28 March 2009

5 minute read

Introduction

Microbial growth due to contamination of wash water, brine chillers, meat marinades and pickle injectors can often result in contamination and shortened shelf life. The threat of contamination is further increased as manufacturers respond to demands for less chemical additives and preservatives.

A non-chemical disinfection method which is gaining increasing acceptance is ultraviolet (UV) disinfection. UV kills all known spoilage microorganisms, including bacteria, viruses, yeasts and moulds (and their spores). It is a low maintenance, environmentally friendly technology which eliminates the need for chemical treatment while ensuring high levels of disinfection.

How UV disinfection works

UV is the part of the electromagnetic spectrum between visible light and X-rays. The specific portion of the UV spectrum between 185-400nm (known as UV-C) has a strong germicidal effect, with peak effectiveness at 265nm. At these wavelengths UV kills microorganisms by penetrating their cell membranes and damaging the DNA, making them unable to reproduce and effectively killing them.

A typical UV disinfection system consists of a UV lamp housed in a protective quartz sleeve and mounted within a cylindrical stainless steel chamber. The liquid to be treated enters at one end and passes along the entire length of the chamber before exiting at the other end. Virtually any liquid can be effectively treated with UV, including raw municipal water, filtered wash water, process water, brines, marinades, pickles and process effluent.

There are two main types of UV technology, based on the type of UV lamps used: low pressure (LP) and medium pressure (MP). LP lamps have a monochromatic UV output (limited to a single wavelength at 254nm), whereas MP lamps have a polychromatic UV output (with an output between 185-400nm).

Benefits of UV Disinfection

UV disinfection has many advantages over alternative methods. Unlike chemical treatment, UV does not introduce toxins or residues into the process and does not alter the chemical composition, taste, odour or pH of the water or liquid being disinfected.

UV treatment can be used for primary disinfection or as a back-up for other purification methods such as carbon filtration, reverse osmosis or pasteurisation. As UV has no residual effect, the best position for a treatment system is immediately prior to the point of use. This ensures incoming microbiological contaminants are destroyed and there is a minimal chance of post-treatment contamination.

UV applications in the meat processing industry

Wash/rinse water
Using UV to disinfect the water used to rinse carcasses and to wash process equipment and work surfaces can dramatically decrease contamination, increasing shelf life. UV also reduces the amount of chlorine needed to disinfect rinse and wash water.

Brine chillers, meat pickle and marinade injectors
Brines, pickles and marinades can be a prime breeding ground for harmful microorganisms like Listeria and E. coli. Fitting UV systems on recirculating brine chillers and meat pickle and marinade injectors are very effective at destroying these microorganisms. Depending on the model, some UV systems can operate very effectively through a wide range of temperatures and applications – from super-cooled brines to very hot sanitation cycles. Additionally, in marinade applications, operating costs are reduced through less frequent fluid change-over.

CIP (Clean-in-Place) rinse water
It is essential that the CIP final rinse water used to flush out foreign matter and disinfecting solutions is microbiologically safe. Fully automated UV disinfection systems can be integrated with CIP rinse cycles to ensure final rinse water does not reintroduce microbiological contaminants. Because of their mechanical strength, MP lamps are not affected by any sudden changes in the temperature of the CIP water.

Filter disinfection
Stored reverse osmosis (RO) and granular activated carbon (GAC) filters can be a breeding ground for bacteria. UV is an effective way of disinfecting both stored RO and GAC filtered water and has been used in the process industries for many years.

Dechlorination
GAC filters are also often used to dechlorinate process water, removing the ‘off’ flavours often associated with chlorine disinfection, meaning the flavour of the final product remains untainted and free from unwanted flavours or odours. Placing UV systems ahead of GAC filters used for dechlorination improves the performance of the filters and results in longer carbon runs, so decreasing operating costs.

Effluent
Increasingly, meat processors are caught between conflicting sets of regulations – while food hygiene regulations in many countries require increased use of water to rinse carcasses, environmental regulations are limiting the amount of fresh water that a plant can consume. With only so much fresh water coming in, plants are forced to reduce capacity in order to meet these conflicting requirements. By reusing disinfected wastewater in non-contact applications like chillers and cooling towers, more fresh water can be devoted to washing and processing. UV systems can be used in conjunction with other waste treatment processes to disinfect wastewater without chemicals, making it fit to use again. By using this low-maintenance technology, plant production capacity can be increased and hazardous chemicals are eliminated.

Environmental benefits
While reusing wastewater means a dramatic reduction in discharges to watercourses, any effluent that does have to be discharged can also be disinfected with UV to meet with local environmental regulations.

Designed to meet the stringent sanitary requirements of the food industry, today’s UV disinfection systems can usually be easily integrated in-line into process systems with little disruption to plant operations. Maintenance requirements are minimal – most UV lamps these days only need replacing once a year, an easy operation which can be carried out by on-site personnel. Automatic internal wipers also keep the UV lamps clean, ensuring optimum UV output at all times – especially important in solutions with a high concentration of suspended solids.

Conclusion

Meeting the increasingly rigorous hygiene standards required in meat processing is a real challenge. If improvements need to be made to plant and equipment, they need to bring quick returns on the investment and measurable improvements in product quality.

For processors seeking to improve the quality of their product, UV is an economic, realistic option for many applications. It is already a well established method of disinfecting drinking water throughout the world, and is also widely used for high purity uses such as pharmaceutical processing and semiconductor manufacturing, where water of the highest quality is essential. UV is also an environmentally friendly technology that allows processors to reuse wastewater, minimising discharges.

UV disinfection systems are easy to install, with minimum disruption to the plant. They need very little maintenance, the only requirement being replacement of the UV lamps every 12 months, depending on use. This is a simple operation that takes only a few minutes and can be carried out by general maintenance staff.

March 2009