High-protein zero-sugar skimmed milk, high-protein zero-sugar milk-containing beverage and preparation method thereof

Abstract

The invention provides high-protein zero-sugar skimmed milk, a high-protein zero-sugar milk-containing beverage and a preparation method thereof. Based on the total mass of the high-protein zero-sugar skimmed milk, the content of protein in the high-protein zero-sugar skimmed milk is greater than or equal to 6.5 g / 100g; the sugar content is less than or equal to 0.5 g / 100g. According to the technical scheme provided by the invention, a production process of combining ultrafiltration with washing filtration is adopted, and specific process parameters including a mixing ratio during washing filtration, ultrafiltration parameters in a circulating washing filtration process and the like are set, so that the high-protein zero-sugar skimmed milk with high protein content and zero sugar and a milk-containing beverage are prepared; and the food is very suitable for people needing to supplement protein, and does not cause any other nutrition burden.

Description

Technical Field

[0001] This invention relates to the field of dairy processing technology, and in particular to a high-protein, sugar-free skim milk, a high-protein, sugar-free dairy beverage, and their preparation methods. Background Technology

[0002] One important nutrient in milk is milk protein, a complete protein containing all nine essential amino acids required by the human body. Branched-chain amino acids such as leucine, isoleucine, and valine are present in a relatively high proportion of milk protein, and these amino acids are crucial for muscle synthesis and reducing muscle damage. Milk protein also has a high digestibility and absorption rate, typically 87-89%, and provides a feeling of fullness, making it particularly suitable for fitness enthusiasts.

[0003] Based on the high nutritional value of milk, various high-protein milk or high-protein shake products targeting fitness enthusiasts have emerged on the market. Most of these products, while achieving high protein content, either increase carbohydrate content, thus increasing the nutritional burden on consumers (even with the use of lactase to convert lactose into smaller monosaccharides, the total carbohydrate content remains unchanged); or they achieve high protein through reconstituted formulas such as milk powder, protein powder, and whey powder, which to some extent diminishes the natural nutrients of milk protein and introduces unpleasant flavors (such as a burnt taste or rotten egg smell due to the high-temperature processing of protein powder and milk powder). These drinks are mostly flavored dairy beverages, marketed for their luxurious flavor and smooth texture. The potential unpleasant flavors from reconstituted formulas like protein powder and whey powder are unacceptable for dairy beverages that prioritize flavor and texture.

[0004] Therefore, how to provide a high-protein, sugar-free dairy beverage without increasing the nutritional burden on consumers, without using reconstituted formulas such as milk powder, protein powder, and whey powder, while ensuring flavor and taste, is a problem that researchers urgently need to solve. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a high-protein, zero-sugar skim milk, a high-protein, zero-sugar dairy beverage, and a method for preparing the same, in order to solve the problems in the prior art.

[0006] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.

[0007] The first aspect of the present invention provides a high-protein, zero-sugar skim milk for use as a raw material for formulated dairy beverages, wherein, based on the total mass of the high-protein, zero-sugar skim milk, the protein content in the high-protein, zero-sugar skim milk is ≥6.5g / 100g and the sugar content is ≤0.5g / 100g.

[0008] A second aspect of the present invention provides a method for preparing high-protein, zero-sugar skim milk as described above, comprising the following steps:

[0009] 1) Separation: The raw milk is separated to obtain light cream and initial skim milk, and the initial skim milk is pasteurized;

[0010] 2) First ultrafiltration: The initial skim milk is filtered through an ultrafiltration membrane to obtain the first ultrafiltration retentate and the first ultrafiltration permeate;

[0011] 3) Repeat washing and filtration until the protein content of the ultrafiltration retentate is ≥6.5g / 100g and the sugar content is ≤0.5g / 100g; a single washing and filtration includes the following steps:

[0012] 3-1) Perform reverse osmosis or nanofiltration on the first ultrafiltration permeate to obtain reverse osmosis or nanofiltration permeate;

[0013] 3-2) Mix the reverse osmosis or nanofiltration permeate with the first ultrafiltration retentate to obtain a mixed solution;

[0014] 3-3) Perform a second ultrafiltration on the mixture to obtain a second ultrafiltration retentate and a second ultrafiltration permeate.

[0015] The washing and filtration process in this application includes the entire process of reverse osmosis or nanofiltration, mixing, and ultrafiltration in step 3); and the ultrafiltration retentate obtained after the washing and filtration cycle is high-protein zero-sugar skim milk.

[0016] Preferably, the raw milk comprises raw cow's milk.

[0017] Preferably, the initial skim milk has a fat content of <0.05 wt%.

[0018] Preferably, in step 2), the conditions during the first ultrafiltration include one or more of the following characteristics:

[0019] The pore size of the ultrafiltration membrane used is 0.002–0.05 μm;

[0020] The temperature for the first ultrafiltration is 2–10°C;

[0021] The concentration ratio of the first ultrafiltration is 1.1 to 4.2.

[0022] Preferably, the conditions for performing the reverse osmosis include one or more of the following characteristics:

[0023] The reverse osmosis membrane used has a pore size of ≤0.5nm;

[0024] The temperature for reverse osmosis is 2–10°C;

[0025] The concentration ratio during reverse osmosis is 1.3 to 15.0.

[0026] Preferably, the conditions for performing the nanofiltration include one or more of the following characteristics:

[0027] The nanofiltration membrane used has a pore size of 0.5–2 nm;

[0028] The temperature for nanofiltration is 2–10 °C;

[0029] The concentration ratio during nanofiltration is 1.3 to 15.0.

[0030] Preferably, during mixing in step 3-2), the volume ratio of the reverse osmosis or permeate to the first ultrafiltration retentate is 1:(0.1-3.2). For example, it can be 1:(0.8-1), 1:(0.8-3.2), or 1:(0.1-1).

[0031] More preferably, in step 3-2), the total solids content in the mixture is 40% to 80% of the total solids content in the initial skim milk in step 1). More preferably, the total solids content in the mixture is 50% of the total solids content in the initial skim milk in step 1).

[0032] In this application, the total solids content in the mixed liquid is a crucial parameter, requiring it to be between 40% and 80% of the total solids content in the initial skim milk in step 1), more preferably between 40% and 60%. Only within this specific parameter range can the subsequent second ultrafiltration proceed smoothly. If the total solids content in the mixed liquid is too high, such as exceeding 80% of the total solids content in the initial skim milk, it will significantly increase the number of repeated washing and filtration, resulting in unnecessary waste of resources. If the number of washing and filtration is not significantly increased, the sugar content cannot be significantly reduced, leading to a high lactose content in the final product. If the total solids content in the mixed liquid is too low, such as below 40% of the total solids content in the initial skim milk, the subsequent second ultrafiltration will result in an extremely high ultrafiltration concentration ratio, even exceeding the capacity of the ultrafiltration equipment, preventing further protein concentration and failing to achieve the technical effect of simultaneously achieving high protein and zero sugar.

[0033] Preferably, in step 3-3), when the mixture is subjected to a second ultrafiltration, the ultrafiltration concentration ratio is higher than the concentration ratio of the first ultrafiltration in step 2).

[0034] In this application, the concentration ratio during the second ultrafiltration is also a very important technical means, which ensures that the protein content in the ultrafiltration retentate is higher after each wash than before the wash. More specifically, when setting the concentration ratio for the second ultrafiltration, the concentration ratio should be set with the goal of achieving a higher protein content than after the previous ultrafiltration concentration.

[0035] In this application, the washing and filtration process is a crucial technical means. Through a washing and filtration cycle with specific parameters, the sugar content in the product gradually decreases while the protein content gradually increases. Specifically, after each washing and filtration cycle, the sugar content in the ultrafiltration retentate is lower than before that washing and filtration cycle. Conversely, after each washing and filtration cycle, the protein content in the ultrafiltration retentate is higher than before that washing and filtration cycle.

[0036] Preferably, the washing and filtering process in step 3) is repeated 3 to 5 times.

[0037] Preferably, the pasteurization temperature in step 1) is 68–75°C and the time is 15–60 seconds.

[0038] The third aspect of the present invention provides a high-protein, zero-sugar dairy beverage, wherein the high-protein, zero-sugar dairy beverage is based on the high-protein, zero-sugar skim milk described above, and after being mixed with other ingredients, it forms a high-protein, zero-sugar dairy beverage.

[0039] Preferably, the temperature during ingredient preparation is 45–60°C.

[0040] Preferably, all ingredients added during preparation are sugar-free food ingredients or food additives. These can include sweeteners, colorings, antioxidants, acidity regulators, and other food ingredients, as long as they meet the requirements of being sugar-free and complying with the dairy beverage standard GB / T21732.

[0041] Preferably, after the ingredients are prepared, a second sterilization process is required, which includes any one or more of pasteurization, high-temperature sterilization, and ultra-high-temperature sterilization.

[0042] Specifically, a homogenization step can be added before the second sterilization to ensure that the various components in the dairy beverage are fully and evenly mixed.

[0043] Preferably, based on the total mass of the high-protein, zero-sugar dairy beverage, the protein content in the high-protein, zero-sugar dairy beverage is ≥6.0g / 100g; the sugar content is ≤0.5g / 100g.

[0044] Preferably, based on the total mass of the high-protein, zero-sugar dairy beverage, the calcium content in the high-protein, zero-sugar dairy beverage is ≥180g / 100g.

[0045] The fourth aspect of the present invention provides a high-protein, zero-sugar dairy beverage, the high-protein, zero-sugar dairy beverage comprising the following raw material components: erythritol, concentrated apple juice, sodium bicarbonate, sodium D-isoascorbate, β-carotene and high-protein, zero-sugar skim milk as described above.

[0046] Preferably, based on the total mass of the high-protein, zero-sugar dairy beverage, the protein content in the high-protein, zero-sugar dairy beverage is ≥6.0g / 100g; the sugar content is ≤0.5g / 100g.

[0047] Preferably, based on the total mass of the high-protein, zero-sugar dairy beverage, the calcium content in the high-protein, zero-sugar dairy beverage is ≥180g / 100g.

[0048] The fifth aspect of the present invention provides a high-protein, zero-sugar dairy beverage, the high-protein, zero-sugar dairy beverage comprising the following raw material components: salt, citric acid, sodium bicarbonate, erythritol, vitamin E, vitamin B6, food flavoring, and high-protein, zero-sugar skim milk as described above.

[0049] Preferably, based on the total mass of the high-protein, zero-sugar dairy beverage, the protein content in the high-protein, zero-sugar dairy beverage is ≥6.0g / 100g; the sugar content is ≤0.5g / 100g.

[0050] Preferably, based on the total mass of the high-protein, zero-sugar dairy beverage, the calcium content in the high-protein, zero-sugar dairy beverage is ≥180g / 100g.

[0051] The beneficial effects of this invention are:

[0052] The technical solution provided by this invention adopts a production process of ultrafiltration combined with washing and filtration. By setting specific process parameters, including the mixing target after washing and filtration and the ultrafiltration parameters during the circulating washing and filtration process, the dairy beverage with high protein content and zero sugar in this application is obtained.

[0053] Compared with other dairy-containing beverages on the market, the dairy-containing beverage provided by the technical solution of this invention has a higher protein content and a lower sugar content (sugar content ≤0.5g / 100g), making it very suitable for people who need to supplement protein without causing any other nutritional burden.

[0054] The raw material formula of the high-protein, zero-sugar dairy beverage in this application does not contain any additional protein powder, whey powder or other raw materials. It only performs specific processing on the raw milk, and no additional water is added during the process. It contains no ingredients that ensure the original refreshing taste and avoids the unpleasant flavor that may be caused by the addition of protein powder, whey powder or other raw materials. Attached Figure Description

[0055] Figure 1 The diagram shown is a process flow chart for the high-protein, zero-sugar dairy beverage provided by this invention. Detailed Implementation

[0056] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0057] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0058] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0059] In existing technologies, when using ultrafiltration to concentrate protein and increase the protein content in raw milk, the carbohydrate (sugar) content does not change significantly. The "high protein, zero sugar" technical effect requires the opposite of a balance between protein and carbohydrate (sugar) in the same raw milk. Therefore, it is extremely difficult to simultaneously increase protein content and significantly reduce sugar content using only membrane separation technology (ultrafiltration).

[0060] Specifically, ultrafiltration concentration results in higher protein content, but the sugar content does not decrease proportionally. Furthermore, higher protein content can increase the total solids content or viscosity of the liquid, further complicating sugar removal. Conversely, reducing sugar content through washing and filtration also leads to a further decrease in protein content after mixing. It is precisely because of these opposing goals of high protein and zero sugar that it is difficult for dairy products to achieve both. Currently, there is no product on the market that can achieve both high protein and zero sugar without adding other food ingredients or additives.

[0061] Through extensive exploration and experimentation, the inventors of this application discovered that by using a specific production process—separating raw milk to obtain skim milk and cream, and then subjecting the skim milk to pasteurization, ultrafiltration, and circulating filtration (NF / RO filtration-mixing-ultrafiltration), and finally adding other ingredients—a high-protein, zero-sugar dairy beverage can be obtained, with a protein content ≥6.0g / 100mL and a sugar content ≤0.5g / 100mL.

[0062] This invention utilizes a combination of membrane filtration processes. Ultrafiltration technology is used to increase protein content while washing and filtering to reduce sugar content. By combining specific mixing targets and washing and filtering process parameters, high-protein, zero-sugar skim milk is ultimately produced without adding any food ingredients or additives. This results in a high-protein, zero-sugar dairy beverage, solving the problems of low protein and low nutritional value in traditional dairy beverages. It also solves the problem that high-protein beverages and milkshakes require the addition of exogenous protein powder, whey powder, etc., which introduces unpleasant flavors.

[0063] The concentration factor (CF) mentioned in this application is the initial feed flow rate / retentate flow rate.

[0064] The term "zero sugar" as used in this application refers to a product with extremely low sugar content, which can be ignored, specifically sugar content ≤ 0.5g / 100g.

[0065] Example 1

[0066] This embodiment provides a specific high-protein, zero-sugar dairy beverage and its preparation method, including the following steps:

[0067] 1) Separation

[0068] Raw milk is heated to 52°C and separated into skim milk and cream using a centrifuge, so that the fat content of the skim milk is 0.05%. The skim milk is then pasteurized at 75°C for 15 seconds and then cooled to below 6°C for later use.

[0069] 2) First ultrafiltration

[0070] The pasteurized skim milk in step 1) is concentrated by ultrafiltration. The ultrafiltration concentration temperature is 8°C, the ultrafiltration membrane pore size is 0.05μm, and the concentration ratio is 1.5 to obtain the first ultrafiltration retentate and the first ultrafiltration permeate.

[0071] 3) Washing and filtering

[0072] 3-1) The first ultrafiltration permeate in step 2) is subjected to reverse osmosis (RO) filtration, wherein the temperature of reverse osmosis filtration is 8°C, the pore size of the reverse osmosis filtration membrane is 0.3nm, the concentration ratio is 6.0, and RO retentate and RO permeate are obtained.

[0073] 3-2) Mix the RO permeate with the first ultrafiltration cutoff solution obtained in step 2) (the mixing ratio is first ultrafiltration cutoff solution: RO permeate solution = 1:0.8) to obtain a mixture.

[0074] 3-3) The mixture is subjected to ultrafiltration concentration again, wherein the ultrafiltration concentration conditions are the same as in step 2), except that the concentration ratio is 2.0, to obtain the second ultrafiltration retentate and the second ultrafiltration permeate.

[0075] Repeat the "RO filtration-mixing-ultrafiltration" process in step 3) three times to obtain high-protein, sugar-free skim milk with protein ≥7.2g / 100g and carbohydrates (sugar) ≤0.4g / 100g.

[0076] 4) Ingredients

[0077] Mix the ingredients according to the following formula at 50°C:

[0078] Based on the total mass of the raw materials for the final product, add 3% erythritol, 7% concentrated apple juice, 0.1% sodium bicarbonate, 0.2% sodium D-isoascorbate, and 0.005% β-carotene, with the remainder being the high-protein, sugar-free skim milk obtained in step 3).

[0079] 5) High-temperature sterilization

[0080] The semi-finished product obtained in step 4) is sterilized at 120°C for 25 seconds and then cooled to 2-6°C to obtain the final product.

[0081] Example 2

[0082] This embodiment provides a specific high-protein, zero-sugar dairy beverage and its preparation method, including the following steps:

[0083] 1) Separation

[0084] Same as in Example 1;

[0085] 2) First ultrafiltration

[0086] The pasteurized skim milk in step 1) was concentrated by ultrafiltration. Except for the concentration ratio of 1.6, the other conditions were the same as in Example 1 to obtain the first ultrafiltration retentate and the first ultrafiltration permeate.

[0087] 3) Washing and filtering

[0088] 3-1) The first ultrafiltration permeate in step 2) is subjected to nanofiltration (NF), wherein the NF filtration temperature is 8°C, the membrane pore size is 1 nm, and the concentration ratio is 6.0, to obtain NF retentate and NF permeate;

[0089] 3-2) Mix the NF permeate with the first ultrafiltration cutoff solution obtained in step 2) (the mixing ratio is ultrafiltration cutoff solution: NF permeate solution = 1:1) to obtain a mixture.

[0090] 3-3) The mixture is subjected to ultrafiltration concentration again, wherein the ultrafiltration concentration temperature conditions are the same as in step 2), except that the concentration ratio is 2.2, to obtain the second ultrafiltration retentate and the second ultrafiltration permeate.

[0091] Repeat the "NF filtration-mixing-ultrafiltration" process in step 3) three times to obtain high-protein, sugar-free skim milk with protein ≥7.2g / 100g and carbohydrates (sugar) ≤0.4g / 100g.

[0092] 4) Ingredients

[0093] Mix the ingredients according to the following formula at 50°C:

[0094] Based on the mass of raw materials for every 100g of final product, add 0.01g salt, 0.15g citric acid, 0.1g sodium bicarbonate, 3g erythritol, 1.8mg α-TE vitamin E, 0.2mg vitamin B6, and 0.05g food flavoring, with the remainder being the high-protein, sugar-free skim milk obtained in step 3).

[0095] 5) High-temperature sterilization

[0096] The semi-finished product obtained in step 4) is sterilized at 120°C for 25 seconds and then cooled to 2-6°C to obtain the final product.

[0097] Example 3

[0098] This embodiment provides a specific high-protein, zero-sugar dairy beverage and its preparation method, including the following steps:

[0099] 1) Separation

[0100] Same as in Example 1;

[0101] 2) First ultrafiltration

[0102] Same as in Example 1; a first ultrafiltration retentate and a first ultrafiltration permeate were obtained;

[0103] 3) Washing and filtering

[0104] 3-1) The first ultrafiltration permeate in step 2) is subjected to reverse osmosis (RO) filtration, wherein the reverse osmosis filtration conditions are the same as in Example 1, to obtain RO retentate and RO permeate;

[0105] 3-2) Mix the RO permeate with the first ultrafiltration retentate obtained in step 2) so that the total solids in the mixture are 50% of the total solids of the initial skim milk after pasteurization in step 1), and obtain the mixture.

[0106] 3-3) The mixture is subjected to ultrafiltration concentration again, wherein the conditions for ultrafiltration concentration are the same as in step 2), except that the concentration ratio is different. The concentration ratio is set with the goal of increasing the protein content by 0.6% compared with the protein content after the previous ultrafiltration concentration, to obtain the second ultrafiltration retentate and the second ultrafiltration permeate.

[0107] Repeat the "RO filtration-mixing-ultrafiltration" process in step 3) twice to obtain high-protein, sugar-free skim milk with protein ≥7.0g / 100g and carbohydrates (sugar) ≤0.5g / 100g.

[0108] 4) Ingredients

[0109] Mix the ingredients according to the following formula at 50°C:

[0110] Based on the total mass of the raw materials for the final product, add 3% erythritol, 7% concentrated apple juice, 0.1% sodium bicarbonate, 0.2% sodium D-isoascorbate, and 0.005% β-carotene, with the remainder being the high-protein, sugar-free skim milk obtained in step 3).

[0111] 5) High-temperature sterilization

[0112] The semi-finished product obtained in step 4) is sterilized at 120°C for 25 seconds and then cooled to 2-6°C to obtain the final product.

[0113] Example 4

[0114] This embodiment provides a specific high-protein, zero-sugar dairy beverage and its preparation method, including the following steps:

[0115] 1) Separation

[0116] Same as in Example 2;

[0117] 2) First ultrafiltration

[0118] Same as in Example 2; except that the concentration ratio is 1.6, a first ultrafiltration retentate and a first ultrafiltration permeate are obtained;

[0119] 3) Washing and filtering

[0120] 3-1) The first ultrafiltration permeate from step 2) is subjected to nanofiltration (NF), wherein the NF conditions are the same as in Example 2, to obtain NF retentate and NF permeate;

[0121] 3-2) Mix the NF permeate with the first ultrafiltration retentate obtained in step 2) so that the total solids in the mixture are 50% of the total solids of the initial skim milk after pasteurization in step 1), and obtain the mixture.

[0122] 3-3) The mixture is subjected to ultrafiltration concentration again, wherein the conditions for ultrafiltration concentration are the same as in step 2), except that the concentration ratio is different. The concentration ratio is set with the goal of increasing the protein content by 0.5% compared with the protein content after the previous ultrafiltration concentration, to obtain the second ultrafiltration retentate and the second ultrafiltration permeate.

[0123] Repeat step 3) of the “NF filtration-mixing-ultrafiltration concentration” process twice to obtain high-protein, zero-sugar skim milk with protein ≥6.8g / 100g and carbohydrates (sugar) ≤0.5g / 100g.

[0124] 4) Ingredients

[0125] Mix the ingredients according to the following formula at 50°C:

[0126] Based on the mass of raw materials for every 100g of final product, add 0.01g salt, 0.15g citric acid, 0.1g sodium bicarbonate, 3g erythritol, 1.8mg α-TE vitamin E, 0.2mg vitamin B6, and 0.05g food flavoring, with the remainder being the high-protein, sugar-free skim milk obtained in step 3).

[0127] 5) High-temperature sterilization

[0128] The semi-finished product obtained in step 4) is sterilized at 120°C for 15 seconds and then cooled to 2-6°C to obtain the final product.

[0129] Comparative Example 1

[0130] This comparative example provides a dairy-containing beverage and its preparation method, including the following steps:

[0131] 1) Separation

[0132] Same as in Example 4;

[0133] 2) First ultrafiltration

[0134] Same as in Example 4;

[0135] 3) Washing and filtering

[0136] Except for step 3-2), where the NF permeate is mixed with the first ultrafiltration retentate obtained in step 2), and the total solids in the mixture are 100% of the initial total solids of the skim milk after pasteurization in step 1), the rest is exactly the same as in Example 4.

[0137] 4) Ingredients

[0138] Same as in Example 4;

[0139] 5) High-temperature sterilization

[0140] Same as in Example 4; the final product is obtained.

[0141] Comparative Example 2

[0142] This comparative example provides a dairy-containing beverage and its preparation method, including the following steps:

[0143] 1) Separation

[0144] Same as in Example 4;

[0145] 2) First ultrafiltration

[0146] Same as in Example 4;

[0147] 3) Washing and filtering

[0148] Except for step 3-2), where the total solids content in the mixture after mixing with the first ultrafiltration retentate obtained in step 2) is 20% of the total solids content of the initial skim milk after pasteurization in step 1), the rest of the NF portion is exactly the same as in Example 4.

[0149] The mixture was then subjected to ultrafiltration concentration again, wherein the ultrafiltration concentration conditions were the same as in Example 4.

[0150] However, the applicant discovered that during the secondary ultrafiltration concentration process, the total solids (including protein) content in the mixed solution was too low. In order to make the protein content in the secondary ultrafiltration retentate higher than that in the first ultrafiltration retentate, the concentration ratio of ultrafiltration concentration needed to be further increased. However, this ideal concentration ratio exceeded the range that the existing ultrafiltration concentration equipment could handle (concentration ratio of 1.1-4.2), making it impossible to further increase the protein content.

[0151] Therefore, when the total solids content in the mixed liquid is too low, it is impossible to obtain the dairy beverage that combines high protein and zero sugar as described in this application.

[0152] Comparative Example 3

[0153] This comparative example provides a method for preparing a milk-containing beverage, comprising the following steps:

[0154] 1) Separation

[0155] Same as in Example 2;

[0156] 2) First ultrafiltration

[0157] Same as in Example 2;

[0158] 3) Washing and filtering

[0159] Except for step 3-3), where the concentration ratio of ultrafiltration is 1.6 when the mixture is concentrated again by ultrafiltration, the rest is exactly the same as in Example 2.

[0160] 4) Ingredients

[0161] Same as in Example 2;

[0162] 5) High-temperature sterilization

[0163] Same as Example 2.

[0164] The applicant discovered that during the washing and filtration cycle in step 3), if the concentration ratio during the second ultrafiltration concentration is too low, i.e. not higher than the first ultrafiltration concentration ratio in step 2), the protein cannot be further concentrated to increase the protein content, and thus a dairy beverage that balances high protein and zero sugar cannot be obtained.

[0165] Comparative Example 4

[0166] This comparative example provides a method for preparing a milk-containing beverage, comprising the following steps:

[0167] 1) Separation

[0168] Same as in Example 2;

[0169] 2) First ultrafiltration

[0170] Same as in Example 2;

[0171] 3) Washing and filtering

[0172] Except for step 3-3), where the concentration ratio of ultrafiltration is 3.0 when the mixture is concentrated again by ultrafiltration, the rest is exactly the same as in Example 2.

[0173] However, due to the excessively high ultrafiltration concentration ratio during the washing process in step 3), the protein and total solids content in the ultrafiltration retentate is too high when the washing process is repeated. The protein forms a weak gel in the solution, which leads to an abnormal increase in equipment pressure and a decrease in overall flow rate, making it impossible to continue concentration.

[0174] Comparative Example 5

[0175] This comparative example provides a method for preparing a milk-containing beverage, comprising the following steps:

[0176] 1) Pasteurize the raw milk at 75°C for 15 seconds, then cool it down to below 6°C for later use; do not defatt the raw milk.

[0177] 2) First ultrafiltration

[0178] Same as Example 1.

[0179] 3) Washing and filtering

[0180] Same as Example 1.

[0181] However, the applicant discovered that during the repeated "RO filtration-mixing-ultrafiltration" process, since the milk was not skimmed, the total solids content of the ultrafiltration retentate was already high during repeated washing and filtration. Even with a lower concentration ratio, the equipment pressure had reached its limit, making it impossible to further concentrate and increase the protein content (protein content ≤5g / 100g). At the same time, it was found that the presence of fat exacerbated the clogging of the ultrafiltration membrane during the ultrafiltration protein concentration process, resulting in a significant reduction in the service life of the equipment.

[0182] Therefore, without defatting the raw milk, it is impossible to obtain the dairy beverage that combines high protein and zero sugar as described in this application.

[0183] Comparative Example 6

[0184] This comparative example provides a method for preparing a milk-containing beverage, comprising the following steps:

[0185] Except for step 1), where the raw milk was not pasteurized after separation, the rest of the steps are exactly the same.

[0186] The applicant investigated the shelf life (in days), protein, sugar, and calcium content of the dairy-containing beverages obtained in Examples 1-4 and Comparative Examples 1-6 under refrigeration at 10°C.

[0187] Shelf life under refrigeration: After the above high-protein milk samples were filled, they were placed in a constant temperature incubator at 10℃ to determine the shelf life. The shelf life was defined as when the total number of colonies in the sample exceeded 10,000 or the appearance was obviously deteriorated.

[0188] Protein content was determined according to the standard GB 5009.5, "National Food Safety Standard - Determination of Protein in Food". Sugar content was determined according to the standard GB 5009.8, "National Food Safety Standard - Determination of Fructose, Glucose, Sucrose, Maltose and Lactose in Food".

[0189] Calcium content was determined according to the standard GB 5009.92 National Food Safety Standard - Determination of Calcium in Food.

[0190] The specific results are shown in Table 1 below.

[0191] Table 1

[0192]

[0193]

[0194] As shown in Table 1, the milk-containing beverages prepared by the technical solution of this application have a protein content of more than 6g / 100g and a sugar content of less than 0.4g / 100g, thus possessing both high protein and near-zero sugar characteristics. They are rich in nutrients and are very suitable for people with fitness needs or those who need to supplement protein. The zero sugar characteristic will not cause a burden on other nutrients.

[0195] Compared to Examples 1-2, the technical solutions in Examples 3-4 only repeated the washing and filtration process (NF / RO filtration-mixing-ultrafiltration concentration) three times. Despite repeating the washing and filtration process one less time than in Examples 1-2, the protein content of the product obtained from the technical solutions in Examples 3-4 is almost the same as, only slightly lower than, the protein content of the product obtained from Examples 1-2, and the sugar content is also lower than 0.4 g / 100 g. This indicates that the technical solutions provided in Examples 3-4 are superior to those provided in Examples 1-2.

[0196] Compared to Example 4, the product obtained in Comparative Example 1 had a lower protein content and a higher sugar content; while Comparative Example 2 also failed to produce a product that met the requirements. This indicates that when using the permeate from the washing filter to mix the ultrafiltration retentate, the total solids content in the resulting mixture is very important and has a specific parameter range. If it is too high or too low, the high-protein, zero-sugar dairy beverage described in this application cannot be obtained.

[0197] Compared to Example 2, the product obtained in Comparative Example 3 had a lower protein content; while Comparative Example 4, due to its high protein content during concentration, formed a weak gel, making it impossible to obtain a product that met the requirements. This indicates that when performing ultrafiltration concentration again on the mixed liquid after washing and filtration, the concentration ratio parameter is very important. If the concentration ratio is set too high or too low, the high-protein, zero-sugar dairy beverage described in this application cannot be obtained.

[0198] Compared to Example 1, the product obtained in Comparative Example 5 has a low protein content because the washing and filtration process (NF / RO filtration-mixing-ultrafiltration concentration) cannot be repeated. Furthermore, the presence of fat exacerbates the clogging of the ultrafiltration membrane, resulting in a significant reduction in the equipment's lifespan.

[0199] Compared with Example 1, Comparative Example 6 did not use pasteurization before ultrafiltration concentration, which led to a large increase in microorganisms during the concentration process, producing heat-resistant microbial enzymes. It also further produced odors and unpleasant flavors. Even after high-temperature sterilization, the enzymes could not be completely inactivated. As time went on, the unpleasant flavors produced by enzyme-catalyzed protein decomposition became more severe, and the shelf life of 4-5 days was unacceptable.

[0200] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A high-protein, zero-sugar skim milk for use as a raw material in formulated dairy beverages, characterized in that, Based on the total mass of the high-protein, zero-sugar skim milk, the protein content in the high-protein, zero-sugar skim milk is ≥6.5g / 100g; the sugar content is ≤0.5g / 100g.

2. A method for preparing high-protein, zero-sugar skim milk as described in claim 1, characterized in that, Includes the following steps: 1) Separation: The raw milk is separated to obtain light cream and initial skim milk, and the initial skim milk is pasteurized; 2) First ultrafiltration: The initial skim milk is filtered through an ultrafiltration membrane to obtain the first ultrafiltration retentate and the first ultrafiltration permeate; 3) Repeat washing and filtration until the protein content of the ultrafiltration retentate is ≥6.5g / 100g and the sugar content is ≤0.5g / 100g; a single washing and filtration includes the following steps: 3-1) Perform reverse osmosis and / or nanofiltration on the first ultrafiltration permeate to obtain reverse osmosis or nanofiltration permeate; 3-2) Mix the reverse osmosis or nanofiltration permeate with the first ultrafiltration retentate to obtain a mixed solution; 3-3) Perform a second ultrafiltration on the mixture to obtain a second ultrafiltration retentate and a second ultrafiltration permeate.

3. The preparation method according to claim 2, characterized in that, The raw milk includes raw cow's milk; And / or, the initial skim milk has a fat content of <0.05 wt%; And / or, in step 2), the conditions during the first ultrafiltration include one or more of the following characteristics: The pore size of the ultrafiltration membrane used is 0.002–0.05 μm; The temperature for the first ultrafiltration is 2–10°C; The concentration ratio of the first ultrafiltration is 1.1 to 4.2; And / or, the washing and filtering process in step 3) is repeated 3 to 5 times.

4. The preparation method according to claim 2, characterized in that, The conditions for performing the reverse osmosis include one or more of the following characteristics: The reverse osmosis membrane used has a pore size of ≤0.5nm; The temperature for reverse osmosis is 2–10°C; The concentration ratio during reverse osmosis is 1.3–15.0; And / or, the conditions for performing the nanofiltration include one or more of the following characteristics: The nanofiltration membrane used has a pore size of 0.5–2 nm; The temperature for nanofiltration is 2–10 °C; The concentration ratio during nanofiltration is 1.3 to 15.

0.

5. The preparation method according to claim 2, characterized in that, When mixing in step 3-2), the volume ratio of the reverse osmosis or nanofiltration permeate to the first ultrafiltration retentate is 1:(0.1~3.2). And / or, in step 3-3), when the mixture is subjected to a second ultrafiltration, the ultrafiltration concentration ratio is higher than the concentration ratio of the first ultrafiltration in step 2); And / or, the pasteurization temperature in step 1) is 68–75°C and the time is 15–60 s.

6. The preparation method according to claim 2, characterized in that, In step 3-2), the total solids content in the mixture is 40% to 80% of the total solids content in the initial skim milk in step 1).

7. A high-protein, zero-sugar dairy beverage, characterized in that, The high-protein, zero-sugar dairy beverage uses the high-protein, zero-sugar skim milk as described in claim 1 as the base ingredient, and after mixing, it forms a high-protein, zero-sugar dairy beverage.

8. A high-protein, zero-sugar dairy beverage, characterized in that, The high-protein, zero-sugar dairy beverage comprises the following ingredients: erythritol, concentrated apple juice, sodium bicarbonate, sodium D-isoascorbate, β-carotene, and the high-protein, zero-sugar skim milk as described in claim 1.

9. A high-protein, zero-sugar dairy beverage, characterized in that, The high-protein, zero-sugar dairy beverage comprises the following ingredients: salt, citric acid, sodium bicarbonate, erythritol, vitamin E, vitamin B6, food flavoring, and the high-protein, zero-sugar skim milk as described in claim 1.

10. The high-protein, zero-sugar dairy beverage according to claim 8 or 9, characterized in that, Based on the total mass of the high-protein, zero-sugar dairy beverage, the protein content in the high-protein, zero-sugar dairy beverage is ≥6.0g / 100g; the sugar content is ≤0.5g / 100g. And / or, based on the total mass of the high-protein, zero-sugar dairy beverage, the calcium content in the high-protein, zero-sugar dairy beverage is ≥180g / 100g.

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