Nutritious and healthy sweet potato probiotic beverage and preparation method therefor

Abstract

A nutritious and healthy sweet potato probiotic beverage and a preparation method therefor, relating to the technical field of sweet potato processing. According to the present invention, in order to solve the problem of how to use sweet potatoes for deep processing to prepare a probiotic beverage, orange-fleshed sweet potatoes or purple-fleshed sweet potatoes are peeled and sliced, and undergo color protection, calcium immersion, and blanching, followed by adding water, pulping, enzymolysis, liquefaction, and saccharification to obtain a feed liquid; and then the feed liquid is fermented by lactic acid bacteria and compounded with white sugar and citric acid to prepare a nutritious and healthy sweet potato probiotic beverage. The present invention is applicable to the development and production of deep-processed sweet potato products.

Description

A nutritious and healthy sweet potato probiotic beverage and its preparation method Technical Field

[0001] This invention relates to the field of sweet potato processing technology, specifically to a nutritious and healthy sweet potato probiotic beverage and its preparation method. Background Technology

[0002] Sweet potato, a tuberous root vegetable belonging to the Convolvulaceae family, is hailed as the world's seventh largest source of carbohydrates. It is renowned for its wide adaptability, tolerance to poor soil, drought resistance, and high and stable yields. In Asia and Africa, sweet potato has long been a major source of carbohydrates, playing a vital role in addressing population growth and food supply issues in developing countries. As a physiologically alkaline food, sweet potato is not only rich in nutrients but also possesses significant medicinal value, earning it the title of "champion vegetable" from the World Health Organization (WHO). It contains abundant starch, mucoprotein, polysaccharides, dehydroepiandrosterone (DHEA), as well as various vitamins and minerals, offering positive effects such as strengthening the spleen, nourishing the heart and mind, boosting energy, reducing swelling and sores, preventing arteriosclerosis, and delaying aging, making it an ideal health food.

[0003] Orange-fleshed sweet potatoes, in addition to containing the starch, dietary fiber, soluble sugars, and various vitamins of regular sweet potatoes, are particularly rich in beta-carotene, a precursor to vitamin A, which has a positive effect on enhancing intercellular connections and inhibiting cancer development. Purple-fleshed sweet potatoes, with their purplish-red or purplish-black tubers, contain not only the nutrients of regular sweet potatoes but also abundant anthocyanins and selenium. These components possess antioxidant, anti-aging, anti-cancer, and anti-atherosclerotic health benefits.

[0004] In recent years, with a deeper understanding of the health benefits of sweet potatoes, they have become increasingly popular as a health food, and the demand for safe, convenient, nutritious, and health-promoting sweet potato products is constantly growing. While probiotic dairy products made from cow's milk and goat's milk are already on the market, many people are allergic to cow's and goat's milk proteins, limiting the market for these products. Probiotic beverages can be produced directly from sweet potato pulp, which not only broadens the range of raw materials for probiotic beverages but also helps preserve the active ingredients in sweet potatoes, while also being beneficial to gut health. Summary of the Invention

[0005] To enrich the variety of probiotic beverages, this invention provides a method for preparing a nutritious and healthy sweet potato probiotic beverage. The sweet potato probiotic beverage is made by peeling, slicing, color-protecting, calcium-soaking, blanching, adding water to orange-fleshed or purple-fleshed sweet potatoes, followed by pulping, enzymatic hydrolysis, liquefaction, and saccharification to obtain a liquid, which is then fermented with lactic acid bacteria and compounded with white sugar and citric acid.

[0006] Further specifying, the lactic acid bacteria is Lactobacillus helveticus CICC 6102.

[0007] This invention also provides a method for preparing the above-mentioned sweet potato probiotic beverage, comprising the following steps:

[0008] (1) Color Protection: Peel orange-fleshed or purple-fleshed sweet potatoes, slice them to a thickness of 3-5 mm, and then protect them with color. The color-protecting agent is one or a mixture of citric acid and ascorbic acid. When the color-protecting agent is citric acid, its mass concentration is 0.05%-0.08%; when the color-protecting agent is an aqueous solution of ascorbic acid, its mass concentration is 0.04%-1.2%; when the color-protecting agent is a mixture of the two, citric acid and ascorbic acid are mixed in any ratio. The standard is that the sweet potato slices are completely immersed in the color-protecting agent, and the color protection time is 5-30 minutes.

[0009] (2) Calcium soaking: The washed and drained sweet potato slices are soaked in calcium. The calcium concentration is 50-75 mg / L and the soaking time is 15-20 min.

[0010] (3) Blanching: Put the washed and drained sweet potato slices into boiling water and blanch for 8-10 minutes. The blanching time varies depending on the variety.

[0011] (4) Pulping: After blanching, the sweet potato slices are mixed with water at a ratio of (1:1) to (1:5) and then pulped to obtain sweet potato pulp;

[0012] (5) Enzymatic hydrolysis: Add pectinase at a rate of 0.01%-0.1% of the weight of sweet potato pulp, and hydrolyze at 55℃-60℃ for 1-3 hours to obtain sweet potato liquid A;

[0013] (6) Liquefaction: Based on the initial sweet potato raw material mass, add 6-8 U / g of medium-temperature amylase to sweet potato solution A, and liquefy for 30-90 min at 60℃-70℃ and pH 6.0-6.4 to obtain sweet potato solution B;

[0014] (7) Saccharification: Based on the mass of sweet potato solution B, add 0.5-1 AGU / g of saccharifying enzyme to sweet potato solution B, and saccharify for 90-180 min at 50℃-70℃ and pH 3.4-5.5 to obtain sweet potato solution C.

[0015] (8) Lactic acid bacteria fermentation: Based on the volume of liquid C, add 1%-5% of the bacteria to liquid C, with a bacterial concentration of 1×10⁻⁵. 7 A slurry was obtained by fermenting a lactic acid bacteria culture of CFU / mL at 25℃-30℃ for 10-24 hours.

[0016] (9) Blending: Add white sugar and citric acid to the obtained slurry for compounding. The amount of each ingredient added is 2%-6% (w / w) of white sugar and 0.1%-0.5% (w / w) of citric acid, based on the mass of the slurry.

[0017] (10) Homogenization: Preheat the prepared mixture to 50-60℃ and homogenize it with a high-pressure homogenizer. The pressure during homogenization is 19-20MPa, and the homogenization time is 10-20min.

[0018] (11) Degassing: Degas at 40-50℃ and a vacuum of 0.06-0.08MPa;

[0019] (12) Filling: Pump the filtered beverage into the filling machine, use hot filling, filling temperature ≥80℃, and seal the beverage can after filling;

[0020] (13) Sterilization and cooling: The beverage can is sent into an ultra-high temperature instantaneous sterilization device. The sterilization parameters are 135-150℃ for 2-8 seconds, and then rapidly cooled to 30-40℃ to obtain sweet potato probiotic beverage.

[0021] Preferably, the orange-fleshed sweet potato in step (1) is a high-carotene type fresh sweet potato with a β-carotene content of more than 10 mg / 100g, and the purple-fleshed sweet potato is a purple fresh sweet potato with an anthocyanin content of more than 75 mg / 100g.

[0022] Preferably, when the color-protecting agent in step (1) is citric acid, its addition amount is 0.08% of the mass of sweet potato pulp; or when the color-protecting agent is ascorbic acid, its addition amount is 1% of the mass of sweet potato pulp.

[0023] Preferably, the calcium immersion in step (2) is performed with a calcium chloride concentration of 70 mg / L and an immersion time of 15 min.

[0024] Preferably, the blanching time in step (3) is determined by the variety and dryness. For dryness greater than 25%, blanching takes 10 minutes, and for dryness less than 25%, blanching takes 8 minutes.

[0025] Preferably, in step (5), the amount of pectinase added during enzymatic hydrolysis is 0.1% of the mass of the purple sweet potato pulp, the hydrolysis temperature is 60℃, and the time is 2h.

[0026] Preferably, the liquefaction in step (6) is as follows: based on the initial mass of purple sweet potato raw material, add 8 U / g of medium-temperature amylase to purple sweet potato liquid A, and liquefy for 30 min at 65°C and pH 6.0 to obtain purple sweet potato liquid B.

[0027] Preferably, in the saccharification process described in step (7): based on the mass of purple sweet potato liquid B, 1 AGU / g of saccharifying enzyme is added to purple sweet potato liquid B, and saccharification is carried out at 70°C and pH 4.2 for 90 min to obtain purple sweet potato liquid C.

[0028] Preferably, in step (8), the lactic acid bacteria fermentation involves adding 5% of the bacteria to the purple sweet potato liquid C, based on the volume of the liquid, resulting in a bacterial concentration of 1×10⁻⁶. 7 A lactic acid bacteria culture of CFU / mL was fermented at 30℃ for 24 hours to obtain mash. Beneficial effects

[0029] Sweet potato probiotic beverage is made from orange-fleshed or purple-fleshed sweet potatoes, primarily through lactic acid bacteria fermentation. It not only retains the nutritional components of sweet potatoes but is also rich in probiotics. The beneficial effects of the preparation method described in this invention are as follows:

[0030] 1. This invention involves steaming fresh sweet potatoes and then treating them with enzymes to obtain sweet potato pulp. The sweet potato pulp contains a high amount of amino acids, vitamins, and minerals, which can serve as a nutrient source for the proliferation of lactic acid bacteria. A sweet potato probiotic beverage is prepared by fermenting with lactic acid bacteria, thus preserving the original nutritional components of the sweet potato. The sweet potato probiotic beverage is rich in bioactive substances such as anthocyanins, polyphenols, and β-carotene, and has high antioxidant activity.

[0031] 2. This invention improves the taste of sweet potato probiotic beverages by fermenting sweet potato pulp with lactic acid bacteria, while being rich in probiotics that are beneficial to the intestines, conforming to current dietary habits, and is an ideal health drink.

[0032] 3. The sweet potato probiotic beverage brewed by this invention has a harmonious and unique sweet potato aroma, a refreshing and smooth taste, and a distinctive style. The orange-fleshed sweet potato probiotic beverage has a bright orange-red color, while the purple-fleshed sweet potato probiotic beverage has a clear purple-red color.

[0033] 4. This invention utilizes calcium immersion treatment to reduce the loss of nutrients such as ascorbic acid, β-carotene, phenolic substances and anthocyanins during the steaming process, thereby maintaining the health benefits of sweet potatoes.

[0034] 5. Use medium-temperature amylase instead of traditional high-temperature amylase to avoid the degradation of β-carotene and anthocyanins by high temperature. Detailed Implementation

[0035] The sweet potatoes, fungicides, reagents, instruments and equipment used in this invention can all be purchased commercially.

[0036] Lactobacillus helveticus was purchased from the China Industrial Microbial Culture Collection Center, with the culture accession number CICC 6102. The frozen Lactobacillus helveticus was cultured in MRS medium at 30°C for 48 hours, and the activation concentration was adjusted to 1×10⁻⁶. 7 CFU / mL.

[0037] The sweet potato probiotic beverage described in the following examples is made by peeling, slicing, color-protecting, calcium-soaking, blanching, and then mixing with water to obtain a pulp, followed by enzymatic hydrolysis, liquefaction, and saccharification. This pulp is then fermented with lactic acid bacteria and combined with white sugar and citric acid. The preparation method of the sweet potato probiotic beverage of this invention is described in detail below.

[0038] Example 1. Preparation method of sweet potato probiotic beverage.

[0039] (1) Color protection: The purple-fleshed sweet potatoes were peeled, sliced ​​into 5mm thick slices, and then protected with color. The color protection agent was 0.05% citric acid and 0.05% ascorbic acid. The standard was that the sweet potato slices were completely immersed in the color protection agent, and the color protection time was 20 minutes.

[0040] (2) Calcium soaking: The washed and drained sweet potato slices are soaked in calcium. The calcium concentration is 70 mg / L and the soaking time is 15 min.

[0041] (3) Blanching: Wash and drain the sweet potato slices and put them into boiling water for 10 minutes.

[0042] (4) Pulping: After blanching, the sweet potato slices are mixed with water at a ratio of 1:1 and then pulped to obtain sweet potato pulp;

[0043] (5) Enzymatic hydrolysis: Add pectinase at a rate of 0.1% of the mass of sweet potato pulp, and hydrolyze at 60°C for 2 hours to obtain sweet potato liquid A;

[0044] (6) Liquefaction: Based on the initial sweet potato raw material mass, add 8 U / g of medium-temperature amylase to sweet potato solution A, and liquefy for 30 days at 65℃ and pH 6.0 to obtain sweet potato solution B;

[0045] (7) Saccharification: Based on the mass of sweet potato solution B, add 1 AGU / g of saccharifying enzyme to sweet potato solution B, and saccharify for 90 minutes at 70℃ and pH 4.2 to obtain sweet potato solution C;

[0046] (8) Lactic acid bacteria fermentation: Based on the volume of liquid C, add 5% of the bacteria to liquid C, with a bacterial concentration of 1×10⁻⁶. 7 A lactic acid bacteria culture of CFU / mL was fermented at 30℃ for 24 hours to obtain a slurry.

[0047] (9) Blending: Add white sugar and citric acid to the obtained slurry for blending. The amount of each ingredient added is 4% (w / w) white sugar and 0.2% (w / w) citric acid, based on the mass of the slurry.

[0048] (10) Homogenization: Preheat the prepared mixture to 60°C and homogenize it using a high-pressure homogenizer at a pressure of 20MPa for 15 minutes.

[0049] (11) Degassing: Degassing at 50℃ and a vacuum of 0.08MPa;

[0050] (12) Filling: Pump the filtered beverage into the filling machine, use hot filling, filling temperature ≥80℃, and seal the beverage can after filling;

[0051] (13) Sterilization and cooling: The beverage can is sent into an ultra-high temperature instantaneous sterilization device. The sterilization parameters are 140°C for 8 seconds, and then rapidly cooled to 35°C to obtain sweet potato probiotic beverage.

[0052] The sweet potato probiotic beverage obtained in this embodiment has a β-carotene content of 0.40 mg / 100g.

[0053] Example 2. Preparation method of sweet potato probiotic beverage.

[0054] (1) Color protection: The orange-fleshed sweet potatoes were peeled, sliced ​​into 4mm thick slices, and then protected with color. The color protection agent was citric acid with a mass concentration of 0.08%. The standard was that the sweet potato slices were completely immersed in the color protection agent, and the color protection time was 30 minutes.

[0055] (2) Calcium soaking: The washed and drained sweet potato slices are soaked in calcium. The calcium concentration is 50 mg / L and the soaking time is 20 min.

[0056] (3) Blanching: Wash and drain the sweet potato slices and put them into boiling water for 8 minutes.

[0057] (4) Pulping: After blanching, the sweet potato slices are mixed with water at a ratio of 1:2 and then pulped to obtain sweet potato pulp.

[0058] (5) Enzymatic hydrolysis: Add pectinase at a rate of 0.08% of the mass of sweet potato pulp, and hydrolyze at 55°C for 3 hours to obtain sweet potato liquid A;

[0059] (6) Liquefaction: Based on the initial sweet potato raw material mass, add 7 U / g of medium-temperature amylase to sweet potato solution A, and liquefy for 60 min at 70℃ and pH 6.0 to obtain sweet potato solution B;

[0060] (7) Saccharification: Based on the mass of sweet potato solution B, add 0.8 AGU / g of saccharifying enzyme to sweet potato solution B and saccharify for 120 min at 60℃ and pH 5.0 to obtain sweet potato solution C;

[0061] (8) Lactic acid bacteria fermentation: Based on the volume of liquid C, add 3% of the bacteria to liquid C, with a bacterial concentration of 1×10⁻⁶. 7 A lactic acid bacteria culture of CFU / mL was fermented at 30℃ for 24 hours to obtain a slurry.

[0062] (9) Blending: Add white sugar and citric acid to the obtained slurry for blending. The amount of each ingredient added is 6% (w / w) white sugar and 0.5% (w / w) citric acid based on the mass of the slurry.

[0063] (10) Homogenization: Preheat the prepared mixture to 50°C and homogenize it using a high-pressure homogenizer at a pressure of 19MPa for 20 minutes.

[0064] (11) Degassing: Degassing at 50℃ and a vacuum of 0.06MPa;

[0065] (12) Filling: Pump the filtered beverage into the filling machine, use hot filling, filling temperature ≥80℃, and seal the beverage can after filling;

[0066] (13) Sterilization and cooling: The beverage can is sent into an ultra-high temperature instantaneous sterilization device. The sterilization parameters are 135℃ for 8 seconds, and then rapidly cooled to 30℃ to obtain sweet potato probiotic beverage.

[0067] The sweet potato probiotic beverage obtained in this embodiment has an anthocyanin content of 2.56 mg / g.

[0068] Example 3. Preparation method of sweet potato probiotic beverage.

[0069] (1) Color protection: Peel the orange-fleshed sweet potato, slice it into 3mm thick slices, and then protect it with color. The color protection agent, ascorbic acid aqueous solution, has a mass concentration of 1.0%, and the standard is that the sweet potato slices are completely immersed in the color protection agent. The color protection time is 15min.

[0070] (2) Calcium soaking: The washed and drained sweet potato slices are soaked in calcium. The calcium concentration is 75 mg / L and the soaking time is 15 min.

[0071] (3) Blanching: Wash and drain the sweet potato slices and blanch them in boiling water for 8 minutes. The blanching time varies depending on the variety.

[0072] (4) Pulping: After blanching, the sweet potato slices are mixed with water at a ratio of 1:5 and then pulped to obtain sweet potato pulp;

[0073] (5) Enzymatic hydrolysis: Add pectinase at a rate of 0.05% of the mass of sweet potato pulp, and hydrolyze at 60°C for 1 hour to obtain sweet potato liquid A;

[0074] (6) Liquefaction: Based on the initial sweet potato raw material mass, add 6 U / g of medium-temperature amylase to sweet potato solution A, and liquefy for 90 min at 70℃ and pH 6.0 to obtain sweet potato solution B;

[0075] (7) Saccharification: Based on the mass of sweet potato solution B, add 0.5 AGU / g of saccharifying enzyme to sweet potato solution B and saccharify for 180 min at 50℃ and pH 5.5 to obtain sweet potato solution C;

[0076] (8) Lactic acid bacteria fermentation: Based on the volume of liquid C, add 1% of the bacteria to liquid C, resulting in a bacterial concentration of 1×10⁻⁶. 7 A lactic acid bacteria culture of CFU / mL was fermented at 30℃ for 24 hours to obtain a slurry.

[0077] (9) Blending: Add white sugar and citric acid to the obtained slurry for blending. The amount of each ingredient added is 6% (w / w) white sugar and 0.5% (w / w) citric acid based on the mass of the slurry.

[0078] (10) Homogenization: Preheat the prepared mixture to 55°C and homogenize it using a high-pressure homogenizer at a pressure of 20MPa for 15 minutes.

[0079] (11) Degassing: Degassing at 50℃ and a vacuum of 0.06MPa;

[0080] (12) Filling: Pump the filtered beverage into the filling machine, use hot filling, filling temperature ≥80℃, and seal the beverage can after filling;

[0081] (13) Sterilization and cooling: The beverage can is sent into an ultra-high temperature instantaneous sterilization device. The sterilization parameters are 150°C for 2 seconds, and then rapidly cooled to 30°C to obtain sweet potato probiotic beverage.

[0082] The sweet potato probiotic beverage obtained in this embodiment has a β-carotene content of 0.067 mg / 100g.

[0083] Anthocyanin content determination in probiotic beverages

[0084] Anthocyanin content is expressed as a percentage of cyanidin-3-glucoside. Accurately weigh 125 mg of purple sweet potato probiotic beverage sample and dilute to a final volume of 50 mL; this is the stock solution for the test sample. Take two 300 μL aliquots of the stock solution and dilute to a final volume of 10 mL each with potassium chloride buffer (pH 1.0) and ammonium acetate buffer (pH 4.5), respectively; these are the sample solutions. After preparing the sample solutions, allow them to equilibrate for 30 min. Then, use a UV spectrophotometer to measure the absorbance of the samples diluted with pH 1.0 and pH 4.5 buffer solutions at wavelengths of 520 nm and 700 nm, respectively, using ultrapure water as a blank. The percentage of cyanidin-3-glucoside is calculated using the following formula:

[0085] C = (A / eL) × M × D × (V / W) × 100

[0086] In the formula, C represents the percentage content of cyanidin-3-glucoside (%); A represents (A 520nm -A 700nm ) pH 1.0 -(A5 20nm -A 700nm ) pH 4.5 e is the molar extinction coefficient of cyanidin-3-glucoside (26900 L·cm⁻¹). -1 ·mol -1 L is the optical path length (1 cm); M is the molecular weight of cyanidin-3-glucoside (449.2 g·mol⁻¹). -1 D is the dilution factor of the stock solution (10mL / 0.3mL); V is the volume of the stock solution (50mL); W is the sample volume (125mg).

[0087] Determination of β-carotene content in probiotic beverages

[0088] Weigh approximately 1.0g of sample, rinse the mortar or homogenizer with the extract, and dilute to 10mL with 80% acetone. Incubate in the dark or wrapped in aluminum foil for 3 hours (inverting twice during this period). Extraction is complete when the bottom residue is nearly white. If the residue is not completely white, continue extraction until it is nearly white. Adjust the wavelength to 440nm, zero the instrument with the extract, and transfer 1mL of the upper extract to a 1mL glass cuvette. Measure the absorbance at 440nm and record it as A440. The formula for calculating carotenoid content is:

[0089] β-carotene content (mg / g mass) = A 440nm ÷(ε×d)×V_sample_total×1000÷W×F=0.04×A 440nm ×F÷W

[0090] Vsample total: Total volume of extract, 0.01 L; 1000: Unit conversion factor, 1 g = 1000 mg; ε: Empirical extinction coefficient of β-carotene, 250 L / g / cm; d: Cuvette path length, 1 cm; F: Dilution factor; W: Sample mass, g.

Claims

1. A nutritious and healthy sweet potato probiotic beverage, characterized in that, This sweet potato probiotic beverage is made by peeling, slicing, color-protecting, calcium-soaking, blanching, adding water to orange-fleshed or purple-fleshed sweet potatoes, followed by pulping, enzymatic hydrolysis, liquefaction, and saccharification to obtain a liquid, which is then fermented with lactic acid bacteria and compounded with white sugar and citric acid.

2. The sweet potato probiotic beverage according to claim 1, characterized in that, The lactic acid bacteria is Lactobacillus helveticus CICC 6102.

3. The method for preparing the sweet potato probiotic beverage according to claim 1 or 2, comprising the following steps: (1) Color protection: Peel the orange-fleshed or purple-fleshed sweet potatoes, slice them into 3-5mm thick slices and then protect the color. (2) Calcium soaking: Soak the washed and drained sweet potato slices in calcium for 15-20 minutes. (3) Blanching: Put the washed and drained sweet potato slices into boiling water and blanch for 8-10 minutes. (4) Pulping: After blanching, the sweet potato slices are mixed with water at a ratio of (1:1) to (1:5) and then pulped to obtain sweet potato pulp; (5) Enzymatic hydrolysis: Add pectinase and hydrolyze at 55℃-60℃ for 1-3 hours to obtain sweet potato liquid A; (6) Liquefaction: Based on the initial sweet potato raw material mass, add 6-8 U / g of medium-temperature amylase to sweet potato solution A, and liquefy for 30-90 min at 60℃-70℃ and pH 6.0-6.4 to obtain sweet potato solution B; (7) Saccharification: Based on the mass of sweet potato solution B, add 0.5-1 AGU / g of saccharifying enzyme to sweet potato solution B, and saccharify for 90-180 min at 50℃-70℃ and pH 3.4-5.5 to obtain sweet potato solution C. (8) Lactic acid bacteria fermentation: Based on the volume of liquid C, add 1%-5% of the bacteria to liquid C, with a bacterial concentration of 1×10⁻⁵. 7 A slurry was obtained by fermenting a lactic acid bacteria culture of CFU / mL at 25℃-30℃ for 10-24 hours. (9) Blending: Add white sugar and citric acid to the obtained slurry for compounding. The amount of each ingredient added is 2%-6% (w / w) of white sugar and 0.1%-0.5% (w / w) of citric acid, based on the mass of the slurry. (10) Homogenization: Preheat the prepared mixture to 50-60℃ and homogenize it with a high-pressure homogenizer. The pressure during homogenization is 19-20MPa, and the homogenization time is 10-20min. (11) Degassing: Degas at 40-50℃ and a vacuum of 0.06-0.08MPa; (12) Filling: Pump the filtered beverage into the filling machine, use hot filling, filling temperature ≥80℃, and seal the beverage can after filling; (13) Sterilization and cooling: The beverage can is sent into an ultra-high temperature instantaneous sterilization device. The sterilization parameters are 135-150℃ for 2-8 seconds, and then rapidly cooled to 30-40℃ to obtain sweet potato probiotic beverage.

4. The method for preparing the sweet potato probiotic beverage according to claim 3, characterized in that, The orange-fleshed sweet potato in step (1) is a high-carotene type fresh sweet potato with a β-carotene content of more than 10 mg / 100g, and the purple-fleshed sweet potato is a purple fresh sweet potato with an anthocyanin content of more than 75 mg / 100g.

5. The method for preparing the sweet potato probiotic beverage according to claim 3, characterized in that, The color-protecting agent in step (1) is a solution of one or two of citric acid and ascorbic acid. When the color-protecting agent is an aqueous solution of citric acid, its mass concentration is 0.05%-0.08%; when the color-protecting agent is an aqueous solution of ascorbic acid, its mass concentration is 0.04%-1.2%. The color-protecting time is 5-30 minutes, based on the standard that the sweet potato slices are completely immersed in the color-protecting agent.

6. The method for preparing the sweet potato probiotic beverage according to claim 3, characterized in that, In step (2), the calcium immersion uses a calcium chloride concentration of 50-75 mg / L.

7. The method for preparing the sweet potato probiotic beverage according to claim 3, characterized in that, The scalding time in step (3) varies depending on the variety.

8. The method for preparing the sweet potato probiotic beverage according to claim 3, characterized in that, The amount of pectinase added in the enzymatic hydrolysis in step (5) is 0.01%-0.1% of the mass of sweet potato pulp.

9. The method for preparing the sweet potato probiotic beverage according to claim 3, characterized in that, In step (8), lactic acid bacteria fermentation is carried out by adding 5% of the bacteria to sweet potato liquid C, based on the volume of the liquid, resulting in a bacterial concentration of 1×10⁻⁶. 7 A lactic acid bacteria culture of CFU / mL was fermented at 30℃ for 24 hours to obtain mash.