A method for preparing grape vinegar using grape seeds and grape skins

Abstract

This invention discloses a method for preparing grape vinegar by fermentation using grape seeds and grape skins, belonging to the field of food processing technology. The method uses grape skins and seeds, byproducts of wine processing, as raw materials. After sorting, low-temperature drying, and microwave cell wall disruption, 30°–52° grain liquor is used as the fat-soluble extraction medium for synergistic crushing and alcohol extraction. An ultrasonic-assisted extraction step can be added as needed. Subsequently, fruit wine yeast is inoculated for anaerobic alcoholic fermentation, followed by deep liquid-ventilated fermentation with acetic acid bacteria. Finally, the product is obtained through centrifugation, filtration, low-temperature aging, instantaneous sterilization, and bottling. This invention significantly improves the dissolution and retention rates of fat-soluble active ingredients such as resveratrol and proanthocyanidins through the synergistic effect of microwave cell wall disruption and alcohol extraction, achieving high-value utilization of grape processing byproducts, reducing waste emissions, and combining environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and in particular to a method for preparing grape vinegar by fermenting grape seeds and grape skins. Background Technology

[0002] As a widely consumed beverage globally, wine production generates a large amount of byproducts such as grape skins and seeds, commonly referred to as grape pomace. Currently, my country's wine industry is expanding annually, producing a massive amount of grape pomace each year. However, most of these valuable byproducts are directly discarded, landfilled, or used as low-cost animal feed, resulting in severe resource waste, environmental pollution, and increased environmental treatment costs for businesses.

[0003] In fact, grape skins and seeds are rich in various natural active ingredients, the most representative of which are resveratrol and proanthocyanidins. Resveratrol is a natural polyphenol with extremely strong antioxidant activity. It can scavenge free radicals in the body, inhibit lipid peroxidation, and also has various physiological and health benefits such as protecting the cardiovascular system, anti-inflammation, antibacterial properties, and delaying aging. It has extremely high application value in the fields of food, medicine, and health products. Proanthocyanidins are a class of complex flavonoids that also have excellent free radical scavenging capabilities. Their antioxidant activity is 20 times that of vitamin C and 50 times that of vitamin E. They also have the effects of improving skin condition, protecting eyesight, enhancing immunity, and preventing chronic diseases. In addition, grape skins and seeds also contain flavonoids, phenolic acids, dietary fiber, and various minerals, possessing extremely high potential for high-value utilization.

[0004] To realize the resource utilization of grape pomace, existing technologies have included research and applications for its use in vinegar production. These technologies attempt to transform the nutrients in grape pomace into edible vinegar products through fermentation, thereby increasing its added value. For example, Chinese invention patent application number CN201010607376.0 discloses a method for preparing grape vinegar, using rice husks, wheat bran, and grape pomace as raw materials, combined with fermentation using acetic acid bacteria inoculated into wine. In addition, some technologies employ traditional water extraction processes to extract active ingredients from grape pomace, which are then mixed with fermentation raw materials for vinegar fermentation, or directly use solid-state fermentation processes to treat grape pomace and prepare grape vinegar.

[0005] However, the aforementioned existing technologies have many core defects in practical applications, which severely limit the high-value utilization of grape pomace, specifically in the following three aspects: First, the dissolution rate of active ingredients is extremely low. Grape seeds and skins have a dense cell wall structure, mainly composed of cellulose, hemicellulose, and lignin, forming a strong barrier that makes it difficult for fat-soluble active ingredients (such as resveratrol and proanthocyanidins) to be released into the extraction system. Existing technologies, such as direct crushing and traditional water extraction, cannot effectively disrupt the integrity of the cell wall and cell membrane structure, resulting in extremely low dissolution rates of active ingredients such as resveratrol and proanthocyanidins. Most of the active ingredients remain in the grape pomace and cannot be fully utilized, leading to a waste of resources.

[0006] Secondly, heat-sensitive active ingredients are easily degraded. Resveratrol, proanthocyanidins, and other active ingredients are all heat-sensitive substances, highly susceptible to degradation and oxidation under high temperatures, leading to the loss of their physiological activity. Existing technologies employ processes such as high-temperature drying, high-temperature fermentation, or high-temperature extraction, which can easily cause the degradation of these heat-sensitive active ingredients, further reducing the product's health benefits. Simultaneously, solid-state fermentation easily generates localized high temperatures and carries a high risk of contamination by other microorganisms, which not only affects fermentation efficiency but also damages the stability of the active ingredients.

[0007] Third, the extraction system has poor compatibility. Traditional water extraction systems are highly polar, while active ingredients such as resveratrol and proanthocyanidins are fat-soluble substances with extremely low solubility in water, resulting in poor extraction efficiency. Even with methods such as extending extraction time and increasing the number of extractions, it is difficult to significantly improve the extraction rate of active ingredients. The final grape vinegar product has a low content of active ingredients, greatly reducing its health benefits. In addition, some existing processes use fermentation methods with poor compatibility, failing to balance the retention of active ingredients with fermentation efficiency, making it difficult to achieve industrial-scale production.

[0008] Furthermore, most existing technologies for making vinegar from grape pomace have not been optimized for the characteristics of grape pomace, resulting in problems such as long fermentation cycles, unstable product quality, and high production costs. Moreover, a complete, industrially applicable technological system has not yet been established. With the increasing demand for healthy foods, functional vinegars that combine edible and health benefits have become a market hotspot, but existing grape vinegar products are struggling to meet this demand.

[0009] Therefore, this invention proposes a method for making vinegar from grape pomace that can efficiently disrupt the cell wall structure of grape seeds and grape skins, directionally retain heat-sensitive active ingredients, is suitable for industrial liquid fermentation, and can significantly enhance the health benefits of the product, thereby improving the overall economic benefits of the wine industry and meeting the market demand for functional vinegar. Summary of the Invention

[0010] The purpose of this invention is to overcome the technical defects of existing technologies, such as low dissolution rate of active ingredients in grape pomace, easy degradation of heat-sensitive active ingredients, insufficient health value of products, poor process adaptability, and difficulty in achieving industrial-scale production, and to provide a method for preparing grape vinegar by fermenting grape seeds and grape skins.

[0011] The core objective of this invention is to disrupt the dense cell wall structure of grape seeds and skins through a synergistic extraction method combining microwave cell disruption and alcohol, thereby increasing the dissolution rate of fat-soluble active ingredients. Simultaneously, a low-temperature, liquid fermentation process is employed to maximize the preservation of the physiological activity of heat-sensitive active ingredients. Furthermore, the fermentation process parameters are optimized to improve fermentation efficiency and product quality, enabling the high-value and large-scale utilization of grape processing byproducts. This results in the production of grape vinegar products with both edible and health benefits, while simultaneously reducing production costs and waste emissions, achieving a win-win situation for both environmental protection and economic efficiency.

[0012] Another objective of this invention is to provide a grape vinegar preparation technology that is stable, easy to operate, and suitable for industrial production, solving problems such as long fermentation cycles, high risk of contamination by miscellaneous bacteria, and unstable product quality in existing processes. This provides a new technical path for the high-value utilization of grape pomace and promotes the coordinated development of the wine and vinegar industries.

[0013] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing grape vinegar by fermenting grape seeds and grape skins includes the following steps: (1) Raw material pretreatment: Collect grape skins and seeds from winemaking by-products, remove impurities and moldy or spoiled parts, dry them at low temperature until the moisture content is less than 10%, and then microwave them. (2) Co-processing of crushing and alcohol extraction: The microwave-treated grape skins and seeds were placed in a crushing extractor, and 30° to 52° grain liquor was added. The mixture was crushed and extracted at a speed of 2000 r / min to 4000 r / min for 5s to 180s to obtain a mixed slurry. The ratio of the total mass of grape skins and seeds to the volume of grain liquor was 1:0.1 to 1:10 (g / mL). (3) Alcoholic fermentation: Activated fruit wine yeast is introduced into the mixed slurry at an inoculation rate of 1% to 8% of the slurry mass. Anaerobic fermentation is carried out at 28℃ to 32℃ for 24 to 48 hours to obtain wine mash with an alcohol content of 7% to 12%. (4) Acetic acid deep liquid fermentation: Activated acetic acid bacteria are introduced into the wine mash at an inoculation rate of 3% to 10% of the mash mass. Sterile air is introduced and stirred at 30℃ to 35℃ with an aeration rate of 1:0.1 to 1:0.2 (v / v•min). Deep liquid fermentation is carried out for 48h to 96h until the acidity no longer increases, and fermented mash is obtained. (5) Post-processing and aging: Centrifuge the fermented mash at 4000r / min to 6000r / min for 10min to 20min, and filter the supernatant. Aging the filtrate at 15℃ to 25℃ for 1 to 3 months, followed by instant sterilization, and then bottling to obtain the finished grape vinegar product.

[0014] Further, the temperature of the low-temperature drying in step (1) is 50℃-65℃, and the drying time is 2h-4h; the power of the microwave treatment is 350W-500W, the treatment time is 0.5h-1.5h, and the microwave treatment is stirred once every 15-20min.

[0015] Furthermore, the moisture content of the raw materials mentioned in step (1) is 6%-9%.

[0016] Further, the grain liquor mentioned in step (2) is edible white wine or yellow wine; the alcohol content of the grain liquor is 30°~35°; the rotation speed of the crushing and extraction is 2500r / min-3500r / min, and the extraction time is 30s-120s.

[0017] Furthermore, between steps (2) and (3), there is also an ultrasonic-assisted extraction step: the mixed slurry is ultrasonically treated at a frequency of 40kHz to 60kHz and a power of 100W to 200W for 5min to 30min, and the temperature of the slurry is kept at 25℃ to 30℃ during the ultrasonic treatment.

[0018] Further, in step (3), the inoculation amount of the fruit wine yeast is 2% to 5%; the temperature of the alcohol fermentation is 29℃-31℃, and the fermentation time is 30h-40h; the fruit wine yeast is Angel Fruit Wine Yeast No. SY.

[0019] Further, in step (4), the inoculation amount of acetic acid bacteria is 4% to 7%; the temperature of the deep liquid fermentation is 31℃ to 33℃, the ventilation rate is 1:0.12 to 1:0.18 (v / v•min), and the stirring speed is 100r / min to 200r / min; the acetic acid bacteria is Pasteurella acetic acid AS1.41.

[0020] Further, in step (5), the centrifugation speed is 4500r / min-5500r / min, and the centrifugation time is 12min-18min; the filtration is plate and frame filtration or 0.22μm membrane filtration; the aging temperature is 18℃-22℃, and the aging time is 1.5-2.5 months; the instantaneous sterilization temperature is 85℃-95℃, and the sterilization time is 20s-30s.

[0021] Furthermore, the activation method of the fruit wine yeast is as follows: inoculate the fruit wine yeast into a malt juice culture medium and culture it at 28℃-30℃ for 12h-24h until a large number of active yeast cells appear in the culture medium.

[0022] Furthermore, the activation method of the acetic acid bacteria is as follows: inoculate the acetic acid bacteria into the acetic acid bacteria culture medium, and culture it under sterile air at 30℃-32℃ for 18h-24h until the acidity of the culture medium reaches more than 3g / 100mL.

[0023] The beneficial effects of this invention are as follows: 1. Synergistic effect of cell wall disruption and extraction, significantly improving the dissolution and retention rates of active ingredients: This invention employs a synergistic approach of microwave pretreatment and alcohol-mediated disruption and extraction. Microwave treatment efficiently disrupts the cell walls and cell membranes of grape seeds and skins, breaking down the release barriers of active ingredients. Simultaneously, low-temperature treatment avoids the degradation of heat-sensitive active ingredients. Grain alcohol, as a fat-soluble extraction medium, rapidly dissolves fat-soluble active ingredients such as resveratrol and proanthocyanidins released after disruption, solving the problem of insufficient solubility of fat-soluble components in traditional water extraction systems. Compared to traditional water extraction processes, this invention increases the resveratrol extraction rate by 2.1–3.5 times and the proanthocyanidin retention rate by over 60%.

[0024] 2. The process is adapted to industrial production, resulting in high production efficiency and stable product quality: This invention adopts a fully liquid fermentation process, which, compared with traditional solid-state fermentation, has advantages such as a shorter fermentation cycle, lower risk of contamination by miscellaneous bacteria, simpler operation, and easier industrial control. Parameters such as temperature, rotation speed, and ventilation volume throughout the process have been optimized to achieve standardized production and ensure stable product quality. The ultrasonic-assisted extraction step can be flexibly selected according to industrial needs, balancing product quality and production costs, making it suitable for large-scale industrial application.

[0025] 3. High added value of the product, with both edible and health benefits: The grape vinegar prepared by this invention fully retains the natural active ingredients such as resveratrol and proanthocyanidins in grape skin and seeds, while also retaining the natural flavor of grapes. The product has a mellow taste, rich vinegar aroma, moderate acidity, and no off-odors.

[0026] 4. Achieving a win-win situation for environmental protection and the economy, and promoting the coordinated development of the industry: This invention uses grape skins and grape seeds, by-products of winemaking, as raw materials, realizing the resource utilization of grape processing by-products, reducing waste emissions, lowering the environmental treatment costs of enterprises, and turning waste into treasure, transforming low-priced by-products into high-value-added grape vinegar products, significantly improving the overall economic benefits of the wine industry.

[0027] 5. The process is safe and reliable, and the product is highly safe for consumption: The raw materials used in this invention are all food-grade. Grape skins and grape seeds are by-products of winemaking, and their sources are safe and pollution-free. No chemical additives, preservatives or other harmful substances are added during the entire process. Low-temperature drying and instant sterilization are used to preserve the natural nutrients and active ingredients of the raw materials to the maximum extent, while ensuring the safety of the product for consumption and meeting national food safety standards. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0031] The following examples are used to further illustrate the present invention, but do not limit the scope of protection of the present invention. All raw materials used in the examples are commercially available conventional products. Angel Yeast SY was purchased from Angel Yeast Co., Ltd., and Pasteurella acetic acid bacteria AS1.41 was purchased from the China General Microbiological Culture Collection Center. The grain liquor was commercially available edible baijiu or huangjiu. Grape skins and grape seeds were fresh by-products provided by wineries. The detection methods were in accordance with national standards: resveratrol content was detected by HPLC (GB / T 22244-2008), proanthocyanidin content by spectrophotometry (GB / T31740.2-2015), total acid content by titration (GB / T 12456-2021), and microbial indicators were detected according to GB2719-2018 "National Food Safety Standard for Vinegar".

[0032] Comparative example (traditional water extraction + liquid fermentation) Grape skins and seeds (mass ratio 2:1) of the same type as in Example 1 were used. After removing impurities, the mixture was dried at 60°C to a moisture content of 8%, and then directly crushed in a high-speed crusher. An equal volume of distilled water was added for extraction, which took 30 minutes. Then, 3% Angel Yeast SY was added to the extract, and the mixture was anaerobic fermented at 30°C for 30 hours to obtain wine mash with an alcohol content of 8%. 4% Pasteurella acetic acid bacteria AS1.41 was added to the wine mash, and the mixture was deep fermented at 30°C to 32°C with an aeration rate of 1:0.15 (v / v•min) for 55 hours until the acidity stabilized. The fermented mash was centrifuged at 4000 r / min for 10 minutes, filtered through a plate and frame filter, aged at 20°C for 2 months, and then sterilized at 90°C for 30 seconds before bottling to obtain traditional grape vinegar.

[0033] Testing revealed that the grape vinegar prepared in this comparative ratio contained 82.6 mg / L of resveratrol, 1.12 g / L of proanthocyanidins, and 5.6 g / 100 mL of total acid. The microbiological indicators met the GB 2719-2018 standard. In terms of taste, the vinegar aroma was mild, with a slightly bitter taste, and the clarity was average. Example 1

[0034] A method for preparing grape vinegar by fermenting grape seeds and grape skins includes the following steps: 1. Raw material pretreatment: Collect grape skins and seeds from winemaking byproducts, manually remove stems, impurities and moldy or spoiled parts, and mix grape skins and seeds (mass ratio 2:1) evenly; place the mixed raw materials in a low-temperature drying oven and dry at 58℃ for 3 hours until the moisture content of the raw materials is 8%; place the dried raw materials in a microwave treatment device and treat at 350W power for 1 hour, stirring once every 15 minutes to ensure that the raw materials are heated evenly.

[0035] 2. Co-processing of crushing and alcohol extraction: Place the microwave-treated grape skins and seeds in a high-speed crusher and extractor, add 32° edible liquor at a material-to-liquid ratio of 1:3 (g / mL), start the crusher and extractor, and crush and extract for 20 seconds at a speed of 2800 r / min to obtain a uniform mixed slurry.

[0036] 3. Ultrasonic-assisted enhanced extraction: The mixed slurry was transferred to an ultrasonic extraction device and ultrasonically treated for 15 minutes at a frequency of 40kHz and a power of 150W. During the ultrasonic treatment, the slurry temperature was kept at around 28℃.

[0037] 4. Alcoholic fermentation: The ultrasonically treated mixed slurry is transferred to an anaerobic fermentation tank, and 3% of activated Angel Fruit Wine Yeast SY is added. The fermentation temperature is controlled at 30℃, and anaerobic fermentation is carried out for 30 hours. During this period, the alcohol content is checked every 8 hours. When the alcohol content reaches 8% at the end of fermentation, wine mash is obtained.

[0038] 5. Submerged liquid fermentation with acetic acid: Transfer the wine mash to a submerged liquid fermentation tank, inoculate with 4% activated pasteurized acetic acid bacteria AS1.41, control the fermentation temperature at 30℃~32℃, the stirring speed at 150r / min, and the aeration rate at 1:0.15 (v / v•min) for submerged liquid fermentation. During the process, the acidity is checked every 12 hours. After 55 hours of fermentation, the acidity no longer rises, and the fermentation is stopped to obtain the fermented mash.

[0039] 6. Post-processing and aging: Place the fermented mash in a high-speed centrifuge and centrifuge at 4000 r / min for 10 min, and take the supernatant; filter the supernatant using a plate and frame filter to remove fine impurities; transfer the filtered liquid to an aging tank and age at 20℃ for 2 months; after aging, sterilize at 90℃ for 30 seconds, cool to room temperature, and aseptically bottle to obtain the finished grape vinegar.

[0040] Test results: The grape vinegar prepared in this example contained 300.3 mg / L of resveratrol, 3.98 g / L of proanthocyanidins, and 5.8 g / 100 mL of total acid. The microbiological indicators met the GB 2719-2018 standard. In terms of taste, it had a rich vinegar aroma, a mellow taste, no bitterness, and was clear and transparent, combining the natural flavor of grapes with the unique flavor of vinegar.

[0041] Compared with the comparative example, the resveratrol extraction rate of this embodiment is increased by about 3.6 times, the proanthocyanidin retention rate is increased by about 2.55 times, and the health value and flavor quality of the product are significantly improved. Example 2

[0042] A method for preparing grape vinegar by fermenting grape seeds and grape skins differs from Example 1 in that the process parameters are adjusted, and the specific steps are as follows: 1. Raw material pretreatment: Grape skin and grape seed weight ratio 2:1, dried at 55℃ for 3.5h with ventilation, moisture content 7%; microwave treatment power 380W, treatment time 0.5h, stirring once every 15min during the process.

[0043] 2. Co-processing of crushing and alcohol extraction: material-to-liquid ratio 1:5 (g / mL), add 35° Shaoxing wine, crushing and extraction speed 2500 r / min, extraction time 60s.

[0044] 3. Ultrasonic-assisted extraction: 45kHz frequency, 180W power, ultrasonic treatment for 12 minutes, with the slurry temperature controlled at around 27℃.

[0045] 4. Alcoholic fermentation: The inoculum amount of fruit wine yeast is 2%, the fermentation temperature is 31℃, the anaerobic fermentation is carried out for 32 hours, and the alcohol content is 7.5% at the end of fermentation.

[0046] 5. Submerged liquid fermentation of acetic acid: 3% acetic acid bacteria inoculum, fermentation temperature 32℃~33℃, stirring speed 130r / min, aeration rate 1:0.16 (v / v•min), fermentation for 60h until acidity stabilizes.

[0047] 6. Post-processing and aging: Centrifuge at 4500 r / min for 12 min; after filtration, age at 22℃ for 1.8 months; sterilize at 90℃ for 30 s, and then aseptically fill.

[0048] Test results: The grape vinegar prepared in this example contained 245.3 mg / L of resveratrol, 3.12 g / L of proanthocyanidins, and 5.7 g / 100 mL of total acid; the microbial indicators met the GB 2719-2018 standard; it had a mellow taste, a rich vinegar aroma, a faint aroma of Shaoxing wine, and good clarity.

[0049] Compared with the comparative example, the resveratrol extraction rate of this embodiment is increased by about 2.94 times, the proanthocyanidin retention rate is increased by about 1.78 times, the product quality is stable, and the flavor is unique.

[0050] Example 3 (Simplified Industrial Version Without Ultrasonic Technology) A method for preparing grape vinegar by fermenting grape seeds and grape skins, which omits the ultrasound-assisted extraction step to adapt to large-scale industrial production, is as follows: 1. Raw material pretreatment: Collect grape skins and seeds, remove impurities and moldy or spoiled parts, and mix evenly; dry at 56℃ for 2.5 hours with ventilation until the moisture content is 9%; microwave treatment power is 450W, treatment time is 0.8 hours, and stirring is performed once every 20 minutes during the process.

[0051] 2. Co-processing of crushing and alcohol extraction: Add 30° edible liquor at a material-to-liquid ratio of 1:2 (g / mL), crush and extract at a speed of 3500 r / min for 30 s to obtain a mixed slurry.

[0052] 3. Alcoholic fermentation: Inoculate 5% of activated Angel Fruit Wine Yeast SY into the mixed slurry, control the fermentation temperature at 31℃, and anaerobic ferment for 26 hours. The alcohol content is 9% at the end of fermentation to obtain wine mash.

[0053] 4. Submerged liquid fermentation of acetic acid: Inoculate the wine mash with 6% activated Pasteurella acetic acid bacteria AS1.41, control the fermentation temperature at 33℃, the stirring speed at 180r / min, and the aeration rate at 1:0.12 (v / v•min), and carry out submerged liquid fermentation for 72h until the acidity no longer increases, and obtain the fermented mash.

[0054] 5. Post-processing and aging: Centrifuge the fermented mash at 5000 r / min for 15 min and collect the supernatant; filter with a 0.22 μm membrane to remove fine impurities; transfer the filtrate to an aging tank and age at 22℃ for 1.5 months; after aging, sterilize at 90℃ for 30 seconds, cool and aseptically bottle to obtain the finished grape vinegar.

[0055] Test results: The grape vinegar prepared in this example contains 186.7 mg / L of resveratrol, 2.85 g / L of proanthocyanidins, and 5.9 g / 100 mL of total acid; the microbial indicators meet the GB 2719-2018 standard; it has a mellow taste, pure vinegar aroma, and is clear and transparent, making it suitable for large-scale industrial production with low production costs.

[0056] Compared with the comparative example, the resveratrol extraction rate of this embodiment is increased by about 2.26 times, and the proanthocyanidin retention rate is increased by about 1.54 times.

[0057] This invention features a stable process, simple operation, and suitability for large-scale industrial production. It enables the high-value utilization of grape processing by-products, reduces waste emissions, and combines environmental and economic benefits. The resulting grape vinegar product has a pure vinegar aroma and mellow taste, fully retains the natural active ingredients in the raw materials, and has both edible and health benefits, with broad market application prospects.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing grape vinegar using fermentation of grape seeds and grape skins, characterized in that, Includes the following steps: (1) Raw material pretreatment: Collect grape skins and seeds from winemaking by-products, remove impurities and moldy or spoiled parts, dry them at low temperature until the moisture content is less than 10%, and then microwave them. (2) Co-processing of crushing and alcohol extraction: The microwave-treated grape skins and seeds were placed in a crushing extractor, and 30° to 52° grain liquor was added. The mixture was crushed and extracted at a speed of 2000 r / min to 4000 r / min for 5s to 180s to obtain a mixed slurry. The ratio of the total mass of grape skins and seeds to the volume of grain liquor was 1:0.1 to 1:10 (g / mL). (3) Alcoholic fermentation: Activated fruit wine yeast is introduced into the mixed slurry at an inoculation rate of 1% to 8% of the slurry mass. Anaerobic fermentation is carried out at 28℃ to 32℃ for 24 to 48 hours to obtain wine mash with an alcohol content of 7% to 12%. (4) Acetic acid deep liquid fermentation: Activated acetic acid bacteria are introduced into the wine mash at an inoculation rate of 3% to 10% of the mash mass. Sterile air is introduced and stirred at 30℃ to 35℃ with an aeration rate of 1:0.1 to 1:0.2 (v / v•min). Deep liquid fermentation is carried out for 48h to 96h until the acidity no longer increases, and fermented mash is obtained. (5) Post-processing and aging: Centrifuge the fermented mash at 4000r / min to 6000r / min for 10min to 20min, and filter the supernatant. Aging the filtrate at 15℃ to 25℃ for 1 to 3 months, followed by instant sterilization, and then bottling to obtain the finished grape vinegar product.

2. The production method according to claim 1, characterized by, The temperature of the low-temperature drying in step (1) is 50℃-65℃ and the drying time is 2h-4h; the power of the microwave treatment is 350W-500W and the treatment time is 0.5h-1.5h. During the microwave treatment, the microwave is stirred once every 15-20min.

3. The preparation method according to claim 1, characterized in that, The moisture content of the raw materials mentioned in step (1) is 6%-9%.

4. The method of claim 1, wherein, The grain liquor mentioned in step (2) is edible white wine or yellow wine; the alcohol content of the grain liquor is 30°~35°; the rotation speed of the crushing and extraction is 2500r / min-3500r / min, and the extraction time is 30s-120s.

5. The preparation method according to claim 1, characterized in that, Between steps (2) and (3), there is also an ultrasonic-assisted extraction step: the mixed slurry is ultrasonically treated at a frequency of 40kHz to 60kHz and a power of 100W to 200W for 5min to 30min, and the temperature of the slurry is kept at 25℃ to 30℃ during the ultrasonic treatment.

6. The method of claim 1, wherein, The inoculation amount of the fruit wine yeast in step (3) is 2% to 5%; the temperature of the alcohol fermentation is 29℃-31℃, and the fermentation time is 30h-40h; the fruit wine yeast is Angel Fruit Wine Yeast No. SY.

7. The preparation method according to claim 1, characterized in that, The inoculation amount of acetic acid bacteria in step (4) is 4% to 7%; the temperature of the deep liquid fermentation is 31℃ to 33℃, the ventilation rate is 1:0.12 to 1:0.18 (v / v•min), and the stirring speed is 100r / min to 200r / min; the acetic acid bacteria is Pasteurella acetic acid AS1.

41.

8. The method of claim 1, wherein, In step (5), the centrifugation speed is 4500 r / min-5500 r / min and the centrifugation time is 12 min-18 min; the filtration is plate and frame filtration or 0.22 μm membrane filtration; the aging temperature is 18℃-22℃ and the aging time is 1.5-2.5 months; the instantaneous sterilization temperature is 85℃-95℃ and the sterilization time is 20s-30s.

9. The method of claim 1, wherein, The activation method of the fruit wine yeast is as follows: inoculate the fruit wine yeast into malt juice culture medium and culture it at 28℃-30℃ for 12h-24h until a large number of active yeast cells appear in the culture medium.

10. The method of claim 1, wherein, The activation method of the acetic acid bacteria is as follows: inoculate the acetic acid bacteria into the acetic acid bacteria culture medium, and culture it under sterile air at 30℃-32℃ for 18h-24h until the acidity of the culture medium reaches more than 3g / 100mL.

Images