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Processing with PEF has several advantages, including energy saving in food production.

High pressure, ultrasound and UV light can keep food fresh and tasty for much longer

If we are to slow down climate change, food production must be made more sustainable.

Communications Manager
Presented by: Nofima The Norwegian Institute of Food, Fisheries and Aquaculture Research
Published

One third of man-made global greenhouse gas emissions are due to food production. However, everyone needs food, and it is therefore urgent that we find new ways of producing food that have less of an impact on the environment whilst also being profitable for the producer.

Additionally, we know that food should be processed as quickly and as gently as possible to preserve quality and nutrition.

Fast, gentle and energy-saving ways of producing and preserving food have been the focus of the four-year international research project iNOBox. The project investigates six innovative processing technologies: high pressure, microwaves, pulsed electric fields, ultrasound, UV light and plasma-activated water.

Scientists, food manufacturers and equipment suppliers have collaborated in order to document the effects these technologies have on food and food production.

Increase shelf life to reduce food waste

Project manager Tone Mari Rode.

One of the most important ways to save the environment is to stop throwing food away. In Norway, we throw away over 450,000 tons of food every year, often because it has passed its expiry date.

“We know that there are major differences between different raw materials and products when it comes to environmental emissions. Despite the fact that fruits and vegetables produce low levels of emissions, these foods have a short shelf life. Therefore, it is really important to give them a longer shelf life and avoid having them end up in the rubbish,” project manager Tone Mari Rode says.

How sustainable is food processing?

When sustainability is calculated, greenhouse gas emissions and shelf life are often studied. However, emissions associated with things such as the production of equipment and transportation must also be taken into account.

In order to get the whole picture and have the opportunity to compare products, scientists use ‘life cycle assessments’ – a systematic review of the environmental impact in all processes related to the type of food, from when the seed is sown in the soil or an animal is bred, all the way up until the food is consumed.

Norsus has investigated a number of products using this method in order to find out the role that food processing itself plays in the emission accounts. Among other things, they compared the CO2 emissions produced by a smoothie, a sandwich and a beef dish.

The thin black line shows high-pressure technology’s contribution to CO2 emissions from a smoothie, a sandwich and beef dish. It is clear that the food product itself contributes the most to the overall climate footprint. In this figure, food waste is not included in the calculation.

The studies show that emissions from most processing technologies make up only a very small part of the entire life cycle accounts of the food product.

“If processing can extend the shelf life of a product, it can reduce the environmental impact of the product, but only if the benefit of this is greater than the environmental impact associated with the processing," Rode says.

Life cycle assessments are complex analyses in which many factors come into play. Studies carried out by Norsus in this project have provided information on energy savings, reduction of food waste, increased shelf life and working conditions.

Processing to improve food

Many consumers are sceptical about raw materials undergoing treatment in order to improve them. Many believe that the least amount of processing is the best, but this is not always the case.

For example, some people who suffer from allergies can eat nuts that have been treated with heat, but not raw. The allergens associated with allergies are destroyed when the nuts are roasted, while other proteins are not affected.

Can processing with the use of new technologies remove specific proteins from foods that cause allergic reactions?

These types of analyses have been carried out by the Norwegian Veterinary Institute and the Dutch partner TNO. They have investigated the extent to which the new processing technologies can remove specific proteins that can cause allergic reactions.

Unfortunately, people who are allergic to eggs are going to be disappointed – the egg analyses showed no differences between raw and processed eggs in terms of allergenic proteins.

Processing can affect the body’s ability to absorb nutrients from food. Nofima has simulated digestion in the laboratory, and specifically investigated the protein digestion of foods that have been processed using the new technologies.

The results showed that treatment with the different technologies does not affect the protein digestion of any of the foods, except in a ‘smart yoghurt’ – a yoghurt that was made using combinations of technologies. The protein digestion was better in this yoghurt than in traditional processing.

Great potential for sustainable processing

As new technologies become available, it may take time for them to become known and adopted. In the food industry, there are several factors that determine whether a technology is interesting to invest in.

Firstly, it must be known and accessible, and interesting to use as part of or a replacement for processes that are already in use. It must also be an affordable investment, and if the technology is to improve a product, the customer must feel that the new changes in the product are for the better.

Food products that have never been made before, or that have been made in new ways, must have EU ‘novel food’ approval in order to enter the European food market.

A similar ‘new food’ regulation can be found in Norway that has common rules and approvals with the EU. Previously, this has entailed a long and demanding process for food manufacturers, but has now been revised and made somewhat smoother.

Nofima has studied these regulations and encourages food manufacturers to seek help from the Norwegian Food Safety Authority and other producers. Nofima’s research shows that transparency between manufacturers is important for the industry to succeed when it comes to innovations.

A number of food produce has been investigated, such as milk, eggs, chicken, broccoli and potatoes. From left, researching innovative processing technologies: Tone Mari Rode, Tem Thi Dang, Dagbjørn Skipnes and Estefanía Noriega Fernández.

The extent to which consumers accept food that has been made in new ways, or brand new products, is another possible obstacle that stands in the way of adopting new technologies. It is not uncommon to be sceptical of something you know little about.

Nofima has therefore conducted extensive consumer studies that have resulted in a practical tool for marketing communication. It enables manufacturers to see what kind of information is most beneficial to use when the product is made using the various processing technologies.

“The extensive studies we have conducted in this project show that new technologies have great potential to contribute to more sustainable food production,” Rode says. “That is why we continue to work on new projects. A lot of development and documentation remains, but there are many different possibilities that lie in these technologies. We hope Norwegian food manufacturers will use the information we have posted online, and get in touch if they want to test the technologies. We food scientists would very much like to contribute to ensuring that food production takes place in partnership with both people and the environment."

Knowledge about processing technologies available online

The strong wish for the research results to be used is the reason why the scientists in this project have put a lot of effort into an online tool specially designed for Norwegian food manufacturers. Useful information and documentation from the project are gathered in one place.

“In order to make more safe, healthy and sustainable food, food manufacturers are dependant on production methods being efficient, profitable and sustainable. In addition, the products must maintain at least the same high quality as today’s products. We want to help them assess new technologies, and have therefore made the information and documentation from the research readily available,” Rode says.

The website provides the food industry with knowledge about the six new processing technologies, how they work, what possibilities lie in them, and examples of the types of products they are suitable for.

The information can be found in both Norwegian and English, and simple animated films have been made that explain what happens when food undergoes treatment using the different technologies.

Results from trials involving the six technologies:

In order to ensure that foods are safe and give them a longer shelf life, it is common for food manufacturers to treat products using heat in an autoclave – a type of pressure cooker in which microorganisms in the food are inactivated. There are several challenges when using autoclaves. For example, the heat needed to kill bacteria often affects food quality, and the treatment often requires a lot of time, water and energy.

Many of the new technologies the scientists have tested have been designed to replace the autoclaves and find better ways to ensure safe food. In addition, they save time, costs and have less of an impact on the environment. The faster and gentler the food is processed, the better the natural quality is preserved both in terms of taste, colour and nutritional content. Here are some of the trial results from the iNOBox project:

High pressure processing improved egg mass and cauliflower

  • When food is exposed to extreme pressures, as high as 6,000 bar, its shelf life can be at least tripled compared to a fresh product. Juice has a shelf life of at least 2-3 months, depending on the type. The treatment takes place at room temperature or in chilled conditions, which preserves the nutritional content well and more importantly is very good at preserving the taste. The treatment takes place on pre-packaged products, or in bulk, where the product is subsequently bottled.
  • The method is well suited for pasteurisation of both solid and liquid products.
  • A whole egg has a long shelf life, but when eggs are cracked and an egg mass is made, the shelf life is significantly reduced. It is common to either add preservatives or give it a mild heat treatment so that it keeps longer.
  • Nofima exposed egg mass to high pressure. As a result, it gained a longer shelf life and several properties were also improved. When the high-pressure treated egg mass was beaten, foaming increased and the foam retained its volume for a long time without collapsing. The mixture also gained increased emulsification capacity, which can be positive in different types of food processing and cooking.
  • In another study, high-pressure processed cauliflower was investigated and compared to regular autoclave cauliflower. After four weeks of storage, the cauliflower had no change in colour and its texture was better than that of the autoclave cauliflower. The same was true of cauliflower treated with microwaves.

Microwaves gave fried chicken a long shelf life

  • Although microwave ovens are a familiar piece of kitchen equipment in many homes, the method is not so widely used in the food industry. One advantage of using microwaves instead of autoclaves is that the heat load on food is much less than in traditional autoclaving.
  • In a trial involving chicken that was fried and packaged in two different ways (vacuum and modified atmosphere), some of the samples were further processed using high pressure or microwaves. They were then stored at 4°C. The vacuum-packed chicken had a shelf life of four weeks, while the high pressure samples kept for over three months. The microwave samples also showed great potential.

Pulsed electric fields (PEF) resulted in faster cured sausage production and carrot blanching

  • Food products can also be exposed to electric fields in short pulses of different intensity – a method called pulsed electric fields (PEF). What happens then is that pores form in the cell membrane of the food product. This results in a number of benefits, including making vegetables more flexible or easier to peel, and giving higher yields during extraction. The method can also kill bacteria in products such as juice, while also preserving the taste and nutrients.
  • In this project, scientists at the University of Zaragoza in Spain investigated what types of effect the method had on cured sausage production. The PEF-treated sausages had a much shorter drying time than those produced in the usual way, and energy consumption was also reduced by 40 per cent.
  • They also conducted trials in which pieces of carrot were blanched (boiled and then rapidly cooled down). When the carrots received PEF treatment, the time it took to blanch the carrots was more than halved.

Ultraviolet light (UV) is good at killing bacteria

  • UV light is already used to kill bacteria on the surface of foods or other surfaces, but the technology is still in development regarding packaged products. There are major differences in how well UV light penetrates through various plastic materials. The surface of the product is important. If it is not smooth, bacteria can hide in folds and cavities.
  • Scientists at the Campden BRI institute in the UK investigated UV light treatment on three different types of packaged meat: chicken, pork and beef. The treatment did not affect colour or rancidity, and the shelf life was the same as in unprocessed meat products. Nevertheless, the scientists see that the technology may have potential in the fight against pathogenic bacteria.
  • UV light can also be used to increase the content of vitamin D in foods.

Ultrasound saves energy in food production

  • When food is treated using ultrasound before other processing takes place, it can speed up the subsequent process. For example, ultrasound treatment allows heat to penetrate the product more quickly, which means that less energy is required. The treatment does not compromise the quality of the product.
  • Chicken breast was frozen and thawed with and without ultrasound treatment. The results showed that the freezing process took place 25 per cent faster using ultrasound pre-treatment, and the thawing process was also faster. Both save time and energy during production, and the shelf life of the chicken also increased.
  • In yoghurt production, the scientists found that the combination of CO2, high pressure treatment and ultrasound can be used to replace traditional homogenisation and heat treatment. A combination of these technologies have a positive effect on inactivating microorganisms and enzymes, the rate of fermentation, and the water-holding capacity of the yoghurt.

Plasma-activated water has potential regarding raw fruit and vegetables

  • This technology is still in the development stage and is not yet in use in the food industry. With the help of electricity, oxygen and nitrogen compounds present in the air can be added to water, which gives the water certain new properties. This is called plasma-activated water, and the idea is to use this water to rinse fruit and vegetables before they are sold. If the water is plasma-activated, bacteria will be inactivated and the shelf life of the produce extended.
  • In this project, scientists at the University of Liverpool have studied the water quality in different countries, and found major differences in things such as pH values. The water from Norway turned out to be very well suited for plasma activation. When water from England was used in plasma activation, E.coli bacteria were inactivated after twenty minutes of treatment, while water from Palestine had no effect on them. This shows that it is important to have control over the water quality when performing such treatment.
  • In another trial conducted by Nofima, baby spinach leaves were rinsed using plasma-activated water and compared to baby spinach that was untreated or rinsed with ordinary water. After eight days of storage, the spinach rinsed using plasma-activated water saw no increase in the number of bacteria. The colour also remained nice.
  • The scientists conclude that the technology has potential, but more research and development is required before it can be relevant to the food industry.

About the research

  • The iNOBox project has run from 2018 to 2022, and is funded by the Research Council of Norway.
  • The technologies investigated: high pressure, microwaves, pulsed electric fields, ultrasound, UV light and plasma-activated water
  • Foods that were included in the trials: Milk, juice, yoghurt, chicken, pork and beef, cauliflower, carrot, celery, potato, baby spinach and eggs. (Optionally: dairy products, meat products and vegetables).
  • Properties investigated: Food safety, shelf life, quality, nutritional value, allergenicity of food. In addition, we have investigated sustainability, consumer preferences and regulations regarding innovative products.
  • Partners: Nofima (project manager), Norsus, the Norwegian Veterinary Institute, University of Zaragoza, University of Liverpool, Campden BRI, TNO, BAMA Group, Den Stolte Hane, Findus, Fjordkjøkken, Fjordland, HOFF, MatBørsen, Advanced Microwave Technologies, Elea, Hiperbaric, UV Technology, ILSI Europe and the Norwegian Asthma and Allergy Association (NAAF).

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