A new way to sterilise packaged foods

Andrew Bosman, process engineer at Campden BRI, explains the benefits of continuous microwave processing.

25 June 2019
healthmanufacturemeet the experttechnology

Meet the Expert

Who: Andrew Bosman

What: Process engineer

Where: Campden BRI


The demand for high-quality food has put pressure on manufacturers to trial new thermal processing technologies that can simultaneously sterilise products while maintaining texture, taste, colour and nutritional value.

By rapidly heating a product, continuous microwave processing (CMP) is one such technology that could potentially achieve this balancing act.

Microwave heating refers to the use of electromagnetic waves of certain frequencies to generate heat in a material. CMP uses this process to heat a product as it continually flows through a chamber – for example, a pumpable soup through a pipe.

CMP can work on any product that can be pumped. This generally applies to products with low viscosity (i.e., products that are less thick and sticky). However, if a suitable pump can be acquired, then the only other requirement is that the product can absorb the microwave energy. For example, CMP can obviously work on liquids such as milk, but it also has the potential to work on more viscous products such as a thick meat slurry.

Improved quality

CMP heats pumpable products rapidly, which can reduce the overall time the product remains at elevated temperatures. This prevents over-processing and ultimately better preserves colour, texture and nutrients, while maintaining a safe pasteurised or sterilised product.

Campden BRI recently conducted a feasibility study which found CMP to be an effective method of preserving the vibrant green colour of pea and ham soup. In fact, when compared to retort processing (heating foods sealed in containers), it evidenced better colour preservation.

Conventional heating of products with scraped surface heat exchangers relies on conduction to heat up the particulates. Microwave processing, however, can rapidly heat both the liquid and particulates simultaneously, minimising the risk of over-processing the product.

Reduced cleaning and consistency

Microwave processing instantly delivers energy throughout the product rather than via its surface. This heats the product without relying on a hot surface, reducing the potential of fouling. Reducing the risk of burnt on food will reduce cleaning time and/or chemicals, allowing longer run times.

An additional benefit of CMP is that energy penetrates directly into the food product and heats through interactions with polar molecules (e.g. water) and ionic compounds (e.g. salt). Heating the entire volume of a flowing product is known as volumetric heating. It avoids relying on heating through conduction and convection alone which circumvents the issue of the heating apparatus's surface becoming much hotter than the product itself.

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