Food Frying Machines

small frying machine
Manual Frying Machine
automatic frying machine
Automatic Frying Machine
automatic continuous frying machine
Continuous Frying Machine
vacuum fryer frying machine
Vacuum Fryer

Food frying is the process of using oil to heat-process various foods at a relatively high temperature. Food can be quickly cooked by high-temperature frying, and a dry layer quickly forms on the surface, making it crispy on the outside and tender on the inside. This can maximize the retention of nutrients in the food, making it less likely to be lost and giving the food a unique golden color and rich oily aroma. At the same time, high-temperature sterilization helps to store food for a short period of time.

The purpose of frying

In the process of frying food, oil can provide fast and uniform heat conduction, firstly causing the surface water of the food to evaporate quickly, dehydrate, and harden, forming a shell layer and certain pores. Caramelization and Maillard reactions occur on the surface of the food, and proteins and other substances are pyrolyzed to produce volatile substances with color and special oil aroma. At the same time, because the food is quickly heated at high temperature, the shell layer formed on its surface will block the evaporation of water inside the food and form a certain vapor pressure, so that the food can be quickly cooked in a short time. Because the food contains more water and part of the collagen is hydrolyzed, fried products are often characterized by being crispy on the outside and tender on the inside.

food frying machine

Choice of frying oil

The oil used for frying requires fresh vegetable oil with low melting point, low peroxide value and low unsaturated fatty acid content. Hydrogenated oils can be used repeatedly for a long time.

At present, the common frying oils are peanut oil, safflower oil, soybean oil, grape seed oil, rapeseed oil, corn oil, olive oil, sesame oil, sunflower oil, etc. The appropriate oil should be selected according to different frying requirements.

oil types for food frying

Effects of frying on food

1. The impact of frying on food sensory quality

The main purpose of frying is to improve the color and flavor of food. Appropriate frying is conducive to the formation of a burnt taste and golden color, and produces a distinct fried aroma; a hard shell is formed on the surface of the fried product, thus forming the appearance of the fried food. However, when frying at high temperature continuously, volatile carbonyl compounds and hydroxy acids are often produced. These substances will produce unpleasant flavors and even burnt smells, resulting in poor quality and reduced commodity value.

2. The impact of frying on the nutritional value of food

The effect of frying on the nutritional value of meat products is related to the frying process conditions. During the frying process, the surface of the food is dehydrated to form a dry shell membrane layer. This hard shell prevents heat from being transferred to the inside of the food and water vapor from escaping. Therefore, the nutrients inside the food are better preserved and the water content is relatively high. At the same time, the oil content of fried products is also significantly increased.

During the frying process, meat products lose a lot of vitamins, especially fat-soluble vitamins (such as vitamin A, vitamin D, vitamin E, etc.) in the products, which will oxidize in the oil, resulting in a decrease in nutritional value or even loss. Changes in retinol (vitamin A), tocopherol (vitamin E), and carotenoids will cause changes in the flavor and color of meat products. During the frying process, water-soluble vitamins (such as vitamin B1, vitamin C, etc.) will also be lost to varying degrees.

3. Impact of frying on food safety

When food is fried at high temperature for a long time, some harmful PAHs will be produced, such as cyclic monomers, dimers and polymers, which can cause harm to the human body, such as nerve paralysis, tumor formation and even cancer. Therefore, the control of frying temperature and time becomes the key to frying technology.

french fries frying machine

Quality control of food frying

When frying, the most appropriate oil temperature and frying time need to be determined based on many factors, including the sensory evaluation of the finished product, quality requirements, the properties of the raw and auxiliary materials, the size of the cut pieces, the amount of food put into the pot, and product seasoning.

1. Frying temperature control

The effective temperature range for frying is between 100 and 230°C. The outstanding characteristic of oil in the heating process is that it heats up quickly. Therefore, the best way to control the oil temperature is to use temperature detection equipment to automatically control the oil temperature to ensure that the oil temperature is constant during the frying process. In general manual production, it is usually controlled by practical experience and process requirements. The most suitable frying temperature needs to be determined by temperature testing of the product. Generally, the frying temperature of meat products does not exceed 190°C.

2. Frying time control

When frying food, avoid frying for too long and repeatedly using frying oil. When using frying oil, pay attention to removing frying accumulation and adding fresh oil. Frying accumulation will accelerate the deterioration of oil and adhere to the fried products to form black spots. Therefore, it is necessary to remove floating objects and sediments in the oil, reduce the number of repeated uses and replace new oil in time (usually 15% to 20% of fresh oil should be added every day) to prevent large accumulation of polymers and ensure the safety of fried meat products.

In order to use frying oil more effectively and extend its service life, in addition to mastering the proper frying conditions, removing accumulated debris and adding fresh oil, antioxidants can also be added to the oil. Silicones are generally added to frying oil to reduce the generation of foaming. Adding metal chelates to frying oil can extend the use time and the shelf life of fried products.

automatic frying machine

The types of food frying technology

Modern food frying technology is no longer limited to traditional frying methods. At present, frying methods can be divided into three categories according to the different frying pressures: normal pressure frying, vacuum frying and high pressure frying. Among them, normal pressure frying is further divided into pure oil frying and water-oil mixed frying.

Normal pressure frying

Normal pressure frying is the process of frying food in an open container at normal pressure. Some traditional frying methods in our lives belong to normal pressure frying. Normal temperature frying can also be divided into pure oil frying and water-oil mixed frying according to the different frying media.

1. Deep frying in pure oil

In pure oil frying, edible oil is used as the frying medium in the frying container. The oil temperature and frying time vary according to different product requirements and can be divided into the following categories:

(1) Deep-frying: After proper processing, the tender raw meat is cut into pieces that meet the product requirements. According to the recipe, salt, cooking wine, and spices such as green onions and ginger are weighed and mixed with the raw meat for marinating. After marinating, the main ingredients are not coated with batter, but fried three times in high-temperature oil over high heat, which is deep-fried. For example, deep-fried pork liver, deep-fried yellow croaker, etc. The finished product features: crispy on the outside and tender on the inside, refreshing and neat.

(2) Dry frying: Take the raw meat, treat it properly, process it into shape, add seasoning, add water, starch, egg to coat it or coat it with paste, and fry it in a hot oil pan at 190-220℃. This is called dry frying. For example, dry fried pork chops, dry fried pork tenderloin, etc. The finished product features: dry and crisp, red and yellow in color, crispy on the outside and tender on the inside, and salty and spicy.

(3) Soft frying: Select tender animal raw meat, such as pork tenderloin, fresh fish, fresh shrimp, etc., and cut it into shapes after fine processing, coat it with starch, dip it in dry starch, and coat it with egg white paste. Then fry it in a hot oil pan at 90-120℃. For example, soft fried prawns, soft fried tenderloin, etc. The finished product features: light, soft surface, tender texture, salty and spicy taste, and the dish is white, slightly yellow, and beautiful.

(4) Deep-frying: After the animal raw materials are processed with knife skills, they are seasoned, dipped in flour, coated with whole protein paste, and dipped in bread crumbs, and then deep-fried in a hot oil pan at 150°C until the surface is dark yellow and crispy. Deep-frying technology requires strict control of the heat and oil temperature. If the oil temperature is too low, the raw materials will lose their paste after entering the pan. If the oil temperature is too high, the surface of the raw materials will easily stick to each other and become burnt after entering the pan. For example, deep-fried hairtail, crispy chicken, etc. Features of the finished product: dark yellow color, crispy surface.

(5) Deep-frying: Remove the bones from the raw meat and process it into a certain shape. After seasoning, dipping it in starch, and coating it with protein paste, put it into a hot oil pan at 150-160℃ and slowly fry it until cooked. Because the surface of the dish is golden and crispy, it is deep-fried. The characteristics of the finished product: golden surface, fluffy and full texture, soft and tender taste, salty but not greasy.

(6) Roll and fry: Cut the tender raw meat into large pieces, add the seasoning to it, roll it up with various flavors of fillings, roll it up, and choose whether to coat it with egg white paste according to the process requirements. Put it into hot oil at 150℃ and fry it until cooked. If the product needs to be coated with egg white paste, it must be rolled tightly to prevent it from falling apart during frying. If the finished product needs to be cut, it should be neatly packed or plated. Features of the finished product: golden color, crispy on the outside and tender on the inside, and fresh and salty taste.

(7) Deep-frying: After removing the feathers from the poultry, remove the internal organs and wash them. Then, scald them with boiling water to make the collagen on the surface shrink and tighten when exposed to heat. Cover the surface with a layer of starch water or other coloring liquid containing a small amount of maltose. After drying, fry them in a high-heat oil pan at 200-210℃ until the surface of the poultry turns red and yellow. For example: crispy chicken, crispy duck, etc. The finished product features: crispy skin and tender meat.

(8) Paper-wrapped fried food: Cut tender animal raw meat, such as pork tenderloin, chicken or duck breast, fresh shrimp and other high-grade raw materials into thin slices, shreds or fine paste, season and coat with starch, wrap them in glutinous rice paper or cellophane into a certain shape (such as triangle, rectangle, etc.), fry them in warm oil at 80-100℃, and then fish them out. This is called paper-wrapped fried food. Features of the finished product: beautiful shape, fresh juice inside, tender but not greasy, mellow taste, and unique flavor. Pay attention to wrapping the paper well so that the juice cannot leak out.

2. Water-oil mixed frying

Pure oil frying often causes the local oil temperature to be too high during the heating process, which accelerates the oxidation of the oil and causes part of the oil to volatilize into smoke, causing serious pollution. In addition, a large amount of food residue will be produced during the frying process and sink to the bottom of the oil pan. The residue will become turbid after repeated frying, thus shortening the service life of the frying oil, contaminating the fried food, and even producing some carcinogens, seriously affecting the health of consumers. Oil-water mixed frying fundamentally solves the above problems, making the development of frying technology more oil-saving, healthy and environmentally friendly.

(1) Principle Water-oil mixed frying means adding water and oil into the same container. The oil with a low relative density will occupy the upper half of the container, while the water with a high relative density will occupy the lower half of the container. A heating tube is installed horizontally in the middle of the oil layer. The heating tube uses a thermostat and a temperature controller to automatically adjust the firepower so that the oil temperature is constant at the preset temperature, effectively controlling the temperature of the upper and lower oil layers during frying, avoiding the occurrence of overheating and dry burning during frying, and slowing down the oxidation of the frying oil. During the frying process, the fried food is in the upper oil layer, and the food residue produced by frying will sink into the water at the bottom. At the same time, the oil contained in the residue can float up after separation and return to the oil layer. Therefore, once the residue is formed, it will quickly separate from the high-temperature oil layer and sink into the low-temperature water, and be discharged along with the water, thereby avoiding the residue from coking and carbonization.

(2) Characteristics Water-oil mixed frying has the following three characteristics:

①The products have good flavor and high quality. Through limit control and zone temperature control, the relative density relationship between vegetable oil and animal oil is scientifically utilized, so that the animal oil leached from the fried meat food naturally sinks into the lower layer of vegetable oil, keeping the purity of the working oil in the middle and upper layers, and can fry various kinds of food at the same time. Food does not have odor, effectively controls the oil content and appearance of food, improves product quality, and extends shelf life.

②Save oil for frying. Heating from the middle of the oil layer, controlling the temperature of the upper and lower oil layers, effectively alleviates the oxidation degree of the frying oil, inhibits the generation of acid value, thereby extending the service life of the frying oil. In addition, in this process, there is almost no oil that is discarded together with food residues and oil that is discharged as waste oil due to oxidation and deterioration. The amount of oil consumed is almost equal to the amount of oil absorbed by the food, and the amount of oil added is also close to the amount of oil consumed by the food. The amount of oil absorbed, so the fuel saving effect is significant.

③ Healthy and environmentally friendly. This method can make the food residues generated during the frying process quickly leave the high temperature area and sink into the low temperature area, and be discharged with water. The fried food will not be coked or carbonized, effectively controlling the production of carcinogens and ensuring the health of the eaters. At the same time, the water-oil mixed frying emits very little oil smoke, which is beneficial to the health of the operator on the one hand, and can protect the environment and reduce air pollution on the other hand.

automatic food frying machine

Vacuum frying

Due to a series of problems such as “nutritional loss”, “polymerization and carcinogen production” and “high oil content in fried foods” caused by room temperature frying, low temperature vacuum frying technology has emerged and received widespread attention in the food industry. This technology organically combines frying and dehydration, making it unique and widely adaptable to the processing of raw materials.

1. The principle of vacuum frying

The essence of vacuum frying is to use the characteristic that the boiling point of water decreases as the air pressure decreases. In a vacuum environment below atmospheric pressure, edible oil is used as a heat transfer medium to reach the boiling point of water at a lower temperature and evaporate the water in the food, so as to carry out the process of frying, dehydration and drying. For example, when the vacuum degree reaches 700mmHg (93.325kPa), the boiling point of water can be reduced to about 40℃. At this time, it is only necessary to heat the oil at a temperature higher than the boiling point of water to make the water in the food evaporate and overflow, so as to achieve frying of food under low temperature and low pressure conditions. In addition, the low oxygen content in the vacuum state can reduce or even avoid oxidation during the frying process, such as fatty acid rancidity, enzymatic browning and oxidative deterioration. Therefore, the vacuum frying process can produce natural and high-quality fried foods, such as vegetable chips, convenient dishes, dried fruits, etc.

2. Process

The general process flow of vacuum fried food is: raw materials → sorting → cleaning → adjustment → enzyme inactivation → pretreatment (predrying) → vacuum frying → vacuum deoiling → packaging → finished product.

The main purpose of enzyme inactivation is to prevent the raw materials from browning. According to the actual process requirements, solution soaking, hot water rinsing and quick freezing can be used.

Pretreatment mainly involves adjusting the sweetness and acidity of the raw materials before frying, or coating the surface of the raw materials, etc. Raw materials with high moisture content should be dried to reduce their moisture content before frying, which can solidify the raw materials and shorten the frying time.

Vacuum frying is the key link in the whole process. The raw materials are put into the frying basket and fixed in the pot. After closing the sealing door, vacuum is drawn and the appropriate heating method is selected. Different raw materials should choose different temperatures, vacuum degrees and frying times according to the product process requirements.

There are many ways to remove oil. Currently, industrial production mainly uses centrifugal filtration to remove oil. After vacuum fried food is deoiled, its oil content is less than 25% and its water content is about 3%.

Vacuum fried foods are best packaged in vacuum aluminum-plastic packaging or vacuum nitrogen-filled aluminum foil packaging. These two packaging methods can keep the vacuum fried products for more than 3 months and maintain a good taste and flavor.

vacuum frying machine

3. Process characteristics

The vacuum frying process has the following main characteristics:

(1) It can maintain the original aroma and color of food. When food is in a low-temperature, low-pressure oil environment, the water-soluble spices in the food will not overflow in the oil. After the dehydration process, the aroma components in the food are further concentrated, thus preserving the original aroma of the food well. In addition, when fried in a low oxygen content state, the food is not easy to fade, change color, or brown, thus well preserving the color of the food itself and covering it with a layer of oil, making the food look bright. However, for fat-soluble pigments such as carotenoids and chlorophyll, they are easy to overflow during the frying process. Therefore, foods containing fat-soluble pigments must be pretreated to ensure the stability of the pigments.

(2) The oil temperature is low, and the loss of food nutrients is small. The inorganic salts, vitamins and other nutrients in the food are less lost under low-temperature vacuum processing, and the effective ingredients in the food are better preserved. It is particularly suitable for frying foods containing heat-sensitive nutrients.

(3) Significant fuel saving effect and good product preservation performance. Vacuum frying can effectively avoid the polymerization reaction of frying oil in high temperature and aerobic conditions, reduce or even prevent the generation of harmful substances, and improve the reuse rate of frying oil. Generally, the oil content of fried foods is 40% to 50%, while the oil content of vacuum fried foods after deoiling is less than 25%. Therefore, vacuum frying has a better fuel-saving effect, the product is crisp but not greasy, and is easy to store.

vacuum fryer frying machine

High pressure frying

High-pressure frying is to increase the pressure in the oil kettle to make the internal pressure higher than normal pressure, thereby increasing the boiling point of the frying oil and shortening the frying time. High-pressure frying technology has high oil temperature, less water and oil evaporation loss, and can effectively solve the problem of normal pressure frying affecting food quality due to long frying time. High-pressure fried products are crispy on the outside and tender on the inside, and are most suitable for fried meat products, such as fried chicken, fried chicken legs, fried lamb chops, etc. In addition, high-pressure frying technology has very strict high-pressure resistance requirements for frying equipment. The safety of the frying equipment should be carefully checked before use, and the pressure in the oil kettle should be controlled within the safe pressure range during operation to avoid safety accidents.

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