Fast food inspection

Microwaves and microwave ovens may not be synonymous with healthy eating, but they may hold the key to finding out how much fat and salt is in your food.

New industrial microwave sensors, which can measure the content of food, have been developed at

and

universities. The sensors can be configured to measure levels of wheat gluten, fibre, salt and, most recently, the fat content in meat.

The Microwave Profiler project — backed by a £400,000 EPSRC grant — is being led by Andrew Gibson from Manchester's Microwave and Communication Group, and Prof Paul Ainsworth from the Department of Food and Tourism Management at Manchester Metropolitan.

'The project stems from measuring cracks in aircraft wings using microwaves and the fact that when you cook something in a microwave oven different parts, such as water and oil, heat up at different rates,' said Ainsworth. He said that by taking this a stage further the researchers believed that they could measure food content.

The team aimed to develop a fast, non-invasive technique that would remove the need to take samples from the production line for extensive tests.

It claimed this type of constant real-time monitoring could help maximise yield, save energy and reduce waste and laboratory testing.

'It's not that far removed from mobile phone or radar frequencies so it's safe and won't cook the food,' claimed Gibson. 'We set up a system and measured the response. At the moment we are doing it in a number of different ways. One is to stick a microwave probe into the food. another method is like sending the signal through a pipe rather like cutting the ends off a metal shoe box. We then put the food in the box and send the signal through and measure the attenuation after it has passed through the food. We are developing a system where meat can be pumped through and measured on the production line,' said Gibson.

'Normally you only get a very small result and little differentation, but we have a frequency that is ideally suited. You get maximum differentation and it produces very robust results. Potentially it could be very useful.

'In the future, just as mobile phones have been miniaturised, it could be made into a hand-held device and used around the supermarket or even the home.

Gibson added: 'It's a great example of how two disciplines can come together to co-operate. Microwaves are normally only used for three things — communication, radar and industrial heating. But we thought, "let's do something different that's current in the media".'

Recent progress has led to PhD student Sing Kwei Ng receiving the Institute of Food Science and Technology's Young Scientist Award for his work to determine the amount of fat in beef.

'Greater awareness regarding food safety and health issues means that consumers are now more concerned than ever about meat products being safe and fresh with a low fat content,' said Ng. 'The potential for our system to overcome current technical barriers to practical measuring could significantly impact upon processing and reprocessing technology.

'Food contents and ingredients have to be disclosed under EU law but cannot be currently measured quickly or cost-effectively.

'The meat industry is under extreme pressure to find new cost- effective methods of meat quality evaluation at every level of food processing. Knowledge of the fat content of meat products is critical.'

The project's previous pilot studies have successfully revealed the fibre content in waste products produced by the brewing industry, moisture content of wheat grain and the salt content of supermarket food. The next food item on its list is sausages, although the team said more research on the capabilities of microwave sensors in industry is needed before the method can be properly introduced.

The researchers have been working with a Leeds company which makes frozen food products, and they hope to get other firms interested in the project.