The autoclave is used for sterilisation and pasteurisation of canned food. (Pictures ©Tata).
They may seem simple and old-fashioned, but food cans are high-tech wonders, researchers have revealed, as they detailed the scientific testing used for modern food cans to ensure they do their job safely and effectively.
The Steel and Metals Institute (SaMI) research team at Swansea University are giving this glimpse into their work to mark their 1000th joint research project with Tata Steel, longtime partners of the University.
Steel is a high-tech 21st century industry. There are over 3,500 grades of steel, 75% of which did not exist 20 years ago. It is essential for construction, transport, manufacturing, wind turbines, and hundreds of other uses, including food packaging.
So-called tin cans are made mainly of a steel base coated with a thin layer of another metal, such as tin, and sometimes an extra internal polymer lining.
- Packaging steels are used to make food tins, aerosol cans, paint tins, promotional packaging and more
- UK-produced packaging steel is enough to make over four billion baked beans cans
- Tata Steel’s plant in Trostre is the primary supplier of packaging steels to many well-known brands
Steel food cans have many advantages. They protect the contents and preserve their nutritional goodness. Tin cans have the longest shelf life of all packaging formats, They are stronger than plastic or cartons and less fragile than glass. They don’t need to be refrigerated, saving energy. They are easily recycled an endless number of times: just one example of how steel is essential for a greener future.
However, like all steel products, food cans must meet the highest standards of performance and quality. Safety is critical, given the can will contain food.
This is why rigorous testing and research is so important. The Swansea University researchers work closely with Tata Steel and other steel companies to research the performance and effectiveness of their products. As the industry moves towards making steel from recycled scrap the same rigorous testing must be applied to scrap metal, which produces far lower carbon emissions than raw materials.
In SaMI’s facility researchers replicate real-life conditions, putting steel products through rigorous tests, to ensure they meet the required exacting standards.
Dr Barrie Goode SaMI’s Director Industrial Research and Development explains how food cans are tested:
“We need to check how different steels interact with different foodstuffs, which may include chemical substances such as salt or vinegar. Of course there must be no spoilage of the food, but the structure of the can must also remain robust and intact.
Our accelerated tests mean we can fast-forward the effects of time on the can and contents - we simulate the effects of several years in just a few weeks.”
Coatings Researcher at Tata Steel, James Edy, explains how SaMI and Tata Steel undertake the rigorous testing:
“A typical testing process involves various steps:
- We fill cans with food simulant solutions, then seam the lid on. We leave a small amount of headspace which creates a vacuum inside when the can is sealed
- We sterilise the cans at over 100 °C under pressure, using saturated steam, hot water, or steam and air. As the pressure increases, the boiling point of water also increases, allowing superheating of water without boiling. This process sterilises the contents and speeds up assessment of any reaction between the can and contents
- We analyse the cans in microscopic detail for any degradation and causes. Our electron microscopes magnify samples up to 1000 times to identify any areas of concern. We then carry out microanalysis using a technique called energy dispersive spectroscopy, which identifies and quantifies the chemical elements in a sample
The key questions for us after the tests are:
- Has the lacquer film on the surface blistered or peeled away from the can?
- Is there any evidence – even at microscopic level – of corrosion?
- Are there any visual changes to the can, like discoloration or blackening, that would be unacceptable to customers?
The overall question is whether the product still meets quality, safety and reliability standards after all these tests. This is vital for our customers to know to assure their customers the highest quality product.
It also means the public can be confident their cans of beans - or anything else – have been scientifically tested and are safe to eat”.
SaMI researchers have also assisted Tata Steel in improving their products and the processes involved in making them and recently have been investigating the effect of hydrogen on steel with a view to future developments in hydrogen transport for example as part of Net Zero efforts.