Effective microbial disinfection in the brewing and beverage industries is essential. Ultraviolet disinfection is already accepted in brewing and is gaining increasing acceptance in beverage manufacturing. UV destroys the DNA of microorganisms, and medium pressure UV in particular is highly effective at permanently inactivating microorganisms. UV reduces the need for chemicals and can be used to disinfect incoming water, syrups, clean-in-place water, waste water, filter systems and the surfaces of packaging. UV systems are easy to install and maintain.
In an increasingly regulated and safety-conscious market, the brewing and beverage industries have to meet ever more stringent standards of quality. Microbial growth in drinks due to contaminated water supplies or sugar syrups can cause discoloration, off flavors and shortened shelf-life, as well as increasing the risk of infection to consumers. The threat of contamination is further increased as manufacturers respond to consumer demand for a reduction in chemical additives and preservatives. Effective microbial disinfection of the whole process is therefore essential.
A non-chemical method of disinfection which has been used in the brewing industry for many years, and which is now gaining increasing acceptance in the beverage industry, is ultraviolet (UV) disinfection. UV kills all known pathogens and 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 (also 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 which is 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 mains water, filtered process water, viscous sugar syrups, beers and beverages, and 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).
Advantages of medium pressure UV
For several reasons, UV systems based on MP lamps are better suited to the brewing and beverage industries. Firstly, only one MP lamp is required to produce the same UV output as many LP lamps – this has obvious cost implications for replacement lamps, not to mention considerations of space. LP lamps are also highly temperature dependant, with variations in the temperature of the incoming liquid adversely affecting their UV output; MP lamps, on the other hand, operate effectively at all temperatures.
Cleaning also needs to be taken into account: if fluids containing high solid concentrations are being treated, deposits can build up on the quartz sleeves surrounding the UV lamps, reducing their efficiency. To overcome this problem MP systems utilize a mechanical wiper which passes back and forth along the length of the quartz sleeve, keeping it clean This is much more difficult with LP systems due to the large number of lamps. It is also more costly and difficult to maintain.
In addition, recent research comparing reactivation of E.coli and Cryptosporidium DNA after exposure to UV emitted by LP and MP lamps showed that the DNA underwent extensive repair following exposure to UV from LP UV lamps, but virtually none following exposure to UV from MP lamps (see references 1, 2 & 3).
Benefits of UV Disinfection
UV disinfection has many advantages over alternative methods. Unlike chemical biocides, UV does not introduce toxins or residues into process water and does not alter the chemical composition, taste, odor or pH of the fluid being disinfected. This feature is especially important in the brewing and beverage industries where the chemical dosing of incoming process water can cause off-flavors and alter the chemical properties of the product or, in the case of brewing specifically, affect the fermentation process.
UV treatment can be used for primary water disinfection or as a back-up for other water purification methods such as carbon filtration, reverse osmosis or pasteurization. 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 brewing and beverage industries
Direct contact water
Although municipal water supplies are normally free from harmful or pathogenic microorganisms, this should not be assumed. In addition, water from private sources such as natural springs or boreholes (often used by breweries to give their product a distinctive flavor) could also be contaminated. UV can disinfect this water without chemicals or pasteurization. It also allows the re-use of process water, saving money and improving productivity without risking the quality of the product.
De-aerated liquor is added as part of a high gravity brewing process, often in the packaging operation. This liquor is added directly to the beer so needs to be kept free from contamination by gram negative bacteria, which can cause off-flavors and acidity.
Sugar syrups can be a prime breeding ground for microorganisms. Although syrups with a very high sugar content do not support microbial growth, any dormant spores may become active after the syrup has been diluted. Treating the syrup and dilution water with UV prior to use will ensure any dormant microorganisms are deactivated.
The problems associated with yeast preparation in breweries are well recognized and include hazes, altered fermentation and surface membranes on packaged beer. A single cell of Sacchoromyces (var. Turbidans) in 16 million cells of pitching yeast will cause detectable hazes. UV destroys all known yeasts and their spores.
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, such as when hot (80oC) liquid is instantly followed by cold (10oC).
Stored reverse osmosis (RO) and granular activated carbon (GAC) filtrate is often used to filter process water, but 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.
GAC filters are also often used to dechlorinate process water, removing the ‘off’ flavors often associated with chlorine disinfection, meaning the flavor of the final product remains untainted and free from unwanted flavors or odors. 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.
Packaging & surface disinfection
Surface disinfection systems are used to reduce microbial counts on all kinds of packaging, including glass and plastic bottles, cans, lids and foils. By irradiating the surfaces with UV prior to filling, food spoilage organisms are eliminated, extending the shelf life of the product and reducing the risk of contamination.
Tank Head Space Disinfection
UV systems can be used to disinfect displacement air for pressuring tanks or pipelines holding perishable fluids. Storage tanks are particularly susceptible to bacterial colonization and contamination by air-borne spores. To prevent this, immersible UV treatment systems have been designed to fit in the tank head air space and disinfect the air present.
Effluent from breweries and beverage manufacturing facilities can be treated without the use of environmentally hazardous chemicals. This ensures all discharges meet with local environmental regulations.
Meeting the increasingly rigorous hygiene standards required in the production of beers and beverages 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 those manufacturers seeking to improve the quality of the end product, UV is an economic, realistic option. It is already well established in the brewing industry and is also widely used for high purity applications such as pharmaceutical processing, where water of the highest quality is required.
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 9 – 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.
The range of applications for UV in the brewing and beverage industries is wide-ranging. This article is designed to illustrate just some of the more common uses. Wherever effective liquid, surface or air disinfection is required, UV should be considered.
1. Hu J. Y., Chu, S. N., Quek, P. H., Feng, Y. Y., and Tan, X. L. (2005). Repair and regrowth of Escherichia coli after low- and medium-pressure ultraviolet disinfection. Water Science and Technology: Water Supply, Vol. 5, No. 5, 101-108.
2. Oguma, K., Katayama, H., and Ohgaki, S. (2005). Spectral impact of inactivating light on photoreactivation of Escherichia coli. Journal of Environmental Engineering and Science, Suppl. 1: S1-S6.
3. Zimmer, J. L. & Slawson, R. M. (2002). Potential repair of Escherichia coli DNA following exposure to UV radiation from both medium- and low-pressure UV sources used in drinking water treatment. Applied & Environmental Microbiology, Vol. 68, No. 7, 3293-3299.