Black potato anthocyanin hydrogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of agricultural and sideline product processing, and particularly relates to black potato anthocyanin hydrogel as well as a preparation method and application thereof. The black potato anthocyanin hydrogel is prepared from the following components in parts by mass: 5 to 20 parts of black potato anthocyanin and 50 to 100 parts of hydrogel, the hydrogel is prepared from gelatin and / or gellan gum; when the hydrogel comprises gelatin and gellan gum, the mass ratio of the gelatin to the gellan gum is (1-2): (1-2). The hydrogel disclosed by the invention is good in flowability and suitable for embedding the black potato anthocyanin, the embedding rate of the black potato anthocyanin can reach 90.81%, and the hydrogel is stable. And when being applied to preparation of the yoghourt, the viscosity of the yoghourt can be improved, the stability of the yoghourt is improved, and a new idea is provided for preparation of the health-care yoghourt.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural and sideline product processing, and in particular relates to a black potato anthocyanin hydrogel and a preparation method and application thereof. Background Art

[0002] Anthocyanin is a natural extract with multiple active functions. It needs to be absorbed and utilized by the small intestine to exert its functional activity to a greater extent. However, anthocyanin will be digested in the stomach for 2 hours after entering the digestive tract. In this process, the concentration and activity of anthocyanin will be affected by the digestive enzymes and gastric juice in the stomach, resulting in a large amount of anthocyanin being destroyed and unable to reach the small intestine smoothly, reducing the bioavailability of anthocyanin. Studies have found that encapsulation can effectively protect anthocyanin from damage by external environmental factors, improve the stability of anthocyanin, and even help anthocyanin release in a specific environment. The selection of a specific preparation method for anthocyanin encapsulation mainly depends on the carrier material of the target sample and the place where the target sample is to be applied. At present, in order to protect anthocyanin from damage, synthetic polymer materials are often used for encapsulation so that anthocyanin can be released smoothly in the small intestine. However, the safety of synthetic materials themselves has attracted people's attention. Therefore, it is necessary to develop a carrier material made of natural materials or high safety to encapsulate anthocyanin to improve the stability of anthocyanin and achieve targeted release of anthocyanin. At present, the encapsulation of anthocyanins with natural ingredients has become a research hotspot. The existing technology has found that rice bran protein can be used to encapsulate anthocyanins in grape juice. The effect of flavor protease enzymatic hydrolysis on the encapsulation characteristics of rice bran protein was evaluated. It was found that the microencapsulation efficiency of flavor protease encapsulated anthocyanins in grape juice after enzymatic hydrolysis was above 70%. Gum substances are not only natural in composition, but can also effectively encapsulate anthocyanins and improve the stability of anthocyanins. With gelatin and gum arabic as wall materials, condensed microcapsules have been developed, which have a good encapsulation effect on black rice bran anthocyanins.

[0003] The prior art has not found a method for preparing black potato anthocyanins into a substance with high stability. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a black potato anthocyanin hydrogel and a preparation method and application thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a black potato anthocyanin hydrogel, comprising the following components in parts by weight:

[0007] 5-20 parts of black potato anthocyanins, 50-100 parts of hydrogel;

[0008] The hydrogel is prepared from gelatin and / or gellan gum;

[0009] When the hydrogel includes gelatin and gellan gum, the mass ratio of gelatin to gellan gum is 1-2:1-2.

[0010] The present invention also provides a method for preparing black potato anthocyanin hydrogel, comprising the following steps:

[0011] (1) Weighing black potato anthocyanidins and hydrogel according to the mass fractions;

[0012] (2) Mix the black potato anthocyanin and the hydrogel, stir for 8 to 12 minutes, let stand for 20 to 28 hours, and dry to obtain the black potato anthocyanin hydrogel.

[0013] Preferably, the temperature during stirring is 23-28°C;

[0014] The stirring speed is 750-850 rpm.

[0015] Preferably, the temperature during the standing is 2 to 6°C;

[0016] It needs to be protected from light when standing.

[0017] Preferably, the drying is freeze drying, and the freeze drying temperature is -75 to -85°C.

[0018] The invention also provides the use of the black potato anthocyanin hydrogel in preparing yogurt with good stability, good taste and flavor.

[0019] The present invention also provides application of the black potato anthocyanin hydrogel prepared by the preparation method in preparing yogurt with good stability, good taste and flavor.

[0020] The present invention also provides a yogurt with good stability, good taste and flavor, comprising the following components in parts by weight:

[0021] 100 parts of fermented yogurt, 0.2-0.3 parts of black potato anthocyanin hydrogel;

[0022] The black potato anthocyanin hydrogel is the black potato anthocyanin hydrogel described or the black potato anthocyanin hydrogel prepared by the preparation method described.

[0023] Preferably, the yogurt also includes jam;

[0024] The jam is strawberry jam and / or mango jam.

[0025] The present invention provides a black potato anthocyanidin hydrogel and a preparation method and application thereof. The black potato anthocyanidin hydrogel of the present invention comprises the following components in mass fractions: 5 to 20 parts of black potato anthocyanidin and 50 to 100 parts of hydrogel; the hydrogel is prepared from gelatin and / or gellan gum; when the hydrogel comprises gelatin and gellan gum, the mass ratio of gelatin to gellan gum is 1 to 2: 1 to 2. The carrier material of the hydrogel of the present invention is obtained through reasonable screening. The carrier material has good fluidity and is suitable for embedding black potato anthocyanidin. The hydrogel prepared by mixing gelatin and gellan gum has good stability in simulated gastric juice and good swelling degree in simulated intestinal juice. The embedding rate of black potato anthocyanidin can reach 90.81%, indicating that the hydrogel of the present invention is more suitable as a carrier material and is more conducive to the release of black potato anthocyanidin in intestinal juice.

[0026] The black potato anthocyanin hydrogel prepared by the method of the present invention is stable under the conditions of 4°C and 37°C.

[0027] The black potato anthocyanin hydrogel prepared by the method of the present invention can more effectively alleviate the phenomenon of post-acidification of yogurt. Adding black potato anthocyanin hydrogel to yogurt has better taste, flavor and quality than adding black potato anthocyanin to yogurt. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Analysis of apparent viscosity of carrier materials;

[0029] Figure 2 Analysis of gel strength of carrier materials;

[0030] Figure 3 The swelling degree analysis of the carrier material in simulated gastric fluid (Figure A) and simulated intestinal fluid (Figure B);

[0031] Figure 4 The effect of different anthocyanin addition amounts on the encapsulation rate of black potato anthocyanin hydrogel;

[0032] Figure 5 To analyze the energy storage modulus of black potato anthocyanin hydrogel;

[0033] Figure 6 The stability of black potato anthocyanin hydrogel stored at different temperatures (Figure A is stored at 4°C, Figure B is stored at 37°C);

[0034] Figure 7 This is the digestion stability analysis of black potato anthocyanin hydrogel in simulated gastric fluid (Figure A) and simulated intestinal fluid (Figure B);

[0035] Figure 8 The effect of potato anthocyanins on the pH value of yogurt for 21 days;

[0036] Fig. 9 The effect of potato anthocyanin hydrogel on pH value of yogurt for 21 days;

[0037] Fig.10 To compare the textural properties of different yogurts;

[0038] Fig.11 This is a comparison of the complex viscosity of different yogurts;

[0039] Fig.12 Comparison of storage energy modulus of different yogurts (12 is the storage energy modulus of yogurt 12, 10 is the storage energy modulus of yogurt 10, A is the storage energy modulus of yogurt A, B is the storage energy modulus of yogurt B, and K is the storage energy modulus of yogurt K). DETAILED DESCRIPTION

[0040] In the present invention, the preparation method of the hydrogel is as follows: gelatin and / or gellan gum is mixed with water at a mass volume ratio of 0.5 g:100 mL to obtain a mixture; the mixture is placed in a water bath for 20 minutes under stirring until the gelatin and / or gellan gum is completely dissolved, and placed in a refrigerator at 4°C for 12 hours to form a hydrogel. The stirring speed is 800 rpm and the temperature of the water bath is 60°C.

[0041] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0042] In an embodiment of the present invention, the preparation method of black potato anthocyanin is as follows: select fresh black potatoes that are not rotten, not sprouted, and have full grains, wash the black potatoes, and cut them into small pieces of uniform size for later use.

[0043] Mix black potato with 50% ethanol (hydrochloric acid adjusts the pH of the ethanol to 3.5) at a mass volume ratio of 1g:1.5mL, place in a juicer for pulping, adjust the pH of the homogenate to 3.5, 25°C, 250W ultrasound for 25min, 4°C, 8000rpm centrifugation for 3min, take the supernatant, and then concentrate the supernatant at 40°C, freeze-dry into powder, and finally obtain the crude black potato anthocyanin, which is placed in a -80°C refrigerator to avoid light. The crude black potato anthocyanin is passed through a macroporous resin AB-8 column, and the anthocyanin sample is collected by absorbance at 530nm, concentrated, freeze-dried, and black potato anthocyanin is obtained for later use. The fresh black potato is the commercially available Liangshan black potato fresh product.

[0044] The preparation method of the simulated gastric fluid described in the embodiment of the present invention is as follows: 234 mL of concentrated hydrochloric acid is diluted with water to 1000 mL to obtain 10% dilute hydrochloric acid. 16.4 mL of dilute hydrochloric acid is added with water to 800 mL, stirred evenly, 10 g of pepsin is added, stirring is continued until completely dissolved, and water is added to make the volume to 1000 mL to obtain simulated gastric fluid.

[0045] The preparation method of the simulated intestinal fluid described in the embodiment of the present invention is as follows: 6.8g of potassium dihydrogen phosphate is dissolved in 500mL of water, and the pH is adjusted to 6.8 with sodium hydroxide solution to obtain an intermediate solution; 10g of pancreatic enzyme is added to the intermediate solution, stirred evenly, and water is added to make the volume to 1000mL to obtain simulated intestinal fluid.

[0046] The gelatin described in the examples of the present invention was purchased from Henan Best Biotechnology Co., Ltd.; the gellan gum described in the examples of the present invention was purchased from Xinjiang Fufeng Biotechnology Co., Ltd.

[0047] Sources of the main instruments and equipment used in the embodiments of the present invention:

[0048] The multi-purpose electric furnace DL-1 was purchased from Beijing Zhongxing Weiye Century Instrument Co., Ltd.; the electric constant temperature incubator DHP-9162D was purchased from Shanghai Qixin Scientific Instrument Co., Ltd.

[0049] Example 1

[0050] Choice of carrier material

[0051] (1) Analysis of surface viscosity of carrier materials

[0052] The gelatin and water were mixed at a mass volume ratio of 0.5 g: 100 mL (0.5%) to obtain a mixture; the mixture was placed in a water bath for 20 minutes under stirring until the gelatin was completely dissolved, and placed in a refrigerator at 4°C for 12 hours to form a gelatin hydrogel. The stirring speed was 800 rpm and the water bath temperature was 60°C.

[0053] Gellan gum and water are mixed at a mass volume ratio of 0.5 g: 100 mL (0.5%) to obtain a mixture; the mixture is placed in a water bath for 20 minutes under stirring until gelatin and / or gellan gum are completely dissolved, and placed in a refrigerator at 4°C for 12 hours to form a gellan gum hydrogel. The stirring speed is 800 rpm and the temperature of the water bath is 60°C.

[0054] 0.25 g of gelatin and 0.25 g of gellan gum are mixed to obtain a mixed gel, and the mixed gel is mixed with water at a mass volume ratio of 0.5 g: 100 mL (0.5%) to obtain a mixture; the mixture is placed in a water bath for 20 minutes under stirring until the gelatin and / or gellan gum are completely dissolved, and placed in a refrigerator at 4°C for 12 hours to form a mixed hydrogel. The stirring speed is 800 rpm and the water bath temperature is 60°C.

[0055] The apparent viscosity of different hydrogels was analyzed by rheometer, with a stainless steel cone plate of 40 mm in diameter, a Gap value of 0.046 mm, and an angular frequency of 10 -1 ~10 2 rad / s. The result is Figure 1 shown.

[0056] The gel strength and viscosity of different hydrogels were measured by texture analyzer. A cylinder with a diameter of 12 mm and a length of 50 mm was selected, and data collection and analysis were performed under the conditions of a pressing speed of 1 mm / s, a speed after the test of 1 mm / s, and a pressing depth of 10 mm. The results are shown in Figure 2 shown.

[0057] Different hydrogels were freeze-dried, and the same mass of the lyophilized materials were weighed and immersed in simulated gastric fluid and simulated small intestinal fluid. Every 30 minutes, a group of parallel samples were weighed to keep the weight constant, and the swelling degree (SR) was calculated according to the formula.

[0058]

[0059] Where: m0: initial mass of hydrogel; m t : The mass of hydrogel at different time.

[0060] The results are as follows Figure 3 shown.

[0061] Figure 1 Display, angular frequency from 10 -1 to 10 2 The complex viscosity of the hydrogel prepared by 0.5% gellan gum and the hydrogel prepared by 0.5% mixed gum showed a gradually decreasing trend, and the greater the shear rate, the greater the viscosity of the hydrogel prepared by 0.5% gellan gum and the hydrogel prepared by 0.5% mixed gum, which is a typical non-Newtonian fluid. -1 to 10 2In the range of 0.5%, the complex viscosity of the hydrogel prepared by 0.5% gelatin showed a slow upward trend, indicating that the complex viscosity of the hydrogel prepared by 0.5% gelatin was very low at this time, showing good fluidity. Therefore, in order to facilitate the subsequent experimental research, through the apparent viscosity analysis of the carrier material, it is inclined to choose 0.5% mixed gel as the embedding carrier material to prepare the hydrogel.

[0062] Figure 2 The results show that the gel strength of the hydrogel prepared by 0.5% mixed gel is the highest, the gel strength of the hydrogel prepared by 0.5% gelatin is the lowest, and the gel strength of the hydrogel prepared by 0.5% mixed gel is higher than the gel strength of the hydrogel prepared by gelatin and gellan gum respectively. The results show that the hydrogel prepared by the compounded 0.5% mixed gel has better gel properties and is more conducive to the embedding of anthocyanins.

[0063] Figure 3The results showed that after being treated in simulated gastric fluid for 0 to 30 minutes, the swelling degrees of the hydrogels prepared with 0.5% gelatin, 0.5% gellan gum and 0.5% mixed gum all showed a rapid upward trend, and the swelling degree of the hydrogel prepared with 0.5% gelatin was the highest, the swelling degree of the hydrogel prepared with 0.5% gellan gum was the lowest, and the swelling degree of the hydrogel prepared with 0.5% mixed gum was close to that of the hydrogel prepared with 0.5% gellan gum. In the range of 30 to 120 minutes, the swelling rate of the hydrogel prepared with 0.5% gelatin in simulated gastric fluid slowed down, with a swelling degree of 78.91%. The hydrogels prepared with 0.5% gellan gum and 0.5% mixed gum showed a steady upward trend, with the highest swelling degrees at 120 minutes, which were 43.70% and 46.32%, respectively. The swelling degree of the hydrogel prepared with 0.5% gellan gum is because gellan gum has a tight network structure in an acidic environment, which makes it swell as little as possible in simulated gastric juice. Under the influence of gellan gum, the hydrogel prepared with 0.5% mixed gum also showed good stability in the simulated gastric acid digestion experiment. The experimental results show that the acid stability of the hydrogel prepared with gelatin is lower than that of the hydrogel prepared with gellan gum. In the simulated small intestine environment for 0 to 30 minutes, the hydrogels prepared with 0.5% gelatin, 0.5% gellan gum and 0.5% mixed gum all showed a rapid rising trend, and the swelling degree of the hydrogel prepared with 0.5% gelatin was the highest, the swelling degree of the hydrogel prepared with 0.5% gellan gum was the lowest, and the swelling degree of the hydrogel prepared with 0.5% mixed gum was close to that of the hydrogel prepared with 0.5% gellan gum. In the range of 30 minutes to 120 minutes, the swelling rate of the hydrogel prepared with 0.5% gelatin in the simulated intestinal fluid slowed down, with a swelling degree of 78.36%. The hydrogels prepared with 0.5% gellan gum and 0.5% mixed gum showed a steady rising trend, with the highest swelling degrees at 120 minutes, which were 67.98% and 71.57%, respectively. It shows that among the three hydrogels, the hydrogel prepared with 0.5% gelatin has poor stability in simulated intestinal fluid, while the hydrogel prepared with 0.5% gellan gum and the hydrogel prepared with 0.5% mixed gum have good stability in simulated intestinal fluid. Taking all factors into consideration, the hydrogel prepared with 0.5% mixed gum has good stability in simulated gastric fluid and good swelling degree in simulated intestinal fluid, and is suitable as a carrier material.

[0064] Example 2

[0065] Preparation of anthocyanin hydrogel from black potato

[0066] (1) Effect of hydrogels prepared with different colloids on the encapsulation efficiency of anthocyanins in black potatoes

[0067] 5 g of black potato anthocyanin was mixed with 100 g of hydrogel, stirred at 25° C. and 800 rpm for 10 min, allowed to stand at 4° C. in the dark for 24 h, and freeze-dried at -80° C. to obtain black potato anthocyanin hydrogel.

[0068] Gelatin, gellan gum and 1:1 gelatin gellan gum were selected to prepare different hydrogels according to the method of Example 1, and then the black potato anthocyanin hydrogel was prepared according to the above method. The encapsulation of black potato anthocyanin by the hydrogels prepared by different colloids was compared. The results are shown in Table 1. The encapsulation efficiency (LE) was calculated according to the formula.

[0069]

[0070] Total anthocyanin (TAC) content: 100 mg of black potato anthocyanin hydrogel and 1 mL of pure water were added to a centrifuge tube and vortexed to mix well, then 10 mL of anhydrous ethanol was added and ultrasonicated for 5 min at room temperature. Centrifuged at 4°C, 3500 rpm for 3 min, and the supernatant was taken to measure the anthocyanin content.

[0071] Surface anthocyanin (SAC) content: Weigh 0.100 g of black potato anthocyanin hydrogel in a centrifuge tube, add 10 mL of ethanol, vortex for 10 seconds, centrifuge at 3500 rpm for 3 minutes at 4°C, and take the supernatant to measure the anthocyanin content.

[0072] Table 1 The results of different colloids encapsulating anthocyanins in black potatoes

[0073] Experiment No. Gelatin addition amount (%) Gellan gum addition amount (%) Embedding rate 1 100 0 86.16％ 2 0 100 88.44％ 3 50 50 90.81％

[0074] Table 1 shows that the encapsulation rate of anthocyanins from black potato can reach 90.81% by preparing a hydrogel from a mixed colloid obtained by mixing gelatin and gellan gum in a mass ratio of 1:1, which indicates that the hydrogel prepared by mixing gelatin and gellan gum is more conducive to the encapsulation of anthocyanins from black potato.

[0075] (2) Effect of the amount of anthocyanin added to black potato on the embedding efficiency

[0076] The amount of anthocyanin added from black potato was set to 5%, 10%, 15% and 20%, and the encapsulation rate of anthocyanin with different addition amounts was studied by preparing a hydrogel prepared by mixing gelatin and gellan gum in a mass ratio of 1:1. Figure 4 The embedding rate is calculated according to the above formula.

[0077] Figure 4 It shows that when the amount of anthocyanidin added to black potato is 5% and 10%, the embedding rate can reach 90%, and when the amount of anthocyanidin added to black potato is 15% and 20%, the embedding rate is lower than 90%. The experimental results show that when the amount of anthocyanidin added to black potato is 15% and 20%, the anthocyanidin in black potato cannot achieve the maximum embedding.

[0078] (3) Analysis of energy storage modulus of black potato anthocyanin hydrogel

[0079] The storage modulus and energy loss modulus of black potato anthocyanin hydrogel were analyzed by rheology. Figure 5 shown.

[0080] A stainless steel cone plate with a diameter of 40 mm, a Gap value of 0.046 mm, and an angular frequency of 10 -1 ~10 2 rad / s.

[0081] Figure 5 It is shown that at an angular frequency of 10 -1 to 10 2 Within the range, the storage modulus and energy loss modulus of the hydrogel prepared by the mixed gel encapsulating black potato anthocyanin showed an upward trend, and neither the storage modulus nor the energy loss modulus of the hydrogel was cross-linked, indicating that a three-dimensional network structure was formed within a very wide range of angular frequency.

[0082] Example 3

[0083] Stability analysis of anthocyanin hydrogel from black potato

[0084] (1) Storage stability

[0085] The black potato anthocyanidin and black potato anthocyanidin hydrogel were stored in a 4°C refrigerator and a 37°C incubator for 30 days, and the changes in the anthocyanidin residues in different samples were observed within 30 days to analyze the storage stability of black potato anthocyanidin. The same mass of black potato anthocyanidin and black potato anthocyanidin hydrogel were taken and prepared into aqueous solutions with an anthocyanidin content of 0.4 mg / mL. Three groups were parallelly placed in a constant temperature environment of 4°C and 37°C, respectively, away from light, to study the storage stability. The results are as follows Figure 6 shown.

[0086] The preparation method of black potato anthocyanin hydrogel is as follows: 5g black potato anthocyanin is mixed with 100g hydrogel (prepared by mixing gelatin and gellan gum in a ratio of 1:1), stirred at 25°C and 800rpm for 10min, allowed to stand at 4°C in the dark for 24h, and freeze-dried at -80°C to obtain black potato anthocyanin hydrogel.

[0087] (2) Digestion stability

[0088] Take 2 portions of 0.25g of black potato anthocyanin powder, named 1 and 2; take two portions of 5g (containing about 0.25g of black potato anthocyanin powder) of hydrogel freeze-dried powder, named 3 and 4. Add 10mL of simulated gastric fluid to 1 and 3 in a test tube, and add 10mL of simulated intestinal fluid to 2 and 4 in a test tube, shake well, and measure the anthocyanin content in the starting liquid. Place it in a shaker at 37°C and 50rpm to simulate digestion, and measure the anthocyanin content in the digestive fluid every 30 minutes until 120 minutes. The black potato anthocyanin hydrogel calculates the amount of undecomposed black potato anthocyanin residue in the digestive fluid based on the swelling degree of the mixed gel. The calculation formula is as follows:

[0089] C 花青素残留量 =C0-(C0×SR-C1);

[0090] Where: C0 is the total amount of anthocyanins in the prepared solution;

[0091] C1 is the anthocyanin content measured in the digestive juice;

[0092] SR is the swelling ratio.

[0093] The results are as follows Figure 7 shown.

[0094] Figure 6 It shows that black potato anthocyanidin and black potato anthocyanidin hydrogel were stored at 4°C (Figure A). It was found that from 0 to 15 days, the anthocyanidin residues in the black potato anthocyanidin solution and the black potato anthocyanidin hydrogel showed a rapid decrease trend. From 15 to 30 days, the anthocyanidin residues in the black potato anthocyanidin solution and the black potato anthocyanidin hydrogel showed a slow decrease trend, and the decrease trends of the black potato anthocyanidin solution and the black potato anthocyanidin hydrogel were very close. The above results show that: with the increase of time, the anthocyanidin content of the two groups showed a gradual decrease trend, and the free anthocyanidin decreased more than the anthocyanidin hydrogel, further indicating that the hydrogel has a certain protective effect on black potato anthocyanidin. The black potato anthocyanin and black potato anthocyanin hydrogel were stored at 37°C (Figure B). It was found that the residual amount of the black potato anthocyanin solution decreased rapidly from 0 to 5 days, and then decreased slowly; while the residual amount of anthocyanin in the black potato anthocyanin hydrogel showed a trend of gradual and slow decrease, and the black potato anthocyanin solution showed a greater decrease trend than the black potato anthocyanin hydrogel. These results show that: with the increase of time, the anthocyanin content of both groups showed a gradual downward trend, and the hydrogel had a better preservation effect on black potato anthocyanin. As shown in Figures A and B, the loss of anthocyanin at 4°C is lower than that at 37°C, indicating that low temperature is more conducive to the long-term preservation of anthocyanin, and at 37°C, the black potato anthocyanin hydrogel is more stable.

[0095] Figure 7The results showed that during the simulated gastric digestion process from 0 to 120 minutes (Figure A), the residual anthocyanin content in black potato anthocyanin showed a trend of first rapid decrease and then slow decrease, while the residual anthocyanin content in black potato anthocyanin hydrogel showed a trend of slow decrease; and at 120 minutes, the residual anthocyanin content in black potato anthocyanin was 0.408 mg / mL, and the residual anthocyanin content in the black potato anthocyanin hydrogel group was 0.527 mg / mL. The above results show that anthocyanin will be degraded in gastric juice, and black potato anthocyanin hydrogel can effectively prevent anthocyanin from decomposing in gastric juice. As shown in Figure B, when black potato anthocyanidins were treated for 0 to 120 minutes during the simulated intestinal fluid digestion process, the residual anthocyanidins in black potato anthocyanidins showed a trend of first rapidly decreasing and then slowly decreasing, while the residual anthocyanidins in black potato anthocyanidin hydrogel showed a trend of first slowly decreasing and then tending to be stable. At 120 minutes, the residual anthocyanidins in black potato anthocyanidins (0.325 mg / mL) were significantly lower than the residual anthocyanidins in black potato anthocyanidin hydrogel (0.449 mg / mL). These results indicate that both black potato anthocyanidins and black potato anthocyanidin hydrogel can remain in the intestinal fluid and be further absorbed and utilized. Comparison Figure 7 It can be seen that in the same concentration of anthocyanin starting solution, the degree of decomposition of anthocyanin in simulated gastric fluid and simulated intestinal fluid is higher than that of anthocyanin hydrogel, and the degree of decomposition of anthocyanin hydrogel in simulated intestinal fluid is higher than that in simulated gastric fluid. These results show that the addition of hydrogel can regulate the targeted release of anthocyanin in the gastrointestinal environment.

[0096] Example 4

[0097] Preparation of black potato anthocyanin yogurt

[0098] (1) Preparation of fermented yogurt

[0099] Follow the steps below to prepare fermented yogurt

[0100] Milk powder 13% (w / w) → dissolved at 50℃ → sterilized (80℃, 10min) → cooled to 30℃ → inoculated (mixed yogurt starter, inoculation amount 0.1%) → mixed on a shaker at 43℃ (speed 150rpm, time 5min) → fermented at 43℃ for 6h → refrigerated (4℃) → ripened (4℃, 24h) → fermented yogurt.

[0101] The mixed yogurt starter culture was purchased from Angel Yeast Co., Ltd.

[0102] (2) Preparation of black potato anthocyanins

[0103] Potato anthocyanidins and potato anthocyanidins hydrogel were added to fermented yogurt at a mass ratio of 0%, 0.1%, 0.2%, and 0.3%, and the changes in pH values ​​of different yogurts were observed over 21 days. Figures 8-9 shown.

[0104] Figure 8 It shows that from 0 to 6 days, the three groups of black potato anthocyanidins and the control group (0%) had little effect on the pH of yogurt, indicating that the microbial growth of yogurt at this time was in a relatively stable state and the yogurt quality was relatively good. From 6 to 21 days, the pH values ​​of the control group (0%) and the group with 0.1% black potato anthocyanidins showed a rapid downward trend, and the pH value of the group with 0.1% anthocyanidins was 4.01 at 21 days. The pH of the yogurt with 0.2% and 0.3% anthocyanidins added showed a slow downward trend, and the decline was smaller than that of the yogurt with 0.1% anthocyanidins added, and the pH values ​​of the yogurt with 0.2% and 0.3% anthocyanidins added were 4.08 and 4.09 at 21 days. The results show that the addition of 0.2% and 0.3% anthocyanidins can effectively prevent the post-acidification phenomenon of yogurt. According to Fig. 9 As shown, from 0 to 6 days, the three added amounts of black potato anthocyanin hydrogel and the control group (0%) had little effect on the pH of yogurt, indicating that the microbial growth of yogurt at this time was in a relatively stable state and the yogurt quality was relatively good. From 6 to 21 days, the pH values ​​of the control group (0%) and the yogurt with 0.1% anthocyanin hydrogel added showed a rapid downward trend, and the pH value of the 0.1% anthocyanin hydrogel group was 3.93 at 21 days. The pH of the yogurt with 0.2% and 0.3% anthocyanin hydrogel added showed a slow downward trend, and the decline was smaller than that of the yogurt with 0.1% anthocyanin hydrogel added, and the pH values ​​of the yogurt with 0.2% and 0.3% anthocyanin hydrogel added were 4.11 and 4.12 at 21 days. The results show that the addition of 0.2% and 0.3% anthocyanin hydrogel can effectively prevent the post-acidification phenomenon of yogurt. Comparison Figure 8 and 9 It was found that anthocyanin hydrogel can more effectively alleviate the post-acidification phenomenon of yogurt. At 21 days, the pH value of yogurt with 0.2% and 0.3% anthocyanin added was lower than that of yogurt with 0.2% and 0.3% anthocyanin hydrogel added, and the pH values ​​of 0.2% anthocyanin hydrogel and 0.3% anthocyanin hydrogel added were very close, so 0.2% anthocyanin hydrogel was added to the yogurt.

[0105] Example 5

[0106] The optimal ratio selection of black potato anthocyanin hydrogel yogurt

[0107] The black potato anthocyanin hydrogel was added to the fermented yogurt at a mass ratio of 0.2% to prepare the black potato anthocyanin hydrogel yogurt. The black potato anthocyanin hydrogel yogurt, strawberry jam and mango jam were configured in a certain proportion and divided into 13 groups, as shown in Table 2. The sensory evaluation table (Table 3) was used for evaluation, and the optimal combination was selected for the experiment.

[0108] Table 2 Proportion Table

[0109] Amount of strawberry added (%) Mango addition amount (%) Yogurt addition amount (%) serial number 0 0 100 1 0 10 90 2 0 20 80 3 0 30 70 4 0 40 60 5 10 0 90 6 20 0 80 7 30 0 70 8 40 0 60 9 10 10 80 10 10 20 70 11 20 10 70 12 20 20 60 13

[0110] Table 3 Sensory evaluation table

[0111]

[0112] 15 reviewers who have some knowledge of yogurt (including students of food science, professionals in the food industry, and ordinary consumers) were selected to ensure that the samples were representative and diverse. Then, the samples were prepared to ensure that the temperature, humidity, and tasting cups were the same; blind testing was performed, and scores were scored according to the sensory evaluation criteria in Table 3, and the scoring results were summarized and recorded. Next, data analysis was performed to calculate the average score of all reviewers. Finally, the results were summarized and reported. The sensory scoring results are shown in Table 4.

[0113] Table 4 Sensory evaluation results (average value)

[0114]

[0115]

[0116] Table 4 shows that the sensory scores of Groups 12 and 10 were relatively high. In order to respect the differences in individuals and tastes, the ratio of Groups 12 and 10 was finally selected for subsequent experiments.

[0117] Example 6

[0118] The texture properties of the yogurt sample were measured using a texture analyzer, that is, the yogurt sample was poured into a cylindrical container with an inner diameter of 50 mm, the cylindrical probe diameter was 35 mm, the descending speed was 1.0 mm / s, the penetration distance was 15 mm, the surface trigger force was 5 g, and the rising speed was 10.0 mm / s. The gel strength and viscosity were calculated using Exponent software, and the results are as follows: Fig.10 shown.

[0119] The yogurt samples include the yogurt of the 12th group in Example 5, referred to as Yogurt 12, the yogurt of the 10th group, referred to as Yogurt 10, the black potato anthocyanin yogurt prepared by adding 0.2% black potato anthocyanin to the fermented yogurt, referred to as Yogurt A, the black potato anthocyanin hydrogel yogurt prepared by adding 0.2% black potato anthocyanin hydrogel to the fermented yogurt, referred to as Yogurt B, and the fermented yogurt, referred to as Yogurt K.

[0120] Fig.10A shows that yogurt 12 has the highest gel strength, and yogurt A has the lowest gel strength. The gel strength shows that yogurt 12> yogurt 10> yogurt B> yogurt K> yogurt A. The higher gel strength of yogurt 12 and yogurt 10 than the control group (yogurt K) shows that the addition of jam will increase the gel strength of yogurt. The gel strength of yogurt 12 with a jam content of 30% is higher than that of yogurt 10 with a jam content of 20%, and the texture of the yogurt is denser and more stable. The higher gel strength of yogurt B with anthocyanin hydrogel than the control group (yogurt K) shows that the addition of anthocyanin hydrogel will improve the quality of yogurt. The lower gel strength of yogurt A with anthocyanin than the control group (yogurt K) shows that the direct addition of black potato anthocyanin will affect the stability of yogurt. According to Fig.10 As shown in Figure B, it was found that yogurt 12 had the highest viscosity and yogurt A had the lowest viscosity, and the viscosity showed yogurt 12> yogurt 10> yogurt B> yogurt K> yogurt A. The higher viscosity of yogurt 12 and yogurt 10 than the control group (yogurt K) indicates that the addition of jam will improve the consistency of yogurt, and the consistency of yogurt 12 with a jam content of 30% is higher than that of yogurt 10 with a jam content of 20%, and the texture of yogurt is denser and more stable; the higher viscosity of yogurt B with anthocyanin hydrogel than the control group (yogurt K) indicates that the addition of anthocyanin hydrogel will improve the consistency of yogurt; and the lower gel strength of yogurt A with anthocyanin than the control group (yogurt K) indicates that the direct addition of black potato anthocyanin will affect the stability of yogurt.

[0121] Example 7

[0122] The complex viscosity and storage modulus of yogurt samples (yogurt 12, yogurt 10, yogurt B, yogurt K and yogurt A) were measured using a rheometer. 20 mL of yogurt was poured into a cylinder and the measurement temperature was 4 °C and the angular frequency was 10 -1 ~10 2 rad / s. The fixed frequency is 1Hz, and the angular frequency is 10 -1 ~10 2 rad / s range, the storage modulus and loss modulus of the yogurt sample were measured to obtain the linear viscoelastic region of the sample. The frequency sweep experiment varied from 0.01 to 10 Hz, with a fixed strain of 0.1% (within the linear viscoelastic region). The storage modulus and loss modulus of the yogurt sample were obtained based on the dynamic stress-strain relationship. The results are shown in Fig.11 and 12 shown.

[0123] Fig.11 Show, in 10 -1 to 10 2 Within the range, the viscosity of yogurt showed a downward trend, and the complex viscosity of yogurt 10 and yogurt 12 was relatively high overall, and the downward trend was more stable than that of the other three groups. The results show that the addition of jam and anthocyanin hydrogel can effectively improve the viscosity and stability of yogurt, giving yogurt excellent properties.

[0124] according to Fig.12 It was found that the storage modulus and energy loss modulus of the five groups of yogurts did not undergo cross-linking, indicating that they all showed relatively stable spatial results. Moreover, the trend lines of the storage modulus and energy loss modulus of yogurt 12 and yogurt 10 were relatively stable, indicating that yogurt 12 and yogurt 10 had better stability and were more conducive to the transportation and storage of yogurt.

[0125] The present invention provides a black potato anthocyanidin hydrogel and a preparation method and application thereof. The black potato anthocyanidin hydrogel of the present invention comprises the following components in mass fractions: 5 to 20 parts of black potato anthocyanidin and 50 to 100 parts of hydrogel; the hydrogel is prepared from gelatin and / or gellan gum; when the hydrogel comprises gelatin and gellan gum, the mass ratio of gelatin to gellan gum is 1 to 2: 1 to 2. The carrier material of the hydrogel of the present invention is obtained through reasonable screening. The carrier material has good fluidity and is suitable for embedding black potato anthocyanidin. The hydrogel prepared by mixing gelatin and gellan gum has good stability in simulated gastric juice and good swelling degree in simulated intestinal juice. The embedding rate of black potato anthocyanidin can reach 90.81%, indicating that the hydrogel of the present invention is more suitable as a carrier material and is more conducive to the release of black potato anthocyanidin in intestinal juice. The black potato anthocyanidin hydrogel prepared by the method of the present invention is stable at 4°C and 37°C. The black potato anthocyanin hydrogel prepared by the present invention can more effectively alleviate the phenomenon of post-acidification of yogurt. Adding the black potato anthocyanin hydrogel to yogurt has better taste, flavor and quality than adding the black potato anthocyanin to yogurt.

[0126] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A black potato anthocyanin hydrogel, characterized in that The composition includes the following components in parts by weight: 5-20 parts of black potato anthocyanins, 50-100 parts of hydrogel; The hydrogel is prepared from gelatin and / or gellan gum; When the hydrogel includes gelatin and gellan gum, the mass ratio of gelatin to gellan gum is 1-2:1-2.

2. A method for preparing anthocyanin hydrogel from black potato, characterized in that: The steps include: (1) Weighing the black potato anthocyanidins and hydrogel according to the mass fractions described in claim 1; (2) Mix the black potato anthocyanin and the hydrogel, stir for 8 to 12 minutes, let stand for 20 to 28 hours, and dry to obtain the black potato anthocyanin hydrogel.

3. The preparation method according to claim 2, characterized in that: The temperature during the stirring is 23-28°C; The stirring speed is 750-850 rpm.

4. The preparation method according to claim 3, characterized in that: The temperature during the standing is 2 to 6°C; It needs to be protected from light when standing.

5. The preparation method according to claim 4, characterized in that: The drying is freeze drying, and the freeze drying temperature is -75 to -85°C.

6. Use of the black potato anthocyanin hydrogel according to claim 1 in preparing yogurt with good stability, good taste and flavor.

7. Use of the black potato anthocyanin hydrogel prepared by the preparation method according to any one of claims 2 to 5 in preparing yogurt with good stability, taste and flavor.

8. A yogurt with good stability, good taste and flavor, characterized in that: The composition includes the following components in parts by weight: 100 parts of fermented yogurt, 0.2-0.3 parts of black potato anthocyanin hydrogel; The black potato anthocyanin hydrogel is the black potato anthocyanin hydrogel according to claim 1 or the black potato anthocyanin hydrogel prepared by the preparation method according to any one of claims 2 to 5.

9. The yogurt according to claim 8, characterized in that The yogurt also includes jam; The jam is strawberry jam and / or mango jam.

Images