Alternatives to the thermal treatments to guarantee the safety of the food
by MAITE PELAYO
publication: on June 18, 2009.
The continuous ultra high pressure homogenisation, allows to obtain sure food and with the same nourishing qualities and organolépticas of the fresh air.
The higienic treatments of food based traditionally on thermal processes, though effective, they do not satisfy the expectations of a consumer increasingly demandingly with the organoleptic and nutritional quality of the products. The application of new alternative technologies like the ultra-high pressure homogenization (UHPH) to support the nutritional value of the food and to improve his safety and functionality is one of the priorities both of the food-processing industry and of the centers of investigation that develop his works in this field.
- Imagen: Nicole Cordeiro - This new technology, capable of submitting to some products to homogenization with pressures of up to 400 megapascals (MPa), it would allow to replace the traditional process of pasteurization and to obtain a raw milk or other lacteal derivatives of better flavor, texture and conservation. In the Special Center of Investigation Plant of Food technology (CERPTA), of the Autonomous University of Barcelona (UAB), the investigators have studied this technology in a joint project with other universities and European companies. The CERPTA, was the specialized center dedicate to the study of the high pressures in food, has been the coordinator of this European project which aim consists of the development and optimization of an equipment in I continue of ultra-high pressure for homogenization (UHPH) for his application in animal milk and different types of vegetable milk, since liquefied of soybean and of almonds.
The effect of the high pressures
The pressure, together with the friction and other physical forces, provokes the unactivation of microorganisms that contaminate the food The technology UHPH, based on the same beginning that the conventional homogenization, is based in making spend the fluid food across a valve and in the resistance that allows to obtain very high pressures. The effect combined of the pressure together with the friction and other physical forces it provokes the unactivation of the microorganisms that contaminate the food simultaneously that also meet affected enzymes, own or foreign to the food, which they can cause his alteration, for what it improves his conservation. Previous investigations already had demonstrated how on having applied pressure there takes place an increase of the permeability or the break of the membrane, causing the cellular death and preventing a regeneration or reactivation of the cell.
The studies realized in the CERPTA on the utilization of this new technology have showed that the utilization of pressures of 300 MPa, with a temperature of entry of 30 º C, had the same microbiological and physicochemical results that a milk pasteurized conventional, with the advantage of which the milk UHPH thermically was not presenting the characteristic flavor to stew of the treated milk and, at the same time, he was avoiding the trend to taken the cream during the storage. Also was observed that UHPH's treatments from 200 to 330 MPa of the milk were modifying the properties of acid coagulation to produce yogurt, diminishing the total time of coagulation and increasing the firmness of these gels. The yogurts elaborated from milk UHPH were showing better results that made in a conventional way, to that it is necessary to add milk in powder in his formulation to obtain a suitable firmness.
At the same time, the yogurts UHPH were showing also better texture and capacity of water retention, which was translated in a minor loss of whey during the storage. This indicates the possibility of using UHPH's technology to elaborate yogures with good sensory characteristics, without having to incorporate solid not oily (as the milk in powder) in the milk. For all this, the technology UHPH is revealed as an excellent alternative to the traditional treatments of cleaning of the milk and his derivatives and offers a few ideal levels of food safety but with advantages added as for quality organoleptics, very valued by the consumer, for what they ensue from great interest for the industry of the sector.
A previous investigation, realized also in the CERPTA on the application of UHPH's treatments, revealed that this technology allows to reduce of significant form the presence of Escherichia coli in food as the milk, the juices of fruits or other liquid food. The serotip O157:H7 of the bacterium Escherichia coli, very virulent, is involved in several serious cases of toxinfection food.
Though the majority they have associated to the consumption of meat contaminated products, the milk and other liquid food also can be vehicles of this microorganism, of there the importance of the discovery. The thermal pasteurization obtains his destruction, but it implies the modification of certain nourishing and sensory important properties. This technology might be applied in the reduction of other pathogenic microorganisms, as Salmonella or Listeria monocytogenes.
The homogenización of the milk is a habitual practice in the lacteal industry that consists of making it happen under pressure raised across orifices or very narrow valves that do that the size of the oily globules diminishes approximately to 1/5 of initial (approximately 5 micrometers). Also there are destroyed partially the conglomerates of casein and the pieces stick fast to the surface of the oily globules. These two phenomena stabilize the emulsion retarding the decantation and coalescence (property of the things of joining or to be fused). The homogenización improves the consistency of the milk, increases his whiteness and makes more digestibles the lipids provided that the lipasas digestibles (enzymes that break the fats and they help to his digestion) penetrate better in a thinner emulsion.
The soft technologies or methods of food conservation without heat application are slightly aggressive and have the advantage of offering products very similar to the fresh air, but without losing his guarantees as for food safety.
• The technology of the electrical pulses is based on the exhibition of the food to an electrical intense field that provokes the formation of pores in the cellular microbial membranes changing his permeability.
• The food irradiation, that is to say his exhibition to doses established of energy in the shape of beams or particles (normally gamma or electrons) in a controlled way, eliminates bacteria, parasites and insects.
• The treatment by means of touched light consists of the successive application of pulses or sparkles of light with a spectrum between the ultraviolet one and the infrared near one with a very short duration, which provokes that the transmitted energy is very intense though the total consumption of the process is moderate.
• The application on the food of a high pressure of a uniform way during a variable time that can range from a few minutes up to enclosedly some hours, takes the destruction of microorganisms as an effect.
• The bioconservation bases on the effect of the so called bioconservants: microflora natural or controlled of the food and / or his antibacterial products that increase the useful life and increase the safety of the food..
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