Method for restoring the flavor and taste of frozen fried rice after reheating

Abstract

The application discloses a method for restoring the flavor and taste of frozen egg fried rice after reheating, and belongs to the technical field of food processing. The method comprises the following steps: firstly, performing heat coating of rice with a curdlan-egg yolk liquid; secondly, performing high-voltage electrostatic field freezing treatment; and finally, performing radio frequency reheating treatment. After the method is used, the quality of the frozen egg fried rice is improved. Compared with ordinary frozen and microwave reheating treatment of frozen egg fried rice, the high-voltage electrostatic field freezing and radio frequency reheating auxiliary curdlan-egg yolk coating liquid can reduce the hardness of the frozen egg fried rice, and improve the flavor and sensory score. The method provided by the application has the advantages of simple preparation process, low cost, safety, non-toxicity and no peculiar smell.

Description

Technical Field

[0001] This invention discloses a method for restoring the aroma and texture of frozen fried rice after reheating, which belongs to the field of food processing technology. Background Technology

[0002] Fried rice, a traditional Chinese food with a long history, is widely popular in many countries and regions. For example, Yangzhou fried rice, shrimp fried rice, and soy sauce fried rice are all representative fried rice dishes in my country. Fried rice has long been exported due to its rich flavor, high nutritional value, high energy conversion rate, and convenient consumption.

[0003] With the accelerating pace of social development, people are spending less time cooking, further prompting the industrialization of traditional Chinese foods towards pre-prepared products. The nutritional value, convenience, and industrialization of rice-based staple foods have become important directions for the development of the convenience food industry. Instant rice, instant rice noodles, rice balls, sushi, and frozen rice products are constantly emerging, catering to people's food needs in a fast-paced world, and their market prospects are broad. However, rice products are prone to starch retrogradation during storage, leading to a decline in food quality, such as a decrease in taste and aroma. Furthermore, starchy grain foods have a high digestible starch content, producing high energy per unit time and being digested and absorbed rapidly, easily triggering various chronic metabolic diseases. Therefore, improving the edible quality of rice products, optimizing processing conditions, and enhancing their competitiveness in the food market are of practical significance.

[0004] In recent years, with the rapid development of food delivery and Chinese chain restaurants, frozen fried rice has gained popularity among consumers and catering businesses. Consumers can simply microwave frozen fried rice and have it ready in 3 minutes, offering convenience, speed, and deliciousness. Fast food chains and delivery shops can quickly and standardizedly prepare meals using microwave heating, robotic woks, or teppanyaki grills, improving operational efficiency and reducing labor costs. However, fried rice products that have undergone quick-freezing are prone to problems such as undercooked rice, aging, hard cores, breakage, and sticking after reheating. These issues severely affect the product's texture, flavor, and color, leading to a decline in product quality and consequently impacting consumer acceptance.

[0005] Zhang et al. (2023) disclosed a composite control method for the deterioration of fried rice processing quality (Publication No.: CN115944047A). This invention uses a thorn-plate type high-voltage electrostatic field to assist curcumin emulsion, controlling the microbial growth and aging of chilled fried rice, and further extending the shelf life of chilled fried rice. This invention mainly studies a method for restoring the aroma and taste of frozen egg fried rice after reheating, involving the refrigeration and reheating process of egg fried rice.

[0006] Zhang et al. (2023) disclosed a composite method for improving the key qualities of frozen prepared fried rice (Publication No.: CN116076654A). This method reduces the quality deterioration of frozen prepared fried rice and decreases the degree of rice retrogradation by adding an appropriate amount of retrogradation-inhibiting composite additive, using ultrasound-assisted sterilization with oregano essential oil nanoemulsion, electrostatic field combined with pulsed magnetic field-assisted quick-freezing, and infrared reheating. This invention mainly studies a method for restoring the aroma and texture of frozen egg fried rice after reheating, addressing the aging and quality of egg fried rice, without adding antibacterial agents, and using a different reheating method.

[0007] Zhang et al. (2020) disclosed a method for improving the quality of pre-prepared boxed meals cooked at room temperature after reheating (Publication No.: CN106721870B). This method combines radio frequency sterilization, cold shock treatment, and radio frequency reheating to reduce the sterilization intensity of the pre-prepared boxed meals and improve their quality after reheating. This invention mainly studies a method for restoring the aroma and texture of frozen fried rice after reheating. It uses guar gum-egg yolk liquid as a coating, which is more suitable for the retention and replenishment of flavor substances.

[0008] Shi Huojie et al. (2018) disclosed a method for radio frequency heating of low thermal conductivity agricultural products and food (Publication No.: CN105554929B). This method uses two large plastic blocks to wrap around the periphery and bottom of the material to be heated, respectively, achieving uniform temperature distribution in the material during radio frequency heating, with significant effect. However, this method is complex to operate and difficult to apply to actual large-scale production. This invention uses radio frequency reheating technology, which simplifies the operation while ensuring uniform heating of the material.

[0009] Dou Dahai et al. (2015) disclosed a method for preparing convenient boxed meals (publication number: CN104256282A). This invention uses microwave heating as a processing method, which excels in maintaining the color and texture of the food. This invention mainly studies a method for restoring the aroma and texture of frozen fried rice after reheating, involving the aging and quality of fried rice. Radio frequency as a reheating method has higher penetration and heating uniformity than microwave.

[0010] Hu et al. (2012) disclosed a method for inhibiting the retrogradation of instant rice (publication number: CN102396675A). The method involves soaking cooked rice in a complex enzyme solution composed of alanine aminotransferase, α-amylase, and β-amylase at 50°C for 15 minutes, followed by soaking in lactic acid for 5 minutes, draining, and then packaging. This invention inhibits the retrogradation of rice to some extent, but the enzyme solution used is expensive, the operation is cumbersome, and the starch in the rice is hydrolyzed into small molecule compounds, altering the texture of the rice. This invention uses a combination of gellan gum-egg yolk coating liquid and radio frequency reheating technology, which not only reduces moisture loss and lowers the hardness due to aging, but also replenishes flavor substances, thereby improving its aroma and texture.

[0011] Edible coatings can delay starch retrogradation while inhibiting hardening and water loss, and can also inhibit microbial growth, thus being considered an effective method to hinder starch retrogradation. In recent years, edible coating technology has become an important means to achieve green and safe storage of starch-based foods. The main components of edible coatings are generally film-forming polymers and their derivatives, such as natural polysaccharides and proteins. Generally speaking, the components of the coating have good biocompatibility and biodegradability. Edible coatings have attracted great interest in maintaining the quality of starch-based foods and extending their shelf life. Lee et al. (2020) and Eom et al. (2018) found that emulsion coatings prepared from starch and edible macromolecular polysaccharides can retain the moisture of rice cakes, reduce hardness, and reduce crystallization rate. Among them, mung bean starch and guar gum reduced the hardness of rice cakes by 29% and the crystallization rate by 24%. Therefore, the newly developed edible coatings can effectively maintain the quality and safety of rice cakes. Coryl gum was first obtained from the natural fermentation of biosafety microorganisms in 1968, with the main bacterial sources being Agrobacterium and Alcaligenes. It is a novel extracellular polysaccharide with a non-branched linear structure composed of d-glucose via β-1,3-glucosidic bonds. In food processing, glucon gum serves as a food additive, acting as a thickener, binder, gelling agent, stabilizer, and water-retaining agent in various foods. Studies have shown that glucon gum can improve the storage modulus and elasticity of sausages. Wang et al. (2019) found that additional glucon gum can increase texture properties but reduce the cooked weight of potato noodles. Glucon gum is widely used to improve food properties (such as tofu, noodles, and cakes) due to its unique thermogelation mechanism. It is insoluble in ethanol and water, but when dispersed in hot water at different temperatures, it can form two types of gels: a thermoreversible gel and a thermoirreversible gel, a property that meets the processing requirements of fried rice. Furthermore, based on its excellent film-forming ability, safety, and biodegradability, it is a good choice.

[0012] High-voltage electrostatic fields, as a novel non-thermal processing method, have been applied in drying, thawing, and freezing. High-voltage electrostatic freezing is a new method with strong commercial value, and it is easily integrated into existing freezing equipment. Furthermore, the freezing process forms smaller ice crystals, improving the quality characteristics of frozen products. Xanthakis et al. (2013) first studied the effect of electrofreezing on pork tenderloin, finding that both the supercooling point and ice crystal size decreased with increasing electric field strength. Dalvi-Isfahan et al. (2016) studied the effect of high-voltage electrostatic freezing on lamb quality. The results showed that applying electric field freezing reduced ice crystal size, decreased juice loss, and improved the textural properties of thawed samples.

[0013] Radio frequency (RF) is an electromagnetic frequency ranging from 300 kHz to 300 MHz. Its reheating primarily relies on thermal effects, where polar molecules move at high speeds under an electromagnetic field, generating heat similar to microwaves. However, compared to microwave reheating, RF operates at a lower frequency, resulting in better penetration and uniformity. Many factors influence the uniformity of RF heating, primarily including the dielectric properties of the material (dielectric constant and dielectric loss factor), the material's size, shape, thickness, and spatial location, and relevant parameters of the RF cavity such as electrode spacing. For a given material, to improve heating uniformity, certain special additives, such as sodium chloride, are needed, as they can significantly increase the dielectric constant and facilitate RF heating. Smaller electrode spacing results in a stronger electric field and better uniformity. Summary of the Invention

[0014] In order to overcome the shortcomings of the prior art, the present invention provides a method for restoring the aroma and taste of frozen fried rice after reheating. The method utilizes guar gum and egg yolk liquid to heat-coat the rice, and combines high-voltage electrostatic freezing and radio frequency reheating treatment to reduce aroma loss and taste loss.

[0015] The technical solution of the present invention is as follows:

[0016] A method for restoring the aroma and texture of frozen fried rice after reheating mainly includes the following steps:

[0017] (1) Washing rice: The rice is washed and drained using a fine-mesh strainer;

[0018] (2) Steaming: Put the washed rice into a rice cooker and steam and keep it warm;

[0019] (3) Cooling: Remove the cooked rice and cool it to room temperature to obtain cooled cooked rice for later use;

[0020] (4) Preparation of coating solution: Prepare solution A and solution B separately, then mix solution A and solution B, and shear at 18000 rpm for 3 minutes using a high-speed shearing machine to obtain coating solution for later use;

[0021] The preparation of solution A is as follows: Weigh 4.-6g of guar gum powder and put it into 100g of 55℃ deionized water. Stir magnetically at 200rpm until dispersed, then shear at 18000rpm for 5min. Next, stir at 400rpm for 15min in a 55℃ water bath. Remove from the water, cool rapidly in an ice bath, and freeze overnight at 4℃ to facilitate hydration. Before use, remove from the water and pulp using a juicer for later use.

[0022] The preparation of liquid B is as follows: the yolk is separated from a fresh egg and magnetically stirred at 200 rpm for 1 hour at room temperature; the yolk liquid is obtained by filtering with three layers of gauze at 25°C.

[0023] (5) Stirring: Weigh the cooled and cooked rice from step (3), add the coating liquid, stir well, so that the coating liquid coats the rice grains, and then place the coated rice.

[0024] (6) Fried rice: Heat cooking oil to 140℃-170℃, pour in the rice and stir-fry in three stages to obtain fried rice;

[0025] The process involves three stages: a stir-frying power of 800-1300W, a first stir-frying stage lasting 25-40 seconds with gentle stirring to promote the thermal coagulation of the coating liquid; a second stir-frying stage lasting 80-100 seconds with rapid stirring to disperse the coated rice, followed by the addition of 20%-40% of the weight of the cooled cooked rice (three-color vegetables) and 0.5-1% of the weight of the cooled cooked rice (salt); and a third stir-frying stage lasting 25-40 seconds with rapid stirring to infuse the vegetables and coated rice with flavor.

[0026] The three-color vegetable is a mixture of green peas, diced carrots, and corn kernels, with the mass ratio of green peas: diced carrots: corn kernels being 1:1:1.

[0027] (7) Cooling: Take out the fried rice from step (6) and cool it to room temperature for later use;

[0028] (8) Packing: Pack the cooled fried rice from step (7) into a cooking bag and heat seal it;

[0029] (9) Freezing: The packaged fried rice bag is placed in a high-voltage electrostatic field at -20℃ for freezing treatment. After reaching the freezing endpoint, it is placed in a regular refrigerator at -20℃ to obtain frozen fried rice.

[0030] (10) Reheating: Place the frozen fried rice into the radio frequency instrument cavity for reheating.

[0031] Furthermore, the rice variety is japonica rice, which is washed 3 times, 5 seconds each time.

[0032] Furthermore, in step (2), the mass ratio of rice to water during the steaming process is 1:1 to 1:1.2, the steaming power is 300-500W, the steaming time is 20-30min, and the heat preservation time is 10-15min.

[0033] Furthermore, in steps (3) and (7), the room temperature is in the range of 23-28°C, and the cooling time is 90-120 min.

[0034] Furthermore, in step (4), the guar gum accounts for 0.5%-1.5% of the total coating liquid mass fraction.

[0035] Furthermore, in step (5), after the coating liquid is applied, the rice is left to stand for 15-30 seconds, and the weight ratio of the cooled rice to the coating liquid is 10:1.5-5:1.

[0036] Furthermore, in step (6), the cooking oil is soybean oil, accounting for 10%-14% of the cooled cooked rice.

[0037] Furthermore, in step (9), the high-voltage electrostatic field voltage is 5kV, and the freezer storage time is 30 days.

[0038] Furthermore, in step (10), the radio frequency is 27.12MHz and the operating power is 6kW.

[0039] Furthermore, in step (10), the electrode spacing of the radio frequency instrument is 130 mm, and the thickness of the frozen fried rice is 45 mm.

[0040] Compared with the prior art, the main beneficial effects of the present invention are:

[0041] (1) This invention introduces guar gum-egg yolk liquid as a heat coating agent. In the presence of guar gum, the egg yolk liquid is directly coated onto the mature rice grains under heat treatment conditions. Furthermore, the guar gum-egg yolk liquid coating plays a barrier role in the freezing, frozen storage and reheating process, thereby further enhancing the texture, flavor and sensory quality of the fried rice.

[0042] (2) This invention introduces a high-voltage electrostatic field to reduce the damage to the structure of fried rice during the freezing process. This is due to the shortening of the freezing time. Studies have shown that the shorter the freezing time, the smaller the ice crystals formed, thereby further improving the quality of the fried rice.

[0043] (3) The present invention also introduces radio frequency reheating to achieve anti-aging function. Heat is a key factor in rearranging or redispersing starch. Radio frequency provides more uniform heat capacity, thereby ensuring the quality of fried rice. Attached Figure Description

[0044] Figure 1 The graph shows the temperature change curves of fried rice under ordinary freezing (Comparative Example 2) and high-voltage electrostatic field freezing (Example 1) treatments.

[0045] Figure 2 This is a comparison chart of reheating times for frozen fried rice under different treatments;

[0046] Figure 3 This is a comparison chart of the hardness of frozen fried rice under different treatments;

[0047] Figure 4 These are comparison images of the flavors of frozen fried rice under different treatments;

[0048] Figure 5This is a comparison chart of sensory scores for frozen fried rice under different treatments. Detailed implementation method:

[0049] The technical solution of the present invention will be further described below with reference to specific comparative examples and embodiments.

[0050] This invention measured the freezing curve, reheat temperature, hardness, and sensory evaluation of egg fried rice. The measurement methods are as follows:

[0051] Freezing curve and endpoint determination: Thermocouples were used to measure and record the temperature change of fried rice during the freezing process. Temperature points were collected every 60 seconds, and the endpoint temperature was -18℃. The time required to freeze the fried rice was then recorded.

[0052] Reheating endpoint determination: Thermocouples were used to measure and record the temperature change of the fried rice during the reheating process. Temperature points were collected every 30 seconds, and the termination signal was when the center temperature reached 73℃. The time required for this was then recorded.

[0053] Hardness Measurement: The change in hardness of fried rice before and after reheating was measured using a TA-XTC-18 texture analyzer. The analyzer parameters were: probe - P / 20, trigger force - 5g, speed before test, speed during test, and speed after test - 1mm / s, time interval between two pressure applications - 5s, and pressure deformation - 50%.

[0054] Flavor determination: The determination was performed using an electronic nose. After reheating, 3g of sample (on a dry basis) was loaded into a 50mL sample vial containing the electronic nose and then kept in a 50°C water bath until the test was completed. The test conditions were 120s of washing and 60s of testing.

[0055] Sensory evaluation: The sensory evaluation of fried rice was conducted using a 9-point scale. Ten sensory evaluators aged 25-45 years (6 women and 4 men) with food-related backgrounds evaluated the color, flavor, texture, and taste characteristics of the fried rice. "Strongly dislike" was scored as 1, while "strongly like" was scored as 9.

[0056] Comparative Example 1: Effect of Uncoated Frozen Fried Rice Processing

[0057] (1) Washing rice: Take 200g of rice, put it in a fine-mesh strainer, and wash it 3 times with clean water for 5 seconds each time. After that, drain the water.

[0058] (2) Steaming: Put the washed rice into the rice cooker at a rice-to-water ratio of 1:1, cook at 400W for 25 minutes, and keep warm for 10 minutes.

[0059] (3) Cooling: Take out the cooked rice and cool it to room temperature to obtain cooled cooked rice for later use.

[0060] (4) Fried rice: Heat 14g of oil to 150℃, pour in 100g of cooled cooked rice and stir-fry at 1000W power for 60s, add 20g of egg liquid and continue to stir-fry for 30s, add 60g of green peas / diced carrots / corn kernels (the mass ratio of green peas: diced carrots: corn kernels = 1:1:1) and 1g of salt, stir-fry for 90s, and remove from heat.

[0061] (5) Cooling: Remove the fried rice and cool it to room temperature for later use.

[0062] (6) Packing: Pack 100g of well-stirred fried rice into a cooking bag and heat seal it for later use.

[0063] (7) Freezing: The processed sample was placed in a -20℃ high voltage electrostatic field freezer for freezing treatment. After the freezing endpoint was reached, the sample was transferred to a regular -20℃ regular freezer for storage for 30 days.

[0064] (8) Reheating: The radio frequency is 27.12MHz, the working power is 6kW, the electrode spacing is set to 130mm, and the thickness of the frozen fried rice is 45mm.

[0065] Comparative Example 2: Effect of Regular Freezing on the Processing Effect of Frozen Egg Fried Rice

[0066] (1) Washing rice: Take 200g of rice, put it in a fine-mesh strainer, and wash it 3 times with clean water for 5 seconds each time. After that, drain the water.

[0067] (2) Steaming: Put the washed rice into the rice cooker at a rice-to-water ratio of 1:1, cook at 400W for 25 minutes, and keep warm for 10 minutes.

[0068] (3) Cooling: Take out the cooked rice and cool it to room temperature to obtain cooled cooked rice for later use.

[0069] (4) Preparation of coating solution: Solution A: Weigh 5.0g of gellan gum powder and put it into 100g of 55℃ deionized water. Stir magnetically at 200rpm until dispersed, shear at 18000rpm for 5min, stir at 400rpm in a 55℃ water bath for 15min, remove, cool rapidly in an ice bath, and refrigerate overnight at 4℃ to facilitate hydration. Before use, remove and pulp using a juicer for later use. Solution B: Separate egg yolks from fresh eggs and stir magnetically at 200rpm for 1h at room temperature. Then, filter through three layers of gauze at 25℃ to obtain egg yolk liquid for later use. The mixing formula is: Weigh 2g of solution A and 18g of solution B into a beaker, and then shear at 18000rpm for 3min using a high-speed shearing machine to obtain 20g of coating solution for later use.

[0070] (5) Stirring: Weigh 100g of cooled cooked rice, slowly add 20g of coating liquid in several batches, stir well, and let stand for 15-30s to allow the coating liquid to coat the cooled cooked rice grains.

[0071] (6) Fried rice: Heat 14g of oil to 150℃, pour in the rice coated with the coating liquid and stir-fry for 90s at 1000W power, add 60g of green peas / diced carrots / corn kernels (the mass ratio of green peas: diced carrots: corn kernels = 1:1:1), 1g of salt, stir-fry for 90s, and remove from heat.

[0072] (7) Cooling: Remove the fried rice and cool it to room temperature for later use.

[0073] (8) Packing: Pack 100g of well-stirred fried rice into a cooking bag and heat seal it for later use.

[0074] (9) Freezing: Place the processed sample in a -20℃ freezer for freezing and storage for 30 days.

[0075] (10) Reheating: The radio frequency is 27.12MHz, the working power is 6kW, the electrode spacing is set to 130mm, and the thickness of the frozen fried rice is 45mm.

[0076] Comparative Example 3: Effect of Microwave Treatment on Frozen Egg Fried Rice

[0077] (1) Washing rice: Take 200g of rice, put it in a fine-mesh strainer, and wash it 3 times with clean water for 5 seconds each time. After that, drain the water.

[0078] (2) Steaming: Put the washed rice into the rice cooker at a rice-to-water ratio of 1:1, cook at 400W for 25 minutes, and keep warm for 10 minutes.

[0079] (3) Cooling: Take out the cooked rice and cool it to room temperature to obtain cooled cooked rice for later use.

[0080] (4) Preparation of coating solution: Solution A: Weigh 5.0g of gellan gum powder and put it into 100g of 55℃ deionized water. Stir magnetically at 200rpm until dispersed, shear at 18000rpm for 5min, stir at 400rpm in a 55℃ water bath for 15min, remove, cool rapidly in an ice bath, and refrigerate overnight at 4℃ to facilitate hydration. Before use, remove and pulp using a juicer for later use. Solution B: Separate egg yolks from fresh eggs and stir magnetically at 200rpm for 1h at room temperature. Then, filter through three layers of gauze at 25℃ to obtain egg yolk liquid for later use. The mixing formula is: Weigh 2g of solution A and 18g of solution B into a beaker, and then shear at 18000rpm for 3min using a high-speed shearing machine to obtain 20g of coating solution for later use.

[0081] (5) Stirring: Weigh 100g of cooled cooked rice, slowly add 20g of coating liquid in several batches, stir well, and let stand for 15-30s to allow the coating liquid to coat the cooled cooked rice grains.

[0082] (6) Fried rice: Heat 14g of oil to 150℃, pour in the rice coated with the coating liquid and stir-fry for 90s at 1000W power, add 60g of green peas / diced carrots / corn kernels (the mass ratio of green peas: diced carrots: corn kernels = 1:1:1), 1g of salt, stir-fry for 90s, and remove from heat.

[0083] (7) Cooling: Remove the fried rice and cool it to room temperature for later use.

[0084] (8) Packing: Pack 100g of well-stirred fried rice into a cooking bag and heat seal it for later use.

[0085] (9) Freezing: The processed sample is placed in a -20℃ high voltage electrostatic field freezer for freezing treatment. After the freezing endpoint is reached, the sample is transferred to a regular -20℃ regular freezer for storage for 30 days.

[0086] (10) Reheating: The microwave frequency is 2450MHz, the working power is 700W, and the thickness of the frozen fried rice is 45mm.

[0087] Example 1: Effect of radio frequency assisted curcumin-egg yolk coating solution on the reheating and freezing of fried rice

[0088] (1) Washing rice: Take 200g of rice, put it in a fine-mesh strainer, and wash it 3 times with clean water for 5 seconds each time. After that, drain the water.

[0089] (2) Steaming: Put the washed rice into the rice cooker at a rice-to-water ratio of 1:1, cook at 400W for 25 minutes, and keep warm for 10 minutes.

[0090] (3) Cooling: Take out the cooked rice and cool it to room temperature to obtain cooled cooked rice for later use.

[0091] (4) Preparation of coating solution: Solution A: Weigh 5.0g of gellan gum powder and put it into 100g of 55℃ deionized water. Stir magnetically at 200rpm until dispersed, shear at 18000rpm for 5min, stir at 400rpm in a 55℃ water bath for 15min, remove, cool rapidly in an ice bath, and refrigerate overnight at 4℃ to facilitate hydration. Before use, remove and pulp using a juicer for later use. Solution B: Separate egg yolks from fresh eggs and stir magnetically at 200rpm for 1h at room temperature. Then, filter through three layers of gauze at 25℃ to obtain egg yolk liquid for later use. The mixing formula is: Weigh 2g of solution A and 18g of solution B into a beaker, and then shear at 18000rpm for 3min using a high-speed shearing machine to obtain 20g of coating solution for later use.

[0092] (5) Stirring: Weigh 100g of cooled cooked rice, slowly add 20g of coating liquid in several batches, stir well, and let stand for 15-30s to allow the coating liquid to coat the cooled cooked rice grains.

[0093] (6) Fried rice: Heat 14g of oil to 150℃, pour in the rice coated with the coating liquid and stir-fry for 90s at 1000W power, add 60g of green peas / diced carrots / corn kernels (the mass ratio of green peas: diced carrots: corn kernels = 1:1:1), 1g of salt, stir-fry for 90s, and remove from heat.

[0094] (7) Cooling: Remove the fried rice and cool it to room temperature for later use.

[0095] (8) Packing: Pack 100g of well-stirred fried rice into a cooking bag and heat seal it for later use.

[0096] (9) Freezing: The processed sample is placed in a -20℃ high voltage electrostatic field freezer for freezing treatment. After the freezing endpoint is reached, the sample is transferred to a regular -20℃ regular freezer for storage for 30 days.

[0097] (10) Reheating: The radio frequency is 27.12MHz, the working power is 6kW, the electrode spacing is 130mm, and the thickness of the frozen fried rice is 45mm.

[0098] from Figure 1 As can be seen, the high-voltage electrostatic field treatment shortened the freezing time of the fried rice by nearly 19 minutes. This provides a basic guarantee for the formation of more uniform and fine ice crystals inside the frozen fried rice, thus protecting the structure of the fried rice from damage by the ice crystals. From Figure 2 As can be seen, there is no significant difference in reheating time between the comparative examples and the examples, but numerically it shows that microwaves do require a shorter reheating time than radio frequency (RF). Furthermore, the results of Example 1 and Comparative Examples 1, 2, and 3 further indicate that RF performs better in terms of texture, flavor, and sensory scores. Figure 3 As can be seen, the hardness of Comparative Example 3 (microwave reheating group) was significantly higher than that of the other groups. This may be related to the uniformity of microwave heating; that is, while the center temperature reached the endpoint temperature, there were still localized areas that did not meet the standard, and the temperature did not reach the redispersibility temperature of the starch granules, thus leading to increased hardness. This further confirms the limitations of the microwave reheating method. Next is Comparative Example 1 (uncoated group), while Comparative Example 2 (ordinary freezing) showed no significant difference from the examples. Figure 4As can be seen from the data collection and comparison of 18 sensor groups, the values ​​of Comparative Example 1 (uncoated group) were all lower than those of the coated groups (Comparative Examples 2, 3, and Example 1), while Example 1 had the highest values. This further confirms that the guar gum-egg yolk coating liquid plays a role in flavor preservation and supplementation in improving the quality of fried rice. The most prominent flavor compounds are S1 (alkanes), S4 (sulfides), S5 (organic amines), S9 (aromatic compounds), S14 (combustible gases), S16 (sulfides), and S17 (nitrides), with S5 being the most prominent. This indicates that sulfides, organic amines, aromatic compounds, and nitrides are well preserved under the combined treatment of coating, high-voltage electrostatic freezing, and radio frequency reheating. Figure 5 As can be seen, there was no significant difference in sensory scores between Comparative Example 1 (uncoated group) and Comparative Example 3 (microwave reheated group). The former's lower score may be related to its flavor, while the latter's score may be more related to its texture. Obviously, the examples effectively avoided both low sensory scores and low flavor scores through the coating liquid and radio frequency reheating. This demonstrates that high-voltage electrostatic freezing combined with radio frequency reheating assisted by guar gum-egg yolk coating liquid can more effectively restore the aroma and texture of frozen fried rice than uncoated, ordinary freezing, or microwave reheating.

[0099] Finally, it should be noted that the above embodiments are only for illustrating the features and technical ideas of the present invention. Obviously, the present invention is not limited to the above embodiments. All modifications and variations made in accordance with the spirit and essence of the present invention should be considered as within the scope of protection of the present invention.

Claims

1. A method for restoring the flavor and mouthfeel of a frozen fried rice after reheating, characterized in that, It comprises the following steps: (1) rice washing: using a dense leak to wash rice and drain water; (2) cooking: put the washed rice into the electric rice cooker for cooking and keeping warm; (3) cooling: take out the cooked rice, cool it to room temperature, and obtain the cooled cooked rice for standby; (4) coating liquid preparation: prepare A liquid and B liquid respectively, then mix A liquid with B liquid, and use a high-speed shearing machine to shear at 18000 rpm for 3 min to obtain the coating liquid for standby; The preparation of A liquid is as follows: take 4-6 g of curdlan powder into 100 g of 55 ℃ deionized water, stir with a magnetic stirrer at 200 rpm until dispersed, then shear at 18000 rpm for 5 min, then stir at 400 rpm in a 55 ℃ water bath for 15 min, take out, ice bath rapid cooling, 4 ℃ refrigerator overnight for hydration, take out before use, and use a juicer to make paste for standby; The preparation of B liquid is as follows: separate the yolk from fresh eggs, and stir at 200 rpm with a magnetic stirrer at room temperature for 1 h; filter with three layers of gauze at 25 ℃ to obtain egg yolk liquid; (5) stirring: take the cooled cooked rice of step (3), add the coating liquid, stir evenly, so that the coating liquid wraps the rice grains, and obtain the coated rice for standby; (6) frying rice: heat edible oil to 140 ℃-170 ℃, pour the coated rice into it for three-stage frying to obtain fried rice; Wherein: the frying power is 800-1300 W, the first frying stage is 25-40 s, the stage is slightly stirred to promote the thermal coagulation of the coating liquid; the second frying stage is 80 s-100 s, the stage is quickly stirred to disperse the coated rice, then add 20%-40% of three-color vegetables and 0.5-1% of salt based on the mass of the cooled cooked rice; the third frying stage is 25-40 s, the stage is quickly stirred to fry the three-color vegetables and the coated rice into taste; The three-color vegetables are a mixture of green peas, carrot cubes and corn kernels, and the mass ratio of green peas: carrot cubes: corn kernels is 1:1:1; (7) cooling: take out the fried rice of step (6) and cool it to room temperature for standby; (8) sample loading: load the cooled fried rice into a cooking bag and heat seal the opening; (9) frozen storage: place the packaged fried rice bag in a high-voltage electrostatic field with a voltage of 5 kV for freezing treatment, and then place it in a-20 ℃ ordinary refrigerator after reaching the freezing endpoint to obtain frozen fried rice; (10) reheating: place the frozen fried rice into the cavity of a radio frequency instrument for reheating, the radio frequency instrument has a radio frequency of 27.12 MHz, a working power of 6 kW, and a plate spacing of 130 mm, and the thickness of the frozen fried rice is 45 mm.

2. The method according to claim 1, wherein the method is characterized by, The rice variety is japonica rice, and it is washed for 3 times, 5 s each time.

3. The method according to claim 1, wherein the method is characterized by, In step (2), the mass ratio of rice to water during cooking is 1:1-1:1.2, the cooking power is 300-500 W, the cooking time is 20-30 min, and the keeping warm time is 10-15 min.

4. The method according to claim 1, wherein the method is characterized by, In steps (3) and (7), the room temperature is 23-28 ℃, and the cooling time is 90-120 min.

5. The method according to claim 1, wherein the method is characterized by, In step (4), the dextrin powder accounts for 0.5%-1.5% of the total coating liquid.

6. The method according to claim 1, wherein the method is characterized by, In step (5), the coated rice is placed for 15-30 s after being coated, and the weight ratio of the cooled cooked rice to the coating liquid is 10:1.5-5:

1.

7. The method according to claim 1, wherein the method is characterized by, In step (6), the edible oil is soybean oil, accounting for 10%-14% of the cooled cooked rice.

8. The method according to claim 1, wherein the method is characterized by, In step (9), the refrigerator freezing time is 30 days.

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