Cacao-derived pulp, cacao-derived cellulose nanofiber, and method for producing same

Abstract

The present invention provides a new technical means for efficiently and safely producing long-fiber CNF and a pulp fraction containing same. More specifically, the present invention relates to a method for producing a cacao-derived pulp, the method comprising a step for steam digesting a cacao-derived raw material in an alkaline solution.

Description

Cocoa-derived pulp, cocoa-derived cellulose nanofiber, and manufacturing method thereof REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority based on Japanese Patent Application No. 2023-215198, filed on December 20, 2023, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to cocoa-derived pulp, cocoa-derived cellulose nanofibers, and methods for producing the same.

[0003] In recent years, nanotechnology has attracted attention for its ability to reduce materials to the nanometer level and achieve new physical properties that differ from their conventional properties. In particular, cellulose nanofibers (hereinafter sometimes abbreviated as "CNF") are known as functional biomass materials, which are wood fibers (pulp) obtained primarily from wood that have been highly refined to nanometer order (less than a few hundredths of a micron). Cellulose produced by plants exhibits the form of tiny fibers called microfibrils. CNF is a nano-sized material in which microfibrils are loosened into bundles of one to several tens or hundreds of microns. Furthermore, because CNF is derived from plant fibers, it has the advantages of low environmental impact during production and disposal, as well as being lightweight. Because the fiber length and width of CNF can significantly affect its functionality and applications, there is potential for the efficient production of CNF with various fiber lengths and widths.

[0004] The raw materials used for CNF are generally woody biomass such as coniferous trees, broad-leaved trees, and bamboo, as well as woody biomass materials derived from woody sources such as construction waste, sawdust, wood chips, and recycled paper. In addition to wood, there are many other plant-derived raw materials, such as straw, bagasse, and agricultural waste, which also contain cellulose and can therefore be used as raw materials for CNF. Various methods for producing CNF using such raw materials have been reported.

[0005] For example, Patent Document 1 reports that when cellulose nanocrystal particles were obtained from wheat bran and their average diameter and average length were measured, the average diameter was 27.5±3.5 nm and the average length was approximately 300 to 1000 nm.

[0006] Furthermore, Patent Document 2 reports the production of cellulose nanofibers and a pulp containing the same using almond skins as a raw material. The conditions for producing pulp using almond skins as a raw material are high-level alkaline concentration and high-temperature conditions, in which the raw material is kept in a 15% sodium hydroxide solution at 170°C.

[0007] However, when using woody biomass raw materials or agricultural waste as described above, pulping is required to obtain CNF, which means that the raw materials must be processed under generally harsh conditions, such as using chemicals or high-temperature treatment, which can result in excessive energy costs. Furthermore, since the functionality and physical properties of CNF can vary depending on their size, it is preferable to be able to selectively and easily obtain CNF of the desired size. In particular, CNF with long fiber lengths is expected to be used as raw materials for producing high-performance materials and functional additives. However, when using conventional wood or waste as raw materials, it has been difficult to stably produce long-fiber CNF under mild conditions while keeping energy costs low.

[0008] On the other hand, cacao (Theobroma cacao) seeds are called cocoa beans, which are prepared into cocoa mass and widely used as a food ingredient. A common method for preparing cocoa mass involves removing cocoa beans from cocoa pods, fermenting the removed cocoa beans, drying the fermented cocoa beans, roasting the dried cocoa beans, and removing the outer skin (cocoa shell) to prepare cocoa nibs. The cocoa nibs are then ground to prepare cocoa mass. In this production process, by-products such as cocoa pods and cocoa shells are generated, but these are usually discarded on farms as organic fertilizer. To the best of the inventors' knowledge, no means have been reported for efficiently obtaining cellulose nanofibers from cocoa-derived materials such as cocoa pods and cocoa shells.

[0009] JP 2022-152003 A JP 2020-165042 A

[0010] One object of the present invention is to provide a new technical means for efficiently and safely producing long fiber CNF and the pulp that produces it.

[0011] As a result of extensive research, the present inventors have now discovered that by subjecting a cacao-derived raw material to a cooking treatment using alkali, it is possible to efficiently and safely produce long-fiber CNF and a pulp component containing the CNF. The present invention is based on this finding.

[0012] According to one embodiment of the present invention, there is provided a method for producing cocoa-derived pulp, comprising the step of cooking a cocoa-derived material with an alkaline solution.

[0013] Another embodiment of the present invention provides cocoa-derived pulp that satisfies at least one of the following (A) to (C): (A) the ratio of the number of fibers having a length of 100 μm or more to the total number of fibers is 50% or more; (B) the ratio of the number of fibers having a length of 250 μm or more to the number of fibers other than fibers derived from parenchyma cells is 30% or more; and (C) the cellulose crystallinity is 40% or more.

[0014] Furthermore, according to another embodiment of the present invention, there is provided a method for producing cocoa-derived cellulose nanofibers, which includes a step of defibrating the above-mentioned cocoa-derived pulp.

[0015] Another embodiment of the present invention provides cocoa-derived cellulose nanofibers that satisfy at least one of the following (D) to (H): (D) the proportion of fibers in the cocoa-derived cellulose nanofibers having a length of 1000 nm or more is 40% or more; (E) the proportion of fibers in the cocoa-derived cellulose nanofibers having a fiber width of 5 nm or less is 50% or more; (F) the average aspect ratio is 200 or more; (G) the cellulose crystallinity is 40% or more; and (H) the viscosity of a 1 w / w% aqueous suspension of the cocoa-derived cellulose nanofiber is 900 mPa s or more.

[0016] According to the present invention, it is possible to efficiently and safely produce CNF with long fiber length and pulp containing the same. According to the present invention, it is possible to efficiently and safely produce CNF with long fiber length and narrow fiber width under mild conditions using cocoa or its processing by-products. According to the present invention, since cooking can be carried out under milder conditions than when using conventional raw materials such as wood materials, fiber decomposition can be avoided and it can be advantageously used to provide CNF with long fiber length and narrow fiber width.

[0017] Furthermore, valorizing agricultural waste and by-products from cocoa processing for higher value-added uses, as in the present invention, not only prevents annual losses at the production site but is also believed to be beneficial to multiple stakeholders, including farmers (additional income), industry (new value-added ingredients), and consumers (new innovative products). Utilizing processing by-products that would otherwise be discarded, as in the present invention, is believed to reduce environmental impact and contribute to the achievement of the SDGs (Sustainable Development Goals).

[0018] The fiber length distribution and cumulative ratio of fibers in cocoa-derived pulp (Ca48, Ca49, Ca50, Ca51) are shown. These are photographs taken with a transmission electron microscope of CNF in a CNF suspension obtained from cocoa shell-derived pulp. A is a photograph at a magnification of 90,000x, B is a photograph at a magnification of 36,000x, and C is a photograph at a magnification of 18,000x. These are photographs taken with a transmission electron microscope of CNF in a CNF suspension obtained from pulp obtained by cooking cedar using soda anthraquinone (AQ) (cedar soda AQ pulp). A is a photograph at a magnification of 90,000x, B is a photograph at a magnification of 35,000x, and C is a photograph at a magnification of 16,000x. The fiber length distribution and cumulative ratio of CNF obtained from cocoa-derived pulp (Ca48, Ca49, Ca50, Ca51) are shown. The fiber width distribution and cumulative ratio of CNF obtained from soft cocoa-derived pulp (Ca48, Ca49, Ca50, Ca51) are shown. The relationship between the crystalline cellulose intensity and amorphous intensity in the profile measured in the 5-40° range using an X-ray diffractometer is shown. The degree of crystallinity is calculated using this intensity. The X-ray diffraction profiles of CNF (Ca75, Ca76, Ca77, Ca78) obtained from cocoa-derived pulp (Ca48, Ca49, Ca50, Ca51) are shown. Here, Ca75 corresponds to Ca48, Ca76 corresponds to Ca49, Ca77 corresponds to Ca50, and Ca78 corresponds to Ca51. 7-1 of Example 7 shows the change over time in sedimentation level for suspension samples obtained by ultrasonically treating (4 minutes) cocoa-derived pulp (Ca48, Ca50, Ca51) or cedar-derived pulp (Kraft process (KP) treated or untreated). 7-2 of Example 7 shows the change over time in sedimentation level for suspension samples obtained by ultrasonically treating (1 minute) cocoa-derived pulp (Ca48, Ca50, Ca51) obtained from cocoa shells. 7-2 are photographs of ultrasonically treated samples of cocoa-derived pulp obtained from cocoa shells (Ca48, Ca50, Ca51) taken 1 hour (1 h) and 5 hours (5 h) after the start of the test. This shows the change in sedimentation level over time in the sedimentation test of Example 7-3 for suspension samples obtained by ultrasonically treating (4 minutes) cocoa-derived pulp (Ca43, Ca44, Ca45, Ca46, and Ca47) obtained from cocoa pods.Photograph of a CNF film made from cocoa-derived pulp.

[0019] <Method for Producing Cocoa-Derived Pulp> According to one embodiment of the present invention, a method for producing cocoa-derived pulp includes a step of digesting a cocoa-derived raw material with an alkaline solution, as described above. This method, despite being produced under mild conditions, makes it possible to easily and efficiently provide CNF with long fiber length and narrow fiber width, which can be applied to the production of various high-performance products. Furthermore, cocoa-derived raw materials can be digested without pretreatment such as pulverization, as is the case with woody biomass raw materials, making them preferable as raw materials in terms of reducing energy costs.

[0020] As mentioned above, when using cocoa-derived raw materials, the energy cost for producing long-fiber, narrow-fiber CNF is much lower than that for woody biomass or agricultural waste. Furthermore, the use of safe chemicals in the cooking process for cocoa-derived raw materials, right down to the nanofiber stage, is advantageous for industrial production.

[0021] According to one embodiment of the present invention, it is preferable to use a manufacturing by-product containing plant fiber as a cocoa-derived raw material. Here, plant fiber refers to a material containing at least cellulose, and although there are some differences depending on the raw material, it usually contains cellulose, hemicellulose, lignin, protein, and lipid. Components necessary for the production of CNF include cellulose and hemicellulose.

[0022] According to a preferred embodiment of the present invention, the plant fiber-containing manufacturing by-products are by-products generated during the selection of food parts during food production. For example, in the case of foods using fruits or seeds, such by-products may include the remainder of the fruit, fruit peel, seeds, etc., excluding the parts used for food purposes, as well as the outer shells, skins, and fragments of seeds. Suitable examples of such cocoa-derived materials include cocoa pods (hereinafter sometimes referring only to the outer shells of cocoa fruits) and cocoa shells.

[0023] According to one embodiment of the present invention, the cocoa-derived material is preferably digested using an alkaline solution containing an alkaline agent. This digestion process removes components other than cellulose and hemicellulose, such as lignin, contained in the cocoa-derived material. Therefore, the digestion process is also called a delignification process.

[0024] The alkaline agent can be an alkali metal hydroxide commonly used in alkaline cooking, preferably lithium hydroxide, sodium hydroxide, potassium hydroxide, or sodium carbonate, with sodium hydroxide (caustic soda) being more preferred. The method of pulping using caustic soda is called soda cooking, in which raw materials are cooked with high-temperature caustic soda to obtain pulp. In the soda cooking method, lignin is subjected to the action of caustic soda, resulting in cleavage of phenyl ethers, which degrades the lignin into smaller molecules and allows them to be eluted.

[0025] Kraft (KP) cooking, which uses sodium sulfide and caustic soda, is commonly used for wood, but the odor emitted from sulfur can be a problem. On the other hand, if soda cooking is used as in the present invention, the problem of sulfur-derived odor does not occur because the cooking liquor does not contain sulfur components.

[0026] The amount of alkaline agent used can be varied appropriately depending on the type and amount of cocoa-derived raw materials used. The concentration of the alkaline agent in the alkaline solution is, for example, 1 wt% to 8 wt% (preferably 1.5 wt% to 5.5 wt%), and more preferably 2 wt% to 5 wt%. Furthermore, 10 to 50 parts by weight (preferably 15 to 30 parts by weight) of alkaline agent may be added per 100 parts by weight of the solid content of the cocoa-derived raw materials. The weight ratio of the solid content of the cocoa-derived raw materials to the alkaline solution (weight of the solid content of the cocoa-derived raw materials:weight of the alkaline solution) can be, for example, 1:3 to 1:50. In this case, it is advisable to adjust the liquid ratio so that the entire solid content of the cocoa-derived raw materials is immersed in the alkaline solution.

[0027] The solvent used for the alkaline solution may be water or a mixture of alcohol and water, but water is usually used.

[0028] In the cooking treatment, a cooking aid may be used in addition to the alkali agent. The cooking aid is a chemical added to the cooking liquor to promote delignification and prevent carbohydrate leaching. Examples of suitable cooking aids include quinone compounds such as anthraquinone, dihydroanthraquinone, tetrahydroanthraquinone, methylanthraquinone, methyldihydroanthraquinone, methyltetrahydroanthraquinone, benzoquinone, naphthoquinone, and phenanthroquinone; hydroquinone compounds such as anthrahydroquinone, methylanthrahydroquinone, and dihydroanthrahydroanthraquinone or their alkali metal salts; and precursors of anthrone, anthranol, methylanthrone, and methylanthranol, as well as polysulfides. Among these, anthraquinone is an excellent cooking aid that promotes delignification and stabilizes carbohydrates, and is used at approximately 0.1 w / w% of the raw material. Anthraquinone oxidizes and stabilizes the terminal aldehyde groups of cellulose and hemicellulose in wood, converting itself to anthrahydroquinone. Anthrahydroquinone then acts as a reducing agent, lowering the molecular weight of lignin in the chips while converting itself back to anthraquinone. This has the advantage of reducing the amount of alkali required to obtain pulp with the same kappa number (an index of the amount of lignin in pulp). The cooking aid is preferably used in a ratio of 0.001 to 1.0 parts by weight per 100 parts by weight of the dry weight of the cocoa-derived raw material.

[0029] The temperature at which the cooking treatment is carried out (cooking temperature) can be set lower than when wood is used as the raw material, for example, 50°C or higher and 160°C or lower, preferably 80°C or higher and 160°C or lower, and more preferably 80°C or higher and 140°C or lower.

[0030] From the viewpoint of reducing energy costs, the cooking treatment time is also preferably short, and the cooking treatment time is, for example, within 3 hours after the target temperature is reached, preferably from 30 minutes to 3 hours, more preferably from 1 hour to 2.5 hours, and even more preferably from 2 hours to 3 hours.

[0031] Furthermore, since the cooking treatment is carried out within the above temperature range, it is preferable to carry out the treatment in a pressure vessel (a first-class pressure vessel if it is large) when the treatment is carried out at a temperature exceeding 100° C. According to one embodiment of the present invention, after completion of cooking, the pressure is released and the material is cooled to a temperature at which it can be removed.

[0032] According to one embodiment of the present invention, after the cooking treatment, the cocoa-derived pulp obtained is preferably washed and rinsed. For example, the cocoa-derived pulp obtained by the cooking treatment may be separated from the cooking liquor, and the cocoa-derived pulp may be washed with water. The water used here may be distilled water, purified water, or water equivalent thereto. Since cocoa-derived pulp typically has a high moisture content, it is advisable to incorporate a rinsing step in which the pulp is forcibly rid of moisture using suction filtration, a centrifugal dehydrator, a press, or the like. The end of the washing and rinsing steps can be determined by checking the pH or turbidity of the rinsing liquid.

[0033] According to one embodiment of the present invention, the cocoa-derived pulp obtained by the cooking treatment may be further subjected to a bleaching treatment. This bleaching treatment can be carried out by treating the cocoa-derived pulp with a bleaching solution containing a bleaching agent. Even if the cooking treatment is carried out, there are cases where lignin cannot be completely removed. In such cases, the remaining lignin can be additionally removed by a bleaching treatment.

[0034] According to one embodiment of the present invention, the bleaching agent used in the bleaching treatment may be, for example, sodium hypochlorite (NaClO), hydrogen peroxide (H ２ O ２ ), ozone (O ３ ), oxygen (O ２ ), persulfuric acid (H ２ SO ５ ), peracetic acid (C ２ H ４ O ３ ) or mixtures thereof can be used.

[0035] Bleaching is preferably carried out by appropriately setting pH and temperature conditions that produce the bleaching effect. For example, the solids concentration of the pulp to be bleached is preferably 1% to 30%, but may be outside this range if necessary. The bleaching process may be a multi-stage bleaching in which the same bleaching step is repeated several times, or a multi-stage bleaching in which different types of bleaching steps are combined.

[0036] For example, when sodium hypochlorite is used as a bleaching agent, it may be prepared by adding sodium hypochlorite in an amount of available chlorine of 0.1 w / w% to 10 w / w% to an alkaline aqueous solution having a pH of 10 or higher. During bleaching, the temperature is usually kept at 0°C to 110°C, and bleaching is preferably completed within 0.25 to 5 hours.

[0037] After bleaching, the resulting cocoa-derived pulp is usually washed and rinsed. After bleaching and washing, the cocoa-derived pulp may be rinsed using suction filtration, a centrifugal dehydrator, a press, or the like until the pH of the filtered water is around 7.

[0038] <Cocoa-Derived Pulp> According to one embodiment of the present invention, there is provided cocoa-derived pulp obtained by the above-described cooking treatment and optional bleaching treatment. According to one embodiment of the present invention, the cocoa-derived pulp contains fibers obtained from parenchyma cells, vascular cells, and fiber cells (fiber cells other than vascular cells). Furthermore, according to a preferred embodiment of the present invention, the cocoa-derived pulp contains vascular bundles or portions of fibers derived therefrom. The inclusion of vascular bundles or portions of fibers derived therefrom in cocoa-derived pulp is preferred from the viewpoint of providing a source of long-fiber CNF.

[0039] In cocoa-derived raw materials, it is generally believed that the length of fibers in fiber cells is 260 to 500 μm, the length of fibers in parenchyma cells is approximately 100 μm, and the fibers in spiral vascular bundles are several mm long when unraveled. Without being bound by theory, by performing a cooking treatment under mild conditions, the spiral fibers that make up the vascular bundles in the cocoa-derived raw materials are unraveled without being damaged, and are contained in the cocoa-derived pulp while maintaining their long fiber length. For this reason, it is believed that the proportion of long fibers in the cocoa-derived pulp increases.

[0040] In this specification, the fiber length of fibers contained in cocoa-derived pulp can be measured with reference to JIS P8226-2 Pulp - Fiber length measurement method by optical automatic analysis - Part 2: Non-polarized light method. Specifically, ImageJ (National Institutes of Health (NIH) Rasband 1997-2023) may be used to measure fiber length after prior calibration to conform to JIS P8226-2.

[0041] According to one embodiment of the present invention, the length-weighted average fiber length of the fibers contained in the cocoa-derived pulp, as defined in JIS P8226-2, is, for example, 300 μm or more and 1000 μm or less, preferably 350 μm or more and 950 μm or less, and more preferably 400 μm or more and 900 μm or less.

[0042] According to one embodiment of the present invention, the number average fiber length of the fibers contained in the cocoa-derived pulp, as defined in JIS P8226-2, is, for example, 150 μm or more and 1000 μm or less, preferably 180 μm or more and 700 μm or less, and more preferably 200 μm or more and 550 μm or less.

[0043] According to one embodiment of the present invention, the ratio of the number of fibers having a fiber length of 100 μm or more to the total number of fibers in the cocoa-derived pulp is, for example, 25% or more, preferably 35% or more, more preferably 45% or more, and even more preferably 50% or more. Herein, the total number of fibers in the cocoa-derived pulp and the ratio of the number of fibers having each fiber length can be determined by the method described in the Examples below.

[0044] Furthermore, according to one embodiment of the present invention, the ratio of the number of fibers having a fiber length of 100 μm or more to the number of fibers other than fibers derived from parenchyma cells in the cocoa-derived pulp is, for example, 50% or more, preferably 55% or more, more preferably 60% or more, and even more preferably 65% ​​or more.

[0045] According to one embodiment of the present invention, the ratio of the number of fibers having a fiber length of 200 μm or more to the total number of fibers in the cocoa-derived pulp is, for example, 25% or more, preferably 30% or more.

[0046] Furthermore, according to one embodiment of the present invention, the ratio of the number of fibers having a fiber length of 200 μm or more to the number of fibers other than fibers derived from parenchyma cells in the cocoa-derived pulp is, for example, 25% or more, preferably 30% or more, more preferably 35% or more, and even more preferably 40% or more.

[0047] According to one embodiment of the present invention, the ratio of the number of fibers having a fiber length of 250 μm or more to the total number of fibers in the cocoa-derived pulp is, for example, 25% or more, preferably 30% or more.

[0048] Furthermore, according to one embodiment of the present invention, the ratio of the number of fibers having a fiber length of 250 μm or more to the number of fibers other than fibers derived from parenchyma cells in the cocoa-derived pulp is, for example, 30% or more, preferably 35% or more, more preferably 40% or more, and even more preferably 45% or more.

[0049] According to one embodiment of the present invention, the ratio of the number of fibers having a fiber length of 450 μm or more to the total number of fibers in the cocoa-derived pulp is, for example, 5% or more, preferably 10% or more.

[0050] Furthermore, according to one embodiment of the present invention, the ratio of the number of fibers having a fiber length of 450 μm or more to the number of fibers other than fibers derived from parenchyma cells in the cocoa-derived pulp is, for example, 10% or more, preferably 20% or more, more preferably 30% or more, and even more preferably 45% or more.

[0051] According to one embodiment of the present invention, the cocoa-derived pulp can exhibit a high level of crystallinity. In this specification, the crystallinity of the cocoa-derived pulp and the CNF obtained therefrom can be determined by taking a profile of a test sample in the range of 5-40° using an X-ray diffractometer (accelerating voltage 40 kV), determining the crystalline intensity and amorphous intensity with reference to the profile, and calculating the crystallinity according to the following formula: Crystallinity (%) = crystalline intensity / (crystalline intensity + amorphous intensity) × 100

[0052] According to one embodiment of the present invention, the crystallinity of the cocoa-derived pulp is, for example, 40% or more, preferably 40% or more and 80% or less, more preferably 40% or more and 70% or less, and even more preferably 42% or more and 65% or less.

[0053] According to a preferred embodiment of the present invention, the cocoa-derived pulp satisfies at least one of the following (A) to (C): (A) the ratio of the number of fibers having a length of 100 μm or more to the total number of fibers is 50% or more; (B) the ratio of the number of fibers having a length of 250 μm or more to the number of fibers other than fibers derived from parenchyma cells is 30% or more; (C) the cellulose crystallinity is 40% or more.

[0054] In the above-described preferred embodiment of the present invention, the cocoa-derived pulp may satisfy all, or one or two of, (A) to (C), but from the viewpoint of use in the production of high-performance materials, it is preferable that the pulp satisfies all of them. In the preferred embodiment of the present invention, further specific embodiments of (A) to (C) can be applied to the numerical values ​​of each parameter described in the above-described embodiments of the present invention.

[0055] Furthermore, as described above, cocoa-derived pulp contains a large amount of elongated fibers, and therefore exhibits the property of remaining dispersed in solution for a long period of time without settling. According to one embodiment of the present invention, the sedimentation velocity measurement method described below can be used as an indicator of the property of dispersing in solution without settling. In the sedimentation velocity measurement method defined below, the scale level on the measuring cylinder serves as an indicator of the sedimentation velocity, and the higher the scale level after the test is completed, the lower the sedimentation rate, indicating that the pulp is dispersed and floating in water.

[0056] Sedimentation velocity measurement method: 0.1 g (dry weight equivalent) of cocoa-derived pulp was added to distilled water to obtain a 0.1 w / w% mixture (100 mL), which was then treated with an ultrasonic homogenizer for 4 minutes to obtain a 0.1 w / w% suspension. The suspension was then poured into a 100 mL measuring cylinder (based on JIS R3505) and allowed to stand, and the upper scale level of the settled cocoa-derived pulp was measured at intervals of time.

[0057] According to a preferred embodiment of the present invention, in the sedimentation velocity measurement method, the cacao-derived pulp has a scale of, for example, 50 cc or more, preferably 60 cc or more, more preferably 70 cc or more, even more preferably 80 cc or more, and even more preferably 90 cc or more at the time of 72 hours.

[0058] <Method for producing cellulose nanofibers (CNF)> According to one embodiment of the present invention, cocoa-derived CNF can be obtained by defibrating the cocoa-derived pulp obtained above. Methods for defibrating cocoa-derived pulp include, for example, mechanical defibration methods (e.g., defibration methods using a grinder or a high-pressure homogenizer such as a water jet machine, and defibration methods using ultrasonic treatment), acid hydrolysis methods (e.g., sulfuric acid hydrolysis), chemical treatment methods (e.g., TEMPO oxidation using 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)), and enzymatic hydrolysis methods (e.g., methods using cellulase). However, mechanical defibration methods are preferred for defibrating cocoa-derived pulp.

[0059] According to the method of the present invention, long-fiber CNF can be produced efficiently and simply by a simple mechanical defibration process. It is generally considered difficult to nanosize pulp components. This is because, in the case of pulp derived from woody biomass, CNF tend to quickly aggregate densely during refining and drying, and once aggregated, a large amount of energy is required to break down these clumps using a high-pressure homogenizer or the like. However, in the present invention, cocoa-derived CNF can be efficiently obtained by subjecting cocoa-derived pulp to a simple mechanical defibration process.

[0060] According to a preferred embodiment of the present invention, the mechanical defibration method is carried out by ultrasonic treatment. It is a surprising fact that CNF can be efficiently produced from cocoa-derived pulp in a short time by a simple method such as ultrasonic treatment.

[0061] The nano-processing step in one embodiment of the present invention will now be described in more detail. Prior to nano-processing, the moisture content of the cocoa-derived pulp is measured and the solids content is calculated. Based on this, the amount of water added is adjusted so that the pulp solids content is 0.01 w / w% to 5 w / w%. Next, using an ultrasonic homogenizer, CNF can be obtained by continuous irradiation for approximately 1 to 4 minutes.

[0062] The processed material that has been converted into nanofibers by mechanical defibration can be dried as needed, and from the viewpoint of preventing bacterial contamination, filled into any container, sterilized, and stored.

[0063] <Cacao-derived cellulose nanofibers (CNF)> According to one embodiment of the present invention, there is provided cacao-derived CNF obtained by the above-described method. The cacao-derived CNF of the present invention has a high proportion of elongated CNF and can be advantageously used in the production of high-performance materials.

[0064] According to one embodiment of the present invention, the length-weighted average fiber length of the fibers contained in the cocoa-derived CNF is, for example, 300 nm or more, preferably 600 nm or more, and more preferably 900 nm or more.

[0065] According to one embodiment of the present invention, the number average fiber length of the cocoa-derived CNF is, for example, 1000 nm or more, preferably 1000 nm or more and 7000 nm or less, preferably 1100 nm or more and 6000 nm or less, and more preferably 1150 nm or more and 5500 nm or less.

[0066] Furthermore, according to one embodiment of the present invention, the ratio of the number of fibers having a fiber length of 1000 nm or more to the total number of fibers of cocoa-derived CNF is, for example, 40% or more, preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and even more preferably 90% or more.

[0067] Furthermore, according to one embodiment of the present invention, the ratio of the number of fibers having a length of 2000 nm or more to the total number of fibers of cocoa-derived CNF is, for example, 50% or more, preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and even more preferably 90% or more.

[0068] According to one embodiment of the present invention, the average fiber width of the cocoa-derived CNF is, for example, 10 nm or more, preferably 8 nm or less, and more preferably 5 nm or less. The average fiber width of the cocoa-derived CNF is preferably 3 nm or more and 8 nm or less, and more preferably 3 nm or more and 5 nm or less.

[0069] Furthermore, according to one embodiment of the present invention, the ratio of the number of fibers having a fiber width of 5 nm or less to the total number of fibers in the cocoa-derived CNF is, for example, 50% or more, preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and even more preferably 90% or more.

[0070] In this specification, the measurement of the average fiber length and average fiber width of CNFs by electron microscope observation can be performed as follows. A CNF-containing slurry is prepared, and the slurry is cast onto a grid coated with hydrophilically treated carbon, plastic, or the like to prepare a sample for transmission electron microscope (TEM) observation. Alternatively, the sample may be cast onto glass or mica, and an atomic force microscope (AFM) image observed. Observation is performed using a transmission electron microscope at magnifications ranging from 1,000x, 5,000x, 10,000x, 20,000x, 50,000x, or 100,000x, depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions: (1) Fibers are dispersed and arranged at any location within the observation image, and the image is captured. (2) Next, the fiber length and fiber width of the fibers present in the captured image are measured using ImageJ (National Institutes of Health (NIH) Rasband 1997-2023). Specifically, for fiber length, ImageJ's fiber length measurement function is used to extend a line along the fiber to the same length for each fiber in the image, and the software is used to measure the distance from the first point to the last point of the resulting line. The actual length is calculated using the Excel spreadsheet function based on the scale recorded on each image for the resulting distance. At least 40 fiber lengths are measured in this manner, and the length-weighted average fiber length and number-average fiber length are measured. Furthermore, for fiber width, ImageJ's fiber length measurement function is used to select a portion of the fiber in the image where the fiber is almost isolated, and the fiber width distance is measured perpendicular to the fiber. The software is then used to measure the resulting fiber thickness distance. As with the fiber length measurement, the actual length is calculated using the Excel spreadsheet function based on the scale recorded on each image for the resulting distance. At least 40 fiber widths are measured in this manner, and the average fiber width is calculated by averaging them.

[0071] According to one embodiment of the present invention, the average aspect ratio of the cocoa-derived CNF is, for example, 200 or more, preferably 300 or more, more preferably 400 or more, and even more preferably 500 or more. In this specification, the average aspect ratio can be calculated using the following formula: (average aspect ratio) = (number average fiber length) / (average fiber width).

[0072] According to one embodiment of the present invention, the cocoa-derived CNF can exhibit a high degree of crystallinity, for example, 40% or more, preferably 40% to 80%, more preferably 40% to 70%, and even more preferably 45% to 65%.

[0073] Furthermore, the cocoa-derived CNF of the present invention can exhibit high viscosity when suspended or dissolved in water. According to one embodiment of the present invention, the viscosity of a 1 wt. % aqueous suspension of cocoa-derived CNF at 22-23°C is, for example, 900 mPa·s or more, preferably 950 mPa·s or more. The upper limit of the viscosity of a 1 wt. % aqueous suspension of cocoa-derived CNF at 22-23°C is, for example, 2000 mPa·s or less, preferably 1500 mPa·s or less. The viscosity range of a 1 wt. % aqueous suspension of cocoa-derived CNF at 22-23°C is, for example, 900 mPa·s or more and 1500 mPa·s or less, preferably 950 mPa·s or more and 1200 mPa·s or less. The viscosity can be measured using a B-type viscometer as described in the Examples below.

[0074] Furthermore, one embodiment of the present invention provides cocoa-derived cellulose nanofibers that satisfy at least one of the following (D) to (H): (D) the proportion of fibers in the cocoa-derived cellulose nanofibers having a length of 1000 nm or more is 40% or more; (E) the proportion of fibers in the cocoa-derived cellulose nanofibers having a fiber width of 5 nm or less is 50% or more; (F) the average aspect ratio is 200 or more; (G) the cellulose crystallinity is 40% or more; and (H) a 1 w / w% aqueous suspension of the cocoa-derived cellulose nanofibers has a viscosity of 900 mPa s or more at 22-23°C.

[0075] In the above-mentioned preferred embodiment of the present invention, the cocoa-derived CNF may satisfy all of (D) to (H), or may satisfy one to four of (D) to (H), but from the viewpoint of use in the production of high-performance materials, it is preferable that it satisfies all of them. In the preferred embodiment of the present invention, further specific embodiments of (D) to (H) can be applied to the numerical values ​​of each parameter described in the above-mentioned embodiment of the present invention.

[0076] Furthermore, as described above, cocoa-derived CNF contains a large amount of long, thin fibers, and thus, like cocoa-derived pulp, can exhibit the property of remaining dispersed in solution for a long period of time and not settling. According to a preferred embodiment of the present invention, in the sedimentation velocity measurement method, the cocoa-derived CNF has a volume of, for example, 80 cc or more, preferably 90 cc or more, at 72 hours.

[0077] The specifications of the cocoa-derived pulp and CNF of the present invention are not limited to those described above, and can be determined by various methods. Specifically, the dry weight, crystalline structure, light transmittance, fiber width and height, fiber length, molecular weight distribution, supernatant solids content, thermal stability, ash content, acid-soluble metal content, organic pollutant content, acetone-soluble substance content, and constituent sugar content can also be determined by methods conforming to the international standard ISO / TS21346.

[0078] According to one embodiment of the present invention, there are provided the following: [1] A method for producing cocoa-derived pulp, comprising a step of cooking a cocoa-derived material with an alkaline solution. [2] The method according to [1], wherein the cocoa-derived material is cocoa shell or cocoa pod. [3] The method according to [1] or [2], wherein the temperature of the alkaline solution is 80°C or higher and 140°C or lower. [4] The method according to any one of [1] to [3], wherein the concentration of the alkaline agent in the alkaline solution is 1 w / w% or higher and 8 w / w% or lower. [5] The method according to any one of [1] to [4], wherein the cooking time is 3 hours or less. [6] Cocoa-derived pulp that satisfies at least one of the following (A) to (C): (A) the ratio of the number of fibers having a length of 100 μm or more to the total number of fibers is 50% or higher; (B) the ratio of the number of fibers having a length of 250 μm or more to the number of fibers other than fibers derived from parenchyma cells is 30% or higher; (C) the cellulose crystallinity is 40% or higher. [7] Cocoa-derived pulp according to [6], in which the ratio of the number of fibers having a length of 200 μm or more to the total number of fibers in (A) is 35% or more. [8] Cocoa-derived pulp according to [6] or [7], in which the total number of fibers is the sum of fibers obtained from parenchyma cells, vascular cells, and fibrous cells. [9] Cocoa-derived pulp according to any of [6] to [8], in which the ratio of the number of fibers having a length of 450 μm or more to the number of fibers other than those derived from parenchyma cells is 40% or more.

[10] Cocoa-derived pulp according to any of [6] to [9], in which, in the sedimentation velocity measurement method specified below, the graduation level of a measuring cylinder (in accordance with JIS R3505), which serves as an indicator of sedimentation velocity, is 80 cc or more after 72 hours. Sedimentation velocity measurement method: 0.1 g (dry weight equivalent) of cocoa-derived pulp is added to distilled water to obtain a 0.1 w / w% mixture, and 100 mL of the resulting mixture is treated with an ultrasonic homogenizer for 4 minutes to obtain a 0.1 w / w% suspension. The suspension is then poured into a 100 mL measuring cylinder and allowed to stand, and the upper scale level of the settled portion of the cocoa-derived pulp is measured at intervals of time.

[11] Cocoa-derived pulp according to any one of [6] to

[10] , obtained by the method described in [1].

[12] A method for producing cocoa-derived cellulose nanofibers, comprising a step of defibrating cocoa-derived pulp.

[13] The method according to

[12] , wherein the cocoa-derived pulp is obtained by the method according to any one of [1] to [5].

[14] The method according to

[12] or

[13] , wherein the defibrating step is carried out by ultrasonic treatment.

[15] Cocoa-derived cellulose nanofibers that satisfy at least one of the following (D) to (H): (D) the proportion of fibers having a length of 1000 nm or more in the cocoa-derived cellulose nanofibers is 40% or more; (E) the proportion of fibers having a fiber width of 5 nm or less in the cocoa-derived cellulose nanofibers is 50% or more; (F) the average aspect ratio is 200 or more; (G) the cellulose crystallinity is 40% or more; (H) a 1 w / w% aqueous suspension of the cocoa-derived cellulose nanofibers has a viscosity of 900 mPa s or more.

[16] Cocoa-derived cellulose nanofibers according to

[15] , wherein the proportion of fibers having a length of 2000 nm or more among the cocoa-derived cellulose nanofibers in (D) is 50% or more.

[17] Cocoa-derived cellulose nanofibers according to

[15] or

[16] , wherein, in a sedimentation velocity measurement method as defined below, the graduation level of a measuring cylinder (based on JIS R3505), which serves as an indicator of sedimentation velocity, is 80 cc or more at the end of 72 hours. Sedimentation velocity measurement method: 0.1 g (equivalent to the dry weight) of cocoa-derived cellulose nanofibers is added to distilled water to obtain 100 mL of a 0.1 w / w% aqueous suspension. The suspension is then poured into a 100 mL measuring cylinder and allowed to stand, and the graduation level of the upper limit of the settled portion of the cocoa-derived cellulose nanofiber is measured at intervals of time.

[18] Cocoa-derived cellulose nanofibers according to any of

[15] to

[17] , wherein the viscosity in (H) is 1500 mPa s or less.

[19] The cocoa-derived cellulose nanofiber according to any one of

[15] to

[18] , obtained by the method according to any one of

[12] to

[14] .

[0079] The present invention will be described in detail below with reference to the following examples, but the present invention is not limited thereto. Furthermore, unless otherwise specified, the measurement methods and units described in this specification are in accordance with the provisions of JIS (Japanese Industrial Standards).

[0080] Example 1: Cooking (pulping) of cocoa shells 15 g (dry weight) of cocoa shells and 150 g of aqueous sodium hydroxide solution (NaOH concentration 1-8 w / w%) were placed in a stainless steel container. The container was then heated in an oil bath, and after the temperature inside the container reached a range of 80-160°C, the container was treated for 2-3 hours. After completion of cooking, the treated product was subjected to solid-liquid separation using filter paper or filter cloth. The resulting solid portion was thoroughly washed with water and finally squeezed to remove as much water as possible, yielding unbleached cocoa-derived pulp.

[0081] The results are shown in Tables 1 and 2. Both results indicated that the milder the reaction conditions, the higher the pulp yield.

[0082]

[0083]

[0084] Example 2: Bleaching of cocoa-derived pulp. 15 g (dry weight) of unbleached cocoa-derived pulp was mixed with an aqueous sodium hydroxide solution (NaOH concentration 1 w / w%) to a total weight of 280 g. This mixture and 20 g of a 5 w / w% aqueous sodium hypochlorite solution (1 g of available chlorine) were placed in a plastic bag and sealed. The bag was heated in a water bath, and bleaching was carried out by treating for 1 hour after the temperature inside the bag reached 40°C. After bleaching was completed, the treated product was subjected to solid-liquid separation using filter paper or filter cloth. The resulting solid portion was thoroughly washed with water and finally squeezed to remove as much water as possible, yielding bleached cocoa-derived pulp. This process was repeated several times until the cocoa-derived pulp reached the desired brightness.

[0085] The results are shown in Tables 3 and 4. Both results indicated a tendency for the pulp yield to increase as the reaction conditions became milder.

[0086]

[0087]

[0088] Example 3: Measurement of Pulp Fiber Length Cocoa-Derived Pulp The prepared undried, unbleached cocoa-derived pulps (Ca48, Ca49, Ca50, and Ca51) were suspended in a small amount of distilled water. Each sample was placed on a slide and observed and photographed using a polarizing microscope (Nikon, ECLIPSE E600 POL). The fiber length of each sample was measured using ImageJ (National Institutes of Health (NIH) Rasband 1997-2023). The fiber lengths (number average fiber lengths) of the cocoa-derived pulps (Ca48, Ca49, Ca50, and Ca51) were as shown in Table 5-1.

[0089]

[0090] The measured fiber lengths and cumulative ratios of the cocoa-derived pulps (Ca48, Ca49, Ca50, and Ca51) were as shown in Tables 5-2 and 5-3, respectively. In particular, the relationship between the fiber lengths and cumulative ratios of the cocoa-derived pulps (Ca48, Ca49, Ca50, and Ca51) in Table 5-3 was as shown in Figure 1.

[0091]

[0092] Cocoa-derived pulp also contains fibers containing parenchyma cells and vascular cells. To determine the composition ratio of fibers derived from parenchyma cells to fibers containing vascular cells, a cocoa-derived pulp sample was placed on a slide glass and observed and photographed using a polarizing microscope. The fiber lengths of the vascular cells and parenchyma cells were measured for multiple photographs using ImageJ (National Institutes of Health (NIH) Rasband 1997-2023).

[0093] For the above cocoa-derived pulps (Ca48, Ca49, Ca50, Ca51), the fiber length (μm) was measured for both the sample containing parenchyma cells and the sample not containing parenchyma cells.

[0094] The results are shown in Table 6. It was confirmed that samples containing parenchyma cells tended to have shorter fiber lengths than samples not containing parenchyma cells. This result is thought to be due to the fact that the fibers derived from parenchyma cells are relatively short. It was also confirmed that samples treated at a low temperature (80°C) tended to have longer fiber lengths than samples treated at a high temperature (140°C). This result suggests that the lower the treatment temperature, the longer the fibers are maintained.

[0095]

[0096] Cedar-derived pulp (reference group): Kraft cooking of cedar wood. 15 g (bone dry weight) of cedar wood and a cooking liquor prepared by dissolving 3 g of sodium hydroxide and 1 g of sodium sulfide in 90 g of water were placed in a stainless steel container. The container was heated in an oil bath, and after the temperature inside the container reached 170°C, the pulp was treated for 2 hours. The treated material was subjected to solid-liquid separation using filter paper or filter cloth. The resulting solid portion was defibrated using a defibrator, thoroughly washed with water, and finally squeezed to remove as much water as possible, yielding cedar-derived pulp (hereinafter also referred to as "unbleached cedar kraft pulp") by the kraft (KP) method. The results are shown in Table 7.

[0097]

[0098] Cedar wood digestion with soda-anthraquinone (soda AQ) 15 g (bone dry mass) of cedar wood, 90 g of sodium hydroxide (caustic soda) aqueous solution (NaOH concentration 2-6 w / w%), and 0.075 g of anthraquinone (AQ) were placed in a stainless steel container. The container was heated in an oil bath, and after the temperature inside the container reached 150-170°C, the digestion was continued for 3 hours. The processed material was subjected to solid-liquid separation using filter paper or filter cloth. The resulting solid portion was defibrated using a fiberizer, thoroughly washed with water, and finally squeezed to remove as much water as possible, yielding unbleached cedar-derived pulp that had undergone soda AQ treatment (hereinafter also referred to as "cedar unbleached soda AQ pulp").

[0099] Bleaching of Unbleached Cedar Kraft Pulp and Unbleached Cedar Soda AQ Pulp: 15 g (dry weight) of unbleached cedar kraft pulp or unbleached cedar soda AQ pulp was mixed with aqueous sodium hydroxide (NaOH concentration 1 w / w%) to a total weight of 145 g. This mixture and 5 g of 5% aqueous sodium hypochlorite solution (available chlorine content 0.25 g) were placed in a plastic bag and sealed. The bag was heated in a water bath and treated for 1 hour after the temperature inside the bag reached 40°C. The treated product was subjected to solid-liquid separation using filter paper or filter cloth. The resulting solid portion was thoroughly washed with water and finally squeezed to remove as much water as possible, yielding bleached cedar pulp. This process was repeated several times until the desired brightness was achieved.

[0100] Example 4: Production of cellulose nanofibers (CNF) 4-1: Nanoization (cocoa-derived pulp) Distilled water was added to 1 g (equivalent to the dry weight) of the prepared undried cocoa shell-derived pulp to prepare a 0.1 wt% aqueous suspension. This suspension was placed in a 100 mL beaker and treated for 4 minutes or 1 minute with an ultrasonic wave crusher (manufactured by Taitec Co., Ltd., VP-30S, 20 kHz) to obtain a CNF suspension.

[0101] Figure 2 shows transmission electron microscope photographs of CNF in a CNF suspension obtained from cocoa shell-derived pulp. In Figure 2, A is a photograph at a magnification of 90,000x, B is a photograph at a magnification of 36,000x, and C is a photograph at a magnification of 18,000x.

[0102] 4-2: Nanonization (Cedar Kraft Pulp, Cedar Soda AQ Pulp) Distilled water was added to 1 g (dry weight equivalent) of the prepared undried Cedar Kraft Pulp or Cedar Soda AQ Pulp to prepare a 1 wt% aqueous suspension. This suspension was processed for approximately 10 cycles in a water jet machine (manufactured by Sugino Machine Co., Ltd.) to obtain a CNF suspension.

[0103] Figure 3 shows photographs of CNF in a CNF suspension obtained from soda cedar AQ pulp taken with a transmission electron microscope. In Figure 3, A is a photograph at a magnification of 90,000x, B is a photograph at a magnification of 35,000x, and C is a photograph at a magnification of 16,000x.

[0104] Example 5: Measurement of Fiber Length and Fiber Width of CNF Obtained from Cocoa-Derived Pulp. A small amount of cocoa CNF suspension prepared from cocoa-derived samples (Ca48, Ca49, Ca50, and Ca51) was suspended in distilled water. The suspension was dropped onto a grid equipped with a plastic support membrane, negatively stained with 4% uranyl acetate, and observed and photographed using a transmission electron microscope (JEOL JEM-2000EX, accelerating voltage 200 kV). The fiber length and fiber width of the CNF were measured using ImageJ (National Institutes of Health (NIH) Rasband 1997-2023) (average values ​​represent number averages). The results are shown in Table 8. Among various conditions, an alkali concentration of 2% and a treatment temperature of 80°C were found to be the most likely to produce the thinnest fiber width and longest fiber length.

[0105]

[0106] The measured fiber lengths and cumulative ratios of the CNFs obtained from the cocoa-derived pulps (Ca48, Ca49, Ca50, and Ca51) were as shown in Tables 9-1 and 9-2. In particular, the relationship between the fiber length distribution and cumulative ratio of the CNFs obtained from the cocoa-derived pulps (Ca48, Ca49, Ca50, and Ca51) in Table 9-2 was as shown in Figure 4.

[0107]

[0108] The measured fiber widths and cumulative ratios of the CNFs obtained from the cocoa-derived pulps (Ca48, Ca49, Ca50, and Ca51) were as shown in Tables 10-1 and 10-2. In particular, the relationship between the fiber width distribution and cumulative ratio of the CNFs obtained from the cocoa-derived pulps (Ca48, Ca49, Ca50, and Ca51) in Table 10-2 was as shown in Figure 5.

[0109]

[0110] Example 6: Study of the crystallinity of cocoa-derived pulp and CNF Using an X-ray diffractometer (Rigaku Corporation, Smart Lab, accelerating voltage 40 kV), profiles of test samples were taken in the range of 5-40°, and the crystallinity was calculated according to the following formula: Crystallinity (%) = crystalline intensity / (crystalline intensity + amorphous intensity) × 100 Here, the crystalline intensity and amorphous intensity are as shown in Figure 6. For the cocoa-derived pulp, air-dried pulp was used as the sample. For the CNF obtained from the cocoa-derived pulp, a cast film made from a 0.1% CNF suspension was used as the sample.

[0111] The X-ray diffraction profiles of the CNFs (Ca75, Ca76, Ca77, Ca78) obtained from the cocoa-derived pulp (Ca48, Ca49, Ca50, Ca51) are shown in Figure 7. Here, Ca75 corresponds to Ca48, Ca76 corresponds to Ca49, Ca77 corresponds to Ca50, and Ca78 corresponds to Ca51. The obtained profiles confirmed that the CNFs were crystalline cellulose type I, which is natural cellulose.

[0112] In addition, the crystallinity of the cocoa-derived pulps (Ca48, Ca49, Ca50, Ca51) and the CNF obtained therefrom was as shown in Table 11.

[0113]

[0114] For reference, the crystallinity of cedar-derived pulp and the CNF obtained therefrom was calculated using the same method as for cocoa-derived pulp. The results are shown in Table 12. Here, "KP" means that the kraft cooking treatment was performed, and soda AQ means that the cooking treatment with soda anthraquinone (soda AQ) was performed.

[0115]

[0116] Example 7: Study of the settling rate of CNF obtained by ultrasonic treatment 7-1: Study on 4 minutes of ultrasonic treatment (cocoa shell-derived pulp) Distilled water was added to 0.1 g (equivalent to dry weight) of cocoa-derived pulp obtained from cocoa shells to prepare 100 mL of a 0.1 wt% suspension, which was then treated for 4 minutes with an ultrasonic homogenizer according to the test conditions shown in Table 13 (hereinafter also referred to as "nanoization"). The obtained CNF-containing liquid was poured into a 100 mL measuring cylinder (JIS R3505) and allowed to stand. The time when the liquid was poured was set to 0 hours, and the scale of the settled portion was read at each elapsed time. Therefore, starting from the scale of 100, if sedimentation was observed, the scale gradually decreased with the elapsed time, meaning that the lower the scale, the more sedimentation occurred. In addition, a similar test as above was conducted using cedar-derived pulp as a reference group.

[0117]

[0118] The results are shown in Figure 8. Here, "US4m" means that ultrasonic treatment was carried out for 4 minutes, and "KP" means that the above-mentioned kraft cooking treatment was carried out.

[0119] The suspension of the sample obtained by ultrasonically treating the cocoa-derived pulp for four minutes showed no sedimentation and was well dispersed. In contrast, the sample obtained by ultrasonically treating the cedar kraft (KP) pulp showed almost no sedimentation and no dispersibility. This result suggests that the cellulose in the cocoa-derived pulp is more easily converted into nanofibers by ultrasonic treatment than the cellulose in the cedar-derived pulp. In Figure 8, the line representing the Ca48 US4m sample overlaps with the line representing the Ca50 US4m sample, but both lines indicate 100 cc.

[0120] 7-2: Study of sedimentation rate after 1 minute of ultrasonic treatment (cocoa shell-derived pulp) Distilled water was added to 0.1 g (equivalent to the dry weight) of cocoa-derived pulp (Ca48, Ca50, Ca51) obtained from cocoa shells to prepare 100 mL of a 0.1 wt% suspension. This was treated with an ultrasonic homogenizer for 1 minute under the test conditions shown in Table 14, and the test was carried out in the same manner as in 7-1.

[0121]

[0122] The results are shown in Figure 9. Here, Figure 9 is a graph showing the change over time in the sedimentation level of suspension samples obtained by ultrasonically treating (1 minute) cocoa-derived pulp (Ca48, Ca50, Ca51).

[0123] The sample in Figure 9 (Ca48, Ca50, Ca51: ultrasonic treatment for 1 minute) showed no sedimentation and was confirmed to be well dispersed and stabilized, despite the shorter ultrasonic treatment time, compared to the cedar-derived ultrasonic treatment sample in Figure 8 (ultrasonic treatment for 4 minutes). Figure 10 shows photographs of the ultrasonic treatment sample of cocoa-derived pulp (Ca48, Ca50, Ca51: ultrasonic treatment for 1 minute) taken 1 hour and 5 hours after the start of the test.

[0124] 7-3: Study on sedimentation rate after 4 minutes of ultrasonic treatment (cocoa pod-derived pulp) In addition, a test was conducted under the conditions in Table 15 in accordance with 7-1, except that cocoa-derived pulp (Ca43-47) obtained from cocoa pods was used.

[0125] The results are shown in Figure 11. In Figure 11, the lines representing CaCa44 to 47 overlap, but they all indicate 100 cc at each point. That is, Ca44 to 47 were well dispersed, and no sedimentation was observed in the suspension. Although some sedimentation was observed in Ca43, the degree of sedimentation (scale) remained at 90 cc or more even after 70 hours, indicating that the CNF was well dispersed and stabilized. Furthermore, Ca44 to 47 showed significant gelation even at a concentration of 0.1 wt%, with Ca46 in particular forming a fairly hard gel, and Ca45 becoming increasingly hard over time.

[0126] Example 8: Viscosity measurement of CNF obtained from cocoa-derived pulp The viscosity of CNF obtained from cocoa-derived pulp was measured under the conditions described in Table 15 (n=3).

[0127]

[0128] The results are shown in Table 16.

[0129] As a reference, the viscosity of CNF obtained from cedar-derived pulp and cedar CNF was measured under the conditions shown in Table 17 (n=3).

[0130]

[0131] The results are as shown in Table 18. Here, "TEMPO oxidation" means that chemical treatment was carried out using TEMPO in accordance with the description in Saito T., Nishiyama Y., Putaux J.-L., Vignon M., Isoga A. "Homogeneous Suspensions of Individualized Microfibrils from TEMPO-Catalyzed Oxidation of Native Cellulose." Biomacromolecules 2006, 7, 1687-1691. "Water jet treatment 10 times" means that mechanical treatment was carried out 10 times using a high-pressure homogenizer of a water jet machine (Sugino Machine Co., Ltd., equipment name: Star Burst 100).

[0132] Example 9: Production of film using CNF obtained from cocoa-derived pulp 9-1 Distilled water was added to 0.1 g (equivalent to the dry weight) of unbleached cocoa-derived pulp obtained from cocoa shells to prepare 100 mL of a 0.1 wt% suspension. This was treated with an ultrasonic homogenizer according to the test conditions shown in Table 19, and tests were carried out in the same manner as in 7-1 to obtain CNF films (n=5). The properties of the obtained films were evaluated by trained panelists (n=3).

[0133] The results are shown in Table 19.

[0134] The CNF film made from cocoa-derived pulp felt flexible and was not easily torn even when force was applied. On the other hand, although not shown in the table, the CNF film made from another material (cedar) using the same method as above felt crunchy and hard to the touch and was easily torn.

[0135] 9-2 Distilled water was added to 0.1 g (dry weight equivalent) of unbleached cocoa-derived pulp obtained from cocoa shells to prepare 100 mL of a 0.1 wt% suspension. This was treated with an ultrasonic homogenizer under the test conditions shown in Table 20, and the test was carried out in the same manner as in 7-1 to obtain CNF films (n=5). The properties of the obtained films were evaluated by a trained panel (n=3).

[0136] The results are shown in Table 20 and FIG.

[0137] A thinner CNF film was obtained with an alkali (NaOH) concentration of 2 (w / w%) than with a concentration of 5 (w / w%). In the above experiment, a well-dispersed suspension was obtained within the first 2 minutes of treatment at 80°C (ultrasonic treatment), but aggregation was observed within the first 2 minutes of treatment at 140°C, so an additional 2 minutes of treatment was required.

Claims

1. A method for producing a cocoa-derived pulp comprising the step of digesting a cocoa-derived material with an alkaline solution.

2. The method of claim 1, wherein the cocoa-derived material is cocoa shells or cocoa pods.

3. The method according to claim 1, wherein the temperature of the alkaline solution is 80°C or higher and 140°C or lower.

4. The method according to claim 1, wherein the concentration of the alkaline agent in the alkaline solution is 1 w / w% or more and 8 w / w% or less.

5. The method of claim 1, wherein the cooking time is 3 hours or less.

6. Cocoa-derived pulp that satisfies at least one of the following (A) to (C): (A) the ratio of the number of fibers having a length of 100 μm or more to the total number of fibers is 50% or more; (B) the ratio of the number of fibers having a length of 250 μm or more to the number of fibers other than fibers derived from parenchyma cells is 30% or more; (C) the cellulose crystallinity is 40% or more.

7. The cocoa-derived pulp according to claim 6, wherein the ratio of the number of fibers having a length of 200 μm or more to the total number of fibers in (A) is 35% or more.

8. The cocoa-derived pulp according to claim 6, wherein the total number of fibers is the sum of fibers obtained from parenchyma cells, vascular cells and fibrous cells.

9. The cocoa-derived pulp according to claim 6, wherein the ratio of the number of fibers having a length of 450 μm or more to the number of fibers other than those derived from parenchyma cells is 40% or more.

10. The cocoa-derived pulp according to claim 6, in which the graduation level of a measuring cylinder (based on JIS R3505), which is an index of the sedimentation rate, is 80 cc or more at the time of 72 hours in the sedimentation rate measurement method specified below. Sedimentation rate measurement method: 0.1 g (equivalent to dry weight) of cocoa-derived pulp is added to distilled water to obtain a 0.1 w / w% mixed solution (100 mL) which is treated with an ultrasonic homogenizer for 4 minutes to obtain a 0.1 w / w% suspension. The suspension is then poured into a 100 mL measuring cylinder and allowed to stand, and the graduation level of the upper limit of the settled portion of the cocoa-derived pulp is measured at each time point.

11. A cocoa-derived pulp according to claim 6, obtained by the process according to claim 1.

12. A method for producing cocoa-derived cellulose nanofibers, comprising a step of defibrating cocoa-derived pulp.

13. The method of claim 12, wherein the cocoa-derived pulp is obtained by the method of claim 1.

14. The method of claim 12, wherein the defibrating step is carried out by ultrasonic treatment.

15. Cocoa-derived cellulose nanofibers satisfying at least one of the following (D) to (H): (D) the proportion of the number of fibers in the cocoa-derived cellulose nanofiber having a length of 1000 nm or more is 40% or more; (E) the proportion of the number of fibers in the cocoa-derived cellulose nanofiber having a fiber width of 5 nm or less is 50% or more; (F) the average aspect ratio is 200 or more; (G) the cellulose crystallinity is 40% or more; (H) the viscosity of a 1 w / w% aqueous suspension of the cocoa-derived cellulose nanofiber is 900 mPa·s or more.

16. The cocoa-derived cellulose nanofiber according to claim 15, wherein the proportion of fibers having a length of 2000 nm or more in the cocoa-derived cellulose nanofiber in (D) is 50% or more.

17. The cocoa-derived cellulose nanofiber according to claim 15, wherein the graduation level of a measuring cylinder (based on JIS R3505), which is an indicator of the sedimentation rate, is 80 cc or higher at the 72-hour mark in the sedimentation rate measurement method defined below. Sedimentation rate measurement method: Distilled water is added to 0.1 g (equivalent to the dry weight) of the cocoa-derived cellulose nanofiber to obtain 100 mL of a 0.1 w / w% aqueous suspension. The suspension is then poured into a 100 mL measuring cylinder and allowed to stand, and the graduation level of the upper limit of the settled portion of the cocoa-derived cellulose nanofiber is measured at each elapsed time.

18. Cocoa-derived cellulose nanofiber as described in claim 15, wherein the viscosity at (H) is 1500 mPa·s or less.

19. The cocoa-derived cellulose nanofiber according to claim 15, obtained by the method according to claim 12 or 13.

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