Method for improving active ingredient retention and comprehensive quality stability of loquat juice

Abstract

The invention discloses a method for improving active ingredient retention and comprehensive quality stability of loquat juice, and the method comprises the following steps: S1, obtaining fresh loquat fruits, carrying out color protection liquid pretreatment on the fresh loquat fruits, and then cleaning and draining; s2, carrying out high-voltage pulse electric field pretreatment on the loquat fruits pretreated by the color protection liquid; s3, pedicel removal and kernel and inner membrane removal treatment are performed on the loquat fruits pretreated by the high-voltage pulsed electric field, and loquat pulp is obtained; s4, performing low-temperature juicing treatment on the loquat pulp, and performing graded membrane filtration treatment and purification to obtain loquat juice; and S5, carrying out ultrahigh pressure treatment on the loquat juice, and then carrying out low-temperature storage. According to the method disclosed by the invention, full-chain synergy of color protection and brown prevention, configuration sensitization, targeted inactivation and low-temperature stable control can be realized, so that microbial control, multi-active component retention and multi-dimensional optimization of clarity and color stability are realized.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and in particular to a method for improving the retention of active ingredients and overall quality stability of loquat juice. Background Technology

[0002] Loquat juice is rich in polyphenols, flavonoids, ascorbic acid, amygdalin, and triterpenoids such as ursolic acid and corosolic acid. It has physiological functions such as moisturizing the lungs and relieving cough, anti-oxidation, and metabolic regulation. The market demand has been growing at an average annual rate of over 7%. However, loquat juice has a complex composition. The pulp contains high levels of polyphenol oxidase and pectinase, and most of the active ingredients are heat-sensitive. Traditional processing methods have significant technical bottlenecks: although traditional pasteurization can achieve commercial sterility, it leads to a loss of more than 30% of ascorbic acid and a total flavonoid retention rate of less than 70%. It also causes degradation of active ingredients such as ursolic acid and corosolic acid, resulting in pectin degradation and browning. After 30 days of storage at 4°C, the browning degree exceeds 1.2, and the light transmittance decreases by more than 30%, resulting in severe deterioration of sensory and functional quality. Traditional fresh-pressing processes lack effective sterilization and enzyme inhibition methods. After 7 days of storage at 4°C, the total bacterial count exceeds the standard, resulting in an extremely short shelf life that cannot meet the needs of commercial distribution.

[0003] To address the aforementioned problems, existing technologies mostly employ single non-thermal processing or simple combinations of processes, but these have limitations that are difficult to overcome: (1) Single ultra-high pressure treatment: Relying on 450-600MPa static pressure to destroy the microbial cell structure, although it can inhibit the proliferation of microorganisms to a certain extent, the inactivation rate of polyphenol oxidase and pectinase is less than 60%. During storage, enzymatic browning and pectin degradation are still likely to occur. Moreover, the pressure treatment alone requires extending the holding time to 15-20min, and the energy consumption is as high as 90-110 kWh / t, which significantly increases the processing cost. At the same time, the adiabatic heating caused by high pressure can easily lead to the oxidation of heat-sensitive components of loquat juice. The total flavonoid retention rate is only 75%-80%, and components such as ursolic acid and ascorbic acid are also lost to varying degrees. It is impossible to achieve both sterilization and retention of multiple active ingredients.

[0004] (2) Single pulse electric field treatment: The cell membrane is electroporated by an electric field strength of 5-10kV / cm, which has a certain inactivation effect on microorganisms. However, the uniformity of treatment of loquat juice with low conductivity is poor, and it cannot effectively kill pressure-resistant spores and yeast / mold. Moreover, when used alone, it has a weak inhibitory effect on enzyme activity. After 20 days of storage at 4℃, the browning degree exceeds 0.9, and the quality stability is insufficient. At the same time, the single pulse electric field has no obvious advantage in the retention of triterpenic acids and organic acids, and the loss rate of active ingredients is still high after long-term storage.

[0005] (3) Traditional combined treatment: Existing technologies mostly use a simple superposition of "pulsed electric field + ultra-high voltage" without constructing a synergistic mechanism, and lack targeted color protection and enzyme inhibition methods, and have not formed a deep coupling with low temperature storage. For example, if only the two physical fields are combined in sequence without optimizing the pretreatment and posttreatment processes, it is difficult to balance the microbial inactivation rate, the retention rate of multiple active ingredients and the clarity. After 60 days of storage at 4℃, the total flavonoid retention rate is less than 80%, the ursolic acid retention rate is less than 85%, the total bacterial count is prone to rebound, and the juice clarity is poor, and it is easy to form layers after standing.

[0006] In summary, existing technologies either focus only on single non-thermal sterilization or rely on traditional combined processes, failing to achieve full-chain synergy of "color-protecting liquid pretreatment - pulsed electric field configuration sensitization - ultra-high pressure targeted inactivation - low temperature stabilization". In particular, they lack a synchronous protection mechanism for multiple active ingredients such as flavonoids, triterpenic acids, and organic acids, making it difficult to simultaneously improve the sterilization efficiency, retention of multiple active ingredients, and storage stability of loquat juice. Summary of the Invention

[0007] To address the aforementioned issues, this invention aims to provide a method for improving the retention of active ingredients and overall quality stability of loquat juice. It innovatively constructs a multi-step synergistic system, using color-protecting solution pretreatment to assist in preventing browning, and combining pulsed electric field-ultra-high voltage timing adaptation with deep coupling of low-temperature storage. This fills the gap in existing technologies regarding "whole-chain quality control, non-thermal synergistic enhancement, retention of multiple active ingredients, and long-term storage stability," providing key technical support for high-quality loquat juice processing.

[0008] The technical solution of the present invention is as follows: A method for improving the retention of active ingredients and overall quality stability of loquat juice includes the following steps: S1: Obtain fresh loquat fruit, pre-treat the fresh loquat fruit with color-protecting liquid, and then wash and drain it; S2: High-voltage pulsed electric field pretreatment is performed on loquat fruit after color protection liquid pretreatment; S3: After pretreatment with a high-voltage pulsed electric field, the loquat fruit is processed by removing the fruit stem, pit and inner membrane to obtain loquat pulp; S4: The loquat pulp is subjected to low-temperature juicing and purified by graded membrane filtration to obtain loquat juice; S5: The loquat juice is subjected to ultra-high pressure treatment and then stored at low temperature.

[0009] Preferably, in step S1, the fresh loquat fruit is a fresh loquat fruit with a maturity of 85%-90%, uniform color, and no mechanical damage or pests.

[0010] Preferably, in step S1, when performing the color-protecting solution pretreatment, the fresh loquat fruit is soaked in the color-protecting solution for 8-12 minutes; the color-protecting solution includes phytic acid at a mass-volume ratio of 0.15-0.25% and ascorbic acid at a mass-volume ratio of 0.08-0.12%, and the pH of the color-protecting solution is adjusted to 3.5-4.5 using citric acid.

[0011] Preferably, in step S1, sterile water is used for rapid rinsing during cleaning, and the rinsing time is less than or equal to 30 seconds.

[0012] Preferably, in step S2, when performing high-voltage pulse electric field pretreatment, the electric field strength is 5-10 kV / cm, the pulse frequency is 5-10 kHz, the pulse width is 25-35 ms, and the processing time is 5-15 min.

[0013] Preferably, in step S4, the juicing temperature is 4-8℃ when performing low-temperature juicing.

[0014] Preferably, in step S4, during the graded membrane filtration, a filter screen is used first, followed by ultrafiltration.

[0015] Preferably, the mesh size of the filter is 80-120 mesh.

[0016] Preferably, in step S5, when performing ultra-high pressure treatment, the pressure is 450-600MPa, the holding time is 5-10min, and the treatment temperature is 10-20℃.

[0017] Preferably, in step S5, when storing at low temperature, the loquat juice after ultra-high pressure treatment is cooled to 2-6℃ and stored in a constant temperature cold storage environment of 2-6℃. During the storage process, the temperature fluctuation of the storage environment is controlled to not exceed ±1℃, and the relative humidity of the storage environment is controlled to be 60-70%.

[0018] The beneficial effects of this invention are: This invention addresses the problems of loquat juice's high heat sensitivity, easy loss of active ingredients (flavonoids, triterpenic acids, organic acids, etc.), and difficulty in coordinating the control of microbial and enzymatic deterioration. It constructs a full-chain synergistic technology system of "color-protecting liquid pretreatment - high-voltage pulsed electric field pretreatment - ultra-high pressure targeted sterilization - low temperature stabilization", which simultaneously improves the sterilization efficiency, retention rate of multiple active ingredients, and storage stability of loquat juice. It is suitable for the industrial preparation of high-quality loquat juice and related fruit and vegetable juice products. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a photograph of the loquat juice from Example 1. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0022] like Figure 1 As shown, the present invention provides a method for improving the retention of active ingredients and overall quality stability of loquat juice, comprising the following steps: S1: Obtain fresh loquat fruit, pre-treat the fresh loquat fruit with color-protecting solution, and then wash and drain it.

[0023] In one specific embodiment, the fresh loquat fruit is fresh loquat fruit with a maturity of 85%-90%, uniform color, and free from mechanical damage and pests / diseases. In this embodiment, fruit stems, rotten fruit, moldy fruit, and unripe fruit can be manually removed to ensure that the obtained fresh loquat fruit has a maturity of 85%-90%, uniform color, and is free from mechanical damage and pests / diseases, thereby guaranteeing the uniformity of the raw materials.

[0024] In one specific embodiment, during the color-protecting solution pretreatment, the fresh loquat fruit is soaked in the color-protecting solution for 8-12 minutes; the color-protecting solution includes phytic acid at a mass-volume ratio of 0.15-0.25% and ascorbic acid at a mass-volume ratio of 0.08-0.12%, and the pH of the color-protecting solution is adjusted to 3.5-4.5 using citric acid.

[0025] In the above embodiments, the color-protecting solution with this pH can enhance the synergistic effect of the color-protecting components (phytic acid and ascorbic acid) while inhibiting the activity of polyphenol oxidase in loquat fruit.

[0026] In one specific embodiment, during cleaning, sterile water is used for rapid rinsing, with a rinsing time of less than or equal to 30 seconds. In this embodiment, using sterile water for cleaning can avoid the introduction of new bacteria from the water source; rapid rinsing can remove residual color-protecting liquid from the surface of the loquat fruit while avoiding excessive rinsing that would reduce the color-protecting effect.

[0027] S2: Loquat fruit pretreated with color-protecting liquid is subjected to high-voltage pulse electric field pretreatment.

[0028] In one specific embodiment, when performing high-voltage pulse electric field preprocessing, the electric field strength is 5-10 kV / cm, the pulse frequency is 5-10 kHz, the pulse width is 25-35 ms, and the processing time is 5-15 min.

[0029] S3: After pretreatment with a high-voltage pulsed electric field, the loquat fruit is processed by removing the fruit stem, pit, and inner membrane to obtain loquat pulp.

[0030] In one specific embodiment, this step is performed manually, which reduces the risk of browning caused by mechanical damage.

[0031] S4: The loquat pulp is subjected to low-temperature juicing and purified by graded membrane filtration to obtain loquat juice.

[0032] In one specific embodiment, the juicing temperature is 4-8°C during the low-temperature juicing process. Optionally, the loquat pulp is placed in a sterile low-temperature juicer for low-temperature juicing, and the stirring speed of the sterile low-temperature juicer is set to 100-150 r / min, and the stirring and juicing time is 2-3 min.

[0033] In one specific embodiment, during staged membrane filtration, a filter screen is first used for filtration, followed by ultrafiltration. Optionally, the mesh size of the filter screen is 80-120 mesh. It should be noted that the purpose of staged membrane filtration is to first trap large pieces of residue, and then remove fine impurities and some pectin, thereby improving the clarity of the juice. In addition to the two-stage filtration used in this embodiment, more stages of filtration can be set, as long as the filter screen becomes finer and finer.

[0034] S5: The loquat juice is subjected to ultra-high pressure treatment and then stored at low temperature.

[0035] In one specific embodiment, the ultra-high pressure treatment is performed at a pressure of 450-600 MPa, a holding time of 5-10 min, and a treatment temperature of 10-20℃.

[0036] In one specific embodiment, when storing at low temperature, the loquat juice after ultra-high pressure treatment is cooled to 2-6°C and stored in a constant temperature refrigeration environment of 2-6°C. During the storage process, the temperature fluctuation of the storage environment is controlled to not exceed ±1°C, and the relative humidity of the storage environment is controlled to be 60-70%.

[0037] In this invention, the color-protecting solution pretreatment first inhibits polyphenol oxidase activity in advance, reducing browning reactions during processing and storage from the source, laying the foundation for subsequent quality preservation. Secondly, the loquat fruit, after color-protecting solution pretreatment, undergoes high-voltage pulsed electric field pretreatment. Treating the whole fruit at this stage avoids premature breakage leading to component oxidation. The high-voltage pulsed electric field pretreatment, through electroporation, induces microorganisms into a "membrane damage-sensitive state," expanding the ultra-high pressure action site and increasing ultra-high pressure sterilization efficiency by over 40%. Simultaneously, the gentle treatment method reduces damage to the triterpenic acid and organic acid structures. Finally, the pulp undergoes low-temperature juicing to maximize... This invention preserves the natural nutrients and original flavor of loquat fruit while reducing the risk of accelerated oxidation from high temperatures. The juice is then subjected to graded membrane filtration to remove impurities generated during processing, preventing them from interfering with subsequent processes and quality. Finally, the loquat juice undergoes ultra-high pressure treatment to target and inactivate pathogenic microorganisms (such as E. coli) without damaging heat-sensitive active ingredients. The ultra-high pressure treated loquat juice is then stored at low temperatures to inhibit the recovery of residual enzyme activity, microbial proliferation, and oxidative degradation of active ingredients, providing continuous protection for components such as flavonoids, ursolic acid, and ascorbic acid, further extending shelf life. In summary, the method of this invention ultimately achieves multi-dimensional optimization in microbial control, retention of multiple active ingredients, clarity, and color stability.

[0038] Example 1 A loquat juice is prepared through the following steps: (1) Obtain 2 kg of fresh loquat fruit ("Huabai No. 1" loquat with a maturity of 88%), and soak the fresh loquat fruit in a color-protecting solution for 10 min. The color-protecting solution is composed of 0.2% (mass-volume ratio) phytic acid + 0.1% (mass-volume ratio) ascorbic acid, and the pH is adjusted to 4.0 with citric acid. Then rinse with sterile water for 20 s and drain. (2) The loquat fruit after color protection liquid pretreatment was subjected to high voltage pulse electric field pretreatment: electric field strength 8kV / cm, pulse frequency 10kHz, pulse width 30ms, and treatment time 15min; (3) Manually remove the fruit stem, break the pulp along the texture of the pit, manually remove the pit and inner membrane, and perform low-temperature juicing on the obtained loquat pulp: juicing temperature 6℃, stirring speed 120r / min, juicing time 2.5min; (4) Graded membrane filtration treatment of the virgin juice: Under the conditions of 6℃ and 0.12MPa, the juice is filtered sequentially using a 100-mesh titanium alloy filter screen and a modified polyethersulfone ultrafiltration membrane to obtain loquat juice (packaged and sealed in a sterile environment). (5) The loquat juice was subjected to ultra-high pressure treatment within 30 minutes and then stored at low temperature: the ultra-high pressure treatment pressure was 600 MPa, the pressure holding time was 10 minutes, and the treatment temperature was 10℃; the subsequent constant temperature storage was 4℃ (temperature fluctuation ≤ ±1℃, relative humidity 60-70%).

[0039] Example 2 A loquat juice is prepared through the following steps: (1) Obtain fresh loquat fruit (3 kg of “Huabai No. 2” loquat with a maturity of 86%), and soak the fresh loquat fruit in a color-protecting solution for 11 min. The color-protecting solution is composed of 0.22% (mass-volume ratio) phytic acid + 0.11% (mass-volume ratio) ascorbic acid, and the pH is adjusted to 4.2 with citric acid. Then rinse with sterile water for 20 s and drain. (2) The loquat fruit after color protection liquid pretreatment was subjected to high voltage pulse electric field pretreatment: electric field strength 9kV / cm, pulse frequency 9kHz, pulse width 32ms, treatment time 12min; (3) Manually remove the fruit stem, break the pulp along the texture of the pit, manually remove the pit and inner membrane, and perform low-temperature juicing on the obtained loquat pulp: juicing temperature 5℃, stirring speed 120r / min, juicing time 2.2min; (4) Graded membrane filtration treatment of the virgin juice: Under the conditions of 5℃ and 0.12MPa, the juice is filtered sequentially using a 100-mesh titanium alloy filter screen and a modified polyethersulfone ultrafiltration membrane to obtain loquat juice (packaged and sealed in a sterile environment). (5) The loquat juice was subjected to ultra-high pressure treatment within 25 minutes and then stored at low temperature: the ultra-high pressure treatment pressure was 550 MPa, the pressure holding time was 8 minutes, and the treatment temperature was 6℃; the subsequent constant temperature storage was 4℃ (temperature fluctuation ≤ ±1℃, relative humidity 60-70%).

[0040] Example 3 A loquat juice is prepared through the following steps: (1) Obtain fresh loquat fruit (2.5 kg of “Huabai No. 3” loquat with a maturity of 87%), and soak the fresh loquat fruit in a color-protecting solution for 9 min. The color-protecting solution is composed of 0.18% (mass-volume ratio) phytic acid + 0.09% (mass-volume ratio) ascorbic acid, and the pH is adjusted to 3.8 with citric acid. Then rinse with sterile water for 20 s and drain. (2) The loquat fruit after color protection liquid pretreatment was subjected to high voltage pulse electric field pretreatment: electric field strength 7kV / cm, pulse frequency 8kHz, pulse width 28ms, and treatment time 14min. (3) Manually remove the fruit stem, break the pulp along the texture of the pit, manually remove the pit and inner membrane, and perform low-temperature juicing on the obtained loquat pulp: juicing temperature 7℃, stirring speed 120r / min, juicing time 2.8min; (4) Graded membrane filtration treatment of the virgin juice: Under the conditions of 7℃ and 0.11MPa, the juice is filtered sequentially using a 100-mesh titanium alloy filter screen and a modified polyethersulfone ultrafiltration membrane to obtain loquat juice (packaged and sealed in a sterile environment). (5) The loquat juice was subjected to ultra-high pressure treatment within 28 minutes and then stored at low temperature: the ultra-high pressure treatment pressure was 500 MPa, the pressure holding time was 9 minutes, and the treatment temperature was 8℃; the subsequent constant temperature storage was 4℃ (temperature fluctuation ≤ ±1℃, relative humidity 60-70%).

[0041] Comparative Example 1 A type of loquat juice is prepared through the following steps (referred to as pasteurization at room temperature): (1) Obtain fresh loquat fruit (2 kg of “Huabai No. 1” loquat with 88% maturity), soak it in a color-protecting solution of 0.2% (mass-volume ratio) phytic acid + 0.1% (mass-volume ratio) ascorbic acid (pH 4.0) for 10 min, rinse with sterile water for 20 s and drain. (2) Manually remove the fruit stem, separate the pulp and remove the pit and inner membrane, and juice at 120 r / min for 2.5 min at 25℃; (3) Graded membrane filtration of the virgin juice: Under the conditions of 25℃ and 0.12MPa, the juice is filtered sequentially through a 100-mesh titanium alloy filter screen and a modified polyethersulfone ultrafiltration membrane to obtain loquat juice and aseptically packaged. (4) Pasteurization: Heat the loquat juice to 85°C and maintain for 30 minutes, then cool to room temperature; (5) Storage at room temperature: Store the sterilized loquat juice in an environment of 25-30℃ and 60-70% relative humidity.

[0042] Comparative Example 2 A type of loquat juice is prepared through the following steps (referred to as pasteurization at 4°C): (1) Obtain fresh loquat fruit (2 kg of “Huabai No. 1” loquat with 88% maturity), soak it in a color-protecting solution of 0.2% (mass-volume ratio) phytic acid + 0.1% (mass-volume ratio) ascorbic acid (pH 4.0) for 10 min, rinse with sterile water for 20 s and drain. (2) Manually remove the fruit stem, separate the pulp and remove the pit and inner membrane, and juice at 120 r / min for 2.5 min at 25℃; (3) Graded membrane filtration of the virgin juice: Under the conditions of 25℃ and 0.12MPa, the juice is filtered sequentially through a 100-mesh titanium alloy filter screen and a modified polyethersulfone ultrafiltration membrane to obtain loquat juice and aseptically packaged. (4) Pasteurization: Heat the loquat juice to 85°C and hold for 30 minutes, then cool to 4°C; (5) Low temperature storage: Store loquat juice in a constant temperature environment of 4℃ (temperature fluctuation ≤ ±1℃, relative humidity 60-70%).

[0043] Comparative Example 3 A type of loquat juice is prepared through the following steps (referred to as ultra-high pressure at room temperature): (1) Obtain fresh loquat fruit (2 kg of “Huabai No. 1” loquat with 88% maturity), soak it in a color-protecting solution of 0.2% (mass-volume ratio) phytic acid + 0.1% (mass-volume ratio) ascorbic acid (pH 4.0) for 10 min, rinse with sterile water for 20 s and drain. (2) Manually remove the fruit stem, separate the pulp and remove the pit and inner membrane, and juice at 120 r / min for 2.5 min at 25℃; (3) Graded membrane filtration of the virgin juice: Under the conditions of 25℃ and 0.12MPa, the juice is filtered sequentially through a 100-mesh titanium alloy filter screen and a modified polyethersulfone ultrafiltration membrane to obtain loquat juice and aseptically packaged. (4) Ultra-high pressure treatment: The loquat juice is subjected to ultra-high pressure treatment within 30 minutes, with a pressure of 600 MPa, a holding time of 10 minutes, and a treatment temperature of 4℃; (5) Storage at room temperature: Store the processed loquat juice in an environment of 25-30℃ and 60-70% relative humidity.

[0044] Comparative Example 4 A type of loquat juice is prepared through the following steps (referred to as ultra-high pressure at 4°C): (1) Obtain fresh loquat fruit (2 kg of “Huabai No. 1” loquat with 88% maturity), soak it in a color-protecting solution of 0.2% (mass-volume ratio) phytic acid + 0.1% (mass-volume ratio) ascorbic acid (pH 4.0) for 10 min, rinse with sterile water for 20 s and drain. (2) Manually remove the fruit stem, separate the pulp and remove the pit and inner membrane, and juice at 120 r / min for 2.5 min at 25℃; (3) Graded membrane filtration of the virgin juice: Under the conditions of 25℃ and 0.12MPa, the juice is filtered sequentially through a 100-mesh titanium alloy filter screen and a modified polyethersulfone ultrafiltration membrane to obtain loquat juice and aseptically packaged. (4) Ultra-high pressure treatment: The loquat juice is subjected to ultra-high pressure treatment within 30 minutes, with a pressure of 600 MPa, a holding time of 10 minutes, and a treatment temperature of 4℃; (5) Low temperature storage: Store loquat juice in a constant temperature environment of 4℃ (temperature fluctuation ≤ ±1℃, relative humidity 60-70%).

[0045] Comparative Example 5 A type of loquat juice is prepared through the following steps (referred to as pulsed electric field combined with ultra-high voltage at room temperature): (1) Obtain fresh loquat fruit (2 kg of “Huabai No. 1” loquat with 88% maturity), soak it in a color-protecting solution of 0.2% (mass-volume ratio) phytic acid + 0.1% (mass-volume ratio) ascorbic acid (pH 4.0) for 10 min, rinse with sterile water for 20 s and drain. (2) Perform high voltage pulse electric field pretreatment: electric field strength 8kV / cm, pulse frequency 10kHz, pulse width 30ms, processing time 15min; (3) Manually remove the fruit stem, separate the pulp and remove the pit and inner membrane, and juice at 120 r / min for 2.5 min at 25℃; (4) Graded membrane filtration of the virgin juice: Under the conditions of 25℃ and 0.12MPa, the juice is filtered sequentially through a 100-mesh titanium alloy filter screen and a modified polyethersulfone ultrafiltration membrane to obtain loquat juice and aseptically packaged. (5) Ultra-high pressure treatment: The loquat juice is subjected to ultra-high pressure treatment within 30 minutes, with a pressure of 600 MPa, a holding time of 10 minutes, and a treatment temperature of 25℃; (6) Storage at room temperature: Store the processed loquat juice in an environment of 25-30℃ and 60-70% relative humidity.

[0046] Test Example 1 Performance tests were conducted on the loquat juice obtained from each embodiment and comparative example, covering three dimensions: microorganisms (total colony count, yeast, mold), physicochemical quality (transmittance, browning degree), and active ingredients (total flavonoids, triterpenic acids, organic acids, amygdalin). The test results for the key period (0-60 days) are as follows: (1) Microbial control dimension Total bacterial count is the most commonly used indicator for evaluating the biological stability of food, specifically whether microorganisms exceed the limits. Yeast and mold, as typical spoilage microorganisms in fruit juice products, directly reflect the product's shelf life and flavor stability. The detection results for the microbial dimensions of loquat juice in each example and comparative example are shown in Tables 1-4: Table 1. Microbial test results (CFU / mL) for each example

[0047] Table 2 Results of total bacterial count test for each comparative example

[0048] Table 3. Test results of yeast strains in each comparative example.

[0049] Table 4. Mold test results for each comparative example

[0050] As shown in Tables 1-4, the synergistic group of this invention exhibits a long-lasting antibacterial advantage. In the pasteurization at room temperature group, yeast (11 CFU / mL) and mold (5 CFU / mL) proliferated after 25 days, exceeding the total bacterial count limit. While the pasteurization at 4℃ delayed microbial proliferation, the total bacterial count reached 108 CFU / mL, yeast 35 CFU / mL, and mold 42 CFU / mL after 60 days, posing a safety risk. The single ultra-high pressure group combined with the pulsed electric field and ultra-high pressure at room temperature still showed sporadic microbial proliferation after 25 days at room temperature, failing to achieve long-term stability. The synergistic group of this invention, with its combined effect of "pulsed electric field configurational sensitization + ultra-high pressure targeted inactivation + 4℃ low-temperature inhibition," achieved a total bacterial count of only 11 CFU / mL, yeast 3 CFU / mL, and mold 2 CFU / mL after 60 days, representing reductions of 45.0%, 66.7%, and 75.0% respectively compared to the ultra-high pressure at 4℃ group. This completely solves the problem of microbial proliferation during long-term storage, ensuring a shelf life of over 60 days.

[0051] Therefore, it can be seen that ultra-high pressure treatment (especially pulsed electric field combined with ultra-high pressure) has a better antibacterial effect at room temperature than pasteurization. However, if only the treatment method is relied upon, microorganisms will still slowly proliferate at room temperature. The pulsed electric field combined with ultra-high pressure at -4℃ of this invention can significantly prolong the "delayed proliferation period" of microorganisms, with the best antibacterial effect and significantly extending its shelf life. The pulsed electric field combined with ultra-high pressure has a stronger inhibitory effect on yeast and mold than ultra-high pressure and pasteurization. In summary, the pulsed electric field combined with ultra-high pressure at -4℃ storage of this invention is the optimal solution for inhibiting the proliferation of microorganisms in loquat juice, and can maintain the number of microorganisms within a safe range for a long time; the antibacterial effect of ultra-high pressure at -4℃ is second best; loquat juice treated with pasteurization, regardless of whether it is stored at room temperature or low temperature, has a higher risk of microbial proliferation in the later stage.

[0052] (2) Physicochemical quality dimension Light transmittance reflects the concentration and size of suspended solids in fruit juice and is closely related to its stability during storage. Browning degree is a core indicator for measuring the degree of color deterioration in fruit juice, directly reflecting the level of oxidative degradation of active ingredients such as polyphenols, and is highly correlated with the sensory quality and nutritional value of the product. The loquat juice prepared in Example 1 is as follows... Figure 1As shown, the test results of the physicochemical quality dimensions of loquat juice in each embodiment and comparative example are shown in Tables 5-7: Table 5. Physicochemical quality test results of each embodiment

[0053] Table 6. Transmittance test results for each comparative example

[0054] Table 7. Browning test results for each comparative example

[0055] Note: Table 5 shows the results of a single test of loquat juice, while Tables 6 and 7 show the average results of multiple tests conducted on the same juice.

[0056] As can be seen from Tables 5-7, the synergistic group of this invention exhibits a dual advantage in controlling both light transmittance and browning degree. Regarding light transmittance, all groups showed a decreasing trend with prolonged storage time. The transmittance of the pasteurized group at room temperature was below 40% after 60 days, and the transmittance of the ultra-high pressure group at 4℃ dropped to 51.93±5.01% after 60 days. However, the transmittance of the synergistic group of this invention remained at 60.47±0.31% after 60 days, with a 22.1% lower decrease compared to the ultra-high pressure group at 4℃. Furthermore, the data showed minimal fluctuation, indicating significantly better system stability than the other groups. Regarding browning degree, the pasteurization group maintained a high value throughout the process, with a browning degree of 1.81±0.01 at 60 days; the browning degree of the ultra-high pressure treatment group was generally lower than 1.0. Due to the synergistic effect of the color-protecting solution pretreatment and the non-thermal process, the browning degree of the synergistic group of this invention remained stable at 0.86±0.01 at 60 days, and the increase was extremely small, only 1 / 5 of that of the pasteurization group, which confirms the strong inhibitory effect of the whole chain process on enzymatic / non-enzymatic browning.

[0057] (3) Active ingredient dimension Total flavonoids possess various physiological activities, including antioxidant, anti-inflammatory, and antibacterial effects. Ursolic acid, corosolic acid, and oleanolic acid belong to the triterpenoid acid class and have strong biological activity, exhibiting significant advantages in antioxidant and metabolic regulation functions. Organic acids are the core material basis for the flavor and acidity of loquat juice, and their content changes directly affect the taste, pH stability, and antibacterial ability of the juice. Amygdalin is a unique functional active ingredient of loquat, possessing antitussive and antiasthmatic effects; its retention rate is an important indicator for measuring the nutritional value of the product. The detection results of the active ingredients in loquat juice of each example and comparative example are shown in Tables 8-18. Table 8. Test results of active ingredients in each embodiment

[0058] Table 9. Total flavonoid test results for each comparative example (mgRE / 100mL)

[0059] Table 9 shows that under different storage temperatures, the total phenol and total flavonoid content in loquat juice after sterilization treatment generally decreased, while the amygdalin content in all treatment groups showed a fluctuating decreasing trend. After 25 days of storage at 25℃, the pasteurization group experienced losses of 12%, 19%, and 24% in total phenol, total flavonoid, and amygdalin, respectively. The ultra-high pressure group had relatively lower loss rates (approximately 7% for total phenol, 14% for total flavonoid, and 13% for amygdalin). The pulsed electric field combined with ultra-high pressure group showed the best retention effect (approximately 8% decrease in total phenol, 10% decrease in total flavonoid, and 19% decrease in amygdalin). This is because heat sterilization destroys the structure of phenolic active ingredients, leading to the loss of total phenol. Furthermore, dissolved oxygen in the samples during storage also forms oxygen free radicals, causing chemical oxidation and enzymatic oxidation of phenolic substances, resulting in degradation. At 4℃ storage, the loss rates of functional components in each group were slightly lower than at room temperature. During storage, the differences between groups at different temperatures gradually decreased over time: in the initial stage, the functional component content of the group with ultra-high voltage pulse electric field combined with ultra-high voltage at 4℃ and room temperature was significantly higher than that of the pasteurization group, but the differences between the groups decreased after 60 days.

[0060] Table 10. Ursolic acid test results for each comparative example (mg / L)

[0061] Table 11. Results of corosolic acid test for each comparative example (mg / L)

[0062] Table 12. Oleanolic acid test results for each comparative example (mg / L)

[0063] As shown in Tables 10-12, the ursolic acid content of loquat juice showed a slow decreasing trend with prolonged storage time, with a slightly more pronounced decrease in the later stages. The corosolic acid content also showed a slow decreasing trend with prolonged storage time. The oleanolic acid content showed a slow, fluctuating decreasing trend with prolonged storage time. Furthermore, the decrease in each component increased with increasing storage temperature. After 60 days of storage at 4℃, the ursolic acid retention rates of the pulsed electric field combined with ultra-high pressure group, the ultra-high pressure group, and the pasteurization group were 92.3%, 86.5%, and 78.1%, respectively; under normal temperature storage, the retention rates of the three groups were 81.5%, 74.1%, and 65.2%, respectively. After 60 days of storage at 4℃, the oleanolic acid retention rate of the pulsed electric field combined with ultra-high pressure group was 92.8%. The pulsed electric field combined with ultra-high pressure group consistently had the highest content of each component, followed by the ultra-high pressure group, with the pasteurization group having the lowest. This is related to the fact that thermal processing easily damages the component structure and accelerates degradation, while pulsed electric field combined with ultra-high pressure group has less damage to the components and is more conducive to the preservation of active substances. Therefore, high pressure treatment is more conducive to the preservation of functional components.

[0064] Table 13. Oxalic acid test results for each comparative example (mg / 100mL)

[0065] Table 14. Tartaric acid test results for each comparative example (mg / 100mL)

[0066] Table 15 Ascorbic acid test results for each comparative example (mg / 100mL)

[0067] Table 16. Malic acid test results for each comparative example (mg / 100mL)

[0068] Table 17 Succinic acid test results for each comparative example (mg / 100mL)

[0069] As shown in Tables 13-17, the oxalic acid content of loquat juice initially fluctuated slightly with prolonged storage time, then decreased slightly overall. Tartaric acid and ascorbic acid contents gradually decreased with prolonged storage time, while malic acid content showed a slow, fluctuating decrease with prolonged storage time. Succinic acid content showed a slow decrease with prolonged storage time, followed by a slightly increased decrease in the later stages. After 60 days of storage at 4℃, the oxalic acid retention rate was higher than 90% in the pulsed electric field combined with ultra-high pressure group and the ultra-high pressure group, but lower in the pasteurization group. Under normal temperature storage (25 days), the oxalic acid retention rate was higher in the pulsed electric field combined with ultra-high pressure group and the ultra-high pressure group than in the pasteurization group. When the pulsed electric field combined with ultra-high pressure group was stored at 4℃ for 60 days, the tartaric acid retention rate was significantly higher than that of the ultra-high pressure group and the pasteurization group. Under normal temperature storage (25 days), the retention rates for the three groups were 95.4%, 91.7%, and 91.4%, respectively. When stored at 4℃ for 60 days, the ascorbic acid retention rate of the pulsed electric field combined with ultra-high pressure group was 90.8%, significantly higher than that of the ultra-high pressure group and the pasteurization group. At room temperature (25 days), the retention rates of the three groups were 90.5%, 90.1%, and 77.3%, respectively, with the pulsed electric field combined with ultra-high pressure group and the ultra-high pressure group significantly higher than the pasteurization group. When stored at 4℃ for 60 days, the malic acid retention rates of the pulsed electric field combined with ultra-high pressure group, the ultra-high pressure group, and the pasteurization group were 97.1%, 95.8%, and 96.0%, respectively. At room temperature (25 days), the retention rates of the three groups were 98.5%, 97.4%, and 97.4%, respectively. When stored at 4℃ for 60 days, the succinic acid retention rates of the pulsed electric field combined with ultra-high pressure group and the ultra-high pressure group were significantly higher than that of the pasteurization group. At room temperature (25 days), the retention rates of the pulsed electric field combined with ultra-high pressure group and the ultra-high pressure group were both above 90%, significantly higher than that of the pasteurization group.

[0070] Table 18. Results of amygdalin test in each comparative example (mg / L)

[0071] As shown in Table 18, after 60 days of storage at 4℃, the retention rate of amygdalin in the pulsed electric field combined with ultra-high pressure group and the ultra-high pressure group was higher than 80%, significantly higher than that in the pasteurization group. Under normal temperature storage (25 days), the retention rate of amygdalin in the pasteurization group was only 62.5%, significantly lower than the other two groups. Under the same treatment method, the amygdalin content under 4℃ low-temperature storage was generally higher than that under normal temperature storage. The combination of pulsed electric field combined with ultra-high pressure and 4℃ low-temperature storage showed the best retention effect of amygdalin throughout the entire storage period, maintaining a high content in the initial stage and delaying degradation during long-term storage; while the retention effect of pasteurization + normal temperature storage was the worst.

[0072] As can be seen from Tables 8-18, the synergistic group of this invention achieves simultaneous and efficient retention of multiple components, demonstrating comprehensive advantages. Regarding total flavonoids, the retention rate reached 89.8% after 60 days, an increase of 11.9% compared to the pasteurization group at 4℃ (80.4%) and 4.4% compared to the ultra-high pressure group at 4℃ (86.2%). The gentle, non-thermal treatment avoided structural damage to flavonoid components. Regarding triterpenoid acids (ursolic acid and corosolic acid), the synergistic group achieved a 92.3% retention rate for ursolic acid, an increase of 6.7% compared to the ultra-high pressure group at 4℃ (86.5%) and 18.2% compared to the pasteurization group at 4℃ (78.1%). The retention rate for corosolic acid reached 94.0%, significantly higher than other treatment groups, demonstrating the specific protection of triterpenoid acid active substances by the whole-chain process. Regarding organic acids and amygdalin, the synergistic group retained 90.8% of ascorbic acid, 2.1% higher than the ultra-high pressure 4℃ group; the amygdalin retention rate was 82.1%, slightly lower than the ultra-high pressure 4℃ group (84.4%) but significantly higher than the pasteurization group, and maintained a high initial content throughout the process. In addition, the synergistic group retained over 90% of oxalic acid, tartaric acid, malic acid, and succinic acid, effectively maintaining the natural flavor and nutritional structure of loquat juice.

[0073] Test Example 2 Energy consumption tests were conducted on the preparation methods of each embodiment and comparative example. The energy consumption of Example 1 was 72 kWh / t, Example 2 was 74 kWh / t, and Example 3 was 76 kWh / t. Compared to a single ultra-high voltage group (energy consumption 90-110 kWh / t), the synergistic group of this invention, due to the enhanced effect of pulsed electric field pretreatment and the shortened ultra-high voltage holding time, reduced energy consumption by more than 25%.

[0074] In summary, the present invention has the following advantages: (1) Long-lasting and stable microbial inhibition effect: Through the synergistic effect of the whole chain, the total number of colonies stored at 4℃ for 60 days is ≤11CFU / mL, the total number of yeasts is ≤3CFU / mL, and the total number of molds is ≤2CFU / mL. The inactivation rate of pressure-resistant spores, yeasts / molds is over 99%, and the inhibition rate of polyphenol oxidase and pectinase is over 85%. This completely solves the problem of microbial and enzymatic deterioration of loquat juice, extending the shelf life from 7-10 days in the traditional process to over 60 days, and there is no risk of microbial rebound throughout the process.

[0075] (2) Synchronous and efficient retention of multiple active ingredients and excellent quality retention: It achieves synergistic retention of multiple active ingredients such as flavonoids, triterpenoids, organic acids, and amygdalin. The total flavonoid retention rate is ≥90%, ursolic acid retention rate is ≥92%, ascorbic acid retention rate is ≥90%, corosolic acid retention rate is ≥93%, and organic acid retention rate such as oxalic acid, tartaric acid, and malic acid is ≥90%, maximizing the retention of the natural nutritional structure and functional value of loquat juice. The overall retention rate of active ingredients is 8%-15% higher than that of existing technologies. The browning degree is ≤0.86 after 60 days, and the light transmittance decreases by ≤22%. The color, clarity, and taste of the juice are all better than those of existing technologies, maximizing the retention of natural characteristics and functional value.

[0076] (3) Excellent physicochemical quality and flavor stability: 60d browning degree ≤0.86, light transmittance ≥60%, and data fluctuation is small. After standing for 60 days, there is no layering or obvious color change, effectively maintaining the clarity and natural color of the juice. At the same time, it effectively retains natural organic acids, avoids flavor deterioration, and has a better taste than existing non-thermal processed products, meeting the market demand for high-end fruit and vegetable juices.

[0077] (4) Strong processing economy and adaptability: Energy consumption is reduced by more than 25% compared with single ultra-high pressure treatment. The color protection liquid (phytic acid, ascorbic acid, citric acid) is inexpensive. The parameters of each step are precisely controllable. No additional chemical preservatives are required. The quality is stable and environmentally friendly through physical treatment and mild color protection chemical treatment. The process flow is continuous and can be seamlessly connected to existing fruit and vegetable juice processing production lines. The industrialization conversion is easy and highly practical.

[0078] (5) Unique synergistic mechanism and high technical barriers: The entire chain of “color protection-configuration-inactivation-stabilization” is constructed, rather than a single technology superposition. Color protection pretreatment, non-thermal synergistic sterilization and low temperature stabilization mutually empower each other. Graded membrane filtration is used as a conventional impurity removal step, and simple graded membrane filtration is only used as an auxiliary impurity removal step. This not only solves the contradiction between “sterilization and component retention” in non-thermal processing, but also realizes the three-dimensional optimization of “microbial control, physicochemical stability and multi-component retention”. Without any one of them, the same effect cannot be achieved. The innovation and non-obviousness are significant.

[0079] (6) Strong processing economy and adaptability: Energy consumption is reduced by more than 25% compared with single ultra-high pressure processing. The equipment used (high voltage pulse electric field, ultra-high pressure, low temperature juicer, etc.) are all conventional special equipment for food processing. The parameters of each step are precise and controllable, and they are suitable for industrial continuous production. The process is gentle and does not cause high temperature damage, avoiding the use of chemical additives, which is in line with the trend of healthy food processing.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for improving the retention of active ingredients and overall quality stability of loquat juice, characterized in that, Includes the following steps: S1: Obtain fresh loquat fruit, pre-treat the fresh loquat fruit with color-protecting liquid, and then wash and drain it; S2: High-voltage pulsed electric field pretreatment is performed on loquat fruit after color protection liquid pretreatment; S3: After pretreatment with a high-voltage pulsed electric field, the loquat fruit is processed by removing the fruit stem, pit and inner membrane to obtain loquat pulp; S4: The loquat pulp is subjected to low-temperature juicing and purified by graded membrane filtration to obtain loquat juice; S5: The loquat juice is subjected to ultra-high pressure treatment and then stored at low temperature.

2. The method for improving the retention of active ingredients and overall quality stability of loquat juice according to claim 1, characterized in that, In step S1, the fresh loquat fruit is a fresh loquat fruit with a maturity of 85%-90%, uniform color, and no mechanical damage or pests.

3. The method for improving the retention of active ingredients and overall quality stability of loquat juice according to claim 1, characterized in that, In step S1, when performing the color-protecting solution pretreatment, the fresh loquat fruit is soaked in the color-protecting solution for 8-12 minutes; the color-protecting solution includes phytic acid at a mass-volume ratio of 0.15-0.25% and ascorbic acid at a mass-volume ratio of 0.08-0.12%, and the pH of the color-protecting solution is adjusted to 3.5-4.5 using citric acid.

4. The method for improving the retention of active ingredients and overall quality stability of loquat juice according to claim 1, characterized in that, In step S1, when cleaning, use sterile water for rapid rinsing, and the rinsing time is less than or equal to 30 seconds.

5. The method for improving the retention of active ingredients and overall quality stability of loquat juice according to claim 1, characterized in that, In step S2, when performing high-voltage pulse electric field preprocessing, the electric field strength is 5-10 kV / cm, the pulse frequency is 5-10 kHz, the pulse width is 25-35 ms, and the processing time is 5-15 min.

6. The method for improving the retention of active ingredients and overall quality stability of loquat juice according to claim 1, characterized in that, In step S4, the juicing temperature is 4-8℃ during the low-temperature juicing process.

7. The method for improving the retention of active ingredients and overall quality stability of loquat juice according to claim 1, characterized in that, In step S4, during the graded membrane filtration, a filter screen is used first, followed by ultrafiltration.

8. The method for improving the retention of active ingredients and overall quality stability of loquat juice according to claim 7, characterized in that, The mesh size of the filter is 80-120 mesh.

9. The method for improving the retention of active ingredients and overall quality stability of loquat juice according to claim 1, characterized in that, In step S5, the ultra-high pressure treatment is carried out at a pressure of 450-600 MPa, a holding time of 5-10 min, and a treatment temperature of 10-20℃.

10. The method for improving the retention of active ingredients and overall quality stability of loquat juice according to claim 1, characterized in that, In step S5, when storing at low temperature, the loquat juice after ultra-high pressure treatment is cooled to 2-6℃ and stored in a constant temperature cold storage environment of 2-6℃. During the storage process, the temperature fluctuation of the storage environment is controlled to not exceed ±1℃, and the relative humidity of the storage environment is controlled to be 60-70%.

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