Extraction method and characterization of soluble dietary fiber from Agave serrata

Abstract

The invention discloses a method for extracting soluble dietary fiber from old mountain celery and its characterization. The specific steps are: fresh old mountain celery is washed, dried to constant weight at 55°C, crushed and passed through a 60-mesh sieve, an appropriate amount of distilled water is added, α-amylase is first added at 40°C, reacted for 30min, inactivated in a water bath at 100°C for 10min, neutral protease is added, reacted at 65°C for 1.5h, and inactivated again. The supernatant is concentrated by stirring and filtration, and then four times 95% ethanol is added to filter the precipitate, and the precipitate is dried after centrifugation to obtain a crude soluble dietary fiber powder, which is then purified by dialysis and freeze-dried to obtain an old mountain celery soluble dietary fiber product. The crude soluble dietary fiber extraction rate of the old mountain celery in the present invention is 10.26%, and the pure soluble dietary fiber extraction rate is 2.27%. The soluble dietary fiber is subjected to scanning electron microscopy analysis, Fourier transform infrared spectroscopy analysis, antioxidant capacity analysis, and X-ray diffraction analysis to obtain its characterization structure results. The process is simple and fast, with high extraction rate, high product purity, and good functionality.

Description

Technical Field

[0001] The invention discloses an extraction method and characterization of soluble dietary fiber from old mountain celery, belonging to the technical field of extraction of effective components of agricultural products, and specifically relates to a processing technology for extracting soluble dietary fiber. The final crude soluble dietary fiber extraction rate is 10.26%, and the pure soluble dietary fiber extraction rate is 2.27%, which provides a basis for the extraction method of soluble dietary fiber. The soluble dietary fiber is subjected to scanning electron microscopy analysis, Fourier transform infrared spectroscopy analysis, antioxidant capacity analysis and X-ray diffraction analysis to obtain its characterization structure results. Background Art

[0002] Old mountain celery is a perennial herbaceous plant in the subarctic region of the genus Angelica of the Apiaceae family. The tender stems and leaves of old mountain celery are emerald green and juicy, refreshing and delicious. It is a wild vegetable with good color, fragrance and taste. It is rich in dietary fiber, amino acids and vitamins and other nutrients. In addition to protein, fat, sugar and other substances, it is also rich in vitamin C, which is dozens of times that of ordinary vegetables. It has the pharmacological effects of clearing away heat and detoxification, lowering blood sugar, lowering blood pressure, removing rheumatism, cleaning blood, treating rheumatism, and relieving bone pain. It is favored by consumers and is known as the "green gold" among wild vegetables.

[0003] Soluble dietary fiber refers to the part of dietary fiber that is not digested by human digestive enzymes, but is soluble in warm and hot water and its aqueous solution can be reprecipitated by 4 times its volume of anhydrous ethanol. The main components of soluble dietary fiber are 6 monosaccharides, namely rhamnose, arabinose, galactose, glucose, mannose and xylose, and the proportions vary depending on the source. Increasing the intake of soluble dietary fiber can help prevent high blood pressure and colon cancer, and also reduce cholesterol and the incidence and mortality of respiratory diseases.

[0004] In the plant cell wall, dietary fiber usually forms a tight structure with starch, protein, and fat substances. The structure can be destroyed by physical, chemical, and biological methods to extract dietary fiber from fruit and vegetable by-products. Fruit and vegetable by-products contain a lot of unused dietary fiber, which not only causes a waste of resources, but also pollutes the environment to a certain extent. Chemical methods mainly include acid method and alkali method; physical methods include microwave method, ultrasonic method, ultrafine grinding method, extrusion cooking method, and high-pressure homogenization method; biological methods include enzyme method and fermentation method. Studies have shown that acid-base method will destroy the pore structure of the extracted dietary fiber, resulting in a decrease in water holding capacity and swelling capacity, and the exhaust gas and wastewater will pollute the environment; excessive ultrasonic power will reduce the extraction rate of dietary fiber, its microstructure will be destroyed, and the adsorption capacity will be greatly reduced; the extrusion cooking method consumes a lot of energy in the whole extraction process. In summary, different extraction methods may change the composition and structure of dietary fiber, thereby affecting its physical and chemical properties and functions. Among them, the soluble dietary fiber extracted by enzyme method is highly safe and easy to use. Summary of the invention

[0005] Technical issues: Acid extraction and alkaline extraction methods easily cause glycosidic bond breakage of soluble dietary fiber, and some soluble dietary fiber is hydrolyzed, which reduces the extraction rate. Water extraction is generally time-consuming, energy-intensive, requires a large amount of extraction solvent, and has a low dietary fiber extraction rate. Excessive ultrasonic power will reduce the dietary fiber extraction rate, destroy its microstructure, and greatly reduce adsorption.

[0006] The purpose of the present invention is to develop a method for extracting soluble dietary fiber from old mountain celery in view of the above-mentioned shortcomings and the current situation of low extraction rate in the process of soluble dietary fiber extraction. The method not only has simple equipment requirements, but also has a crude extraction rate of 10.26%, and the product is finely purified, of excellent quality, and is safe, green and pollution-free.

[0007] Technical solution: A method for extracting soluble dietary fiber from old mountain celery, specifically comprising the following steps:

[0008] (1) Raw material pretreatment: Wash fresh celery, dry at 55°C until constant weight, grind in a universal high-speed grinder, and pass through a 60-mesh sieve to obtain celery powder for later use;

[0009] (2) Double enzyme treatment: Mix old celery powder and distilled water in a solid-liquid ratio of 1:30, place in a beaker, and then add 0.3% α-amylase in a 40°C water bath for 30 minutes. Heat the mixture at 100°C for 10 minutes to inactivate the enzyme, and then cool to room temperature. Use 0.8% neutral protease to react at 65°C for 1.5 hours;

[0010] (3) Extraction of crude dietary fiber: stirring, filtering and concentrating the supernatant, adding four times 95% ethanol to filter the precipitate, centrifuging and drying the precipitate to obtain crude soluble dietary fiber powder of old celery;

[0011] (4) Dialysis purification: Dissolve the soluble dietary fiber in a hot water bath, cool it down and put it into a 3400D dialysis bag. Dialyze it with deionized water for 48 hours. After dialysis, freeze-dry it to obtain a pure soluble dietary fiber product.

[0012] (5) Determination of soluble dietary fiber index

[0013] SEM analysis: The microstructure and morphology of the DF samples were analyzed using SEM. The SDF samples were attached to a sample holder containing double-sided tape, and then gold powder was sprayed onto these samples using a sputter coater. The samples were placed in a vacuum chamber and evaluated using a SEM at an accelerating voltage of 5.0 kV.

[0014] Fourier transform infrared spectroscopy analysis: The dried SDF samples were ground with potassium bromide (KBr) powder and then pressed into pellets (2 mg SDF sample / 200 mg KBr) for FT-IR scanning in the frequency range of 4000-400 cm-1.

[0015] Antioxidant activity determination: Take 0.1 mL of sample solution of different concentration gradient A0 of soluble dietary fiber of old celery, add 3.9 mL of ABTS free radical solution, mix well, react at room temperature for 6 minutes, and measure the absorbance at 734 nm, which is recorded as A1. Take 3.9 mL of ABTS+ free radical solution, add 0.1 mL of 70% ethanol solution by volume to measure the absorbance, which is recorded as A2, and VC is used as a positive control.

[0016] Accurately weigh 0.0026g of DPPH and dilute it with anhydrous methanol to make its absorbance at 517nm wavelength 0.600+0.020, which is used as a control and recorded as A 对照 During the measurement, the absorbance was measured after incubation in the dark for 30 minutes and recorded as A 样品 .

[0017] X-ray diffraction analysis: The crystal structure of SDF samples was determined by X-ray diffractometer covering the 2θ angle range of 5-55° with a scanning speed of 2° / step.

[0018] Beneficial effects of the present invention:

[0019] 1. The extraction raw materials adopted in the present invention are wild vegetables with medicinal and edible properties, which are rich in nutrients and functional substances. The dual enzyme extraction system is used to replace the commonly used acid-base, acetone and other solvents and ultrasonic extraction methods. The equipment requirements are simple, the extraction rate is improved, and safe and green products are harvested.

[0020] 2. The raw material pretreatment in the present invention adopts a high-speed pulverizer for pulverization, and the obtained standby old celery powder can better facilitate the subsequent extraction of soluble dietary fiber, thereby indirectly improving the extraction efficiency.

[0021] 3. The double enzyme extraction method greatly shortens the extraction time compared with the traditional water extraction method, avoids long-term heating, destroys the polysaccharide components in the soluble dietary fiber that are sensitive to long-term heating and denatured, has a high extraction yield, and the final crude soluble dietary fiber extraction rate is 10.26%; compared with the acid-base method, the chemical residue of the extract is lower, and the product is green and healthy. The soluble dietary fiber extraction process route based on this method maintains the effective components of the soluble dietary fiber to the greatest extent, with high purity and less pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Fourier infrared spectra of three kinds of soluble dietary fibers

[0023] Depend on Figure 1 It can be seen that their infrared absorption spectra are similar, both of which have typical polysaccharide absorption peaks; at 3365cm -1 There are broad peaks on the left and right, which are the stretching vibration caused by -OH and are the characteristic peaks of sugars. -1 The characteristic absorption peaks near 1743 and 1653 cm are caused by the CH stretching vibration of the CH2 group of the polysaccharide; -1 The absorption peak near 1419 cm is due to C=O stretching vibration. -1 The absorption peaks around 1240cm are CH denaturation vibrations, containing acetyl or carboxylate groups, which may be caused by galacturonic acid. -1 It is CO, indicating that it contains ester groups; 1143cm -1 and 1123cm -1 It is the stretching vibration peak of COC and C-OH, 1123cm -1 The absorption peak, attributed to the overlap of ring vibration with the stretching vibration of the C-OH side group and the vibration of the COC glycoside band, is 1020 cm -1 is the bending vibration peak of OH, 970cm -1 These peaks indicate the presence of pyranose polysaccharide structures.

[0024] Figure 2 Scanning electron microscopic analysis of three soluble dietary fibers

[0025] like Figure 2 As shown in the figure, scanning electron microscopy analysis was used to describe the surface microstructure changes of the samples. The surface of the soluble dietary fiber (E-SDF) extracted by the dual enzyme method was rough with many irregular protrusions. The soluble dietary fiber (EC-SDF) extracted by the enzyme-chemical method showed an irregular layered structure. The overall structure was discontinuous, but the individual layered structure shrank, which was mainly caused by the strong oxidation of sodium hydroxide during the extraction process. The SEM image of the soluble dietary fiber (F-SDF) extracted by the fermentation method was looser, probably because after the fermentation treatment, lactic acid bacteria utilized substances such as protein and starch, making the microstructure of the fermented SDF more loose and porous. The enzyme extraction conditions were mild, and the structure was more complete than that of the enzyme-chemical extraction.

[0026] Figure 3 Analysis of the antioxidant capacity of three dietary fibers

[0027] The different antioxidant activities of three soluble dietary fiber solutions were investigated by comparing ABTS ( Figure 3 A) and DPPH( Figure 3B) The free radical scavenging ability of the three soluble dietary fibers is reflected in the concentration-dependent scavenging ability of ABTS and DPPH free radicals, among which MSDF has a higher scavenging ability of ABTS free radicals than MCSDF and FSDF. When the mass concentration of the soluble dietary fiber solution is 10 mg / ml, the scavenging rate of MSDF on DPPH free radicals reaches 86.4%, which is much higher than MCSDF (52.9%) and FSDF (62.4%), which shows that the activity of MSDF in scavenging DPPH is better than that of MCSDF and FSDF.

[0028] Figure 4 X-ray diffraction analysis of three dietary fibers

[0029] It can be observed from the figure that ECSDF has a gentle and broad absorption peak near 22.7°, while FSDF and ESDF have almost no absorption peaks. The above results show that there is no obvious difference in the crystal structure of the old celery SDF extracted by these three methods. They are all non-crystalline substances with an amorphous structure. DETAILED DESCRIPTION

[0030] The present invention is further explained below in conjunction with specific examples. This specific implementation method is implemented on the premise of the technical solution of the present invention. It should be understood that these methods are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0031] Example 1

[0032] Wash the fresh old mountain celery, dry it at 55℃ to constant weight, put it into a universal high-speed grinder and grind it through a 60-mesh sieve after drying, add an appropriate amount of distilled water according to the solid-liquid ratio of 1:30, add 0.3% α-amylase at 40℃, react for 30min, inactivate it in a water bath at 100℃ for 10min, then add 0.8% neutral protease, react at 65℃ for 1.5h, and inactivate it again. Stir and filter to take the supernatant and concentrate it, then add four times 95% ethanol to filter the precipitate, dry the precipitate after centrifugation, and obtain the crude soluble dietary fiber powder of old mountain celery, and then dialysis purification and freeze drying to obtain the soluble dietary fiber product of old mountain celery. The soluble dietary fiber was analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, antioxidant capacity analysis and X-ray diffraction analysis to obtain its characterization structure results.

[0033] Example 2

[0034] Wash the fresh old mountain celery, dry it at 55℃ to constant weight, put it into a universal high-speed grinder after drying, crush it and pass it through a 60-mesh sieve, add an appropriate amount of distilled water according to the solid-liquid ratio of 1:30, add 0.3% α-amylase at 40℃, react for 30min, inactivate it in a water bath at 100℃ for 10min, and then cool it to room temperature. Add 2% NaOH and react at 65℃ for 100min. Stir and filter to take the supernatant and concentrate it, then add four times 95% ethanol to filter the precipitate, centrifuge and dry the precipitate to obtain the crude soluble dietary fiber powder of old mountain celery, and then dialysis purification and freeze drying to obtain the soluble dietary fiber product of old mountain celery. The soluble dietary fiber was analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, antioxidant capacity analysis and X-ray diffraction analysis to obtain its characterization structure results.

[0035] Example 3

[0036] Wash the fresh old celery, dry it at 55℃ to constant weight, put it into a universal high-speed grinder and grind it through a 60-mesh sieve after drying. After adding 400g of distilled water to 20g of old celery powder, add 2% skim milk powder and 1.5% white sugar, mix well and sterilize, cool quickly, add 6% mixed bacteria, and ferment at 40℃ for 24h. Stir and filter to take the supernatant and concentrate it, then add four times 95% ethanol to filter the precipitate, dry the precipitate after centrifugation, and obtain the old celery crude soluble dietary fiber powder, which is then purified by dialysis and freeze-dried to obtain the old celery soluble dietary fiber product. The soluble dietary fiber is analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, antioxidant capacity analysis and X-ray diffraction analysis to obtain its characterization structure results.

[0037] The three implementation modes described above are merely examples for ease of understanding. It should be pointed out that, for those skilled in the art, several improvements can be made based on the description of the technical solution of the present invention and its preferred embodiments without departing from the principle of the present invention, and these improvements should also fall within the scope of protection of the present invention.

Claims

1. A method for extracting soluble dietary fiber from old celery, characterized in that: After drying and crushing the old celery, add an appropriate amount of distilled water, first add α-amylase at 40°C, react for 30 minutes, inactivate in a water bath at 100°C for 10 minutes, then add neutral protease, react at 65°C for 1.5 hours, and inactivate again; stir and filter to obtain the supernatant and concentrate it, then add four times 95% ethanol to filter the precipitate, dry the precipitate after centrifugation to obtain the old celery crude soluble dietary fiber powder, and then dialysis purification and freeze drying to obtain the old celery soluble dietary fiber product; specifically comprising the following steps: (1) Raw material pretreatment: Wash fresh celery, dry at 55°C until constant weight, grind in a universal high-speed grinder, and pass through a 60-mesh sieve to obtain celery powder for later use; (2) Double enzyme treatment: old celery powder and distilled water were mixed in a solid-liquid ratio of 1:30, placed in a beaker, and then 0.3% α-amylase was added in a 40°C water bath for 30 minutes; the mixture was heated at 100°C for 10 minutes to inactivate the enzyme, and then cooled to room temperature; 0.8% neutral protease was used for reaction at 65°C for 1.5 hours; (3) Extraction of crude dietary fiber: stirring, filtering and concentrating the supernatant, adding four times 95% ethanol to filter the precipitate, centrifuging and drying the precipitate to obtain crude soluble dietary fiber powder of old mountain celery; (4) Dialysis purification: Dissolve the soluble dietary fiber in a hot water bath, cool it, and place it in a 3400 kDa dialysis bag. Dialyze it with deionized water for 48 hours. After dialysis, freeze-dry it to obtain a pure soluble dietary fiber product.

2. The method for extracting soluble dietary fiber from Rhizoma Cibotii according to claim 1, characterized in that: The centrifugal conditions of the dietary fiber extract of the aged celery are: rotation speed 7000 rpm, and centrifugation time 10 min.

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