A method for simultaneous extraction of soluble and insoluble dietary fibers

Abstract

The application provides a synchronous extraction method of soluble and insoluble dietary fibers, and belongs to the technical field of dietary fiber processing. The synchronous extraction method comprises the following steps: S1, taking pineapple pomace as raw material, diluting with water to obtain a sample liquid; S2, mixing the sample liquid, salt and an organic solvent, adding an acid-alkali reagent to adjust pH, obtaining a composite system, and placing the composite system in a multi-frequency ultrasonic field to perform separation and extraction, thereby obtaining a composite extraction system; S3, centrifuging the composite extraction system, removing the obtained upper liquid phase, and washing the middle layer solid phase to obtain pineapple insoluble dietary fiber; and performing dialysis desalting on the lower liquid phase to obtain pineapple soluble dietary fiber. The method has the advantages of simple process, short time consumption, high extraction rate and excellent product quality. In particular, the total extraction time is short, the extraction rates of soluble dietary fiber and insoluble dietary fiber are high, and the comprehensive utilization rate of pineapple processing by-products is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of dietary fiber processing technology, and particularly relates to a method for simultaneous extraction of soluble and insoluble dietary fiber. Background Technology

[0002] Pineapple, a specialty fruit of Lingnan, boasts a unique flavor and texture, making it popular among consumers. It can be consumed naturally or processed into various products. The processing steps generate a series of byproducts, such as the crown, stem, leaves, and pulp residue, accounting for 60% of the whole fruit. Improper handling may have environmental impacts. The pineapple pomace, a byproduct of concentrated pineapple juice production, contains a large amount of dietary fiber, considered the seventh essential nutrient, which promotes intestinal motility and regulates immunity.

[0003] Currently, the processes for preparing soluble and insoluble dietary fiber from fruits are relatively independent. Soluble dietary fiber is commonly extracted using hot water extraction, where the crude extract undergoes steps such as protein removal and depigmentation, followed by further purification using ethanol fractionation and column chromatography to obtain soluble dietary fiber. The extraction cycle is approximately 6-7 days, which is quite lengthy. Insoluble dietary fiber is often extracted using a combination of enzymatic hydrolysis and physical methods (enzyme combined with ultrasonic treatment, high-pressure homogenization, etc.). Enzymatic hydrolysis removes substances such as proteins and starches, and the extraction cycle also requires 4-5 days. It is evident that preparing both types of dietary fiber involves complex processes, numerous purification steps, and is time-consuming, yielding only one target compound each time, which is not conducive to the efficient utilization of raw materials. Summary of the Invention

[0004] This invention proposes a method for the simultaneous extraction of soluble and insoluble dietary fiber, which combines multi-frequency ultrasound technology with a highly selective extraction method based on the salting-out effect and the principle of like dissolves like, so that two different types of dietary fiber can be obtained in one preparation.

[0005] This invention proposes a method for the simultaneous extraction of soluble and insoluble dietary fiber, comprising the following steps:

[0006] S1. Using pineapple pomace as raw material, dilute with water to obtain sample solution;

[0007] S2. Mix the above sample solution, salt and organic solvent, add acid and base reagents to adjust the pH, and then place the composite system in a multi-frequency ultrasonic field for separation and extraction to obtain a composite extraction system.

[0008] S3. Centrifuge the above-mentioned composite extraction system to separate the upper liquid phase, the middle solid phase, and the lower liquid phase;

[0009] The process involves removing the upper liquid phase, washing the middle solid phase with water to obtain pineapple insoluble dietary fiber, and dialysis the lower liquid phase to remove salt, yielding pineapple soluble dietary fiber.

[0010] Furthermore, in step S1, the mass-to-volume ratio of pineapple pulp to water is 1:10 to 1:40.

[0011] Further, in step S2, the salt includes at least one of sodium citrate and potassium dihydrogen phosphate;

[0012] Preferably, in step S2, the organic solvent includes at least one of n-butanol, n-propanol, and dimethyl carbonate.

[0013] Further, in step S2, the mass-to-volume ratio of the salt to the sample solution is (10%~60%):1;

[0014] Preferably, in step S2, the volume ratio of the organic solvent to the sample solution is (0.5~2.5):1.0.

[0015] Further, in step S2, the acid-base reagent includes hydrochloric acid and alkaline solution; wherein the concentration of hydrochloric acid is 0.1M; and the concentration of alkaline solution is 0.1M.

[0016] Preferably, in step S2, the pH range is 6 to 9.

[0017] Furthermore, in step S2, the frequencies of the multi-frequency ultrasonic field are combined in different frequencies from 1 to 100 kHz.

[0018] Furthermore, in step S2, the temperature of the multi-frequency ultrasonic field is 30~90 ℃.

[0019] Furthermore, in step S2, the separation and extraction time is 20-50 min.

[0020] Furthermore, in step S3, the centrifugation speed is 3000~5000 r / min.

[0021] Furthermore, the method includes step S4, which involves drying the above-mentioned pineapple insoluble dietary fiber to a moisture content of ≤10% to obtain dried pineapple insoluble dietary fiber; and freeze-drying the above-mentioned pineapple soluble dietary fiber to obtain dried pineapple soluble dietary fiber.

[0022] This invention has the following advantages:

[0023] The present invention proposes a method for the simultaneous extraction of soluble and insoluble dietary fiber. A sample solution is prepared by mixing pineapple pomace and water, and salt and organic solvent are added to construct a composite system. The pH is adjusted, and the solution is extracted in a multi-frequency ultrasonic field. After centrifugation, the middle solid phase is insoluble dietary fiber, and the lower liquid phase is soluble dietary fiber, thereby achieving rapid and simultaneous separation and extraction of soluble and insoluble dietary fiber from the pomace.

[0024] This invention utilizes the strong cavitation effect and high shear force provided by multi-frequency ultrasonic fields to enhance molecular collisions, accelerating solid-liquid separation and significantly shortening the extraction time of dietary fiber. Simultaneously, it employs the salting-out effect within the composite system to remove protein from the pomace and utilizes the similarity-compatibility effect to enrich soluble dietary fiber, eliminating the need for traditional stepwise enzymatic hydrolysis and alcohol washing processes, thus simultaneously obtaining both soluble and insoluble dietary fiber from pineapple. Under multi-frequency ultrasonic treatment, cellulose and lignin degradation are promoted, increasing the surface wrinkles of insoluble dietary fiber, exposing active groups, and enhancing the starch digestibility of insoluble dietary fiber. This method is simple, time-efficient, has a high extraction rate, and produces excellent product quality. The total extraction time is approximately 2 hours, with high extraction rates for both soluble and insoluble dietary fiber, significantly improving the comprehensive utilization rate of pineapple processing byproducts and making it suitable for large-scale industrial production. Attached Figure Description

[0025] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 This is a schematic diagram of the products obtained after extraction and separation in the embodiments and control examples of the present invention;

[0027] Figure 2 A comparison of the digestibility of pineapple soluble dietary fiber (PSDF) extracted by different methods in the embodiments of the present invention;

[0028] Figure 3 This is a comparison of the adsorption capacity of pineapple insoluble dietary fiber (PIDF) extracted by various methods in the embodiments of the present invention for 50 mM glucose. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0030] This invention provides a method for the simultaneous extraction of soluble and insoluble dietary fiber, comprising the following steps:

[0031] S1. Using pineapple pomace as raw material, dilute with water to obtain sample solution;

[0032] S2. Mix the sample solution, salt and organic solvent, add acid and base reagents to adjust the pH, and then place the composite system in a multi-frequency ultrasonic field for separation and extraction to obtain a composite extraction system.

[0033] S3. Centrifuge the above-mentioned composite extraction system to separate the upper liquid phase, the middle solid phase, and the lower liquid phase;

[0034] The process involves removing the upper liquid phase, washing the middle solid phase with water to obtain pineapple insoluble dietary fiber, and dialysis the lower liquid phase to remove salt, yielding pineapple soluble dietary fiber.

[0035] The method for simultaneous extraction of soluble and insoluble dietary fiber proposed in this invention involves preparing a sample solution from pineapple pomace and water, adding salt and organic solvents to construct a composite system, adjusting the pH, and extracting the sample in a multi-frequency ultrasonic field. After centrifugation, the middle solid phase is insoluble dietary fiber, and the lower liquid phase is soluble dietary fiber, thus achieving rapid and simultaneous separation and extraction of soluble and insoluble dietary fiber from the pomace.

[0036] In this embodiment of the invention, the strong cavitation effect and high shear force provided by the multi-frequency ultrasonic field enhance molecular collisions, accelerating solid-liquid separation and significantly shortening the extraction time of dietary fiber. Furthermore, the multi-frequency ultrasonic treatment promotes the degradation of cellulose and lignin, increasing surface wrinkles and exposing active groups on the insoluble dietary fiber, thus improving its resistance to starch digestion. Additionally, the salting-out effect within the composite system removes protein from the fruit pomace, while the compatibility effect enriches soluble dietary fiber. Therefore, soluble and insoluble dietary fiber from pineapple can be obtained simultaneously without the need for traditional stepwise enzymatic hydrolysis and alcohol washing processes.

[0037] This method effectively removes oils, pigments, and phenolic substances from pineapple pomace, resulting in high raw material utilization. All reagents used are non-toxic, and organic reagents are recyclable and reusable. It is energy-saving, environmentally friendly, and has low production costs, thus increasing the added value of agricultural products. Compared to traditional methods, it eliminates the need for deproteinization and enzymatic hydrolysis, simplifying production steps and significantly shortening production time. The total extraction time is approximately 2 hours, with a soluble dietary fiber extraction rate exceeding 80% (protein content less than 5%) and an insoluble dietary fiber extraction rate exceeding 57%. This greatly improves the comprehensive utilization rate of pineapple processing byproducts and is suitable for large-scale industrial production.

[0038] In one embodiment of the present invention, in step S1, the mass-to-volume ratio of pineapple pulp to water is 1:10 to 1:40. The unit of mass-to-volume ratio is g / mL.

[0039] In this embodiment of the invention, in step S2, impurities such as pigments, oils, proteins, and polyphenols in dietary fiber are removed through the salting-out effect and the like-soluble-like-like-dissolve-like effect.

[0040] In one embodiment of the present invention, in step S2, the salt includes at least one of sodium citrate and potassium dihydrogen phosphate. In this embodiment, if salt is not added, the interaction force between insoluble pineapple dietary fiber (PIDF) and water molecules in the extraction system will be reduced, which is detrimental to system equilibrium. Therefore, soluble dietary fiber (PSDF) cannot separate into layers during the extraction process.

[0041] In one embodiment of the present invention, in step S2, the organic solvent includes at least one of n-butanol, n-propanol, and dimethyl carbonate.

[0042] In one embodiment of the present invention, in step S2, the mass-to-volume ratio of the salt to the sample solution is (10%~60%):1. The unit of the mass-to-volume ratio is g / mL.

[0043] In one embodiment of the present invention, in step S2, the volume ratio of the organic solvent to the sample solution is (0.5~2.5):1.0.

[0044] In one embodiment of the present invention, in step S2, the acid-base reagent includes hydrochloric acid and alkaline solution; wherein the concentration of hydrochloric acid is 0.1M; and the concentration of alkaline solution is 0.1M.

[0045] In one embodiment of the present invention, in step S2, the pH range is 6 to 9.

[0046] In one embodiment of the present invention, in step S2, the frequency of the multi-frequency ultrasonic field is a combination of different frequencies ranging from 1 to 100 kHz. Specifically, it can be a combination of two different frequencies, or a combination of three different frequencies, etc. For example, it can be 20+40 kHz, 20+60 kHz, 20+80 kHz, 28+45 kHz, 40+80 kHz, 20+40+80 kHz, 45+80+100 kHz, or 28+45+100 kHz. In this embodiment of the present invention, the multi-frequency ultrasonic field is beneficial to improving extraction efficiency and achieving the purpose of modifying dietary fiber. Multi-frequency ultrasound accelerates the dissolution of soluble dietary fiber in the cell walls of pineapple pomace, accelerates the degradation of cellulose and lignin, and can effectively improve the yield. More specifically, during multi-frequency ultrasound, the pulse works for 5 seconds and then stops for 5 seconds.

[0047] In one embodiment of the present invention, in step S2, the temperature of the multi-frequency ultrasonic field is 30~90 ℃.

[0048] In one embodiment of the present invention, the separation and extraction time in step S2 is 20~50 min.

[0049] In this embodiment of the invention, in step S3, the upper liquid phase, the middle solid phase, and the lower liquid phase are separated. The upper layer consists of oils, phenolic substances, and pigments, the middle layer consists of insoluble dietary fiber, and the lower layer consists of soluble dietary fiber.

[0050] In one embodiment of the present invention, in step S3, the centrifugation speed is 3000~5000 r / min.

[0051] In one embodiment of the present invention, step S4 is further included: drying the above-mentioned pineapple insoluble dietary fiber to a moisture content ≤10% to obtain dried pineapple insoluble dietary fiber; and freeze-drying the above-mentioned pineapple soluble dietary fiber to obtain dried pineapple soluble dietary fiber. The highly active pineapple dietary fiber prepared by the present invention achieves efficient recycling of pineapple by-products and increases the added value of agricultural products.

[0052] In this embodiment of the invention, the extraction rates of soluble and insoluble dietary fiber are over 80% and 57%, respectively, while the oil and protein content is less than 5%. More importantly, the simultaneous extraction of soluble and insoluble dietary fiber can be completed in just about 2 hours, which can greatly save the time required for the traditional water extraction method to prepare soluble dietary fiber and the enzymatic hydrolysis method to prepare insoluble dietary fiber (the extraction cycle of soluble dietary fiber is about 7 days, while the enzymatic hydrolysis and desaccharification steps alone require 8-10 hours in the process of insoluble dietary fiber), thus reducing production costs.

[0053] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0054] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0055] Test Example 1: Test Methods Related to the Invention

[0056] 1. Testing of basic indicators

[0057] Total sugar content determination: Refer to national standard GB / T15672 2009, Phenol-Sulfuric Acid Process;

[0058] Determination of soluble protein content: Refer to national standard GB 5009.5 2016, Coomassie Brilliant Blue method;

[0059] Determination of insoluble dietary fiber content: Refer to GB / T 9822-2008.

[0060] 2. Digestive characteristics

[0061] Take 1.0 mL of 5.0 mg / mL PSDF solution, add 0.3 mL of α-amylase solution (enzyme activity 6 U / mL) and 0.4 mL of 1% soluble starch solution, heat in a water bath at 37 ℃ for 5 min, add 1 mL of 3,5-dinitrosalicylic acid solution for color development, and immediately react in a boiling water bath for 10 min. After cooling to room temperature, measure the absorbance A1 at 540 nm; measure the absorbance A2 when the PSDF solution is replaced with phosphate buffer; measure the absorbance A3 when the enzyme solution is replaced with PBS buffer; measure the absorbance A4 when both the sample solution and enzyme solution are replaced with PBS buffer. Acarbose was used as a positive control in the same way, and all solvents were PBS buffer (0.1 mol / L, pH 7.0). The formula for calculating the α-amylase inhibition rate (Y, %) is as follows: Y = 1 - (A1 - A3) / (A2 - A4) × 100; where: Y is the α-amylase inhibition rate, %; A1 is the absorbance of the sample solution + enzyme solution; A2 is the absorbance of the PBS buffer + enzyme solution; A3 is the absorbance of the sample solution + PBS buffer; and A4 is the absorbance of the PBS buffer.

[0062] 3. Glucose adsorption capacity

[0063] Take 50 mL centrifuge tubes, add 1.0 g of sample and 15 mL of 50 mmol / L glucose solution respectively, and incubate at 37℃ for 2 h for adsorption. After reaching adsorption equilibrium, centrifuge and then determine the glucose concentration in the supernatant using the DNS method. The control group uses an equal volume of deionized water instead of glucose solution. The glucose adsorption capacity is calculated using the following formula: GAC (μmol / g) = (M1 - M2) / M; where: GAC is the glucose adsorption capacity, μmol / g; M is the mass of the sample taken, g; M1 is the mass of glucose in the solution before adsorption, mg; M2 is the mass of glucose in the supernatant after centrifugation, mg.

[0064] Example 1: A method for simultaneously preparing highly active soluble and insoluble dietary fiber from pineapple (three-frequency ultrasound)

[0065] Take 100 g of pineapple pomace and mix it with primary water at a material-to-liquid ratio of 1:30 (g / mL) to obtain a sample solution. Place the sample solution in a multi-frequency ultrasonic device and add 20% (w / v) of the sample solution sequentially. g / mL Sodium citrate was added to an organic solvent at a sample solution: dimethyl carbonate ratio of 1:1 (v / v). The pH was adjusted to 6. The ultrasonic frequency was set to 20 ± 40 ± 80 kHz, with a pulse duration of 5 s on and 5 s off. The temperature was 40 ℃, and the extraction time was 30 min. After extraction, the solid and liquid were separated by centrifugation at 4500 r / min. The obtained product is as follows: Figure 1As shown. The middle solid phase was washed with water and dried to a moisture content ≤10%, then pulverized and sieved to obtain insoluble pineapple dietary fiber (named PIDF). The lower liquid phase was dialyzed to remove salts, and then freeze-dried to obtain soluble pineapple dietary fiber (named PSDF).

[0066] Following the method described in Example 1, dietary fiber from two types of pineapple was collected. The extraction rate of soluble dietary fiber, the content of soluble protein, the extraction rate of insoluble dietary fiber, digestive properties, and glucose adsorption capacity of the products were determined. The results are shown in Table 1. Figure 2 and Figure 3 .

[0067] The extraction rate of PSDF was 85.67±1.13%, with a soluble protein content of 1.67±0.85%, and the extraction rate of PIDF (insoluble dietary fiber) was 65.79±0.24%. At 5 mg / mL, PSDF inhibited α-amylase by 48.46±2.12%; PIDF showed a glucose adsorption capacity of 16.70±1.25 µmol / g, exhibiting good hypoglycemic activity. This method, including sample preparation, ultrasonic extraction, and centrifugation, requires only 2 hours to prepare both types of pineapple dietary fiber.

[0068] Example 2: A method for simultaneously preparing highly active soluble and insoluble dietary fiber from pineapple (dual-frequency ultrasound)

[0069] Take 100 g of pineapple pomace and mix it with primary water at a material-to-liquid ratio of 1:30 (g / mL) to obtain a sample solution. Place the sample solution in a multi-frequency ultrasonic device, and add 20% (w / v, g / mL) sodium citrate to the sample solution. Add organic solvent at a sample solution:dimethyl carbonate ratio of 1:1 (v / v), adjust the pH to 6, set the ultrasonic frequency to 20±40 kHz, pulse for 5 s on and 5 s off, temperature to 50℃, and ultrasonic time to 40 min. Centrifuge at 4500 r / min to separate the solid and liquid. Take the solid phase, wash it with water, and dry it to ensure the moisture content is ≤10%. Crush and sieve to obtain insoluble pineapple dietary fiber. Dialyze the liquid phase and freeze-dry to obtain soluble pineapple dietary fiber.

[0070] Following the method described in Example 1, dietary fiber from two types of pineapple was collected. The extraction rate of soluble dietary fiber, the content of soluble protein, the extraction rate of insoluble dietary fiber, digestive properties, and glucose adsorption capacity of the products were determined. The results are shown in Table 1. Figure 2 and Figure 3 .

[0071] The PSDF extraction rate was 83.85±0.89%, with a soluble protein content of 1.38±0.56%, and the PIDF insoluble dietary fiber extraction rate was 59.45±0.87%. At 5 mg / mL, PSDF inhibited α-amylase by 40.43±3.03%; PIDF had a glucose adsorption capacity of 14.25±2.19 µmol / g. This method, including sample solution preparation, ultrasonic extraction, and centrifugation, requires only 2 hours to prepare both products simultaneously.

[0072] Example 3: A method for simultaneously preparing highly active soluble and insoluble dietary fiber from pineapple (dual-frequency ultrasound)

[0073] Take 100 g of pineapple pomace and mix it with primary water at a material-to-liquid ratio of 1:30 (g / mL) to obtain a sample solution. Place the sample solution in a multi-frequency ultrasonic device, and add 20% (w / v, g / mL) sodium citrate of the sample solution sequentially. Add organic solvent at a sample solution:dimethyl carbonate ratio of 1:1 (v / v), adjust the pH to 6, set the ultrasonic frequency to 40 ± 80 kHz, pulse for 5 s on and 5 s off, temperature to 50 ℃, and ultrasonic time to 40 min. Centrifuge at 4500 r / min to separate the solid and liquid. Take the middle solid phase, wash it with water, and dry it to ensure the moisture content is ≤10%. Crush and sieve to obtain insoluble pineapple dietary fiber. Take the lower liquid phase, dialyze to remove salt, and freeze-dry to obtain soluble pineapple dietary fiber.

[0074] Following the method described in Example 1, dietary fiber from two types of pineapple was collected. The extraction rate of soluble dietary fiber, the content of soluble protein, the extraction rate of insoluble dietary fiber, digestive properties, and glucose adsorption capacity of the products were determined. The results are shown in Table 1. Figure 2 and Figure 3 .

[0075] The PSDF extraction rate was 84.66±0.43%, with a soluble protein content of 2.11±1.33%, and the PIDF insoluble dietary fiber extraction rate was 57.66±3.50%. At 5 mg / mL, PSDF inhibited α-amylase by 36.89±0.48%; PIDF had a glucose adsorption capacity of 9.79±0.96 µmol / g. This method, including sample solution preparation, ultrasonic extraction, and centrifugation, requires only 2 h to prepare both products simultaneously.

[0076] Compare with Example 1, which describes the traditional method for preparing soluble and insoluble dietary fiber from pineapple.

[0077] Preparation of insoluble dietary fiber from pineapple: Insoluble dietary fiber was prepared from pineapple pomace using a compound enzymatic method. 100 g of fruit powder was placed in a 2 L beaker, and 1 L of distilled water was added. The pH was adjusted to 6.0 with 1 M NaOH. 2% thermostable α-amylase and cellulase were added to the sample solution for enzymatic hydrolysis, and the mixture was continuously hydrolyzed for 60 min in a 95 ℃ constant-temperature magnetic stirrer. After cooling, the sample solution was placed at 60 ℃, and 0.8% papain was added, followed by continuous enzymatic hydrolysis for 60 min. The sample solution was washed with water and alcohol, and the insoluble solids were collected by vacuum filtration. The insoluble dietary fiber was obtained by drying, a process that took 10 h.

[0078] Preparation of pineapple soluble dietary fiber: The sample was extracted with primary water at a ratio of 1:30 at 80℃ for 3 h. After extraction, the sample was filtered through 200-mesh gauze to remove the residue. The extract was concentrated to one-tenth of its original volume under reduced pressure at 60℃. The concentrated extract was centrifuged (3500 r / min, 15 min) and the supernatant was collected. The supernatant was mixed with Sevage reagent (chloroform: n-butanol = 4:1) at a volume ratio of 5:1 and stirred at room temperature for 1 h. After stirring, the extract was centrifuged at 12000 r / min for 20 min to extract the aqueous layer. Three volumes of anhydrous ethanol were added to the aqueous layer and stirred rapidly. The mixture was allowed to stand at 4℃ for 24 h and then centrifuged (3500 r / min, 10 min) to collect the precipitate. The precipitate was reconstituted with tertiary water and dialyzed at 4℃ for three days using a 6000 Da dialysis bag. The pineapple soluble dietary fiber was obtained by drying. Excluding dialysis time, the entire process took 28 h.

[0079] Following the method described in Example 1, dietary fiber from two types of pineapple was collected. The extraction rate of soluble dietary fiber, the content of soluble protein, the extraction rate of insoluble dietary fiber, digestive properties, and glucose adsorption capacity of the products were determined. The results are shown in Table 1. Figure 2 and Figure 3 .

[0080] The PSDF extraction rate was 80.31±0.28%, the soluble protein content was 2.56±0.41%, and the PIDF insoluble dietary fiber extraction rate was 60.40±2.62%. At 5 mg / mL, PSDF inhibited α-amylase by 36.46±2.88%; the glucose adsorption capacity of PIDF was 9.50±0.88 µmol / g.

[0081] Comparative analysis (Table 1) revealed that the traditional water extraction method for preparing soluble dietary fiber from pineapple pomace is complex, requiring a large amount of organic reagents for protein removal, often repeated more than five times to achieve the desired effect, taking approximately 4 hours. Traditional enzymatic hydrolysis for extracting insoluble dietary fiber from pineapple pomace requires 6 hours; the enzymes used in enzymatic hydrolysis are expensive, and a large volume of ethanol is needed after hydrolysis to wash away reducing sugars (the ethanol washing process takes approximately 8-10 hours). Furthermore, the filter cartridges used in filtration need to be re-washed with acid solutions and ethanol of different concentrations, resulting in significantly longer extraction times than the method described above. In contrast, the extraction rates of the products prepared in Examples 1-3 of this invention are close to and reach the levels achieved by traditional extraction methods, and their α-amylase inhibition rate and glucose adsorption capacity are significantly higher than those of traditional separation methods. Figures 2-3 This demonstrates that the method described in this invention can rapidly prepare and enrich bioactive substances, thereby improving their bioactivity.

[0082] Comparative Example 2: A method for simultaneously preparing highly active soluble and insoluble dietary fiber from pineapple (single-frequency ultrasound)

[0083] Take 100 g of pineapple pomace and mix it with primary water at a material-to-liquid ratio of 1:30 (g / mL) to obtain a sample solution. Place the sample solution in an ultrasonic cleaner and add 20% (w / v, g / mL) sodium citrate to the sample solution. Add organic solvent at a sample solution:dimethyl carbonate ratio of 1:1 (v / v). Adjust the pH to 6, set the ultrasonic frequency to 40 kHz, pulse for 5 seconds and pause for 5 seconds, temperature to 40℃, and ultrasonic time to 30 min. Centrifuge at 4500 r / min to separate the solid and liquid phases. Wash the solid phase with water and dry it to ensure a moisture content of ≤10%. Crush and sieve to obtain insoluble pineapple dietary fiber. Dialyze the liquid phase and freeze-dry to obtain soluble pineapple dietary fiber.

[0084] Following the method described in Example 1, dietary fiber from two types of pineapple was collected. The extraction rate of soluble dietary fiber, the content of soluble protein, the extraction rate of insoluble dietary fiber, digestive properties, and glucose adsorption capacity of the products were determined. The results are shown in Table 1. Figure 2 and Figure 3 .

[0085] The PSDF extraction rate was 74.88±0.89%, with a soluble protein content of 4.21±1.85%; the PIDF insoluble dietary fiber extraction rate was 46.79±0.24%. At 5 mg / mL, PSDF inhibited α-amylase by 40.57±1.37%; the glucose adsorption capacity of PIDF was 8.91±1.18 µmol / g.

[0086] Comparative Example 3: A method for simultaneously preparing highly active soluble and insoluble dietary fiber from pineapple (without added salt)

[0087] Take 100 g of pineapple pomace and mix it with primary water at a material-to-liquid ratio of 1:30 (g / mL) to obtain a sample solution. Place the sample solution in a multi-frequency ultrasonic device, add organic solvent at a sample solution:dimethyl carbonate ratio of 1:2 (v / v), adjust the pH to 6, set the ultrasonic frequency to 20+40+80 kHz, pulse operation for 5 seconds and pause for 5 seconds, temperature to 40℃, and ultrasonic time for 30 min. Afterward, centrifuge at 4500 r / min to separate the solid and liquid. The obtained product is as follows. Figure 1 As shown. After washing with solid water and drying to a moisture content ≤10%, insoluble pineapple dietary fiber was obtained by pulverizing and sieving. Soluble pineapple dietary fiber was obtained by dialysis with liquid phase and freeze-drying.

[0088] Following the method described in Example 1, dietary fiber from two types of pineapple was collected. The extraction rate of soluble dietary fiber, the content of soluble protein, the extraction rate of insoluble dietary fiber, digestive properties, and glucose adsorption capacity of the products were determined. The results are shown in Table 1. Figure 2 and Figure 3 .

[0089] Because no salt (such as sodium citrate) was added, the interaction force between PIDF and water molecules in the extraction system was reduced under these conditions, which was detrimental to system equilibrium. Therefore, the product PSDF could not separate into layers during the extraction process. Figure 1 (Comparative Example 3) Total sugar extraction rate, protein content, and digestibility indicators could not be calculated. The extraction rate of insoluble dietary fiber from product PIDF was 56.08±2.41%; the glucose adsorption capacity of PIDF was 13.79±1.03 µmol / g.

[0090] Comparative Example 4: A method for simultaneously preparing highly active soluble and insoluble dietary fiber from pineapple (using different types of organic solvents).

[0091] Same as Example 1, except that ethanol is used instead of dimethyl carbonate, an organic solvent.

[0092] Take 100 g of pineapple pomace and mix it with primary water at a material-to-liquid ratio of 1:30 (g / mL) to obtain a sample solution. Place the sample solution in a multi-frequency ultrasonic device, and add 20% (w / v, g / mL) sodium citrate of the sample solution sequentially. Add organic solvent at a sample solution:ethanol ratio of 1:2 (v / v), adjust the pH to 6, set the ultrasonic frequency to 20+40+80 kHz, pulse for 5 seconds on and 5 seconds off, temperature at 40℃, and ultrasonic time for 30 min. Centrifuge at 4500 r / min to separate the solid and liquid. Dry the solid phase to ensure a moisture content ≤10%, pulverize and sieve to obtain insoluble pineapple dietary fiber. Dialyze the liquid phase and freeze-dry to obtain soluble pineapple dietary fiber.

[0093] Following the method described in Example 1, dietary fiber from two types of pineapple was collected. The extraction rate of soluble dietary fiber, the content of soluble protein, the extraction rate of insoluble dietary fiber, digestive properties, and glucose adsorption capacity of the products were determined. The results are shown in Table 1. Figure 2 and Figure 3 .

[0094] Since ethanol is not considered a congesting agent in the system, it does not easily penetrate into the interior of folded protein molecules, making it difficult for intermolecular interactions to occur, which is not conducive to system equilibrium. Therefore, PIDF cannot be tightly concentrated in the intermediate phase, and there are more suspended PIDF and other impurities in the lower phase.

[0095] The extraction rate of soluble dietary fiber from PSDF was 48.90±1.64%; the soluble protein content was 4.38±1.43%. The extraction rate of insoluble dietary fiber from PIDF was 30.79±3.11%. At 5 mg / mL, PSDF inhibited α-amylase by 27.50±2.16%; the glucose adsorption capacity of PIDF was 6.28±1.43 µmol / g.

[0096] Table 1 shows the basic indicators of dietary fiber in pineapples prepared in the examples and control examples.

[0097]

[0098] Table 1 compares the extraction rates and extraction times of PSDF and PIDF in different embodiments and control examples. As shown in Table 1, Examples 1-3 used the extraction method of this patent, therefore the entire extraction process took only 2 hours, and the maximum extraction rate of PSDF reached 85.67%, with good protein removal (only 1.67% residue). The maximum extraction rate of PIDF also reached 65.79%. Control Example 1 used a traditional extraction method, which took a long time (28 hours), and the extraction rate was lower compared to this invention. Control Example 2 used single-frequency ultrasound treatment. Since single-frequency ultrasound is less effective than multi-frequency ultrasound, the extraction rates of PSDF and PIDF were lower. Control Example 3 did not add salt (sodium citrate or potassium dihydrogen phosphate) to the system, failing to reach equilibrium, thus PSDF was not obtained. Control Example 4 used ethanol to replace the organic solvent dimethyl carbonate in the system. Because ethanol has weak interactions with other molecules, it failed to reach equilibrium, resulting in lower extraction rates of PSDF and PIDF.

[0099] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0100] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for simultaneous extraction of soluble and insoluble dietary fiber, characterized in that, Includes the following steps: S1. Using pineapple pomace as raw material, dilute with water to obtain sample solution; S2. Mix the above sample solution, salt, and organic solvent, add acid and base reagents to adjust the pH, and then place the composite system in a multi-frequency ultrasonic field for separation and extraction to obtain a composite extraction system. The pH range is 6-9; the salt is sodium citrate; the organic solvent is dimethyl carbonate; the mass-to-volume ratio of the salt to the sample solution is (10%-60%):1; the volume ratio of the organic solvent to the sample solution is (0.5-2.5):1.0; and the separation and extraction time is 20-50 min. S3. Centrifuge the above-mentioned composite extraction system to separate the upper liquid phase, the middle solid phase, and the lower liquid phase; The process involves removing the upper liquid phase, washing the middle solid phase with water to obtain pineapple insoluble dietary fiber, and dialysis the lower liquid phase to remove salt, yielding pineapple soluble dietary fiber.

2. The synchronous extraction method according to claim 1, characterized in that, In step S1, the mass-to-volume ratio of pineapple pulp to water is 1:10 to 1:

40.

3. The synchronous extraction method according to claim 1, characterized in that, In step S2, the acid-base reagents include hydrochloric acid and alkaline solution; wherein the concentration of hydrochloric acid is 0.1M; and the concentration of alkaline solution is 0.1M.

4. The synchronous extraction method according to claim 1, characterized in that, In step S2, the frequencies of the multi-frequency ultrasonic field are combined in different ways from 1 to 100 kHz.

5. The synchronous extraction method according to claim 1, characterized in that, In step S2, the temperature of the multi-frequency ultrasonic field is 30~90 ℃.

6. The synchronous extraction method according to claim 1, characterized in that, In step S3, the centrifugation speed is 3000~5000 r / min.

7. The synchronous extraction method according to claim 1, characterized in that, The method also includes step S4, which involves drying the above-mentioned pineapple insoluble dietary fiber to a moisture content of ≤10% to obtain dried pineapple insoluble dietary fiber; and freeze-drying the above-mentioned pineapple soluble dietary fiber to obtain dried pineapple soluble dietary fiber.

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