Compressed air has numerous applications in the process industries. Pharmaceuticals, chemical plants, water companies, bulk materials handlers, oil and gas producers all use compressed air in abundance. It’s a versatile utility that is used for many purposes. But its valuable contribution to food engineering is perhaps the least well known of all.
The UK food and drink industry is the country’s largest manufacturing sector (16% by value), employing well over a million people in both direct and indirect labour. The industry is subject to rigorous legislation; perhaps not surprising considering its potential impact on human health. We naturally expect our food and drink to be above reproach.
Until recent years, however, there was a lack of specific guidance on the required quality of compressed air when used in food production—apart from the general standards produced by the International Organization for Standardization (for example ISO 8573 Compressed air andISO 12500 Filters for compressed air. Test methods. Particulates).
In response to this, the British Compressed Air Society (BCAS) and the British Retail Consortium (BRC) jointly produced, in 2007, their Food Grade Compressed Air – A Code of Practice. The latest revision of this industry standard document, titled BCAS Food Grade Compressed Air Best Practice Guideline 102, is available from bcas.org.uk.
Guideline 102, according to BCAS, ‘includes information on what type of compressed air equipment could be used, how it should be installed, maintained and audited and, perhaps most importantly, the levels of air purity required to reduce the risk of contamination’. It defines three types of compressed air system in the food industry.
OH CRUMBS! THE BISCUITS ARE CONTAMINATED!
‘Non-contact low risk’ is the definition that BCAS uses for plant air. This is used to power pneumatic tools and machinery (in fact more than half of the compressed air used in food engineering is plant air). Plant air does not have any contact with the food products or the packaging process, so it has no adverse effect on the quality of the end product.
The definition ‘non-contact high risk’ is used to describe compressed air that exhausts into the local atmosphere of the processing area. This can potentially compromise food products during their storage, preparation or packing. Non-contact high risk air must comply with Guideline 102’s specified ‘Contact’ level of purity for dirt, humidity and oil.
BCAS’s definition ‘contact’ means air that comes into direct contact with food products; its purity is therefore essential. Contact air must comply with the ‘Contact’ purity level as specified in Guideline 102. Contact air is used for tasks such as cutting and shaping foodstuffs, mixing dry ingredients, peeling vegetables and blowing away bread crumbs.
Achieving the specified purity level for compressed air requires a high level of filtration and dehydration. The three main negative influences on air quality are water content (humidity), microbiological and solid particles (spores or particulates) and oil presence (aerosols or vapours). Each of these must be eliminated to ensure that the air is pure.
Compliance with Guideline 102 ensures that airborne contaminants are kept out of the compressed air—and therefore out of the production process. This minimises the potential effects on appearance, taste, shelf-life or safety of the product. Additional reassurance can be provided by an air compressor monitor such as the Analox ACG+.