One of the many consequences of civilisation is the need to preserve food. The methods used up to now are unable to meet the expectations of modern consumers, moreover, many of them have a negative effect on the quality of the products. High temperature causes loss of components sensitive to its action, i.e. thiamine, folic acid, riboflavin, vitamin C. In addition, it affects the denaturation of proteins and causes changes in texture, colour and, above all, flavour of the product.
These changes are known to be counteracted by the pasteurisation process, but unfortunately this ensures a much shorter shelf life (even if we keep the food at low temperatures). Another method is to dry and freeze foods, but unfortunately these processes also reduce the nutritional value of foods (especially if you want to keep them for longer). When shopping, today’s consumer is looking for healthier products but with a longer shelf life, the current focus is on ionising radiation, electric fields and high hydrostatic pressure
Radiation sterilisation is an innovative method aimed at preserving foodstuffs and ensuring their longer shelf life. However, this method still causes concern among consumers and is widely unacceptable in the European Union (in Poland the use of this method in food production is regulated by respective provisions – EU Directives No: 1999/2/EC and 1999/EC 3/EC), in contrast to the USA and China, where this method has been continuously implemented in the food industry. According to the literature, radiation treatment of food is safe for humans and the environment, cheap and quick. Every year 400,000 people are treated this way. tons of vegetables, grains, fruit, meat and spices. Ionising radiation blocks the growth of parasites, fungi, bacteria and pathogens. The types of radiation sources are regulated by standards and ensure that food is free from harmful substances. Food preserved in this way stays fresh longer, as the parasites, fungi and moulds responsible for its decomposition are killed. It is important to note that this method does not alter the taste of the products and does not affect their nutritional value, and the shelf life of ripening or germinated products is extended. The following methods are used in the processes of radiation fixation of foodstuffs: Radapertization .(reduces the number of microorganisms to a level where they are unable to spoil food), radiation (destroys vegetative forms of pathogens, this method uses higher doses of radiation), radurization (uses high doses of radiation – 30 kGy. killing spores, as in thermal sterilization, but this method is rarely used because it changes the organoleptic characteristics of products.
Electric field – pulsed electric field (PEF)
This method is not widely used in the food industry. It consists of exposing products to short-term electrical pulses of high intensity. These pulses damage the membranes of bacterial cells by creating a significant difference in electric field potential between the outer and inner layers of the cytoplasmic membrane. If the generated potential reaches a critical value of 1 V for the membrane, it is damaged. This process leads to the formation of transmembrane pores filled with protein and lipid solutions (because they conduct electricity). The exposure time of the personal protective equipment products required to fight pathogens is shorter the higher the voltage applied. Effective destruction of bacteria is possible by using several pulses of different voltages. This method lowers the pH and increases the temperature, but does not cause loss of nutrients in the food and changes (but only to a small extent) its organoleptic properties.
High hydrostatic pressure – HP technology
The high pressure method is most often used to prolong the shelf life of food by reducing the number of microbes or reducing the activity of enzymes. The most important criterion when using new methods of food preservation is to preserve properties of the product, i.e. taste, colour, smell and high nutritional value. At the moment, this method is used as an alternative method of food preservation – mainly thermal
The destruction of harmful microorganisms lies in the fact that this method disrupts the cellular functions of the organisms through adverse biochemical reactions, causing irreversible changes in the cell membrane . The vegetative cells of Gram-negative bacteria are the most sensitive to high pressure. Gram-positive bacteria of the families Bacillus and Clostridium are more resistant. The high pressure technology (HP – high pressure) eliminates the following bacteria from meat and meat products: Salmonella , Listeria monocytogenes , Aeromonas hydrophila and Campylobacter jejuni.Importantly, this method has no negative impact on the texture profile and organoleptic properties of products and no negative impact on nutritional content. HP opens up new possibilities in the food industry (including meat processing), both as a non-thermal method of preserving foodstuffs as well as processing them and imparting new organoleptic and functional characteristics. Depending on the pressure level applied, this technology makes it possible to control pathogens. The applied pressure levels are in the range of 400÷600 MPa.
The presented methods of food preservation are non-traditional and little known. Knowledge about them is constantly increasing and most of them are widely used outside the European Union. Radiation preservation of food has been approved in more than 50 countries, and recently even in Poland. In addition to the methods mentioned, methods such as: induction heating, light pulse method, ultrasound or electric discharge method are also presented in this article. Each of these is used in food production, but time will tell whether they will be introduced permanently into the industry. Moreover, despite misgivings and aversions (including the radiation method), products recorded in a non-traditional way must be labelled appropriately.