Apparatus for keeping food hot. Apparatus for keeping food hot and heating
The specificity of public catering enterprises lies not only in the use of modern equipment and production technology, but also in its implementation in a short time at the appropriate cultural and aesthetic level with the help of a variety of auxiliary thermal and refrigeration equipment, as well as automated dispensing facilities individual species culinary products.
Equipment for dispensing food combines a group of thermal apparatus designed to perform various operations not related to the process of thermal processing of products. This includes: heat racks, used for short-term snoring of hot dishes and heating plates; thermostats used to keep drinks hot; food warmers used to keep first and second courses, sauces, and various culinary products hot.
Used for heating and keeping food hot various types gas and electric stoves.
The most common is the electric bain-marie stove EPM-ZM (Fig.), used mainly for the service sale of first courses.
Rice. Diagram of the electric bain-marie stove EPM-ZM: a - design; 1 - body; 2 - input panel; 3 - switch; 4 - board; 5 - burner; b - communication wiring diagram
The main working part of the stove is a cast iron burner mounted on support adjustment screws that allow the planes of the burner to be aligned with the side surface of the body. To regulate the power of the burner, the stove is equipped with an input panel and a packet switch. In the first 20 ... 30 minutes, the stove is turned on at maximum power to heat it up. After this, the burner is switched to medium or low heat, depending on the required temperature and the amount of product to be heated. The power consumption of the stove is 2.5 kW. Electrical safety is ensured by grounding and protective shutdown (Fig.).
Rice. Electrical diagram of the EPM-ZM stove: a - general scheme; E - burner; S - switch; X- terminal block; b - communication wiring diagram
For heating and keeping hot first courses in large containers when serving them in self-service canteens, they are used. electric stove bain-marie EPM-5 (Fig.).
Rice. Diagram of the electric bain-marie stove EPM-5: 1 - frame; 2 - input shield; 3 - switch; 4 - burner; 5 - table; 6 - shelf; 7 - bushing for cable entry; 8 - grounding bolt
The electric stove looks like an open counter, in the lower part of which there is metal frame Three electric burners are installed. The base is a frame lined on the sides. At the top of the counter there is a shelf mounted on brackets for placing plates. There is also a table here.
The burners are switched on and off using batch switches. Each burner is switched on separately to any of three power levels.
Electrical wiring installation and damage protection system electric shock made in accordance with the rules for electrical installations. Starting and protective equipment is installed on the switchboard. Fundamental electrical diagram EPM-5 slabs, the total power consumption of which is 3.75 kW, is shown in Fig.
Rice. Schematic diagram of the EPM-5 plate: SI, S2, S3 - batch switches; E7, E2, EZ - electric burners; X - terminal block
At specialized catering establishments with a bar (buffet) method of service, a tabletop electric stove PNEK-2 is used to heat first and second courses in a stove-top dish (Fig.).
Rice. Electric tabletop stove PNEK-2: 1 - burner; 2 - lifting table; 3 - pallet; 4-switch
The stove has two burners, each of them is equipped with a switch, through which the power of the burner is turned on and adjusted in steps. The total nominal power of the burners is 2.4 kW.
For heating various culinary products, as well as for steaming meat, fish and vegetables, an electric steamer APE-1B is used (Fig.).
Rice. Electric steamer APE-1B: 1 - cap; 2 - perforated saucepan; 3 - sector tanks; 4 - non-perforated saucepans with a lid; 5- working chambers; 6- gratings; 7- cap with holes in the level tube; 8 - steam generator; 9 - heating elements; 10 - terminal panel; 11 - base; 12 - anchor bolt; 13 - drain tube; 14 - float ball; 15 - nutrient tank
The main working parts of the device are a steam generator, a nutrient tank, and four retractable chambers.
The steam generator is filled with water from the feed tank through a communicating vessel system, the constant level of which is maintained by a float valve. Three heating elements are attached to the bottom of the steam generator. Above the steam generator there is a working chamber of the apparatus, consisting of four rotary containers. Under them there is a fixed cap, connected to the base by three vertical posts and an axis around which all rotating chamber containers can rotate independently of one another. Each rotary container is equipped with a textolite handle with a spring lock, allowing it to be fixed in the closed position.
The principle of operation of the device is that steam from the steam generator, rising from bottom to top, sequentially passes through all the containers of the chamber, where, in contact with the heated products, it condenses, giving off heat to them.
To protect the steam generator from overflowing with water in the event of a failure of the float valve, the steam generator is equipped with a level tube through which excess water is drained into the sewer.
In Fig. A diagram of the communication lines to the device with the required installation dimensions is shown.
Rice. Scheme of supply lines to a thermal apparatus of the APE type: 1 - supply pipeline cold water; 2 - box supply and exhaust ventilation; 3 - valve; 4 - ladder
To heat and keep various drinks hot (coffee, cocoa, milk, etc.), electric thermostats LSB-6M, ET-20, TE-25 are used. They are usually installed on buffet counters, cafeteria counters and self-service lines.
In Fig. shown design diagram electric thermostat LSB-6M.
Rice. Electric thermostat LSB-6M: 1 - tank; 2 - heating element; 3 - body; 4 - tap; 5 - pallet
It is a steel cylindrical tank, turning into a rectangular flange. Heating of drinks is carried out by heating elements installed in its lower part. The thermostat is connected to the mains via a cord with plug equipped with a grounding contact. The required temperature of the drink poured into the electric thermostat is maintained by the electric heater toggle switch. The tank capacity is 20 l, power consumption is 0.4 kW. Drinks are poured using a stopper.
The operating principle of the electric thermostat ET-20 is the same as that of LSB-6M. The difference is that the drink in it is heated by a tubular electric heater located in the lower part of the tank.
The TE-25 thermostat has a removable pull-out container with a tap. It is heated by analogy with LSB-6M.
Regulation temperature regime The thermostat is controlled by a temperature sensor-relay, the dial of which is displayed on the control panel. The thermostat is equipped with a lamp indicating that the electric heater is turned on. The useful capacity of the tank is 25 l, power consumption is 0.5 kW.
Processes that occur when liquids boil. Technological aspects of use and classification of water heating equipment.
Designs and principles of operation of water heaters and boilers.
Safety regulations.
Self-test questions.
157. Give a drawing of a filling boiler of the KNE-50 type, explain its structure.
158. Give a diagram of the design of a continuous electric boiler of the KNE type, explain the principle of operation.
159. Provide a drawing, explain the device, principle of operation, technical characteristics of electric boilers of the KNE-25 type.
160. Give a drawing of a universal gas boiler-water heater type KNG-200, describe its structure and principle of operation.
161. Draw a diagram, describe the structure and operating rules of a solid fuel (fire) boiler of the KNT-200 type.
162. Provide a drawing of a water heater of the NE-1A and NE-1B types, describe the structure and principle of operation.
163. Provide a drawing of an AGV-80 type water heater, describe the device and operating principle.
Topic 12. Universal equipment. Auxiliary equipment and equipment for keeping food hot.
Types universal equipment for thermal processing of food products.
Heat treatment methods and their differences. Microwave devices, classification, design features, principle of operation.
Types of apparatus for keeping food hot. Apparatus for keeping food hot. Classification, designs and applications.
Equipment for cleaning potatoes and vegetables. Possibility of using them in potato processing production lines.
Self-test questions.
164. Give a classification of devices for heat treatment of products in the microwave field.
165. Give a drawing of a high-frequency microwave cabinet “Electronics”, describe its structure.
166. Describe the device of a microwave generator (electric heaters of the third type). Give a drawing of the magnetron design.
167. Give a drawing and describe the structure of a food warmer of the MSESM-3K type.
168. Give a drawing of food warmers for second courses of the MSESM-60 and MSESM-110 types, describe their design.
169. Provide a drawing of a stationary electric food warmer of the ITU-84 type, describe the device and principle of operation.
170. Provide a drawing, describe the purpose and design of the MP-28 mobile food warmer.
171. Give a drawing of a mobile thermal cabinet SHTPE-1.5 and describe the design of thermal cabinets of the types ShTPE-1, ShTE-1, ShTE-1-01.
172. Describe the purpose, design and operating principle of functional containers.
173. Provide a drawing, describe the purpose and design of the SRTESM type dispensing rack.
174. Describe the purpose and features of mechanized self-service dispensing lines, their operating principle, and also provide a drawing of mobile food warmers of the MEP type.
175. Classification of electric food warmers for short-term storage of dishes.
176. Describe the purpose, technical characteristics and features of self-service lines.
The main quality criterion is the product sales temperature, which varies within 60...85 °C. At these temperatures the main biochemical processes Heating-related problems continue even when the product is stored, resulting in changes that cause additional weight loss, destruction of vitamins and deterioration of organoleptic properties.
To ensure that these changes are minimal, the following basic requirements must be met:
The temperature of storage and sale should be the lowest permissible levels;
The period of storage and sale should not exceed the permissible period and should be reduced as much as possible.
Classification of preservation equipment hot food
According to their functional purpose they are divided into three groups:
Apparatus for storing food hot;
Devices for selling food;
Devices that combine the above functions and are capable of transporting hot food from the storage or preparation area to the sales area.
Products can also be stored in devices designed for heat treatment: digester boilers, steam chambers, etc. To do this, use the lower stages of thermal power. However, from an energy point of view this is inefficient and economically unfeasible.
Marmites.
These are thermal devices designed for short-term storage of food in a hot state during the period of its sale or in the process of manufacturing culinary products.
The design feature of food warmers is that culinary products are placed in cookware or in functional containers (gastronomy containers), or in special food warmers. Warehouses are available in floor and tabletop versions.
The containers used in food warmers (bain-marie pots) are not thermally insulated and can be separated from the food warmer and used for other purposes other than storage finished products, but also for its preparation.
Food warmers intended for product sales are installed in the distribution line and are, as a rule, sectional modular devices. Such food warmers are divided into food warmers for second and first courses.
Food warmers for second courses.
Depending on the heating method, food warmers for second courses are divided into water, steam and air (“dry”).
Water warmers for main courses.
In water bain-marines, as part of dispensing lines, the bain-marie bowls are immersed in a bath of hot water. The bath is located under work surface bain-marie table. The water in the bath is heated either by water heating elements located inside the bath, or by air heating elements mounted on the outside of the bath wall. There is usually no thermal insulation, and its role is played by an air gap between the heating bath and the front panels. The temperature of the heating water in the bath is maintained by a thermostat. The temperature sensor is most often placed directly in the water. Accurate provision optimal temperature storage guarantees high quality food.
Flaws: a large mass of heating water leads to an increase in heating duration and, accordingly, increased energy consumption. In the process of selling products, pots become lighter and can float, which leads to a change in the water level in the heating bath. Heating of pots with different degrees of filling may not be the same.
Steam food warmers for second courses.
To heat the pots, a steam generator is located in the lower part of the heating bath. In this case, the heating of the food warmers is the same regardless of their filling. The bain-marie heats up quickly and does not require much energy consumption.
Flaws. During storage, there is a danger of overheating of culinary products and deterioration in their quality, since the steam temperature, close to 100°C, is not regulated.
Air warmers for second courses.
Their design differs little from their steam counterparts. Air heating elements are used to heat the air in the heating bath. They are placed either on the outside of the bath and pressed against its wall with brackets, or directly in the bath under the martens. To control the temperature, a thermostat with a control range of up to 100 °C is used. Such food warmers quickly heat up and reach operating mode and are easy to use.
Food warmers for first courses
They can be classified as specialized “bain-marie” plates. These are devices that use electric or gas burners. Unlike stoves, food warmers for first courses use burners with reduced power, round or rectangular with a cast iron body with a power of up to 2 kW. They are connected to the network through packet power switches.
Thermal showcases.
Thermal display cases are closed chambers with shelves for displaying portioned products. The walls of the chambers are transparent: glass or plexiglass. Heating is carried out either by air heating elements or by a fan heater. With the help of a thermostat, the temperature required for food storage is maintained in the volume within 40...70 °C.
Thermal racks.
Unlike showcases, they have open heating surfaces. Dishes are heated by heated surfaces of the production table or shelves included in the design of the apparatus.
Heating surfaces can be continuous or local (burner) and have operating temperature within 60...85 °C.
In thermal racks with a continuous heating surface in electric design, air heating elements attached to the heating wall are used to heat it. In devices with local heating, cast iron burners with reduced power are most often used.
There are known designs of thermal racks in which a box-shaped flow-through heat exchanger is used as a heater, inside which an intermediate coolant circulates.
IR – heaters.
Externally similar to table lamp lighting. The thermal unit includes IR generators and a reflector. Quartz emitters or emitting heating elements most often serve as sources of IR energy. IR heaters are produced as separate tabletop devices or are included in the design of thermal racks, located above the working surface of the table or shelves.
Thermal cabinets.
Heating cabinets are a simplified version of ovens. The main element of the design is a box-shaped working chamber, in the lower part of which there are heating elements. Unlike ovens, they do not have an upper group of heating elements and have a thermostat with control limits of 30... 100 °C.
The heating air in the working chamber is heated due to natural air convection.
Heating cabinets can be built into the main technological devices (oven, stove or heating rack), sometimes completely devoid of heating.
The most effective are heating cabinets with forced circulation air, which are designed to preserve cooking products under the condition of forced movement of heating air and controlled humidification. In the box-shaped, heat-insulated working chamber of these cabinets, there will be placed on baking sheets food product. To “mix” the air in the chamber, a centrifugal fan impeller is installed. The Finnish company Metos was the first to offer such cabinets from the Vineton series.
Optimal values of humidity and air temperature exclude drying of the product, preserve the original structure and composition, and, therefore, organoleptic properties during long-term storage.
Thermostats.
Thermostats are designed for long-term preservation and transportation of first courses and hot drinks at a constant temperature.
Their distinctive feature is that the working chamber is an integral and completely thermally insulated part of the entire apparatus. The food intended for storage is placed directly in this chamber.
The main part of the thermostat is a cylindrical or box-shaped working chamber, tightly closed on top with a lid. To seal the lid, a gasket made of heat-resistant food rubber is used, and special mechanical devices, often screw or cam.
Depending on the capacity and method of transportation, thermostats are divided into portable, mobile and stationary.
Portable thermostats are designed not only for storing and transporting hot food inside the enterprise, but also for transporting it in transport.
Mobile thermostats are used for intra-shop movements.
Stationary Thermostats are usually installed in the line for completing and selling finished products.
Thermal devices for thermostating food can be divided according to functional purpose into three main groups:
– devices intended for storing food in a hot state;
– devices designed for selling food;
– devices that combine the above functions and are capable of transporting hot food from the storage or preparation area to the sales area.
The last direction is the most promising, since overload operations are excluded, which not only creates certain organizational conveniences, but also reduces the mass and heat losses that inevitably arise in this case.
In principle, it is possible to store finished culinary products in the main thermal apparatus designed for culinary heat treatment: digesters, steam chambers, etc. For this, the lower stages of thermal power are used, providing the temperatures necessary for storage. Obviously, the use of basic thermal apparatus for storing food is not economically feasible, since the cost of this type of equipment is high.
The most common devices currently used in domestic catering establishments for storing food in a hot state include: food warmers, heating racks, thermostats and heating cabinets.
Marmites. These are thermal devices designed to keep food hot while it is being sold on the distribution line. The design feature of food warmers, which distinguishes them from other thermostatic devices, is that food is placed in cookware or in functional containers, or in special containers that are part of the food warmer - food warmers, and the food warmer itself is, as a rule, stationary. Food storage containers are not thermally insulated and can be separated from the food warmer and used not only for storing finished products, but also for preparing them.
Since food warmers are also intended for sale, i.e. installed in the distribution line, they are, as a rule, sectional modulated devices. In this case, the area for placing pots is most often a plane corresponding to the surface of the desktop and located at a distance of 800...900 mm from the floor level. IN in some cases, when thermostatting of cookware of significant volume (20 dm3 or more) occurs, the surface of the compensation heaters on which the containers are installed is located from the floor level at a distance of 20...30 cm, which reduces the physical costs of lifting the containers and improves the working conditions of the operator personnel.
The tabletop circuit is usually used in food warmers designed for thermostating first courses and side dishes (potato torte, cereals and pasta). This scheme provides a set of steam dishes for all types of culinary products. During the storage process, as needed, hot food is removed from the steamer to complete the dishes and sell them. Empty pots are replaced with filled ones.
When heating pots with a water bath by changing the power of heating elements (or steam flow in a tubular steam exchanger), the heating water temperature is reached from 70 to 90 °C. In this case, there is practically no vaporization of water. When using a steam bath, the heating steam has a temperature equal to the boiling point.
Water baths with a water bath, despite the ability to regulate the temperature of the heating medium, due to their significant mass and high thermal inertia, are inferior in efficiency to their counterparts with steam heating; for this reason, the latter find much wider application in practice.
Design of food warmers with air heating The design of a food warmer is similar to that of a water bath, but in the heating volume, instead of water, there is hot air; The heating volume in this case is significantly reduced.
Food warmers with a floor-mounted heating surface most often represent an electric stove with burners that heat the bottom of the cookware in which the food is thermostatically controlled.
Thermal racks. These are devices designed for heating dishes (plates, cups, glasses) and portioned and prepared for sale dishes placed in them.
The main thermal elements are those heated to temperatures of 60... 90 °C horizontal surfaces(shelves). In electric thermal racks, electric heaters are often used as a heater. closed type, operating in the mode of low specific thermal loads (W< 2 Вт/см 2).
When using a centralized heat supply scheme for the working surfaces of heating racks, in addition to electric heating, gas or steam heating can be used. In this case, the intermediate coolant is heated in a steam generator and pumped through a group of flat heat exchangers by a gear pump. As it moves, the temperature of the coolant changes from 85...90°C at the entrance to the first group of heat exchangers to 60...70°C at the tail sections. These operating characteristics correspond to the requirements for thermostating food and, in turn, are the initial ones for determining the power of the apparatus, as well as the power and productivity of the gear pump. Either heavy mineral (motor) oil or organosilicon fluids (polyorganosiloxanes) are used as an intermediate coolant.
Thermostats. Thermal devices intended for long-term storage write at a constant temperature are called thermostats.
Distinctive design feature thermostats is that the working chamber (temperature control volume) is an integral and completely thermally insulated part of the entire apparatus. The food intended for storage is placed directly in this chamber.
The main part of the thermostat is the working chamber cylindrical, or made in the shape of a parallelepiped. The loading opening of the working chamber is tightly closed with a lid. To seal the joint, a gasket made of heat-resistant food grade rubber is usually used. To press the lid, use various kinds mechanical devices, often screw or cam.
Depending on the capacity and method of transportation, thermostats are divided into mobile, portable and stationary.
Portable ones are designed not only for storing and transporting hot food inside the enterprise, but also for transporting it in transport. For intra-shop movements, mobile thermostats are used, and stationary ones are usually installed in the line for completing and selling finished products.
Currently, foreign companies produce various thermostats (from simple portable to combined carts), made of heat-resistant plastic and filled with thermal insulation. Their practical use is constantly increasing.
Electric thermostats are widely used for heating and keeping coffee, cocoa, milk and other drinks hot during their sale. They are installed on buffet counters, cafeteria counters and in self-service lines. Structurally, they are directly heated boilers, in which the heating element is located in the lower part of the cooking vessel.
To ensure gentle heating of drinks placed in an electric thermostat, it is advisable to use oil heating elements rather than water ones. In this case, the specific surface power of the heating element tube is reduced from 10 to 6 W/cm2, which significantly reduces the degree of destruction of drinks, especially when they are reheated.
Thermal cabinets. Heating cabinets are a simplified version of frying cabinets and, unlike them, either lack heating elements or are equipped with low-power heaters. The complete absence of heaters is justified in cases where the heating cabinet is an auxiliary part of the main apparatus (oven, stove or heating rack) and utilizes the heat generated by this apparatus. Heating cabinets are used to keep individual components of portioned dishes hot. The main structural element of a heating cabinet is a box-shaped working chamber, in the lower part of which, if necessary, heating elements are installed. The stored food product is placed on special shelves or in special boxes. In the first case, the working chamber has a common door, and in the second, the drawers are pulled out independently of one another.
Large-volume heating cabinets usually have a power regulator and a thermostat.
The thermostatic devices discussed above operate on electrical heating. This is due to the fact that the devices are most often installed in a distribution line together with other electrical devices. Installed power their power is small and usually does not exceed 5 kW. This power is used only to warm up the device, and for stationary mode, 1/6... 1/9 of it is sufficient.
When using a steam heat exchanger or gas burner provide regulation and protection systems determined by the properties of energy carriers and discussed in detail above when studying the main types thermal equipment for thermal cooking of food.
When comparing the designs of various thermostatic devices, they usually proceed from the following considerations: the lower the specific heat consumption per unit of stored product, the more efficient the device for storing food in a hot state. Another important indicator that indirectly characterizes the degree of perfection of the thermostat is the cooling rate of the product when the heaters are turned off, measured in degrees per second (in K/s) or per hour (in K/h). The cooling rate of the product in perfect portable thermostats should not exceed 2 K/h, in mobile thermostats 10, and in stationary thermostats, food warmers and heating cabinets 15 K/h.
In some cases, characterized by short-term episodic use of a thermostatting device, they go to simplify the design while deliberately increasing both the rate of cooling of the product and specific costs energy. This is justified due to the short duration of the entire process and, as a consequence, due to the low overall energy costs.
