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A sweet alternative to pasteurisation

27 June 2016

Diane White explains how UV systems can provide a cost effective and energy saving alternative to pasteurisation of liquid sugar solutions in food and beverage production. 

Syrups – solutions of sugars like sucrose, fructose and glucose – are key ingredients in thousands of food and beverage products, adding sweetness to soft drinks, fruit juices, confectionery and even tomato ketchup. In concentrations above 66°Brix (1°Bx is 1 grime of sucrose in 100 grams of solution) the osmotic pressure of the solution becomes so high that bacteria cannot survive. However, 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, these bacteria can cause discolouration, adverse flavours, 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. To avoid the changes in product quality that chemical additives can produce, and to respond to consumer demands for reductions in additives and preservatives, food and beverage manufacturers need to find alternative techniques to protect their products from bacterial damage. For products that can tolerate the temperature, pasteurisation may be an option. However, however rising energy costs and the requirement for large plant rooms to install costly equipment has led many manufacturers to look at UV irradiation as a low energy consumption, physical, chemical free alternative.

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, while at the same time protecting against a wide range of micro-organisms including thermophilic spores that are tolerant to pasteurisation. Using high intensity UVC radiation at 254nm wavelength, UV treatment will, typically, provide a 99.99% reduction in microorganisms in a single pass.

UV disinfection treatment has been around for many years and was first applied to sugar solutions in the 1980s, so it is a proven technology. However, the properties of syrups make the application unsuitable for standard UV disinfection units. Syrups have high viscosities and ultraviolet transmittance (UVT) can be as low as 10-15%, so a specialist UV chamber, using a ‘thin-film’ design that ensures the syrup is evenly exposed to the UV light is necessary. Most food and beverage manufacturing is carried out in batch processes and if the flow of syrup stops with the UV unit full and in normal operating mode there is a danger that excess heat generated from the UV lamps will caramelise the sugar. Automatically adjusting the UV system’s operating power in response to the flow or batch controller avoids this problem.

A range of UV disinfection systems has been designed by atg UV Technology overcome the problems of the high viscosities encountered in sugar solutions up to 69°Bx at 10% UVT. The SSL range utilises thin-film quartz and UVC lamp and chamber designs. It features UV chambers which are specially designed for high viscosity non-Newtonian flow and constructed to sanitary standards in 316L stainless steel. The control system features automatic power adjustment as standard and is designed to interface with most SCADA systems via MODBUS or PROFIBUS networks. UV systems have been proven to work effectively on syrups made from both cane and beet sugar make-ups by leading brands including Britvic, Cevital, Coca-Cola and Pepsi.
Diane White works at atg UV Technology.

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