Preparation method of red date wine and red date wine

Abstract

The invention provides a preparation method of red date wine and the red date wine, and relates to the technical field of wine brewing. The preparation method of the red date wine comprises the following steps: S1, mixing sterilized and enzyme-deactivated enzymolysis red date juice with lactic acid bacteria, and performing lactic acid bacteria fermentation to obtain fermentation liquor; s2, mixing the fermentation liquor with saccharomycetes, and performing saccharomycetes fermentation to obtain red date wine; the lactic acid bacteria in the S1 are alcohol-tolerant lactic acid bacteria, and the saccharomycetes in the S2 are BV818 saccharomycetes; the fermentation liquor in the step S2 is not sterilized before being mixed with the saccharomycetes. According to the preparation method of the red date wine, damage to heat-sensitive functional components such as polyphenols and flavones in the red dates is avoided, microbial fermentation is more sufficient, low alcohol is achieved, the content of the functional components and the oxidation resistance are reserved and improved, the red date wine further contains rich flavor substances, and the taste of the red date wine is improved. Pure natural fruity flavor and fine and soft taste of the wine body are guaranteed, and the comprehensive quality of the product is excellent.

Description

Technical Field

[0001] This invention relates to the field of brewing technology, and in particular to a method for preparing jujube wine and the jujube wine itself. Background Technology

[0002] In recent years, with the deepening of the concept of healthy consumption, consumers' demand for alcoholic beverages has gradually shifted from "high alcohol content and strong stimulation" to "low alcohol, safety, nutrition, and pure flavor." Low-alcohol fruit wines, with their advantages of low alcohol content and low levels of harmful substances such as methanol and heteropolyols, have become a new hot spot in the alcoholic beverage market. Among them, jujube fruit wine is particularly favored by consumers because jujubes are naturally rich in functional components such as polyphenols, flavonoids, and terpenes, and also have antioxidant, spleen-strengthening, qi-boosting, and beauty-enhancing properties. Its market attention and demand continue to rise.

[0003] The core value of low-alcohol fruit wine lies not only in its "low alcohol" content, but also in the preservation and enhancement of nutritional and functional components such as polysaccharides, polyphenols, flavonoids, and anthocyanins in fruits. These components directly determine the product's health benefits and quality level. Currently, most low-alcohol jujube wines on the market follow the traditional brewing process of wine or spirits, requiring subsequent de-alcoholization processes such as distillation and filtration to reduce alcohol content. This method not only destroys the inherent typical flavor of jujubes, resulting in a lack of jujube characteristics, a bland taste, and poor flavor harmony, but more seriously, the de-alcoholization process causes a significant loss of heat-sensitive functional components such as polyphenols and flavonoids, while also inhibiting the formation of the wine's own antioxidant properties, ultimately creating the industry pain point of "low alcohol content being unable to balance flavor and nutritional benefits."

[0004] In existing technologies, some studies have attempted to prepare low-alcohol fruit wine through direct fermentation, but most of these studies focus on controlling alcohol content or improving single flavors, without optimizing the process based on the nutritional characteristics of jujubes. On the one hand, the selection of fermentation strains and the design of fermentation modes lack specificity, making it difficult to achieve a precise balance between "low-alcohol control" and "aroma enhancement." On the other hand, the release and transformation mechanisms of polyphenols, flavonoids, and other components during fermentation have not been considered, resulting in weak antioxidant properties in the product and failing to fully realize the nutritional value of jujubes.

[0005] Therefore, it is necessary to develop a low-alcohol jujube wine preparation technology that can simultaneously achieve "low-alcohol characteristics, rich flavor, high antioxidant activity, and high content of functional components" to solve the shortcomings of existing processes that "lose some aspects while focusing on others". Summary of the Invention

[0006] This invention addresses the shortcomings of existing red wine brewing processes, which struggle to retain antioxidants and other functional components while achieving "low-alcohol control." It provides a method for preparing jujube wine using a specific two-stage fermentation process to produce low-alcohol jujube wine. This method ensures the wine retains its pure natural fruit aroma and delicate, smooth taste, while simultaneously enhancing its antioxidant properties and the content of total phenols and flavonoids, resulting in a product of excellent overall quality.

[0007] Another objective of this invention is to provide a jujube wine.

[0008] In a first aspect, this invention protects a method for preparing jujube wine, comprising the following steps: S1. Sterilized and enzyme-inactivated enzymatically hydrolyzed jujube juice is mixed with lactic acid bacteria and then fermented with lactic acid bacteria to obtain fermentation liquid; S2. Mix the fermentation liquid with yeast and then ferment with yeast to obtain jujube wine; The lactic acid bacteria mentioned in S1 are lactic acid bacteria that can tolerate alcohol concentrations of 5-8% (v / v), and the yeast mentioned in S2 is yeast BV818. The fermentation broth described in S2 is not sterilized before being mixed with yeast.

[0009] According to the method for preparing jujube wine protected by the present invention, preferably, the fermentation temperature of the lactic acid bacteria fermentation in S1 is 30~37℃, the fermentation time is 40~50h, and preferably the amount of lactic acid bacteria added is 1~2% of the volume of the enzymatically hydrolyzed jujube juice, with absorbance OD... 600 The value is measured for lactic acid bacteria activation solution of 0.6~0.8.

[0010] According to the method for preparing jujube wine protected by the present invention, preferably, the fermentation temperature of the yeast fermentation in step S2 is 28~35℃, the fermentation time is 40~50h, and preferably the amount of yeast added is 0.5~1.5% of the volume of the enzymatically hydrolyzed jujube juice, with absorbance OD... 600 The value is 0.6~0.8 for yeast activation solution.

[0011] According to the method for preparing jujube wine protected by the present invention, preferably, the lactic acid bacteria in S1 is Lactobacillus fermentum, and the ratio of Lactobacillus fermentum to BV818 yeast is 1:1.

[0012] According to the method for preparing jujube wine protected by the present invention, preferably, the enzymatically hydrolyzed jujube juice in S1 is prepared by steaming and enzymatically hydrolyzing jujubes, and the enzymatic hydrolysis is a mixed enzymatic hydrolysis of cellulase and pectinase, preferably the total amount of cellulase and pectinase is 1 to 2% of the mass of jujubes.

[0013] According to the method for preparing jujube wine protected by the present invention, preferably, the enzymatic hydrolysis is performed at a pH of 4.5-5.5, a temperature of 45-55°C, and a time of 10-14 hours; more preferably, the enzymatic hydrolysis is performed at a pH of 5, a temperature of 50°C, and a time of 12 hours.

[0014] According to the method for preparing jujube wine protected by the present invention, preferably, the soluble solids content of the enzymatically hydrolyzed jujube juice reaches 12-14°Brix.

[0015] Secondly, the present invention also specifically protects a jujube wine prepared by the method for preparing jujube wine protected according to the present invention.

[0016] According to the jujube wine protected by the present invention, preferably, the jujube wine satisfies at least one of the following characteristics: (a) The total phenol content of the jujube wine, calculated as gallic acid, is ≥291.76 mg / 100 ml; (b) The total flavonoid content of the jujube wine, calculated as rutin, is ≥2.37 mg / 100 ml; (c) The total acid content of the jujube wine is ≥0.62g / L, and the pH value is reduced to 4.0~4.3.

[0017] The jujube wine protected by the present invention preferably contains one or more of the following flavor substances: 3-Heptanol, 1-Octanol, n-Butanol, 4-Heptanone, 2-Methyl-3-Heptanone, 2-Heptanone, 1-Pentanol, 3-Methyl-1-Butanol Acetate, 1-Hexanal, Butyl Propionate, 2-Methyl-1-Propanol, Butyl Formate.

[0018] Beneficial effects: This invention provides a method for preparing jujube wine. The method involves fermenting sterilized and enzyme-inactivated enzymatically hydrolyzed jujube juice through a two-step process using alcohol-tolerant lactic acid bacteria, Lactobacillus fermentum, and BV818 yeast. Fermentation is not terminated, and there is no need for de-alcoholization processes such as distillation or membrane filtration. This avoids the destruction of heat-sensitive functional components such as polyphenols and flavonoids in jujubes during the de-alcoholization process, and allows for more complete microbial fermentation. While achieving low-alcohol characteristics, this method maximizes the retention and enhancement of functional component content, laying the foundation for enhanced antioxidant properties.

[0019] The method for preparing jujube wine of the present invention has a short fermentation time, low cost, and simple and safe production method. While precisely controlling the low alcohol content, the jujube wine also contains rich flavor substances, ensuring the pure natural fruit aroma and delicate and mellow taste of the wine, resulting in excellent overall product quality. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a graph showing the alcohol content test results for different amounts of yeast added.

[0022] Figure 2 The image shows the test results for jujube wine fermented with different yeasts.

[0023] Figure 3 This is a radar diagram of the electronic nose data of the jujube wine in Example 1.

[0024] Figure 4 Principal component analysis (PCA) plot of electronic nose data for jujube wine in Example 1.

[0025] Figure 5 This is a radar diagram of the electronic tongue data of the jujube wine in Example 1.

[0026] Figure 6 Principal component analysis (PCA) plot of electronic tongue data for jujube wine in Example 1. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] In a specific embodiment, the present invention provides a method for preparing jujube wine, comprising the following steps: S1. Sterilized and enzyme-inactivated enzymatically hydrolyzed jujube juice is mixed with lactic acid bacteria and then fermented with lactic acid bacteria to obtain fermentation liquid; S2. Mix the fermentation liquid with yeast and then ferment with yeast to obtain jujube wine; The lactic acid bacteria mentioned in S1 are lactic acid bacteria that can tolerate alcohol concentrations of 5-8% (v / v), and the yeast mentioned in S2 is yeast BV818. The fermentation broth described in S2 is not sterilized before being mixed with yeast.

[0029] It should be noted that: The method for preparing jujube wine in this invention involves direct fermentation without terminating the fermentation process. It eliminates the need for distillation, membrane filtration, or other de-alcoholization treatments, thus avoiding the destruction of heat-sensitive functional components such as polyphenols and flavonoids in jujubes during the de-alcoholization process. This also allows for more complete microbial fermentation, achieving low-alcohol characteristics while maximizing the retention and enhancement of functional component content, laying the foundation for enhanced antioxidant properties.

[0030] The fermentation method of this invention adopts a two-stage fermentation process to synergistically achieve the triple goals of "low alcohol, enhanced aroma, and high functionality": First, lactic acid bacteria fermentation produces abundant organic acids, peptides, and other precursor substances, which provide a flavor foundation for subsequent yeast fermentation. While producing a small amount of alcohol (the core of low alcohol) and a large number of aroma components, it promotes the polymerization and transformation of phenolic substances, significantly increases the content of total phenols and total flavonoids, and thus enhances antioxidant properties.

[0031] This invention selects lactic acid bacteria with good alcohol tolerance as the fermentation strain, and the lactic acid bacteria are not inactivated during the fermentation process. By utilizing their symbiotic characteristics with BV818 yeast, the functional components and antioxidant properties are synergistically enhanced, resulting in increased total phenolic and total flavonoid content in the prepared jujube wine. In addition, the total antioxidant capacity, DPPH free radical scavenging rate, and ABTS free radical scavenging rate are significantly improved.

[0032] The method for preparing jujube wine of the present invention has a short overall fermentation time, low cost, and simple and safe production method. While precisely controlling the low alcohol content, it can also produce rich flavor substances such as 3-heptanol and (Z)-6-nonenal, ensuring the pure natural fruit aroma and delicate and mellow taste of the wine. It also achieves simultaneous improvement in antioxidant performance and total phenol and flavonoid content, resulting in excellent overall product quality.

[0033] The present invention produces a jujube beverage with an alcohol content as low as about 1% vol by using the above method after the yeast has fully fermented.

[0034] In some specific embodiments, to better facilitate the fermentation and produce abundant organic acids, peptides, and other precursor substances and aroma compounds, promote the polymerization and conversion of phenolic substances, and control alcohol production, the specific parameters for lactic acid bacteria fermentation mentioned in S1 of this invention can be: fermentation temperature of 30~37℃, fermentation time of 40~50h, preferably with the amount of lactic acid bacteria added being 1~2% of the volume of the enzymatically hydrolyzed jujube juice, and the absorbance OD... 600 The value is measured for lactic acid bacteria activation solution of 0.6~0.8.

[0035] In some specific embodiments, to further promote the synergistic enhancement of the content of functional components and antioxidant components, the specific parameters of yeast fermentation mentioned in S2 of this invention can be: fermentation temperature of 28~35℃, fermentation time of 40~50h, and the amount of yeast added is 0.5~1.5% of the volume of enzymatically hydrolyzed jujube juice, measured by absorbance OD. 600 The value is 0.6~0.8 for yeast activation solution.

[0036] In some specific embodiments, the strains used in the lactic acid bacteria fermentation of the present invention are preferably Lactobacillus fermentum, and more preferably, the ratio of Lactobacillus fermentum to BV818 yeast is 1:1.

[0037] In some specific embodiments, the enzymatically hydrolyzed jujube juice mentioned in this invention can be prepared by the following method: The product is prepared by steaming and enzymatically hydrolyzing red dates. The enzymatic hydrolysis is a mixture of cellulase and pectinase, and preferably the total amount of cellulase and pectinase used is 1-2% of the weight of the red dates.

[0038] In some specific exemplary embodiments, the conditions for the mixed enzymatic hydrolysis of cellulase and pectinase are preferably: the pH value of the enzymatic hydrolysis is 4.5~5.5, the temperature of the enzymatic hydrolysis is 45~55°C, and the time of the enzymatic hydrolysis is 10~14h, preferably the pH value of the enzymatic hydrolysis is 5, the temperature of the enzymatic hydrolysis is 50°C, and the time of the enzymatic hydrolysis is 12h.

[0039] The dried jujubes used in this invention can be selected from any variety of jujubes, with Ruoqiang jujubes being preferred. The dried jujubes are washed, drained, and then steamed and enzymatically hydrolyzed to prepare enzymatically hydrolyzed jujube juice.

[0040] The specific operation of sterilization and enzyme inactivation mentioned in S1 of this invention is as follows: the prepared jujube juice is subjected to high-temperature sterilization and enzyme inactivation treatment at 85°C for 30 minutes, and then cooled to room temperature to obtain sterilized and enzyme-inactivated enzymatically hydrolyzed jujube juice.

[0041] In some specific exemplary embodiments, in order to further improve the fermentation speed and at the same time form a good flavor and taste of fermented jujube wine, the soluble solids content of the enzymatically hydrolyzed jujube juice obtained by the mixed enzymatic hydrolysis of cellulase and pectinase of the present invention reaches 12-14°Brix.

[0042] °Brix is ​​a standard indicator used in the food fermentation field to characterize the content of soluble solids in sugar solutions.

[0043] In a specific embodiment, the present invention also provides a jujube wine prepared according to the above-described method for preparing jujube wine.

[0044] The jujube wine provided by this invention preferably has the following characteristics: (a) The total phenol content of the jujube wine, calculated as gallic acid, is ≥291.76 mg / 100 ml; (b) The total flavonoid content of the jujube wine, calculated as rutin, is ≥2.37 mg / 100 ml; (c) The total acid content of the jujube wine is ≥0.62g / L, and the pH value is reduced to 3.7~4.3.

[0045] The jujube wine provided by this invention also has specific flavor substances, including at least one or more of the following substances: 3-Heptanol, 1-Octanol, n-Butanol, 4-Heptanone, 2-Methyl-3-Heptanone, 2-Heptanone, 1-Pentanol, 3-Methyl-1-Butanol Acetate, 1-Hexanal, Butyl Propionate, 2-Methyl-1-Propanol, Butyl Formate.

[0046] The raw materials used in the following embodiments and comparative examples of the present invention are described below: Pectinase: Novozymes.

[0047] Cellulase: Novozymes.

[0048] Lactobacillus fermentum: alcohol tolerance concentration 5-8% (v / v), National Culture Collection Center, CICC 21828, 2007-12-28.

[0049] BV818 yeast: Angel yeast.

[0050] Anomalous Wickham yeast: National Culture Collection Center, CGMCC 2.338, 1 / 1 / 1952.

[0051] BF16 yeast: Angel Yeast.

[0052] RV171 Yeast: Angel Yeast.

[0053] Among them, the fermentation of Lactobacillus was prepared into a bacterial suspension using a culture medium, and the absorbance OD was detected at a wavelength of 600 nm. 600 The value is 0.6~0.8.

[0054] Yeast cells were prepared into bacterial suspensions using YPD medium, and the absorbance (OD) was measured at a wavelength of 600 nm. 600 The value is 0.7~0.8.

[0055] Example 1 A method for preparing jujube wine includes the following steps: S1. Wash, soak, and steam 500g of red dates to obtain Brix red date juice (with residue) with a sugar content of 12-14° Brix. Cool and set aside. Add pectinase (5mL) and cellulase (5mL) to the cooled jujube juice, place it in a 55℃ incubator, and enzymatically hydrolyze for 12 hours. After 12 hours, remove it, filter it, and place it in an 85℃ water bath for sterilization for 30 minutes. Let it cool before fermentation. Sterilized and enzyme-inactivated jujube juice was mixed with Lactobacillus fermentum (1% of the jujube juice volume) and then fermented with lactic acid bacteria for 50 hours at 30°C to obtain fermentation liquid. S2. After mixing the fermentation liquid with yeast, ferment with BV818 yeast (1% of the volume of jujube juice) for 43 hours at a fermentation temperature of 28℃ to obtain jujube wine. Red date wine is sterilized by heating in an 85℃ water bath.

[0056] Example 2 A method for preparing jujube wine is basically the same as in Example 1, except that the amount of yeast inoculated is 0.5% of the volume of jujube juice.

[0057] Example 3 A method for preparing jujube wine is basically the same as in Example 1, except that the amount of yeast inoculated is 1.5% of the volume of jujube juice.

[0058] Example 4 A method for preparing jujube wine is basically the same as in Example 1, except that the amount of yeast inoculated is 2.0% of the volume of jujube juice.

[0059] Example 5 A method for preparing jujube wine is basically the same as in Example 1, except that the amount of yeast inoculated is 2.5% of the volume of jujube juice.

[0060] Comparative Example 1 Compared with Example 1, the yeast in this comparative example was replaced with abnormal Wickham yeast.

[0061] Comparative Example 2 Compared with Example 1, the yeast in this comparative example was replaced with BF16 yeast.

[0062] Comparative Example 3 Compared with Example 1, the yeast in this comparative example was replaced with RV171 yeast.

[0063] Comparative Example 4 1. Wash, soak, and steam 500g of red dates to obtain Brix red date juice (with residue) with a sugar content of 12-14° Brix. Cool and set aside. Add pectinase (5mL) and cellulase (5mL) to the cooled jujube juice, place it in a 55℃ incubator, and enzymatically hydrolyze for 12 hours. After 12 hours, remove it, filter it, and place it in an 85℃ water bath for sterilization for 30 minutes. Let it cool before fermentation. Sterilized and enzyme-inactivated jujube juice was mixed with Lactobacillus fermentum (1% of the jujube juice volume) and then fermented with lactic acid bacteria for 50 hours at 30°C. Sterilization was then performed to terminate the fermentation, and the fermentation liquid was obtained. S2. After mixing the fermentation liquid with yeast, ferment with BV818 yeast (1% of the volume of jujube juice) for 43 hours at a temperature of 28°C. Sterilize to terminate fermentation and obtain jujube wine.

[0064] Result detection (1) Alcohol content detection The alcohol content of the jujube wines prepared by methods in Example 1 and Comparative Examples 1-3 was measured for comparison.

[0065] Specific method: The determination was made in accordance with the national standard GB 5009.225-2023 National Food Safety Standard for Determination of Ethanol Concentration in Wine and Edible Alcohol.

[0066] The specific steps for testing the alcohol content of alcoholic beverages are as follows: Non-volatile substances in the sample were removed by distillation. The volume fraction of alcohol was measured using an alcohol meter. Temperature correction was performed by referring to a conversion table between alcohol meter temperature and ethanol concentration (alcohol content) at 20 °C to determine the ethanol concentration (alcohol content) of the sample at 20 °C. The results are shown in Table 1. Basic physicochemical properties of the wine The basic properties of the low-alcohol jujube wine prepared in Example 1 were tested: color, antioxidant properties, pH value, solids content, total acid, total phenols and total flavonoids, to comprehensively evaluate the quality of the low-alcohol wine.

[0067] The specific steps are as follows: ① Color detection: Color parameters, including L* (lightness, from light to dark), a* (green to red), and b* (blue to yellow), were evaluated using a Hunter colorimeter (Hunter Labs, USA), with values ​​ranging from positive to negative. A blank control was established for calibrating the colorimeter (L* = 100, a* = -0.01, b* = 0.01). Each wine sample was then analyzed sequentially.

[0068] ②Total acid content detection: Based on the possible total acid content of the sample, pipette 1 ml of the sample solution into a 50 ml Erlenmeyer flask and dilute it 10 times. Add 2-4 drops (10 g / L) of phenolphthalein indicator solution and titrate with 0.1 mol / L sodium hydroxide standard titration solution until a faint pink color persists for 30 seconds. Record the volume of 0.1 mol / L sodium hydroxide standard titration solution consumed.

[0069] ③ Antioxidant performance test: Total antioxidant capacity determination 150 μL of FRAP working solution was added to a 96-well microplate. The microplate reader was heated to 37°C, and the absorbance was measured at 593 nm. Then, 20 μL of sample solutions of different concentrations were added to the wells of the microplate. After 10 min, the absorbance was read at the same wavelength. The change in absorbance before and after the reaction was used to derive the corresponding FeSO4 solution concentration at each location from the standard curve, and then converted into FRAP values. The higher the FRAP value, the stronger the reducing power of the antioxidant, i.e., the stronger the total antioxidant capacity. The positive control group consisted of a vitamin C solution.

[0070] DPPH antioxidant capacity assay Preparation of DPPH test solution: Dissolve 1 mg of DPPH in 20 mL of anhydrous ethanol and sonicate for 5 min. Mix 2 mL of this DPPH solution with 1 mL of anhydrous ethanol thoroughly and measure the absorbance at 519 nm. Mix 2 mL of DPPH test solution with 1 mL of a low-alcohol sample of gradient concentration thoroughly and measure the absorbance at 519 nm. Take 1.6 mL of DPPH test solution and mix it with 0.6 mL of water to measure the absorbance at 734 nm. The experiment is repeated three times independently.

[0071] ABTS Antioxidant Capacity Assay First, prepare the ABTS+· solution: Mix ABTS with potassium persulfate and let it stand in the dark for a certain period of time to obtain a stable ABTS+· solution. Dilute the low-alcohol jujube juice sample 25 times. Mix the treated sample with the ABTS+· solution, shake well, and let it stand for a certain period of time to allow the reaction to proceed fully. Preheat the spectrophotometer to 724 nm for half an hour beforehand, measure the absorbance of the solution before and after the reaction, and calculate the ABTS+· scavenging rate.

[0072] ④ Determination of soluble solids content: Measured using a benchtop refractometer. ⑤ pH value measurement: pH value was measured using a pH meter.

[0073] ⑥ Determination of total phenol content: The total phenol content was determined by the Folin-Ciocalteu colorimetric method.

[0074] Gallic acid standard solutions of 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, and 25 mg / L were prepared. 1 mL of each standard solution was pipetted into a test tube, and 2 mL of Folin-Ciocalteu reagent and 2 mL of 10% sodium carbonate solution were added. After mixing thoroughly with a shaker, the mixture was reacted in a dark room for 1 hour. The instrument was zeroed with distilled water, and the absorbance (A765 mm) was measured to plot a standard curve. Subsequently, the samples were analyzed. A certain amount of sample was diluted with deionized water, and 1 mL of the diluted sample solution was measured using the method described above. The absorbance of the sample solution was measured and substituted into the standard curve to determine the total phenolic content (calculated as gallic acid). Deionized water was used as a blank control. The total phenolic content of the sample is expressed as gallic acid equivalent (mgGAE / g) per gram of extract.

[0075] ⑦ Determination of total flavonoid content: The sodium nitrite-aluminum nitrate colorimetric method was used.

[0076] Prepare rutin standard solutions of 0.08 mg / mL, 0.16 mg / mL, 0.24 mg / mL, 0.32 mg / mL, 0.4 mg / mL, and 0.48 mg / mL. Pipette 1 mL of each concentration of rutin standard solution into a centrifuge tube, add 1 mL of 5% NaNO2 solution, vortex to mix, let stand for 5 min, add 1 mL of 1% Al(NO3)3 solution, vortex to mix, let stand for 6 min, add 1 mol / L NaOH solution, vortex to mix, incubate in a water bath for 10 min (45℃), centrifuge for 10 min (4000 rpm), collect the supernatant, and determine A. 505 Zero the instrument with distilled water and plot a standard curve. Take a certain amount of sample and dilute it with methanol by a certain factor. Then, take 6 mL of the methanol-diluted sample and add 1 mL of 5% NaNO2 solution, shake to mix, let stand for 5 min, add 1 mL of 1% Al(NO3)3 solution, shake to mix, let stand for 6 min, add 1 mol / L NaOH solution, shake to mix, incubate in a 45℃ water bath for 10 min, centrifuge at 4000 rpm for 10 min, take the supernatant, and determine A. 505 mm, zeroed with distilled water.

[0077] The measurement results are shown in Table 1: Table 1 Serial Number Alcohol content / % Example 1 0.96% Example 2 0.91% Example 3 1.32% Example 4 1.31% Example 5 1.28% Comparative Example 1 1.6% Comparative Example 2 1.6% Comparative Example 3 2.4% Comparative Example 4 1.7% Experimental results: such as Figure 1 As shown, after adding different proportions of yeast, the alcohol content of jujube wine increased with the increase of the inoculum concentration within the range of 0.5% to 1.5%. The alcohol content remained stable when the inoculum concentration was 2% to 2.5%, and reached its highest level of 1.3% Vol when the inoculum concentration was 1.5%. Further addition of yeast had little effect on the alcohol content.

[0078] To further verify the effects of different yeast strains on the clarification of jujube wine, following the preparation method in Example 1, BV818 yeast was replaced with *V. aberrant* Wickham yeast, BF16, and RV171, respectively. A blank control (sterilized jujube juice) was also set up, and changes in the alcohol content and solids content of the finished product were observed. The results are as follows: Figure 2 As shown.

[0079] Figure 2 The trends of alcohol content and solids content were presented for the blank control, BV818, abnormal Wickham yeast, BF16, and RV171 under the same fermentation conditions. BV818 rapidly consumed the sugars in the jujube juice within the same timeframe, producing more alcohol. This is beneficial for shortening the fermentation cycle and increasing yield. Other yeasts produced less alcohol within the same timeframe, indicating a significantly longer fermentation cycle compared to BV818.

[0080] The specific physicochemical test results of Example 1 are shown in Table 2.

[0081] Table 2 Serial Number Unfermented After fermentation Comparative Example 4 Alcohol content %Vol 0.09 1.34 1.7 Color measurement L* 10.31 16.34 15.56 a* 6.62 11.01 10.13 B* 10.85 22.68 21.76 Total antioxidant capacity % 63.58 85.52 79.45 DPPH free radical scavenging capacity % 90.13 98.26 93.13 ABTS free radical scavenging ability % 91.63 98.42 94.11 pH value 5.14 4.17 4.53 Solid content °Brix 10.3 3.8 4.1 Total acid content (g / L) 0.09 0.62 0.71 Total phenol content (mg / 100ml) 277.82 291.76 284.33 Total flavonoid content (mg / 100ml) 1.85 2.37 2.04 As shown in Table 2, the antioxidant properties of the jujube wine prepared by this invention are enhanced: the total phenol content (calculated as gallic acid) increased from 277.82 mg / 100ml before fermentation to 291.76 mg / 100ml, and the total flavonoid content (calculated as rutin) increased from 1.85 mg / 100ml to 2.37 mg / 100ml, with increases of 4.98% and 28.11%, respectively. The FRAP method, DPPH free radical scavenging method, and ABTS free radical scavenging method showed that the total antioxidant capacity of the wine increased from 63.58% to 85.52%, and the DPPH and ABTS free radical scavenging rates reached 98.26% and 98.42%, respectively. This confirms that polyphenols and flavonoids are the core material basis for antioxidant activity, and the increase in their content is significantly positively correlated with the enhancement of antioxidant properties. In addition, during fermentation, the total acid content increased from 0.09 g / L to 0.62 g / L, and the pH value decreased to 4.17 (the suitable taste range for fruit wine is 3.0-4.5). This, along with the flavor compounds, resulted in a uniform orange-red color (L*=16.34, a*=11.01, b*=22.68) and a delicate and smooth taste.

[0082] Sensory analysis of red date low-alcohol beverage ① Sensory evaluation using electronic nose and electronic tongue Electronic nose measurement conditions: The specific operating steps for detecting volatile flavor substances based on an electronic nose are as follows: Accurately pipette 15 mL of wine sample into a 60 mL electronic nose sample bottle, and cover the sample bottle with a permeable silicone diaphragm as a cap to ensure airtightness. Let it stand at room temperature for 2 hours to allow the volatile odor of the sample to permeate the entire sample bottle.

[0083] The electronic nose sampling time interval was set to 1 second; cleaning time to 90 seconds; zero-point adjustment time to 5 seconds; sample connection time to 5 seconds; measurement time to 120 seconds; sensor chamber flow rate to 300 ml / min; and sample flow rate to 300 ml / min. Measurement results were selected based on three seconds of stable response (114 seconds, 115 seconds, and 116 seconds), and the average value was calculated as the test value. Each sample was measured in triplicate.

[0084] Electronic tongue measurement conditions: 80 mL of wine sample and 80 mL of ultrapure water were placed in a 120 mL beaker specifically designed for electronic tongue measurement, and both were positioned on the corresponding location on the automatic detection device. During the detection process, the sensor came into contact with the sample liquid and generated a signal. The built-in Alphasof software of the electronic tongue recorded one data point every second. After each sample was detected, the sensor automatically entered a cleaning process. In this study, the detection time of the electronic tongue was 120 seconds, and the cleaning time was 10 seconds.

[0085] The results are as follows Figure 3 As shown.

[0086] An electronic nose was used to monitor changes in the flavor characteristics of jujube juice during fermentation at different temperatures. Radar plot results based on electronic nose data are shown in Figures 3-4. The response values ​​of several sensors—W1S (sensitive to methyl compounds), W1W (sensitive to sulfides), W2S (sensitive to alcohols, ketones, and aldehydes), W2W (sensitive to aromatic components and organosulfur compounds), and W6S (selective to hydrides)—increased significantly throughout the fermentation process, with W1S, W2W, W2S, and W2W showing particularly significant increases in flavor. Simultaneously, an electronic tongue was used to evaluate taste attributes. As shown in Figures 5-6, between the original sample and the fermented product, saltiness, sourness, bitterness, and umami were significantly increased.

[0087] Combining the response regions of the electronic nose radar map (Figures 3-4) and the performance of the PEN3 sensor (such as W1C corresponding to aromatic components, W2W corresponding to organic sulfur compounds, and W2S corresponding to alcohols), it can be seen that the HZM group has a more obvious response to aroma substances containing sulfur / chlorine, alcohols, and organic sulfur.

[0088] (4) Analysis of aroma components in red date low-alcohol beverages ② The flavor compounds in the wine were determined using GC-IMS. Volatile compounds were analyzed using an advanced FlavorSpec® Static Headspace (SHS) gas chromatography-ion mobility spectrometry (GC-IMS) instrument (Gesellschaft für Analytische Sensorsysteme mbH (GAS) GmbH, Dortmund, Germany), equipped with a heated splitless injector. The analytical method was based on that of Li, Jiang et al. (2020), with some modifications to parameters. GC-IMS operating conditions are shown in Table S2. The drift gas (nitrogen) flow rate was set to 150 mL / min. Each spectrum was averaged 12 scans. All analyses were repeated three times.

[0089] The results are shown in Table 3.

[0090] ③ The compounds that differed between different fermentation modes were determined by HS-SPME-GC-MS. 4.0 mL of sample, 1.5 g of sodium chloride, and 10 μL of internal standard (2-octanol, 1760 μg / L) were mixed in a 20 mL headspace vial. The volatiles were then extracted for 45 min at 50°C using a solid-phase microextraction fiber (100 μm, Supelco, Bellefontein, PA, USA) coated with divinylbenzene / carboxylene / polydimethylsiloxane (DVB / CAR / PDMS). The extracted volatiles were desorbed at 250°C for 3 min at the injection port and analyzed in splitless mode on an Agilent 7890B / 5977B gas chromatograph-mass spectrometer (Agilent Technologies, CA, USA) using an HP-INNOWax gas chromatograph column (30 m × 0.25 mm × 0.25 μm, Agilent) with helium as the carrier gas at a flow rate of 1 mL / min.

[0091] The results are shown in Table 4, indicating that the fermentation process of the jujube wine preparation method of the present invention promotes the increase of aroma substance content.

[0092] Table 3. Flavor compounds detected by GC-IMS English name Chinese name Shelf number Molecular structure molecular weight RI Rt [sec] Dt [au] Butyl sulfide Butyl sulfide 544-40-1 <![CDATA[C8H 18 S]]> 146.3 1284.7 586.133 1.30046 3-heptanol 3-Heptanol 589-82-2 <![CDATA[C7H 16 O]]> 116.2 1283.6 584.218 1.65233 1-octanal Octal 124-13-0 <![CDATA[C8H 16 O]]> 128.2 1294.9 604.373 1.40702 1-butanol-M 1-Butanol-M 71-36-3 <![CDATA[C4H 10 O]]> 74.1 1142.6 371.89 1.1827 4-Heptanone 4-Hepanotone 123-19-3 <![CDATA[C7H 14 O]]> 114.2 1142.3 371.406 1.21969 1-butanol-D 1-Butanol-D 71-36-3 <![CDATA[C4H 10 O]]> 74.1 1142.5 371.685 1.37874 2-methyl-3-heptanone 2-Methyl-3-heptanone 13019-20-0 <![CDATA[C8H 16 O]]> 128.2 1206.2 460.269 1.27552 Allyl sulfide Allyl sulfide 592-88-1 <![CDATA[C6H 10 S]]> 114.2 1142.2 371.341 1.32444 2-Heptanone 2-Hepagonone 110-43-0 <![CDATA[C7H 14 O]]> 114.2 1232.6 499.172 1.62873 1-Pentanol n-Pentanol 71-41-0 <![CDATA[C5H 12 O]]> 88.1 1232.6 499.169 1.79873 1-Butanol, 3-methyl-, acetate 3-Methylbutyl acetate 123-92-2 <![CDATA[C7H 14 O2]]> 130.2 1119.4 342.653 1.75046 1-hexanal hexanol 66-25-1 <![CDATA[C6H 12 O]]> 100.2 1104.5 325.097 1.25897 Butanoicac id propyl ester Butyl propionate 105-66-8 <![CDATA[C7H 14 O2]]> 130.2 1142.2 371.311 1.27161 1,4-Dioxan 1,4-Dioxane 123-91-1 <![CDATA[C4H8O2]]> 88.1 1093 312.237 1.33843 1-Propanol, 2-methyl 2-Methyl-1-propanol 78-83-1 <![CDATA[C4H 10 O]]> 74.1 1091.2 310.228 1.37455 Ethyl thioacetate Ethioethyl thiocarbamate 625-60-5 <![CDATA[C4H8OS]]> 104.2 1083 301.935 1.13381 Butyl formate Butyl formate 592-84-7 <![CDATA[C5H 10 O2]]> 102.1 1048 270.775 1.20578 Pyrrolidine pyrrolidine 123-75-1 <![CDATA[C4H9N]]> 71.1 1037.6 262.12 1.27132 Table 4. Detection of Differential Compounds by HS-SPME-GC-MS

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing jujube wine, characterized in that, Includes the following steps: S1. Sterilized and enzyme-inactivated enzymatically hydrolyzed jujube juice is mixed with lactic acid bacteria and then fermented with lactic acid bacteria to obtain fermentation liquid; S2. Mix the fermentation liquid with yeast and then ferment with yeast to obtain jujube wine; The lactic acid bacteria mentioned in S1 are lactic acid bacteria that can tolerate alcohol concentrations of 5-8% (v / v), and the yeast mentioned in S2 is BV818 yeast. The fermentation broth described in S2 is not sterilized before being mixed with yeast.

2. The method for preparing jujube wine according to claim 1, characterized in that, The fermentation temperature of the lactic acid bacteria described in S1 is 30~37℃, and the fermentation time is 40~50h. Preferably, the amount of lactic acid bacteria added is 1~2% of the volume of the enzymatically hydrolyzed jujube juice, measured by absorbance OD. 600 The value is measured for lactic acid bacteria activation solution of 0.6~0.

8.

3. The method for preparing jujube wine according to claim 1 or 2, characterized in that, The yeast fermentation described in S2 is carried out at a temperature of 28-35℃ for 40-50 hours. Preferably, the amount of yeast added is 0.5-1.5% of the volume of the enzymatically hydrolyzed jujube juice. The absorbance OD is used as the indicator. 600 The value is 0.6~0.8 for yeast activation solution.

4. The method for preparing jujube wine according to any one of claims 1 to 3, characterized in that, The lactic acid bacteria mentioned in S1 is Lactobacillus fermentum, and the ratio of Lactobacillus fermentum to BV818 yeast is 1:

1.

5. The method for preparing jujube wine according to any one of claims 1 to 4, characterized in that, The enzymatically hydrolyzed jujube juice described in S1 is prepared by steaming and enzymatically hydrolyzing jujubes. The enzymatic hydrolysis is a mixture of cellulase and pectinase, and preferably the total amount of cellulase and pectinase used is 1-2% of the weight of the jujubes.

6. The method for preparing jujube wine according to claim 5, characterized in that, The enzymatic hydrolysis is performed at a pH of 4.5-5.5, a temperature of 45-55°C, and a time of 10-14 hours. Preferably, the enzymatic hydrolysis is performed at a pH of 5, a temperature of 50°C, and a time of 12 hours.

7. The method for preparing jujube wine according to any one of claims 1 to 6, characterized in that, The soluble solids content of the enzymatically hydrolyzed jujube juice reaches 12-14°Brix.

8. A jujube wine prepared by the method of any one of claims 1 to 7.

9. The jujube wine according to claim 8, characterized in that, The jujube wine must meet at least one of the following characteristics: (a) The total phenol content of the jujube wine, calculated as gallic acid, is ≥291.76 mg / 100 ml; (b) The total flavonoid content of the jujube wine, calculated as rutin, is ≥2.37 mg / 100 ml; (c) The total acid content of the jujube wine is ≥0.62g / L, and the pH value is 3.7~4.

3.

10. The jujube wine according to any one of claims 8 to 9, characterized in that, It contains one or more of the following flavor compounds: 3-Heptanol, 1-Octanol, n-Butanol, 4-Heptanone, 2-Methyl-3-Heptane, 2-Heptanone, 1-Pentanol, 3-Methyl-1-Butanol Acetate, 1-Hexanal, Butyl Propionate, 2-Methyl-1-Propanol, Butyl Formate.

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