WO2007055435A1

WO2007055435A1 - Manufacturing method of vinegar by using filtered water of bean-curd and vinegar manufactured thereby

Info

Publication number: WO2007055435A1
Application number: PCT/KR2005/004020
Authority: WO
Inventors: Kyung-Ho Lee
Original assignee: Kyung-Ho Lee
Priority date: 2005-11-11
Filing date: 2005-11-28
Publication date: 2007-05-18
Also published as: KR100743644B1; KR20070050598A

Abstract

The present invention relates to a method of manufacturing vinegar by using filtered water of bean-curd or bean-curd dregs which are produced as by-products or wastes after the manufacture of soybean products such as soya milk and bean curd such that a variety of active ingredients included in the filtered water of bean-curd or bean-curd dregs can be utilized to be helpful to the health, and a vinegar manufactured by the method. The manufacturing method of the present invention comprises the steps of (1) a sterilizing step of preparing filtered water of bean-curd as a raw material and sterilizing the prepared filtered water of bean-curd; (2) a sugar supplementing step of adding sugar to the sterilized raw material to adjust sweetness to 5.5 to 39.2 Brix; (3) a mixing step of adding 0.02 to 0.13 wt% of brewer's yeast and 0.007 to 0.05 wt% of yeast nutrients with respect to a total amount of the sugar-supplemented raw material, and mixing them to prepare a fermentation mixture; (4) an alcohol fermentation step of fermenting the fermentation mixture at a temperature of 20 to 29°C for 3 to 30 days to obtain an alcohol fermentation product with an alcohol content of 5 to 20%; (5) an alcohol content adjustment step of adjusting the alcohol content of the alcohol fermentation product obtained from the alcohol fermentation step to 2 to 10%; and (6) an acetic acid fermentation step of inoculating Acetobacter in an amount of 0.5 to 1.5 wt% (an amount of a strain itself) with respect to a total amount of the alcohol fermentation product obtained from the alcohol content adjustment step and effecting an acetic acid fermentation at a temperature of 20 to 30°C until acidity of the acetic acid fermentation product becomes 5 to 12%.

Description

MANUFACTURING METHOD OF VINEGAR BY USING FILTERED WATER OF BEAN-CURD AND VINEGAR MANUFACTURED THEREBY

Technical Field

[1] The present invention relates to a method of manufacturing vinegar by using filtered water of bean-curd and vinegar manufactured by the method. More particularly, the present invention relates to a method of manufacturing vinegar by using filtered water of bean-curd or bean-curd dregs produced as by-products or wastes after the manufacture of soybean products such as soya milk and bean curd such that a variety of active ingredients included in the filtered water of bean-curd or bean-curd dregs can be utilized to be beneficial to the health, and vinegar manufactured by the method.

[2]

Background Art

[3] Soybean is a kind of edible crops which are easily cultivated in a number of places inside and outside of the country. Soybean is rich in nutrients including 30 to 50% of protein, 13 to 25% of fat and vitamins and is very widely used depending on its ingredients and qualities. Particularly in the Republic of Korea, soybean is mostly used for food and is cooked together with rice or used in either processed foodstuffs such as soybean paste, soy sauce, hot pepper paste, bean curd and bean-curd dregs or side dishes such as soybean sprouts. Further, soybean oil obtained by squeezing the soybean is used in various applications, and soybean cake is also widely used as manure and livestock feed.

[4] Furthermore, soybean is used as a variety of industrial raw materials such as a casein adhesive, a celluloid substitute article, plastic, a water-soluble paint, glycerin, soap and the like.

[5] It has been discovered by the modern science and medicine that soybean is particularly rich in ingredients such as isoflavone and saponin which are beneficial to human body. Thus, the interest in soybean as health foods has been gradually increased.

[6] It has been known that filtered water of bean-curd among the filtered water of bean- curd (the filtrate left after squeezing the solidified bean curd) and bean-curd dregs which are produced as by-products during the processing of soybean is rich in various kinds of nutrients including minerals such as soluble nitrogen, phosphoric acid, potassium, calcium, magnesium and the like, protein and phosholipid, isoflavone, and amino acids such as glycine, serine and the like, and is significantly rich in saponin. The aforementioned isoflavone refers to a vegetable hormone and is a kind of vegetable hormone (Phytoestrogen). Isoflavone is called as phytoestrogen which combines 'phyto' having a meaning derived from a plant with 'estrogen having a meaning of functions similar to those of estrogen. Major isoflavones in soybean are daidzein and genistein.

[7] Common filtered water of bean-curd has the chemical components as shown in the following Table 1.

[8] [9] Table 1

[10] [H] Filtered water of bean-curd contains a large amount of isoflavone, which in turn is known to be effective in the treatment of post-menopausal symptoms such as osteoporosis and the like, the prevention of premenstrual syndrome (PMS), the reduction in cholesterol, the prevention of hypertension, and anti- arteriosclerosis and the like. Further, the filtered water of bean-curd is known to inhibit the incidence of cancers. However, only an extremely limited amount of the filtered water of bean-curd has been used as a raw material for producing isoflavone, and almost the whole amount of the filtered water has been dumped.

[12] In the meantime, it has been known that bean-curd dregs are rich in nutrients such as dietary fiber and minerals (calcium etc.), protein and phospholipid, and isoflavone. In particular, the protein in bean-curd dregs has been evaluated as a good protein, since it is rich in sulfur-containing amino acids and lysine.

[13] Common bean-curd dregs have the chemical components as shown in the following Table 2.

[14] [15] Table 2

[16] [17] Bean-curd dregs have been recognized as a very good food in view of the fact that they have antioxidative effects because of Vitamin A, Vitamin C, tocopherol and the like contained therein, and that they have a lower fat content as compared to the beef and thus the production of peroxidized lipid is suppressed to thereby prevent cell aging, and they are helpful to peripheral vasodilation and the prevention of cancers and also are very effective in preventing the diseases of adult people.

[18] In the process of preparing bean curd, filtered water of bean-curd is produced in an amount of 300 to 600 wt% and bean-curd dregs are produced in an amount of about 150 wt%, of the total weight of the dry soybean, and such a large amount of filtered water of bean-curd which is daily produced from respective bean-curd manufacturing factories is substantially dumped as environmental wastes. Considering that like the bean-curd dregs, filtered water of bean-curd is rich in various active ingredients of soybean, this waste of the filtered water of bean-curd is resources extravagance. Further, the bean-curd dregs have been used partially for food or for feed such as livestock feed, but a degree of practical applications is still low.

[19] Korean Patent Laid-open Publication No. 2000-6751 (entitled "A method of manufacturing kimchi to which filtered water of bean-curd is added") discloses a method of manufacturing kimchi by adding 7 to 8 % of filtered water of bean-curd by weight of main materials of kimchi to salted radishes or cabbages during the process of seasoning.

[20] Korean Patent No. 10-377959 (entitled "A method of manufacturing wine by using bean-curd dregs") discloses a method of manufacturing wine comprising the steps of adding lemon shell, banana, ginger or the like to bean-curd dregs and then subjecting to a primary fermentation, and adding sugar syrup and then subjecting to further fermentation and aging.

[21] Vinegar is a sour and slightly sweet liquid condiment which contains about 4% of acetic acid and serves to stimulate the sense of taste and thus appetite.

[22] Vinegar includes grain vinegar made by adding malt to rice, barley, corn and the like, and fruit vinegar made by adding sugar to fruits. Vinegar contains taste and flavor components such as essential amino acids and organic acids, and sugars and the like.

[23] Vinegar serves to facilitate fatigue heal, digestion and absorption, improve physical constitution into an alkaline state and inhibit the occurrence of bacteria, and stimulates the appetite by promote the secretion of saliva or gastric juice. Further, vinegar is used to remove fishy smell.

[24] Korean Patent No.10-368058 (entitled "a method of manufacturing soybean vinegar") discloses a method of manufacturing soybean vinegar containing active ingredients of soybean by extracting the extract liquid of soybean and then mixing hard- boiled rice, malted wheat with the extracted liquid to ferment the mixture. However, in this method, the vinegar is only a kind of grain vinegar (vinegar of rice which is a raw material of the hard-boiled rice) except that the extract liquid of soybean is added.

[25] Consequently, a large amount of filtered water of bean-curd containing active ingredients has been produced in the manufacture of bean curd, but it has been substantially dumped. Furthermore, vinegar manufactured by using such filtered water of bean-curd has not yet been developed.

[26]

Disclosure of Invention Technical Problem

[27] Accordingly, the present invention is conceived to solve the aforementioned problems. The present invention is based on intensive studies on a method which can be beneficial to the health by using by-products or wastes, such as filtered water of bean-curd or bean-curd dregs, which are left after the manufacture of soybean products. From the repeated studies, the inventors of the present invention have found a method of manufacturing vinegar by using the filtered water of bean-curd or a mixture of the filtered water of bean-curd and bean-curd dregs and thus completed the present invention. Accordingly, an object of the present invention is to provide a manufacturing method of vinegar containing active ingredients of filtered water of bean- curd and having an improved taste and functionality by using the filtered water of bean-curd, and vinegar manufactured by the method.

[28]

Technical Solution

[29] According to an aspect of the present invention for achieving the object of the present invention, there is provided a method of manufacturing vinegar by using filtered water of bean-curd, comprising (1) a sterilizing step of preparing filtered water of bean-curd as a raw material and sterilizing the prepared filtered water of bean-curd; (2) a sugar supplementing step of adding sugar to the sterilized raw material to adjust sweetness to 5.5 to 39.2 Brix; (3) a mixing step of adding 0.02 to 0.13 wt% of brewer's yeast and 0.007 to 0.05 wt% of yeast nutrients with respect to a total amount of the sugar-supplemented raw material, and mixing them to prepare a fermentation mixture; (4) an alcohol fermentation step of fermenting the fermentation mixture at a temperature of 20 to 29°C for 3 to 30 days to obtain an alcohol fermentation product with an alcohol content of 5 to 20%; (5) an alcohol content adjustment step of adjusting the alcohol content of the alcohol fermentation product obtained from the alcohol fermentation step to 2 to 10%; and (6) an acetic acid fermentation step of inoculating Acetobacter in an amount of 0.5 to 1.5 wt% (an amount of a strain itself) with respect to a total amount of the alcohol fermentation product obtained from the alcohol content adjustment step and effecting acetic acid fermentation at a temperature of 20 to 30°C until acidity of the acetic acid fermentation product becomes 5 to 12%.

[30] Preferably, bean-curd dregs as the raw material in the sterilizing step are further mixed with the filtered water of bean-curd at a weight ratio of filtered water of bean- curd to bean-curd dregs of 1:0.2 to 1:0.5.

[31] Preferably, the sterilizing step may comprise a high temperature sterilization step of heating the raw material at a temperature of 120°C and 130°C for 1 to 3 seconds to sterilize the raw material.

[32] Preferably, the sterilizing step may comprise a pharmaceutical sterilization step of adding sulfite in an amount of 0.1 to 0.5 wt% with respect to a total amount of the fermentation mixture and then allowing the raw material to stand for 20 to 28 hours.

[33] Preferably, the sugar used in the sugar supplementing step is sucrose or glucose.

[34] Preferably, the acid is incorporated such that pH of the fermentation mixture obtained in the mixing step can be within a range of 3.5 to 4.5.

[35] Preferably, the brewer's yeast used in the mixing step is Saccharomyces cerevisiae or Saccharomyces baynus.

[36] Preferably, an acid is further added in the mixing step, and the acid is a mixed acid in which succinic acid, malic acid and citric acid are mixed at a weight ratio of 3:2: 1.

[37] Preferably, the yeast nutrients used in the mixing step is ammonium phosphate.

[38] A stirring step of stirring the fermentation mixture two to five times per day may be further executed during the alcohol fermentation step.

[39] After the alcohol fermentation step, a secondary fermentation step of separating only fermented liquid from the alcohol fermentation product obtained in the alcohol fermentation step to effect a secondary fermentation at a temperature of 15 to 18°C for 20 to 60 days in a state where air can be blocked and produced carbon dioxide can be discharged may be further executed.

[40] In the secondary fermentation step, clarifying agents selected from the group consisting of bentonite, agar, papain, isinglass or a mixture of two or more thereof may be further incorporated into the fermented liquid obtained from the alcohol fermentation step in an amount of 0.25 to 0.5 wt% with respect to a total amount of the fermented liquid.

[41] Preferably, an aging step of aging the fermented liquid at a temperature of 15 to 18°

C for 30 to 90 days is further executed after the alcohol fermentation step.

[42] Preferably, a racking step of separating only clear vinegar portion from its sediment settled during the aging step to prevent the sediment from being incorporated therein and aging only the separated clear vinegar portion is further executed two or three times.

[43] Preferably, if the bean-curd dregs as a raw material in the sterilizing step are mixed with the filtered water of bean-curd, a pressing step of removing solid portions is further executed after the alcohol fermentation step.

[44] The alcohol adjustment step may comprise the step of diluting the alcohol fermentation product (an alcohol content of 5 to 20%) obtained from the alcohol fermentation step with distilled water to an alcohol content of 2 to 10%.

[45] The alcohol adjustment step may comprise the step of heating the alcohol fermentation product (an alcohol content of 5 to 20%) obtained from the alcohol fermentation step to volatilize and remove an alcohol component such that the alcohol content of the alcohol fermentation product can be adjusted to 2 to 10%.

[46] The alcohol adjustment step may comprise the step of adjusting the alcohol fermentation product (an alcohol content of 5 to 20%) obtained from the alcohol fermentation step to an alcohol content of 3 to 8%.

[47] The Acetobacter used in the acetic acid fermentation step may be Acetobacter sp. or

Acetobacter aceti.

[48] The inoculation with the Acetobacter in the acetic acid fermentation step is performed by mixing 5 to 15 wt% of the Acetobacter with 85 to 95 wt% of an MA medium, incubating the mixture at a temperature of 25 to 35°C for 1 to 3 days to obtain Acetobacter liquid and then inoculating the Acetobacter liquid in an amount of 5 to 15 wt% (the amount of the bacteria liquid obtained from the incubation of the strain) with respect to a total amount of the alcohol fermentation product.

[49] Preferably, a fermentation extending step is further executed, which comprises the steps of harvesting 5 to 50% of the acetic acid fermentation product obtained from the acetic acid fermentation step when acidity of the acetic acid fermentation product reaches 5 to 12%, adding the alcohol fermentation product obtained from the alcohol fermentation step (an alcohol content of 5 to 20%) to the remaining acetic acid fermentation product in an equivalent amount of the harvested acetic acid fermentation product, and then effecting additional acetic acid fermentation until the acidity of the acetic acid fermentation product reaches 5 to 12%.

[50] Preferably, a packing step of bottling the vinegar and packing the bottle is further executed after the acetic acid fermentation step.

[51] Preferably, a sterilizing step is further executed after the aging step.

[52] Preferably, a filtering step of filtering the vinegar using a filter medium with a pore size of not greater than 0.5 microns is further executed after the aging step.

[53]

Advantageous Effects

[54] According to the present invention, there is an advantageous effect capable of providing a method of manufacturing vinegar by using filtered water of bean-curd or bean-curd dregs produced as by-products or wastes after the manufacture of soybean products such as soya milk and bean curd such that a variety of active ingredients included in the filtered water of bean-curd or bean-curd dregs can be utilized to be beneficial to the health, and vinegar manufactured by the method.

[55]

Brief Description of the Drawings

[56] Fig. 1 is a view illustrating a manufacturing process of preparing filtered water of bean-curd and bean curd-dregs used in the present invention.

[57] Fig. 2 is a view illustrating a manufacturing process of preparing vinegar using filtered water of bean-curd according to the present invention.

[58]

Best Mode for Carrying Out the Invention

[59] Hereinafter, the present invention will be described in detail with reference to the specific embodiments and the accompanying drawings.

[60] The present invention is characterized in that vinegar is manufactured by using filtered water of bean-curd or a mixture of the filtered water of bean-curd and bean- curd dregs, which is produced as by-products or wastes when manufacturing soybean products, such that makes active ingredients, such as isoflavone, included in the filtered water of bean-curd or bean-curd dregs are recovered to be beneficial to the human body.

[61] As shown in Fig. 2, a method of manufacturing vinegar by using filtered water of bean-curd according to the present invention comprises (1) a sterilizing step of preparing filtered water of bean-curd as a raw material and sterilizing the prepared filtered water of bean-curd; (2) a sugar supplementing step of adding sugar to the sterilized raw material to adjust sweetness to 5.5 to 39.2 Brix; (3) a mixing step of adding 0.02 to 0.13 wt% of brewer's yeast and 0.007 to 0.05 wt% of yeast nutrients with respect to a total amount of the sugar-supplemented raw material, and mixing them to prepare a fermentation mixture; (4) an alcohol fermentation step of fermenting the fermentation mixture at a temperature of 20 to 29°C for 3 to 30 days to obtain an alcohol fermentation product having 5 to 20% of an alcohol content; (5) an alcohol content adjustment step of adjusting the alcohol content of the alcohol fermentation product obtained from the alcohol fermentation step to 2 to 10%; and (6) an acetic acid fermentation step of inoculating Acetobacter in an amount of 0.5 to 1.5 wt% (the amount of the strain itself) with respect to a total amount of the alcohol fermentation product obtained from the alcohol content adjustment step and effecting an acetic acid fermentation at a temperature of 20 to 30°C until the acidity of the acetic acid fermentation product becomes 5 to 12%.

[62] In the method of manufacturing vinegar according to the present invention, filtered water of bean-curd or a mixture of the filtered water of bean-curd and bean-curd dregs can be used as a raw material. In a case where a mixture of filtered water of bean-curd and bean-curd dregs is used as a raw material, bean-curd dregs can be further added to and mixed with the filtered water of bean-curd such that a weight ratio of filtered water of bean-curd to bean-curd dregs becomes 1:0.2 to 1:0.5. If the content of the bean-curd dregs is used less than 0.2 parts by weight, the content of active ingredients derived from the bean-curd dregs in the obtained vinegar becomes too low. On the contrary, if the content of the bean-curd dregs is greater than 0.5 parts by weight, there may be a problem in that it takes more time and efforts to execute the separation of fermented liquid in the subsequent acetic acid fermentation stepand the racking and filtering in an aging step, since the bean-curd dregs are solid. The filtered water of bean-curd can be commercially available. Alternatively, as shown in Fig. 1, the filtered water of bean- curd may also be obtained by soaking soybean in water, grinding the soybean to obtain soybean juice, heating and filtering the soybean juice, coagulating the soybean juice to obtain uncurdled bean curd, and then dehydrating the bean curd.

[63] The sterilizing step (1) comprises the steps of preparing filtered water of bean-curd as a raw material and sterilizing the filtered water of bean-curd. The sterilizing step (1) may comprise a high temperature sterilization step of heating the raw material at a temperature of 120°C to 130°C for 1 to 3 seconds to sterilize the raw material or a pharmaceutical sterilization step of adding sulfite in an amount of 0.1 to 0.5 wt% with respect to the total amount of the fermentation mixture and then standing for 20 to 28 hours if the high temperature sterilization step is not appropriate. If the high temperature sterilization step is executed at a temperature less than 120°C or for less than 1 second, the sterilization effect is not sufficient, and thus, abnormal fermentation may occur. On the contrary, if the high temperature sterilization step is executed at a temperature of greater than 130°C or for 3 seconds or more, off-odor may occur due to heat denaturation of components included in the filtered water of bean-curd or mixture of the filtered water of bean-curd and bean-curd dregs, the denaturation of protein constituting the bean-curd dregs, or the like. The sulfite used in the pharmaceutical sterilization may be selected from a group consisting of sodium sulfite, sodium hy- drosulfite, potassium metabisulfite, and sodium metabisulfite. If the sulfite is used less than 0.1 wt% in the pharmaceutical sterilization, the sterilization effect is not also sufficient, and thus, abnormal fermentation may occur. On the contrary, if the sulfite is used more than 0.5wt%, an excessive amount of sulfite is included in the obtained vinegar, and thus, it is not appropriate for food standards. Furthermore, if it is taken in a large amount, there may occur safety problems such as stomach irritation, headache, abdominal pain, nausea, circulatory disorder and the like. It is preferred that the sterilization be executed within 6 hours after preparing the filtered water of bean-curd. [64] The sugar supplementing step (2) comprises the step of adding sugar to the filtered water of bean-curd or the mixture of filtered water of bean-curd and bean-curd dregs serving as a raw material to facilitate alcohol fermentation. It has been known to those skilled in the art that this sugar supplementing step makes it possible to facilitate the alcohol fermentation even in the manufacture of general fruit vinegar when the sweetness of raw material is not enough. In the sugar supplementing step, sugar is added to the raw material to adjust the sweetness to a range of 5.5 to 39.2 Brix. If the sweetness is less than 5.5 Brix in the foregoing step even after sugar is added, there may be a problem in that the content of alcohol is not sufficient and the rancidification by acetic acid occurs at an early stage of the alcohol fermentation. On the contrary, if the sweetness exceeds 39.2 Brix after sugar is added, there may be another problem in that the content of alcohol is too high and sugar cannot be sufficiently fermented, thereby resulting in extremely sweet vinegar. The sugar used in the above sugar supplementing step (2) may be sucrose or glucose.

[65] The above mixing step (3) is a process of preparing a fermentation mixture for alcohol fermentation and comprises the steps of adding and mixing 0.02 to 0.13 % of brewer's yeast and 0.007 to 0.05 % of yeast nutrients by the total weight of the sugar- supplemented raw material. If the brewer's yeast is used in an amount of less than 0.02 wt%, there may be a problem in that it takes much time for fermentation. On the contrary, if the yeast is used more than 0.05 wt%, there may be another problem in that abnormal fermentation occurs. An acid can be added and mixed such that pH of the fermentation mixture obtained in the mixing step (3) can be within a range of 3.5 to 4.5. The acid may be added in an amount of 0.04 to 0.2wt%. If an amount of acid used is out of the aforementioned range, there may be another problem in that hydrogen ion concentration, which is one of conditions for the smooth fermentation, is not sufficient, whereby appropriate alcohol fermentation due to the yeast cannot be executed. Further, the brewer's yeast used in the mixing step (3) may be Saccharomycescerevisiae or Sac- charomyces baynus. The yeasts are particularly suitable for brewing and are known to a degree that they are commercially available from leading manufacturers inside and outside of the country. In addition, the acid used in the mixing step (3) may be a mixed acid in which succinic acid, malic acid and citric acid are mixed with one another in a weight ratio of 3:2: 1. The mixed acid is a mixture of edible acids, i.e. acids which can be taken by the human, and is also known to be beneficial to the human body, i.e. effective in fatigue heal. Further, the mixed acid serves to provide suitable flavor to the vinegar obtained according to the present invention and to adjust pH of the fermentation mixture to appropriately accomplish the alcohol fermentation. The yeast nutrients used in the mixing step (3) may be ammonium phosphate. The ammonium phosphate helps the growth of yeast, allows the yeast to be sufficiently viable during the fermentation period and to sufficiently proliferate such that the sugar can be easily decomposed into alcohol.

[66] During the alcohol fermentation step (4), a stirring step of stirring the mixture at an interval of 2 to 5 times per day can be further executed. Such a stirring step is executed such that oxygen is supplied to the yeast to facilitate the fermentation since carbon dioxide is produced during the aforementioned alcohol fermentation. If the number of times of stirring per day is too low, i.e. one (1), there may be a problem in that the above supply of oxygen is not sufficient. On the contrary, if it exceeds 5 times per day, there may be another problem in that the flavor of the finally obtained vinegar is much lost and thus the preference decreases.

[67] The alcohol fermentation step(4) comprises the step of fermenting the fermentation mixture at 20 to 29°C for 3 to 30 days to obtain an alcohol fermentation product having 5 to 20% of an alcohol content, and corresponds to a main process of breaking down sugar into alcohol and proliferating yeasts. The fermentation period may vary according to a fermentation temperature. According to the experiment results repeated by the inventor(s) of the present invention, it has been confirmed that the fermentation made at temperature of 20 to 29°C for 3 to 30 days is optimal. If the fermentation temperature is less than 20°C or the fermentation period is less than 3 days, there may be a problem in that the alcohol fermentation is not sufficient. On the contrary, if the temperature exceeds 29°C, there may be another problem in that the flavor of alcohols to be obtained is reduced or acetic acid fermentation occurs. If the fermentation period exceeds 30 days, it is not also preferable in view of the productivity and a problem such as abnormal fermentation or rancidification by acetic acid occurs. In this case, an alcohol content of the alcohol fermentation product may be 5 to 20%, but it can also be less than 5% or more than 20% depending on the fermentation conditions, which will be appreciated by those skilled in the art.

[68] The above alcohol content adjustment step (5) is a process of adjusting the alcohol content of the alcohol fermentation product obtained from the alcohol fermentation step to 2 to 10%, and also a process of leading to a situation where Acetobacter are well inoculated without dying during the inoculation for the subsequent acetic acid fermentation such that the acetic acid fermentation can be well made. In general, the Acetobacter may die without proliferation or acetic acid fermentation if the alcohol content of the Acetobacter is too high. However, it will be appreciated by those skilled in the art that the present invention is not limited to the aforementioned range of the alcohol content, and the present invention can be employed when the Acetobacter which can also proliferate on the fermented product having an alcohol content beyond the aforementioned range and be subjected to the acetic acid fermentation even though the alcohol content exceeds the aforementioned range. If the alcohol content is less than 2% in the alcohol content adjustment step, there may be a problem in that since the content of alcohol to be converted into acetic acid by means of the acetic acid fermentation is too low, the yield of acetic acid becomes too low. On the contrary, if the content exceeds 10%, there may be another problem in that most of the currently known Acetobacter may die without the sufficient proliferation or acetic acid fermentation. However, it will be appreciated by those skilled in the art that the fermented product with the alcohol content more than 10% can be used as a raw material for the acetic acid fermentation if the alcohol-resistant Acetobacter and the like, which can survive, proliferate and do the acetic acid fermentation in the alcohol concentration more than 10%, are used. Therefore, the alcohol content of the alcohol fermentation product obtained from the alcohol fermentation step usually exceeds at least 5%. However, if the alcohol content is less than 2%, the alcohol content may be adjusted by further adding an alcohol.

[69] The alcohol adjustment step may comprise the step of diluting the alcohol fermentation product obtained from the alcohol fermentation step with water to an alcohol content of 2 to 10%. This step can be understood as a step of diluting the alcohol fermentation product by the addition of water to lower the alcohol concentration in the alcohol fermentation product in order to prevent a problem in that the Acetobacter can properly neither proliferate nor do the acetic acid fermentation as described above because the alcohol fermentation product obtained from the alcohol fermentation step usually has an alcohol concentration of 5 to 20%.

[70] Alternatively, the alcohol adjustment step may comprises the step of heating the alcohol fermentation product obtained from the alcohol fermentation step to volatilize and remove the alcohol portion such that the alcohol content can be adjusted to 2 to 10%. This step can be understood as a step of allowing the proliferation of the Acetobacter and the acetic acid fermentation to be normally performed in the subsequent fermentation process while preventing the taste and flavor of the vinegar finally obtained by concentrating the alcohol fermentation product serving as a raw material and lowering the alcohol content at the same time.

[71] The alcohol adjustment step may comprise the step of adjusting the alcohol content of the alcohol fermentation product obtained from the alcohol fermentation step to an alcohol content of 3 to 8%. According to the repeated test results performed by the inventor(s) of the present invention, it has been confirmed that the alcohol content at the early stage of the acetic acid fermentation step is preferably 3 to 8% to obtain the optimum conditions for the fermentation of Acetobacter in the acetic acid fermentation and the optimum acetic acid in view of its taste and smell, flavor and the like.

[72] The acetic acid fermentation step (6) comprises the step of, after the alcohol fermentation step, inoculating Acetobacter in an amount of 0.5 to 1.5 wt% with respect to a total amount of the alcohol fermentation product obtained and effecting acetic acid fermentation at a temperature of 20 to 30°C to obtain an acetic acid. Such an acetic acid fermentation step produces acetic acid through the oxidative fermentation of alcohol with the Acetobacter. If the Acetobacter are inoculated in an amount of less 0.5 wt% with respect to a total amount of the alcohol fermentation product, there may be a problem in that the productivity is decreased due to the slow proliferation and acetic acid fermentation of the Acetobacter. On the contrary, if it exceeds 1.5 wt%, there may be another problem in that inefficiency in production costs is caused. Further, if the acetic acid fermentation step is effected at a temperature less than 20°C, there may be a problem in that the alcohol fermentation is not sufficient. On the contrary, if the temperature exceeds 30°C, there may be another problem in that the taste of vinegar is changed or the rancidification occurs due to abnormal proliferation of the Acetobacter. The Acetobacter used in the acetic acid fermentation step may be preferably Acetobacter aceti. Such Acetobacter produce acetic acid through the oxidative fermentation of ethanol. The acetic acid fermentation can be effected either by a static fermentation method in which Acetobacter are inoculated and then allowed to stand at the aforementioned temperature range for a certain period of time or alternatively by a submerged fermentation method accompanied by stirring and aeration. However, the static fermentation method has disadvantages in it take much time to perform the acetic acid fermentation, the value of products are lowered due to non-uniformity of the products, and it not suitable for mass production. Therefore, the submerged fermentation method is preferable. It will be appreciated by those skilled in the art that the submerged fermentation method and the static fermentation method can be used together.

[73] The Acetobacter used in the acetic acid fermentation step may be Acetobacter sp. or

Acetobacter aceti among commercially available strains inside and outside of the country, and preferably Acetobacter aceti. It will be understood by those skilled in the art that such Acetobacter are known to such a degree that they are commercially available from leading manufacturers inside and outside of the country.

[74] In the acetic acid fermentation step, the inoculation with the Acetobacter can be made by mixing 5 to 15 wt% of the Acetobacter with 85 to 95 wt% of an MA medium, incubating the mixture at a temperature of 25 to 35°C for 1 to 3 days to obtain the Acetobacter liquid and then inoculating the Acetobacter liquid in an amount of 5 to 15 wt% (the amount of the bacteria liquid obtained from the incubation of the strain) with respect to a total amount of the alcohol fermentation product. The Acetobacter used in the acetic acid fermentation step can be used by inoculating the strain itself on the alcohol fermentation product as described above, but the Acetobacter may be used by growing the bacteria on a medium, preferably on an MA medium, to perform more exact and fast acetic acid- fermentation. The growth of the acetic acid on the MA medium may be accomplished by mixing 5 to 15wt% of Acetobacter with 85 to 95wt% of MA medium and incubating the mixture at a temperature of 25 to 35°C for 1 to 3 days. The MA medium comprises 7.0 g/1 K HPO , 2.0 g/1 KH PO , 0.1 g/1 MgSO , 1.0 g/1 (NH ) SO , 1.0 g/1 trisodium citrate, 0.5 g/1 sodium pyruvate, 0.7 g/1 sodium fumarate, 1.0 g/1 yeast extract and remainder water. It will be understood by those skilled in the art that such an MA medium is known to such a degree that it is commercially available from leading manufacturers inside and outside of the country. If the Acetobacter are inoculated on the MA medium in an amount of less 5 wt%, there may be a problem in that the proliferation and growth of the Acetobacter become too slow. On the contrary, if it exceeds 15 wt%, there is no particular problem. Further, if the Acetobacter liquid is inoculated in an amount of less 5 wt% with respect to a total amount of the alcohol fermentation product, there may be a problem in that the proliferation and the growth of the Acetobacter become too slow. On the contrary, if it exceeds 15 wt%, there is no particular problem. [75] In the acetic acid fermentation step, a fermentation extending step is further executed, which comprises the steps of harvesting 5 to 50% of the acetic acid fermentation product obtained from the acetic acid fermentation step when the acidity of the acetic acid fermentation product reaches 5 to 12%, adding the alcohol fermentation product obtained from the alcohol fermentation step (an alcohol content of 5 to 20%) to the remaining acetic acid fermentation product in an equivalent amount of the harvested acetic acid fermentation product, and then effecting additional acetic acid fermentation until the acidity of the acetic acid fermentation product reaches 5 to 12%. Such a fermentation extending step makes it possible to produce acetic acid on a large scale while maintaining the conditions for acetic acid fermentation of the acetic acid by supplying unconverted alcohol and removing some parts of the acetic acid such that the acetic acid fermentation in which the Acetobacter continuously converts alcohol into acetic acid can be performed by using the acetic acid fermentation product stably inserted with the Acetobacter without repeating a step of inoculating the Acetobacter and the like. Such a fermentation extending step is helpful for the mass production of vinegar since a certain amount of the alcohol fermentation product obtained from the alcohol fermentation step can be continuously fed into the acetic acid fermentation product depending the amount of acetic acid as required, a certain amount of acetic acid can be harvested when the acidity reaches 5 to 12% after the acetic acid fermentation has been sufficiently performed by standing for around 2 to 5 days, and then a certain amount of the alcohol fermentation product obtained from the alcohol fermentation step can be repeatedly fed into the acetic acid fermentation product. In this step, if the additional amount of the acetic acid fermentation product is less than 5% as mentioned above, there may be a problem in that an amount of alcohol fed to be converted into acetic acid is too small to sufficiently increase the yield of acetic acid. If it exceeds 50%, the Acetobacter are killed and the acetic acid fermentation is stopped due to instantaneous increase of the alcohol concentration.

[76] In the acetic acid fermentation step, clarifying agents selected from the group consisting of bentonite, agar, papain, isinglass (a dry product obtained by washing air bladders of fishes) or a mixture of two or more thereof may be further incorporated into the fermented liquid obtained from the alcohol fermentation step. The clarifying agents are widely used in the manufacture of wine and vinegar and have been illustrated by an example in the present invention. The clarifying agents, however, should not be construed to limit the scope of the present invention. The clarifying agents are removed through filtering in the subsequent filtering step after the acetic acid fermentation has been completed in the acetic acid fermentation step. The clarifying agents usually serve to remove impurities through the adsorption of the impurities such as fine floatage in the alcohol fermentation product and the subsequent filtering of the agents adsorbed with the impurities in the filtering step and to clear (clarify) the wine and vinegar manufactured by the method of the present invention. A mixed amount of the clarifying agents can vary according to the kinds of the clarifying agents used. It will be understood that those skilled in the art can easily determine the amount of use for the commercially available clarifying agents. For example, in a case where the bentonite is used as the clarifying agent, it can be mixed in an amount of 0.25 to 0.5 wt% of the total amount of the alcohol fermentation product.

[77] Before or after the acetic acid fermentation step, an aging step of aging the fermented liquid at 15 to 18°C for 30 to 90 days can be further executed. It will be appreciated that the aging step is a process of softening the taste and flavor of the vinegar to be obtained and is a technique widely used in the manufacture of vinegar, particularly, fermented vinegar such as fruit vinegar and grain vinegar.

[78] In particular, a racking step of separating only clear vinegar portion from its sediment settled during the aging step to prevent the sediment from being incorporated therein and aging only the separated clear vinegar portion may be further executed two or three times. It will be appreciated that the racking step is also a process of preventing the sediment from being formed in the finally obtained vinegar to enhance the value of products and the storage stability of the vinegar and is a technique widely used in the manufacture of vinegar, particularly, fermented vinegar such as fruit vinegar and grain vinegar.

[79] After the acetic acid fermentation step, a packing step of bottling the vinegar and then packing the bottle can be further executed. The packing step makes it easy to bottle the obtained vinegar and to preserve, transport and store the bottled vinegar as it is.

[80] After the aging step, a sterilizing step may be further executed. Such a sterilizing step makes it possible to sterilize even yeasts and/or Acetobacter thus to prevent the additional alcohol and/or acetic acid fermentation from occurring. Therefore, the storage stability of the vinegar manufactured by the method of the present invention can be greatly enhanced.

[81] After the aging step, a filtering step of filtering the vinegar using a filter medium with a pore size of not greater than 0.5 microns can be further executed. Such a filtering step makes it possible to remove even fine solid portions remaining in the obtained vinegar and thus to prevent precipitates from being formed during the preservation. Therefore, the value of products of the obtained vinegar can be enhanced.

[82] The vinegar thus manufactured by the method of manufacturing vinegar by using filtered water of bean-curd is rich in active ingredients such as isoflavone and the like contained in filtered water of bean-curd and the like and also becomes a tasty product.

[83] Hereinafter, the present invention will be described in detail with reference to specific examples of the present invention.

[84] Example 1

[85] Soybean was commercially obtained and prepared. The prepared soybean was clearly washed, and then soaked for 24 hours in water having weight three times greater than the dry soybean, followed by grinding the soaked soybean into soybean juice. A portion of the prepared soybean juice was heated to 100°C for 2 to 3 minutes, and then filtered to prepare soybean milk. Thereafter, a coagulant (generally, electrolyte such as bittern) was added to the soybean milk to obtain uncurdled bean curd, which in turn was dehydrated to prepare filtered water of bean-curd as a raw material. The remaining portion of the soybean juice was heated to 100°C for 2 to 3 minutes, and then filtered to prepare bean-curd dregs.

[86] The prepared filtered water of bean-curd was subjected to high temperature sterilization at 130°C for 3 seconds.

[87] 4 kg of sugar was added to 10 kg of the sterilized filtered water of bean-curd to supplement sugar such that the sweetness became about 27.75 Brix. Then, a mixed acid in which succinic acid, malic acid and citric acid had been mixed at the weight ratio of 3:2: 1 was prepared.

[88] 5 g of brewer's yeast, 10 g of the mixed acid and 2 g of ammonium phosphate were added to the sugar- supplemented raw material, and the resultant material was subjected to alcohol fermentation at 25°C for 10 days while stirring 3 times per day.

[89] After the alcohol fermentation step, the obtained alcohol fermentation product was heated to adjust the alcohol concentration of the product to 3%. Here, the measurement of the alcohol concentration was subject to quantitative analysis by taking 100 ml of water to distill it and then performing color reaction with the obtained distillate. A reduction reaction of chromic acid (CrO ) into bluish green, opaque chromium by alcohol was used as the color reaction. Absorbance at 600 nm was measured, and the measured absorbance was then determined by comparison with the absorbance of standardized alcohol solution.

[90] The Acetobacter liquid was added in an amount of 10 wt% with respect to a total amount of the alcohol fermentation product with adjusted alcohol concentration and mixed with each other. As the Acetobacter liquid, one obtained by mixing 10 ml of Acetobacter aceti as Acetobacter with 90 ml of an MA medium and proliferating the mixture while stirring the mixture at 30°C at a rate of 200 rpm was used. The acetic acid fermentation was effected at 29°C for 3 days. During the acetic acid fermentation, the amount of air was rendered as little as possible. To this end, air injection was controlled in such a degree that bubbles are not continuously formed. Even during the acetic acid fermentation, the acidity was continuously measured and the time when the concentration of acetic acid reaches 6% is determined as an endpoint of the acetic acid fermentation. At that point, the acetic acid fermentation was stopped and vinegar was harvested. Here, the acidity was measured through neutralization titration using 0.1 N sodium hydroxide. That is, 1 g of sample was exactly measured and placed in a beaker, and 10 drops of 1% phenolphthalein solution was then added drop wise. Thereafter, 0.1 N sodium hydroxide was titrated until a pink color of the solution in the beaker lasts for 30 seconds, and the amount of sodium hydroxide used was then measured. The acidity was determined by the following equation (1):

[91]

[92] Acidity (wt%)

[93] = Amount of sodium hydroxide used (ml)*0.006*(100/weight of sample (g))

[94] - (1)

[95] Example 2

[96] Except that the alcohol concentration was adjusted to 5%, this Example was effected in the same way as described in Example 1. The obtained vinegar was aged at 160°C for 30 days.

[97] Example 3

[98] Except that the alcohol concentration was adjusted to 7%, this Example was effected in the same way as described in Example 1.

[99] Comparative Example 1

[100] Except that the alcohol concentration was adjusted to 9%, this Example was effected in the same way as described in Example 1.

[101] Comparative Example 2

[102] As Control, commercially available unpolished rice vinegar was used in the subsequent experiment.

[103] Experimental Example 1 [104] Determination of growth rates for Acetobacter [105] The growth rates of Acetobacter in Examples 1 to 3 and Comparative Example 1 were determined by the microscopic examination and the acidity measurement of the fermented product. As a result, it was confirmed that the acetic acid fermentations occurred at 3% of the alcohol content (Example 1) and 5% of the alcohol content (Example 2). Furthermore, it was confirmed in a case where the alcohol content is 7% (Example 3) that the productivity was not high and it took a long time due to low growth rate, but the acetic acid could be produced. On the other hand, it was confirmed in a case where the alcohol content is 9% (Comparative Example 1) that the Acetobacter were not grown well and vinegar was not properly produced. From these results, it is considered that contrary to a case where Acetobacter grow well even in 7% of the initial alcohol concentration in the manufacture of other vinegar such as persimmon vinegar, saponin, isoflavone and the like contained in the filtered water of bean-curd as a raw material have influence on the growth of Acetobacter.

[106] Experimental Example 2 [107] Sensory test [108] The vinegar manufactured by Example 1 was evaluated through the sensory test. The sensory test was conducted by classifying test items according to the taste, flavor and appearance and then using a 9-point scoring method for each item. Considering age and sex, total 50 adult men and women, i.e. 10 persons for each age group from their teens to fifties were selected as panels for the sensory test. The test results are shown in the following Table 3

[109] [HO] Table 3

[111] [112] As shown in Table 3, it was proven that the vinegar obtained by using the filtered water of bean-curd according to Examples 1 and 2 of the present invention has excellent taste and flavor and thus obtains high preference. Further, since filtered water of bean-curd or a mixture of filtered water of bean-curd and bean-curd dregs is used as a raw material, active ingredients included in the filtered water of bean-curd or bean- curd dregs can be easily taken and reused.

[113] Meanwhile, according to the sensory test, the following opinions on the products were presented as compared with commercially available apple vinegar, unpolished rice vinegar, persimmon vinegar and the like. That is, there were many opinions that the vinegar using filtered water of bean-curd of the present invention is particularly different from the apple vinegar or unpolished rice vinegar in view of their appearance preference, but the former is nutritionally superior to the latter. Therefore, there were opinions that the vinegar of the present invention is suitable for dressing salad or mixing vegetables or seaweeds with seasonings, for sauce for children who do not like stimulating taste, and for drinking for health and that it is suitable to fish dishes and is very sweet and palatable.

[114] On the contrary, it was proven that the vinegar obtained without using filtered water of bean-curd is inferior to the vinegar obtained by using the bean-curd dregs and filtered water of bean-curd of the present invention in view of the taste and flavor, thereby obtaining low preference.

[115] Meanwhile, as a result of the analysis of components of the vinegar obtained by using filtered water of bean-curd according to Examples 1 and 2 of the present invention, it was confirmed that a great amount of daidzein, genistein and the like, which are main active ingredients of isoflavone, was contained in the vinegar. The comparison results of contents of daidzein, genistein and the like between Comparative Example 1 and grain vinegar of which main materials is rice can be summarized in the following Table 4.

[116] [117] Table 4

[118] [119] Further, as a result of the analysis of components of the vinegar obtained by using filtered water of bean-curd according to Example 1 of the present invention, it was confirmed that a great amount of free amino acids and the like was contained in the vinegar. The comparison results of contents of free amino acids and the like between Example 1 and Control can be summarized in the following Table 5.

[120] [121] Table 5

[122] [123] As shown in Table 5, Example 1 of the present invention exhibits a little less content of free amino acids as compared with the grain vinegar of Control. However, since rice serving as a source for food is used as a raw material in Control, whereas Example 1 uses filtered water of bean-curd which has been dumped as wastes after the manufacture of soybean products, Example 1 of the present invention is very useful in view of the fact that it can recover from wastes a high content of amino acids similar to those of Control using rice as a raw material such that the recovered amino acids can be easily taken. Further, it is widely known that amino acids are helpful to cure the hangover. Therefore, since the vinegar obtained by the method of the present invention contains a large amount of amino acids, there is an advantage in that it is helpful to the health.

[124] Furthermore, on the basis of a single domestic manufacturing company for soybean products, the amount of the raw material used is 184.4 ton/month, and the amount of filtered water of bean-curd produced is 488.4 ton/month and the expense required for disposing the filtered water of bean-curd is 21 million Korean Won/month. Thus, it can be seen that the economical effects of the vinegar manufactured by using filtered water of bean-curd according to the present invention are very remarkable. On the assumption that the maximum amount of the raw material is used in this company, the amount of the raw material used is 405 ton/month, the amount of filtered water of bean-curd produced is 1073 ton/month, and the expense required for disposing the filtered water of bean-curd is 31.5 million Korean Won/month, it can be seen that the economical spillover effects of the vinegar of the present invention are very excellent. Further, the advantageous effects of the present invention are remarkably great since nutritionally good vinegar can be produced at reduced disposal costs.

[125]

Industrial Applicability

[126] According to the present invention as described above, there is an advantageous effect of providing a method of manufacturing vinegar and vinegar manufactured by the method, wherein filtered water of bean-curd or bean-curd dregs produced as byproducts or wastes after the manufacture of soybean products such as soya milk and bean curd are used to manufacture vinegar such that a variety of active ingredients included in the filtered water of bean-curd or bean-curd dregs can be utilized, which can be helpful to the health.

[127]

[128]

Claims

Claims [1] A method of manufacturing vinegar by using filtered water of bean-curd, comprising:

(1) a sterilizing step of preparing filtered water of bean-curd as a raw material and sterilizing the prepared filtered water of bean-curd;

(2) a sugar supplementing step of adding sugar to the sterilized raw material to adjust sweetness to 5.5 to 39.2 Brix;

(3) a mixing step of adding 0.02 to 0.13 wt% of brewer's yeast and 0.007 to 0.05 wt% of yeast nutrients with respect to a total amount of the sugar- supplemented raw material and mixing them to prepare a fermentation mixture;

(4) an alcohol fermentation step of fermenting the fermentation mixture at a temperature of 20 to 29°C for 3 to 30 days;

(5) an alcohol content adjustment step of adjusting an alcohol content of the alcohol fermentation product obtained from the alcohol fermentation step to 2 to 10%; and

(6) an acetic acid fermentation step of inoculating Acetobacter in an amount of 0.5 to 1.5 wt% (an amount of a strain itself) with respect to a total amount of the alcohol fermentation product obtained from the alcohol content adjustment step and effecting acetic acid fermentation at a temperature of 20 to 30°C until acidity of the acetic acid fermentation product becomes 5 to 12%.

[2] The method as claimed in claim 1, wherein bean-curd dregs as the raw material in the sterilizing step are further mixed with the filtered water of bean-curd at a weight ratio of filtered water of bean-curd to bean-curd dregs of 1 :0.2 to 1 :0.5.

[3] The method as claimed in claim 1, wherein the sterilizing step comprises a high temperature sterilization step of heating the raw material at a temperature of 120° C to 130°C for 1 to 3 seconds to sterilize the raw material.

[4] The method as claimed in claim 1, wherein the sterilizing step comprises a pharmaceutical sterilization step of adding sulfite in an amount of 0.1 to 0.5 wt% with respect to a total amount of the fermentation mixture and then allowing the raw material to stand for 20 to 28 hours.

[5] The method as claimed in claim 1, wherein the sugar used in the sugar supplementing step is sucrose or glucose.

[6] The method as claimed in claim 1, wherein 0.04 to 0.2 wt% of acid is incorporated such that pH of the fermentation mixture obtained in the mixing step can be within a range of 3.5 to 4.5.

[7] The method as claimed in claim 1, wherein the brewer's yeast used in the mixing step is Saccharomyces cerevisiae or Saccharomyces baynus.

[8] The method as claimed in claim 6, wherein the acid used in the mixing step is a mixed acid in which succinic acid, malic acid and citric acid are mixed at a weight ratio of 3:2: 1.

[9] The method as claimed in claim 1, wherein the yeast nutrients used in the mixing step is ammonium phosphate.

[10] The method as claimed in claim 1, wherein a stirring step of stirring the fermentation mixture two to five times per day is further executed during the alcohol fermentation step.

[11] The method as claimed in claim 1, wherein after the alcohol fermentation step, a secondary fermentation step of separating only fermented liquid from the alcohol fermentation product obtained in the alcohol fermentation step and effecting secondary fermentation at a temperature of 15 to 18°C for 20 to 60 days in a state where air can be blocked and produced carbon dioxide can be discharged is further executed.

[12] The method as claimed in claim 1, wherein in the secondary fermentation step, clarifying agents selected from the group consisting of bentonite, agar, papain, isinglass or a mixture of two or more thereof is further incorporated into the fermented liquid obtained from the alcohol fermentation step in an amount of 0.25 to 0.5 wt% with respect to a total amount of the fermented liquid.

[13] The method as claimed in claim 1, wherein an aging step of aging the fermented liquid at a temperature of 15 to 18°C for 30 to 90 days is further executed after the alcohol fermentation step.

[14] The method as claimed in claim 13, wherein a racking step of separating only clear vinegar portion from its sediment settled during the aging step to prevent the sediment from being incorporated therein and aging only the separated clear vinegar portion is further executed two or three times.

[15] The method as claimed in claim 2, wherein if the bean-curd dregs as a raw material in the sterilizing step are mixed with the filtered water of bean-curd, a pressing step of removing solid portions is further executed after the alcohol fermentation step.

[16] The method as claimed in claim 1, wherein the alcohol adjustment step comprises the step of diluting the alcohol fermentation product obtained from the alcohol fermentation step with distilled water to an alcohol content of 2 to 10%.

[17] The method as claimed in claim 1, wherein the alcohol adjustment step comprises the step of diluting the alcohol fermentation product obtained from the alcohol fermentation step with filtered water of bean-curd as a raw material to an alcohol content of 2 to 10%.

[18] The method as claimed in claim 1, wherein the alcohol adjustment step comprises the step of heating the alcohol fermentation product obtained from the alcohol fermentation step to volatilize and remove an alcohol component such that the alcohol content of the alcohol fermentation product can be adjusted to 2 to 10%.

[19] The method as claimed in claim 1, wherein the alcohol content of the alcohol fermentation product is adjusted to 3 to 8%.

[20] The method as claimed in claim 1, wherein the Acetobacter used in the acetic acid fermentation step are Acetobacter sp. or Acetobacter aceti.

[21] The method as claimed in claim 1, wherein the inoculation with the Acetobacter in the acetic acid fermentation step is performed by mixing 5 to 15 wt% of the Acetobacter with 85 to 95 wt% of an MA medium, incubating the mixture at a temperature of 25 to 35°C for 1 to 3 days to obtain Acetobacter liquid and then inoculating the Acetobacter liquid in an amount of 5 to 15 wt% (the amount of the bacteria liquid obtained from the incubation of the strain) with respect to a total amount of the alcohol fermentation product.

[22] The method as claimed in claim 1, wherein a fermentation extending step is further executed, which comprises the steps of harvesting 5 to 50% of the acetic acid fermentation product obtained from the acetic acid fermentation step when acidity of the acetic acid fermentation product reaches 5 to 12%, adding the alcohol fermentation product obtained from the alcohol fermentation step (an alcohol content of 5 to 20%) to the remaining acetic acid fermentation product in an equivalent amount of the harvested acetic acid fermentation product, and then effecting additional acetic acid fermentation until the acidity of the acetic acid fermentation product reaches 5 to 12%.

[23] The method as claimed in claim 1, wherein a packing step of bottling the vinegar and packing the bottle is further executed after the acetic acid fermentation step.

[24] The method as claimed in claim 13, wherein a sterilizing step is further executed after the aging step.

[25] The method as claimed in claim 13, wherein a filtering step of filtering the vinegar using a filter medium with a pore size of not greater than 0.5 microns is further executed after the aging step.

[26] Vinegar manufactured by a method according to any one of claims 1 to 25.