A desalted whey product and its preparation method and application

Abstract

The present invention relates to the technical field of dairy products, and specifically discloses a desalted whey product and a preparation method and application thereof. The method for preparing a desalted whey product of the present invention comprises: (1) using natural whey or defatted sweet whey as a raw material for nanofiltration to obtain a nanofiltration retentate with a dry matter content of 18-32 g / 100g; the pore size of the nanofiltration membrane is 200Da-1000Da; (2) adjusting the pH value of the nanofiltration retentate to 8-9 to obtain a whey solution after pH adjustment; (3) subjecting the whey solution after pH adjustment to electrodialysis to obtain a desalted whey solution. The preparation method of the present invention can reduce the loss rate of active protein in the raw material, thereby improving the utilization rate of the raw material, and the obtained product has a low furosine content, a high proportion of undenatured protein, and good bioavailability.

Description

Technical Field

[0001] The invention relates to the technical field of dairy products, in particular to a desalted whey product and a preparation method and application thereof. Background Art

[0002] Desalted whey is made from cheese sweet whey or natural whey obtained by membrane filtration, and is prepared through pasteurization, desalination, and drying processes. According to the degree of desalination, it can be divided into desalted whey powder products with a desalination degree of 40%, 50%, 70%, and 90%, namely D40, D50, D70, and D90. D40 and D50 products are widely used in the food field such as baked goods, condensed milk, ice cream, candy, and dairy products. They can also be used to make protein drinks to provide protein and carbohydrates. D70 and D90 desalted whey powders are mostly used in the production of infant formula milk powder. At present, in order to improve the quality of infant formula milk powder, D90 desalted whey powder with a higher degree of desalination is usually used. Due to the different structures of the dairy industry, in the absence of a native cheese industry, there will be a lack of whey raw materials for the production of desalted whey powder. Therefore, the prior art also provides a method of using whey powder as a raw material, dissolving it, desalting it, and drying it to produce desalted whey powder, or using fresh milk as a raw material, using membrane filtration to obtain natural whey, and then desalting and drying it to produce desalted whey powder.

[0003] The process of desalting whey powder mainly includes two links, one is desalting, and the other is evaporation, concentration and drying. Common desalting methods include ion exchange, nanofiltration, electrodialysis, etc. Ion exchange + nanofiltration or ion exchange + nanofiltration + electrodialysis are commonly used desalting methods, but the use of ion exchange system consumes a lot of acid, alkali and water for resin regeneration. On the other hand, during the ion exchange process, the pH of whey drops from above 6 to 2-3. After passing through the isoelectric point of casein and some whey proteins, precipitation will occur during the ion exchange process, causing changes in protein structure, loss and blockage of the ion exchange system. The conventional process of evaporation, concentration and drying is evaporation-crystallization-spray drying, among which the crystallization link is crucial. The size of the crystal particle size and the crystallization rate will affect the fluidity, dispersibility and storage performance of the final product powder. In the evaporation, concentration and drying process, the whey raw material must undergo long-term high-temperature treatment. High-temperature treatment often brings about changes in protein structure, denaturation, and Maillard reaction, which brings about amino acid glycosylation, resulting in reduced bioavailability of whey protein. At the same time, the Maillard reaction will also bring about lactose loss.

[0004] Therefore, further research on the preparation method of desalted whey is needed. Summary of the invention

[0005] One of the objects of the present invention is to provide a method for preparing a desalted whey product and its application which can reduce the loss of protein and lactose in raw materials.

[0006] The present invention provides a method for preparing a desalted whey product, comprising:

[0007] (1) Using natural whey or defatted sweet whey as raw material for nanofiltration, obtaining a nanofiltration retentate having a dry matter content of 18-32 g / 100 g; the pore size of the nanofiltration membrane is 200 Da to 1000 Da;

[0008] (2) adjusting the pH value of the nanofiltration retentate to 8-9 to obtain a pH-adjusted whey solution;

[0009] (3) The pH-adjusted whey solution is subjected to electrodialysis to obtain a desalted whey solution.

[0010] The present invention has found that when the existing skim whey products are prepared, the protein and lactose in the raw materials will be lost, thereby affecting the function of the product and reducing the utilization rate of the raw materials to the product. To this end, the present invention has developed a new method for preparing desalted whey, which first removes ash from a part of the raw materials by nanofiltration to obtain a nanofiltration retentate with a specific dry matter content, and then the pH value of the nanofiltration retentate is specifically adjusted before continuing to remove the remaining ash by electrodialysis. This method can effectively remove the ash, reduce the precipitation of protein during the electrodialysis process, avoid the irreversible transformation of the whey protein structure, and overall reduce the loss of active protein during the electrodialysis process, thereby ensuring the efficacy of the product.

[0011] The raw material in the preparation method of the present invention can be sweet whey or natural whey, both of which can be prepared by methods known in the art, with a fat content of ≤1.5%. Specifically, sweet whey is a liquid product obtained by fermenting with a starter to produce acid, curdling with rennet, and separating the curd blocks in the process of producing cheese. It can be used as a raw material for the method of the present invention after milk purification, defatting, and pasteurization. The preferred pH of sweet whey is 6.0-6.5, which is conducive to shortening the desalination time and improving the flavor and taste. Natural whey is a product obtained by directly using defatted animal milk as a raw material and removing casein through membrane separation. In the present invention, animal milk is the milk of mammals, which can be cow's milk, sheep's milk, camel's milk, donkey's milk, horse's milk, deer's milk, etc.

[0012] The pH adjusting agent used in the present invention to adjust the pH value of the nanofiltration retentate includes one or more of potassium hydroxide, sodium hydroxide, sodium bicarbonate, potassium bicarbonate, and sodium citrate; preferably potassium hydroxide and / or sodium hydroxide, so as to take into account the needs of pH adjustment and meet the mineral requirements of the final product.

[0013] In the method for preparing a desalted whey product of the present invention, the temperature of the nanofiltration is 3-25° C., and the pressure of the nanofiltration is 5-40 bar.

[0014] In the method for preparing desalted whey products of the present invention, the temperature of the electrodialysis is 3-25°C, preferably 15°C, taking into account both production efficiency and protein retention rate. If the temperature is too low, the electrodialysis time is long and the efficiency is low, and if the temperature is too high, the loss of active protein will increase.

[0015] Preferably, in the method for preparing a desalted whey product of the present invention, during the electrodialysis, the same batch of whey liquid to be treated is circulated through the same electrodialyzer for electrodialysis. The present invention adopts batch electrodialysis operation, which can realize flexible adjustment of the electrodialysis endpoint and save energy consumption. It avoids the need for materials to pass through all electrodialysis modules as in the existing conventional continuous electrodialysis process, which may lead to excessive desalination and increase energy consumption and auxiliary material consumption.

[0016] According to the electrodialysis target defined in the present invention, those skilled in the art can select the number of membrane pairs in the electrodialyser and the voltage applied to each membrane pair (eg, 1.0-2.0 V) based on common sense and material processing capacity.

[0017] In the method for preparing desalted whey products of the present invention, the conductivity of the desalted whey liquid at the end point of electrodialysis is 0.1-0.8 mS / cm; and the mass percentage of ash content in dry matter is ≤1.5%.

[0018] The method for preparing a desalted whey product of the present invention further comprises, before nanofiltration, a step of adjusting the protein and lactose content in the raw material by ultrafiltration;

[0019] The pore size of the ultrafiltration membrane used in the ultrafiltration is 3000Da-12000Da, the ultrafiltration temperature is 3-25°C, the ultrafiltration pressure is 1-4bar, and the mass ratio of lactose to protein in the ultrafiltration retentate is (3-7): 1. Preferably, the pore size of the ultrafiltration membrane is 3000Da-5000Da, so as to reduce the loss of protein in the retentate.

[0020] Those skilled in the art can adjust the concentration ratio by controlling the conditions during ultrafiltration according to common knowledge in the art to obtain the target mass ratio of lactose to protein.

[0021] The ultrafiltration step of the present invention can not only achieve protein concentration and increase the protein content in the product, but also adjust the mass ratio of lactose to protein, thereby ensuring that the ratio of lactose to protein in the product is appropriate, and then obtaining a higher crystallization rate and crystallization speed when the desalted whey powder is subsequently prepared for crystallization. When the mass ratio of lactose to protein is 3:1, desalted whey powder with a high protein content can be prepared. However, if the mass ratio of lactose to protein in the product is further reduced, the crystallization rate and crystallization speed will be reduced.

[0022] In the method for preparing a desalted whey product of the present invention, after step (3), the method further includes sterilizing the desalted whey liquid, or mixing the desalted whey liquid with minerals and then sterilizing the mixture to obtain the sterilized whey liquid.

[0023] The sterilization method of the present invention preferably uses pasteurization, and the sterilization conditions are: temperature 70-90°C, time 10-60 seconds; more preferably, temperature 72-75°C, time 15-30 seconds, so as to achieve effective sterilization and avoid protein denaturation caused by excessively high temperatures.

[0024] The addition of minerals in the present invention can be selected according to product requirements, and the specific types and contents are not limited. For example, the contents of K, Na, Ca, Mg, P, and Cl in the product can be adjusted by adding minerals to obtain a standardized whey liquid; wherein the K element content can be 0-4000 mg / kg, the Na element content can be 0-1200 mg / kg, the Ca element content can be 0-1200 mg / kg, the Mg element content can be 0-500 mg / kg, the P element content can be 0-2000 mg / kg, and the Cl element content can be 0-1000 mg / kg.

[0025] The method for preparing a desalted whey product of the present invention further comprises the step of concentrating the sterilized whey liquid to a dry matter content of 55-65 g / 100 g, and then crystallizing to obtain a crystallized whey liquid;

[0026] The temperature of the concentrated whey liquid is 65-80°C. The crystallization method comprises: flash evaporating the concentrated whey liquid until the temperature of the whey liquid drops to 30-45°C, then cooling the temperature of the whey liquid to 20°C at a rate of 1-3°C / h to complete the first stage of cooling, and then cooling the temperature of the whey liquid to 10-15°C at a rate of 1.5-4°C / h to complete the second stage of cooling, wherein the cooling rate of the first stage is slower than that of the second stage; the flash evaporation pressure is 0.04Mpa-0.08Mpa.

[0027] The concentration method of the sterilized whey liquid of the present invention is not limited, and the evaporation concentration method known in the art can be selected. The evaporation system can adopt a falling film evaporation system, specifically a two-stage to four-stage falling film evaporation system, with an evaporation temperature of 70-85° C. and a pressure of 0.070-0.099 MPa.

[0028] The present invention concentrates the sterilized whey liquid, first processes it with a flash evaporation system, and then performs crystallization in conjunction with a specific cooling method. The pressure during flash evaporation affects the initial temperature of the subsequent cooling and crystallization stage, and further affects the particle morphology and quantity of the final crystals. If the pressure is too high, the final crystal particle size is large and the fluidity is poor. If it is too low, it will also affect the fluidity and dispersibility of the final crystals. The present invention can adjust the particle size distribution of lactose crystals and improve the mobile phase, dissolution rate and dispersibility of whey powder through a flash evaporation process after specific concentration.

[0029] The present invention also specifically studies the cooling gradient of the crystals, and finds that crystallization under the specific conditions defined in the present invention can make the crystal particle size uniform, the final product powder has good fluidity, and the final product is not easy to absorb moisture during storage.

[0030] The method for preparing desalted whey products of the present invention also includes the step of adding lactose seeds to the concentrated whey liquid or the flash evaporated whey liquid; the amount of lactose seeds added is one ten-thousandth to one thousandth of the mass of the whey liquid, and the particle size of the lactose seeds is less than 5µm.

[0031] The addition of seed crystals can shorten the crystallization time. On the other hand, if the seed crystal particle size is uniform (narrow particle size distribution), the particle size distribution of the final product desalted whey powder will also be narrow, which can increase the fluidity of the powder. Preferably, the particle size of the lactose seed crystal is 2-3µm.

[0032] The method for preparing a desalted whey product of the present invention further comprises the step of spray drying the crystallized whey liquid; the air inlet temperature during the spray drying is 160-200° C., and the air outlet temperature is 60-90° C. The drying temperature of the present invention is relatively low, which can avoid problems such as increased protein denaturation, accelerated Maillard reaction rate, poor powder solubility, increased impurities, reduced protein bioavailability, and reduced digestibility caused by excessively high temperatures.

[0033] The present invention also provides a desalted whey product, which is the desalted whey liquid or desalted whey powder prepared by the above method.

[0034] The desalted whey product of the invention changes the retention of lactose and protein and the denaturation of protein in the final product through process adjustment, thereby obtaining a product with high retention rate of lactose and active protein and thus high bioavailability.

[0035] The present invention also provides application of the desalted whey product in preparing infant formula milk powder.

[0036] The desalted whey liquid prepared by the method of the present invention can be directly used in the preparation and production of infant formula milk powder. By reducing the thermal processing steps such as evaporation, concentration, spray drying and the like in the whey powder production process, the amino acid glycosylation caused by the Maillard reaction is reduced, the reduction of protein bioavailability and digestibility is avoided, the protein can maintain its original structure as much as possible, the loss of function caused by thermal denaturation is avoided, and the product quality is improved.

[0037] The present invention also provides an infant formula milk powder, which comprises the desalted whey product.

[0038] The beneficial effects of the present invention are at least:

[0039] The preparation method of the desalted whey product of the present invention can reduce the loss rate of lactose and protein in the raw materials, thereby improving the utilization rate of the raw materials. The obtained product has low furosine content, low amino acid glycosylation level, high proportion of undenatured protein, and good bioavailability. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0041] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are commercially available or prepared according to conventional methods in the art unless otherwise specified.

[0042] Example 1 - Preparation of whey powder from sweet whey raw materials

[0043] The present embodiment provides a method for preparing whey powder, which is as follows:

[0044] 1. Obtaining and processing whey: Add lactic acid bacteria to pasteurized fresh milk, ferment at 37°C for 1 hour, add rennet, coagulate at 37°C for 1 hour, drain the whey, collect the whey immediately and perform milk purification, degreasing and pasteurization. The time from whey draining to pasteurization is 30 minutes, and sweet whey with a pH of 6.3 is obtained, and the proportion of fat in dry matter is 1.2%. The pasteurization temperature is 72°C for 15 seconds.

[0045] 2. Adjustment of the ratio of protein to lactose: The pasteurized whey obtained in step 1 is passed through an ultrafiltration membrane system to obtain a retentate 1 and a permeate 1. The pore size of the ultrafiltration membrane is 5000Da, the ultrafiltration temperature is 5°C, and the ultrafiltration pressure is 1 bar; after ultrafiltration separation, the mass ratio of protein to lactose in the retentate 1 is 1:6;

[0046] 3. Whey desalination:

[0047] 3.1 The retentate 1 obtained in step 2 is passed through a nanofiltration system to remove a portion of the ash to obtain a retentate 2 and a permeate 2; the pore size of the nanofiltration membrane is 200Da-350Da, the nanofiltration temperature is 15°C, and the nanofiltration pressure is 28bar; the dry matter content of the retentate 2 is 26g / 100g;

[0048] 3.2 Add potassium hydroxide to the retentate 2 to adjust the pH to 8.0 to obtain a pH-adjusted whey solution;

[0049] 3.3 The pH-adjusted whey liquid is desalted by electrodialysis to remove the second part of ash to obtain desalted whey liquid. The electrodialysis adopts batch operation (that is, the same batch of whey liquid to be treated is circulated as a whole for electrodialysis until the target end point), and the electrodialysis temperature is selected to be 15°C. The conductivity of the desalted whey liquid at the end point of electrodialysis is 0.55mS / cm, and the mass percentage of ash in dry matter is 0.8%;

[0050] 4. Sterilization

[0051] The desalted whey liquid obtained in step 3 is pasteurized to obtain pasteurized whey liquid, the sterilization conditions are: 72° C., time: 15 seconds;

[0052] 5. Whey Concentrate

[0053] The pasteurized whey liquid is evaporated and concentrated to obtain concentrated whey liquid; the evaporation system adopts a three-stage falling film evaporation system with an evaporation temperature of 72°C and a pressure of 0.095MPa. The dry matter content of the concentrated whey liquid is 60g / 100g, and the discharge temperature is 70°C;

[0054] 6. Crystallization

[0055] 6.1 Flash evaporation: The concentrated whey liquid passes through the flash evaporation system to obtain flash evaporation whey liquid. The pressure of the flash evaporation system is 0.060MPa. After passing through the flash evaporation system, the temperature of the flash evaporation whey liquid drops to 35°C. Lactose seeds (seed particle size is 2-3µm) with a mass fraction of 0.05% of the whey liquid are added to the flash evaporation whey liquid.

[0056] 6.2 Crystallization cooling: The flash evaporated whey liquid with added crystals obtained in 6.1 is cooled and crystallized. Specifically, the flash evaporated whey liquid with added crystals at 35°C is cooled to 20°C at a rate of 1.0°C / h, and then cooled to 15°C at a rate of 1.5°C / h, and kept at this temperature for later use;

[0057] 7. Spray Drying

[0058] The crystallized whey liquid obtained in 6.2 is spray dried to obtain desalted whey powder. The spray drying air inlet temperature is 170°C and the air outlet temperature is 70°C.

[0059] Example 2 - Preparation of desalted whey powder from natural whey

[0060] The present embodiment provides a method for preparing whey powder, which is as follows:

[0061] 1. Obtaining and processing whey: Using raw milk as raw material, it is defatted and pasteurized. After defatting, the fat accounts for 0.4% of the dry matter. The pasteurization temperature is 72℃ for 15s. Then it passes through the microfiltration membrane system to obtain membrane-separated natural whey. The pore size of the microfiltration membrane is 0.1µm and the microfiltration temperature is 4℃.

[0062] Steps 2-7 are the same as in Example 1.

[0063] Example 3

[0064] The present embodiment provides a method for preparing whey powder, which is as follows:

[0065] 1. Obtaining and processing whey: Add lactic acid bacteria to pasteurized fresh milk, ferment at 37°C for 40 minutes, add rennet, coagulate at 37°C for 40 minutes, drain the whey, collect the whey immediately and perform milk purification, degreasing and pasteurization. The time from draining the whey to pasteurization is 30 minutes, and sweet whey with a pH of 6.5 is obtained, and the proportion of fat in dry matter is 1.2%. The pasteurization temperature is 72°C for 15 seconds.

[0066] 2. Adjustment of the ratio of protein to lactose: The pasteurized whey obtained in step 1 is passed through an ultrafiltration membrane system to obtain a retentate 1 and a permeate 1. The pore size of the ultrafiltration membrane is 12000Da, the ultrafiltration temperature is 25°C, and the ultrafiltration pressure is 1 bar; after ultrafiltration separation, the mass ratio of protein to lactose in the retentate 1 is 1:3;

[0067] 3. Whey desalination:

[0068] 3.1 The retentate 1 obtained in step 2 is passed through a nanofiltration system to remove a portion of the ash to obtain a retentate 2 and a permeate 2; the pore size of the nanofiltration membrane is 350Da-1000Da, the nanofiltration temperature is 25°C, and the nanofiltration pressure is 5bar; the dry matter content of the retentate 2 is 18g / 100g;

[0069] 3.2 Add sodium hydroxide to the retentate 2 to adjust the pH to 9.0 to obtain a pH-adjusted whey solution;

[0070] 3.3 The pH-adjusted whey liquid is desalted by electrodialysis to remove the second part of ash to obtain desalted whey liquid. The electrodialysis adopts batch operation (that is, the same batch of whey liquid to be treated is circulated as a whole for electrodialysis until the target end point), and the electrodialysis temperature is selected to be 25°C. The conductivity of the desalted whey liquid at the end point of electrodialysis is 0.10mS / cm, and the mass percentage of ash in dry matter is 0.4%;

[0071] 4. Sterilization

[0072] The desalted whey liquid obtained in step 3 is pasteurized to obtain pasteurized whey liquid, wherein the sterilization conditions are: 90° C., and the time is 10 seconds;

[0073] 5. Whey Concentrate

[0074] The pasteurized whey liquid is evaporated and concentrated to obtain concentrated whey liquid; the evaporation system adopts a two-stage falling film evaporation system, the evaporation temperature is 85°C, and the pressure is 0.099MPa. The dry matter content of the concentrated whey liquid is 55g / 100g, and the discharge temperature is 80°C;

[0075] 6. Crystallization

[0076] 6.1 Flash evaporation: The concentrated whey liquid passes through the flash evaporation system to obtain flash evaporation whey liquid. The pressure of the flash evaporation system is 0.080 MPa. After passing through the flash evaporation system, the temperature of the flash evaporation whey liquid drops to 45°C.

[0077] 6.2 Crystallization and cooling: The flash evaporated whey liquid obtained in 6.1 is cooled and crystallized, specifically, the flash evaporated whey liquid at 45°C is cooled to 20°C at a rate of 3.0°C / h, and then cooled to 10°C at a rate of 4°C / h, and kept at this temperature for later use;

[0078] 7. Spray Drying

[0079] The crystallized whey liquid obtained in 6.2 is spray dried to obtain desalted whey powder. The spray drying air inlet temperature is 200°C and the air outlet temperature is 90°C.

[0080] Example 4

[0081] The present embodiment provides a method for preparing whey powder, which is as follows:

[0082] 1. Obtaining and processing whey: Add lactic acid bacteria to pasteurized fresh milk, ferment at 37°C for 90 minutes, add rennet, coagulate at 37°C for 40 minutes, drain the whey, collect the whey immediately and perform milk purification, degreasing and pasteurization. The time from draining the whey to pasteurization is 30 minutes, and the sweet whey with a pH of 6.0 is obtained, and the fat content of dry matter is 1.2%. The pasteurization temperature is 70°C for 15 seconds.

[0083] 2. Adjustment of the ratio of protein to lactose: The pasteurized whey obtained in step 1 is passed through an ultrafiltration membrane system to obtain a retentate 1 and a permeate 1. The pore size of the ultrafiltration membrane is 3000 Da, the ultrafiltration temperature is 3°C, and the ultrafiltration pressure is 4 bar; after ultrafiltration separation, the mass ratio of protein to lactose in the retentate 1 is 1:7;

[0084] 3. Whey desalination:

[0085] 3.1 The retentate 1 obtained in step 2 is passed through a nanofiltration system to remove a portion of the ash to obtain a retentate 2 and a permeate 2; the pore size of the nanofiltration membrane is 200Da-350Da, the nanofiltration temperature is 3°C, and the nanofiltration pressure is 40bar; the dry matter content of the retentate 2 is 32g / 100g;

[0086] 3.2 Add potassium hydroxide to the retentate 2 to adjust the pH to 8.5 to obtain a pH-adjusted whey solution;

[0087] 3.3 The pH-adjusted whey liquid is desalted by electrodialysis to remove the second part of ash to obtain desalted whey liquid. The electrodialysis adopts batch operation (that is, the same batch of whey liquid to be treated is circulated as a whole for electrodialysis until the target end point), and the electrodialysis temperature is selected to be 3°C. The conductivity of the desalted whey liquid at the end point of electrodialysis is 0.80mS / cm, and the mass percentage of ash in dry matter is 1.5%;

[0088] 4. Sterilization

[0089] The desalted whey liquid obtained in step 3 is pasteurized to obtain pasteurized whey liquid, the sterilization conditions are: 72° C., time: 60 seconds;

[0090] 5. Whey Concentrate

[0091] The pasteurized whey liquid is evaporated and concentrated to obtain concentrated whey liquid; the evaporation system adopts a four-stage falling film evaporation system, the evaporation temperature is 70°C, and the pressure is 0.070MPa. The dry matter content of the concentrated whey liquid is 65g / 100g, and the discharge temperature is 65°C;

[0092] 6. Crystallization

[0093] 6.1 Flash evaporation: The concentrated whey liquid passes through the flash evaporation system to obtain flash evaporation whey liquid. The pressure of the flash evaporation system is 0.040 MPa. After passing through the flash evaporation system, the temperature of the flash evaporation whey liquid drops to 30°C.

[0094] 6.2 Crystallization and cooling: The flash evaporated whey liquid obtained in 6.1 is cooled and crystallized, specifically, the flash evaporated whey liquid at 30°C is cooled to 20°C at a rate of 1.0°C / h, and then cooled to 15°C at a rate of 1.5°C / h, and kept at this temperature for later use;

[0095] 7. Spray Drying

[0096] The crystallized whey liquid obtained in 6.2 is spray dried to obtain desalted whey powder. The spray drying air inlet temperature is 160°C and the air outlet temperature is 60°C.

[0097] Example 5

[0098] This embodiment provides a method for preparing whey powder, which is basically the same as the method in Embodiment 2, except that step 2 is not performed (i.e., the ratio of protein to lactose is not adjusted); and after 6.1 flash evaporation, no seed crystals are added, and 6.2 crystallization and cooling is performed directly.

[0099] Comparative Example 1

[0100] This comparative example provides a method for preparing whey powder, which is basically the same as the method in Example 1, except that in step 3.2, the pH of the retentate 2 is adjusted to 7.2 to obtain a pH-adjusted whey solution; the remaining steps are the same as in Example 1.

[0101] Comparative Example 2

[0102] This comparative example provides a method for preparing whey powder, which is basically the same as the method in Example 1, except that in step 6.1, the pressure of the flash evaporation system is adjusted to 0.03 MPa, so that the temperature of the flash evaporation whey liquid is reduced to 27° C. (i.e., the initial temperature of crystallization is reduced), and the remaining steps are the same as those in Example 1.

[0103] Comparative Example 3

[0104] This comparative example provides a method for preparing whey powder, which is basically the same as the method in Example 1, except that the cooling crystallization condition in step 6.2 is changed to: the flash whey liquid at 35° C. is cooled uniformly at a rate of 3° C. / h to 15° C. The remaining steps are the same as in Example 1.

[0105] Comparative Example 4

[0106] This comparative example provides a method for preparing whey powder, which is basically the same as the method in Example 1, except that the temperature reduction crystallization condition is changed in step 6.2: the flash whey liquid at 35°C is uniformly cooled to 20°C at a rate of 0.5°C / h, and then the temperature is reduced to 15°C at a rate of 0.8°C / h. The remaining steps are the same as in Example 1.

[0107] Experimental example

[0108] This experimental example evaluates the preparation results of each embodiment and comparative example, as follows:

[0109] 1. For the desalted whey powder prepared in step 7 of each embodiment and comparative example, the desalting effect (ash content), main substance content, proportion of undenatured whey protein, Maillard reaction degree (furosine content), powder state and thermal stability were tested. The results are shown in Table 1.

[0110] Among them, the ash test method is GB 5009.3. The protein test method is GB5009.5, the lactose determination method is GB5009.8, the fat determination method is GB5009.6, and the moisture determination method is GB5009.3. The test method for the proportion of undenatured whey protein is whey protein nitrogen index (WPN) × 6.38 / 10 / protein content in whey powder (g / 100g). The WPN detection method refers to the #006 method of the American Dairy Product Institute, which represents the content of undenatured whey protein nitrogen in 1g of sample, in mg / g sample. The test method for furosine content refers to NY / T939, in mg / 100g protein.

[0111] Table 1

[0112]

[0113] 2. For the desalted whey powder prepared in step 7 of each embodiment and comparative example, the uniformity of particle size distribution, compression, particle size, crystallization rate, fluidity, dispersibility in water and hygroscopicity were tested, and the results are shown in Table 2. The following indicators are all indicators of whey powder after spray drying. Uniformity indicates the uniformity of particle size, which is expressed by D60 / D10. Compression indicates the degree of compression of the powder after compaction and before compaction. Crystallization rate refers to the mass ratio of crystalline lactose to total lactose. For the test method of fluidity index, please refer to GB / T 31057.3. The dispersion time in water is to sprinkle 0.5g of powder in a test tube with a diameter of 1.8mm filled with water, and count the time it takes for the powder to be wetted by water and completely diffuse in water; hygroscopicity is to place the powder in an environment with a relative humidity of 75% and 30°C for 1 week, and the increase in mass of the powder after absorbing water.

[0114] Table 2

[0115]

[0116] 3. The proportion of undenatured whey protein and the content of furosine in the pasteurized whey liquid prepared in step 4 of each embodiment and comparative example were tested. The results of the pasteurized desalted whey liquid are shown in Table 3.

[0117] Table 3

[0118]

[0119] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a desalted whey product, characterized in that: include: (1) Using natural whey or defatted sweet whey as raw material for nanofiltration, obtaining a nanofiltration retentate having a dry matter content of 18-32 g / 100 g; the pore size of the nanofiltration membrane is 200 Da to 1000 Da; (2) adjusting the pH value of the nanofiltration retentate to 8-9 to obtain a pH-adjusted whey solution; (3) subjecting the pH-adjusted whey solution to electrodialysis to obtain a desalted whey solution; After step (3), the method further includes sterilizing the desalted whey liquid, or mixing the desalted whey liquid with minerals and then sterilizing the desalted whey liquid to obtain sterilized whey liquid; and concentrating the sterilized whey liquid to a dry matter content of 55-65 g / 100 g, and then crystallizing the desalted whey liquid to obtain crystallized whey liquid. The temperature of the concentrated whey liquid is 65-80°C. The crystallization method comprises: flash evaporating the concentrated whey liquid until the temperature of the whey liquid drops to 30-45°C, then cooling the temperature of the whey liquid to 20°C at a rate of 1-3°C / h to complete the first stage of cooling, and then cooling the temperature of the whey liquid to 10-15°C at a rate of 1.5-4°C / h to complete the second stage of cooling, wherein the cooling rate of the first stage is slower than that of the second stage; the flash evaporation pressure is 0.04Mpa-0.08Mpa.

2. The method for preparing a desalted whey product according to claim 1, characterized in that: The temperature of the nanofiltration is 3-25°C, and the pressure of the nanofiltration is 5-40bar; And / or, the temperature of the electrodialysis is 3-25°C; And / or, during the electrodialysis, the same batch of whey liquid to be treated is circulated through the same electrodialyzer for electrodialysis; And / or, the conductivity of the desalted whey liquid at the end point of electrodialysis is 0.1-0.8 mS / cm; and the mass percentage of ash content in dry matter is ≤1.5%.

3. The method for preparing a desalted whey product according to claim 1, characterized in that: Before nanofiltration, the method further includes a step of adjusting the protein and lactose content in the raw material by ultrafiltration; The pore size of the ultrafiltration membrane used in the ultrafiltration is 3000Da-12000Da, the ultrafiltration temperature is 3-25°C, the ultrafiltration pressure is 1-4 bar, and the mass ratio of lactose to protein in the ultrafiltration retentate is (3-7):

1.

4. The method for preparing a desalted whey product according to any one of claims 1 to 3, characterized in that: The method also includes the step of adding lactose seed crystals to the concentrated whey liquid or the flash evaporated whey liquid; the amount of the lactose seed crystals added is one ten-thousandth to one thousandth of the mass of the whey liquid, and the particle size of the lactose seed crystals is less than 5µm.

5. The method for preparing a desalted whey product according to any one of claims 1 to 3, characterized in that: The method also includes the step of spray drying the crystallized whey liquid; the air inlet temperature during the spray drying is 160-200°C, and the air outlet temperature is 60-90°C.

6. The method for preparing a desalted whey product according to claim 4, characterized in that: The method also includes the step of spray drying the crystallized whey liquid; the air inlet temperature during the spray drying is 160-200°C, and the air outlet temperature is 60-90°C.

7. A desalted whey product, characterized in that The desalted whey product is a desalted whey powder prepared by the method according to any one of claims 1 to 6.

8. Use of the desalted whey product according to claim 7 in the preparation of infant formula milk powder.

9. An infant formula milk powder, characterized in that: The desalted whey product according to claim 7.

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