Главная Production technology Drying of fruit and vegetables

Drying of fruit and vegetables

 

Infrared drying

Infrared drying. The most relevant and promising at the moment is drying food using infrared radiation. Infrared radiation of solids due to the excitation of molecules and atoms in the body due to their thermal motion. In the absorption of infrared radiation irradiated body it increases the thermal motion of atoms and molecules, which causes heating it. Energy transfer occurs from the body with a large capacity of heat transfer to the body with a lower potential. For foods infrared ray penetration depth is 6 - 12 mm. At this depth penetrates a small portion of energy of radiation, but the bed temperature lying at a distance of 6-7 mm from the surface of the material increases significantly more intense than with convection heating method. Shortwave infrared rays have a greater impact on food as due to the large penetration depth and better impact on the molecular structure of products. 

      infrared drying foods like process, based on the fact that the infrared radiation of a certain wavelength is actively absorbed by water contained in the product, but is not absorbed by the product to be dried with a cloth, so the removal of moisture possible at low temperature (40-60 degrees Celsius), which gives almost completely preserve vitamins, biologically active substances, natural color, flavor and aroma were dried products. Equipment for drying fruits and vegetables, meat and fish, grains, cereals and other food and non-food materials based on the use of infrared radiation is the most promising at the moment.

Drying of products using this technology allows you to save the content of vitamins and other biologically active substances in the dry product at the level of 80-90% of the feedstock. For short soaking (10-20 min.) Last drying product restores all its natural organoleptic, physical and chemical properties and can be used fresh or subjected to any type of cooking. Drying of products (drying fruits and vegetables, dry fish, meat, cereals, etc.) in such a way enables the production of a variety of food concentrates noodles: the first, second, third, meals, snacks, cereals, grains, fruit and vegetable powders that used in baking and confectionery industry, as a component of dry baby formula. Compared with the traditional drying vegetables, processed infrared drying after recovery have taste, as close to fresh. Furthermore, powders, past infrared drying, possess anti-inflammatory, and antioxidant properties detoksiruyuschimi. Application of products that have passed the infrared drying in the dairy, confectionery, bakery industry an opportunity to expand the range of food products with specific flavor characteristics. infrared drying gives products containing no preservatives and other contaminants, these products are not exposed to harmful electromagnetic fields and radiation. Needless infrared radiation is harmless to the environment and humans, as well as using its equipment for drying fruits, equipment for drying vegetables, meat, fish, grains, cereals, etc.

Last drying product is not critical to the storage conditions and is resistant to the development of microflora. To suhoprodukty can be stored without special packaging (at a low humidity environment), with the loss of vitamins comprise 5-15%. In airtight containers suhoprodukt can be stored up to two years. Drying gives the product a reduction in the amount of 3-4 times and 4.8 times in weight as compared with the feedstock (depending on the species). Reconstituted by soaking in water suhoprodukt can undergo any traditional cooking: boiling, frying, stewing, etc., and can also be eaten raw or dry form.
      However, attention should be paid not only the properties of the resulting suhoproduktov but especially drying equipment products using infrared radiation and processes based on this principle. Technology infrared drying wet products allows almost 100% use decal to suhoproduktu energy.

Since the water molecules in the product are to absorb infrared rays and agitated, heated, i.e., unlike all other types of drying energy is applied directly to the product water, thus achieving high efficiency at such a heat input is not necessary significantly to increase the temperature were dried product and the drying process can be carried out at a temperature of 40-60 degrees. Such drying of the product gives two advantages: First, with maximum temperatures of the product is preserved: the cells do not break, the vitamins are not killed without caramelizing sugar; second low temperature not heat drying equipment, ie there is no heat loss through the walls, ventilation. At the same time, infrared radiation at a temperature of 40-60 degrees to successfully destroy all of the microflora on the surface of the product, making suhoprodukt virtually sterile.
     Besides all the above drying equipment is universal and can process any vegetable and animal products to produce rapidly reconstituted dry foods. Equipment for drying fruits, equipment for drying fruits like all drying equipment used in this type of drying fruits and vegetables and other products, has the following advantages:
lowest specific energy consumption per 1 kg of evaporated water;
less than 1 kWh / kg (half of any dryers);
drying products are produced at a low temperature - 50-60 degrees Celsius;
Product drying is performed at a high rate - 30-200 min;
simplicity and reliability, low cost and high return on investment.

 

Microwave drying

 

Microwave technology - a major achievement of science and technology, product research decadal agricultural scientists and the military-industrial complex, which has no analogues in the world. With the help of microwave equipment can really solve actual problems of many industries - dried fish, meat, grains, fruits and vegetables, lumber, brick and fleeces, raw cotton, herbs, improve the quality of animal feed, extract from plant material compound, alternate toxic chemicals (pesticides natural nature). Microwave technology and created on its basis microwave equipment for drying fruits, vegetables drying equipment can not only dry products, but get food dyes, defrosted fish, meat, vegetables, berries and other foods carry bestemperaturnoe canning and more.
In the modern history of science and technology, micro technology has an unusual way - from the defense industry, bypassing the other branches of the economy, in household appliances, and only then - in science and industry. Currently intensification under microwave irradiation is used in many industrial processes: drying food (drying fish, meat, grains and cereals, fruits and vegetables drying), drying and gluing of wood, manufacture of porcelain and pottery products, construction, and development of oil fields etc. Microwave equipment becomes necessary technology component of large profitable industries. Microwave drying method based on the impact on the dewatered product of intense electromagnetic field of ultrahigh frequency (UHF). Under the influence of the microwave field water molecules (dipoles) are beginning to make the vibrational and rotational motion, focusing on the field with the frequency of its electric lines. Movement of molecules - this is thermal energy.The more water in a predetermined volume, the larger the molecules participating in this movement, the greater the heat energy is released. Thus, the heating occurs throughout the product, and the wetter areas receive greater energy. This occurs due to the removal of moisture, drying of the product and, simultaneously, - alignment of the humidity in the volume of the product. And while reducing raw material moisture drying process the product does not slow down, because the mechanism of the thermal conductivity does not play a key role here. Microwave drying of fish, meat, mushrooms, cereals, vegetables and fruit has a small time and relatively low temperature process that applied to foods causes a very high persistence of nutrients and vitamins. Energy source of microwave energy is the only energy source that provides their exceptional ecological purity. The only limitation of this method is relatively low (60%) of the energy conversion efficiency of the electric current to the energy of the microwave field in the microwave equipment. In this connection it is advisable to use microwave equipment at low humidities (below 50%), i.e. humidities in the range where the energy intensity of this method is lower than that of the convection method. It should be noted that under the influence of intense microwave field is almost complete destruction of the microflora (decontamination product), which greatly increases the shelf life obtained suhoprodukta and makes microwave equipment more effective means of industrial production. Drying fish, meat, mushrooms, grains, cereals, fruits and vegetables by microwave radiation has a high speed and high efficiency. Microwave equipment for drying fruits, equipment for drying vegetables and other foods, drying of the product with the use of microwave energy to replace currently used in most coolants being operated drying equipment can greatly simplify the process flow diagram of drying product, excluding all the processes and devices associated with the preparation of the coolant, and harmful emissions. Nowadays food products, dried using microwave technology in microwave equipment used in food production following:

Production of food for the first and second dishes, sauces and spices.
      Production of fast food.
      Production of baby foods.
      Manufacture of dietary products.
      Manufacture of products for athletes.
      Bakery.
      Milk production.
      Meat and sausage production.
      Confectionery manufacturing fillings, jellies, jams.
      Production of alcoholic and non-alcoholic beverages.
      Fish canning and preserves.

Health-care, recreation, catering, catering to children and schools. The use of natural dried ingredients, made ​​by microwave drying method allows food producers: Enrich product is dried, vitamins, biologically active substances, microelements and other beneficial substances.
To give the product taste, color and aroma of a natural product.
Apply suhoprodukt off-season and during the absence of fresh vegetables.
Ensure production of high quality products, microbiologically clean.
Significantly reduce waste production, waste management to resolve issues after processing raw materials.
Reduce the cost of storage and transportation of the product.
Significantly shorten the cooking time, energy and labor costs associated with the processing of raw vegetables, increase productivity in cooking catering up to 48 times.
Increase the shelf life of up to 1 year without additional chemical processing facilities.
Reduce production costs.

Convection drying

 

One of the most common methods of drying products is currently convective drying method. This method of drying products based on the transmission of heat dries the product due to the energy of the heated drying agent - air or gas mixture. Drying of foods with this method occurs when washing the product gas heated air, flue gases, superheated steam or other heat transfer fluids, which have a temperature different from the temperature of the material undergoing drying. In this drying process due to the heat energy imparted to the product is located in the evaporation product moisture, ash and moisture vapor drying agent carried. Distinguish convective drying of materials in the layer in which the dryer used in the washing of the material layer or article, the drying agent (tunnel, tube, loop, roll, turbine, belt, shaft dryers) and convection drying with the blowing nozzle of flat materials. Besides distinguish convective drying of materials or products in suspension and semi-weighted condition, which can be carried in a drum kit in a fluidized bed units, pneumatic tubes-dryers in a vortex, as well as by spray-drying. Equipment for drying vegetables, equipment for drying the fruit and any drying equipment based on this method has a simple apparatus. The plants have high specific energy, which range from 1.6 to 2.5 kWh / kg. However, this method has certain disadvantages relating to inefficient use of energy settings, such as, drying method is inevitably accompanied by heat loss to heating structures and the environment. The intensification of the drying processes such products need to raise the temperature of the coolant, which leads to overheating suhoprodukta, particularly during the final drying. In addition to this method of drying products have disadvantages, considerably reduce the quality of the final product. In this drying evaporation occurs only from the surface, which leads to the appearance of the film, drying and hinders quality deteriorates suhoprodukta: changes the color, taste and natural flavor of the product, reducing its recoverability soaking. High temperature and long duration of the drying contribute to the development of oxidation processes and lead to loss of vitamins and biologically active substances in suhoprodukte and does not contribute to suppression of primary microflora.

 

Sublimation drying

 

Sublimation drying products (freeze vacuum drying, also known as lyophilization or sublimation) - the removal of moisture from the frozen food in a vacuum.
      Currently, this method of drying products the most perfect, but at the same time also most expensive. This method was discovered in the early twentieth century, but was only used for the production of a rather limited number and range suhoproduktov for the military and aerospace.
      The principle of freeze drying is based on the physical fact that when the atmospheric pressure is below a certain threshold - the so-called "triple point" (for pure water: 6.1 mbar at 0 degrees Celsius) water can be in only two aggregate states - solid and gaseous, moving water in the liquid state under such conditions is impossible. If the partial pressure of water vapor in the environment is lower than the partial pressure of the ice, the ice product is transferred directly to a gaseous state without going through the liquid phase.
      The freeze drying product physically consists of two main stages (freezing, drying), and phase to dryness. The first step is to freeze the product at a temperature below its solidification point. The second stage - sublimation, ice or solvent crystals at very low temperatures, ie, drying of the product directly. A considerable effect on the quality suhoprodukta and time required for drying is freeze stage. The quicker and more deeply frozen product, the smaller the ice crystals formed in the product, the faster they will evaporate during the drying step for the second product and the higher the quality of the resulting product. Since the removal of the bulk of the moisture from the drying objects occurs at low temperatures (-20 ... -30 degrees Celsius), and their final drying is carried out also while sparing (above 40 degrees) temperature range, the result is a high degree of safety of all most biologically valuable components of the feedstock.

The largest application freeze vacuum drying technology has received in production of pharmaceuticals, enzymes, yeasts, herbal extracts and other objects that need to ensure the safety of all useful components suhoprodukte raw materials over long periods of time. sublimation drying of the product is one of the most modern methods of reversible preservation of microorganisms and biological products, which provides the best quality and high recoverability suhoprodukta lactobacilli with a minimum duration of the process and, consequently, the lowest cost.
      Since the ultimate humidity-vacuum sublimation materials is very low (about 2-5%), it creates all the prerequisites for long-term storage under uncontrolled temperature. Preserving freeze-drying in the above industries is advanced technology, and in some cases - has no alternative.
      In food production sublimatsonno-vacuum drying is used as a means of preservation by freezing fresh foods and remove them from the liquid, which allows almost completely, up to 95%, save them in nutrients, trace elements, vitamins and even original shape, natural flavor, color and smell for a long time (from two to five years) at varying ambient temperature (-50 to +50 degrees Celsius). Freeze-vacuum drying of food makes it unnecessary to use any whatsoever flavors, preservatives and dyes. One of the most important advantages of the vacuum drying of a small shrinkage starting material that gives the possibility to avoid their destruction and quickly restore sublimated suhoprodukty having a porous structure after drying by addition of water.

Method of freeze-drying preserved fruits, vegetables, dairy products, meat, fish, porridge and soups, mushrooms, spices. Products freeze-vacuum-drying have a very broad scope for use both as finished products noodles, or as semi-finished products for further industrial processing (confectionery, FOOD CONCENTRATE, meat and milk, perfume and other industries).
      High quality and usefulness of biological finished sublimated products due to the fact that treatment may be subject only to the fresh feed. Spoiled food freeze-drying is not maintained. Preservation of freeze-drying does not require the addition of any chemicals and other flavorings, preservatives, stabilizers and the like, which is another advantage. This fact is remarkable that the last freeze dried product is suitable for children and dietary.
      Weight sublimated suhoproduktov average taken from 1/5 to 1/10 of the initial mass. So lightweight sublimated suhoproduktov is extremely important for a substantial reduction in costs during transportation.
      Usually packed in sublimated suhoprodukty metallic sandwich bags with nitrogen filling weighing up to 2g 5000g, depending on the product.

Earlier in the food industry freeze-drying, vacuum was used mainly to fulfill the orders of military, defense and space industries, now it has been asked to prepare premium products.

 

Acoustic Drying

Acoustic method of drying products based on the impact on the dewatered product of intense ultrasonic waves. This drying process is cyclical wave knocks the moisture on the surface of the product, then the remaining moisture is evenly distributed through the capillaries, and the process is repeated. This occurs as long as the product does not reach a predetermined humidity. 

      Acoustic method allows to dry a wide range of materials: agricultural products (grains, vegetables, fruits, etc.), wood, cotton, drugs and herbs, paper, chemical and other industries.
      When acoustic drying of moisture is extracted from the product were dried under the influence of sound with the appropriate characteristics. The principal feature of the process: drying products occurs without increasing the temperature of products. Implemented "cold" drying. This circumstance removes all the negative consequences associated with the thermal effects on suhoprodukt. It therefore is the only drying method is suitable for drying heat-sensitive materials and is easily oxidizable. Processing of products of high intensity acoustic oscillations is beneficial to the physical and chemical properties and consumer suhoprodukta (eg, increases seed germination, etc.).
      Drying of products acoustic method differs from conventional methods and speed of production suhoprodukta. For example, when drying enzymes (disintegrating at a temperature of 40 degrees Celsius) in the acoustic field, the drying rate compared to the product by vacuum increases in 3-4 times.

 

Conductive drying

 

Conductive method for drying food products based on a dried product of the heat transfer through direct contact with the heated surface of the drying equipment.
      For drying of foodstuffs used this method is not frequently. High quality final suhoprodukta can not be achieved due to uneven moisture content of the final product; product contacting the heated surface during drying, is overdried, resulting in the recovery process irreversibility, and due to the high temperature (320-340 degrees centigrade) into the drying chamber of the equipment, the end suhoprodukt loses 30-40% of vitamins and biologically active substances becomes brittle. Greater use of this method of drying is when drying lumber, as well as raw materials and products in the textile industry.
      When the conductive heat-drying of the product is reported only on the wet material and the heating surface is transferred to the exposed surface of the product, followed by its return to the environment. The amount of heat received from the heating surface is expended in the evaporation of moisture on heat loss by radiation and convection surface suhoprodukta open to the environment. The share of these losses in the total heat consumption is low and is at most 5.3%, which makes drying equipment sufficiently effective. However suhoproduktov consumer quality and the content of starting materials make this method of drying products are rarely used.

 

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