Compressed Air in the Food Industry

Manufacturing foodstuff

Compressed air utilised in the manufacturing and treatment processes for foodstuff must always be oil-free and germ-free, as the compressed air comes into direct contact with the product. A corresponding compressed air processing is therefore required e.g. with a sterile filter for direct product contact Since there are no requirements in place for monitoring the compressed air, the manufacturers are responsible and should implement appropriate hazard and risk management (HACCP). Continuous monitoring of the compressed air quality ensures process safety and reduces incorrect production. This can easily occur, for instance in the context of ice cream production. Compressed air is blown into the base ice cream mass to make it creamier. If the compressed air does not have this necessary purity class, then the ice cream consistency is negatively affected.

Compressed air is utilised in additional foodstuff processes, among other things for cooling down bakery products and chocolate, blowing away dough and chocolate residue, spraying and glazing of dough-based products as well for coating potato products.

In addition, compressed air can be used for cleaning, blowing out shapes, for CIP cleaning of production plants or systems or for washing fruits and vegetables. Compressed air is hereby routed into the water so that it moves and achieves better washing effects.

Packing and filling

The transfer of mineral oil hydrocarbons (MOSH/MOAH) to foodstuffs is considered particularly critical in the case of packaging materials - especially recycled corrugated board and the newspaper printing inks containing mineral oil used in the recycling chain. For a long time, compressed air as a source of contamination was not considered.

The condition of the final product must remain unchanged when packing and filling products. Beverages and food must therefore be treated very gently and there cannot be any resulting contamination. This means that compressed air utilised in this area must be oil-free and germ-free. So-called sterile air is required for processes in the packaging and filling food sector e.g. with deep withdrawal for beakers, thermal shaping of other packaging, inflating of packaging and filling liquid products. Compressed air is also utilised to blow out incorrect products or for cleaning of packaging materials.

Compressed air is also required in the beverages industry for, among other things, when PET bottles are used in filling processes. The bottles are inflated by a so-called stretch blowing process with compressed air. In addition, compressed air is generally used for cleaning the bottles, contamination such as dust can be removed as one example. Bottles are sealed with bottle tops in breweries, which are transported with compressed air. If compressed air is hereby contaminated with, then this subsequently reduces foam formation for the beer. This clearly demonstrates to which extent compressed air can have important effects on the sensory characteristics of the product.

Transportation of suppliers

Many raw materials are processed and transported in the food and beverage industry. Loose foodstuffs such as granulates, rice, cereals, sugar or coffee are transported in silos and tanks. The general rules for food transport state, among other things, that foodstuffs may only be transported in marked transport containers and are subject to special hygiene requirements. Compressed air is often used for unloading, which then comes into direct contact with the foodstuffs. The previous measures for the containers would be void if the compressed air is contaminated, thus causing contamination.

A special feature is the hazard potential at transition points in the production process in the food industry. Their safety standards also apply to suppliers, e.g. for packaging, raw materials, foodstuffs, silo transport. The transition points should therefore be considered in the hazard analysis (HACCP).

Controlling plants and systems

A wide variety of products as well as different machines and tools are required in the production of foodstuff and beverages, also pneumatic devices among others. Compressed air is mostly utilised here as control air i.e. as a pneumatic actuator for the control of grippers or valves. The materials of the pneumatic devices must comply with stringent requirements, such as being corrosion resistant, non-toxic and non-absorbent. The requirements for the compressed air itself especially depend on whether they come into direct contact with the food or not.

Compressed air pressure rarely comes into direct contact with the food when utilised for controlling a process although optimum compressed air processing remains important. Contaminations in the compressed air can accelerate the wear on the components and cause jamming in the components. Retaining the quality of the compressed air and an optimal design can therefore minimise downtimes and energy costs as well as preventing product contamination.
 

Fermentation

Mechanical processes are not the only important element in food manufacturing, biotechnological processes, so-called fermentation processes, are also important. This process is disrupted by foreign organisms, which is why it is imperative that process-foreign organisms are removed. The materials involved and the application utilised must therefore be sterile. This of course also applies for the compressed air, whereby a sterile filter is often utilised for treating it. Compressed air is utilised, for example, for the ventilation of seasoning in brewing processes, for the production of nitrogen or for mixing and transporting yeast during the fermentation process.

With the exception of blowing off crown corks of already closed bottles, the compressed air is in direct contact with the foodstuff and must therefore meet the highest purity standards, in terms of residual oil content even better than class 1. Sterile air should be used for wort aeration and destoning.

Hazard Analysis Critical Control Points

HACCP stands for the principle approach to the identification and assessment of risks associated with the processing of food. After this basic recording and assessment of all factors that could affect food safety, the aim is to determine suitable measures for the entire production chain. The critical control points (CCP - Critical Control Points) for the process of compressed air preparation must be defined and suitable measures for risk minimisation - so-called operational prevention programmes (oPRP) - must be established and documented.

The HACCP concept is anchored in food law and applies to all companies that are commercially active in the process chain of food production or trade with food. Every food business operator is obliged to prove the application of an HACCP concept by means of suitable documentation.

A continuous monitoring of the compressed air quality with suitable sensor technology and monitoring systems is essential. The measurement data must be compared and documented with the required compressed air quality and the manufacturer's in-house compressed air specifications. A complete documentation ensures an optimal monitoring of the compressed air quality also during internal and external audits.

Critical Control Points

Process steps or the points in the compressed air system at which control is possible. Depending on the result of the hazard analysis, it is necessary to define critical control points (CCP).

In the CCP, minimum and maximum values are defined, above which intervention with preventive programs is require

Mineral Oil Saturated Hydrocarbons | Mineral Oil Aromatic Hydrocarbons

MOSH, (Mineral Oil Saturated Hydrocarbons) paraffinic, saturated mineral oil hydrocarbons

MOAH, (Mineral Oil Aromatic Hydrocarbons) aromatic petroleum hydrocarbons

Mineral oils can get into a foodstuff in many different ways. Contamination by lubricating oil from harvesting machines or hydraulics is already possible during harvesting. Mineral oils in product packaging made of recycled cardboard and the printing inks used for the design of a package can also contaminate a foodstuff.

When considering the generation of compressed air, oil-injected or even oil-free screw compressors are used in most cases. Here mineral oil is used in the compressor for cooling and sealing purposes of the compressor stage. The generated compressed air is inevitably contaminated with mineral oil. Therefore, there is always a compressed air treatment downstream to reduce oil ingress, moisture content and particles.

"Oil-free" compressors are often used as an alternative. With the oil-free compressing principle, no oil is added to the compressed air by the compression process, but hydrocarbons from the environment (ambient air), e.g. incompletely burnt diesel or emissions from industrial plants, are drawn in and compressed and concentrated by the compressor.

Oil-free compression does not automatically mean oil-free compressed air. This is because here, too, appropriate post-processing is required to reduce the hydrocarbon content.

Direct or indirect contact with compressed air

Direct contact is when the compressed air is directed specifically at the product or at the primary packaging that comes into contact with the product. For example, compressed air is used to evaporate liquids or as a transport medium for dry food. Powdery substances such as coffee, flour or powdered milk or even ground spices are transported with it. Such dry products are subject to high requirements in terms of humidity, as they come into intensive contact with residual moisture due to their large surface area. To prevent the powder from clumping or becoming contaminated, the compressed air must be absolutely dry and clean.  Compressed air also comes into direct contact with the product when processing non-dry food. In some applications the compressed air is even introduced directly into the product. A high degree of care is therefore required when it comes into direct contact with food.

Indirect contact with foodstuffs occurs when the expanded compressed air reaches a product over a certain distance and diluted with ambient air. Typical compressed air applications with indirect product contact are cleaning and drying, e.g. the blowing off of packaging surfaces for quality control, and the transport of food packaging. In the case of indirect contact between the compressed air and the foodstuff, the compressed air quality requirements are not as high as for direct contact. Nevertheless, it must be noted that the food can also be contaminated via the packaging.