Fruit and vegetable juice capable of keeping fresh at normal temperature and preparation method of fruit and vegetable juice

Abstract

The invention belongs to the technical field of food processing, and particularly relates to fruit and vegetable juice capable of being preserved at normal temperature and a preparation method thereof. The method comprises the following steps: mixing pretreated fruits and vegetables with water, and then performing wet crushing to obtain fruit and vegetable pulp with the particle size of less than or equal to 100 microns; the preparation method comprises the following steps: mixing the fruit and vegetable juice with supercritical CO2, putting the mixture into a high-energy fluid mill, mixing the mixture with supercritical CO2, performing ultrahigh-pressure sterilization under the pressure of 200-280 MPa, performing ultrasonic vibration at the same time, degassing after sterilization to discharge residual CO2, and finally performing ultraviolet sterilization treatment to obtain the fruit and vegetable juice. The method comprises the following steps: firstly, performing ultrahigh-pressure sterilization through a high-energy fluid mill, and efficiently killing most microorganisms in fruit and vegetable juice by utilizing instantaneous high temperature, high pressure and strong shearing force generated by ultrahigh-pressure collision and combining an ultrasonic strengthening effect; residual high-pressure-resistant microorganisms are further killed through ultraviolet sterilization, the total number of bacterial colonies of the fruit and vegetable juice subjected to synergistic sterilization is smaller than or equal to 10 cfu / mL, and the sterilization requirement of normal-temperature storage is met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of food processing, and particularly relates to a fruit and vegetable juice capable of normal-temperature preservation and a preparation method thereof. BACKGROUND

[0002] As a common healthy beverage, fruit and vegetable juice is rich in nutrients such as vitamins, minerals and dietary fiber, and is favored by consumers. However, fruit and vegetable juice is prone to microbial contamination during processing, and contains rich nutrients, which provides favorable conditions for the growth and reproduction of microorganisms, resulting in a short shelf life and difficulty in achieving normal-temperature storage.

[0003] At present, fruit and vegetable juice sterilization mainly adopts traditional heat sterilization technology (such as pasteurization and ultra-high temperature instantaneous sterilization UHT). However, high temperature in the heat sterilization process can destroy heat-sensitive nutrients (such as vitamin C and polyphenols) in the fruit and vegetable juice, resulting in nutrient loss. At the same time, high temperature can also cause Maillard reaction, caramelization reaction and other reactions, making the fruit and vegetable juice dark in color and producing burnt smell and other undesirable flavors, affecting the sensory quality of the product. In addition, the traditional heat sterilization equipment has high energy consumption, large floor area and high processing cost.

[0004] Therefore, how to ensure the deep sterilization effect of fruit and vegetable juice to meet the normal-temperature storage requirement, and maximize the retention of its nutrients and sensory quality, has become a technical problem to be solved in the current fruit and vegetable juice processing field. SUMMARY

[0005] The purpose of the present application is to solve the problems of the prior art, at least to solve the problem that the existing single sterilization technology cannot simultaneously consider the sterilization effect, nutrient retention and normal-temperature storage requirement of fruit and vegetable juice. Through the synergistic effect of ultra-high pressure and ultraviolet, deep sterilization is achieved, the normal-temperature shelf life of fruit and vegetable juice is prolonged, and its nutrient content and sensory quality are retained. Specifically, a fruit and vegetable juice capable of normal-temperature preservation and a preparation method thereof are provided, which specifically adopt the following technical solutions: In a first aspect, the present application provides a preparation method of a fruit and vegetable juice capable of normal-temperature preservation, comprising the following steps: S1: mixing pretreated fruits and vegetables with water, and then performing wet grinding to obtain fruit and vegetable slurry with a particle size of ≤100 μm; S2: placing the fruit and vegetable slurry in a high-energy fluid mill, mixing with supercritical CO2, and then placing it under a pressure of 200 MPa-280 MPa for ultra-high pressure sterilization, while performing ultrasonic vibration. After sterilization, the residual CO2 is removed and discharged to obtain fruit and vegetable juice. S3: placing the fruit and vegetable juice in ultraviolet light for ultraviolet sterilization treatment to obtain the fruit and vegetable juice.

[0006] As a further preferred embodiment, the temperature of the water in S1 is 0℃-4℃; the mass ratio of the fruit and vegetable to the water is 1:3-1:5.

[0007] As a further preferred embodiment, the rotating speed during the wet milling is 1500 r / min-2000 r / min, and the milling time is 5-10 min.

[0008] As a further preferred embodiment, the frequency of the ultrasonic vibration in S2 is 20 kHz-30 kHz.

[0009] As a further preferred embodiment, the temperature during the mixing with supercritical CO2 in S2 is 31-35℃, and the mixing time is 10-15 min.

[0010] As a further preferred embodiment, the ultraviolet irradiation dose during the ultraviolet sterilization treatment in S3 is 30 J / mL-50 J / mL.

[0011] As a further preferred embodiment, the ultraviolet sterilization treatment of the fruit and vegetable juice primary product under ultraviolet light is specifically as follows: The fruit and vegetable juice primary product is delivered to an ultraviolet sterilization equipment with an 8-shaped pipe configuration, and ultraviolet sterilization treatment is performed at a flow rate of 120 mL / min-180 mL / min; The inner diameter of the 8-shaped pipe is 2.5 mm, the length of the pipe is 7 m, two 120 W UV-C lamp tubes are wrapped around the pipe, and the Dean number De is 180-200.

[0012] The 8-shaped pipe configuration of the ultraviolet sterilization system adopted in the present application satisfies the Dean number De=180-200, ensures the formation of strong Dean flow of the fruit and vegetable juice in the pipe, improves the mixing uniformity, and avoids the ultraviolet irradiation dead angle.

[0013] In a second aspect, the present application provides a fruit and vegetable juice that can be preserved at room temperature, which is prepared by the above preparation method.

[0014] As a further preferred embodiment, the retention rate of vitamin C in the fruit and vegetable juice is ≥85%, the retention rate of total flavonoids is ≥90%, and the retention rate of anthocyanins is ≥88%.

[0015] As a further preferred embodiment, the fruit and vegetable juice includes apple juice, orange juice, strawberry juice, or blueberry juice.

[0016] The present application has the following beneficial effects: (1) Synergistic bactericidal effect is obvious: the present application firstly kills most of the microorganisms (such as E. coli, Staphylococcus aureus) in fruit and vegetable juice by high-energy fluid mill ultra-high pressure sterilization, using the instantaneous high temperature, high pressure and strong shear force generated by ultra-high pressure collision, combined with the ultrasonic strengthening effect; then uses the 8-shaped pipe configuration ultraviolet sterilization system to improve the mixing uniformity of fruit and vegetable juice by Dean flow, solves the problem of limited penetration of ultraviolet light, further kills the residual high-pressure resistant microorganisms (such as Bacillus spores), and the total number of colonies of fruit and vegetable juice after synergistic sterilization is ≤10 cfu / mL, which meets the sterilization requirements of normal temperature storage, and the shelf life can reach 6-12 months, solving the problem that traditional non-thermal sterilization cannot make fruit and vegetable juice store at room temperature.

[0017] (2) Good retention of nutrition and sensory quality: high-energy fluid mill ultra-high pressure sterilization is a non-thermal sterilization technology, which causes less damage to heat-sensitive nutritional ingredients in fruit and vegetable juice, with vitamin C retention rate ≥85%, total flavone retention rate ≥90%, and anthocyanin retention rate ≥88%; ultraviolet sterilization has no high temperature process, and the energy utilization rate of the 8-shaped pipe configuration is high, avoiding excessive irradiation leading to degradation of nutritional ingredients; the whole processing process does not add chemical additives, and the color and flavor of fruit and vegetable juice are close to those of fresh fruit and vegetable juice, with excellent sensory quality.

[0018] (3) Low energy consumption and environmental protection: the high-pressure pump of the high-energy fluid mill adopts a three-plunger reciprocating structure, which has low energy consumption, and the ice water pretreatment and the degassing function of the high-energy fluid mill are combined to save independent heat exchangers and degassing tanks, reduce the equipment area by 20-30%, reduce the processing energy consumption by 15-20%, and the supercritical CO2 can be recycled and purified for reuse; the energy consumption of the ultraviolet sterilization system is only 1 / 3-1 / 5 of that of traditional thermal sterilization equipment, which meets the low-carbon and environmentally friendly processing concept; at the same time, there is no need to set up a large sterilization equipment separately, which simplifies the processing technology and reduces the equipment area and processing cost.

[0019] (4) Wide applicability: the processing method of the present application is suitable for the processing of various fruit and vegetable juices, such as apple juice, orange juice, strawberry juice, blueberry juice, etc., and only needs to adjust the parameters such as the speed of the wet grinding millstone, the pressure of ultra-high pressure sterilization and the ultraviolet irradiation dose according to the characteristics of different fruit and vegetable juices, so as to achieve good sterilization effect and normal temperature storage performance, which has wide industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1The preparation of the fruit and vegetable juice with normal temperature preservation is shown in the schematic diagram. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0023] The high-energy fluid grinder used in the following embodiments is purchased from Jiangxi Nandai Guochuang Institute of Food Technology Co., Ltd., and the model is HEFM-1500. The ultraviolet sterilization equipment is purchased from Foshan Wellyter Optoelectronics Technology Co., Ltd., and the model is UV320W19A-D1554.

[0024] Embodiment 1 A preparation method of a fruit and vegetable juice (apple juice) with normal temperature preservation, which specifically comprises the following steps: (1) Pretreatment of fruit and vegetable raw materials: fresh apples are selected, rotten and diseased fruits are removed, the surface mud and sand are washed with clean water, and then the apple skins and cores are removed, and the apples are cut into 2-3 cm cubes; (2) Wet crushing and slurry preparation: the apple cubes are sent into a wet crushing assembly, low-temperature water (0-4 ℃ purified water) is added, and the mass ratio of the apple cubes to the low-temperature water is controlled to be 1:4; the wet crushing assembly is started, the first-stage grinding disc rotates at 1800 r / min, the second-stage grinding disc rotates at 2000 r / min, the crushing time is 8 min, and apple slurry with a particle size of ≤80 μm is obtained; (3) High-energy fluid grinder ultrahigh-pressure sterilization: S1. The apple slurry is pumped into a mixing tank through a gas-liquid booster pump, high-pressure CO2 is introduced, the pressure of the mixing tank is controlled to be 10 MPa, the temperature is 33 ℃, the mixing roller rotates at 300 r / min, the mixing time is 12 min, the apple mixture containing supercritical CO2 is formed, and the mixture is filtered through an 80 μm filter screen; S2. The mixture is sent into a high-pressure pump through an ultrahigh-pressure stop valve, the high-pressure pump is pressurized to 220 MPa, the pressurized mixture enters a containing space, is accelerated to 900 m / s through a flow divider, and collides in a collision chamber; S3. The ultrasonic assembly is started, the ultrasonic frequency is 25 kHz, and the mixture in the collision process is acted on to obtain the apple juice primary product after ultrahigh-pressure sterilization.

[0025] (4) Degassing treatment: the apple juice primary product is discharged through the self-degassing device of the high-energy fluid grinder, CO2 is sent into a gas storage tank after being recovered and purified, and the apple juice after degassing is obtained. (5) UV synergistic sterilization: the apple juice was sent into the UV sterilization system by peristaltic pump, the flow rate was 150 mL / min, the wavelength of UV-C lamp was 254 nm, the irradiation dose was 30 J / mL, the Dean number De of 8-shaped tube was 190, the apple juice product after synergistic sterilization was obtained, the microbial detection showed that the killing rate of Bacillus spore was 99.99%, and the total number of microorganisms was 5 cfu / mL; (6) Aseptic filling and normal temperature storage: the apple juice product was filled into the PET / aluminum foil / PE composite film packaging container in the aseptic filling chamber, the filling temperature was 28°C, and after sealing, it was stored in a 25°C normal temperature environment, after 6 months, the total number of microorganisms was 8 cfu / mL, the retention rate of vitamin C was 88%, and there was no obvious change in color and flavor.

[0026] Example 2 A method for preparing a fruit and vegetable juice (orange juice) that can be preserved at room temperature, which specifically comprises the following steps: (1) Pretreatment of fruit and vegetable raw materials: fresh navel oranges were selected, washed with water, peeled and peeled to obtain orange segments; (2) Wet crushing and slurry preparation: the orange segments were sent into the wet crushing assembly, low-temperature water was added, and the mass ratio of orange segments to low-temperature water was controlled at 1:3; the wet crushing assembly was started, the first-stage grinding disc rotated at 1500 r / min, the second-stage grinding disc rotated at 1800 r / min, and the crushing time was 6 min, to obtain orange juice slurry with a particle size of ≤90 μm; (3) High-energy fluid mill ultra-high pressure sterilization: S1. The orange juice slurry was pumped into the mixing tank by the gas-liquid booster pump, high-pressure CO2 gas was introduced, the pressure in the mixing tank was controlled at 8 MPa, the temperature was 31°C, the mixing roller was started (rotating at 250 r / min), the orange juice slurry and supercritical CO2 were stirred, the mixing time was 10 min, the orange juice mixture containing supercritical CO2 was formed, and after filtering through a 50 μm filter screen, it was sent into the discharge space; S2. The mixture was sent into the three-plunger reciprocating high-pressure pump through the ultra-high pressure stop valve and pressurized to 200 MPa; the pressurized mixture entered the high-energy fluid mill containing space, accelerated to 800 m / s through the diverging channel (the sum of the cross-sectional areas is 1 / 8 of the containing space), and collided with each other in the collision chamber; S3. Start the ultrasonic assembly, the ultrasonic frequency is 20 kHz, the ultrasonic transducer assembly is in close contact with the collision chamber, and the cavitation effect and shear action are strengthened, to obtain the orange juice primary product after ultra-high pressure sterilization.

[0027] (4) Degassing treatment: the orange juice primary product was discharged from the high-energy fluid mill through the built-in degassing device, and the CO2 was sent to the gas storage tank after recovery and purification, to obtain the degassed orange juice.

[0028] (5) UV synergistic sterilization: the degassed orange juice is pumped into the UV sterilization system through a peristaltic pump, and the flow rate is controlled at 120 mL / min; the Dean number De of the 8-shaped pipe of the UV sterilization system is 180, the pipe body is surrounded by two 120 W UV-C lamp tubes (wavelength 254 nm), the outside of the pipe is wrapped with a flexible and curlable reflector, and the UV irradiation dose is 30 J / mL; the orange juice is uniformly mixed by Dean flow in the pipe and fully receives UV irradiation, and the killing rate of residual Bacillus spores reaches 99.99%, obtaining the orange juice product, and the total number of microorganisms is 7 cfu / mL.

[0029] (6) Aseptic filling and normal temperature storage: the orange juice product is filled into a PET / aluminum foil / PE composite film packaging container in an aseptic filling room, the filling temperature is 25°C, and after sealing, it is stored in a 20°C normal temperature environment; after 12 months of detection, the total number of microorganisms is 9 cfu / mL, the retention rate of vitamin C is 85%, the orange juice is bright orange and yellow, the sweet and sour flavor is rich, there is no odor and stratification phenomenon, and the sensory quality is good.

[0030] Example 3 A method for preparing a fruit and vegetable juice (strawberry juice) that can be preserved at room temperature, specifically comprising the following steps: (1) Fruit and vegetable raw material pretreatment: fresh strawberries are selected, the fruit peduncle and rotten parts are removed, and the surface impurities are washed with clean water (strawberries do not need to be peeled and cored).

[0031] (2) Wet crushing and slurry preparation: the drained strawberries are sent to the wet crushing assembly, low-temperature water is added, and the mass ratio of strawberries to low-temperature water is controlled at 1:5; the wet crushing assembly is started, the first-stage grinding disc rotates at 2000 r / min, the second-stage grinding disc rotates at 2200 r / min, and the crushing time is 10 min, obtaining strawberry slurry with a particle size of ≤70 μm.

[0032] (3) High-energy fluid mill ultra-high pressure sterilization: S1. The strawberry slurry is pumped into the mixing tank through the gas-liquid booster pump, high-pressure CO2 gas is introduced, the pressure in the mixing tank is controlled at 12 MPa, the temperature is 35°C, the mixing roller is started (rotating at 350 r / min), and the strawberry slurry and supercritical CO2 are stirred, the mixing time is 15 min, and the strawberry mixture containing supercritical CO2 is formed and filtered through a 60 μm filter screen (the mixing roller drives the brush to clean the filter screen to avoid blockage); S2. The mixture is sent into the three-plunger reciprocating high-pressure pump through the ultra-high pressure stop valve and pressurized to 220 MPa; the pressurized mixture enters the high-energy fluid mill containing space, accelerates to 1000 m / s through the flow divider (the sum of the cross-sectional areas is 1 / 5 of the containing space), and collides with each other in the collision chamber. S3. Start the ultrasonic assembly, ultrasonic frequency 30 kHz, the ultrasonic transducer assembly transmits vibration to the collision chamber, strengthens the sterilization effect, and obtains strawberry juice primary product after ultrahigh pressure sterilization.

[0033] (4) Degassing treatment: the strawberry juice primary product is discharged through the high-energy fluid mill self-degassing device CO2, and the CO2 is sent to the gas storage tank after purification, and the degassed strawberry juice is obtained.

[0034] (5) Ultraviolet synergistic sterilization: the degassed strawberry juice is sent into the ultraviolet sterilization system through the peristaltic pump, the flow rate is controlled at 180 mL / min; the Dean number De of the 8-shaped tube is 200, the UV-C lamp tube irradiation dose is 30 J / mL, the external reflector enhances the ultraviolet energy utilization rate; the strawberry juice is fully mixed and uniformly irradiated in the tube, the spore killing rate of bacillus spores is 99.99%, the total microbial count of the strawberry juice is 6 cfu / mL.

[0035] (6) Aseptic filling and normal temperature storage: the strawberry juice product is filled into a PET / aluminum foil / PE composite film packaging container in an aseptic filling room, the filling temperature is 30°C, and after sealing, it is stored in a normal temperature environment at 30°C; after 8 months of detection, the total number of microorganisms is 9 cfu / mL, the retention rate of vitamin C is 86%, the strawberry juice has bright red color and bright color, has rich natural strawberry flavor, and has no oxidation and deterioration.

[0036] Comparative Example 1 A fruit and vegetable juice (apple juice) sterilization and preservation method, the specific process is similar to that of Example 1, except that step (5) ultraviolet sterilization is not performed, and the ultrahigh pressure sterilization process is pressurized to 280 MPa, and the rest of the process is the same, and apple juice is obtained.

[0037] Comparative Example 2 A fruit and vegetable juice (apple juice) sterilization and preservation method, the specific process is similar to that of Example 1, except that steps (3) and (4) high-energy fluid mill ultrahigh pressure sterilization are not performed, and the ultraviolet irradiation dose during ultraviolet sterilization is increased to 50 J / mL, and the rest of the process is the same, and apple juice is obtained.

[0038] Comparative Example 3 A fruit and vegetable juice (orange juice) sterilization and preservation method, the specific process is similar to that of Example 1, except that step (5) ultraviolet sterilization is not performed, and the ultrahigh pressure sterilization process is pressurized to 280 MPa, and the rest of the process is the same, and orange juice is obtained.

[0039] Comparative Example 4 A fruit and vegetable juice (orange juice) sterilization and preservation method, the specific process is similar to that of Example 1, except that steps (3) and (4) high-energy fluid mill ultra-high pressure sterilization are not performed, and the ultraviolet sterilization dose is increased to 50 J / mL during the ultraviolet sterilization process, and the rest of the process is the same, and orange juice is obtained.

[0040] Comparative Example 5 A fruit and vegetable juice (strawberry juice) sterilization and preservation method, the specific process is similar to that of Example 1, except that step (5) ultraviolet sterilization is not performed, and the pressure is increased to 280 MPa during the ultra-high pressure sterilization process, and the rest of the process is the same, and strawberry juice is obtained.

[0041] Comparative Example 6 A fruit and vegetable juice (strawberry juice) sterilization and preservation method, the specific process is similar to that of Example 1, except that steps (3) and (4) high-energy fluid mill ultra-high pressure sterilization are not performed, and the ultraviolet sterilization dose is increased to 50 J / mL during the ultraviolet sterilization process, and the rest of the process is the same, and strawberry juice is obtained.

[0042] Comparative Example 7 A fruit and vegetable juice (apple juice) sterilization and preservation method, the specific process is similar to that of Example 1, except that steps (3), (4) high-energy fluid mill ultra-high pressure sterilization and step (5) ultraviolet sterilization are not performed, and are replaced by pasteurization at 85°C for 15s, and the rest of the process is the same, and apple juice is obtained.

[0043] Comparative Example 8 A fruit and vegetable juice (apple juice) sterilization and preservation method, the specific process is similar to that of Example 1, except that steps (3), (4) high-energy fluid mill ultra-high pressure sterilization and step (5) ultraviolet sterilization are not performed, and are replaced by ultra-high temperature instantaneous sterilization (UHT) at 135°C for 5s, and the rest of the process is the same, and apple juice is obtained.

[0044] Comparative Example 9 A fruit and vegetable juice (orange juice) sterilization and preservation method, the specific process is similar to that of Example 2, except that steps (3), (4) high-energy fluid mill ultra-high pressure sterilization and step (5) ultraviolet sterilization are not performed, and are replaced by pasteurization at 85°C for 15s, and the rest of the process is the same, and orange juice is obtained.

[0045] Comparative Example 10 A fruit and vegetable juice (orange juice) sterilization and preservation method, the specific process is similar to that of Example 2, except that steps (3), (4) high-energy fluid mill ultra-high pressure sterilization and step (5) ultraviolet sterilization are not performed, and are replaced by ultra-high temperature instantaneous sterilization (UHT) at 135°C for 5s, and the rest of the process is the same, and orange juice is obtained.

[0046] Comparative Example 11 A fruit and vegetable juice (strawberry juice) sterilization and preservation method, the specific process is similar to that of Example 3, except that steps (3) and (4) high-energy fluid mill ultra-high pressure sterilization and step (5) ultraviolet sterilization are not performed, and pasteurization is used instead, at 85°C for 15s, and the rest of the process is the same, obtaining strawberry juice.

[0047] Comparative Example 12 A fruit and vegetable juice (strawberry juice) sterilization and preservation method, the specific process is similar to that of Example 3, except that steps (3) and (4) high-energy fluid mill ultra-high pressure sterilization and step (5) ultraviolet sterilization are not performed, and ultra-high temperature instantaneous sterilization (UHT) is used instead, at 135°C for 5s, and the rest of the process is the same, obtaining strawberry juice.

[0048] Example 4 The fruit and vegetable juices prepared in Examples 1-3 and Comparative Examples 1-6 were subjected to microbial residue determination, and the specific process was as follows: 1. Sample pretreatment The strawberry juice sample was thoroughly shaken in a sterile operation table, 25mL of the sample was taken with a sterile pipette and injected into a triangular flask containing 225mL of sterile physiological saline, shaken and mixed for 10min to prepare a 1:10 sample homogenate; according to the detection requirements, further gradient dilution (such as 1:100, 1:1000) was performed for standby.

[0049] 2. Total bacterial count determination (refer to GB 4789.2-2016) 1mL of sample homogenate at 1:10, 1:100 and 1:1000 dilution was taken and injected into sterile petri dishes, 3 parallel samples were prepared for each dilution; About 15mL of nutrient agar medium was quickly poured into the melted and cooled to 46°C, the petri dishes were gently rotated to mix the homogenate and the medium thoroughly, and after the agar solidified, it was placed in a 36°C constant temperature incubator upside down for 48h; After the incubation was completed, the number of colonies on each petri dish was counted, and the petri dishes with colony counts between 30 and 300 were selected for statistics, and the average value was calculated, and the result was expressed as CFU / mL.

[0050] 3. Mold and yeast determination (refer to GB 4789.15-2016) 1mL of sample homogenate at 1:10 and 1:100 dilution was taken and injected into sterile petri dishes, 3 parallel samples were prepared for each dilution; About 15mL of melted and cooled to 46°C Bengal red medium was poured, shaken and solidified, and then placed in a 28°C constant temperature incubator upside down for 5d; During the culture period, daily observation was performed, and mold colonies (filamentous, woolly) and yeast colonies (circular, smooth) on the culture dishes were counted. The culture dishes with 10-150 colonies were selected for statistics, and the average value was calculated, with the result expressed as CFU / mL. If the number of colonies was <1, it was recorded as not detected.

[0051] 4. Coliform group determination (refer to GB 4789.3-2016 plate count method) 1 mL of sample homogenate at 1:10, 1:100, and 1:1000 dilutions was taken and injected into sterile culture dishes, respectively, with 3 parallel samples for each dilution; About 15 mL of lauryl sulfate trypsin (LST) agar medium was poured after melting and cooling to 46℃, and after shaking to solidify, it was placed in a 36℃ constant temperature incubator upside down and cultured for 24 h; Suspected coliform group colonies (red, shiny, with a precipitate ring around) were picked and inoculated into brilliant green lactose bile salt (BGLB) broth tubes, which were cultured at 36℃ for 24 h, and whether gas was produced was observed; The number of colonies corresponding to the gas-producing positive tubes was counted, and the average value was calculated, with the result expressed as CFU / mL.

[0052] 5. Salmonella determination (refer to GB 4789.4-2016) 25 mL of strawberry juice sample was taken and injected into a flask containing 225 mL of buffered peptone water (BPW), which was cultured at 36℃ for 18 h for pre-enrichment; 1 mL of pre-enrichment liquid was taken and inoculated into 10 mL of brilliant green sodium tetrathionate (TTB) broth, which was cultured at 42℃ for 24 h for selective enrichment; at the same time, 1 mL of pre-enrichment liquid was inoculated into 10 mL of selenite cysteine (SC) broth, which was cultured at 36℃ for 24 h for parallel enrichment; The above two kinds of enrichment liquid were taken respectively and streaked onto salmonella chromogenic medium and SS agar medium, which were cultured at 36℃ for 24 h, and suspected colonies (colorless transparent, central black or characteristic colonies on the chromogenic medium) were observed; Suspected colonies were picked for biochemical identification (such as ferric triose, lysine decarboxylase test) and serological identification to confirm whether they were salmonella; if salmonella was not detected, it was recorded as "not detected (25 mL)".

[0053] 6. Staphylococcus aureus determination (refer to GB 4789.10-2016 plate count method) 1 mL of sample homogenate at 1:10, 1:100, and 1:1000 dilutions was taken and injected into sterile culture dishes, respectively, with 3 parallel samples for each dilution; Pour about 15 mL into Baird-Parker agar medium melted and cooled to 46℃, shake to solidify, and then place in a 36℃ constant temperature incubator for 48h after inversion; Pick suspected Staphylococcus aureus colonies (black, shiny, surrounded by a transparent circle), perform Gram staining and plasma coagulase test for confirmation; Count the number of positive colonies confirmed, calculate the average value, and the result is expressed in CFU / mL.

[0054] Table 1 Microbial residue table of apple juice As can be seen from the data in Table 1, the sterilization effect and room temperature storage stability of the ultrahigh pressure and ultraviolet synergistic sterilization (Example 1) on apple juice are optimal, meeting the requirements of room temperature preservation, and the shelf life at room temperature can reach 12 months. The sterilization effect of ultrahigh pressure sterilization alone (Comparative Example 1) and ultraviolet sterilization alone (Comparative Example 2) is limited, and after 6 months of storage, it is not suitable for consumption, and after 12 months, mold and yeast, coliform bacteria, and Staphylococcus aureus content are close to higher, which cannot achieve long-term room temperature storage, fully embodying the synergistic effect of synergistic sterilization.

[0055] Table 2 Microbial residue table of orange juice As can be seen from the data in Table 2, the sterilization effect and room temperature storage stability of the ultrahigh pressure and ultraviolet synergistic sterilization (Example 2) on orange juice are optimal, meeting the requirements of room temperature preservation, and the shelf life at room temperature can reach 12 months. The sterilization effect of ultrahigh pressure sterilization alone (Comparative Example 3) and ultraviolet sterilization alone (Comparative Example 4) is limited, and after 6 months of storage, it is not suitable for consumption, and after 12 months, mold and yeast, coliform bacteria, and Staphylococcus aureus content are close to higher, which cannot achieve long-term room temperature storage, fully embodying the synergistic effect of synergistic sterilization.

[0056] Table 3 Microbial residue table of strawberry juice As can be seen from the data in Table 3, the sterilization effect and room temperature storage stability of the ultrahigh pressure and ultraviolet synergistic sterilization (Example 3) on strawberry juice are optimal, meeting the requirements of room temperature preservation, and the shelf life at room temperature can reach 12 months. The sterilization effect of ultrahigh pressure sterilization alone (Comparative Example 5) and ultraviolet sterilization alone (Comparative Example 6) is limited, and after 6 months of storage, it is not suitable for consumption, and after 12 months, mold and yeast, coliform bacteria, and Staphylococcus aureus content are close to higher, which cannot achieve long-term room temperature storage, fully embodying the synergistic effect of synergistic sterilization.

[0057] Table 4 Comparison table of nutrient retention rate of fruit and vegetable juice under different sterilization methods From the data in Table 4, it can be seen that the synergistic sterilization of ultra-high pressure and ultraviolet has the best effect on the retention of heat-sensitive nutritional components in the three fruit and vegetable juices: the retention rate of vitamin C in apple juice is 88%, the total flavonoid is 94%, the retention rate of vitamin C in orange juice is 85%, the total flavonoid is 90%, the retention rate of vitamin C in strawberry juice is 86%, and the anthocyanin is 95%, which are significantly higher than those of the single sterilization group, and meet the technical indicators of "the retention rate of vitamin C ≥ 85%, the retention rate of total flavonoid ≥ 90%, and the retention rate of anthocyanin ≥ 88%" in the claims of the application. The retention rate of nutrients in the single ultra-high pressure sterilization and single ultraviolet sterilization groups is lower than that in the synergistic group, while the destruction of nutritional components by pasteurization and UHT heat sterilization is significant, among which the retention rate of vitamin C in strawberry juice after UHT treatment is only 48%, the total flavonoid is 56%, and the total flavonoid in apple juice is 60%, which is much lower than that in the non-heat sterilization group, verifying the balanced advantage of synergistic sterilization between "deep sterilization" and "nutrient retention".

[0058] The embodiments of the application are described above in conjunction with the accompanying drawings, and the principles and implementation modes of the application are described herein. The above description of the embodiments is only used to help understand the core idea of the application, but the application is not limited to the above specific implementation modes. The above specific implementation modes are only illustrative and not restrictive, and those skilled in the art can make many forms under the inspiration of the application without departing from the scope of the application and the protection scope of the claims.

Claims

1. A method for preparing fruit and vegetable juice that can be preserved at room temperature, characterized in that, Includes the following steps: S1: Mix the pretreated fruits and vegetables with water, and then perform wet pulverization to obtain a fruit and vegetable slurry with a particle size ≤100 μm; S2: The fruit and vegetable pulp is placed in a high-energy fluid mill and mixed with supercritical CO2. Then it is subjected to ultra-high pressure sterilization at a pressure of 200 MPa-280 MPa, while ultrasonic vibration is performed. After sterilization, the residual CO2 is degassed to obtain the initial product of fruit and vegetable juice. S3: Place the initial fruit and vegetable juice sample under ultraviolet light for ultraviolet sterilization treatment to obtain fruit and vegetable juice.

2. The preparation method according to claim 1, characterized in that, The water temperature described in S1 is 0℃-4℃; the mass ratio of fruits and vegetables to water is 1:3-1:

5.

3. The preparation method according to claim 2, characterized in that, The rotation speed during wet pulverization is 1500 r / min-2000 r / min, and the pulverization time is 5-10 min.

4. The preparation method according to claim 1, characterized in that, The frequency of ultrasonic vibration in S2 is 20 kHz-30 kHz.

5. The preparation method according to claim 1, characterized in that, The temperature for mixing S2 with supercritical CO2 is 31-35℃, and the mixing time is 10-15 min.

6. The preparation method according to claim 1, characterized in that, The UV irradiation dose during the UV sterilization treatment described in S3 is 30 J / mL-50 J / mL.

7. The preparation method according to claim 6, characterized in that, The specific process of placing the initial fruit and vegetable juice sample under ultraviolet light for ultraviolet sterilization is as follows: The initial fruit and vegetable juice is transported to an 8-shaped tube-type ultraviolet sterilization device for ultraviolet sterilization treatment at a flow rate of 120 mL / min-180 mL / min. The figure-eight tube has an inner diameter of 2.5 mm and a length of 7 m. It surrounds two 120 W UV-C lamp tubes and has a Dean number of De = 180-200.

8. A fruit and vegetable juice that can be preserved at room temperature, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The fruit and vegetable juice according to claim 8, characterized in that, The fruit and vegetable juices retain ≥85% of vitamin C, ≥90% of total flavonoids, and ≥88% of anthocyanins.

10. The fruit and vegetable juice according to claim 7, characterized in that, The fruit and vegetable juices mentioned include apple juice, orange juice, strawberry juice, or blueberry juice.

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