A method for preparing a sparkling wine of the pear variety

Abstract

The application discloses a preparation method of a sparkling wine of fragrant pear, and relates to the field of fruit wine brewing. The preparation method comprises the following steps: fruit juice is subjected to ultrasonic-composite enzyme synergistic pretreatment, two-stage time sequence differentiation ultrasonic fermentation, addition of immobilized beta-glucosidase in the later fermentation period, and extraction of a base wine from fruit residue to refill an aroma, so that the sparkling wine is prepared. The process can controllably release a fragrant pear bonding state aroma precursor, improve the content of ester substances, shorten the fermentation period, and stabilize the bubbles by relying on the autolysis of yeast to generate mannose proteins, without adding chemical stabilizers, so that the finished product is full of fruit aroma and has long-lasting effervescence.

Description

Technical Field

[0001] This invention belongs to the field of fruit wine brewing and bioprocessing technology, specifically relating to a method for preparing pear sparkling wine. Background Technology

[0002] As a new type of alcoholic beverage, pear sparkling wine is characterized by its refreshing taste, low alcohol content, and rich fruit aroma, and is becoming increasingly popular among young consumers.

[0003] Currently, sparkling pear wine is mainly produced through tank fermentation. Fresh pears are first pressed and clarified at low temperature to obtain clear juice. This juice is then fermented at a controlled temperature in a stainless steel tank to produce a dry fruit wine base. After adjusting the composition of the base wine, selected yeast and sugar solution are added, and the wine is transferred to a sealed high-pressure fermentation tank for a second fermentation at 8~16℃ and 0.5~0.7MPa, allowing carbon dioxide to fully dissolve in the liquid. Once the target alcohol content and pressure are reached, fermentation is terminated at low temperature (0~4℃) under pressure to stabilize the quality of the wine. After pressure filtration, sediment removal, and flavoring (liquid replenishment), the wine is aseptically bottled under isobaric conditions to quickly obtain sparkling pear wine.

[0004] However, sparkling pear wine faces several technical challenges during tank fermentation, including insufficient aroma, a single aroma profile, a lack of complexity, low fermentation efficiency, and poor bubble stability. Summary of the Invention

[0005] This invention provides a method for preparing sparkling wine made from fragrant pears. By combining two-stage differentiated fermentation with ultrasonic time-series treatment, the secondary fermentation cycle is shortened from 39 days to 30 days, a reduction of 23.08%. By using the natural aroma backfilling technology of fragrant pear pomace, the total ester content in the sparkling wine is increased by 105.6% compared with the conventional process (Comparative Example 1).

[0006] This invention provides a method for preparing pear sparkling wine, specifically including the following steps:

[0007] (1) Raw material pretreatment: Select ripe pears, wash, crush, juice, coarsely filter, adjust the sugar content to 16-18 °Brix, adjust the pH to 3.2~3.5 to obtain pretreated pear juice; (2) Ultrasonic-complex enzyme synergistic treatment: The pretreated pear juice obtained above is first subjected to ultrasonic treatment, and then enzymatic hydrolysis is carried out by adding complex enzymes in steps. First, β-glucosidase is added for preliminary enzymatic hydrolysis, and then esterase and protease are added for further enzymatic hydrolysis. After the enzymatic hydrolysis is completed, the enzymes are inactivated and cooled to obtain enzymatically hydrolyzed pear juice. (3) Two-stage fermentation: First stage fermentation: Inoculate the enzymatically hydrolyzed pear juice obtained in step (2) above with brewing yeast for open fermentation, filter and let stand to obtain base wine; Second stage fermentation: Champagne yeast was inoculated into the base wine obtained above, and the wine was sealed and fermented under a pressure of 5-6 bar. Differential ultrasonic-assisted treatment was performed twice on the 7th and 21st days of the sealed fermentation. Immobilized β-glucosidase was added on the 21st day. Fermentation was terminated when the residual sugar content was ≤2.0 g / L and the pressure remained constant. The initial sparkling wine was obtained by filtration. (4) Aroma backfilling: Collect the pomace obtained from coarse filtration in step (1) and the pomace separated after filtration in the two-stage fermentation process in step (3), dry and pulverize to obtain pomace powder; use the base wine obtained in step (3) as the extraction solvent to perform ultrasonic-assisted extraction on the pomace powder to obtain an extract; concentrate the extract under reduced pressure to obtain a natural aroma backfill liquid for pear pomace; add the aroma backfill liquid to the initial product of sparkling wine, and let it stand under a pressure of 0.4~0.5 bar to obtain sparkling wine after aroma backfilling; (5) Post-processing: After the aroma is backfilled, the sparkling wine is refrigerated and left to stand for 14 to 16 days under a pressure of 0.4 to 0.5 bar and a temperature of 4°C. It is then filtered through diatomaceous earth and then through a ceramic membrane before being pasteurized to obtain pear sparkling wine.

[0008] Further, the conditions for ultrasonic treatment in step (2) are a frequency of 40kHz, a power of 150~180W, a temperature of 25~28℃, and a time of 5~7min.

[0009] Furthermore, the particle size of the pear cell wall fragments generated after the above ultrasonic treatment is controlled within the range of 50-100μm.

[0010] Furthermore, the specific conditions for the two differentiated ultrasound-assisted treatments on day 7 and day 21 in step (3) are as follows: the ultrasound treatment conditions on day 7 are a frequency of 40kHz, a power of 150~180W, and a time of 3~5 min; the ultrasound treatment conditions on day 21 are a frequency of 40kHz, a power of 120~150W, and a time of 5~8 min.

[0011] Furthermore, in step (3), the amount of immobilized β-glucosidase added during the second stage of fermentation is 500~600 U / mL.

[0012] Furthermore, in step (3), the inoculation amount of brewing yeast in the first stage of fermentation is 1×10⁻⁶. 6 ~1.2×10 6 CFU / mL; the open fermentation conditions are a temperature of 20~22℃, a pH of 3.2~3.5, and a time of 7~10 days; the static setting temperature is 4℃ and the time is 20~24 h.

[0013] Furthermore, in step (3), before inoculating the base wine with Champagne yeast during the second stage of fermentation, sugar needs to be added to adjust the sugar content of the base wine to 20~22 °Brix; the inoculation amount of the Champagne yeast is 0.5×10 6 ~0.6×10 6 CFU / mL; the fermentation conditions for the sealed fermentation are a temperature of 14~16℃ and a pH of 3.0~3.2.

[0014] Further, the cleaning in step (1) is a three-stage cleaning process, specifically rinsing with clean water 3-5 times, soaking in 0.1% sterile saline solution for 10 minutes, rinsing with sterile distilled water twice, and draining the surface water; the particle size of the crushing is 3-5 mm, and 0.05-0.1% sodium isoascorbate is added after crushing; the coarse filtration is to pass the juice obtained by juicing through a 150-200 mesh filter; the pH adjuster includes citric acid, malic acid, tartaric acid, and lactic acid.

[0015] Further, in step (2), the enzyme activity of β-glucosidase is ≥10000 U / mL, and the addition amount is 0.05~0.06%; the enzyme activity of esterase is ≥5000 U / mL, and the addition amount is 0.03~0.04%; the enzyme activity of protease is ≥8000 U / mL, and the addition amount is 0.02-0.03%; the enzymatic hydrolysis temperature is 25~28℃, and the time is 60~80min; the enzyme inactivation temperature is 85~90℃, and the time is 8~10min; the cooling refers to cooling the juice after enzyme inactivation to below 25℃.

[0016] Further, the drying and pulverizing in step (4) specifically involves drying the fruit pomace at 60°C until the moisture content is ≤10%, and then pulverizing it through a 40-mesh sieve; the amount of base wine added is based on a material-liquid ratio of 1:3 to 1:5 (g:mL) between the mass of the fruit pomace powder and the volume of the base wine; the temperature of the ultrasonic-assisted extraction is 50°C and the frequency is 40KHz; the extraction liquid filtration refers to filtration through a 350-450 mesh filter; the temperature of the vacuum concentration is 50°C and the pressure is 0.08MPa, with the concentration endpoint being 1 / 10 to 1 / 8 of the original volume of the extraction liquid; the amount of aroma backfill liquid added is 0.5-1.0% (v / v) of the sparkling wine obtained from the second stage fermentation; the settling time is 20-24 h and the temperature is 14-16°C; Furthermore, the precision of the diatomaceous earth filtration in step (5) is 5 μm; the pore size of the ceramic membrane filtration is 0.22 μm; and the pasteurization is specifically carried out at a temperature of 65~68℃ for a time of 25~30 min.

[0017] Furthermore, the above pasteurization process requires slow heating and cooling, with both heating and cooling rates at 1°C / min, to avoid sudden temperature increases or decreases that could alter the flavor of the wine and cause bubbles to burst.

[0018] The aforementioned differentiated ultrasound refers to two ultrasound sessions using different combinations of power and duration, adapted to the two fermentation stages of yeast proliferation and yeast autolysis, respectively.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes a synergistic pretreatment of ultrasound and a compound enzyme to break down the residual intact pulp cells and lignified cell wall fragments in the juice after juicing using the cavitation effect of ultrasound. This process releases bonded aroma precursors. The median particle size D50 of the pulp cell wall fragments is controlled at 68 μm, the particle size distribution D10~D90 is 25~105 μm, and the main particles are concentrated in the 50~100 μm range. The cell wall breakage rate of the pear reaches more than 88.4%, the total ester content increases from 8920 μg / L to 20150 μg / L, an increase of 125.9%, and the content of bitter polyphenols is reduced.

[0020] 2. This invention, by adding immobilized β-glucosidase on day 21 of the second stage of fermentation, works synergistically with the microjet generated by ultrasound to enable the enzyme to continuously hydrolyze bound aroma glycosides in the later stages of fermentation. The total ester content reaches 20150 μg / L, which is 32.6% higher than that of Comparative Example 4 (15200 μg / L) without immobilized enzyme, and the aroma complexity score is improved by 33.8%. This solves the problems of insufficient aroma release and monotonous aroma in existing processes.

[0021] 3. This invention combines sequential ultrasonic treatment during the two-stage fermentation process. On day 7, ultrasonic waves with a frequency of 40kHz, power of 150-180W, and a treatment time of 3-5 minutes are used. These ultrasonic energy parameters only cause a reversible increase in the permeability of the yeast cell membrane without causing cell rupture, thereby promoting transmembrane sugar transport, accelerating ethanol metabolism and CO2 generation, and increasing the CO2 production rate by 97.9%. On day 21, ultrasound promotes yeast autolysis, increasing the release of mannoproteins by 85.7%. The synergistic effect of these two stages shortens the secondary fermentation cycle from 39 days to 30 days, a reduction of 23.08%. This solves the problem of inhibited yeast activity and long fermentation cycles in pears grown under high sugar and low acid conditions.

[0022] 4. This invention induces programmed micro-damage to the yeast cell wall using ultrasound on day 21 of the two-stage fermentation process, controlling the release of mannoproteins (molecular weight 50-200 kDa, concentration up to 312 mg / L). These mannoproteins are amphiphilic, adsorbing onto the surface of CO2 bubbles to form a stable film, reducing the bubble surface tension from 72 mN / m to 46 mN / m and extending the bubble duration from 22 min to 58 min (a 164% increase). Simultaneously, the combined post-treatment process of "constant pressure + staged filtration + gentle sterilization + pressure bottling" further ensures the uniformity and fineness of the bubbles. No chemical stabilizers are required throughout the entire process.

[0023] 5. This invention uses the base wine obtained from the first stage of fermentation as the extraction solvent to perform ultrasonic-assisted extraction on the pear pomace. After vacuum concentration, a high-concentration aroma backfill liquid is obtained. Compared with 70% ethanol, the total ester content is increased from 19610 μg / L to 20150 μg / L, an increase of 540 μg / L, and there is no off-flavor of exogenous alcohol. At the same time, 100% resource utilization of pomace is achieved. Attached Figure Description

[0024] Figure 1 The images show a comparison of the appearance of the pear sparkling wine of Example 1 and Comparative Example 1, where (A) is the finished pear sparkling wine prepared in Example 1, (B) is the finished pear sparkling wine prepared in Comparative Example 1, and (C) is the effervescent state of the pear sparkling wine of Example 1. Detailed Implementation

[0025] The following embodiments are merely illustrative of the present invention and do not limit the scope of protection of the present invention in any way. For those skilled in the art, all equivalent implementations or modifications made without departing from the spirit of the present invention are within the scope of protection of the present invention.

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments.

[0027] Example 1 (1) Raw material pretreatment: Select Korla fragrant pears with a maturity of 90% and a single fruit weight of 150g, remove rotten, diseased, damaged, immature and overripe fruits; rinse 3 times with running water, soak in 0.1% sterile saline for 10 min, rinse 2 times with sterile distilled water, and drain the surface water; crush the fruit pulp to a particle size of 4mm, add 0.05% sodium isoascorbate for color protection; juice the fruit pulp, collect the juice and pomace separately, refrigerate the pomace at 4℃ for later use, filter the juice through 200 mesh, add sugar to the juice to 18 °Brix, and adjust the pH to 3.4.

[0028] (2) Ultrasonic-compound enzyme synergistic treatment: The juice was ultrasonically treated at 40kHz, 180W, and 28℃ for 7 min. 0.06% of β-glucosidase with an enzyme activity of 11000U / mL was added to the juice by mass ratio and stirred evenly. Then, 0.04% of esterase with an enzyme activity of 5000U / mL and 0.03% of protease with an enzyme activity of 8200U / mL were added to the juice by mass ratio. The juice after adding the enzyme preparation was kept at 28℃ for 70 min for enzymatic hydrolysis. Then, the juice was heated to 88℃ for 10 min to inactivate the enzyme and completely terminate the enzyme activity. The juice was then rapidly cooled to 25℃.

[0029] (3) Two-stage fermentation: First stage fermentation: Inoculate the enzymatically hydrolyzed juice with 1.2 × 10⁻⁶ Uvaferm 43 Saccharomyces cerevisiae. 6 Fermentation was carried out in an open environment for 8 days at CFU / mL, temperature 22℃, and pH 3.2 until the sugar content reached 1.2 °Brix and the alcohol content reached 11.8% v / v. The mixture was then filtered through a 300-mesh sterile filter and allowed to stand at 4℃ for 24 hours to obtain the base wine.

[0030] Second stage fermentation: The base wine is transferred to a high-pressure fermentation tank. The base wine is then supplemented with sugar to 22° Brix and inoculated with 0.6 x 10⁶ Champagne yeasts. 6 Fermentation was carried out under sealed conditions at 15℃, pH 3.0, and 5.5 bar. Fermentation was terminated when the residual sugar content was ≤2.0 g / L and the CO2 pressure remained constant. On day 7, the mixture was ultrasonically treated at 40kHz and 180W for 5 min, and on day 21, it was ultrasonically treated at 40kHz and 150W for 8 min. Simultaneously, immobilized β-glucosidase at 600 U / mL was added on day 21. After termination, the mixture was filtered to obtain the initial sparkling wine.

[0031] (4) Aroma Refilling: Collect the pomace from the first stage of juicing and the pomace separated after the second stage of fermentation, dry it at 60℃ until the moisture content is 10%, and pulverize it through a 40-mesh sieve to obtain pomace powder. Use the base wine obtained from the first stage of fermentation as a solvent to extract aroma substances from the pomace powder at a material-to-liquid ratio of 1:3 (g:mL). The extraction process is controlled at 50℃, and ultrasonic extraction is used at 40kHz for 35 minutes to fully dissolve the aroma active ingredients. After extraction, the resulting extract is filtered through a 400-mesh filter and transferred to a rotary evaporator. It is concentrated under reduced pressure at 50℃ and 0.08MPa to 1 / 10 of the original volume to obtain the natural aroma refill liquid of pear pomace. Add it back to the initial product of sparkling wine at a volume ratio of 0.8%, adjust the pressure to 0.45 bar, and let it stand at 15℃ for 24 h.

[0032] (5) Post-treatment: After aroma refilling, the sparkling wine is left to stand at 4℃ and 0.45 bar for 15 days; it is first filtered through diatomaceous earth with a filtration precision of 5μm to remove small sediments and impurities, and then filtered through a 0.22 μm ceramic membrane to remove small particles, residual yeast cells, and microorganisms. The graded and filtered sparkling wine is then pasteurized at 66℃ for 28 min, with the heating and cooling rate maintained at 1℃ / min, to obtain the sparkling wine (the sparkling wine state is as follows). Figure 1 (As shown). The sparkling wine was cooled to 10°C, isobarically bottled at 0.55 bar, sealed, and stored at 4°C. The resulting pasteurized wine... Example 2 (1) Raw material pretreatment: Select Korla fragrant pears with a maturity of 90% and a single fruit weight of 120g, remove rotten, diseased, pest-damaged, mechanically damaged, immature and overripe fruits; rinse 3 times with running water, soak in 0.1% sterile saline for 10 min, rinse 2 times with sterile distilled water, and drain the surface water; crush the fruit pulp to a particle size of 3 mm, add 0.05% sodium isoascorbate for color protection; juice the fruit pulp, collect the juice and pomace separately, refrigerate the pomace at 4℃ for later use, filter the juice through 200 mesh, add sugar to the juice to 16 °Brix, and adjust the pH to 3.2.

[0033] (2) Ultrasonic-compound enzyme synergistic treatment: The juice was ultrasonically treated at 40kHz, 150W, and 25℃ for 5 min. 0.05% of β-glucosidase with an enzyme activity of 12000U / mL was added to the juice by mass ratio and stirred evenly. Then, 0.03% of esterase with an enzyme activity of 5100U / mL and 0.02% of protease with an enzyme activity of 8000U / mL were added to the juice by mass ratio. The juice after adding the enzyme preparation was kept at 25℃ for 60 min for enzymatic hydrolysis. Then, the juice was heated to 85℃ for 8 min to inactivate the enzyme and completely terminate the enzyme activity. The juice was then rapidly cooled to 24℃.

[0034] (3) Two-stage fermentation: First stage fermentation: Inoculate the enzymatically hydrolyzed juice with 1.0 × 10⁻⁶ Uvaferm 43 Saccharomyces cerevisiae. 6 Fermentation was carried out in an open environment for 7 days at CFU / mL, 20℃, and pH 3.2 until the sugar content reached 1.5 °Brix and the alcohol content reached 11.5% v / v. The mixture was then filtered through a 300-mesh sterile filter and allowed to stand at 4℃ for 24 hours to obtain the base wine.

[0035] Second stage fermentation: The base wine is transferred to a high-pressure fermentation tank. The base wine is then supplemented with sugar to 20° Brix and inoculated with 0.5 x 10g of Champagne yeast. 6Fermentation was carried out under sealed conditions at 14℃, pH 3.0, and 5 bar. Fermentation was terminated when the residual sugar content was ≤2.0 g / L and the CO2 pressure remained constant. On day 7, the mixture was ultrasonically treated for 3 min at 40 kHz and 150 W, and on day 21, it was ultrasonically treated for 5 min at 40 kHz and 120 W. Simultaneously, 500 U / mL of immobilized β-glucosidase was added on day 21. After termination, the mixture was filtered to obtain the initial sparkling wine.

[0036] (4) Aroma Refilling: Collect the pomace from the first stage of juicing and the pomace separated after the second stage of fermentation, dry it at 60℃ until the moisture content is 10%, and pulverize it through a 40-mesh sieve to obtain pomace powder. Use the base wine obtained from the first stage of fermentation as a solvent to extract aroma substances from the pomace powder at a material-to-liquid ratio of 1:3 (g:mL). The extraction process is controlled at 50℃, and ultrasonic extraction is used at 40kHz for 30 minutes to fully dissolve the aroma active ingredients. After extraction, the resulting extract is filtered through a 400-mesh filter and transferred to a rotary evaporator. It is concentrated under reduced pressure at 50℃ and 0.08MPa to 1 / 8 of the original volume to obtain the natural aroma refill liquid of pear pomace. Add it back to the initial product of sparkling wine at a volume ratio of 0.5%, adjust the pressure to 0.4 bar, and let it stand at 14℃ for 24 h.

[0037] (5) Post-processing: After aroma refilling, the sparkling wine is left to stand at 4℃ and 0.4 bar for 14 days. It is first filtered through diatomaceous earth with a filtration precision of 5 μm to remove small sediments and impurities, and then filtered through a ceramic membrane with a 0.22 μm filter to remove small particles, residual yeast cells and microorganisms. The graded and filtered sparkling wine is pasteurized at 65℃ for 25 min with a heating and cooling rate of 1℃ / min. The sparkling wine is then cooled to 10℃, isobarically bottled at 0.5 bar, sealed, and stored at 4℃.

[0038] Example 3 (1) Raw material pretreatment: Select Korla fragrant pears with a maturity of 90% and a single fruit weight of 150g, remove rotten, diseased, pest-damaged, mechanically damaged, immature and overripe fruits; rinse 3 times with running water, soak in 0.1% sterile saline for 10 min, rinse 2 times with sterile distilled water, and drain the surface water; crush the fruit pulp to a particle size of 5 mm, add 0.1% sodium isoascorbate for color protection; juice the fruit pulp, collect the juice and pomace separately, refrigerate the pomace at 4℃ for later use, filter the juice through 200 mesh, add sugar to the juice to 18 °Brix, and adjust the pH to 3.5.

[0039] (2) Ultrasonic-compound enzyme synergistic treatment: The juice was ultrasonically treated at 40kHz, 180W, and 28℃ for 7 min. 0.06% of β-glucosidase with an enzyme activity of 12000U / mL was added to the juice by mass ratio and stirred evenly. Then, 0.04% of esterase with an enzyme activity of 5100U / mL and 0.03% of protease with an enzyme activity of 8000U / mL were added to the juice by mass ratio. The juice after adding the enzyme preparation was kept at 28℃ for 80 min for enzymatic hydrolysis. Then, the juice was heated to 90℃ for 10 min to inactivate the enzyme and completely terminate the enzyme activity. The juice was then rapidly cooled to 24℃.

[0040] (3) Two-stage fermentation: First stage fermentation: Inoculate the enzymatically hydrolyzed juice with 1.2 × 10⁻⁶ Uvaferm 43 Saccharomyces cerevisiae. 6 Fermentation was carried out in an open environment for 10 days at CFU / mL, temperature 22℃, and pH 3.5 until the sugar content reached 1.0 °Brix and the alcohol content reached 12.0% v / v. The mixture was then filtered through a 300-mesh sterile filter and allowed to stand at 4℃ for 24 hours to obtain the base wine.

[0041] Second stage fermentation: The base wine is transferred to a high-pressure fermentation tank. The base wine is then supplemented with sugar to 22° Brix and inoculated with 0.6 x 10⁶ Champagne yeasts. 6 Fermentation was carried out under sealed conditions at 16℃, pH 3.2, and 6 bar. Fermentation was terminated when the residual sugar content was ≤2.0 g / L and the CO2 pressure remained constant. On day 7, the mixture was ultrasonically treated at 40 kHz and 180 W for 5 min, and on day 21, it was ultrasonically treated at 40 kHz and 150 W for 8 min. Simultaneously, immobilized β-glucosidase at 600 U / mL was added on day 21. After termination, the mixture was filtered to obtain the initial sparkling wine.

[0042] (4) Aroma Refilling: Collect the pomace from the first stage of juicing and the pomace separated after the second stage of fermentation. Dry the pomace at 60℃ until the moisture content is 10%, then pulverize it through a 40-mesh sieve to obtain pomace powder. Use the base wine obtained from the first stage of fermentation as a solvent to extract aroma substances from the pomace powder at a material-to-liquid ratio of 1:5 (g:mL). The extraction process is controlled at 50℃, and ultrasonic extraction is used at 40kHz for 35 minutes to fully dissolve the aroma active ingredients. After extraction, the resulting extract is filtered through a 400-mesh filter and transferred to a rotary evaporator. It is concentrated under reduced pressure at 50℃ and 0.08MPa to 1 / 9 of the original volume to obtain the natural aroma refill liquid of pear pomace. Add it back to the initial product of sparkling wine at a volume ratio of 1.0%, adjust the pressure to 0.4 bar, and let it stand at 14℃ for 24 h.

[0043] (5) Post-processing: After aroma refilling, the sparkling wine is left to stand at 4℃ and 0.5 bar for 16 days. It is first filtered through diatomaceous earth with a filtration precision of 5μm to remove small sediments and impurities, and then filtered through a ceramic membrane with a 0.22μm filter to remove small particles, residual yeast cells and microorganisms. The graded and filtered sparkling wine is pasteurized at 68℃ for 30 min with a heating and cooling rate of 1℃ / min. The sparkling wine is then cooled to 8℃, isobarically bottled at 0.6 bar, sealed, and stored at 4℃.

[0044] Comparative Example 1 The method for preparing pear sparkling wine samples is the same as in Example 1, except that step (2) does not involve ultrasonic treatment and proceeds directly to the enzymatic hydrolysis step.

[0045] Comparative Example 2 The method for preparing the pear sparkling wine sample is the same as in Example 1, except that the ultrasonic treatment parameters in step (2) are: ultrasonic frequency 40 kHz, power 100 W, treatment time 3 minutes, and temperature 28℃.

[0046] Comparative Example 3 The method for preparing the pear sparkling wine sample is the same as in Example 1, except that in step (2), the ultrasonic frequency is 40kHz, the power is 200W, the processing time is 10 minutes, and the temperature is 28℃.

[0047] The pear sparkling wine samples obtained from Comparative Examples 1-3 and Example 1 were tested using the following specific methods: (1) Cell disruption rate: determined by microscopic counting using a hemocytometer. Take 1.0 mL of the treated pear juice sample, dilute it 50 times, add 2 drops of 0.1% methylene blue staining solution, mix well and let stand for 2 min; after shaking well, take a small amount and add it to the counting chamber of the hemocytometer, place it under an optical microscope (×400x), select five squares (four corners and center), and count the number of intact cells (colorless or light blue) and the number of disrupted cells (dark blue) respectively, with the untreated juice sample as a control. Cell disruption rate (%) = (1 - number of intact cells in the treated group / number of intact cells in the control group) × 100%, each sample was measured three times in parallel, and the average value was taken.

[0048] (2) Total ester content: The total ester content was determined by colorimetric method according to GB / T 15038-2006 "General Analytical Methods for Wine and Fruit Wine". Accurately pipette 10.0 mL of the wine sample, heat in a boiling water bath for 30 min to remove ethanol, cool, and then transfer to a final volume of 50 mL. Take 2.0 mL of the above solution into a 25 mL colorimetric tube, add 1.0 mL of alkaline hydroxylamine solution (mix 2 mol / L hydroxylamine hydrochloride and 3.5 mol / L sodium hydroxide in equal volumes before use), and let stand at room temperature for 10 min; add 1.0 mL of ferric chloride colorimetric reagent (20 g FeCl3·6H2O dissolved in distilled water, add 12.5 mL concentrated hydrochloric acid, and bring to a final volume of 500 mL), let stand for 15 min, and measure the absorbance at 525 nm. A standard curve was plotted using 0–500 mg / L ethyl acetate standard solutions. Each sample was measured in triplicate, and the results were expressed as ethyl acetate equivalents (μg / L).

[0049] (3) Bubble duration: Refer to method T / BWDP 0010-2025. The sample was refrigerated at 4℃. After opening the bottle, it was slowly poured into an ISO sparkling wine glass (about 100 mL) along the glass wall. The time was started from the end of pouring and stopped when there were fewer than 3 bubbles per second when they were visible in the glass. The total duration (min) was recorded. Each sample was measured 3 times and the average value was taken.

[0050] (4) Sensory evaluation: In accordance with the sensory evaluation requirements in GB / T 15038-2006 "General Analytical Methods for Wine and Fruit Wine", quantitative descriptive sensory analysis (QDA) was adopted: 12 trained tasters (at least 6 of whom had experience in fruit wine tasting) were selected and received consistency training before the evaluation; the samples were refrigerated at 4℃, opened and decanted for 15 min, and about 50 mL of wine was poured into each glass. After random numbering, blind sample evaluation was conducted with an interval of no less than 5 min between samples, and the samples were rinsed with purified water and unsalted soda crackers; a 10-point scoring system was used to comprehensively evaluate appearance (20%), aroma (35%), taste (35%), and typicality (10%), where 9-10 points were excellent quality, 7-8.9 points were good quality, 5-6.9 points were medium quality, 3-4.9 points were poor quality, and 0-2.9 points were very poor quality; the final average score was taken.

[0051] (5) Cell wall fragment particle size: Take an appropriate amount of fruit juice or wine sample from the early stage of fermentation and dilute it with deionized water to a suitable concentration. Measure the particle size using a laser particle size analyzer. Measurement parameters: particle refractive index 1.33, dispersant refractive index 1.33, ultrasonic dispersion power 50 W, time 30 seconds to avoid particle aggregation. Each sample was measured in triplicate, and the D50 (median particle size) and particle size distribution range (D10-D90) were recorded. D50 represents the particle size value corresponding to a cumulative volume distribution of 50%; D10 and D90 represent the particle size values ​​corresponding to a cumulative volume distribution of 10% and 90%, respectively.

[0052] (6) Polyphenol content (expressed as gallic acid equivalents): The Folin-Ciocalteu colorimetric method was used. Accurately pipette 1.0 mL of the wine sample, add 5.0 mL of distilled water and 1.0 mL of Folin-Ciocalteu reagent (diluted 10 times), mix well, let stand for 5 min, then add 5.0 mL of 7.5% Na₂CO₃ solution, mix well, and react at room temperature in the dark for 60 min. Measure the absorbance at 765 nm. Plot a standard curve using gallic acid as a standard (0, 20, 40, 60, 80, 100 mg / L), and express the results as gallic acid equivalents (mg / L GAEs). Each sample was measured three times, and the average value was taken.

[0053] The results are shown in Table 1 below.

[0054] Table 1:

[0055] The results showed that, compared with Comparative Example 1 without ultrasonic pretreatment, Example 1, using limited ultrasonic parameters of 40 kHz, 150-180 W, 5-7 min, and 25-28 °C, effectively controlled the disruption of pear pulp cells by relying on cavitation effect, achieving a median particle size (D50) of 68 μm and a particle size distribution (D10-D90) of 25-105 μm, thus controlling the cell wall fragment particle size within the range of 50-100 μm. Examples 2 and 3, due to their lower ultrasonic power, had slightly higher median particle size (D50) and slightly wider particle size distribution. Compared with no ultrasonic process (Comparative Example 1), Example 1 increased the cell disruption rate from 35.2% to 88.4% and the total ester content by 125.9%. Compared with excessive ultrasonic process (Comparative Example 3), while maintaining a similar total ester content, it significantly reduced the total phenolic content (calculated as gallic acid equivalent) from 197 mg / L to 163 mg / L. mg / L effectively avoids the bitterness of the wine, resulting in the best sensory properties and bubble stability in the finished product.

[0056] Comparative Example 4 The method for preparing the pear sparkling wine sample is the same as in Example 1, except that immobilized β-glucosidase is not added on the 21st day of the second stage of fermentation in step (3), and only ultrasonic treatment with corresponding parameters is performed.

[0057] Comparative Example 5 The method for preparing pear sparkling wine samples is the same as in Example 1, except that immobilized β-glucosidase is added on the 7th day of the second stage of fermentation in step (3).

[0058] Comparative Example 6 The method for preparing the pear sparkling wine sample is the same as in Example 1, except that immobilized β-glucosidase is added on the 24th day of the second stage of fermentation in step (3).

[0059] The pear sparkling wine samples obtained in Comparative Examples 4-6 and Example 1 were tested using the following specific testing methods: (1) Content of bonded aroma glycosides: Take 10 mL of wine sample, adjust the pH to 5.0 with 1 mol / L Na2CO3 solution, add 100 μL of β-glucosidase solution (enzyme activity ≥10000 U / mL), and enzymatically hydrolyze in a 40℃ water bath for 12 hours. After enzymatic hydrolysis, heat the reaction solution at 85℃ for 10 minutes to inactivate the enzyme. After cooling, determine the total amount of aglycones released by enzyme decomposition using the above Folin-Ciocalteu colorimetric method, and plot a standard curve with rutin as standard (0-100 mg / L). The results are expressed as rutin equivalents (mg / L RE). Each sample was measured in triplicate, and the average value was taken.

[0060] (2) Total ester content: The total ester content was determined by colorimetric method according to GB / T 15038-2006 "General Analytical Methods for Wine and Fruit Wine". The specific steps are the same as the "Determination Method of Total Ester Content" of this invention. The results are expressed as ethyl acetate equivalent (μg / L). Each sample was measured in parallel three times and the average value was taken.

[0061] (3) Aroma Complexity Scoring (10-point scale): A blind sensory evaluation method was adopted. The evaluation environment followed GB / T 13868-2009 "General Guidelines for Establishing Sensory Analysis Laboratories". No fewer than 8 evaluators with fruit wine sensory evaluation qualifications were selected, and a single-blind evaluation method was adopted. The scores were comprehensively based on four dimensions: aroma level, fruit aroma purity, aroma persistence, and off-flavors. The total score was 10 points, and the average score was taken.

[0062] The results are shown in Table 2 below.

[0063] Table 2:

[0064] The results showed that the residual amount of bound aroma glycosides in Example 1 was 76 mg / L, which was significantly lower than that in Comparative Examples 4-6. Correspondingly, the total ester content (20150 μg / L) and aroma complexity score (9.1 points) of Example 1 were significantly higher than those of the three comparative examples. The reasons are as follows: (1) when fermentation enters the later stage, the free sugars are basically exhausted. At this time, the addition of immobilized enzyme can avoid the enzyme being competitively inhibited by a large amount of sugar substrates and focus on hydrolyzing glycoside aroma precursors; (2) the microjet generated by the second ultrasonic treatment can promote the contact mass transfer between the immobilized enzyme microspheres and the fermentation broth and improve the catalytic efficiency; (3) after the addition, the enzyme can act for about 10 days, and the time window just matches the slow release process of glycoside aroma precursors in the later stage of fermentation.

[0065] Comparative Example 7 The method for preparing the pear sparkling wine sample is the same as in Example 1, except that no ultrasonic-assisted treatment is performed on the 7th and 21st days of the second fermentation process in step (3).

[0066] Comparative Example 8 The method for preparing the pear sparkling wine sample is the same as in Example 1, except that in step (3), ultrasonic treatment is performed only on the 7th and 14th days of the second fermentation process. The parameters for the two treatments are the same: frequency 40 kHz, power 180W, and time 5 min.

[0067] Comparative Example 9 The method for preparing the pear sparkling wine sample is the same as in Example 1, except that in step (3), during the second stage of fermentation, the ultrasonic conditions on day 7 are 40 kHz, 120 W, and 8 min, and the ultrasonic conditions on day 21 are 40 kHz, 180 W, and 5 min.

[0068] The pear sparkling wine samples obtained from Comparative Examples 7-9 and Example 1 were tested using the following specific testing methods: (1) Fermentation time: The second stage of fermentation was terminated when the residual sugar content was ≤2.0 g / L and the CO2 pressure remained constant. The residual sugar content and CO2 pressure were measured daily. When the residual sugar content was ≤2.0 g / L, the pressure change was monitored. If the CO2 pressure fluctuation was ≤0.1 bar for 24 consecutive hours, it was determined that the pressure was constant and no longer changed. At this time, the fermentation was terminated and the fermentation time was recorded.

[0069] (2) Mannose protein content: determined by the phenol-sulfuric acid colorimetric method. Take 10.0 mL of wine sample, add an equal volume of 10% trichloroacetic acid, let stand overnight at 4℃, centrifuge at 10000 r / min for 15 min, and take the supernatant. Take 2.0 mL of the supernatant in a test tube, add 1.0 mL of 5% phenol solution, shake well, quickly add 5.0 mL of concentrated sulfuric acid, let stand at room temperature for 20 min, and measure the absorbance at 490 nm. Plot a standard curve using mannose standards (0~100 mg / L). The results are expressed as mannose equivalents (mg / L).

[0070] (3) CO2 production rate: The pressure monitoring method was used. In a closed fermenter equipped with a pressure sensor, the pressure value was recorded daily from the time of inoculation with Champagne yeast (temperature constant 15±0.5℃). The pressure data from day 2 to day 8 of fermentation (logarithmic growth phase) were used to calculate the CO2 production rate (g / L·d) according to the formula R = ΔP × V / (Δt × 44.01), where ΔP is the pressure difference between two adjacent days (bar), V is the headspace volume (L), and 44.01 is the molar mass of CO2 (g / mol).

[0071] (4) Bubble duration: Refer to method T / BWDP 0010-2025. The sample was refrigerated at 4℃. After opening the bottle, it was slowly poured into an ISO sparkling wine glass (about 100 mL) along the glass wall. The time was started from the end of pouring and stopped when there were fewer than 3 bubbles per second when they were visible in the glass. The total duration (min) was recorded. Each sample was measured 3 times and the average value was taken.

[0072] The results are shown in Table 3 below.

[0073] Table 3:

[0074] The results showed that, compared with Comparative Example 7 (without ultrasonic treatment), the fermentation time of Example 1 was shortened from 39 days to 30 days, the mannose protein content increased from 168 mg / L to 312 mg / L, the CO2 production rate increased from 0.47 g / L·d to 0.93 g / L·d, and the bubble duration was extended from 22 min to 58 min. Although Comparative Examples 8 and 9 also underwent two ultrasonic treatments, their fermentation time, mannose protein content, and bubble duration did not reach the levels of Example 1. This demonstrates that only by using a specific timing and parameter combination—high-power short-duration ultrasound (180 W, 5 min) on day 7 of the second stage fermentation to promote yeast metabolism and low-power long-duration ultrasound (150 W, 8 min) on day 21 to control the release of mannose protein—can the fermentation efficiency and bubble stability be synergistically improved. This timing and parameter combination produced unexpected technical effects far exceeding those of a single ultrasound treatment or parameter interchange schemes.

[0075] Comparative Example 10 The method for preparing the pear sparkling wine sample is the same as in Example 1, except that in step (4) aroma backfilling process, the aroma substances in the pomace powder are extracted with an equal volume of 60% edible ethanol as solvent at a material-liquid ratio of 1:3 (g:mL).

[0076] Comparative Example 11 The method for preparing the pear sparkling wine sample is the same as in Example 1, except that in step (4) aroma backfilling process, the aroma substances in the pomace powder are extracted with an equal volume of 70% edible ethanol as solvent at a material-liquid ratio of 1:3 (g:mL).

[0077] Comparative Example 12 The method for preparing the pear sparkling wine sample is the same as in Example 1, except that in step (4) aroma backfilling process, the aroma substances in the pomace powder are extracted with an equal volume of 80% edible ethanol as solvent at a material-liquid ratio of 1:3 (g:mL).

[0078] The pear sparkling wine samples obtained in Comparative Examples 10-12 and Example 1 were tested using the following specific testing methods: (1) Total ester content: The total ester content was determined by colorimetric method according to GB / T 15038-2006 "General Analytical Methods for Wine and Fruit Wine". The specific steps are the same as the "Determination Method of Total Ester Content" of this invention. The results are expressed as ethyl acetate equivalent (μg / L). Each sample was measured in parallel three times and the average value was taken.

[0079] (2) Sensory Harmony Scoring (10-point scale): A blind sensory evaluation method was adopted, with 12 trained tasters (at least 6 of whom had experience in fruit wine tasting) selected to conduct the evaluation in a sensory analysis laboratory that meets the requirements of GB / T 13868-2009. The evaluation mainly assesses the balance and integration of various elements in the wine, such as fruit aroma, wine aroma, acidity, sweetness, and bitterness. The sensory harmony score is based on a 10-point scale, and the final score is the average value.

[0080] The results are shown in Table 4 below.

[0081] Table 4:

[0082] The results showed that, compared with Comparative Examples 10-12, which were extracted using different concentrations of edible ethanol, Example 1, using the first-stage base wine as the extraction solvent, achieved a total ester content of 20150 μg / L, a 2.8% increase compared to Comparative Example 11 (19610 μg / L), and a sensory harmony score of 9.4, with no detected exogenous off-odors. Comparative Example 10, while odorless, had lower total ester content and sensory scores than Example 1; Comparative Examples 11 and 12 exhibited slight and obvious alcoholic odors, respectively, and their sensory harmony scores decreased with increasing ethanol concentration. This demonstrates that the base wine extraction solvent used in this invention not only avoids the off-odor problem introduced by exogenous ethanol but also utilizes the naturally occurring ethanol and organic acids in the base wine to achieve efficient extraction of aroma components from the pomace.

Claims

1. A method for preparing a pear-infused sparkling wine, characterized in that, Includes the following steps: (1) Raw material pretreatment: Select ripe pears, wash, crush, juice, coarsely filter, adjust the sugar content to 16-18 °Brix, adjust the pH to 3.2~3.5 to obtain pretreated pear juice; (2) Ultrasonic-complex enzyme synergistic treatment: The pretreated pear juice obtained above is first subjected to ultrasonic treatment, and then enzymatic hydrolysis is carried out by adding complex enzymes in steps. First, β-glucosidase is added for preliminary enzymatic hydrolysis, and then esterase and protease are added for further enzymatic hydrolysis. After the enzymatic hydrolysis is completed, the enzymes are inactivated and cooled to obtain enzymatically hydrolyzed pear juice. (3) Two-stage fermentation: First stage fermentation: Inoculate the enzymatically hydrolyzed pear juice obtained in step (2) above with brewing yeast for open fermentation, filter and let stand to obtain base wine; Second stage fermentation: Champagne yeast was inoculated into the base wine obtained above, and the wine was sealed and fermented under a pressure of 5-6 bar. Differential ultrasonic-assisted treatment was performed twice on the 7th and 21st days of the sealed fermentation. Immobilized β-glucosidase was added on the 21st day. Fermentation was terminated when the residual sugar content was ≤2.0 g / L and the pressure remained constant. The initial sparkling wine was obtained by filtration. (4) Aroma backfilling: Collect the pomace obtained from coarse filtration in step (1) and the pomace separated after filtration in the two-stage fermentation process in step (3), dry and pulverize to obtain pomace powder; use the base wine obtained in step (3) as the extraction solvent to perform ultrasonic-assisted extraction on the pomace powder to obtain an extract; concentrate the extract under reduced pressure to obtain a natural aroma backfill liquid for pear pomace. The aroma backfill liquid is added to the initial sparkling wine sample and allowed to stand under a pressure of 0.4~0.5 bar to obtain the aroma backfilled sparkling wine. (5) Post-processing: After the aroma is backfilled, the sparkling wine is refrigerated and left to stand for 14 to 16 days under a pressure of 0.4 to 0.5 bar and a temperature of 4°C. It is then filtered through diatomaceous earth and then through a ceramic membrane before being pasteurized to obtain pear sparkling wine.

2. The preparation method according to claim 1, characterized in that, The conditions for ultrasonic treatment in step (2) are: frequency 40kHz, power 150~180W, temperature 25~28℃, and time 5~7min.

3. The preparation method according to claim 1, characterized in that, The specific conditions for the two differentiated ultrasound-assisted treatments on day 7 and day 21 in step (3) are as follows: the ultrasound treatment conditions on day 7 are 40kHz frequency, 150~180W power, and 3~5 min time; the ultrasound treatment conditions on day 21 are 40kHz frequency, 120~150W power, and 5~8 min time.

4. The preparation method according to claim 1, characterized in that, In step (3), the amount of immobilized β-glucosidase added in the second stage of fermentation is 500~600 U / mL.

5. The preparation method according to claim 1, characterized in that, In step (3), the inoculation amount of brewing yeast in the first stage of fermentation is 1×10⁻⁶. 6 ~1.2×10 6 CFU / mL; the open fermentation conditions are a temperature of 20~22℃, a pH of 3.2~3.5, and a time of 7~10 days; the static setting temperature is 4℃ and the time is 20~24 h.

6. The preparation method according to claim 1, characterized in that, In step (3), before inoculating the base wine with Champagne yeast during the second stage of fermentation, sugar needs to be added to adjust the sugar content of the base wine to 20~22 °Brix; the inoculation amount of the Champagne yeast is 0.5×10 6 ~0.6×10 6 CFU / mL; the fermentation conditions for the sealed fermentation are a temperature of 14~16℃ and a pH of 3.0~3.

2.

7. The preparation method according to claim 1, characterized in that, The cleaning in step (1) is a three-stage cleaning process, specifically rinsing with clean water 3-5 times, soaking in 0.1% sterile saline solution for 10 minutes, rinsing with sterile distilled water twice, and draining the surface water; the particle size of the crushing is 3-5 mm, and 0.05-0.1% sodium isoascorbate is added after crushing; the coarse filtration is to pass the juice obtained by juicing through a 150-200 mesh filter; the pH adjuster includes citric acid, malic acid, tartaric acid, and lactic acid.

8. The preparation method according to claim 1, characterized in that, In step (2), the enzyme activity of β-glucosidase is ≥10000 U / mL, and the addition amount is 0.05~0.06%; the enzyme activity of esterase is ≥5000 U / mL, and the addition amount is 0.03~0.04%; the enzyme activity of protease is ≥8000 U / mL, and the addition amount is 0.02~0.03%; the enzymatic hydrolysis temperature is 25~28℃, and the time is 60~80min; the enzyme inactivation temperature is 85~90℃, and the time is 8~10min; the cooling refers to cooling the juice after enzyme inactivation to below 25℃.

9. The preparation method according to claim 1, characterized in that, The drying and pulverizing in step (4) specifically involves drying the fruit pomace at 60°C until the moisture content is ≤10%, and then pulverizing it through a 40-mesh sieve; the amount of base wine added is based on a material-liquid ratio of 1:3 to 1:5 (g:mL) between the mass of the fruit pomace powder and the volume of the base wine; the temperature of the ultrasonic-assisted extraction is 50°C and the frequency is 40KHz; the filtration of the extract refers to filtration through a 350-450 mesh filter; the temperature of the vacuum concentration is 50°C and the pressure is 0.08MPa, with the concentration endpoint being 1 / 10 to 1 / 8 of the original volume of the extract; the amount of aroma backfill liquid added is 0.5-1.0% (v / v) of the sparkling wine obtained from the second stage fermentation; the settling time is 20-24 h and the temperature is 14-16°C.

10. The preparation method according to claim 1, characterized in that, The precision of the diatomaceous earth filtration in step (5) is 5 μm; the pore size of the ceramic membrane filtration is 0.22 μm; the pasteurization is specifically carried out at a temperature of 65~68℃ for a time of 25~30 min.

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