Preparation method and application of Chinese yam peel water extraction concentrated solution rich in polysaccharide and polyphenol

Abstract

The invention discloses a preparation method and application of a Chinese yam peel water extraction concentrated solution rich in polysaccharide and polyphenol. The preparation process comprises the following steps: pretreating a Chinese yam peel raw material, drying, pulverizing, extracting, concentrating, canning and sterilizing to finally obtain a Chinese yam peel water extraction concentrated solution finished product. The by-product Chinese yam peel in the Chinese yam processing process is subjected to resource utilization, the vibration type ultrafine pulverizer is adopted for pulverizing, the extraction surface area is increased, the preparation efficiency is improved, the multifunctional extraction and concentration equipment is used for conducting water extraction on the Chinese yam peel, extraction, vacuum concentration and solvent recovery are integrated, high efficiency and environment friendliness are achieved, and large-scale production is easy to achieve. The Chinese yam peel water extraction concentrated solution prepared by the invention is rich in nutritional active ingredients, the total polysaccharide content is 10.41-29.43 mg / mL, the total polyphenol content is 539.92-1002.80 mu g / mL, and the Chinese yam peel water extraction concentrated solution has good oxidation resistance, alpha-glycosidase inhibitory activity and excellent pancreatic lipase inhibitory activity, and can be used for developing lipid-lowering products.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of yam peel extracts, and particularly relates to a preparation method and application of a yam peel water extract concentrate rich in polysaccharides and polyphenols. Background Art

[0002] Chinese yam, also known as yam and yam medicine, belongs to the Dioscoreaceae family and the genus Dioscorea. It is an annual or perennial vine herb and one of the early Chinese medicinal and edible plants. Chinese yam is rich in bioactive substances such as yam polysaccharides, saponins, flavonoids, allantoin, choline, etc. It has a variety of pharmacological and health-care effects, such as nourishing the lungs and spleen, benefiting the kidneys and consolidating essence, helping digestion, anti-oxidation, protecting the liver, anti-cancer, lowering blood sugar, lowering blood lipids, enhancing the body's immunity, delaying aging, etc. It can effectively prevent hypertension, hyperlipidemia, cancer, cardiovascular disease and other diseases. There are many functional applications of yam currently under development. For example, patent document CN201110165499.8 discloses the use of water extraction to extract yam, and finds that its yam concentrate can effectively inhibit tyrosinase, and then inhibit the synthesis of melanin, achieving the effect of whitening and removing spots; patent document ZL202210071491.3 discloses the use of freeze-drying and spray-drying methods to prepare yam extract, and verifies that the prepared extract has a significant blood sugar-lowering effect.

[0003] At present, there are various yam products on the market, but they are mainly processed using yam meat. There is a process of removing yam skin in the production process. The treatment of yam skin is mostly discarded or used as feed for animals, resulting in a waste of resources. Simply discarding it will cause environmental pollution. And yam skin still contains rich nutrients, such as polyphenols, saponins, crude fiber, polysaccharides, flavonoids, etc. Studies have shown that the polyphenols distributed in yam skin are more than those contained in yam meat. Phenolic compounds, as a type of secondary metabolites, are widely distributed in plants and have antioxidant, anti-inflammatory, anti-tumor and other effects. Appropriate intake of polyphenols can effectively reduce the prevalence of chronic diseases. In addition, yam polysaccharides have multiple effects such as antioxidant, lowering blood sugar, and sobering up. In the prior art, a variety of methods are used to extract the active ingredients in yam peel, such as the patent document CN201811474689.6, which discloses a method for extracting total polyphenols from yam peel using microwave-assisted extraction; the patent document CN201110008886.0 discloses a method for extracting diosgenin from yam peel; the patent document CN201410699521.0 discloses a method for extracting anthocyanins from purple yam peel; the patent document ZL202211462558.2 discloses the preparation of a yam peel extract, but an extractant is added thereto, which is used for weight loss and lipid reduction. At present, the effective development of yam peel-related products has important research significance and application prospects for improving the comprehensive utilization value of yam. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a yam peel water extract concentrate rich in polysaccharides and polyphenols and its application, the method adopts ultrafine grinding, extraction and concentration for extraction, avoids the use of organic solvents in the extraction process, and is green and environmentally friendly. In addition, the direct water extraction conditions are optimized, which can reach a level equivalent to that of enzymatic hydrolysis, reduce the heating and cooling steps, save energy and time, and can effectively improve the efficiency of preparing the yam peel water extract concentrate. The obtained product, the yam peel water extract concentrate, is rich in polysaccharides and polyphenols, has good antioxidant capacity, α-glucosidase inhibitory activity and excellent pancreatic lipase inhibitory activity, and can be used in the development of functional foods such as lipid-lowering products.

[0005] The present invention adopts the following technical solution to solve the above technical problems, a method for preparing a yam peel water extract concentrate rich in polysaccharides and polyphenols, characterized by the specific steps of:

[0006] Step S1, pretreatment of yam peel raw materials: yam peel obtained as a byproduct during yam processing is washed with clean water to remove impurities;

[0007] Step S2, yam peel pretreatment: drying the yam peel obtained in step S1 in an oven, and crushing to obtain yam peel powder;

[0008] Step S3, preparation of yam peel water extract: adding the yam peel powder obtained in step S2 and purified water into a multifunctional extraction and concentration device, and continuously stirring and mixing in an extraction tank under a constant temperature condition to complete the extraction and obtain the yam peel water extract;

[0009] Step S4, concentration treatment of the yam peel water extract: transferring the yam peel water extract obtained in step S3 to a concentration tank, heating it, exhausting the air, and concentrating it in a vacuum environment to obtain a yam peel water extract concentrate;

[0010] Step S5: Canning and sterilizing the yam peel water extract concentrate: Centrifuge the yam peel water extract concentrate obtained in step S4, take the supernatant and fill it into a product bottle, seal it, and sterilize it.

[0011] It is further defined that the drying temperature in step S2 is 55-65° C., the drying time is 24-26 h, and the powder making process uses a vibrating ultrafine grinder to grind the yam peel into fine powder, which is then sieved through a 40-80 mesh sieve for later use.

[0012] It is further defined that the feeding ratio of yam peel powder and pure water in step S3 is 1 g: 20-25 mL, the temperature for preparing the yam peel extract in the extraction tank is 50-60° C., and the extraction time is 2-4 h.

[0013] It is further defined that in step S4, the concentration tank is heated to 60-70° C., and the concentration multiple is 1:4-6.

[0014] It is further defined that the sterilization treatment in step S5 is pasteurization, the sterilization temperature is 68-70° C., and the sterilization time is 30-35 min.

[0015] It is further defined that the total polysaccharide content of the yam peel water extract concentrate in step S5 is 10.41-29.43 mg / mL, and the total polyphenol content is 539.92-1002.80 μg / mL. It has good antioxidant capacity, α-glycosidase inhibitory activity and excellent pancreatic lipase inhibitory activity. The pancreatic lipase inhibition rate is as high as 82.35%-93.92%, and can be used in the development of functional foods such as lipid-lowering products.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] 1. The method for preparing the yam peel water extract concentrate of the present invention adopts ultrafine grinding, extraction and concentration for extraction, and no organic solvent is used in the extraction process, which is green and environmentally friendly. After optimizing the direct water extraction conditions, the total polysaccharide and total polyphenol content in the extract can reach a level equivalent to that of enzymatic hydrolysis, but the heating and cooling steps are reduced, which saves energy and time, improves the preparation efficiency of the yam peel water extract concentrate, has a simple preparation process, strong operability, and is easy to achieve large-scale production.

[0018] 2. The yam peel water extract concentrate prepared by the present invention is rich in nutrients such as polyphenols, polysaccharides, flavonoids, etc., has good antioxidant activity, and has the potential to anti-inflammatory effect and enhance the body's immunity; the yam peel water extract concentrate of the present invention is fat-free and contains trace elements, which meets the needs of the public; the yam peel water extract concentrate of the present invention contains dietary fiber, which can promote intestinal digestion, lower blood lipids, prevent energy excess and obesity, has good α-glucosidase inhibitory activity and superior pancreatic lipase inhibitory activity, and can be used for the development of functional products such as lipid-lowering.

[0019] 3. The yam peel water extract concentrate prepared by the present invention uses yam peel, a by-product of yam processing, as its raw material. The yam peel can be rationally applied to turn waste into treasure, protect the ecological environment, improve the comprehensive utilization of yam, and be applied to the development of functional foods, thereby increasing product added value, increasing farmers' income, and promoting the development of the agricultural economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an analysis of the volatile components of the yam peel water extract concentrate, where A is the GC-MS spectrum of the yam peel water extract concentrate; B is the relative content of the volatile components in the yam peel water extract concentrate.

[0021] Figure 2 This is the LC-MS spectrum (280nm) of the yam peel water extract concentrate. DETAILED DESCRIPTION

[0022] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0023] The present invention first explores the pretreatment of yam peel, mainly selecting four methods of beating, slicing, dry powder and pulp powder for comparison, and finally selecting dry powder for subsequent experiments, and then preparing yam peel extract. On the one hand, different extraction methods are explored, including direct water extraction, extracting polysaccharides first and then polyphenols, extracting phenolic substances first and then water extraction and enzymatic hydrolysis, and direct water extraction is a better process technology; on the other hand, the influence of different material-liquid ratios on the extract is explored, and the process preparation parameters of yam peel extract are obtained. Then the yam peel extract is concentrated, canned, and the sterilization method is optimized, and finally a yam peel water extract concentrate rich in polysaccharides and polyphenols is obtained.

[0024] Example 1

[0025] Step SS1, pretreatment of yam peel raw material: washing the yam peel, a byproduct of yam processing, with clean water to remove impurities;

[0026] Step S2, pre-treatment of yam peel: placing the yam peel obtained in step S1 in an oven and drying at 60° C. for 24 h, crushing the yam peel into fine powder using a vibrating cell-level ultrafine grinder, passing through a 40-mesh sieve, and collecting for later use;

[0027] Step S3, preparation of yam peel extract: use a multifunctional extraction and concentration instrument to prepare a yam peel extract, add the yam peel powder obtained in step S2 and purified water in a multifunctional extraction and concentration instrument at a material-liquid ratio of 1 g:20 mL, extract in an extraction tank at a temperature of 50° C. for 2 h, and continuously stir and mix to obtain a yam peel extract;

[0028] Step S4, concentration treatment of the yam peel extract: the yam peel extract obtained in step S3 is transferred to a concentration tank, slowly heated to 60° C., and after the temperature is constant, the air is discharged, and the yam peel water extract concentrate is concentrated in a vacuum environment at a ratio of 1:4 to obtain the yam peel water extract concentrate;

[0029] Step S5, canning and sterilizing the yam peel water extract concentrate: centrifuge the yam peel water extract concentrate obtained in step S4 at 4000 rpm for 10 min, take the supernatant and fill it into a 30 mL product bottle, seal it with an intelligent sealing machine, and then place it in a 70°C environment for pasteurization for 30 min.

[0030] Comparative Example 1

[0031] The difference from Example 1 is that during the pretreatment of the yam peel, a pulping method is selected, specifically, an appropriate amount of yam peel is added to a juicer, 80-100 mL of water is added, and the juice is squeezed for 1 min. After the yam peel is squeezed into a paste, an appropriate amount of yam peel and water are added, and the juice is squeezed for 1 min. This is repeated until the yam peel and water are added, and all are taken out and stirred evenly. The rest of the treatment methods are the same to prepare a yam peel water extract concentrate.

[0032] Comparative Example 2

[0033] The difference from Example 1 is that the yam peel is pre-treated by slicing, specifically, the yam peel is cut into 1-2 cm long slices with scissors and used immediately after cutting. The rest of the treatment methods are the same to prepare the yam peel water extract concentrate.

[0034] Comparative Example 3

[0035] The difference from Example 1 is that during the pre-treatment of the yam peel, pulp residue powder is used, specifically, the residue filtered during pulping in Comparative Example 1 is freeze-dried to prepare dry powder. The remaining treatment methods are the same to prepare the yam peel water extract concentrate.

[0036] Comparative Example 4

[0037] The difference from Example 1 is that when preparing the yam peel extract, the material-liquid ratio of yam peel powder to pure water is 1g:30mL, and the rest of the processing methods are the same to prepare the yam peel water extract concentrate.

[0038] Comparative Example 5

[0039] The difference from Example 1 is that when preparing the yam peel extract, the material-liquid ratio of yam peel powder to pure water is 1g:40mL, and the rest of the processing methods are the same to prepare the yam peel water extract concentrate.

[0040] Comparative Example 6

[0041] The difference from Example 1 is that when preparing the yam peel extract, the material-liquid ratio of yam peel powder to pure water is 1g:50mL, and the rest of the processing methods are the same to prepare the yam peel water extract concentrate.

[0042] Comparative Example 7

[0043] The difference from Example 1 is that when preparing the yam peel water extract concentrate, no concentration process technology is adopted, and the other processing methods are the same to prepare the yam peel water extract concentrate.

[0044] Comparative Example 8

[0045] The difference from Example 1 is that no sterilization technology is used when the yam peel water extract concentrate is canned and sterilized, and the other processing methods are the same to prepare the yam peel water extract concentrate.

[0046] Table 1 Effects of different pretreatment methods on the content of total polysaccharides and total polyphenols extracted from yam peel

[0047]

[0048] Table 2 Effects of different solid-liquid ratios on the content of total polysaccharides and total polyphenols extracted from yam peel

[0049]

[0050] Table 3 Effect of concentration on the total polysaccharide and total polyphenol content of yam peel water extract

[0051] Example (concentration ratio 1:4) Comparative Example 7 (concentration ratio 1:0) Total polysaccharide concentration (mg / mL) 29.35±0.18 9.10±0.02 Total polyphenol concentration (μg / mL) 986.95±15.85 503.84±4.28

[0052] Table 4 Effects of different sterilization methods on the total polysaccharide and total polyphenol contents of yam peel water extract concentrate

[0053] Example (Pasteurization) Comparative Example 8 (unsterilized) Total polysaccharide concentration (mg / mL) 10.72±0.31 12.49±0.24 Total polyphenol concentration (μg / mL) 540.48±0.56 596.60±13.29

[0054] Conclusion, by comparing the total polysaccharide and total polyphenol contents of Example 1 with those of Comparative Examples 1 to 7, it can be seen that the process technology of the present invention can effectively increase the content of polysaccharides and polyphenols in the yam peel extract concentrate; by comparing Example 1 with Comparative Example 8, it can be seen that pasteurization has little effect on the yam peel concentrate, and the contents and active functions of other components in the yam peel water extract concentrate of the present invention are further detected.

[0055] Detection of nutritional ingredients in the examples

[0056] Table 5 Nutritional content

[0057] project Per 100g energy 24KJ protein 0.49g Fat 0.0g carbohydrate 1.4g Dietary fiber 0.12g sodium 3.81mg Reducing sugar 0.72g Total flavonoids 66.28mg

[0058] GC-MS qualitative analysis of detection examples

[0059] like Figure 1 As shown in the figure, the volatile components of the yam peel water extract concentrate were analyzed by GC-MS. The results showed that the yam peel extract concentrate was rich in odor components such as aldehydes, alcohols, lipids, acids, ketones, etc. Among them, oleic acid has the ability to lower blood lipids, and nonanal has herbal, medicinal, almond and other aromas, and has strong nutritional and health functions.

[0060] Table 6 Volatile components and relative contents in yam peel water extract concentrate

[0061]

[0062] LC-MS qualitative analysis of detection examples

[0063] like Figure 2As shown in the figure, the polyphenols and other bioactive components of the yam peel water extract concentrate were analyzed by LC-MS. The results showed that the yam peel extract concentrate is rich in bioactive components, including the characteristic components of yam, yam I, yam III, yam IV, trans-N-p-coumaryl tyramine, cis-N-p-coumaryl tyramine, etc.; there are also sugars such as gluconic acid and glucose-1-phosphate; it contains a variety of phenolic substances, such as quinic acid, cinnamic acid, phthalic acid, vanillic acid, vitexin glucoside, fumaric acid, etc.; it contains fatty acids such as glyceric acid, succinic acid, palmitic acid, etc.; it is rich in amino acids such as tryptophan - calming the nerves and helping sleep, leucine —Prevent muscle loss, serine—neurotransmitter; rich in vitamins, such as niacin—treat gastrointestinal diseases, D-pantothenic acid—participate in fatty acid metabolism, vitamin B6—maintain immune function, vitamin B2—maintain the functions of skin mucosa, muscles and nervous system; various nucleic acid bases, such as thymine, cytosine, uracil, guanine, adenine, hypoxanthine, etc.; in addition, there are salidroside—anti-fatigue, anti-aging, immune regulation, adenosine—participate in myocardial energy metabolism, itaconic acid—promote metabolism, and have strong nutritional and health care functions.

[0064] Table 7 Components and relative contents of yam peel water extract concentrate (yellow part repeated)

[0065]

[0066]

[0067] Merge, remove duplicates, and reformat

[0068]

[0069]

[0070] Detection of Antioxidant Activity of Examples

[0071] The antioxidant activity of the yam peel water extract concentrate was analyzed by measuring the iron ion reducing ability (FRAP method), DPPH free radical scavenging ability, and ABTS free radical scavenging ability. The results showed that the yam peel water extract concentrate had certain antioxidant activity, could reduce iron ions, and scavenge DPPH free radicals and ABTS free radicals.

[0072] Table 8 Antioxidant activity of yam peel water extract concentrate

[0073]

[0074]

[0075] Detection of enzyme inhibitory activity in Example

[0076] By measuring the inhibition rates of α-amylase, α-glucosidase and pancreatic lipase, the ability of the yam peel water extract concentrate to regulate glucose and lipid metabolism was analyzed. The results showed that the α-glucosidase inhibition rate and pancreatic lipase inhibition rate of the yam peel water extract concentrate were both over 50%, which was comparable to the positive control drugs 0.1 μg / mL acarbose or orlistat, and had great potential for lowering blood sugar and losing weight.

[0077] Table 9 Enzyme inhibition activity of yam peel water extract concentrate

[0078]

[0079] The following is a selection experiment of the method in the preparation of yam peel extract:

[0080] Method for detecting total polysaccharides

[0081] Take 1mL of yam peel concentrate and dilute to an appropriate multiple. Take 1mL of the dilution, add 0.5mL of 6wt% phenol and 2.5mL of concentrated sulfuric acid, shake well and cool at room temperature for 20min, measure the absorbance at 490nm, calculate the polysaccharide concentration in the extract according to the standard curve (standard curve is made with glucose standard), and calculate the total amount of polysaccharide extraction in the corresponding yam peel.

[0082] Methods for detecting total polyphenols

[0083] Dilute the yam peel concentrate (80 Vol% methanol-water solution) with methanol, take 500 μL of the diluted yam peel extract, add it to 2.5 mL of 0.2 mol / L folin solution, and shake it thoroughly; after 4 minutes, add 2 mL of 75 g / L Na 2 CO 3 The solution was thoroughly shaken and mixed, and then incubated in the dark at room temperature for 2 h. The absorbance of the mixed solution at 760 nm was measured, and the total polyphenol content in the extract was calculated according to the standard curve (the standard curve was made with gallic acid), and the total amount of phenolic substances extracted in the corresponding yam peel was calculated.

[0084] Method for detecting antioxidant activity - FRAP assay

[0085] 180 μL of freshly prepared FRAP working solution was mixed and placed in a 37°C water bath for 30 min, mixed with 5 μL of sample solution of each concentration in a 96-well ELISA plate, and double distilled water was used as a blank control. After shaking for 1 min in an ELISA reader, the reaction was incubated at 37°C for 10 min, and the absorbance was measured at 593 nm to draw a standard curve. The standard curve was prepared with different concentrations of FeSO 4 7H 2 O standard solution: 10 mM FeSO 4 The solutions were diluted to 0.15mM, 0.3mM, 0.6mM, 0.9mM, 1.2mM and 1.5mM respectively; FeSO4 7H 2 O was diluted with pure water to adjust the concentration. The antioxidant activity was calculated according to the standard curve and the results were expressed as FeSO 4 Equivalent concentration (μmolFeSO 4 / mL).

[0086] Method for detecting antioxidant activity-DPPH free radical scavenging ability assay

[0087] Take a certain amount of DPPH and 80Vol% methanol to prepare a 120μmol / L DPPH solution, and measure the absorbance at 515nm to be between 0.6 and 1.0; take a certain amount of Trolox and dilute it with 50Vol% ethanol to prepare 0μM / L, 50μM / L, 100μM / L, 200μM / L, 400μM / L, and 600μM / L Trolox solutions. Add 100μLTrolox solution and 1.9mL DPPH dilution solution to the test tube, mix well and place in the dark to react for 2h. After the reaction, measure the absorbance of the reaction solution at 515nm with an enzyme marker to prepare a standard curve. Calculate the in vitro antioxidant capacity of the sample by the linear equation of the standard curve, and its unit is μmol Trolox / L.

[0088] Method for detecting antioxidant activity-ABTS free radical scavenging ability assay

[0089] Take a certain amount of ABTS to prepare a 7mM / L ABTS solution, and take a certain amount of potassium persulfate to prepare a 2.45mM / L K 2 S 2 O 8 Solution, ABTS solution and K 2 S 2 O 8 The solutions were mixed evenly in equal proportions and stored in the dark for more than 16 hours to obtain an ABTS mixed solution; a certain amount of Trolox was diluted with 50Vol% ethanol to prepare 0μM / L, 50μM / L, 100μM / L, 200μM / L, 400μM / L, and 600μM / L Trolox solutions. The ABTS mixed solution was diluted 20 times with 80Vol% methanol, and the absorbance was measured at about 0.7 at 734nm; 200μLTrolox solution and 1.8mLABTS diluted solution were added to the test tube successively, mixed thoroughly, and placed in the dark to react for 6 minutes. After the reaction, the absorbance of the reaction solution was measured at 734nm with an enzyme marker to prepare a standard curve. The in vitro antioxidant capacity of the sample was calculated by the linear equation of the standard curve, and its unit was μmol Trolox / L.

[0090] Method for detecting α-amylase inhibitory activity

[0091] The sample and acarbose were respectively prepared with PBS into standard solutions with gradient mass concentrations of 0.05 mg / mL, 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, and 0.5 mg / mL, and then α-amylase solution with a concentration of 1 mg / mL and 1 wt% soluble starch solution were prepared. 50 μL of α-amylase solution and sample solution were added to the experimental group; 50 μL of α-amylase solution and PBS were added to the sample control group; 50 μL of PBS solution and sample solution were added to the blank control group; and 100 μL of PBS buffer was added to the solvent control group. The above four groups of solutions were placed in a 37°C water bath for 10 minutes, and then 100 μL of 1wt% starch solution was added to each of them, and then kept at 37°C for 10 minutes. Finally, 400 μL of DNS (3.5-dinitrosalicylic acid) solution was added, and the solution was placed in a 100°C water bath for 10 minutes. After cooling, the absorbance was measured at 540 nm. Acarbose, a hypoglycemic drug, was used as a positive control group to calculate the inhibition rate (%).

[0092] Method for detecting α-glucosidase inhibitory activity

[0093] The sample and acarbose were respectively prepared with PBS into standard solutions with gradient mass concentrations of 0.05 mg / mL, 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, and 0.5 mg / mL, and then α-glucosidase solution with a concentration of 1 mg / mL and 1wt% pNPG p-nitrophenyl-α-D-pyranoglucoside (6 mM / L) solution were prepared. 50 μL of α-glucosidase solution and sample solution were added to the experimental group; 50 μL of α-glucosidase solution and PBS were added to the sample control group; 50 μL of PBS solution and sample solution were added to the blank control group; and 100 μL of PBS buffer was added to the solvent control group. The above four groups of solutions were placed in a 37°C water bath for 10 minutes, and then 100 μL of 1wt% pNPG was added to each of them, and then kept at 37°C for 30 minutes. Finally, 500 μL of Na 2 CO 3 The absorbance of the solution was measured at 405 nm and the inhibition rate (%) was calculated.

[0094] Method for detecting pancreatic lipase inhibitory activity

[0095] The sample was prepared at a concentration of 1.0 mg / mL and diluted 2, 4, 6, and 8 times to prepare sample solutions of different concentrations. 50 μL of sample solution, 50 μL of pancreatic lipase solution (1.0 U / mL), and 50 μL of 100 mM sodium phosphate buffer (pH 6.8) were mixed together and reacted at 37°C for 10 minutes. After the reaction, 100 μL of 5 mM 4-nitrophenylbutyrate (p-NPB) solution was added and reacted under the same conditions for 10 minutes. Then, 0.75 mL of 100 mM Na 2 CO 3 The reaction was terminated, the absorbance at 420 nm was measured, and the weight loss drug orlistat was used as a positive control to calculate the pancreatic lipase inhibition rate (%).

[0096] Selection of extraction method for yam peel

[0097] (1) Direct water extraction method: Take yam peel powder or yam peel slices and add them to water at a certain ratio of solid to liquid (the yam peel pulp is supplemented with water to the same solid to liquid ratio), stir with a magnetic stirrer, and keep at a constant temperature of 80°C for 30 minutes. After heating and stirring, divide into 50mL centrifuge tubes and centrifuge at 5000rpm for 20 minutes at room temperature. After centrifugation, collect the supernatant, and freeze-dry the yam peel residue obtained by centrifugation for later use. Filter the supernatant using a Buchner funnel, and save the filtrate as the extract.

[0098] (2) Extract polysaccharides first and then polyphenols: Segmented enzymatic hydrolysis method: add 40g of dry powder to ultrapure water (solid-liquid ratio 1g:10mL), add high-temperature resistant α-amylase and perform enzymatic hydrolysis at 80℃ with magnetic stirring for 1h; add papain at 60℃ and perform enzymatic hydrolysis for 1h; inactivate in a 100℃ water bath for 30min; add saccharifying enzyme in a 60℃ water bath and perform enzymatic hydrolysis for 1h; inactivate in a 100℃ water bath for 30min; keep the enzymatic hydrolysis solution in an 80℃ water bath for 3h, centrifuge at 3000rpm for 15min, repeat the centrifugation until no precipitation is produced, and combine the filtrate.

[0099] Protein removal: Take the filtrate and perform Sevage (n-butanol: chloroform = 1:4) method to remove protein. Add the filtrate to the test tube at a volume of 4:1. Shake the mixture vigorously for 20-30 minutes and centrifuge at 4000 rpm for 10 minutes. Take the supernatant and repeat the process until there is no denatured protein layer at the junction of the two phases. Centrifuge at 3000 rpm for 15 minutes.

[0100] Alcohol precipitation: Combine and concentrate the supernatants after centrifugation to 100 mL, add anhydrous ethanol dropwise to 300 mL, incubate at 4°C overnight, centrifuge at 3000 rpm for 15 min, and the precipitate is the crude burdock polysaccharide, which is freeze-dried and stored dry.

[0101] (3) Extract phenolic substances first and then extract with water: weigh 10g of dry powder and add 200mL of 80Vol% methanol-water solution (solid-liquid ratio 1:20); mix thoroughly and put into an ultrasonic device, ultrasonicate at 45℃ and 400W for 30min; take out from the ultrasonic device and let it stand to cool to room temperature, centrifuge at 3000rpm for 15min, remove methanol from the supernatant at 55℃ and obtain a water-soluble concentrate for total polyphenol determination.

[0102] Table 10 Effects of different extraction methods on the total polysaccharide and total polyphenol content of yam peel concentrate

[0103] Direct water extraction Extract polysaccharides first and then polyphenols Extract polyphenols first and then extract polysaccharides with water Total polysaccharide content (mg / gDW) 162.81±10.56 70.48±2.54 132.27±3.11 Total polyphenol content (mg / gDW) 2.56±0.12 0.017±0.002 2.57±0.12

[0104] In summary, direct water extraction is better than enzymatic hydrolysis.

[0105] Further optimization of the extraction method

[0106] (1) Segmented water extraction: Weigh 2 g of dry powder and add 40 mL of water, extract at 80°C for 30 min with stirring, centrifuge at 5000 rpm for 20 min at room temperature, collect the supernatant, and determine the sugar content and total polyphenol content; add 40 mL of water to the yam peel residue obtained by centrifugation for two extractions, extract at 80°C for 30 min with stirring, centrifuge at 5000 rpm for 20 min at room temperature, collect the supernatant, and determine the sugar content and total polyphenol content; add 20 mL of water to the yam peel residue obtained by centrifugation for three extractions, extract at 80°C for 30 min with stirring, centrifuge at 5000 rpm for 20 min at room temperature, collect the supernatant, and determine the sugar content and total polyphenol content.

[0107] (2) Direct water extraction: Weigh another 2g of dry powder and add it to 100mL of water. Stir and extract at 80℃ for 30min. Centrifuge at 5000rpm for 20min. Collect the supernatant and determine the sugar content and total polyphenol content. The three extractions were compared with the extraction of 2g of dry powder directly into 100mL of water.

[0108] (3) Segmented alcohol extraction: Weigh 2 g of dry powder and add 10 mL of 80 Vol% methanol-water solution, ultrasonicate at 45°C and 400 W for 30 min, centrifuge at 3000 rpm for 15 min, and determine the total polyphenol content of the supernatant; add 10 mL of 80 Vol% methanol-water solution to the yam peel residue obtained by centrifugation for a second extraction, ultrasonicate at 45°C and 400 W for 30 min, centrifuge at 3000 rpm for 15 min, and determine the total polyphenol content of the supernatant; add 5 mL of 80 Vol% methanol-water solution to the yam peel residue obtained by centrifugation for a third extraction, ultrasonicate at 45°C and 400 W for 30 min, centrifuge at 3000 rpm for 15 min, and determine the total polyphenol content of the supernatant; add 20 mL of water to the yam peel residue obtained by centrifugation, extract at 80°C with constant temperature stirring for 30 min, centrifuge at 5000 rpm for 20 min at room temperature, collect the supernatant, and determine the sugar content and total polyphenol content.

[0109] (4) Direct alcohol extraction: Weigh 2 g of dry powder and add it to 25 mL of 80 Vol% methanol-water solution, ultrasonicate at 45°C and 400 W for 30 min, centrifuge at 3000 rpm for 15 min, and measure the total polyphenol content of the supernatant; add 20 mL of water to the yam peel residue obtained by centrifugation, extract at 80°C for 30 min, centrifuge at 5000 rpm for 20 min, collect the supernatant, and measure the sugar content and total polyphenol content.

[0110] The three extractions were compared with one extraction with 2g of dry powder directly added into 25mL of 80Vol% methanol-water solution.

[0111] Table 11 Total polysaccharide and total polyphenol content after optimized extraction of yam peel

[0112]

[0113]

[0114] In summary, the total amount of three extractions is relatively high, and direct water extraction has better effect.

[0115] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a yam peel water extract concentrate rich in polysaccharides and polyphenols, characterized in that The specific steps are: Step S1, pretreatment of yam peel raw materials: yam peel obtained as a byproduct during yam processing is washed with clean water to remove impurities; Step S2, yam peel pretreatment: drying the yam peel obtained in step S1 in an oven, and crushing to obtain yam peel powder; Step S3, preparation of yam peel water extract: adding the yam peel powder obtained in step S2 and purified water into a multifunctional extraction and concentration device, and continuously stirring and mixing in an extraction tank under a constant temperature condition to complete the extraction and obtain the yam peel water extract; Step S4, concentration treatment of the yam peel water extract: transferring the yam peel water extract obtained in step S3 to a concentration tank, heating it, exhausting the air, and concentrating it in a vacuum environment to obtain a yam peel water extract concentrate; Step S5: Canning and sterilizing the yam peel water extract concentrate: Centrifuge the yam peel water extract concentrate obtained in step S4, take the supernatant and fill it into a product bottle, seal it, and sterilize it.

2. The method for preparing the yam peel water extract concentrate rich in polysaccharides and polyphenols according to claim 1, characterized in that: The drying temperature in step S2 is 55-65° C., and the drying time is 24-26 hours. In the powder making process, a vibrating superfine grinder is used to grind the yam peel into fine powder, which is then sieved through a 40-80 mesh sieve for later use.

3. The method for preparing the yam peel water extract concentrate rich in polysaccharides and polyphenols according to claim 1, characterized in that: In step S3, the mass ratio of yam peel powder to pure water is 1:20-25, the temperature for preparing the yam peel extract in the extraction tank is 50-60° C., and the extraction time is 2-4 hours.

4. The method for preparing the yam peel water extract concentrate rich in polysaccharides and polyphenols according to claim 1, characterized in that: In step S4, the concentration tank is heated to 60-70° C., and the concentration ratio is 1:4-6.

5. The method for preparing the yam peel water extract concentrate rich in polysaccharides and polyphenols according to claim 1, characterized in that: The sterilization treatment in step S5 is pasteurization, the sterilization temperature is 68-70° C., and the sterilization time is 30-35 min.

6. The method for preparing the yam peel water extract concentrate rich in polysaccharides and polyphenols according to claim 1, characterized in that: The total polysaccharide content of the yam peel water extract concentrate in step S5 is 10.41-29.43 mg / mL, the total polyphenol content is 539.92-1002.80 μg / mL, and the yam peel water extract concentrate has good antioxidant capacity, α-glycosidase inhibitory activity and excellent pancreatic lipase inhibitory activity, and the pancreatic lipase inhibition rate is as high as 82.35%-93.92%.

7. Use of the yam peel water extract concentrate rich in polysaccharides and polyphenols obtained according to the method of any one of claims 1 to 6 in the preparation of lipid-lowering products.

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