A low-methanol fermentation method for fruit wine brewing suitable for high pectin fruits

Abstract

The application discloses a low-methanol fermentation fruit wine brewing method suitable for high-pectin fruits and belongs to the technical field of fruit wine brewing. The method comprises the following steps: step 1, raw material pretreatment; step 2, addition of brewing accessories; step 3, component adjustment; step 4, stage-by-stage fermentation and pith residue separation: including a pre-fermentation stage and a main fermentation stage; and step 5, pectin removal, clarification and filtration and bottling. The technical scheme of the application significantly improves the fermentation efficiency, and after 3 months of storage, the sensory score is higher, the taste is better, and the aroma quality is better.

Description

Technical Field

[0001] This invention belongs to the field of fruit wine brewing technology, and relates to a low-methanol fermentation method for fruit wine brewing suitable for fruits with high pectin content. Background Technology

[0002] Methanol is a harmful byproduct produced during fruit wine fermentation, posing a clear risk to human health, particularly the optic and central nervous systems. High-pectin fruits (such as apples, hawthorns, apricots, plums, and some berries) are important raw materials for brewing specialty fruit wines, but their cell walls and mesoglea are rich in pectin, a major precursor to methanol production during fermentation. Therefore, methanol control is an unavoidable issue in winemaking techniques using these fruits.

[0003] Due to factors such as the characteristics of brewing raw materials, processing techniques, and quality standards, fruit wine products on the market generally suffer from quality problems such as insufficient fruit aroma, bland flavor, and oxidative browning. Especially for fruit raw materials with high pectin content and low juice yield, large amounts of exogenous commercial pectinase are usually added during production to increase the juice yield. However, this can easily lead to the methanol content in the fermented wine exceeding the national standard limit (400 mg / L), posing a potential threat to human health.

[0004] Currently, for fermented wines made from non-grape fruits, my country only specifies a methanol limit of ≤0.4 g / L in the agricultural industry standard NY / T 1508-2017 "Green Food Fruit Wine"; the newly released QB / T 5476-2020 "General Technical Requirements for Fruit Wine" also does not include a methanol content limit. Methanol in fruit wine mainly originates from the enzymatic hydrolysis of pectin in the raw materials by pectin methyl esterase, with only a small amount coming from the glycine metabolism pathway of yeast. During the fruit wine brewing process, methanol production is primarily related to the pectin content of the raw materials, the addition of commercial pectinase, and the role of yeast.

[0005] Although there are individual research reports on methanol control or fruit wine process optimization in existing technologies, it is difficult to achieve synergistic optimization between reducing methanol content and improving product quality (such as yield and flavor) in the brewing of fruit wines made from high-pectin fruits, especially in terms of the lack of systematic research on key processing technologies and the control of their core parameters.

[0006] Therefore, there is an urgent need to develop a new fruit wine brewing process that combines low methanol content with high-quality characteristics, taking into account the physicochemical properties of fruit raw materials. This process will not only help to fully explore and utilize local specialty fruit resources, but also significantly improve the flavor characteristics, quality and safety, and market competitiveness of fruit wine. Summary of the Invention

[0007] In order to overcome the shortcomings of the existing technology, the present invention provides a low-methanol fermentation method for fruit wine making suitable for high-pectin fruits. This method significantly improves fermentation efficiency, and after 3 months of storage, the sensory score is higher, the taste is better, and the aroma quality is superior.

[0008] The technical solution is as follows:

[0009] Embodiments of the present invention provide a method for brewing low-methanol fermented fruit wine suitable for high-pectin fruits, comprising the following steps:

[0010] Step 1, Raw material pretreatment: Select healthy, disease-free, ripe fruits; apples, cherries, pears, peaches, etc. need to be pitted; other fruits are washed, stems are removed, cut into pieces and crushed appropriately, and put into the can along with the skin and pulp. The filling amount is controlled at 70%-80% of the can volume, preferably 70%;

[0011] Step 2, Addition of brewing adjuncts: During the fruit crushing and loading process, add 50-100 mg / L of SO2 (in the form of potassium metabisulfite), let stand for 30 minutes, then add 60-80 mg / L of commercial pectinase; before fermentation, add 0.4-0.8 g / L of bentonite, preferably 0.4 g / L, to improve the clarification effect of the fruit wine during fermentation and reduce the amount of clarifying agent used later; then macerate at a low temperature of 10-15℃ for 24-48 hours, preferably 24 hours.

[0012] Step 3, Ingredient Adjustment:

[0013] Based on the brewing characteristics of the raw materials, the target alcohol content of the fermented wine is controlled at 8%-12% by volume, with 8% being preferred;

[0014] For fruits such as jujubes and dogwood that are difficult to juice, the ratio of material to liquid should be controlled at 1:1 to 1:2 (water:fruit, by weight) to fully extract soluble components.

[0015] Step 4: Staged Fermentation and Pomace Separation: This includes a pre-fermentation stage and a main pre-fermentation stage. The pre-fermentation stage involves fermentation with pomace, aiming to fully extract sugars and other nutrients from the raw materials. During this stage, 200-250 mg / L of commercial yeast (or the recommended dosage according to the product instructions) is inoculated, and fermentation is carried out at a constant temperature of 13-18 ℃. When the specific gravity of the fermentation mash drops to 1.015-1.000, the pomace is separated, and the process moves to the main fermentation stage. The main fermentation stage is clear liquor fermentation. First, the required sugar is added according to the target alcohol content. After the tank is full, alcoholic fermentation continues at a constant temperature of 15±3 ℃. When the specific gravity of the mash drops to 0.995-0.998 or the residual sugar content is <4 g / L, 50-100 mg / L SO2 is added to terminate fermentation. The mash is then aged at low temperatures for 3-6 months to promote flavor compound formation and enhance the stability of the wine.

[0016] Step 5: Fining, clarification, filtration and bottling: After aging, the fermented fruit wine is fined and clarified by adding 0.8-1.0 g / L bentonite and / or 0.3-0.5 g / L chitosan, and then filtered and bottled.

[0017] Furthermore, in step 2, the amount of commercial pectinase added is 60-80 mg / L, preferably 80 mg / L, and preferably fruit juice or wine-specific pectinase or low-methanol pectinase.

[0018] Furthermore, for fruit raw materials with high sugar content and low acidity (total sugar content of fruit >200 g / L (calculated as glucose), total acid content <5 g / L (calculated as tartaric acid), sugar-acid ratio >30:1) (such as persimmon, apple, pear, etc.), the total acid content of the juice is adjusted to 6-8 g / L (calculated as tartaric acid) by adding organic acids, and the pH value is ensured to be below 3.5 to maintain good microbial stability and flavor balance; for fruit raw materials with low sugar content and high acidity (total sugar content of fruit <100 g / L, total acid content >9 g / L, sugar-acid ratio <10:1) (such as kiwi, smooth-skinned papaya, cherry, etc.), the main approach is to supplement exogenous sugars (such as sucrose) and adjust to a suitable sugar-acid ratio of not less than 14 to ensure smooth fermentation and a harmonious taste of the finished wine. It should be noted that, based on the initial sugar content of the raw materials and the target alcohol content, sugar should be added during the primary fermentation stage (each 17-18 g / L of added sugar can increase the alcohol content by about 1%) to achieve the target alcohol content.

[0019] Furthermore, adding 0.4 g / L of bentonite before fermentation improves the clarification effect of the fruit wine during fermentation and reduces the amount of clarifying agent used later.

[0020] Furthermore, in step 4, the pre-fermentation stage is fermentation with the skin and residue, designed to fully extract the sugars and other nutrients from the raw materials. During this stage, 200 mg / L of commercial yeast (or the recommended dosage according to the product instructions) is inoculated, and constant-temperature fermentation is carried out at 15 °C. When the specific gravity of the fermentation mash drops to 1.015, the skin and residue are separated, and the process proceeds to the main fermentation stage.

[0021] Furthermore, the main fermentation stage is clear juice fermentation. First, the required sugar is added according to the target alcohol content. After the tank is full, alcoholic fermentation continues at a constant temperature of 15°C. When the specific gravity of the mash drops to 0.995-0.998, preferably 0.996, or the residual sugar content is <4 g / L, 50-100 mg / L SO2, preferably 50 mg / L SO2, is added to terminate the fermentation. Subsequently, the mash is aged for 3-6 months under low temperature conditions to promote the formation of flavor compounds and enhance the stability of the wine.

[0022] Furthermore, in step 5, 50-80 mg / L SO2 is added before bottling, preferably 50 mg / L SO2, to ensure that the free SO2 content in the wine is not less than 30 mg / L.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) Based on the characteristics of raw material brewing, the juice composition is optimized, including the ratio of raw material to liquid, target alcohol content and sugar-acid balance, so as to effectively control the flavor and quality of fermented fruit wine from the source.

[0025] (2) Based on the methanol generation pathway during fruit wine fermentation, the key technologies and process parameters of low-temperature maceration fermentation were systematically optimized, including the timing of adding brewing auxiliary materials, the timing of separating pomace, the synergistic control of pre-fermentation and main fermentation, and clarification technology, which effectively inhibited methanol generation and significantly improved the safety and stability of fruit wine products.

[0026] (3) It is suitable for the large-scale production of fermented wine from fruits with high pectin content and low juice yield, while taking into account both a high alcohol yield and the retention of nutritional active ingredients. Attached Figure Description

[0027] Figure 1 Effects of different processing techniques on the content of total phenols (a), total flavonoids (b), and antioxidant activity (c) in kiwifruit wine;

[0028] Figure 2 The effects of different processing techniques on the content of total phenols (a), total flavonoids (b), and antioxidant activity (c) in apple wine;

[0029] Figure 3 The effects of different processing techniques on the taste and quality of kiwi fruit wine (a) and apple fruit wine (b);

[0030] Figure 4 The effects of different processing techniques on the characteristic aromas of kiwifruit wine (a) and apple wine (b). Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] 1. Test method:

[0033] 1.1 Fermentation of Fruit Wine

[0034] 1.1.1 Test Materials

[0035] Xu Xiang kiwifruit (harvested from Rougu Town, Yangling City, Shaanxi Province) was allowed to ripen naturally at room temperature after harvest. The firmness of the ripened fruit was 2.50 kg / cm². 2 The pectin content is 3.49 g / kg, the total sugar content is 128.0 g / L, the total acid content is 17.97 g / L, and the pH value is 3.33.

[0036] Red Fuji apples (harvested from Heyang County, Weinan City, Shaanxi Province) had a pectin content of 2.30 g / kg, a total sugar content of 130.0 g / L, a total acid content of 2.49 g / L, and a pH value of 3.89 at the time of harvest.

[0037] Based on the brewing characteristics of the raw materials, the target alcohol content was set at 11% vol. In the brewing process of kiwi fruit wine, the adjustment of raw material components mainly focuses on sugar content, while apple fruit wine requires adjustment not only of sugar content but also of acidity and pH value. The fermentation tanks were 10 L glass jars, with replicates for both the control and treatment processes.

[0038] 1.1.2 Fermentation Process of Fruit Wine

[0039] Low-methanol fermented fruit wine processing technology (low-temperature maceration fermentation): Fruit raw materials → sorting and cleaning → destemming and crushing → adding with skins and pomace into tanks → adding brewing adjuncts → component adjustment → low-temperature maceration → pre-fermentation → separation of skins and pomace → primary fermentation → termination of fermentation → low-temperature aging → fining and clarification → filtration and bottling

[0040] Traditional process (clear juice fermentation): Fruit raw materials → sorting and washing → destemming, crushing and pressing → clear juice entering tanks → adding brewing adjuncts → adjusting sugar → alcoholic fermentation → stopping fermentation → low-temperature aging → fining and clarification → filtering and bottling

[0041] Processing technology of low-methanol kiwifruit fermented wine:

[0042] Ripe Xu Xiang kiwifruit, after removing the stems, was crushed and placed directly into a container. 100 mg / L SO2 was added, and the mixture was allowed to stand for 30 minutes. Then, 80 mg / L commercial pectinase and 400 mg / L activated bentonite were added, and the mixture was macerated at a low temperature (10-15 ℃) for 24 hours. After maceration, 200 mg / L commercial active dry yeast was inoculated to initiate pre-fermentation, with the fermentation temperature controlled at 15±2 ℃. Once fermentation began, the temperature and specific gravity of the fermentation mash were monitored and recorded twice daily (morning and evening), and circulation was performed as needed to promote yeast fermentation. When the specific gravity of the fermentation mash dropped to 1.010, the pomace was separated promptly. Based on the target alcohol content of 11.0% vol., an appropriate amount of sucrose was added to the liquid to initiate the primary fermentation stage, with the primary fermentation temperature controlled at 15±2 ℃. Temperature and specific gravity changes were continuously monitored during this period. When the specific gravity dropped to 0.996, 50 mg / L SO2 was added to terminate fermentation, and the mixture was sealed and placed in a 4 ℃ cold storage for low-temperature aging. After 3 months of aging, racking is performed, and 600 mg / L bentonite is added for fining and clarification. Before bottling, 50 mg / L SO2 is added again, and the product is filtered before bottling.

[0043] Processing technology of low-methanol apple fermentation wine:

[0044] After washing, core, and chopping the Fuji apples, crush them and place them directly into a fermentation tank. Add 100 mg / L SO2, and after 30 minutes, add 80 mg / L commercial pectinase and 400 mg / L activated bentonite. Simultaneously, add organic acids to adjust the total acidity of the apple juice to 6-8 g / L and adjust the pH to below 3.5. Then, macerate at a low temperature (10-15 ℃) for 24 hours. Inoculate with 200 mg / L commercial active dry yeast and pre-ferment at 15±2 ℃. Monitor the temperature and specific gravity of the fermentation mash daily and circulate the mash. When the specific gravity of the fermentation mash drops to 1.008, press and separate the pomace. Based on the target alcohol content of 11.0% vol., add an appropriate amount of sucrose and proceed to the main fermentation stage. The fermentation temperature is controlled at 15±2 ℃, and temperature and specific gravity changes are continuously monitored during this period. When the specific gravity drops to 0.996, 50 mg / L SO2 is added to stop fermentation, and the mixture is sealed and transferred to a 4 ℃ cold storage for low-temperature aging. After 3 months of aging, racking is performed, and 600 mg / L bentonite is added for fining and clarification. Before bottling, 50 mg / L SO2 is added, and the mixture is filtered before bottling.

[0045] It should be noted that the traditional process in this experiment mainly adopts the clear juice fermentation method, that is, after the ripe fruit is crushed, the juice is directly pressed to obtain the clarified juice, and then only sucrose is added to adjust to the target alcohol content, brewing adjuncts are added, and then commercial active dry yeast is inoculated and the primary fermentation is carried out under controlled temperature conditions. The addition of brewing adjuncts (such as sulfur dioxide, commercial pectinase, bentonite, etc.), fermentation conditions (including yeast type, fermentation temperature, etc.), and subsequent operating parameters are all consistent with the "low methanol fermentation fruit wine processing technology".

[0046] 1.2 Determination of basic physicochemical indicators

[0047] Referring to GB / T 15038-2006 "General Analytical Methods for Wine and Fruit Wine", total sugar (calculated as glucose, g / L) was determined by Fehling's reagent hot titration method; total acid (calculated as tartaric acid, g / L) was determined by indicator method; alcohol content (%vol.) and dry extract (g / L) were determined by density bottle method; pH value was determined by pH meter method; and total SO2 content was determined by oxidation method.

[0048] 1.3 Determination of methanol content

[0049] The methanol content was determined using an ultraviolet spectrophotometer, with units of mg / L, in accordance with GB / T 15038-2006 "General Analytical Methods for Wine and Fruit Wine" and the method of Zhu Lijuan (2014).

[0050] 1.4 Determination of CIELab color parameters

[0051] CIELab color parameters refer to SN / T 4675.25-2016 "Determination of color of export wines CIE 1976 (L*a*b*) color space method". The absorbance of the sample is measured in the wavelength range of 380-780 nm. The absorbance, retrograde relative color stimulus function and color matching function are integrated and then compared with the standard tristimulus values.

[0052] 1.5 Determination of phenolic substances and antioxidant activity

[0053] Following the method of Bozovic et al. (2025): total phenols were determined by the modified Folin-Schowal method; total flavonoids were determined by the sodium nitrite and aluminum chloride colorimetric method. All results were expressed as catechins: (+)-catechin equivalent value, in mg / L.

[0054] Following the method of Lan et al. (2021), antioxidant activity was evaluated using the ABTS free radical scavenging method, and the results were expressed as Trolox equivalent value TEAC in μmol / L.

[0055] 1.6 Sensory Analysis

[0056] 1.6.1 Establishment of Sensory Evaluation Panel

[0057] Following the method of Yang Jie (2021), the tasters were trained and assessed, and a panel of experts was formed to conduct sensory analysis of the fruit wine samples. The panel consisted of 10-12 members, with a male-to-female ratio of approximately 1:1, aged 18-25, and comprised of undergraduate and graduate students from the College of Enology at Northwest A&F University. Personnel were selected from this panel for the training and assessment of the tasters.

[0058] 1.6.2 Sensory characteristics description and quantitative descriptive analysis of aroma

[0059] Referring to the "Tasting Record Sheet for the Asian Wine Quality Competition (Still Wine)" (Li Hua et al., 2022), the wine samples were scored and qualitatively and descriptively analyzed from the aspects of appearance (15 points), aroma (30 points), taste (44 points), and balance (11 points). Simultaneously, referring to GB / T 16861-1997 "Sensory Analysis: Identification and Selection of Descriptors for Establishing Sensory Profiles using Multivariate Analysis Methods": First, each taster was required to evaluate the characteristic aromas of the wine sample using 3-5 aroma descriptors; second, for each aroma descriptor used, and the designated taste descriptors (sweetness, acidity, bitterness, astringency, and balance), the taster was required to quantitatively quantify the intensity of the perceived aroma using a 0-5 discontinuous scale (0 indicates no sensation, 5 indicates strong sensation); finally, based on the frequency of use and evaluation intensity of each sensory descriptor, its geometric mean M was calculated. The larger the M value, the higher the contribution of the descriptor to the sensory characteristics of the product.

[0060]

[0061] In the formula: F is the percentage of times a descriptor is actually mentioned out of the maximum possible total number of times the descriptor is mentioned; I is the percentage of the strength of a descriptor actually given by the evaluation team out of the maximum possible strength of the descriptor.

[0062] 1.7 Data Processing

[0063] The physicochemical indicators and sensory analysis data were analyzed for significant differences and multiple comparisons (new multiple range method) using the statistical analysis software DPS V6.55. The results were recorded in the form of mean ± standard deviation, with a significance level of P<0.05. Sensory analysis data were analyzed using Origin 2025b(10.25).

[0064] 2. Experimental Results

[0065] 2.1 Effects of different processes on the fermentation cycle of kiwifruit and apple fruit wine

[0066] During the alcoholic fermentation stage, the average fermentation temperature for both types of fruit wine was 15±2 ℃. Compared to the traditional process (i.e., clear juice fermentation, as a control), the kiwi fruit wine produced using the low-methanol fruit fermentation process (referred to as the "new process") also had a fermentation cycle of 11 days. For apple fruit wine, the control had a fermentation cycle of 20 days, while the new process shortened the fermentation cycle to 13 days, significantly improving fermentation efficiency.

[0067] 2.2 Effects of different processes on the basic physicochemical properties of fermented kiwifruit and apple wine

[0068] As shown in Table 1, all the fruit wines were dry: (1) The yield of kiwi fruit wine made using the traditional process (control) was 59.85%, while the yield of the new process reached 70.07%, which was about 10% higher than the traditional process; the yield of apple fruit wine made using the traditional process was 61.98%, while the yield of the new process reached 73.23%, which was about 11% higher than the control. (2) Compared with the traditional process, the new process (especially apple wine) significantly increased the methanol content in fermented fruit wines. At the end of fermentation, the methanol content in fruit wines brewed using the new process exceeded 400 mg / L. However, after 3 months of storage, the methanol content in the treated wine samples decreased to below 400 mg / L, which met the requirements of my country's NY / T 1508-2017 "Green Food Fruit Wine" for methanol in fruit wine (≤400 mg / L). The methanol content in kiwi fruit wine brewed using the new process was 377.06 mg / L, while the methanol content in apple wine was 394.14 mg / L. (3) Compared with the traditional process, the new process did not significantly affect the basic physicochemical indicators of the two fermented fruit wines.

[0069]

[0070] 2.3 Effects of different processes on the color of fermented fruit wine made from kiwifruit and apple

[0071] Table 2 shows that the a content of kiwi fruit wine * A negative value indicates a greenish tint, b * A positive value indicates a yellowish hue, with an overall yellowish-green tone; at the end of fermentation, the L value of the kiwi fruit wine produced using the new process... * The value was not significantly different from the control, but after 3 months of storage, its L... * Value, C * ab Value and ΔE * ab The values ​​were all higher than the control, indicating that the wine samples were superior in terms of gloss and color saturation. Similarly, the apple wine was also yellowish-green (slightly lighter), and the wine samples made using the new process were superior in both gloss and color saturation to those made using the traditional process.

[0072]

[0073] 2.4 Effects of different processing techniques on phenolic compounds and antioxidant activity in fermented kiwifruit and apple wines

[0074] Depend on Figure 1 It can be seen that compared with the traditional process (control), the total phenol and total flavonoid content of the kiwi fruit wine brewed by the new process is significantly increased (P<0.05), but its scavenging activity against ABTS free radicals is not significantly different from that of the control.

[0075] Figure 1 In the middle, 0 months, i.e., the end of alcoholic fermentation; for the same storage time, different letters indicate significant differences between treatments (P<0.05). The same applies below.

[0076] Depend on Figure 2 It can be seen that, compared with the traditional process, the apple wine brewed using the new process has significantly higher content of total phenols and total flavonoids, and the wine sample also has significantly enhanced scavenging activity against ABTS free radicals (P<0.05).

[0077] 2.5 Effects of different processing techniques on the sensory quality of fermented kiwifruit and apple wine

[0078] 2.5.1 Effects of different processing techniques on the sensory scores of kiwifruit and apple fermented fruit wine

[0079] Table 3 shows that at the end of fermentation, the sensory score of the kiwi wine made using the new process was higher than that of the control. After three months of storage, its scores in aroma and taste further improved, reaching a total score of 80-85 points, which is considered "very good" and superior to the control sample. For apple wine, the sensory score of the new process was slightly lower than that of the control at the end of fermentation, but after three months of storage, it showed significant improvement in appearance, aroma, taste, and balance, reaching a total score of 82.50 points, which is considered "very good" (80-94 points). The control sample, on the other hand, scored 78.92 points, which is considered "good" (70-79 points). The results indicate that the new process helps improve the sensory quality of fruit wine during storage, especially in terms of aging potential.

[0080] Table 3: Effects of different processing techniques on the sensory scores of kiwifruit and apple fermented fruit wine

[0081]

[0082] Rating criteria: Perfect, 85-100; Very good, 80-94; Good, 70-79; Average, 50-69; Poor, <50.

[0083] 2.5.2 Effects of different processing techniques on the taste and aroma characteristics of fermented kiwi and apple wines

[0084] Figure 3 The effects of different processing techniques on the taste and quality of two types of fermented fruit wines were shown, with results expressed as the geometric mean M of sensory characteristic descriptors. The taste radar chart revealed that for kiwi fruit wine, at the end of fermentation, the wine produced using the new process had higher sweetness, astringency, alcohol content, and balance than the control; after 3 months of storage, its acidity and bitterness were lower than the control, while its balance was higher. For apple fruit wine, at the end of fermentation, the wine produced using the new process had lower sweetness, astringency, alcohol content, and balance than the control, but after 3 months of storage, its sweetness, alcohol content, and balance were all higher than the control. This indicates that after 3 months of aging, the taste of the fruit wine produced using the new process was significantly improved, resulting in superior overall quality.

[0085] To further clarify the characteristic aromas of fermented fruit wines, we compared the characteristic aroma descriptors of the two types of fermented fruit wines (taking the top 10 descriptors with the highest M-values) to reveal the differences and characteristics of their aroma profiles. Figure 4 It was found that after three months of storage, the kiwi wine brewed using the new process exhibited more prominent aromas of mango and pineapple compared to the control; while the apple wine brewed using the new process also surpassed the control in terms of aroma characteristics of grass, peach, and grapefruit. This indicates that the new process helps to improve the quality of the original varietal aromas in fruit wines.

[0086] The sensory analysis results above indicate that, compared with the traditional process, the kiwi and apple fermented fruit wine brewed using the new process has a higher sensory score, better taste, and superior aroma quality after 3 months of storage.

Claims

1. A method for brewing fruit wine with low methanol fermentation suitable for high-pectin fruits, characterized in that, Includes the following steps: Step 1: Raw material pretreatment: Select healthy, disease-free, ripe fruits, remove the pits, wash them, remove the stems, cut them into pieces and crush them appropriately, and put them into the can along with the skin and pulp. The filling amount should be controlled at 70%-80% of the can volume. Step 2, Addition of brewing adjuncts: During the fruit crushing and loading process, add 50-100 mg / L of SO2; after standing for 30 minutes, add 60-80 mg / L of commercial pectinase; before fermentation, add 0.4-0.8 g / L of bentonite; then soak at a low temperature of 10-15℃ for 24-48 hours. Step 3, Ingredient Adjustment: Based on the brewing characteristics of the raw materials, the target alcohol content of the fermented wine is controlled at 8%-12% by volume. For fruit raw materials that are difficult to juice, the ratio of material to liquid should be controlled between 1:1 and 1:

2. Step 4, Staged Fermentation and Pomace Separation: This includes a pre-fermentation stage and a main pre-fermentation stage. The pre-fermentation stage involves fermentation with pomace, inoculated with 200-250 mg / L commercial yeast, and carried out at a constant temperature of 13-18 ℃. When the specific gravity of the fermented mash drops to 1.015-1.000, the pomace is separated, and the fermentation proceeds to the main fermentation stage. The main fermentation stage involves clear juice fermentation. First, the required sugar is added according to the target alcohol content. After the tank is full, alcoholic fermentation continues at a constant temperature of 15±3 ℃. When the specific gravity of the mash drops to 0.995-0.998 or the residual sugar content is <4 g / L, 50-100 mg / L SO2 is added to terminate the fermentation. Subsequently, the mash is aged for 3-6 months at low temperature. Step 5: Fining, Clarification, Filtration and Bottling: After aging, the fermented fruit wine is fined and clarified by adding 0.8-1.0 g / L bentonite and / or 0.3-0.5 g / L chitosan, followed by filtration and bottling.

2. The method according to claim 1, characterized in that, In step 2, the amount of commercial pectinase added is 80 mg / L, and 0.4 g / L of bentonite is added before fermentation.

3. The method according to claim 1, characterized in that, In step 3, for fruit raw materials with high sugar content and low acidity, the total acid content of the juice is adjusted to 6-8 g / L (calculated as tartaric acid) by adding organic acids, and the pH value is ensured to be below 3.5; for fruit raw materials with low sugar content and high acidity, exogenous sugars are added to adjust the sugar-acid ratio to be not less than 14.

4. The method according to claim 1, characterized in that, In step 4, during the pre-fermentation stage, 200 mg / L of commercial yeast is inoculated and fermented at a constant temperature of 15 °C. When the specific gravity of the fermentation mash drops to 1.015, the husks and residues are separated, and the process is transferred to the main fermentation stage.

5. The method according to claim 1, characterized in that, During the main fermentation stage, the temperature is controlled at 15°C and constant temperature fermentation continues; when the specific gravity of the mash drops to 0.996, 50 mg / L SO2 is added.

6. The method according to claim 1, characterized in that, In step 5, add 50-80 mg / L SO2 before bottling to ensure that the free SO2 content in the wine is not less than 30 mg / L.

7. The method according to claim 6, characterized in that, Add 50 mg / L SO2 before bottling.

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