Standardized brewing method of sweet potato vinegar

Abstract

The application discloses a standardized brewing method of sweet potato dregs and baijiu vinegar, and relates to the technical field of fermented food processing.The application comprises the following steps: selecting fresh sweet potatoes and indica rice; washing and peeling the sweet potatoes, then soaking and sterilizing the sweet potatoes with salt water, and crushing the sweet potatoes to obtain sweet potato fragments; washing and soaking the indica rice, and cooking the indica rice until it is fully cooked without white core, and then cooling the indica rice to obtain matured rice; mixing the sweet potato fragments and the matured rice, adding mixed brewing yeast, uniformly stirring, and then sealing the mixture into a fermentation tank to perform alcohol fermentation; when the alcohol content reaches 6-8% and the pH value decreases to 4.0-4.5, adding compound acetic acid bacteria to the material after the completion of the alcohol fermentation, and performing fermentation for 15-20 days until the total acid content is greater than or equal to 4.5 g / 100 mL and the pH value is stable at 3.2-3.8; and adding spice extract liquid to the acetic acid fermentation liquid to age for 30 days.The application can improve the release efficiency of sweet potato flavor substances, shorten the fermentation period and enhance the product quality stability through accurate pretreatment of the sweet potatoes, synergistic fermentation of compound strains and segmented control of fermentation parameters.

Description

Technical Field

[0001] This invention belongs to the field of fermented food processing technology, and in particular relates to a standardized brewing method for sweet potato lees vinegar. Background Technology

[0002] Fermented rice vinegar is an acidic condiment made primarily from grains or tubers through microbial fermentation. It combines regional flavors with the nutritional properties of fermented foods and is widely consumed in parts of southern my country. Sweet potato rice fermented rice vinegar is a unique type of fermented rice vinegar made primarily from sweet potatoes, fermented together with rice. Its flavor relies on the synergistic presentation of the unique sweet aroma of sweet potatoes and the mellow fragrance of fermented rice, making it a typical representative of regional fermented condiments.

[0003] Traditional sweet potato lees vinegar production relies heavily on natural fermentation, a process that depends on naturally occurring microbial communities (such as yeast, lactic acid bacteria, and acetic acid bacteria) to complete the saccharification, alcoholic fermentation, and acetic acid fermentation stages, eliminating the need for artificial inoculation with specialized microbial strains. The core pain points of this production model are the long fermentation cycle and unstable product quality: natural fermentation depends on environmental microbial communities, with a fermentation cycle of 7-10 days, resulting in low production efficiency. Simultaneously, these communities are susceptible to factors such as temperature, humidity, and contamination by other microorganisms, leading to uncontrollable fermentation processes. This results in uneven formation of flavor compounds (such as lactic acid and esters), large fluctuations in the sweet-sour ratio, and difficulty in consistently releasing the unique sweet aroma of sweet potatoes. Consumer palatability evaluations vary significantly, failing to meet the consistent quality requirements of large-scale industrial production.

[0004] Current technologies lack a precise pretreatment, microbial strain, and fermentation parameter control scheme tailored to the characteristics of sweet potato raw materials. This results in the inability to efficiently release sweet potato flavor compounds, shorten the fermentation cycle, and stabilize fermentation quality. Consequently, sweet potato rice residue vinegar has long been limited to small-scale workshop production, hindering industrial-scale promotion and restricting the market development potential of this specialty condiment. Therefore, the following solutions are proposed to address these issues. Summary of the Invention

[0005] The purpose of this invention is to provide a standardized brewing method for sweet potato lees vinegar. By precisely pre-treating sweet potatoes, synergistic fermentation with compound microorganisms, and segmented control of fermentation parameters, the method can improve the release efficiency of sweet potato flavor substances, shorten the fermentation cycle, and enhance the stability of product quality. This solves the problems in the prior art, such as difficulty in releasing flavor due to improper sweet potato pre-treatment, long natural fermentation cycle and susceptibility to contamination, and large fluctuations in the sweet-sour ratio due to constant fermentation parameters.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: This invention relates to a standardized brewing method for sweet potato lees vinegar, comprising the following steps: Step S1: Raw material preparation: Select fresh sweet potatoes with a starch content ≥65% and indica rice for later use; Step S2, Sweet potato pretreatment: After washing and peeling the sweet potatoes, soak them in 0.5% salt water to sterilize them, and then crush them to a particle size of 5-8mm to obtain sweet potato fragments; Step S3, Rice pretreatment: Wash and soak the indica rice, steam until fully cooked and without any white core, and cool to below 30℃ to obtain cooked rice; Step S4, Mixing and Fermentation Start: Mix sweet potato pieces and cooked rice at a mass ratio of 1:0.5, add brewing yeast at 0.3% of the total mass of the mixed raw materials, stir well, seal and put into a fermentation tank for alcoholic fermentation; Step S5, alcoholic fermentation: Ferment at 28-30℃ for 7-10 days until the alcohol content reaches 6%-8% and the pH value drops to 4.0-4.5; Step S6, Acetic acid fermentation: Add 0.5% of the total mass of the mixed raw materials to the material after alcoholic fermentation, and ferment for 15 to 20 days at 30 to 32℃ and an aeration rate of 0.05 to 0.1 vvm until the total acid content is ≥4.5g / 100mL and the pH value is stable at 3.2 to 3.8. Step S7, Aging and Flavoring: Add spice extract to the acetic acid fermentation liquid and age for 30 days at 10-15℃; Step S8, Filtration and Bottling: The aged fermented liquid is sequentially filtered through coarse filtration, fine filtration, and sterilization before being bottled to obtain the finished product.

[0007] Furthermore, the sweet potatoes are selected from fresh sweet potatoes produced in Wenchang, Hainan, with a starch content ≥65% and a reducing sugar content ≤3%.

[0008] Furthermore, in the sweet potato pretreatment step, the soaking time in 0.5% saline solution is 10 minutes; the particle size of the crushed sweet potato fragments is 5-8 mm.

[0009] Furthermore, in the rice pretreatment step, the soaking is to soak in 1.5 times the volume of sterile water for 30 minutes; the steaming is to steam at normal pressure for 50 minutes; and the cooling is to cool to below 30°C.

[0010] Furthermore, in the mixing and fermentation start-up step, 0.1% of yeast extract, 0.05% of trehalose and 0.02% of calcium lactate by total mass of the mixed raw materials are added together with the brewing yeast and stirred evenly.

[0011] Furthermore, in the alcohol fermentation step, the temperature is controlled at 28°C for the first 1 to 3 days of fermentation and at 30°C for the 4 to 7 days; the material is turned over once on the 3rd day and once on the 5th day during the fermentation process.

[0012] Furthermore, the compound acetic acid bacteria is composed of Acetobacter and Pasteurella in a 1:1 mass ratio, and is activated to an activity ≥ 1 before use. CFU / g Furthermore, the spice extract is prepared by mixing star anise, cinnamon, and cloves in a mass ratio of 2:1:1, extracting by reflux with 60% ethanol for 2 hours, filtering, and concentrating to 1 / 5 of the original volume; in the aging step, the amount of spice extract added is 0.5% of the total volume of the fermentation liquid, and 0.1% of trehalose is added at the same time.

[0013] Furthermore, in the filtration and filling steps, the coarse filtration is performed through a 200-mesh filter cloth; the fine filtration is performed through a 0.45μm membrane filtration system; and the sterilization is performed by pasteurization at 85°C for 15 minutes.

[0014] Furthermore, the finished product has a total acid content ≥4.5g / 100mL, a pH value of 3.2~3.8, a reducing sugar content ≤2.0%, and an alcohol content ≤0.5%.

[0015] The present invention has the following beneficial effects: 1. This invention utilizes a pretreatment process designed specifically for the characteristics of sweet potato raw materials, enabling the flavor precursors in sweet potatoes to be fully transformed during subsequent fermentation. The peeling process removes the fibrous parts that affect fermentation, and the soaking in salt water kills surface bacteria. The appropriate crushing further increases the specific surface area of ​​the raw materials, which is beneficial for starch activation and enzymatic hydrolysis. The above pretreatment method allows the unique sweet aroma of sweet potatoes to be released during fermentation and blends with the mellow aroma produced by rice fermentation, providing a flavor foundation for the finished product.

[0016] 2. This invention employs a co-fermentation method using a compound microbial strain. By combining brewing yeast with a compound acetic acid bacteria, the two stages of alcoholic fermentation and acetic acid fermentation are smoothly connected. Temperature is controlled in stages during fermentation, with different temperature conditions used in the early and late stages of alcoholic fermentation to promote yeast growth and alcohol accumulation. During acetic acid fermentation, a stable temperature is maintained and aeration is controlled to provide a suitable growth environment for the acetic acid bacteria. These process controls reduce the impact of environmental factors on the fermentation process and improve batch-to-batch consistency.

[0017] 3. This invention introduces a low-temperature aging process after acetic acid fermentation and adds spice extract during the aging process. During aging, the flavor components in the fermentation liquid slowly reach equilibrium under low temperature conditions, the acidity changes from sharp to mild, and the original flavor of sweet potato and the flavor of spices gradually blend together. The spice extract has a high content of effective components after extraction with organic solvents, and the amount added is easy to control, without masking the flavor characteristics of the sweet potato raw material itself. The finished product has a mild acidity, a richer aroma, and an overall improved flavor harmony compared to traditional processes.

[0018] 4. This invention replaces traditional natural fermentation with pure culture fermentation, shortening the fermentation start-up time and reducing the risk of contamination by other microorganisms. In the alcohol fermentation stage, the yeast metabolic efficiency is maintained at a good level through segmented temperature control and material turning operations. In the acetic acid fermentation stage, the acid production rate is kept stable through aeration control and the use of compound strains. The processes are closely linked, and the overall production cycle is shorter than that of natural fermentation, which is conducive to improving equipment utilization efficiency and adapting to the needs of large-scale production.

[0019] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

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

[0021] Figure 1 This is a schematic diagram of the standardized brewing method for sweet potato lees vinegar according to the present invention. Detailed Implementation

[0022] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please see Figure 1 As shown, this invention provides a standardized brewing method for sweet potato lees vinegar, which includes the following steps: Step S1: Raw material preparation Step S11, Sweet Potato Screening: Select fresh sweet potatoes from Wenchang, Hainan, and remove rotten, spoiled, insect-infested, and mechanically damaged individuals. Ensure that the raw materials have a starch content ≥65%, a reducing sugar content ≤3%, and no obvious impurities. Store the screened sweet potatoes in a cool, ventilated place, avoiding direct sunlight and moisture.

[0024] Step S12, Rice Preparation: Select high-quality indica rice from Hainan, ensuring the grains are plump, free from insect damage and mold. Indica rice has a high starch content, making it suitable for saccharification and fermentation, and it can form a good synergistic fermentation system with sweet potatoes.

[0025] Step S13, Preparation of Compound Microbial Strains: This includes brewing yeast (Saccharomycescerevisiae), compound saccharifying bacteria (containing Aspergillus oryzae and Aspergillus niger), and compound acetic acid bacteria (containing Acetobacter aceti and Acetobacter pasteurianus). All strains must be activated before use to ensure activity ≥ FU / g.

[0026] Step S14, Preparation of auxiliary raw materials: Spices extract (prepared from star anise, cinnamon and cloves in a mass ratio of 2:1:1, extracted by reflux of 60% ethanol for 2 hours, filtered and concentrated to 1 / 5 of the original volume), trehalose, yeast extract, and calcium lactate.

[0027] Step S2: Sweet potato pretreatment Step S21, Washing and Peeling: Place the selected sweet potatoes in running water and use a soft brush to wash away the surface mud and debris. After washing, manually peel off the skin and surface fibrous parts to avoid the fibers affecting the subsequent fermentation efficiency.

[0028] Step S22, Salt water soaking for sterilization: Soak the peeled sweet potatoes in 0.5% edible salt water for 10 minutes to kill any remaining microorganisms on the surface. After soaking, remove them, rinse once with sterile water, and drain off the surface moisture.

[0029] Step S23, Crushing Process: Cut the sweet potatoes into small pieces and then crush them in a crusher until they are granular with a particle size of 5-8mm. Avoid over-crushing during the crushing process, as this will cause juice loss and affect the uniformity of the subsequent fermentation substrate.

[0030] Step S3: Rice pretreatment Step S31, Rinsing and Soaking: Rinse the rice three times with sterile water to remove surface impurities and some starch. After rinsing, add 1.5 times the volume of sterile water and soak for 30 minutes to allow the rice grains to fully absorb water and swell.

[0031] Step S32, Steaming and Gelatinization: Drain excess water from the soaked rice, place it in a steamer, and steam under normal pressure for 50 minutes, until the rice grains are fully cooked, have no white core, and the surface of the rice grains is slightly transparent. Stir occasionally during steaming to ensure even heating.

[0032] Step S33, Cooling: Remove the steamed rice and let it cool to below 30℃ to avoid heat damage to the yeast and bacteria added later.

[0033] Step S4: Mixing and Fermentation Start Step S41, Raw material mixing: Mix the crushed sweet potato pieces with the cooled rice at a mass ratio of 1:0.5, place them in a mixer and stir evenly to ensure that the sweet potato particles and rice grains are evenly distributed.

[0034] Step S42: Add yeast and auxiliary ingredients: Add activated brewing yeast at 0.3% of the total mass of the mixed raw materials, along with 0.1% yeast extract, 0.05% trehalose, and 0.02% calcium lactate, and stir well. These ingredients help stabilize the initial growth and metabolism of the yeast.

[0035] Step S43, Filling and Sealing: Fill the well-stirred mixture into a sterilized fermentation tank, compact it, and seal it, leaving about 10% empty space inside the tank to prevent foam from overflowing in the early stages of fermentation. Place the fermentation tank in a constant temperature room, controlling the temperature at 28-30℃, for the first stage of alcoholic fermentation.

[0036] Step S5, Alcoholic Fermentation Stage Step S51, Fermentation Process Monitoring: Days 1-3 of fermentation are the rapid yeast reproduction period, and the temperature inside the tank is controlled at 28℃. Days 4-7 are the peak period of alcohol production, and the temperature is increased to 30℃. The temperature, pH value, and alcohol concentration inside the tank are monitored daily.

[0037] Step S52, Turning and Venting: On the 3rd and 5th day of fermentation, turn the material slightly to promote contact between the raw materials at the bottom and the yeast, and at the same time release the CO2 accumulated in the tank to prevent local rancidity.

[0038] Step S53, Determining the fermentation endpoint: When the alcohol concentration reaches 6% to 8% (volume fraction) and the pH value drops to 4.0 to 4.5, the alcohol fermentation stage ends. The entire process takes about 7 to 10 days.

[0039] Step S6, Acetic Acid Fermentation Stage Step S61, Inoculation with acetic acid bacteria: After the alcoholic fermentation is completed, open the fermentation tank and inoculate with activated compound acetic acid bacteria (acetic acid bacteria and pasteurella bacteria in a mass ratio of 1:1) at 0.5% of the total mass of the mixed raw materials, and stir evenly.

[0040] Step S62, Aeration and Fermentation: Convert the fermenter to a semi-closed state, maintaining a micro-aerobic environment inside the tank. Control the aeration rate at 0.05–0.1 vvm. Maintain the temperature at 30–32℃, and the fermentation cycle is 15–20 days.

[0041] Step S63: Regular testing: Test the total acid content and pH value daily. When the total acid content reaches 4.5g / 100mL or higher and the pH value stabilizes between 3.2 and 3.8, the acetic acid fermentation stage ends.

[0042] Step S7, Aging and Flavoring Step S71: Add spice extract: Add the prepared spice extract at 0.5% of the total volume of the fermentation liquid, and add 0.1% trehalose as a flavor stabilizer, and stir well.

[0043] Step S72, Low-Temperature Aging: Transfer the mixed fermentation liquid to an aging tank, seal it, and age it at a low temperature of 10-15℃ for 30 days. Stir it every 7 days during aging to promote the integration of flavor compounds.

[0044] Step S73, Endpoint Judgment of Aging: After aging, take samples for sensory evaluation and physicochemical testing. The samples should have a harmonious flavor, mild acidity, and a unique sweet potato aroma and complex spicy flavor.

[0045] Step S8, Filtration and Filling Step S81, Coarse filtration: The aged fermented liquid is coarsely filtered through a 200-mesh filter cloth to remove large particles of residue and microorganisms.

[0046] Step S82, Fine filtration: The coarse filtrate is then finely filtered through a 0.45μm membrane filtration system to ensure that the product is clear and transparent.

[0047] Sterilization and filling: The filtered liquid is pasteurized at 85°C for 15 minutes, rapidly cooled to room temperature, and then aseptically filled into sterilized glass bottles or food-grade plastic bottles for storage.

[0048] One specific application of this embodiment is: Example 1 Sweet potato pulp vinegar was prepared according to the methods described in steps S1 to S8 above, with the following key parameters: Raw material ratio: Hainan Wenchang sweet potato (starch content 68%, reducing sugar 2.8%) to Hainan indica rice in a mass ratio of 1:0.5; Sweet potato pretreatment: Soak in 0.5% salt water for 10 minutes, then crush to a particle size of 5-8mm; Rice preparation: Soak for 30 minutes, steam for 50 minutes, and cool to below 30℃; Fermentation strain: 0.3% brewing yeast (containing 0.1% yeast extract, 0.05% trehalose, and 0.02% calcium lactate); Alcoholic fermentation: 28-30℃, 7-10 days, final alcohol content 6-8%, pH 4.0-4.5; Acetic acid fermentation: compound acetic acid bacteria (acetic acid bacillus: pasteurella = 1:1) 0.5%, aeration rate 0.05-0.1 vvm, 30-32℃, 15-20 days; Aging process: 0.5% spice extract (star anise: cinnamon: cloves = 2:1:1), 0.1% trehalose, aged at 10-15℃ for 30 days; Finished product specifications: Total acid ≥ 4.5 g / 100 mL, pH 3.2-3.8.

[0049] Comparative Example 1 Based on Example 1, the fermentation method was changed to traditional natural fermentation, and the specific modifications are as follows: No added microbial strains: No brewing yeast or compound acetic acid bacteria are added; fermentation relies entirely on the natural fermentation of wild microorganisms in the environment. Eliminate pretreatment sterilization: Do not soak sweet potatoes in 0.5% saline solution for sterilization after crushing; Fermentation conditions: Open fermentation at room temperature (fluctuating between 20-35℃), without temperature or oxygen control; Other steps, such as raw material ratio, pretreatment, and aging, are consistent with those in Example 1.

[0050] Comparative Example 2 Based on Example 1, the specific pretreatment of sweet potatoes is cancelled, and the specific modifications are as follows: Eliminate brine sterilization: Do not soak sweet potatoes in 0.5% salt water before crushing; Eliminate peeling: Wash the sweet potatoes only to remove surface dirt and sand, keeping the skin and fibrous parts intact; Crushing particle size: crushed to 10-15mm (larger than 5-8mm in Example 1); Other steps, such as adding microbial strains, fermentation parameters, and aging, are consistent with those in Example 1.

[0051] Comparative Example 3 Based on Example 1, the compound microbial strain was changed to a single microbial strain for fermentation. The specific modifications are as follows: Alcoholic fermentation stage: Only brewing yeast (0.3%) is added, without yeast extract, trehalose, calcium lactate or other auxiliary ingredients; Acetic acid fermentation stage: only Acetic acid bacteria (0.5%) are added, without adding Pasteurella multocida; Other steps, such as raw material pretreatment, fermentation parameters, and aging, are consistent with those in Example 1.

[0052] Comparative Example 4 Based on Example 1, the segmented temperature control process and aging step are eliminated, and the specific modifications are as follows: Fermentation temperature: The alcoholic fermentation and acetic acid fermentation are kept at a constant 30℃ throughout the entire process, without segmented temperature control; Aging cancelled: After the acetic acid fermentation is completed, the product is filtered and bottled directly without the addition of spice extracts or low-temperature aging. Other steps, such as raw material pretreatment and bacterial strain addition, are consistent with those in Example 1.

[0053] Performance test and comparison results To objectively evaluate the technical effects of each scheme, the physicochemical indicators, fermentation cycle, sensory quality and flavor substance content of the finished products of Example 1 and Comparative Examples 1-4 were tested, and the results are shown in Tables 1 and 2.

[0054] Test method description: Total acid content: acid-base titration method (calculated as lactic acid); Fermentation cycle: The total number of days from the start of raw material mixing to the end of acetic acid fermentation; Vinegar yield: The final volume (L) of vinegar obtained per 100kg of mixed raw materials (sweet potato + rice); Sensory evaluation: Ten professional sensory evaluators will give a comprehensive score to the product’s color, aroma, acidity balance, and smoothness of taste (out of 100 points). Characteristic flavor compounds: The content of characteristic aroma components of sweet potato (β-ionone, linalool oxide) was determined by GC-MS.

[0055] Table 1 Comparison of main physicochemical indicators and fermentation efficiency

[0056] Results Analysis: Example 1 had the highest total acid content (4.8 g / 100 mL), a stable pH value of 3.5, a fermentation cycle of only 28 days, and a vinegar yield of 82 L / 100 kg, demonstrating the best overall performance. Comparative Example 1 (natural fermentation) had the lowest total acid content (3.2 g / 100 mL), a fermentation cycle of 45 days, and a vinegar yield of only 55%, indicating that contamination by miscellaneous bacteria led to raw material waste and quality decline. Comparative Example 2 (no pretreatment) had all indicators worse than Example 1, indicating that peeling, brine sterilization, and proper crushing of sweet potatoes were crucial for releasing starch and inhibiting miscellaneous bacteria. Comparative Example 3 (single strain) had slightly lower total acid and vinegar yield than Example 1, indicating that synergistic fermentation with compound strains could improve acid production efficiency and raw material conversion rate. Comparative Example 4 (no segmented temperature control and no aging) had a shorter fermentation cycle, but the total acid and vinegar yield were still lower than Example 1, and subsequent sensory evaluation would show flavor defects.

[0057] Table 2 Comparison of sensory qualities and flavor compounds

[0058] Results analysis: Example 1 had the highest sensory score (92 points), with higher levels of characteristic flavor compounds β-ionone (128 μg / L) and linalool oxide (76 μg / L) than other comparative examples, indicating that the characteristic aroma of sweet potato was fully released and that the aging process promoted the integration and enhancement of flavor. Comparative Example 1 (natural fermentation) had the lowest sensory score (65 points), with extremely low levels of characteristic flavor compounds and off-odors, proving that natural fermentation cannot effectively release the aroma of sweet potato and is susceptible to contamination by other microorganisms. Comparative Example 2 (no pretreatment) had significantly lower levels of characteristic aroma compounds than Example 1, indicating that peeling and brine sterilization play a key role in the release of flavor precursors. Comparative Example 3 (single strain) had lower levels of flavor compounds than Example 1, and sensory evaluation indicated that the flavor profile was simple, confirming the importance of complex strains in the formation of complex flavors. Comparative Example 4 (no segmented temperature control and no aging) had lower levels of characteristic flavor compounds than Example 1, and sensory evaluation indicated that the sour taste was pungent and the aroma was thin, indicating that segmented temperature control and aging processes are indispensable for a mellow and harmonious flavor.

[0059] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0060] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A standardized brewing method for sweet potato lees vinegar, characterized in that, The method includes the following steps: Step S1: Raw material preparation: Select fresh sweet potatoes with a starch content ≥65% and indica rice for later use; Step S2, Sweet potato pretreatment: After washing and peeling the sweet potatoes, soak them in 0.5% salt water to sterilize them, and then crush them to a particle size of 5-8mm to obtain sweet potato fragments; Step S3, Rice pretreatment: Wash and soak the indica rice, steam until fully cooked and without any white core, and cool to below 30℃ to obtain cooked rice; Step S4, Mixing and Fermentation Start: Mix sweet potato pieces and cooked rice at a mass ratio of 1:0.5, add brewing yeast at 0.3% of the total mass of the mixed raw materials, stir well, seal and put into a fermentation tank for alcoholic fermentation; Step S5, alcoholic fermentation: Ferment at 28-30℃ for 7-10 days until the alcohol content reaches 6%-8% and the pH value drops to 4.0-4.5; Step S6, Acetic acid fermentation: Add 0.5% of the total mass of the mixed raw materials to the material after alcoholic fermentation, and ferment for 15 to 20 days at 30 to 32℃ and an aeration rate of 0.05 to 0.1 vvm until the total acid content is ≥4.5g / 100mL and the pH value is stable at 3.2 to 3.

8. Step S7, Aging and Flavoring: Add spice extract to the acetic acid fermentation liquid and age for 30 days at 10-15℃; Step S8, Filtration and Bottling: The aged fermented liquid is sequentially filtered through coarse filtration, fine filtration, and sterilization before being bottled to obtain the finished product.

2. The standardized brewing method for sweet potato lees vinegar according to claim 1, characterized in that, The sweet potatoes mentioned are selected from fresh sweet potatoes produced in Wenchang, Hainan, with a starch content of ≥65% and a reducing sugar content of ≤3%.

3. The standardized brewing method for sweet potato lees vinegar according to claim 1, characterized in that, In the sweet potato pretreatment step, the soaking time in 0.5% saline solution is 10 minutes; the particle size of the crushed sweet potato fragments is 5-8 mm.

4. The standardized brewing method for sweet potato lees vinegar according to claim 1, characterized in that, In the rice pretreatment steps, the soaking step involves adding 1.5 times the volume of sterile water and soaking for 30 minutes; the steaming step involves steaming at normal pressure for 50 minutes; and the cooling step involves cooling to below 30°C.

5. The standardized brewing method for sweet potato lees vinegar according to claim 1, characterized in that, In the mixing and fermentation start-up step, 0.1% of yeast extract, 0.05% of trehalose and 0.02% of calcium lactate by weight of the total mixed raw materials are added together with the brewing yeast and stirred evenly.

6. The standardized brewing method for sweet potato lees vinegar according to claim 1, characterized in that, In the alcohol fermentation process, the temperature is controlled at 28°C for the first 3 days and 30°C for the 4th to 7th days; the material is turned over once on the 3rd day and once on the 5th day during the fermentation process.

7. A standardized brewing method for sweet potato lees vinegar according to claim 1, characterized in that, The compound acetic acid bacteria are composed of Acetobacter and Pasteurella multocida in a 1:1 mass ratio, and are activated to an activity ≥ 1 before use. CFU / g.

8. A standardized brewing method for sweet potato lees vinegar according to claim 1, characterized in that, The spice extract is prepared by mixing star anise, cinnamon, and cloves in a mass ratio of 2:1:1, extracting by reflux with 60% ethanol for 2 hours, filtering, and concentrating to 1 / 5 of the original volume; in the aging step, the amount of spice extract added is 0.5% of the total volume of the fermentation liquid, and 0.1% of trehalose is added at the same time.

9. A standardized brewing method for sweet potato lees vinegar according to claim 1, characterized in that, In the filtration and filling steps, the coarse filtration is performed through a 200-mesh filter cloth; the fine filtration is performed through a 0.45μm membrane filtration system; and the sterilization is performed by pasteurization at 85°C for 15 minutes.

10. A standardized brewing method for sweet potato lees vinegar according to claim 1, characterized in that, The finished product has a total acid content ≥4.5g / 100mL, a pH value of 3.2~3.8, a reducing sugar content ≤2.0%, and an alcohol content ≤0.5%.

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