A product such as potatoes is used for both home processing and food processing. In the first case, starch, alcohol, and fine flour are produced from potatoes, and in the second case, chips, crackers, mashed potatoes, etc. are made from it. Producers divide the entire range of potato processing products into four conditional groups: dried (these semi-finished products are intended for long-term storage for at least one year), fried (such products have a short shelf life of not more than three months), frozen (these products have a short shelf life - during t months or more) and, finally, canned (for short-term storage for a period not exceeding three months).
Raw materials for each of the above processing methods are subject to special requirements in terms of variety, shape, size, dry matter content and reducing sugars in tubers. For example, potato varieties with a high starch content (it should be at least 13-18%) are used for processing in order to obtain starch and alcohol. But in food production, preference is given to varieties with a low content of reducing sugars and high dry matter content, which determines the taste of the product. Accordingly, each of these methods of processing potatoes has its own characteristics. So, in the drying process, a significant mass of the water contained in it is removed from the feedstock. When moisture evaporates, the nutrients that are contained in the cells of fresh plant-derived products in dissolved form turn into a concentrate. At a certain concentration of nutrients in the solution, the osmotic pressure, which as a result of this occurs in it, prevents the absorption of nutrients by the cells of microorganisms.
As you know, it is the development of microorganisms that leads to rapid spoilage of products, therefore, at high concentrations, products can be stored without compromising quality and spoilage for a relatively long time. True, with an increase in the moisture content during storage, the development of microorganisms resumes. For this reason, the moisture level in dried vegetables should not exceed 12-14%. When drying from the surface of the processed product, crushed into small pieces, water evaporates with the subsequent removal of the formed vapors. For this, the raw material is heated, and the vapors are absorbed by some material and discharged with it.
The best option is to use hot air for drying. Heated moving air acts as a coolant, and then absorbs the resulting water vapor. With this processing method, certain varieties of potatoes are used. Preference is given to tubers of regular round shape, with thin skin and small eyes. The tubers should be large enough, and the solids content in them should not be less than 21%. The varieties bred for the middle zone of our country (Berlichingen, Oktyabrenok, Majestic, Epron, Lorch) are considered optimal. However, you can also use local varieties of potatoes, which meets the above requirements. The drying process involves several stages.
First, the potatoes enter the drying workshop. There, using special equipment, it is washed and calibrated to size. Then, on mechanical (or abrasive) potato peelers or on steam-thermal units, the washed and sorted potatoes are peeled. In modern factories, a more modern method of peeling is also used - using alkaline solutions. This processing method has certain advantages: it can significantly reduce waste during cleaning. Even the most even tubers still have numerous irregularities on their surface and indentations (the so-called eyes). You can’t leave your eyes, otherwise it will negatively affect the quality of the product, so all irregularities after general cleaning are cleaned by production workers using ordinary knives. Potatoes peeled from peel and extraneous inclusions are cut into plates or circles of equal thickness. The thickness and dimensions of the workpieces should not differ, because otherwise the pieces will not dry out evenly.
Sliced potatoes are sent to the so-called spariteres, where they are blanched. As a result of this procedure, enzymes are destroyed in the raw materials, which lead to darkening of the product. Since blanching is carried out using very hot water, in order to prevent raw potatoes from boiling and to wash starch off its surface, the raw materials are washed with cold water in a special shower wash. The processed pieces are laid on drying sieves at the rate of 15-18 kg of semi-finished product per one square meter of sieve surface. In most cases, for drying potatoes a belt dryer is used with the possibility of setting a certain temperature above each belt. For example, a temperature of about 55-60 ° is set above the upper tape, 65 ° above the second, 60 ° above the third, etc. The humidity of the finished product should not exceed 12%. To achieve this indicator, processing within 4-5 hours is required.
In second place in popularity among the methods of canning potatoes is freezing. Low temperatures are used to cool fruits and vegetables, as well as to freeze them. And in fact, and in another case, there are distinctive features.
For example, during cooling during processing, the raw material receives a minimum of mechanical damage. In addition, the integrity and viability of its cells is maintained. When frozen, vegetables undergo mechanical and technological processing (washing, cleaning, slicing, blanching), which leads to a violation of their physiological and biochemical processes. After that, they can only be stored at temperatures below 0 °. When freezing, the moisture that is contained in the cells and intercellular fluid turns into ice, which violates the integrity of the cell membranes in the entire mass of the product. Fast freezing with intensive cold supply helps to improve the quality of frozen vegetables. Modern freezers allow you to freeze vegetables at a temperature of the refrigerant (in its quality brine or air can act) from -25 ° to -35 °. By the end of the freezing procedure, the temperature of the product itself is -18 °. Frozen vegetables are stored at a temperature not exceeding -18 °.
This method of preserving potatoes is more expensive than drying. It requires sophisticated refrigeration equipment, and it is necessary not only for freezing, but also for the subsequent storage of semi-finished products. However, the demand for quick-frozen vegetables and fruits is growing (especially in winter), so such investments will quickly pay off. Processing of raw materials for freezing practically does not differ from the preparation of potatoes for canning in other ways. It includes washing, sizing, cleaning, cutting and blanching. The main difference is that in the production of frozen convenience foods, potatoes are rarely used on their own. Usually it is part of vegetable mixtures. Mixes are called semi-finished products for dishes. For their preparation, all vegetables are blanched, mixed and frozen in boxes and bags with a capacity of 0.5-1 kg or in banks with a capacity of up to 10 kg, which are sold to public catering networks. For industrial freezing, a cold store with a low temperature is used.
First, liquid coolants are cooled (a concentrated solution of calcium chloride, which does not freeze at low temperatures, may act as such) using a compressor working with liquid ammonia or another refrigeration unit. The chilled brine is piped into the freezers, cooling the air there, which in turn freezes the food. Also, the air can be cooled outside the freezer. Sometimes conveyor quick-freezing devices equipped with a conveyor with a metal belt are used.
So, for processing potatoes (without additional canning) you will need the following equipment: a lifting and emptying device, a receiving container, a unit for preliminary cleaning of the earth, dirt and sand, a washing unit with a discharge conveyor, a unit for dry cleaning, a sorting and sorting table, a calibration table mesh or radial (universal) installation, filling installation, conveyors, conveyors, elevators. Also, machines for slicing potatoes are needed, with which you can solve tubers with straws of rectangular cross-section (for french fries) and slices 1-1.5 mm thick (for chips). Almost all of this equipment can be used to process any fruits and vegetables with a rigid structure, not limited to one potato. As a rule, such technological complexes for processing vegetables are used at the enterprises of the canning, vegetable-drying and processing industries, at farmers and private enterprises.
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