Method for removing iminosugar in silkworm powder and method for producing silkworm powder with reduced-iminosugar content

Abstract

The present invention addresses the problem of providing a method for reducing the iminosugar content in silkworm powder. The method that solves this problem is characterized by comprising a step for obtaining an extraction residue extracted from processed silkworms by using a nonpolar organic solvent.

Description

Method for removing iminosugars from silkworm powder and method for producing silkworm powder with low iminosugar content

[0001] The present invention relates to a method for removing imino sugars from silkworm powder and a method for producing silkworm powder with a low imino sugar content.

[0002] Silkworms are relatively rich in protein and have therefore attracted attention as an alternative protein source. Silkworms grow by feeding on mulberry leaves, which contain imino sugars such as 1-deoxynojirimycin, and imino sugars accumulate in the bodies of silkworms that have ingested mulberry leaves. Imino sugars such as 1-deoxynojirimycin are known to have effects such as suppressing blood sugar elevation, and mulberry leaves are used for purposes such as improving diabetes. It is also known that ingesting silkworms containing imino sugars can have an effect of suppressing blood sugar elevation (Patent Document 1).

[0003] However, silkworms may be ingested primarily as a protein source, and the physiological effects of imino sugars may not be necessary. Furthermore, when blood sugar levels are low, such as after strenuous exercise, the blood sugar elevation suppression effect of imino acids may not be desirable.

[0004] Japanese Patent Application Publication No. 8-337530

[0005] An object of the present invention is to provide a method for adjusting the imino sugar content in silkworm powder.

[0006] As a result of intensive research to solve the above-mentioned problems, the inventors discovered that when treated silkworm material is extracted with an organic solvent, including a non-polar organic solvent, iminosugars, although water-soluble compounds, are transferred to the organic solvent and removed, thereby completing the present invention.

[0007] That is, the present invention includes the following aspects.

[0008] [1] A method for removing iminosugars from silkworm powder, comprising the step of extracting treated silkworm material with an organic solvent containing a nonpolar organic solvent and obtaining an extraction residue. [2] The method for removing iminosugars according to [1], wherein the nonpolar organic solvent is hexane. [3] The method for removing iminosugars according to [1] or [2], wherein the iminosugar is one or more selected from the group consisting of 1-deoxynojirimycin, 2-O-α-D-galactopyranosyl-1-deoxynojirimycin, and fagomine. [4] A method for producing silkworm powder with a low iminosugar content, comprising the step of extracting treated silkworm material with an organic solvent containing a nonpolar organic solvent and obtaining an extraction residue. [5] A method for producing silkworm powder with a low iminosugar content according to [4], wherein the iminosugar is 1-deoxynojirimycin, and the 1-deoxynojirimycin content per 100 g of silkworm powder is 0.4 g or less on a dry weight basis.

[0009] According to the method of the present invention, imino sugars contained in silkworms can be removed, and the imino sugar content in silkworm powder can be reduced.

[0010] The method for removing iminosugars from silkworm powder and the method for producing silkworm powder with low iminosugar content of the present invention (hereinafter collectively referred to as the "method of the present invention") comprise the steps of extracting treated silkworm material with an organic solvent, including a non-polar organic solvent, and obtaining an extraction residue.

[0011] Silkworm powder is obtained by drying and powdering silkworms. The growth stage of the silkworms used as the raw material is not particularly limited, and any of larvae, pupae, and adults may be used, with larvae being preferred. Examples of methods for producing silkworm powder include those described in JP-A-08-337530, which describes a method in which fourth- to fifth-instar silkworms, which are the most heavily loaded at the end of their life, are subjected to an antioxidant treatment using nitrogen gas, followed by freeze-drying and powdering. This method can be used.

[0012] The method of the present invention includes a step of extracting the treated silkworm product obtained by each of the above treatments with an organic solvent, including a non-polar organic solvent, to obtain an extraction residue. The treated silkworm product to be subjected to extraction is not particularly limited and may be a treated silkworm product obtained by any of the treatments, but from the viewpoint of the effect of removing iminosugars, it is preferable to subject the dried powder obtained by drying and crushing to extraction.

[0013] Examples of organic solvents used as extraction solvents include nonpolar organic solvents such as n-hexane, n-heptane, n-octane, n-nonane, n-decane, and cyclohexane, and polar organic solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, isobutyl alcohol, butyl alcohol, ethyl acetate, acetone, and acetonitrile. These can be used alone or in combination. Among these, from the viewpoint of the iminosugar removal effect, it is preferable to include a nonpolar organic solvent, and n-hexane is preferably used as the nonpolar organic solvent. The nonpolar organic solvent preferably accounts for 50% by mass or more of the organic solvent, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 100% by mass.

[0014] The extraction method is not particularly limited, and for example, the treated silkworm material may be mixed with and immersed in an organic solvent containing a nonpolar organic solvent in an amount 1 to 10 times by mass relative to the treated silkworm material, and extraction treatment may be carried out at 30 to 60°C for about 0.5 to 12 hours.

[0015] After the extraction treatment, the extract and the extraction residue are separated by solid-liquid separation treatment. The solid-liquid separation treatment method is not particularly limited, and examples thereof include known methods such as suction filtration and centrifugation.

[0016] The extraction residue is further dried and / or crushed as necessary to obtain silkworm powder. Known drying methods can be used, such as hot air drying, low-temperature drying, and freeze-drying, with freeze-drying being preferred. The crushing method is not particularly limited, and can be performed using known crushing devices, such as a cutter mill, roll mill, hammer mill, ball mill, and bead mill.

[0017] Imino sugars such as 1-deoxynojirimycin are water-soluble compounds, but in the extraction treatment using the organic solvent containing the nonpolar solvent, at least a portion of them is transferred to the organic solvent containing the nonpolar solvent and removed, resulting in a decrease in the imino sugar content in the extraction residue.

[0018] The silkworm powder obtained by the method of the present invention has a reduced iminosugar content compared to the treated silkworm product before extraction. For example, the 1-deoxynojirimycin (1-DNJ) content can be reduced by preferably 20% by mass or more, more preferably 30% by mass or more, and particularly preferably 40% by mass or more. The 2-O-α-D-galactopyranosyl-1-deoxynojirimycin (GAL-DNJ) content can be reduced by preferably 10% by mass or more, more preferably 20% by mass or more, and the fagomine content can be reduced by preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

[0019] The content of each iminosugar in the silkworm powder obtained by the method of the present invention is, for example, preferably 0.4 g or less, more preferably 0.3 g or less, of 1-deoxynojirimycin, preferably 6 mg or less, more preferably 5 mg or less, of 2-0-α-D-galactopyranosyl-1-deoxynojirimycin, and preferably 20 mg or less, more preferably 10 mg or less, per 100 g of silkworm powder on a dry weight basis.

[0020] In the method of the present invention, an extract is obtained by removing the extraction residue after the extraction process using solid-liquid separation. This extract is rich in unsaturated fatty acids such as oleic acid, α-linolenic acid, and linoleic acid, and plant sterols such as β-sitosterol. Therefore, this extract can be used for applications such as reducing LDL cholesterol and neutral fat, and can also be incorporated into cosmetics and topical skin preparations as an ingredient to enhance emulsion stability, skin affinity, skin permeability, and liposome stability. This silkworm extract can also be rich in iminosugars. The extract may be further processed by concentration, purification, drying, etc.

[0021] The silkworm powder obtained as described above can also be blended with known food additives and / or food ingredients to form foods and beverages. The manufacturing method is not particularly limited and can be prepared according to conventional methods. The form is also not particularly limited, and examples include protein bars, protein powders, starch-based foods such as bread, biscuits, pancakes, noodles, and tablet candies; confectioneries such as gum, candy, and Japanese sweets; meat foods such as ham and sausage; fish foods such as chikuwa (fish cake) and kamaboko (fish paste); seafood foods; seasonings such as dressings, soy sauce, jam, and furikake (rice toppings); protein drinks; tea, juice, soft drinks, and alcoholic beverages. Among food ingredients, it is particularly suitable for combining with matcha powder, resulting in foods and beverages with an excellent flavor. Foods and beverages include foods for specified health uses, functional foods, and dietary supplements that have been approved or notified for mineral supplementation or for preventing or improving mineral deficiency.

[0022] It can also be made into a form of feed or pet food, which is prepared according to a conventional method by appropriately blending the silkworm powder with known feed ingredients, gelling agents, shape-retaining agents, pH adjusters, seasonings, preservatives, nutritional supplements, etc. The form is not particularly limited, and any form such as pellets, flakes, or mash can be exemplified, and it can be used as, for example, feed for livestock such as cows, pigs, chickens, sheep, and horses, pet food for dogs and cats, and aquatic feed for fish and shellfish.

[0023] Furthermore, the silkworm powder can be formulated by combining it with a pharmaceutically acceptable carrier, if necessary. Examples of pharmaceutically acceptable carriers include glucose, lactose, starch, mannitol, dextrin, fatty acid glycerides, polyethylene glycol, hydroxyethyl starch, ethylene glycol, polyoxyethylene sorbitan fatty acid esters, amino acids, gelatin, albumin, water, and physiological saline. Furthermore, conventional additives such as stabilizers, humectants, emulsifiers, binders, isotonicity agents, and excipients can be added as needed. The formulation is not particularly limited, and examples include liquids, powders, granules, capsules, and tablets, which can be prepared according to conventional methods.

[0024] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0025] Example 1: Production of Silkworm Powder: 5000 mL of hexane was added to 1000.18 g of dried silkworm powder (MorSilk® Powder; Morus Corporation) as a processed silkworm product, and extraction was carried out with stirring at 40-45°C for 1 hour. After the treatment, the mixture was suction filtered to separate the extraction residue (900.34 g) and the extract (1029.81 g). The extraction residue was vacuum dried (-0.09 MPa) at 40°C or below and dried for 74 hours until it reached a constant weight, yielding a dried product (884.51 g), which was then pulverized to obtain silkworm powder.

[0026] The silkworm powder before and after the solvent extraction treatment was subjected to component analysis by the following method. The results are shown in Table 1.

[0027] (Analysis Methods) Moisture, protein, lipid, ash, dietary fiber, and sodium were analyzed using the known atmospheric pressure heating and drying method, combustion method, Soxhlet extraction method, direct ashing method, enzymatic gravimetric method, and atomic absorption spectrometry, respectively. Carbohydrate, sugar, and energy were calculated using the following formula. <Calculation Formula> Carbohydrate: 100 - (moisture + protein + lipid + ash) Sugar: 100 - (moisture + protein + lipid + ash + dietary fiber) Energy: Protein x 4 + lipid x 9 + sugar x 4 + dietary fiber x 2. 1-DNJ, fagomin, and GAL-DNJ were analyzed using liquid chromatography-mass spectrometry. Specifically, the analysis was performed as follows. First, 30 mL of a mixture of water, methanol, and acetic acid (50:50:1) was added to 0.4 g of silkworm powder, and the mixture was extracted (shaken) for 10 minutes. This extraction was then repeated three times. After centrifugation, the mixture was adjusted to 100 mL and then diluted appropriately before being analyzed by liquid chromatography under the following conditions: <Liquid chromatography mass spectrometry operating conditions> Column: TSKgel Amide-80, φ4.6 mm × 250 mm, particle size 5 μm Mobile phase: Acetonitrile and 1% acetic acid mixture (65:35) Flow rate: 1.0 mL / min Column temperature: 40°C Ionization method: Electrospray (positive ion detection mode) Set mass number (m / z) 1-DNJ: 164.1 → 110.0 Fagomine: 148.2 → 85.9 GAL-DNJ: 326.0 → 163.8

[0028]

[0029] It was confirmed that the water-soluble iminosugars (1-deoxynojirimycin, fagomine, 2-O-α-D-galactopyranosyl-deoxynojirimycin) were significantly reduced by the solvent extraction treatment.

[0030] The extract obtained after suction filtration was also analyzed by the following method, and the results are shown in Table 2.

[0031] (Analysis Method) Total fatty acids, saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, n-3 unsaturated fatty acids, n-6 unsaturated fatty acids, and n-9 unsaturated fatty acids were analyzed by gas chromatography under the following conditions. Gas chromatograph operating conditions: Model: 7890B [Agilent Technologies] Detector: FID Column: DB-23 [Agilent Technologies] φ0.25 mm x 30 m, film thickness: 0.25 μm Temperature: Sample injection port 250 °C Column 50 °C (1 min hold) → 10 °C / min increase → 170 °C → 1.2 °C / min increase → 210 °C Sample introduction system: Split (1:20) Gas flow rate: Hydrogen 35 mL / min, air 300 mL / min, nitrogen (make-up) 20 mL / min Gas pressure: Helium (carrier gas) 115 kPa Injection volume: 1 μL Cholesterol was analyzed by known column chromatography and gas chromatography using a silica column. Sterols were analyzed by silica gel column chromatography and gas chromatography using a DB-1 (Agilent Technologies) column under the following conditions. <Gas chromatograph operating conditions> Model: GC2010 Plus [Shimadzu Corporation] Detector: FID Column: DB-1 [Agilent Technologies] φ0.25 mm x 15 m, film thickness 0.25 μm Temperature: Sample injection port 290°C, detector 290°C Column 240°C → 3°C / min temperature increase → 280°C Sample introduction system: Split (1:30) Gas flow rate: Helium (carrier gas) 1.0 L / min, helium (make-up gas) 30 mL / min, hydrogen 40 mL / min, air 400 mL / min Injection volume: 1 μL

[0032]

[0033] The extract contained large amounts of unsaturated fatty acids, such as oleic acid (n-9), α-linolenic acid (n-3), and linoleic acid (n-6), as well as plant sterols, such as β-sitosterol, at concentrations approximately three times higher than those found in mulberry leaves.

[0034] The method of the present invention makes it possible to adjust the imino sugar content in silkworm powder, and is therefore useful as a method for producing raw materials for foods, beverages, etc.

Claims

1. A method for removing iminosugars from silkworm powder, comprising the steps of extracting treated silkworm material with an organic solvent including a non-polar organic solvent and obtaining an extraction residue.

2. The method for removing iminosugars according to claim 1, wherein the non-polar organic solvent contains hexane.

3. The method for removing iminosugars according to claim 1 or 2, wherein the iminosugar is one or more species selected from the group consisting of 1-deoxynojirimycin, 2-O-α-D-galactopyranosyl-1-deoxynojirimycin and fagomine.

4. A method for producing silkworm powder with a low iminosugar content, comprising the step of extracting treated silkworm material with an organic solvent including a non-polar organic solvent to obtain an extraction residue.

5. A method for producing silkworm powder with a low iminosugar content according to claim 4, wherein the silkworm powder contains 1-deoxynojirimycin as the iminosugar, and the content of 1-deoxynojirimycin per 100 g of silkworm powder is 0.4 g or less on a dry weight basis.

6. A method for producing a silkworm extract, comprising the steps of extracting treated silkworm material with an organic solvent including a non-polar organic solvent, and removing the extraction residue to obtain an extract.

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