Method for producing leather, and leather precursor

Abstract

To provide a method for producing leather with low environmental load, and a leather precursor.SOLUTION: This method for producing leather involves: an immersion step of immersing a pelt in a treatment liquid including sugar and yeast of the genus Saccharomyces; and a first fermentation step of immersing the pelt in a treatment liquid and fermenting the same.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a method for making leather and to a leather precursor. [Background technology]

[0002] Leather is produced by washing rawhide, removing fat and hair, and then tanning it. In the process of processing rawhide into leather, it may be transported from the place where it was collected to a processing factory. When transporting to the processing factory, the rawhide is subjected to a preservative treatment such as salting with salt to prevent deterioration such as rotting. In the leather processing process, processing steps such as soaking, which removes salt from the rawhide (leather precursor), which is the preservative-treated rawhide, and liming, which removes hair and unnecessary protein from the rawhide, are carried out. These processing steps generate large amounts of wastewater containing salt and lime, which places a heavy burden on the environment.

[0003] Patent Document 1, which concerns a method for preserving rawhide using salt, points out the problems that a large amount of salt is required to preserve rawhide, and that wastewater discharged from storage buildings and tanneries is significantly contaminated by soluble salt. It also points out that it is difficult to remove salt from wastewater without incurring large costs, and that in some countries used salt is recognized as hazardous waste. It also points out that rawhide can be ruined by bacteria resistant to salt, and that the amount of salt required for short-term storage of rawhide is almost the same as that required for long-term storage.

[0004] Patent Document 2 points out the problem that in the leather manufacturing method, a large amount of sludge containing slaked lime and hair detached from the hide is generated and must be disposed of as alkaline sludge. In relation to this problem, Patent Document 2 discloses a leather manufacturing method capable of reducing the amount of sludge containing slaked lime, and slaked lime used therein. This leather manufacturing method includes a step of treating animal raw hides with slaked lime, and when manufacturing leather from the raw hides, the specific surface area of ​​the slaked lime is set within a predetermined range. Patent Document 2 discloses, as an example of the dehairing step in this leather manufacturing method, an example of a dehairing step in which five salted pig hides are soaked in water and lined, and then dehaired after completely removing salt, meat pieces, etc. In this dehairing process, the backed hide (total weight 23.5 kg), water (200% based on the backed hide), and slaked lime (2% based on the backed hide, 0.47 kg) are placed in a stainless steel drum and rotated while stirring, and sodium sulfide (2%) and a nonionic surfactant (0.3%) are added in that order while stirring, and then stirred overnight. Patent Document 2 also discloses an example of a re-liming process after the dehairing process. In this re-liming process, the grain side hide (total weight 18.8 kg), water (200% based on the hide), and slaked lime (1% based on the hide, 0.188 kg) are placed in the same drum as in the dehairing process and stirred, and then a nonionic surfactant (0.3%) is added, and then stirred for two days and nights.

[0005] Patent Document 3 discloses a method for preserving baked bakery products. The method includes a step of applying a solution containing a live leaven and / or live yeast onto the surface of the baked bakery product after a step of baking the dough. As an example of the yeast in this method, a Saccharomyces cerevisiae strain is mentioned. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 62-600 [Patent Document 2] JP 2000-45000 A [Patent Document 3] Special Publication No. 2023-504068 Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional leather manufacturing method, a large amount of salt is used to preserve rawhide, which is a large environmental burden. In addition, a large amount of lime is used in the intermediate process of processing rawhide, and waste liquid containing a large amount of lime is a large environmental burden. Therefore, it is desired to provide a leather manufacturing method and a leather precursor that are less environmentally burdensome.

[0008] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a method for producing leather and a leather precursor that have a low environmental impact. [Means for solving the problem]

[0009] In order to achieve the above object, the method for producing leather according to the present disclosure comprises: a soaking step of soaking the rawhide in a treatment solution containing sugar and yeast of the genus Saccharomyces; and a first fermentation step in which the rawhide is immersed in the treatment liquid and fermented.

[0010] In order to achieve the above object, the leather precursor according to the present disclosure comprises: The method includes the steps of: sugar, yeast of the genus Saccharomyces, and rawhide. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a method for producing leather and a leather precursor that have a low environmental impact. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a method for producing leather and a leather precursor according to an embodiment of the present disclosure will be described. First, an overview of the method for producing leather and the leather precursor according to the present embodiment will be described.

[0013] The method for manufacturing leather according to this embodiment includes a soaking step of soaking rawhide in a treatment solution containing sugar and yeast of the genus Saccharomyces, and a first fermentation step of soaking the rawhide in this treatment solution and fermenting it.

[0014] The leather precursor according to this embodiment contains sugar, yeast of the genus Saccharomyces, and rawhide.

[0015] According to the method for producing leather according to the present embodiment, it is possible to produce leather precursors and leather with reduced environmental impact.

[0016] The method for producing leather and the leather precursor according to this embodiment will be described in detail below.

[0017] As an example, the method for producing leather according to this embodiment may further include, in addition to the above-mentioned soaking step and first fermentation step, a dehydration step of dehydrating a first precursor obtained by fermenting rawhide in the fermentation step, a sugar addition step of attaching sugar to the surface of the first precursor after the dehydration step, a second fermentation step of fermenting the first precursor after the sugar addition step, a dehairing step of dehairing the second precursor obtained by fermenting the first precursor in the second fermentation step, and a dehairing step performed after the dehairing step.

[0018] The concept of the leather precursor according to this embodiment includes the first precursor and the second precursor before the dehairing step in each of the above steps.

[0019] In this embodiment, the rawhide may be a hide taken from an animal such as a cow, a buffalo, a pig, a wild boar, a goat, a sheep, a lizard, a snake, a crocodile, or a fish. The rawhide may be taken, for example, as a residue when the animal is slaughtered for meat processing. A certain amount of meat is allowed to be attached to the rawhide. Animal hair may remain on the front surface (body surface side, animal hair surface) of the rawhide. After initial washing, the rawhide is subjected to a soaking process described below.

[0020] During the initial cleaning, dirt adhering to the skin is removed, unnecessary parts such as the legs and tail are cut off, and meat and fat are removed using a fleshing machine or similar. A disinfectant may be used during the initial cleaning to prevent initial contamination or rapid spoilage.

[0021] The soaking step is a step of soaking the rawhide in a treatment solution. The treatment solution contains sugar and yeast of the genus Saccharomyces. The dispersion medium or solvent of the treatment solution may be water.

[0022] An example of a yeast of the genus Saccharomyces is Saccharomyces cerevisiae, which may be included in the so-called baker's yeast, glutinous rice yeast, and cassava yeast.

[0023] The yeast of the genus Saccharomyces used in the treatment liquid may be a mixture of yeasts of multiple origins. For example, 10 parts by weight of baker's yeast containing Saccharomyces cerevisiae may be mixed with another yeast containing Saccharomyces cerevisiae, such as glutinous rice yeast or cassava yeast, in a ratio of 1 to 5 parts by weight, preferably 3 parts by weight, and this mixture of yeasts of the genus Saccharomyces may be used in the treatment liquid.

[0024] The yeast serves as a fermenting bacterium in the first fermentation step and the second fermentation step described below. The yeast metabolizes sugar to cause alcoholic fermentation, which will be described later.

[0025] The sugar may be any sugar that can be fermented by the yeast. Examples of suitable sugars in this embodiment include glucose, fructose, and sucrose. The sugar does not need to be pure, and may be molasses, java sugar fructose, palm sugar fructose, tapioca sugar, granulated sugar, or the like.

[0026] The treatment liquid may be prepared by mixing water containing sugar with a starter, which is a mixture of yeast, a small amount of sugar and water, and pre-fermented.

[0027] The immersion of the rawhide in the treatment solution, i.e., the immersion step, may be carried out, for example, as follows.

[0028] First, the weight of the rawhide is measured after the initial washing. Next, it is pre-treated by soaking it in a pre-treatment solution (pH 8 to 9) containing soap or antibacterial (a cleaning agent with germicidal properties) and soda ash (sodium carbonate) for about 10 to 15 minutes.

[0029] A starter is prepared separately from the above pretreatment. The starter can be prepared by putting about 5 g of yeast and about 10 g of sugar into a container containing 30 ml to 70 ml, preferably about 40 ml to 60 ml, of warm water (e.g., 40° C. to 60° C.), sealing the container, and fermenting for 15 to 20 minutes or until the liquid in the container starts to bubble.

[0030] Then, water of the same weight as the rawhide, specifically, water of 50% to 100% of the weight of the rawhide (at room temperature, for example, 25°C) is weighed out, and sugar of 3% to 30% of the weight of the rawhide is added to this water and dissolved to prepare a sugar solution. For example, granulated sugar is used as the sugar. Furthermore, the entire amount of the above-mentioned starter is added to this sugar solution to prepare a treatment liquid. It is preferable to stir the treatment liquid after adding the starter. The amount of water used in preparing the treatment liquid is preferably 80% to 120% of the weight of the rawhide. The amount of sugar used in preparing the treatment liquid is preferably 5% or more of the weight of the rawhide.

[0031] The rawhide after pretreatment is immersed in the treatment solution prepared as described above. The rawhide may be immersed in the treatment solution in a rotating drum. The drum may be, for example, a cylindrical drum with a horizontal axis and a diameter of about 2 m to 4 m. An example of the rotation speed of the drum is 5 to 30 revolutions per minute, preferably 6 to 10 revolutions per minute.

[0032] The first fermentation step is the first step of fermenting the rawhide immersed in the treatment solution. In the first fermentation step, the rawhide is kept immersed in the treatment solution. This allows the treatment solution to permeate the rawhide, while yeast grows in the rawhide, and fermentation progresses. Ethanol is produced in the rawhide through fermentation. That is, the first precursor is rawhide containing sugar and yeast of the genus Saccharomyces. The first precursor may also contain ethanol depending on the fermentation state.

[0033] In the first fermentation step, the rawhide is kept immersed in the treatment solution for 2 to 72 hours, preferably 3 to 6 hours, and more preferably 4 to 5 hours. In this embodiment, the rawhide that has undergone the first fermentation step is called the first precursor. By keeping the rawhide immersed in the treatment solution for 2 hours or more, the treatment solution is sufficiently permeated into the rawhide, making it easy for fermentation to proceed. By keeping the rawhide immersed in the treatment solution for 12 hours or more, fermentation is sufficiently proceeded in the rawhide.

[0034] The atmosphere of the space, such as a room or a warehouse, in which the first fermentation step is carried out may have a temperature of 15° C. or higher and 40° C. or lower and a relative humidity of 30% or higher and 80% or lower. The atmosphere preferably has a temperature of 15° C. or higher and 30° C. or lower and a relative humidity of 30% or higher and 80% or lower, and more preferably has a temperature of 20° C. or higher and 30° C. or lower and a relative humidity of 60% or lower.

[0035] The first precursor is in a state where bacteria that promote spoilage (hereinafter simply referred to as bacteria) are less likely to grow due to the ethanol produced by yeast metabolizing sugar and the proliferated yeast. That is, the first precursor is one in which the progression of spoilage is inhibited without the use of salt. Hereinafter, the inhibition of the progression of spoilage may be referred to as being preserved, etc. Furthermore, the inhibition of the progression of spoilage may be referred to as preserving, etc.

[0036] Since the first precursor is prevented from decaying as described above, it can withstand storage for several days to a week when raw hides are transported between factories. As described above, no salt is required in the production of the first precursor. Therefore, wastewater containing a large amount of salt is not generated in the production process of the first precursor.

[0037] In this embodiment, the first precursor may be further subjected to a second fermentation step, in which the first precursor is further fermented.

[0038] In order to carry out the second fermentation step, it is preferable to additionally supply sugar that the yeast metabolizes. In this embodiment, the first precursor may be subjected to the second fermentation step after carrying out a sugar addition step in which sugar is attached to the surface of the first precursor. The attachment of sugar to the surface of the first precursor may be carried out by sprinkling or applying sugar particles (powder or granules) to the surface of the first precursor. The attachment of sugar to the surface of the first precursor may also be carried out by applying a sugar paste in which sugar is dissolved at a high concentration to the surface of the first precursor. When using a sugar paste, the sugar concentration in the paste is preferably 40% by weight or more, more preferably 50% by weight or more.

[0039] The sugars that can be used in the second fermentation step are the same as those exemplified as the sugars that can be used in the treatment liquid in the first fermentation step.

[0040] The attachment of sugar to the surface of the first precursor may be carried out at least on either the front surface (epidermis, animal hair surface) or the back surface (dermis) of the hide. The attachment of sugar to the surface of the first precursor is preferably carried out on the back surface.

[0041] In the sugar addition step, an antibacterial agent may be added together with the sugar. When an antibacterial agent is added, it is sufficient to add the antibacterial agent in an amount of 0.3% by weight to 1% by weight based on the weight of the sugar. One example of the antibacterial agent is p-cresol.

[0042] In this embodiment, a dehydration step for dehydrating the first precursor may be performed prior to the second fermentation step. The dehydration of the first precursor in the dehydration step may be performed, for example, by a thumbing machine or a press machine. By squeezing out a certain amount of water from the first precursor in the dehydration step, it is possible to facilitate the attachment of sugar to the surface of the first precursor. Furthermore, the dehydration step can suppress the growth of unwanted bacteria. Furthermore, by attaching sugar to the first precursor after dehydration, the free water in the first precursor can be reduced, and the growth of unwanted bacteria can be suppressed. In other words, the dehydration step can provide better preservation.

[0043] In the sugar-adding step, sugar is attached to the surface of the first precursor in an amount of 10% to 30%, preferably 20% to 25%, of the rawhide by weight. Adding sugar to the first precursor in this ratio makes it easier for the sugar to be attached to the surface of the first precursor, is effective in inhibiting the growth of bacteria, and promotes fermentation in the second fermentation step to provide better preservation.

[0044] In the second fermentation step, the first precursor to which sugar is attached as described above is fermented. The fermentation in the second fermentation step may be carried out in a dry or normal humidity space. The second fermentation step may be carried out, for example, in a fixed factory or warehouse, or in a warehouse that doubles as a transport container such as a cargo container for a truck, train, ship, or airplane.

[0045] The atmosphere in the room or warehouse where the second fermentation step is carried out is preferably dry, specifically, the relative humidity is 30% or more and 70% or less. The humidity of the atmosphere is preferably 40% or more and 60% or less. The temperature of the space where the second fermentation step is carried out may be, for example, 20°C to 40°C. The temperature of the atmosphere is preferably 20°C or more and 30°C or less.

[0046] The period for carrying out the second fermentation step is preferably from 1 day to 50 days, more preferably from 3 days to 30 days.

[0047] In the second fermentation step, the first precursor may be stored by folding the surfaces to which sugar is attached, overlapping each other. Specifically, for example, the surfaces to which sugar is attached may be folded in half, and then folded again into a four-fold state. The folded first precursor may be stored in a pile. By folding the surfaces to which sugar is attached, overlapping each other, it is possible to prevent the sugar attached to the first precursor from falling off the surface of the first precursor, and suppress a decrease in the preservative effect.

[0048] In the second fermentation step, fermentation in the rawhide, i.e., the proliferation of yeast in the rawhide and the production of ethanol through the metabolism of the yeast, proceeds. In this embodiment, the rawhide after sugar is attached to the surface of the first precursor and fermentation in the second fermentation step is started is called the second precursor. That is, the second precursor is rawhide that contains sugar and yeast of the genus Saccharomyces, like the first precursor. The second precursor may also contain ethanol depending on the fermentation state.

[0049] The second precursor in the second fermentation step is extremely well preserved without the use of salt due to at least one of the effects of reducing free water by the addition of sugar, the effect of yeast proliferation, and the effect of ethanol produced by fermentation.

[0050] Since the second precursor is extremely well preserved as described above, the second precursor is suitable for long-term storage, for example, from 1 day to 50 days, and for long-term transportation, such as import and export from a rawhide producing country to a user country where the rawhide is processed into leather. As described above, no salt is required in the production of the second precursor. Therefore, wastewater containing a large amount of salt is not generated in the production process of the second precursor.

[0051] In the second fermentation step, if the rawhide has animal hair, the second precursor has the effect of making the animal hair more likely to fall off. Some of the animal hair falls off as the fermentation progresses in the second fermentation step. This makes the dehairing step, which will be described later, easier.

[0052] The dehairing step is a step of dehairing the second precursor. In the dehairing step, potassium hydroxide or sodium hydroxide in a weight of 0.3% to 1.0% and sodium sulfide in a weight of 0.8% to 2.0% based on the weight of the rawhide are added to the second precursor and stirred. The amount of potassium hydroxide or sodium hydroxide added is preferably 0.6% to 0.9% based on the weight of the rawhide. In the dehairing step, sodium hydroxide is preferably used. The amount of sodium sulfide added is preferably 0.8% to 1.50% based on the weight of the rawhide.

[0053] The stirring in the unhairing step may be carried out in a rotating drum, as in the immersion step. The drum rotates at a speed of 5 to 12 revolutions per minute, preferably 5 to 9 revolutions per minute, and more preferably 7 to 8 revolutions per minute. The stirring time is about 15 minutes. The stirring time is usually 10 minutes or more and 15 minutes or less. By such a unhairing step, the animal hair is completely separated from the hide (second precursor).

[0054] In the hair removal process of this embodiment, unlike the conventional technology, a large amount of water or a large amount of lime (slaked lime, calcium hydroxide) is not used. In the hair removal process of this embodiment, the use of lime is not required, and the so-called liming process in the conventional technology is not necessary. In other words, the hair removal process of this embodiment does not discharge a large amount of lime sludge as in the conventional technology, and has a small environmental impact. Furthermore, the hair removal process of this embodiment uses a small amount of sodium sulfide.

[0055] The desulfurization process is a process for removing sulfur content (sulfur groups) from the second precursor after the dehairing process. In the desulfurization process, an oxidizing agent is added to the second precursor in an amount of 0.8% to 2.0% by weight based on the weight of the rawhide, and the mixture is stirred. This removes sodium sulfide and other substances. The stirring may be performed in a rotating drum, as in the soaking process. The drum rotates at a speed of, for example, 5 to 12 revolutions per minute.

[0056] An example of an oxidizing agent that can be used in the desulfurization process is a peroxide such as H2S, Na2O2, Na2H3CO6 or H2O2.

[0057] The desulfurization step is carried out for, for example, 30 minutes to 60 minutes. Usually, about 45 minutes is sufficient for the desulfurization step. The desulfurization step does not need to be timed, and can be carried out until the odor of hydrogen sulfide gas disappears from the second precursor, or until the color of the liquid seeping out of the second precursor becomes light brown.

[0058] After the desulfurization step, a so-called dealkalization step is carried out in which potassium hydroxide and sodium hydroxide are removed from the third precursor using a mixture of weak acids such as acetic acid, citric acid, and formic acid. In this step, a bleaching agent such as sodium hydrogen sulfate may be used in combination, if necessary. The dealkalization step may be carried out in a drum subsequent to the previous step.

[0059] After the dealkalization step, the third precursor can be finished into leather by carrying out tanning, dyeing, etc.

[0060] In this way, it is possible to provide a method for producing leather and a leather precursor that have a low environmental impact and do not require the use of large amounts of salt to preserve rawhide or large amounts of lime or water for dehairing. EXAMPLES

[0061] Example 1 Cowhide was prepared as the rawhide. First, the rawhide was initially washed, weighed, and pretreated with soap and soda ash. In the following, when the weight of the rawhide is simply stated, it means the weight of the rawhide measured after the initial washing. Then, water (25°C) with an equal weight to the rawhide and granulated sugar (5%, 10%, 15%, and 20% of the weight of the rawhide) were placed in the container.

[0062] In parallel with the above, a starter was prepared by adding 10 g of yeast (Saccharomyces cerevisiae), 5 g of sugar, and 50 ml of warm water (50°C) to a separate container and fermenting for 20 minutes in a sealed container.

[0063] The prepared starters were added to the containers containing the rawhide and other materials, the contents of the containers were stirred, the lids were put on, and the containers were stored at room temperature to start fermentation of the four samples. The room temperature was generally 25°C to 35°C, and the relative humidity was 40% to 70%. After that, the condition of the rawhide was checked at regular intervals.

[0064] After one day, no hair loss was observed with the naked eye, and no hair loss occurred when the rawhide was pinched or rubbed with the fingertips.

[0065] After two days, the amount of hair that had fallen out had not changed from the first day. There had been a change in odor compared to the first day. The same change was observed in all four samples containing different amounts of sugar.

[0066] After three days, hair loss (hereinafter referred to as hair loss) was observed in thin-haired areas such as the abdomen in the samples containing 5%, 10%, and 15% sugar.

[0067] After four days, hair loss was observed evenly in the thin hair areas for all four samples containing different amounts of sugar.

[0068] After five days, all four samples showed uniform hair loss in the thin hair areas.

[0069] After six days, about 80% of the hair in each of the four samples was easily removable.

[0070] After 4 weeks, the odor of hydrogen sulfide gas and ammonia began to be detected, as well as odors indicative of the decomposition of keratin and globular proteins. The odor of alcohol also increased.

[0071] After seven weeks, complete hair loss was observed in all four samples, but there was also a decrease in the tear strength of the hide.

[0072] As described above, the rawhide fermented in the treatment solution, i.e., the first precursor, could be preserved and preserved for less than 7 weeks. In addition, after fermentation for a certain number of days (e.g., 3 days), the effect of promoting depilation was observed.

[0073] Example 2 Fermentation of the four samples was started in the same manner as in Example 1, and after 12 hours, the rawhide was squeezed and dehydrated using a press. The squeezing rate was 40%. The squeezing rate is the ratio (%) of the weight of the dehydrated water to the weight of the rawhide including water just before dehydration, which is taken as 100%.

[0074] After dehydration, the back side of each rawhide sample was evenly sprinkled with sugar (sucrose) in an amount of 20% by weight relative to the weight of the rawhide. Each sugar-sprinkled sample was folded in half with the sugar-sprinkled side facing each other, then folded in quarters again and stacked, and stored in a dry room (warehouse). The room temperature was generally between 20°C and 30°C, and the relative humidity was between 40% and 60%. After that, the condition of the rawhide was checked at regular intervals.

[0075] After one day, no hair loss was observed with the naked eye, and no hair loss occurred when the rawhide was pinched or rubbed with the fingertips.

[0076] After two days, the amount of hair that had fallen out had not changed from the first day. There had been a change in odor compared to the first day. The same change was observed in all four samples containing different amounts of sugar.

[0077] After three days, hair loss (hereinafter referred to as hair loss) was observed in thin-haired areas such as the abdomen in the samples containing 5%, 10%, and 15% sugar.

[0078] After four days, hair loss was observed evenly in the thin hair areas for all four samples containing different amounts of sugar.

[0079] After five days, all four samples showed uniform hair loss in the thin hair areas.

[0080] After six days, for all four samples, approximately 80% of the hair had fallen out easily, and approximately 95% of the hair was in a state that could be easily removed.

[0081] After 4 weeks, the odor of hydrogen sulfide gas and ammonia began to be detected, as well as odors indicative of the decomposition of keratin and globular proteins. The odor of alcohol also increased.

[0082] After seven weeks, no deterioration of the hide was visible in any of the four samples. Since there was no decrease in tear strength and no visible deterioration of the hide, it was determined that the protein degradation of the rawhide had not progressed.

[0083] No differences were observed after 12 weeks or after 7 weeks.

[0084] As described above, even after the rawhide was removed from the treatment solution, the fermentation continued and the effect of promoting depilation was obtained. Furthermore, the rawhide coated with sugar, i.e., the second precursor, could be preserved and stored for at least 12 weeks.

[0085] Compared with the samples of Example 1, the samples of Example 2 did not show any decrease in the tear strength of the hide after 7 weeks. This is believed to be because when rawhide is stored in the treatment solution for a long time, fermentation proceeds excessively, producing acids such as acetic acid, which makes the treatment solution acidic. As a result, in the sample of Example 1, the acid causes protein decomposition (hydrolysis), which reduces the tear strength. It was found that for longer-term storage of rawhide, it is more preferable to complete the first fermentation process at a specified time, move on to the second fermentation process, and store the rawhide in the state of a second precursor.

[0086] Thus, it was found that, particularly in the state of the second precursor, it can be well preserved at room temperature for at least 12 weeks without deterioration in appearance or physical properties (tear strength).

[0087] In addition, it was found that rawhide preserved in the above manner (treated in the first fermentation process or the first and second fermentation processes) has accelerated dehairing during preservation. Therefore, the dehairing process after the first fermentation process or the second fermentation process, which is required in the prior art, is no longer necessary, and this reduces the environmental impact.

[0088] In this way, a method for producing leather and a leather precursor that place less of a burden on the environment can be provided.

[0089] [Another embodiment] (1) In the above embodiment, the hair removal step of removing hair from the second precursor has been described. However, the hair removal step is not limited to the case of removing hair from the second precursor. The hair removal step can be performed in the same manner even when the first precursor is removed.

[0090] Note that the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited thereto, and may be modified as appropriate within the scope of the purpose of the present disclosure. [Industrial Applicability]

[0091] The present disclosure is applicable to methods for making leather and leather precursors.

Claims

1. a soaking step of soaking the rawhide in a treatment solution containing sugar and yeast of the genus Saccharomyces; A first fermentation step of immersing the rawhide in the treatment solution and fermenting it.

2. The treatment liquid is Water in an amount of 50% or more and 100% or less by weight of the rawhide; The method for producing leather according to claim 1, further comprising: a weight of said sugar being 3% or more and 30% or less of the weight of said rawhide.

3. 3. The method for producing leather according to claim 1 or 2, wherein in the first fermentation step, the rawhide is immersed in the treatment solution for a period of time of 2 hours to 72 hours.

4. a dehydration step of dehydrating a first precursor obtained by fermenting the rawhide in the fermentation step; a sugar-adding step of attaching sugar to a surface of the first precursor after the dehydration step; The method for producing leather according to claim 1 or 2, further comprising a second fermentation step of fermenting the first precursor after the sugar addition step.

5. 5. The method for producing leather according to claim 4, wherein in the sugar-adding step, sugar is attached to the surface of the first precursor in an amount of 10% to 30% by weight of the rawhide.

6. The method further includes a depilation step of depilating a second precursor obtained by fermenting the first precursor in the second fermentation step, In the dehairing step, the second precursor is treated with: 0.3% or more and 1.0% or less by weight of potassium hydroxide or sodium hydroxide; Sodium sulfide in an amount of 0.8% or more and 2.0% or less by weight; The method for producing leather according to claim 4, further comprising adding and stirring the above.

7. Further comprising a desulfurization step carried out after the dehairing step, 7. The method for producing leather according to claim 6, wherein in the desulfurization step, an oxidizing agent is added to the second precursor in an amount of 0.8% or more and 2.0% or less by weight based on the weight of the rawhide, and the mixture is stirred. Manufacturing method.

8. A leather precursor comprising sugar, yeast of the genus Saccharomyces, and rawhide.

9. 9. The leather precursor of claim 8, further comprising ethanol.