Food Processing microwave
Proper application of microwaves in food reduces the deterioration of their components and improves the organoleptic characteristics
Although heat treatment microwave foods known since late 1940, it was not until the 60's when the household microwave became popular, especially in the U.S., where he began to use first. The advantages over conventional treatments are speed, cleanliness, selective heating of food, lack of contact hot surfaces, reducing costs, improving quality and saving energy.
Microwaves are part of the electromagnetic spectrum in the frequency range covered between the areas of infrared and radio waves (300 MHz-300 GHz), this range corresponds to wavelengths between 1 m and 1 mm. Because of the proximity between the bands of microwave and radio waves can overlap the first in the area of \u200b\u200bthe radar waves. In order not to interfere with these uses, domestic and industrial microwave ovens operate at frequencies of 2450 MHz and 915 MHz
The microwaves are generated in the magnetron, a device that converts electrical energy into an electromagnetic field. When microwaves are applied to food, the polarity of the electromagnetic field changes direction causes several million times per second. Thus, polar and ionizable components (water and mineral salts, mainly) trying to orient with the direction of the electromagnetic field, producing friction and collisions between molecules that lead to an increase in temperature inside the food, the fact that unlike microwave heating with traditional heat treatments. Once heat is generated in the food, it is transferred by conduction and convection heat. Limits
microwave
The lack of uniformity in the distribution of temperature is one of the biggest drawbacks of the microwave as it affects the final product quality in relation to the effects of microwaves on microorganisms Some studies raised the possibility a few years ago that there were non-thermal effects causing the fatality. However, after it has been shown that the microbial inactivation exclusively due to the heat generated inside the food, with microbial inactivation curves similar to those of conventional heat treatments. Despite the many advantages offered by microwave treatment, there are disadvantages such as limited application to foods high volume, high cost of facilities and, above all, lack of uniformity in the temperature distribution inside the food, one of the aspects that affects the final quality of the treated product.
When there is no adequate control of the uniformity of heating may appear "cold spots" in which the microbial inactivation is incomplete, and "Hot spots", where thermal degradation can occur with consequent excessive expense on the sensory properties and nutritional value of food. Therefore, we need to know and control the factors affecting the heating of both those related to equipment (furnace type, frequency, power) as the characteristics inherent to the food (composition, physical properties, size, shape). One option to improve the uniformity of heating liquid foods is making continuous flow treatments. In general, we have seen that these treatments provide effective heating for pasteurization, for example, milk and orange juice, retaining and even improving their nutritional and sensory properties compared to conventional treatments carried out in heat exchangers.
microwave applications
addition to the well-known uses in the home for heating, cooking and thawing, have developed various industrial equipment that has greatly expanded the range of application of microwaves in food. Thus, the microwaves have been used in recent years in applications such as drying process for the manufacture of pasta, blanching vegetables and pasteurization of packaged foods.
Perhaps the most successful industrial use is the use of microwaves to raise the temperature of frozen pieces of meat, fish, poultry, vegetables and fruits. Today, in the U.S. there are over 400 plants that work for this purpose. This application is particularly appropriate where large pieces of meat and fish. During this process, parts found at -20 ° C must pass or -2 to -5 ° C, with the aim of enhancing, well, your cutting or filleted for subsequent packaging and marketing. Traditionally, the process is carried out leaving in cold weather for several days, which caused loss of fluids such as blood and protein solutions, significantly impairing quality. However, when using the microwave for this purpose, the process is very fast. For example, in parts of 10-40 kg is achieved by reaching the required temperature in 5-10 minutes.
Similarly, in the dairy industry, the microwaves are also used in the treatment of frozen butter, which must remain frozen at very low temperature until further cutting and marketing to prevent the development of rancidity. An effective method to raise the temperature of the butter and, thus, facilitate cutting, the microwave treatment. Currently, there are at least four large-scale plants working in England. Another application of microwaves which is proving attractive to industries is the pre-cooked bacon. We have seen that when the bacon is heated in a traditional team like the grill, there are substantial losses of water and fat, and, therefore, food structure shrinks. In addition, the fat melts into the hot grill surface and deteriorates significantly, reducing its quality. However, the microwaved bacon better preserved in its original composition and, consequently, product dimensions vary little. In the U.S. alone there are over 30 teams for continuous process.
In recent years it has developed a team to carry out heating by microwave continuous flow of various types food more or less viscous, and even inhomogeneous. It has been found that could be particularly useful for treatment of high temperature pasteurization and short and UHT milk, cream, yogurt, sauces, purees and baby foods. Due to the absence of hot surfaces in contact with food and speed of the process (140 ° C are reached in less than 1 second), prevents overheating, while preserving product quality and reducing processing costs.
For the application of microwaves in packaged foods, have also devoted much effort in developing specific types of packaging for microwave treatment. Depending on the purpose of warming, there are passive containers (glass, ceramics, paper, cardboard and plastic), which do not interfere with microwave and active packaging, consisting of thin metal pieces between sheets of cardboard or metallic polyester, which affect food warming improving uniformity. The latter are particularly useful in the case of heterogeneous foods, for example, lasagna, pizza, croissant, potato chips and foods that have to reach high temperatures, as is the case of popcorn.
EFFECTS "?
Microwaves are non-ionizing radiation, ie do not break chemical bonds or molecular cause changes in food components. The nature of chemical reactions that occur is identical to that of conventional heating.
However, if there is proper control of heat distribution during the process, hopefully in quantity less deterioration of the components and even better organoleptic characteristics, when subjected to microwave food compared with those treated by conventional process conducted under identical conditions of heating, holding and cooling temperature.
Although sometimes studies have emerged that seemed to point to possible adverse health effects of processed food products with microwave, after more than half a century of use in the home, could not corroborate any of the adverse effects identified.
http://www.consumer.es/seguridad-alimentaria/ciencia-y-tecnologia/2006/04/05/23073.php
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