Three-stage sterilization method and equipment for freshly squeezed tomato juice through cooperation of multi-frequency ultrasound and pasteurization

Abstract

The invention belongs to the technical field of food sterilization, and relates to a multi-frequency ultrasonic and pasteurization combined three-stage sterilization method and equipment for freshly squeezed tomato juice, and the equipment comprises a storage tank, a multi-frequency ultrasonic sterilizer, a synergistic sterilizer, a heat exchanger, a temperature holding pipe, a hot water tank, an intelligent controller, a control valve and a flowmeter. Then carrying out multi-frequency ultrasonic synergistic sterilization in a multi-frequency ultrasonic sterilizer, and destroying microbial cell structures, passivating enzymes in the fruit and vegetable juice and reducing enzyme activity through an ultrasonic cavitation effect; then entering a synergetic sterilizer, and further consolidating the sterilization effect through the combination of ultrasonic waves and heating; and the sterilized freshly squeezed tomato juice enters the heat exchanger as a heat source. The invention provides a sterilization scheme which is green, efficient, low in energy consumption and capable of keeping heat-sensitive nutritional ingredients and natural flavor of the liquid food to the maximum extent, is suitable for sterilization treatment of various liquid foods, and meets the requirements of modern food safety and environmental protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of food sterilization, and relates to a three-stage sterilization method and device for freshly squeezed tomato juice by multi-frequency ultrasound synergistic with pasteurization. Background Art

[0002] Sterilization is an important process in the production of fresh fruit and vegetable juices, which has an important impact on the nutritional value, storage characteristics and shelf life of products. Traditional fruit and vegetable juice processing uses thermal sterilization technologies, including pasteurization (60 - 80°C, 15 - 30 min), high-temperature short-time sterilization (90 - 95°C, 2 - 5 min), ultra-high temperature instantaneous sterilization (121°C, 3 - 5 s), etc. High-temperature or long-time thermal sterilization leads to problems such as browning, off-flavors and other sensory quality degradation of fruit and vegetable juices, stratification and precipitation, and destruction of heat-sensitive nutrients. At the same time, the fruit and vegetable juice processing industry is an energy-intensive industry.

[0003] Currently, the development of the fruit and vegetable juice beverage market has emerged in segmented fields, including traditional juices, niche juices, and NFC juices (non-concentrate reconstituted juices), etc. The emergence of these segmented fields reflects the increasing advanced demand of consumers for healthy, nutritious and natural foods. NFC freshly squeezed fruit and vegetable juices have shown great market potential because they can preserve the vast majority of natural flavors, nutritional components and bioactive substances in fruits and vegetables, and have the characteristics of "original flavor".

[0004] As an efficient, environmentally friendly and energy-saving non-thermal assisted sterilization technology, ultrasound can not only sterilize efficiently, but also effectively retain the original flavor. Compared with high-temperature or long-time sterilization technologies, the mechanical shear force (1.5 kg / cm 2 ) and local instantaneous high temperature and high pressure (5000 K, 1800 atm) generated by ultrasonic cavitation cause irreversible damage to the cell membranes, DNA and bioenzymes of microorganisms. At the same time, the chemical action of ultrasonic cavitation generates free radicals (H + , OH - and H2O2), promotes oxidative stress reactions, interferes with energy metabolism, and ultimately induces the death of microorganisms. In addition, ultrasound has a homogenizing effect, which can improve the suspension stability of fruit juices, effectively retain heat-sensitive nutrients and promote the release of bioactive substances.

[0005] Chinese Patent CN201682998U discloses an ultrasonic continuous sterilization device, including a raw material tank, a heating device, a heat exchange device, an ultrasonic treatment device, a liquid storage device and a controller. Using the technology of combining low-temperature heating with ultrasound, although it has good sterilization effect and high efficiency, heating with a barrel-shaped material tank is prone to uneven heating, resulting in residual microbial "cold spots".

[0006] Chinese Patent CN216627370U discloses a continuous ultrasonic-microwave combined sterilization device, which includes a feeding unit, a microwave pre-processor, an ultrasonic sterilizer, and a storage unit connected in sequence. By utilizing the dispersion effect of comprehensive ultrasound and the unique heating advantage of microwave, the overall action time is reduced, and the overall temperature change is minimized, thereby reducing the loss of heat-sensitive substances in fruit and vegetable juice materials. However, the thermal effect of microwave heating may cause local carbonization, which is likely to lead to product browning. In addition, the uneven distribution of the microwave field results in local overheating, and it is difficult for ultrasonic assistance to disperse heat evenly. Moreover, when microwave and ultrasound operate simultaneously, the power consumption is large and the operating cost is high.

[0007] Therefore, there is a need for a sterilization device and method with low energy consumption, high heat exchange efficiency, high-efficiency broad-spectrum sterilization, and intelligent control. Summary of the Invention

[0008] In order to overcome the deficiencies of the prior art, the present invention provides a three-stage sterilization method and device for freshly squeezed tomato juice with multi-frequency ultrasound synergistic pasteurization. By using preheating, multi-frequency ultrasonic technology, and the synergistic sterilization mechanism of ultrasound and heating, high-efficiency and low-energy consumption sterilization effects are achieved, while maximizing the preservation of the original quality of food.

[0009] The technical solution of the present invention is as follows:

[0010] On the one hand, the present invention discloses a three-stage sterilization device for freshly squeezed tomato juice with multi-frequency ultrasound synergistic pasteurization, which includes a storage tank, a multi-frequency ultrasonic sterilizer, a synergistic sterilizer, a heat exchanger, a holding tube, a hot water tank, an intelligent controller, a control valve, and a flow meter. The storage tank has a raw material inlet and a raw material outlet. The raw material outlet is connected to the shell side / tube side inlet of the heat exchanger through a pipeline. The shell side / tube side outlet of the heat exchanger is connected to the feed inlet of the multi-frequency ultrasonic sterilizer through a pipeline. The discharge outlet of the multi-frequency ultrasonic sterilizer is connected to the feed inlet of the synergistic sterilizer through a pipeline. The discharge outlet of the synergistic sterilizer is connected to the inlet of the holding tube through a pipeline. The outlet of the holding tube enters the tube side / shell side inlet of the heat exchanger through a pipeline. The tube side / shell side outlet of the heat exchanger is connected to the product discharge outlet through a pipeline. The outlet of the hot water tank is connected to the hot water inlet of the synergistic sterilizer through a pipeline. The hot water outlet of the synergistic sterilizer is connected to the inlet of the hot water tank through a pipeline. The intelligent controller is connected to the hot water tank, the heat exchanger, the multi-frequency ultrasonic sterilizer, the synergistic sterilizer, and the control valve through lines.

[0011] Further, a plurality of ultrasonic phased arrays I are provided inside the multi-frequency ultrasonic sterilizer.

[0012] Further, a plurality of ultrasonic phased arrays II are provided inside the synergistic sterilizer.

[0013] Further, a first control valve and a first flowmeter are sequentially arranged on the raw material inlet pipeline of the storage tank, and a second flowmeter, a second control valve and a first transfer pump are sequentially arranged on the raw material outlet pipeline of the storage tank.

[0014] Further, a sixth control valve and a fifth flowmeter are arranged on the outlet pipeline of the tube side / shell side of the heat exchanger, and a third control valve is arranged on the outlet pipeline of the shell side / tube side of the heat exchanger; a fourth control valve, a second transfer pump and a third flowmeter are sequentially arranged on the discharge pipeline of the multi-frequency ultrasonic sterilizer.

[0015] Further, a fourth flowmeter and a hot water circulation pump are arranged on the outlet pipeline of the hot water tank, and a fifth control valve is arranged on the inlet pipeline.

[0016] The second aspect of the present invention discloses a three-stage sterilization method for freshly squeezed tomato juice with multi-frequency ultrasonic synergistic pasteurization for the equipment, including:

[0017] (1) Preheating of freshly squeezed tomato juice:

[0018] Open the second control valve and start the first transfer pump to send the freshly squeezed tomato juice in the storage tank to the heat exchanger for heat exchange with the freshly squeezed tomato juice after sterilization, and obtain the preheated freshly squeezed tomato juice.

[0019] (2) The preheated freshly squeezed tomato juice enters the multi-frequency ultrasonic sterilizer for primary sterilization:

[0020] Open the third control valve, and the preheated freshly squeezed tomato juice enters the multi-frequency ultrasonic sterilizer under the action of the first transfer pump. Start the ultrasonic phased array one in the multi-frequency ultrasonic sterilizer with a power of 500W and frequencies of 20KHz and 40KHz distributed at intervals. The material stays in the multi-frequency ultrasonic sterilizer for 3-4 minutes to obtain the freshly squeezed tomato juice after ultrasonic sterilization, and the sterilization rate is over 70%.

[0021] (3) The freshly squeezed tomato juice after ultrasonic sterilization enters the synergistic sterilizer for consolidated sterilization:

[0022] Open the fourth control valve and start the second transfer pump to send the freshly squeezed tomato juice after ultrasonic sterilization to the synergistic sterilizer. Start the ultrasonic phased array two in the synergistic sterilizer with a power of 500W and a frequency of 40KHz. Heat the freshly squeezed tomato juice to 55-60°C in the synergistic sterilizer and keep it for 5-7 minutes to obtain the freshly squeezed tomato juice after synergistic sterilization, and the sterilization rate is 100%; the specific detection method of the sterilization rate is based on the national standard GB 7101-2022 "National Food Safety Standard Beverages".

[0023] (4) The freshly squeezed tomato juice after synergistic sterilization is sent to a holding tube and maintained for 2 min at a temperature of 53 - 56°C. Then, the freshly squeezed tomato juice is pumped into a heat exchanger to exchange heat with cold materials and cooled to 30 - 35°C to obtain the freshly squeezed tomato juice after sterilization, which is then pumped into a material tank for filling.

[0024] Further, the method for preparing the freshly squeezed tomato juice in step (1) is as follows: The washed and cut tomatoes and water are cold-pressed at a mass ratio of 1 - 1.5:1 - 2, 0.8 - 1.0% ascorbic acid is added for crushing and pulping, and then filtered. The filtered tomato juice is treated at a pressure of 110 - 130 MPa for 8 - 10 min. After homogenization, the temperature of the tomato juice is 36 ± 1°C, and the freshly squeezed tomato juice is collected in a storage tank for standby.

[0025] Further, the color indexes of the freshly squeezed tomato juice in step (1) are: L is 25.21 - 27.35, a is 2.35 - 2.50, b is - 1.32 - 1.29, the soluble solids content is 1.6 - 1.7 °Brix, the browning index is 0.039 - 0.047, the total phenol content is 187.59 - 206.34 μg GAE / mL, the lycopene content is 101.86 - 107.57 μg / mL, and the temperature of the tomato juice is 25 - 27°C.

[0026] Further, for the freshly squeezed tomato juice after sterilization in step (5), the brightness L is 28.48 - 31.31, ΔE is 2.47 - 3.42, the soluble solids content is 1.4 - 1.6 °Brix, the browning index is 0.044 - 0.052, the total phenol content is 217.21 - 232 μg GAE / mL, and the lycopene content is 119.43 - 134.69 μg / mL.

[0027] The freshly squeezed tomato juice sterilized by the method of the present invention has improvements in terms of brightness, soluble solids content, browning index, total phenol content, and lycopene content. This is because: The combined action of ultrasonic waves and mild heat (55 - 60°C). On the one hand, the cavitation and shearing action of multi-frequency ultrasonic waves makes the particle size of the pulp tissue in the tomato juice finer. At the same time, ultrasonic waves inactivate oxidase, reducing enzymatic browning during the sterilization process of tomato juice. Meanwhile, the temperature of 55 - 60°C avoids non-enzymatic browning caused by high temperature, thereby improving the brightness of tomato juice and effectively controlling browning during the sterilization process of tomato juice.

[0028] Total phenols and lycopene are bioactive substances in tomato juice and have strong antioxidant activity. On the one hand, the cavitation effect of ultrasonic waves has a high-intensity mechanical shear force, which destroys the cell wall and cell membrane structures of tomatoes, making the phenols and lycopene bound inside the cells more easily released into the tomato juice. On the other hand, moderate heat can soften the matrix tissues of the tomato cell wall, such as cellulose and pectin, further promoting the release of cell contents such as phenols and lycopene (such as cellulose and pectin). In addition, ultrasonic cavitation can quickly inactivate oxidases (such as peroxidase), preventing the oxidative loss of phenols, while traditional high-temperature treatment may lead to the degradation of more heat-sensitive phenols.

[0029] The advantages and positive effects of the present invention are as follows:

[0030] (1) The application of multi-frequency ultrasonic technology dynamically adjusts the ultrasonic frequency to achieve precise sterilization;

[0031] (2) A synergistic sterilization mechanism where ultrasonic waves and heating are combined to improve the sterilization efficiency;

[0032] (3) Low-energy consumption design, and the hot water circulation system and heat exchanger effectively recover and utilize heat;

[0033] (4) An intelligent control system that monitors and adjusts each parameter in real time to ensure the safety and stability of the process.

[0034] The present invention achieves high-efficiency sterilization (sterilization rate of 100%) through three stages of sterilization: preheating, multi-frequency ultrasonic sterilization, and synergistic sterilization of ultrasonic waves and heating, while retaining the nutritional components of tomato juice (such as 217.21 - 226.45 μg GAE / mL of total phenols and 119.43 - 125.79 μg / mL of lycopene). It has low energy consumption and is applicable to the sterilization treatment of various liquid and semi-solid foods, meeting the requirements of modern food safety and environmental protection. Brief Description of the Drawings

[0035] Figure 1 is a schematic diagram of the device of the present invention;

[0036] Figure 2 is an internal structure schematic diagram of the multi-frequency ultrasonic sterilizer in the device of the present invention;

[0037] Figure 3 is a top view of the multi-frequency ultrasonic sterilizer in the device of the present invention;

[0038] Figure 4 is an internal structure schematic diagram of the synergistic sterilizer in the device of the present invention;

[0039] Figure 5 is a half-sectional top view of the synergistic sterilizer in the device of the present invention.

[0040] 1 - First control valve, 2 - First flowmeter, 3 - Storage tank, 4 - Second flowmeter, 5 - Second control valve, 6 - First transfer pump, 7 - Heat exchanger, 8 - Third control valve, 9 - Multi - frequency ultrasonic sterilizer, 10 - Fourth control valve, 11 - Second transfer pump, 12 - Third flowmeter, 13 - Synergistic sterilizer, 14 - Hot water circulation pump, 15 - Fourth flowmeter, 16 - Hot water tank, 17 - Fifth control valve, 18 - Holding tube, 19 - Fifth flowmeter, 20 - Sixth control valve, 21 - Feed inlet of the multi - frequency ultrasonic sterilizer, 22 - Ultrasonic phased array one, 23 - Motor, 24 - Discharge outlet of the multi - frequency ultrasonic sterilizer, 25 - Feed inlet of the synergistic sterilizer, 26 - Ultrasonic phased array two, 27 - Hot water outlet, 28 - Discharge outlet of the synergistic sterilizer, 29 - Hot water inlet. Detailed implementation mode

[0041] The present invention will be further described in detail below through specific embodiments. The following embodiments are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0042] Embodiment 1

[0043] As Figure 1 shown, a three - stage sterilization device for freshly squeezed tomato juice with multi - frequency ultrasonic synergistic pasteurization includes a storage tank 3, a multi - frequency ultrasonic sterilizer 9, a synergistic sterilizer 13, a heat exchanger 7, a holding tube 18, a hot water tank 16, an intelligent controller and control valves.

[0044] The storage tank 3 is used to store the raw materials to be processed to ensure the continuous supply of materials. The storage tank 3 has a raw material inlet and a raw material outlet. A first control valve 1 and a first flowmeter 2 are sequentially arranged on the raw material inlet pipeline of the storage tank 3, and a second flowmeter 4, a second control valve 5 and a first transfer pump 6 are sequentially arranged on the raw material outlet pipeline of the storage tank 3. The first transfer pump 6 is responsible for transferring the materials in the storage tank 3 to the heat exchanger 7 and the multi - frequency ultrasonic sterilizer 9.

[0045] The heat exchanger 7 is used to preliminarily heat the materials to improve the efficiency of the subsequent sterilization stage. It also serves as the heat source of the cooling device to recover heat and reduce energy consumption. The heat exchanger 7 optimizes the efficiency and effect of the subsequent sterilization stage by adjusting the initial temperature of the materials, and at the same time cools the sterilized materials, effectively recycling and using heat to reduce the impact on the subsequent canning step. By adopting efficient heat exchange technology, it ensures that the materials are quickly cooled after sterilization to prevent the impact of over - heating on food quality. A third control valve 8 is arranged on the shell - side outlet pipeline of the heat exchanger 7; the raw material outlet of the storage tank 3 is connected to the shell - side inlet of the heat exchanger 7 through a pipeline.

[0046] The shell - side outlet of the heat exchanger 7 is connected to the feed inlet 21 of the multi - frequency ultrasonic sterilizer through a pipeline. The multi - frequency ultrasonic sterilizer 9 uses ultrasonic waves of multiple frequencies to sterilize the materials, such as Figures 2 - 3Schematic diagram of the internal structure and top view of the multi-frequency ultrasonic sterilizer 9 shown. Multiple ultrasonic phased arrays I 22 and motors 23 are radially distributed inside, and the frequency and intensity of ultrasonic waves can be dynamically adjusted according to the material characteristics and sterilization requirements to achieve the best sterilization effect.

[0047] The discharge port 24 of the multi-frequency ultrasonic sterilizer is connected to the feed port 25 of the collaborative sterilizer through a pipeline. A fourth control valve 10, a second transfer pump 11, and a third flowmeter 12 are sequentially arranged on the discharge pipeline of the multi-frequency ultrasonic sterilizer 9. The second transfer pump 11 is responsible for sending the materials of the multi-frequency ultrasonic sterilizer 9 to the collaborative sterilizer 13. As Figures 4 - 5 Schematic diagram of the internal structure and semi-sectional top view of the collaborative sterilizer 13 shown. Multiple ultrasonic phased arrays II 26 are provided inside the collaborative sterilizer 13, combining ultrasonic waves and heating to further consolidate the sterilization effect and ensure that all harmful microorganisms are completely killed. The hot water tank 16 is equipped with a temperature sensor and an automatic water replenishing device to ensure the stability and safety of hot water supply. The hot water tank 16 heats the collaborative sterilizer 13. A fourth flowmeter 15 and a hot water circulation pump 14 are arranged on the outlet pipeline of the hot water tank 16. The hot water circulation pump 14 ensures the recycling of hot water, improves energy utilization efficiency, and a fifth control valve 17 is arranged on the inlet pipeline. There are a hot water outlet 27 and a hot water inlet 29 inside the collaborative sterilizer 13. The hot water outlet 27 is connected to the inlet of the hot water tank 16 through a pipeline, and the hot water inlet 29 is connected to the outlet of the hot water tank 16 through a pipeline.

[0048] The discharge port 28 of the collaborative sterilizer is connected to the inlet of the holding tube 18 through a pipeline. The holding tube 18 is used to extend the residence time of the material at high temperature to ensure sufficient sterilization. The outlet of the holding tube 18 enters the tube-side inlet of the heat exchanger 7 through a pipeline. The tube-side outlet of the heat exchanger 7 is connected to the product discharge port through a pipeline. A sixth control valve 20 and a fifth flowmeter 19 are arranged on the tube-side outlet pipeline of the heat exchanger 7.

[0049] The intelligent controller is not drawn in Figure 1 to be responsible for coordinating the work of each component, monitoring and adjusting each parameter such as temperature, pressure, flow rate, etc. in real time to ensure the safety and stability of the entire sterilization process. The controller is connected to the hot water tank 16, the heat exchanger 7, the multi-frequency ultrasonic sterilizer 9, the collaborative sterilizer 13 and each control valve and flowmeter through lines. Each control valve and flowmeter precisely controls the flow rate and pressure of the material through a closed-loop control equipment system to ensure the continuity and stability of the sterilization process.

[0050] Example 2

[0051] A three-stage sterilization method for freshly squeezed tomato juice with multi-frequency ultrasonic collaborative pasteurization for the equipment described in Example 1, including:

[0052] (1) Prepare freshly squeezed tomato juice

[0053] After the raw fruits are washed with water, the raw materials are cut into pieces, and the cold pressing method is used to crush and pulp according to tomato: water (1-1.5:1-2). When pulping, 0.8-1.0% ascorbic acid is added. The skin residues and large particle impurities are filtered out with two layers of gauze. The freshly squeezed tomato juice after filtration is treated at a pressure of 110-130 MPa for 8-10 min. After homogenization, the temperature of the freshly squeezed tomato juice is 36±1°C. The freshly squeezed tomato juice is collected and stored in the storage tank 3 for standby. The color indexes of the obtained freshly squeezed tomato juice are L 26.46, a 2.5, b 1.02, soluble solids 1.6°Brix, browning index 0.043, total phenols 192.37 μg GAE / mL, lycopene 103.45 μg / mL, and the tomato juice temperature is 25°C.

[0054] The color differences L, a, b are measured by a color difference meter.

[0055] The soluble solids are measured by a hand-held refractometer. For the browning index, 5 mL of fruit juice is taken, an equal volume of 95% ethanol is added, mixed well, centrifuged at 10000 r / min for 15 min at 4°C, and the absorbance of the supernatant is measured at 420 nm, with 80% ethanol solution as the blank.

[0056] The browning index BD = A×V1 / V2, where: A is the absorbance value, V1 is the volume of the extract, mL, and V2 is the sample volume, (5 mL).

[0057] Total phenol determination method: After mixing 2 mL of tomato juice with 8 mL of absolute ethanol for 20 min, centrifuge at 5000 r / min for 10 min; take 0.5 mL of the supernatant, add 2.5 mL of 10% Folin-Ciocalteu reagent and react for 5 min, then add 2 mL of saturated sodium carbonate solution to the mixture and react at room temperature for 2 h. 300 μL of each treatment is pipetted into a 96-well plate, and the absorbance is measured at 765 nm using a microplate reader. The total phenol content is expressed as milligrams of gallic acid equivalent per 100 mL (mg GAE / 100 mL)

[0058] Lycopene determination method: 2 mL of the tomato juice sample is mixed with 25 mL of the extraction solvent of n-hexane, ethanol and acetone (2:1:1, v / v / v). The mixture is vortex-extracted in the dark at room temperature for 20 min. After centrifuging at 6000×g for 10 min at 4°C (TGL-16, Sichuan, China), the supernatant is collected. The residue is extracted 2 more times. Then these collected supernatants are mixed and used as the extract. Using n-hexane as the control, the absorbance is measured at 503 nm. TLC (μg / mL) is calculated according to the formula. TLC (μg / mL) = A 503×Mr×n×1000 / L×ε. In the formula, Mr is the molecular weight of lycopene (536.9 g / mol), n is the dilution ratio, L is the optical path length (1 cm), and ε is the extinction coefficient of lycopene (172000 L / mol·cm).

[0059] (2) Preheating of freshly squeezed tomato juice:

[0060] Open the second control valve 5 and start the first transfer pump 6 to send the freshly squeezed tomato juice in the storage tank 3 to the heat exchanger 7 for heat exchange with the freshly squeezed tomato juice that has completed sterilization, obtaining preheated freshly squeezed tomato juice;

[0061] (3) The preheated freshly squeezed tomato juice enters the multi-frequency ultrasonic sterilizer 9 for primary sterilization:

[0062] Open the third control valve 8, and the preheated freshly squeezed tomato juice enters the multi-frequency ultrasonic sterilizer 9 under the action of the first transfer pump 6. Start the ultrasonic phased array one 22 in the multi-frequency ultrasonic sterilizer 9 with a power of 500 W and frequencies of 20 KHz and 40 KHz distributed at intervals. The material stays in the multi-frequency ultrasonic sterilizer 9 for 4 minutes. The material is subjected to ultrasonic waves of multiple frequencies, and the cavitation effect generated by the ultrasonic waves destroys the microbial cell structure. At the same time, the enzymes in the material are inactivated, reducing their activity, and maintaining the color and flavor of the juice, obtaining freshly squeezed tomato juice after ultrasonic sterilization with a sterilization rate of 70%; The specific detection method of the sterilization rate is based on the national standard GB7101-2022 "National Food Safety Standard Beverages".

[0063] (3) The freshly squeezed tomato juice after ultrasonic sterilization enters the synergistic sterilizer 13 for consolidated sterilization:

[0064] Open the fourth control valve 10 and start the second transfer pump 11 to send the freshly squeezed tomato juice after ultrasonic sterilization to the synergistic sterilizer 13. Start the ultrasonic phased array two 26 in the synergistic sterilizer 13 with a power of 500 W and a frequency of 40 KHz. The freshly squeezed tomato juice is heated to 55 °C in the synergistic sterilizer 13 and stays for 7 minutes, obtaining freshly squeezed tomato juice after synergistic sterilization with a sterilization rate of 100%;

[0065] (4) The freshly squeezed tomato juice after synergistic sterilization is sent to the holding tube 18 and kept for 2 min at a temperature maintained at 53 °C. Then, the freshly squeezed tomato juice is pumped into the heat exchanger 7 for heat exchange with cold materials and cooled to 35 °C, obtaining freshly squeezed tomato juice that has completed sterilization, which is pumped into the material tank for filling. The brightness L of the freshly squeezed tomato juice that has completed sterilization is 29.79, ΔE is 2.87, the soluble solids are 1.4 °Brix, the browning index is 0.049, the total phenol content is 220.43 μg GAE / mL, and the lycopene content is 127.51 μg / mL.

[0066] Example 3

[0067] A three-stage sterilization method for freshly squeezed tomato juice using multi-frequency ultrasound in cooperation with pasteurization for the device described in Example 1, comprising: (1) preparing freshly squeezed tomato juice (the steps are the same as in Example 2);

[0068] (2) preheating the freshly squeezed tomato juice (the steps are the same as in Example 2);

[0069] (3) The preheated freshly squeezed tomato juice enters the multi-frequency ultrasonic sterilizer 9 for primary sterilization:

[0070] Open the third control valve 8, and the preheated freshly squeezed tomato juice enters the multi-frequency ultrasonic sterilizer 9 under the action of the first transfer pump 6. Start the ultrasonic phased array one 22 in the multi-frequency ultrasonic sterilizer 9 with a power of 600 W, and the frequencies 40 KHz and 20 KHz are distributed at intervals. The freshly squeezed tomato juice stays in the multi-frequency ultrasonic sterilizer 9 for 3 minutes. The material is subjected to ultrasonic waves of multiple frequencies, and the cavitation effect generated by the ultrasonic waves destroys the microbial cell structure. At the same time, the enzymes in the material are inactivated, reducing their activity, maintaining the color and flavor of the juice, and obtaining freshly squeezed tomato juice sterilized by ultrasound with a sterilization rate of more than 70%. The specific detection method for the sterilization rate is based on the national standard GB7101-2022 "National Food Safety Standard Beverages".

[0071] (3) The freshly squeezed tomato juice sterilized by ultrasound enters the cooperative sterilizer 13 for enhanced sterilization:

[0072] Open the fourth control valve 10, start the second transfer pump 11, send the freshly squeezed tomato juice sterilized by ultrasound to the cooperative sterilizer 13, start the ultrasonic phased array two 26 in the cooperative sterilizer 13 with a power of 600 W and a frequency of 40 KHz. The freshly squeezed tomato juice is heated to 55 °C in the cooperative sterilizer 13 and stays for 5 minutes to obtain freshly squeezed tomato juice after cooperative sterilization with a sterilization rate of 100%;

[0073] (4) The freshly squeezed tomato juice after cooperative sterilization is sent to the holding tube 18 and kept for 2 min at a temperature maintained at 56 °C. Then, the freshly squeezed tomato juice is pumped into the heat exchanger 7 to exchange heat with cold materials and cooled to 30 °C to obtain freshly squeezed tomato juice after sterilization, which is pumped into the material tank for filling. The brightness L of the freshly squeezed tomato juice after sterilization is 31.31, ΔE is 3.42, the soluble solids are 1.5 °Brix, the browning index is 0.052, the total phenol content is 231.73 μg GAE / mL, and the lycopene content is 134.69 μg / mL.

[0074] Comparative Example 1

[0075] The difference from Example 2 is only that the frequency of the multi-frequency ultrasonic sterilizer 9 is a single frequency of 20 KHz. The parameters of the freshly squeezed tomato juice after sterilization are shown in Table 1.

[0076] Comparative Example 2

[0077] The difference from Example 2 is only that the sterilization temperature of the synergistic sterilizer 13 is 70°C. The parameters of the freshly squeezed tomato juice after sterilization are shown in Table 1.

[0078] Comparative Example 3

[0079] The difference from Example 2 is only that the freshly squeezed tomato juice after synergistic sterilization is sent to the holding tube 18, without staying, and immediately cooled to below 30°C. The parameters of the freshly squeezed tomato juice after sterilization are shown in Table 1.

[0080] Table 1 Parameters of the freshly squeezed tomato juice after sterilization in Examples 2-3 and Comparative Examples

[0081]

[0082] In Comparative Example 1, single-frequency ultrasonic sterilization was adopted. In Comparative Example 2, the temperature of ultrasonic synergistic pasteurization was 70°C, which was 10-15°C higher than the temperature of 55-60°C used in the present invention. In Comparative Example 3, there was no constant-temperature sterilization in the holding tube. Compared with the examples of the present application, the brightness L of the tomato juice after sterilization treatment in Comparative Example 1 was low, there was no significant difference in color difference ΔE, the total phenol and lycopene contents were low, and the bacteria could not be completely killed, but it met the national standard GB 7101-2022 "National Food Safety Standard Beverages" with the total number of bacteria < 1000 CFU / mL. Compared with the present application, the brightness L of the tomato juice after sterilization treatment in Comparative Example 2 decreased, the color difference ΔE increased, the total phenol and lycopene were severely damaged, and the total number of bacteria was not detected. Compared with the present application, the brightness L and color difference ΔE of the tomato juice after sterilization treatment in Comparative Example 3 had no significant difference, the total phenol and lycopene decreased, and the bacteria could not be completely killed, but it met the national standard GB 7101-2022 "National Food Safety Standard Beverages" with the total number of bacteria < 1000 CFU / mL.

[0083] In summary, the three-stage sterilization method of freshly squeezed tomato juice using multi-frequency ultrasound synergistic mild pasteurization in the present invention can completely sterilize bacteria, while improving the brightness of freshly squeezed juice, reducing color difference, reducing browning, and significantly increasing the total phenol and lycopene contents.

[0084] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

Claims

1. A three-stage sterilization equipment for freshly squeezed tomato juice using multi-frequency ultrasound and pasteurization, characterized in that: The invention comprises a material storage tank (3), a multi-frequency ultrasonic sterilizer (9), a collaborative sterilizer (13), a heat exchanger (7), a temperature holding tube (18), a hot water tank (16), an intelligent controller, a control valve and a flow meter, wherein the material storage tank (3) has a raw material inlet and a raw material outlet, the raw material outlet is connected to the shell side / tube side inlet of the heat exchanger (7) through a pipeline, the shell side / tube side outlet of the heat exchanger (7) is connected to the feed port (21) of the multi-frequency ultrasonic sterilizer through a pipeline, the discharge port (24) of the multi-frequency ultrasonic sterilizer is connected to the feed port (25) of the collaborative sterilizer through a pipeline, and the discharge port (28) of the collaborative sterilizer is connected to the feed port (26) of the collaborative sterilizer through a pipeline. The hot water tank (16) is connected to the inlet of the temperature-holding tube (18) through a pipeline, the outlet of the temperature-holding tube (18) enters the tube-side / shell-side inlet of the heat exchanger (7) through a pipeline, and the tube-side / shell-side outlet of the heat exchanger (7) is connected to the product discharge port through a pipeline; the outlet of the hot water tank (16) is connected to the hot water inlet (29) of the collaborative sterilizer (13) through a pipeline, and the hot water outlet (27) of the collaborative sterilizer (13) is connected to the inlet of the hot water tank (16) through a pipeline, and the intelligent controller is respectively connected to the hot water tank (16), the heat exchanger (7), the multi-frequency ultrasonic sterilizer (9), the collaborative sterilizer (13) and the control valve through lines.

2. The device according to claim 1, characterized in that The multi-frequency ultrasonic sterilizer (9) is provided with a plurality of ultrasonic phased arrays (22) inside.

3. The device according to claim 1, characterized in that A plurality of ultrasonic phased arrays 2 (26) are arranged inside the collaborative sterilizer (13).

4. The device according to claim 1, characterized in that A first control valve (1) and a first flowmeter (2) are sequentially arranged on the raw material inlet pipeline of the storage tank (3), and a second flowmeter (4), a second control valve (5) and a first material transfer pump (6) are sequentially arranged on the raw material outlet pipeline of the storage tank (3); a sixth control valve (20) and a fifth flowmeter (19) are arranged on the tube side / shell side outlet pipeline of the heat exchanger (7), and a third control valve (8) is arranged on the shell side / tube side outlet pipeline of the heat exchanger (7); a fourth control valve (10), a second material transfer pump (11) and a third flowmeter (12) are sequentially arranged on the discharge pipeline of the multi-frequency ultrasonic sterilizer (9); a fourth flowmeter (15) and a hot water circulation pump (14) are arranged on the outlet pipeline of the hot water tank (16), and a fifth control valve (17) is arranged on the inlet pipeline.

5. A three-stage sterilization method for freshly squeezed tomato juice using multi-frequency ultrasound and pasteurization for the equipment according to any one of claims 1 to 4, characterized in that: include: (1) Preheating of freshly squeezed tomato juice: The second control valve (5) is opened, and the first transfer pump (6) is started to send the freshly squeezed tomato juice in the storage tank (3) to the heat exchanger (7) to exchange heat with the sterilized freshly squeezed tomato juice, thereby obtaining preheated freshly squeezed tomato juice; (2) The preheated freshly squeezed tomato juice enters the multi-frequency ultrasonic sterilizer (9) for initial sterilization: The third control valve (8) is opened, and the preheated freshly squeezed tomato juice enters the multi-frequency ultrasonic sterilizer (9) under the action of the first material transfer pump (6), and the ultrasonic phased array 1 (22) in the multi-frequency ultrasonic sterilizer (9) is started. The material stays in the multi-frequency ultrasonic sterilizer (9) for 3-4 minutes to obtain ultrasonically sterilized freshly squeezed tomato juice, with a sterilization rate of more than 70%; (3) The freshly squeezed tomato juice after ultrasonic sterilization enters the coordinated sterilizer (13) to consolidate the sterilization: Open the fourth control valve (10), start the second material transfer pump (11), send the ultrasonically sterilized fresh tomato juice to the collaborative sterilizer (13), start the ultrasonic phased array 2 (26) in the collaborative sterilizer (13), heat the fresh tomato juice to 55-60° C. in the collaborative sterilizer (13), and keep it for 5-7 minutes to obtain the fresh tomato juice after collaborative sterilization, with a sterilization rate of 100%; (4) The freshly squeezed tomato juice after synergistic sterilization is sent to the temperature holding tube (18) and kept at 53-56°C for 2-5 minutes. The freshly squeezed tomato juice is then pumped into the heat exchanger (7) to exchange heat with the cold material and cooled to 30-35°C to obtain the sterilized freshly squeezed tomato juice, which is then pumped into the material tank for filling.

6. The sterilization method according to claim 5, characterized in that: The preparation method of freshly squeezed tomato juice in step (1) is as follows: wash and cut tomatoes and water are cold squeezed according to a mass ratio of 1-1.5:1-2, 0.8-1.0% ascorbic acid is added to crush and pulp, and filtered. The filtered tomato juice is treated with a pressure of 110-130 MPa for 8-10 minutes. The temperature of the tomato juice after homogenization is 36±1° C. The freshly squeezed tomato juice is collected in a storage tank (3) for standby use.

7. The sterilization method according to claim 5, characterized in that: The color index of the freshly squeezed tomato juice in step (1) is as follows: L is 25.21-27.35, a is 2.35-2.50, b is -1.32-1.29, soluble solids are 1.6-1.7° Brix, browning index is 0.039-0.047, total phenols are 187.59-206.34 μg GAE / mL, lycopene is 101.86-107.57 μg / mL, and the tomato juice temperature is 25-27°C.

8. The sterilization method according to claim 5, characterized in that: The multi-frequency ultrasonic sterilizer (9) has a power of 500W, and the frequencies are distributed at intervals of 20KHz and 40KHz.

9. The sterilization method according to claim 5, characterized in that: The power of the collaborative sterilizer (13) is 500W and the frequency is 40KHz.

10. The sterilization method according to claim 5, characterized in that: The freshly squeezed tomato juice after sterilization in step (5) has a brightness L of 28.48-31.31, a ΔE of 2.47-3.42, a soluble solid content of 1.4-1.6° Brix, a browning index of 0.044-0.052, a total phenol content of 217.21-232 μg GAE / mL, and a lycopene content of 119.43-134.69 μg / mL.

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