Raw material cleaning is one of the most labor-intensive operations in food preservation technology. When cleaning, inedible parts of raw materials are removed - fruit stalks, sepals of berries, grape ridges, seed chambers, skins of some types of raw materials. Many of these operations are mechanized. There is, for example, a machine for cutting grains from corn cobs, peeling coops and tubers with abrasive materials, etc. However, when cleaning raw materials, manual piles are often used. The same can be said about the subsequent processes of grinding raw materials, which are often combined with cleaning operations.
Grinding of raw materials is carried out to give it a certain shape, for best use container capacity, to facilitate subsequent processes (for example, roasting, evaporation, pressing) . These operations are usually carried out by machine, although sometimes the use of manual labor is also found here.
Abroad, for example in Germany, they produce machines for peeling and cutting apples, pears and citrus fruits. The machines peel the fruit from the skin, cut them into slices, halves and slices, and also remove the core from apples and pears. These machines are carousel type. Fruits are loaded manually. All subsequent operations - cutting the skin, cutting the fruit, removing the core with a punch and cutting into halves or slices - are performed automatically.
It is very difficult to carry out mechanized cleaning of peppers from the seed chamber. In many factories, this operation is still carried out manually using special conical tubes. Prototypes of a machine for cleaning peppers were made at the Odessa Cannery. Canning plants in our country are supplied with Hungarian pepper-cleaning and cutting machines for large-fruited peppers. The fruits are loaded into the carriers of the machine manually. All other operations are mechanized: squeezing the fruits to fix them, drilling the core with rotating knives, cutting the fruits into slices, pushing them through the punch grid and unloading.
It is especially difficult to mechanize the removal of integumentary leaves from onions. Although the so-called intermittent pneumococci cleanings work quite successfully, however, before entering these machines, it is necessary to manually cut off the lobes and necks of the bulbs. After the connection of the skin with the bulb is broken, the bulbs enter the grater type machine, in which they rub against each other and against the side surface and the rotating bottom with notches, while the skin is blown off by compressed air at a pressure of 0.6 MPa. A significant number of bulbs peeled on these machines have to be cleaned by hand.
To remove the skin from coops, graters with an abrasive surface and steam treatment under steam pressure of 0.2–0.3 MPa for 10–30 s are also used. When leaving the zone high blood pressure outwards as a result of self-evaporation of moisture in the subcutaneous layer, the peel is torn and then easily separated in a washer-cleaner under the action of rotating brushes and water jets.
Some types of fruit and vegetable raw materials can be chemically peeled. For this purpose, the processing of fruits in hot solutions of caustic soda is used. When exposed to hot alkali, hydrolysis of protopectin occurs, with which the skin is attached to the surface of the fruit, and soluble pectin is formed. The same happens with the cells of the skin itself. As a result, the skin is separated from the pulp of the fruit and is easily washed off with water jets during subsequent showering. For alkaline peeling of peaches, a 10% solution of caustic soda is used, heated to 90 ° C, in which the peaches are kept for 3-5 minutes. Coops are treated with a 2.5-3% solution of caustic soda at a temperature of 80-90 ° C for 3 minutes. After alkaline cleaning, the shells are washed from the skin and alkali in carborundum washing machines with the abrasive surface removed. There are other options for alkaline cleaning of carrots, according to which carrots are treated with a 5-8% solution of caustic soda at a temperature of 95-100 ° C, after which they are washed in a drum washing machine with water supplied under a pressure of 0.8-1.0 MPa.
When cleaning the fruits, the stalks can be separated from the fruits and berries on rubber-coated rolls rotating towards each other. The diameter of the rolls and the gap between them must be selected so as to ensure the capture and separation of the stalks without damaging the fruit.
A wide variety of mechanical devices are used to grind raw materials into shapeless pieces or a homogeneous puree-like mass, which is done, for example, before the subsequent squeezing of the pulp on presses or when preparing raw materials for moisture evaporation. All kinds of crushers are used here (two-roller, one-and two-drum, knife), plunger and disk homogenizers (machines for fine grinding, creating a homogeneous-homogeneous mass), mashers, etc. In many of them, fruits and vegetables are subjected not only destruction or crushing, but also a strong impact on a fixed deck with the help of a working body that develops a large centrifugal force during rotation. As a result of this treatment, the cytoplasmic membranes (shells) of fruit cells are damaged, cell permeability increases irreversibly, and the juice yield during subsequent pressing is quite high. The same can be said about chopping tomatoes on mashers before their subsequent boiling in vacuum-drying apparatus. Typically, the grinding of tomato pulp 30 is carried out sequentially on two or three mashers with a gradually decreasing diameter of the perforations (holes) of the sieves. For example, in built-in rubbing machines, the sieves have the following perforation diameters (in mm): the first -1.2; the second is 0.7; third - 0.5.
The finer the grinding, the greater the evaporation surface area and, consequently, the greater the moisture evaporation rate. Calculations show that the evaporation surface area during crushing of tomato pulp particles to a diameter of 0.7 mm increases by 71% compared to the surface area of particles with a diameter of 1.2 mm, and by another 42% when leaving the third sieve.
The purpose of removing inedible parts of fruits and vegetables is to increase the nutritional value of the finished product and intensify diffusion processes during preliminary technological processing. The inedible parts of raw materials include peel, seeds, bones, stalks, seed chambers, etc.
In machines and apparatus for peeling root crops, a mechanical method, thermal or chemical effect on the processed product can be applied.
Equipment for mechanical cleaning of raw materials
Continuous potato peeler KNA-600M (Fig. 1) is designed for peeling potatoes. The working bodies are 20 rollers 7 with an abrasive surface, forming four sections with a wavy surface with the help of partitions 4. Shower 5 is installed above each of the sections. All elements of the machine are enclosed in case 1.
The raw material moves along the rollers in the water from the inlet to the outlet. Due to the smooth movement and continuous irrigation, the blows of the tubers against the walls of the machine are weakened. The peel is removed by rollers in the form of thin scales. The raw material is loaded into hopper 2 and enters the first section on fast-rotating abrasive rollers that peel the tubers from the skin. Raw materials move along a wavy surface
Rice. 1. Potato peeler KNA-600M
rollers while peeling. After passing through four sections, the tubers, cleaned and washed in a shower, approach the unloading window and fall into tray 6.
The water supply is regulated by a valve 3, the waste water with the peel is released through the pipe 9.
The length of stay of the tubers in the machine and the degree of their cleaning are regulated by changing the width of the window in the partitions, the height of the flap at the unloading window and the angle of the machine to the horizon (lift mechanism 8).
Technical characteristics of the KNA-600M potato peeler: productivity for peeled potatoes 600...800 kg/h; specific water consumption 2...2.5 dm3/kg; electric motor power 3 kW; roller speed 1000 min-1; overall dimensions 1490 X1145 x 1275 mm; weight 480 kg.
The machine for dry peeling of root crops was developed by the Dutch company GMF - Conda (Fig. 2).
The machine consists of a belt conveyor and brushes rotating around its own axis. The brushes are installed in such a way that they contact the conveyor belt through the roots being cleaned. Peeled root crops from the hopper fall into the gap between the conveyor belt and the first brush. The rotation of the brushes informs the root crops of the translational movement along the length of the tape, and the tape itself moves in the opposite direction, resulting in a long-term contact of the brushes with the root crops. First, the rough parts of the peel are removed, which are cleaned with a brush, under the action of centrifugal force they fall onto a stainless steel tray.
Rice. 2. Root dry cleaning machine
Cleaning ends at the end of the tape. The machine can handle vegetables of various sizes, and by changing the speed of the brushes, the distance between the belt and the brushes and the inclination of the machine, a good cleaning quality is achieved.
The amount of waste depends on the preliminary treatment of root crops (steam, alkaline, etc.).
The brushes are made of high-strength synthetic fibers that clean well. A feature of the design is the high speed of the brushes. Root crops are processed within 5...10 s.
The RZ-KChK onion peeling machine is designed to remove cover leaves, wash and inspect it (Fig. 3).
The machine consists of a loading conveyor 1 for feeding onions with a pre-cut neck and bottom to the cleaning mechanism 4, a paddle conveyor 3 for moving the bulbs through the cleaning mechanism, an inspection conveyor 8 for selecting unpeeled bulbs, a screw conveyor 6 for removing waste and a conveyor 9 for returning unpeeled bulbs back to the car. All conveyors are installed on the frame. The machine has frame 2, air cleaner 7, right 5 and left 10 collectors.
The machine works as follows. Bulbs, which have cut off the neck and bottom, in portions (0.4 ... 0.5 kg) are fed by the loading conveyor to the cleaning mechanism. Here, the outer leaves are torn by the abrasive surface of the rotating discs and blown away by compressed air, which enters through the left and right collectors. After cleaning, the bulbs go to the inspection conveyor, where unpeeled or incomplete specimens are manually selected and returned to the loading conveyor using a special conveyor. The peeled bulbs are washed with clean water coming from the collectors.
Waste (2...7%) is removed using a screw conveyor.
Machine capacity 1300 kg/h; energy consumption 2.2 kWh, air 3.0 m 3 /min, water 1.0 m 3 /h; compressed air pressure 0.3...0.5 MPa; overall dimensions 4540x700x1800 mm; weight 700 kg.
Garlic peeling machine A9-KChP is designed to divide its heads into slices, separate from the husk and remove it to a special collection.
Rice. 3. Onion peeling machine RZ-KChK
Machine A9-KChP of rotary type, which operates continuously, consists of a loading hopper, a cleaning unit, an external inspection conveyor and a device for removing and collecting husks. All units of the machine are mounted on a common frame.
The loading hopper is a container, the front wall of which is made in the form of a flat gate for regulating the supply of the product. The bottom of the hopper has two parts: one is fixed, the other is movable, swinging around the axis and providing a continuous supply of product from the hopper to the receiver.
The main body of the machine is the cleaning unit, which consists of four rotating working chambers. Each of them is a cast aluminum cylindrical body, open at the top and bottom, with an internal fixed stainless insert, mounted on a guide pin to match the compressed air holes in it and in the body. The bottom of the chamber is a fixed stainless disc, and the lid is a middle fixed disc made of textolite.
Compressed air is supplied to the working chambers with the help of nozzles that ensure the achievement of sonic and supersonic jet velocities. The cut-off and supply of compressed air to the chambers are performed by a cylindrical spool on a hollow shaft.
The device for removing and collecting the husk includes an air duct, a fan and a collector.
Garlic (in heads) is fed along an inclined conveyor into a hopper, the bottom of which makes an oscillatory movement, due to which the product evenly enters the feeder, and from there to the dispensers. When garlic is fed into the bunker of the machine manually, its technical productivity is reduced to 30...35 kg/h.
Four dispensers rotating with a disc periodically pass under the feeder and are filled with garlic (2...4 heads). After exiting from under the loading opening, the chamber is covered from above with a disk, forming a closed cavity into which compressed air is supplied. Dry heads of garlic are satisfactorily cleaned at an operating pressure of compressed air of about 2.5-10~:5 Pa, moistened - up to 4-10~5 Pa. Next, the peeled garlic is fed to the inspection conveyor.
Technical characteristics of the machine A9-KChP: productivity 50 kg/h; operating pressure of compressed air 0.4 MPa; its consumption is up to 0.033 m 3 / s; the degree of purification of garlic 80.. .84%; installed capacity 1.37 kW; overall dimensions 1740x690x1500 mm; weight 332 kg.
The main methods of cleaning raw materials
In food production, some raw materials (such as potatoes, root vegetables, fish) are cleaned to remove the outer coverings (skins, scales, etc.).
At catering establishments, there are mainly two methods for removing the surface layer from products - mechanical and thermal.
mechanical method used for cleaning root crops and fish. The essence of the cleaning process of vegetables with a mechanical method is to abrade the surface layer (peel) of the tubers on the abrasive surface of the working parts of the machine and remove the particles of the peel with water.
thermal method It has two varieties - steam and fire.
The essence of the steam cleaning method is that during short-term treatment of root crops with live steam at a pressure of 0.4 ... 0.7 MPa, the surface layer of the product is boiled to a depth of 1 ... 1.5 mm, and with a sharp decrease in steam pressure to atmospheric peel cracks and easily peels off as a result of the instantaneous conversion of the moisture of the surface layer of the tuber into steam. Then the heat-treated product is washed with water with simultaneous mechanical action of rotating brushes, which leads to the removal of the peel and partially cooked layer from the tubers.
Steam potato peeler (Fig. 3) consists of an inclined cylindrical chamber 3, inside which the screw rotates 2. Its shaft is made in the form of a hollow perforated pipe, through which steam is supplied at a pressure of 0.3 ... 0.5 MPa, with a temperature of 140 ... 160 ° C. The product arriving for processing is loaded and unloaded through lock chambers 1 and 4, which ensures the tightness of the working cylindrical chamber 3 in the process of loading and unloading the product. The screw drive is provided with a variator that allows you to change the rotational speed, and, consequently, the duration of product processing. It has been established that the higher the pressure, the less time is required for the processing of raw materials. In a continuous steam potato peeler, the raw material is exposed to the combined effect of steam, pressure drop and mechanical friction when the product is moved by the screw. The auger distributes the tubers evenly, ensuring uniform steaming.
Fig 3. Schemes of continuous steam potato peeler:
1 - unloading lock chamber; 2 - auger; 3 - working chamber;
4 - loading lock chamber
From the steam potato peeler, the tubers enter the washing machine (piler), where they are cleaned and peeled off.
With the fire cleaning method, tubers in special thermal units are fired for several seconds at a temperature of 1200 ... 1300 ° C, as a result of which the peel is charred and the upper layer of tubers is boiled (0.6 ... 1.5 mm). Then the processed potatoes enter the peeler, where the peel and the partially cooked layer are removed.
The thermal cleaning method is used on production lines for processing potatoes at large catering establishments. Most catering establishments mainly use the mechanical method of cleaning potatoes and root crops, which, along with the significant disadvantages of this method (a fairly high percentage of waste, the extreme importance of manual post-cleaning - removing eyes), has certain advantages, the main of which are: the obvious simplicity of the root crops cleaning process using abrasive tools, compact machine design of the process, as well as lower energy and material costs compared to thermal methods of root crops cleaning (absence of the extreme importance of steam, fuel consumption and the use of a washer-cleaning machine).
The mechanical method of cleaning potatoes and root crops is implemented on special technological machines that have a number of modifications in terms of productivity, design and applicability.
Sorting of raw materials by quality (inspection) is carried out especially carefully. Remove fruits with a damaged surface, immature, rotten, moldy, as well as foreign matter. As a rule, raw materials are sorted manually at conveyors, although for some types of raw materials, in particular tomatoes, green peas, automatic systems for express quality analysis have been developed, which include devices that sort by size, color and weight. For tomatoes, an automatic electronic sorter is used.
Sorting by size (calibration) is necessary in order to conduct the technological process, to provide a marketable, attractive appearance the finished product, adjust the intensity of heat treatment depending on the size of the fruit and reduce the amount of waste during mechanical cleaning.
Raw material cleaning
The purpose of cleaning is to get rid of inedible or low-value parts (pits, skin, sepals, stalks, seed nest, bones, viscera, scales, etc.).
Chemical, steam-thermal, pneumatic, refrigeration and mechanical cleaning methods are used.
The peel of the fruit is chemically removed. To do this, they are processed in a hot (80 - 90 ° C) solution of caustic soda, the concentration of which varies from 3 to 18%, depending on the type of processed fruit.
Root crops and potatoes are peeled in a steam-thermal way, for which a steam-thermal apparatus and steam blanchers are used.
Steam-thermal cleaning, in comparison with chemical cleaning, is more in line with the conditions of the saving technology, but is accompanied by significant losses of vitamins.
The refrigeration method for cleaning raw materials is based on instant, sharp freezing of the skin and subcutaneous layer of the fruit with a refrigerant and subsequent removal of the exfoliated skin in a brush washer. This method preserves the biochemical composition of raw materials, but requires special expensive equipment.
The pneumatic method is used to peel onions. The bulbs are taken one by one by grippers from the loading hopper and dumped into the pneumatic chamber, where they are exposed to compressed air from a nozzle installed tangentially to the inner surface of the pneumatic chamber. The peeled bulbs are set with the rhizome down by means of conical rotating rollers, while the upper and lower knives cut off the rhizome and the neck of the bulbs.
Root crops and potatoes can also be peeled mechanically on root peelers with an abrasive surface. The mechanical method is the least economical, since an increased amount of waste is generated. However, this method does not affect the biochemical composition of the raw material and there is no need to use chemical reagents. Therefore, the application mechanical cleaning raw materials sent for the preparation of canned food for baby food is quite justified.
In food production, some raw materials (such as potatoes, root vegetables, fish) are cleaned to remove the outer coverings (skins, scales, etc.).
At catering establishments, there are mainly two methods for removing the surface layer from products - mechanical and thermal.
mechanical method used for cleaning root crops and fish. The essence of the cleaning process of vegetables with a mechanical method is to abrade the surface layer (peel) of the tubers on the abrasive surface of the working parts of the machine and remove the particles of the peel with water.
thermal method It has two varieties - steam and fire.
The essence of the steam cleaning method is that during short-term treatment of root crops with live steam at a pressure of 0.4 ... 0.7 MPa, the surface layer of the product is boiled to a depth of 1 ... 1.5 mm, and with a sharp decrease in steam pressure to atmospheric peel cracks and easily peels off as a result of the instantaneous conversion of the moisture of the surface layer of the tuber into steam. Then the heat-treated product is washed with water with simultaneous mechanical action of rotating brushes, which leads to the removal of the peel and partially cooked layer from the tubers.
Steam potato peeler (Fig. 3) consists of an inclined cylindrical chamber 3, inside which the screw rotates 2. Its shaft is made in the form of a hollow perforated pipe, through which steam is supplied at a pressure of 0.3 ... 0.5 MPa, with a temperature of 140 ... 160 ° C. The product arriving for processing is loaded and unloaded through lock chambers 1 and 4, which ensures the tightness of the working cylindrical chamber 3 in the process of loading and unloading the product. The screw drive is provided with a variator that allows you to change the rotational speed, and, consequently, the duration of product processing. It has been established that the higher the pressure, the less time is required for the processing of raw materials. In a continuous steam potato peeler, the raw material is exposed to the combined effect of steam, pressure drop and mechanical friction when the product is moved by the screw. The auger distributes the tubers evenly, ensuring uniform steaming.
Fig 3. Schemes of a continuous steam potato peeler:
1 - unloading lock chamber; 2 - auger; 3 - working chamber;
4 - loading lock chamber
From the steam potato peeler, the tubers enter the washing machine (piler), where they are cleaned and peeled off.
With the fire cleaning method, tubers in special thermal units are fired for several seconds at a temperature of 1200 ... 1300 ° C, as a result of which the peel is charred and the upper layer of tubers is boiled (0.6 ... 1.5 mm). Then the processed potatoes enter the peeler, where the peel and the partially cooked layer are removed.
The thermal cleaning method is used on production lines for processing potatoes at large catering establishments. Most catering establishments mainly use a mechanical method of cleaning potatoes and root crops, which, along with significant disadvantages of this method (a fairly high percentage of waste, the need for manual post-cleaning - removing eyes), has certain advantages, the main of which are: the obvious simplicity of the process of cleaning root crops with the use of abrasive tools, compact machine design of the process, as well as lower energy and material costs compared to thermal methods of cleaning root crops (no need to use steam, fuel and the use of a washer-cleaner).
The mechanical method of cleaning potatoes and root crops is implemented on special technological machines that have a number of modifications in terms of productivity, design and applicability.
