Meet the Expert
Who: Danny Bayliss
What: New Technology Research Team Leader
Where: Campden BRI
The introduction of microwave heating food in the 1940s sparked a revolution in the way we process foods, both commercially and domestically.
The industry has since found many ways to apply this technology, from raw meat cooking to ready meal sterilisation. It continues to develop methods to this day, with new technologies such as continuous-flow microwave processing.
However, while they may be ubiquitous, it is evident that traditional magnetron microwaves still have some issues almost 70 years on.
What are the issues with traditional microwaves?
Magnetron microwaves can suffer from non-uniformity of heating, which means they generate hot and cold spots that impact on a product’s quality (as shown in Figure 1).
Turntables/stirrers can help to reduce this non-uniformity, but they are not a completely satisfactory solution – for the whole product to reach a targeted temperature for a specified hold time, some parts of the product will be over-processed.
The non-uniform temperature distribution also raises the issue of food safety, with the possibility of microorganisms within the cold spots not being destroyed.
An unexpected solution to this problem may well have come from a relatively recent development: the advent of smartphones.
What are solid-state microwaves?
The rapid developments in the telecommunications sector to accommodate smartphone wireless communications has led to the advancement of solid-state semiconductors. These devices can generate and amplify radio frequency (RF) signals that the phones use for data transmissions.
However, the solid-state semiconductors can produce variable frequencies, including the microwave frequencies (2.4-5GHz) that we’re interested in. This creates the potential for these devices to also be used for food heating applications.
How could solid-state microwaves overcome the issue of non-uniformity?
Solid-state RF technology has the potential to enable users to adjust power output, measure the energy for feedback and shift the frequency and phase in ‘real time.’ When heating food, this could minimise standing waves and potential hot spots, improving product quality by heating it more uniformly. It could also reduce the chance of over-processing and the risk of under-processing.
Uniformity may also be improved with multiple energy sources. Traditional magnetron microwaves usually only have one energy source (magnetron); however, the multiple microwave generators of solid-state microwaves allow simultaneous heat penetration from several energy sources.
As part of its research into emerging technologies, food science and research organisation Campden BRI is exploring the potential benefits of this technology. It is doing this by evaluating the heating performance of a solid-state RF cooker on a model food product, investigating whether the solid-state microwave can reduce hot and cold spots in a product as it applies the mechanisms discussed above.
For now, solid-state microwaves hold potential in combination ovens. But as the technology develops and the price comes down, it’s possible that these microwaves will challenge or replace traditional magnetron microwaves.
The applications for these microwaves will then depend solely on our creativity.