Method for improving quality and anthocyanin content of selenium-rich purple sweet potato raw whole flour

Abstract

The invention discloses a method for improving quality and anthocyanin content of selenium-rich purple sweet potato raw whole flour, which comprises the following steps: S1, cleaning, peeling and dicing fresh selenium-rich purple sweet potatoes to obtain purple sweet potato dices; s2, soaking the diced purple sweet potatoes in a selenium-rich enzyme inhibitor solution to obtain enzyme-treated diced purple sweet potatoes; s3, performing low-dose irradiation on the diced purple sweet potatoes subjected to enzyme treatment; s4, sequentially drying, cooling and crushing the irradiated purple sweet potato dices to obtain the selenium-rich purple sweet potato raw whole powder; the content of organic selenium in the prepared raw whole purple sweet potato flour reaches 0.36 mg / kg, the loss of anthocyanin in the raw whole purple sweet potato flour in the drying process is greatly reduced, and the thermal stability of the anthocyanin is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of food products, and particularly to a method for improving the quality and anthocyanin content of raw whole purple sweet potato powder. Background Art

[0002] Purple sweet potato is an annual herbaceous plant of the Convolvulaceae family and Ipomoea genus. The flesh of the sweet potato is purple-black. In addition to containing nutrients such as starch, crude protein, dietary fiber, and minerals, the tuberous roots of purple sweet potato have a relatively high content of anthocyanins. As a type of plant flavonoid substance, this special bioactive substance has received increasing attention due to its multiple effects on the body. Research shows that anthocyanins have good medicinal and health care values for the human body. It not only has antioxidant functions of scavenging human free radicals and inhibiting the oxidation of linoleic acid, but also can significantly reduce blood lipid, blood sugar, blood pressure and prevent obesity. With people's attention to green, healthy, nutritious and pollution-free foods, replacing synthetic pigments with natural pigments is more in line with consumers' requirements for food safety. As a type of water-soluble plant pigment, anthocyanins are a powerful choice to replace synthetic pigments in foods. Purple sweet potato can be used as a food additive or dietary supplement. However, the water content of fresh purple sweet potato fruits is about 65%, and it is prone to rot and deterioration during transportation and storage, which limits its application in food processing. Processing purple sweet potato into powder can maximize the retention of the original color, flavor and nutritional components of purple sweet potato. It has the characteristics of small volume, long shelf life and better stability. It can be used as a thickener for soups, gravies, ready-to-eat snacks and baked products, and can also be used as a natural colorant, sweetener and nutrient supplement to enhance the sensory quality and nutritional value of foods.

[0003] The processing methods of purple sweet potato whole powder mainly include raw whole powder and cooked whole powder. Purple sweet potato raw whole powder refers to the product obtained by directly drying and pulverizing fresh purple sweet potatoes after screening, washing, peeling and cutting; compared with purple sweet potato raw powder, purple sweet potato cooked whole powder is prepared by adding a steaming process after cutting and then drying and pulverizing. Compared with fresh purple sweet potato, the water content in purple sweet potato raw whole powder is greatly reduced, the retention of nutrients is high, the health care effect is enhanced, which is beneficial to storage and transportation. At the same time, the flavor of fresh sweet potato is also retained. The whole powder has a low cell breakage rate, good dispersibility and balanced rehydration. During the processing process, polyphenolic substances such as anthocyanins in purple sweet potato are easily affected by environmental factors such as temperature, pH value, light and oxygen, and degrade to varying degrees, resulting in the loss of nutritional components.

[0004] Selenium, as an essential trace element for the human body, is crucial in maintaining normal physiological functions. It participates in the formation of various selenium-containing enzymes and proteins, such as glutathione peroxidase, etc. These substances play a core role in the antioxidant defense system, can effectively scavenge free radicals in the body, reduce the damage of oxidative stress to cells and tissues, and lower the risk of various chronic diseases such as cardiovascular diseases, cancers, and neurodegenerative diseases. With the improvement of people's health awareness, the demand for selenium-rich foods is increasing day by day. Selenium-rich agricultural products can supplement selenium elements for the human body and are highly favored by consumers. Selenium-rich purple sweet potatoes stand out among many selenium-rich agricultural products due to their rich nutritional components and unique health care functions. By applying selenium-containing fertilizers and other special planting methods in the soil, purple sweet potato varieties with higher selenium content can be cultivated. These selenium-rich purple sweet potatoes not only retain the characteristics of ordinary purple sweet potatoes rich in nutrients such as anthocyanins, but also add the advantage of selenium element, having higher nutritional value and market potential.

[0005] However, during the process of processing selenium-rich purple sweet potatoes into raw whole powder, selenium elements face many problems. On the one hand, existing processing technologies, such as high temperature, high humidity, and long-time treatment in the drying and crushing processes, may cause some selenium elements to oxidize or volatilize, reducing the final selenium content of the raw whole powder and affecting the nutritional value of the product. On the other hand, the selenium forms in selenium-rich purple sweet potatoes are diverse, including organic selenium and inorganic selenium. Among them, organic selenium (such as selenomethionine, etc.) has a relatively high bioavailability. However, improper processing technologies may cause the transformation of the organic selenium form, reducing its effectiveness for the human body. In addition, the interaction relationship between selenium elements and other components such as anthocyanins in purple sweet potatoes is complex. If the processing conditions are not well controlled, selenium elements may chemically react with anthocyanins, affecting the stability and content of anthocyanins, and thus having a negative impact on the overall quality of the product.

[0006] Therefore, it is necessary to develop a method to improve the quality and anthocyanin content of selenium-rich purple sweet potato raw whole powder, in order to provide a basis for optimizing the processing technology of purple sweet potato raw whole powder. Summary of the Invention

[0007] In view of this, the present application provides a method for improving the quality and anthocyanin content of selenium-rich purple sweet potato raw whole powder, which is used to solve the problem of improving the quality and anthocyanin content of purple sweet potato raw whole powder.

[0008] To achieve the above technical objectives, the present application adopts the following technical solutions: In the first aspect, the present application provides a method for improving the quality and anthocyanin content of selenium-rich purple sweet potato raw whole powder, including the following steps: S1. Wash, peel, and dice fresh selenium-rich purple sweet potatoes to obtain purple sweet potato dices; S2. Immerse the purple sweet potato dices in a selenium-rich enzyme inhibitor solution to obtain enzyme-treated purple sweet potato dices; S3. Perform low-dose irradiation on the enzyme-treated purple sweet potato dices; S4. Dry, cool, and pulverize the enzyme-treated purple sweet potato dices in sequence to obtain the raw whole powder of selenium-enriched purple sweet potato.

[0009] Preferably, the enzyme inhibitor includes one or more of L-cysteine, phytic acid, ascorbic acid, citric acid, and selenomethionine.

[0010] Preferably, the enzyme inhibitor solution includes: 0.03wt%-0.07wt% of L-cysteine, 0.01wt%-0.05wt% of phytic acid, 0.1wt%-0.5wt% of ascorbic acid, 0.1%-0.5% of citric acid, and 0.01%-0.03% of selenomethionine.

[0011] Preferably, in step S3, the drying temperature is 60°C.

[0012] Preferably, the mass ratio of the purple sweet potato dices to the enzyme inhibitor solution is 3:5-8.

[0013] Preferably, the soaking duration in the enzyme inhibitor solution is 30-50 min.

[0014] Preferably, before the drying step, it further includes: drying the enzyme-treated purple sweet potato dices and then performing low-dose irradiation of 1-4 kGy.

[0015] Preferably, the size of the purple sweet potato dices is (8-10) mm × (8-10) mm × 10 mm.

[0016] In a second aspect, the present application provides a raw whole powder of selenium-enriched purple sweet potato.

[0017] The beneficial effects of the present application are as follows: 1. The present application provides a method for improving the quality and anthocyanin content of the raw whole powder of selenium-enriched purple sweet potato, and improves the color, edible quality, and physicochemical properties of the raw whole powder of purple sweet potato; compared with the traditional raw whole powder of purple sweet potato without soaking in the enzyme inhibitor, the anthocyanin and organic selenium contents of the raw whole powder of purple sweet potato prepared by soaking in the selenium-enriched enzyme inhibitor and then drying at 60°C are significantly increased, and it can improve the thermal stability of purple sweet potato anthocyanin during the drying process. The treatment method is simple and convenient, non-toxic and harmless, without adding any non-edible chemical additives, and has good application prospects for anthocyanin in thermally processed foods; 2. The enzyme inhibitor solution used for preparing the selenium-rich purple sweet potato raw whole powder in this application is simply prepared. The processing technology of the purple sweet potato raw whole powder is simple, with low investment cost, high anthocyanin content, organic selenium content reaching 0.36 mg / kg, and good edible quality. During preparation, only the cut purple sweet potato dices need to be soaked in the prepared selenium-rich enzyme inhibitor solution for 30 minutes, irradiated with a low dose of 4 kGy, and then dried and powdered. This can improve the color and quality, anthocyanin and organic selenium content of the purple sweet potato raw whole powder, and also improve the edible quality of the purple sweet potato raw whole powder, such as gelatinization degree, iodine blue value, microstructure, and freeze-thaw water separation capacity. This application greatly reduces the loss of anthocyanin during the drying process, increases the organic selenium content of the purple sweet potato raw whole powder. At the same time, it can meet the requirements of people for low energy consumption and high quality in the production of purple sweet potato raw whole powder. This application uses the inhibition of polyphenol oxidase activity and selects the optimal drying temperature to prepare the purple sweet potato raw whole powder. The processing technology is simple, the formula is scientific, and it can be industrially produced, solving the technical problems of low organic selenium content, poor quality, and serious color loss of the purple sweet potato raw whole powder during the processing process. Description of the Drawings

[0018] Figure 1 Anthocyanin content diagrams of raw and cooked whole purple sweet potato powders prepared at different drying temperatures; Figure 2 Analysis diagrams of antioxidant activities of raw and cooked whole purple sweet potato powders prepared at different drying temperatures; Figure 3 Analysis diagrams of edible qualities of raw and cooked whole purple sweet potato powders prepared at different drying temperatures. Detailed Embodiments

[0019] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] The following further illustrates this solution through specific embodiments.

[0021] Examples 1 - 9 A method for improving the quality and anthocyanin content of selenium-rich purple sweet potato raw whole powder, comprising the following steps: S1. Wash fresh selenium-rich purple sweet potatoes (fresh potatoes meeting the local standard of selenium-rich agricultural products in Guangxi, with a selenium content of 0.05 mg / kg), remove the rotten and mechanically damaged parts, peel the fresh purple sweet potatoes, and evenly cut them into 300 g of dices with a size of 8 mm × 8 mm × 10 mm to obtain purple sweet potato dices; S2. Soak 300 g of purple sweet potato dices in 500 mL of enzyme inhibitor solution for 30 minutes. The composition of the enzyme inhibitor solution (500 ml) is shown in Table 1, and the addition amount of selenomethionine is fixed at 0.1 g to obtain enzyme-treated purple sweet potato dices; S3. After drying the surface moisture of the purple sweet potato dices with kitchen paper, perform low-dose irradiation of 2 kGy; S4. Place the purple sweet potato dices in a 60 °C blast dryer and dry until the moisture content does not exceed 8%. Place the dried purple sweet potato dices in a dry place to cool. Crush the cooled purple sweet potato dices through a flour mill and sieve through an 80-mesh sieve, then package to obtain raw whole purple sweet potato powder rich in selenium.

[0022] Table 1 Component preparation of enzyme inhibitors in Examples 1-9

[0023] Example 10 A method for improving the quality and anthocyanin content of raw whole purple sweet potato powder rich in selenium, comprising the following steps: S1. Wash the fresh purple sweet potatoes, remove the rotten and mechanically damaged parts, peel the fresh purple sweet potatoes, and evenly cut them into 300 g of dices with a size of 8 mm × 8 mm × 10 mm to obtain purple sweet potato dices; S2. Soak 300 g of purple sweet potato dices in 500 mL of enzyme inhibitor solution for 30 min. The enzyme inhibitor is prepared by adding 0.20 g of L-cysteine, 0.10 g of phytic acid, 1.5 g of ascorbic acid, 1.5 g of citric acid, and 0.2 g of selenomethionine to 500 mL of pure water to obtain enzyme-treated purple sweet potato dices; S3. After drying the surface moisture of the purple sweet potato dices with kitchen paper, perform low-dose irradiation of 4 kGy; S4. Place it in a 60 °C blast dryer and dry until the moisture content does not exceed 8%. Place the dried purple sweet potato dices in a dry place to cool. Crush the cooled purple sweet potato dices through a flour mill and sieve through a 100-mesh sieve, then package to obtain raw whole purple sweet potato powder rich in selenium.

[0024] Comparative Example 1 A kind of raw whole purple sweet potato powder, the preparation method is as follows: Wash the fresh purple sweet potatoes (fresh sweet potatoes of the local standard of selenium-rich agricultural products in Guangxi, with a selenium content of 0.05 mg / kg), remove the rotten and mechanically damaged parts, peel the fresh purple sweet potatoes, and evenly cut them into 300 g of dices with a size of 8 mm × 8 mm × 10 mm. Place them in a 60 °C blast dryer and dry until the moisture content does not exceed 8%. Place the dried purple sweet potato dices in a dry place to cool. Crush the cooled purple sweet potato dices through a flour mill and sieve through an 80-mesh sieve, then package to obtain raw whole purple sweet potato powder.

[0025] Comparative Examples 2-5 A kind of raw whole purple sweet potato powder, the other contents of the preparation method are the same as those of Comparative Example 1. The difference is that the drying temperatures of the blast dryer are 70 °C, 80 °C, 90 °C, and 100 °C in sequence.

[0026] Comparative Example 6 A kind of cooked purple sweet potato whole powder, and the preparation method is as follows: Wash fresh purple sweet potatoes (fresh sweet potatoes that meet the local standard of selenium-rich agricultural products in Guangxi, with a selenium content of 0.05 mg / kg), remove the rotten and mechanically damaged parts, steam them in a steamer for 15 minutes, peel the cooked purple sweet potatoes, mash the pulp, place them in a blast dryer at 60°C and dry until the moisture content does not exceed 8%, place the dried purple sweet potato mud in a dry place to cool, crush the cooled purple sweet potato mud through a grinding machine, and pass through an 80-mesh sieve, then package it to obtain the cooked purple sweet potato whole powder.

[0027] Comparative Examples 7 - 10 A kind of cooked purple sweet potato whole powder, the other contents of the preparation method are the same as those of Comparative Example 6, the difference is that the drying temperatures of the blast dryer are 70°C, 80°C, 90°C, and 100°C in sequence.

[0028] Comparative Example 11 A kind of raw purple sweet potato whole powder, the other contents of the preparation method are the same as those of Comparative Example 1, the difference is that fresh purple sweet potatoes that are not selenium-rich are used.

[0029] Detection and evaluation The products prepared in the examples and comparative examples are detected as follows: (1) Determination of the anthocyanin content in purple sweet potato whole powder: Extract the prepared purple sweet potato whole powder with acidified ethanol, and measure the absorbance of anthocyanin at 520 nm and 700 nm. Calculate the anthocyanin content according to the following formula.

[0030]

[0031] In the formula: C: Anthocyanin content / (mg / g); A b = (A 520nm - A7 00 nm ) pH 1.0 - (A 520nm - A 700 nm ) pH 4.5 ; MW: Molar mass of cyanidin-3-glucoside (449.2 g / mol); D: Dilution factor; V: Sample volume / mL; ε: Molar extinction coefficient of cyanidin-3-glucoside (26900 L / (mol·cm)); L: Cuvette width (1 cm); M: Sample mass / g.

[0032] (2)Determination of the activity of PPO enzyme in purple sweet potato: Purple sweet potato whole powder was mixed with phosphate buffer (0.05 mol / L, pH 6.8, pre-cooled at 4 °C) at a ratio of 1:10 (g:mL) to make a homogenate, centrifuged at 10000 r / min for 15 min, and the supernatant was the PPO enzyme solution VT. Then, 2 mL of phosphate buffer, 1 mL of 0.1 mol / L catechol, and 0.2 mL of the enzyme solution were added to the test tube in sequence and shaken well immediately. The absorbance was measured immediately at 410 nm, and the timing started. The absorbance was recorded every 30 s for a total of 3 min. An enzyme activity unit was defined as a change in absorbance of 0.01 per minute.

[0033]

[0034] In the formula: EA: Activity of PPO enzyme, U / mL; ΔA410: Change in absorbance during the reaction time; VT: Total volume of the extracted enzyme solution, mL; W: Mass of the purple sweet potato whole powder used, g; VS: Volume of the enzyme solution required for measuring enzyme activity, mL; t: Measurement time, min.

[0035] (3)Determination of the DPPH free radical scavenging ability: 3 mL of the appropriately diluted sample solution was accurately pipetted, 3 mL of DPPH methanol solution was added, and the mixture was thoroughly mixed and reacted in the dark for 30 min. Vc was used as the positive control, and the absorbance was measured at 517 nm.

[0036] The calculation formula for the DPPH free radical scavenging rate is as follows:

[0037] In the formula: A0 is the absorbance of the blank sample; Ae is the absorbance of the test sample.

[0038] (4)Determination of the ferric ion reducing ability (FRAP): 1 mL of the appropriately diluted sample solution was mixed with 4.5 mL of FRAP working reagent (pre-heated at 37 °C for 30 min), and the mixture was reacted in the dark for 15 min. Vc was used as the positive control, and the absorbance was measured at 593 nm.

[0039] The calculation formula for the ferric ion reducing ability:

[0040] In the formula: A1 is the absorbance of the test sample; A2 is the absorbance of the blank sample.

[0041] (5)Determination of water-holding capacity and freeze-thaw bleeding water rate of purple sweet potato whole powder: Weigh 0.2 g of purple sweet potato whole powder \(m_0\) (g), add water \(V_1\) (mL) to prepare a 2% solution by mass. Keep it in a constant temperature water bath at 100 °C for 20 min. After cooling, centrifuge at 3000 r / min for 25 min, and take the supernatant \(m_1\) (g). Freeze the precipitate at -20 °C for 24 h. After thawing, centrifuge at 3000 r / min for 25 min again, and take the supernatant \(m_2\) (g). Calculate the water-holding capacity and freeze-thaw bleeding water rate of purple sweet potato whole powder according to the following formulas.

[0042] Water-holding capacity / (g·g⁻¹) = (\(V_1 - m_1\)) / \(m_0\) Freeze-thaw bleeding water rate / (g·g⁻¹) = \(m_2\) / \(m_0\) (6)Determination of iodine blue value of purple sweet potato whole powder: Preheat distilled water at 65.5 °C and make up the volume to the scale line of a 50 mL volumetric flask. Weigh 0.25 g of purple sweet potato whole powder, pour it into the preheated distilled water, stir at 65.5 °C for 5 min, and filter after standing. Take 1 mL of the filtrate and 1 mL of 0.02 mol / L iodine standard solution, make up the volume to 50 mL, and measure the absorbance A at 650 nm.

[0043] Iodine blue value = A × 54.2 + 5 (7)Determination of gelatinization degree of purple sweet potato whole powder: Weigh 50 mg of the sample, add buffer solution to 15 mL, keep it in a boiling water bath at 1 h, make up the volume to 15 mL to prepare a fully gelatinized sample; for another sample, add buffer solution to 15 mL as the sample to be measured, and add 1 mL of enzyme solution to each. Keep it at 60 °C for 1 h, add 2 mL of 10% \(ZnSO_4·7H_2O\) and 1 mL of 0.5 mo / L \(NaOH\) solution in sequence, mix well, make up the volume to 25 mL after mixing, and then filter. Add 1 mL of the filtrate to 2 mL of DNS reagent, keep it in a boiling water bath for 5 min, add distilled water to make up the volume to 25 mL after cooling, and measure the absorbance value at 540 nm. The gelatinization degree is calculated according to the following formula: M = \(m_1\) / \(m_2\) M is the gelatinization degree of the sample, \(m_1\) is the absorbance value of the measured sample, and \(m_2\) is the absorbance value of the fully gelatinized sample.

[0044] (8)Determination of chromaticity value of purple sweet potato whole powder: Use a spectrophotometer colorimeter to measure the color coefficients of purple sweet potato whole powder. Record the L value (brightness) and a value (red-green value). Calculate the C value (color saturation) and h value (hue).

[0045]

[0046] h = arctg(b / a) (a > 0, b > 0) (9)Determination of the organic selenium content in purple sweet potato whole powder: For the determination of the total selenium content, the hydride generation atomic fluorescence spectrometry in National Food Safety Standard Determination of Selenium in Foods (GB 5009.93-2017) was referred to; for the determination of the proportion of organic selenium, the atomic fluorescence speciation analysis method in Local Food Safety Standard Determination Method of Inorganic Selenium in Selenium-enriched Foods (DBS 42 / 010-2018) was referred to. The organic selenium content was calculated by subtraction.

[0047] Organic selenium content = Total selenium content - Inorganic selenium content Taking Examples 1-10 as the test objects, the effects of the compound enzyme inhibitor combination on the activity of purple sweet potato polyphenol oxidase and the content of anthocyanins were tested. The purple sweet potato raw whole powder prepared in Example 10 had the lowest polyphenol oxidase activity, which was 643.27 U / g·min, and the highest purple sweet potato anthocyanin content, which was 1.69 mg / g. The test results are shown in Table 2.

[0048] Table 2 Test results of anthocyanin content and PPO enzyme activity under different enzyme inhibitor formulations

[0049] By preparing purple sweet potato dices and taking Comparative Examples 1-10 as the test objects, the purple sweet potatoes were dried at different drying temperatures (60°C, 70°C, 80°C, 90°C, 100°C) until the moisture content did not exceed 8%, and the effects of different temperatures on the quality, color, physicochemical properties and anthocyanin content of purple sweet potato whole powder were observed. Figure 1 It can be seen that for the raw and cooked purple sweet potato whole powders prepared at drying temperatures of 60°C, 70°C, 80°C, 90°C, and 100°C, the anthocyanin content was the highest at 60°C, and the anthocyanin content of the raw purple sweet potato whole powder showed a trend of first decreasing and then increasing with the increase of the drying temperature, while there was no significant difference in the anthocyanin content of the cooked whole powder. This shows that due to the thermal instability of the anthocyanins in the raw purple sweet potato whole powder, long-term high-temperature drying will cause a large amount of degradation of the anthocyanins.

[0050] From Table 3, Figures 2-3 It can be seen that the color and antioxidant activity of the raw purple sweet potato whole powder are significantly lower than those of the cooked purple sweet potato whole powder; however, the iodine blue value of the raw purple sweet potato whole powder is lower than that of the cooked purple sweet potato whole powder, indicating that the degree of cell fragmentation of the raw whole powder is low; the gelatinization degree is significantly lower than that of the cooked whole powder, indicating that the processing performance of the raw purple sweet potato whole powder is good; the water holding capacity and freeze-thaw water separation capacity are higher than those of the cooked whole powder, indicating that the raw purple sweet potato whole powder is more soluble in water. All in all, the edible quality of the raw purple sweet potato whole powder is higher than that of the cooked purple sweet potato whole powder, but the color, anthocyanin content and antioxidant activity are lower than those of the cooked purple sweet potato whole powder. In addition, when the drying temperature is 60°C, the total anthocyanin content and the content of each monomer anthocyanin in the raw purple sweet potato whole powder are higher than those at other drying temperatures. Therefore, the examples of this application are carried out under the condition of a drying temperature of 60°C.

[0051] Table 3 Color analysis table of raw and cooked purple sweet potato whole powders at different drying temperatures

[0052] The physicochemical properties of Example 10, Comparative Example 1, and Comparative Example 6 were tested, and the test results are shown in Tables 4 - 6.

[0053] Table 4 Analysis Results of the Color of Purple Sweet Potato Whole Powder

[0054] Table 5 Analysis Results of the Edible Quality of Purple Sweet Potato Whole Powder

[0055] Table 6 Physicochemical Property Analysis of Purple Sweet Potato Whole Powder

[0056] As can be seen from Tables 4 - 6, for the raw purple sweet potato whole powder prepared by soaking in enzyme inhibitors and then drying, the contents of purple sweet potato anthocyanins and organic selenium are significantly increased, and the polyphenol oxidase is significantly reduced. For the purple sweet potato whole powder prepared in Example 10, the contents of purple sweet potato anthocyanins and organic selenium are the highest, and the activity of polyphenol oxidase is the lowest. Therefore, the method of Example 10 is selected to prepare the raw purple sweet potato whole powder. As can be seen from Tables 4 - 6, compared with the raw purple sweet potato whole powder prepared by the traditional process in Comparative Example 1, the edible quality of the purple sweet potato whole powder prepared in Example 10 is improved, the color is significantly increased, the physicochemical properties are significantly improved, the anthocyanin content is significantly increased, and the organic selenium is well preserved. In addition, the quality of the cooked purple sweet potato whole powder in Comparative Example 6 is poor, but the anthocyanin content is high and the physicochemical properties are good. There is no significant difference in the physicochemical properties and anthocyanin content between the raw purple sweet potato whole powder prepared in Example 10 of the present invention and the cooked purple sweet potato whole powder in Comparative Example 6.

[0057] From the above conclusions, it can be seen that the present application effectively protects the original purple color of purple sweet potatoes, improves the content of organic selenium in the raw purple sweet potato whole powder, and ensures the original good processing performance of the raw purple sweet potato whole powder by inhibiting the activity of purple sweet potato polyphenol oxidase and then improving the thermal stability of purple sweet potato anthocyanins during the drying process. This method is simple to operate, non-toxic and harmless, and has good application prospects in the thermal processing of fruits and vegetables rich in polyphenol oxidase. The raw purple sweet potato whole powder prepared by this method can greatly improve the disadvantages of low anthocyanin content and poor color of the raw purple sweet potato whole powder prepared by the traditional process, supplement the content of organic selenium in food, and can be used to prepare various new foods rich in purple sweet potatoes, anthocyanins and organic selenium.

[0058] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for improving the quality and anthocyanin content of selenium-enriched purple sweet potato raw whole flour, characterized in that: The following steps are involved: S1. Wash, peel and dice fresh selenium-enriched purple sweet potatoes to obtain purple sweet potato dices; S2. soaking the purple sweet potato cubes in a selenium-rich enzyme inhibitor solution to obtain enzyme-treated purple sweet potato cubes; S3. The enzyme-treated purple sweet potato cubes are subjected to low-dose irradiation; S4. The enzyme-treated purple sweet potato cubes are dried, cooled, crushed, and sieved in sequence to obtain selenium-enriched purple sweet potato raw whole powder.

2. The method for improving the quality and anthocyanin content of selenium-enriched purple sweet potato raw whole powder according to claim 1, characterized in that: The selenium-rich enzyme inhibitor includes one or more of L-cysteine, phytic acid, ascorbic acid, citric acid, and selenomethionine.

3. The method for improving the quality and anthocyanin content of selenium-enriched purple sweet potato raw whole powder according to claim 1, characterized in that: The selenium-rich enzyme inhibitor solution comprises: 0.03wt%-0.07wt% of L-cysteine, 0.01wt%-0.05wt% of phytic acid, 0.1wt%-0.5wt% of ascorbic acid, 0.1%-0.5% of citric acid, and 0.01%-0.03% of selenomethionine.

4. The method for improving the quality and anthocyanin content of selenium-enriched purple sweet potato raw whole powder according to claim 1, characterized in that: In step S3, the drying temperature is 60°C.

5. The method for improving the quality and anthocyanin content of selenium-enriched purple sweet potato raw whole powder according to claim 1, characterized in that: The mass ratio of the purple sweet potato cubes to the enzyme inhibitor solution is 3:5-8.

6. The method for improving the quality and anthocyanin content of selenium-enriched purple sweet potato raw whole powder according to claim 1, characterized in that: The duration of immersion in the enzyme inhibitor solution is 30-50 minutes.

7. The method for improving the quality and anthocyanin content of selenium-enriched purple sweet potato raw whole powder according to claim 1, characterized in that: Before the drying step, the method further comprises: wiping the enzyme-treated purple sweet potato cubes dry and then irradiating them with a dose of 1-4 kGy.

8. The method for improving the quality and anthocyanin content of selenium-enriched purple sweet potato raw whole flour according to claim 1, characterized in that: The size of the purple sweet potato cubes is (8-10) mm×(8-10) mm×10 mm.

9. The method for improving the quality and anthocyanin content of selenium-enriched purple sweet potato raw whole powder according to claim 1, characterized in that: After drying, the purple sweet potato cubes are crushed into 80-100 mesh.

10. A selenium-enriched purple sweet potato raw whole powder obtained by the method according to any one of claims 1 to 9.

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