Preparation method of dietary fiber coffee solid beverage

Abstract

The invention discloses a preparation method of a dietary fiber coffee solid beverage, and belongs to the technical field of food processing solid beverages, the preparation method of the dietary fiber coffee solid beverage provided by the invention comprises the following steps: performing wet processing on fresh coffee fruits to obtain coffee beans and coffee pericarp, baking, grinding and sieving the coffee beans to obtain coffee pericarp; extracting the coffee powder to obtain coffee liquid, and concentrating and drying the coffee liquid to obtain instant coffee powder; the preparation method comprises the following steps: drying coffee pericarp, crushing, sieving, carrying out enzymolysis, centrifuging or filtering, and filtering by using a modified ultrafiltration membrane to obtain soluble dietary fiber oligosaccharide; the instant coffee powder and the soluble dietary fiber oligosaccharide are mixed in proportion, sealed and packaged, and the dietary fiber coffee solid beverage is prepared. The soluble dietary fiber oligosaccharide is obtained by separating the soluble dietary fiber obtained after enzymolysis of the coffee pericarp through the modified ultrafiltration membrane, and high-valued application of the coffee pericarp which is a coffee byproduct is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of food processing solid beverages, in particular to a method for preparing a dietary fiber coffee solid beverage. Background Art

[0002] Dietary fiber is classified as a variety of indigestible nutrients extracted from plant cell walls. It is called the seventh important nutrient for organisms and plays an important role in the health of the body, such as reducing the risk of cancer, diabetes and asthma. According to its solubility in water, dietary fiber can be divided into two types: soluble dietary fiber and insoluble dietary fiber. Compared with insoluble dietary fiber, soluble dietary fiber has more excellent properties, such as better solubility, water and oil holding capacity, surface properties, and molecular binding ability. The sources of dietary fiber mainly include grain by-products, fruit and vegetable by-products, algae, etc. As one of the three major beverages in the world, the demand for coffee is increasing year by year. Among them, coffee peel is a major by-product that cannot be ignored in the coffee processing process. It is rich in various bioactive substances. Coffee peel is mainly composed of the skin and pulp of coffee berries. It is the main source of solid waste generated during wet processing, accounting for 40% to 50% of the weight of fresh fruit. Coffee peel contains 35% sugar, 5.2% protein, 30.8% fiber, 10.7% minerals, and a small amount of fat. It has been proven that it has considerable value in producing high-efficiency antioxidant and antibacterial dietary fiber products. At present, the separation and extraction methods of soluble dietary fiber from coffee peel mainly use crude separation, chemical, enzymatic, fermentation, etc., so that the soluble dietary fiber is dissolved and then separated by alcohol precipitation. However, other substances insoluble in ethanol will be precipitated during the ethanol precipitation process, making the soluble dietary fiber of coffee peel darker in color than the soluble dietary fiber sold on the market. In addition, oligosaccharides of soluble dietary fiber are widely used in the beverage field due to their good solubility, but it is difficult to precipitate oligosaccharides of soluble dietary fiber using alcohol precipitation, which affects the potential application value of soluble dietary fiber from coffee peel. Summary of the invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a method for preparing a dietary fiber coffee solid beverage, wherein instant coffee powder and soluble dietary fiber are obtained by separately processing coffee beans and coffee peels, and dopamine and branched polysulfonate betaine co-deposition ultrafiltration membrane are used to separate the soluble dietary fiber to obtain soluble dietary fiber oligosaccharides, thereby preparing a dietary fiber coffee solid beverage, thereby realizing high-value utilization of coffee peels.

[0004] The technical solution for achieving the purpose of the present invention is as follows:

[0005] A method for preparing a dietary fiber coffee solid beverage comprises the following steps:

[0006] S1. Coffee beans and coffee peels are obtained by wet processing of fresh coffee fruits;

[0007] S2. After roasting, the coffee beans are ground and sieved to obtain coffee powder, the coffee powder is subjected to countercurrent extraction to obtain coffee liquid, and the coffee liquid is concentrated and freeze-dried to obtain instant coffee powder;

[0008] S3. After the coffee peel is dried, it is crushed and sieved to obtain coffee peel powder; the coffee peel powder, pectinase and deionized water are mixed, ultrasonically treated for 10 to 30 minutes, and then the pH value is adjusted to 5 to 6, cellulase is added, and the enzyme is heated at 50 to 60°C for 4 to 8 hours; after the enzymatic hydrolysis is completed, the temperature is raised to 100°C and maintained for at least 10 minutes to inactivate the enzyme, and the insoluble matter is removed by filtration or centrifugation, and the solution is retained; the solution is filtered using a modified ultrafiltration membrane, and the filtrate is further concentrated and vacuum freeze-dried to obtain soluble dietary fiber oligosaccharides; the modified ultrafiltration membrane is a dopamine and branched polysulfonate betaine co-deposition ultrafiltration membrane;

[0009] The preparation method of the branched polysulfonate betaine is as follows: dissolving dimethyl propyl sulfonamide ethyl methacrylate monomer and trimethylol propane triacrylate monomer in deionized water, heating to 60-80° C., bubbling nitrogen for 20-40 minutes to remove oxygen, adding hydrogen peroxide and ascorbic acid as initiators under a nitrogen atmosphere, stirring and reacting at 60-80° C. for 4-12 hours, stopping the reaction, adding sodium hydroxide to adjust the pH to 6-7, dialyzing the solution in pure water to remove unreacted small molecular monomers, initiators and oligomers, and then freeze-drying to obtain the branched polysulfonate betaine;

[0010] S4. Mix instant coffee powder and soluble dietary fiber oligosaccharide in a mass ratio of (8-9):(1-2), seal and package, and obtain a dietary fiber coffee solid beverage.

[0011] In view of the technical problem that soluble dietary fiber oligosaccharides are difficult to precipitate and separate in ethanol, the present invention adopts a membrane separation method to selectively separate the soluble dietary fiber oligosaccharides produced after the enzymatic hydrolysis of coffee peel. In general, the molecular weight of oligosaccharides is between 300 and 3000Da, and the pore size of ultrafiltration membrane is between 10 and 100nm, and substances of 1000 to 500000Da can be intercepted according to its different pore sizes, so the ultrafiltration membrane with a suitable pore size can effectively separate the polysaccharides and oligosaccharides of soluble dietary fiber. However, the ultrafiltration membranes sold on the market are mostly hydrophobic membranes with fixed pore sizes, and organic substances such as proteins are easily adsorbed during the separation process, so the present invention uses dopamine and branched polysulfonated betaine to co-precipitate and modify the ultrafiltration membrane, which can adjust the ultrafiltration membrane pore size to an ideal state on the one hand, and improve the hydrophilicity of the membrane on the other hand, and has an anti-pollution effect.

[0012] Sulfobetaine, i.e., methyl methacrylate dimethylpropyl sulfonamide ethyl ester monomer, is a zwitterionic compound having both positive ion groups and negative ion groups, having special anti-pollution properties, and having strong hydrophilicity. In the prior art, it is generally polymerized into linear polysulfobetaine and deposited on the surface of the membrane with high-adhesion substances such as dopamine to modify the membrane. The inventors of the present application have found that by preparing sulfobetaine into a branched structure, the degree of entanglement of the molecular chain is improved, the cross-linking points and interaction forces between molecules can be increased, the chemical stability and mechanical strength of the membrane are improved, and thus the service life of the modified ultrafiltration membrane is extended. In addition, the branched structure makes the molecular arrangement on the membrane surface more complex, and more hydrophilic groups are exposed to the outside, which can further improve the hydrophilicity and anti-pollution performance of the membrane.

[0013] Preferably, the molar ratio of the dimethylpropyl sulfonamide ethyl methacrylate monomer to the trimethylolpropane triacrylate monomer is (2-5):1.

[0014] Preferably, the mass ratio of dopamine to branched polysulfonated betaine is 1:(1-5).

[0015] Preferably, the wet processing steps of step S1 are fresh coffee fruit flotation, mechanical peeling and degumming, water washing and drying.

[0016] Preferably, the baking temperature of step S2 is 230-250° C., the baking time is 10-20 min, the sieving mesh size is 40-80 mesh; the extraction temperature is 90-150° C., and the liquid-to-solid ratio is (5-20):1.

[0017] Preferably, the drying conditions of step S3 are hot air drying at 40-60° C.; the mesh size of the sieve is 60-100 mesh; the material-liquid ratio of the coffee peel powder to deionized water is 1:(30-40), and the ultrasonic power is 200-400w.

[0018] Preferably, the ultrafiltration membrane is one of a polysulfone ultrafiltration membrane, a polyethersulfone ultrafiltration membrane, a polyimide ultrafiltration membrane, a polyacrylonitrile ultrafiltration membrane, a polyethylene ultrafiltration membrane, and a polypropylene ultrafiltration membrane.

[0019] Preferably, the preparation method of the modified ultrafiltration membrane comprises the following steps: the ultrafiltration membrane is immersed in an acetone solution to remove surface impurities, and vacuum dried at 40 to 60° C. for standby use; dopamine and branched polysulfonated betaine are respectively dissolved in a Tris-HCl solution, and then the membrane is pre-wetted with ethanol, and then immersed in a mixed solution of dopamine and branched polysulfonated betaine, and shaken for reaction at room temperature for 10 to 20 hours. After the reaction is completed, it is rinsed with deionized water to obtain a modified ultrafiltration membrane.

[0020] A dietary fiber coffee solid beverage, characterized in that it is prepared by the above-mentioned preparation method.

[0021] In a specific embodiment, a specific formula of the dietary fiber coffee solid beverage is: 4.6g instant coffee powder, 4.6g lactitol, 1.4g polydextrose, 1.3g oligofructose, 1.1g galactomannan, 0.4g xylo-oligosaccharide, 0.4g galacto-oligosaccharide, 0.4g inulin, 0.4g resistant dextrin, and 0.4g stachyose.

[0022] Specifically, the fructooligosaccharides, xylo-oligosaccharides, galactomannan, polydextrose and galacto-oligosaccharides are products derived from soluble dietary fiber oligosaccharides from coffee peels separated and purified by chromatographic columns, and the stachyose, lactitol, inulin and resistant dextrin are commercially available products.

[0023] Beneficial Effects

[0024] The present invention provides a method for preparing a dietary fiber coffee solid beverage, which has the following beneficial effects:

[0025] (1) By separately processing coffee beans and coffee byproduct coffee peels, instant coffee powder and soluble dietary fiber are produced, and a coffee solid beverage containing dietary fiber is produced. Dietary fiber can slow down the digestion and absorption rate of carbohydrates in the gastrointestinal tract. When dietary fiber is added to coffee and consumed together, it can slow down the absorption of a small amount of sugar that may be contained in coffee and carbohydrates in other foods, help regulate blood sugar levels, and realize the high-value utilization of coffee peels.

[0026] (2) A membrane separation method is used to selectively separate the soluble dietary fiber oligosaccharides produced by enzymatic hydrolysis of coffee peels, wherein dopamine and branched polysulfonated betaine are used to co-precipitate and modify the ultrafiltration membrane, which can adjust the pore size of the ultrafiltration membrane to an ideal state on the one hand, and improve the hydrophilicity of the membrane on the other hand, and has an anti-pollution effect. The sulfonated betaine is prepared into a branched structure, the degree of entanglement of the molecular chain is improved, the cross-linking points and interaction forces between molecules can be increased, the chemical stability and mechanical strength of the membrane are improved, and the service life of the modified ultrafiltration membrane is extended. In addition, the branched structure makes the molecular arrangement on the membrane surface more complex, and more hydrophilic groups are exposed to the outside, which can further improve the hydrophilicity and anti-pollution performance of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The infrared spectra of dimethylpropyl sulfonamide ethyl methacrylate monomer and branched polysulfonate betaine;

[0028] Figure 2 This is the monosaccharide ion current chromatogram of soluble dietary fiber oligosaccharides. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0031] The raw materials used in the embodiments and comparative examples are described below:

[0032] Coffee cherries: Yunnan Arabica coffee from coffee plantations in Hougu, Dehong, Yunnan;

[0033] Pectinase: 30,000 U / g, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0034] Cellulase: 50 u / mg, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0035] Ultrafiltration membrane: UltraPES ultrafiltration membrane, membrane material SPES sulfonated polyethersulfone, membrane pore size 6-7nm, cut-off molecular weight 80000Da, Membrana, Germany;

[0036] Dimethylpropylsulfonamide ethyl methacrylate: 97%, Sigma-Aldrich, USA;

[0037] Trimethylolpropane triacrylate: 99%, Qingdao Reinars Polymer Materials Co., Ltd.

[0038] Dopamine: dopamine hydrochloride, 99%, Hangzhou Weibolai Biotechnology Co., Ltd.;

[0039] Tris-HCl solution: tris(methylhydroxy)aminomethane and concentrated hydrochloric acid dissolved in deionized water, pH-8.5, 50mmol / L;

[0040] Branched polysulfonate betaine 1: dissolving dimethyl propyl sulfonamide ethyl ester monomer and trimethylol propane triacrylate monomer in deionized water at a molar ratio of 3:1 to a concentration of 10wt%, heating to 70°C, bubbling nitrogen for 30 minutes to remove oxygen, adding hydrogen peroxide and ascorbic acid as initiators under a nitrogen atmosphere, the initiator being 3wt% of the total mass of the monomers, and the mass ratio of hydrogen peroxide to ascorbic acid being 1:1, stirring and reacting at 70°C for 8 hours, stopping the reaction, adding sodium hydroxide to adjust the pH to 6, dialyzing the solution in pure water to remove unreacted small molecule monomers, initiators and oligomers, and then freeze-drying to obtain branched polysulfonate betaine 1;

[0041] Branched polysulfonate betaine 2: Compared with the preparation method of branched polysulfonate betaine 1, the difference is that the molar ratio of dimethylpropyl sulfonamide ethyl methacrylate monomer and trimethylolpropane triacrylate monomer is 2:1;

[0042] Branched polysulfonate betaine 3: Compared with the preparation method of branched polysulfonate betaine 1, the difference is that the molar ratio of dimethylpropyl sulfonamide ethyl methacrylate monomer and trimethylolpropane triacrylate monomer is 5:1;

[0043] The infrared spectra of the dimethylpropyl sulfonylamine ethyl methacrylate monomer and the branched polysulfonate betaine 1 are as follows: Figure 1 As shown, from Figure 1 It can be seen that after the polymerization reaction, the -1 The C=C characteristic peak disappears, and the peak at 1330 cm -1 and 1397cm -1 The characteristic peak of the tert-butyl group of trimethylolpropane triacrylate appears at , indicating that the polymerization reaction is successfully carried out.

[0044] Linear polysulfonated betaine: dissolving dimethyl propyl sulfonamide ethyl methacrylate monomer in deionized water at a concentration of 10 wt%, heating to 70°C, bubbling nitrogen for 30 min to remove oxygen, adding hydrogen peroxide and ascorbic acid as initiators under a nitrogen atmosphere, the initiator being 3 wt% of the total mass of the monomer, the mass ratio of hydrogen peroxide to ascorbic acid being 1:1, stirring and reacting at 70°C for 8 hours, stopping the reaction, adding sodium hydroxide to adjust the pH to 6, dialyzing the solution in pure water to remove unreacted small molecule monomers, initiators and oligomers, and then freeze-drying to obtain linear polysulfonated betaine;

[0045] The molecular weight and molecular weight distribution coefficient of branched polysulfonate betaine 1 to 3 and linear polysulfonate betaine were tested by gel permeation chromatography (GPC). The results are shown in Table 1:

[0046] Table 1 Molecular weight and molecular weight distribution coefficient of branched betaine

[0047]

[0048] Unless otherwise specified, the components and raw materials used in the embodiments and comparative examples of the present invention are all commercially available raw materials, and the components and raw materials used in each parallel experiment are all of the same kind.

[0049] Preparation Example 1

[0050] Preparation of modified ultrafiltration membrane 1: The ultrafiltration membrane is immersed in an acetone solution for 12 hours to remove surface impurities, and is vacuum dried at 40°C for standby use; dopamine and branched polysulfonated betaine are dissolved in Tris-HCl solution respectively, wherein the concentration of dopamine is maintained at 2 g / L, and the mass ratio of dopamine to branched polysulfonated betaine is 1:1; the membrane is then pre-wetted with ethanol, and then immersed in a mixed solution of dopamine and branched polysulfonated betaine, and shaken for reaction at room temperature for 12 hours. After the reaction is completed, it is rinsed with deionized water to obtain a modified ultrafiltration membrane 1;

[0051] Preparation Example 2

[0052] Preparation of modified ultrafiltration membrane 2: The preparation method is different from that of modified ultrafiltration membrane 1, except that branched polysulfonate betaine 1 is replaced by branched polysulfonate betaine 2;

[0053] Preparation Example 3

[0054] Preparation of modified ultrafiltration membrane 3: The preparation method is different from that of modified ultrafiltration membrane 1, except that branched polysulfonate betaine 1 is replaced by branched polysulfonate betaine 3;

[0055] Preparation Example 4

[0056] Preparation of modified ultrafiltration membrane 4: The preparation method is different from that of modified ultrafiltration membrane 1, except that the mass ratio of dopamine to branched polysulfonated betaine is 1:5;

[0057] Preparation Example 5

[0058] Preparation of modified ultrafiltration membrane 5: The preparation method is different from that of modified ultrafiltration membrane 1, except that the mass ratio of dopamine to branched polysulfonated betaine is 1:8;

[0059] Preparation Example 6

[0060] Preparation of modified ultrafiltration membrane 6: The preparation method is different from that of modified ultrafiltration membrane 1, except that the deposition time is 20 hours of shaking reaction of the membrane in a mixed solution of dopamine and branched polysulfonate betaine at room temperature.

[0061] Preparation Example 7

[0062] Preparation of modified ultrafiltration membrane 7: The preparation method is different from that of modified ultrafiltration membrane 1, except that branched polysulfonated betaine is replaced by linear polysulfonated betaine;

[0063] The modified ultrafiltration membrane samples of Preparation Examples 1 to 7 were subjected to the following performance tests, and the results are shown in Table 2:

[0064] (1) Static water contact angle: The contact angle was tested using a G10Kruss contact angle meter. Each film was randomly tested 5 times at different positions and the average value was taken.

[0065] (2) Molecular cutoff of the membrane: Polyethylene glycol with molecular weights of 800, 1000, 2000, 3000, 4000, 6000, and 10000 was prepared as standard solution, and then the modified ultrafiltration membrane was used for filtration experiment. The retention rate of each solute by the membrane was determined by detecting the concentration of the solute in the filtrate. When the retention rate was about 90%, the molecular weight of the solute was considered to be the molecular weight cutoff of the membrane.

[0066] (3) Anti-fouling test: The adsorption amount of bovine serum albumin on the membrane surface was used to reflect the anti-fouling ability of the membrane surface under static conditions. The membrane (5 cm × 5 cm) was placed in a beaker containing 50 mL of bovine serum albumin solution (1 g / L) and left to stand for 24 h without stirring. The adsorption amount on the membrane surface was calculated based on the concentration of the bovine serum albumin solution before and after the adsorption test.

[0067] (4) Mechanical stability test: The mechanical stability of the modified ultrafiltration membrane was tested by sticking and tearing with a sticky substance to examine the functional changes before and after. Transparent glue was adhered to the surface of the modified ultrafiltration membrane and the membrane was repeatedly torn 30 times to compare the changes in the ultrafiltration membrane coating thickness before and after, and the ultrafiltration membrane coating thickness retention rate was calculated.

[0068] Table 2 Performance of modified ultrafiltration membranes of preparation examples 1 to 7

[0069]

[0070] Example 1

[0071] A method for preparing a dietary fiber coffee solid beverage comprises the following steps:

[0072] S1. After the fresh coffee berries are harvested, they are subjected to fresh fruit flotation, mechanical peeling and degumming, water washing, drying and other wet processing steps to obtain coffee beans and coffee berries; the drying is performed by hot air drying at 40°C;

[0073] S2. After roasting the coffee beans at 240°C for 10 min, they were ground and passed through a 60-mesh sieve to obtain coffee powder. The coffee powder was countercurrently extracted with deionized water at a temperature of 93°C and a liquid-to-solid ratio of 5:1 to obtain coffee liquid 1. Deionized water was added again to extract the remaining coffee grounds again at a temperature of 93°C and a liquid-to-solid ratio of 5:1 to obtain coffee liquid 2. Coffee liquid 2 was heated to 93°C and extracted with new coffee powder to obtain coffee liquid 3. Deionized water was added again to extract the remaining coffee grounds again at a temperature of 93°C and a liquid-to-solid ratio of 5 :1, obtain coffee liquid 4, heat the coffee liquid 4 to 93°C, extract the new coffee powder to obtain coffee liquid 5, repeat the above steps, and finally mix the coffee liquids, concentrate them to 1 / 4 of the original volume, and then freeze-dry them to obtain instant coffee powder; wherein high temperature and short time baking can minimize the volatilization of coffee aromatic substances, so that the coffee can have a more suitable taste during extraction; using the second extracted coffee liquid to extract the new coffee powder can ensure that the effective ingredients in the coffee powder are completely extracted, and the concentration of the coffee liquid will not drop significantly, thereby ensuring the coffee flavor;

[0074] S3. The coffee peel is dried at 40°C to a moisture content of less than 10%, and then crushed using a high-speed universal grinder, passed through a 60-mesh sieve, the coffee peel powder, pectinase and deionized water are mixed, and ultrasonically treated at 300W for 10 minutes, and then the pH value is adjusted to 5, cellulase is added, and heated at 50°C for enzymatic hydrolysis for 4 hours, wherein the solid-liquid ratio of coffee peel powder to deionized water is 1:40 (g / ml), and the added amounts of pectinase and cellulase are both 1wt% of the mass of the coffee peel powder; after the reaction is completed, the temperature is raised to 100°C and maintained for 10 minutes to inactivate the enzyme, the residue is removed by centrifugation, the supernatant is retained, the supernatant is filtered using a modified ultrafiltration membrane 1, the filtrate is concentrated to 1 / 6 of the original volume, and then vacuum freeze-dried to obtain soluble dietary fiber oligosaccharides;

[0075] Use high performance anion exchange chromatography-pulse amperometry to determine the types of monosaccharides in soluble dietary fiber oligosaccharides. Weigh 50 mg of dried soluble dietary fiber sample, add 2 ml of 2 mol / L trifluoroacetic acid to seal the tube; hydrolyze in a 110°C oven for 2 h, cool, filter out the residue, rinse with water 3 times, and evaporate under reduced pressure to remove the remaining trifluoroacetic acid. The hydrolyzed soluble dietary fiber is pretreated with 10 mg of hydroxylamine hydrochloride and 1 ml of anhydrous pyridine, shake well and keep at 90°C for 0.5 h, cool, add 1 ml of anhydrous acetic anhydride, continue to shake well and keep at 90°C for 0.5 h, cool, add 1 ml of water, shake slightly, add 2 ml of chloroform and extract twice, combine the extracts, add anhydrous sodium sulfate to dry, and use a disposable syringe to absorb 1 ml of the lower layer of chloroform for GC-MS testing. The results are as follows: Figure 2 shown.

[0076] from Figure 2 It can be seen that the monosaccharides of soluble dietary fiber oligosaccharides are mainly 13.31-fructose, 14.43-erythrose, 23.47-rhamnose, 24.38-arabinose, 24.78-fucose, 30.15-talose, 30.53-mannose, 31.14 galactose, 31.37-xylose, 33.20-glucose, etc.;

[0077] S5. Mix instant coffee powder and soluble dietary fiber in a mass ratio of 9:1, seal and package, and obtain a dietary fiber coffee solid beverage.

[0078] Example 2

[0079] The preparation method is different from that in Example 1, in that the modified ultrafiltration membrane 1 is replaced by the modified ultrafiltration membrane 2;

[0080] Example 3

[0081] The preparation method is different from that in Example 1, in that the modified ultrafiltration membrane 1 is replaced by the modified ultrafiltration membrane 3;

[0082] Example 4

[0083] The preparation method is different from that in Example 1, in that the modified ultrafiltration membrane 1 is replaced by the modified ultrafiltration membrane 4;

[0084] Example 5

[0085] The preparation method is different from that in Example 1, in that the modified ultrafiltration membrane 1 is replaced by the modified ultrafiltration membrane 5;

[0086] Example 6

[0087] The preparation method is different from that in Example 1, in that the modified ultrafiltration membrane 1 is replaced by the modified ultrafiltration membrane 6;

[0088] Example 7

[0089] The preparation method is different from that in Example 1 in that the enzymatic hydrolysis time is extended to 8 hours;

[0090] Comparative Example 1

[0091] The preparation method is different from that in Example 1, except that the enzymolysis time is 2 hours;

[0092] Comparative Example 2

[0093] The preparation method is different from that in Example 1, in that the modified ultrafiltration membrane 1 is replaced by the modified ultrafiltration membrane 7;

[0094] The yield of soluble dietary fiber oligosaccharides from coffee peel in Examples 1 to 7 and Comparative Examples 1 to 2 was calculated by the ratio of the mass of soluble dietary fiber oligosaccharides after freeze drying to the mass of coffee peel after drying × 100%. The results are shown in Table 3:

[0095] Table 3 Yield of soluble dietary fiber oligosaccharides from coffee peel

[0096]

[0097] It can be seen from Preparation Examples 1 to 3 and 7 that the branched polysulfonate betaine and dopamine co-deposited membrane has better hydrophilicity and anti-fouling performance than the linear polysulfonate betaine and dopamine co-deposited membrane, the molecular retention amount is closer to the design level, and the mechanical strength is better.

[0098] It can be seen from Examples 1 and 7 and Comparative Example 1 that increasing the enzymatic hydrolysis time is beneficial to the decomposition of soluble dietary fiber into oligosaccharides, thereby increasing the yield of soluble dietary fiber oligosaccharides.

[0099] It can be seen from Preparation Examples 1, 4, and 5 that when the mass ratio of dopamine to branched polybetaine sulfonate is within the preferred range, the comprehensive performance of the membrane is the best. When the branched polybetaine sulfonate is too much, although the hydrophilicity increases and the anti-pollution performance improves, the mechanical strength decreases.

[0100] It can be seen from Preparation Examples 1 and 6 that a longer deposition time of dopamine and branched polysulfonated betaine will result in a thicker coating and a smaller molecular retention capacity of the membrane, thereby causing a decrease in yield.

[0101] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a dietary fiber coffee solid beverage, characterized in that: The following steps are involved: S1. Coffee beans and coffee peels are obtained by wet processing of fresh coffee fruits; S2. After roasting, the coffee beans are ground and sieved to obtain coffee powder, the coffee powder is subjected to countercurrent extraction to obtain coffee liquid, and the coffee liquid is concentrated and freeze-dried to obtain instant coffee powder; S3. After the coffee peel is dried, it is crushed and sieved to obtain coffee peel powder; the coffee peel powder, pectinase and deionized water are mixed, ultrasonically treated for 10 to 30 minutes, and then the pH value is adjusted to 5 to 6, cellulase is added, and the enzyme is heated at 50 to 60°C for 4 to 8 hours; after the enzymatic hydrolysis is completed, the temperature is raised to 100°C and maintained for at least 10 minutes to inactivate the enzyme, and the insoluble matter is removed by filtration or centrifugation, and the solution is retained; the solution is filtered using a modified ultrafiltration membrane, and the filtrate is further concentrated and vacuum freeze-dried to obtain soluble dietary fiber oligosaccharides; the modified ultrafiltration membrane is a dopamine and branched polysulfonate betaine co-deposition ultrafiltration membrane; The preparation method of the branched polysulfonate betaine is as follows: dissolving dimethyl propyl sulfonamide ethyl methacrylate monomer and trimethylol propane triacrylate monomer in deionized water, heating to 60-80° C., bubbling nitrogen for 20-40 minutes to remove oxygen, adding hydrogen peroxide and ascorbic acid as initiators under a nitrogen atmosphere, stirring and reacting at 60-80° C. for 4-12 hours, stopping the reaction, adding sodium hydroxide to adjust the pH to 6-7, dialyzing the solution in pure water to remove unreacted small molecular monomers, initiators and oligomers, and then freeze-drying to obtain the branched polysulfonate betaine; S4. Mix instant coffee powder and soluble dietary fiber oligosaccharide in a mass ratio of (8-9):(1-2), seal and package, and obtain a dietary fiber coffee solid beverage.

2. The dietary fiber coffee solid beverage according to claim 1, characterized in that The molar ratio of the dimethylpropyl sulfonamide ethyl methacrylate monomer to the trimethylolpropane triacrylate monomer is (2-5):

1.

3. The dietary fiber coffee solid beverage according to claim 1, characterized in that: The mass ratio of dopamine to branched polysulfonated betaine is 1:(1-5).

4. The dietary fiber coffee solid beverage according to claim 1, characterized in that: The wet processing steps of step S1 are fresh coffee fruit flotation, mechanical peeling and degumming, water washing and drying.

5. The dietary fiber coffee solid beverage according to claim 1, characterized in that: The baking temperature of step S2 is 230-250° C., the baking time is 10-20 min, the sieving mesh is 40-80 mesh; the extraction temperature is 90-150° C., and the liquid-to-solid ratio is (5-20):

1.

6. The dietary fiber coffee solid beverage according to claim 1, characterized in that: The drying conditions of step S3 are hot air drying at 40-60° C.; the mesh size of the sieve is 60-100 meshes; the material-liquid ratio of the coffee peel powder to deionized water is 1:(30-40), and the ultrasonic power is 200-400w.

7. The dietary fiber coffee solid beverage according to claim 1, characterized in that: The ultrafiltration membrane is one of a polysulfone ultrafiltration membrane, a polyethersulfone ultrafiltration membrane, a polyimide ultrafiltration membrane, a polyacrylonitrile ultrafiltration membrane, a polyethylene ultrafiltration membrane, and a polypropylene ultrafiltration membrane.

8. The dietary fiber coffee solid beverage according to claim 1, characterized in that: The preparation method of the modified ultrafiltration membrane comprises the following steps: soaking the ultrafiltration membrane in an acetone solution to remove surface impurities, and vacuum drying at 40-60°C for standby use; dissolving dopamine and branched polysulfonated betaine in a Tris-HCl solution respectively, and then pre-wetting the membrane with ethanol, and then soaking it in a mixed solution of dopamine and branched polysulfonated betaine, shaking and reacting at room temperature for 10-20 hours, and after the reaction is completed, rinsing with deionized water to obtain the modified ultrafiltration membrane.

9. A dietary fiber coffee solid beverage, characterized in that: Calculated by weight, it is prepared by the preparation method according to any one of claims 1 to 8.

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