High-pressure processing preserves the taste, texture, appearance and nutritional value of foods and is used in producing juices, soups, baby food, packaged meals and many other foods. —PIXABAY/Pexels
Since the WHO classification of processed meats as Group 1 carcinogens in 2015, many people became more wary of eating meats containing preservatives such as nitrites and nitrates. And the food industry has responded to these concerns.
Many common packaged foods in the supermarkets here in France are now promoted as containing no preservatives. Even two years ago, I started to notice packets of ham and bacon were labelled as free of sodium nitrite (a known carcinogen), and many meats contained no chemicals for conservation at all. Now many more foods are also promoted as being free from artificial preservation compounds, such as specialty sausages, fish delicacies and chicken slices, even though the packaging indicates Use By/Expiry Dates similar to products containing nitrites and other artificial preservatives.
This puzzled me for some time, as the food items look and taste precisely the same as before, and it was only recently that I found out how they were processed. And you might also find it interesting because such foods may actually be healthier. In any case, they are definitely coming your way soon, if they are not already available, whether you know it or not. What is more curious is that such foods are prepared at room temperature (using unusual processes that do not require heat); this non-use of heat also helps preserve nutrients, taste, and textures.
New advancements
Food processing has advanced significantly over the years, with the emergence of innovative techniques that can improve food safety, extend shelf life, and maintain nutritional quality without any use of chemical additives or preservatives. Two such innovations are (i) High-Pressure Processing (HPP) and, (ii) non-thermal technologies, and most people would have never heard of them.
High-Pressure Processing (HPP)
HPP is a non-thermal (non-heat-based) technique gaining momentum in the West. It utilises intense pressure rather than heat to inactivate microorganisms and enzymes that can cause food spoilage and deterioration.
Some processed foods like specialty sausages and bacon are now labelled as free of sodium nitrite and artificial preservation compounds. — VALERIA BOLTNEVA/Pexels
HPP relies on the isostatic principle which states that the uniform application of pressure acts equally in all directions, and therefore the shapes of the treated food items do not matter. HPP offers several advantages over traditional thermal (cooking) methods, including the preservation of taste, texture, appearance, and nutritional values of food products.
The process of HPP involves placing food in specially designed baskets, which are then conveyed into a high-pressure vessel. Water is added to the vessel, and the pressure is increased up to 600 megapascals, which is equivalent to the pressure of being six kilometers under the ocean.
The pressure is evenly applied throughout the food, without causing any damage or crushing. This intense pressure disrupts the cell membranes of microorganisms and structures of enzymes in the food, rendering them inactive in just a few minutes, significantly slowing down the decay processes.
One of the key benefits of HPP is the effective destruction of harmful bacteria such as Listeria monocytogenes, Salmonella, E. coli, etc. By eliminating these dangerous microorganisms, HPP enhances food safety without relying on chemical additives or high heat. Furthermore, by not using heat, HPP preserves the nutritional content of food, minimising the loss of essential nutrients, amino acids, vitamins, and minerals.
HPP is suitable for a wide range of foods, including low to medium-moisture solid or semisolid products, high-moisture solid foods, and high-moisture liquid foods. The process does not require any specific packaging; however, plastic containers made of PET, PE, PP, or EVOH are commonly used due to their flexibility and water barrier properties to hold foods treated by HPP.
Generally, foods with a higher water content respond better to HPP, and sometimes water is injected into certain foods to improve the HPP process.
HPP is currently used for a variety of foods, such as juices/beverages/soups, food sauces, meats, seafood, baby food, fruit purees, packaged meals, dairy products, etc.
Non-thermal technologies
Non-thermal technologies are alternative methods of food processing that do not rely on traditional thermal methods such as heating or pasteurisation. These technologies offer advantages in terms of improved food safety, extended shelf life, preservation of nutrients, enhanced food quality, and clean “healthy” labeling. Some of the non-thermal technologies used in food processing are:
Pulsed Electric Fields (PEF): PEF involves applying short pulses of high-voltage electricity to food products. This disrupts the cellular structure of microorganisms, resulting in their inactivation or reduced growth. PEF is particularly effective for liquid foods and can help preserve their nutritional content.
Ultrasound: Ultrasound technology utilises high-frequency sound waves to disrupt microorganisms and enzymes in food. It can improve preservation and quality by enhancing the texture and sensory attributes of certain foods, such as dairy products.
UV-C Light: UV-C light is a type of ultraviolet light that possesses germicidal properties. It is used in food processing to kill bacteria, viruses, and molds without the use of heat. UV-C treatment is commonly applied to food surfaces and packaging materials to reduce the risk of contamination.
Ozone treatment: Ozone is a highly reactive gas that acts as an antimicrobial agent. It can be used to disinfect and preserve food products by killing bacteria, yeasts, molds, and viruses. Ozone treatment is particularly effective for fruits, vegetables, and water disinfection.
Irradiation: Of all the non-thermal technologies, this is the one most commonly known by the public. Irradiation involves exposing food products to ionizing radiation, such as gamma rays or X-rays. This process helps to kill bacteria, parasites, and insects, thereby reducing the risk of foodborne illnesses and extending shelf life. Irradiation is commonly applied to spices, meat, poultry, and dried fruits.
Although generally acknowledged to be safe, there are still some negative perceptions of the use of irradiation on foods. One might be due to the formation of radiolytic compounds created when the ionising radiation interacts with food compounds. It is possible taste and texture may be affected as a result. Research is ongoing on this matter.
Benefits
Apart from the above-mentioned benefits of preservation of nutritional value and improved food safety resulting in extended shelf lives for such foods, it has also been claimed that HPP and non-thermal technologies can generally maintain the sensory characteristics of food products, including taste, texture, colour, and aroma. This often gives consumers a higher-quality food experience, without compromising on safety or nutritional value.
Additionally, HPP and non-thermal technologies align with consumer demands for minimally processed and natural foods. As these methods do not require chemical additives or preservatives, they contribute to clean labeling, providing consumers with transparently healthier food options.
Furthermore, HPP and non-thermal technologies are now applied to an ever-widening range of foods. This versatility makes these techniques useful for preserving and extending the shelf life of exotic fruits/foods, raw meats, raw seafood, etc, without the need for expensive deep refrigeration or freezing during transportation.
Challenges and limitations
While HPP and non-thermal technologies offer numerous advantages, they also face certain challenges and limitations. These include:
Equipment cost: Implementing HPP or non-thermal technologies may require specialised equipment that is costly to purchase and maintain. This can pose challenges for small-scale food producers.
Irradiation is one of the most common non-thermal technologies and is commonly applied to spices. — MARTA BRANCO/Pexels
Energy consumption: HPP machines and some non-thermal technologies may consume significant amounts of energy to generate and maintain the required pressure or treatment conditions. This can impact the overall sustainability and operational costs of food processing.
Processing time: Some non-thermal technologies, including HPP, may require longer processing times compared to traditional thermal methods. This can impact production efficiency and throughput.
Packaging considerations: HPP and certain non-thermal technologies require packaging materials that can withstand high pressures or treatment conditions. This might limit the range of packaging options available to food producers.
Product quality changes: HPP can cause changes in the sensory qualities of food products, such as texture and flavour. Some products may experience a loss of crispness or colour changes during processing. Non-thermal technologies may also impact certain desirable important food attributes, such as aroma or taste.
Adiabatic heating: The process of applying immense pressures during HPP will cause the temperature of food to rise by around 3°C per 100 megapascals of pressure due to adiabatic heating (the rise in temperature due to the change in the internal energy of pressurized foods). This may induce a small degree of heat cooking during HPP.
Non-sterilisation: HPP and non-thermal technologies generally do not result in sterilised food products. While the actual microorganisms causing decay are often eradicated, the spores of these microorganisms are not always deactivated, and they may germinate later in processed foods.
Finally
High-pressure processing (HPP) and non-thermal technologies may not be applied interchangeably across the whole spectrum of foods. Certain processes may be more suited for particular foods, and additionally, there are significant differences in the various costs of the processes.
It may end up being decided by economics. For example, irradiation is probably cheaper to use and apply on common fruits, vegetables, hot dogs, pet food, etc, than HPP. Hence, more premium foods such as specialty hams may use more expensive processes that protect textures and taste to enhance their presentation, shelf life, and attractiveness for consumers, while more regular consumer foods may be treated with, for example, cheaper UV-C or irradiation.
At present, probably less than 1% of the world’s food is processed by HPP and non-thermal technologies, though the market is growing. UV-C, for example, was applied to roughly USD 2.9 billion of foods and is expected to increase to treat USD 6.7 billion of foods by 2026.
The current rules for consumer information about such processes are haphazard. In the USA, only irradiated food must be labeled. In the UK, only foods treated with UV-C need to be labeled while the EU requires labelling only for HPP foods.
The views expressed here are entirely the writer’s own.
