Preparation method of low-astringent berry juice
Through the physical method of gradient quick freezing-thawing combined with multi-stage centrifugation and pH adjustment, the astringent taste problem of berry juice is solved, effective removal of condensation tannins and protection of anthocyanins is achieved, and it is suitable for the industrial production of low-astringy berry juice.
Patent Information
- Application Number
- CN202510583966.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-07
- Publication Date
- 2025-08-08
AI Technical Summary
The prior art is difficult to effectively remove condensed tannins in berry juice, resulting in a strong astringent taste. At the same time, chemical treatment methods may destroy active ingredients such as anthocyanins and have a risk of chemical residues.
Gradient freeze-thawing method is used to induce condensation tannins to form macromolecular aggregates, combined with multi-stage centrifugation and pH adjustment, and astringent substances are separated by physical methods, and ultra-high pressure homogenization and sterilization are carried out under low temperature conditions.
Effectively reduce the condensation tannin content in berry juice, reduce astringent taste, and protect the active ingredients of anthocyanins and avoid chemical additives. It is suitable for industrial production.
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Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing low-astringency berry juice, belonging to the technical field of food processing. Background Art
[0002] Aronia melanocarpa (scientific name: Aronia melanocarpa), whose fruit is rich in highly active anthocyanins, is considered a novel food ingredient with both nutritional and functional properties. Its processed product, aronia juice, holds a prominent position in the health food market due to its high antioxidant activity, portability, and ease of storage. However, the high amount of tannins in aronia berries imparts an extremely astringent taste to aronia juice, far exceeding the acceptable threshold for consumers. Furthermore, the high degree of polymerization of these tannin molecules makes them difficult for the body to absorb and utilize as active ingredients. If the tannin content in aronia juice could be effectively reduced to a level acceptable to the human mouth, the astringency of aronia juice could be effectively reduced, increasing its market acceptance.
[0003] Currently, the main methods for reducing tannin content are chemical treatment and enzymatic treatment. Chemical treatment methods typically use strong acids or affinity reagents, and due to potential safety risks, they are difficult to apply in the food processing industry. Enzymatic treatment methods generally hydrolyze tannins, but the tannins in berry fruit are mostly condensed tannins, which cannot be depolymerized using hydrolytic enzymes. Furthermore, while the addition of flavor masking agents can address the palatability of the juice to a certain extent, none of these technologies completely solves the problem of juice astringency, and they are highly likely to destroy active ingredients such as anthocyanins and even introduce chemical residues. With increasing attention to food safety in recent years, the concept of additive-free food processing is gradually gaining favor with consumers. Therefore, if physical methods can be used to reduce the astringency of berry juice without destroying active ingredients such as anthocyanins, it will help improve the nutritional value of the product and enhance its competitiveness in the industry. Summary of the Invention
[0004] To address the existing issues of difficulty in removing condensed tannins, the primary astringent in berry juice, and the significant damage to active ingredients such as anthocyanins during removal, the present invention provides a method for preparing low-astringency berry juice. This method first induces the formation of macromolecular aggregates from condensed tannins through a gradient freeze-thaw process, and then combines multi-stage centrifugation with pH adjustment to achieve targeted separation of astringent substances. The method provided by the present invention is a physical method that does not require the addition of chemical reagents and is simple and easy to operate. Furthermore, the method is performed entirely at low temperatures, effectively removing astringent substances without damaging active ingredients such as anthocyanins.
[0005] A method for preparing low-astringency berry juice comprises the following steps: quickly freezing berry fruits at -20°C to -25°C for 8 to 12 hours, then slowly thawing at 2 to 6°C until completely melted, and repeating the steps 2 to 3 times; then squeezing and crushing the completely thawed fruits, filtering, and adjusting the pH to 3.5 to 4.0 after low-speed centrifugation, performing high-speed centrifugation again, and finally homogenizing and sterilizing the fruits under ultrahigh pressure to obtain the low-astringency juice.
[0006] The berry fruit of the present invention is a berry substance containing active ingredients such as condensed tannins and anthocyanins.
[0007] Preferably, the berry fruit is raspberry, blueberry or blueberry fruit.
[0008] Further preferably, the berry fruit is an aronia fruit.
[0009] Preferably, the quick freezing time is 8 to 10 hours.
[0010] More preferably, the quick freezing time is 9 to 10 hours.
[0011] Preferably, the quick freezing and thawing are repeated three times.
[0012] The present invention uses a gradient quick freezing-thawing method to allow ice crystals to grow repeatedly, thereby destroying the cell walls of the fruit, promoting the combination of condensed tannins with pectin, protein, etc. in the cell fragments to form macromolecular aggregates, which is beneficial for subsequent separation.
[0013] Preferably, the squeezing and crushing method is screw pressing at 2-6°C.
[0014] Further preferably, the squeezing and crushing method is screw pressing at 4°C.
[0015] The invention can release active ingredients such as anthocyanins to the maximum extent by squeezing the fruit at 4°C.
[0016] Preferably, the filtering condition is to first use a 100-150 mesh screen for coarse filtration and then use a 200 mesh screen for fine filtration.
[0017] In the above technical solution, the low-speed centrifugation condition is centrifugation at a speed of 2000-3000 r / min at 4-8°C for 10-15 minutes.
[0018] Preferably, the low-speed centrifugation condition is centrifugation at 2500 r / min at 6°C for 12 min.
[0019] In the above technical solution, the pH can be adjusted by citric acid or malic acid.
[0020] In the above technical solution, the high-speed centrifugation condition is centrifugation at a speed of 8000-10000 r / min at 4-8°C for 15-20 minutes.
[0021] Preferably, the high-speed centrifugation condition is centrifugation at 9000 r / min at 6°C for 18 min.
[0022] The invention realizes effective separation through multi-stage centrifugation, wherein the first low-temperature and low-speed coarse filtration removes large particle aggregates, the pH is adjusted to enhance the precipitation effect, and the second low-temperature and high-speed filtration removes condensed tannin-protein and other complexes.
[0023] In the above technical solution, the ultra-high pressure homogenization pressure is 100-200 MPa.
[0024] In the above technical solution, the ultra-high pressure sterilization condition is to treat at a pressure of 400-550 MPa for 3-5 minutes.
[0025] The present invention uses physical means combined with pH control to achieve targeted separation, which can not only effectively reduce the astringent substance in berry juice - condensed tannins, but also effectively protect the functional active substance - anthocyanins through low-temperature treatment during the processing process. It is an efficient technology for removing the astringency of berry juice.
[0026] Beneficial effects of the present invention:
[0027] 1. Solve the problem of prominent astringency in berry juice: Taking advantage of the low solubility of condensed tannins at low temperatures, the berry cell walls are quickly destroyed by freezing to release tannins, and then the low-temperature environment after thawing promotes their precipitation. Repeated cycles can not only maximize the precipitation of condensed tannins, but also allow them to combine with cell fragments, which is more conducive to subsequent separation, ensuring a low concentration of condensed tannins in the juice, and thus solving the industry-wide problem of high astringency in juice.
[0028] 2. Applicability for industrial production: The preparation method of the present invention is simple and easy to control, and the required equipment is relatively easy to obtain, which can achieve large-scale, high-quality and rapid preparation of low-astringency juice.
[0029] 3. No chemical additives throughout the process: This invention strictly abandons artificial additives such as chemical de-astringents, flavor masking agents and preservatives during the preparation process, and achieves efficient removal of tannins through a physical synergistic process, which not only avoids the potential risks of chemical residues to consumer health, but also ensures the natural properties of the product.
[0030] 4. Anthocyanin Activity Protection: Anthocyanins, the main functional component of berries, are extremely sensitive to light and heat. This invention utilizes low-temperature pressing and ultra-high pressure sterilization to inhibit anthocyanin degradation through non-thermal action throughout the process, ensuring the stability of their molecular structure and maximizing the preservation of active ingredients such as anthocyanins, imparting their natural color and health benefits to the juice. DETAILED DESCRIPTION
[0031] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.
[0032] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are all commercially available unless otherwise specified.
[0033] The preparation method of the low-astringency berry juice described in the following examples can be carried out according to the following process route:
[0034] Raw material cleaning → quick freezing → thawing → quick freezing and thawing cycle → screw pressing → filtration → low-speed centrifugation → pH adjustment → high-speed centrifugation → ultra-high pressure homogenization → ultra-high pressure sterilization → aseptic filling → finished product
[0035] One of the specific implementation methods:
[0036] Step 1: Select fresh, non-rotten berry fruits, wash them, and then use a quick-freezing device to quickly freeze them at -20°C to -25°C. Store them at this temperature for 8 to 12 hours, and then thaw them at 2 to 6°C. Then, perform 2 to 3 quick-freezing and thawing cycles.
[0037] Step 2: Use a screw press to crush the completely thawed berries at 2-6°C.
[0038] Step 3: The squeezed juice is coarsely filtered through a 100-150 mesh sieve, and then finely filtered through a 200 mesh sieve; low-speed centrifugation is performed at 2000-3000 rpm at 4°C-8°C for 10-15 minutes to separate the sediment;
[0039] Step 4: Adjust the pH of the centrifuged juice to 3.5-4.0 with citric acid or malic acid to enhance the precipitation of the complex in the juice;
[0040] Step 5: Perform a second centrifugation at 8000-10000 rpm for 15-20 min at 4-8°C.
[0041] Step 6: The treated juice is subjected to ultra-high pressure homogenization at a homogenization pressure of 100-200 MPa, followed by ultra-high pressure sterilization technology at a pressure of 400-550 MPa for 3-5 minutes;
[0042] Step 7: Finally, the mixture is packaged through an aseptic filling process to obtain the low-astringency berry juice.
[0043] Anthocyanin content was determined using the pH differential method. The specific steps are as follows:
[0044] Pipette two 1 mL juice samples into test tubes, add 9 mL of pH 1.0 and pH 4.5 buffer solutions, respectively. After equilibration in the dark for 15-30 minutes, measure the absorbance at 520 nm and 700 nm using a UV-visible spectrophotometer. Use the following formula:
[0045]
[0046] The total anthocyanins in the sample are expressed as cyanidin-3-O-glucoside equivalents, where ΔA = (A 520 -A 700 ) pH1.0 -(A 520 -A 700 ) pH4.5 , MW = 449.2 g / mL, DF is the dilution factor, V is the total volume of the liquid, ε = 26900 L / (mol.cm), and m is the sample mass.
[0047] All operations were completed at 25°C in the dark, and the same sample was measured three times in parallel to obtain the average value.
[0048] The condensed tannin content was determined by the vanillin-sulfuric acid spectrophotometric method. The specific steps are as follows:
[0049] Step 1: Sample liquid pretreatment: fresh berry juice was centrifuged at 8000 rpm for 10 min to remove the pomace, the supernatant was diluted to the linear range (0.05-0.5 mg / mL), and centrifuged to obtain an untreated juice sample; the finished juice treated by the method provided by the present invention was centrifuged to obtain a finished juice sample;
[0050] Step 2: Take 0.5 mL of sample solution, add 2.5 mL of 3% vanillin-methanol solution and 2.5 mL of 30% sulfuric acid-methanol solution, react at 30°C in the dark for 20 min, and measure the absorbance at 500 nm.
[0051] Step 3: Using catechin as the standard sample, according to the standard curve Y = 0.0024X + 0.0088 (R 2 =0.995) to calculate the tannin content. The results showed that the tannin content of the original berry juice was 1200 mg / L.
[0052] The calculation formula for tannin removal rate is as follows:
[0053]
[0054] Where, X 初始 is the tannin content in untreated juice, X 处理后 It is the tannin content in the finished juice.
[0055] Example 1
[0056] A method for preparing low-astringency berry juice comprises the following steps:
[0057] Step 1: Select fresh, non-rotten berry fruits, wash them, and then use a quick-freezing device to quickly freeze them at -25°C, freeze them at this temperature for 8 hours, and then thaw them at 4°C, followed by two quick-freeze-thaw cycles;
[0058] Step 2: Keep the thawed berries at 4°C and crush the pulp using a screw press;
[0059] Step 3: The juice was coarsely filtered through a 100-mesh sieve and then finely filtered through a 200-mesh sieve; the juice was centrifuged at 2000 rpm for 10 min at 4°C to separate the precipitate;
[0060] Step 4: Adjust the pH of the centrifuged juice to 3.5 by adding citric acid;
[0061] Step 5: Perform a second centrifugation at 8000 rpm for 15 min at 4°C.
[0062] Step 6: The treated juice is subjected to ultra-high pressure homogenization at a homogenization pressure of 100 MPa, followed by ultra-high pressure sterilization technology at a pressure of 400 MPa for 3 minutes;
[0063] Step 7: Finally, the product is packaged through an aseptic filling process to obtain a low-astringency berry juice, wherein the anthocyanin retention rate is 90%, the tannin content after the above steps is 408 mg / L, and the tannin removal rate is 68%.
[0064] Example 2
[0065] A method for preparing low-astringency berry juice comprises the following steps:
[0066] Step 1: Select fresh, non-rotten berry fruits, wash them, and then use a quick-freezing device to quickly freeze them at -22°C and store them at this temperature for 10 hours; then thaw them at 4°C, and then perform three quick-freeze-thaw cycles;
[0067] Step 2: Keep the thawed berries at 4°C and crush the pulp using a screw press;
[0068] Step 3: The juice was coarsely filtered through a 120-mesh sieve and then finely filtered through a 200-mesh sieve; the juice was centrifuged at 2500 rpm for 12 minutes at 6°C to separate the precipitate;
[0069] Step 4: Adjust the pH of the centrifuged juice to 3.8 by adding citric acid;
[0070] Step 5: Perform a second centrifugation at 9000 rpm for 18 min at 6°C.
[0071] Step 6: The treated juice is subjected to ultra-high pressure homogenization at a homogenization pressure of 150 MPa, followed by ultra-high pressure sterilization technology at a pressure of 475 MPa for 4 minutes;
[0072] Step 7: Finally, the juice is packaged through an aseptic filling process to obtain low-astringency berry juice, wherein the anthocyanin retention rate is 94%, the tannin content after the above steps is 324 mg / L, and the tannin removal rate is 73%.
[0073] Example 3
[0074] A method for preparing low-astringency berry juice comprises the following steps:
[0075] Step 1: Select fresh, non-rotten berry fruits, wash them, and then use a quick-freezing device to quickly freeze them at -25°C and store them at this temperature for 12 hours; then thaw them at 4°C, and then perform three quick-freeze-thaw cycles;
[0076] Step 2: Keep the thawed berries at 4°C and crush the pulp using a screw press;
[0077] Step 3: The juice was coarsely filtered through a 150-mesh sieve and then finely filtered through a 200-mesh sieve; the juice was centrifuged at 3000 rpm for 15 minutes at 8°C to separate the sediment;
[0078] Step 4: Adjust the pH of the centrifuged juice to 4.0 by adding malic acid;
[0079] Step 5: Perform a second centrifugation at 8°C and high-speed centrifugation at 10,000 rpm for 20 min.
[0080] Step 6: The treated juice is subjected to ultra-high pressure homogenization at a homogenization pressure of 200 MPa, followed by ultra-high pressure sterilization technology at a pressure of 550 MPa for 5 minutes;
[0081] Step 7: Finally, the juice is packaged through an aseptic filling process to obtain low-astringency berry juice, wherein the anthocyanin retention rate is 92%, the tannin content after the above steps is 360 mg / L, and the tannin removal rate is 70%.
[0082] Comparative Example 1
[0083] A method for preparing berry juice comprises the following steps:
[0084] Step 1: Select fresh, non-rotten berry fruits, wash them, and then use quick-freezing equipment to freeze them at -25°C and store them at this temperature for 8 hours;
[0085] Step 2: Slowly thaw the frozen berry fruit to 4°C and crush the fruit pulp using a screw press;
[0086] Step 3: The juice was coarsely filtered through a 100-mesh sieve and then finely filtered through a 200-mesh sieve; the juice was centrifuged at 2000 rpm for 10 min at 4°C to separate the precipitate;
[0087] Step 4: Add malic acid to adjust the pH of the centrifuged juice to 3.5 to enhance the precipitation of the complex in the juice;
[0088] Step 5: Perform a second centrifugation at 8000 rpm for 15 min at 4°C.
[0089] Step 6: The treated juice is subjected to ultra-high pressure homogenization at a homogenization pressure of 100 MPa, followed by ultra-high pressure sterilization technology at a pressure of 400 MPa for 3 minutes;
[0090] Step 7: Finally, the berry juice is packaged through an aseptic filling process to obtain the berry juice, in which the anthocyanin retention rate is 65%. After the above steps, the tannin content is 960 mg / L, and the removal rate is only 20%.
[0091] The difference between Comparative Example 1 and Example 1 is that no freeze-thaw cycle was performed, and filtration and centrifugation were performed directly after thawing. Other steps such as centrifugation speed and temperature remained unchanged. The test results are shown in Table 1.
[0092] Table 1 Anthocyanin retention rate and tannin removal rate of Example 1 and Comparative Example 1
[0093]
Claims
1. A method for preparing low-astringency berry juice, characterized by: The berry fruits are quickly frozen at -20℃ to -25℃ for 8 to 12 hours, then slowly thawed at 2 to 6℃ until completely melted, and repeated 2 to 3 times; the completely thawed fruits are then squeezed and crushed, filtered, centrifuged at low speed, and the pH is adjusted to 3.5 to 4.0, and high-speed centrifugation is performed again. Finally, low-astringency juice is obtained after ultra-high pressure homogenization and sterilization.
2. The preparation method according to claim 1, wherein: The berry fruit is berry, raspberry or blueberry fruit.
3. The preparation method according to claim 1, wherein: The quick freezing time is 8 to 10 hours.
4. The preparation method according to claim 1, wherein: The quick freezing-thawing was repeated 3 times.
5. The preparation method according to claim 1, wherein: The squeezing and crushing method is to perform screw squeezing at 2-6°C.
6. The preparation method according to claim 1, wherein: The filtering conditions are as follows: firstly using a 100-150 mesh screen for coarse filtration, and then using a 200 mesh screen for fine filtration.
7. The preparation method according to claim 1, wherein: The low-speed centrifugation condition is centrifugation at 4-8° C. and a speed of 2000-3000 r / min for 10-15 minutes.
8. The preparation method according to claim 1, wherein: The high-speed centrifugation condition is to centrifuge at a speed of 8000-10000 r / min at 4-8° C. for 15-20 min.
9. The preparation method according to claim 1, wherein: The ultra-high pressure homogenization pressure is 100-200 MPa.
10. The preparation method according to claim 1, characterized in that: The ultra-high pressure sterilization condition is to treat at a pressure of 400-550 MPa for 3-5 minutes.