What are the applications of frying technology in prepared foods?

Prepared foods (Prepared foods), also known as convenience prepared foods, refers to agricultural, livestock, aquatic products as raw materials, after appropriate conditioning, properly packaged, in the frozen (18 ℃), refrigerated (7 ℃ or below) or by the gas conditioning and other treatments can be stored at room temperature, trafficking, and can be directly consumed or eaten before a simple processing or heat treatment can be consumed products.
Conditioned food is in essence a convenience food, with convenience, speed, delicious flowers, nutrition, safety and other characteristics. Because of its high value-added products and the demand for localized tastes, it is recognized as one of the products with development potential in the domestic food industry. With the innovation of technology, the improvement of cold chain circulation system, the updating of packaging materials and the development of high-efficiency defrosting equipment, the new type of prepared food has an unlimited market prospect.
Deep-fried seasoned food has a unique flavor, simple seasoning can be eaten, can be stored at room temperature and other advantages, can be accepted by the majority of consumers. In today’s fast-paced life, although people have mixed feelings about it, but one thing is indisputable, fried instant noodles, French fries and fruit and vegetable crisps and other representative of the bulk of fried seasoned food has become indispensable to people’s food.
Frying technology can be divided into three categories: atmospheric pressure frying, reduced pressure frying and high pressure frying. Atmospheric pressure deep-frying kettle pressure and environmental atmospheric pressure is the same, usually open, is the most common way of deep-frying, applicable to a wider range, but the food in the process of atmospheric pressure deep-frying nutrients and natural pigment loss is greater, so the atmospheric pressure deep-frying is more suitable for grain food deep-frying. Such as fried pastries, fried bread, fried instant noodles dehydration.
Low-pressure deep-frying, also known as vacuum deep-frying, food in the edible oil for deep-frying dehydration and drying, so that the water in the raw material is fully evaporated off the process. The frying temperature in the frying kettle is generally below 100 ℃, and the vacuum degree is 92~98.7 kPa. This method can make the products maintain good color, shape and crispness, and due to the low-oxygen environment, the products as well as the degradation of fats and oils will be reduced accordingly, and the loss of nutrients will be less.
High-pressure deep-frying is a method of deep-frying in which the pressure in the frying kettle is higher than the normal pressure. High-pressure deep-frying can solve the problem of affecting the quality of food due to the need for long-time deep-frying, this method of high temperature, water and oil volatilization loss is less, the product is crispy on the outside and tender on the inside, which is most suitable for the deep-frying of meat products, such as deep-fried chicken thighs, deep-fried steak and so on.
Microwave heating compared with conventional heating has significant differences, mainly due to the heating form, heating speed of the different, resulting in different distribution of heat energy and moisture in the food, thus affecting the intrinsic quality of food. Conventional heating requires heating environment and heat medium, it takes a relatively long time to reach the desired heating temperature, while microwave heating can make the food directly absorb microwave and can be heated immediately.
Microwave heating of food is through the microwave electric field and magnetic field alternating cycle changes, so that the dipole molecules in the food (such as water, proteins, etc.) with the magnetic field changes continue to turn back and forth, molecules and molecules of friction, collision, vibration, extrusion and other roles to generate heat, so that the food is heated, and the heating speed, time-consuming short, high quality products. The combination of microwave and vacuum deep-frying can not only rapidly dehydrate in a short time, but also maintain the quality of the product under negative pressure, thus realizing the microwave efficient deep-frying of seasoned food.
Atmospheric Frying Conditioned Food
1, atmospheric pressure deep-frying atmospheric pressure deep-frying as a means of food processing can be traced back to 1600 BC and the ancient Egyptian era. Although there is no clear record of the time when deep-frying was actually used as a means of food processing, the word “frying” is derived from the Latin and Greek word “roasting”, which suggests that deep-frying may have been developed by the roasting technique. Normal pressure deep-frying because of its earlier origin, domestic and foreign research on the deep-frying technology and equipment is more mature, and is now more popular at home and abroad.
2, atmospheric pressure deep-frying equipment, atmospheric pressure deep-frying equipment, mainly electric heating deep-frying equipment, gas frying equipment, continuous deep-fryer, oil and water mixing deep-frying equipment, microwave atmospheric pressure deep-frying equipment.
When the electric heating frying equipment is in operation, the material will be placed in the material net basket and put into the oil for frying. After frying, the basket is taken out together. This frying method has the following disadvantages:
1) The oil is at high temperature during the frying process, the oil oxidizes and deteriorates very quickly, the viscosity rises, and the oil becomes black-brown after repeated use for several times, which is inedible.
2) the bottom of the ash accumulation residue, with the prolongation of the frying time. The oil becomes more turbid, and the residue attached to the surface of the product will accelerate the deterioration of food, seriously affecting the health of consumers.
3) high temperature for a long time repeatedly frying food oil will generate a variety of forms of toxicity of different oil polymers, these substances can lead to nerve paralysis, stomach tumors and even death.
Gas frying equipment to gas as an energy source of a frying equipment, equipped with automatic ignition and manual ignition, flame control, frying time, temperature control, air pressure adjustment, etc., the use of safe, convenient, sanitary, is the more ideal frying equipment.
Continuous deep fat fryer equipment is characterized by no frying cage, but can make the material all submerged in the oil for continuous frying.
The heating of the oil is carried out outside the pot, with a hydraulic device that can raise the whole conveyor frame and its accessory parts and components from the oil tank, easy maintenance. The oil-water mixing fryer completely changes the structure of the traditional atmospheric pressure frying equipment. Scientifically adopting oil-water mixing technology, through the use of a new type of burner. Sealed heating, in the process of warming up the lower oil temperature is effectively controlled, slowing down the oxidation of frying, extending the service life of frying oil and improving the quality of products. Greatly enrich and revolutionize the deep-frying technology.
3, atmospheric pressure deep-frying research progress atmospheric pressure for deep-frying process, the oil temperature above 160 ℃, in the case of high temperature, will produce a special flavor. Some scholars have studied the oil intake and textural changes in fried potato chips, will be hot in 85 ℃ hot water for 3.5 min potato chips and untreated samples at 120, 150, 180 ℃ oil temperature for deep-frying. The results showed that the frying temperature and pretreatment method could significantly affect the final fat content of fried potato chips, and the higher the temperature, the lower the fat intake of potato chips. However, the frying temperature and pretreatment method had no significant effect on the final texture of fried potato chips.
In recent years, the use of microwave heating instead of traditional frying methods has become increasingly popular. Some scholars have studied the effect of pre-drying time on microwave low-oil potato chips. In order to potato chips have the flavor of fried food, while avoiding the low fat content of atmospheric pressure frying, the surface of the potato chips before baking with a brush coated with a layer of oil, so that the potato chips in the microwave treatment process to produce a “fried” environment. The purpose of microwave treatment is to dry and cook the potato chips, and the chips are baked in a microwave oven after being coated with oil until they are cooked. The results showed that the use of microwaves in the production of potato chips reduced the oil content to less than 20%. Microwave frying can be regarded as a suitable alternative to traditional frying.
4, atmospheric deep-frying problems atmospheric deep-frying due to the high temperature will bring a lot of problems, such as food nutrients at high temperatures are damaged, color, aroma, taste and so on affected. In addition, the high temperature makes the oil fuming, pollution of the environment, increasing oil consumption, while repeated use of deep-frying at high temperatures, will produce thermal oxidation reaction, the generation of unsaturated fatty acid peroxides, which can directly impede the body on the absorption of fats and proteins, reduce the nutritional value of food.
The components in the oil undergo many chemical reactions, leading to acidic degradation of the fried oil, thickening of the oil, producing bad taste. Even produce some harmful and even carcinogenic substances, affecting the health of consumers, such as acrylamide. Atmospheric pressure and high temperature fried food oil content are very high, so that some special groups (such as obese people, cardiovascular patients, etc.) want to eat and do not dare to eat, so that the scope of atmospheric pressure deep-fried food processing and sales have been greatly restricted. Therefore, reducing the oil content of atmospheric pressure frying products is also an urgent problem.
Vacuum Frying Conditioned Food
Vacuum deep-frying is a new food processing technology developed in the late 1960s and early 1970s, which organically combines dehydration technology and deep-frying technology, giving it many unique features and a wide range of adaptability to raw materials. The technology in the 1970s ~ 80s in the United States, Europe and Japan has been a great development, the international community has studied a lot of vacuum fried foods are fruit: apple crisp, banana chips, mango slices, etc.; Vegetables: carrots, potatoes, beans, sweet potatoes, etc.; Meat and aquatic products: fish, beef, shrimp and so on. In recent years, China has developed a soybean, jujube, taro, broad beans, sea asparagus and other fruits and vegetables vacuum frying products, vacuum frying technology research is constantly in-depth.
1, the principle of vacuum deep-frying technology vacuum deep-frying in essence is under negative pressure conditions, food in the edible oil for deep-frying dehydration and drying. The boiling point of water at atmospheric pressure is 100 ℃. Vacuum system relative to atmospheric pressure is in a negative state, with a significant reduction in pressure, the boiling point of water will be reduced accordingly. At 10-100 mm Hg vacuum. The boiling point of water is at 10-55°C. In the gasification separation operation of water-containing foodstuffs, vacuum is closely linked to low temperature. Operation under vacuum can effectively avoid a series of problems brought about by high-temperature treatment, such as polymerization deterioration of frying oil, browning reaction of the food itself, loss of nutrients and other closed.
2, vacuum deep-frying process features 1) puffing effect of vacuum deep-frying produced by the product has a significant puffing effect. This is because in the negative-pressure state, oil as a heat transfer medium, the water inside the food (free water and part of the combined water) will quickly evaporate and ejected, so that the organization of the formation of loose porous structure closed.
(2) Preservation of color and aroma using vacuum deep-frying, raw materials in the low-temperature, low-pressure oil and grease environment for processing. As most of the spices in the food are water-soluble, after the dehydration process, these flavor components are further concentrated, so the original flavor of the food can be well preserved. In addition, due to the low-oxygen environment, the food is easy to brown and fade, and the original color is maintained. But for containing oil-soluble pigments. Such as chlorophyll, carotenoids, etc., the pigments are easy to dissolve in the process of deep-frying, so it is necessary to carry out pretreatment to ensure the stability of pigments.
(3) Low oil content of the product due to the negative pressure . When frying, the gas diffuses into the pores of the foodstuff very quickly, which hinders the penetration of oil into the pores of the product. After the end of frying, the product is still kept under vacuum conditions for degreasing, in order to prevent that when the pressure is restored from negative pressure to atmospheric pressure, the pressure in the pores of the product increases rapidly to the level of atmospheric pressure, and the oil from the surface of the product penetrates into the pores, so that the product contains low oil content.
3, vacuum deep-frying pretreatment research progress due to consumer health concerns, in the processing of fried products, fat content has become a very important control indicators. Therefore, many experts and scholars are devoted to the research of reducing the fat content of fried products, which often requires pre-treatment of the samples: such as hot blanching, impregnation, coating, pre-drying.
4, the problems of vacuum deep-frying technology in China’s fruit and vegetable resources are abundant, expanding the production of fruit and vegetable crisps has great advantages, not only easy to carry, but also fully and reasonably utilize the resources. Vacuum frying technology is becoming more mature, processing more and more types of products are being developed day by day, but there are still some problems:
(1) the high fat content of products on the market fruit and vegetable crisps products with high fat content. Too much fat not only increases the production cost, but also shortens the storage period of the product, more importantly, the health of consumers to bring certain hazards, such as coronary heart disease, heart disease. Therefore, reducing the fat content of fried foods should become a goal that food researchers and food companies strive to achieve.
At present, the feasible and simple solution is to increase the solids content and coating technology, but there are still some problems for coating technology. Because edible colloids can hinder the penetration of oil at the same time. It also hinders the evaporation of water. So the final moisture content of the product will be all on the high side. We can research and cultivate the special quality of frying with high solids content according to the need. Both can reduce the fat content of the product and production costs, but also improve storage stability.
(2) the lack of certain products process research although many fruits and vegetables have been applied to vacuum deep-frying technology, and the establishment of a relatively perfect process and process parameters. But some new varieties of fruit and vegetable raw materials, due to its unique physicochemical composition, and can not use the ordinary vacuum frying process flow and parameters for processing. Therefore, in order to promote the comprehensive development and application of vacuum frying technology and the development of new products, for special fruits and vegetables vacuum frying process research is also very important.
(3) Lack of process research to maintain the quality of fried products in the stability of the storage period and shelf life of vacuum fried products have a fluffy and crispy structure, because it is easy to absorb moisture, and because it contains a lot of fat. It is easy to rancidity and fat oxidation phenomenon. One of the most important qualities of vacuum fried products is their crunchiness. And to maintain this state, its moisture content should be well controlled below 3%, so how to control the moisture content as well as the oxygen content in the packaging of fried products to avoid moisture absorption and fat oxidation is the focus of the research.
(4) Save energy consumption at present the domestic use of vacuum deep-frying technology using the heating source is generally steam energy or electricity, energy consumption, production costs are higher. How to make vacuum deep-frying can be carried out efficiently, there is an urgent need to develop new technologies, such as the use of microwave sources as a heating source, microwave heating and vacuum deep-frying technology combined to improve production efficiency, while improving product quality.
Conditioned food frying technology and equipment are varied, and various equipment have their own characteristics and scope of application. But each equipment and technology are more or less exist some defects, so people are constantly a variety of new technologies, new methods, can produce high-quality, low-fat products. The use of microwave vacuum technology and deep-frying technology and some pretreatment methods, can make the product in a shorter period of time, rapid dehydration, reduce the company’s production costs, improve the quality of the product, to achieve the effect of high efficiency and energy saving.