Heat treatment or thermal processing of food is used in order to kill or inactivate bacteria, increase the shelf-life, or create products with an attractive appearance. Nofima is carrying out research into several thermal methods, and how to optimise them, from sous vide processing to food canning.
- Advice within equipment investment for the industry
- Unique expertise in the heat treatment of all raw materials
- Advanced experimental facilities for thermal and high-pressure processing
- Courses in hygiene, critical control points, heat treatment, autoclave operation, packaging and packaging technology
- Heat measurement as specified in the IFTPS protocol
Today’s cooled displays contain healthy and palatable ready-to-eat meals several weeks after they were produced. This is possible because the food has undergone heat treatment during production.
The scientists at Nofima have long experience and extensive expertise in these technologies. We help food producers with the complete process from the composition of the products, the choice of production and processing method, packaging and equipment, and finding the optimal heat treatment with respect to time, temperature and pressure.
Some of the areas in which we carry out research, provide documentation, and provide advice are listed below.
We advise on how to keep the product quality when using traditional heat treatment equipment such as autoclaves and retorts, but also using innovative and novel technologies such as agitation and microwaves. (Link to High pressure and new technology.)
Mininmal thermal processing
The food is heated to a low temperature for a short period and acquires a fresh and attractive appearance, while retaining most of the nutrients. The technique is particularly suitable for food that does not need a shelf-life of longer than 7-12 days. Catering establishments for canteens, sheltered accommodation and hospitals often use this technique, and it is used also by restaurants and other food outlets.
The cook-chill method is used to preserve as much flavour and moisture as possible in the products. The food is heat treated at a temperature and time depending on raw material and desired product quality. After rapid cooling the food is packaged and stored at chilled temperatures.
The shelf-life of such products is generally limited to 10-14 days, depending on the storage conditions and raw material. The method is often combined with modified atmosphere packaging
Sous vide is used to describe food that has been vacuum-packed and given mild heat treatment before being stored in at chilled conditions. The heat treatment takes place after packaging and under controlled conditions of time and temperature, and the food is subsequently rapidly cooled. The products are kept chilled until they are heated before serving.
Nofima was involved in the development of Fjordland’s ready-to-eat meals, which can now be found in retail stores all over Norway. Sous vide is now also used with a more intense heat treatment, and this has made it possible to produce ready-to-eat food that has a shelf-life of several weeks. Testing the nutritional value of four ready-to-eat meals has shown the method to be just as good as corresponding home-cooking.
Pasteurisation is a classic thermal processing to reduce the number of harmful bacteria. A typical pasteurisation process designed to control cold-tolerant Clostridium bacteria is heat treatment corresponding to 10 minutes at 90 °C at the coldest point of the product. Temperature and time is depended on the targeted food pathogen. Pasteurised products must be stored under chilled conditions, and can have shelf-lives up to 6 months.
Canning and sterile products
The most common form of sterile packaging is stainless steel or aluminium cans. Other materials used are glass, plastic (stand-up bags and trays) and fibre-based materials (cardboard). Both pasteurisation and sterilisation generally take place after packaging. As long as the package integrity is not broken, canned foods can be stored for many years at room temperature.
Nofima has high expertise in this field and carries out, among other operations, heat measurement and heat documentation for exporters of canned products.
Novel thermal technologies
Classic heat treatment is a tough process for many products, and may influence the texture, nutritional value or colour. Because of this, we have an increased research emphasis into novel and more gentle processes to keep the quality more effectively and reduced the negative changes, while giving equally high food safety and shelf-life.
Examples include the sous-vide process described above, heat treatment under agitation (shaka autoclave) , the use of microwaves or steam to optimize the the heat treatment, and make it more effective and gentle.