Sweet potato vinegar and preparation method thereof

Abstract

The invention relates to the technical field of food processing, in particular to sweet potato vinegar and a preparation method thereof. The brewing method of the sweet potato vinegar comprises the steps that sweet potatoes are pretreated to obtain cooked sweet potato pulp, the cooked sweet potato pulp is sequentially subjected to liquefaction treatment and saccharification treatment, then sterilization is performed, fermentation treatment is performed under the sterile condition, and finally ultrasonic waves and microwaves are used for synergistically accelerating aging. Wherein the fermentation treatment comprises the following steps: firstly inoculating monascus and saccharomycetes into the saccharified material for synergistic fermentation, and then inoculating acetic bacteria for fermentation. Quantitative liquefaction and saccharification, monascus and saccharomycetes synergistic fermentation, acetic acid bacteria fermentation and ultrasonic wave / microwave synergistic aging acceleration are combined, so that the flavor, the nutritional function and the production efficiency of the sweet potato vinegar can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, in particular to sweet potato vinegar and a preparation method thereof. Background Art

[0002] Sweet potatoes are the fifth most important food crop after rice, wheat, corn, and potatoes, and play a crucial role in current economic development. Rich in nutrients and functional ingredients such as starch, protein, dietary fiber, vitamins, and minerals, they possess potential anti-cancer, antioxidant, cardiovascular, and immune-boosting properties, making them a globally recognized nutritious food. Currently, sweet potatoes are primarily used to process starch and its products (vermicelli noodles, rice noodles, and rice paper), as well as whole starch. This results in a limited product mix and a short industrial chain. Furthermore, the processing of sweet potato starch generates significant amounts of waste residues, waste liquids, and other byproducts, placing significant pressure on the environment and severely hindering the healthy development of the sweet potato industry.

[0003] Sweet potato vinegar is made from fresh sweet potatoes through a series of processes, including liquefaction and saccharification, alcoholic fermentation, acetic acid fermentation, filtration, sterilization, and filling. However, current sweet potato vinegar production is primarily in households and workshops, using solid-state fermentation to add wheat and peas to the raw materials. This process presents the following challenges, limiting its widespread consumption in my country: 1) The acetic acid bacteria strains used in different households and workshops are unknown, significantly affecting the brewing process by varying temperatures across different regions, resulting in unstable product quality and unavailability throughout the year; 2) Solid-state fermentation is cumbersome and time-consuming, making it unsuitable for large-scale industrial production; and 3) the addition of wheat and peas to the raw materials to increase the available carbon source significantly impacts the flavor, taste, and nutritional value of the product.

[0004] Therefore, using sweet potato as raw material, selecting suitable fermentation strains and fermentation methods is crucial to improving the production efficiency of sweet potato vinegar, reducing production costs, and improving the flavor and nutritional functions of sweet potato vinegar. Summary of the Invention

[0005] In order to solve the above problems in the prior art, the present invention provides a sweet potato vinegar and a preparation method thereof.

[0006] Based on this, the present invention has the following technical solutions: In a first aspect, the present invention provides a method for brewing sweet potato vinegar, comprising: pre-treating sweet potatoes to obtain cooked sweet potato slurry, sequentially liquefying and saccharifying the cooked sweet potato slurry, sterilizing the slurry, fermenting the slurry under aseptic conditions, and finally accelerating aging by using ultrasound and microwaves; The fermentation treatment comprises: first inoculating the saccharified material with Monascus and yeast for collaborative fermentation, and then inoculating acetic acid bacteria for fermentation.

[0007] In the present invention, the Monascus and yeast synergistic fermentation involves sterilizing sweet potatoes that have been quantitatively liquefied and saccharified, and then inoculating Monascus and yeast under aseptic conditions for alcohol fermentation. Monascus is a filamentous fungus that can be used as both food and medicine. While retaining the proteins, organic acids, minerals, and flavor substances such as aldehydes, ketones, and esters in the fermentation substrate, it can utilize the various carbohydrates in the quantitatively liquefied and saccharified sweet potatoes as a carbon source, metabolizing them to produce enzymes such as glucoamylase, glucosidase, proteolytic enzymes, and esterases. It also secretes extracellular enzymes that directly catalyze the synthesis of ethyl hexanoate from hexanoic acid and ethanol. Furthermore, Monascus can synthesize various vitamins such as biotin, thiamine, riboflavin, and ergosterol, and produce functional substances such as monascus pigment, lovastatin, γ-aminobutyric acid, and sterols, exhibiting antioxidant, antibacterial, lipid-lowering, and blood sugar-lowering activities. Yeast has two prominent roles in the alcohol fermentation process: alcoholization and esterification. On the one hand, yeast can use the glucose in the fermentation substrate to metabolize and convert it into alcohol through the EMP pathway; on the other hand, yeast can produce ester substances through esterification reactions, such as the reaction of ethanol and acetic acid to produce ethyl acetate with an aromatic smell. Ester substances are the main components of aroma and are the basic condition for enhancing the aroma and taste of sweet potato vinegar.

[0008] The present invention finds that by utilizing Monascus and yeast to synergistically ferment, the metabolites produced can not only increase the nutritional content of the sweet potato vinegar, but also improve the appearance, color, taste, flavor and other qualities of the sweet potato vinegar, effectively solving the problems of relatively insufficient flavor and low nutritional quality of the sweet potato vinegar.

[0009] In the present invention, acetic acid bacteria fermentation refers to the production of acetic acid and other substances by inoculating acetic acid bacteria under sterile conditions after the coordinated alcohol fermentation by Monascus and yeast has concluded. Different acetic acid bacteria have different fermentation effects. Selecting superior acetic acid bacteria strains can increase sweet potato vinegar yield, maintain stable quality, and conserve raw materials. The most suitable carbon sources for acetic acid fermentation are hexose sugars such as alcohol, glucose, and fructose, followed by sucrose and maltose. Acetic acid bacteria cannot directly utilize polysaccharides such as starch. Furthermore, acetic acid bacteria possess strong oxidase activities such as alcohol dehydrogenase and aldehyde dehydrogenase, enabling them to oxidize other alcohols and sugars to produce corresponding organic acids and ketones. Examples include butyric acid, gluconic acid, xylonic acid, arabinonic acid, pyruvic acid, succinic acid, and lactic acid, as well as oxidize glycerol to diketones and mannitol to fructose. Acetic acid bacteria also have the ability to produce esters. Incorporating acetic acid bacteria strains that produce a high concentration of aromatic esters into the fermentation can enhance the flavor of the sweet potato vinegar.

[0010] In the present invention, the sweet potato includes any one or more of purple-fleshed sweet potato, yellow-fleshed sweet potato, orange-fleshed sweet potato, white-fleshed sweet potato, etc., and is not specifically limited here.

[0011] Preferably, the acetic acid bacteria is selected from one or more of CICC20001, CICC20011, CICC2762, CICC21684, CICC20441, and CICC24873.

[0012] Preferably, the Monascus is selected from one or more of CICC41601, CICC5007, CICC41739, and CICC40269.

[0013] Preferably, the yeast is selected from one or more of CICC31134, CICC1001, CICC1312, CICC21819, and CICC33179.

[0014] Preferably, the inoculation amount of the Monascus is 0.5% to 3%.

[0015] Preferably, the inoculation amount of the yeast is 8% to 14%.

[0016] Preferably, the inoculation amount of the acetic acid bacteria is 8% to 14%.

[0017] Preferably, the concentration of the Monascus bacterial suspension is 1×10 5 ~1×10 8 CFU / mL.

[0018] Preferably, the yeast suspension concentration is 1×10 6 ~1×10 9 CFU / mL.

[0019] Preferably, the concentration of the acetic acid bacteria suspension is 1×10 6 ~1×10 9 CFU / mL.

[0020] Preferably, the fermentation temperature of the Monascus is 26-32°C.

[0021] Preferably, the fermentation temperature of the yeast is 26-32°C.

[0022] Preferably, the fermentation temperature of the acetic acid bacteria is 25-30°C.

[0023] Preferably, the fermentation time of the Monascus is 6 to 10 days.

[0024] Preferably, the fermentation time of the yeast is 6 to 10 days.

[0025] Preferably, the fermentation time of the acetic acid bacteria is 12 to 20 days.

[0026] Preferably, the ultrasonic frequency is 20-40 kHz, the ultrasonic density is 35-65 W / 100 mL, and the microwave power is 30-80 W; more preferably, the ultrasonic / microwave temperature is 25-45° C., and the time is 50-180 min.

[0027] The ultrasonic / microwave synergistic aging method described in the present invention refers to the use of ultrasonic / microwave synergistic aging after acetic acid fermentation by acetic acid bacteria. Ultrasound and microwaves have the characteristics of high frequency, short wavelength, good directionality, and strong penetration. The present invention has discovered that when the ultrasonic frequency is higher than 20 kHz and the microwave power is higher than 30 W, the medium can enter a vibrating state, generating a cavitation effect that promotes the orderly arrangement of polar molecules in the medium and the polymerization and condensation reactions of low-molecular compounds. This accelerates reactions such as esterification, condensation, and redox, promotes association, and enhances the affinity between polar molecules such as water, alcohol, aldehyde, and ester. This facilitates the formation of ester-flavored substances in sweet potato vinegar, improving vinegar quality and production efficiency.

[0028] Preferably, the dosage of α-amylase is 0.1-1.5 mL / 100 g, the liquefaction temperature is 85-97° C., and the liquefaction time is 0.5-3 hours.

[0029] More preferably, the dosage of α-amylase is 0.3-1.2 mL / 100 g, the liquefaction temperature is 87-96° C., and the liquefaction time is 1-2 hours.

[0030] Preferably, the dosage of saccharifying enzyme is 0.1-1 g / 100 g, the saccharification temperature is 55-70° C., and the saccharification time is 1-4 hours.

[0031] More preferably, the dosage of saccharifying enzyme is 0.2-0.8 mL / 100 g, and the saccharification temperature is 58-68° C.; more preferably, the saccharification time is 2-3 hours.

[0032] In the present invention, the quantitative liquefaction and saccharification treatment can transform and degrade the starch in the fresh sweet potato under fixed enzyme dosage, temperature and time conditions by relying on the action of endogenous α-amylase and saccharifying enzyme to form glucose, fructose, sucrose, maltose and other sugar substances; wherein, the α-amylase can randomly act on the α-1,4-glycosidic bonds at any position inside the starch, and the hydrolysis products are dextrin, oligosaccharides and monosaccharides, and the viscosity of the gelatinized starch can be rapidly reduced to convert it into liquefied starch; the saccharifying enzyme sequentially cuts the separated α-1,4-glycosidic bonds from the non-reducing end of the starch, and the liquefied starch can be further converted into soluble sugars such as sucrose, glucose and fructose; the increase in the content of sugar substances can provide more carbon sources for the growth and reproduction of Monascus and yeast, thereby increasing the alcohol content of the fermentation substrate metabolism; at the same time, the sugar substances will undergo Maillard reaction and caramelization reaction during the high-temperature sterilization stage to produce substances such as tetramethylpyrazine and melanoidin, thereby improving the flavor and function of the sweet potato vinegar. If liquefaction and saccharification are carried out at too low or too high a temperature, the activity of the enzyme will be reduced or inactivated, and most of the starch in the sweet potato will not be converted into soluble sugar, which will not provide sufficient carbon source for the subsequent growth and reproduction of microorganisms. As a result, the microorganisms cannot produce enough enzymes, alcohol, acetic acid and other fermentation products, which will lead to problems such as slow fermentation efficiency, low product acidity and poor flavor.

[0033] Preferably, the brewing method of the sweet potato vinegar comprises: S1: peeling fresh sweet potatoes, steaming and blending them into a puree, and then mixing them with water to obtain a sweet potato slurry; S2: adding α-amylase to the sweet potato slurry for liquefaction treatment, the amount of α-amylase used is 0.3-1.2 mL / 100 g, and the liquefaction temperature is 87-96° C.; then adding saccharifying enzyme to the material obtained after liquefaction treatment for saccharification treatment, the amount of saccharifying enzyme used is 0.2-0.8 mL / 100 g, and the saccharification temperature is 58-68° C.; S3: The material obtained in S2 is sterilized, and then inoculated with Monascus and yeast under sterile conditions for fermentation; wherein the concentration of Monascus suspension is 1×10 5 ~1×10 8 CFU / mL, the concentration of yeast suspension is 1×10 6 ~1×10 9 CFU / mL, the inoculum amounts of Monascus and yeast were 0.5%-3% and 8%-14%, respectively, the fermentation temperature was 26-32°C, and the fermentation time was 6-10 days; S4: The material obtained in S3 is inoculated with one or more of acetic acid bacteria CICC20001, CICC20011, CICC2762, CICC21684, CICC20441, and CICC24873 for fermentation; wherein the concentration of the bacterial suspension is 1×10 6~1×10 9 CFU / mL, the inoculum size is 8%~14%, the fermentation temperature is 25%~30℃, and the fermentation time is 12~20 days; S5: The material obtained in S4 is subjected to ultrasonic and microwave assisted aging; wherein the ultrasonic frequency is 20-40 kHz, the ultrasonic density is 35-65 W / 100 mL, and the microwave power is 30-80 W; preferably, the ultrasonic / microwave temperature is 25-45°C, and the time is 50-180 min; S6: Filter, centrifuge and sterilize the material obtained in S5.

[0034] In the present invention, the sterilization includes: pasteurization (60-80°C, 20 seconds to 30 minutes), high-temperature steam sterilization (90-100°C, 8-20 seconds), high hydrostatic pressure sterilization (400-700 MPa, 10-30 minutes) or microwave sterilization (200-600 W, 10-60 minutes), etc.

[0035] As a preferred embodiment of the present invention, the brewing method of sweet potato vinegar comprises: (1) After washing, peeling, cutting, steaming, and stirring the sweet potatoes to make a paste, water is added at a material-liquid ratio of (1-3): (1-3) to prepare the paste; (2) Adding thermostable α-amylase to the material obtained in step (1) in an amount of 0.3-1.2 mL / 100 g, with a liquefaction temperature of 87-96°C and a liquefaction time of 1-2 hours; (3) Add saccharifying enzyme to the material obtained in step (2) in an amount of 0.2-0.8 mL / 100 g, at a saccharification temperature of 58-68°C and a saccharification time of 2-3 hours; (4) The material obtained in step (3) was sterilized in a high-temperature steam autoclave, cooled to room temperature, and inoculated with Monascus and yeast under sterile conditions. The concentration of the Monascus suspension was 1×10 5 ~1×10 8 CFU / mL, the concentration of yeast suspension is 1×10 6 ~1×10 9 CFU / mL, the inoculum amounts of Monascus and yeast were 0.5%-3% and 8%-14%, respectively, the fermentation temperature was 26-32°C, and the fermentation time was 6-10 days; (5) Under sterile conditions, one or more of acetic acid bacteria CICC20001, CICC20011, CICC2762, CICC21684, CICC20441, and CICC24873 were inoculated into the material obtained in step (4) at a bacterial suspension concentration of 1×10 6 ~1×10 9CFU / mL, the inoculation amount is 8%~14%, the fermentation temperature is 25%~30℃, and the fermentation time is 12~20 days.

[0036] (6) The material obtained in step (5) was subjected to ultrasonic / microwave synergistic aging at a frequency of 20-40 kHz, an ultrasonic density of 35-65 W / 100 mL, a microwave power of 30-80 W, an ultrasonic / microwave temperature of 25-45°C, and a time of 50-180 minutes.

[0037] (7) The material obtained in step (6) is filtered, centrifuged, sterilized, and then bottled to obtain the sweet potato vinegar product.

[0038] In a second aspect, the present invention provides a sweet potato vinegar prepared by the above-mentioned preparation method.

[0039] In a third aspect, the present invention provides a bacterial agent, comprising Monascus, yeast and acetic acid bacteria; wherein, Monascus and yeast are packaged separately or in combination, and acetic acid bacteria are packaged separately; the Monascus is selected from one or more of CICC41601, CICC5007, CICC41739, and CICC40269; the yeast is selected from one or more of CICC31134, CICC1001, CICC1312, CICC21819, and CICC33179; and the acetic acid bacteria is selected from one or more of CICC20001, CICC20011, CICC22762, CICC21684, CICC20441, CICC24873, and CICC23559.

[0040] The sweet potato vinegar and preparation method provided by the present invention can improve the flavor, nutritional function and production efficiency of the sweet potato vinegar by combining quantitative liquefaction saccharification - coordinated fermentation of monascus and yeast - fermentation of acetic acid bacteria - and coordinated aging of ultrasound / microwave. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 The present invention provides a process flow chart for preparing sweet potato vinegar. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0044] Unless otherwise specified, the various raw materials used in the examples and comparative examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0045] In the following examples, the culture media for fermenting Monascus and yeast were YM and MEA media, respectively, and the culture medium for fermenting acetic acid bacteria contained 1% glucose, 1% yeast extract, and was sterilized with high-pressure steam at 121°C for 15 min, followed by the addition of 3% anhydrous ethanol. The "%" herein refers to the mass ratio.

[0046] Example 1 This embodiment provides a brewing process and a product prepared by combining quantitative liquefaction saccharification - Monascus and yeast cooperative fermentation - acetic acid bacteria fermentation - ultrasonic / microwave coordinated aging to improve the flavor, nutritional function and production efficiency of sweet potato vinegar, and the product is prepared according to the following steps (see the preparation process flow chart Figure 1 ): (1) Wash, peel, cut, steam, and stir the sweet potatoes to make a paste, then add water to make a paste with a material-liquid ratio of 1:1.5; (2) Adding high-temperature resistant α-amylase to the material obtained in step (1) in an amount of 0.5 mL / 100 g, the liquefaction temperature is 95°C, and the liquefaction time is 1.5 hours; (3) Add saccharifying enzyme to the material obtained in step (2) at an amount of 0.3 mL / 100 g, a saccharification temperature of 60°C, and a saccharification time of 2.5 hours; (4) The material obtained in step (3) was sterilized in a high-temperature steam autoclave (121°C, 15 minutes), cooled to room temperature, and inoculated with Monascus CICC41601 and yeast CICC31134 in sequence under sterile conditions. The concentration of the Monascus suspension was 1×10 6 CFU / mL, the concentration of yeast suspension is 1×10 8 CFU / mL, the inoculum amounts of Monascus and yeast were 1% and 10%, respectively, the fermentation temperature was 28°C, and the fermentation time was 7 days; (5) Under sterile conditions, acetic acid bacteria CICC20001 was inoculated into the material obtained in step (4) at a bacterial suspension concentration of 1×10 8 CFU / mL, the inoculation amount was 10%, the fermentation temperature was 28°C, and the fermentation time was 18 days.

[0047] (6) The material obtained in step (5) was subjected to ultrasonic / microwave synergistic aging, with an ultrasonic frequency of 30 kHz, an ultrasonic density of 50 W / 100 mL, a microwave power of 35 W (ultrasonic / microwave power to sweet potato vinegar volume ratio), an ultrasonic / microwave temperature of 35 °C, and a time of 100 min.

[0048] (7) The material obtained in step (6) is filtered and centrifuged, pasteurized (75° C., 15 seconds), and then bottled to obtain the sweet potato vinegar product.

[0049] Example 2 This embodiment provides a brewing process and a product prepared by combining quantitative liquefaction saccharification, Monascus and yeast cooperative fermentation, acetic acid bacteria fermentation, and ultrasonic / microwave coordinated aging to improve the flavor, nutritional function, and production efficiency of sweet potato vinegar. The process is prepared according to the following steps: (1) Wash, peel, cut, steam, and stir the sweet potatoes to make a paste, then add water to make a paste with a material-liquid ratio of 1:2; (2) Adding high-temperature resistant α-amylase to the material obtained in step (1) at a dosage of 1 mL / 100 g, a liquefaction temperature of 92°C, and a liquefaction time of 1 hour; (3) Add saccharifying enzyme to the material obtained in step (2) at a dosage of 0.5 mL / 100 g, a saccharification temperature of 60°C, and a saccharification time of 2 hours; (4) The material obtained in step (3) was sterilized in a high-temperature steam autoclave (121°C, 15 minutes), cooled to room temperature, and inoculated with Monascus CICC41601 and yeast CICC31134 in sequence under sterile conditions. The concentration of the Monascus suspension was 1×10 7 CFU / mL, the concentration of yeast suspension is 1×10 7 CFU / mL, the inoculum amounts of Monascus and yeast were 8% and 2%, respectively, the fermentation temperature was 30°C, and the fermentation time was 10 days; (5) Under sterile conditions, acetic acid bacteria CICC20011 was inoculated into the material obtained in step (4) at a bacterial suspension concentration of 1×10 7 CFU / mL, the inoculation size was 8%, the fermentation temperature was 28°C, and the fermentation time was 19 days.

[0050] (6) The material obtained in step (5) was subjected to ultrasonic / microwave synergistic aging, with an ultrasonic frequency of 25 kHz, an ultrasonic density of 35 W / 100 mL, a microwave power of 40 W (ultrasonic / microwave power to sweet potato vinegar volume ratio), an ultrasonic / microwave temperature of 28 ° C, and a time of 60 min.

[0051] (7) The material obtained in step (6) is filtered and centrifuged, sterilized with high-temperature steam (temperature 100°C, time 10 seconds), and then filled to obtain the sweet potato vinegar product.

[0052] Example 3 This embodiment provides a brewing process and a product prepared by combining quantitative liquefaction saccharification, Monascus and yeast cooperative fermentation, acetic acid bacteria fermentation, and ultrasonic / microwave coordinated aging to improve the flavor, nutritional function, and production efficiency of sweet potato vinegar. The process is prepared according to the following steps: (1) Wash, peel, cut, steam, and stir the sweet potatoes to make a paste, then add water to make a paste with a material-liquid ratio of 1:2; (2) Adding high-temperature resistant α-amylase to the material obtained in step (1) at an amount of 0.8 mL / 100 g, the liquefaction temperature is 90°C, and the liquefaction time is 2 hours; (3) Add saccharifying enzyme to the material obtained in step (2) at a dosage of 0.3 mL / 100 g, a saccharification temperature of 60°C, and a saccharification time of 2 hours; (4) The material obtained in step (3) was sterilized in a high-temperature steam autoclave (121°C, 15 minutes), cooled to room temperature, and inoculated with Monascus CICC41601 and yeast CICC31134 in sequence under sterile conditions. The concentration of the Monascus suspension was 1×10 7 CFU / mL, the concentration of yeast suspension is 1×10 9 CFU / mL, the inoculum amounts of Monascus and yeast were 9% and 0.5%, respectively, the fermentation temperature was 27°C, and the fermentation time was 6 days; (5) Under sterile conditions, acetic acid bacteria CICC20441 was inoculated into the material obtained in step (4) at a bacterial suspension concentration of 1×10 9 CFU / mL, the inoculation amount was 10%, the fermentation temperature was 30°C, and the fermentation time was 15 days.

[0053] (6) The material obtained in step (5) was subjected to ultrasonic / microwave synergistic aging at a frequency of 35 kHz, an ultrasonic density of 60 wW / 100 mL, a microwave power of 40 W (ultrasonic / microwave power to sweet potato vinegar volume ratio), an ultrasonic / microwave temperature of 42 ° C, and a time of 110 min.

[0054] (7) The material obtained in step (6) is filtered and centrifuged, sterilized under high hydrostatic pressure (700 MPa, 10 minutes), and then filled to obtain the sweet potato vinegar product.

[0055] Example 4 This embodiment provides a brewing process and a product prepared by combining quantitative liquefaction saccharification, Monascus and yeast cooperative fermentation, acetic acid bacteria fermentation, and ultrasonic / microwave coordinated aging to improve the flavor, nutritional function, and production efficiency of sweet potato vinegar. The process is prepared according to the following steps: (1) Wash, peel, cut, steam, and stir the sweet potatoes to make a paste, then add water to make a paste with a material-liquid ratio of 2:1; (2) Adding high-temperature resistant α-amylase to the material obtained in step (1) at a dosage of 0.7 mL / 100 g, with a liquefaction temperature of 96°C and a liquefaction time of 2 hours; (3) Add saccharifying enzyme to the material obtained in step (2) at a dosage of 0.5 mL / 100 g, a saccharification temperature of 60°C, and a saccharification time of 2 hours; (4) The material obtained in step (3) was sterilized in a high-temperature steam autoclave (121°C, 15 minutes), cooled to room temperature, and inoculated with Monascus CICC41601 and yeast CICC31134 in sequence under sterile conditions. The concentration of the Monascus suspension was 1×10 8 CFU / mL, the concentration of yeast suspension is 1×10 8 CFU / mL, the inoculum amounts of Monascus and yeast were 6% and 1%, respectively, the fermentation temperature was 27°C, and the fermentation time was 9 days; (5) Under sterile conditions, acetic acid bacteria CICC22762 was inoculated into the material obtained in step (4) at a bacterial suspension concentration of 1×10 8 CFU / mL, inoculum size was 7%, fermentation temperature was 30°C, and fermentation time was 16 days; (6) The material obtained in step (5) was subjected to ultrasonic / microwave synergistic aging at a frequency of 28 kHz, an ultrasonic density of 40 W / 100 mL, a microwave power of 40 W (ultrasonic / microwave power to sweet potato vinegar volume ratio), an ultrasonic / microwave temperature of 40 ° C, and a time of 90 minutes.

[0056] (7) The material obtained in step (6) is filtered and centrifuged, sterilized under high hydrostatic pressure (700 MPa, 10 minutes), and then filled to obtain the sweet potato vinegar product.

[0057] Example 5 Compared with Example 1, this example is different in that the acetic acid bacteria is replaced by CICC23559.

[0058] Comparative Example 1 The difference between this comparative example and Example 1 is that the sweet potato is not subjected to the coordinated fermentation treatment of Monascus and yeast, but is fermented only with yeast (temperature 28° C., fermentation for 7 days).

[0059] Comparative Example 2 The difference between this comparative example and Example 1 is that the sweet potato vinegar is directly filtered and centrifuged without being aged by ultrasonic / microwave synergistic treatment.

[0060] Comparative Example 3 Compared with Example 1, this comparative example is different in that the sweet potato is directly subjected to alcohol fermentation and acetic acid fermentation without undergoing quantitative liquefaction and saccharification treatment.

[0061] Experimental Example 1: Sensory Evaluation of Sweet Potato Vinegar Products 50 volunteers who like to eat vinegar on a daily basis, aged 20 to 30 years old, half male and half female, were randomly selected. The sweet potato vinegar products of Examples 1-4 and Comparative Examples 1-4 were subjected to sensory evaluation according to the standards shown in the table below. The average score was taken. The results are shown in the table below: Table 1 Scoring criteria

[0062] 2. Experimental results Table 2 Sensory evaluation results of sweet potato vinegar products

[0063] As can be seen from Table 1, the vinegar products (Examples 1-5) prepared by the brewing process for improving the flavor, nutritional function and production efficiency of sweet potato vinegar based on the combination of quantitative liquefaction saccharification - Monascus and yeast collaborative fermentation - acetic acid bacteria fermentation - ultrasonic / microwave collaborative aging provided by the present invention have significantly better sensory evaluation scores than the sweet potato vinegar products provided by Comparative Examples 1-3; among them, the sweet potato vinegar product provided in Comparative Example 1 without the use of Monascus and yeast collaborative fermentation has a significantly lower sensory score than the sweet potato vinegar products with the addition of Monascus fermentation (Implementation Cases 1-5 and Comparative Case 2); the sweet potato vinegar product provided by Comparative Example 3 has the lowest sensory score, indicating that the lack of quantitative liquefaction and saccharification of sweet potatoes will result in less subsequent fermentation products, resulting in relatively insufficient aroma and taste of the sweet potato vinegar, followed by the sweet potato vinegar product provided by Comparative Example 2, indicating that the sweet potato vinegar has less ester flavor substances due to the lack of ultrasonic / microwave collaborative aging, resulting in a lower sensory score.

[0064] Experimental Example 2: Determination of physical and chemical indicators and functional active ingredients of sweet potato vinegar products This experimental example analyzes the total acid, non-volatile acid, soluble salt-free solids, lovastatin, anthocyanins, etc. of the sweet potato vinegar products in each embodiment and comparative example: The data obtained in Experimental Example 2 were measured for the sweet potato vinegars of Examples 1-5 and Comparative Examples 1-3.

[0065] 1. Determination of total acid content: Determine by potentiometric titration with a pH meter according to the method of GB 12456-202.

[0066] Use a pipette to transfer 25.00 mL of sweet potato vinegar to a 250 mL volumetric flask, dilute to the mark with carbon dioxide-free water, and shake well. Filter with fast filter paper and collect the filtrate. Use a pipette to transfer 50 mL of the filtrate into a 150 mL beaker. Turn on the power of the pH meter. Once it stabilizes, calibrate the pH meter according to the calibration procedure of the pH meter being used or with pH 8.0 buffer solution. Place the beaker containing 50 mL of filtrate on a magnetic stirrer and immerse the pH meter electrode. Press the pH reading switch, start the stirrer, and quickly titrate with 0.1 mol / L sodium hydroxide standard titrant, observing the change in the solution pH at any time. When approaching the titration endpoint, slow down the titration speed. Add half a drop at a time (one drop at most) until the solution reaches the endpoint of pH = 8.2, and record the volume of sodium hydroxide standard titrant consumed. For a blank control, perform a blank test using the same volume of carbon dioxide-free water instead of the filtrate as described above, and record the volume of sodium hydroxide standard titrant consumed. The formula for calculating total acid is: X——total acid content in sweet potato vinegar, g / L; c ——Concentration of sodium hydroxide standard titration solution, mol / L; V 1 ——The volume of sodium hydroxide standard titration solution consumed when titrating the filtrate, mL; V 2 ——The volume of sodium hydroxide standard titration solution consumed during the blank test, mL; k - Conversion factor for acid, acetic acid, 0.060; F ——Dilution factor of the test solution; V 2 ——Volume of the sample absorbed, mL.

[0067] 2. Determination of non-volatile acid content: Determined according to the method of GB / T 18187-2000.

[0068] After shaking the sweet potato vinegar, accurately pipette 2.00 mL into the distillation tube of a single-boiling distillation apparatus, add 8 mL of water and shake well, then distill. When the distillate reaches 180 mL, open the exhaust port and turn off the power. Pour the residual liquid into a 200 mL beaker, repeatedly rinse the distillation tube and the air inlet on the tube with water, add the washing liquid into the beaker, and then add water until the total amount of solution in the beaker is about 120 mL. Place the beaker containing 120 mL of residual liquid on the tray of the acidity meter, start the magnetic stirrer, and use 0.05 mol / L sodium hydroxide standard titration solution to drop to pH 8.2, and record the number of milliliters consumed (V). Perform a blank test at the same time. The formula for calculating the non-volatile acid content is: X——the content of non-volatile acid in sweet potato vinegar (calculated as lactic acid), g / 100mL; V ——The volume of sodium hydroxide standard titration solution consumed when titrating the sample, mL; V 0 ——The volume of sodium hydroxide standard titration solution consumed in the blank test, mL; c ——Concentration of sodium hydroxide standard titration solution, mol / L; 0.090 ——The mass of lactic acid equivalent to the standard titration solution of sodium hydroxide [c(NaOH)=1.000mol / L], g.

[0069] 3. Determination of soluble salt-free solids content: Determined according to the method of GB / T 18187-2000.

[0070] Pipette 2.00 mL of sweet potato vinegar into a weighing bottle that has been dried to constant weight. Transfer the bottle to a (103±2)°C electric constant-temperature drying oven with the bottle cap tilted to the side. After 4 hours, cap the bottle, remove it, transfer it to a desiccator, cool it to room temperature, and weigh it to constant weight. Calculate the soluble total solids content in the sweet potato vinegar and record it as X3. Pipette 2.00 mL of sweet potato vinegar into a 250 mL conical flask, add 100 mL of water and 1 mL of potassium chromate solution, mix well, and titrate with 0.1 mol / L silver nitrate standard titrant against a white tile background until an orange-red color appears. Simultaneously, perform a blank test and calculate the sodium chloride content in the sweet potato vinegar and record it as X2. The soluble salt-free solids content = X3. X2.

[0071] 4. Determination of anthocyanin content: The anthocyanin content of sweet potato vinegar (Examples 1-4, Comparative Examples 1-4) was determined using the pH differential method. 1.00 mL of sweet potato vinegar was pipetted into a 50 mL volumetric flask, diluted to the mark with carbon dioxide-free water, and shaken. Potassium chloride buffer solution (0.25 mol / L, pH 1.0) and sodium acetate buffer solution (0.4 mol / L, pH 1.0) were prepared. Dilute the sample at pH 4.5. Take 180 μL of potassium chloride buffer solution and sodium acetate buffer solution and 20 μL of sample and read the absorbance at wavelengths of 510 nm and 700 nm using a spectrophotometer. The formula for calculating the non-volatile acid content is: A——absorbance; C3G / (mg / g)——cyanidin-3-glucoside equivalent; ——Relative molecular mass of C3G (449.2); DF ——Dilution factor;³——Molar absorptivity [26900 L / (mol·cm)].

[0072] 5. Determination of lovastatin content: Determine according to the method of QB / T 2847-2007 with slight modifications.

[0073] HPLC chromatographic conditions: ODS-SP (4.6×150 mm, 5 μg) as the chromatographic column, acetonitrile (A)-0.1% phosphoric acid (B) as the mobile phase, gradient elution (1-5 min, 60%-65% A; 5-20 min, 65% A), volume flow rate 1.0 mL / min, column temperature 28°C, detection wavelength 238 nm, injection volume 10 μL.

[0074] Table 3 Analysis results of total acid, non-volatile acid, soluble salt-free solids, anthocyanins and lovastatin in sweet potato vinegar

[0075] As can be seen from the above table, the vinegar products (Examples 1-5) prepared by the brewing process of the present invention combining quantitative liquefaction and saccharification of fresh sweet potatoes - coordinated fermentation of Monascus and yeast - fermentation of acetic acid bacteria - ultrasonic / microwave coordinated aging to improve the flavor, nutritional function and production efficiency of sweet potato vinegar, except for the soluble salt-free solids content, the total acid, non-volatile acid, anthocyanin and lovastatin contents are all higher than those of the sweet potato vinegar products provided by Comparative Examples 1-3; among them, the sweet potato vinegar product provided in Comparative Example 1 without the use of Monascus and yeast coordinated fermentation has lower total acid, non-volatile acid, anthocyanin and lovastatin contents than the sweet potato vinegar products with the addition of Monascus fermentation (Implementation Cases 1-5 and Comparative Case 3); the sweet potato vinegar product provided in Comparative Example 3 has the lowest total acid, non-volatile acid and anthocyanin contents, indicating that the lack of quantitative liquefaction and saccharification of sweet potatoes will result in less subsequent fermentation products; the higher soluble salt-free solids content in Comparative Examples 1 and 3 is because more proteins and sugars in the raw materials are not utilized by microorganisms.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for brewing sweet potato vinegar, characterized in that: include: The sweet potatoes are pretreated to obtain cooked sweet potato slurry, the cooked sweet potato slurry is sequentially subjected to liquefaction and saccharification, then sterilized, fermented under aseptic conditions, and finally aged using ultrasound and microwave assisted methods; The fermentation treatment comprises: first inoculating the saccharified material with Monascus and yeast for collaborative fermentation, and then inoculating acetic acid bacteria for fermentation.

2. The method for brewing sweet potato vinegar according to claim 1, wherein The acetic acid bacteria is selected from one or more of CICC20001, CICC20011, CICC2762, CICC21684, CICC20441, and CICC24873; And / or, the Monascus is selected from one or more of CICC41601, CICC5007, CICC41739, and CICC40269; And / or, the yeast is selected from one or more of CICC31134, CICC1001, CICC1312, CICC21819, and CICC33179.

3. The brewing method of sweet potato vinegar according to claim 1 or 2, characterized in that The inoculation amount of the Monascus is 0.5% to 3%; and / or, the yeast inoculation amount is 8% to 14%; And / or, the inoculation amount of the acetic acid bacteria is 8% to 14%.

4. The method for brewing sweet potato vinegar according to any one of claims 1 to 3, wherein The concentration of the Monascus bacterial suspension is 1×10 5 ~1×10 8 CFU / mL; And / or, the yeast suspension concentration is 1×10 6 ~1×10 9 CFU / mL; And / or, the concentration of the acetic acid bacteria suspension is 1×10 6 ~1×10 9 CFU / mL.

5. The method for brewing sweet potato vinegar according to any one of claims 1 to 4, wherein The fermentation temperature of the Monascus is 26-32°C; and / or, the fermentation temperature of the yeast is 26-32°C; And / or, the fermentation temperature of the acetic acid bacteria is 25-30°C.

6. The method for brewing sweet potato vinegar according to any one of claims 1 to 5, wherein The fermentation time of the monascus is 6 to 10 days; And / or, the fermentation time of the yeast is 6 to 10 days; And / or, the fermentation time of the acetic acid bacteria is 12 to 20 days.

7. The method for brewing sweet potato vinegar according to any one of claims 1 to 6, wherein The ultrasonic frequency is 20-40 kHz, the ultrasonic density is 35-65 W / 100 mL, and the microwave power is 30-80 W; preferably, the ultrasonic / microwave temperature is 25-45° C., and the time is 50-180 min.

8. The method for brewing sweet potato vinegar according to any one of claims 1 to 7, wherein: include: S1: peeling fresh sweet potatoes, steaming and blending them into a puree, and then mixing them with water to obtain a sweet potato slurry; S2: adding α-amylase to the sweet potato slurry for liquefaction treatment, the amount of α-amylase used is 0.3-1.2 mL / 100 g, and the liquefaction temperature is 87-96° C.; then adding saccharifying enzyme to the material obtained after liquefaction treatment for saccharification treatment, the amount of saccharifying enzyme used is 0.2-0.8 mL / 100 g, and the saccharification temperature is 58-68° C.; S3: The material obtained in S2 is sterilized, and then inoculated with Monascus and yeast under sterile conditions for fermentation; wherein the concentration of Monascus suspension is 1×10 5 ~1×10 8 CFU / mL, the concentration of yeast suspension is 1×10 6 ~1×10 9 CFU / mL, the inoculum amounts of Monascus and yeast were 0.5%-3% and 8%-14%, respectively, the fermentation temperature was 26-32°C, and the fermentation time was 6-10 days; S4: The material obtained in S3 is inoculated with one or more of acetic acid bacteria CICC20001, CICC20011, CICC2762, CICC21684, CICC20441, and CICC24873 for fermentation; wherein the concentration of the bacterial suspension is 1×10 6 ~1×10 9 CFU / mL, the inoculum size is 8%~14%, the fermentation temperature is 25%~30℃, and the fermentation time is 12~20 days; S5: The material obtained in S4 is subjected to ultrasonic and microwave assisted aging; wherein the ultrasonic frequency is 20-40 kHz, the ultrasonic density is 35-65 W / 100 mL, and the microwave power is 30-80 W; preferably, the ultrasonic / microwave temperature is 25-45°C, and the time is 50-180 min; S6: Filter, centrifuge and sterilize the material obtained in S5.

9. A sweet potato vinegar, characterized in that The brewing method is prepared by the brewing method according to any one of claims 1 to 8.

10. A bacterial agent, characterized in that The invention comprises Monascus, yeast and acetic acid bacteria; wherein Monascus and yeast are packaged separately or in combination, and acetic acid bacteria are packaged separately; preferably, the Monascus is selected from one or more of CICC41601, CICC5007, CICC41739 and CICC40269; the yeast is selected from one or more of CICC31134, CICC1001, CICC1312, CICC21819 and CICC33179; and the acetic acid bacteria is selected from one or more of CICC20001, CICC20011, CICC22762, CICC21684, CICC20441, CICC24873 and CICC23559.

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