A method for improving the stability of whipping cream based on directional back addition of membrane separation milk protein components

Abstract

The application discloses a method for improving the stability of whipped cream by adding functional milk protein components extracted from skim milk through membrane separation, comprising the following steps: first, preheat skim milk to 45-55 DEG C, and concentrate it through ultrafiltration with an ultrafiltration membrane with a molecular weight cut-off of 10-30 kDa; then, wash the obtained retentate through ultrafiltration with an ultrafiltration membrane with a molecular weight cut-off of 50-100 kDa to remove part of lactose and small-molecule minerals, and obtain a functional milk protein concentrate component (MPC-F) with a protein content of greater than or equal to 65% (dry basis) and a mass ratio of casein to whey protein of 3:1-4:1; the application extracts functional milk protein components from skim milk of the same milk source through membrane separation and adds them into whipped cream, and constructs a dense natural protein interface film on the surface of fat globules, thereby solving the problems that the prior art relies on exogenous additives to cause flavor distortion, the whipped cream is prone to instability during long-term storage, and the whipped cream is prone to stratification under the temperature fluctuation of a cold chain, and simultaneously realizing high-value utilization of by-products and clean label production.

Description

Technical Field

[0001] This invention relates to the field of dairy processing technology, specifically to a method for improving the stability of light cream based on the directional reintroduction of milk protein components separated by membrane. Background Technology

[0002] Whipping cream is an O / W emulsion with a milk fat content of ≥30% obtained from cow's milk through centrifugation. It is widely used in baking, desserts, coffee beverages, and the catering industry. During storage, whipping cream is prone to instability phenomena such as fat floating, protein precipitation, emulsion flocculation, and oil-water separation, which seriously restricts its shelf life and distribution radius.

[0003] Current technologies generally improve the stability of light cream by adding exogenous emulsifiers and thickeners. For example: Chinese patent CN101731361B discloses a type of whipping cream, its preparation method, and its uses. The whipping cream formula contains 0.1-0.55% stabilizer, 0.05-0.35% emulsifier, and 0.005-0.15% buffer salt. Although it can be stored at room temperature for 6-9 months, the large amount of exogenous additives affects the natural flavor of the product and its clean label attributes.

[0004] Chinese patent CN111248294A describes an emulsifying stabilizer for whipped cream, its preparation method, and its application. It uses α-crystalline mono- and diglyceride fatty acid esters as emulsifying stabilizers, which can improve the foam stability of whipped cream, but still relies on exogenous synthetic emulsifiers.

[0005] Chinese patent CN115530242B describes a compound agent for improving the stability of butter, its preparation method, and its application. It uses a compound emulsifier (propylene glycol alginate, glyceryl citrate, etc.), thickener, and antioxidant. Although it can improve acid resistance and whipping stability, the formula is complex and costly.

[0006] Chinese patent CN120501153A describes a highly stable cream and its preparation method, which uses sodium caseinate and xanthan gum to form a stabilizer under pH 4-6 conditions. Although this reduces the amount of stabilizer used, xanthan gum and sodium caseinate still need to be added exogenously.

[0007] The common drawbacks of the above technologies are that they all rely on exogenous food additives, which does not conform to the current "clean label" consumption trend; and the compatibility of exogenous stabilizers with the natural milk fat system is limited, and excessive addition can easily lead to a sticky texture, obvious gelatinous feel, and distorted flavor.

[0008] Currently, Chinese patent CN115363097A discloses a liquid dairy product and its preparation method and application, which involves heat treatment (95-105℃ / 15-30s) of light cream alone, followed by secondary homogenization (40-50bar / 200-250bar) and nitrogen filling (10-18% by volume). Although this can improve the problem of oxidized taste in the later stages of shelf life, it is an improvement on the overall process of liquid dairy products and does not specifically strengthen the stability of the fat globule interface unique to light cream.

[0009] Chinese patent CN115399375A discloses a low-fat frozen margarine and its preparation method, which uses a combination of a mixer and a high-speed shear mixer to suppress the growth of ice crystals. However, it is mainly aimed at frozen scenarios and has limited effect on improving the stability of conventional refrigerated shelf life.

[0010] Chinese patent CN118077780A discloses a low-fat whipped cream and its preparation method. The method involves controlling the adsorption amount on the surface of fat globules by combining casein components in different aggregation states to construct a stable low-fat whipped cream system. However, this technology focuses on the physical state control of casein components and does not involve the technical route of obtaining specific functional protein components from the same milk source through membrane separation and re-adding them.

[0011] In summary, the existing technology has the following unresolved technical problems: (1) There is a lack of technology to use the membrane separation equipment owned by dairy companies to separate specific functional protein components from the by-products (skim milk or whey) of the same batch of raw milk and add them back into light cream to enhance the interfacial stability. (2) There is a lack of technology to achieve long shelf-life stability of light cream by “targeted fortification of endogenous protein components” while reducing or replacing exogenous stabilizers; (3) There is a lack of technology to improve the stability of cream in scenarios where China’s cold chain storage and transportation system is imperfect and products frequently encounter temperature fluctuations (4-25℃ cycles).

[0012] To address this issue, a method for improving the stability of light cream based on the targeted reintroduction of membrane-separated milk protein components is proposed. Summary of the Invention

[0013] The purpose of this invention is to provide a method for improving the stability of cream by directionally adding milk protein components based on membrane separation. Functional milk protein components are extracted from skim milk from the same milk source through membrane separation and directionally added back to cream. A dense natural protein interface membrane is constructed on the surface of fat globules, thereby solving the problems of flavor distortion caused by reliance on exogenous additives, easy instability of cream during long-term storage, and easy stratification under cold chain temperature fluctuations in existing technologies. At the same time, it realizes high-value utilization of by-products and clean label production.

[0014] To achieve the above objectives, the present invention provides the following technical solution: a method for improving the stability of light cream based on the directional reintroduction of membrane-separated milk protein components, comprising the following steps: Step 1: Skim milk membrane separation: First, the skim milk is preheated to 45-55°C and concentrated by ultrafiltration through an ultrafiltration membrane with a molecular weight cutoff of 10-30 kDa. Then, the resulting retentate is washed through an ultrafiltration membrane with a molecular weight cutoff of 50-100 kDa to remove some lactose and small molecule minerals, obtaining a functional milk protein concentrate (MPC-F) with a protein content of ≥65% on a dry basis and a casein to whey protein ratio of 3:1 to 4:1. Step 2: Activation of whey protein: The obtained MPC-F is then prepared into an aqueous dispersion with a protein concentration of 8-15%. It is preheated at 60-70°C for 10-20 minutes to allow the whey protein to undergo moderate thermal denaturation (denaturation rate controlled at 20-40%), exposing more hydrophobic groups and enhancing its interfacial activity. Subsequently, it is rapidly cooled to 4-8°C and allowed to stand for aging for 2-4 hours to allow the protein molecules to form moderate pre-aggregates, thus obtaining the activated MPC-F aqueous dispersion. Step 3: Preparation of whipped cream base: At the same time, whipped cream base with a fat content of 35-40% is obtained by separating the raw milk through a disc centrifuge. Step 4: Targeted Refilling: Then, the activated MPC-F aqueous dispersion is refilled into the cream base at a ratio of 2.0-6.0% of the total mass of the finished cream (0.5-2.0% based on dry protein). Step 5: Specific Processing: Finally, the above-mentioned mixed materials are preheated and degassed, subjected to two-stage high-pressure homogenization, UHT sterilization, and directional cooling aging processes, and then filled under aseptic conditions to obtain a high-stability light cream product.

[0015] Preferably, in step 1, the operating pressure for ultrafiltration concentration is 0.15–0.35 MPa, the membrane surface flow rate is 2.5–4.0 m / s, and the concentration factor is 2.5–4.0 times.

[0016] Preferably, in step 1, MPC-F is derived from skim milk separated by centrifugation from the same batch of raw milk as the cream, or from whey produced as a byproduct during the cream production process; preferably from skim milk from the same batch of raw milk to ensure the natural compatibility of the protein components with the fat globules of the cream.

[0017] Preferably, in step 3, the centrifugation temperature of the disc centrifuge is 50-60°C, and the separation factor is ≥6000 to ensure the integrity of the fat globule structure.

[0018] Preferably, in step 4, when MPC-F is refilled, 0.02% to 0.08% of edible salt can be selectively added to adjust the ionic strength and promote the adsorption of protein at the fat globule interface.

[0019] Preferably, in step 4, the backfilling method is online injection mixing, the mixing temperature is 50-60℃, and the mixture is stirred for 10-15 minutes after mixing to ensure uniform dispersion.

[0020] Preferably, in step 5, the preheating and degassing process is as follows: the mixed material is preheated to 65-75°C and degassed for 5-10 minutes under a vacuum of -0.06 to -0.08 MPa, thereby removing dissolved oxygen and bubbles from the material, reducing the risk of oxidation and bubble interference before homogenization.

[0021] Preferably, in step 5, the two-stage high-pressure homogenization process is as follows: Primary homogenization: pressure 15-20 MPa (150-200 bar), temperature 60-70℃, its function is to break up fat globules and initially reduce the dispersion of particle size distribution; Secondary homogenization: pressure 3-5 MPa (30-50 bar), temperature 50-60℃, its function is to further refine the size of fat globules and reduce the damage to the natural structure of milk fat by mechanical shearing.

[0022] After homogenization, the volume average particle size D[4,3] of the target fat globules was controlled between 0.6 and 1.2 μm, and the particle size distribution was unimodal or narrow bimodal, with a span value ((D90-D10) / D50) ≤ 1.5.

[0023] Preferably, in step 5, the UHT sterilization adopts an indirect UHT sterilization process with a temperature of 135-140°C and a time of 3-5 seconds, which can achieve commercial sterility while minimizing the damage to the functionality of milk proteins.

[0024] Preferably, in step 5, the directional cooling aging process is as follows: the sterilized material is rapidly cooled to 4-8°C via a plate heat exchanger, and then placed in an aging tank for directional aging treatment. First stage: Aging at 4-6℃ for 4-8 hours to fully reconstruct and stabilize the protein membrane on the surface of fat globules; The second stage involves slowly heating the product to 8-10℃ at a rate of 0.5-1.5℃ / h, and continuing to age it at this temperature for 8-12 hours to promote moderate crystallization of triglycerides within the fat globules (with the solid fat content (SFC) controlled at 15-25%), thus forming a stable fat crystal network.

[0025] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention patent involves activating a functional milk protein concentrate (MPC-F) obtained through a specific membrane separation process and then adding it back to light cream. This component contains casein that retains its natural micelle structure, whey protein with a low degree of denaturation, and abundant milk fat globule membrane protein fragments. After activation, more hydrophobic groups are exposed, forming a dense, thick, and uniform protein interface film on the surface of the fat globule, which greatly enhances steric hindrance and electrostatic repulsion effects. Experimental verification shows that the endogenous protein interface enhancement strategy of this invention is significantly superior to the exogenous additive route in terms of long-term storage stability. 2. The light cream prepared by this invention benefits from the high interfacial shear elastic modulus and good structural plasticity of the interfacial protein film formed by MPC-F on the surface of fat globules. During the process of fat globules expanding and contracting due to temperature changes, the interfacial film can maintain its integrity and rapid self-recovery ability, effectively inhibiting bridging flocculation and aggregation between fat globules. It is particularly suitable for actual storage and transportation scenarios where cold chain infrastructure is imperfect and products frequently experience temperature fluctuations during circulation. 3. The whipping time of the light cream in this invention is faster, which helps to improve the output efficiency of baking and catering terminals; the higher foaming rate means that the same weight of light cream can obtain a larger whipping volume, effectively reducing the terminal use cost; the lower whey leakage rate also ensures the long-lasting setting ability of piping and decorative cream at room temperature. 4. This invention uses endogenous milk protein components from the same milk source for targeted stability enhancement. While maintaining equal or even better stability, it can reduce the amount of exogenous stabilizers (such as carrageenan, xanthan gum, monoglycerides, fatty acid esters, etc.), which is in line with the current global food industry's "clean label" development trend and meets consumers' growing demand for natural, minimally processed, and simple ingredients. At the same time, by avoiding the problems of thickening and flavor distortion caused by exogenous thickeners, the product has a purer and richer natural milky aroma, a smooth and delicate taste, and sensory quality that is significantly better than products with exogenous additives. 5. This invention forms a dense and uniform protein interface film on the surface of fat globules in light cream, with a significantly increased film thickness and minimal flocculation and aggregation between fat globules. This optimized interface structure is directly derived from the synergistic interfacial adsorption effect of casein natural micelles, low-denatured whey protein, and MFGM protein fragments in MPC-F, as well as the strong affinity between the hydrophobic groups exposed by specific activation treatment and the surface of fat globules. Because MPC-F uses the same milk source and retains the natural micelle structure, the interfacial adsorption capacity and interfacial elastic modulus are significantly higher. Attached Figure Description

[0026] Figure 1 This is a comparison diagram of the storage stability of the embodiments and comparative examples of the present invention; Figure 2This is a comparison chart showing the temperature fluctuation resistance capabilities of the embodiments and comparative examples of the present invention; Figure 3 This is a comparison diagram of the mixing characteristics of the embodiments and comparative examples of the present invention; Figure 4 This is a comparison diagram of the interface characteristics of the embodiments and comparative examples of the present invention. Detailed Implementation

[0027] The present invention will now be described in more detail by way of examples. These examples are merely illustrative and do not limit the scope of the present invention in any way. Example 1

[0028] This embodiment provides a technical solution: a method for improving the stability of light cream based on the targeted reintroduction of membrane-separated milk protein components, comprising the following steps: Step 1: MPC-F Preparation: 1000L of skim milk (protein content 3.2%) was preheated to 50℃ and concentrated using a polyethersulfone ultrafiltration membrane with a molecular weight cutoff of 30kDa at an operating pressure of 0.25MPa and a membrane flow rate of 3.0m / s to a final volume of 350L (concentration factor of 2.9 times). The resulting retentate was then washed with an ultrafiltration membrane with a molecular weight cutoff of 50kDa, and 350L of deionized water was added to remove lactose and small molecule salts, yielding 180L of functional milk protein concentrate retentate. The protein content of this retentate was 68% on a dry basis, with a casein to whey protein mass ratio of 3.5:1. Step 2: MPC-F activation: Dilute the MPC-F retentate to a protein concentration of 10%, preheat at 65°C for 15 min, then rapidly cool to 6°C and allow to stand for aging for 3 h to obtain an aqueous dispersion of the activated functional milk protein concentrate. Step 3: Preparation of light cream base: The same batch of raw milk is separated by a disc centrifuge at a centrifuge temperature of 55℃ and a separation factor of 6000 to obtain light cream base with a fat content of 38%. Step 4: Re-mixing: Add the activated MPC-F aqueous dispersion back into the cream base at 4.0% of the total mass of the finished cream (1.2% of the dry protein content). At the same time, add 0.05% of the total mass of the finished cream and stir at 55°C for 12 minutes. Step 5: Preheating and degassing: Preheat the obtained mixture to 70°C and degas it for 8 minutes under a vacuum of -0.07 MPa; Step 6: Two-stage high-pressure homogenization: The obtained mixture is subjected to two-stage high-pressure homogenization, wherein the first-stage homogenization pressure is 18MPa and the temperature is 65℃, and the second-stage homogenization pressure is 4MPa and the temperature is 55℃; after homogenization, the volume average particle size D[4,3] of the fat globules is 0.85μm, and the span value is 1.2; Step 7: UHT sterilization: The obtained mixture is sterilized by UHT indirect heating at a temperature of 137℃ for 4 seconds. Step 8: Directional cooling aging: The resulting mixture is rapidly cooled to 5°C and aged at 5°C for 6 hours; then the temperature is increased to 9°C at a rate of 1.0°C / h, and aging continues for 10 hours. Step 9: Aseptic filling: After aging, the cream is filled under aseptic conditions to obtain a highly stable finished product. Example 2

[0029] This embodiment provides another alternative technical solution: a method for improving the stability of light cream based on the targeted reintroduction of membrane-separated milk protein components. The difference from Example 1 is that the MPC-F reintroduction amount is 2.5% of the total mass of the finished light cream (approximately 0.8% dry protein basis), and 0.03% microcrystalline cellulose is added as an auxiliary stabilizer, including the following steps: Step 1: MPC-F Preparation: 1000L of skim milk (protein content 3.2%) was preheated to 50℃ and concentrated using a polyethersulfone ultrafiltration membrane with a molecular weight cutoff of 30kDa at an operating pressure of 0.25MPa and a membrane flow rate of 3.0m / s to a final volume of 350L (concentration factor of 2.9 times). The resulting retentate was then washed with an ultrafiltration membrane with a molecular weight cutoff of 50kDa, and 350L of deionized water was added to remove lactose and small molecule salts, yielding 180L of functional milk protein concentrate retentate. The protein content of this retentate was 68% on a dry basis, with a casein to whey protein mass ratio of 3.5:1. Step 2: MPC-F activation: Dilute the MPC-F retentate to a protein concentration of 10%, preheat at 65°C for 15 min, then rapidly cool to 6°C and allow to stand for aging for 3 h to obtain an aqueous dispersion of the activated functional milk protein concentrate. Step 3: Preparation of light cream base: The same batch of raw milk is separated by a disc centrifuge at a centrifuge temperature of 55℃ and a separation factor of 6000 to obtain light cream base with a fat content of 38%. Step 4: Re-mixing: Add 2.5% of the activated MPC-F aqueous dispersion (0.8% of the total mass of the finished cream) back into the cream base, along with 0.03% of microcrystalline cellulose and 0.05% of edible salt by mass of the finished cream. Stir and mix at 55°C for 12 minutes. Step 5: Preheating and degassing: Preheat the obtained mixture to 70°C and degas it for 8 minutes under a vacuum of -0.07 MPa; Step 6: Two-stage high-pressure homogenization: The obtained mixture is subjected to two-stage high-pressure homogenization, wherein the first-stage homogenization pressure is 18MPa and the temperature is 65℃, and the second-stage homogenization pressure is 4MPa and the temperature is 55℃; after homogenization, the volume average particle size D[4,3] of the fat globules is 0.85μm, and the span value is 1.2; Step 7: UHT sterilization: The obtained mixture is sterilized by UHT indirect heating at a temperature of 137℃ for 4 seconds. Step 8: Directional cooling aging: The resulting mixture is rapidly cooled to 5°C and aged at 5°C for 6 hours; then the temperature is increased to 9°C at a rate of 1.0°C / h, and aging continues for 10 hours. Step 9: Aseptic filling: After aging, the cream is filled under aseptic conditions to obtain a highly stable finished product. Example 3

[0030] This embodiment provides another alternative technical solution: a method for improving the stability of light cream based on the targeted reintroduction of milk protein components separated by membrane. The difference from Example 1 is that MPC-F is derived from whey, a byproduct of light cream production. The whey is concentrated using a 10kDa ultrafiltration membrane and then treated with a 50kDa washing membrane to obtain MPC-F with a protein content of 70%. The reintroduction amount is 5.0% (approximately 1.8% dry protein). The method includes the following steps: Step 1: MPC-F preparation: Using whey, a byproduct of cream production, as raw material, the whey is concentrated through an ultrafiltration membrane with a molecular weight cutoff of 10 kDa, and then washed through an ultrafiltration membrane with a molecular weight cutoff of 50 kDa to obtain a functional milk protein concentrate. The protein content of this concentrate is 70% on a dry basis. Step 2: MPC-F activation: MPC-F was prepared into an aqueous dispersion with a protein concentration of 12%, preheated at 65°C for 15 min, then rapidly cooled to 6°C and allowed to stand for 3 h to obtain the activated functional milk protein concentrate aqueous dispersion. Step 3: Preparation of light cream base: The same batch of raw milk is separated by a disc centrifuge at a centrifuge temperature of 55℃ and a separation factor of 6000 to obtain light cream base with a fat content of 38%. Step 4: Re-mixing: Add 5.0% of the activated MPC-F aqueous dispersion (1.8% of the total mass of the finished cream) back into the cream base, and add 0.05% of edible salt of the finished cream. Stir and mix at 55°C for 12 minutes. Step 5: Preheating and degassing: Preheat the obtained mixture to 70°C and degas it for 8 minutes under a vacuum of -0.07 MPa; Step 6: Two-stage high-pressure homogenization: The obtained mixture is subjected to two-stage high-pressure homogenization, wherein the first-stage homogenization pressure is 18MPa and the temperature is 65℃, and the second-stage homogenization pressure is 4MPa and the temperature is 55℃; after homogenization, the volume average particle size D[4,3] of the fat globules is 0.85μm, and the span value is 1.2; Step 7: UHT sterilization: The obtained mixture is sterilized by UHT indirect heating at a temperature of 137℃ for 4 seconds. Step 8: Directional cooling aging: The resulting mixture is rapidly cooled to 5°C and aged at 5°C for 6 hours; then the temperature is increased to 9°C at a rate of 1.0°C / h, and aging continues for 10 hours. Step 9: Aseptic filling: After aging, the cream is filled under aseptic conditions to obtain a highly stable finished product. Example 4

[0031] This embodiment provides another alternative technical solution: a method for improving the stability of light cream based on the directional reintroduction of membrane-separated milk protein components. The difference from Example 1 is that the primary homogenization pressure is 15 MPa, and the secondary homogenization pressure is 3 MPa. After homogenization, the fat globules D[4,3] = 1.05 μm, span = 1.4, and the method includes the following steps: Step 1: MPC-F Preparation: 1000L of skim milk (protein content 3.2%) was preheated to 50℃ and concentrated using a polyethersulfone ultrafiltration membrane with a molecular weight cutoff of 30kDa at an operating pressure of 0.25MPa and a membrane flow rate of 3.0m / s to a final volume of 350L (concentration factor of 2.9 times). The resulting retentate was then washed with an ultrafiltration membrane with a molecular weight cutoff of 50kDa, and 350L of deionized water was added to remove lactose and small molecule salts, yielding 180L of functional milk protein concentrate retentate. The protein content of this retentate was 68% on a dry basis, with a casein to whey protein mass ratio of 3.5:1. Step 2: MPC-F activation: Dilute the MPC-F retentate to a protein concentration of 10%, preheat at 65°C for 15 min, then rapidly cool to 6°C and allow to stand for aging for 3 h to obtain an aqueous dispersion of the activated functional milk protein concentrate. Step 3: Preparation of light cream base: The same batch of raw milk is separated by a disc centrifuge at a centrifuge temperature of 55℃ and a separation factor of 6000 to obtain light cream base with a fat content of 38%. Step 4: Re-mixing: Add the activated MPC-F aqueous dispersion back into the cream base at 4.0% of the total mass of the finished cream (1.2% of the dry protein content). At the same time, add 0.05% of the total mass of the finished cream and stir at 55°C for 12 minutes. Step 5: Preheating and degassing: Preheat the obtained mixture to 70°C and degas it for 8 minutes under a vacuum of -0.07 MPa; Step 6: Two-stage high-pressure homogenization: The obtained mixture is subjected to two-stage high-pressure homogenization, wherein the first-stage homogenization pressure is 15MPa and the temperature is 65℃, and the second-stage homogenization pressure is 3MPa and the temperature is 55℃; after homogenization, the volume average particle size D[4,3] of the fat globules is 1.05μm and the span value is 1.4; Step 7: UHT sterilization: The obtained mixture is sterilized by UHT indirect heating at a temperature of 137℃ for 4 seconds. Step 8: Directional cooling aging: The resulting mixture is rapidly cooled to 5°C and aged at 5°C for 6 hours; then the temperature is increased to 9°C at a rate of 1.0°C / h, and aging continues for 10 hours. Step 9: Aseptic filling: After aging, the cream is filled under aseptic conditions to obtain a highly stable finished product. Example 5

[0032] This embodiment provides three comparative examples that mutually verify the above technical solutions: Comparative Example 1: Compared with the above technical solution, a conventional process was adopted without MPC-F refill. A light cream base with a fat content of 38% was obtained by separating the raw milk from the same batch. 0.15% carrageenan + 0.1% monoglyceride + 0.05% xanthan gum were added as stabilizers. After preheating at 65°C, it was homogenized at 18MPa / 4MPa for two stages, sterilized at 137°C / 4s UHT, cooled to 5°C and aged for 16 hours, and aseptically filled. The remaining steps were the same as in Example 1.

[0033] Comparative Example 2: Compared with the above technical solution, a cream base with a fat content of 38% was obtained by separating the raw milk from the same batch without MPC-F or stabilizers. No stabilizers were added. After preheating at 65°C, it was homogenized at 18MPa / 4MPa, sterilized at 137°C / 4s UHT, cooled to 5°C and aged for 16 hours, and aseptically filled. The remaining steps were the same as in Example 1.

[0034] Comparative Example 3: Compared with the above technical solution, sodium caseinate (1.2% protein dry basis) purchased from external sources was used to replace MPC-F for refilling, and the remaining steps were the same as in Example 1.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for improving the stability of light cream based on the targeted reintroduction of milk protein components separated by membrane, characterized in that: Includes the following steps: Step 1: Skim milk membrane separation: Skim milk is preheated to 45-55°C and concentrated by ultrafiltration through an ultrafiltration membrane with a molecular weight cutoff of 10-30 kDa. The resulting retentate is then washed through an ultrafiltration membrane with a molecular weight cutoff of 50-100 kDa to remove some lactose and small molecule minerals, yielding a functional milk protein concentrate (MPC-F) with a protein content of ≥65% on a dry basis and a casein to whey protein ratio of 3:1-4:

1. Step 2: Activation of whey protein: Prepare an aqueous dispersion of MPC-F with a protein concentration of 8-15% by preheating at 60-70℃ for 10-20 min to induce moderate thermal denaturation of whey protein (denaturation rate controlled at 20-40%), exposing more hydrophobic groups and enhancing its interfacial activity. Then, rapidly cool to 4-8℃ and allow to stand for aging for 2-4 h to allow protein molecules to form moderate pre-aggregates, thus obtaining the activated MPC-F aqueous dispersion. Step 3: Preparation of light cream base: The raw milk is separated by a disc centrifuge to obtain a light cream base with a fat content of 35-40%. Step 4: Targeted Refilling: The activated MPC-F aqueous dispersion is refilled into the cream base at a ratio of 2.0-6.0% of the total mass of the finished cream (0.5-2.0% based on dry protein). Step 5: Specific process treatment: After the above mixed materials are preheated and degassed, subjected to two-stage high-pressure homogenization, UHT sterilization, and directional cooling aging process, they are filled under aseptic conditions to obtain high-stability light cream product.

2. The method for improving the stability of light cream based on the directed reintroduction of membrane-separated milk protein components according to claim 1, characterized in that: In step 1, the operating pressure for ultrafiltration concentration is 0.15–0.35 MPa, the membrane surface flow rate is 2.5–4.0 m / s, and the concentration factor is 2.5–4.0 times.

3. The method for improving the stability of light cream based on the directed reintroduction of membrane-separated milk protein components according to claim 1, characterized in that: In step 1, MPC-F is derived from skim milk separated by centrifugation from the same batch of raw milk as the cream, or from whey produced as a byproduct during the cream production process; preferably from skim milk from the same batch of raw milk to ensure the natural compatibility of the protein components with the fat globules of the cream.

4. The method for improving the stability of light cream based on the directed reintroduction of membrane-separated milk protein components according to claim 1, characterized in that: In step 3, the centrifugation temperature of the disc centrifuge is 50-60℃, and the separation factor is ≥6000 to ensure the integrity of the fat globule structure.

5. The method for improving the stability of light cream based on the directed reintroduction of membrane-separated milk protein components according to claim 1, characterized in that: In step 4, when MPC-F is refilled, 0.02% to 0.08% of edible salt can be selectively added to adjust the ionic strength and promote the adsorption of protein at the fat globule interface.

6. The method for improving the stability of light cream based on the directed reintroduction of membrane-separated milk protein components according to claim 1, characterized in that: In step 4, the method of refilling is online injection mixing, the mixing temperature is 50-60℃, and the mixture is stirred for 10-15 minutes after mixing to ensure uniform dispersion.

7. The method for improving the stability of light cream based on the directed reintroduction of membrane-separated milk protein components according to claim 1, characterized in that: In step 5, the preheating and degassing process is as follows: the mixed material is preheated to 65-75°C and degassed for 5-10 minutes under a vacuum of -0.06 to -0.08 MPa, thereby removing dissolved oxygen and bubbles from the material, reducing the risk of oxidation and the interference of bubbles before homogenization.

8. The method for improving the stability of light cream based on the directed reintroduction of membrane-separated milk protein components according to claim 1, characterized in that: In step 5, the secondary high-pressure homogenization process is as follows: Primary homogenization: pressure 15-20 MPa (150-200 bar), temperature 60-70℃, its function is to break up fat globules and initially reduce the dispersion of particle size distribution; Secondary homogenization: pressure 3-5 MPa (30-50 bar), temperature 50-60℃, the purpose is to further refine the fat globule size and reduce the damage of mechanical shear to the natural structure of milk fat; After homogenization, the volume average particle size D[4,3] of the target fat globules was controlled between 0.6 and 1.2 μm, and the particle size distribution was unimodal or narrow bimodal, with a span value ((D90-D10) / D50) ≤ 1.

5.

9. The method for improving the stability of light cream based on the directed reintroduction of membrane-separated milk protein components according to claim 1, characterized in that: In step 5, the UHT sterilization adopts an indirect UHT sterilization process with a temperature of 135-140℃ and a time of 3-5 seconds, which can achieve commercial sterility while minimizing the damage to the functionality of milk proteins.

10. The method for improving the stability of light cream based on the directed reintroduction of membrane-separated milk protein components according to claim 1, characterized in that: In step 5, the directional cooling aging process involves rapidly cooling the sterilized material to 4–8°C using a plate heat exchanger, followed by directional aging treatment in an aging tank. First stage: Aging at 4-6℃ for 4-8 hours to fully reconstruct and stabilize the protein membrane on the surface of fat globules; The second stage involves slowly heating the product to 8-10℃ at a rate of 0.5-1.5℃ / h, and continuing to age it at this temperature for 8-12 hours to promote moderate crystallization of triglycerides within the fat globules (with the solid fat content (SFC) controlled at 15-25%), thus forming a stable fat crystal network.

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