Green and efficient method for preparing sweet potato thick pulp with high solid content

Abstract

The invention discloses a green and efficient method for preparing sweet potato thick pulp with high solid content. The method comprises the following steps: crushing and drying sweet potatoes to obtain sweet potato powder; uniformly dispersing at least one of medium-temperature alpha-amylase, high-temperature alpha-amylase and saccharifying enzyme in purified water to prepare enzymatic hydrolysate; performing twin-screw extrusion on the enzymatic hydrolysate and the sweet potato powder to obtain sweet potato coarse pulp; and grinding, centrifuging, homogenizing, sterilizing and filling the sweet potato coarse pulp to obtain sweet potato thick pulp. An enzymolysis technology and an extrusion technology are combined, the effect of enzyme on a substrate is enhanced through extrusion, and the utilization rate of the enzyme is increased. The double-screw extrusion technology is adopted, short time and high efficiency are achieved, energy is saved, and continuous production of the sweet potato thick pulp can be achieved; the stability, sweetness, liquefaction degree and taste of the thick sweet potato pulp are remarkably improved, no stabilizer or thickener needs to be additionally added, the taste requirement of consumers for the thick sweet potato pulp is met, and the consumer market of the thick sweet potato pulp is expanded.

Description

Technical Field

[0001] The invention relates to the technical field of efficient biological conversion in food processing, and in particular to a method for preparing a sweet potato slurry with high solid content in an environmentally friendly and efficient manner. Background Art

[0002] Sweet potato, also known as sweet potato, sweet potato, sweet potato, etc., is a nutritious crop. Sweet potato contains a large amount of dietary fiber, vitamins, minerals and antioxidants. Its nutritional ingredients and functional properties make it a healthy food with a wide range of health and potential medicinal value. The main component of sweet potato is starch, which contains up to 20% to 30%, and is a high-quality source of carbohydrates. Sweet potato is rich in dietary fiber (2-3%), vitamin A, vitamin C, vitamin B group, essential amino acids and minerals for the human body, etc. Because it is rich in antioxidants, polysaccharides and phenolic compounds, it has a series of health functional characteristics, including preventing chronic diseases and delaying aging, and has a strong antioxidant function; inhibiting the proliferation of tumor cells and having anti-cancer function; slowing down the absorption rate of glucose and having the function of regulating blood sugar; reducing total cholesterol levels and the risk of cardiovascular diseases, and having the function of regulating blood lipids; fighting infection and inflammatory response, and having the function of enhancing the body's immunity; increasing intestinal peristalsis, maintaining the balance of intestinal flora, and having the function of promoting intestinal health.

[0003] Sweet potato is widely used in daily diet with its rich nutrients and multiple health functions, and is an ideal healthy food. At present, plant-based cereal drinks are becoming more and more popular. Sweet potato beverages, as a plant-based potato beverage with sweet potato as the main raw material, are widely loved by consumers because of their strong sweet potato flavor and unique taste, rich dietary fiber, vitamins and other bioactive substances. However, the preparation of high-solids cereal beverages, i.e., sweet potato slurry, is difficult. At present, the prior art mostly uses traditional enzymatic hydrolysis methods to prepare sweet potato beverages. CN 109549038 A discloses a process for comprehensive processing and utilization of sweet potato multi-stage co-production products. The process not only involves multiple enzymatic hydrolysis, but also combines vacuum concentration, resulting in large energy consumption and high preparation cost. CN 107279625 B discloses a method for preparing a low-sugar sweet potato beverage rich in soluble dietary fiber. The enzymatic hydrolysis heat preservation time of this process is long, and the use of multiple additives increases food safety risks. The sweet potato beverages prepared by the above method usually have problems such as low solid content, poor stability, and easy precipitation. Not only is the enzymatic hydrolysis time long and the enzymatic hydrolysis conditions strict, but the production cost is also high. In addition, when using the traditional enzymatic hydrolysis method to prepare sweet potato beverages, it is often necessary to add various stabilizers or thickeners and compound with other auxiliary materials. The use of stabilizers or thickeners will not only lead to a worse taste, but may also cause safety problems. The addition of auxiliary materials often makes it difficult to fully utilize the effective ingredients in the sweet potato. Summary of the invention

[0004] In view of the above problems, the object of the present invention is to provide a method for preparing a sweet potato slurry with high solid content in a green and efficient manner, wherein an extruder is used as an enzymatic reactor to induce the enzyme to exhibit high-efficiency activity. The method combines enzymatic hydrolysis technology with extrusion technology, achieves short-term enzymatic hydrolysis, and efficiently liquefies to achieve continuous production. The relevant enzymatic hydrolysis products have high solid content and good product stability. With the changes in market demand and the improvement of people's health awareness, sweet potato slurry is expected to become the mainstream of healthy food consumption, thereby promoting the development of local economy and human health.

[0005] The present invention first provides a green and efficient method for preparing a high-solids sweet potato slurry, comprising the following steps:

[0006] (1) cleaning the sweet potatoes, crushing and drying them to obtain sweet potato powder;

[0007] (2) uniformly dispersing the enzyme preparation in purified water to prepare an enzymatic solution;

[0008] (3) placing the sweet potato powder obtained in step (1) and the enzymatic hydrolyzate obtained in step (2) in a solid hopper and a liquid feeder of a twin-screw extruder respectively, and reacting and extruding them in the twin-screw extruder to obtain an extruded enzymatic hydrolyzed sweet potato pulp;

[0009] (4) grinding the extruded enzymatically hydrolyzed sweet potato pulp obtained in step (3) using a colloid mill;

[0010] (5) separating the residue from the product obtained in step (4) by horizontal screw centrifugation;

[0011] (6) homogenizing the product obtained in step (5) using a homogenizer;

[0012] (7) sterilizing and filling the product obtained in step (6) to obtain a final product, an extruded enzymatically hydrolyzed sweet potato slurry.

[0013] In one embodiment of the present invention, the sweet potato flour obtained in step (1) is the sweet potato flour sieved through a 40-80 mesh sieve.

[0014] In one embodiment of the present invention, the enzyme preparation in step (2) comprises at least one of mesophilic α-amylase, thermophilic α-amylase and saccharifying enzyme.

[0015] In one embodiment of the present invention, in step (2), the activity of the medium-temperature α-amylase is 300-600 KUN / g, the activity of the high-temperature α-amylase is 50-200 KUN / mL, and the activity of the saccharifying enzyme is 100-500 AGU / g.

[0016] In one embodiment of the present invention, in step (2), the amount of the enzyme preparation in the enzymatic hydrolysis solution is 1‰ to 10‰ of the mass of the sweet potato flour.

[0017] In one embodiment of the present invention, in step (3), the six areas of the extrusion cavity are divided into: areas I to V are extrusion enzymatic hydrolysis areas, and area VI is a high-temperature enzyme inactivation area; the temperatures of the various areas of the extrusion cavity are: 50-80°C in area I, 60-85°C in area II, 65-90°C in area III, 70-100°C in area IV, 80-110°C in area V, and 90-120°C in area VI.

[0018] In one embodiment of the present invention, in step (3), the extrusion temperature is 50°C to 120°C, the solid feeding rate (sweet potato powder) is 3 to 30 kg / h, the liquid feeding rate (enzyme hydrolysate) is 5 to 50 L / h, and the screw speed is 50 to 500 r / min.

[0019] In one embodiment of the present invention, in step (4), the grinding fineness of the colloid mill is 200-400 mesh, and the grinding time is 0.5-2 min.

[0020] In one embodiment of the present invention, the centrifugal process in step (5) has a rotation speed of 2000-3000 r / min and a centrifugal time of 1-5 min.

[0021] In one embodiment of the present invention, the homogenization process pressure in step (6) is 30-60 MPa, and the homogenization times are 1-2 times.

[0022] In one embodiment of the present invention, the sterilization conditions in step (7) are: sterilization temperature 105-135° C., sterilization time 5-60 s.

[0023] In one embodiment of the present invention, the solid content of the finished sweet potato slurry in step (7) is 25% to 45%.

[0024] The invention also discloses a sweet potato concentrated pulp prepared according to the method.

[0025] Beneficial effects of the present invention:

[0026] (1) Extrusion is a high-temperature, short-time, continuous and multifunctional thermomechanical technology that saves time, effort and energy and can achieve sustained high productivity.

[0027] (2) Enzymatic hydrolysis technology is combined with extrusion technology, and the extruder is used as an enzyme-catalyzed bioreactor to induce the enzyme to exhibit high-efficiency activity and improve the utilization rate of the enzyme, which is conducive to reducing costs and significantly improving the stability, sweetness, liquefaction and taste of sweet potato pulp.

[0028] (3) Compared with the technical solutions of using medium-temperature α-amylase alone, using medium-temperature α-amylase in combination with high-temperature α-amylase, or combining medium-temperature α-amylase with saccharifying enzyme, using only high-temperature α-amylase to perform extrusion enzymatic hydrolysis on sweet potato flour can significantly improve the stability and sensory properties of sweet potato concentrate, significantly increase the reducing sugar content in the concentrate, and improve the sweetness of the concentrate.

[0029] (4) The solid content of the sweet potato slurry prepared by the present invention can reach up to 31.35%, the reducing sugar content can reach up to 251.84 mg / g, the DE value can reach up to 80.33%, and the sensory score can reach up to 95.6 points. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the reducing sugar standard curve;

[0031] Figure 2 The present invention is a schematic diagram of the process for preparing the sweet potato slurry. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be described in a complete and clear manner below. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them.

[0033] Raw materials: The enzyme preparations used in the examples and comparative examples were purchased from Beijing Novozymes Co., Ltd. The medium-temperature α-amylase activity was 480 KUN / g, the high-temperature α-amylase activity was 120 KUN / mL, and the saccharifying enzyme activity was 300 AGU / g.

[0034] Example 1

[0035] A green and efficient method for preparing a high-solids sweet potato slurry comprises the following steps:

[0036] (1) cleaning the sweet potato, crushing and drying the sweet potato, and 100% of the sweet potato powder passes through a 60-mesh sieve to obtain sweet potato powder;

[0037] (2) Dispersing the medium-temperature α-amylase in purified water to prepare an enzymatic hydrolyzate, wherein the amount of the medium-temperature α-amylase added to the enzymatic hydrolyzate is 5‰ of the mass of the sweet potato flour.

[0038] (3) putting sweet potato powder into a solid feeding bin, putting enzymatic hydrolyzate into a liquid feeder, and reacting and extruding in a twin-screw extruder, wherein the temperatures of zones I to VI of the extruder are 70° C., 75° C., 80° C., 85° C., 90° C., and 95° C., respectively, the feeding rate is 5 kg / h, the screw speed is 150 r / min, and the liquid feeding rate is 10 L / h, to obtain enzymatic hydrolyzed sweet potato crude slurry;

[0039] (4) The sweet potato pulp is ground into a 300 mesh colloid, the grinding time is 1 min, and then centrifuged at 2500 r / min for 3 min. The mixture is homogenized once with a homogenizer at a pressure of 40 MPa for 30 s each time, sterilized at 115° C. for 60 s, and aseptically cold-filled to obtain a finished sweet potato pulp.

[0040] Example 2

[0041] A green and efficient method for preparing a high-solids sweet potato slurry comprises the following steps:

[0042] (1) cleaning the sweet potato, crushing and drying the sweet potato, and 100% of the sweet potato powder passes through a 60-mesh sieve to obtain sweet potato powder;

[0043] (2) High temperature α-amylase is dispersed in purified water to prepare an enzymatic hydrolysate, wherein the amount of high temperature α-amylase added to the enzymatic hydrolysate is 5‰ of the mass of sweet potato flour.

[0044] (3) putting sweet potato powder into a solid feeding bin, putting enzymatic hydrolyzate into a liquid feeder, and reacting and extruding in a twin-screw extruder, wherein the temperatures of zones I to VI of the extruder are 80° C., 85° C., 90° C., 95° C., 105° C., and 115° C., respectively, the feeding rate is 5 kg / h, the screw speed is 150 r / min, and the liquid feeding rate is 10 L / h, to obtain enzymatic hydrolyzed sweet potato crude slurry;

[0045] (4) The sweet potato pulp is ground into a 300 mesh colloid, the grinding time is 1 min, and then centrifuged at 2500 r / min for 3 min. The mixture is homogenized once with a homogenizer at a pressure of 40 MPa for 30 s each time, sterilized at 115° C. for 60 s, and aseptically cold-filled to obtain a finished sweet potato pulp.

[0046] Example 3

[0047] A green and efficient method for preparing a high-solids sweet potato slurry comprises the following steps:

[0048] (1) cleaning the sweet potato, crushing and drying the sweet potato, and 100% of the sweet potato powder passes through a 60-mesh sieve to obtain sweet potato powder;

[0049] (2) Dispersing the medium-temperature α-amylase and the high-temperature α-amylase in purified water to prepare an enzymatic hydrolyzate, wherein the amount of the medium-temperature α-amylase added to the enzymatic hydrolyzate is 2‰ of the mass of the sweet potato flour, and the amount of the high-temperature α-amylase added to the sweet potato flour is 3‰ of the mass of the sweet potato flour.

[0050] (3) putting sweet potato powder into a solid feeding bin, putting enzymatic hydrolyzate into a liquid feeder, and reacting and extruding in a twin-screw extruder, wherein the temperatures of zones I to VI of the extruder are 75° C., 80° C., 85° C., 95° C., 105° C., and 115° C., respectively, the feeding rate is 5 kg / h, the screw speed is 150 r / min, and the liquid feeding rate is 10 L / h, to obtain enzymatic hydrolyzed sweet potato crude slurry;

[0051] (4) The sweet potato pulp is ground into a 300 mesh colloid, the grinding time is 1 min, and then centrifuged at 2500 r / min for 3 min. The mixture is homogenized once with a homogenizer at a pressure of 40 MPa for 30 s each time, sterilized at 115° C. for 60 s, and aseptically cold-filled to obtain a finished sweet potato pulp.

[0052] Example 4

[0053] A green and efficient method for preparing a high-solids sweet potato slurry comprises the following steps:

[0054] (1) cleaning the sweet potato, crushing and drying the sweet potato, and 100% of the sweet potato powder passes through a 60-mesh sieve to obtain sweet potato powder;

[0055] (2) Dispersing mesophilic α-amylase and saccharifying enzyme in purified water to prepare enzymatic hydrolysate, wherein the amount of mesophilic α-amylase added to the enzymatic hydrolysate is 3‰ of the mass of sweet potato flour, and the amount of saccharifying enzyme added to the enzymatic hydrolysate is 2‰ of the mass of sweet potato flour.

[0056] (3) putting sweet potato powder into a solid feeding bin, putting enzymatic hydrolyzate into a liquid feeder, and reacting and extruding in a twin-screw extruder, wherein the temperatures of zones I to VI of the extruder are 55° C., 65° C., 70° C., 75° C., 85° C., and 95° C., respectively, the feeding rate is 5 kg / h, the screw speed is 150 r / min, and the liquid feeding rate is 10 L / h, to obtain enzymatic hydrolyzed sweet potato crude slurry;

[0057] (4) The sweet potato pulp is ground into a 300 mesh colloid, the grinding time is 1 min, and then centrifuged at 2500 r / min for 3 min. The mixture is homogenized once with a homogenizer at a pressure of 40 MPa for 30 s each time, sterilized at 115° C. for 60 s, and aseptically cold-filled to obtain a finished sweet potato pulp.

[0058] Comparative Example 1

[0059] A green and efficient method for preparing a high-solids sweet potato slurry comprises the following steps:

[0060] (1) cleaning the sweet potato, crushing and drying the sweet potato, and 100% of the sweet potato powder passes through a 60-mesh sieve to obtain sweet potato powder;

[0061] (2) Disperse the medium-temperature α-amylase in purified water and mix it with sweet potato powder in advance. The water content of the mixture is 25%. The water is balanced at room temperature of 25°C for 12 hours. The required amount of medium-temperature α-amylase added is 5‰ of the mass of the sweet potato powder.

[0062] (3) putting the premixed sweet potato powder into a solid feeding bin, putting purified water into a liquid feeder, and reacting and extruding in a twin-screw extruder, wherein the temperatures of zones I to VI of the extruder are 70° C., 75° C., 80° C., 85° C., 90° C., and 95° C., respectively, the feeding rate is 5 kg / h, the screw speed is 150 r / min, and the liquid feed rate is 10 L / h, to obtain an enzymatically hydrolyzed sweet potato pulp;

[0063] (4) The sweet potato pulp is ground into a 300 mesh colloid, the grinding time is 1 min, and then centrifuged at 2500 r / min for 3 min. The mixture is homogenized once with a homogenizer at a pressure of 40 MPa for 30 s each time, sterilized at 115° C. for 60 s, and aseptically cold-filled to obtain a finished sweet potato pulp.

[0064] Test Method

[0065] Solid content:

[0066] The moisture content of sweet potato slurry was determined by the first method direct drying method according to the national standard GB 5009.3-2016 to obtain its solid content.

[0067] Solid content = 100% - moisture content

[0068] Reducing sugar content:

[0069] First, prepare a glucose standard solution with a concentration of 1 mg / mL. Take 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mL of the glucose standard solution in a centrifuge tube, add deionized water to 1.0 mL, accurately add 1.5 mL of DNS color developer, heat in a boiling water bath for 5 min, and then quickly cool to room temperature. Accurately add 1.5 mL of deionized water to dilute and mix, measure the absorbance at a wavelength of 540 nm, and draw a standard curve, such as Figure 1 As shown. Secondly, take 1.0g sample, add 20mL deionized water, vortex for 1min, centrifuge at 8000g for 10min, separate the supernatant; take the precipitate, add 20mL deionized water, centrifuge at 8000g for 10min, combine the two supernatants, and make up to volume in a 100mL volumetric flask for later use. Take 200μL of the fixed-volume supernatant in a 2ml centrifuge tube, add 200μL deionized water and 300μL DNS colorimetric agent, boil in a water bath for 5min and quickly cool to room temperature, add 300μL deionized water again, mix well, and color at a wavelength of 540nm on an enzyme reader, and read the absorbance; finally, use the standard curve to calculate the reducing sugar content of the sample.

[0070] DE value:

[0071] The percentage of reducing sugar content (calculated as glucose) in the sample to dry matter is called DE value. The calculation formula of DE value is as follows:

[0072] DE value = (reducing sugar content%) / (dry matter content%) × 100%

[0073] Among them, dry matter refers to the mass of solid matter remaining after the sample is dried and all water is removed.

[0074] Sensory evaluation:

[0075] Invite 50 professionally trained test volunteers to evaluate the appearance, flavor, taste, etc. of the sweet potato puree. The specific evaluation method is shown in Table 1. A total of 48 valid results were collected.

[0076] Table 1 Scoring rules for sensory evaluation of sweet potato milk

[0077]

[0078] Except for sensory evaluation, all experiments were repeated three times, and the results were expressed as mean ± standard deviation. SPSS25.0 software was used to analyze the data with one-way analysis of variance and Duncan test, and p < 0.05 was considered statistically significant.

[0079] Table 2 Solid content, reducing sugar content and DE value of sweet potato pulp

[0080]

[0081] Table 3 Sensory evaluation scores of sweet potato puree

[0082]

[0083] Solid content is usually used to measure the proportion of solid matter in a liquid or semi-solid sample, and is an important parameter for evaluating food, beverages, etc. The solid content of the sweet potato slurry prepared in Examples 1 to 4 is about 30%, indicating that the enzymatic hydrolysis co-extrusion technology can significantly increase the product concentration, while the traditional enzymatic hydrolysis technology can only obtain enzymatic hydrolysis products with a solid content of less than 20%. The traditional enzymatic hydrolysis technology not only takes a long time to hydrolyze, but also requires the addition of thickeners to increase the product concentration. Compared with traditional enzymatic hydrolysis, the enzymatic hydrolysis co-extrusion technology used in the present invention can prepare a high-concentration sweet potato slurry product without the addition of thickeners by a short and efficient enzymatic hydrolysis, which significantly improves food safety and reduces the production costs of enterprises.

[0084] The reducing sugar content is closely related to the degree of enzymatic hydrolysis and liquefaction of the sweet potato concentrate, the sweetness of the product, etc. Amylase can cut the glycosidic bonds in the starch molecules. Under the action of amylase, the sweet potato starch is decomposed into small molecule sugars and dextrins, and finally glucose is generated. The higher the reducing sugar content, the higher the degree of enzymatic hydrolysis of the sweet potato concentrate and the better the liquefaction. The DE value is an important indicator to measure the reducing sugar content in starch or starch hydrolysis products. The DE value reflects the degree of starch hydrolysis. The higher the value, the more thorough the starch hydrolysis and the more simple sugars are generated.

[0085] Compared with Examples 1 to 4, the reducing sugar content and DE value of the sweet potato slurry prepared in Example 2 are the highest, and it has better stability, palatability and sweetness. This is attributed to the high action temperature of high-temperature amylase, which makes the sweet potato starch gelatinized completely, and the wide action range of high-temperature amylase makes the starch liquefaction more complete. At the same time, the enzyme is not easy to inactivate, thereby increasing the reducing sugar content and product sweetness. Compared with the compound enzyme formula, the enzymatic liquefaction sample of the single enzyme formula has high sweetness, low viscosity, and the best effect, which effectively reduces the production cost of the enterprise. Comparative Example 1 is to mix the enzyme with the sweet potato powder in advance, but because the enzyme preparation is not in complete contact with the sweet potato powder, the starch molecular chain cannot be effectively sheared, the small molecule sugar or dextrin obtained by liquefaction is less, the enzymatic hydrolysis effect is poor, and the reducing sugar content of the obtained enzymatic sweet potato slurry is low.

[0086] The sensory evaluation scores of Examples 1 to 4 were compared. In terms of smell, Examples 1 and 4 had a fresh sweet potato aroma, while Examples 2 and 3 had a stronger aroma. In terms of appearance, Examples 2 to 4 were all in a stable state without dehydration and stratification, while Example 1 was slightly dehydrated. The colors were consistent with the color of the sweet potato itself. In terms of taste, Examples 2, 3, and 4 had a suitable sweet potato sweetness, while Example 1 had a slightly lighter sweetness. In terms of taste, Examples 1 to 2 had a moderate taste. In a comprehensive comparison, Example 2 had a higher sensory score, followed by Examples 3 and 4, and Example 1 had the lowest score.

[0087] In short, the reducing sugar content, DE value, sensory score, etc. of Example 2 are better. The reason is that the twin-screw extrusion method of the present invention has multiple extrusion temperature zones, a long extrusion cavity, a large contact area, a long action time, and a large number of shearing times, which is conducive to the deep liquefaction of starch. The extrusion temperature zone has a stable action temperature and a concentrated temperature, which is conducive to the enzyme preparation to exert the maximum enzymolysis effect, save costs, extend the action time of related enzyme preparations, and improve utilization efficiency, thereby achieving efficient production, improving the stability of sweet potato slurry, palatability and sensory score, and increasing the application value of sweet potato slurry.

[0088] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A green and efficient method for preparing a high-solids sweet potato slurry, characterized in that: The following steps are involved: (1) cleaning the sweet potato, crushing and drying it, and passing it through a 40-80 mesh sieve to obtain sweet potato powder; (2) uniformly dispersing the enzyme preparation in purified water to prepare an enzymatic hydrolyzate; (3) placing the sweet potato powder obtained in step (1) and the enzymatic hydrolyzate obtained in step (2) in a solid hopper and a liquid feeder of a twin-screw extruder respectively, and reacting and extruding them in the twin-screw extruder to obtain an extruded enzymatic hydrolyzed sweet potato pulp; (4) grinding the extruded enzymatically hydrolyzed sweet potato pulp obtained in step (3) using a colloid mill; (5) separating the residue from the product obtained in step (4) by horizontal screw centrifugation; (6) homogenizing the product obtained in step (5) using a homogenizer; (7) sterilizing and filling the product obtained in step (6) to obtain a final product, an extruded enzymatically hydrolyzed sweet potato slurry.

2. The method according to claim 1, characterized in that The enzyme preparation in step (2) comprises at least one of a medium-temperature α-amylase, a high-temperature α-amylase and a saccharifying enzyme, wherein the medium-temperature α-amylase has an activity of 300 to 600 KUN / g, the high-temperature α-amylase has an activity of 50 to 200 KUN / mL, and the saccharifying enzyme has an activity of 100 to 500 AGU / g.

3. The method according to claim 1, characterized in that In step (2), the amount of the enzyme preparation in the enzymatic hydrolysis solution is 1‰ to 10‰ of the mass of the sweet potato flour.

4. The method according to claim 1, characterized in that: In step (3), the six areas of the extrusion cavity are divided into: areas I to V are extrusion enzymatic hydrolysis areas, and area VI is an extrusion enzymatic hydrolysis and high-temperature enzyme inactivation area; the temperatures of the various areas of the extrusion cavity are: 50-80°C in area I, 60-85°C in area II, 65-90°C in area III, 70-100°C in area IV, 80-110°C in area V, and 90-120°C in area VI.

5. The method according to claim 1, characterized in that In step (3), the extrusion temperature is 50°C to 120°C, the solid feeding rate is 3 to 30 kg / h, the liquid feeding rate is 5 to 50 L / h, and the screw speed is 50 to 500 r / min.

6. The method according to claim 1, characterized in that In step (4), the grinding fineness of the colloid mill is 200-400 meshes, and the grinding time is 0.5-2 min.

7. The method according to claim 1, characterized in that In step (5), the centrifugal process speed is 2000-3000 r / min, and the centrifugal time is 1-5 min.

8. The method according to claim 1, characterized in that In step (6), the homogenization process pressure is 30-60 MPa, and the homogenization times are 1-2 times.

9. The method according to claim 1, characterized in that: The sterilization conditions in step (7) are: sterilization temperature 105-135°C, sterilization time 5-60s.

10. The sweet potato concentrate prepared according to the method of any one of claims 1 to 9, wherein the solid content of the sweet potato concentrate is 25% to 45%.

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