A team of young scientists from Piotrków Trybunalski has made a ground-breaking discovery in the area of natural preservatives. Will it revolutionise the market and give us access to truly healthy food? Let’s hope so!
Fruit and vegetable preservation nowadays consists mainly in adding chemical substances that prevent them from rotting.
Such a procedure entails lowering the product quality and poses a threat to human health. The consequence of the use of “E” compounds are great financial expenditures which are used for food testing for toxicity. Stored food undergoes negative chemical changes that often render it unfit for consumption. Factors contributing to food spoilage are: oxygen, light, as well as microorganisms causing various changes in the food products. Food may be fit for consumption for a longer period of time thanks to numerous technological processes such as pasteurisation, salting, smoking, pickling or adding stabilisers, usually chemical compounds. The level of chemical compounds is strictly specified for a particular type of food.But is “artificial” preservation necessary?
First of all, tradition
Acetic acid and lactic acid preserve vegetables and fruit in a natural way while changing their flavour. The chemical properties of these compounds were used to find an alternative method of preservation by Joanna Jurek, Żaneta Wewiura and Kacper Bąbol, students of the Bolesław Chrobry High School No. 1 in Piotrków Trybunalski, under the supervision of Dr Izabela Masłowska.
Preservation using acetic acid, commonly called ‘pickling’, is a popular method of food preservation. It is based on lactic acid fermentation. Thanks to it, the simple sugars decompose into lactic acid that stops putrefaction by acidifying the environment and prevents the growth of putrefactive bacteria. Both the acetic acid and the lactic acid are well-known to man – 10% acetic acid is vinegar used for cooking. Lactic acid can be found mainly in dairy products. It is produced by the lactic acid bacteria, Lactobacillus, responsible for the proper functioning of the gastrointestinal tract. The selection of the substrates administered to plants was based on that characteristic. By selecting two compounds, it was estimated which one is more effective as a natural preservative.
The plant is constantly exposed to many stress factors, especially abiotic ones: temperature fluctuations, the excess or insufficiency of water or mechanical damages. All of the above are stimuli that may interfere with the functioning of a plant or damage it. In the course of evolution, plants had to adapt to the conditions of the environment, and at the same time build up resistance to stress factors.
A plant’s stress reaction syndrome begins with interference in its vital functions e.g. by destabilising the structural features.
In the alarm phase, some of the processes may dominate and the electrolyte balance may be disturbed. In the restitution phase, the repair systems are triggered to eliminate the danger. Metabolic process disturbances lead to osmotic adaptation and the rearrangement of cell structures. It is a part of the resistance phase that aims at preventing the action of that stress factor in the future – building up resistance.
When a plant starts to lose water, the osmotic adaptation responsible for maintaining the electrolyte balance in its cells begins. It involves faster synthesis and accumulation in a vacuole.
The storage of simple sugars is also possible. It is not a stress factor because the method of restoring balance is a natural process that allows for adaptation to salty conditions and an insufficiency of water.
The information mentioned above was vital for designing the method of protection and preservation of plants. Stress factors, such as the change of the environment pH, were used to stimulate the immunodeficiency system of a plant, which was supposed to trigger the osmotic adaptation and restore the electrolyte balance. Vacuoles storing water from the environment played a major role.
Acid administration was not only a stress factor, but also protected the plant from the inside and outside by means of preventing putrefaction. Natural pH of the environment lowered insignificantly, but allowed the plant to maintain its vital functions.
The procedure above all
The most important element of the method is determining the adequate period of acid administration. Experiments conducted on the Mila radish were aimed at determining if the preservation through the administration of acid into the ground is possible.
Step by step
About 3 weeks after acid administration, the radishes were in an excellent condition, even better than the control sample.
Curiosity won and the studies began. None of the project participants knew that the plant absorbed the acid and therefore the contents of the juice from each radish sample was analysed. It turned out that the absorption was high, around 60-70%. How did the acids impact the cell structure of a plant? Surprisingly, the cell membrane in radishes fed with acids was thicker than in the control sample. After a thorough analysis of the preliminary studies, the mechanism of the acid absorption by the radish without a negative impact on its cells became a subject for consideration. For that purpose, the cell membrane responsible for the transport of compounds was analysed. Conducting such testing as FCS (fluorescence correlation spectroscopy) and FLIM (fluorescence lifetime imagining microscopy) was possible thanks to the National Children’s Fund and the Institute of Physics of the Polish Academy of Sciences. Thanks to those studies, serious conclusions regarding the cell membrane were drawn – diffusion through the membrane occurs much faster in radishes fed with acid, and as a result the pressure balance is achieved more easily. Moreover, the study samples were filled completely with the model dye, whereas it was not observed in the control sample.
The hypothesis relates to the interaction of the cell membrane with hydrons leading to the so-called membrane potential.
It causes microdomains – cracks in the membrane structure. When ions appear, other nutrients are transported from the outside of the cell, which results in the better condition of the plants in the study sample than in the control sample.
Apart from the radishes, the acids were administered to the arabidopsis. The purpose of the experiment was to find out which phenotypic changes occur following the administration of acids, and if those can be observed in the amino acids sequence. The analysis of the translocation protein for eight varieties of the arabidopsis has shown how the presence of the selected amino acids helps reduce stress factor. In the case of one of the varieties, the presence of the valine amino acid is beneficial because it helps the plant regenerate faster and, therefore, maintain a good condition. Osmoregulation is much more effective due to a greater absorption of water from the environment. On the other hand, the removal of the saline amino acid in two other varieties caused damage to the plant and the lack of regeneration. After the completion of the study, the team concluded that the acids administration at an early stage of plant development leads to an increased absorption of water and nutrients that results in a good condition of a plant. The process uses a temporary change of environmental conditions (acidifying) that influences a young radish. It acquires new characteristics that allow for facilitating the diffusion through the cell membrane. The obtained results show that the preservation of plants during cultivation can be done using the natural protection mechanisms of a plant, such as adaptation to environment by building up resistance to a stress factor. The mechanism of action is clear and understandable thanks to microscopy and spectroscopy. The method of protection and preservation of plants can be successfully used in plant cultivation. It is not expensive or difficult to implement. It could be an alternative to GMO, because it is based on the natural mechanisms of a plant and the process of adaptation, not genetic modification.
Thanks to the method based on the acids present in the products well-known to a man, a plant acquires new characteristics that make it fresh and fit for consumption for a longer period of time. The initial calculation of costs made by a food producers is also promising. The cost of the preservation of one thousand young radishes is about PLN 5.
The survey carried out by the group showed that the greatest advantage of the method, in contrast to the existing industrial preservatives in the form of pesticides, is ensuring health and safety. The next stages of the research look promising. The students are now focusing on the genetic characteristics of the preserved plants.