A composite method for improving key qualities of frozen prepared fried rice

Abstract

The invention discloses a composite method for improving the key quality of frozen prepared fried rice, and belongs to the technical field of convenient food processing. The invention selects polished round-grained rice, soaks the polished round-grained rice and then cooks it, breaks it up and cools it after cooking, adds a composite additive for inhibiting regeneration during frying, and mixes it evenly. After frying, it is naturally cooled to 40-50°C, vacuum-sealed and packaged, and then sterilized by ultrasound and oregano essential oil nanoemulsion. The frozen prepared fried rice product is obtained by using an electrostatic field combined with a pulsed magnetic field to assist quick freezing, and an edible frozen prepared fried rice is obtained by using an infrared reheating method. The frozen prepared fried rice prepared by the invention has no obvious regeneration phenomenon within a storage period of 90 days, and has high sensory quality after reheating. Compared with the frozen prepared fried rice that is not improved by the method, the sensory score is increased by more than 15%, and the regeneration is significantly inhibited. The invention effectively improves the edible quality of frozen prepared fried rice.

Description

Technical Field

[0001] The invention relates to a composite method for improving key qualities of frozen prepared fried rice, and belongs to the technical field of instant food processing. Background Art

[0002] Due to the accelerated pace of life, the demand for convenience foods is increasing. More than two-thirds of the population in my country eat rice as their staple food, so convenience rice products have a broad market prospect. Prepared fried rice is a type of convenient rice product that is more popular with consumers. It has the advantages of good taste and convenience. At the same time, with the improvement of living standards, people have higher requirements for the quality of convenience foods. However, the quality of commercially available prepared fried rice is far lower than that of fresh fried rice, which has an adverse impact on the sales of prepared fried rice.

[0003] Rice can be divided into japonica rice and indica rice according to its amylose content and stickiness. Japonica rice has a low amylose content and high stickiness, so the cooked rice is soft and sticky; indica rice has a high amylose content and low stickiness, so the cooked rice has distinct grains and good looseness. Therefore, indica rice is often used as a raw material for making fried rice. However, compared with japonica rice, cooked indica rice has the disadvantages of higher hardness, lower taste quality, and higher degree of recovery, which makes the quality of indica rice fried rice not ideal. Therefore, it is necessary to explore the method of using japonica rice as a raw material to produce a loose and non-sticky frozen prepared fried rice product.

[0004] Yan Zijun et al. (2022) studied the effects of production technology and freezing conditions on the quality of quick-frozen instant rice. The results showed that soaking temperature, cooking time and cooking pressure had a significant effect on the sensory quality and texture characteristics of rice, and that low freezing temperature could effectively slow down the rate of quality change of quick-frozen instant rice, which was beneficial to its storage and shelf life. Huang Meihua (2014) studied the effect of processing technology on the quality of quick-frozen rice. The results showed that different soaking conditions would affect the water absorption rate and moisture content of rice, and that quick-frozen rice that was steamed and then simmered for 15 minutes could obtain the best edible quality. Li Ping et al. (2021) studied the effects of cooking water quality combined with water addition and soaking time on the taste of japonica rice. The results showed that japonica rice processed with pure water had a higher taste value.

[0005] Chen Haixu (patent application number: CN201711145405.4) disclosed a method for processing rice suitable for fried rice, selecting high-quality indica rice as raw material, soaking it in a soaking solution prepared with mulberry tree juice, fresh lemon juice and water before putting it into the pot, and spraying it with a treatment solution obtained by boiling lotus leaves and mulberry leaves after the rice is mature. The obtained rice has a strong aroma, a good full taste, and distinct grains without connection. However, this method uses indica rice with a lower taste value, and the anti-sticking effect is not good when using japonica rice as raw material, and the edible quality is not high.

[0006] Ding Wenping et al. (patent application number: CN201811434818.9) disclosed a method for preparing anti-aging instant rice, adding 0.5% to 1% of α-amylase and 0.1% to 0.6% of β-cyclodextrin as two anti-aging agents in a mixture of rice and water, and exerting the anti-aging effect more significantly through the synergistic effect of the two. This method has the characteristics of simple steps and significant anti-aging effect, and can improve the anti-aging effect while reducing costs in industrial production. He Guoqing et al. (patent application number: CN201310512937.2) disclosed a quality improver for rice and a method for preparing quick-frozen rice, the quality improver is composed of 1 to 10% of monoglyceride of lauric acid, 30 to 75% of β-cyclodextrin and 20 to 65% of ethanol. After washing and draining the rice, put it into the quality improver solution for soaking, and directly steam it after soaking to obtain rice. The quick-frozen instant rice prepared by the method is soft and delicious, fluffy and non-sticky, and at the same time delays the aging of the rice. Hu Jie et al. (patent application number: CN201010286639.2) invented a method for inhibiting the retrogradation of instant rice. The main component of the composite retrogradation inhibitor is a composite enzyme liquid composed of alanine aminotransferase, α-amylase and β-amylase. The method of use is to naturally cool the cooked rice to 50°C, add the composite enzyme liquid and soak it for 15 minutes, and then soak it in lactic acid for 5 minutes. The invention inhibits the retrogradation of rice to a certain extent. Zhang Min et al. (patent application number: CN201810126400.5) disclosed a method for improving the quality of Yangzhou conditioned fried rice and extending its shelf life. In this method, when the fried rice is cooled to 50-60°C, 1% of an anti-regeneration composite additive is added by mass, and the main components are 6% α-amylase, 48% soy protein isolate, 14% citric acid, 30% monoglyceride and 4% tricalcium phosphate. The mixture is evenly mixed, and the resulting fried rice is poured into CO2 and N2 gas-controlled packaging and then pressurized and heated for sterilization for 20 minutes, and refrigerated at 4±1°C. The refrigerated Yangzhou fried rice is reheated using 27.12MHZ, high-to-low variable power radio frequency, which extends the shelf life of Yangzhou fried rice and effectively improves the reheating quality of Yangzhou fried rice. No regeneration occurs during the 30-day storage period. The above method of inhibiting the regeneration of rice and improving the edible quality of rice by adding quality improvers has outstanding effects, but it also has shortcomings. The formula of some improvers is too complicated, and the preparation and use are cumbersome, time-consuming and costly. Improvers containing enzyme preparations are not only costly and unstable, but also enzyme preparations often hydrolyze large molecular starch into small molecular compounds, which will change the original taste of rice.

[0007] Traditional thermal sterilization methods have the disadvantages of high energy consumption, long heating and cooling time, and damage to the sensory quality and flavor of food. Cold sterilization technologies that can effectively maintain the color, aroma and nutritional content of food are gaining more and more attention, including cold plasma, ultraviolet rays, ultrahigh pressure, ultrasound, etc. Chemical preservatives are potentially toxic and harmful to human health. Botanical antibacterial agents are not only highly efficient and non-toxic, but also have multiple biological activities such as antioxidant and immunomodulatory. Cold sterilization technology alone cannot completely kill harmful microorganisms, and long-term or high-intensity treatment will also have adverse effects on the quality of food. Studies have shown that the combined use of cold sterilization technology and botanical antibacterial agents can reduce the treatment intensity of cold sterilization technology, shorten the treatment time, reduce the concentration of antibacterial agents, and enhance the antibacterial effect. Liu Donghong et al. (patent application number: CN202110486995.7) disclosed a non-thermal sterilization method for high-frequency ultrasound synergistic plasma activated water treatment, in which sterile water is treated with a plasma generator to obtain plasma activated water; the object to be treated is mixed with plasma activated water and then high-frequency ultrasonic treatment is started. This invention combines ultrasound and plasma activated water, effectively avoiding the problem of drug residues after sterilization, while achieving better sterilization effects in a shorter time.

[0008] The mechanical damage caused by the generation and growth of ice crystals during the freezing process is another key factor that limits the edible quality of frozen fried rice. Electric field is an effective means to reduce the mechanical damage of ice crystals. Water molecules generate dipole moments under the action of electric field forces, and tend to turn toward the external electric field. During the low-temperature freezing process, the supercooling is reduced, nucleation is rapid, the freezing time is shortened, and the ice crystal growth is mainly carried out along the direction of the external electric field, which inhibits the growth of ice crystals in other directions, making the size of the formed ice crystals smaller. Magnetic field is another effective means to reduce the mechanical damage of ice crystals. The magnetic field can delay the formation of ice crystals by strengthening the hydrogen bonds in water molecules and reducing the supercooling of water. Zhang Min et al. (patent application number: CN202210166852.2) disclose a static magnetic field assisted liquefied CO2 pulse spraying quick freezing device and a pressurized high-efficiency freezing method, which uses liquefied CO2 as a freezing medium, and is equipped with a pulse spraying to make thick piles of materials freeze evenly and quickly, and is equipped with a static magnetic field generating device to assist freezing, which can reduce the size of ice crystals. The freezing method includes evacuation, precooling and CO2 pressurization, magnetic field-assisted quick freezing, and deep freezing. This method combines CO2 pressurization pretreatment and pulse spraying to significantly reduce the freezing time, the ice nucleation process is regulated, and the freezing is uniform. Compared with industrial air blast quick freezing, the time for frozen materials to pass through the maximum ice crystal formation zone is shortened by more than 20%, the product ice crystal size is reduced by more than 20%, and the product juice loss rate after thawing is reduced by more than 4%. Zhang Min et al. (patent application number: CN201910852663.9) disclosed a method for improving the quality of frozen waffle dough during the shelf life by combining ultrasonic combined with electrostatic field assisted quick freezing and refrigeration. This method effectively improves the quality of frozen waffle dough during the frozen storage process and extends the shelf life of frozen waffle dough.

[0009] Microwaves have been widely accepted by the public as a common heating method, and almost every household is equipped with a microwave oven. However, microwave ovens have disadvantages such as small dielectric constant, low heat transfer efficiency, and uneven heating. Nowadays, some new physical field heating methods are attracting people's attention, such as radio frequency and infrared. Zhang Min et al. (patent application number: CN201710037033.7) disclosed a method for improving the quality of pre-made lunch boxes with normal temperature dishes after reheating. The method combines radio frequency sterilization with cold shock treatment and radio frequency reheating. While meeting the sterilization conditions, it reduces the intensity of high temperature and high pressure sterilization, and uses radio frequency reheating instead of conventional reheating, which reduces the damage to the nutritional components and organizational structure of lunch boxes, especially dishes. Zhang Min et al. (patent application number: CN201710092544.9) disclosed a method for improving the crispness of frozen pot stickers after reheating by combining infrared and microwave reheating. By adding ultra-finely crushed soy protein isolate, corn starch, composite phosphate, maltodextrin, and xanthan gum, the formula of traditional pot stickers is improved. The moisture diffusion phenomenon during the reheating process is greatly weakened by the combination of microwave and infrared reheating, thus better maintaining the crispness of the dough.

[0010] The above are some reports on improving the edible quality of instant rice and some new food sterilization, quick freezing and reheating methods. Most of the methods that have been applied to instant rice improve the quality of instant rice by improving the processing technology and adding composite regeneration inhibitors. However, they have limitations such as complex formula, high cost, long time and change in the taste of instant rice, and the impact on the improvement of the quality of instant rice is very limited. The new food sterilization, quick freezing and reheating methods mentioned above have not yet been seen in the application of instant rice. This method effectively improves the key quality of frozen prepared fried rice in a relatively simple, efficient and low-cost way through the control of processing technology, the addition of regeneration inhibitors, ultrasound synergistic oregano essential oil nanoemulsion sterilization, electrostatic field combined with pulsed magnetic field assisted quick freezing and infrared reheating, and is easy to be applied to industrial production. Summary of the invention

[0011] The purpose of the present invention is to provide a composite method for improving the key qualities of frozen fried rice. The method reduces the quality deterioration of frozen fried rice and the degree of rice recovery by adding an appropriate amount of regeneration inhibition composite additive, ultrasound-assisted oregano essential oil nanoemulsion sterilization, electrostatic field combined with pulsed magnetic field assisted quick freezing and infrared reheating. Compared with other schemes for improving the key qualities of frozen fried rice, the method saves time and cost, and effectively achieves the goal of improving the edible quality of frozen fried rice.

[0012] The technical solution of the present invention:

[0013] A composite method for improving the key qualities of frozen prepared fried rice mainly comprises the following steps:

[0014] (1) Preparation of cooked rice: Select polished japonica rice, soak it in clean water at 25°C for 30 min at a ratio of 1:3, drain the water after soaking, add clean water at a ratio of 1:1, cook for 25 min, simmer for 15 min after cooking, then break the cooked rice, spread it flat and cool it at 25°C for 1 h, and cover the surface of the rice with a layer of gauze to prevent excessive water loss;

[0015] (2) Preparation of fried rice: Take an appropriate amount of cooked rice and fry it into a finished fried rice product. During the frying process, add the anti-retrogradation composite additive to the fried rice and mix them evenly. The anti-retrogradation composite additive is added in an amount of 1% of the mass of the rice and contains: 40% modified soybean lecithin and 60% gum arabic.

[0016] (3) Vacuum packaging and sterilization of fried rice: The fried rice is naturally cooled to 40-50° C., oregano essential oil nanoemulsion is added, mixed evenly and packed into plastic boxes, 300 g per portion, and vacuum-sealed using a vacuum packaging machine. The packaged fried rice is placed in an ultrasonic bath for ultrasonic sterilization;

[0017] (4) Quick freezing and frozen storage of fried rice: The fried rice after ultrasonic sterilization is placed in an ice storage with an electrostatic field combined with a pulsed magnetic field to assist quick freezing for quick freezing. After the quick freezing is completed, the fried rice is placed in a -18°C ice storage for frozen storage;

[0018] (5) Reheating: The frozen fried rice was reheated using medium and short wave infrared, with a wavelength of 2.5 to 6 μm, a box temperature of 150 °C, an irradiation distance of 15 cm, and a time of 120 s.

[0019] Preferably, the raw materials used for frying the fried rice product in step (2) are frozen mixed fried rice raw materials, mainly including: 100 parts of glutinous rice, 10 parts of edible oil, 15-20 parts of egg liquid, 5 parts of carrots, 5 parts of peas, 5 parts of corn kernels, 3 parts of ham sausage, and 0.5 parts of salt.

[0020] Preferably, the raw materials used for frying the fried rice product in step (2) are Yangzhou fried rice raw materials, which mainly include: 100 parts of glutinous rice, 10 parts of cooking oil, 15-20 parts of egg liquid, 3 parts of ham, 5 parts of chicken, 3 parts of shrimp, 4 parts of mushrooms, 4 parts of fresh bamboo shoots, 3 parts of peas, 1 part of scallop, 0.5 parts of salt, and 3 parts of cooking wine.

[0021] The amount of the oregano essential oil nanoemulsion added in the above step (3) is 1% of the mass of the fried rice, and the ingredients are: 2% of oregano essential oil, 2% of emulsifier Tween 80, pH=3.5, and 96% of 0.1 mol / L citric acid buffer. The preparation method is: mixing the oregano essential oil, Tween 80 and citric acid buffer, using a high-speed disperser to shear for 2 minutes at a speed of 14000 r / min, and then ultrasonicating for 15 minutes under ice bath conditions to obtain oregano essential oil nanoemulsion with uniform particle size.

[0022] The conditions for the ultrasonic treatment in step (3) are as follows: adding 4000 ml of pure water, an ultrasonic frequency of 30 kHz, an ultrasonic power of 2000 W, and an ultrasonic treatment time of 15 min.

[0023] The temperature of the ice storage with electrostatic field combined with pulse magnetic field assisted quick freezing function in step (4) is set to -65°C. After quick freezing, the center temperature of the bagged fried rice reaches -18 to -19°C. The electrostatic field strength is 400V / m, and the working cycle is 10s; the pulse magnetic field strength is 10mT, and the working cycle is 10s.

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention can effectively improve the taste of rice by strictly controlling the quality and temperature of clean water added during soaking and cooking.

[0026] 2. The invention adds a high temperature resistant composite additive for inhibiting retrogradation during the preparation of fried rice, so that the retrogradation inhibitor and the rice can be mixed more completely, and the anti-retrogradation efficiency can be further improved; and the composite additive for inhibiting retrogradation of the invention has a simple formula, and does not add expensive ingredients such as enzymes, thereby reducing the production cost.

[0027] 3. The present invention adopts cold sterilization technology - ultrasound assisted oregano essential oil nanoemulsion for sterilization, which effectively reduces the loss of nutrients and flavor substances in frozen fried rice, and is simple to operate and low in cost.

[0028] 4. The present invention adopts an electrostatic field combined with a pulse magnetic field to assist quick freezing to prepare frozen prepared fried rice, which is simple to operate and has low cost, and effectively improves the quality of the prepared fried rice after freezing, and is suitable for industrial production.

[0029] 5. The present invention uses medium and short wave infrared to reheat the frozen cooked fried rice, which has the advantages of high heat transfer efficiency, uniform heat transfer and high product quality stability. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] Comparative Example 1: A method for preparing frozen assorted fried rice

[0032] Fried rice recipe: 100 parts of glutinous rice, 10 parts of cooking oil, 15-20 parts of egg liquid, 5 parts of carrots, 5 parts of peas, 5 parts of corn kernels, 3 parts of ham, and 0.5 parts of salt.

[0033] First, soak the raw japonica rice in 25℃ water at a ratio of 1:3 (the ratio is mass volume ratio) for 30 minutes, drain the water after soaking, add water at a ratio of 1:1, cook for 25 minutes, and simmer for 15 minutes after cooking. Then take out the cooked rice, spread it flat and cool it, cool it at 25℃ for 1 hour, and cover the surface of the rice with a layer of gauze to prevent excessive water loss. Take an appropriate amount of cooked rice, add the corresponding ingredients and seasonings according to the corresponding fried rice recipe, and fry it into a finished fried rice product; the fried rice is naturally cooled to 40-50℃, packed into a plastic box, each portion is 300g, and vacuum-sealed using a vacuum packaging machine. Place it in a -65℃ freezer to quickly freeze it to a material center temperature of -18--19℃, and place it in a -18℃ freezer for refrigeration. Use microwave to reheat the frozen fried rice. The reheating power is 1000W and the reheating time is 3min.

[0034] Comparative Example 2: A method for preparing frozen assorted fried rice with addition of a retrogradation inhibitor

[0035] First, soak the raw japonica rice in 25℃ water at a rice-water ratio greater than 1:3 for 30 minutes, drain the water after soaking, add water at a rice-water ratio of 1:1, cook for 25 minutes, simmer for 15 minutes after cooking, then take out the cooked rice, spread it flat and cool it, cool it at 25℃ for 1 hour, and cover the surface of the rice with a layer of gauze to prevent excessive water loss. Take an appropriate amount of cooked rice, add corresponding ingredients and seasonings according to the corresponding fried rice formula to fry it into a fried rice product, add 1% by mass of the regeneration inhibition composite additive to the fried rice during frying, and mix it evenly; the regeneration inhibition composite additive composition is: 40% modified soybean lecithin, 60% gum arabic, and the fried rice is naturally cooled to 40-50℃, packed into a plastic box, each portion is divided into 300g, and vacuum-sealed using a vacuum packaging machine. Place it in a -65℃ ice storage for quick freezing until the center temperature of the material is -18--19℃, and place it in a -18℃ ice storage for refrigeration. The frozen fried rice was reheated in a microwave at a reheating power of 1000W and a reheating time of 3min.

[0036] Comparative Example 3: A method for preparing frozen assorted fried rice by electrostatic field combined with pulsed magnetic field assisted freezing

[0037] First, soak the raw japonica rice in 25℃ water at a ratio of 1:3 for 30 minutes, drain the water after soaking, add water at a ratio of 1:1, cook for 25 minutes, and simmer for 15 minutes after cooking. Then take out the cooked rice, spread it flat and cool it, cool it at 25℃ for 1 hour, and cover the surface of the rice with a layer of gauze to prevent excessive water loss. Take an appropriate amount of cooked rice, add the corresponding ingredients and seasonings according to the corresponding fried rice recipe, and fry it into a finished fried rice. The fried rice is naturally cooled to 40-50℃, packed into a plastic box, 300g per portion, and vacuum-sealed using a vacuum packaging machine. Place it in a -65℃ ice storage with an electrostatic field combined with a pulsed magnetic field to assisted quick freezing function and quickly freeze it to a material center temperature of -18--19℃, and place it in a -18℃ ice storage for refrigeration. Among them, the electrostatic field intensity is 400V / m, the working cycle is 10s; the pulsed magnetic field intensity is 10mT, and the working cycle is 10s. The frozen fried rice was reheated in a microwave at a reheating power of 1000W and a reheating time of 3min.

[0038] Comparative Example 4: A method for preparing frozen assorted fried rice with ultrasound-assisted oregano essential oil nanoemulsion sterilization

[0039] First, soak the raw japonica rice in 25℃ water at a ratio of 1:3 for 30min, drain the water after soaking, add water at a ratio of 1:1, cook for 25min, simmer for 15min after cooking, then take out the cooked rice, spread it flat and cool it, cool it at 25℃ for 1h, and cover the surface of the rice with a layer of gauze to prevent excessive water loss. Take an appropriate amount of cooked rice, add corresponding ingredients and seasonings according to the corresponding fried rice recipe to fry it into a fried rice product, cool the fried rice naturally to 40-50℃, add 1% of the mass of oregano essential oil nanoemulsion of the fried rice, put it into a plastic box, pack 300g per portion, and use a vacuum packaging machine for vacuum sealing packaging. Among them, the amount of oregano essential oil nanoemulsion added is 1% of the mass of the fried rice, and the ingredients are: oregano essential oil 2%, emulsifier stabilizer Tween 80 2%, pH=3.5, 0.1mol / L citric acid buffer 96%. The packaged fried rice was placed in an ultrasonic pool for ultrasonic treatment, wherein the ultrasonic treatment conditions were to add 4000 ml of pure water, an ultrasonic frequency of 30 kHz, an ultrasonic power of 2000 W, and an ultrasonic treatment time of 15 min. It was placed in a -65°C ice storage with an electrostatic field combined with a pulsed magnetic field to assisted quick freezing function, and the material center temperature was -18 to -19°C, and then placed in a -18°C ice storage for refrigeration. The electrostatic field strength was 400 V / m, and the working cycle was 10 s; the pulsed magnetic field strength was 10 mT, and the working cycle was 10 s. The frozen fried rice was reheated with microwaves. The reheating power was 1000 W, and the reheating time was 3 min.

[0040] Comparative Example 5: A method for preparing frozen assorted fried rice by infrared reheating

[0041] First, soak the raw japonica rice in 25℃ water at a ratio of 1:3 for 30 minutes, drain the water after soaking, add water at a ratio of 1:1, cook for 25 minutes, simmer for 15 minutes after cooking, then take out the cooked rice, spread it flat and cool it, cool it at 25℃ for 1 hour, and cover the surface of the rice with a layer of gauze to prevent excessive water loss. Take an appropriate amount of cooked rice, add the corresponding ingredients and seasonings according to the corresponding fried rice recipe, and fry it into a finished fried rice product; the fried rice is naturally cooled to 40-50℃, packed into a plastic box, each portion is 300g, and vacuum-sealed using a vacuum packaging machine. Place it in a -65℃ freezer for quick freezing until the center temperature of the material is -18--19℃, and place it in a -18℃ freezer for refrigeration. Use medium and short wave infrared to reheat the frozen fried rice. The wavelength of medium and short wave infrared is 2.5-6 μm, the box temperature is 150°C, the irradiation distance is 15 cm, and the time is 120 s.

[0042] Example 1: A composite method for improving key qualities of frozen assorted fried rice

[0043] Fried rice recipe: 100 parts of glutinous rice, 10 parts of cooking oil, 15-20 parts of egg liquid, 5 parts of carrots, 5 parts of peas, 5 parts of corn kernels, 3 parts of ham, and 0.5 parts of salt.

[0044] First, soak the raw material japonica rice in 25℃ water at a ratio of 1:3 for 30 minutes, drain the water after soaking, add water at a ratio of 1:1, cook for 25 minutes, simmer for 15 minutes after cooking, then take out the cooked rice, spread it flat and cool it, cool it at 25℃ for 1 hour, and cover the surface of the rice with a layer of gauze to prevent excessive water loss. Take an appropriate amount of cooked rice, add corresponding ingredients and seasonings according to the corresponding fried rice formula to fry it into a fried rice product, add 1% by mass of the regeneration inhibition composite additive to the fried rice during frying, and mix it evenly; the composition of the rice regeneration inhibition composite additive is: 40% modified soybean lecithin, 60% gum arabic, the fried rice is naturally cooled to 40-50℃, 1% of the mass of oregano essential oil nanoemulsion is added to the fried rice, and it is packed into a plastic box, each portion is divided into 300g, and a vacuum packaging machine is used for vacuum sealing packaging. The amount of oregano essential oil nanoemulsion added is 1% of the mass of the fried rice, and the ingredients are: 2% oregano essential oil, 2% emulsifier Tween 80, pH=3.5, 96% of 0.1mol / L citric acid buffer. The packaged fried rice is placed in an ultrasonic tank for ultrasonic treatment, wherein the conditions for ultrasonic treatment are adding 4000ml of pure water, ultrasonic frequency 30kHZ, ultrasonic power 2000W, and ultrasonic treatment time 15min. It is placed in a -65℃ ice storage with an electrostatic field combined with a pulse magnetic field to assist quick freezing and freeze the material to a central temperature of -18 to -19℃, and then placed in a -18℃ ice storage for refrigeration. The electrostatic field strength is 400V / m, the working cycle is 10s; the pulse magnetic field strength is 10mT, and the working cycle is 10s. The frozen fried rice is reheated with medium and short wave infrared. The wavelength of medium and short wave infrared is 2.5 to 6μm, the box temperature is 150℃, the irradiation distance is 15cm, and the time is 120s.

[0045] Example 2: A composite method for improving key qualities of frozen Yangzhou fried rice

[0046] Fried rice recipe: 100 parts of glutinous rice, 10 parts of cooking oil, 15-20 parts of egg liquid, 3 parts of ham, 5 parts of chicken, 3 parts of shrimps, 4 parts of mushrooms, 4 parts of fresh bamboo shoots, 3 parts of peas, 1 part of scallops, 0.5 parts of salt, and 3 parts of cooking wine.

[0047] First, soak the raw material japonica rice in 25℃ water at a ratio of 1:3 for 30 minutes, drain the water after soaking, add water at a ratio of 1:1, cook for 25 minutes, simmer for 15 minutes after cooking, then take out the cooked rice, spread it flat and cool it, cool it at 25℃ for 1 hour, and cover the surface of the rice with a layer of gauze to prevent excessive water loss. Take an appropriate amount of cooked rice, add corresponding ingredients and seasonings according to the corresponding fried rice formula to fry it into a fried rice product, add 1% by mass of the regeneration inhibition composite additive to the fried rice during frying, and mix it evenly; the composition of the rice regeneration inhibition composite additive is: 40% modified soybean lecithin, 60% gum arabic, the fried rice is naturally cooled to 40-50℃, 1% of the mass of oregano essential oil nanoemulsion is added to the fried rice, and it is packed into a plastic box, each portion is divided into 300g, and a vacuum packaging machine is used for vacuum sealing packaging. The amount of oregano essential oil nanoemulsion added is 1% of the mass of the fried rice, and the ingredients are: 2% oregano essential oil, 2% emulsifier Tween 80, pH=3.5, 0.1mol / L citric acid buffer 96%. The packaged fried rice is placed in an ultrasonic tank for ultrasonic treatment, wherein the conditions for ultrasonic treatment are adding 4000ml of pure water, ultrasonic frequency 30kHZ, ultrasonic power 2000W, and ultrasonic treatment time 15min. It is placed in a -65℃ ice storage with an electrostatic field combined with a pulsed magnetic field to assist quick freezing and freeze the material to a central temperature of -18 to -19℃, and then placed in a -18℃ ice storage for refrigeration. The electrostatic field strength is 400V / m, the working cycle is 10s; the pulsed magnetic field strength is 10mT, and the working cycle is 10s. The frozen fried rice is reheated with medium and short wave infrared. The wavelength of medium and short wave infrared is 2.5 to 6μm, the box temperature is 150℃, the irradiation distance is 15cm, and the time is 120s.

[0048] As shown in Table 1, after 90 days of frozen storage, the regeneration inhibitor, electrostatic field combined with pulse magnetic field assisted freezing and infrared reheating can improve the sensory quality of frozen fried rice alone. The sterilization method of ultrasound synergistic oregano essential oil nanoemulsion has no significant effect on the sensory quality of frozen fried rice. After the combined action, the sensory quality of frozen fried rice increased by 15.63%. As shown in Table 2, the addition of regeneration inhibitor can significantly reduce the degree of recovery of frozen fried rice. Electrostatic field combined with pulse magnetic field assisted freezing and infrared reheating also have a certain contribution to inhibiting the regeneration of frozen fried rice. Sterilization cannot inhibit the regeneration of frozen fried rice. After the combined action, the degree of regeneration is reduced by 26.08%. As shown in Table 3, no Escherichia coli, Staphylococcus aureus and mold were detected in the frozen fried rice sterilized by ultrasound synergistic oregano essential oil nanoemulsion, and the total colony count was also much smaller than that of Comparative Example 1, indicating that ultrasound synergistic oregano essential oil nanoemulsion sterilization has a high antibacterial effect.

[0049] Table 1 Sensory evaluation table of frozen fried rice

[0050]

[0051] Table 2 Regeneration of frozen fried rice

[0052]

[0053] Table 3 Ultrasound synergistic nano oregano essential oil emulsion sterilization effect on frozen fried rice

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Claims

1. A composite method for improving the key qualities of frozen cooked fried rice, characterized in that: The main steps include: (1) Preparation of cooked rice: Select polished japonica rice, soak it in clean water, drain the water after soaking, then add clean water to cook, and after cooking, break the cooked rice and flatten it to cool; (2) Preparation of fried rice: Take an appropriate amount of cooked rice and fry it into a finished fried rice product. During the frying process, add the anti-retrogradation composite additive to the fried rice and mix them evenly. The anti-retrogradation composite additive is added in an amount of 1% of the mass of the rice and contains: 40% modified soybean lecithin and 60% gum arabic. (3) Vacuum packaging and sterilization of fried rice: The fried rice is naturally cooled to 40-50° C., oregano essential oil nanoemulsion is added, mixed evenly and packed into plastic boxes, 300 g per portion, and vacuum-sealed using a vacuum packaging machine. The packaged fried rice is placed in an ultrasonic bath for ultrasonic sterilization; The oregano essential oil nanoemulsion is added in an amount of 1% by weight of the fried rice, and comprises: 2% oregano essential oil, 2% emulsifier Tween 80, pH=3.5, and 96% 0.1 mol / L citric acid buffer. The preparation method comprises: mixing the oregano essential oil, Tween 80 and citric acid buffer, using a high-speed disperser to shear for 2 minutes at a speed of 14000 r / min, and then ultrasonicating for 15 minutes under ice bath conditions to obtain the oregano essential oil nanoemulsion with uniform particle size. The ultrasonic treatment conditions are as follows: adding 4000 ml of pure water, ultrasonic frequency 30 kHz, ultrasonic power 2000 W, and ultrasonic treatment time 15 min; (4) Quick freezing and frozen storage of fried rice: the fried rice after ultrasonic sterilization is placed in an ice storage with an electrostatic field combined with a pulsed magnetic field to assist quick freezing for quick freezing, and after quick freezing, the fried rice is placed in a -18°C ice storage for frozen storage; the temperature of the ice storage with an electrostatic field combined with a pulsed magnetic field to assist quick freezing is set to -65°C, and after quick freezing, the center temperature of the bagged fried rice reaches -18 to -19°C; during the electrostatic field combined with a pulsed magnetic field to assist quick freezing, the electrostatic field strength is 400V / m, the working cycle is 10s; the pulsed magnetic field strength is 10mT, and the working cycle is 10s; (5) Reheating: The frozen fried rice is reheated using medium and short wave infrared, wherein the wavelength of the medium and short wave infrared is 2.5 to 6 μm, the box temperature is 150° C., the irradiation distance is 15 cm, and the time is 120 s.

2. A composite method for improving the key qualities of frozen cooked fried rice according to claim 1, characterized in that: In step (1), the soaking time is 30 minutes, and the temperature of the soaking water is 25° C.; the rice-water ratio during cooking is 1:1, the cooking time is 25 minutes, and the rice is simmered for 15 minutes after cooking is completed.

3. A method for improving key qualities of frozen cooked fried rice according to claim 1, characterized in that: In step (1), during cooling, the air temperature is 25° C. and the surface of the rice needs to be covered with gauze to prevent excessive loss of surface moisture.

4. A composite method for improving key qualities of frozen cooked fried rice according to claim 1, characterized in that: In step (2), the raw materials used to fry the fried rice product are frozen mixed fried rice raw materials, mainly including: 100 parts of glutinous rice, 10 parts of edible oil, 15-20 parts of egg liquid, 5 parts of carrots, 5 parts of peas, 5 parts of corn kernels, 3 parts of ham sausage, and 0.5 parts of salt.

5. The method for improving key qualities of frozen cooked fried rice according to claim 1, characterized in that: In step (2), the raw materials used for frying the fried rice product are the raw materials of Yangzhou fried rice, which mainly include: 100 parts of glutinous rice, 10 parts of edible oil, 15-20 parts of egg liquid, 3 parts of ham, 5 parts of chicken, 3 parts of shrimps, 4 parts of mushrooms, 4 parts of fresh bamboo shoots, 3 parts of peas, 1 part of scallops, 0.5 parts of salt and 3 parts of cooking wine.

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