipment.

Is caustic soda edible?

No. Concentrated caustic soda is not edible and can cause severe burns. Its use in food processing is permitted only under specific conditions and approved procedures.

Why is caustic soda used in milk processing?

Caustic soda is mainly used to clean milk processing equipment, including tanks, pipes, and production lines. It is not a permitted method for making spoiled milk fresh again. Its cleaning use must be followed by proper rinsing before production resumes.

What is the difference between caustic soda and sodium hydroxide?

They are two names for the same chemical compound, NaOH. Caustic soda is the common industrial name, while sodium hydroxide is its chemical name.

What is E524 in food?

E524 is the European food additive number for sodium hydroxide. It identifies the chemical in food additive regulations. Its permitted uses depend on the applicable food category and regulations.

Is caustic soda used for cleaning food factories?

Yes. It is commonly used in Cleaning in Place (CIP) systems. The alkaline solution helps remove fats, proteins, and other organic residues from production equipment.

What forms of caustic soda are available for industrial buyers?

Caustic soda is commonly available as flakes, pearls, and liquid. Buyers should select the form based on their production requirements, storage facilities, and handling systems.

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Conclusion

Caustic soda has several applications in the food industry. It is used in fruit peeling, olive processing, pretzel production, cocoa treatment, edible oil refining, and cleaning food manufacturing equipment.

For industrial buyers, choosing the right product involves more than comparing prices. Product quality, concentration, documentation, packaging, and supply requirements all matter.

Understanding these factors helps buyers make better purchasing decisions and select a product that meets their intended application.