JP2020141597A - Fruit wine filtration and clarification method - Google Patents

Abstract

To provide a fruit wine filtration and clarification process, in which the change in chromaticity component before and after filtration is small, the removal rate of grounds component is high, and the water permeability recovery after the cleaning step and the resistance to the cleaning solution (chemical solution) are also high.SOLUTION: A method for producing fruit wine, including the following steps: a fermentation step of fermenting a fruit to yield a fruit wine that contains aggregates of grounds components; and a filtration/clarification step of passing the fruit wine obtained in the fermentation step through a porous membrane composed of a resin having a three-dimensional network structure to separate the filtrate from the aggregates of the grounds components, and in which, characterized, the porous membrane is a particular membrane having a high intercommunication property, and, when setting the absorbance, at an arbitrary wavelength of 250 nm to 650 nm, of the fruit wine before the filtration/clarification step as X1 and the absorbance of fruit wine after the filtration/clarification step as X2, satisfies the relationship of X2/X1≥0.75.SELECTED DRAWING: None

Description

The present invention relates to a method for producing fruit liquor, which comprises filtering and clarification of fruit liquor using a porous membrane. More specifically, the present invention relates to a method for producing fruit liquor, which comprises a filtration / clarification step using a porous membrane for removing the aggregates from the fruit liquor containing yeast and starch components after fermentation, before and after filtration. The present invention relates to a method in which the change in the chromaticity component is small, the removal rate of the yeast component is high, the water permeability recovery after the cleaning step of the porous film and the resistance to the cleaning liquid (chemical solution) are high.

Conventionally, fruit liquor is produced by preparing fruit raw materials and undergoing a fermentation process, a clarification process, and an aging process, but there are various elements required to stabilize the quality. For example, in the case of red wine, it is important to stabilize its color tone from the viewpoint of quality maintenance. In addition, darker red wines tend to be preferred because they give consumers a sense of luxury and are rich in useful ingredients such as anthocyanins.
The chromaticity of red wine is greatly influenced by the grape varieties used as raw materials and the cultivation environment. For example, Cabernet Sauvignon and Merlot, which are typical varieties of red wine, are known as varieties that can express a deep redness, but red wine that uses sunshine hours that could not be secured due to the weather and cultivation area is used as a raw material. , It may not reach the expected chromaticity.
Even in white wine, the color of the produced wine changes depending on the variety of raw materials, the area where it is cultivated, and the weather. In the case of white wine, some brands have a certain lower limit for chromaticity from the viewpoint of production control. As with red wine, the chromaticity mainly depends on the raw material, so it may be difficult to always secure a chromaticity above a certain level.
To deal with such problems related to color tone and chromaticity, a method of applying ultrasonic waves before or during the brewing period (see Patent Document 1 below), or by adding pectinase to wine raw materials to produce grape skins. Has been reported as a method for efficiently eluting the chromaticity component in the pericarp (see Patent Document 2 below).

Japanese Unexamined Patent Publication No. 2001-258540 Japanese Unexamined Patent Publication No. 11-46747

However, when ultrasonic waves are applied, the chromaticity component in the pericarp can be efficiently eluted, but other useful components may be decomposed. Further, although the elution of the chromaticity component can be promoted by adding pectinase, there is a complexity that the amount of addition must be adjusted for each raw material.
As a result of diligent studies and experiments on the problem of chromaticity decrease in fruit wine, the factors that determine the chromaticity of fruit wine are the raw materials and the chromaticity component from the raw materials. It was discovered that it is affected not only by the extraction method of but also by the manufacturing process of the subsequent stage. Among them, in the diatomaceous earth filtration conventionally performed for clarification of fruit wine after alcoholic fermentation, a considerable amount of components related to chromaticity are adsorbed, and the chromaticity after filtration is lower than that before filtration. I found out that there was a problem.

On the other hand, in recent years, a membrane filtration method has been reported as an alternative turbidity method to diatomaceous earth filtration. The advantages of the membrane filtration method are (1) the turbidity level of the obtained water is high and stable (the safety of the obtained water is high), and (2) the installation space of the filtration device is small. It can be done, (3) automatic operation is easy, and (4) the disposal cost of used diatomaceous earth can be suppressed. For the turbidity operation by membrane filtration, a flat membrane or hollow filament-like porous ultrafiltration membrane or microfiltration membrane having an average pore diameter in the range of several nm to several hundred nm is used. As described above, the turbidity operation by the membrane filtration method has many advantages over the diatomaceous earth filtration, and therefore, it is being adopted for various filtration applications as an alternative or complementary means to the conventional method.
However, when a porous filtration membrane is produced from a resin material, the microstructure of the material constituting the membrane differs depending on the film forming method. Further, in the filtration for removing the starch component contained in the fruit wine after fermentation, it is required to suppress the above-mentioned decrease in the chromaticity component as much as possible while maintaining a high removal rate of the starch component. Further, since the membrane is usually clogged when the filtration operation is continued, the operation of the filtration method using the porous filtration membrane involves a cleaning step. On the other hand, the use of chemicals in the cleaning process induces deterioration of the strength of the membrane. At this time, if there is a difference in the microstructure of the materials constituting the porous filtration membrane, the degree of damage to the porous filtration membrane by the cleaning solution (chemical solution) used in the repeated cleaning process differs, resulting in filtration performance and life. There is also the problem of affecting.

In view of this problem, the problem to be solved by the present invention is a fruit including a filtration / clarification step using a porous membrane for removing the aggregate from the fermented fruit liquor containing the aggregate of the starch component. Provided is a method for producing liquor, which has a low change in chromaticity component before and after filtration, a high removal rate of starch component, a high water permeability recovery after a cleaning process of a porous membrane, and a high resistance to a washing liquid (chemical solution). Is.

As a result of diligent studies and repeated experiments in order to solve the above-mentioned problems, the present inventors have found that the pores extending from the inside of the membrane on the liquid side to be treated to the outside of the membrane on the filtrate side of the porous filtration membrane. In a method for producing fruit liquor, which comprises a filtration step using a porous membrane for removing the aggregates from the fruit liquor containing aggregates of starch components by using a membrane having good communication properties, before and after filtration. The change in the color component of fruit liquor is low, the removal rate of the starch component is high, and the cleaning solution (chemical solution) used in the cleaning process is hot water at 50 ° C to 90 ° C and / or 0.05% by weight or more 0. Even when an aqueous solution containing 5% by weight or less of sodium hypochlorite or 0.4% by weight or more and 4% by weight or less of sodium hydroxide is used, deterioration of the membrane can be minimized. Unexpectedly, the present invention was completed.

That is, the present invention is as follows.
[1] The following steps:
Fermentation step of fermenting fruits to obtain fruit liquor containing aggregates of starch components; and passing the fruit liquor obtained in the fermentation step through a porous membrane composed of a resin having a three-dimensional network structure. A filtration / clarification step that separates the filtrate from the aggregates of the starch components;
It is a method of producing fruit liquor containing
In the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film, the visual field including the inner surface, the visual field including the outer surface of the film, and the visual fields between these visual fields were photographed at equal intervals. Total of visual fields In each region of the four visual fields, the total area of the resin portion having an area of 1 μm ² or less is 70% or more of the total area of the resin portion, and
When the absorbance of fruit wine before the filtration / clarification step is X1 and the absorbance of fruit wine after the filtration / clarification step is X2 at an arbitrary wavelength of 250 nm to 650 nm, X2 / X1 ≧ 0.75. Satisfy the relationship,
A method for producing fruit wine, which is characterized by the fact that.
[2] The following steps:
Fermentation step of fermenting fruits to obtain fruit liquor containing aggregates of starch components; and passing the fruit liquor obtained in the fermentation step through a porous membrane composed of a resin having a three-dimensional network structure. A filtration / clarification step that separates the filtrate from the aggregates of the starch components;
It is a method of producing fruit liquor containing
In the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film, the visual field including the inner surface, the visual field including the outer surface of the film, and the intervals between these visual fields were photographed at equal intervals. Total of the visual fields In each region of the four visual fields, the total area of the resin portion having an area of 10 μm ² or more is 15% or less of the total area of the resin portion, and at an arbitrary wavelength of 250 nm to 650 nm. When the absorbance of the fruit liquor before the filtration / clarification step is X1 and the absorbance of the fruit liquor after the filtration / clarification step is X2, the relationship of X2 / X1 ≧ 0.75 is satisfied.
A method for producing fruit wine, which is characterized by the fact that.
[3] The following steps:
Fermentation step of fermenting fruits to obtain fruit liquor containing aggregates of starch components; and passing the fruit liquor obtained in the fermentation step through a porous membrane composed of a resin having a three-dimensional network structure. A filtration / clarification step that separates the filtrate from the aggregates of the starch components;
It is a method of producing fruit liquor containing
In the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film, the visual field including the inner surface, the visual field including the outer surface of the film, and the intervals between these visual fields were photographed at equal intervals. A resin having an area of 10 μm ² or more and 70% or more of the total area of the resin portion having an area of 1 μm ² or less in each region of the total four visual fields. The total area of the part is 15% or less of the total area of the resin part, and the absorbance of the fruit liquor before the filtration / clarification step at an arbitrary wavelength of 250 nm to 650 nm is X1, the filtration / When the absorbance of the fruit liquor after the clarification step is X2, the relationship of X2 / X1 ≧ 0.75 is satisfied.
A method for producing fruit wine, which is characterized by the fact that.
[4] The porous film is a visual field including the inner surface, a visual field including the outer surface of the film, and a visual field thereof in an SEM image of a film cross section in a film thickness direction orthogonal to the inner surface of the porous film. in 2 field each region a total of four field of between was taken at regular intervals of, 1 [mu] m ² total area of the resin portion having an area of less than super 10 [mu] m ² is at most 15% of the total area of the resin portion The method according to any one of the above [1] to [3].
[5] In the filtration / clarification step, a mixture of fruit wine and bentonite obtained in the fermentation step is passed through a porous membrane made of a resin having a three-dimensional network structure. 4] The method according to any one of.
[6] The method according to any one of [1] to [5] above, wherein the surface aperture ratio of the porous membrane is 25 to 60%.
[7] The method according to any one of [1] to [6] above, wherein the porous membrane is a hollow fiber membrane.
[8] The method according to any one of [1] to [7] above, wherein the resin constituting the porous film is a thermoplastic resin.
[9] The method according to [8] above, wherein the thermoplastic resin is a fluororesin.
[10] The fluororesin includes vinylidene fluoride resin (PVDF), chlorotrifluoroethylene resin, tetrafluoroethylene resin, ethylene-tetrafluoroethylene copolymer (ETFE), and ethylene-monochromelotrifluoroethylene copolymer (ECTFE). ), Hexafluoropropylene resin, and any one selected from the group consisting of a mixture of these resins, according to the method according to [9] above.
[11] The method according to [8] above, wherein the thermoplastic resin is polyethylene (PE).
[12] After the filtration / clarification step, a cleaning step of passing or immersing the cleaning liquid in the porous membrane to clean the inside of the porous membrane is further included, and the cleaning liquid is hot water at 50 ° C. to 90 ° C. The method according to any one of the above [1] to [11].
[13] After the filtration / clarification step, a cleaning step of passing or immersing the cleaning liquid in the porous membrane to clean the inside of the porous membrane is further included, and the cleaning liquid is 0.05% by weight or more 0. The method according to any one of the above [1] to [11], which is an aqueous solution containing 5% by weight or less of sodium hypochlorite or 0.4% by weight or more and 4% by weight or less of sodium hydroxide.
[14] The relationship between the tensile elongation at break E0 of the porous membrane before the cleaning step and the tensile elongation at break E1 of the porous membrane after the cleaning step is E1 / E0 × 100 ≧ 80%. , The method according to the above [12] or [13].
[15] The tensile elongation at break E0 of the porous membrane before the cleaning step, and the porous membrane after repeating the cleaning step X times (where X is an integer of 2 to 100). The method according to the above [12] or [13], wherein the relationship with the tensile elongation at break EX is EX / E0 × 100 ≧ 70%.
[16] The relationship between the flux L0 of the porous membrane before the filtration / clarification step and the flux L1 of the porous membrane after the cleaning step is L1 / L0 × 100 ≧ 95%. 12] or the method according to [13].
[17] The flux L0 of the porous membrane before the filtration / clarification step and the cleaning step of the porous membrane after being repeated X times (where X is an integer of 2 to 100). The method according to the above [12] or [13], wherein the relationship with the flux LX is X / L0 × 100 ≧ 90%.
[18] The cleaning step of the above [12] to [17] includes a cleaning liquid step of cleaning with the cleaning liquid and a rinsing step of rinsing with rinsing water for removing the remaining cleaning liquid component. The method described in either.
[19] The method according to [18], wherein the amount of rinse water used in the rinse step is 100 L / m ² or less per unit area of the porous membrane.
[20] The chlorine concentration in the filtrate after restarting the filtration / clarification step after the rinsing step is 0.1 ppm or less, and the pH of the filtrate is 8.6 or less. ] Or the method according to [19].

In the filtration / clarification step in the method for producing fruit liquor according to the present invention, the pores from the inside of the membrane on the liquid side to be treated to the outside of the membrane on the filtrate side of the porous filtration membrane have good communication. Since a membrane is used, the change in color of fruit liquor before and after filtration is low, the removal rate of starch components is high, and as a cleaning solution (chemical solution) used in the cleaning process, hot water at 50 ° C to 90 ° C and / Alternatively, even when an aqueous solution containing 0.05% by weight or more and 0.5% by weight or less of sodium hypochlorite or 0.4% by weight or more and 4% by weight or less of sodium hydroxide is used, the film is deteriorated. Can be minimized. Therefore, the method for producing fruit liquor according to the present invention is a method having excellent filtration performance, its resilience, chemical resistance, and a long life. Specifically, since the porous film used in the filtration / clarification step in the method for producing fruit wine according to the present invention has high porous communication, the chromaticity component of fruit wine is less adsorbed on the film, and before and after filtration. The change in chromaticity is 25% or less, and the removal rate of the starch component is more than 95%. Further, even when an aqueous sodium hydroxide solution having a relatively low concentration of 4% by weight is used as the cleaning liquid in the cleaning step, the water permeability of the porous membrane can be sufficiently restored.

This is an example of an SEM image of a cross section of a porous membrane used in the filtration / clarification step in the method for producing fruit wine of the present embodiment (black portion indicates resin, white portion indicates pores (opening)). In the SEM image of the membrane cross section in the film thickness direction orthogonal to the inner surface of the porous membrane used in Example 1, the visual field including the inner surface, the visual field including the outer surface of the membrane, and the space between these visual fields, etc. 6 is a histogram showing the ratio (%) of the total area of the resin portion having a predetermined area to the total area of the resin portion in each region (circles 1 to 4) of a total of 4 visual fields of 2 visual fields photographed at intervals. In the SEM image of the membrane cross section in the film thickness direction orthogonal to the inner surface of the porous membrane used in Example 2, the visual field including the inner surface, the visual field including the outer surface of the membrane, and the space between these visual fields, etc. 6 is a histogram showing the ratio (%) of the total area of the resin portion having a predetermined area to the total area of the resin portion in each region (circles 1 to 4) of a total of 4 visual fields of 2 visual fields photographed at intervals. In the SEM image of the membrane cross section in the film thickness direction orthogonal to the inner surface of the porous membrane used in Example 3, the visual field including the inner surface, the visual field including the outer surface of the membrane, and the space between these visual fields, etc. 6 is a histogram showing the ratio (%) of the total area of the resin portion having a predetermined area to the total area of the resin portion in each region (circles 1 to 4) of a total of 4 visual fields of 2 visual fields photographed at intervals. In the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film used in Comparative Example 3, the field of view including the inner surface, the field of view including the outer surface of the film, and the space between these fields of view, etc. 6 is a histogram showing the ratio (%) of the total area of the resin portion having a predetermined area to the total area of the resin portion in each region (circles 1 to 4) of a total of 4 visual fields of 2 visual fields photographed at intervals.

Hereinafter, embodiments of the present invention (hereinafter, also referred to as the present embodiment) will be described in detail. The present invention is not limited to the present embodiment.

<Manufacturing method of fruit wine>
The method for producing fruit wine of the present embodiment is as follows:
Fermentation step of fermenting fruits to obtain fruit liquor containing aggregates of starch components; and passing the fruit liquor obtained in the fermentation step through a porous membrane composed of a resin having a three-dimensional network structure. A filtration / clarification step that separates the filtrate from the aggregates of the starch components;
It is a method of producing fruit liquor containing
In the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film, the visual field including the inner surface, the visual field including the outer surface of the film, and the visual fields between these visual fields were photographed at equal intervals. Total of visual fields In each region of the four visual fields, the total area of the resin portion having an area of 1 μm ² or less is 70% or more of the total area of the resin portion, and
When the absorbance of fruit wine before the filtration / clarification step is X1 and the absorbance of fruit wine after the filtration / clarification step is X2 at an arbitrary wavelength of 250 nm to 650 nm, X2 / X1 ≧ 0.75. Satisfy the relationship,
It is characterized by that.
It is preferable that X2 / X1 ≧ 0.85, and more preferably X2 / X1 ≧ 0.9.
The shape of the porous membrane is not particularly limited and may be a flat membrane, a tubular membrane, or a hollow fiber membrane, but from the viewpoint of space saving of the filtration device, that is, the membrane area per unit volume of the membrane module is increased. Hollow fiber membranes are preferred because they can be used.

As a filtration step in the method for producing fruit liquor of the present embodiment, for example, fruit liquor (processed liquid) containing agglomerates of starch components aggregated by fermentation in the hollow portion (inner surface) of the porous hollow fiber membrane is used. It may be a so-called internal pressure type filtration step in which the liquid is supplied, passed through the film thickness (thickness) portion of the porous hollow fiber membrane, and the liquid exuded from the outer surface of the porous hollow fiber membrane is taken out as a filtrate. Even in the so-called external pressure type filtration step, in which the liquid to be treated is supplied from the outer surface of the porous hollow fiber membrane and the filtrate exuded from the inner surface of the porous hollow fiber membrane is taken out through the hollow portion. Good. In addition, examples of the types of fruit liquor include, but are not limited to, red wine, white wine, cider (apple liquor), anzu liquor, yuzu liquor, and plum wine. Further, the clarification of soft drinks that do not include the brewing process is not limited.
In the present specification, the term "inside of a porous membrane" refers to a film thickness (thickness) portion in which a large number of pores are formed.

Preferably, the method for producing fruit wine of the present embodiment further includes a cleaning step of passing or immersing a cleaning liquid in the porous membrane to clean the inside of the porous membrane after the filtration / clarification step. The cleaning liquid can be hot water at 50 ° C. to 90 ° C. (hereinafter, also referred to as hot water).
More preferably, in the method for producing fruit liquor of the present embodiment, after the filtration / clarification step, a cleaning step of passing or immersing the cleaning solution in the porous membrane to clean the inside of the porous membrane is further performed. An aqueous solution (hereinafter, also referred to as a chemical solution) containing 0.05% by weight or more and 0.5% by weight or less of sodium hypochlorite or 0.4% by weight or more and 4% by weight or less of sodium hydroxide. Can be. In the above cleaning step, it is preferable to perform chemical solution cleaning after hot water cleaning.
The cleaning step can include a cleaning liquid step of cleaning with the cleaning liquid and a rinsing step of rinsing with rinsing water for removing the remaining cleaning liquid component. When the cleaning liquid is hot water, the temperature of the hot water can be preferably 55 ° C. or higher and 85 ° C. or lower, more preferably 60 ° C. or higher and 80 ° C. or lower. When the cleaning liquid is the chemical solution, the temperature of the chemical solution can be preferably 15 ° C. or higher and 35 ° C. or lower, and more preferably 20 ° C. or higher and 35 ° C. or lower. The concentration of sodium hydroxide in the chemical solution is more preferably 0.7% by weight or more and 4% by weight or less, and further preferably 1% by weight or more and 4% by weight or less. The concentration of sodium hypochlorite in the chemical solution is more preferably 0.1% by weight or more and 0.5% by weight or less, and further preferably 0.2% by weight or more and 0.5% by weight or less. In the cleaning step, for example, deposits are deposited from the filtration surface (stock solution side surface) of the porous membrane by passing the cleaning solution in the direction opposite to the flow direction of the fruit liquor in the filtration step, that is, from the filtrate side to the stock solution side. Examples thereof include reverse pressure water washing that separates and removes (insoluble components), and air scrubbing that shakes the porous membrane with air to shake off the insoluble components adhering to the porous membrane. The amount of rinsing water used in the rinsing step, it is preferable that the porous film per unit area 100L / m ² or less of, and more preferably at 50L / m ² or less. Further, it is preferable that the chlorine concentration in the filtrate after restarting the filtration step after the rinsing step is 0.1 ppm or less and the pH of the filtrate is 8.6 or less.
A filtration aid may be added in advance to the undiluted solution before the filtration / clarification step. Examples of the filtration aid include activated carbon, polyvinylpolypyrrolidone (PVPP), colloidal silica, bentonite and the like. The concentration at the time of addition depends on the type of the stock solution, but can be appropriately adjusted between about 50 ppm and 5000 ppm. If the concentration at the time of addition is too low, the aggregation effect may not be sufficient. In addition, if the concentration at the time of addition is too high, it may adversely affect the filtration. The size of the filtration aid depends on the substance to be adsorbed, but one that is sufficiently large in the pores of the hollow fiber membrane, is hard to be clogged, and is hard to scratch the surface of the hollow fiber membrane is preferably used.
The structure, material (material), and production method of the porous membrane used in the filtration step in the method for producing fruit wine of the present embodiment will be described in detail below.

<Porous membrane>
The porous film is defined as a field of view including the inner surface, a field of view including the outer surface of the film, and between these fields in an SEM image of a film cross section in a film thickness direction orthogonal to the inner surface of the porous film. The total area of the resin part having an area of 1 μm ² or less is 70% or more with respect to the total area of the resin part in each region of a total of 4 visual fields of 2 visual fields photographed at intervals; in each region. The total area of the resin part having an area of 10 μm ² or more is 15% or less of the total area of the resin part; in each region, the total area of the resin part having an area of 1 μm ² or less. However, the total area of the resin part having an area of 10 μm ² or more is 15% or less with respect to the total area of the resin part, which is 70% or more with respect to the total area of the resin part; Is one of. Preferred porous membranes in the respective regions, the total area of the resin portion having an area of 1 [mu] m ² or less, is 70% or more of the total area of the resin portion, an area of less than 1 [mu] m ² Ultra 10 [mu] m ² The total area of the resin part is 15% or less of the total area of the resin part, and the total area of the resin part having an area of 10 μm ² or more is the total area of the resin part. It is less than 15%.

FIG. 1 is an example of an SEM image of a cross section of a porous membrane used in the filtration / clarification step in the method for producing fruit wine of the present embodiment. Such an SEM image is a field of view including the inner surface, a field of view including the outer surface of the film, and between these fields of view in the SEM image of the membrane cross section in the film thickness direction orthogonal to the inner surface of the hollow yarn porous film. An image obtained by binarizing an SEM image photograph obtained by photographing a predetermined field of view in the area closest to the inside and the area closest to the inside among the areas of a total of 4 fields of view of 2 fields taken at equal intervals. is there.
In each of the regions, the difference in the presence distribution of the resin portion between the cross section in the film thickness direction orthogonal to the inner surface of the hollow fiber porous membrane and the cross section parallel to the inner surface, that is, the pores. The anisotropy of communication is virtually negligible.
In the present specification, the term "resin portion" is a dendritic skeleton portion having a three-dimensional network structure composed of resin, which forms a large number of pores in a porous membrane. The black portion in FIG. 1 is the resin portion, and the white portion is the hole.
Inside the porous membrane, communication holes that communicate while bending from the inside to the outside of the membrane are formed, and the inside of the SEM image of the membrane cross section in the film thickness direction orthogonal to the inner surface of the porous membrane. The total area of the resin portion having an area of 1 μm ² or less in each region of the visual field including the surface, the visual field including the outer surface of the film, and the two visual fields photographed at equal intervals between the two visual fields. However, if it is 70% or more of the total area of the resin portion, the pores have high communication properties (that is, the presence ratio of the communication holes inside the membrane is high), and the flux of the liquid to be treated (water permeability, (Water permeability), the water permeability retention rate after washing is high, and damage to the membrane after washing with a chemical solution, which is an index of tensile elongation at break, is also reduced. However, if the total ratio of the total area of the resin portion having an area of 1 μm ² or less to the total area of the resin portion is too high, a tree having a three-dimensional network structure composed of resin that forms a large number of pores in the porous film. Since the skeleton portion is too thin, the total area of the resin portion having an area of 1 μm ² or less is 70% or more of the total area of the resin portion, and the total area is more than 1 μm ² . It is preferable that the total area of the resin part having an area is 2% or more and 30% or less with respect to the total area of the resin part, and the total area of the resin part having an area of 10 μm ² or more is the resin. more preferably those present in more than 15% of the total area of the parts, 1 [mu] m ² total area of the resin portion having an area of less than super 10 [mu] m ² is located at less than 15% relative to the total area of the resin portion Moreover, it is more preferable that the total area of the resin portion having an area of 10 μm ² or more is 2% or more and 15% or less with respect to the total area of the resin portion. If the total area of the resin portion having an area of more than 1 μm ² is 2% or more and 30% or less with respect to the total area of the resin portion, the dendritic skeleton portion of the three-dimensional network structure composed of the resin is formed. Since it is not too thin, the strength of the porous film and the tensile elongation at break can be appropriately maintained.

2 to 5 show the inner surface in the SEM image of the membrane cross section in the film thickness direction orthogonal to the inner surface of the porous membrane used in Example 1, Example 2, Example 3, and Comparative Example 3, respectively. Predetermined with respect to the total area of the resin portion in each region (circles 1 to 4) of a total of 4 visual fields (rounds 1 to 4) of the visual field including, the visual field including the outer surface of the film, and 2 visual fields photographed at equal intervals between these visual fields. It is a histogram which shows the ratio (%) of the total area of the resin part which has an area. In FIG. 1, the resin portion appears in granular form. In FIGS. 2 to 5, the area of each of the granular resin portions is measured, and the area ratio of the area ratio of the granular resin portion to the total area of the total resin portion in the visual field of a predetermined size in each region is used as a histogram. Shown. Circles 1 in FIGS. 2 to 5 indicate a field of view including the inner surface, a field of view including the outer surface of the film, and these fields of view in the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film. The number of the region closest to the innermost side is the number of the region closest to the innermost side, and the circle 4 is the number of the region closest to the innermost side, out of the total four fields of view of the two fields of view taken at equal intervals. For example, Example 1 circle 1 is a histogram when a visual field of a predetermined size in the innermost region of the porous hollow fiber membrane of Example 1 is photographed. The method for measuring the area distribution of the resin portion in each region of the porous hollow fiber membrane will be described later.

The surface aperture ratio of the porous membrane is preferably 25 to 60%, more preferably 25 to 50%, and even more preferably 25 to 45%. When the surface aperture ratio on the side in contact with the liquid to be treated is 25% or more, the deterioration of the water permeability due to clogging and scratching of the film surface is reduced, so that the filtration stability can be improved. On the other hand, if the surface aperture ratio is high and the pore diameter is too large, the required separation performance may not be exhibited. Therefore, the average pore diameter of the porous membrane is preferably 100 to 700 nm, more preferably 100 to 600 nm. When the average pore diameter is 100 to 700 nm, the separation performance is sufficient and the pore communication can be ensured. The methods for measuring the surface aperture ratio and the average pore diameter will be described later.

The film thickness of the porous film is preferably 80 to 1,000 μm, more preferably 100 to 300 μm. When the film thickness is 80 μm or more, the strength of the film can be ensured, while when the film thickness is 1000 μm or less, the pressure loss due to the film resistance becomes small.

Examples of the shape of the porous hollow fiber membrane include an annular single-layer membrane, but a multilayer film having different pore diameters between the separation layer and the support layer that supports the separation layer may be used. Further, the inner surface and the outer surface of the film may have irregular cross-sectional structures such as having protrusions.

(Material of porous membrane (material))
The resin constituting the porous film is preferably a thermoplastic resin, and a fluororesin is more preferable. Examples of the fluororesin include vinylidene fluoride resin (PVDF), chlorotrifluoroethylene resin, tetrafluoroethylene resin, ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-monochromelotrifluoroethylene copolymer (ECTFE), and hexa. At least one selected from the group consisting of fluoropropylene resins and mixtures of these resins can be mentioned.
Examples of the thermoplastic resin include polyolefins, copolymers of olefins and halogenated olefins, halogenated polyolefins, and mixtures thereof. Examples of the thermoplastic resin include polyethylene (PE), polypropylene, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride (which may contain a domain of hexafluoropropylene), and the like. Can be mentioned. These resins are excellent as a film material because they are thermoplastic and therefore easy to handle and tough. Among these, vinylidene fluoride resin, tetrafluoroethylene resin, hexafluoropropylene resin or a mixture thereof, homopolymers or copolymers of ethylene, tetrafluoroethylene and chlorotrifluoroethylene, or mixtures of homopolymers and copolymers are mechanical. It is preferable because it has excellent strength and chemical strength (chemical resistance) and good moldability. More specifically, fluororesins such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, and ethylene-chlorotrifluoroethylene copolymer can be mentioned.

The porous membrane may contain components (impurities, etc.) other than the thermoplastic resin up to about 5% by mass. For example, a solvent used in producing a porous membrane is included. As will be described later, the first solvent (hereinafter, also referred to as non-solvent) used as a solvent in the production of the porous membrane, the second solvent (hereinafter, also referred to as good solvent or poor solvent), or both are included. .. These solvents can be detected by thermal decomposition GC-MS (gas chromatography-mass spectrometry).

The first solvent is sebacic acid ester, citric acid ester, acetyl citric acid ester, adipic acid ester, trimellitic acid ester, oleic acid ester, palmitic acid ester, stearic acid ester, phosphoric acid ester, carbon number 6 or more and 30 or less. It can be at least one selected from the group consisting of the ester of the ester and the epoxidized vegetable oil.
The second solvent is different from the first solvent in that it contains sebacic acid ester, citric acid ester, acetyl citric acid ester, adipic acid ester, trimellitic acid ester, oleic acid ester, palmitic acid ester, stearic acid ester, and phosphorus. It can be at least one selected from the group consisting of acid esters, fatty acids having 6 to 30 carbon atoms, and epoxidized vegetable oils. Examples of fatty acids having 6 to 30 carbon atoms include capric acid, lauric acid, and oleic acid. Examples of the epoxidized vegetable oil include epoxy soybean oil and epoxidized linseed oil.
The first solvent is a first mixed solution in which the ratio of the thermoplastic resin to the first solvent is 20:80, and even if the temperature of the first mixed solution is raised to the boiling point of the first solvent, the first solvent is thermoplastic. It is preferable that the resin is a non-solvent that does not uniformly dissolve in the first solvent.
The second solvent is a second mixed solution in which the ratio of the thermoplastic resin to the second solvent is 20:80, and the temperature of the second mixed solution is higher than 25 ° C. and lower than the boiling point of the second solvent. It is preferable that the thermoplastic resin is a good solvent that is uniformly dissolved in the second solvent at such a temperature.
The second solvent is a second mixed solution in which the ratio of the thermoplastic resin to the second solvent is 20:80, and when the temperature of the second mixed solution is 25 ° C., the thermoplastic resin is uniform with the second solvent. It is more likely that the thermoplastic resin is a poor solvent that does not dissolve in the second solvent and the temperature of the second mixed solution is higher than 100 ° C. and lower than the boiling point of the second solvent. preferable.

Further, in the filtration / clarification step in the method for producing fruit wine of the present embodiment, a porous hollow fiber membrane using polyvinylidene fluoride (PVDF) as a thermoplastic resin is used as a first solvent (non-solvent). Can be used.
In this case, the first solvent is sebacic acid ester, citric acid ester, acetyl citric acid ester, adipic acid ester, trimellitic acid ester, oleic acid ester, palmitic acid ester, stearic acid ester, phosphoric acid ester, carbon number 6 The first mixture in the first mixture, which is at least one selected from the group consisting of 30 or less fatty acids and epoxidized vegetable oils and has a ratio of polyvinylidene fluoride to the first solvent of 20:80. Even if the temperature of the liquid is raised to the boiling point of the first solvent, the polyvinylidene fluoride can be a non-solvent that does not uniformly dissolve in the first solvent. As the non-solvent, bis2-ethylhexyl adipate (DOA) is preferable.
Further, the porous hollow fiber membrane may contain a second solvent different from the first solvent. In this case, the second solvent is sebacic acid ester, citric acid ester, acetyl citric acid ester, adipic acid ester, trimellitic acid ester, oleic acid ester, palmitic acid ester, stearic acid ester, phosphoric acid ester, carbon number 6 A second mixture in a second mixture having a ratio of polyvinylidene fluoride and a second solvent of 20:80, which is at least one selected from the group consisting of 30 or less fatty acids and epoxidized vegetable oils. It is preferable that the temperature of the liquid is higher than 25 ° C. and the polyvinylidene fluoride is uniformly dissolved in the second solvent at any temperature below the boiling point of the second solvent. Further, in the second solvent, when the temperature of the second mixed solution is 25 ° C., polyvinylidene fluoride does not dissolve uniformly in the second solvent, and the temperature of the second mixed solution is higher than 100 ° C. and the second solvent is used. It is more preferable that the polyvinylidene fluoride is a poor solvent that is uniformly dissolved in the second solvent at any temperature below the boiling point of. As the poor solvent, tributyl acetylcitrate (ATBC) is preferable.

(Physical properties of porous membrane)
The initial value of the tensile elongation at break of the porous membrane is preferably 60% or more, more preferably 80% or more, still more preferably 100% or more, and particularly preferably 120% or more. The method for measuring the tensile elongation at break will be described later.

From a practical point of view, the compressive strength of the porous membrane is preferably 0.2 MPa or more, more preferably 0.3 to 1.0 MPa, and even more preferably 0.4 to 1.0 MPa.

<Manufacturing method of porous membrane>
Hereinafter, a method for producing a porous hollow fiber membrane will be described. However, the method for producing the porous hollow fiber membrane used in the filtration / clarification step in the method for producing fruit wine of the present embodiment is not limited to the following production methods.
The method for producing a porous hollow fiber membrane used in the filtration / clarification step in the method for producing fruit liquor of the present embodiment includes (a) a step of preparing a melt-kneaded product and (b) spinning a melt-kneaded product having a multiple structure. It can include a step of obtaining a hollow fiber membrane by supplying it to a nozzle and extruding a melt-kneaded product from the spinning nozzle, and (c) a step of extracting a plasticizer from the hollow fiber membrane. If the melt-kneaded product contains an additive, the step (c) may be followed by the step (d) of extracting the additive from the hollow fiber membrane.

The concentration of the thermoplastic resin in the melt-kneaded product is preferably 20 to 60% by mass, more preferably 25 to 45% by mass, and further preferably 30 to 45% by mass. If this value is 20% by mass or more, the mechanical strength can be increased, while if it is 60% by mass or less, the water permeability can be increased. The melt-kneaded product may contain additives.
The melt-kneaded product may be composed of two components of a thermoplastic resin and a solvent, or may be composed of three components of a thermoplastic resin, an additive, and a solvent. The solvent includes at least a non-solvent, as described below.
As the extractant used in the step (c), it is preferable to use a liquid such as methylene chloride or various alcohols, which is insoluble in thermoplastic resins but has a high affinity with the plasticizer.
When a melt-kneaded product containing no additive is used, the hollow fiber membrane obtained through the step (c) may be used as the porous hollow fiber membrane. When a porous hollow fiber membrane is produced using a melt-kneaded product containing an additive, (d) the additive is extracted and removed from the hollow fiber membrane after the step (c) to obtain a porous hollow fiber membrane. It is preferable to go through further steps. As the extractant in the step (d), it is preferable to use a liquid that can dissolve hot water or additives such as acid and alkali but does not dissolve the thermoplastic resin.

Inorganic substances may be used as additives. The inorganic substance is preferably an inorganic fine powder. The primary particle size of the inorganic fine powder contained in the melt-kneaded product is preferably 50 nm or less, more preferably 5 nm or more and less than 30 nm. Specific examples of the inorganic fine powder include silica (including fine powder silica), titanium oxide, lithium chloride, calcium chloride, organic clay and the like, and among these, fine powder silica is preferable from the viewpoint of cost. The above-mentioned "primary particle size of inorganic fine powder" means a value obtained from the analysis of electron micrographs. That is, first, a group of inorganic fine powders is pretreated by the method of ASTM D3849. Then, the diameters of 3000 to 5000 particles captured in the transmission electron micrograph are measured, and the primary particle size of the inorganic fine powder can be calculated by arithmetically averaging these values.
By identifying the element existing in the inorganic fine powder inside the porous hollow fiber membrane by fluorescent X-ray or the like, the material of the existing inorganic fine powder can be identified.
When an organic substance is used as an additive, hydrophilicity can be imparted to the hollow fiber membrane by using a hydrophilic polymer such as polyvinylpyrrolidone or polyethylene glycol. Further, the viscosity of the melt-kneaded product can be controlled by using a highly viscous additive such as glycerin or ethylene glycol.

Next, the step (a) of preparing the melt-kneaded product in the method for producing the porous hollow fiber membrane of the present embodiment will be described in detail.
In the method for producing a porous hollow fiber membrane of the present embodiment, a non-solvent of a thermoplastic resin is mixed with a good solvent or a poor solvent. The mixed solvent after mixing is a non-solvent of the thermoplastic resin used. When a non-solvent is used as the raw material of the membrane in this way, a porous hollow fiber membrane having a three-dimensional network structure can be obtained. Although the mechanism of action is not always clear, it is considered that polymer crystallization is moderately inhibited and a three-dimensional network structure is likely to be formed by using a solvent in which a non-solvent is mixed and the solubility is lowered. .. For example, non-solvents and poor or good solvents are phthalates, sebacic acids, citrates, acetylcitrates, adipates, trimellitic acids, oleic acids, palmitates, stearate. , Phosphoric acid esters, fatty acids with 6 to 30 carbon atoms, various esters such as epoxidized vegetable oils, and the like.
A good solvent is a solvent that can dissolve a thermoplastic resin at room temperature, a solvent that cannot be dissolved at room temperature but can be dissolved at a high temperature is a poor solvent for the thermoplastic resin, and a solvent that cannot be dissolved even at a high temperature. Although it is called a non-solvent, a good solvent, a poor solvent, and a non-solvent can be determined as follows.
Put about 2 g of thermoplastic resin and about 8 g of solvent in a test tube, heat it to the boiling point of the solvent in steps of about 10 ° C with a block heater for test tubes, and mix the inside of the test tube with a spatula or the like to release the thermoplastic resin. Those that dissolve are good or poor solvents, and those that do not dissolve are non-solvents. A solvent that dissolves at a relatively low temperature of 100 ° C. or lower is determined to be a good solvent, and a solvent that does not dissolve unless the temperature is 100 ° C. or higher and a boiling point or lower is determined to be a poor solvent.
For example, when polyvinylidene fluoride (PVDF) is used as the thermoplastic resin and tributyl acetylcitrate (ATBC), dibutyl sebacate or dibutyl adipate is used as the solvent, PVDF is uniformly mixed with these solvents at about 200 ° C. Dissolve. On the other hand, when bis2-ethylhexyl adipate (DOA), diisononyl adipate, or bis2-ethylhexyl sebacate is used as the solvent, PVDF does not dissolve in these solvents even when the temperature is raised to 250 ° C.
When ethylene-tetrafluoroethylene copolymer (ETFE) is used as the thermoplastic resin and diethyl adipate is used as the solvent, ETFE is uniformly mixed and dissolved at about 200 ° C. On the other hand, when bis2-ethylhexyl adipate (DIBA) is used as the solvent, it does not dissolve.
Further, when ethylene-monochromelotrifluoroethylene copolymer (ECTFE) is used as the thermoplastic resin and triethyl citrate is used as the solvent, it dissolves uniformly at about 200 ° C., and when triphenylphosphorous acid (TPP) is used, it dissolves. do not do.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. The physical property values in Examples and Comparative Examples were obtained by the following methods.

(1) Outer diameter and inner diameter of the porous hollow fiber membrane The porous hollow fiber membrane was sliced thinly with a razor at a cross section orthogonal to the length direction, and the outer diameter and inner diameter were measured with a 100x magnifying glass. .. One sample was measured at 60 cut surfaces at intervals of 30 mm according to the length method, and the average values were taken as the outer diameter and inner diameter of the hollow fiber membrane.

(2) Electron Microscopy A porous hollow fiber membrane was cut into an annular shape with a cross section orthogonal to the length direction, stained with 10% phosphotungstate + osmium tetroxide, and embedded in an epoxy resin. Next, after trimming, the sample cross section was subjected to BIB processing to prepare a smooth cross section, which was subjected to conductive treatment to prepare a speculum sample. Using the electron microscope SU8000 series manufactured by HITACHI, the prepared microscope sample was used to obtain an electron microscope (SEM) image of the cross section of the film at an acceleration voltage of 1 kV at a magnification of 5,000 to 30,000 times, and a film thickness (thick part) cross section. Within each region (circles 1 to 4 in FIGS. 2 to 5) of the visual field including the inner surface of the film, the visual field including the outer surface of the film, and the two visual fields photographed at equal intervals between these visual fields. Was taken with a predetermined field of view. The magnification can be changed according to the average pore diameter, and specifically, when the average pore diameter is 0.1 μm or more, it is 5000 times, and when the average pore diameter is 0.05 μm or more and less than 0.1 μm, it is measured. When it was 10,000 times and the average pore size was less than 0.05 μm, it was set to 30,000 times. The size of the field of view was 2560 × 1920 pixels.
ImageJ was used for the image processing, and the SEM image taken was subjected to Thrashold processing (Image-Adjust-Treshold: Otsu method (selecting Otsu)) to binarize the hole portion and the resin portion. ..
Surface aperture ratio: The surface aperture ratio was measured by calculating the ratio of the resin portion and the hole portion of the binarized image.
Area distribution of resin part: Using ImageJ's "Analyze Particle" command (Analyz Partile: Size0.10-Infinity), the size of the binarized granular resin part contained in the captured SEM image was measured. .. When the total area of all resin parts included in the SEM image is ΣS and the area of the resin part of 1 μm ² or less is ΣS (<1 μm ² ), ΣS (<1 μm ² ) / ΣS is calculated to be 1 μm. The area ratio of the resin portion having an area of ² or less was calculated. Similarly, the area ratio of the resin portion having an area within a predetermined range was calculated.
Regarding noise removal during the binarization treatment, the resin portion having an area of less than 0.1 μm ² was removed as noise, and the resin portion having an area of 0.1 μm ² or more was analyzed. Further, the noise removal was performed by performing a median filter treatment (Process-Filters-Media: Radius: 3.0pixels).
In addition, the granular resin portion cut off at the edge of the SEM image was also measured. In addition, the treatment of "Incube Holes" (filling holes) was not performed. In addition, the process of correcting the shape of the "snowman" type to the "flat" type was not performed.
Average pore size: Measured using the ImageJ "Plugins-Bone J-Thickness" command. The space size was defined as the maximum circle size that fits in the void.

(3) Flux (water permeability, initial pure water flux)
After immersing the porous hollow fiber membrane in ethanol and repeating soaking in pure water several times, one end of the wet hollow fiber membrane having a length of about 10 cm is sealed, and an injection needle is inserted into the hollow portion of the other end. Inject pure water at 25 ° C from an injection needle in an environment of ° C at a pressure of 0.1 MPa, measure the amount of pure water permeating from the outer surface of the membrane, and use the following formula:
Initial pure water flux [L / m ² / h] = 60 × (permeated water amount [L]) / {π × (membrane outer diameter [m]) × (membrane effective length [m]) × (measurement time [min] )}
The pure water flux was determined and the water permeability was evaluated.
The "effective membrane length" refers to the net membrane length excluding the portion where the injection needle is inserted.

(4) Permeability retention rate during actual liquid filtration Next, (i) Pour pure water into the circulation tank, perform circulation filtration so that the differential pressure between membranes = 0.05 MPa, and collect permeated water for 1 minute. The initial water permeability was used.
Then, (ii) after draining the water in the pipe, the undiluted fruit liquor was put into the circulation tank and circulated and filtered so that the intermembrane differential pressure = 0.15 MPa.
Next, after draining the residual liquid of fruit wine in the (iii) pipe, pure water was put into the circulation tank, and the mixture was circulated and filtered so that the differential pressure between the membranes was 0.05 MPa, and washed with water.
Next, after draining the water in the (iv) pipe, the prepared chemical solution was put into the circulation container, membrane circulation filtration was performed, and the chemical solution was washed for 30 minutes. An aqueous solution prepared by mixing 0.2% by weight of sodium hypochlorite and 1% by weight of caustic soda was used as the chemical solution.
Next, (v) after cleaning the chemical solution, drain the chemical solution in the pipe, put pure water into the circulation tank, perform circulation filtration so that the differential pressure between the membranes = 0.05 MPa, and remove the permeated water that has come out. Repeated sampling at a timing of 10 L / m ² , washing was completed when the chlorine concentration of the permeated water became 0.1 ppm or less and the pH became 8.6 or less, and the amount of rinse water was recorded. Further, continuous circulation filtration was performed with the same intermembrane differential pressure, and permeated water was collected for 1 minute to obtain the water permeation amount, which was compared with the initial water permeation amount and used as the water permeation performance retention rate during actual liquid filtration.
Each parameter was calculated by the following formula:
Intermembrane differential pressure = {(input pressure) + (extrusion pressure)} / 2
Surface area in the membrane [m ² ] = π × (hollow fiber membrane inner diameter [m]) × (hollow fiber membrane effective length [m])
Membrane surface linear velocity [m / s] = 4 × (circulating water volume [m ³ / s]) / {π × (membrane inner diameter [m]) ² }. All operations were performed at 25 ° C. and a film surface linear velocity of 1.0 m / sec.

(5) Tensile breaking elongation (%)
Using the porous hollow fiber membrane as it is as a sample, the stretch elongation at break was calculated according to JIS K 7161. The load and displacement at the time of tensile break were measured under the following conditions.
Measuring equipment: Instron type tensile tester (AGS-5D manufactured by Shimadzu Corporation)
Distance between chucks: 5 cm
Tensile speed: 20 cm / min

(6) Absorbance UVmini-1240 manufactured by SHIMADZU was used for the measurement of absorbance. The scan range was set to 250 nm to 700 nm, and fruit wine before and after filtration was placed in a quartz cell for measurement. Two types of optical path lengths, 1 cm or 5 cm, were appropriately selected depending on the type of fruit wine and the dilution ratio. The liquid temperature was measured at 20 ° C. Prior to the measurement of fruit liquor before and after filtration, background measurement was performed with pure water in advance, and then the cells were co-washed with the sample solution three times before measurement. After the measurement, the color tone and color intensity of each sample solution were calculated from the absorbances at 420 nm, 520 nm, and 620 nm. The color tone referred to here is a value of (absorbance at 420 nm) / (absorbance at 520 nm), and is used as an index of the vividness of fruit wine. The color intensity is a value of (absorbance at 420 nm) + (absorbance at 520 nm) + (absorbance at 620 nm), and was used as an index indicating the color intensity of fruit wine.

(7) pH
HORIBA's pH METER F-22 was used to measure the pH of fruit wine. After calibration with a standard solution of pH = 4.01, 6.86, 9.18 before measurement, the pH of the fruit solution before and after filtration was measured at a solution temperature of 20 ° C.

(8) Sugar content A ATAGO pocket sugar content meter PAL-S was used to measure the sugar content of fruit wine. 0.5 mL of the sample solution was added dropwise to the stage, and the sugar content of the sample solution was measured at a solution temperature of 20 ° C.

(9) Turbidity A HACH 2100P TURBI DIMETER was used to measure the turbidity of fruit wine. 15 mL of the sample solution was placed in a glass cell, and the turbidity of the sample solution was measured at a solution temperature of 20 ° C.

(10) Viscosity A VISCOMATE viscometer MODEL VM-1G manufactured by Yamaichi Electric Co., Ltd. was used to measure the viscosity of fruit wine. 30 mL of the sample solution was placed in a 50 mL container glass beaker, and the viscosity of the sample solution was measured at a solution temperature of 20 ° C.

(11) Haze
The Haze Meter NDH4000 manufactured by Nippon Denshoku Industries Co., Ltd. was used to measure the haze of fruit wine. 20 mL of the sample solution was placed in a glass cell, and the cloudiness of the sample solution was measured at a solution temperature of 20 ° C.

(12) Alkali resistance test After the actual solution filtration described in (4) above, the porous hollow fiber membrane is cut to 10 cm, 20 of them are immersed in 500 ml of a 4% sodium hydroxide aqueous solution, and kept at 40 ° C. for 10 days. did. The tensile elongation at break of the film before and after immersion in sodium hydroxide was measured at n20, and the average value was calculated. The elongation retention rate after immersion in NaOH is calculated by the following formula:
Elongation retention after NaOH immersion = (tensile breaking elongation after immersion) / (tensile breaking elongation before immersion) x 100
And the alkali resistance was evaluated. The tensile elongation at break before immersion corresponds to the elongation at break before the cleaning step, and the elongation at break after immersion corresponds to the elongation at break after the cleaning step.
Further, after the above-mentioned actual liquid filtration, the washing step by immersing in the above-mentioned 4% sodium hydroxide aqueous solution was repeated 10 times. Then, the initial value of the tensile elongation at break (tensile elongation at break before immersion) is set to E0, and the value of the tensile breaking strength of the porous hollow fiber membrane after repeating the cleaning step 10 times is set to EX, and EX / E0 × 100 was calculated as "elongation retention rate after repeated washing for 10 cycles" to evaluate alkali resistance.
Further, after the above-mentioned actual liquid filtration, the hollow fiber membrane was immersed in a 4% aqueous sodium hydroxide solution and kept at 40 ° C. for 10 days. After immersion in sodium hydroxide, filtration is performed for 10 minutes at the same filtration pressure as when the above-mentioned initial pure water permeability was measured, and permeated water is collected for 2 minutes from the 8th to 10th minutes of filtration, and a washing step is performed. The amount of water permeation was used. The initial pure water permeability was LO (flux L0), the water permeability after the cleaning step was L1 (flux L1), and L1 / L0 × 100 was calculated as the water permeability retention rate after immersion in NaOH.
Further, after the above-mentioned actual liquid filtration, the washing step of immersing the hollow fiber membrane in the above-mentioned 4% sodium hydroxide aqueous solution was repeated 10 times. Then, filtration is performed for 10 minutes at the same filtration pressure as when the above-mentioned initial amount of pure water permeation is measured, and permeated water is collected for 2 minutes from the 8th to 10th minutes of filtration. did. The initial pure water permeability is LO (flux L0), the water permeability after the repeated cleaning step is LX (flux LX, X = 10), and LX / L0 × 100 is calculated as the “water permeability retention rate after 10 cycles of repeated cleaning”. did.

[Example 1]
40% by mass of PVDF resin (KF-W # 1000, manufactured by Kureha) as a thermoplastic resin, 23% by mass of fine powder silica (primary particle size: 16 nm), and bis2-ethylhexyl adipate (DOA) 27. A melt-kneaded product was prepared using 7% by mass and 9.3% by mass of tributyl acetylcitrate (ATBC, boiling point 343 ° C.) as a poor solvent. The temperature of the obtained molten mixture was 240 ° C. The obtained molten mixture was passed through a spinning nozzle having a double tube structure, a hollow filamentous extruded product was passed through an idle distance of 120 mm, and then solidified in water at 30 ° C., and a porous structure was obtained by a heat-induced phase separation method. Developed. The obtained hollow filamentous extruded product was taken up at a speed of 5 m / min and wound up in a skein. The wound hollow fiber extruded product was immersed in isopropyl alcohol to extract and remove DOA and ATBC, then immersed in water for 30 minutes to replace the hollow fiber membrane with water, and then 70 in a 20 mass% NaOH aqueous solution. The mixture was immersed at ° C. for 1 hour and then washed with water repeatedly to extract and remove fine silica powder to prepare a porous hollow fiber membrane.
Table 1 below shows the composition, production conditions, and various physical properties of the obtained porous membrane. The obtained porous hollow fiber membrane had a three-dimensional network structure. In addition, the membrane had high flux (water permeability) and high communication.

A filtration and clarification step was carried out using the obtained hollow fiber membrane. Red wine (Akita Winery) from Koyama Sauvignon was used as the treatment liquid. A filtration experiment system was constructed using the following instruments. For the liquid feed pump, Masterflex (registered trademark, model number 7523-60) manufactured by Cole Palmer was used. For the pump head, Masterflex (registered trademark) Easy Road (model number 7518-10) also manufactured by Cole Palmer was used. The liquid delivery tube used was Farmed (registered trademark) BPT pump tube (model number 06508-25) and Masterflex (registered trademark) silicon tube (model number 96400-16). A module with an effective film area of 120 cm ² and a total length of 130 mm was prepared and used for filtration evaluation.
After connecting the pump tube so that the lower part of the module is on the supply side, the upper part is on the circulation side, and the upper side nozzle is on the filtration side so that the undiluted solution can be introduced into the inner surface side of the hollow fiber membrane, 100 mL of the undiluted solution is placed in an ice cold bath. The inside of the module was washed together by circulating the liquid at a speed of 600 L / min with a liquid feed pump while cooling the temperature to 20 ° C or lower. After 10 minutes of co-washing, all circulating fluid was drained. After that, 2000 mL of the undiluted solution was cooled to 20 ° C. or lower in an ice-cooled bath, and the solution was pumped at a rate of 600 L / min. The filtration valve was opened so that the output pressure on the circulation side was 55 kPa, and cross-flow filtration was performed for 20 minutes. At that time, the filtrate was transferred to the undiluted solution tank and mixing was continued. After that, the filtration valve was opened so that the output pressure on the circulation side became 55 kPa, and cross-flow filtration was performed for 20 minutes. A total of 1900 mL of filtrate was collected in a graduated cylinder. After completion of filtration, the absorbance, pH, sugar content, turbidity, viscosity, and haze of the undiluted solution and the filtered solution were measured and evaluated.
When the absorbance of red wine before and after the filtration step was measured, the ratio of the absorbance before and after filtration was 0.98 at 420 nm, 0.98 at 520 nm, and 0.95 at 620 nm, as shown in Table 2 below. The ratio of color intensity before and after filtration was 0.99.
The water permeability retention rate during actual liquid filtration is 75%, the elongation retention rate after NaOH immersion is 80%, the water permeability retention rate after NaOH immersion is 99%, and the elongation after repeated cleaning for 10 cycles. The degree retention was 70%, and the water permeability retention after repeated washing for 10 cycles was 95%.
Further, in the measurement of the water permeability performance retention rate at the time of (4) actual liquid filtration, the rinse when the water washing is completed when the chlorine concentration of the permeated water becomes 0.1 ppm or less and the pH becomes 8.6 or less. The amount of water in the water was 40 (L / m ² ).

[Example 2]
40% by mass of ETFE resin (TL-081 manufactured by Asahi Glass Co., Ltd.) as a thermoplastic resin, 23% by mass of fine powder silica (primary particle size: 16 nm), and 18.5% by mass of bis2-ethylhexyl adipate (DOA) as a non-solvent. A melt-kneaded product was prepared using% and 18.5% by mass of diisobutyl adipate (DIBA) as a poor solvent. The temperature of the obtained molten mixture was 240 ° C. The obtained molten mixture was passed through a spinning nozzle having a double tube structure, a hollow filamentous extruded product was passed through an idle distance of 120 mm, and then solidified in water at 30 ° C., and a porous structure was obtained by a heat-induced phase separation method. Developed. The obtained hollow filamentous extruded product was taken up at a speed of 5 m / min and wound up in a skein. The wound hollow fiber extruded product was immersed in isopropyl alcohol to extract and remove DOA and DIBA, then immersed in water for 30 minutes to replace the hollow fiber membrane with water, and then 70 in a 20 mass% NaOH aqueous solution. The mixture was immersed at ° C. for 1 hour and then washed with water repeatedly to extract and remove fine silica powder to prepare a porous hollow fiber membrane.
Table 1 below shows the composition, production conditions, and various physical properties of the obtained porous membrane. The obtained porous hollow fiber membrane had a three-dimensional network structure. In addition, the membrane had high flux (water permeability) and high communication.
A filtration step was carried out using the obtained hollow fiber membrane. As the treatment liquid, red wine of Koyama Sauvignon was used as in Example 1. The filtration experiment method was carried out with the same specifications as in Example 1. When the absorbance of red wine before and after the filtration step was measured, the ratio of the absorbance before and after filtration was 0.98 at 420 nm, 0.98 at 520 nm, and 0.97 at 620 nm, as shown in Table 2 below. The ratio of color intensity before and after filtration was 1.00.
In addition, the water permeability retention rate during actual liquid filtration is 70%, the elongation retention rate after NaOH immersion is 98%, the water permeability retention rate after NaOH immersion is 100%, and the elongation after repeated washing for 10 cycles. The degree retention was 90%, and the water permeability retention after 10 cycles of repeated washing was 96%.
Further, in the measurement of the water permeability performance retention rate at the time of (4) actual liquid filtration, the rinse when the water washing is completed when the chlorine concentration of the permeated water becomes 0.1 ppm or less and the pH becomes 8.6 or less. The amount of water in the water was 35 (L / m ² ).

[Example 3]
As a thermoplastic resin 40% by mass of ECTFE resin (Halar901, manufactured by Solvay Specialty Polymers) as a thermoplastic resin, 23% by mass of fine powder silica (primary particle size: 16 nm), and triphenylphosphorous acid (TPP) 29 as a non-solvent. A melt-kneaded product was prepared using .6% by mass and 7.4% by mass of bis2-ethylhexyl adipate (DOA) as a poor solvent. The temperature of the obtained molten mixture was 240 ° C. The obtained molten mixture was passed through a spinning nozzle having a double tube structure, a hollow filamentous extruded product was passed through an idle distance of 120 mm, and then solidified in water at 30 ° C., and a porous structure was obtained by a heat-induced phase separation method. Developed. The obtained hollow filamentous extruded product was taken up at a speed of 5 m / min and wound up in a skein. The wound hollow fiber extruded product was immersed in isopropyl alcohol to extract and remove TPP and DOA, then immersed in water for 30 minutes to replace the hollow fiber membrane with water, and then 70 in a 20 mass% NaOH aqueous solution. The mixture was immersed at ° C. for 1 hour and then washed with water repeatedly to extract and remove fine silica powder to prepare a porous hollow fiber membrane.
Table 1 below shows the composition, production conditions, and various physical properties of the obtained porous membrane. The obtained porous hollow fiber membrane had a three-dimensional network structure. In addition, the membrane had high flux (water permeability) and high communication.
A filtration step was carried out using the obtained hollow fiber membrane. As the treatment liquid, unfiltered red wine (Akita Winery) of Koyama Sauvignon was used as in Example 1. The filtration experiment method was carried out with the same specifications as in Example 1. When the absorbance of red wine before and after the filtration step was measured, the ratio of the absorbance before and after filtration was 0.99 at 420 nm, 0.98 at 520 nm, and 0.98 at 620 nm, as shown in Table 2 below. The ratio of color intensity before and after filtration was 0.99.
The water permeability retention rate during actual liquid filtration is 80%, the elongation retention rate after NaOH immersion is 97%, and the water permeability retention rate after NaOH immersion is 98%, and the elongation after repeated cleaning for 10 cycles. The degree retention was 95%, and the water permeability retention after 10 cycles of repeated washing was 95%.
Further, in the measurement of the water permeability performance retention rate at the time of (4) actual liquid filtration, the rinse when the water washing is completed when the chlorine concentration of the permeated water becomes 0.1 ppm or less and the pH becomes 8.6 or less. The amount of water in the water was 50 (L / m ² ).

[Comparative Example 1]
The wine after the fermentation process was mixed with diatomaceous earth of Standard Supercell (manufactured by Celite) and filtered by a filter press manufactured by Naigai Brewery Co., Ltd. so that the pressure was 1.0 MPa. As the treatment liquid, red wine of Koyama Sauvignon was used as in Example 1. When the absorbance of red wine before and after the filtration step was measured, the ratio of the absorbance before and after filtration was 0.68 at 420 nm, 0.67 at 520 nm, and 0.64 at 620 nm, as shown in Table 2 below. The ratio of color intensity before and after filtration was 0.67.

[Comparative Example 2]
A film was formed in the same manner as in Example 1 except that the solvent was only ATBC, to obtain a hollow fiber membrane of Comparative Example 2. Table 1 below shows the composition, production conditions, and various physical properties of the obtained porous membrane. The obtained porous hollow fiber membrane had a spherulite structure. In addition, the film had a low flux and low communication.
A filtration step was carried out using the obtained hollow fiber membrane. As the treatment liquid, red wine of Koyama Sauvignon was used as in Example 1. The filtration experiment method was carried out with the same specifications as in Example 1. When the absorbance of red wine before and after the filtration step was measured, the ratio of the absorbance before and after filtration was 0.70 at 420 nm, 0.70 at 520 nm, and 0.69 at 620 nm, as shown in Table 2 below. The ratio of color intensity before and after filtration was 0.7.
Further, the water permeability retention rate during actual liquid filtration is 30%, the elongation retention rate after NaOH immersion is 30%, the water permeability retention rate after NaOH immersion is 150%, and the elongation after repeated washing for 10 cycles. The degree retention was 20%, and the water permeability retention after 10 cycles of repeated washing was 200%.
Further, in the measurement of the water permeability performance retention rate at the time of (4) actual liquid filtration, the rinse when the water washing is completed when the chlorine concentration of the permeated water becomes 0.1 ppm or less and the pH becomes 8.6 or less. The amount of water in the water was 140 (L / m ² ).

[Comparative Example 3]
A film was formed in the same manner as in Example 1 except that the fine silica was 0% and the solvent was only γ-butyrolactone, to obtain a hollow fiber membrane of Comparative Example 3. Table 1 below shows the composition, production conditions, and various physical properties of the obtained porous membrane. The obtained porous hollow fiber membrane had a spherulite structure. In addition, the flux was low and the film had low connectivity.
A filtration step was carried out using the obtained hollow fiber membrane. As the treatment liquid, red wine of Koyama Sauvignon was used as in Example 1. The filtration experiment method was carried out with the same specifications as in Example 1. When the absorbance of red wine before and after the filtration step was measured, the ratio of the absorbance before and after filtration was 0.68 at 420 nm, 0.68 at 520 nm, and 0.67 at 620 nm, as shown in Table 2 below. The ratio of color intensity before and after filtration was 0.68. Further, the water permeability retention rate during actual liquid filtration is 30%, the elongation retention rate after NaOH immersion is 30%, the water permeability retention rate after NaOH immersion is 160%, and the elongation after repeated washing for 10 cycles. The degree retention was 20%, and the water permeability retention after 10 cycles of repeated washing was 180%.
Further, in the measurement of the water permeability performance retention rate at the time of (4) actual liquid filtration, the rinse when the water washing is completed when the chlorine concentration of the permeated water becomes 0.1 ppm or less and the pH becomes 8.6 or less. The amount of water in the water was 150 (L / m ² ).

[Comparative Example 4]
A film was formed in the same manner as in Example 3 except that the solvent was only DOA, to obtain a hollow fiber membrane of Comparative Example 4. Table 1 below shows the composition, production conditions, and various physical properties of the obtained porous membrane. The obtained porous hollow fiber membrane had a spherulite structure. In addition, the flux was low and the film had low connectivity.
A filtration step was carried out using the obtained hollow fiber membrane. As the treatment liquid, red wine of Koyama Sauvignon was used as in Example 1. The filtration experiment method was carried out with the same specifications as in Example 1. When the absorbance of red wine before and after the filtration step was measured, the ratio of the absorbance before and after filtration was 0.61 at 420 nm, 0.60 at 520 nm, and 0.57 at 620 nm, as shown in Table 2 below. The ratio of color intensity before and after filtration was 0.6.

[Example 4]
The film formation conditions of the hollow fiber membrane were the same as those in Example 1. Table 3 below shows the composition, production conditions, and various physical properties of the obtained porous membrane. As the treatment liquid, red wine immediately after fermenting the concentrated juice obtained by blending multiple types was used as the undiluted solution. The filtration experiment method was carried out with the same specifications as in Example 1. Table 4 below shows the results of various analyzes before and after the filtration process.

[Comparative Example 5]
As the filtration method, diatomaceous earth filtration was selected as in Comparative Example 1. The same stock solution as in Example 4 was used as the treatment solution. The filtration experiment method was carried out with the same specifications as in Example 1. Table 2 below shows the results of various analyzes before and after the filtration process.

[Example 5]
The film formation conditions of the hollow fiber membrane were the same as those in Example 1. Table 3 below shows the composition, production conditions, and various physical properties of the obtained porous membrane. Riesling Forte unfiltered white wine (Asahimachi wine) was used as the undiluted solution. The filtration experiment method was carried out with the same specifications as in Example 1. Table 4 below shows the results of various analyzes before and after the filtration process.

[Comparative Example 6]
As the filtration method, diatomaceous earth filtration was selected as in Comparative Example 1. The same stock solution as in Example 5 was used as the treatment solution. The filtration experiment method was carried out with the same specifications as in Example 1. Table 4 below shows the results of various analyzes before and after the filtration process.

[Example 6]
The film formation conditions of the hollow fiber membrane were the same as those in Example 1. Table 3 below shows the composition, production conditions, and various physical properties of the obtained porous membrane. Unfiltered cider (Hirosaki Cider Kobo) using apples from Aomori prefecture was used as the undiluted solution. The filtration experiment method was carried out with the same specifications as in Example 1. Table 4 below shows the results of various analyzes before and after the filtration process.

[Comparative Example 7]
As the filtration method, diatomaceous earth filtration was selected as in Comparative Example 1. The same stock solution as in Example 6 was used as the treatment solution. The filtration experiment method was carried out with the same specifications as in Example 1. Table 4 below shows the results of various analyzes before and after the filtration process.

[Example 7]
The film formation conditions of the hollow fiber membrane were the same as those in Example 1. Table 3 below shows the composition, production conditions, and various physical properties of the obtained porous membrane. Kirin Beverage was used as the undiluted solution for the treatment solution. The filtration experiment method was carried out with the same specifications as in Example 1. Table 4 below shows the results of various analyzes before and after the filtration process.

[Comparative Example 8]
As the filtration method, diatomaceous earth filtration was selected as in Comparative Example 1. The same stock solution as in Example 7 was used as the treatment solution. The filtration experiment method was carried out with the same specifications as in Example 1. Table 4 below shows the results of various analyzes before and after the filtration process.

From the above results, it was found that a film having good communication properties has excellent filtration performance, chromaticity component permeability, chemical resistance, and a long life.

In the filtration / clarification step in the method for producing fruit liquor according to the present invention, the pores of the porous filtration membrane (from the inside of the membrane on the side to be treated to the outside of the membrane on the filtrate side) have good communication. Since a thin film is used, the decrease in color of fruit liquor before and after filtration is small, the removal rate of starch components is high, and the cleaning solution (chemical solution) used in the cleaning process is hot water at 50 ° C to 90 ° C and / Or even when an aqueous solution containing 0.05% by weight or more and 0.5% by weight or less of sodium hypochlorite or 0.4% by weight or more and 4% by weight or less of sodium hydroxide is used. Deterioration can be minimized. Therefore, the method for producing fruit liquor according to the present invention is a method having excellent filtration performance, chemical resistance, and long life.

Claims (20)

The following steps:
Fermentation step of fermenting fruits to obtain fruit liquor containing aggregates of starch components; and passing the fruit liquor obtained in the fermentation step through a porous membrane composed of a resin having a three-dimensional network structure. A filtration / clarification step that separates the filtrate from the aggregates of the starch components;
It is a method of producing fruit liquor containing
In the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film, the visual field including the inner surface, the visual field including the outer surface of the film, and the visual fields between these visual fields were photographed at equal intervals. Total of visual fields In each region of the four visual fields, the total area of the resin portion having an area of 1 μm ² or less is 70% or more of the total area of the resin portion, and
When the absorbance of fruit wine before the filtration / clarification step is X1 and the absorbance of fruit wine after the filtration / clarification step is X2 at an arbitrary wavelength of 250 nm to 650 nm, X2 / X1 ≧ 0.75. Satisfy the relationship,
A method for producing fruit wine, which is characterized by the fact that. The following steps:
Fermentation step of fermenting fruits to obtain fruit liquor containing aggregates of starch components; and passing the fruit liquor obtained in the fermentation step through a porous membrane composed of a resin having a three-dimensional network structure. A filtration / clarification step that separates the filtrate from the aggregates of the starch components;
It is a method of producing fruit liquor containing
In the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film, the visual field including the inner surface, the visual field including the outer surface of the film, and the intervals between these visual fields were photographed at equal intervals. Total of the visual fields In each region of the four visual fields, the total area of the resin portion having an area of 10 μm ² or more is 15% or less of the total area of the resin portion, and at an arbitrary wavelength of 250 nm to 650 nm. When the absorbance of the fruit liquor before the filtration / clarification step is X1 and the absorbance of the fruit liquor after the filtration / clarification step is X2, the relationship of X2 / X1 ≧ 0.75 is satisfied.
A method for producing fruit wine, which is characterized by the fact that. The following steps:
Fermentation step of fermenting fruits to obtain fruit liquor containing aggregates of starch components; and passing the fruit liquor obtained in the fermentation step through a porous membrane composed of a resin having a three-dimensional network structure. A filtration / clarification step that separates the filtrate from the aggregates of the starch components;
It is a method of producing fruit liquor containing
In the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film, the visual field including the inner surface, the visual field including the outer surface of the film, and the intervals between these visual fields were photographed at equal intervals. A resin having an area of 10 μm ² or more and 70% or more of the total area of the resin portion having an area of 1 μm ² or less in each region of the total four visual fields. The total area of the part is 15% or less of the total area of the resin part, and the absorbance of the fruit liquor before the filtration / clarification step at an arbitrary wavelength of 250 nm to 650 nm is X1, the filtration / When the absorbance of the fruit liquor after the clarification step is X2, the relationship of X2 / X1 ≧ 0.75 is satisfied.
A method for producing fruit wine, which is characterized by the fact that. The porous film is formed between a field of view including the inner surface, a field of view including the outer surface of the film, and between these fields of view in an SEM image of a film cross section in a film thickness direction orthogonal to the inner surface of the porous film. in each area of a total of four field of 2 field taken at regular intervals, the total area of the resin portion having an area of less than 1 [mu] m ² ultra 10 [mu] m ² is 15% or less relative to the total area of the resin portion, wherein Item 3. The method according to any one of Items 1 to 3. Any one of claims 1 to 4, wherein in the filtration / clarification step, a mixture of fruit wine and bentonite obtained in the fermentation step is passed through a porous membrane made of a resin having a three-dimensional network structure. The method described in the section. The method according to any one of claims 1 to 5, wherein the surface aperture ratio of the porous membrane is 25 to 60%. The method according to any one of claims 1 to 6, wherein the porous membrane is a hollow fiber membrane. The method according to any one of claims 1 to 7, wherein the resin constituting the porous film is a thermoplastic resin. The method according to claim 8, wherein the thermoplastic resin is a fluororesin. The fluororesin includes vinylidene fluoride resin (PVDF), chlorotrifluoroethylene resin, tetrafluoroethylene resin, ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-monochromelotrifluoroethylene copolymer (ECTFE), and hexa. The method according to claim 9, wherein the method is any one selected from the group consisting of a fluoropropylene resin and a mixture of these resins. The method according to claim 8, wherein the thermoplastic resin is polyethylene (PE). After the filtration / clarification step, a cleaning step of passing or immersing the cleaning liquid in the porous membrane to clean the inside of the porous membrane is further included, and the cleaning liquid is hot water at 50 ° C. to 90 ° C. The method according to any one of claims 1 to 11. After the filtration / clarification step, a cleaning step of passing or immersing the cleaning liquid in the porous membrane to clean the inside of the porous membrane is further included, and the cleaning liquid is 0.05% by weight or more and 0.5% by weight. The method according to any one of claims 1 to 11, which is an aqueous solution containing% or less sodium hypochlorite or 0.4% by weight or more and 4% by weight or less of sodium hydroxide. The claim that the relationship between the tensile elongation at break E0 of the porous membrane before the cleaning step and the tensile elongation at break E1 of the porous membrane after the cleaning step is E1 / E0 × 100 ≧ 80%. 12 or 13 according to the method. The tensile elongation at break E0 of the porous membrane before the cleaning step and the tensile elongation at break of the porous membrane after repeating the cleaning step X times (where X is an integer of 2 to 100). The method according to claim 12 or 13, wherein the relationship with the degree EX is EX / E0 × 100 ≧ 70%. Claim 12 or 13 that the relationship between the flux L0 of the porous membrane before the filtration / clarification step and the flux L1 of the porous membrane after the cleaning step is L1 / L0 × 100 ≧ 95%. The method described in. The flux L0 of the porous membrane before the filtration / clarification step and the flux LX of the porous membrane after repeating the cleaning step X times (where X is an integer of 2 to 100). The method according to claim 12 or 13, wherein the relationship is X / L0 × 100 ≧ 90%. The cleaning step according to any one of claims 12 to 17, wherein the cleaning step includes a cleaning liquid step of cleaning with the cleaning liquid and a rinsing step of rinsing with rinsing water for removing the remaining cleaning liquid component. the method of. The method according to claim 18, wherein the amount of rinse water used in the rinse step is 100 L / m ² or less per unit area of the porous membrane. 18 or 19, claim 18 or 19, wherein the chlorine concentration in the filtrate after restarting the filtration / clarification step after the rinsing step is 0.1 ppm or less, and the pH of the filtrate is 8.6 or less. The method described.