High-flavon high-clearing high-clarification high-bitterness-free huqu yellow rice wine and preparation method thereof

Abstract

This invention provides a non-bitter, highly clarified, and flavonoid-rich pomelo rice wine and its preparation method, belonging to the field of functional rice wine technology. This invention uses pomelo juice, rice wine body, vitamin C, and citric acid as raw materials. It employs a targeted enzymatic debittering process to specifically degrade bitter precursors such as naringin and limonene, completely eliminating bitterness and astringency. A low-temperature, oxygen-free extraction technique is used to accelerate the gentle dissolution of pomelo flavor and functional components, avoiding the release of bitter substances and the degradation of heat-sensitive components. A β-cyclodextrin encapsulation technique is used to selectively encapsulate bitter substances such as naringin and limonene, achieving debittering without loss of functional components and flavor. A freeze-sedimentation process is used to fully extract unstable substances and easily crystallized components that are difficult to settle at room temperature, further improving shelf-life stability. The pomelo rice wine prepared by this invention has the advantages of a non-bitter taste, high stability, and high flavonoid content, making it easy to achieve large-scale mass production.

Description

Technical Field

[0001] This invention relates to the field of functional rice wine technology, specifically to a bitter-free, highly clear, and flavonoid-rich pomelo rice wine and its preparation method. Background Technology

[0002] The pomelo is a unique citrus fruit in my country, used both as food and medicine. It is rich in flavonoids, dietary fiber, vitamin C, volatile oils, and other active ingredients, offering antioxidant, throat-soothing, thirst-quenching, and metabolism-boosting benefits. It is a distinctive agricultural product with both nutritional and health-promoting value. While the pomelo has a large yield and unique flavor, the fresh fruit does not store well, resulting in a relatively low conversion rate during deep processing.

[0003] Yellow rice wine is one of the world's oldest brewed wines, with a brewing history spanning thousands of years. It is made from glutinous rice, rice, and other grains through saccharification and fermentation using wheat koji, rice koji, or yeast. Its alcohol content is generally 14%–20%, classifying it as a low-alcohol brewed wine. Yellow rice wine contains more than 18 kinds of amino acids, including the eight essential amino acids for the human body. It is also rich in polysaccharides, polyphenols, minerals, and functional peptides, ranking among the top brewed wines in terms of nutritional value. Furthermore, it is a core base wine for traditional medicinal wines. Developing pomelo-flavored yellow rice wine can both realize the utilization of fresh fruit resources and enhance the functionality and flavor of traditional yellow rice wine, possessing significant market value.

[0004] Existing processed products related to pomelo are mostly juice, dried fruit, and canned goods. There is relatively little research and products related to pomelo rice wine. The publicly disclosed technologies or pilot-scale processes generally have the following key technical defects: 1) Prominent bitterness and numbing sensation in the throat: Grapefruit contains bitter substances such as naringin and limonene. Simply mixing or soaking it will make the rice wine noticeably bitter and astringent, and the taste will deteriorate, making it difficult for consumers to accept.

[0005] 2) The wine is cloudy and has poor stability: Grapefruit contains a lot of pectin, protein, crude fiber, etc., which can easily cause flocculation, precipitation and stratification when added directly to rice wine. It has a short shelf life at room temperature and cannot meet the requirements for commercialization.

[0006] 3) Low dissolution rate and easy loss of functional ingredients: Heat-sensitive functional ingredients such as flavonoids and volatile oils are severely degraded and have low retention rates under conventional high-temperature treatment and long-term extraction conditions, resulting in products without clear functional advantages.

[0007] 4) The process is crude and cannot be industrialized: traditional methods such as direct soaking, simple blending, and natural clarification are mostly used. The parameters are uncontrollable, the quality fluctuates greatly, and the flavor is not harmonious. A standardized and mass-producible complete process has not been formed. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide a bitter-free, highly clear, and flavonoid-rich pomelo rice wine and its preparation method. The pomelo rice wine prepared by this invention has the advantages of a bitter-free taste, high stability, and high flavonoid content, and is easy to mass-produce.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a bitter-free, highly clear, and flavonoid-rich pomelo rice wine, comprising the following steps: The pomelo pulp was enzymatically hydrolyzed using cellulase and pectinase to obtain pomelo juice. The pomelo juice is mixed with rice wine, vitamin C and citric acid to obtain the blended wine. The blended liquor was subjected to oxygen-free extraction, and β-cyclodextrin was added to the resulting extract to encapsulate bitterness, thus obtaining a debittered liquor. The debittered wine liquid was subjected to clarification, freeze sedimentation and sterilization in sequence to obtain a bitter-free, highly clarified, and flavonoid-rich grapefruit wine.

[0010] Preferably, the method for preparing the rice wine includes the following steps: The base spirit of rice wine and the base spirit of white wine are mixed to obtain the rice wine body; The alcohol content of the rice wine base is 10-15 vol%, and the total sugar content is 15-25 g / L; the alcohol content of the baijiu base is 40-53 vol%, and the total sugar content is 0.8-2.5 g / L; the volume ratio of the rice wine base to the baijiu base is (2-4):(0-2).

[0011] Preferably, the mass of the cellulase is 0.05-0.2% of the mass of the pomelo pulp; the mass of the pectinase is 0.08-0.25% of the mass of the pomelo pulp. The enzymatic hydrolysis was performed at a temperature of 40-45°C for 20-40 minutes, with a pH value of 3.5-4.5.

[0012] Preferably, the mass of the pomelo juice is 8-15% of the total mass of the pomelo juice and rice wine; the mass of the vitamin C is 0.05-0.1% of the total mass of the pomelo juice and rice wine; and the mass of the citric acid is 0.05-0.1% of the total mass of the pomelo juice and rice wine.

[0013] Preferably, the oxygen-free extraction temperature is 30~40℃ and the time is 60~120min.

[0014] Preferably, the mass of the β-cyclodextrin is 0.2-0.5% of the mass of the extract; and the bitterness encapsulation time is 15-20 min.

[0015] Preferably, the clarification process includes sequential chitosan flocculation, diatomaceous earth filtration, and ultrafiltration membrane filtration.

[0016] Preferably, the freezing and settling temperature is -4 to 0°C, and the time is 7 to 14 days; The sterilization is pasteurization, and the sterilization temperature is 75~80℃, and the time is 15~20min.

[0017] This invention provides a bitter-free, highly clear, and flavonoid-rich grapefruit wine prepared by the above-mentioned method.

[0018] Preferably, the indicators of the bitter-free, highly clear, and flavonoid-rich pomelo wine include: alcohol content 13~15 vol%, total sugar 16~19 g / L, total acid 5.0~6.2 g / L, light transmittance ≥95%, total flavonoids ≥300 mg / L, total polyphenols ≥0.35 mg / g, amino acid nitrogen ≥0.10 g / 100 mL, naringin 2.2~4.8 mg / L, limonene 0.7~1.5 mg / L, and fusel oil ≤0.03 g / 100 mL.

[0019] This invention provides a method for preparing a bitter-free, highly clear, and flavonoid-rich pomelo rice wine. Using pomelo juice, rice wine body, vitamin C, and citric acid as raw materials, this invention employs scientific proportioning and targeted process design, combined with a flavor sensory evaluation system, comprehensively considering the wine's flavor, alcohol content, sugar content, acidity, clarity, and retention of functional components, to construct a bitter-free, highly clear, and flavonoid-rich pomelo rice wine framework.

[0020] Compared to existing pomelo-flavored rice wine products, the advantages of this invention are: ① No bitterness - bitterness completely removed: This invention uses targeted enzymatic hydrolysis of cellulase and pectinase + β-cyclodextrin encapsulation for synergistic debittering, precisely removing the characteristic bitter substances of pomelo, naringin and limonene, with a debittering rate of ≥85%. The wine is free of bitterness, numbing sensation in the throat, and aftertaste, fundamentally solving the industry's fatal defect of pomelo rice wine being "difficult to swallow".

[0021] ② High retention of functional components: This invention employs a low-temperature, oxygen-free extraction process to maximize the protection of heat-sensitive total flavonoids, vitamin C, limonene, polyphenols, and other functional components. The total flavonoid retention rate is ≥90%, and the content is ≥300mg / L, far exceeding that of conventional high-temperature processes and simple soaking processes (where flavonoid loss often exceeds 40%). This upgrades pomelo rice wine from a "flavored wine" to a functional rice wine with antioxidant properties, soothing effects on the throat, and relieving internal heat and promoting saliva production, thus possessing clear health benefits.

[0022] ③ High clarification stability: By combining with subsequent clarification processes (such as chitosan flocculation - diatomaceous earth filtration - ultrafiltration membrane filtration), this invention can completely remove turbid substances such as pomelo pectin, suspended protein, and starch particles. The light transmittance of the wine is ≥95%, and there is no turbidity, sedimentation, or stratification after standing at room temperature for 6 months.

[0023] ④ Harmonious Flavor: The pomelo aroma and mellow aroma of rice wine obtained by this invention are naturally integrated, with prominent fruit aroma, mellow wine aroma, and pleasant sweet and sour taste. There is no raw fruit taste, no fermented bitterness, and no pungent alcohol smell. It can solve the common problems of conventional fruit rice wine such as "weak fruit aroma, strong wine taste, and disjointed flavor". Its flavor quality is significantly better than existing similar products.

[0024] ⑤ The process is replicable and the parameters are quantifiable, making it suitable for large-scale industrial production: The entire process of this invention adopts precise control of temperature, time, enzymatic hydrolysis parameters, clarification parameters, and extraction parameters. It does not rely on experience or use special equipment, resulting in high batch stability, low defect rate, and controllable cost. Attached Figure Description

[0025] Figure 1 The sensory evaluation results of the pomelo rice wine obtained in Example 1 are as follows; Figure 2 The sensory evaluation results of the pomelo rice wine obtained in Example 2 are as follows; Figure 3 The sensory evaluation results of the pomelo rice wine obtained in Example 3 are as follows; Figure 4 The sensory evaluation results of the pomelo yellow wine obtained in Comparative Example 1 are as follows; Figure 5 The sensory evaluation results of the pomelo yellow wine obtained in Comparative Example 2 are as follows; Figure 6 The sensory evaluation results of the pomelo yellow wine obtained in Comparative Example 3 are as follows; Figure 7 The sensory evaluation results of the pomelo yellow wine obtained in Comparative Example 4 are as follows; Figure 8 The sensory evaluation results of the pomelo wine obtained in Comparative Example 5 are as follows. Detailed Implementation

[0026] This invention provides a method for preparing a bitter-free, highly clear, and flavonoid-rich pomelo rice wine, comprising the following steps: The pomelo pulp was enzymatically hydrolyzed using cellulase and pectinase to obtain pomelo juice. The pomelo juice is mixed with rice wine, vitamin C and citric acid to obtain the blended wine. The blended liquor was subjected to oxygen-free extraction, and β-cyclodextrin was added to the resulting extract to encapsulate bitterness, thus obtaining a debittered liquor. The debittered wine liquid was subjected to clarification, freeze sedimentation and sterilization in sequence to obtain a bitter-free, highly clarified, and flavonoid-rich grapefruit wine.

[0027] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0028] This invention uses cellulase and pectinase to enzymatically hydrolyze pomelo pulp to obtain pomelo juice. Preferably, the pomelo pulp is prepared from pomelo through washing, peeling, seed removal, crushing, and pulping.

[0029] In this invention, the preferred mass of the cellulase is 0.05-0.2% of the pomelo pulp mass, more preferably 0.1-0.12%; the preferred mass of the pectinase is 0.08-0.25% of the pomelo pulp mass, more preferably 0.15-0.2%. In this invention, the enzymatic hydrolysis is preferably carried out under stirring conditions, with a stirring rate preferably 40-50 r / min, more preferably 45 r / min; the preferred temperature for enzymatic hydrolysis is 40-45℃, more preferably 42-44℃; the preferred time is 20-40 min, more preferably 30 min; and the preferred pH value is 3.5-4.5, more preferably 4.0. This invention, through low-speed stirring enzymatic hydrolysis, can efficiently degrade pectin and cellulose, significantly improve the dissolution rate of functional components such as pomelo flavonoids and polyphenols, and reduce the risk of subsequent turbidity and sedimentation in the wine. After enzymatic hydrolysis, this invention preferably inactivates the enzymes and filters the resulting pomelo juice, with the filtration preferably being coarse filtration.

[0030] This invention involves mixing pomelo juice with rice wine, vitamin C, and citric acid to obtain a blended liquor. The preparation method of the rice wine in this invention includes the following steps: The base spirit of rice wine is obtained by mixing rice wine base spirit with white wine base spirit.

[0031] In this invention, the alcohol content of the rice wine base is 10-15 vol%, preferably 12-14 vol%; the total sugar content is preferably 15-25 g / L, more preferably 18-20 g / L; the alcohol content of the baijiu base is preferably 40-53 vol%, more preferably 45-50 vol%, and the total sugar content is preferably 0.8-2.5 g / L, more preferably 1-2 g / L. In this invention, the volume ratio of the rice wine base to the baijiu base is preferably (2-4):(0-2), more preferably 2:1. When the amount of baijiu base is 0, it means that no baijiu base is added.

[0032] As a specific embodiment of the present invention, the preferred formulation of the rice wine is as follows: 2008 winter-brewed rice wine (12.5% ​​vol, total sugar 18.7 g / L), 2017 winter-brewed rice wine (12.8% vol, total sugar 17.4 g / L), and 2021 winter-brewed rice wine (14.5% vol, total sugar 20.7 g / L) are mixed in a volume ratio of 14:3:3 as the rice wine base wine, and a sauce-flavored baijiu (53% vol, total sugar 1.7 g / L) is used as the baijiu base wine, and the rice wine base wine and the baijiu base wine are mixed in a volume ratio of 2:1.

[0033] In this invention, the preferred mass of the pomelo juice is 8-15% of the total mass of the pomelo juice and rice wine, more preferably 10-12%; the preferred mass of the vitamin C is 0.05-0.1% of the total mass of the pomelo juice and rice wine, more preferably 0.06-0.08%; and the preferred mass of the citric acid is 0.05-0.1% of the total mass of the pomelo juice and rice wine, more preferably 0.06-0.08%. In this invention, the vitamin C and citric acid serve to protect the color. After obtaining the blended wine, this invention preferably stores it temporarily in an oxygen-free and light-protected environment to prevent browning and aroma loss.

[0034] The blended liquor is subjected to oxygen-free extraction. β-cyclodextrin is added to the resulting extract to encapsulate bitterness, yielding a debittered liquor. In this invention, the oxygen-free extraction is preferably carried out in a sealed tank, with nitrogen gas purging to replace air and create a slightly positive pressure oxygen-free environment, controlling the oxygen content to ≤2%. In this invention, the pressure of the slightly positive pressure is preferably 0.02~0.05 MPa, more preferably 0.03 MPa. In this invention, the oxygen-free extraction is preferably carried out under light-proof and stirring conditions. The stirring rate is preferably 30~60 r / min, more preferably 40~50 r / min; the temperature of the oxygen-free extraction is preferably 30~40℃, more preferably 35℃; and the time is preferably 60~120 min, more preferably 90 min. In this invention, the pH value of the oxygen-free extraction system is preferably 3.5~4.5, more preferably 4. This invention utilizes the aforementioned low-temperature oxygen-free extraction technology to accelerate the full and gentle dissolution of pomelo flavonoids, polyphenols, and aroma components, while avoiding the release of bitter substances and the degradation of heat-sensitive components.

[0035] In this invention, the mass of the β-cyclodextrin is preferably 0.2-0.5% of the mass of the extracted wine, more preferably 0.3-0.4%, and most preferably 0.35%. The bitterness encapsulation is preferably carried out under stirring conditions, the bitterness encapsulation temperature is preferably 30-40℃, more preferably 35℃, and the time is preferably 15-20 min, more preferably 16-18 min. This invention, by adding β-cyclodextrin for bitterness encapsulation, can selectively encapsulate bitter substances such as naringin and limonene, achieving debittering without loss of functional components and flavor, while not affecting subsequent filtration and clarification effects.

[0036] This invention controls the order of extraction in an oxygen-free environment before adding β-cyclodextrin. Extraction first facilitates the full release of active ingredients, and the low-temperature, oxygen-free environment gently opens the grapefruit cells, allowing flavonoids, polyphenols, and aroma compounds to dissolve to the maximum extent. If β-cyclodextrin is added first, it will immediately encapsulate a large number of components, hindering the dissolution of functional substances and leading to a significant decrease in flavonoid content. This invention uses a post-addition of cyclodextrin, encapsulating only bitterness, not active ingredients. This is because bitter substances (naringin, limonene) have low polarity and suitable molecular weight, making them most easily selectively encapsulated by β-cyclodextrin. Since beneficial components such as flavonoids, aroma compounds, and amino acids are fully dissolved during the extraction stage, they are not encapsulated in large quantities, achieving the effect of "removing bitterness without losing nutrition or flavor." Furthermore, this invention's method of extraction followed by the addition of β-cyclodextrin avoids premature complexation of cyclodextrin with pectin and protein, preventing filter blockage and ensuring light transmittance.

[0037] This invention involves sequentially clarifying, freezing, and sterilizing the debittered wine liquor to obtain a highly clarified, flavonoid-rich pomelo wine free of bitterness. In this invention, the clarification process preferably includes sequential chitosan flocculation, diatomaceous earth filtration, and ultrafiltration membrane filtration. The amount of chitosan added during chitosan flocculation is preferably 0.05-0.2% of the mass of the debittered wine liquor, more preferably 0.1%. The pH value during chitosan flocculation is preferably 3.5-4.5, more preferably 4. The chitosan flocculation process preferably includes sequential stirring and settling. The stirring time is preferably 20-30 minutes, more preferably 25 minutes, and the settling time is preferably 30-60 minutes, more preferably 40-50 minutes. This invention, through chitosan flocculation, enables the colloid and suspended particles to fully flocculate.

[0038] In this invention, the particle size of the diatomaceous earth is preferably 200-400 mesh, more preferably 300 mesh; the flow rate of the debittered liquor during diatomaceous earth filtration is preferably 80-150 L / h, more preferably 100 L / h. This invention, through diatomaceous earth filtration, can remove flocculated sediment and coarse particles.

[0039] In this invention, the pore size of the ultrafiltration membrane used for ultrafiltration is preferably 0.05~0.22μm, more preferably 0.1μm, and the circulation filtration time of the ultrafiltration membrane is preferably 5~10min, more preferably 6~8min. This invention, through a chitosan flocculation-diatomaceous earth filtration-ultrafiltration process, can thoroughly remove residual colloids, macromolecular proteins, and microorganisms. While fully preserving flavor substances, total flavonoids, polyphenols, amino acids, and other nutritional components, it significantly improves the clarity and storage stability of the wine, resulting in a clear, bright, and highly stable pomelo wine.

[0040] In this invention, the preferred temperature for freeze-drying is -4 to 0°C, and the preferred time is 7 to 14 days, more preferably 10 to 12 days. Through freeze-drying, this invention enables the full release of unstable substances and easily crystallizing components that are difficult to settle at room temperature, further improving shelf-life stability.

[0041] In this invention, the sterilization is preferably pasteurization, the sterilization temperature is preferably 75-80℃, and the sterilization time is preferably 15-20 minutes, more preferably 16-18 minutes. This invention, through a gentle sterilization method, can maximize the protection of heat-sensitive total flavonoids, vitamin C, limonene, polyphenols, and other functional components. After sterilization, this invention preferably involves aseptically filling the resulting pomelo rice wine into sterilized containers, sealing them, and storing them at 0-10℃ in the dark.

[0042] This invention provides a bitter-free, highly clear, and flavonoid-rich grapefruit wine prepared by the above-mentioned method.

[0043] In this invention, the preferred indicators for the bitter-free, highly clear, and flavonoid-rich pomelo rice wine include: alcohol content 13-15 vol%, total sugar 16-19 g / L, total acid 5.0-6.2 g / L, transmittance ≥95%, total flavonoids ≥300 mg / L, total polyphenols ≥0.35 mg / g, amino acid nitrogen ≥0.10 g / 100 mL, naringin 2.2-4.8 mg / L, limonene 0.7-1.5 mg / L, and fusel oil ≤0.03 g / 100 mL. The pomelo rice wine obtained by this invention exhibits no sedimentation, turbidity, or layering after 6 months at room temperature, with no bitterness or numbing sensation in the throat, a harmonious fruity aroma, and a fresh, clean, and mellow taste.

[0044] The following detailed description, in conjunction with embodiments, illustrates the bitter-free, highly clear, and flavonoid-rich pomelo wine and its preparation method provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1 1) Raw material preparation: Take 88L of glutinous rice wine base liquor with an alcohol content of 14% vol and a total sugar content of 18.5g / L, and fresh pomelo is washed, peeled, seeded, crushed and pulped to obtain pomelo pulp; Add 0.12% (w / w) cellulase and 0.15% (w / w) pectinase to pomelo pulp, adjust the pH of the system to 4.0, stir and enzymatically hydrolyze for 30 min at 42℃ and 45 r / min, and after enzyme inactivation, coarsely filter to obtain 12 L of pomelo juice. 2) Color protection and blending: Mix pomelo juice with rice wine base, add 0.08% vitamin C and 0.08% citric acid, and mix well; 3) Low-temperature oxygen-free extraction: The mixed wine is placed in a sealed blending tank, and nitrogen is introduced to replace the air in the tank until the oxygen content is ≤2%, forming a slightly positive pressure oxygen-free environment of 0.03 MPa. The mixture is stirred and extracted for 90 minutes under the conditions of avoiding light, 35℃, and 50r / min. 4) Synergistic debittering: Add 0.35% β-cyclodextrin to the extracted wine and continue stirring at low speed for 20 minutes to complete the selective encapsulation of bitter substances; 5) Three-stage clarification treatment: Add 0.10% chitosan to the wine, stir slowly for 25 minutes, and let stand for 45 minutes to complete flocculation; then filter with 300 mesh diatomaceous earth, controlling the filtration flow rate at 100 L / h; then circulate and filter with a 0.1 μm ultrafiltration membrane for 8 minutes to obtain clarified wine. 6) Freeze-sedimentation: Place the clarified wine at -4℃ and let it stand for 14 days; 7) Sterilization and filling: After pasteurization, the product is aseptically dispensed and stored at low temperature (0~4℃).

[0046] Performance testing (a) Sensory preference evaluation was conducted using a facial expression recognition device (with the consent of the volunteers and the test results were not used as commercial marketing data): 10-20 adult volunteers with wine experience were selected to taste the Huyou yellow wine in front of the facial expression recognition device camera. Each sample was repeated 2-3 times. After each tasting, the subjects were cleansed with room temperature mineral water and soda crackers. The camera was paused during the process to prevent residual emotions from interfering. After the tasting, the emotional intensity and subjective preference scores were extracted based on the recorded emotional information, and the results were output.

[0047] The sensory evaluation results of the pomelo rice wine obtained in Example 1 are as follows: Figure 1 As shown. By Figure 1 It can be seen that the sensory evaluation showed mainly happy expressions, indicating that drinking rice wine brings people a pleasant mood and has a high acceptance rate.

[0048] (II) Relevant indicator detection methods: (1) Determination of alcohol content Take 100.0 mL of rice wine sample (20℃) and distill it. The distillate is then diluted to volume in a 20℃ water bath. The mass of ultrapure water and distillate at 20℃ is determined using a constant density flask. The alcohol content (%vol) is calculated according to the method in GB 5009.225-2023.

[0049] (2) Determination of total sugar Take 10 mL of the rice wine sample into a 500 mL volumetric flask, add 50 mL of water and 5 mL of hydrochloric acid solution, and heat in a water bath at 68-70℃ for 15 min. After cooling, add methyl red indicator solution and neutralize with sodium hydroxide solution until the red color disappears. Add water to make up to volume, shake well, filter with filter paper, and set aside for later use. During the determination, use the sample hydrolysate instead of the glucose standard solution, record the volume of sample hydrolysate consumed, and calculate the total sugar content in the sample.

[0050] (3) Determination of organic acids Weigh 5.0 g of rice wine sample, add water to a final volume of 25 mL, filter through a 0.45 μm filter membrane, and inject directly. A hydrophilic column (250 mm × 4.0 mm, 5 μm) was used with a mobile phase of 0.1% phosphoric acid solution-methanol (97.5:2.5), a flow rate of 0.8 mL / min, a column temperature of 40℃, and detection at a wavelength of 210 nm. Qualitative analysis was performed by retention time, and quantification was performed using the external standard method. The organic acid content was calculated using the formula.

[0051] (4) Determination of total flavonoids Pipette 5–10 mL of rice wine sample into an Erlenmeyer flask, add 30 mL of anhydrous ethanol, and ultrasonically extract for 1 h (shaking well every 20 min). Dilute the extract to 50 mL with anhydrous ethanol. Take 1.0 mL of the diluted extract into a 50 mL volumetric flask, add 15 mL of anhydrous ethanol, 1 mL of aluminum nitrate solution (100 g / L), and 1 mL of potassium acetate solution (98 g / L), shake well, and dilute to volume. Let stand in the dark for 1 h. Using 30% ethanol solution as a blank, measure the absorbance at 420 nm. Calculate the total flavonoid content using the rutin standard curve.

[0052] (5) Determination of total polyphenols Take an appropriate amount of rice wine sample, add Folin-Ciocalteu reagent to the diluted sample, mix well, and react in the dark for 5 minutes. Then add sodium carbonate solution and react at room temperature in the dark for 60 minutes. Measure the absorbance at 760 nm. Calculate the total polyphenol content using the gallic acid standard curve.

[0053] (6) Measurement of transmittance The transmittance of rice wine was measured using a ColorFlex EZ color analyzer.

[0054] (7) Determination of fusel oil Distill 50.0 mL of rice wine sample, collecting 50 mL of colorless distillate. Pipette 1.0 mL of the distillate into a colorimetric tube, cool in an ice-water bath, and slowly add 2 mL of p-dimethylaminobenzaldehyde-sulfuric acid colorimetric reagent (5 g / L). Shake well and heat in a boiling water bath for 15 minutes to develop color, then immediately cool to room temperature. Using a fusel oil-free ethanol solution as a blank, measure the absorbance at 520 nm. Plot a standard curve using a mixed standard series of isobutanol-isoamyl alcohol for simultaneous color development, and calculate the fusel oil content using the standard curve.

[0055] (8) Determination of biogenic amines An appropriate amount of rice wine sample was taken, and dansyl chloride derivatizing reagent was added. Derivatization was performed in a 60℃ water bath for 15 minutes under alkaline conditions with saturated sodium bicarbonate. The reaction was terminated by adding monosodium glutamate. The sample was purified by ether extraction, concentrated by nitrogen blowing, redissolved in acetonitrile, and filtered through a 0.22 μm filter. Separation was performed using a C18 column with gradient elution using acetonitrile-ammonium acetate solution as the mobile phase, and detection was performed at 254 nm using a UV detector. Quantification was performed using 1,7-diaminoheptane as an internal standard via the internal standard method.

[0056] (9) Determination of naringin content (high performance liquid chromatography) Accurately pipette 5.0 mL of pomelo rice wine sample into a 10 mL centrifuge tube, add 5.0 mL of anhydrous ethanol, and vortex to mix for 2 min; centrifuge at 8000 r / min for 10 min, and filter the supernatant through a 0.45 μm organic phase filter membrane for injection; chromatographic conditions: use a C18 column (4.6 mm × 250 mm, 5 μm), mobile phase acetonitrile:water = 22:78 (V / V), flow rate 1.0 mL / min, detection wavelength 283 nm, column temperature 30 ℃, injection volume 20 μL; calculate the naringin content in the sample using the external standard method, in mg / L.

[0057] (10) Determination of limonene content (high performance liquid chromatography) Accurately pipette 10.0 mL of the pomelo wine sample into a separatory funnel, extract with 10 mL of ethyl acetate, shake for 5 min, allow to stand and separate into layers, and collect the organic phase; repeat the extraction twice, and combine all organic phases; concentrate to dryness under reduced pressure at 45℃, dissolve the residue with acetonitrile:water = 45:55 (V / V) solution and make up to 5 mL, filter through a 0.45 μm organic phase filter membrane, and prepare for injection; chromatographic conditions: use a C18 column (4.6 mm × 250 mm, 5 μm), mobile phase is acetonitrile:water = 45:55 (V / V), flow rate is 1.0 mL / min, detection wavelength is 210 nm, column temperature is 30℃, and injection volume is 20 μL; calculate the limonene content in the sample using the external standard method, in mg / L.

[0058] (11) Determination of DPPH free radical scavenging rate Accurately weigh 10 mg of DPPH reagent, dissolve it in anhydrous ethanol, and dilute to 250 mL to obtain a 0.04 mg / mL DPPH working solution. Store in the dark for later use. Accurately pipette 2.0 mL of the rice wine sample solution into a test tube, add 2.0 mL of the DPPH working solution, vortex to mix, and react at room temperature in the dark for 30 min. Measure the absorbance A1 at 517 nm. Simultaneously, prepare a blank group: 2.0 mL of sample solution + 2.0 mL of anhydrous ethanol, and measure the absorbance A2. Prepare a control group: 2.0 mL of DPPH working solution + 2.0 mL of anhydrous ethanol, and measure the absorbance A0. Calculate the scavenging rate using the formula: DPPH free radical scavenging rate (%) = [A0 - (A1 - A2)] ÷ A0 × 100%.

[0059] (12) Determination of ABTS free radical scavenging rate Mix equal volumes of 7 mmol / L ABTS solution and 2.45 mmol / L potassium persulfate solution, and let stand in the dark for 12–16 h to obtain ABTS stock solution. Dilute the stock solution with anhydrous ethanol until the absorbance at 734 nm is 0.70 ± 0.02, which is the ABTS working solution. Accurately pipette 0.2 mL of sample solution, add 2.0 mL of ABTS working solution, vortex to mix, and react at room temperature in the dark for 6 min. Measure the absorbance A1 at 734 nm. Blank group: 0.2 mL of sample solution + 2.0 mL of anhydrous ethanol, measure the absorbance A2. Control group: 2.0 mL of ABTS working solution + 0.2 mL of anhydrous ethanol, measure the absorbance A0. Calculate the scavenging rate using the formula: ABTS free radical scavenging rate (%) = [A0 - (A1 - A2)] ÷ A0 × 100%.

[0060] (13) Total antioxidant capacity (T-AOC) determination (Fe 3+ (Reduction method) Accurately pipette 0.2 mL of rice wine sample, add 3.0 mL of total antioxidant test reagent, vortex to mix; place in a 37℃ constant temperature water bath for 30 min, remove and cool to room temperature; measure the absorbance value at a wavelength of 520 nm; prepare a standard curve using Trolox standard, calculate the total antioxidant capacity of the sample based on the absorbance, and express the result as U / mL.

[0061] According to the test results, the original naringin content of the pomelo juice in Example 1 was 42.6 mg / L, and the naringin content of the finished pomelo rice wine was 3.6 mg / L; the original limonene content of the pomelo juice was 16.8 mg / L, and the limonene content of the finished pomelo rice wine was 1.1 mg / L.

[0062] The resulting pomelo-flavored rice wine exhibited a DPPH free radical scavenging rate of 82.7%, an ABTS free radical scavenging rate of 78.3%, and a total antioxidant capacity (T-AOC) of 16.8 U / mL. It had an alcohol content of 13.8% vol, total sugar of 17.5 g / L, total acid of 5.84 g / L, transmittance of 96.2%, total flavonoids of 312 mg / L, total polyphenols of 0.394 mg / g, fusel oil of 0.027 g / 100 mL, and biogenic amines of 3.7 mg / L. The resulting pomelo-flavored rice wine was free of bitterness and sediment, possessed a harmonious fruity aroma, and had a smooth taste. Therefore, the rice wine prepared by the method of this invention not only provides a pleasant drinking experience but also boasts rich nutritional components, with relatively high levels of total polyphenols and total flavonoids, and low levels of fusel oil and biogenic amines. This indicates that the rice wine not only has an excellent taste and is easily welcomed by consumers but also possesses good health benefits.

[0063] Example 2 The difference from Example 1 is that the amount of glutinous rice wine base liquor used is 92L, and the amount of pomelo juice used is 8L, while the rest of the operation is the same.

[0064] The sensory evaluation results of the pomelo rice wine obtained in Example 2 are as follows: Figure 2 As shown. By Figure 2 It can be seen that sensory evaluations were mainly characterized by happy and neutral expressions.

[0065] According to the test results, the original naringin content of the grapefruit juice in Example 2 was 42.6 mg / L, and the naringin content of the finished grapefruit rice wine was 2.2 mg / L; the original limonene content of the grapefruit juice was 16.8 mg / L, and the limonene content of the finished grapefruit rice wine was 0.7 mg / L.

[0066] The resulting pomelo wine exhibited a DPPH free radical scavenging rate of 71.4%, an ABTS free radical scavenging rate of 66.8%, a total antioxidant capacity (T-AOC) of 12.3 U / mL, a light transmittance of 97.1%, a total flavonoid content of 315 mg / L, a very mild bitterness, a mellow flavor, and excellent stability.

[0067] Example 3 The difference from Example 1 is that the amount of glutinous rice wine base liquor used is 85L and pomelo juice is 15L, while the rest of the operation is the same.

[0068] The sensory evaluation results of the pomelo rice wine obtained in Example 3 are as follows: Figure 3 As shown. By Figure 3 It can be seen that sensory evaluations were mainly based on happy expressions.

[0069] According to the test results, the original naringin content of the grapefruit juice in Example 3 was 42.6 mg / L, and the naringin content of the finished grapefruit rice wine was 4.8 mg / L; the original limonene content of the grapefruit juice was 16.8 mg / L, and the limonene content of the finished grapefruit rice wine was 1.5 mg / L.

[0070] The resulting pomelo wine exhibited a DPPH free radical scavenging rate of 87.9%, an ABTS free radical scavenging rate of 83.6%, a total antioxidant capacity (T-AOC) of 19.2 U / mL, a light transmittance of 96.8%, a total flavonoid content of 368 mg / L, a rich fruity aroma, no bitterness, and no turbidity or precipitation during its shelf life.

[0071] Comparative Example 1 Compared with Example 1, the conditions for oxygen-free extraction were changed to: extraction at 55°C under normal pressure and open environment, and extraction time of 90 min.

[0072] The sensory evaluation results of the pomelo rice wine obtained in Comparative Example 1 are as follows: Figure 4 As shown. By Figure 4 It can be seen that the sensory evaluations showed feelings of anger and disgust.

[0073] Tests showed that the original naringin content of the grapefruit juice in Comparative Example 1 was 42.6 mg / L, while the naringin content of the finished grapefruit rice wine was 9.7 mg / L; the original limonin content of the grapefruit juice was 16.8 mg / L, while the limonin content of the finished grapefruit rice wine was 3.8 mg / L.

[0074] The resulting pomelo rice wine had a DPPH free radical scavenging rate of 51.2%, an ABTS free radical scavenging rate of 46.7%, and a total antioxidant capacity (T-AOC) of 7.6 U / mL. The total flavonoid retention rate was only 62%, with significant aroma loss and a slightly astringent taste, highlighting the necessity of low-temperature oxygen isolation.

[0075] Comparative Example 2 In comparison with the traditional soaking method in existing technology, the method is as follows: Take 88L of glutinous rice wine base liquor with an alcohol content of 14% vol and a total sugar content of 18.5g / L, add 12kg of fresh pomelo slices, soak at room temperature for 7 days, and then filter and bottle the resulting liquor.

[0076] The sensory evaluation results of the pomelo rice wine obtained in Comparative Example 2 are as follows: Figure 5 As shown. By Figure 5 It can be seen that sensory evaluations are mainly based on anger, sadness, and disgust.

[0077] Tests showed that the pomelo wine obtained in Comparative Example 2 was bitter and astringent, had a numbing effect on the throat, was cloudy, and developed sediment after 2 weeks; the total flavonoids were only 110 mg / L; the fusel oil content was 0.156 g / 100 mL, and the biogenic amine content was 12.3 mg / L; the original naringin content in the pomelo juice was 42.6 mg / L, and the finished product naringin content was 31.6 mg / L; the original limonene content in the pomelo juice was 16.8 mg / L, and the finished product limonene content was 10.2 mg / L; the DPPH free radical scavenging rate was 28.5%, the ABTS free radical scavenging rate was 24.3%, and the total antioxidant capacity (T-AOC) was 3.2 U / mL.

[0078] Comparative Example 3 Based on Example 1, step 4) of synergistic debittering is omitted.

[0079] The sensory evaluation results of the pomelo rice wine obtained in Comparative Example 3 are as follows: Figure 6 As shown. By Figure 6 It can be seen that the sensory evaluation of facial expression recognition is biased towards the negative.

[0080] Tests showed that the pomelo rice wine obtained in Comparative Example 3 had a noticeably bitter taste upon entry and a heavy aftertaste, making it unsuitable for commercialization; the original naringin content of the pomelo juice was 42.6 mg / L, while the finished product had a naringin content of 22.7 mg / L; the original limonene content of the pomelo juice was 16.8 mg / L, while the finished product had a limonene content of 7.8 mg / L; the DPPH free radical scavenging rate was 47.8%, the ABTS free radical scavenging rate was 42.6%, the total antioxidant capacity (T-AOC) was 7.1 U / mL; the light transmittance was 88.6%, and the total flavonoids were 286 mg / L.

[0081] Comparative Example 4 Based on Example 1, step 6) freezing and settling is omitted.

[0082] The sensory evaluation results of the pomelo rice wine obtained in Comparative Example 4 are as follows: Figure 7 As shown. By Figure 7 It can be seen that the sensory evaluation of facial expression recognition is biased towards the negative.

[0083] Tests showed that the pomelo rice wine obtained in Comparative Example 4 exhibited flocculent precipitation after 3-4 months, indicating poor stability; the original naringin content in the pomelo juice was 42.6 mg / L, while the finished product contained 4.1 mg / L; the original limonene content in the pomelo juice was 16.8 mg / L, while the finished product contained 1.3 mg / L; the DPPH free radical scavenging rate was 80.2%, the ABTS free radical scavenging rate was 75.4%, the total antioxidant capacity (T-AOC) was 15.6 U / mL; the light transmittance was 91.7%, and the total flavonoids were 308 mg / L.

[0084] Comparative Example 5 Based on Example 1, the ultrafiltration membrane circulation filtration step in step 5) is omitted.

[0085] The sensory evaluation results of the pomelo rice wine obtained in Comparative Example 5 are as follows: Figure 8 As shown. By Figure 8 It can be seen that the sensory evaluation of facial expression recognition is biased towards the negative.

[0086] Tests showed that the grapefruit rice wine obtained in Comparative Example 5 was not clear and was prone to cloudiness; the original naringin content of the grapefruit juice was 42.6 mg / L, and the finished product naringin content was 5.2 mg / L; the original limonene content of the grapefruit juice was 16.8 mg / L, and the finished product limonene content was 1.6 mg / L; the DPPH free radical scavenging rate was 78.3%, the ABTS free radical scavenging rate was 73.2%, the total antioxidant capacity (T-AOC) was 14.2 U / mL; the light transmittance was 78.5%, and the total flavonoids were 295 mg / L.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a bitter-free, highly clear, and flavonoid-rich grapefruit rice wine, characterized in that, Includes the following steps: The pomelo pulp was enzymatically hydrolyzed using cellulase and pectinase to obtain pomelo juice. The pomelo juice is mixed with rice wine, vitamin C and citric acid to obtain the blended wine. The blended liquor was subjected to oxygen-free extraction, and β-cyclodextrin was added to the resulting extract to encapsulate bitterness, thus obtaining a debittered liquor. The debittered wine liquid was subjected to clarification, freeze sedimentation and sterilization in sequence to obtain a bitter-free, highly clarified, and flavonoid-rich grapefruit wine.

2. The preparation method according to claim 1, characterized in that, The method for preparing the rice wine includes the following steps: The base spirit of rice wine and the base spirit of white wine are mixed to obtain the rice wine body; The alcohol content of the rice wine base is 10-15 vol%, and the total sugar content is 15-25 g / L; the alcohol content of the baijiu base is 40-53 vol%, and the total sugar content is 0.8-2.5 g / L; the volume ratio of the rice wine base to the baijiu base is (2-4):(0-2).

3. The preparation method according to claim 1, characterized in that, The mass of the cellulase is 0.05-0.2% of the mass of the pomelo pulp; the mass of the pectinase is 0.08-0.25% of the mass of the pomelo pulp. The enzymatic hydrolysis was performed at a temperature of 40-45°C for 20-40 minutes, with a pH value of 3.5-4.

5.

4. The preparation method according to claim 1 or 3, characterized in that, The mass of the pomelo juice is 8-15% of the total mass of the pomelo juice and rice wine; the mass of the vitamin C is 0.05-0.1% of the total mass of the pomelo juice and rice wine; and the mass of the citric acid is 0.05-0.1% of the total mass of the pomelo juice and rice wine.

5. The preparation method according to claim 1, characterized in that, The oxygen content in the oxygen-free extraction environment is ≤2%; the temperature of the oxygen-free extraction is 30~40℃, and the time is 60~120min.

6. The preparation method according to claim 1 or 5, characterized in that, The mass of the β-cyclodextrin is 0.2-0.5% of the mass of the extract; the bitterness encapsulation time is 15-20 min.

7. The preparation method according to claim 1, characterized in that, The clarification process includes sequential chitosan flocculation, diatomaceous earth filtration, and ultrafiltration membrane filtration.

8. The preparation method according to claim 1 or 7, characterized in that, The freezing and settling temperature is -4 to 0°C, and the time is 7 to 14 days; The sterilization is pasteurization, and the sterilization temperature is 75~80℃, and the time is 15~20min.

9. The bitter-free, highly clear, and high-flavonoid pomelo wine prepared by the preparation method according to any one of claims 1 to 8.

10. The bitter-free, highly clear, and flavonoid-rich pomelo rice wine according to claim 9, characterized in that, The specifications for the bitter-free, highly clear, and flavonoid-rich pomelo wine include: alcohol content 13-15 vol%, total sugar 16-19 g / L, total acid 5.0-6.2 g / L, light transmittance ≥95%, total flavonoids ≥300 mg / L, total polyphenols ≥0.35 mg / g, amino acid nitrogen ≥0.10 g / 100 mL, naringin 2.2-4.8 mg / L, limonene 0.7-1.5 mg / L, and fusel oil ≤0.03 g / 100 mL.

Images