The continued growth in the market for bottled waters and flavoured waters means increasing demands for water purification at formulation and packaging facilities. To ensure that products have a long shelf life, disinfection of both water and flavour concentrates is critical. But there is a warning note. Reporting the boom in mineral water sales, Udo Kremer, CEO of the Association of German Mineral Springs, pointed out that consumers are becoming more discerning, and like to feel that the products they are buying are as natural as possible.
What are the options?
Whilst the EU Directive 2009/54/EC on mineral and spring waters proscribes disinfection, other water and near water products must comply, as a minimum, with the microbiological requirements of the drinking water directive 98/83/EC. Traditional water disinfection processes use oxidising biocides like sodium hypochlorite, chlorine dioxide or ozone. However, in the presence of organic matter, even at low concentrations, chlorine based chemicals can produce a range of potentially carcinogenic by-products including trihalomethanes (THMs), haloacetic acids (HAAs) and nitrosodimethylamine (NDMA), whilst ozone can generate bromates from bromide in the raw water. All of these by-products will pass through reverse osmosis membranes into the product water. As a result, manufacturers are turning to non-chemical ultraviolet irradiation as an alternative. This disinfection process uses electromagnetic waves in the UV-C band – a natural component of sunlight – to prevent bacteria from reproducing, UV-C has a wavelength around 250nm which is very close to the absorbance wavelength of the amino acid bases which form the “rungs” of the DNA double helix. UV radiation fuses adjacent amino acid groups making it impossible for the molecule to replicate and permanently damaging the thymine strand of the DNA helix. This means that bacteria exposed to UV radiation are not actually killed but cannot reproduce and will not be detected by a plate count: as far as disinfection is concerned that is the same thing. It is a broad spectrum technique that inactivates a wide range of micro-organisms and is entirely chemical-free with no health and safety or environmental issues. All it needs is an electricity supply.
Why choose UV?
Different microorganisms have a different sensitivity to UV-C light. Inactivation of most bacteria requires a relatively low dose whilst protozoans, moulds and yeasts need higher doses but, typically, a single pass through a UV system generating a dose of 40mJ/cm2 will achieve a 4 log to 5 log (99.99% to 99.999%) reduction of most microorganisms. The hydraulic design of the reaction chamber ensures that all the water is exposed to equal intensity of radiation with no short circuiting. This should always be validated by a third party to a recognised test protocol, such as that set out in the US EPA 2006 Ultraviolet Disinfection Guidance Manual, and reputable suppliers will have validation certificates for their products. Given that assurance, a UV disinfection system is simple to install and has low operating and maintenance cost – only a few cents per cubic metre of water depending on the bacteria reduction required – and it can give operational and economic benefits.
Whilst UV has long been used for water disinfection, what is less well known is that it can be equally effective for the syrups, juices, flavourings and concentrates that are key ingredients in flavoured waters, soft drinks and fruit juices. In concentrations above 66° Brix (1°Bx is 1 gram of sucrose in 100 grams of solution) the osmotic pressure of a sucrose or fructose solution is so high that bacteria cannot survive, but many produce spores which lie dormant until the concentration is reduced when the syrup is added to the product. Then they start to multiply. Once active, bacteria can cause discolouration, changes to flavour, unwanted odours, changes in texture, reduced product shelf-life and critically, an increased risk of causing infection and ill-health. Controlling bacterial growth is, therefore, an important issue. Due to the need to avoid changes in taste, pH and texture and to respond to consumer demands for reductions in chemical additives and preservatives, beverage manufacturers are looking for alternative techniques to protect their products from bacterial damage. For some products, pasteurisation may be an option, but ever rising energy costs and the requirement for large plant rooms to install the equipment has led many manufactures to look to UV irradiation. Unlike chemicals, UV treatment does not introduce any residual agents or by products into the liquid and will not change the organoleptic properties of a product, whilst protecting against a wide range of micro-organisms including thermophilic spores that are tolerant to Pasteurisation.
What about sugar solutions?
An important factor to consider when designing UV systems to treat liquid sugar solutions is the properties of the syrup. Due to high viscosities encountered in sugar solutions up to 66°Bx, Ultraviolet Transmittance (UVT) can be as low as 10-15%. Therefore a specialist UV chamber, using a ‘thin-film’ design that ensures the syrup is evenly exposed to the UV light is essential. atg UV have designed a specific range of Liquid Sugar UV disinfection systems to deal with the high viscosities encountered in sugar solutions up to 69°Bx and UVT at as low as 10-15%. The Sugar Solution (SS) range utilises the latest in advanced thin-film quartz technology and medium pressure lamps with specially designed UV chambers. Systems are usually installed in-line after the storage tank discharge point so that the syrup is treated prior to dilution into the product and prior to the addition of additives, flavourings or colourings, all of which reduce UV transmission.
Typical of atg UV Technologies customers is Dayla, now part of Vimto, whose new bag-and-box packaging facility is Kore accredited by Coca-Cola. It has a daily output of 15,000 litres of juice products and 37,000 litres syrup products for clients including Barr Soft Drinks, Coca-Cola and Sunkist. Their UVLX-3800-14 UV system is capable of delivering a UV Dose of 120mJ/m2 into a flow of up to 20 m3/hr with UVT 98% ensuring a 4-log inactivation of cryptosporidium and adenoviruses and 5-log reduction in viable bacteria. To learn more about chemical-free microbiological control systems visit www.atguv.com/food-beverage