Method for producing sweet potato shochu

Abstract

The purpose of this disclosure is to provide: a method for producing sweet potato shochu having a relatively low methanol concentration by using a raw sweet potato as a raw material for sweet potato shochu; and related features. One embodiment of the this disclosure provides a method for producing sweet potato shochu, the method comprising: processing a raw sweet potato to obtain a first raw sweet potato piece; reducing the water content of the first raw sweet potato piece to obtain a second raw sweet potato piece having a lower water content than the first raw sweet potato piece; and producing sweet potato shochu from the second raw sweet potato piece.

Description

How sweet potato shochu is made

[0001] The present disclosure relates to a method for producing sweet potato shochu.

[0002] A typical method for producing sweet potato shochu involves steaming sweet potatoes, which are used as a main ingredient. The steamed sweet potatoes are processed into sweet potato shochu through various processes such as fermentation, distillation, and aging. For example, the fermentation process is carried out by fermenting a mixture containing steamed sweet potatoes, primary mash, and water. In contrast, Patent Document 1 below discloses a method for fermenting sweet potatoes by adding primary mash and water during the crushing process of unheated sweet potatoes to produce sweet potato shochu with a rich flavor.

[0003] JP 2017-158525 A

[0004] However, when sweet potato shochu is produced without steaming the sweet potatoes, the amount of methanol produced during the production process tends to increase. For example, methanol is produced by the enzymatic decomposition of pectin in plant cells. An increase in the amount of methanol produced leads to an increase in the methanol concentration in sweet potato shochu. As a result, the methanol concentration in sweet potato shochu produced from unsteamed sweet potatoes is higher than the methanol concentration in sweet potato shochu produced from steamed sweet potatoes. Therefore, the present disclosure has the following objectives. One objective of the present disclosure is to provide a method for producing sweet potato shochu with a relatively low methanol concentration using raw sweet potatoes as a raw sweet potato shochu ingredient. One objective of the present disclosure is to provide sweet potato shochu with a relatively low methanol concentration using raw sweet potatoes as a raw sweet potato shochu ingredient.

[0005] The present disclosure encompasses the following embodiments: (1) A method for producing sweet potato shochu, comprising processing raw sweet potato to obtain first raw sweet potato pieces, reducing the water content of the first raw sweet potato pieces to obtain second raw sweet potato pieces having a lower water content than the first raw sweet potato pieces, and producing sweet potato shochu from the second raw sweet potato pieces. (2) The method for producing sweet potato shochu according to (1), wherein reducing the water content of the first raw sweet potato pieces comprises reducing the total mass of the first raw sweet potato pieces by 25% or more. (3) The method for producing sweet potato shochu according to (1) or (2), wherein reducing the water content of the first raw sweet potato pieces comprises blowing gas onto the first raw sweet potato pieces. (4) The method for producing sweet potato shochu according to (3), wherein the temperature of the gas is 30°C or less. (5) The method for producing sweet potato shochu according to (3) or (4), wherein the time for blowing gas onto the first raw sweet potato pieces is within the range of 1 to 20 hours. (6) The method for producing sweet potato shochu according to any one of (1) to (5), wherein producing the sweet potato shochu comprises fermenting a mixture containing the second raw sweet potato pieces and the first moromi to obtain the second moromi, and distilling the second moromi to obtain the sweet potato shochu. (7) The method for producing sweet potato shochu according to any one of (1) to (6), wherein the methanol concentration represented by the following formula 1 is 500 mg / L or less. Formula 1: Methanol concentration (mg / L) = [methanol concentration in sweet potato shochu (mg / L)] × 25% by volume ÷ [ethanol concentration in sweet potato shochu (% by volume)]

[0006] At least one embodiment of the present disclosure provides a method for producing sweet potato shochu having a relatively low methanol concentration using raw sweet potatoes as a raw material for the sweet potato shochu.At least one embodiment of the present disclosure provides sweet potato shochu having a relatively low methanol concentration using raw sweet potatoes as a raw material for the sweet potato shochu.

[0007] In the present disclosure, at least one embodiment may be modified without departing from the spirit of the present disclosure. In the present disclosure, at least two embodiments may be combined without departing from the spirit of the present disclosure. In the present disclosure, the upper limit of a certain numerical range may be replaced with the upper limit of another numerical range related to the said numerical range or a numerical value shown in an example. In the present disclosure, the lower limit of a certain numerical range may be replaced with the lower limit of another numerical range related to the said numerical range or a numerical value shown in an example. In the present disclosure, ordinal numbers (e.g., "first" and "second") are terms used to formally distinguish multiple elements and do not limit the quantity, order, or superiority of each element. Hereinafter, embodiments of the present disclosure will be described in detail.

[0008] <Method for Producing Sweet Potato Shochu> The present disclosure provides a method for producing sweet potato shochu. The method for producing sweet potato shochu includes the following three steps: (S1) processing raw sweet potatoes to obtain first raw sweet potato pieces; (S2) reducing the water content of the first raw sweet potato pieces to obtain second raw sweet potato pieces having a lower water content than the first raw sweet potato pieces; and (S3) producing sweet potato shochu from the second raw sweet potato pieces. A method for producing sweet potato shochu including the above three steps reduces the amount of methanol produced during the sweet potato shochu production process. As a result, the methanol concentration in the sweet potato shochu is lower. The reason for this effect is presumed to be as follows: When the water content of the first raw sweet potato pieces obtained by processing the raw sweet potatoes is reduced, the pectin contained in the sweet potato is thought to become insoluble and remain within the cells. As a result, the amount of pectin eluted from the sweet potato during the sweet potato shochu production process is reduced, and the amount of methanol produced by pectin decomposition is also reduced. Therefore, the method for producing sweet potato shochu including the above three steps can reduce the methanol concentration in sweet potato shochu, even though raw sweet potatoes are used as the raw material for sweet potato shochu. Furthermore, the method for producing sweet potato shochu including the above three steps can contribute to increasing the concentration of terpenes, particularly monoterpene alcohols, in sweet potato shochu. The processing of raw sweet potatoes in step S1 and the reduction in the water content of the raw sweet potato pieces in step S2 physically stimulate the raw sweet potatoes. When raw sweet potatoes are subjected to physical stimulation, a self-defense reaction of the raw sweet potatoes is activated, which is thought to result in an increase in monoterpene alcohols or precursors of monoterpene alcohols. Therefore, the concentration of monoterpene alcohols in sweet potato shochu tends to be high. The method for producing sweet potato shochu is described in detail below.

[0009] (Step S1) The method for producing sweet potato shochu includes processing raw sweet potatoes to obtain first raw sweet potato pieces.

[0010] In the present disclosure, the term "raw potato" means a potato that has not been heated after harvest to the extent that gelatinization proceeds. A raw potato may be a potato that has not been heated at a temperature of 40°C or higher. A raw potato may be a potato that has not been heated. A raw potato may be a potato that has not been steamed at a temperature of 40°C or higher. A raw potato may be a potato that has not been steamed. If necessary, a raw potato that has been pre-treated may be used. Examples of pre-treatment include washing, removal of unnecessary parts, and sterilization. Sterilization performed under heating conditions that do not cause gelatinization to proceed is also acceptable.

[0011] One or more types of raw sweet potato may be used. Examples of potatoes include potato, taro, and sweet potato. In a preferred embodiment, the raw sweet potato is a raw sweet potato. Examples of sweet potato include Koganesengan, Hamakomachi, Annoimo, Shiroyutaka, Konaishin, and Silk Sweet. In a preferred embodiment, the raw sweet potato is at least one raw sweet potato selected from the group consisting of Koganesengan, Hamakomachi, Annoimo, Shiroyutaka, Konaishin, and Silk Sweet. In a preferred embodiment, the raw sweet potato is at least one raw sweet potato selected from the group consisting of Koganesengan and Hamakomachi. In a preferred embodiment, the raw sweet potato is at least one raw sweet potato selected from the group consisting of Shiroyutaka, Konaishin, and Silk Sweet.

[0012] The first raw potato pieces are produced by processing raw potatoes and are independently existing parts of the raw potatoes. One or more first raw potato pieces may be formed from one raw potato. The at least one first raw potato piece obtained by processing at least one raw potato may be a plurality of first raw potato pieces. The number and amount of first raw potato pieces obtained in step S1 may be selected taking into consideration the flavor of the sweet potato shochu and the production scale of the sweet potato shochu.

[0013] Examples of methods for processing raw sweet potatoes include cutting the raw sweet potato and crushing the raw sweet potato. From the viewpoint of increasing the monoterpene alcohol concentration and reducing the methanol concentration in sweet potato shochu, in a preferred embodiment, processing the raw sweet potato includes cutting the raw sweet potato. The method for processing the raw sweet potato into the first raw sweet potato pieces may be selected from known food processing methods, taking into account the shape and size of the desired first raw sweet potato pieces. The method for processing the raw sweet potato into the first raw sweet potato pieces may be mechanical processing. Examples of equipment used for processing raw sweet potatoes include a crusher, a slicer, and a dicer.

[0014] The size of the first raw potato pieces is not limited as long as they are smaller than the raw potatoes before processing. If the first raw potato pieces are small, the amount of monoterpene alcohols or monoterpene alcohol precursors tends to increase during the sweet potato shochu production process. As a result, the concentration of monoterpene alcohols in sweet potato shochu increases. If the concentration of monoterpene alcohols in sweet potato shochu is high, the flavor of the sweet potato shochu tends to be richer.

[0015] The maximum length of the first raw potato pieces may be 10 mm or less. The upper limit of the maximum length of the first raw potato pieces may be 8 mm, 7 mm, 6 mm, 5 mm, or 4 mm. The maximum length of the first raw potato pieces may be 0.5 mm or more. The lower limit of the maximum length of the first raw potato pieces may be 1 mm, 2 mm, or 3 mm. The maximum length of the first raw potato pieces may be in the range of 0.5 mm to 10 mm. In the present disclosure, the term "maximum length" refers to the maximum distance between two imaginary parallel lines that sandwich the object and touch the outline of the object when the object is placed on a horizontal plane and observed from directly above.

[0016] The length of one side of the first raw potato piece may be 10 mm or less. The upper limit of the length of one side of the first raw potato piece may be 8 mm, 7 mm, 6 mm, 5 mm, or 4 mm. The length of one side of the first raw potato piece may be 0.5 mm or more. The lower limit of the length of one side of the first raw potato piece may be 1 mm, 2 mm, or 3 mm. The length of one side of the first raw potato piece may be within a range of 0.5 mm to 10 mm.

[0017] Examples of the planar shape of the first raw potato pieces include a sector, a semicircle, a circle, an ellipse, and a polygon. In this disclosure, the term "planar shape" means the shape of an object observed by viewing an object placed on a horizontal surface from directly above. Examples of the shape of the first raw potato pieces include a sphere, a hemisphere, a cone, a cylinder, and a polyhedron. Examples of polyhedrons include a pyramid, a rectangular prism, and a hexahedron. The first raw potato pieces may be thin slices. In a preferred embodiment, the first raw potato pieces are in the shape of a hexahedron (e.g., a cube). In a preferred embodiment, the first raw potato pieces are in the shape of a hexahedron with a side length ranging from 3 mm to 5 mm.

[0018] The first raw potato pieces may be sterilized, if necessary, before step S2 described below. For example, the first raw potato pieces may be sterilized under heating conditions that do not cause gelatinization. Examples of sterilization methods include steam sterilization. The steam sterilization time may be 30 to 60 seconds.

[0019] (Step S2) The method for producing sweet potato shochu includes reducing the water content of the first raw sweet potato pieces to obtain second raw sweet potato pieces having a lower water content than the first raw sweet potato pieces.

[0020] If the water content of the first raw potato pieces lost in step S2 is high, the monoterpene alcohol concentration in the sweet potato shochu tends to be high, while the methanol concentration in the sweet potato shochu tends to be low. If the water content of the first raw potato pieces lost in step S2 is low, the monoterpene alcohol concentration in the sweet potato shochu tends to be high due to the prevention or reduction of decomposition or excessive evaporation of aroma components in the first raw potato pieces. Because a decrease in the water content of the first raw potato pieces is accompanied by a decrease in the mass of the first raw potato pieces, the decrease in mass of the first raw potato pieces can be used as an indicator of the decrease in the water content of the first raw potato pieces. The mass of the first raw potato pieces reduced in step S2 is considered to be the mass of water reduced in step S2. In the present disclosure, the water content may be measured by a heat drying method.

[0021] In a preferred embodiment, reducing the water content of the first raw potato pieces comprises reducing the total mass of the first raw potato pieces by 10% or more. The lower limit of the reduction in the total mass of the first raw potato pieces may be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60%. The upper limit of the reduction in the total mass of the first raw potato pieces may be 65%, 60%, 55%, 50%, 45%, 40%, 35%, or 30%. The reduction in the total mass of the first raw potato pieces is preferably within the range of 10% to 65%, more preferably 20% to 60%, and even more preferably 20% to 30%.

[0022] In a preferred embodiment, reducing the water content of the first raw potato pieces comprises reducing the total mass of the first raw potato pieces by 10% or more within 20 hours. The upper limit of the time limit may be 15 hours, 10 hours, or 5 hours. The lower limit of the time limit may be 0.5 hours, 1 hour, 2 hours, or 3 hours. Reducing the water content of the first raw potato pieces may comprise reducing the total mass of the first raw potato pieces by at least 10% within a range of 0.5 hours to 20 hours. The preferred range of the reduction rate of the total mass of the first raw potato pieces is as described above.

[0023] The water content of the first raw potato pieces may be reduced under non-heating conditions or under heated conditions. The water content of the first raw potato pieces may be reduced under reduced pressure conditions. From the viewpoint of increasing the monoterpene alcohol concentration and decreasing the methanol concentration in sweet potato shochu, it is preferable to reduce the water content of the first raw potato pieces under non-heating conditions. It is also preferable to reduce the water content of the first raw potato pieces at a temperature of 40°C or less, regardless of whether heating is performed. Reducing the water content of the first raw potato pieces at a relatively low temperature can prevent or reduce decomposition or excessive evaporation of aroma components in the first raw potato pieces. As a result, the monoterpene alcohol concentration in sweet potato shochu tends to be high, while the methanol concentration in sweet potato shochu tends to be low. The upper limit of the temperature when reducing the water content of the first raw potato pieces may be 35°C, 30°C, or 25°C. The lower limit of the temperature when reducing the water content of the first raw potato pieces may be 10°C, 15°C, or 20°C. The temperature when reducing the water content of the first raw potato pieces may be within the range of 10°C to 40°C.

[0024] In a preferred embodiment, reducing the water content of the first raw potato pieces includes blowing a gas onto the first raw potato pieces. Blowing a gas onto the first raw potato pieces can prevent or reduce decomposition or excessive evaporation of aroma components in the first raw potato pieces while reducing the water content of the first raw potato pieces. As a result, the monoterpene alcohol concentration in sweet potato shochu tends to be high, while the methanol concentration in sweet potato shochu tends to be low. One or more types of gas may be used. Examples of gases include air and inert gases. The device for blowing a gas onto the first raw potato pieces may be selected from known blowers.

[0025] The gas blown onto the first raw potato pieces may be unheated or heated. In a preferred embodiment, regardless of whether heating is performed, the temperature of the gas is 40°C or less. The upper limit of the gas temperature may be 35°C, 30°C, or 25°C. In a preferred embodiment, the gas temperature is 10°C or higher. The lower limit of the gas temperature may be 15°C or 20°C. The gas temperature is preferably within the range of 10°C to 40°C, more preferably 15°C to 35°C, and even more preferably 20°C to 30°C. A relatively high temperature of the gas can promote a reduction in the water content of the first raw potato pieces. A relatively low temperature of the gas can prevent or reduce decomposition or excessive evaporation of aroma components in the first raw potato pieces while reducing the water content of the first raw potato pieces.

[0026] The time for blowing gas onto the first raw potato pieces may be adjusted taking into consideration other conditions and the progress of reduction in the water content of the first raw potato pieces. In a preferred embodiment, the time for blowing gas onto the first raw potato pieces is 0.5 hours or more. The lower limit of the blowing time may be 1 hour, 2 hours, or 3 hours. In a preferred embodiment, the time for blowing gas onto the first raw potato pieces is 20 hours or less. The upper limit of the blowing time may be 15 hours, 10 hours, or 5 hours. The time for blowing gas onto the first raw potato pieces is preferably within the range of 0.5 hours to 20 hours, more preferably 1 hour to 20 hours, even more preferably 1 hour to 15 hours, and even more preferably 2 hours to 5 hours. Increasing the blowing time can promote the reduction in the water content of the first raw potato pieces. Decreasing the blowing time can prevent or reduce decomposition or excessive evaporation of aroma components in the first raw potato pieces.

[0027] The second raw potato pieces are obtained by reducing the water content of the first raw potato pieces and have a lower water content than the first raw potato pieces. If the water content of the first raw potato pieces is high in step S2, the difference between the water content of the first raw potato pieces and the water content of the second raw potato pieces will be large. As a result, the difference between the mass of the first raw potato pieces and the mass of the second raw potato pieces will also be large. In a preferred embodiment, the ratio of the total mass of the second raw potato pieces to the total mass of the first raw potato pieces is 90% by mass or less. The upper limit of this ratio may be 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, or 40% by mass. The lower limit of this ratio may be 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70% by mass. The above ratio is preferably in the range of 35% by mass to 90% by mass, more preferably 40% by mass to 80% by mass, and even more preferably 70% by mass to 80% by mass.

[0028] (Step S3) The method for producing sweet potato shochu includes producing sweet potato shochu from the second raw sweet potato pieces.

[0029] The method for producing sweet potato shochu is not limited as long as the second raw sweet potato pieces are used as a raw material for sweet potato shochu. In a preferred embodiment, the second raw sweet potato pieces are used as the main raw material for sweet potato shochu, excluding water and alcohol. Sweet potato shochu can also be produced by reference to known sweet potato shochu production methods. The amount of the second raw sweet potato pieces used in step S3 may be selected taking into consideration the flavor of the sweet potato shochu and the production scale of the sweet potato shochu. In a preferred embodiment, producing sweet potato shochu includes fermenting the second raw sweet potato pieces. In a preferred embodiment, producing sweet potato shochu includes fermenting a mixture containing the second raw sweet potato pieces and the first moromi to obtain the second moromi, and distilling the second moromi to obtain sweet potato shochu. The mixture containing the second raw sweet potato pieces and the first moromi may further contain water, if necessary. In order to increase the monoterpene alcohol concentration in the sweet potato shochu, in a preferred embodiment, producing sweet potato shochu does not include steaming the second raw sweet potato pieces. In other words, it is preferable to produce sweet potato shochu from the second raw sweet potato pieces without steaming the second raw sweet potato pieces.

[0030] The method for obtaining the first moromi is not limited. The first moromi can be obtained by referring to known moromi production methods. For example, the first moromi can be obtained by fermenting a mixture containing koji, water, and yeast. Moromi obtained by fermenting a mixture containing koji, water, and yeast is generally called primary moromi. The first moromi may be obtained through multiple fermentations. That is, the first moromi may be an nth moromi, where n is an integer of 1 or greater. n may be an integer from 1 to 5. n may be an integer from 1 to 3. n may be 1 or 2. n may be 1. The first moromi may be an n+1th moromi. For example, the n+1th moromi is obtained by fermenting a mixture containing second raw potato pieces, nth moromi, and optionally water. Examples of koji include barley koji and rice koji. In a preferred embodiment, the koji is rice koji. The koji mold used to produce koji may be selected from known koji molds. Examples of koji molds include white koji mold, black koji mold, and yellow koji mold. The yeast may be selected from known shochu yeasts. The fermentation conditions may be adjusted taking into consideration the type of raw material and the flavor of the desired sweet potato shochu. The fermentation temperature may be within a range of 15°C to 35°C. The fermentation temperature may be within a range of 20°C to 30°C. In the first moromi production method, the fermentation period of the mixture containing koji, water, and yeast may be 3 to 5 days. In the first moromi production method, the total fermentation period of the mixture containing the second raw sweet potato pieces, the nth-order moromi, and optionally water may be 8 to 10 days.

[0031] The fermentation conditions for the mixture containing the second raw sweet potato pieces, the first mash, and optionally water are not limited. The fermentation conditions may be adjusted taking into consideration the type of raw material and the desired flavor of the sweet potato shochu. The fermentation temperature may be within a range of 15°C to 35°C. The fermentation temperature may be within a range of 20°C to 30°C. The fermentation period may be 8 to 14 days.

[0032] The distillation method and conditions may be selected based on the distillation method and conditions used in known methods for producing sweet potato shochu. The distillation may be atmospheric distillation or reduced pressure distillation. The distillation apparatus may be a pot still. The sweet potato shochu obtained by distillation may be filtered and aged as necessary. The sweet potato shochu may be diluted to adjust the ethanol concentration. The sweet potato shochu may be a mixture of sweet potato shochu obtained by a pot still and raw material alcohol obtained by a continuous still.

[0033] The ethanol concentration in sweet potato shochu (i.e., the ratio of the volume of ethanol to the volume of sweet potato shochu) may be within the range of 10% to 45% by volume. The lower limit of the ethanol concentration in sweet potato shochu may be 20% or 25% by volume. The upper limit of the ethanol concentration in sweet potato shochu may be 40% or 35% by volume. In the present disclosure, the ethanol concentration in sweet potato shochu may be measured by a gas chromatograph equipped with a flame ionization detector (i.e., FID). The method for preparing a sample used to measure the ethanol concentration is described below in the description related to the method for measuring the methanol concentration.

[0034] Sweet potato shochu obtained by the sweet potato shochu production method including steps S1, S2, and S3 has a relatively low methanol concentration. In a preferred embodiment, the methanol concentration represented by the following formula 1 is 500 mg / L or less. The upper limit of the methanol concentration represented by the following formula 1 may be 450 mg / L, 400 mg / L, 350 mg / L, 300 mg / L, 250 mg / L, or 200 mg / L. With the aim of reducing the methanol concentration in sweet potato shochu, the lower limit of the methanol concentration represented by the following formula 1 is not limited. The lower the methanol concentration, the better. The lower limit of the methanol concentration represented by the following formula 1 may be 0 mg / L, 50 mg / L, or 100 mg / L. The following formula 1 represents the methanol concentration in sweet potato shochu to be measured as the methanol concentration in sweet potato shochu with an ethanol concentration of 25% by volume. As a result, even if the ethanol concentration in the sweet potato shochu to be measured is not 25% by volume, it is possible to evaluate and compare the methanol concentration in various sweet potato shochu under conditions of a constant ethanol concentration. The methanol concentration in sweet potato shochu in the following formula 1 is measured using a gas chromatograph equipped with a flame ionization detector (i.e., FID). A sample is obtained by leaving the sweet potato shochu in a refrigerator overnight and then filtering it through a membrane filter with a pore size of 0.45 μm. The sample preparation method is also applicable to the measurement of ethanol concentration and monoterpene alcohol concentration in this disclosure. The specific conditions for quantitative analysis of methanol using a gas chromatograph are as follows. In quantitative analysis of methanol, the methanol concentration is determined by the internal standard method. (1) Capillary column: "DB-WAX" (Agilent Technologies, Inc., length: 30 m, inner diameter: 0.25 mm, film thickness: 0.25 μm) (2) Carrier gas: He (3) Detector temperature: 240°C (4) Front injection port temperature: 240°C

[0035] Equation 1: Methanol concentration (mg / L) = [methanol concentration in sweet potato shochu (mg / L)] × 25% by volume ÷ [ethanol concentration in sweet potato shochu (% by volume)]

[0036] As described above, the method for producing sweet potato shochu, which includes steps S1, S2, and S3, can contribute to increasing the concentration of terpenes, particularly monoterpene alcohols, in sweet potato shochu. Examples of monoterpene alcohols contained in sweet potato shochu include linalool, α-terpineol, citronellol, nerol, and geraniol. In a preferred embodiment, sweet potato shochu contains at least one monoterpene alcohol selected from the group consisting of linalool, α-terpineol, citronellol, nerol, and geraniol.

[0037] In a preferred embodiment, the total concentration of linalool, α-terpineol, citronellol, nerol, and geraniol represented by the following formula 2 is 100 μg / L or more. The lower limit of the total concentration of the above components may be 150 μg / L, 200 μg / L, 250 μg / L, 300 μg / L, 350 μg / L, 400 μg / L, 450 μg / L, 500 μg / L, 550 μg / L, 600 μg / L, 650 μg / L, 700 μg / L, 750 μg / L, or 800 μg / L. The upper limit of the total concentration of the above components may be 1000 μg / L, 950 μg / L, 900 μg / L, 850 μg / L, 800 μg / L, 750 μg / L, 700 μg / L, 650 μg / L, 600 μg / L, 550 μg / L, 500 μg / L, 450 μg / L, or 400 μg / L. When the total concentration of the above components is high, the aroma derived from the above components tends to be stronger. As a result, the aroma of sweet potato shochu becomes even richer.

[0038] Equation 2: Total concentration of linalool, α-terpineol, citronellol, nerol, and geraniol (μg / L) = [Total concentration of linalool, α-terpineol, citronellol, nerol, and geraniol in sweet potato shochu (μg / L)] × 25% by volume ÷ [Ethanol concentration in sweet potato shochu (% by volume)]

[0039] In a preferred embodiment, when the variety of raw sweet potato is Koganesengan, the total concentration of linalool, α-terpineol, citronellol, nerol, and geraniol represented by Formula 2 is 100 μg / L or more. The lower limit of the total concentration of the above components may be 150 μg / L, 200 μg / L, 250 μg / L, 300 μg / L, 350 μg / L, 400 μg / L, 450 μg / L, 500 μg / L, 550 μg / L, 600 μg / L, 650 μg / L, 700 μg / L, 750 μg / L, or 800 μg / L. The upper limit of the total concentration of the above components may be 1000 μg / L, 950 μg / L, 900 μg / L, 850 μg / L, 800 μg / L, 750 μg / L, 700 μg / L, 650 μg / L, 600 μg / L, 550 μg / L, 500 μg / L, 450 μg / L, or 400 μg / L. When the total concentration of the above components is high, the aroma derived from the above components tends to be stronger. As a result, the aroma of sweet potato shochu becomes even richer.

[0040] In a preferred embodiment, when the raw potato variety is Shiroyutaka, the total concentration of linalool, α-terpineol, citronellol, nerol, and geraniol represented by Formula 2 is 150 μg / L or more. The lower limit of the total concentration of the above components may be 250 μg / L, 300 μg / L, 350 μg / L, 400 μg / L, 450 μg / L, 500 μg / L, 550 μg / L, 600 μg / L, 650 μg / L, 700 μg / L, 750 μg / L, or 800 μg / L. The upper limit of the total concentration of the above components may be 1000 μg / L, 950 μg / L, 900 μg / L, 850 μg / L, 800 μg / L, 750 μg / L, 700 μg / L, 650 μg / L, 600 μg / L, 550 μg / L, 500 μg / L, 450 μg / L, or 400 μg / L. When the total concentration of the above components is high, the aroma derived from the above components tends to be stronger. As a result, the aroma of sweet potato shochu becomes even richer.

[0041] In a preferred embodiment, when the raw potato variety is Conysin, the total concentration of linalool, α-terpineol, citronellol, nerol, and geraniol represented by Formula 2 is 100 μg / L or more. The lower limit of the total concentration of the above components may be 150 μg / L, 200 μg / L, 250 μg / L, 300 μg / L, 350 μg / L, 400 μg / L, 450 μg / L, 500 μg / L, 550 μg / L, 600 μg / L, 650 μg / L, 700 μg / L, 750 μg / L, or 800 μg / L. The upper limit of the total concentration of the above components may be 1000 μg / L, 950 μg / L, 900 μg / L, 850 μg / L, 800 μg / L, 750 μg / L, 700 μg / L, 650 μg / L, 600 μg / L, 550 μg / L, 500 μg / L, 450 μg / L, or 400 μg / L. When the total concentration of the above components is high, the aroma derived from the above components tends to be stronger. As a result, the aroma of sweet potato shochu becomes even richer.

[0042] In a preferred embodiment, when the raw sweet potato variety is Silk Sweet, the total concentration of linalool, α-terpineol, citronellol, nerol, and geraniol represented by Formula 2 is 100 μg / L or more. The lower limit of the total concentration of the above components may be 150 μg / L, 200 μg / L, 250 μg / L, 300 μg / L, 350 μg / L, 400 μg / L, 450 μg / L, 500 μg / L, 550 μg / L, 600 μg / L, 650 μg / L, 700 μg / L, 750 μg / L, or 800 μg / L. The upper limit of the total concentration of the above components may be 1000 μg / L, 950 μg / L, 900 μg / L, 850 μg / L, 800 μg / L, 750 μg / L, 700 μg / L, 650 μg / L, 600 μg / L, 550 μg / L, 500 μg / L, 450 μg / L, or 400 μg / L. When the total concentration of the above components is high, the aroma derived from the above components tends to be stronger. As a result, the aroma of sweet potato shochu becomes even richer.

[0043] In a preferred embodiment, the linalool concentration represented by the following formula 3 is 20 μg / L or more. The lower limit of the linalool concentration represented by the following formula 3 may be 50 μg / L, 100 μg / L, 150 μg / L, 200 μg / L, 250 μg / L, 300 μg / L, 350 μg / L or 400 μg / L. The upper limit of the linalool concentration represented by the following formula 3 may be 500 μg / L, 450 μg / L, 400 μg / L, 350 μg / L, 300 μg / L, 250 μg / L or 200 μg / L. When the linalool concentration is high, the scent derived from linalool tends to be stronger.

[0044] Equation 3: Linalool concentration (μg / L) = [Linalool concentration in sweet potato shochu (μg / L)] × 25% by volume ÷ [ethanol concentration in sweet potato shochu (volume%)]

[0045] In a preferred embodiment, the α-terpineol concentration represented by the following formula 4 is 20 μg / L or more. The lower limit of the α-terpineol concentration represented by the following formula 4 may be 50 μg / L, 100 μg / L, 150 μg / L, 200 μg / L, 250 μg / L, or 300 μg / L. The upper limit of the α-terpineol concentration represented by the following formula 4 may be 500 μg / L, 450 μg / L, 400 μg / L, 350 μg / L, 300 μg / L, 250 μg / L, or 200 μg / L. When the α-terpineol concentration is high, the scent derived from α-terpineol tends to be stronger.

[0046] Equation 4: α-Terpineol concentration (μg / L) = [α-Terpineol concentration in sweet potato shochu (μg / L)] × 25% by volume ÷ [ethanol concentration in sweet potato shochu (% by volume)]

[0047] In a preferred embodiment, the citronellol concentration represented by the following formula 5 is 20 μg / L or more. The lower limit of the citronellol concentration represented by the following formula 5 may be 50 μg / L, 100 μg / L, 150 μg / L, 200 μg / L, 250 μg / L, or 300 μg / L. The upper limit of the citronellol concentration represented by the following formula 5 may be 500 μg / L, 450 μg / L, 400 μg / L, 350 μg / L, 300 μg / L, 250 μg / L, or 200 μg / L. When the citronellol concentration is high, the scent derived from citronellol tends to be stronger.

[0048] Equation 5: Citronellol concentration (μg / L) = [Citronellol concentration in sweet potato shochu (μg / L)] × 25% by volume ÷ [Ethanol concentration in sweet potato shochu (% by volume)]

[0049] In a preferred embodiment, the nerol concentration represented by the following formula 6 is 20 μg / L or more. The lower limit of the nerol concentration represented by the following formula 6 may be 50 μg / L, 100 μg / L, 150 μg / L, 200 μg / L, 250 μg / L, or 300 μg / L. The upper limit of the nerol concentration represented by the following formula 6 may be 500 μg / L, 450 μg / L, 400 μg / L, 350 μg / L, 300 μg / L, 250 μg / L, or 200 μg / L. When the nerol concentration is high, the fragrance derived from nerol tends to be stronger.

[0050] Equation 6: Nerol concentration (μg / L) = [Nerol concentration in sweet potato shochu (μg / L)] × 25% by volume ÷ [Ethanol concentration in sweet potato shochu (% by volume)]

[0051] In a preferred embodiment, the geraniol concentration represented by the following formula 7 is 20 μg / L or more. The lower limit of the geraniol concentration represented by the following formula 7 may be 50 μg / L, 100 μg / L, 150 μg / L, 200 μg / L, 250 μg / L, or 300 μg / L. The upper limit of the geraniol concentration represented by the following formula 7 may be 500 μg / L, 450 μg / L, 400 μg / L, 350 μg / L, 300 μg / L, 250 μg / L, or 200 μg / L. When the geraniol concentration is high, the scent derived from geraniol tends to be stronger.

[0052] Equation 7: Geraniol concentration (μg / L) = [geraniol concentration in sweet potato shochu (μg / L)] × 25% by volume ÷ [ethanol concentration in sweet potato shochu (% by volume)]

[0053] In the present disclosure, the concentrations of linalool, α-terpineol, citronellol, nerol, and geraniol in sweet potato shochu are measured by dynamic headspace-gas chromatography-mass spectrometry. Specifically, aroma components are collected from a sample in a collection tube, and the concentrations of target components are measured by gas chromatography-mass spectrometry (i.e., GC / MS). Quantitative analysis by GC / MS employs an internal standard method, using linalool-d3 as the internal standard. Linalool-d3 is added to the sample to adjust the concentration of linalool-d3 in the sample to 200 μg / L. Specific analytical conditions for GC / MS are as follows: (1) Capillary column: "DB-WAX" (Agilent Technologies, Inc., length: 30 m, inner diameter: 0.25 mm, film thickness: 0.25 μm) (2) Oven temperature: 40°C (3 min) → 5°C / min → 130°C (8 min) → 8°C / min → 240°C (8 min) (3) Carrier gas: He (4) Ion source temperature: 230°C (5) Front injection port temperature: 240°C (6) Ions used for quantification: m / z = 93 (linalool), m / z = 59 (α-terpineol), m / z = 69 (citronellol), m / z = 93 (nerol), m / z = 123 (geraniol)

[0054] The present disclosure will be described below based on examples. However, the present disclosure is not limited to the following examples. The following technical matters may be appropriately modified within the scope of the present disclosure.

[0055] Reference Example 1: Rice koji (400 g), water (480 mL), and shochu yeast (0.1 g) were mixed and fermented to obtain a primary mash. Sweet potato varieties were selected according to the information in Table 1, and steamed sweet potatoes were prepared. The primary mash, steamed sweet potatoes (2,000 g), and water (1,200 mL) were mixed and fermented to obtain a secondary mash. The secondary mash was subjected to pot distillation. Water was added to the resulting distillate to adjust the ethanol concentration to 25% by volume, thereby obtaining a type 2 sweet potato shochu.

[0056] Comparative Example 1: Rice koji (400 g), water (480 mL), and shochu yeast (0.1 g) were mixed and fermented to obtain a primary mash. The fermentation temperature was between 25°C and 30°C, and the fermentation period was 4 days. Sweet potato varieties were selected according to the information in Table 1, and raw sweet potatoes were washed. The raw sweet potatoes were shredded using a shredding machine (DC2110A, Urschel Japan Co., Ltd.) to obtain raw sweet potato pieces. Each sweet potato piece was a hexahedron with a side length of 3.2 mm. Sweet potato pieces (2000 g), the primary mash, and water (1200 mL) were mixed and fermented to obtain a secondary mash. The fermentation temperature was between 25°C and 30°C, and the fermentation period was 10 days. The secondary mash was subjected to pot distillation. Water was added to the obtained distillate to adjust the ethanol concentration to 25% by volume, thereby obtaining type 2 sweet potato shochu.

[0057] Example 1: Rice koji (400 g), water (480 mL), and shochu yeast (0.1 g) were mixed and fermented to obtain a primary mash. The fermentation temperature was between 25°C and 30°C, and the fermentation period was 4 days. Sweet potato varieties were selected according to the information in Table 1, and raw sweet potatoes were washed. The raw sweet potatoes were shredded using a shredding machine (DC2110A, Urschel Japan Co., Ltd.) to obtain raw sweet potato pieces. Each sweet potato piece was hexahedral in shape, with a side length of 3.2 mm. Air was blown through the sweet potato pieces (2000 g) at an ambient temperature of 25°C to 30°C according to the information in Table 1 to reduce the water content of the sweet potato pieces. The air temperature was between 25°C and 30°C. The sweet potato pieces after ventilation, the primary mash, and water (1200 mL + X mL) were mixed and fermented to obtain a secondary mash. X mL corresponds to the amount of water lost from the sweet potato due to ventilation. The fermentation temperature was between 25°C and 30°C, and the fermentation period was 10 days. The secondary mash was subjected to pot distillation. Water was added to the resulting distillate to adjust the ethanol concentration to 25% by volume, yielding a type B sweet potato shochu.

[0058] <Sensory Test> A sensory test was conducted by five evaluators using the Otsu-type sweet potato shochu. Specifically, the aroma and taste shown in Table 1 were evaluated using a five-point scale from 1 to 5 below. The scores of 1 to 5 below are relative values ​​based on Reference Example 1, and the score of Reference Example 1 used as the standard is 3. The average score for each evaluation item was calculated. The results of the sensory test are shown in Table 1. Score: (Weak) 1-2-3-4-5 (Strong)

[0059]

[0060] The concentration of each component shown in Table 1 is represented by an appropriate formula selected from the previously described formulas 1 to 7. Comparative Example 1 and Example 1 (specifically, Example 1A and Example 1B) used raw sweet potatoes as the raw material for sweet potato shochu, whereas Reference Example 1 used steamed sweet potatoes as the raw material for sweet potato shochu. The monoterpene alcohol concentrations in the sweet potato shochu obtained in Comparative Example 1 and Example 1 are higher than the monoterpene alcohol concentration in the sweet potato shochu obtained in Reference Example 1. This result indicates that the method of producing sweet potato shochu from raw sweet potatoes rather than steamed sweet potatoes contributes to an increase in the monoterpene alcohol concentration in sweet potato shochu. Appropriate selection of the conditions for the aeration process led to a further increase in the monoterpene alcohol concentration in sweet potato shochu.

[0061] However, the methanol concentration in the sweet potato shochu obtained in Comparative Example 1 was higher than that in the sweet potato shochu obtained in Reference Example 1. This result is consistent with the previously mentioned explanation that the methanol concentration in sweet potato shochu increases when sweet potato shochu is produced without steaming the sweet potatoes.

[0062] In contrast, the methanol concentration in each sweet potato shochu obtained in Example 1 was lower than the methanol concentration in the sweet potato shochu obtained in Comparative Example 1. Example 1 reduced the water content of the raw sweet potato pieces, while Comparative Example 1 did not. Therefore, the results shown in Table 1 indicate that the series of steps S1, S2, and S3 of the present disclosure contribute to a reduction in the methanol concentration in sweet potato shochu produced from raw sweet potatoes. Furthermore, the results shown in Table 1 indicate that the series of steps S1, S2, and S3 of the present disclosure also contribute to an increase in the monoterpene alcohol concentration in sweet potato shochu produced from raw sweet potatoes.

[0063] <Reference Example 2> Rice koji (400 g), water (480 mL), and shochu yeast (0.1 g) were mixed and fermented to obtain a primary mash. Sweet potato varieties were selected according to the information in Table 2, and steamed sweet potatoes were prepared. The primary mash, steamed sweet potatoes (2000 g), and water (1200 mL) were mixed and fermented to obtain a secondary mash. The secondary mash was subjected to pot distillation. Water was added to the resulting distillate to adjust the ethanol concentration to 25% by volume, thereby obtaining a type 2 sweet potato shochu.

[0064] Comparative Example 2: Rice koji (400 g), water (480 mL), and shochu yeast (0.1 g) were mixed and fermented to obtain a primary mash. The fermentation temperature was between 25°C and 30°C, and the fermentation period was 4 days. Sweet potato varieties were selected according to the information in Table 2, and raw sweet potatoes were washed. The raw sweet potatoes were shredded using a shredding machine (DC2110A, Urschel Japan Co., Ltd.) to obtain raw sweet potato pieces. Each sweet potato piece was a hexahedron with a side length of 3.2 mm. Sweet potato pieces (2000 g), the primary mash, and water (1200 mL) were mixed and fermented to obtain a secondary mash. The fermentation temperature was between 25°C and 30°C, and the fermentation period was 10 days. The secondary mash was subjected to pot distillation. Water was added to the obtained distillate to adjust the ethanol concentration to 25% by volume, thereby obtaining type 2 sweet potato shochu.

[0065] Example 2: Rice koji (400 g), water (480 mL), and shochu yeast (0.1 g) were mixed and fermented to obtain a primary mash. The fermentation temperature was between 25°C and 30°C, and the fermentation period was 4 days. Sweet potato varieties were selected according to the information in Table 2, and raw sweet potatoes were washed. The raw sweet potatoes were shredded using a shredding machine (DC2110A, Urschel Japan Co., Ltd.) to obtain raw sweet potato pieces. Each sweet potato piece was hexahedral in shape, with a side length of 3.2 mm. Air was blown through the sweet potato pieces (2000 g) at an ambient temperature of 25°C to 30°C according to the information in Table 2 to reduce the water content of the sweet potato pieces. The air temperature was between 25°C and 30°C. The sweet potato pieces after ventilation, the primary mash, and water (1200 mL + X mL) were mixed and fermented to obtain a secondary mash. X mL corresponds to the amount of water lost from the sweet potato due to ventilation. The fermentation temperature was between 25°C and 30°C, and the fermentation period was 10 days. The secondary mash was subjected to pot distillation. Water was added to the resulting distillate to adjust the ethanol concentration to 25% by volume, yielding a type B sweet potato shochu.

[0066] <Sensory Test> Following the procedure for the sensory test described above, a sensory test was conducted by five evaluators using the sweet potato shochu of the second type. The results of the sensory test are shown in Table 2.

[0067]

[0068] The concentration of each component shown in Table 2 is represented by an appropriate formula selected from the above-mentioned formulas 1 to 7. In Comparative Example 2 and Example 2, raw sweet potatoes were used as the raw material for sweet potato shochu, whereas in Reference Example 2, steamed sweet potatoes were used as the raw material for sweet potato shochu. The monoterpene alcohol concentrations in the sweet potato shochu obtained in Comparative Example 2 and Example 2 are higher than the monoterpene alcohol concentration in the sweet potato shochu obtained in Reference Example 2. This result indicates that the method of producing sweet potato shochu from raw sweet potatoes rather than steamed sweet potatoes contributes to an increase in the monoterpene alcohol concentration in sweet potato shochu.

[0069] However, the methanol concentration in the sweet potato shochu obtained in Comparative Example 2 was higher than that in the sweet potato shochu obtained in Reference Example 2. This result is consistent with the previously mentioned explanation that the methanol concentration in sweet potato shochu increases when sweet potato shochu is produced without steaming the sweet potatoes.

[0070] In contrast, the methanol concentration in the sweet potato shochu obtained in Example 2 was lower than that in Comparative Example 2. Example 2 reduced the water content of the raw sweet potato pieces, whereas Comparative Example 2 did not. Therefore, the results shown in Table 2 indicate that the series of steps S1, S2, and S3 of the present disclosure contribute to a reduction in the methanol concentration in sweet potato shochu produced from raw sweet potatoes. Furthermore, the results shown in Table 2 indicate that the series of steps S1, S2, and S3 of the present disclosure also contribute to an increase in the monoterpene alcohol concentration in sweet potato shochu produced from raw sweet potatoes.

Claims

1. A method for producing sweet potato shochu, comprising: processing raw potatoes to obtain first raw potato pieces; reducing the water content of the first raw potato pieces to obtain second raw potato pieces having a lower water content than the first raw potato pieces; and producing sweet potato shochu from the second raw potato pieces.

2. The method for producing sweet potato shochu according to claim 1, wherein reducing the water content of the first raw potato pieces comprises reducing the total mass of the first raw potato pieces by 25% or more.

3. A method for producing sweet potato shochu as described in claim 1 or claim 2, wherein reducing the water content of the first raw potato pieces includes blowing gas onto the first raw potato pieces.

4. A method for producing sweet potato shochu as described in claim 3, wherein the temperature of the gas is 30°C or lower.

5. The method for producing sweet potato shochu according to claim 3, wherein the time for blowing gas onto the first raw potato pieces is within the range of 1 hour to 20 hours.

6. A method for producing sweet potato shochu as described in claim 1 or claim 2, wherein producing the sweet potato shochu includes fermenting a mixture containing the second raw sweet potato pieces and the first mash to obtain a second mash, and distilling the second mash to obtain the sweet potato shochu.

7. The method for producing sweet potato shochu according to claim 1 or 2, wherein the methanol concentration represented by the following formula 1 is 500 mg / L or less. Formula 1: Methanol concentration (mg / L) = [methanol concentration in sweet potato shochu (mg / L)] x 25% by volume ÷ [ethanol concentration in sweet potato shochu (volume %)]

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