Casein powder and natural antioxidant composition as well as preparation method and food thereof

Abstract

The invention provides a casein powder and natural antioxidant composition as well as a preparation method and food thereof. The composition comprises micelle casein, compound enzyme and a natural antioxidant, the compound enzyme comprises pepsin, trypsin and chymotrypsin; the natural antioxidants refer to spearmint extract and rosemary extract. The composition contains the micelle casein and the compound enzyme, the hydrolysis degree of the micelle casein in vivo can be improved by adding the compound enzyme, rapid and complete absorption and utilization of the micelle casein are facilitated, the nutritional value is improved, the protein subjected to enzymolysis is protected from being attacked by oxidation of free radicals by adding the natural antioxidant, and the enzymolysis effect is improved. And bad bitter taste and metal taste generated by hydrolyzed protein can be masked.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of food, in particular, the present application relates to a casein powder and a natural antioxidant composition and a preparation method thereof and a food. BACKGROUND

[0002] Casein is one of the main proteins in bovine milk, accounting for about 80% of the total amount of bovine milk protein. It is a complex high molecular protein composed of multiple amino acid residues, with high solubility and stability. In bovine milk, casein is mainly composed of three subtypes of β-CN, α-CN and κ-CN, and α-CN is composed of αs1-CN and αs2-CN. These proteins are combined together through non-covalent bonds and combined with colloidal calcium phosphate (CCP) to form casein micelles with a diameter of about 40-300 nm. At present, micellar casein is mainly obtained by membrane filtration technology.

[0003] The existing micellar casein powder has the following problems in practical application: 1) The casein powder produced by the conventional process has poor solubility due to high heat intensity in the preparation process, which also leads to low hydrolysis efficiency (Sauer, A., & Moraru, C. I. (2012). Heat stability of micellar casein concentrates as affected by temperature and pH. Journal of dairy science, 95(11), 6339-6350); 2) Natural casein mainly exists in the form of micelles, and part of the hydrophobic groups and enzyme cutting sites exist in the micelles, so that the hydrolysis of casein is difficult, the degree of hydrolysis is low, and the complete absorption and utilization of casein by the human body are affected; 3) The metabolism of casein in the human body is long, which cannot meet the demand of the human body for rapid absorption of amino acids or proteins (Rehan, F., Ahemad, N., & Gupta, M. (2019). Casein nanomicelle as an emerging biomaterial—A comprehensive review. Colloids and Surfaces B: Biointerfaces, 179, 280-292); 4) The protein decomposed by the enzyme exposes more reaction sites and is more easily attacked by free radical oxidation (Griffiths, H. R. (2000). Antioxidants and protein oxidation. Free Radical Research, 33(Supplement), S47-S58); 5) The flavor and taste of the protein decomposed by the enzyme will change, and a certain degree of bitterness and metallic taste will be generated (Fennema, O. R. (1996). Food chemistry (Vol. 76). CRC Press).

[0004] Therefore, the current micellar casein powder still needs to be researched. SUMMARY

[0005] The present application provides a casein powder and a natural antioxidant composition, as well as a preparation method and a foodstuff. The composition contains micellar casein, natural antioxidants and complex enzymes. The addition of complex enzymes can improve the degree of hydrolysis of micellar casein in the body, which is beneficial to its rapid and complete absorption and utilization, and improves the nutritional value. The addition of natural antioxidants helps to protect the protein after enzymolysis from oxidation attack by free radicals, and helps to prevent the production of undesirable bitter and metallic taste by protein hydrolysis.

[0006] One object of the present invention is to provide a composition comprising: micellar casein, a complex enzyme, and a natural antioxidant; the complex enzyme comprising pepsin, trypsin, and chymotrypsin.

[0007] This invention, by combining micellar casein with the aforementioned complex enzyme, can enhance the degree of hydrolysis of micellar casein in vivo. Chymotrypsin can specifically hydrolyze micellar casein, while pepsin and trypsin are enzymes that hydrolyze a wide range of proteins. They can hydrolyze not only micellar casein but also the products of micellar casein hydrolysis, thereby facilitating its rapid and complete absorption and utilization and improving its nutritional value.

[0008] The composition may also have the following additional technical features:

[0009] The pepsin, trypsin, and chymotrypsin are derived from cattle; the mass ratio of the pepsin, trypsin, and chymotrypsin is (1-5):(1-5):(1-3).

[0010] The composition further comprises rosemary extract and spearmint extract; the rosemary extract or spearmint extract in the composition accounts for 1% to 2% by mass.

[0011] The mass ratio of the pepsin, trypsin, chymotrypsin and rosemary extract is (1-5):(1-5):(1-3):(1-7).

[0012] The mass of the complex enzyme is 0.1‰ to 1‰ of the micelle casein protein.

[0013] The composition is provided in powder form.

[0014] In another aspect of the invention, a food product is provided. The food product comprises the aforementioned composition.

[0015] In another aspect of the invention, this application provides a method for preparing the aforementioned composition. The method comprises mixing the micellar casein, a natural antioxidant, and a complex enzyme to obtain the composition.

[0016] The micelle casein is provided in the form of a micelle casein solution; the method further includes: spray drying the mixture to obtain a powder of the composition.

[0017] The preparation method of the micelle casein solution includes: sequentially defatting, sterilizing, separating by microfiltration membrane, and concentrating by reverse osmosis membrane to obtain the micelle casein solution; the mixing temperature is 4℃~9℃; the spray drying treatment includes electrostatic spray drying treatment, and the electrostatic spray drying treatment meets at least one of the following conditions: inlet air temperature is 100℃~140℃; outlet air temperature is 70℃~90℃; feed temperature is 70℃~90℃; atomization pressure is 2.5mPa~3.5mPa; electrostatic field voltage is 10kV~15kV; and the process is carried out under an inert atmosphere.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present application. Detailed Implementation

[0019] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0020] In this invention, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0021] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is understood that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this invention, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers, and ranges defined in this way can include endpoints a and b. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0022] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0023] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0024] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0025] This application discloses compositions, methods for preparing the same, and food products thereof, which will be described in detail below.

[0026] 1. Composition

[0027] In one aspect of the invention, this application provides a composition. According to an embodiment of this application, the composition comprises: a micellar casein natural antioxidant and a complex enzyme; the natural antioxidant mainly comprises spearmint extract and rosemary extract; the complex enzyme comprises pepsin, trypsin, and chymotrypsin.

[0028] Natural casein mainly exists in the form of micelles. Once inside the body, micellar casein undergoes hydrolysis under the low pH conditions of the stomach and the combined action of pepsin, facilitating digestion and absorption. However, because some hydrophobic groups and enzyme cleavage sites of micellar casein are located within the micelles, hydrolysis is difficult and the degree of hydrolysis is low, affecting the complete absorption and utilization of casein by the body.

[0029] Therefore, the inventors of this invention, through extensive research, analysis, and screening, have concluded that chymotrypsin can specifically hydrolyze micellar casein, while pepsin and trypsin are broadly proteolytic enzymes that can hydrolyze both micellar casein and its hydrolyzed products. Pepsin, trypsin, and chymotrypsin work synergistically in the gastric and intestinal environments, rapidly and thoroughly hydrolyzing micellar casein to a high degree, thus meeting the body's need for rapid absorption of proteins and amino acids. Furthermore, compared to consuming micellar casein and complex enzymes alone, providing them in a combined form helps improve digestion, and the micellar casein structurally protects the complex enzymes, reducing enzyme loss and further enhancing digestibility.

[0030] On the other hand, the use of enzymes also brings some new challenges: proteins broken down by enzymes expose more reaction sites, making them more susceptible to free radical oxidation and altering their flavor and texture, producing a certain degree of bitterness and metallic taste. Adding natural antioxidants helps protect the enzymatically hydrolyzed proteins from free radical oxidative attacks and helps mask the unpleasant bitterness and metallic taste of hydrolyzed proteins.

[0031] Pepsin, trypsin, and chymotrypsin are derived from cattle. Micellar casein is usually derived from cow's milk. Selecting these three enzymes from cattle can improve the affinity and catalytic efficiency between the enzyme and the substrate, thereby achieving faster and more thorough protein breakdown during hydrolysis. This results in a high degree of hydrolysis while maintaining the biological activity and nutritional value of the protein, which helps improve the body's absorption efficiency of amino acids and proteins.

[0032] The mass ratio of pepsin, trypsin, and chymotrypsin is (1–5):(1–5):(1–3), for example (2–5):(2–5):(1.5–2.5), (3–5):(3–5):(1.5–2.5), (4–5):(4–5):(1.5–2.5). Under these ratios, the three enzymes can work synergistically to decompose micellar casein more quickly and thoroughly, resulting in a high degree of hydrolysis and promoting digestion and absorption.

[0033] The composition further includes rosemary extract and spearmint extract. Proteins broken down by enzymes expose more reactive sites, making them more susceptible to free radical oxidative attack and altering their flavor and texture, producing a degree of bitterness and metallic taste. Adding natural antioxidants helps protect the enzymatically hydrolyzed proteins from free radical oxidative attack and helps mask the unpleasant bitterness and metallic taste of hydrolyzed proteins.

[0034] The composition contains spearmint extract at a mass ratio of 0.1% to 0.2%, for example, 0.1%, 0.15%, or 0.2%. This can provide the composition with a suitable taste and antioxidant protection.

[0035] The mass ratio of pepsin, trypsin, chymotrypsin, and rosemary extract in the composition is (1-5):(1-5):(1-3):(1-7), for example (2-5):(2-5):(1.5-2.5):(1.5-2.5), (3-5):(3-5):(1.5-2.5):(1.5-2.5), (4-5):(4-5):(1.5-2.5):(1-7). Under these conditions, the three enzymes can work synergistically to decompose micellar casein more quickly and thoroughly, promoting digestion and absorption. Simultaneously, the rosemary extract better protects the protein, and its herbal flavor is not tasted in the system.

[0036] The mass of the complex enzyme is 0.1‰ to 1‰ of the micelle casein mass, for example, 0.1‰, 0.2‰, 0.3‰, 0.4‰, 0.5‰, 0.6‰, 0.7‰, 0.8‰, 0.9‰, or 1‰. When the amount of complex enzyme meets the above conditions, it can enable faster and more complete breakdown of micelle casein, promoting digestion and absorption by the body.

[0037] The composition is provided in powder form. This facilitates carrying and storage, reduces protein activity loss, extends shelf life, and improves solubility. In this application, the "composition" may also be referred to as "micelle casein powder".

[0038] 2. Food

[0039] In another aspect of the invention, this application proposes a food product. The food product comprises the aforementioned composition. The food product of this application contains micellar casein and a complex enzyme. The addition of the complex enzyme can increase the degree of hydrolysis of micellar casein in the body, which is beneficial for its rapid and complete absorption and utilization, thereby enhancing its nutritional value.

[0040] According to embodiments of this application, the food includes liquid dairy products, such as flavored milk, yogurt, etc.; cheese; ice cream, etc.

[0041] It should be noted that the features and advantages described above for the composition also apply to this food product, and will not be repeated here.

[0042] 3. Method for preparing the composition

[0043] In another aspect of this application, a method for preparing the aforementioned composition is provided. The method includes mixing the micellar casein with a complex enzyme to obtain the composition. By mixing the micellar casein with the complex enzyme, a homogeneous composition can be obtained. The addition of the complex enzyme can increase the degree of hydrolysis of the micellar casein in vivo, which is beneficial for its rapid and complete absorption and utilization, thereby enhancing its nutritional value.

[0044] According to an embodiment of this application, the micelle casein is provided in the form of a micelle casein solution.

[0045] According to an embodiment of this application, the method for preparing the micelle casein solution includes: sequentially defatting, sterilizing, separating via microfiltration membrane, and concentrating via reverse osmosis membrane to obtain a micelle casein solution. The microfiltration membrane separation method prepares casein that retains the natural micelle structure, thereby improving the purity and activity of the micelle casein and enhancing hydrolysis efficiency.

[0046] In some embodiments, defatting includes: defatting raw milk by centrifugation, wherein the temperature is 40-60°C, the centrifugation speed is 4000-8000 rpm, and the fat content is adjusted to 0.06%.

[0047] In some embodiments, sterilization includes pasteurizing skim milk at a temperature of 70-90°C for 15-60 seconds.

[0048] In some embodiments, microfiltration membrane separation includes: microfiltration membrane separation of pasteurized skim milk, wherein the separation parameters include: the microfiltration membrane used has a pore size of 0.1 μm-0.4 μm, a transmembrane pressure of 0.05 mPa-0.1 mPa, a temperature of 40-60°C, a washing process is used, the washing water volume: skim milk volume = (1.5-0.5):1, the concentration factor VCF is 1-3, and a micelle casein solution is obtained, with a total solids content of 9-13 g / 100 g, a protein content of 7-11 g / 100 g, a casein content of 84%-88% of the total protein, and a rosemary extract content of 1%-3%.

[0049] In some embodiments, reverse osmosis membrane concentration includes: concentrating a micelle casein solution obtained by microfiltration membrane separation through reverse osmosis, wherein the concentration parameters are: reverse osmosis membrane flow channel of 28-40 mil, concentration pressure of 2-4 mPa, concentration temperature of 5-15°C, to obtain a micelle casein concentrate with a total solids content of 23-27 g / 100 g, a protein content of 17-23 g / 100 g, a casein content of 84-88% of the total protein, and a rosemary extract content of 2-5 g / 100 g.

[0050] According to embodiments of this application, the mixing treatment temperature is 5°C to 15°C, for example, 5°C, 6°C, 8°C, 10°C, 12°C, 14°C, or 15°C. This is to maintain protein activity during the mixing treatment.

[0051] According to embodiments of this application, the spray drying process is electrostatic spray drying. The inventors have discovered that spray drying a mixture containing micellar casein at low temperatures results in micellar casein powder with better solubility, which is beneficial for the micellar casein powder to fully undergo hydrolysis with complex enzymes in the digestive system. Traditional spray drying technology is usually carried out at high temperatures, which, while allowing for rapid drying, may reduce the solubility of the micellar casein powder. Setting traditional spray drying equipment at low temperatures makes it difficult to effectively form powder. Electrostatic spray drying technology transforms the liquid material to be dried into fine droplets and rapidly dries it into powder or granular products using hot air. By setting it to relatively low temperature conditions, highly soluble micellar casein powder can be obtained. Furthermore, the colloidal properties of casein allow for the formation of natural microcapsule structures during the drying process to protect enzyme activity and control the onset time of the enzymatic reaction.

[0052] According to an embodiment of this application, the inlet air temperature is 100°C to 140°C, and the outlet air temperature is 70°C to 90°C. Therefore, electrostatic spray drying under these temperature conditions yields micellar casein powder with high solubility.

[0053] According to embodiments of this application, the feed temperature is 70°C to 90°C, for example, 70°C, 72°C, 75°C, 76°C, 78°C, 80°C, 82°C, 84°C, 85°C, 86°C, 88°C, or 90°C; the atomization pressure is 2.5mPa to 3.5mPa, for example, 2.5mPa, 2.6mPa, 2.8mPa, 3.0mPa, 3.2mPa, 3.4mPa, or 3.5mPa; the electrostatic field voltage is 10kV to 15kV, for example, 10kV, 11kV, 12kV, 13kV, 14kV, or 15kV; and the process is carried out under an inert atmosphere, which includes nitrogen and / or helium.

[0054] Electrostatic spray drying under the above conditions can yield micellar casein powder with high solubility.

[0055] It should be noted that the features and advantages described above for the composition also apply to the method for preparing the composition, and will not be repeated here.

[0056] The following will explain the solution of this application with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0057] Example 1

[0058] In this embodiment, the composition was prepared according to the following method:

[0059] 1. Skimming: Raw milk is skimmed by centrifugation at a temperature of 50°C and a speed of 5000 rpm until the fat content is adjusted to 0.06%.

[0060] 2. Pasteurization: The skim milk is pasteurized at a temperature of 85°C for 30 seconds.

[0061] 3. Microfiltration membrane separation: The pasteurized skim milk was separated by microfiltration membrane. The separation parameters were as follows: the pore size of the microfiltration membrane was 0.2 μm, the transmembrane pressure was 0.075 mPa, the temperature was 50℃, the washing process was used, the washing water volume: skim milk volume = 1:1, the concentration factor VCF was 2, and a micelle casein solution was obtained, with a total solids content of 11 g / 100 g, a protein content of 9 g / 100 g, a casein content of 86% of the total protein, and a rosemary extract content of 1.5%.

[0062] 4. Reverse osmosis membrane concentration: The micelle casein solution obtained by microfiltration membrane separation is concentrated by reverse osmosis. The concentration parameters are: reverse osmosis membrane flow channel of 31mil, concentration pressure of 3mPa, and concentration temperature of 10℃. The resulting micelle casein concentrate has a total solids content of 25g / 100g, a protein content of 20g / 100g, a casein content of 86% of the total protein, and a rosemary extract content of 3g / 100g.

[0063] 5. Mixing: Add a compound enzyme to the concentrated micelle casein solution at a concentration of 0.3‰ of the micelle casein content. The ratio of pepsin, trypsin, chymotrypsin, X, and rosemary extract in the compound enzyme is 5:5:2:2:1. Mix thoroughly at 10℃.

[0064] 6. Spray drying: The micelle casein concentrate after mixing with the complex enzymes is spray dried. The parameters for spray drying are as follows: nitrogen is used as the protective gas, the atomization pressure is 3 mPa, the electrostatic field pressure is 12 kV, the feed temperature is 80℃, the inlet air temperature is 120℃, and the outlet air temperature is 80℃.

[0065] Example 2

[0066] The difference between this embodiment and Embodiment 1 is that,

[0067] Step 5: Mixing: Add a compound enzyme to the concentrated micelle casein solution at a concentration of 0.45‰ of the micelle casein protein. The ratio of pepsin, trypsin, chymotrypsin, and rosemary extract in the compound enzyme is 1:1:3:3. Mix at 15°C until fully combined.

[0068] Step 6: Spray drying: The micelle casein concentrate after mixing with the complex enzyme is spray dried. The parameters for spray drying are as follows: nitrogen is used as the protective gas, the atomization pressure is 3 mPa, the electrostatic field pressure is 12 kV, the feed temperature is 70℃, the inlet air temperature is 100℃, and the outlet air temperature is 70℃.

[0069] Example 3

[0070] The difference between this embodiment and Embodiment 1 is that,

[0071] Step 5: Mixing: Add a compound enzyme to the concentrated micelle casein solution at a concentration of 0.15‰ of the micelle casein protein. The ratio of pepsin, trypsin, chymotrypsin and rosemary extract in the compound enzyme is 3:3:1:2. Mix thoroughly at 10°C.

[0072] Step 6: Spray drying: The micelle casein concentrate after mixing with the complex enzyme is spray dried. The parameters for spray drying are as follows: nitrogen is used as the protective gas, the atomization pressure is 3 mPa, the electrostatic field pressure is 12 kV, the feed temperature is 90℃, the inlet air temperature is 140℃, and the outlet air temperature is 90℃.

[0073] Example 4

[0074] The difference between this embodiment and Embodiment 1 is that the amount of compound enzyme added is 0.08‰ of the micelle casein protein content.

[0075] Example 5

[0076] The difference between this embodiment and Embodiment 1 is that the amount of compound enzyme added is 1.5‰ of the micelle casein protein content.

[0077] Example 6

[0078] The difference between this embodiment and Example 1 is that the mass ratio of pepsin, trypsin, chymotrypsin and rosemary extract is 6:0.5:0.5:4.

[0079] Comparative Example 1

[0080] The difference between this comparative example and Example 1 is that step 5 is omitted, and the concentrated micelle casein solution obtained in step 4 is directly subjected to step 6.

[0081] Comparative Example 2

[0082] The difference between this comparative example and Example 1 is that the complex enzyme does not contain pepsin.

[0083] Comparative Example 3

[0084] The difference between this comparative example and Example 1 is that the complex enzyme does not contain trypsin.

[0085] Comparative Example 4

[0086] The difference between this comparative example and Example 1 is that the complex enzyme does not contain chymotrypsin.

[0087] Comparative Example 5

[0088] The difference between this comparative example and Example 1 is that the complex enzyme does not contain rosemary extract.

[0089] Comparative Example 6

[0090] The difference between this comparative example and Example 1 is that trypsin is replaced with papain.

[0091] Test case

[0092] I. The degree of hydrolysis of the compositions prepared in Examples 1-6 and Comparative Examples 1-6 was determined using in vitro simulated digestion. The determination method is as follows:

[0093] (I) In vitro digestion simulation experiment section

[0094] 1. Gastric Digestion Simulation Section:

[0095] (1) Prepare simulated gastric juice, wherein the simulated gastric juice formula is: NaCl 94mM, KCl 13mM, pH adjusted to 5.3 with 1mM HCl, add pepsin (268U / mL), and adjust pH to 3 with 1mM HCl;

[0096] (2) Simulated digestion experiment: Weigh the composition and prepare a 5% concentration (w / w) micelle casein solution. Mix the simulated gastric juice at a mass ratio of 1:1. After incubation at 37℃ for 2 hours, adjust the pH to 7 with 1mM NaOH to obtain simulated gastric digestive juice.

[0097] 2. Small Intestine Digestion Simulation Section:

[0098] (1) Preparation of simulated intestinal fluid: The formula of simulated intestinal fluid is: NaCl 164mM, KCl 10mM, NaHCO3 85mM, CaCl2 3mM, bile salts (bovine bile) 3.1mM, add trypsin (100U / mL), and adjust the pH to 7 with 1mM NaOH.

[0099] (2) Simulated digestion experiment: Weigh the simulated gastric digestive fluid, mix it with the simulated intestinal fluid at a volume ratio of 1:1, add trypsin (100U / mL), keep warm at 37℃ for 2 hours, and then stop digestion by boiling water bath for 10 minutes to obtain the simulated intestinal digestive fluid.

[0100] (II) OPA method for determining degree of hydrolysis:

[0101] The degree of hydrolysis was determined using the o-phthalaldehyde (OPA) method. The specific method is as follows:

[0102] (1) Preparation of OPA reagent: Dissolve 7.62g sodium tetraborate and 200mg sodium dodecyl sulfate in ultrapure water, add 160mg OPA (dissolved in 4mL ethanol) and 176mg thiothreitol (dissolved in ultrapure water), and finally adjust the volume to 200mL. Store in the dark.

[0103] (2) Preparation of serine standard solution: 50 mg L-serine was dissolved in 500 mL of ultrapure water (0.9516 meqv / L).

[0104] (3) Sample solution preparation: Dissolve 0.5g of simulated intestinal digestion fluid in 100ml of deionized water.

[0105] (4) Under light-protected conditions, add 3 mL of OPA reagent and 400 μL of the test solution (serine standard solution or sheep milk protein hydrolysate) to the test tube, mix well for 5 s, react at room temperature for 2 min, and measure the absorbance at a wavelength of 340 nm. Serine is used as the standard solution and ultrapure water is used as the blank control.

[0106] (5) Calculate the degree of protein hydrolysis using the following formula:

[0107]

[0108] In the formula: DH is the degree of protein hydrolysis, %; h is the number of peptide bonds hydrolyzed in milk protein, meqv / g; htot is the total number of peptide bonds in milk protein, meqv / g. The formula for calculating h is:

[0109]

[0110] In the formula: serine-NH2 is the amount of serine-NH2 per gram of protein, meqv / g; β and α are constants, 0.40 and 1.00, respectively. The formula for calculating Serine-NH2 is:

[0111]

[0112] In the formula: V is the sample volume, L; X is the sample mass, g; P is the protein content in the sample, %.

[0113] 2. The insolubility index of the compositions prepared in Examples 1-7 and Comparative Examples 1-6 was tested respectively, with reference to the national standard: GB 5413.29-2010.

[0114] III. Results and Analysis

[0115] The results are shown in Table 1. Compared with Comparative Examples 1-6, the compositions prepared in Examples 1-7 have better overall characteristics. The combined action of pepsin, trypsin, chymotrypsin and X can effectively improve the hydrolysis of micelle casein.

[0116] As can be seen from Example 1, the use of low-temperature electrostatic spray drying helps to maintain the enzymatic activity of the enzyme, thereby better hydrolyzing micelle casein and improving the solubility of the composition.

[0117] Table 1. Degree of hydrolysis and solubility

[0118]

[0119]

[0120] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A composition of casein powder and natural antioxidants, characterized in that, include: Micellar casein, complex enzymes, and natural antioxidants; The complex enzyme includes pepsin, trypsin, and chymotrypsin.

2. The casein powder and natural antioxidant composition according to claim 1, characterized in that, The pepsin, trypsin, and chymotrypsin were derived from cattle; The mass ratio of the pepsin, trypsin and chymotrypsin is (1-5):(1-5):(1-3).

3. The casein powder and natural antioxidant composition according to claim 1, characterized in that, The natural antioxidants include rosemary extract and spearmint extract; The composition contains 1% to 2% rosemary extract and 0.5% to 1% spearmint extract by mass.

4. The composition of casein powder and natural antioxidant according to claim 1, characterized in that, The mass ratio of the pepsin, trypsin, chymotrypsin and natural antioxidant is (1-5):(1-5):(1-3):(1-7).

5. The casein powder and natural antioxidant composition according to claim 1, characterized in that, The mass of the complex enzyme is 0.1‰ to 1‰ of the micelle casein protein.

6. A method for preparing the composition according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Mix micellar casein solution with natural antioxidants and complex enzymes to obtain a combined solution; (2) The mixture obtained by mixing is spray-dried to obtain the powder of the composition.

7. The method for preparing the composition according to claim 6, characterized in that... The preparation method of the micelle casein solution in step (1) is as follows: raw milk is defatted, sterilized, separated by microfiltration membrane, and concentrated by reverse osmosis membrane in sequence to obtain the micelle casein solution.

8. The method for preparing the composition according to claim 6, characterized in that... The temperature of the mixing process is 5℃~15℃; the spray drying process is electrostatic spray drying; the electrostatic spray drying process meets at least one of the following conditions: The inlet air temperature is 110℃~150℃; The outlet air temperature is 90℃~95℃; The feed temperature is 70℃~90℃; The atomization pressure is 2.5 MPa to 3.5 MPa; The electrostatic field voltage is 10kV~15kV; The experiment was conducted in an inert gas environment.

9. The method for preparing the composition according to claim 7, characterized in that, The method for preparing the micelle casein solution includes: sequentially defatting, sterilizing, separating by microfiltration membrane, and concentrating by reverse osmosis membrane to obtain the micelle casein solution; The temperature for the mixing process is 5℃~15℃; The spray drying process includes electrostatic spray drying. The electrostatic spray drying process satisfies at least one of the following conditions: The inlet air temperature is 110℃~150℃; The outlet air temperature is 90℃~95℃; The feed temperature is 70℃~90℃; The atomization pressure is 2.5 MPa to 3.5 MPa; The electrostatic field voltage is 10kV~15kV; The experiment was conducted in an inert gas environment.

10. The use of the composition containing casein powder according to claim 1 in food.

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