In an industrial food facility, cleanliness and sanitation are essential. That’s why appropriate procedures must be designed so that all the surfaces in contact with food, be it equipment, pipelines or utensils, are sanitised. Also surfaces that are not in direct contact with food, such as walls and ceilings, protective partitions or ventilation systems, must be cleaned appropriately.
The objectives of these cleaning processes are to remove substrates that may allow microbiological growth and to eliminate the presence of bacteria. Once achieved, equipment and surfaces must be dried and maintained in appropriate conditions to prevent bacterial growth.
Cleaning and disinfection procedures should be designed and protocolised to effectively meet the objectives, and should be carried out under the instructions of the procedures, with controls in place to ensure effectiveness, and regular evaluation on a comprehensive basis. Compliance with written procedures should be monitored and records should be kept to assess long-term compliance.
Cleaning of food surfaces usually involves 4 steps:
Dirt in the food industry
Food-generated dirt includes undesired materials on surfaces in contact with food, whether visible or invisible. The main source of dirt is the handled food product itself. However, minerals in water or residues from cleaning products contribute to the formation of films on surfaces. This dirt can promote the growth of microbiological biofilms.
Given the variability of dirt, no detergent is capable of completely removing these accumulated compounds, and a selection must be made on the basis of their solubility properties. The staff in charge must know the nature of the products to be removed and select an appropriate detergent or cleaning protocol in each case. In general, acidic cleaners dissolve alkaline dirt (minerals) and alkaline cleaners dissolve acidic dirt and food debris.
Inappropriate use of detergents can promote the adherence of dirt making it more difficult to remove. The build-up of certain types of dirt requires more sophisticated solutions. An example would be cleaners that include oxidising agents (e.g., chlorinated detergents) for its removal.
Types of dirt
A general classification of types of dirt can be made according to their solubility:
- Soluble in water (sugars and salts).
- Soluble in acidic media (most mineral deposits).
- Soluble in basic media (proteins and fats).
Furthermore, if cleaning processes are carried out on freshly deposited dirt, they are often easier and more effective than on older, dry or even baked-on substrates.
In general, fat can be removed with hot water at a temperature above its melting point. Fat and oil residues can be removed with alkaline cleaners which act as saponification agents and facilitate emulsification.
Proteins are often a challenge in industrial detergency processes in the food industry, especially the more complex ones. Heat-denatured proteins can be extremely difficult to remove.
Generally, highly alkaline detergents with wetting properties are needed for this type of dirt.
If proteins are film-forming on surfaces, the use of chlorinated alkaline cleaners is likely to be necessary.
Simple sugars are readily soluble in warm water and are not a challenge to clean. Starch residues can be removed by mild detergents. Starches associated with proteins or fat are usually easily removed by alkaline detergents.
Mineral salts may be easy to remove with acidic detergents, but they can also be found in the form of deposits or films and pose major problems. Calcium and magnesium are very present in wash water and are associated with the most difficult mineral films to remove. Under hot and alkaline conditions, calcium and magnesium combine with carbonates to form insoluble complexes.
Acidic cleaners, especially those containing organic acids forming complexes with salts, are recommended for the removal of mineral dirt.
Chelating agents are also recommended in alkaline cleaners to act on mineral dirt.
Under certain conditions, micro-organisms form films (biofilms) on surfaces. These films are generally difficult to remove and require cleaners and disinfectants with strong oxidising properties.
Greases and Lubricating Oils
These types of fats are insoluble in water, both at acidic and basic pH, and therefore require different solutions than food fats. As they often melt at high temperatures, they can be partially removed with hot water or steam, but surfactants must be used to emulsify the residues.
Chemistry of detergents for CIP cleaning
Detergents and cleaning products are formulated with ingredients that interact with different types of dirt, altering physical characteristics such as solubility or colloidal stability, and/or modifying the components to make them more soluble and therefore easier to remove.
The main ingredients of detergents for CIP cleaning for the food industry are listed below:
They are organic molecules whose chemical structure has a hydrophilic and a hydrophobic zone. They are responsible for the emulsification, penetration, wetting and foaming of detergents.
Foaming is often associated with an effective detergency process. However, this is not always the case. In detergents for CIP cleaning, surfactants with low foaming power, or even surfactants capable of destabilising foam (low foaming surfactants and antifoaming agents), are usually required, because foaming itself hinders the cleaning and rinsing process of the product.
The main alkaline agents used in CIP cleaning are caustic soda (sodium hydroxide) and caustic potash (potassium hydroxide). Alkaline detergents saponify fats by forming soap.
These agents are often used in CIP systems and bottle washing applications.
Moderately alkaline detergents include phosphate, silicate or carbonate salts. Trisodium phosphate is one of the oldest and most effective. Silicates are most often used as corrosion inhibitors. Carbonate-based detergents have a limited use due to interaction with calcium and magnesium.
Acidic detergents include organic and inorganic acids. The most common inorganic acids used are phosphoric, nitric, sulphamic and hydrochloric acids. Organic acids, such as hydroxyacetic, citric and gluconic acids, are also common.
Acidic detergents are often used in two steps, in a sequential cleaning regime with alkaline detergents.
Sequestering agents are used in CIP cleaning to prevent the accumulation of various mineral deposits (water hardness, etc.). Sequestering agents form soluble complexes with calcium and magnesium. Some of the most commonly used are phosphonates, sodium gluconate, EDTA and GLDA.
The most frequently used oxidising agent in CIP cleaning is hypochlorite (also of interest for its disinfectant capacity). Chlorinated detergents are frequently used to clean protein residues.