A method, system, and the resulting diced tomatoes

Abstract

This invention discloses a method, system, and the resulting diced tomatoes, belonging to the field of food processing technology. The method includes: washing and removing the stems from the raw materials, dicing, first sieving and filtering the juice, microwave heating and venting, second sieving and filtering, filling and sealing, secondary microwave heating, and water bath sterilization. Specifically, the microwave heating and venting step controls the heating rate to 0.5~1.0℃ / s, rapidly heating the diced tomatoes from room temperature to 85~90℃. This invention effectively overcomes the technical problem of easily bursting the skin of diced tomatoes during microwave heating through the synergistic effect of a specific heating rate window and two sieving processes, achieving efficient venting without peeling. The resulting diced tomatoes have a ≥90% intact diced ratio, a stable solid content of over 70%, high lycopene retention, and clear broth, achieving high-quality, efficient production of diced tomatoes.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a method, system, and the resulting diced tomatoes that can significantly improve the block yield and solid content. Background Technology

[0002] Packaged diced tomatoes are an important product in the fruit and vegetable processing industry. Their traditional preparation process typically includes steps such as raw material washing, stem removal, scalding and peeling, dicing, heat treatment to remove air, filling, adding juice, sealing, and sterilization. Among these steps, the air removal process is crucial, aiming to remove air from the interstitial spaces to prevent packaging deformation or oxidation of the contents due to gas expansion during sterilization and storage, while also increasing the solids content.

[0003] Current technologies generally employ steam blanching or hot water rinsing for degassing and pre-sterilization. However, this process has significant drawbacks: First, it severely damages the tomato's shape. Traditional blanching requires 10-15 minutes to reach the target core temperature. Prolonged moist heat causes significant pectin degradation and cell wall softening, resulting in mushy and broken tomato pieces. The percentage of intact pieces (side length ≥25mm) is typically only around 80%, severely impacting appearance and economic value. Second, it leads to nutrient loss and low solids content. Prolonged boiling causes a large amount of vitamin C, lycopene, and flavor compounds to dissolve, not only reducing nutritional value but also making it difficult to exceed the national standard minimum solids content of 60%, failing to meet the demands of the high-end market. Furthermore, prolonged heat treatment easily induces browning, resulting in dull color and deteriorated flavor.

[0004] To overcome the aforementioned shortcomings, although microwave heating technology has been applied in the field of food sterilization and drying, its direct application in the degassing process of diced tomatoes has long been considered a taboo and has not been adopted by those skilled in the art. This is mainly due to deep-rooted technical prejudice: diced tomatoes are high-moisture, irregularly shaped lumps, and often have the peel attached. It is generally believed in the industry that the selective heating characteristics of microwaves easily create hot spots at areas of concentrated moisture or at the skin-flesh interface, causing a sudden increase in internal vapor pressure and triggering severe skin bursting and explosion (boiling over). Once the skin bursts, the shape of the diced tomatoes is completely destroyed.

[0005] Therefore, in order to avoid the risk of peeling, existing technologies often have to adopt two compromise solutions when trying microwave treatment: one is to completely peel the fruit, but this directly leads to the complete loss of nutrients in the peel, which is rich in dietary fiber and lycopene; the other is to heat the fruit at extremely low power for a long time, which not only loses the advantage of microwave efficiency, but also cannot completely prevent it from becoming soft and mushy.

[0006] In conclusion, the key technical challenge that urgently needs to be addressed in this field is how to overcome the technical prejudice that microwave heating inevitably leads to the cracking of diced tomatoes with skin, and how to use microwaves instead of traditional blanching without completely removing the skin. This would achieve efficient degassing and sterilization while avoiding cracking and nutrient loss, thus ensuring or even improving the quality of diced tomatoes and solving industry pain points. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method, system and the resulting tomato cubes that can significantly improve the block formation rate and solid content.

[0008] Therefore, one of the objectives of this invention is to provide a method for preparing diced tomatoes, comprising the following steps: (1) Raw material pretreatment: Select fresh, unrotten tomatoes with a maturity of over 90% but not overripe, and wash and remove the stems; (2) Dice: Cut the tomatoes processed in step (1) into diced pieces; (3) First sieve and filtration: The tomato cubes obtained in step (2) are sieved and filtered for the first time through the first sieve unit to obtain the initial filtered tomato cubes that are initially separated from the juice. (4) Microwave heating and exhaust: The primary filtered tomato pieces are evenly spread out in a thickness of 2-3cm and microwave heated. The conveying speed, microwave power and material thickness of the microwave treatment zone are configured so that microwave energy can penetrate the interior of the tomato pieces without causing irreversible collapse of the cell walls of the epidermis or outer layer. (5) Second sieve and filtration: The microwave-treated tomato cubes are sieved and filtered for the second time through the second sieve unit to separate the free juice and residual seeds added after microwave treatment, and to obtain tomato cubes to be bottled. (6) Filling and sealing: Fill the diced tomatoes to be filled into the container, backfill with hot juice and seal; (7) Secondary microwave heating: After sealing, a second microwave heating is performed to raise the center temperature of the diced tomatoes to 70-80℃; (8) After water bath heating and sterilization, the product with a solid content of more than 70% is obtained.

[0009] Furthermore, in step (2), the side length of the T-block is 25~30mm.

[0010] Furthermore, in step (4), the frequency of microwave heating is 2400~2500MHz; the heating rate is controlled at 0.5~1.0℃ / s to heat the diced tomatoes from room temperature to a core temperature of 85~90℃; the unit energy consumption of microwave heating is 180~220kWh / t raw material.

[0011] Furthermore, in steps (3) and (5), both the first screening unit and the second screening unit are hexagonal drum screens; The sieve aperture diameter of the first screening unit is configured within a first aperture range to separate seeds and juice that are free in their natural state. The sieve aperture diameter of the second screening unit is configured within the second aperture range to separate the seeds and juice released due to micro-rupture of the cell wall after microwave treatment; Furthermore, both the first aperture range and the second aperture range are 5mm-10mm, and they may be the same or different.

[0012] Furthermore, in step (6), the temperature of the diced tomatoes is maintained above 60°C after filling; the temperature of the hot tomato juice used for adding the juice is 85~95°C; and the hot tomato juice accounts for 5~10 wt% of the total amount of diced tomatoes.

[0013] Furthermore, in step (6), the hot tomato juice is at least partially derived from the juice screened out in step (3) and / or step (5) and then prepared and sterilized.

[0014] In step (7), the microwave heating time is 0.5-1.5 min, the microwave heating power is 30-40 KW, and the microwave frequency is 2450 MHz ± 25 MHz.

[0015] The present invention also discloses a preparation system for preparing diced tomatoes, comprising: A dicing device used to dice or cut pre-treated tomatoes into cubes; The first hexagonal drum sieve is connected to the outlet of the dicing device and is used to perform the first sieve and juice filtration on the diced tomatoes. A first microwave heating device is located downstream of the first hexagonal drum screen and is used to microwave heat and exhaust the filtered tomato pieces. The first microwave heating device has a control unit that can adjust the microwave frequency and power. The second hexagonal drum sieve is located downstream of the first microwave heating device and is used to perform a second sieve and juice filtration on the microwave-treated diced tomatoes. A filling and sealing device is located downstream of the second hexagonal drum screen. It is used to fill the diced tomatoes after secondary screening into containers and seal them after filling. And a juice recycling pipeline, connected between the juice outlet of the second hexagonal drum screen and the juice inlet of the filling device, for returning the juice separated after microwave treatment to the container; The second microwave heating device is located downstream of the filling and sealing device and is used to perform a second microwave heating on the sealed part. A water bath heating sterilization device is connected to the outlet of the second microwave heating device and is used to sterilize the filled containers.

[0016] The present invention also discloses a tomato cube prepared by the above preparation method, wherein the solid content of the finished product is consistently above 70%.

[0017] The advantages and positive effects of this invention are: This invention successfully overcomes the shortcomings of traditional blanching processes and the technical bias of microwave heating of diced tomatoes with skin prone to cracking by using a synergistic process of dual screening and microwave heating with specific parameters. The main technical effects are as follows: The microwave heating rate is strictly controlled within a critical window of 0.5~1.0℃ / s. This rate avoids both the bursting and cracking caused by the instantaneous accumulation of internal vapor pressure due to excessively rapid heating, and the prolonged heat damage and pectin degradation caused by excessively slow heating. As a result, the percentage of intact cubes with a side length ≥25mm in the finished product increases from approximately 80% to over 90%, and the cubes are plump with clear edges and corners.

[0018] Utilizing the efficient volumetric heating characteristics of microwaves, the heat treatment time is shortened from the traditional 10-15 minutes to about 2 minutes, greatly reducing the loss of water-soluble vitamins, sugars, and flavor substances, while also preventing a large amount of free water from entering the broth. Combined with a second sieving and filtration process to remove the heat-released liquid, the finished product's solids content remains stable at over 70% (far exceeding the national standard lower limit of 60%), and the lycopene retention rate is increased by over 15%.

[0019] No traditional peeling process is needed, preserving the skin rich in dietary fiber and lycopene, thus solving the problem of nutrient loss. Simultaneously, the first sieving process removes free water, eliminating the risk of localized boiling during microwave heating and ensuring even heating and the safety of the diced tomatoes. If microwave heating is moved before the first sieving, the diced tomatoes will clog the sieve due to excessive juice adhering to them; if it's moved after the second sieving, excess juice cannot be separated.

[0020] The secondary microwave heating process not only significantly shortens the water bath sterilization and cooking cycle and effectively reduces the product loss caused by high-temperature and long-term heat treatment, but also preserves the shape and structure of the tomato chunks, ensuring a firm texture and maximizing the locking in of the product's natural nutrients and flavor, thus comprehensively improving the quality of the diced tomatoes.

[0021] The diced tomatoes are a bright red and natural color, the broth is clear and free of turbidity or sediment; and there is no obvious water separation during long-term storage, which significantly extends the shelf life. Attached Figure Description

[0022] Figure 1 This is a scene diagram of microwave heating in step (5) of Embodiment 1 of the present invention; Figure 2In the middle: (a) is the tomato cubes before microwave heating in Example 1 of the present invention; (b) is the tomato cubes after microwave heating in Example 1 of the present invention; Figure 3 This is a picture of the product after 6 months of storage in Embodiment 1 of the present invention; Figure 4 This is a picture of the product after conventional hot stamping in Comparative Example 1 of the present invention; Figure 5 This is a picture of the product after microwave heating in Comparative Example 2 of the present invention; Figure 6 This is a picture of the product after microwave heating in Comparative Example 3 of the present invention; Figure 7 This is a picture of the product after microwave heating in Comparative Example 4 of the present invention; Figure 8 This is a picture of the product after microwave heating in Comparative Example 5 of the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below; obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that the description of this invention only elaborates on the technical features related to the inventive point. Auxiliary steps, selection of conventional equipment, and optimization methods of known process parameters not mentioned are all within the scope of conventional design or experimentation for those skilled in the art, and can be implemented by those skilled in the art based on their general technical knowledge; therefore, they do not need to be described in detail in this specification.

[0025] The product definitions, test methods, and inspection rules of all the following embodiments shall be in accordance with the provisions of Q / TWT0001S-2022.

[0026] Example 1 This embodiment provides a method for preparing diced tomatoes, the specific steps of which are as follows: S1. Raw material pretreatment: The inspected and qualified tomatoes are put into the bubbling tank for thorough washing to remove surface mud and impurities; after washing, the tomatoes are screened by the platform and then the stems are removed manually or mechanically; in this embodiment, the stem removal operation only removes the fruit stalk and calyx, and does not perform deep peeling, or only performs slight skin scratches to facilitate subsequent air release, so as to retain the peel and the subcutaneous tissue rich in lycopene to the greatest extent. S2. Dicing: The peeled tomatoes are fed to a dicing machine and cut into cubes with sides of approximately 25-30mm. This is a common size for tomato cubes, and the 25-30mm particle size matches the 2450MHz microwave wavelength, which is beneficial for the uniform distribution of the microwave field inside the material and avoids localized overheating caused by edge effects. S3. First sieving and filtration of seeds and juice: The diced tomatoes are sent to a hexagonal drum sieve for the first sieving and filtration of seeds and juice. The key purpose of this step is to remove the free juice and some scattered seeds generated during the dicing process by using the rotation of the drum sieve and the sieve mesh. This step is crucial for successful microwave heating. If the free juice isn't removed, this free water will preferentially absorb energy in the microwave field, rapidly boiling and producing violent bubbles and splashing (boiling over), leading not only to uneven heating but also causing the tomato pieces to burst open. Removing the free juice ensures that microwave energy primarily acts on the bound water inside the tomato pieces, achieving a gentle and even heating process. S4. Microwave heating and exhaust: Spread the diced tomatoes treated in S3 evenly on the conveyor belt of the tunnel microwave heating device for heating and exhaust treatment; preferably spread the diced tomatoes in one layer with a thickness of 2-3cm. Preferably, in this embodiment, the microwave frequency is selected as 2400~2500MHz, and more preferably 2450MHz; the purpose of selecting this frequency is that: for block materials with a side length of 25~30mm, 2450MHz has a suitable penetration depth, which can achieve uniform heating inside and outside of the material, and avoid the situation where the surface is overheated while the inside is not cooked. The process begins when diced tomatoes enter the tunnel-type microwave heating equipment and ends when they leave. The microwave power is precisely matched with the material flow rate. Calculations show that when the processing capacity of diced tomatoes is 5 tons / hour, the total input power is 950~1050kW, preferably 1000kW, and the unit energy consumption is approximately 200kWh / t of raw material. During the heating process, the process parameters are strictly controlled so that the diced tomatoes can be rapidly heated from room temperature to 85~90℃ at a rate of 0.5~1.0℃ / s within about 2 minutes of conveying. This step is the core of the entire invention. The heating rate of 0.5~1.0℃ / s and the short treatment time of about 2 minutes are the critical window determined through a large number of experiments. At this rate, the water inside the tomato cubes is heated and vaporized to generate vapor pressure. However, the rate at which this pressure rises is slower than the rate at which the steam diffuses outward through the micropores and intercellular spaces of the peel, thus avoiding the skin bursting caused by the accumulation of internal pressure. The core temperature of the tomato cubes rises rapidly to 85~90℃, which is sufficient to kill pathogenic bacteria and inactivate enzymes, but the time is much shorter than the traditional blanching of 10~15 minutes. This greatly reduces the thermal degradation of heat-sensitive nutrients such as vitamin C and lycopene, and also avoids the excessive softening and shape collapse caused by the traditional long blanching time. like Figure 1 ,2 As shown, the diced tomatoes heated in this step have a bright red and natural color, are plump, and show no obvious signs of softening or water separation, resulting in excellent sensory quality.

[0027] S5. Second sieving and filtration: The diced tomatoes, after being microwaved, are at a high temperature. Due to thermal expansion and contraction and the action of internal steam, the cell walls will rupture slightly, releasing some intracellular fluid. At this point, the material should be immediately fed back into the hexagonal drum screen for a second sieving and filtration.

[0028] Microwave heating causes the cell walls of some diced tomatoes to rupture, releasing new juice and seeds. Secondary sieving can separate the newly released juice and seeds during heating, preventing them from precipitating out during subsequent filling and storage. This ensures that the final solids content of the diced tomatoes can reach more than 70%, maintains the clarity of the broth, and extends the shelf life of the diced tomatoes. S6. Filling and Sealing: The tomato cubes that have undergone the second screening are metered and filled. The microwave heating process will cause the temperature of the tomato cubes to drop, and the subsequent equipment will use heat sterilization to sterilize the packaging. Therefore, it is necessary to ensure that the temperature of the tomato cubes inside the packaging is maintained above 60°C. Specifically, after microwave heating, the second screening and filtration of the seeds and juice should be completed in about 5 minutes and then proceed to step S6. 5-10 wt% of hot tomato juice at 90°C is added to the packaging, and then it is sealed immediately. Finally, the sealed packaging is sent to the sterilization equipment for final sterilization and cooling to obtain the finished tomato cubes. The hot tomato juice is preferably made by mixing and pasteurizing the screened juice to recycle and save costs.

[0029] Based on a review of multiple batches of production experimental data, it was found that after the initial microwave heating and degassing, the core temperature of the diced tomatoes was 85-90℃. However, after subsequent continuous processes such as seed sieving, juice filtering, filling, and sealing (lasting 3-4 minutes), the core temperature quickly dropped to 55-65℃. This lower temperature directly prolongs the water bath sterilization time, easily causing the tomato pieces to become soft, deformed, and loose in texture, while also depleting the product's original nutrients and affecting the final product quality. To optimize the production process, shorten the water bath sterilization time, and stabilize product quality, a second microwave heating process was added, significantly increasing the initial temperature of the product entering the sterilization process. Specifically, this step is as follows: S7. Secondary Microwave Heating: After sealing, a second microwave heating process is performed. The heating time is 0.5-1.5 minutes, the microwave power is 30-40KW, the microwave frequency is 2450MHz±25MHz, the microwave cavity size is 8200×1200×2600mm, and the processing capacity is approximately 2 tons per hour. These parameters can raise the center temperature of the diced tomatoes by about 15℃, reaching 70-80℃. For plastic packaging bags, excessive heating time may cause deformation.

[0030] Experiments have verified that secondary microwave heating can effectively increase the core temperature of tomato products. This improved process not only significantly shortens the water bath sterilization and cooking cycle and effectively reduces the product loss caused by long-term high-temperature heat treatment, but also preserves the shape and structure of tomato chunks, ensuring a firm texture and maximizing the locking in of the product's natural nutrients and flavor, thus comprehensively improving the quality of diced tomatoes.

[0031] S8. After water bath heating and sterilization, the product is cooled to obtain a finished product with a solid content of over 70%. This step is existing technology and will not be described in detail here.

[0032] Due to effect verification like Figure 3 As shown, the tomato cubes prepared using the method of this embodiment are plump, with clear edges and corners, and no peeling or cracking. Testing revealed a solid content ≥70%, clear broth within the packaging, and no significant water separation after 6 months of storage. Calculations using the sieving and weighing method showed that over 90% of the cubes were intact with a side length ≥25mm, and the lycopene retention rate was more than 15% higher than that of traditional processes.

[0033] Example 2 This embodiment discloses a preparation system for preparing the diced tomatoes in Example 1, mainly comprising: A dicing device used to dice or cut pre-treated tomatoes into cubes; The first hexagonal drum sieve is connected to the outlet of the dicing device and is used to perform the first sieve and juice filtration on the diced tomatoes. A first microwave heating device is located downstream of the first hexagonal drum screen and is used to microwave heat and exhaust the filtered tomato pieces. The first microwave heating device has a control unit that can adjust the microwave frequency and power. The second hexagonal drum sieve is located downstream of the first microwave heating device and is used to perform a second sieve and juice filtration on the microwave-treated diced tomatoes. A filling and sealing device is located downstream of the second hexagonal drum screen. It is used to fill the diced tomatoes after secondary screening into containers and seal them after filling. And a juice recycling pipeline, connected between the juice outlet of the second hexagonal drum screen and the juice inlet of the filling device, for returning the juice separated after microwave treatment to the container; The second microwave heating device is located downstream of the filling and sealing device and is used to perform a second microwave heating on the sealed part. A water bath heating sterilization device is connected to the outlet of the second microwave heating device and is used to sterilize the filled containers.

[0034] The first and second microwave heating devices used in this embodiment are conventional tunnel-type microwave heating devices in the art. Their basic structure includes: a microwave generator, a waveguide transmission system, a tunnel-type heating cavity, a wave-transparent conveyor belt made of polytetrafluoroethylene or fiberglass, a material conveying speed control system, a dehumidification and heat dissipation system, and an electrical control system. The specific mechanical structure and working principle of this device are well known to those skilled in the art and will not be described in detail here.

[0035] Comparative Example 1 In this embodiment, S5 uses a conventional blanching process, that is, after dicing, blanching in 95°C hot water for 12 minutes and then degassing. The remaining steps are the same as in embodiment 1.

[0036] Effect detection: like Figure 4 As shown, testing revealed significant defects in the finished product prepared using this traditional process: First, due to prolonged high-temperature and humid heat, the pectin in the tomato pulp underwent severe degradation, leading to softening of the cell walls. This resulted in a large number of tomato cubes exhibiting rounded edges, collapsed shapes, and even breakage; the percentage of intact cubes with a side length ≥25mm was only 79%. Second, the prolonged water bath caused a large amount of water-soluble vitamins, sugars, and flavor compounds to dissolve into the broth, resulting in a solids content of only 61%, barely meeting the lower limit of the national standard. Finally, sensory evaluation showed that the tomato cubes were dark in color, had a soft and mushy texture, and the broth was cloudy. These results clearly demonstrate that the traditional blanching process cannot simultaneously maintain both shape and nutritional value, and cannot solve the problem of quality deterioration caused by prolonged heating.

[0037] Comparative Example 2 This embodiment aims to investigate the effect of excessively rapid microwave heating rate on the quality of diced tomatoes. The preparation steps are basically the same as in Example 1, except that microwave heating is used in S5, but the heating rate is set to 2.5℃ / s.

[0038] Effect detection: like Figure 5 As shown, the quality of the finished product under this process is severely damaged, with the percentage of intact tomato cubes plummeting to 65%. Microscopic observation revealed that because the heating rate far exceeded the tolerance limit of the peel and cell tissue, the internal moisture of the tomato cubes instantly and violently vaporized. The resulting high-pressure steam broke through the peel and cell walls, causing a large number of cubes to crack, their internal tissues to turn inside out, and even break into a paste-like state. This comparative example strongly demonstrates that uncontrolled increases in the microwave heating rate will cause severe "skin cracking" and "cracking," verifying the crucial role of strictly controlling the heating rate at 0.5~1.0℃ / s in preventing skin cracking and maintaining morphological integrity.

[0039] Comparative Example 3 This comparative example aims to investigate the effect of a slow microwave heating rate on the quality of diced tomatoes. The preparation steps are basically the same as in Example 1, except that microwave heating is used in S5, but the heating rate is only 0.15℃ / s, and the dwell time needs to be extended to 10 minutes to reach 85℃.

[0040] Effect detection: like Figure 6 As shown, although no obvious boiling or cracking occurred under this process, the percentage of intact tomato cubes was only 75%, and the cubes were severely soft and mushy, losing their elasticity. Their sensory quality was similar to Comparative Example 1 (traditional blanching). This is because the excessively slow heating rate resulted in an excessively long total heat treatment time, causing the rapid heating advantage of microwaves to be lost, and the pectin continued to degrade during prolonged heating. Furthermore, the energy consumption of this process also increased significantly. These results demonstrate that high-quality tomato cubes cannot be obtained by using microwave equipment alone without controlling a reasonable heating rate window, further highlighting the necessity of the specific heating rate parameter of 0.5~1.0℃ / s in this invention.

[0041] Comparative Example 4 This embodiment omits the first sieve and filtrate step S4, while the remaining conditions are the same as in Embodiment 1.

[0042] like Figure 7 As can be seen, during microwave heating, the presence of free juice caused violent boiling (explosive boiling) in localized areas, and the resulting bubbles and fluid impact damaged the structure of some of the diced tomatoes. Final product testing showed a significant increase in the number of broken pieces, a decrease in the percentage of intact pieces, and a lower solids content than in Example 1. These results indicate that the first sieving step is not only a process of removing impurities but also a crucial pretreatment step to eliminate potential risks during microwave heating and ensure heating uniformity; omitting this step would directly lead to the destruction of the diced tomatoes due to overheating and explosive boiling of the free juice.

[0043] Comparative Example 5 This embodiment omits the second sieving and filtering of the seeds in step S6, while the other conditions are the same as in embodiment 1.

[0044] like Figure 8 As can be seen from the initial test, the solids content of the diced tomatoes was acceptable. However, after one month of storage at room temperature, a retest revealed a significant layer of juice separation at the bottom of the can, making the broth cloudy. Some of the diced tomatoes had separated seeds adhering to their surface, resulting in a significantly inferior sensory quality compared to Example 1. This is because microwave heating causes some cell walls to break down, releasing intracellular fluid. If this fluid is not separated in time through a second sieving process, it will gradually separate during subsequent storage, reducing not only the effective solids content but also affecting the clarity of the broth and its shelf-life stability. This result demonstrates that a second sieving is an indispensable post-processing step to ensure high solids content and long-term storage stability of diced tomatoes.

[0045] Comparative Examples 4 and 5 demonstrate that the first sieving and filtration of the seeds is a prerequisite for ensuring the uniformity of microwave heating, while the second sieving and filtration of the seeds is the key to ensuring the long-term storage stability of diced tomatoes. The two sieving steps are closely coordinated with the microwave heating steps, further ensuring high solids content and product uniformity.

[0046] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing diced tomatoes, characterized in that, Includes the following steps: (1) Raw material pretreatment: Select tomato raw materials for washing and stem removal; (2) Dice: Cut the tomatoes processed in step (1) into diced pieces; (3) First sieve and filtration: The tomato cubes obtained in step (2) are sieved and filtered for the first time through the first sieve unit to obtain the initial filtered tomato cubes that are initially separated from the juice. (4) Microwave heating and exhaust: The primary filtered tomato pieces are evenly spread out in a thickness of 2-3cm and microwave heated. The conveying speed, microwave power and material thickness of the microwave treatment zone are configured so that microwave energy can penetrate the interior of the tomato pieces without causing irreversible collapse of the cell walls of the epidermis or outer layer. (5) Second sieve and filtration: The microwave-treated tomato cubes are sieved and filtered for the second time through the second sieve unit to separate the free juice and residual seeds added after microwave treatment, and to obtain tomato cubes to be bottled. (6) Filling and sealing: Fill the diced tomatoes to be filled into the container, backfill with hot juice and seal; (7) Secondary microwave heating: After sealing, a second microwave heating is performed to raise the center temperature of the diced tomatoes to 70-80℃; (8) After water bath heating and sterilization, the product with a solid content of more than 70% is obtained.

2. The method for preparing diced tomatoes according to claim 1, characterized in that, In step (2), the side length of the T-block is 25~30mm.

3. The method for preparing diced tomatoes according to claim 2, characterized in that, In step (4), the microwave heating frequency is 2400~2500MHz; the heating rate is controlled at 0.5~1.0℃ / s to heat the diced tomatoes from room temperature to a core temperature of 85~90℃; the unit energy consumption of microwave heating is 180~220 kWh / t raw material.

4. The method for preparing diced tomatoes according to claim 1, characterized in that, In steps (3) and (5), both the first screening unit and the second screening unit are hexagonal drum screens; The sieve aperture diameter of the first screening unit is configured within a first aperture range to separate seeds and juice that are free in their natural state. The sieve aperture diameter of the second screening unit is configured within the second aperture range to separate the seeds and juice released due to micro-rupture of the cell wall after microwave treatment.

5. The method for preparing diced tomatoes according to claim 4, characterized in that, The first aperture range and the second aperture range are both 5mm-10mm, and they may be the same or different.

6. The method for preparing diced tomatoes according to claim 1, characterized in that, In step (6), the temperature of the diced tomatoes is maintained above 60°C after filling; the temperature of the hot tomato juice used for adding the juice is 85~95°C; the hot tomato juice accounts for 5~10 wt% of the total amount of diced tomatoes.

7. The method for preparing diced tomatoes according to claim 6, characterized in that, In step (6), the hot tomato juice is at least partially derived from the juice screened out in step (3) and / or step (5) and then prepared and sterilized.

8. The method for preparing diced tomatoes according to claim 6, characterized in that, In step (7), the microwave heating time is 0.5-1.5 min, the microwave heating power is 30-40 KW, and the microwave frequency is 2450 MHz ± 25 MHz.

9. A preparation system for preparing diced tomatoes, characterized in that, include: A dicing device used to dice or cut pre-treated tomatoes into cubes; The first hexagonal drum sieve is connected to the outlet of the dicing device and is used to perform the first sieve and juice filtration on the diced tomatoes. A first microwave heating device is located downstream of the first hexagonal drum screen and is used to microwave heat and exhaust the filtered tomato pieces. The first microwave heating device has a control unit that can adjust the microwave frequency and power. The second hexagonal drum sieve is located downstream of the first microwave heating device and is used to perform a second sieve and juice filtration on the microwave-treated diced tomatoes. A filling and sealing device is located downstream of the second hexagonal drum screen. It is used to fill the diced tomatoes after secondary screening into containers and seal them after filling. And a juice recycling pipeline, connected between the juice outlet of the second hexagonal drum screen and the juice inlet of the filling device, for returning the juice separated after microwave treatment to the container; The second microwave heating device is located downstream of the filling and sealing device and is used to perform a second microwave heating on the sealed part. A water bath heating sterilization device is connected to the outlet of the second microwave heating device and is used to sterilize the filled containers.

10. A type of diced tomato, characterized in that, The product is prepared by any one of claims 1 to 8, and the solid content of the finished product is consistently above 70%.

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