Product category:
Filters and Centrifuges
News Release from: Hanovia | Subject: UV treatment
Edited by the Processingtalk Editorial
Team on 16 January 2004
UV disinfection in the manufacture of
liquid sugar
The many roles for UV disinfection in the manufacture of liquid sugar are discussed, in relation to both low pressure annd medium pressure UV disinfection systems.
In an increasingly regulated and safety-conscious market, the sugar industry has to meet ever more stringent standards of quality Concentrated sugar syrups (typically at 25 to 67 Brix) have a high osmotic pressure, and although this prevents micro-organisms from growing and reproducing, they can still survive in spore form and may grow once the syrup is diluted
This article was originally published on Processingtalk on 24 Feb 2003 at 8.00am (UK)
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Microbial growth in foods and beverages can cause food discolouration, off flavours and shortened shelf-life as well as increasing the risk of infection and ill-health.
The threat of contamination is further increased as manufacturers respond to consumer demand for reductions in chemical additives and preservatives.
A non-chemical method of controlling microbial contamination which is gaining increasing acceptance is ultraviolet (UV) disinfection.
Further reading
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British company Hanovia will supply Sasol Technology Ltd with four medium pressure UV disinfection systems for its South African production plant, to enable secondary effluent re-use
Medium pressure UV for sugar syrup disinfection
To ensure sugar and fructose syrups used in soft drink manufacturing remain free from yeast and mould contamination, the Coca Cola Spanish plants have installed medium pressure UV disinfection systems
Life cycle costs reduced with medium pressure UV
The total life cycle cost of plant and equipment is an increasingly important factor in procurement decision-making for operators of large-scale ultraviolet (UV) water disinfection systems
UV kills all known food spoilage organisms, including bacteria, moulds, viruses 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 does UV disinfection work? UV is the part of the electromagnetic spectrum between visible light and X-rays.
The specific portion of the UV spectrum between 240-280nm has a strong germicidal effect, with peak effectiveness at 265nm.
At these wavelengths UV kills micro-organisms by penetrating cell membranes and destroying DNA.
A typical UV treatment system contains an arc tube (UV lamp), housed in a protective quartz sleeve, which is mounted along the central axis of 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.
There are two types of arc tube used for sugar treatment: low pressure and medium pressure.
Low pressure arc tubes are typically rated at 32-100W and a large number are required in each UV chamber to effectively treat a dense fluid such as sugar syrup.
In addition, they are temperature-dependant, making them less suitable for warm fluids.
More recently, Hanovia has developed far more powerful medium pressure arc tubes.
These are not temperature-dependant, and with power ratings up to 5kW, a single arc tube can effectively treat large flows of syrup.
UV technology can also be applied to other applications such as water treatment, surface treatment and the disinfection of moving or static air.
UV dose is a function of UV intensity x time and is expressed as millijoules per square centimetre (mJ/cm2).
The dose received by a micro-organism depends on the energy output of the lamp and its exposure time to the UV.
The effect of UV dose varies depending on the organism, the measure of comparison being referred to as the D10, or the dose required for one log reduction.
The D10 for any micro-organism is defined as the UV dose necessary to affect a 90 percent reduction.
The relationship between dose and kill rate is logarithmic.
A significant application has been in Liquid Sugar Syrup.
Hanovia UV chambers are specifically designed to eliminate the wild yeasts and moulds which are responsible for taste and flavour problems in sugar solutions.
As sugar syrups have a high density, they have a low UV transmission.
To ensure adequate exposure, each UV-S (UV-Sugar) chamber is equipped with a high intensity medium pressure arc tube, which can treat continuous or batch flows.
The system is installed in-line after the storage tank discharge point, so the syrup is treated prior to dilution into the food and beverage, but prior to the addition of additives, flavourings or colourants, all of which reduce UV transmission.
Modern hot dissolving systems can leave the headspace above the syrup in the mixing and storage vessels as an ideal growing environment for spoilage organisms.
Condensation, containing micro-organisms, forms on the tank surface and can drip off the inner wall of the vessel resulting in surface growth and infection of the syrup.
The Hanovia UV-I (UV-Immersion) range overcomes this problem by disinfecting the air drawn into the tanks when the liquids are drawn off.
Mounted on the ceiling of the vessel, it provides continuous disinfection of the tank headspace.
The UV-I is fully immersible in the syrup, eliminating the problem of having to monitor liquid levels.
Although municipal water supplies should be relatively free from harmful micro-organisms, this should not be assumed - they will also contain naturally occurring moulds and yeasts.
In addition, water from private sources such as boreholes could well be contaminated.
UV treatment of all incoming water supplies ensures all contamination is stopped at source.
It also allows the re-use of water, improving availability and plant productivity without risking the quality of the product.
Softeners, demineralisers and filters are often installed at water intake points to improve the water quality.
All such equipment can become infected and release micro-organisms into unprotected water.
UV treatment at this stage therefore ensures water quality is maintained.
The final rinse water of the CIP should be the purest source water available, but may contain micro-organisms.
If chemical sterilants are used, solutions can remain in pipework, tankers and tanks, where they can mix with the incoming product and may produce a taint.
UV treatment of rinse water is better as it is unaffected by acid or alkali in cleaning fluids, is compatible with hot detergent and leaves no taint.
In addition, it is extremely cost effective and safe.
Air conditioning and ventilation systems are prime sources of contamination from air-borne spoilage organisms.
The increasingly strict standards for cleanliness are not always met by air filtration alone, and it is now common to use UV in conjunction with, or instead of, sterile filters in air ducts.
In recent independent tests, a ventilation duct was sprayed at one end with aerosol contaminated with Penicillium chrysogenum, a pump at the other end drawing air through the duct.
A UV-V (UV-Ventilation) unit was situated in the middle of the duct, with air samplers on either side, extracting contaminated air through a filter.
The UV unit achieved kill rates well in excess of 99 percent in a single pass.
Ducted air is often humidified by spray humidifiers in the ventilation system.
As water is a potential source of infection, particularly when dispersed in aerosol form, extra protection can be achieved by UV treatment of the water prior to its entry into the sprayer.
Medium pressure UV is one of the most efficient and cost-effective forms of disinfection available.
It has no detrimental effects on pH, colour, flavour, aroma or product stability.
A new control system, Photon, is designed for interfacing with automated or computer-controlled process plant and provides data logging and permanent records of all disinfection procedures, so all batches can be traced.
UV is also superior to alternatives such as pasteurisation, which is expensive in capital equipment and running costs, or sterile filtration, which does not remove all micro-organisms from syrup.
UV has many applications throughout the plant, from the treatment of incoming water supplies to the disinfection of sugar syrups and treating the air in air conditioning and ventilation ducts.
The systems are easy to install, with minimum disruption to the plant required.
They require very little maintenance, the only requirement being the replacement of the arc tube every 6-9 months, depending on use.
This is a simple operation that takes only a few minutes and can be carried out by general maintenance staff.
Meeting the ever-more rigorous standards required in the production of liquid sugar is a real challenge for manufacturers.
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, medium pressure UV is an economic, realistic option.
It is a well-known and trusted technology in industries ranging from pharmaceutical, food and microchip manufacturing to swimming pool and drinking water treatment.
It is one of the most effective methods of ensuring consistently high levels of disinfection and has been adapted for many situations.
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