New technologies for improved food preservation
Citizens of developed countries have good reason to worry about the quality and safety of the food they eat. The number of food-borne diseases has increased over the past 20 years. It is estimated that today and every year, 1 in 3 European and 1 in 4 Americans have a consumption-borne by spoiled food.
These diseases cause 20 deaths per million inhabitants and cost to their governments "billions of euros." The World Health Organization (WHO) estimates that 2 million children die each year from diseases transmitted by food and water. Moreover, the "travelers' diarrhea, the disease is most commonly contracted by visitors to developing countries has been estimated affecting between 20 and 50% of the 35 million travelers who annually cross the borders of these countries.
What are the causes of the problem?
The new foods that are processed with old technology or new methods not yet sufficiently tested is one of the most important. This is the cause of the "appearance" of microorganisms called "emerging pathogens, including species of bacteria that were not traditionally a major health problem. The development of new power foods, sometimes, its growth relative to other pathogens "traditional."
change conventional methods of plant and animal production favors the emergence of new diseases (syndrome of mad cow disease, dioxin poisoning etc..) And the spread of large groups of animals and plants with well-known pathogenic species.
concentration in large agribusiness companies causes a breakdown in quality control systems affects a large number of consumers, even from different countries. For the same reasons, the change in lifestyle, with the creation of great eating places, is also a major cause of the problem.
Finally, changes demographic developed countries have experienced have led to a substantial increase in population particularly sensitive (yopis = young, elderly, pregnant and immunosuppressed).
"What are the limitations of traditional technologies?.
Currently, the only preservation method that simultaneously guarantees the health safety of food is heat. However, recently it has been shown that various microbial species pathogenic to man (that cause disease) are able to survive the current heat treatment. In addition, seemingly well-unpasteurized foods have been responsible of severe food poisoning.
The main problem of the heat treatment lies in its specificity, since, while microorganisms and inactivate enzymes produce a series of chemical changes in food components whose consequences are the loss of its nutritional value, sensory and functional . This prevents, in many cases, increase the intensity of the treatments currently used, and therefore their health security.
Moreover, changes in consumer habits and the main concern of the average for the quality of the food they eat, have prompted the food industry to develop new minimally processed. One of the major constraints to industrial expansion in this area is the lack of conservation methods and adequate sanitation, ensuring the preservation and safety of these foods, minimally affecting their quality.
Are there solutions to this problem?
Food Technology is currently undertaking a major effort to develop new methods of preservation and cleanliness of food. On the one hand, trying to improve on current treatments possible to search for more efficient thermal heating such as microwave, ohmic heating, etc. Second, they attempt to combine various technologies to reduce the intensity of treatment and, thus, its effect on the loss of quality (eg acid addition reduces the temperature and time of sterilization of some canned vegetables) . Finally, try to find new treatment methods, more specific, allowing effectively destroy microorganisms and minimally affect the quality of food. Within this latter group, ultrasound, and pulsed electric fields are two of the most promising technologies under investigation.
"What is Ultrasound? How can be used?
Ultrasound is sound waves that are inaudible to humans because of its high frequency. Passing through the liquid media, ultrasounds generate alternating cycles of compression and expansion and, therefore, the appearance of gas bubbles in the liquid mass. In successive cycles, the bubbles grow, they reach a critical size and, to overcome this, implode (similar to suddenly remove the air inside a balloon). When molecules collide fluid as a result of the collapse, there are pressure waves that are transmitted through the middle inactivating bacteria and disruption suspended matter. Although the effect This phenomenon, called cavitation, is known from ancient, its usefulness is very limited given the low efficiency in the normal process of treatment.
Our group has investigated the possibility of increasing the intensity of cavitation through the application of ultrasound under pressure (Manosonicación), and enhance the lethal efficiency of the process through the simultaneous application of heat (Manotermosonicación). Our laboratory has designed a facility that allows you to apply ultrasound and heat in perfectly controlled conditions of temperature, pressure and amplitude of ultrasonic waves. This facility has enabled us to demonstrate that inactivation Ultrasonic microbial increases with system pressure, so it is possible to design treatments manosonicación increase up to 100 times the health security afforded by ultrasound treatment of pressure and temperature. On the other hand, it is possible to design processes manotermosonicación (ultrasound under pressure + heat) at moderate temperatures that can act synergistically to increase "thousands" of times health security that confer heat treatment at the same temperature. The Manosonicación and / or Manotermosonicación can be particularly useful for food pasteurization and sterilization of contaminated liquids very heat resistant microorganisms, and for those whose composition significantly increases the microbial heat resistance (jams, pickles, etc.) or hinders the transmission of heat (ie liquid egg). You may also be useful for the decontamination of raw vegetables and commonly used tools in the food industry.
What are pulsed electric fields? What can you use?
One of the new technologies that could replace conventional heat treatments are pulsed electric fields (CEP), produced by applying electric shocks high voltage in controlled conditions. Electric fields produce the accumulation of charges of different signs on both sides of cell membranes. When the field strength (E) reaches a critical value (Ec), the attraction between charges overcomes the mechanical resistance of the membranes and pores occur. If the field strength exceeds the critical value (Ec), the pores produced are numerous, large and irreversible leading to cell death.
Our group has worked with the group of Prof. D. Knorr, Technical University of Berlin, to develop a new set of electrical pulses that is currently and globally, the better to control treatment parameters. It has been shown that the effectiveness of pulsed electric fields increases with the applied electric field strength. Although to achieve microbial inactivation is necessary to apply electric fields that generally exceed 10000-15000 volts / cm, the mean treatment temperature increases just as the electrical pulses that generate only last a few millionths of a second. This is the reason why this technology only affects the quality of food.
Its main uses food sanitation would be particularly sensitive to heat liquids (eg fruit juice) and, since that breaks the cell envelopes, the application on plant and animal tissues as a prelude to the process of extracting its components (eg to extract starch from potatoes, sugar beets, fruit juice etc).
Activities of the group "New Technologies in Food Preservation at the University of Zaragoza
Our group pioneered the study of these new methods of microbial inactivation in Europe, has designed and patented a new process of preserving / sanitation based on the application of ultrasound, working with research groups in Europe and the United States and has trained its members in aspects are considered more important in some of the most prestigious in the field (University of Washington, Technical University of Berlin, University of Reading, etc). Now, our efforts are focused on the study of food preservation by ultrasound and pulsed electric fields, but in the medium term, we intend to expand our research to other technologies such as pulses of light, high magnetic fields, etc. .
Our working method is to study the biological basis governing the effects of these technologies, the design of new processes and as a last step, conducting research specific food applications for transfer to industry. Logically, the state of development of our research differs with the different technologies, whereas in the study of ultrasound we are almost at the last stage, in terms of pulsed electric fields we are in the first.
http://www.consumer.es/seguridad-alimentaria/ciencia-y-tecnologia/2006/07/05/24173.php
early twentieth century began to study the feasibility of using electrical treatments for the sanitization of milk. In those years it came to using this technology to process large quantities of milk that were intended for human consumption without affecting consumer health. Despite the satisfactory results achieved so far, this technology was no longer used, no clear reason, and has been in recent decades when there has been a growing interest to the PEF, probably due to further improvement of technology and, above all, the rise of minimally processed foods. 
Treatment of milk with PEF is effective to inactivate vegetative forms but not spores and enzymes as required PEF treatment combined with other technologies. For example, PEF with mild heat or bacteriocins were obtained in this way, synergy between the combined technologies. Studies carried out so far with PEF were performed at laboratory scale and pilot plant. There is a large-scale plant with a capacity of 2000 L / h which allows the processing of liquid foods, particularly tomato juice. 
Ohmic heating is faster and has greater capacity penetration of microwaves, which makes it particularly useful in the case of particulate foods, sauces, fruit purees, liquid egg or meat products, among others. This type of treatment avoids overheating, allowing less deterioration in the constituents and reduced deposit formation, the latter being particularly important in foods rich in salts and proteins, for example, milk. 
Although ohmic heating is a promising technology for the moment little is known about the effect of this type of heating in the constituents of food. In the case of enzymes, inactivation occurs, as happens with microorganisms by thermal effect. 