Method for preparing soluble dietary fiber by solid-state fermentation of wheat bran

Abstract

This invention belongs to the field of soluble dietary fiber, specifically relating to a method for preparing soluble dietary fiber through solid-state fermentation of wheat bran. The invention uses wheat bran, *Zygosporum tobira*, auxiliary carbon source, nitrogen source, and inorganic salts for solid-state fermentation, ultrasonic extraction, centrifugation, low-temperature settling, filtration, and drying to obtain soluble dietary fiber. This invention is based on the nucleophilic addition between a thiol group (R-SH) and an amino group (R-NH2). In the reaction, the sulfur atom of the thiol group attacks the nitrogen atom of the amino group, forming a C-S bond and nitrogen (N2) molecules, while simultaneously releasing hydrogen ions (H+). + Because 3-mercapto-2-butanone gas contains ketone groups, the soluble dietary fiber containing butanone groups produced after reacting with amino groups has a unique aroma. This aroma can improve the taste of dietary fiber, making it easier to eat and more palatable.

Description

Technical Field

[0001] This invention relates to the field of soluble dietary fiber, and in particular to a method for preparing soluble dietary fiber by solid-state fermentation of wheat bran. Background Technology

[0002] Wheat bran is rich in cellulose and hemicellulose, as well as relatively abundant protein, fat, oligosaccharides, phytic acid, and natural antioxidants. Therefore, wheat bran is a representative dietary fiber resource that combines compounds beneficial to health.

[0003] Chinese Patent CN109170922B discloses a method for preparing soluble dietary fiber from wheat bran, belonging to the field of agricultural product deep processing technology. The method includes the following steps: ultrafinely pulverized wheat bran is treated with α-amylase and papain respectively, filtered through gauze, and the filter residue is dried at 105℃; the pretreated wheat bran is added to a citric acid aqueous solution with a pH of 4.6 and ultrasonically treated for 30 min; the ultrasonically pretreated mixture is added to a subcritical extraction vessel for extraction, and cooled after extraction; the cooled sample is centrifuged, the supernatant is concentrated, precipitated with 95% ethanol, centrifuged again, dissolved, dialyzed, and spray-dried to obtain white powdered soluble dietary fiber from wheat bran.

[0004] Chinese Patent CN104187746B: A process for preparing soluble dietary fiber from mung bean husks by fermentation. The process uses mung bean husks, a byproduct of bean sprout production, as raw material. A mixture of *Lactobacillus bulgaricus* and *Streptococcus thermophilus* is used as a fermenting agent. The mung bean husk slurry, obtained after drying, pulverizing, seasoning, sterilizing, and cooling, is inoculated, fermented, filtered, the filtrate is precipitated with alcohol, dried, and ground to obtain soluble dietary fiber. This method avoids the destruction of nutrients during the preparation of soluble dietary fiber, ensuring the physiological activity of the obtained soluble dietary fiber, and increasing the extraction rate of soluble dietary fiber from mung bean husks to 10.67%.

[0005] Chinese Patent CN106136249A discloses a method for producing soluble soybean dietary fiber via fermentation. The method uses soybean residue as the main raw material, adds KH₂PO₄, FeSO₄, and VB₁ to prepare a fermentation medium, inoculates with Pleurotus ostreatus mycelium, and controls the fermentation temperature and time for liquid fermentation. After freeze-drying and pulverization, a soluble soybean dietary fiber product with high soluble dietary fiber content and safe for consumption is obtained. This invention produces soluble soybean dietary fiber with low cost, high yield, and strong activity. The product is a light yellow powder with a purity of 90-95%.

[0006] The above-mentioned patents and existing technologies for the fermentation preparation of soluble dietary fiber involve a relatively complex operation process, difficult-to-control fermentation conditions, and low yield of soluble dietary fiber. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing soluble dietary fiber through solid-state fermentation of wheat bran, the operation steps of which are as follows:

[0008] S1: Weigh 5-10 parts of wheat bran, grind and sterilize it, then add 8-16 parts of good serotoninus with a concentration of 107 cells / mL, 0.6-1.2 parts of auxiliary carbon source, 0.6-1.2 parts of nitrogen source, 0.1-1 parts of inorganic salt, and 60-90 parts of water for solid-state fermentation.

[0009] S2: After fermentation, dry, grind through a 60-mesh sieve, add 80-100 parts of distilled water, heat to 40-60℃, and perform ultrasonic extraction;

[0010] S3: After ultrasonic extraction, cool to room temperature and centrifuge. Add 200-300 parts of ethanol to the clear liquid after centrifugation, let stand at low temperature for 20-30 hours, filter, and dry to obtain soluble dietary fiber.

[0011] As a preferred embodiment of the present invention, the auxiliary carbon source is glucose, sucrose, maltose, α-lactose, or D-xylose.

[0012] As a preferred embodiment of the present invention, the nitrogen source is CO(NH2)2, peptone, (NH4)2SO4, yeast extract, or soybean residue.

[0013] As a preferred embodiment of the present invention, the inorganic salts are zinc sulfate, magnesium sulfate, dipotassium hydrogen phosphate, sodium chloride, calcium chloride, and copper sulfate.

[0014] As a preferred embodiment of the present invention, the solid-state fermentation temperature is 25-45℃ and the solid-state fermentation time is 96-144h.

[0015] As a preferred embodiment of the present invention, the ultrasonic extraction power is 500-600W and the time is 60-80min.

[0016] As a preferred embodiment of the present invention, the drying temperature of S3 is 40-50℃ and the drying time is 40-70 min.

[0017] Furthermore, the soluble dietary fiber is modified using the following method:

[0018] Soluble dietary fiber is subjected to plasma modification in a plasma device under a mixed gas atmosphere of hydrogen and nitrogen in a volume ratio of 1:2-5 for 30-60 minutes to obtain amino-containing soluble dietary fiber. Then, 3-mercapto-2-butanone gas with a volume ratio of 3-10% of hydrogen is introduced to continue plasma modification for 30-60 seconds, so that the thiol groups and amino groups can undergo an addition reaction to obtain butanone-based soluble dietary fiber with a fragrant odor.

[0019] As a preferred embodiment of the present invention, the plasma modification conditions are as follows:

[0020] 500W radio frequency power source plasma equipment; the radio frequency power source has a frequency of 12-23MHz; the gas flow rate is 5-15ml / min.

[0021] Reaction mechanism:

[0022] Soluble dietary fiber was plasma modified in a plasma device under a mixed gas atmosphere of hydrogen and nitrogen in a volume ratio of 1:2-5 to obtain amino-containing soluble dietary fiber; then 3-mercapto-2-butanone gas was introduced to continue plasma modification, causing the mercapto groups to undergo a Michael addition reaction with the amino groups to obtain soluble dietary fiber containing butanone groups.

[0023] Technical effects:

[0024] The present invention provides a method for preparing soluble dietary fiber by solid-state fermentation of wheat bran. Compared with the prior art, the present invention has the following significant advantages:

[0025] 1. This invention is based on the nucleophilic addition between a thiol group (R-SH) and an amino group (R-NH2). In the reaction, the sulfur atom of the thiol group attacks the nitrogen atom of the amino group, forming a CS bond and nitrogen gas (N2) molecules, while releasing hydrogen ions (H+). Since 3-mercapto-2-butanone gas contains a ketone group, the soluble dietary fiber containing butanone groups generated after reacting with the amino group has a unique aroma. This aroma can improve the taste of the dietary fiber, making it easier to eat and more palatable.

[0026] 2. The soluble dietary fiber prepared by this invention has high swelling power and water holding capacity, and has good functional properties;

[0027] 3. This invention uses ultrasound-assisted solid-state fermentation of *Saurospora hygroscopica* to extract soluble dietary fiber from wheat bran, which can effectively improve the yield of soluble dietary fiber. Detailed Implementation

[0028] The present invention will be described in detail with reference to the embodiments, but the claims of the present invention are not intended to limit the scope of the invention.

[0029] Example 1

[0030] A method for preparing soluble dietary fiber by solid-state fermentation of wheat bran, comprising the following steps:

[0031] S1: Weigh 5g of wheat bran, crush and sterilize it, then add 8g of *Neurospora sinensis* with a concentration of 107 cells / mL, 0.6g of auxiliary carbon source, 0.6g of nitrogen source, 0.1g of inorganic salt, and 60g of water for solid-state fermentation;

[0032] S2: After fermentation, dry, grind through a 60-mesh sieve, add 80g of distilled water, heat to 40℃, and perform ultrasonic extraction;

[0033] S3: After ultrasonic extraction, cool to room temperature and centrifuge. Add 200g of ethanol to the clear liquid after centrifugation, let stand at low temperature for 20h, filter, and dry to obtain soluble dietary fiber.

[0034] The auxiliary carbon source is glucose.

[0035] The nitrogen source is CO(NH2)2.

[0036] The inorganic salt mentioned is zinc sulfate.

[0037] The solid-state fermentation temperature is 25℃ and the solid-state fermentation time is 96h.

[0038] The ultrasonic extraction power was 500W and the time was 60min.

[0039] The drying temperature of S3 is 40℃ and the drying time is 40 min.

[0040] Furthermore, the soluble dietary fiber is modified using the following method:

[0041] Soluble dietary fiber was plasma modified in a plasma device under a mixed gas atmosphere of hydrogen and nitrogen in a volume ratio of 1:2 for 30 minutes to obtain amino-containing soluble dietary fiber. Then, 3-mercapto-2-butanone gas, accounting for 3% of the hydrogen volume ratio, was introduced to continue plasma modification for 30 seconds, so that the thiol groups and amino groups could undergo an addition reaction to obtain butanone-based soluble dietary fiber with a fragrant odor.

[0042] The plasma modification conditions are as follows:

[0043] A 500W radio frequency power source plasma device; the radio frequency power source has a frequency of 12MHz; the gas flow rate is 5ml / min.

[0044] Example 2

[0045] A method for preparing soluble dietary fiber by solid-state fermentation of wheat bran, comprising the following steps:

[0046] S1: Weigh 6g of wheat bran, crush and sterilize it, then add 10g of good serotonin with a concentration of 107 cells / mL, 0.8g of auxiliary carbon source, 0.8g of nitrogen source, 0.5g of inorganic salt, and 70g of water for solid-state fermentation;

[0047] S2: After fermentation, dry, grind through a 60-mesh sieve, add 85g of distilled water, heat to 45℃, and perform ultrasonic extraction;

[0048] S3: After ultrasonic extraction, cool to room temperature and centrifuge. Add 240g of ethanol to the clear liquid after centrifugation, let stand at low temperature for 23h, filter, and dry to obtain soluble dietary fiber.

[0049] The auxiliary carbon source is sucrose.

[0050] The nitrogen source is peptone.

[0051] The inorganic salt mentioned is magnesium sulfate.

[0052] The solid-state fermentation temperature is 30℃ and the solid-state fermentation time is 108h.

[0053] The ultrasonic extraction power was 550W and the time was 65 minutes.

[0054] The drying temperature of S3 is 45℃ and the drying time is 50 min.

[0055] Furthermore, the soluble dietary fiber is modified using the following method:

[0056] Soluble dietary fiber was plasma modified in a plasma device under a mixed gas atmosphere of hydrogen and nitrogen in a volume ratio of 1:3 for 40 minutes to obtain amino-containing soluble dietary fiber. Then, 3-mercapto-2-butanone gas with a volume ratio of 6% hydrogen was introduced to continue plasma modification for 40 seconds, so that the thiol groups and amino groups could undergo an addition reaction to obtain butanone-based soluble dietary fiber with a fragrant odor.

[0057] The plasma modification conditions are as follows:

[0058] A 500W radio frequency power source plasma device; the radio frequency power source has a frequency of 16MHz; the gas flow rate is 8ml / min.

[0059] Example 3

[0060] A method for preparing soluble dietary fiber by solid-state fermentation of wheat bran, comprising the following steps:

[0061] S1: Weigh 9g of wheat bran, crush and sterilize it, then add 14g of good serotonin with a concentration of 107 cells / mL, 1g of auxiliary carbon source, 1g of nitrogen source, 0.8g of inorganic salt, and 80g of water for solid-state fermentation;

[0062] S2: After fermentation, dry, grind through a 60-mesh sieve, add 95g of distilled water, heat to 55℃, and perform ultrasonic extraction;

[0063] S3: After ultrasonic extraction, cool to room temperature and centrifuge. Add 280g of ethanol to the clear liquid after centrifugation, let stand at low temperature for 28h, filter, and dry to obtain soluble dietary fiber.

[0064] The auxiliary carbon source is maltose.

[0065] The nitrogen source is (NH4)2SO4.

[0066] The inorganic salt mentioned is dipotassium hydrogen phosphate.

[0067] The solid-state fermentation temperature is 40℃ and the solid-state fermentation time is 133h.

[0068] The ultrasonic extraction power was 550W and the time was 75min.

[0069] The drying temperature of S3 is 45℃ and the drying time is 60min.

[0070] Furthermore, the soluble dietary fiber is modified using the following method:

[0071] Soluble dietary fiber was plasma modified in a plasma device under a mixed gas atmosphere of hydrogen and nitrogen in a volume ratio of 1:4 for 50 min to obtain amino-containing soluble dietary fiber. Then, 3-mercapto-2-butanone gas with a volume ratio of 9% hydrogen was introduced to continue plasma modification for 50 s, so that the thiol groups and amino groups could undergo an addition reaction to obtain butanone-based soluble dietary fiber with a fragrant odor.

[0072] The plasma modification conditions are as follows:

[0073] A 500W radio frequency power source plasma device; the radio frequency power source has a frequency of 20MHz; the gas flow rate is 13ml / min.

[0074] Example 4

[0075] A method for preparing soluble dietary fiber by solid-state fermentation of wheat bran, comprising the following steps:

[0076] S1: Weigh 10g of wheat bran, crush and sterilize it, then add 16g of good basal saponins with a concentration of 107 cells / mL, 1.2g of auxiliary carbon source, 1.2g of nitrogen source, 1g of inorganic salt, and 90g of water for solid-state fermentation;

[0077] S2: After fermentation, dry, grind through a 60-mesh sieve, add 100g of distilled water, heat to 60℃, and perform ultrasonic extraction;

[0078] S3: After ultrasonic extraction, cool to room temperature and centrifuge. Add 300g of ethanol to the clear liquid after centrifugation, let stand at low temperature for 30h, filter, and dry to obtain soluble dietary fiber.

[0079] The auxiliary carbon source is D-xylose.

[0080] The nitrogen source is soybean residue.

[0081] The inorganic salt mentioned is sodium chloride.

[0082] The solid-state fermentation temperature is 45℃ and the solid-state fermentation time is 144h.

[0083] The ultrasonic extraction power was 600W and the time was 80min.

[0084] The drying temperature of S3 is 50°C and the drying time is 70 min.

[0085] Furthermore, the soluble dietary fiber is modified using the following method:

[0086] Soluble dietary fiber was plasma modified in a plasma device under a mixed gas atmosphere of hydrogen and nitrogen in a volume ratio of 1:5 for 60 min to obtain amino-containing soluble dietary fiber. Then, 3-mercapto-2-butanone gas with a volume ratio of 10% of hydrogen was introduced to continue plasma modification for 60 s, so that the thiol groups and amino groups could undergo an addition reaction to obtain butanone-based soluble dietary fiber with a fragrant odor.

[0087] The plasma modification conditions are as follows:

[0088] A 500W radio frequency power source plasma device; the radio frequency power source has a frequency of 23MHz; the gas flow rate is 15ml / min.

[0089] Comparative Example 1

[0090] Soluble dietary fiber was plasma modified in a plasma device under a mixed gas atmosphere of hydrogen and nitrogen in a volume ratio of 1:2 to obtain amino-containing soluble dietary fiber; then 3-mercapto-2-butanone gas was introduced to continue plasma modification, causing the mercapto groups to undergo a Michael addition reaction with the amino groups to obtain soluble dietary fiber containing butanone groups.

[0091] No modification was performed on the soluble dietary fiber; otherwise, it was the same as in Example 1.

[0092] Comparative Example 2

[0093] No 3-mercapto-2-butanone gas was added; otherwise, it was the same as in Example 1.

[0094] Example Evaluation:

[0095] Evaluation method:

[0096] 1. Soluble dietary fiber yield = (mass of soluble dietary fiber / mass of wheat bran) x 100%

[0097] 2. Water-holding capacity: Weigh 1g of soluble dietary fiber and place it in a beaker. Add water at 20℃ and soak for 1 hour. After draining on filter paper, transfer it to a petri dish and weigh it. Water-holding capacity = (weight of soaked dietary fiber (g) - weight of dry dietary fiber (g)) / weight of dry dietary fiber (g) x 100%

[0098] 3. Swelling Power: Weigh 1g of soluble dietary fiber and place it in a graduated cylinder. Read the volume (mL) of the dietary fiber. Then, add an appropriate amount of water, shake well, and let it stand at room temperature (with the graduated cylinder sealed) for 24 hours. Read the volume (mL) of the dietary fiber after it has absorbed water and swelled. Swelling Power = (Volume of swelled dietary fiber (mL) - Volume of dry dietary fiber (mL)) / Weight of dry dietary fiber (g) x 100%

[0099] Evaluation results:

[0100]

[0101]

[0102] Based on the analysis of the above examples and comparative data, the modified soluble dietary fiber of the present invention has higher swelling power and water holding capacity, and has a unique aroma. This aroma can improve the taste of dietary fiber, making it easier to eat and more palatable. The process of the present invention significantly improves the yield of soluble dietary fiber.

[0103] It is understood that the above detailed description of the present invention is for illustrative purposes only and is not intended to limit the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effects; as long as the usage requirements are met, they are all within the protection scope of the present invention.

Claims

1. A method for preparing soluble dietary fiber by solid-state fermentation of wheat bran, characterized in that, The method includes: S1: Weigh out 5-10 parts by weight of wheat bran, grind and sterilize it, then add 8-16 parts of a 10% concentration. 7 Solid-state fermentation is carried out using good Neurospora spp. (cells / mL), 0.6-1.2 parts auxiliary carbon source, 0.6-1.2 parts nitrogen source, 0.1-1 parts inorganic salt, and 60-90 parts water. S2: After fermentation, dry, grind through a 60-mesh sieve, add 80-100 parts of distilled water, heat to 40-60℃, and perform ultrasonic extraction; S3: After ultrasonic extraction, cool to room temperature and centrifuge. Add 200-300 parts of ethanol to the clear liquid after centrifugation, let stand at low temperature for 20-30 hours, filter, and dry to obtain soluble dietary fiber. Soluble dietary fiber can be modified using methods including: Soluble dietary fiber was placed in a plasma device and subjected to plasma modification in a mixed gas atmosphere of hydrogen and nitrogen in a volume ratio of 1:2-5 for 30-60 minutes to obtain amino-containing soluble dietary fiber. Then, 3-mercapto-2-butanone gas with a hydrogen volume ratio of 3-10% was introduced to continue plasma modification for 30-60 seconds, so that the thiol groups and amino groups could undergo an addition reaction to obtain butanone-based soluble dietary fiber with a fragrant aroma. The conditions for plasma modification are: a 500W radio frequency power source plasma device, with a frequency of 12-23MHz, and a gas flow rate of 5-15ml / min.

2. The method for preparing soluble dietary fiber by solid-state fermentation of wheat bran according to claim 1, characterized in that: The auxiliary carbon source is one of glucose, sucrose, maltose, or D-xylose.

3. The method for preparing soluble dietary fiber by solid-state fermentation of wheat bran according to claim 1, characterized in that: The nitrogen source is one of CO(NH2)2, peptone, (NH4)2SO4, or soybean residue.

4. The method for preparing soluble dietary fiber by solid-state fermentation of wheat bran according to claim 1, characterized in that: The inorganic salt is one of zinc sulfate, magnesium sulfate, dipotassium hydrogen phosphate, and sodium chloride.

5. The method for preparing soluble dietary fiber by solid-state fermentation of wheat bran according to claim 1, characterized in that: The solid-state fermentation temperature is 25-45℃, and the solid-state fermentation time is 96-144h.

6. The method for preparing soluble dietary fiber by solid-state fermentation of wheat bran according to claim 1, characterized in that: The ultrasonic extraction power is 500-600W, and the ultrasonic extraction time is 60-80min.

7. The method for preparing soluble dietary fiber by solid-state fermentation of wheat bran according to claim 1, characterized in that: The drying temperature of S3 is 40-50℃, and the drying time is 40-70 min.

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