Method for increasing content of phenolic compounds

Abstract

The invention discloses a pretreatment method of bran for preparing phenolic compounds. The method comprises the following steps: 1) performing enzymolysis on a bran aqueous solution; 2) centrifuging to obtain a precipitate and a supernatant; (3) detecting the centrifugal supernate obtained in the step (2); wherein the step of detecting the centrifugal supernate in the step (3) comprises the following steps: a) carrying out heat treatment on the supernate to obtain a heat treatment product, and b) detecting the transparency, the 550nm transmissivity and the L value of the heat treatment product obtained in the step a), if the heat treatment product does not meet the requirement, redissolving the precipitate in the step (2), and repeating the steps (2) and (3). The invention also provides a method for increasing the content of phenolic compounds. The method provided by the invention can increase the content of phenolic compounds.

Description

Technical Field

[0001] The present invention belongs to the technical field of food, and particularly relates to a method for increasing the content of phenolic compounds. Background Art

[0002] 4-Vinylguaiacol (4VG), with the chemical name of 2-methoxy-4-vinylphenol, is volatile, has a unique fermented aroma and a relatively high olfactory recognition degree. It is an important flavor substance in soy sauce, white wine, wine and beer, and is also an essential characteristic component for the comprehensive flavor evaluation of these fermented products (Li Qingzhuo. Research progress on flavor substance 4-vinylguaiacol. 2021).

[0003] In recent years, there have been many studies on guaiacol and 4-vinylguaiacol. MISHRA S et al. reviewed 7 different metabolic pathways for the microbial conversion of ferulic acid to 4-vinylguaiacol. (MISHRA S, SACHAN A, VIDYARTHI AS, 2014).

[0004] There have also been many studies on the production of 4-vinylguaiacol by enzymatic methods. For example, using ferulic acid as a substrate and under the action of phenolic acid decarboxylase from Bacillus pumilus, the yield of 4-vinylguaiacol can reach 1.25 g / (L·h) (LEE I Y et al., 1998). This method has the defects of a long production process and being difficult to control.

[0005] Zhao Ting et al. used wheat as a raw material, inoculated yeast, and under the conditions of a yeast inoculation amount of 1.4×10 7 CFU / mL and a fermentation temperature of 20.1°C, the highest mass concentration of 4-VG in wheat beer reached 2.30 mg / L. (Zhao Ting et al. Optimization of the conditions for the production of 4-vinylguaiacol by top-fermenting yeast in wheat beer and construction of its fermentation kinetic model. 2022) However, the production process of this method is relatively long.

[0006] CN 115120521 A mentions a method of using raw lignocellulose as a raw material, mixing it with at least one of the catalysts Ni / C, Ru / C, Pt / C, Pd / C, and performing a solvothermal reaction to obtain a polyphenol-containing active composition. This method requires the use of reagents and catalysts.

[0007] Therefore, there is an urgent need in this field to provide an easy-to-operate method for increasing phenolic compounds. Summary of the Invention

[0008] The present invention provides a pretreatment method for bran for the preparation of phenolic compounds.

[0009] The method provided by the present invention includes:

[0010] 1), steps of enzymatic hydrolysis of wheat bran aqueous solution;

[0011] 2), centrifugation to obtain a precipitate and a supernatant;

[0012] 3), steps of detecting the centrifuged supernatant of step 2);

[0013] Among them, the step of detecting the centrifuged supernatant in step 3) includes: a) heat-treating the supernatant to obtain a heat-treated product, b) detecting the transparency, 550 nm transmittance, and L value of the heat-treated product obtained in step a). If the heat-treated product is opaque, then filter it and then detect the 550 nm transmittance and L value;

[0014] If the heat-treated product does not meet the requirements of being transparent, having a 550 nm transmittance less than 2.0, and an L value less than 30, then redissolve the precipitate of step 2) and repeat steps 2 and 3.

[0015] In some specific embodiments of the present invention, the step of enzymatic hydrolysis of wheat bran aqueous solution includes:

[0016] Treating the wheat bran aqueous solution with a composite enzyme composition, the composite enzyme composition includes amylase, pectinase, and optionally glucoamylase.

[0017] In some specific embodiments of the present invention, based on the weight of wheat bran being 100%, the amylase is 0.01 - 3%, preferably 0.1 - 0.5%, the pectinase is 0.1 - 5%, preferably 0.15 - 1%, and the glucoamylase is 0 - 3%, preferably 0.25 - 1%;

[0018] In some specific embodiments of the present invention, the composite enzyme composition treats the wheat bran aqueous solution at 30 - 50 °C for 1 - 20 h, preferably for 3 - 12 h.

[0019] In some specific embodiments of the present invention, the wheat bran aqueous solution is prepared by mixing wheat bran and water in a ratio of 1:2 - 1:10, preferably 1:3 - 1:5.

[0020] In some specific embodiments of the present invention, the centrifugation is carried out at 1000 - 10000 rpm, preferably 2000 - 8000 rpm, for 10 min - 6 h, preferably 0.5 - 1 h.

[0021] In some specific embodiments of the present invention, the heat treatment of the supernatant is to add 1% (w / w) lysine to the supernatant, stir evenly, and react at 130 °C for 1 h.

[0022] In some specific embodiments of the present invention, the "redissolving the precipitate of step 2) and repeating steps 2 and 3" is carried out 1 - 3 times.

[0023] In some specific embodiments of the present invention, after reconstitution, a step of treating the reconstituted solution with saccharifying enzyme and / or pectinase may be further included.

[0024] In some specific embodiments of the present invention, the enzyme is selected from: Longkote medium temperature alpha amylase, alpha amylase Ban480, kleistase SD80, Dextrozyme, HighDEX, GA-260, Pectinex-Ultra SP-L, Rohapectin PTE100, and / or Pectinase PL.

[0025] The invention also provides a method for increasing the content of phenolic compounds in bran preparation.

[0026] The method provided by the present invention comprises:

[0027] The step of pretreating bran using the above-mentioned pretreatment method of the present invention to obtain a pretreated bran precipitate; and,

[0028] The invention relates to a process for preparing phenolic compounds using the pretreated bran.

[0029] In some specific embodiments of the present invention, the step of preparing phenolic compounds using pretreated bran includes: preparing a bran solution using the bran precipitate obtained after pretreatment, reacting at 140-190°C for 10min-6h, removing the precipitate, and obtaining a solution containing phenolic substances, optionally, further comprising the step of preparing a phenolic substance from the obtained phenolic substance-containing solution, preferably drying the obtained phenolic substance-containing solution to prepare a phenolic substance-containing step.

[0030] The present invention also provides a phenolic substance-containing solution or a phenolic substance-containing composition prepared by the above method.

[0031] By using the method of the present invention, the content of phenolic compounds and the proportion of 4-vinylguaiacol in phenolic compounds can be increased, and the method of the present invention is simple to operate and has low cost. DETAILED DESCRIPTION

[0032] The following is a detailed description of the present invention. The following description of the technical features is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that, unless otherwise defined:

[0033] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0034] In this specification, a numerical range expressed using "above" or "below" means a numerical range including the recited number.

[0035] In this specification, the meaning expressed using "may" includes both the meaning of performing a certain treatment and the meaning of not performing a certain treatment.

[0036] In this specification, the use of "optional" or "optionally" means that certain substances, components, performing steps, applied conditions, and other factors may or may not be used, and there is no limitation on the usage method.

[0037] In this specification, all unit names used are international standard unit names, and unless otherwise specified, the "%" used represents weight or mass percentage content.

[0038] In this specification, the "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc. mentioned refer to the specific elements (e.g., features, structures, properties, and / or characteristics) related to the embodiment, which are included in at least one of the embodiments described herein, and may or may not exist in other embodiments. Additionally, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0039] The present invention provides a pretreatment method for bran for preparing phenolic compounds.

[0040] The method provided by the present invention includes:

[0041] 1), a step of enzymatically hydrolyzing an aqueous bran solution;

[0042] 2), centrifuging to obtain a precipitate and a supernatant;

[0043] 3), a step of detecting the centrifuged supernatant of step 2);

[0044] Among them, the step of detecting the centrifuged supernatant in step 3) includes: a) performing heat treatment on the supernatant to obtain a heat treatment product; b) detecting the transparency, 550 nm transmittance, and L value of the heat treatment product obtained in step a). If the heat treatment product is opaque, then filter it and then detect the 550 nm transmittance and L value.

[0045] If the heat treatment product does not meet the requirements of being transparent, having a 550 nm transmittance less than 2.0, and an L value less than 30, then redissolve the precipitate in step 2) and repeat steps 2 and 3.

[0046] In some specific embodiments of the present invention, the step of enzymatically hydrolyzing the aqueous bran solution includes:

[0047] Treat the aqueous bran solution with a composite enzyme composition, which includes amylase, pectinase, and optionally glucoamylase.

[0048] In some specific embodiments of the present invention, based on 100% of the weight of the bran, the amylase is 0.01 - 3%, preferably 0.1 - 0.5%, the pectinase is 0.1 - 5%, preferably 0.15 - 1%, and the glucoamylase is 0 - 3%, preferably 0.25 - 1%;

[0049] In some specific embodiments of the present invention, based on 100% of the weight of the bran, the amylase is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3.0%.

[0050] In some specific embodiments of the present invention, based on 100% of the weight of the bran, the pectinase is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, or 5.0%.

[0051] In some specific embodiments of the present invention, based on the weight of bran being 100%, the glucoamylase is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3.0%.

[0052] In some specific embodiments of the present invention, the complex enzyme composition treats the aqueous bran solution at 30 - 50°C for 1 - 20 h, preferably for 3 - 12 h.

[0053] In some specific embodiments of the present invention, the complex enzyme composition treats the aqueous bran solution at 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, or 50°C for 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, or 20 h.

[0054] In some specific embodiments of the present invention, the aqueous bran solution is prepared by uniformly mixing bran and water in a ratio of 1:2 - 1:10, preferably 1:3 - 1:5.

[0055] In some specific embodiments of the present invention, the aqueous bran solution is prepared by uniformly mixing bran and water in a ratio of 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.

[0056] In some specific embodiments of the present invention, the centrifugation is carried out at 1000 - 10000 rpm, preferably 2000 - 8000 rpm, for 10 min - 6 h, preferably 0.5 - 1 h.

[0057] In some specific embodiments of the present invention, the centrifugation is carried out at 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, or 10000 rpm for 10 min, 20 min, 30 min, 40 min, 50 min, 1 h, 1.5 h, 2 h, 3 h, 4 h, 5 h, or 6 h.

[0058] In some specific embodiments of the present invention, the heat treatment of the supernatant is to add 1% (w / w) lysine to the supernatant, stir evenly, and react at 130 °C for 1 h.

[0059] In some specific embodiments of the present invention, the step of "redissolving the precipitate in step 2) and repeating steps 2 and 3" is carried out 1-3 times.

[0060] In some specific embodiments of the present invention, the step of "redissolving the precipitate in step 2) and repeating steps 2 and 3" is carried out 1 time.

[0061] In some specific embodiments of the present invention, the step of "redissolving the precipitate in step 2) and repeating steps 2 and 3" is carried out 2 times.

[0062] In some specific embodiments of the present invention, the step of "redissolving the precipitate in step 2) and repeating steps 2 and 3" is carried out 3 times.

[0063] In some specific embodiments of the present invention, after redissolving, it may further include the step of treating the redissolved solution with glucoamylase and / or pectinase.

[0064] In some specific embodiments of the present invention, the enzyme is selected from: Lonza medium-temperature α-amylase, α-amylase Ban480, kleistase SD80, Dextrozyme, HighDEX, GA-260, Pectinex-Ultra SP-L, Rohapectin PTE100, and / or Pectinase PL

[0065] The present invention also provides a method for increasing the content of phenolic compounds prepared from bran.

[0066] The method provided by the present invention includes:

[0067] The step of pretreating bran with the above pretreatment method of the present invention to obtain a pretreated bran precipitate; and,

[0068] The step of preparing phenolic compounds using the pretreated bran.

[0069] In some specific embodiments of the present invention, the step of preparing phenolic compounds using the pretreated bran includes: preparing a bran solution using the obtained bran precipitate after pretreatment, reacting at 140-190 °C for 10 min-6 h, removing the precipitate to obtain a phenolic substance-containing solution, optionally, it further includes the step of preparing a phenolic substance-containing product from the obtained phenolic substance-containing solution, preferably drying the obtained phenolic substance-containing solution to prepare a phenolic substance-containing product step.

[0070] In some specific embodiments of the present invention, the method of drying the obtained phenolic substance-containing solution may include: oven drying, drum drying, vacuum drying, and spray drying.

[0071] In some specific embodiments of the present invention, the bran solution is prepared using the bran precipitate obtained after pretreatment, and the reaction is carried out at 140°C, 150°C, 160°C, 170°C, 180°C, or 190°C for 10 min, 20 min, 30 min, 40 min, 50 min, 1 h, 1.5 h, 2 h, 3 h, 4 h, 5 h, or 6 h.

[0072] The present invention also provides a phenolic substance-containing solution or a phenolic substance-containing composition prepared by the above method.

[0073] Example

[0074] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods for the unrecorded specific conditions in the following examples are usually measured according to national standards. If there is no corresponding national standard, then according to general international standards, normal conditions, or according to the conditions recommended by the manufacturer, proceed. Unless otherwise stated, all parts are by weight, and all percentages are by weight percentages.

[0075] Unless otherwise defined or indicated, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein can be applied to the method of the present invention.

[0076] In the following embodiments of the present invention,

[0077] Supernatant heat treatment method:

[0078] Take a certain amount of supernatant, add 1% (w / w) lysine, stir evenly and transfer to a hydrothermal reactor, and react at 130 degrees for 1 hour. After the reaction is completed, transfer to a transparent glass test tube and observe whether the product is transparent under strong light. If the product is a transparent solution, directly use a Trix colorimeter to measure the 550nm transmittance and L value; if the product is an opaque solution, use a quick filter paper to filter to obtain a clear liquid, and then use a Trix colorimeter to measure the 550nm transmittance and L value of the clear liquid. (Refer to Liang Xiaofang, The Effect of Glutathione Addition on Dry White Wine, 2019, Winemaking Technology)

[0079] In the following embodiments of the present invention, the following are used:

[0080] Bran: commercially available;

[0081] Amylase A was purchased from Shandong Longkete Enzyme Preparation Co., Ltd., with the trade name of Longkete Medium-temperature α-Amylase and an enzyme activity of 20,000 u / g;

[0082] Amylase B was purchased from Novozymes, with the trade name of α-Amylase Ban480 and an enzyme activity of 480 KNU / g;

[0083] Amylase C was purchased from Amano Corporation, with the trade name of kleistase SD80 and an enzyme activity of 65,000 u / g;

[0084] Glucoamylase A was purchased from Novozymes, with the trade name of Dextrozyme and an enzyme activity of 680 NPUN / g;

[0085] Glucoamylase B was purchased from Bestzyme, with the trade name of HighDEX and an enzyme activity of 90,000 U / g;

[0086] Glucoamylase C was purchased from Angel Yeast Co., Ltd., with the trade name of GA-260 and an enzyme activity of 260,000 u / mL;

[0087] Pectinase A was purchased from Novozymes, with the trade name of Pectinex-Ultra SP-L and an enzyme activity of 3300 PGNU / g;

[0088] Pectinase B was purchased from AB Enzyme Preparation Company, with the trade name of Rohapectin PTE100 and an enzyme activity of 100 PTF / mg;

[0089] Pectinase C was purchased from Amano Corporation, with the trade name of Pectinase PL and an enzyme activity of 2000 u / mL.

[0090] Example 1:

[0091] The bran was crushed and passed through a 20-mesh sieve. 200 g of the crushed bran was taken and 800 g of water was added and stirred evenly. The ratio of bran to water was 1:4 (w / v) to obtain a bran aqueous solution.

[0092] After adjusting the pH to 6, 1 g of amylase A, 2 g of glucoamylase A, and 2 g of pectinase A were added and stirred evenly. The reaction was carried out at 50 °C for 4 h. After the reaction was completed, centrifugation was carried out at 8000 rpm for 1 h to separate the supernatant. 454.5 g of the lower precipitate was obtained and labeled as 1-1. The supernatant was heat-treated. The obtained product was opaque. After the product was filtered through a filter paper and detected, the transmittance at 550 nm was 4.34 and the L value was 27.24.

[0093] Take 450 g of the precipitate and add 800 g of water again. Stir for 30 min at 50 °C. Centrifuge the solution at 8000 rpm for 1 h to separate the supernatant, obtaining 440.6 g of the lower-layer precipitate. Heat-treat the supernatant. The obtained product is transparent. After testing, the transmittance at 550 nm is 1.66, and the L value is 25.93.

[0094] Take 400 g of the precipitate and add 800 g of water to adjust the pH to 4 to obtain the mother liquor. Take 500 g of the mother liquor and transfer it to a high-pressure reaction kettle. The reaction temperature is 170 °C, and the reaction time is 1 h. After the reaction is completed, filter to remove the precipitate to obtain a solution containing phenolic substances. After testing, the total phenolic content contained therein is 10.8 mg / kg of bran. Determine the percentage of 4-vinylguaiacol in the phenolic substances. The results are shown in Table 1.

[0095] Example 2:

[0096] Take the bran, crush it and pass it through a 20-mesh sieve. Take 200 g of the crushed bran and add 800 g of water and stir evenly. Bran: water = 1:4 (w / v) to obtain an aqueous bran solution.

[0097] After adjusting the pH to 5, add 0.4 g of amylase B, 0.5 mL of glucoamylase C, and 0.8 g of pectinase B, and stir evenly. React at 45 °C for 6 h. After the reaction is completed, centrifuge at 8000 rpm for 0.5 h to separate the supernatant, obtaining 447.4 g of the lower-layer precipitate. Heat-treat the supernatant. The obtained product is opaque. After filtering the product with filter paper and testing, the transmittance at 550 nm is 10.54, and the L value is 56.38.

[0098] Take 440 g of the precipitate and add 800 g of water again. Stir for 30 min at 45 °C. Centrifuge the solution at 8000 rpm for 0.5 h to separate the supernatant, obtaining 437.9 g of the lower-layer precipitate. Heat-treat the supernatant. The obtained product is transparent. After testing, the transmittance at 550 nm is 1.73, and the L value is 27.32.

[0099] Take 400 g of the precipitate and add 800 g of water to adjust the pH to 4.5 to obtain the mother liquor. Take 500 g of the mother liquor and transfer it to a high-pressure reaction kettle. The temperature is 170 °C, and the reaction is carried out for 1 h. After the reaction is completed, filter to remove the precipitate to obtain a solution containing phenolic substances. After testing, the total phenolic content contained therein is 9.6 mg / kg of bran. Determine the percentage of 4-vinylguaiacol in the phenolic substances. The results are shown in Table 1.

[0100] Example 3:

[0101] Take the bran, crush it and pass it through a 20-mesh sieve. Take 200 g of the crushed bran and add 800 g of water and stir evenly. Bran: water = 1:4 (w / v) to obtain an aqueous bran solution.

[0102] After adjusting the pH to 5.5, add 1 g of amylase B, 1 mL of glucoamylase C, and 1 g of pectinase A, stir evenly, react at 50 °C for 5 h. After the reaction is completed, centrifuge at 7000 rpm for 0.5 h, separate the supernatant, and obtain 451.2 g of the lower precipitate. Heat-treat the supernatant. The obtained product is opaque. After filtering the product with a filter paper and detecting, the transmittance at 550 nm is 9.03, and the L value is 42.28.

[0103] Take 450 g of the precipitate and add 800 g of water again, stir at 50 °C for 30 min. Centrifuge the solution at 7000 rpm for 0.5 h, separate the supernatant, and obtain 445.3 g of the lower precipitate A. Heat-treat the supernatant. The obtained product is opaque. After detection, the transmittance at 550 nm is 3.41, and the L value is 36.95.

[0104] Take 440 g of precipitate A and add 800 g of water again, stir at 50 °C for 30 min. Centrifuge the solution at 7000 rpm for 0.5 h, separate the supernatant, and obtain 434.6 g of the lower precipitate B. It is found that the product is transparent after heat-treating the supernatant. The transmittance at 550 nm is 0.95, and the L value is 16.08.

[0105] Take 400 g of precipitate B and add 800 g of water, adjust the pH to 3.5 to obtain the mother liquor. Take 500 g of the mother liquor and transfer it to a high-pressure reactor. The reaction temperature is 170 °C, and the reaction time is 1 h. After the reaction is completed, filter to remove the precipitate to obtain a solution containing phenolic substances. After detection, the total phenolic content in it is 12.3 mg / kg of bran. Measure the percentage of 4-vinylguaiacol in phenolic substances. The results are shown in Table 1.

[0106] Example 4:

[0107] Take the bran, crush it and pass it through a 16-mesh sieve. Take 1000 g of the crushed bran, add 3000 g of water and stir evenly. Bran: water = 1:3 (w / v) to obtain an aqueous bran solution.

[0108] After adjusting the pH to 4.5, add 1 g of amylase A and 1.5 g of pectinase B, stir evenly, react at 45 °C for 12 h. After the reaction is completed, centrifuge at 2000 rpm for 0.5 h, separate the supernatant, and obtain 2540.1 g of the lower precipitate A. Heat-treat the supernatant. The obtained product is opaque. After filtering the product with a filter paper and detecting, the transmittance at 550 nm is 15.17, and the L value is 48.25. Take 100 g of precipitate A and add 400 g of water, adjust the pH to 4 to obtain the mother liquor. Take the mother liquor and transfer it to a high-pressure reactor. The reaction temperature is 160 °C, and the reaction time is 2 h. After the reaction is completed, filter to remove the precipitate to obtain a solution containing phenolic substances, labeled as 4-1. After detection, the total phenolic content in it is 6.2 mg / kg of bran. Measure the percentage of 4-vinylguaiacol in phenolic substances. The results are shown in Table 1.

[0109] Take 2400 g of precipitate A, add 2700 g of water, stir at 45 °C for 30 min, centrifuge the solution at 4000 rpm for 1 h, separate the supernatant, and obtain 2372.4 g of lower-layer precipitate B. Heat-treat the supernatant. The obtained product is opaque. After filtering the product with filter paper and testing, the transmittance at 550 nm is 12.24, and the L value is 32.59. Take 100 g of precipitate B, add 400 g of water, and adjust the pH to 4 to obtain the mother liquor. Transfer the mother liquor to a high-pressure reactor, with a reaction temperature of 160 °C and a reaction time of 2 h. After the reaction is completed, filter to remove the precipitate to obtain a solution containing phenolic substances, labeled as 4-2. After testing, the total phenolic content contained therein is 9.4 mg / kg of bran. Determine the percentage of 4-vinylguaiacol in phenolic substances. The results are shown in Table 1.

[0110] Take 2200 g of precipitate B, add 2200 g of water, stir at 40 °C for 30 min, centrifuge the solution at 8000 rpm for 1 h, separate the supernatant, and obtain 2163.5 g of lower-layer precipitate C. After heat-treating the supernatant, it is found that the product is transparent, the transmittance at 550 nm is 1.95, and the L value is 26.25. Take 100 g of precipitate C, add 400 g of water, and adjust the pH to 4 to obtain the mother liquor. Transfer the mother liquor to a high-pressure reactor, with a reaction temperature of 160 °C and a reaction time of 2 h. After the reaction is completed, filter to remove the precipitate to obtain a solution containing phenolic substances, labeled as 4-3. After testing, the total phenolic content contained therein is 14.8 mg / kg of bran. Determine the percentage of 4-vinylguaiacol in phenolic substances. The results are shown in Table 1.

[0111] Example 5:

[0112] Crush the bran and pass it through a 16-mesh sieve. Take 1000 g of crushed bran, add 5000 g of water and stir evenly. The ratio of bran to water is 1:5 (w / v) to obtain an aqueous bran solution.

[0113] After adjusting the pH to 5.2, add 3 g of amylase C, 5 g of glucoamylase A, and 1.5 g of pectinase B, stir evenly, react at 40 °C for 3 h. After the reaction is completed, centrifuge at 3000 rpm for 0.5 h, separate the supernatant, and obtain 2556.1 g of lower-layer precipitate A. Heat-treat the supernatant. The obtained product is opaque. After filtering the product with filter paper and testing, the transmittance at 550 nm is 17.22, and the L value is 44.59. Take 100 g of precipitate A, add 400 g of water, and adjust the pH to 4 to obtain the mother liquor. Transfer the mother liquor to a high-pressure reactor, with a reaction temperature of 180 °C and a reaction time of 0.5 h. After the reaction is completed, filter to remove the precipitate to obtain a solution containing phenolic substances, labeled as 5-1. After testing, the total phenolic content contained therein is 5.7 mg / kg of bran. Determine the percentage of 4-vinylguaiacol in phenolic substances. The results are shown in Table 1.

[0114] Take 2000 g of precipitate A, add 4000 g of water, adjust the pH to 5, stir at 40 °C for 30 min, add 10 g of glucoamylase B and 5 g of pectinase C, stir evenly, react at 40 °C for 6 h. After the reaction is completed, centrifuge at 3000 rpm for 1 h to separate the supernatant, and obtain 1964.7 g of the lower-layer precipitate B. Heat-treat the supernatant. The obtained product is opaque. After filtering the product with a filter paper and detecting, the transmittance at 550 nm is 2.22 and the L value is 35.21. Take 100 g of precipitate B, add 400 g of water, and adjust the pH to 4 to obtain the mother liquor. Transfer the mother liquor to an autoclave, with a reaction temperature of 180 °C and a reaction time of 0.5 h. After the reaction is completed, filter to remove the precipitate, and obtain a phenolic substance-containing solution, labeled as 5-2. After detection, the total phenolic content contained therein is 8.7 mg / kg of bran. Determine the percentage of 4-vinylguaiacol in the phenolic substances, and the results are shown in Table 1.

[0115] Take 1500 g of precipitate B, add 3000 g of water, adjust the pH to 5, stir at 40 °C for 30 min, add 5 g of pectinase C, stir evenly, react at 40 °C for 6 h. After the reaction is completed, centrifuge at 6000 rpm for 2 h to separate the supernatant, and obtain 1477.6 g of the lower-layer precipitate C. Heat-treat the supernatant. The obtained product is transparent, the transmittance at 550 nm is 0.48, and the L value is 16.22. Take 100 g of precipitate C, add 400 g of water, and adjust the pH to 4 to obtain the mother liquor. Transfer the mother liquor to an autoclave, with a reaction temperature of 180 °C and a reaction time of 0.5 h. After the reaction is completed, filter to remove the precipitate, and obtain a phenolic substance-containing solution, labeled as 5-3. After detection, the total phenolic content contained therein is 13.2 mg / kg of bran. Determine the percentage of 4-vinylguaiacol in the phenolic substances, and the results are shown in Table 1.

[0116] Comparative Example 1:

[0117] Take 200 g of the precipitate in Example 1-1, add 800 g of water, and adjust the pH to 4 to obtain the mother liquor. Take 500 g of the mother liquor and transfer it to an autoclave, with a reaction temperature of 170 °C and a reaction time of 1 h. After the reaction is completed, filter to remove the precipitate, and obtain a phenolic substance-containing solution. After detection, the total phenolic content contained therein is 7.6 mg / kg of bran. Determine the percentage of 4-vinylguaiacol in the phenolic substances, and the results are shown in Table 1.

[0118] Comparative Example 2:

[0119] Crush the bran and pass it through a 20-mesh sieve. Take 200 g of the crushed bran, add 800 g of water and stir evenly, with bran:water = 1:4 (w / v) to obtain an aqueous bran solution. Adjust the pH of the aqueous solution to 5 and react at 50 °C for 4 h to obtain the mother liquor M. Take 100 g of the mother liquor M and centrifuge at 8000 rpm for 0.5 h to separate the supernatant. After heat-treating the supernatant, it is found that the product is opaque. After filtering the product with a filter paper and detecting, the transmittance at 550 nm is 55.49 and the L value is 20.08.

[0120] Another 500 g of mother liquor M was adjusted to pH 4, transferred to a high-pressure reactor, and reacted at 170 °C for 1 h. After the reaction was completed, the precipitate was removed by filtration to obtain a solution containing phenolic substances. After testing, the total phenol content in it was 3.5 mg / kg of bran. The percentage of 4-vinylguaiacol in phenolic substances was measured, and the results are shown in Table 1.

[0121] Determination of phenolic substances

[0122] Refer to Yan Ruyu, "Analysis of the metabolic law of 4-methyl / ethyl guaiacol during the fermentation process of Luzhou-flavor liquor". 2022;

[0123] Gas chromatography conditions: DB-FFAP type capillary column (60 m × 250 μm × 0.25 μm), carrier gas is He, flow rate is 1 mL / min; splitless mode, injection volume: 1 μL, equilibration time: 1 min, injection port temperature 250 °C; column flow rate 1 mL / min; temperature programming: initial temperature 40 °C, hold for 0 min; increase the temperature to 200 °C at a rate of 15 °C / min and hold for 6 min; then increase the temperature to 250 °C at a rate of 50 °C / min and hold for 10 min. Mass spectrometry conditions: electron impact ion source, electron energy is 70 eV; ion source temperature 230 °C; quadrupole temperature 150 °C; transfer line temperature 280 °C, solvent delay 8 min. Quantitative analysis was performed using selected ion monitoring mode. The total phenol content was calculated as the sum of the amounts of guaiacol, 4-vinylguaiacol, 4-ethylphenol, phenol, and 2-methoxy-4-ethylphenol.

[0124] The percentage of 4-vinylguaiacol in phenolic substances, percentage = 4-vinylguaiacol / total phenol * 100%. The total phenol includes: guaiacol, 4-vinylguaiacol, 4-ethylphenol, phenol, and 2-methoxy-4-ethylphenol.

[0125] Table 1. Result comparison

[0126]

[0127] It can be seen from the results that the process of the present invention effectively improves the content of 4-vinylguaiacol and significantly increases the percentage of 4-vinylguaiacol in phenolic substances.

Claims

1. Pretreatment method of bran for preparing phenolic compounds, characterized in that, the method comprises: 1), the step of enzymatically hydrolyzing the aqueous bran solution; 2), centrifuging to obtain a precipitate and a supernatant; 3), the step of detecting the centrifuged supernatant of step 2); wherein, the step of detecting the centrifuged supernatant in step 3) includes, a) heat-treating the supernatant to obtain a heat-treated product, b) detecting the transparency, 550 nm transmittance and L value of the heat-treated product obtained in step a), if the heat-treated product is opaque, then filter and then detect the 550 nm transmittance and L value; if the heat-treated product does not meet the requirements of being transparent, having a 550 nm transmittance less than 2.0, and an L value less than 30, then redissolve the precipitate in step 2) and repeat steps 2 and 3.

2. The method according to claim 1, characterized in that, the step of enzymatically hydrolyzing the aqueous bran solution includes: treating the aqueous bran solution with a composite enzyme composition, the composite enzyme composition includes amylase, pectinase, and optionally glucoamylase; preferably, based on 100% by weight of bran, the amylase is 0.01 - 3%, preferably 0.1 - 0.5%, the pectinase is 0.1 - 5%, preferably 0.15 - 1%, and the glucoamylase is 0 - 3%, preferably 0.25 - 1%; preferably, the composite enzyme composition treats the aqueous bran solution at 30 - 50 °C for 1 - 20 h, preferably for 3 - 12 h; preferably, the aqueous bran solution is prepared by mixing bran and water in a ratio of 1:2 - 1:10, preferably 1:3 - 1:

5.

3. The method according to claim 1, characterized in that, the centrifuging is carried out at 1000 - 10000 rpm, preferably 2000 - 8000 rpm, for 10 min - 6 h, preferably 0.5 - 1 h.

4. The method according to claim 1, characterized in that, the heat treatment of the supernatant is to add 1% (w / w) lysine to the supernatant, stir evenly, and react at 130 °C for 1 h.

5. The method according to claim 1, characterized in that, the step of "redissolving the precipitate in step 2) and repeating steps 2 and 3" is carried out 1 - 3 times.

6. The method according to claim 1, characterized in that, after redissolving, it further includes the step of treating the redissolved solution with glucoamylase and / or pectinase.

7. The method according to claim 2 or 6, characterized in that, the enzyme is selected from: Lonza medium-temperature α-amylase, α-amylase Ban480, kleistase SD80, Dextrozyme, HighDEX, GA-260, Pectinex-Ultra SP-L, Rohapectin PTE100, and / or Pectinase PL.

8. A method for increasing the content of phenolic compounds prepared from bran, characterized in that, the method comprises: the step of pretreating bran by the method according to any one of claims 1 - 7 to obtain a pretreated bran precipitate; the step of preparing phenolic compounds using the pretreated bran.

9. The method according to claim 8, characterized in that, The steps for preparing phenolic compounds using the pretreated bran include: preparing a bran solution using the bran precipitate obtained after pretreatment, reacting at 140 - 190 °C, preferably 160 - 180 °C, for 10 min - 6 h, preferably 0.5 - 2 h, removing the precipitate to obtain a solution containing phenolic substances. Optionally, it further includes the step of preparing a composition containing phenolic substances from the obtained solution containing phenolic substances, preferably drying the obtained solution containing phenolic substances to prepare the composition containing phenolic substances.

10. A solution containing phenolic substances, or a composition containing phenolic substances, prepared by the method according to claim 8 or 9.

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