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 6000 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%.
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% 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 yogurt 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 yogurt.
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.