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Little known pasteurisation facts

30 January 2017

As food and drink processing becomes more complex and food chains become longer, the importance of pasteurisation has increased, says Matt Hale

Today, while simple plate heat exchangers may still be suitable for the pasteurisation of simple fluids such as milk and fruit juices, more textured and viscous products, such as cooking sauces, creams and curds require different solutions to ensure they maintain their quality and texture. 

There are many long held beliefs in industry relating to pasteurisation which are, in reality, untrue. These include the belief that pasteurisation is expensive.

While the exact costs will vary with each installation, there is no doubt that there is a capital cost to pasteurisation. However, compared with the potential losses due to food spoilage, or worse a food safety incident, these costs are insignificant. In the US, the costs of recalling food products have been shown to average $10 million, before accounting for brand damage. In the UK, in 2012 alone, there were 80 food related product recalls in the UK and the Food Standards Agency estimates that Listeriosis cost the UK economy £245 million every year.

Against these potential costs, the capital cost of a corrugated tube heat exchanger based pasteurisation system is a good investment. Alongside the capital costs, however, the running costs of a pasteurisation unit need must also be considered. Pasteurisation is also a relatively simple process which requires that a material is held for a certain time at a certain temperature in order to kill microorganisms. While it does add an additional step in the overall manufacturing process, if well designed it should not slow down throughput or place additional management burdens on the plant.

Many consider that pasteurisation is only suitable for simple fluid materials. However, it can 
be used on a wide variety of liquid and semi-liquid materials. While simple Newtonian fluids will be the easiest to work with, and can often be effectively pasteurised with a simple plate heat exchanger, there are solutions for almost any material. The availability of corrugated tube and scraped surface heat exchangers will enable  a unit to deal with anything, from viscous fluids requiring gentle handling or with low rates of heat transfer through to complex mixtures such as curd cheese, which could otherwise foul the heat exchanger reducing thermal efficiency and requiring regular cleaning and maintenance.  

The amount of energy used in food pasteurisation is highly variable, depending on the process used, the nature of the material being treated and the heat exchanger used. The bulk of any energy requirement is used to raise the temperature of the foodstuff. Traditional pasteurisation units simply dump this heat afterwards, meaning they are incredibly wasteful and inefficient. However, it is often possible for a heat exchanger to recapture the heat and use it again, and this can make a system up to 70% more efficient. 

Pasteurisation equipment no longer needs to be high maintenance. The use of corrugated tubes, together with integrated cleaning-in-process (CIP) will minimise the amount of fouling and therefore the amount of cleaning necessary to maintain the efficiency of a pasteurisation system. 

There is also a general belief that it is not possible to pasteurise viscous fluids. It is true that subjecting viscous and non-Newtonian fluids, such as cooking sauces, to shear stress during the manufacturing process can damage the quality and texture of the material which may preclude the use of certain designs of heat exchanger for pasteurisation. However, systems are now available which prevent fouling while maintaining relatively low pressure, overcoming these traditional, but unwanted effects.

It is important to note that pasteurisation is not the same as sterilisation. Unlike sterilisation, it does not completely eliminate microorganisms which may be present in the foodstuff. Pasteurisation reduces the microbial load by a significant factor (for example by 5-logs) which in normal circumstances reduces the level of contaminating pathogens to a level at which they do not pose a hazard.

Conclusion
Pasteurisation need not to be overly onerous or detrimental to the quality of the product. With the correct choice of equipment, it should not need to have a negative effect on plant throughput or efficiency and a well-designed system, incorporating heat regeneration and corrugated tubes, will enhance the overall facility, helping to add flexibility to the business.

Matt Hale is international sales manager at HRS Heat Exchangers.


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