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Air quality: getting the right flow

By Ahmed ElAmin , 03-Aug-2005

Controlling air quality is key to food safety in processing plants according to updated guidelines published by Campden & Chorleywood.

Consumer demand and an increased focus on food safety through regulator oversight and new legislation is a driving trend in the processing market. The increasing use of aseptic processing techniques has also put pressure on plant managers to improve their aging air control systems.

Air filtration for environmental and process use is a critical part of ensuring the final air quality in a food processing environment. Air is a potential source of food contamination and is key to food preservation and worker productivity.

The reference publication outlines the general principles and technical advances useful to all food processors throughout the EU.

The Campden & Chorleywood publication deals with air in relation to processing, contamination, aerated products andworking conditions. The document outlines the steps plant managers need to take in risk assessment using hazard analysis and critical control point (HACCP) analysis.

In relation to aseptic systems, air is used for filling and to overpressure the line and any holding tanks. Air systems are also used to protect the aseptic or sterile zone. The filler head,packaging and the unsealed packs must be filtered to regulatory standards.

Air knives may be used to remove excess chemicals from packaging. In high care and high risk operations there may be five to 25 air changes per hour, the publication states.

Air also an ingredient in many foods, such as aerated and fermented products. Increasingly products are being moved through the production line using fluidised bed technology. Process air may alsoinclude modified atmosphere gases that come into direct contact with product.

"A properly designed air handling system will control airborne particulates and odours and minimise the risks to product from airborne contamination by pathogens such as Salmonella,Listeria, E.coli and toxigenic pathonegens, such as Staphylococcus aureus and clostridia, and spoilage microroganisms such as yeast mods pseudomonads and lactic acid bacteria," the authorsstate.

The difference between ventilation and air conditioning is outlined. Ventilation deals with ensuring the proper changes of air is made throughout a plant. Air condition is a means ofcontrolling climate in a defined area. Air systems will perform all functions.

Air systems work mainly to prevent airborne product contamination by blanketing the product in an air of known microbilogical quality, limiting microbial growth and survival through humidity,temperature and air distribution control.

Correct air flows can help restrict the ingress of airborne particle to a processing area but flows that are too high may disperse particles.

Most chilled ready-to-eat food factories operate with ambient factor air between 10C to 16C. UK regulations indicate that temperatures below 13C should only be used when food safety is a factor.

In staff areas UK standards recommend that air is changed at a rate of eight liters per second per person. In Germany the recommend rate is 13.9 litres. Higher air flows cost more and in extremecases can lead to difficulty in closing and opening doors.

The distribution system must work efficiently to remove the heat load imposed by food processing and to provide staff with sufficient fresh air. The system must prevent the ingress ofcontaminants.

Temperature also affects working efficiency. Productivity decreases when temperature is too hot or too cold.

An optimum system requires plant managers specify the system requirements and have a knowledge of the engineering of air handling systems. They will need to call on reliable contactors orconsultants who deal with air handling, filtration and refrigeration technology.

"The requirements for microbiological safety and environmental control for particular types of product are often understood, however the engineering, rather than other functions in thecompany often carry responsibility for the specification and design of air handling systems that will ensure that air quality does not limit product quality and safety," the authors state.

The new edition of the guideline publication updates the first edition in 1997 with reference to technical developments in the sector. The guide spans the complete air handling chain particular tofood production.

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