The use of sugars in cooking technology. From cooking to cooking chemistry
Lecture number 1. Introduction
Plan:
1.Subject and objectives of the course
2.Folk cuisine and modernity
3.Professional cooking
1. - a technical discipline that studies the rational preparation of culinary products in conditions of mass production.
The purpose of the discipline is the acquisition by students of theoretical knowledge about the technological processes of processing raw materials, preparation, design and distribution of culinary products, assessing its quality and safety.
The subject of the discipline is: the technology of production of semi-finished products and finished products at public catering establishments; physicochemical and biochemical processes occurring in products during their culinary processing; requirements for the quality of culinary products; way of managing technological processes.
Objectives of the course:
Ensuring the quality and safety of culinary products;
Production of culinary products balanced in terms of the main nutritional factors (amino acid, fat, mineral, vitamin composition, etc.)
Ensuring good assimilation of food by giving it the necessary aroma, taste, appearance;
Reduction of waste and loss of food substances during culinary processing of products;
use of little waste and non-waste technologies;
maximum mechanization and automation of production processes, reducing the cost of manual labor, energy, materials.
Interdisciplinary connections with other disciplines. The basis for the study of the discipline is the knowledge acquired by students in the study of general education and a number of related general technical and special disciplines.
During the processing of products and the production of finished products, a number of chemical processes take place: hydrolysis of disaccharides, caramelization of sugars, oxidation of fats, etc. Most of the culinary processes are colloidal: coagulation of proteins (when heating meat, fish, eggs) , obtaining stable emulsions (many sauces), obtaining foam (whipping cream, proteins, etc.), aging jellies (stale baked goods, cereals, separation of liquids from jelly, jelly), adsorption (clarification of broths).
Knowledge of chemistry is necessary to manage numerous processes in food preparation and control the quality of raw materials and finished products.
Data on the composition and consumer properties of products, which a student receives while studying the course on food products, allow the technologist to correctly solve the problem of rational use of raw materials and serve as important criteria for justifying and organizing technological processes.
Recommendations of nutritional physiology are necessary for the organization of a balanced diet. They take into account the needs for irreplaceable nutritional factors of various contingents of the population, make it possible to use products in a differentiated manner. Academician I.P. Pavlov said that physiological data put forward a new point of view regarding the comparative value of nutrients. It is not enough to know how many proteins, fats, carbohydrates and other substances are contained in food. It is practically important to compare different forms of cooking the same food (boiled and fried meat, hard-boiled and soft-boiled eggs, raw and boiled milk, etc.).
The most important indicator of the quality of food is its safety for the consumer. Knowledge and observance of the rules of food hygiene and sanitation ensure the production of hygienic products and allow the establishment of a strict sanitary regime at public catering establishments.
The processing of raw materials, the preparation of culinary products are associated with the operation of complex mechanical, heating and refrigeration equipment, which requires the technologist to acquire knowledge obtained in a cycle of technical disciplines.
The discipline "Cooking technology" is directly related to such disciplines as the economics of public catering and the organization of production and service. The study of these disciplines is an indispensable condition for the correct organization of production and increasing its economic efficiency, rational use of the material and technical base and labor resources, and reducing the cost of production. Public catering specialists constantly communicate with consumers, and the organization of service depends on their general culture, knowledge of psychology, ethics.
Catering enterprises receive from food industry enterprises not only raw materials, but also semi-finished products of varying degrees of readiness. At the enterprises of the food industry there are workshops for the production of culinary products suitable for direct consumption: chips, ready-made sauces (mayonnaise, ketchup, etc.), soups concentrate .. meat, fish, vegetable culinary from -products, frozen meals, etc. Acquaintance with the technologies used in the food industry, with special types of equipment will improve the technological processes at public catering enterprises.
The technology of cooking is based on the traditions of folk cuisine, the experience of past professional chefs, as well as on the achievements of nutritional science.
2. From generation to generation people passed on the experience of cooking. They carefully preserved all the traditions associated with food, realizing that food is the basis of life, health and well-being.
Even in Ancient Greece, the cult of Asclepius, a mythical doctor-healer, who received the name Aesculapius in Rome, arose. His Hygeya was considered the patroness of health science, and "their faithful assistant was the cook Kulina. She became the patroness of the cooking business, which received the name" cooking "(from the Latin culina - kitchen).
The cuisine of each "people, traditions and customs associated with food, is one of the most important parts of its material culture. Folk cuisine is original and reflects the history of the people, its national tastes, character.
The main features of the national cuisine were formed under the influence of natural conditions and the characteristics of the economic structure. For example, the diet of the peoples of the North was dominated by venison and meat of sea animals; among the peoples of Central Asia - rice and lamb dishes; among Moldovans - from corn, etc.
The national cuisine was formed in accordance with the living conditions and the level of development of culinary technology. Among the peoples who led a nomadic way of life in the past, dishes cooked in hanging cauldrons still prevail, among the peoples of the Caucasus - fried on spits, in Russian cuisine - dishes cooked in a Russian oven (meat fried in a large piece, stews, dishes baked in pans, etc.).
The national cuisine reflects the religious beliefs of the people: Muslims do not eat pork; many Buddhists are vegetarians and some do not eat beef; Judaists divide food into kosher and tref (permissible and unlawful); all dishes of Orthodox Christians are divided into lean and quick.
Catering specialists must respect national traditions and customs, reflecting them in the range of dishes, methods of preparation, decoration and table setting. Do not mechanically transfer the methods of cooking dishes and culinary products at home to catering establishments.
The task of technologists is to creatively develop and improve the traditions of folk cuisine in relation to modern conditions, the level of development of technology, new types of food raw materials and the peculiarities of mass production of culinary products.
3 Even in primitive society, there was a division of labor among members of the family, clan and tribe. Most often men were engaged in obtaining food, and women were engaged in its preparation. So it was in Russian peasant families. They prepared food in living quarters. For this, a place was allocated near the Russian stove (upechye, kut). Already in Ancient Russia, professional cooks appeared in princely households, homes of rich people and monasteries. At the same time, cooks appeared in residential buildings, and then in yards and gardens. The word "kitchen" was borrowed from the German language only in the era of Peter 1. In the Moscow Kremlin already in the XV-XVI centuries. there was a whole food supply system: a bread dormitory with numerous bakeries; the stern palace, which was in charge of the cooks; a hearty palace in charge of making drinks. Numerous highly qualified cooks, henchmen (assistants to cooks), and apprentices of cooks worked in the palaces.
The development of professional cooking is associated with the emergence of out-of-home catering enterprises. They arose even in Ancient Russia. At first, these were shortcuts (from the Slavic root "feed"), in which travelers could find shelter and food.
Then there were roadside taverns (from the Latin tract - path, stream) - hotels with a dining room and kitchens. In the 16th century. taverns were opened in cities, and in the 19th century. inns without hotels became widespread.
At the same time, along with taverns in large cities of Russia, restaurants began to appear (from the French restoration - restoration).
In taverns and restaurants, professional cookery developed, based on folk cuisine. Professional chefs developed and improved the national cuisine, enriching it by borrowing the best achievements of European culinary specialists.
In these out-of-home catering establishments, food preparation was not regulated by any regulatory documents. Everything depended on the skill and intuition of the cook. This is the fundamental difference between the old tavern-making establishments and modern catering establishments, which include restaurants, bars, cafes, snack bars, canteens.
Lecture No. 2. Theoretical foundations of the technology of public catering products.
Plan:
1. Basic concepts.
2. Technological cycle of production of culinary products.
3. Technological principles of the production of culinary products.
1. To ensure mutual understanding between the developers of culinary products, their producers and consumers, the development of regulatory documents, the certification of public catering establishments, GOST R 50647-94 "Public catering. Terms and definitions" has been developed. According to this GOST, a number of concepts used in writing a textbook are given below.
Raw materials - initial products intended for further processing.
Semifinished (semi-finished culinary product) - a food product or a combination of products that have passed one or more stages of culinary processing without bringing to readiness.
Semi-finished product of high degree of readiness - a culinary semi-finished product from which, as a result of the minimum necessary technological operations, a dish or culinary product is obtained.
Culinary product - a food product or a combination of products brought to culinary readiness.
Flour culinary product - a culinary product of a given form made of dough, in most cases with minced meat (pi-horns, kulebyaki, belyashi, donuts, pizza).
Confectionery - a product made of dough of a given shape, with a high content of sugar and fat (pastries, cakes, muffins, cookies, waffles). Dish- a food product or a combination of products and semi-finished products, brought to culinary readiness, portioned and decorated.
Culinary products - a set of dishes, culinary products and culinary semi-finished products.
Culinary ready (or readiness) - a set of specified physicochemical, structural and mechanical, organoleptic indicators of the quality of a dish and culinary product, which determine their suitability for eating.
Culinary processing - impact on food products in order to impart properties to them, thanks to which they become suitable for further processing and (or) consumption in food.
Mechanical cooking - culinary processing of food products by mechanical methods for the purpose of making dishes, culinary products, semi-finished products.
Thermal cooking - culinary processing of food products, which consists in heating them in order to bring them to a given degree of readiness.
^ Waste from cooking - food and technical residues formed in the process of mechanical culinary processing.
Cooking loss- reduction of the mass of food products in the process of production of culinary products.
Recipe (culinary products) - a standardized list of raw materials, products, semi-finished products for the production of a set amount of culinary products.
2. One of the main tasks of technologists is the production of competitive high quality culinary products.
Quality public catering products - a set of consumer properties of food, which determine its suitability to meet the needs of the population in good nutrition.
The set of useful properties of culinary products is characterized by nutritional value, organoleptic indicators, digestibility, safety.
The nutritional value is a complex property that combines energy, biological, physiological value, as well as assimilation and safety.
Energy value characterized by the amount of energy released from food substances in the process of their biological oxidation.
Biological value - is determined mainly by the quality of food proteins - the digestibility and the degree of balance of the amino acid composition.
. Physiological value - due to the presence of substances that have an active effect on the human body (beet sa-ponins, caffeine in coffee and tea, etc.).
Organoleptic indicators - (appearance, color, consistency, smell, taste) characterize the subjective attitude of a person to food and are determined using the senses.
Digestibility - the degree of utilization of food components by the human body.
Safety is the absence of unacceptable risk associated with the possibility of damage to human health (life). If the permissible level of safety indicators is exceeded, culinary products are transferred to the category of dangerous. Hazardous products must be destroyed.
There are the following types of safety of culinary products: chemical, sanitary and hygienic, radiation.
Chemical safety - absence of unacceptable risk that can be caused by toxic substances to the life and health of consumers. Substances affecting the chemical safety of culinary products are subdivided into the following groups: toxic elements (salts of heavy metals); mycotoxins, nitrates and nitrites, pesticides, antibiotics; hormonal drugs; prohibited food additives and dyes.
Sanitary and hygienic safety - absence of unacceptable risk that may arise from micro-biological and biological contamination of culinary products caused by bacteria and fungi. At the same time, toxic substances accumulate in the products (mycotoxins during mold, toxins of botulinus, salmonella, staphylococcus, Escherichia coli, etc.), which cause poisoning of varying severity.
Radiation 6sensitivity - absence of unacceptable risk that can be caused to life, health of consumers by radioactive substances or their ionizing radiation.
The quality of culinary products is formed during the entire technological cycle of production. Its main stages are:
marketing;
product design and development;
planning and development of a technological process;
material and technical supply;
production of products;
quality control (check);
packing, transportation, storage;
implementation;
recycling.
In the process of marketing research, the market demand must be precisely determined, for example, what type of enterprise should be "opened, what will be the range of culinary products in it, its approximate quantities, etc. The marketing function also includes feedback from consumers. All information Anything related to product quality should be analyzed and reported to the manufacturer.
Product design and development include the preparation of menus, the development of recipes for new or branded dishes, the preparation of regulatory (technical and technological maps, technical conditions - technical specifications, enterprise standards - STP) and technological (technological maps, technological instructions) documentation.
Process design and development . On the basis of the developed normative and technological documentation, technological schemes for the preparation of individual dishes are drawn up, the sequence of operations is determined, and the technological process of production is being developed.
Culinary products in the enterprise as a whole. The need for raw materials, equipment, inventory, utensils is determined.
Material and technical supplies . Raw materials, products, semi-finished products used in the technological process of production become part of the manufactured products, directly affect the quality and must comply with hygienic requirements for the quality and safety of food raw materials and food products (SanPiN 2.3.2-96). Equipment, inventory, utensils must also comply with sanitary and hygienic requirements and have hygienic certificates or certificates of conformity.
Production of products consists of three stages: 1) processing of raw materials and preparation of semi-finished products (for enterprises operating on raw materials); 2) preparation of dishes and culinary products; 3) preparation of dishes for sale (portioning, decoration). All three stages have an impact on the formation of the quality of the finished product and must be carried out in accordance with the requirements of technological standards and sanitary rules.
Quality control - checking the compliance of the quality indicators of culinary products with the established requirements, this is one of the most important stages of the technological production cycle. Quality control is conventionally divided into three types: preliminary (input), operational (production), output (acceptance).
Preliminary is the control of incoming raw materials and semi-finished products.
Operational control is carried out in the course of the technological process: from raw materials and (or) semi-finished products accepted in terms of quality to the release of finished products. It includes checking:
Organization of the technological process (sequence of operations, observance of temperature, duration of heat treatment, etc.) and individual workplaces;
Equipment and condition of equipment, compliance with its parameters of the technological process;
Hygienic parameters of production (temperature at the workplace, ventilation, illumination of workplaces, noise level, etc.);
Availability of regulatory and technological documents at workplaces, knowledge of their performers;
Availability of measuring equipment, its serviceability and timeliness of verification;
Ensuring the output and quality of semi-finished products and finished products in accordance with the established requirements.
Output (continuous) control - checking the quality of finished products. The enterprise carries out rejection of food, laboratory control for the completeness of the input of raw materials, safety, etc.
The quality of culinary products, their safety is controlled by organoleptic, physico-chemical and micro-biological indicators. The manufacturer is obliged to ensure constant technological control of production, state supervision and control bodies in the established order - selective control.
Organoleptic evaluation the quality of semi-finished products is carried out in appearance, color, smell; culinary products and dishes - in appearance, color, smell, consistency, taste.
Physical and chemical indicators characterize the nutritional value of culinary products, their component composition, compliance with the recipe. The list of standardized indicators (mass fraction of fat, sugar, salt, moisture or dry matter, total acidity, alkalinity, toxicity of elements, etc.) is established for each group of culinary products.
microbiological indicators culinary products are characterized by compliance with technological and sanitary requirements during their production, transportation, storage and sale.
Packing, transportation, storage . The purpose of this stage is to maintain the achieved level of quality. Cooking products delivered from procurement factories to pre-procurement enterprises and sold to consumers outside public catering enterprises are packed in transport containers. Semi-finished products, culinary products, dishes (chilled and frozen), which the consumer buys directly at the manufacturing plant, in the cooking departments and order tables, are packed in consumer containers.
Containers and packaging materials in the process of storage, transportation and sale have a significant impact on maintaining the quality of culinary products. Therefore, the following requirements are imposed on packaging: safety, compatibility, reliability, economic efficiency, etc.
They transport culinary products in accordance with the sanitary rules for the transportation of perishable products. Particularly perishable products are transported in refrigerated or insulated vehicles. A sanitary passport must be issued for each car. The conditions and terms of storage of such products are regulated by sanitary rules (SanPiN 42-123-4117-86).
^ Sales of culinary products . Culinary products should be prepared in such batches that can be sold within strictly defined sanitary rules. When selling, hot soups and drinks must have a temperature of at least 75 0 С, sauces and main dishes - at least 65 0 С, cold soups and drinks - not higher than 14 0 С. later than 3 hours after their manufacture. Salads, vinaigrettes, gastronomic products, other cold snacks and drinks should be displayed in portioned form on refrigerated display cases, which should be replenished with products as they are sold.
Dishes, culinary products left over from the previous day are not allowed to be sold: salads, vinaigrettes, studios, aspic dishes and other especially perishable cold dishes; milk soups, cold, sweet, puree soups; boiled meat for soups, pancakes with meat-catfish and cottage cheese, minced products from meat, poultry, fish; co-mustache; omelets; mashed potatoes, pasta; com-pots and drinks of our own production.
Each batch of culinary products sold outside the hall of a catering establishment must have a quality certificate. The shelf life specified in the certificate is the shelf life of culinary products and includes the residence time of the product at the manufacturing enterprise (from the end of the technological process), the time of transportation, storage and sale.
During the production and sale of culinary products, the personnel must comply with the rules of personal hygiene, periodically undergo a medical examination in accordance with the current rules.
^ Recycling , obtained during mechanical processing of raw materials, food residues, culinary products with violated sales dates is the final stage of the technological cycle. Non-food waste can be sent for industrial processing, for example, bones of large and small livestock. Food waste is partly used at the enterprise itself (for example, fish heads, fins, scales are used for cooking broths, early beet tops are used for making soups, etc.), partly sent to livestock feed. Food leftovers, as well as products with violated sales dates, are used for fattening livestock or are destroyed. Sending them to specialized enterprises for the destruction of waste is controlled by representatives of the sanitary-epidemiological supervision.
3.Principle security. Changing the forms of ownership, providing catering enterprises with greater independence, the lack of regular control over their work by higher organizations have led to the fact that this principle has become one of the most important. Physicochemical and microbiological indicators affecting the safety of culinary products are provided for in all types of regulatory documents. The development of each new type of dish, culinary, confectionery product should be accompanied by the establishment of safety indicators.
^ The principle of interchangeability. Supply conditions, seasonality in the receipt of products often necessitate the replacement of some products with others (for example, fresh vegetables - dried, tomatoes - tomato puree, margarine - vegetable oil, natural milk _ dry). Replacement is permissible if the quality of the dish, culinary, confectionery product does not deteriorate, and it is unacceptable if the culinary product acquires a different taste, structural and mechanical properties, and the nutritional value decreases. Replacement of some products with others is carried out taking into account the coefficient of interchangeability established by regulatory documents.
^ Compatibility principle. It is associated with the principle of interchangeability and often "- with the principle of safety. So, for many, milk is incompatible with sour foods, cucumbers (both fresh and salted), fish. Spinach, sorrel, rhubarb are incompatible with fermented milk products, not only in taste, they reduce the absorption of calcium.
The incompatibility of products depends on individual characteristics, habits, national tastes. For example, for most Europeans, combining garlic with fish is unacceptable, and in Jewish cuisine, fish with garlic is one of the common dishes. There are no direct sanitary prohibitions on certain combinations of products.
^ The principle of balance. A person's daily diet should cover the body's need for energy and vital substances (nutrients): proteins, fats, carbohydrates, vitamins, mineral elements, dietary fiber. All these substances in the diet must be balanced, that is, they must be contained in certain quantities and ratios. There are no products that are completely balanced in composition: one has a high energy value, the other: - low; one contains a lot of proteins, the other - few proteins, but a large amount of carbohydrates, etc. One of the advantages of cooking technology is the ability to obtain a balanced composition of culinary products by rational selection of raw materials, development of recipes and technological processes. So, boiled cabbage (cauliflower, white cabbage) contains little fat, its energy value is low. But if cabbage is served with rusk, Polish or Dutch sauce, the fat content in the dish increases, its energy value increases 2-3 times. Meat and fish dishes contain a lot of proteins, but little carbohydrates, dietary fiber, alkaline minerals, vitamin C. The nutritional value of meat and fish is complemented by vegetable side dishes.
^ The principle of rational use of raw materials and waste. It provides for the best use of the consumer properties of raw materials. So, you should use large-sized semi-finished meat products in accordance with their culinary purpose (for frying, boiling, stewing, etc.); some types of fish (bream, carp, roach, etc.) are recommended to be fried, not boiled; young potatoes are best served boiled rather than used for mashed potatoes, soups, etc.
^ The principle of reducing the loss of nutrients and the mass of finished products. This principle requires adherence to the heat cooking regimes (temperature, heating duration). So, when laying vegetables in boiling water, the loss of soluble substances, and primarily minerals, is reduced by 20-30%. Frying them in devices with infrared heating or on a well-heated frying surface helps to reduce the loss of mass of meat and poultry.
^ The principle of shortening the cooking time.
The methods of intensification of technological processes known in culinary practice, as a rule, at the same time contribute to an increase in the quality of the finished product. They include: preliminary loosening of the structure of products by soaking dry products (mushrooms, legumes, cereals, dried fruits, etc.), mechanical action (beating and loosening meat, grinding it in a meat grinder), chemical and biochemical effects (pickling and enzymatic processing of meat), etc.; intensification of heat transfer by increasing the surface of contact with the heating medium (grinding products, cutting them so that the heating area is the largest), increasing the temperature of the coolant; the use of electrophysical methods of heat treatment of products (IR heating, microwave heating).
^ The principle of the best use of equipment.
In accordance with this principle, machines and devices with the required performance should have a low energy consumption, a stable mode, be convenient and safe in operation, and maintainable. The principle is successfully used, for example, in highly specialized enterprises (donut, pies).
^ The principle of the best use of energy. This principle means intelligently reducing the energy intensity of culinary products. The energy intensity of products can be characterized using the energy intensity coefficient, which is defined as the ratio of the cost of energy consumed in production to the cost of production. Energy intensity can be reduced by using modern, less energy-intensive equipment, a reasonable reduction in energy-intensive methods of processing products, timely shutdown of energy (use of accumulated heat), strict adherence to technological regimes.
In the overall assessment of the technological process, water consumption, labor and other costs should also be taken into account.
Control questions.
Lecture number 3. Cooking food processing methods.
Plan:
1.Classification of culinary processing methods.
2. Mechanical methods of processing.
3. Hydromechanical processing methods.
4. Mass transfer methods of processing.
1. The variety of raw materials and products used in culinary practice, a wide range of culinary products determine the variety of processing methods.
The methods of culinary processing of raw materials and semi-finished products depend on:
Waste amount; so, with mechanical processing of potatoes, the amount of waste is 20-40%, and with chemical processing - 10-12%;
The amount of nutrient loss; for example, when cooking potatoes with steam, soluble substances are lost 2.5 times less than when cooking in water;
Loss of mass; so, when cooking potatoes, the mass decreases by 8%, and when deep-fried - by 50%;
The taste of the dish (boiled and fried meat);
Digestibility of finished products; so, dishes made from boiled and stewed foods are digested, as a rule, faster and easier than from fried foods.
The choice of culinary processing method largely depends on the properties of the product. So, some parts of beef carcasses reach culinary readiness only when boiling, while others up to a hundred: just fry. Using various methods of culinary processing, a technologist can obtain culinary products with desired properties and appropriate quality.
Methods for processing raw materials and products are classified:
By stages of the production process
Culinary products;
By the nature of the active principle.
The positions of the technical process differ in the following ways:
Used in the processing of raw materials in order to obtain semi-finished products;
Used at the stage of thermal culinary processing of semi-finished products in order to obtain finished products;
Used at the stage of selling finished products. By the nature of the active principle, the methods of processing raw materials and products are divided into:
mechanical;
hydromechanical;
mass transfer;
thermal;
electrophysical.
Sorting... Products are sorted by size or culinary. This allows you to significantly reduce the amount of waste during further mechanical cleaning. In large enterprises, sorting machines are used for this purpose.
Of great importance is the division of products according to culinary use: sorting through tomatoes, they separate whole dense specimens for making salads, crumpled ones for sauces and soups; parts of carcasses are divided into suitable for frying, cooking, stewing, etc.
When sorting, products of inadequate quality and mechanical impurities are removed.
Screening... Sift flour, cereals. In this case, fractional separation is used: first, larger impurities are removed, and then smaller ones. For this, sieves with openings of various sizes are used. Sieves are metal with punched holes, wire from round metal wire, as well as fiber, silk, nylon. In addition to manual sieves, the enterprises use sifters with a mechanical drive for flour.
Mixing... In the manufacture of many dishes and culinary products, it is necessary to combine various products and obtain a homogeneous mixture FROM them. For this purpose, stirring is used. So, mixing chopped meat, black bread soaked in milk or water, pepper, salt, get minced meat.
For mixing, special machines are used - meat mixers, dough mixers, etc. Small quantities of products are manually mixed with special shovels, paddles and other devices. The quality of the finished products largely depends on the thoroughness of mixing.
Cleaning- the purpose of cleaning. is the removal of inedible or damaged parts of the product (vegetable skins, fish scales, crustacean shells, etc.). It is produced manually or using special machines (potato peelers, flake-cleaning machines, etc.). For manual cleaning, use knives, scrapers, graters and other devices.
Shredding... The process of mechanical division of the processed product into parts for the purpose of its better technological use is called grinding. Depending on the type of raw material and its structural and mechanical properties, mainly two methods of grinding are used: crushing and cutting.
Products with low moisture content (coffee grains, some spices, crackers) are subjected to crushing, products with high moisture content (vegetables, fruits, meat, fish, etc.) are cut.
Bones), use saws.
Pressing... Pressing of products is mainly used to separate them into two fractions: liquid (juices) and dense (pulp, pulp). In the process of pressing, the cellular structure of the product is destroyed, as a result of which juice is released.
Compression, in addition, is used to give a certain shape to plastic materials (dough, creams, etc.).
Molding... This method of mechanical processing is used to give a product a certain shape. Poultry carcasses are shaped for greater compactness, cutlets and meatballs, pies and Pies, blanks for cookies, etc. This process is carried out manually or using machines: cutlet-molding machines, automatic machines for making pancakes, dumplings, dumplings, etc. ...
Dosage... To obtain culinary products of the appropriate quality, it is necessary to strictly observe the established recipes. For this purpose, products are dosed by weight or volume. Dishes, drinks, confectionery products are released to visitors of public catering establishments in a certain amount - in portions (portioning),
The mass or volume of which is called "output". Dosing is carried out manually using measuring equipment, scales, as well as special machines and devices (dough dividers, dispensers, etc.).
Breeding. This is a mechanical culinary treatment, which consists in applying breading (flour, rusks, sliced wheat bread, etc.) to the surface of a semi-finished kata. As a result of breading, the flow of juice and evaporation of water during frying decreases, and the finished culinary product has a beautiful golden brown crust.
Stuffing... This mechanical culinary treatment consists in filling specially prepared products with minced meat.
Spigging... Mechanical culinary processing, in the process of which vegetables or other products provided for by the recipe are introduced into special cuts in pieces of meat, carcasses of poultry, game or fish.
Loosening. Mechanical culinary processing of products, which involves partial destruction of the connective tissue structure of animal products to accelerate the cooking process.
3 ... The hydromechanical effect on products consists in removing contaminants from the surface and reducing microbial contamination, as well as in soaking some types of products (legumes, cereals) in order to intensify heat treatment processes, in soaking salty products, in separating mixtures consisting of parts of different specific gravity and dr.
^ Rinsing and soaking ... Almost all products entering the bp are washed. Washing meat with warm water using a shower brush can reduce the contamination of its surface by 80-90%. Washing vegetables allows for rational use of waste, extends the life of potato peelers
Roots and tubers are washed mechanically in washing machines, as well as manually in baths with running water. Meat carcasses, half carcasses are washed using fountain brushes, the effectiveness of washing devices depends on the speed of water movement.
Soaking food before cooking (such as cereals, legumes, dry fruits and vegetables) will speed up the cooking process.
Flotation. For the separation of mixtures consisting of particles of different specific gravity, flotation is used. An inhomogeneous mixture is immersed in a liquid, while the lighter particles float up, and the heavier ones sink. For example, to separate stones, before cleaning, potatoes are immersed in a 20% solution of table salt, where the tubers float, and the stones are chickpeas. When cereals are immersed in water (when washing), light impurities float, and the grains sink to the bottom of the dish.
^ Sedimentation, filtration ... As a result of carrying out a number of technological processes, suspensions are obtained - mixtures of two (or more) "substances, of which one (solid) is distributed in the other (liquid) in the form of particles of different dispersion, which are in a suspended state. Suspensions include, for example, starch milk obtained in the production of starch, or fruit juice containing pulp particles of various sizes and shapes.Filtering and precipitation are used to separate suspensions into liquid and solid parts.
Sedimentation- the process of release of solid particles of suspensions under the influence of gravity. At the end of the deposition, the clarified liquid is separated from the sediment.
Filtration e - the process of separating suspensions by passing them through a porous partition (cloth, sieve, etc.), capable of retaining suspended particles and passing the filtrate. In this way, you can almost completely free the liquid from suspended particles.
Emulsification... For some culinary products, emulsification is used. During emulsification, one liquid (dispersed phase) is broken into small droplets in another liquid (dispersed medium). To do this, combine two immiscible liquids (oil and water) and quickly stir them, while the interface between the liquids significantly increases. In the surface layer, surface tension forces act and therefore individual droplets tend to enlarge, as a result of which free energy decreases. This leads to the destruction of the emulsion. To give stability to the emulsion, emulsifiers are used. These are substances that either reduce the surface tension or "form protective films around the droplets of crushed liquid (oil). Emulsifiers are of two types: powder-like and molecular.
Powder-like emulsifiers are fine powders of mustard, ground pepper and other products that create a protective layer at the interface between two liquids and prevent droplets from sticking together. Powdered emulsifiers are used to obtain low-stability emulsions (dressings in vegetable oil). , /
Molecular emulsifiers (stabilizers) are substances whose molecules consist of two parts: long hydrocarbon chains, which have an affinity for fat, and polar groups, which have an affinity for water. The molecules are located at the interface between two liquids so that the hydrocarbon-hydrogen chains are directed towards the fat phase, and the polar radicals are directed towards the water phase. Thus, a strong protective film is formed on the surface of the emulsion droplets. These emulsifiers (substances contained in egg yolks, etc.) are used in the preparation of stable emulsions, such as mayonnaise and Dutch sauce.
Foaming(whipping). This is a mechanical culinary treatment, which consists in intensively mixing one or more products in order to obtain a fluffy or foamy mass.
Foaming, like emulsification, is associated with an increase in surface area. The interface is the boundary of two different phases: gas and liquid. In foams, gas bubbles are separated by the thinnest liquid films that form a film frame. The stability of the foams depends on the strength of this framework. Foams are characterized by two indicators: expansion rate and durability.
Brevity is the ratio of the volume of the foam to the liquid phase.
Persistence is the half-life of the foam during storage.
3 ... Mass transfer methods are characterized by the transfer (transition) of one or more substances from one phase to another. For example, when food is dried, water turns into steam. The basis of various mass transfer methods of processing is the difference in concentration, therefore they are often called diffusion-based.
In culinary practice, such mass transfer methods of processing are used as dissolution, extraction, drying, thickening.
Dissolution- transition of the solid phase to the liquid. In kuli-narnoi practice, salt and sugar solutions of various concentrations are often prepared.
Extraction (extraction) - selective extraction of a substance from a liquid or solid porous body with a liquid. In culinary practice, extraction takes place when salted fish, beef kidneys, a number of mushrooms are soaked before cooking, etc.
Drying, thickening is the removal of moisture from solid plastic and liquid products by evaporation. In culinary practice, this happens when drying croutons, homemade noodles, boiling tomato puree, concentrated broth (fume), thickening cream, etc.
Chemical, biochemical, microbiological processing methods.
The purpose of these methods of culinary processing is to impart certain properties to culinary products by the action of chemicals, enzymes, microorganisms.
Sulphitation- chemical culinary treatment of peeled potatoes with sulfurous anhydride or solutions of salts of sulfurous acid in order to prevent browning.
Pickling- chemical culinary treatment, which consists in keeping products in solutions of food acids in order to impart specific taste, aroma and consistency to finished products.
^ Fixation of fish semi-finished products - keeping them in a cooled saline solution to reduce the loss of juice during storage and transportation.
Chemical loosening of the dough- the use of sodium hydro-carbonate, ammonium carbonate and special baking powders to give the dough a fine-pored structure.
^ Alcoholic and lactic acid fermentation cause yeast and lactic acid bacteria in the manufacture of yeast dough, kvass, etc.
Fermentation of meat- the use of proteolytic enzymes (hydrolyzing protein), softening the connective tissue of meat in the process of heating it. This allows you to expand the range of dishes by using parts of the carcass that are not intended for frying.
Enzyme preparations acting on the protein-carbon-water complex are widely used in the preparation of dough products. With their help, you can prepare different types of dough from the same batch of flour.
Control questions.
Lecture number 4 Heat treatment of food.
Plan.
1. The meaning of heat treatment and the classification of methods.
2. The main methods of heat treatment.
3. Auxiliary and combined methods of heat treatment.
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The main chemical processes occurring during the thermal cooking of products
The nature of the processes occurring during the heat treatment of plant and animal products is significantly different.
A distinctive feature of plant products is their high carbohydrate content - over 70% of dry matter. The vast majority of plant products used in human nutrition are plant parts containing living parenchymal cells. They contain substances of interest in nutrition - mono- and oligosaccharides and starch. These cells have a primary membrane consisting of low molecular weight cellulose and low molecular weight fractions of hemicelluloses, a distinctive feature of which is the predominance of the p-1,4 bond between the structural units (this is important, since it is this bond that is not destroyed by human digestive enzymes). In the median lamina and intercellular spaces there are pectin substances. They are based on the remains of galacturonic acid, interconnected by a-1,4-bonds (this bond is also not destroyed by human digestive enzymes). However, the degree of their polymerization, depending on the phase of development of a living cell, can vary greatly: from 20 to 200 or more residues. With an increase in the degree of polymerization, the solubility of pectin substances and water decreases and the mechanical strength increases. Thus, the reclaimed "protopectin", with which the mechanical hardness of fruits, berries and vegetables is associated, is actually a high molecular weight pectin, which forms a "secondary" structure due to the binding of water, which, due to the special properties of the "bound" "ode," imparts mechanical strength to plant products. At the same time, all plants contain active pectinesterases and somewhat less active polygalacturonases, which are activated at a certain period of plant life and begin to destroy the secondary structure of pectin with the formation of low molecular weight pectins and water. In this case, the product softens (this enzymatic process can also occur during storage). Since the primary wall is easily permeable, and the secondary, and even more so tertiary, there are no walls in living cells, the low molecular weight pectin and water formed under the action of non-political enzymes partially pass into the protoplasm of the cells.
When cooking under pressure, when the temperature rises against the usual by 2-3 C, the cooking duration is reduced by about 1.5 times. Small pieces warm up (up to 70-80 CC in the entire volume) faster than large ones, but at the same time, the extraction of water-soluble substances increases. Therefore, the grinding cannot be very strong. Practice has established the optimal product size and cooking duration.
Cooking products in the skins (for example, potatoes in the skins, beets and carrots in the skins) does not affect the duration, but leads to a noticeable decrease in the loss of nutrients, since the dense surface layer (epidermis, peridermis) prevents extraction. Steaming also reduces the loss of nutrients compared to boiling in water, since only the outermost layers are affected by the extraction.
During frying, the thermal decomposition of the "secondary" structure of pectins occurs mainly with the formation of soluble pectins and water. Starch grains and low molecular weight pectin begin to react with water, and they partially become gelatinous. However, if the evaporation of water from the product during frying occurs quite intensively, then the gel dries up and the product becomes solid again - its mechanical strength increases several times. To reduce the evaporation of water, frying is carried out in the presence of fat, which, enveloping the product, reduces the surface temperature and the rate of evaporation of moisture. With frequent stirring, a crust forms, which also retards evaporation, and the product becomes juicier.
You can generally fry in a layer of fat ("deep fat"). In fact, this is not frying, but cooking in fat. At the same time, the temperature of the medium is higher than with conventional cooking and softening occurs faster. There are few fat-soluble substances in plant products, therefore, the loss of nutrients during deep-frying is insignificant, with the exception, of course, of the vitamins that break down in this case.
In conclusion, about the heat treatment of plant products containing a small amount of pectin, but a lot of starch (cereals, legumes). Their processing consists mainly in the kleisterization of starch at elevated temperatures and in the presence of external water. Therefore, only cooking is applied to them. Water absorption of gelatinized starch reaches 100-200%,
In animal products, proteins are the most valuable in food and culinary terms (it is more correct to say not “protein”, but “proteins”, that is, there are many individual proteins that differ in composition and properties).
The mechanical strength of a meat product is determined by a certain rigidity of the “tertiary” structure of proteins. The highest rigidity is possessed by proteins of connective tissues (collagen and elastin). One of the main, but not the only factor determining the rigidity of the "tertiary" structure of most proteins of animal origin (with the exception of eggs, eggs) is the presence of water in them (in the form of "tightly bound", "hydrated", etc., which are not considered here) ... In meat products, the water in the "tertiary structure is associated mainly with muscle weakness and not with connective tissue. The content of connective tissue proteins depends on the nature of the raw material, the age of the animals and a number of other conditions.
At the same time, the mechanical strength of meat products decreases markedly.The temperature coagulation of proteins, depending on the nature, starts from 60 ° C, and for the majority of 70 ° C When cooking and frying meat, the temperature inside the product, depending on the type of meat and the size of the cusp, usually reaches 75 -95 ° C. However, frying meat with a large amount of connective tissue is not recommended, since the water released when the “tertiary” structure of muscle proteins is destroyed may not be enough for gelatinization (moreover, some of the water evaporates). Such "stringy" meat is best cooked or stewed. Since the acidic reaction of the medium contributes to the gelation of connective tissue proteins, it is advisable to soak the meat in acidic solutions (in vinegar, in dry wine) or stew in the presence of vegetables containing organic acids (for example, tomatoes), or with tomato paste - in these cases, the tissues soften significantly faster. Mechanical destruction of connective tissue has the same effect.
With traditional frying of meat products, despite the fact that fat is added, there is a rather intense evaporation of water; the product simply dries out during prolonged frying and becomes harder again. To reduce this undesirable process, it is recommended to first fry a piece of meat from different sides until a partially waterproof crust is formed (which also gives a pleasant specific taste) or bread it in flour or ground breadcrumbs. As a result, the moisture content does not drop so sharply and the meat is more tender.
Loss of nutrients during cooking occurs due to partial melting of fat and the extraction of a number of extractive components from tissues (nitrogenous and non-nitrogenous substances, minerals and vitamins). When frying, losses occur as a result of melting a large amount of fat, partial release of juice, thermal destruction of vitamins.
Oddly enough, at first glance, water losses occur not only during frying, but also during cooking, in water, and they reach noticeable values (in comparison with plant products) - on average, from 30 to 50%, depending on the type of meat. These losses occur due to the destruction of the "tertiary" structure of muscle proteins during their coagulation. At the same time, the "secondary" structure is no longer able to hold a large amount of water, which is released together with water-soluble substances into external water.
Pressure cooking, by increasing the temperature, accelerates the gelatinization and thus shortens the time to obtain the finished product.
You will get some idea of the amount of loss of basic nutrients in various methods of thermal cooking by looking at table. 23.
Summarizing what has been said about the heat treatment of foodstuffs, the following conclusions can be drawn.
The most rational heat treatments from the point of view of preserving valuable nutrients are: for vegetable products - cooking without draining the broth and cooking in the peel; for animals - stewing, baking, using meat in the form of cutlets, especially steam.
With any heat treatment, the most intense destruction of vitamins, especially vitamin C.
What practical advice can you give a housewife to choose a method of heat treatment, which is better - to boil, fry or stew?
It seems that for the preparation of everyday food it is necessary to use the most rational methods of heat treatment. At the same time, greens, fresh vegetables and cabbage are often served for appetizers and side dishes in order to compensate for the loss of vitamins that occur during heat treatment. Rational methods of heat treatment are also very useful for those who need a dietary diet: there are no mechanical irritants in the gastrointestinal tract (toasted kidney) in the products.However, it would be wrong to completely abandon the taste of their fried foods for practically healthy adults. But it is better to postpone cooking until Sundays and holidays. Such a variety in the diet can be given.
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Home cooking basicsHome cooking technology
METHODOLOGICAL MATERIAL ON THE TOPIC:
"CHEMICAL BASES
HOME COOKING "
We will try to make some generalizations that allow
identify general patterns of changes in the chemical composition of products
in culinary treatments.
The main chemical processes taking place
during thermal cooking
About 80% of food products are heat treated, when
which increases the digestibility, softening of the products occurs.
Exposure to heat destroys harmful microorganisms, and
this ensures the sanitary and hygienic safety of products, in the first
queue of animal origin.
Various types of heat treatment allow for varied taste
products. But the heat treatment of food is not without its drawbacks:
it destroys vitamins and some biologically active substances,
proteins, fats, minerals valuable for the body. Thus,
the task of rational cooking is to ensure that the necessary
the goal was achieved with minimal loss of useful properties of the product.
Herbal products.
The vast majority of herbal products used in
human nutrition - these are parts of plants with living cells, in which
contains mono, oligosaccharides and starch. Heat treatment
plant foods containing a noticeable amount of pectins,
aimed at partial release of water. This process begins at
temperature over 60 ° C and then accelerates approximately twice for every
10 ° C rise in temperature. As a result, in the finished product its
the mechanical strength is reduced by more than 10 times. It should be noted,
that the mechanical strength of plant products depends on the content
there is water in them. The less water in the product, the greater its strength at
other conditions being equal.
During cooking, the cells are saturated with water. Although the starch remains
in the cell plasma, and pectin - in the intercellular space, extraction
starch and pectin occurs not only from the surface of the destroyed
cells, but also from the inner layers. At the same time, during cooking, it is extracted
a number of water-soluble substances (sugars, amino acids, organic acids,
minerals and vitamins) from the layers of the product in contact with
water.
Steam boiling reduces the loss of substances compared to boiling in water,
since the extraction takes place only from the most superficial layers.
When frying, mainly thermal decomposition of the structure occurs.
pectins and water. Starch grains and low molecular weight pectin begin
react with water and partially pass into a foamy state.
However, if the evaporation of water from the food during frying occurs
intensively enough, the gel dries and the product hardens again.
Its mechanical strength increases several times.
Heat treatment of plant products,
containing
a small amount of pectin, but a lot of starch, accompanied by
gelatinization of starch and consists, as a rule, in boiling in water.
The water absorption of gelatinized starch reaches 100–120%.
Animal products.
In animal products, the most valuable in food and
the culinary relation is protein.
The mechanical strength of meat products is due to a certain
the rigidity of the tertiary structure of proteins. The greatest rigidity is possessed by
proteins of connective tissues. One of the factors that determine
rigidity of the tertiary structure of most animal proteins
origin is the presence of water in them. Water in meat products
in the tertiary structure of the protein it is associated mainly with muscle proteins,
and not with proteins of connective tissues.
Heat treatment of animal products consists in partial
destruction of connective tissue, as well as muscle proteins. Destruction
occurs due to water participating in the formation of the tertiary structure
muscle proteins and released during their temperature coagulation.
During heat treatment, the released water is introduced into the secondary
the structure of proteins, breaking down and bringing connective tissue proteins into
gelatinous state. Mechanical strength of meat products
at the same time it decreases markedly.
Changes in the nutritional value of foods
during heat treatment
In plant products, most of the nutrients are lost when
frying: an average of 5% protein and 10% fat. The loss of carbohydrates is great (10-20
%) and minerals (up to 20%) as a result of juice leakage and
crust formation. Cooking loss is highly dependent on the method
heat treatment. If cooking is done without draining (cooking soups,
jelly, compotes), the loss of almost all nutrients is minimal: 2-5%
proteins, fats, carbohydrates and minerals. When cooking most
vegetables, pasta, where plums are made, loss with decoction
proteins, fats, vitamins, minerals increases 2-3 times and
approaching frying losses.
The greatest losses of important nutrients in the process of heat
processing of animal products are observed during cooking: proteins - 10%,
fats - 25%, minerals and vitamins of group B - 30%, A - 50%,
C - 70% (due to the transition to broth and partial decay). When frying meat
loss of minerals and vitamins is about 1.5 times less than
when cooking, protein - the same, and fat - a little more. Minimum losses -
15% proteins, fats and minerals, 15-30 percent vitamins -
observed when stewing and baking.
The loss of proteins in animal products is higher than in plant products, since
the absolute protein content in the latter, as a rule, is quite low, and it,
obviously more tightly bound. The same can be said for fats. Losses
there are twice as many minerals in animal products than in
vegetable. As for vitamins, their main losses are explained by
not change or removal during cooking or frying, but destruction due to
high temperature.
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Ministry of Education and Science of the Russian Federation
Kuban State Technological University
Department of technology and catering
Examination number 1 in the discipline:
Physical and chemical foundations of technology of public catering products
Completed: 3rd year student
Oleg Shevelev
Specialty: 260800
Reviewer: Severina Natalia Alexandrovna
Krasnodar 2013
Introduction
1. Destruction of proteins
1.1 The essence of the destruction process
3. Carotenoids and chlorophylls
List of sources used
Introduction
Currently, the main principle of the production of public catering products is the creation of dishes and products with increased nutritional value and meeting modern requirements of sanitary and hygienic standards.
The scientific and theoretical substantiation of technological processes of production of public catering products was first given by the Technological Department of the Institute of Nutrition of the Russian Academy of Medical Sciences. The first experimental and theoretical studies in this area were carried out in 1935 - 1960. In subsequent years, technological science deepened and expanded thanks to the contribution of many scientists, both in our country and abroad.
Food raw materials and food products are complex multicomponent biological systems that undergo irreversible changes at different stages of the technological process of manufacturing products in public catering establishments. The main changes occur during the mechanical, hydromechanical processing of raw materials and products, as well as during the heat treatment of semi-finished products and the preparation of ready-made food.
Physicochemical processes occurring in food systems during the culinary processing of raw materials of plant and animal origin, the impact of these processes on the nutritional value and safety of products, changes in the structural and mechanical characteristics of raw materials and semi-finished products, as well as other issues will be considered in this course.
The study and understanding of the physical and chemical processes occurring during the production of products is a prerequisite for the creation of high-quality products, as they allow you to enhance the positive and minimize the negative impact of culinary processing on the quality of finished products.
1. Destruction of proteins
protein cooking oil vegetable
1.1 The essence of the process of destruction of proteins
When food is cooked, changes in proteins are not limited to denaturation. To bring the product to full readiness, it is necessary to heat it at temperatures close to 100? C, more or less a long time. Under these conditions, proteins undergo further changes associated with the destruction of their macromolecules. This leads to the destruction of the protein molecule. Destruction is a change in the composition of protein molecules with prolonged exposure. Destruction is characterized by the rupture of peptide bonds and depolymerization of polypeptide chains and the formation of soluble and volatile compounds that determine the taste and smell of products.
Distinguish between mechanical, enzymatic and thermal destruction.
An example of mechanical degradation of protein is the whipping of egg whites in order to obtain a stable foam. However, as a result of prolonged mechanical action, the egg white begins to flow.
Enzymatic destruction occurs as a result of the use of various enzymatic preparations.
Thermal destruction of proteins is accompanied by the formation of such volatile products as ammonia, hydrogen sulfide, carbon dioxide and other substances.
The exception is the protein of meat and fish raw materials collagen, the destruction of which leads to the formation of glutin - a protein soluble in hot water. The amino acid composition of glutin is similar to that of collagen. On their surface, glutins, like protein substances, have functional groups and regions. Functional groups are hydrophilic. (The softening of meat and fish products during thermal cooking is associated with the destruction of connective tissue collagen and its transition to glutin).
1.2 Factors causing the breakdown of proteins in the culinary processing of raw materials
The conversion of collagen to glutin is influenced by the following technological factors:
a) the temperature of the environment. When frying meat, poultry, fish, when the temperature in the thickness of the product does not exceed 80 - 85 ° C, the transition of collagen into glutin proceeds slowly. In this regard, culinary processing by frying is possible only for parts of carcasses in which collagen is relatively small and the morphological structure of the connective tissue is simple (collagen fibers are thin, located parallel to the direction of muscle fibers). Fish collagen undergoes destruction much easier than meat (beef), since the connective tissue of fish has a relatively simple morphological structure, there is less hydroxyproline in the collagen, it undergoes denaturation and destruction at lower temperatures.
b) the reaction of the environment. Acidification of the environment with food acids or foods containing these acids accelerates the conversion of collagen to glutin.
The destruction of collagen to glutin is accelerated in an alkaline environment. It is used in the meat industry to make gelatin, which is dried glutin.
c) grinding. It helps to reduce the hydrothermal stability of collagen. This is due to the fact that when chopping meat or loosening portioned pieces of meat, collagen fibers are cut into smaller fragments, the surface of contact of the protein with the environment increases many times over.
The behavior of the protein-glutin in solution depends on the temperature. At high temperatures, aqueous solutions of glutin have the properties of a normal (Newtonian) liquid, glutin molecules, regardless of their molecular weight, are isolated from each other. As the solution cools, at a temperature below 40 ° C, its molecular-dispersed state is disturbed, and the properties of an elastic-viscous liquid, characteristic of pseudo-solutions, appear. Further cooling of the glutin aqueous solution is accompanied by the gradual appearance of elastic properties with the formation of jelly. In the solution, the process of structure formation takes place, during which the glutin molecules form a three-dimensional framework, connecting with each other and providing a certain strength of the system. The stability of the mesh framework is provided by hydrogen bonds that arise between the hydrophilic regions of glutin and water.
The more polar the glutin molecules are, the more they are attracted to each other and the stronger the interaction.
When heated, the jellies return to a liquid state. Under the influence of heat, water molecules acquire kinetic energy. This energy is higher than the energy of hydrogen bonds of their mutual attraction, and therefore, under the action of water, the glutin molecules move away from each other and the water comes out.
2. Changes in fat when deep-fried
The duration of deep-frying food is short. So, at a deep-frying temperature of 180 ° C, portioned pieces of fish are fried for about 5 minutes, pies, donuts, pasties - 6 minutes. The readiness of the fried product is assessed by the formation of a specific crust on its surface. Thus, the depth of physical and chemical changes in fat is influenced not so much by the process of frying products, but by the duration of using the deep fat itself (2 - 3 shifts or more).
An important factor influencing the course of physicochemical processes in fats is the temperature of deep-frying fat. So, at a temperature of 200 ° C, fat hydrolysis proceeds 2.5 times faster than at 180 C. At the same time, the processes of polymerization of glycerides and fatty acids are noticeably accelerated. Overheating of frying fat is possible for two reasons:
Due to its local overheating near the heating elements of the fryer (deep fryer),
During the idle heating period, when the fried product has been removed from the fat, and a new batch of product has not yet been incorporated into the fat.
Deep-fried frying can be continuous or intermittent.
In continuous deep frying, fat is continuously removed from the frying vat containing the finished product and replenished by adding fresh fat. As a result of the changeability of the heated fat, its oxidation state quickly reaches a stable state and subsequently changes little. The higher the coefficient of fat turnover, the slower it undergoes oxidative changes.
Fat is most destructively affected by intermittent deep-frying. In this case, the fat is heated for a long time without food (idle heating) and is periodically used for frying various foods. Idle heating also occurs during reheating. Alternating heating and cooling is more damaging to fat than continuous heating for the same time. This is due to the acceleration of the autooxidation of the previously heated fat during the period of its cooling.
2.1 Measures to preserve the quality of frying fats
An important factor in maintaining the quality of deep-frying fats during the frying period is the degree of contact of the fat with air oxygen, without which even prolonged heating at 180 - 200 ° C does not cause noticeable oxidative changes in the fat. Heating the fat in a thin layer, frying products with a porous structure, intensive foaming and mixing of the fat contribute to an increase in contact with air.
The chemical composition of fried products also has a noticeable effect on the rate of thermal fat oxidation. Thus, the proteins included in the composition of the products are capable of exerting an antioxidant effect, and some substances formed as a result of melanoid formation reactions have a reducing effect and can interrupt the chain of oxidative transformations.
The more noticeable oxidation of deep-frying fats during idle heating compared to their oxidation during frying products can be explained by the anti-oxidative effect of other components that make up the fried foods in small quantities (ascorbic acid, some amino acids, glutathione).
At the first stage of deep-frying products, the same physicochemical changes in lipids occur as in conventional frying: the acid and peroxide numbers increase, the iodine number decreases. Subsequent deep-fat frying is accompanied by the decomposition of peroxides, hydroperoxides and hydroxy acids and the formation of thermostable oxidation products: carbonyl and dicarbonyl compounds, fatty acids with conjugated double bonds, polymerization products. Accordingly, the refractive index, the iodine number of the fat and the optical density increase.
Medical and biological research in recent years has shown that the greatest danger to humans is represented by products of oxidation, pyrolysis and polymerization, which are absent in natural edible fats.
3. Carotenoids and chlorophylls
Carotenoids are highly unsaturated hydrocarbons. Their molecules contain a large number of conjugated double bonds. Carotenoids dissolve well in fats and are resistant to heat. Therefore, the native (yellow, orange) coloration of cooked foods does not disappear. Discoloration occurs under the influence of atmospheric oxygen.
Carotene is found in many fruits, vegetables, and green leaves along with chlorophyll and xanthophyll. Carotene is found in three isomers. All of them are capable of autooxidation.
The color of lycopene is orange-red, more intense than that of carotene. It has thirteen double bonds and consists of eight isoprene residues.
Xanthophyll and its isomer zeaxanthin are carotene derivatives. They are yellow in color and are found in the chloroplasts of green leaves.
Chlorophylls give fruits and vegetables a green color. The chlorophyll molecule has four pyrrole nuclei and a metal atom - magnesium. There are chlorophyll and chlorophyll. During heat treatment, chlorophyll darkens, as its destruction occurs, and it passes into phyophytin.
3.1 Changing the color of vegetables and fruits with green and yellow coloring in the process of their culinary processing
The green color of vegetables (sorrel, spinach, green peas, legume pods) and some fruits (gooseberries, grapes, plums, etc.) is due to the presence of chlorophyll pigment, mainly b-chlorophyll.
By its chemical nature, a-chlorophyll is an ester of a dibasic acid and two alcohols: methyl and phytol.
Green vegetables and fruits turn brown when boiled and stewed. This happens due to the interaction of chlorophyll with organic acids or acidic salts of these acids contained in the cell juice of vegetables and fruits, with the formation of a new brown substance - pheophytin:
In raw products, this reaction does not occur, since chlorophyll is separated from organic acids or their salts contained in vacuoles by tonoplast.
In addition, chlorophyll, which is in a complex with protein and lipids (in chloroplasts), is protected by these substances from external influences. Only when the integrity of the cells of the parenchymal tissue is disturbed, brown spots appear in the damaged areas of vegetables.
During thermal cooking of vegetables and fruits, the protein associated with chlorophyll is split off as a result of denaturation, plastid membranes and tonoplast are destroyed, as a result of which organic acids are able to interact with chlorophyll.
The degree of change in the green color of vegetables and fruits depends on the duration of the heat treatment and the concentration of organic acids in the product and the cooking medium. The longer green vegetables and fruits are boiled, the more pheophytin is formed and the more noticeable their browning. The color of vegetables with a high content of organic acids (for example, sorrel) changes significantly.
To preserve the color of green vegetables, it is recommended to cook in a large amount of water with the lid open and boil intensively for a strictly defined time required to bring them to readiness. Under these conditions, part of the volatile acids is removed with water vapor, the concentration of organic acids in the products and the cooking medium decreases, and the formation of pheophytin slows down.
The color of green vegetables and fruits is better preserved when boiled in hard water: the calcium and magnesium salts contained in it neutralize some of the organic acids and acidic salts of cell juice.
When boiling and stewing, green vegetables and fruits, in addition to brown color, can acquire other shades due to a change in the already formed pheophytin under the influence of ions of some metals. For example, if iron ions are present in the cooking medium, vegetables may turn brown, if aluminum ions are grayish, Cu ions are bright green.
The yellow-orange color of vegetables (carrots, tomatoes, pumpkin) and some fruits is due to the presence of carotenoids in them.
In the process of culinary processing, the color of these vegetables and fruits does not noticeably change. It is believed that carotenoids are practically not destroyed in this case. On the contrary, boiled carrots contain even more carotenoids than raw carrots. The increase in the content of carotenoids during the cooking of carrots can be explained by the destruction of protein-carotenoid complexes and the release of carotenoids that occurs during this process.
When frying tomatoes, pumpkins and sautéing carrots, carotenoids are partially converted into fat, as a result of which the color intensity of vegetables decreases slightly.
List of used literature
1. Technology of production of public catering. In 2v. Vol. 1. Physicochemical processes occurring in food products during their culinary processing / A.S. Ratushny, V.I. Khlebnikov, B.A. Baranov et al. / Ed. A.S. Town Hall. - M .: Mir, 2003 .-- 351 p.
2. Technology of cooking / N.I. Kovalev, M.N. Kutkina, V.A. Kravtsova. - M .: Publishing house "Business Literature", Publishing house "Omega - L", 2003. - 480 p.
3. Technologies of food production / Ed. A.P. Nechaev. - M .: Publishing house "KolosS", 2005. - 768 p.
4. Mogilny M.P. Public catering technology: ref. allowance. - M .: DeLi print, 2005 .-- 320 p.
5. Food chemistry / A.P. Nechaev, S.E. Traubenberg, A.A. Kochetkova et al. / Ed. A.P. Nechaev. - SPb .: "GIORD", 2012. - 672 p.
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Rice. 1.3. Starch grain structure:
1 - the structure of amylose; 2 - the structure of amylopectin; 3 - starch grains of raw potatoes; 4 - starch grains of boiled potatoes; 5 - starch grains in raw dough; 6 - starch grains after baking
When heated from 55 to 80 ° C, starch grains absorb a large amount of water, increase in volume several times, lose their crystal structure and, consequently, anisotropy. The starch suspension turns into a paste. The process of its formation is called gelatinization. Thus, gelatinization is the destruction of the native structure of the starch grain, accompanied by swelling.
The temperature at which the anisotropy of most grains is destroyed is called the temperature gelatinization... The gelatinization temperature of different types of starch is not the same. So, the gelatinization of potato starch occurs at 55-65 ° C, wheat - at 60-80, corn - at 60-71 °, rice - at 70-80 ° C.
The process of gelatinization of starch grains is carried out in stages:
* at 55-70 ° C, the grains increase in volume several times, lose optical anisotropy, but still retain their layered structure; a cavity ("bubble") is formed in the center of the starch grain; a suspension of grains in water turns into a paste - a low-concentrated sol of amylose, in which swollen grains are distributed (the first stage of gelatinization);
* when heated above 70 ° C in the presence of a significant amount of water, starch grains increase in volume dozens of times, the layered structure disappears, the viscosity of the system increases significantly (the second stage of gelatinization); at this stage, the amount of soluble amylose increases; its solution partly remains in the grain, and partly diffuses into the environment.
With prolonged heating with excess water, starch bubbles burst, and the viscosity of the paste decreases. An example of this in culinary practice is the liquefaction of jelly as a result of excessive heating.
The starch of tuberous plants (potatoes, Jerusalem artichoke) gives transparent pastes of a jelly-like consistency, and cereals (corn, rice, wheat, etc.) - opaque, milky white, pasty consistency.
The consistency of the paste depends on the amount of starch: when its content is from 2 to 5%, the paste turns out to be liquid (liquid jelly, sauces, mashed soups); at 6-8% - thick (thick jelly). An even thicker paste forms inside potato cells, in cereals, pasta dishes.
The viscosity of the paste is influenced not only by the starch concentration, but also by the presence of various nutrients (sugars, mineral elements, acids, proteins, etc.). Thus, sucrose increases the viscosity of the system, reduces salt, proteins have a stabilizing effect on starch pastes.
When starch-containing products are cooled, the amount of soluble amylose in them decreases as a result of retrogradation (precipitation). At the same time, aging of starch jellies (syneresis) occurs, and the products become stale. The aging rate depends on the type of products, their humidity and storage temperature. The higher the humidity of the dish, culinary product, the more intensively the amount of water-soluble substances decreases in it. Aging occurs most rapidly in millet porridge, slower in semolina and buckwheat. An increase in temperature slows down the retrogradation process, therefore, dishes from cereals and pasta, which are stored on bain-marie with a temperature of 70-80 ° C, have good organoleptic characteristics for 4 hours.
Starch hydrolysis. Starch polysaccharides are capable of breaking down to the molecules of their constituent sugars. This process is called hydrolysis, as it goes with the addition of water. Distinguish between enzymatic and acid hydrolysis.
The enzymes that break down starch are called amylases. There are two types of them:
α-amylase, which causes partial degradation of starch polysaccharide chains with the formation of low molecular weight compounds - dextrins; with prolonged hydrolysis, the formation of maltose and glucose is possible;
β-amylase, which breaks down starch to maltose.
Enzymatic hydrolysis of starch occurs when making yeast dough and baking products from it, boiling potatoes, etc. Wheat flour usually contains β-amylase; maltose, formed under its influence, is a breeding ground for yeast. In flour from sprouted grain α-amylase predominates, the dextrins formed under its influence give the products stickiness and unpleasant taste.
The degree of hydrolysis of starch under the action)
