Microwave-hot air synergistic efficient processing method for freezing and pre-frying French fries

Abstract

The invention discloses a microwave-hot air synergistic efficient processing method for frozen pre-fried French fries. The method comprises the following steps: flatly laying the frozen pre-fried French fries in the middle of a baking tray, placing the frozen pre-fried French fries on a middle layer of a micro-steaming and baking integrated machine, adjusting the microwave-hot air processing time, and performing four-stage treatment; wherein in the first stage, microwave pulse intervenes, and the stage accounts for 12.5% of the total processing time; in the second stage, hot air heating is continuously carried out, and the stage accounts for 62.5% of the total processing time; in the third stage, microwave pulse intervention accounts for 12.5% of the total processing time; the fourth stage is a hot air balance stage, and the stage accounts for 12.5% of the total processing time. According to the method, the intervention time of microwave energy in the hot air drying process is accurately controlled, so that the cooperation of water migration is realized, and the drying efficiency and the quality of a final product are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and in particular to a microwave-hot air synergistic high-efficiency processing method for frozen pre-fried French fries. Background Technology

[0002] Frozen pre-fried French fries, a core derivative product of the global potato industry, occupy an important position in modern diets due to their superior convenience and wide applicability. Through industrial processing including washing, blanching, pre-frying, and freezing, the product achieves highly stable quality, allowing consumers to obtain near-ideal sensory quality with simple end-of-pipe heating. In home settings, common reheating methods include frying, oven baking, hot air convection, and pan-frying, with the core goal of restoring the unique crispy texture and flavor characteristics formed by industrial processing. In recent years, based on health and convenience consumption trends, countertop convection ovens and air fryers, which utilize hot air convection as their core principle, have become increasingly widely used, becoming the preferred home heating solution due to their significantly reduced oil consumption. From a processing method perspective, they mainly rely on hot surface convection and conduction, which inherently has lower heat transfer efficiency, often requiring a longer time to reach the target temperature at the center of the product. This not only results in a time-consuming heating process but also low energy efficiency.

[0003] Microwave heating technology, with its unique volumetric heating effect, offers significant advantages in improving food processing efficiency. This technology is based on the interaction between electromagnetic waves and polar molecules (primarily water molecules) in materials, causing rapid internal heating and thus achieving rapid temperature rise. Due to its fast heating speed and high nutrient retention rate, microwave technology has been widely applied in various fields such as food drying, thawing, sterilization, and temperature control. Compared to traditional surface heating methods, microwave processing better preserves the natural flavor, color, and texture of food, and its powerful internal heat penetration capability provides an efficient supplement to traditional processes. However, despite the great potential of microwave-assisted processing in industrial production, it still has significant drawbacks, including high system energy consumption, poor heating uniformity, and a tendency to cause localized overheating.

[0004] While existing technologies have attempted to combine microwaves with other heating methods to address the aforementioned issues, they still lack in-depth and systematic solutions regarding how to effectively coordinate the two heating modes, avoid quality deterioration caused by localized overheating, and optimize processes to meet the reheating requirements of specific products like frozen pre-fried fries. In particular, existing technologies have not provided an effective way to simultaneously achieve efficiency, uniformity, and the sensory quality of the final product for key parameters such as the timing of microwave intervention, power distribution, and precise control of coupling with hot air. For example, patent CN117598456A proposes using a pulsed electric field to pre-treat fresh potato fries before frying them in an air fryer, significantly improving the quality and taste of the fries. However, its core technology relies on pre-treatment with a pulsed electric field to alter cell structure, a process requiring additional specialized equipment, increasing system complexity and cost. Patent CN116806990A uses a two-stage microwave continuous processing method for fresh potato fries to replace traditional blanching and drying, reducing water consumption and waste during processing and minimizing nutrient loss. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a microwave-hot air synergistic high-efficiency processing method for frozen pre-fried French fries. This method achieves synergistic moisture migration by precisely controlling the timing of microwave energy intervention during the hot air drying process, significantly improving drying efficiency and the quality of the final product.

[0006] The technical solution of the present invention is as follows: The first objective of this invention is to provide a microwave-hot air synergistic high-efficiency processing method for frozen pre-fried French fries, comprising the following steps: Arrange the frozen pre-fried fries evenly in the center of a baking tray, place it on the middle rack of a microwave-steam-grill combination oven, and adjust the microwave-hot air processing time for a four-stage process; among which, The first stage, microwave pulse intervention: At the 0-minute mark after the initial hot air heating stage begins, microwaves and hot air are introduced for microwave pulse treatment lasting 1.5-3 minutes. This stage accounts for 12.5% ​​of the total processing time. The second stage involves continuous hot air heating; after stopping the microwave, hot air heating continues for 7.5-15 minutes, accounting for 62.5% of the total processing time. The third stage involves microwave pulse intervention: when the total heating time reaches 9-18 minutes, microwaves are intervened again for microwave pulse treatment lasting 1.5-3 minutes. This stage accounts for 12.5% ​​of the total processing time. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 1.5-3 minutes until the total heating time reaches 12-24 minutes to prepare French fries; this stage accounts for 12.5% ​​of the total processing time.

[0007] In one embodiment of the present invention, the frozen pre-fried French fries undergo a freezing pretreatment, the pretreatment conditions being: freezing at -18°C for 24 hours. In one embodiment of the present invention, the length of the frozen pre-fried French fries is 8-12 cm; the water content is 75-80%.

[0008] In one embodiment of the present invention, the microwave power is 1300-1500W.

[0009] In one embodiment of the present invention, the hot air power is 1700-1900W.

[0010] In one embodiment of the present invention, the final hot air temperature is 180-220°C.

[0011] In one embodiment of the present invention, frozen pre-fried French fries are laid flat in the middle of a baking tray and placed in the middle layer of a microwave-steam-grill combination machine. The weight of the French fries is controlled to be 270±3g, and the microwave-hot air processing time is adjusted to perform a four-stage processing. The first stage, microwave pulse intervention: At the 0-minute mark after the start of the initial hot air heating stage, microwaves and hot air are introduced for a 1.5-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time; The second stage is the continuous hot air heating stage; the microwave is stopped and hot air heating continues for 7.5 minutes, which accounts for 62.5% of the total processing time. The third stage involves microwave pulse intervention: when the total heating time reaches 9 minutes, microwaves are intervened again for 1.5 minutes of microwave pulse treatment. This stage accounts for 12.5% ​​of the total processing time. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 1.5 minutes until the total heating time reaches 12 minutes to prepare French fries; this stage accounts for 12.5% ​​of the total processing time.

[0012] In one embodiment of the present invention, frozen pre-fried French fries are laid flat in the middle of a baking tray and placed in the middle layer of a microwave-steam-grill combination machine. The weight of the French fries is controlled to be 270±3g, and the microwave-hot air processing time is adjusted to perform a four-stage processing. The first stage, microwave pulse intervention: At the 0-minute mark after the start of the initial hot air heating stage, microwaves and hot air are introduced for a 2-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time; The second stage is the continuous hot air heating stage; after microwave is stopped, hot air heating continues for 10 minutes, accounting for 62.5% of the total processing time. The third stage involves microwave pulse intervention: when the total heating time reaches 12 minutes, microwaves are intervened again for a 2-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 2 minutes until the total heating time reaches 16 minutes to prepare French fries; this stage accounts for 12.5% ​​of the total processing time.

[0013] In one embodiment of the present invention, frozen pre-fried French fries are laid flat in the middle of a baking tray and placed in the middle layer of a microwave-steam-grill combination machine. The weight of the French fries is controlled to be 270±3g, and the microwave-hot air processing time is adjusted to perform a four-stage processing. The first stage, microwave pulse intervention: At the 0-minute mark after the start of the initial hot air heating stage, microwaves and hot air are introduced for a 2.5-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time; The second stage is the continuous hot air heating stage; the microwave is stopped and hot air heating continues for 12.5 minutes, which accounts for 62.5% of the total processing time. The third stage involves microwave pulse intervention: when the total heating time reaches 15 minutes, microwaves are intervened again for 2.5 minutes of microwave pulse treatment. This stage accounts for 12.5% ​​of the total processing time. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 2.5 minutes until the total heating time reaches 20 minutes to prepare French fries; this stage accounts for 12.5% ​​of the total processing time.

[0014] In one embodiment of the present invention, frozen pre-fried French fries are laid flat in the middle of a baking tray and placed in the middle layer of a microwave-steam-grill combination machine. The weight of the French fries is controlled to be 270±3g, and the microwave-hot air processing time is adjusted to perform a four-stage processing. The first stage, microwave pulse intervention: At the 0-minute mark after the start of the initial hot air heating stage, microwaves and hot air are introduced for a 3-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time; The second stage is the continuous hot air heating stage; after microwave is stopped, hot air heating continues for 15 minutes, accounting for 62.5% of the total processing time. The third stage involves microwave pulse intervention: when the total heating time reaches 18 minutes, microwaves are intervened again for a 3-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 3 minutes until the total heating time reaches 24 minutes to prepare French fries; this stage accounts for 12.5% ​​of the total processing time.

[0015] A second objective of this invention is to provide French fries prepared by the above-described processing method.

[0016] The beneficial technical effects of this invention are as follows: This invention introduces microwave energy in stages, creating a synergistic processing technique with continuous hot air heating. First, microwaves are applied during the initial heating phase, utilizing their volumetric heating effect to quickly penetrate the interior of the fries, achieving instantaneous thawing and initiating a phase change in internal moisture, creating channels for subsequent moisture migration. Then, microwaves are applied again during the later heating phase. At this point, a specific structure and moisture gradient have formed inside the fries, and the microwave energy effectively drives the detachment of bound water, forcefully expelling residual moisture as steam. This microwave-assisted heating increases processing efficiency by approximately 33.3% while maintaining essentially the same product quality. Furthermore, as the microwave exposure time increases, the product's moisture content further decreases, the change in hardness becomes more pronounced, and the Maillard reaction is promoted, leading to a deeper golden-yellow to brown color transition.

[0017] This invention effectively utilizes the changes in the internal properties of materials at different heating stages to induce structural evolution that is conducive to quality improvement. The initial microwave treatment promotes thawing and forms a network of micropores inside the fries; the subsequent microwave intervention, based on these structures, promotes the formation of a dense and crispy outer shell through intense moisture vaporization and migration, ultimately increasing the product hardness to over 5760g and achieving an ideal texture that is crispy on the outside and soft on the inside. Attached Figure Description

[0018] Figure 1 The diagram shows the processing procedures for different embodiments and comparative examples.

[0019] Figure 2 The moisture content at the end of the French fries in different microwave pulse stages in Comparative Example 2 is shown.

[0020] Figure 3 This is a graph showing the temperature changes during the microwave-hot air processing from 0 to 6 minutes in Comparative Example 3.

[0021] Figure 4 The moisture content of French fries under different microwave-hot air treatment conditions in Comparative Example 1 and Examples 1-4 is shown.

[0022] Figure 5 To compare the hardness of French fries under different microwave-hot air treatment conditions in Comparative Example 1 and Examples 1-4.

[0023] Figure 6 The images show the morphology of Comparative Example 1 and Examples 1-4 under different microwave-hot air treatment conditions. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] Test method: 1. Determination of moisture content in frozen pre-fried French fries: Take approximately 5g of the test sample and measure it according to the direct drying method in GB 5009.3-2016.

[0026] 2. Test on the appearance of frozen pre-fried French fries after microwave-hot air heating: After microwaving and hot air heating, take three fries from each of the following positions: top right (UR), bottom left (LL), bottom right (LR), top left (UL), and center (C), and take a top view of the fries using a digital camera.

[0027] 3. Determination of surface color difference of frozen pre-fried French fries: The surface color change of frozen pre-fried fries was measured using a portable spectrophotometer based on the CIE color space. The instrument was calibrated with standard black / white ceramic tiles before use. The total color difference was calculated according to formula (1): (1) 4. Determination of the texture of frozen pre-fried French fries: The surface hardness of the fries was measured using a TA.XT texture analyzer. A cylindrical probe was used for puncture testing at a speed of 2 mm / s, with a trigger force of 10 g and a penetration depth of 4 mm.

[0028] Comparative Example 1 A method for hot air preparation of frozen pre-fried French fries includes the following steps: (1) Select whole frozen pre-fried fries that have been placed in a -18℃ freezer for 24 hours, with uniform size and shape, and a length of 8-12cm; the frozen pre-fried fries are commercially available products; (2) Place the fries flat in the center of the baking tray. Place the baking tray in the middle layer of the microwave-steam-baking unit and process it in a constant hot air power mode. The total hot air power is 1800W. Heat for 24 minutes to obtain the final product.

[0029] Comparative Example 2 While keeping other conditions consistent with Comparative Example 1, the 24-minute hot air heating process was improved. Specifically, while keeping the total duration unchanged, a microwave pulse with a duration of 3 minutes and a power of 1450W (P10 setting) was fed in sequentially at time points of 0, 3, 6, 9, 12, 15, 18 or 21 minutes, thereby forming a stage of coordinated heating of microwave and hot air, while the remaining time period is only hot air heating. The heating scheme is as follows: When introduced at 0 minutes, microwave-hot air combined heating is used for 0-3 minutes, and hot air heating is used for 3-24 minutes; when introduced at 3 minutes, hot air heating is used for 0-3 minutes, microwave-hot air combined heating is used for 3-6 minutes, and hot air heating is used for 6-24 minutes; when introduced at 6 minutes, hot air heating is used for 0-6 minutes, microwave-hot air combined heating is used for 6-9 minutes, and hot air heating is used for 9-24 minutes; when introduced at 9 minutes, hot air heating is used for 0-9 minutes, microwave-hot air combined heating is used for 9-12 minutes, and hot air heating is used for 12-24 minutes; when introduced at 12 minutes... The process involves heating in three stages: 0-12 minutes with hot air heating, 12-15 minutes with microwave-hot air combined heating, and 15-24 minutes with hot air heating; when introduced at 15 minutes, the process continues with hot air heating for 0-15 minutes, microwave-hot air combined heating for 15-18 minutes, and hot air heating for 18-24 minutes; when introduced at 18 minutes, the process continues with hot air heating for 0-18 minutes, microwave-hot air combined heating for 18-21 minutes, and hot air heating for 21-24 minutes; and when introduced at 21 minutes, the process continues with hot air heating for 0-21 minutes and microwave-hot air combined heating for 21-24 minutes to prepare French fries. The specific process flow is as follows: Figure 1 The resulting French fries were subjected to performance testing, and the test results are as follows: Figure 2 As shown. Figure 2 The moisture content at the end of the French fries at different microwave pulse stages.

[0030] The moisture content has a decisive impact on the drying efficiency and quality of pre-fried frozen French fries. Studies have shown that simple hot air drying has a bottleneck, with the moisture content only reaching around 75%. Using microwave-hot air synergistic heating can significantly improve efficiency, with the timing of microwave intervention being particularly crucial. The optimal effect is achieved by applying microwave energy for 3 minutes between the 18th and 21st minute of hot air drying; that is, feeding in 12.5% ​​microwave energy at 75% of the total processing time yields the best processing results, reducing the moisture content to 24%. At this stage, the internal structure and moisture state of the material are most suitable for microwave energy conversion, enabling efficient dehydration and texture improvement. Premature intervention leads to moisture redistribution, while late intervention restricts dehydration due to structural densification. Feeding in microwave energy in the seventh stage maximizes processing efficiency, reducing the moisture content to the optimal level.

[0031] Comparative Example 3 While keeping other conditions the same as in Comparative Example 1, the heating method was changed to simultaneously feed 1800W hot air and 1450W pulsed microwaves within 0-6 minutes to prepare French fries. The resulting French fries were subjected to performance testing, and the test results are as follows: Figure 3 As shown. Figure 3 This is a graph showing the temperature changes during microwave-hot air processing.

[0032] The experimental group rapidly heated up after microwave intervention, with temperatures at each monitoring point quickly exceeding 50℃ and approaching 100℃, while the pure hot air group heated up slowly. Once the temperature reached 100℃, all curves showed a plateau, consistent with the phase transition law of water evaporation. The advantage of microwave treatment lies in its ability to quickly reach the boiling point, entering the effective dehydration stage earlier, shortening the initial heating time, and gaining valuable time for subsequent dehydration, thus improving overall processing efficiency. Temperature curve analysis shows that introducing microwave energy in the initial stage significantly improves the processing efficiency of French fries. Simultaneously feeding microwave energy in the initial stage achieves rapid thawing and heating, creating favorable conditions for subsequent dehydration.

[0033] Example 1 Arrange the frozen pre-fried fries evenly in the center of a baking tray, place it on the middle rack of a microwave-steam-grill combination oven, and control the weight of the fries to 270±3g. Adjust the microwave-hot air processing time and perform a four-stage processing; among which... The first stage of microwave pulse intervention: at the 0th minute after the start of the initial hot air heating stage, microwaves and hot air are intervened to perform microwave pulse treatment for a duration of 1.5 minutes; The second stage involves continuous hot air heating: microwave energy is stopped, and hot air heating continues for 7.5 minutes. The third stage involves microwave pulse intervention: when the total heating time reaches 9 minutes, microwave energy is intervened again for 1.5 minutes of microwave pulse treatment. The fourth stage, hot air balancing: stop the microwave energy and continue heating with hot air for 1.5 minutes until the total heating time reaches 12 minutes to prepare French fries.

[0034] Example 2: Frozen pre-fried French fries were laid flat in the middle of a baking tray and placed in the middle layer of a microwave-steam-grill combination machine. The weight of the French fries was controlled to be 270±3g. The microwave-hot air processing time was adjusted, and the process was carried out in four stages. The first stage, microwave pulse intervention: At the 0th minute after the start of the initial hot air heating stage, microwave and hot air are intervened to perform microwave pulse treatment for a duration of 2 minutes; The second stage is the continuous hot air heating stage; after stopping the microwave, the hot air heating will continue for 10 minutes. The third stage involves microwave pulse intervention: when the total heating time reaches 12 minutes, microwaves are intervened again for a 2-minute microwave pulse treatment. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 2 minutes until the total heating time reaches 16 minutes to prepare French fries.

[0035] Example 3 Arrange the frozen pre-fried fries evenly in the center of a baking tray, place it on the middle rack of a microwave-steam-grill combination oven, and control the weight of the fries to 270±3g. Adjust the microwave-hot air processing time and perform a four-stage processing; among which... The first stage, microwave pulse intervention: at the 0th minute after the start of the initial hot air heating stage, microwaves and hot air are intervened to perform microwave pulse treatment for a duration of 2.5 minutes; The second stage is continuous hot air heating: microwave energy is stopped, and hot air heating continues for 12.5 minutes; The third stage involves microwave pulse intervention: when the total heating time reaches 15 minutes, microwave energy is intervened again for 2.5 minutes of microwave pulse treatment. The fourth stage, hot air balancing: stop the microwave energy and continue heating with hot air for 2.5 minutes until the total heating time reaches 20 minutes to prepare French fries.

[0036] Example 4 Arrange the frozen pre-fried fries evenly in the center of a baking tray, place it on the middle rack of a microwave-steam-grill combination oven, and control the weight of the fries to 270±3g. Adjust the microwave-hot air processing time and perform a four-stage processing; among which... The first stage, microwave pulse intervention: At the 0th minute after the start of the initial hot air heating stage, microwave and hot air are intervened to perform microwave pulse treatment for a duration of 3 minutes; The second stage is the continuous hot air heating stage; after stopping the microwave, the hot air heating will continue for 15 minutes. The third stage involves microwave pulse intervention: when the total heating time reaches 18 minutes, microwaves are intervened again for a 3-minute microwave pulse treatment. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 3 minutes until the total heating time reaches 24 minutes to prepare French fries.

[0037] Test example: The resulting French fries were subjected to performance testing, and the test results are as follows: Figure 4 , 5 As shown in Figure 6. Figure 4 The moisture content of French fries under different microwave-hot air treatment conditions; Figure 5 The hardness of French fries under different microwave-hot air treatment conditions; Figure 6 Table 1 shows the morphology of samples under different microwave-hot air treatment conditions; Table 1 shows the brightness of the sample surfaces under different microwave-hot air treatment conditions. ), Green-redness ( ), Blue-yellowness ( ) and total color difference (ΔE).

[0038] Table 1

[0039] Comparative analysis of Example 2 and Comparative Example 1 shows that, under the premise that the key quality indicators of the final product, such as moisture content, hardness, and surface color, are not significantly different or even better, the total processing time is shortened from 24 minutes to 16 minutes after introducing the staged microwave synergistic heating described in this invention, a reduction of 33.3%, demonstrating a significant efficiency improvement. Specifically: Regarding moisture content, the moisture ratio at each measurement point (UR, LL, LR, UL, C) in Comparative Example 1 is between 50-60%, and the moisture content in Example 2 is also within this range, indicating that microwave intervention significantly promotes overall moisture removal in a short time. Regarding texture and hardness, there are significant differences in hardness between different locations. A horizontal comparison between Comparative Example 1 and Example 2 shows a hardness difference of 5-12%, with relatively small overall hardness differences. This indicates that, by introducing microwave pulses in stages, this invention not only achieves better dehydration and significantly enhanced texture while greatly shortening the processing time, but also improves heating uniformity, proving that the microwave-hot air synergistic mechanism has a true synergistic enhancement effect in terms of efficiency and quality.

[0040] The microwave-hot air synergistic heating method significantly improves the quality characteristics of French fries through its unique volumetric heating effect, specifically manifested in a significant reduction in moisture content and a sharp increase in hardness. In Example 4, experimental data showed that after 360 seconds of microwave treatment, the moisture content of the French fries could be reduced to 22%, while the hardness value at the RU monitoring point jumped from 445g to 5767g, an increase of more than an order of magnitude. This textural change stems from the starch gelatinization and protein denaturation processes promoted by microwave heating, which in turn promotes the formation of a dense outer shell structure. In contrast, the microwave-hot air treatment was significantly less effective in Examples 1 and 3. In Example 1, the microwave pulse intervention occurred in the first 2 minutes of hot air heating, reducing the moisture content to 30% and the hardness to only 432g, failing to effectively remove internal moisture, resulting in a relatively soft and moist surface for the French fries, lacking ideal crispness. In Example 3, the microwave pulse intervention occurred from 0 to 2.5 minutes. Although the duration of the microwave pulse was longer, the moisture content only decreased to 28%, and the hardness was 1000g, far lower than the 5767g in Example 4, resulting in a still poor texture. In contrast, the microwave-hot air processing in Example 4 significantly promoted the uniform migration and rapid evaporation of moisture inside the fries, and effectively improved the texture of the fries. After this treatment, the moisture content of the fries was reduced to 22%, and the hardness significantly increased to 5767g, significantly improving the texture and overall quality. Therefore, Example 4 demonstrates the significant advantages of microwave-hot air synergistic heating in moisture removal, hardness improvement, and texture improvement, far exceeding that of Examples 1 and 3, indicating that optimizing the timing of microwave pulses is crucial for improving the quality of fries. Table 1 and Figure 6This demonstrates the color change of French fries after heating. All samples darkened during the drying process, but the color change was more pronounced upon microwave input. The control group... The value decreased only slightly, while in the MHAH treatment group The value decreased significantly—the brightness of the RU point decreased by approximately 5.7%. Under microwave action, and The values ​​also shifted negatively, indicating a tendency to turn green and blue due to pigment decomposition. For example, RU's... The value changed from 0.03 to -1.76 after 360 seconds. The values ​​decreased by approximately 37%. These changes reflect the brown Maillard pigments formed by the Maillard reaction and the thermal degradation of carotenoids during intense heating. In Comparative Example 1, drying had little effect on color, while the addition of microwaves produced intense browning. Therefore, while microwave pulses improve drying efficiency, they also enhance surface browning, which, if left uncontrolled, could darken the product. Thus, appropriate cooking times and, possibly, intermittent cooking strategies are crucial for balancing the final taste and color of the fries.

[0041] Based on a comprehensive analysis of the moisture content, hardness, and appearance quality of the French fries, it was found that the microwave processing time has a decisive impact on the final product quality. A comparative analysis of Example 2 and Comparative Example 1 shows that, under the premise that there are no significant differences in key quality indicators such as moisture content, hardness, and surface color of the final product, the total processing time was shortened from 24 min to 16 min after introducing microwave synergistic heating, a reduction of 33.3%. Further comparison of Example 4 with Examples 1 and 3 reveals that as the microwave-hot air synergistic effect time increases, the moisture content of the French fries shows a further decreasing trend, and the change in hardness is more significant. Simultaneously, due to the enhanced local heating effect of microwaves, the Maillard reaction is promoted, resulting in a deeper golden-yellow to brown color transition in the product.

[0042] This comparative example further illustrates that the microwave-hot air processing method for French fries described in this patent can improve the quality of French fries and significantly increase production efficiency while ensuring product quality.

[0043] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A microwave-hot air synergistic high-efficiency processing method for frozen pre-fried French fries, characterized in that, Includes the following steps: Arrange the frozen pre-fried fries evenly in the center of a baking tray, place it on the middle rack of a microwave-steam-grill combination oven, and adjust the microwave-hot air processing time for a four-stage process; among which, The first stage, microwave pulse intervention: At the 0-minute mark after the initial hot air heating stage begins, microwaves and hot air are introduced for microwave pulse treatment lasting 1.5-3 minutes. This stage accounts for 12.5% ​​of the total processing time. The second stage is the continuous hot air heating stage; after stopping the microwave, the hot air continues to heat for 7.5-15 minutes, which accounts for 62.5% of the total processing time. The third stage involves microwave pulse intervention: when the total heating time reaches 9-18 minutes, microwaves are intervened again for microwave pulse treatment lasting 1.5-3 minutes. This stage accounts for 12.5% ​​of the total processing time. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 1.5-3 minutes until the total heating time reaches 12-24 minutes to prepare French fries; this stage accounts for 12.5% ​​of the total processing time.

2. The processing method according to claim 1, characterized in that, Frozen pre-fried French fries undergo a freezing pretreatment process, with the pretreatment conditions being: freezing at -18℃ for 24 hours.

3. The processing method according to claim 1, characterized in that, Frozen pre-fried French fries are 8-12cm long and have a moisture content of 75-80%.

4. The processing method according to claim 1, characterized in that, The microwave power is 1300-1500W.

5. The processing method according to claim 1, characterized in that, The hot air power is 1700-1900W.

6. The processing method according to claim 1, characterized in that, Arrange the frozen pre-fried fries evenly in the center of a baking tray, place it on the middle rack of a microwave-steam-grill combination oven, and control the weight of the fries to 270±3g. Adjust the microwave-hot air processing time and perform a four-stage processing; among which... The first stage, microwave pulse intervention: At the 0-minute mark after the start of the initial hot air heating stage, microwaves and hot air are introduced for a 1.5-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time; The second stage is the continuous hot air heating stage; the microwave is stopped and hot air heating continues for 7.5 minutes, which accounts for 62.5% of the total processing time. The third stage involves microwave pulse intervention: when the total heating time reaches 9 minutes, microwaves are intervened again for 1.5 minutes of microwave pulse treatment. This stage accounts for 12.5% ​​of the total processing time. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 1.5 minutes until the total heating time reaches 12 minutes to prepare French fries; this stage accounts for 12.5% ​​of the total processing time.

7. The processing method according to claim 1, characterized in that, Arrange the frozen pre-fried fries evenly in the center of a baking tray, place it on the middle rack of a microwave-steam-grill combination oven, and control the weight of the fries to 270±3g. Adjust the microwave-hot air processing time and perform a four-stage processing; among which... The first stage, microwave pulse intervention: At the 0-minute mark after the start of the initial hot air heating stage, microwaves and hot air are introduced for a 2-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time; The second stage is the continuous hot air heating stage; after microwave is stopped, hot air heating continues for 10 minutes, accounting for 62.5% of the total processing time. The third stage involves microwave pulse intervention: when the total heating time reaches 12 minutes, microwaves are intervened again for a 2-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 2 minutes until the total heating time reaches 16 minutes to prepare French fries; this stage accounts for 12.5% ​​of the total processing time.

8. The processing method according to claim 1, characterized in that, Arrange the frozen pre-fried fries evenly in the center of a baking tray, place it on the middle rack of a microwave-steam-grill combination oven, and control the weight of the fries to 270±3g. Adjust the microwave-hot air processing time and perform a four-stage processing; among which... The first stage, microwave pulse intervention: At the 0-minute mark after the start of the initial hot air heating stage, microwaves and hot air are introduced for a 2.5-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time; The second stage is the continuous hot air heating stage; the microwave is stopped and hot air heating continues for 12.5 minutes, which accounts for 62.5% of the total processing time. The third stage involves microwave pulse intervention: when the total heating time reaches 15 minutes, microwaves are intervened again for 2.5 minutes of microwave pulse treatment. This stage accounts for 12.5% ​​of the total processing time. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 2.5 minutes until the total heating time reaches 20 minutes to prepare French fries; this stage accounts for 12.5% ​​of the total processing time.

9. The processing method according to claim 1, characterized in that, Arrange the frozen pre-fried fries evenly in the center of a baking tray, place it on the middle rack of a microwave-steam-grill combination oven, and control the weight of the fries to 270±3g. Adjust the microwave-hot air processing time and perform a four-stage processing; among which... The first stage, microwave pulse intervention: At the 0-minute mark after the start of the initial hot air heating stage, microwaves and hot air are introduced for a 3-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time; The second stage is the continuous hot air heating stage; after microwave is stopped, hot air heating continues for 15 minutes, accounting for 62.5% of the total processing time. The third stage involves microwave pulse intervention: when the total heating time reaches 18 minutes, microwaves are intervened again for a 3-minute microwave pulse treatment, which accounts for 12.5% ​​of the total processing time. The fourth stage, the hot air balancing stage: stop the microwave and continue heating with hot air for 3 minutes until the total heating time reaches 24 minutes to prepare French fries; this stage accounts for 12.5% ​​of the total processing time.

10. French fries produced by the processing method according to any one of claims 1-9.

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