A sterilization process for fruit juice production

Abstract

This invention relates to the field of fruit juice processing technology, particularly a sterilization process for fruit juice production, comprising the following steps: selecting fruit and subjecting it to crushing and pressing; placing the initial fruit juice into a homogenizing device for homogenization; placing the homogenized fruit juice into an ultrasonic treatment device to further release intracellular active substances and initially reduce biological and enzyme activity; and pumping the ultrasonically pretreated fruit juice into a continuous PEF treatment chamber to disrupt microbial cell membranes through electroporation. This invention employs a combined ultrasonic + PEF non-thermal sterilization process, synergistically enhancing the sterilization effect: ultrasonic pretreatment increases cell membrane permeability, making subsequent PEF electroporation more efficient; experiments show that this combined process achieves a kill rate of 5-7 log for Escherichia coli, Staphylococcus aureus, and yeast, reducing POD and PPO enzyme activity by more than 80%, meeting commercial sterility requirements; ultrasonic pretreatment can increase juice yield by 5-15%; and PEF further improves juice clarity and stability, reducing sedimentation.

Description

Technical Field

[0001] This invention relates to the field of fruit juice processing technology, specifically a sterilization process for fruit juice production. Background Technology

[0002] Fruit juice is a beverage made from the juice obtained from fruits through physical methods such as pressing, centrifugation, and extraction.

[0003] The existing technology has the following defects or problems: Traditional fruit juice sterilization mainly uses heat treatment methods, such as pasteurization (60-85℃, a few seconds to tens of minutes) or ultra-high temperature instantaneous sterilization (UHT, 135-150℃, 3-5 seconds). Although these methods can effectively kill microorganisms and inactivate enzymes, heat treatment will cause a large loss of heat-sensitive nutrients in the fruit juice (such as vitamin C, antioxidant polyphenols, and flavonoids), resulting in a "cooked taste," browning color, and loss of volatile aroma components, which seriously affects the sensory quality and nutritional value of the product. With the increasing demand from consumers for "fresh", "zero additives" and "high nutrition" juices, non-thermal sterilization technology has become a research hotspot. Existing non-thermal technologies include high pressure treatment (HPP), pulsed electric field (PEF), ultrasound, pulsed light, and ultraviolet light. However, single technologies often have problems such as insufficient sterilization intensity, limited enzyme inactivation effect, or high equipment cost. Although HPP sterilizes thoroughly, it can easily cause packaging deformation for large-particle suspended fruit juices. PEF has high requirements for liquid light transmittance and its effect is reduced for turbid fruit juices. Ultrasound alone is difficult to achieve commercial sterility requirements.

[0004] It should be noted that the above content falls within the inventor's technical knowledge and does not necessarily constitute prior art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a sterilization process for fruit juice production, solving the current problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a sterilization process for fruit juice production, comprising the following steps: Step 1: Select fresh, ripe fruit, pre-process it, then crush and press it to obtain the initial fresh juice. Step 2: Place the initial juice sample into a homogenizer for homogenization to ensure that the pulp particles are evenly dispersed and to prevent separation during subsequent processing. Step 3: Place the homogenized juice in an ultrasonic treatment device and use intermittent ultrasonic mode to break down the cell walls of the juice through cavitation effect, further releasing intracellular active substances and initially reducing biological and enzyme activity. Step 4: Pump the ultrasonically pretreated juice into a continuous PEF processing chamber, where the microbial cell membrane is destroyed through the electroporation effect, achieving efficient non-thermal sterilization and further inactivating polyphenol oxidase and peroxidase. Step 5: Conduct systematic testing on the treated juice, including microbial indicators, enzyme activity residues, physicochemical indicators, sensory evaluation, and accelerated storage stability test. Step Six: The qualified juice is quickly filled under aseptic conditions, and samples are taken regularly for shelf-life monitoring.

[0007] In some embodiments, the pretreatment includes washing, peeling, and cutting, and the crushing and pressing temperature needs to be controlled between 5 and 10 degrees Celsius.

[0008] In some embodiments, the homogenization process is carried out under a pressure of 15-25 MPa.

[0009] In some embodiments, the ultrasonic frequency of the ultrasonic processing device is controlled between 20-40 kHz, its power density is 150-300 W / cm², its temperature is below 30 degrees Celsius, the ultrasonic operation in the intermittent ultrasonic mode is 2-4 seconds, the interval time is controlled between 3-6 seconds, and the cumulative effective ultrasonic time is maintained between 4-6 minutes.

[0010] In some embodiments, the PEF processing chamber is configured with coaxial cylindrical electrodes made of food-grade stainless steel. The interior of the PEF processing chamber is required to have flow channels to ensure that the juice is uniformly treated.

[0011] In some embodiments, the internal electric field strength of the PEF treatment chamber is controlled between 2.5-4.0 kV / cm, the pulse width is 2-10 μs, the pulse frequency is 200-800 Hz, the total energy input for processing is 80-150 kJ / L, and the temperature during the processing needs to be below 40 degrees Celsius.

[0012] In some embodiments, the microbial index detection is specifically performed by plate counting to detect various data within the finished fruit juice, including total colony count, coliform bacteria, molds and yeasts, and pathogenic bacteria; The enzyme activity residue detection specifically measures the residual activity of polyphenol oxidase, peroxidase, and pectin methyl esterase inside the finished fruit juice to ensure that there is no obvious browning or stratification during its storage period. The physicochemical indicators tested include the pH value, soluble solids, titratable acidity, turbidity, color difference, vitamin C content, total phenol content, and antioxidant capacity of the finished fruit juice. The sensory evaluation is conducted by staff on four dimensions: flavor, color, taste, and aroma, to evaluate the finished fruit juice product. The specific steps of the accelerated storage stability test are as follows: The finished fruit juice was stored at 4 and 10 degrees Celsius. Samples were taken at 0, 7, 14, 30, and 45 days to repeat the enzyme activity residue test, physicochemical index test, and sensory evaluation. If any key indicator showed a problem, the relevant technical parameters of ultrasonic treatment and PET treatment were adjusted accordingly. In some embodiments, rapid filling is carried out using high-barrier packaging containers, specifically PET bottles and composite flexible packaging. After filling, the packaging must be cooled to 0-4 degrees Celsius immediately, and the airtightness of the packaging must be tested.

[0013] Compared with the prior art, the present invention provides a sterilization process for fruit juice production, which has the following beneficial effects: This invention relates to a sterilization process for fruit juice production. The process employs a combined ultrasonic and PEF (polyelectrofiltration) non-thermal sterilization method, synergistically enhancing the sterilization effect. Ultrasonic pretreatment increases cell membrane permeability, making subsequent PEF electroporation more efficient. Experiments show that this combined process achieves a 5-7 log kill rate against Escherichia coli, Staphylococcus aureus, and yeast, reducing POD and PPO enzyme activities by over 80%, meeting commercial sterility requirements. Ultrasonic pretreatment can increase juice yield by 5-15%, while PEF further improves juice clarity and stability, reducing sedimentation. Meanwhile, the temperature is controlled below 40 degrees Celsius throughout the process to avoid heat-sensitive nutrient loss. Compared with traditional pasteurization, the vitamin C retention rate is increased by 25-40%, the total phenols and flavonoids retention rate is increased by more than 30%, the color difference value is significantly reduced, and the flavor is closer to freshly squeezed juice. At the same time, the process has low energy consumption, no chemical additives, meets the requirements of clean labeling, and is suitable for high-end freshly squeezed refrigerated juice production lines. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the sterilization process for fruit juice production according to the present invention. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0016] It should be understood that the step numbers used in the text are for ease of description only and are not intended to limit the order in which the steps are performed.

[0017] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0018] The terms “comprising” and “including” indicate the presence of the described feature, whole, step, operation, element and / or component, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0019] The term “and / or” refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes these combinations.

[0020] Example 1: Navel oranges were selected as the raw material for the juice. A sterilization process for fruit juice production includes the following steps: Step 1: Select fresh, ripe navel oranges, wash, peel, and segment them, then crush and press them under low-temperature conditions, with the temperature controlled between 5-10 degrees Celsius, to obtain the initial fresh juice. Step 2: Place the initial juice sample into a homogenizer and homogenize it under a pressure of 20MPa to ensure that the pulp particles are evenly dispersed and to prevent separation during subsequent processing. Step 3: Place the homogenized juice in an ultrasonic treatment device and use intermittent ultrasonic mode to break down the cell walls of the juice through cavitation effect, further releasing intracellular active substances and initially reducing biological and enzyme activity. The ultrasonic frequency of the ultrasonic processing equipment is controlled at 28 kHz, its power density is 200 W / cm², its processing temperature is 28 degrees Celsius, and it operates in intermittent ultrasonic mode for 3 seconds with an interval time of 4 seconds. The total effective ultrasonic time is 6 minutes. Step 4: Pump the ultrasonically pretreated juice into a continuous PEF processing chamber, where the microbial cell membrane is destroyed through the electroporation effect, achieving efficient non-thermal sterilization and further inactivating polyphenol oxidase and peroxidase. The PEF processing chamber uses coaxial cylindrical electrodes made of food-grade stainless steel. Flow channels must be reserved inside the PEF processing chamber to ensure that the juice is evenly distributed. The PEF treatment chamber's internal electric field strength was controlled at 3.0 kV / cm, the pulse width was 4 μs, the pulse frequency was 500 Hz, the total energy input for treatment was 120 kJ / L, and the temperature during treatment was 38 degrees Celsius. Step 5: The qualified juice is quickly filled under aseptic conditions, and samples are taken regularly for shelf-life monitoring; High-barrier packaging containers, specifically PET bottles, are used for rapid filling. After filling, the bottles must be cooled to 4 degrees Celsius immediately, and the airtightness of the packaging must be tested.

[0021] Example 2: Peaches were selected as the raw material for the juice. A sterilization process for fruit juice production includes the following steps: Step 1: Select fresh, ripe peaches, wash, peel, and remove the pits, then crush and press them under low-temperature conditions, with the temperature controlled between 5-10 degrees Celsius, to obtain the initial fresh juice. Step 2: Place the initial juice sample into a homogenizer and homogenize it under a pressure of 25 MPa to ensure that the pulp particles are evenly dispersed and to prevent stratification during subsequent processing. Step 3: Place the homogenized juice in an ultrasonic treatment device and use intermittent ultrasonic mode to break down the cell walls of the juice through cavitation effect, further releasing intracellular active substances and initially reducing biological and enzyme activity. The ultrasonic frequency of the ultrasonic processing equipment is controlled at 28 kHz, its power density is 200 W / cm², its processing temperature is 28 degrees Celsius, and it operates in intermittent ultrasonic mode for 3 seconds with an interval time of 4 seconds. The total effective ultrasonic time is 6 minutes. Step 4: Pump the ultrasonically pretreated juice into a continuous PEF processing chamber, where the microbial cell membrane is destroyed through the electroporation effect, achieving efficient non-thermal sterilization and further inactivating polyphenol oxidase and peroxidase. The PEF processing chamber uses coaxial cylindrical electrodes made of food-grade stainless steel. Flow channels must be reserved inside the PEF processing chamber to ensure that the juice is evenly distributed. The PEF treatment chamber's internal electric field strength was controlled at 3.5 kV / cm, the pulse width was 4 μs, the pulse frequency was 500 Hz, the total energy input for treatment was 140 kJ / L, and the temperature during treatment was 38 degrees Celsius. Step 5: The qualified juice is quickly filled under aseptic conditions, and samples are taken regularly for shelf-life monitoring; High-barrier packaging containers, specifically PET bottles, are used for rapid filling. After filling, the bottles must be cooled to 4 degrees Celsius immediately, and the airtightness of the packaging must be tested.

[0022] The finished orange and peach juice products from Examples 1 and 2 were subjected to systematic testing, including microbial indicators, enzyme activity residues, physicochemical indicators, sensory evaluation, and accelerated storage stability tests. The microbial index detection is specifically performed by plate counting to detect various data within the finished fruit juice, including total colony count, coliform bacteria, molds and yeasts, and pathogenic bacteria. The enzyme activity residue detection specifically measures the residual activity of polyphenol oxidase, peroxidase, and pectin methyl esterase inside the finished fruit juice to ensure that there is no obvious browning or stratification during its storage period. The physicochemical indicators tested include the pH value, soluble solids, titratable acidity, turbidity, color difference, vitamin C content, total phenol content, and antioxidant capacity of the finished fruit juice. The sensory evaluation is conducted by staff on four dimensions: flavor, color, taste, and aroma, to evaluate the finished fruit juice product. The specific steps of the accelerated storage stability test are as follows: The finished fruit juice was stored at 4 and 10 degrees Celsius. Samples were taken at 0, 7, 14, 30 and 45 days to repeat the enzyme activity residue test, physicochemical index test and sensory evaluation. If any key index had a problem, the relevant technical parameters of ultrasonic treatment and PET treatment were adjusted accordingly.

[0023] The test report for Example 1 is shown in the table below: Table 1

[0024] After ultrasonic + PEF composite treatment, the orange juice achieves >5 log microbial killing, effective inactivation of key enzymes, high retention of nutrients (vitamin C, total phenols), and color and flavor close to freshly squeezed juice. The quality remains stable after 45 days of refrigeration at 4℃, making it suitable for the production of high-end refrigerated freshly squeezed orange juice.

[0025] The test report for Example 1 is shown in the table below: Table 2

[0026] After being treated with high-intensity PEF, peach juice undergoes more thorough enzyme inactivation and retains aroma compounds well (as commonly seen in literature, peach juice has minimal loss of volatile esters). It remains of excellent quality even after 50 days of refrigeration, and its shelf life is predicted to reach 50-60 days.

[0027] For Example 1, using traditional pasteurization (85 degrees Celsius, 30 seconds), the test report for the same batch of freshly squeezed orange juice is shown in the table below: Table 3

[0028] While traditional pasteurization ensures microbial safety and thorough enzyme inactivation, it results in significant loss of heat-sensitive nutrients (such as vitamin C) (retention rate is only 65%), produces a cooked taste, and causes significant color changes (ΔE>5), making its sensory quality noticeably inferior to freshly squeezed juice and the non-thermal process of this invention.

[0029] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0030] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A sterilization process for fruit juice production, characterized in that, The steps include the following: Step 1: Select fresh, ripe fruit, pre-process it, then crush and press it to obtain the initial fresh juice. Step 2: Place the initial juice sample into a homogenizer for homogenization to ensure that the pulp particles are evenly dispersed and to prevent separation during subsequent processing. Step 3: Place the homogenized juice in an ultrasonic treatment device and use intermittent ultrasonic mode to break down the cell walls of the juice through cavitation effect, further releasing intracellular active substances and initially reducing biological and enzyme activity. Step 4: Pump the ultrasonically pretreated juice into a continuous PEF processing chamber, where the microbial cell membrane is destroyed through the electroporation effect, achieving efficient non-thermal sterilization and further inactivating polyphenol oxidase and peroxidase. Step 5: Conduct systematic testing on the treated juice, including microbial indicators, enzyme activity residues, physicochemical indicators, sensory evaluation, and accelerated storage stability test. Step Six: The qualified juice is quickly filled under aseptic conditions, and samples are taken regularly for shelf-life monitoring.

2. The sterilization process for fruit juice production according to claim 1, characterized in that: The pretreatment in step one includes washing, peeling and cutting. The crushing and pressing temperature needs to be controlled between 5 and 10 degrees Celsius.

3. The sterilization process for fruit juice production according to claim 1, characterized in that: The homogenization process described in step two is carried out under a pressure environment of 15-25 MPa.

4. The sterilization process for fruit juice production according to claim 1, characterized in that: In step three, the ultrasonic frequency of the ultrasonic processing equipment is controlled between 20-40 kHz, its power density is 150-300 W / cm², and its temperature must be below 30 degrees Celsius. In the intermittent ultrasonic mode, the ultrasonic operation lasts for 2-4 seconds, and the interval time is controlled between 3-6 seconds. At the same time, the cumulative effective ultrasonic time must be maintained between 4-6 minutes.

5. The sterilization process for fruit juice production according to claim 1, characterized in that: The PEF processing chamber described in step four uses a coaxial cylindrical electrode configuration, and the electrode material is food-grade stainless steel. The interior of the PEF processing chamber needs to have a flow channel to ensure that the juice is evenly distributed.

6. The sterilization process for fruit juice production according to claim 1, characterized in that: In step four, the electric field strength inside the PEF treatment chamber is controlled between 2.5-4.0 kV / cm, the pulse width is 2-10 μs, the pulse frequency is 200-800 Hz, the total energy input for treatment is 80-150 kJ / L, and the temperature during the treatment process must be below 40 degrees Celsius.

7. The sterilization process for fruit juice production according to claim 1, characterized in that: The microbial index detection mentioned in step five is specifically performed by plate counting to detect various data within the finished fruit juice product. The data includes total colony count, coliform bacteria, molds and yeasts, and pathogenic bacteria. The enzyme activity residue detection specifically measures the residual activity of polyphenol oxidase, peroxidase, and pectin methyl esterase inside the finished fruit juice to ensure that there is no obvious browning or stratification during its storage period. The physicochemical indicators tested include the pH value, soluble solids, titratable acidity, turbidity, color difference, vitamin C content, total phenol content, and antioxidant capacity of the finished fruit juice. The sensory evaluation is conducted by staff on four dimensions: flavor, color, taste, and aroma, to evaluate the finished fruit juice product. The specific steps of the accelerated storage stability test are as follows: The finished fruit juice was stored at 4 and 10 degrees Celsius. Samples were taken at 0, 7, 14, 30 and 45 days to repeat the enzyme activity residue test, physicochemical index test and sensory evaluation. If any key index had a problem, the relevant technical parameters of ultrasonic treatment and PET treatment were adjusted accordingly.

8. The sterilization process for fruit juice production according to claim 1, characterized in that: The rapid filling described in step eight uses high-barrier packaging containers, specifically PET bottles and composite flexible packaging. After filling, the container must be cooled to 0-4 degrees Celsius immediately, and the airtightness of the packaging must be tested.

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