Dairy product and preparation method thereof

Abstract

The invention provides a dairy product and a preparation method thereof, and the preparation method comprises the following steps: sequentially carrying out ultrasonic treatment and microwave radiation treatment on raw milk to obtain modified raw milk; performing crosslinking treatment on the base material containing the modified raw milk in the presence of polyphenol oxidase to obtain a material to be fermented; and fermenting the to-be-fermented material in the presence of a leavening agent to obtain the dairy product. The stability, water binding capacity and other properties of dairy products such as gas-containing yoghourt can be improved.

Description

Technical Field

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

[0002] Dairy products such as yogurt are common nutritional products. However, dairy products generally have problems such as poor stability and water retention, which need to be solved urgently. Summary of the invention

[0003] The present invention provides a dairy product and a preparation method thereof, which can improve the stability and water holding capacity of the dairy product and effectively overcome the defects of the prior art.

[0004] The invention provides a method for preparing a dairy product, comprising the following steps: subjecting raw milk to ultrasonic treatment and microwave radiation treatment in sequence to obtain modified raw milk; subjecting a base material containing the modified raw milk to cross-linking treatment in the presence of polyphenol oxidase to obtain a material to be fermented; and subjecting the material to be fermented to fermentation in the presence of a fermentation agent to obtain a dairy product.

[0005] According to one embodiment of the present invention, the power of the ultrasonic treatment is greater than or equal to 100 W; and / or the time of the ultrasonic treatment is 8 to 12 min; and / or the process of the ultrasonic treatment includes: performing intermittent ultrasonic treatment on the raw milk, during which the working time of each treatment is 1 to 2 s and the intermittent time of each treatment is 1 to 2 s.

[0006] According to one embodiment of the present invention, the power of the ultrasonic treatment is 100-400W.

[0007] According to one embodiment of the present invention, the power of the microwave radiation treatment is 300 to 500 W; and / or the time of the microwave radiation treatment is 2 to 6 minutes.

[0008] According to one embodiment of the present invention, the base material further contains a sweetener, a stabilizer and an emulsifier; wherein the sweetener includes white sugar; and / or the stabilizer includes one or more of carrageenan, konjac gum, gellan gum, xanthan gum, pectin, locust bean gum and guar gum; and / or the emulsifier includes one or more of mono- and diglycerol fatty acid esters, diacetyl tartaric acid mono- and diglycerides, monostearate glyceryl, succinic acid monoglyceride, propylene glycol fatty acid esters, and propylene glycol alginate; and / or, in the base material, the mass percentage of the sweetener is 5-7%; and / or, in the base material, the mass percentage of the stabilizer is 0.2-0.5%; and / or, in the base material, the mass percentage of the emulsifier is 0.1%-0.2%; and / or, the base material further contains sodium citrate, and the mass percentage of the sodium citrate is 0.15-0.3%.

[0009] According to one embodiment of the present invention, the preparation process of the base material comprises: degassing, homogenizing and sterilizing a mixture containing the modified raw milk, a sweetener, a stabilizer and an emulsifier in sequence to obtain the base material; wherein the degassing pressure is 18 to 20 MPa, and the degassing temperature is 60 to 70°C; and / or the homogenization pressure is 200 to 220 bar; and / or the sterilization temperature is 93 to 95°C, and the sterilization time is 280 to 300s; and / or the mixture further contains sodium citrate.

[0010] According to one embodiment of the present invention, the polyphenol oxidase includes catechol oxidase and / or laccase; and / or, the amount of the polyphenol oxidase is 40-80 nkat / g; and / or, the conditions of the cross-linking treatment are: temperature of 40-42°C, time of 2-2.5h; and / or, the preparation method further comprises: after the base material containing the modified raw milk is cross-linked in the presence of polyphenol oxidase, the obtained material system is subjected to enzyme inactivation treatment to obtain the material to be fermented; wherein, the temperature of the enzyme inactivation treatment is 75-80°C, and the time is 2-5min.

[0011] According to one embodiment of the present invention, the fermentation agent includes one or more of Lactococcus lactis lactic acid subsp. lactis, Lactococcus lactis cremoris subsp. and Leuconostoc mesenteroides subsp. mesenteroides; and / or, the mass of the fermentation agent is 0.001% to 0.002% of the mass of the material to be fermented; and / or, the fermentation temperature is 28 to 32°C; and / or, the fermentation is carried out until the acidity of the system reaches 78 to 82°T to obtain the dairy product.

[0012] According to one embodiment of the present invention, the dairy product is aerated yogurt.

[0013] Another aspect of the present invention provides a dairy product, which is prepared according to the above preparation method.

[0014] The dairy product and preparation method provided by the present invention can improve the cross-linked network structure in the dairy product through ultrasonic treatment, microwave treatment, and enzyme treatment of polyphenol oxidase, and then cooperate with the subsequent fermentation process to obtain a dairy product with high stability and water retention, which can reduce whey precipitation, overcome the problem of water separation of dairy products, and optimize the quality of the dairy product such as texture and taste, for example, the prepared dairy product can have the characteristics of sufficient taste, delicate taste, rich milk flavor, pleasant flavor, good texture, etc. Therefore, the present invention can improve the stability and water retention of dairy products and optimize the quality of the dairy product such as texture and taste while ensuring the nutritional value of the dairy product. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0016] Dairy products such as yogurt are common nutritional products. However, dairy products generally have problems such as poor stability and water retention. This is especially true for carbonated dairy products such as carbonated yogurt. The presence of gas in the system makes it easier for the system to be destroyed. For example, casein in carbonated yogurt is more likely to precipitate, resulting in water precipitation (usually the whey and water in dairy products will form whey liquid, which separates from the dairy base (milk base) to produce water precipitation).

[0017] In view of this, an embodiment of the present invention provides a method for preparing a dairy product, comprising the following steps: subjecting raw milk to ultrasonic treatment and microwave radiation treatment in sequence to obtain modified raw milk; subjecting a base material containing the modified raw milk to cross-linking treatment in the presence of polyphenol oxidase to obtain a material to be fermented; and fermenting the material to be fermented in the presence of a fermentation agent to obtain a dairy product.

[0018] The embodiments of the present invention can improve the stability and water retention of the prepared dairy products (fermented milk products), reduce whey precipitation, avoid water separation, and especially solve the water separation problem of carbonated dairy products such as carbonated yogurt.

[0019] According to the research and analysis of the inventors, in the above-mentioned preparation process, the raw milk is subjected to ultrasonic treatment and microwave treatment in sequence. Through the microwave-assisted ultrasonic modification process, the raw milk protein can be physically modified to form a physically modified protein with a suitable structure. Combined with the subsequent cross-linking treatment (enzyme treatment) in the presence of polyphenol oxidase, the physically modified protein in the base material can be cross-linked with components such as polyphenol oxidase to form a highly water-holding network structure. Combined with the subsequent fermentation process, a dairy product with high stability and water retention can be obtained, which can reduce whey precipitation and overcome the problem of water precipitation of dairy products. At the same time, the texture and taste of the dairy products can be optimized. For example, the prepared dairy products can have the characteristics of full taste, delicate taste, rich milk flavor, pleasant flavor, good texture, etc.

[0020] Among them, the intensity of ultrasonic treatment is greater, while the intensity of microwave radiation treatment is relatively gentle. The raw milk protein is first subjected to ultrasonic treatment to preliminarily open the raw milk protein structure, and then subjected to microwave radiation treatment to further open the raw milk protein structure and avoid excessive damage to the texture of the raw milk. Therefore, the raw milk protein is subjected to composite physical modification through the synergistic cooperation of ultrasonic treatment and microwave radiation treatment, so that the formed modified raw milk can have a larger amount of physically modified protein with a more suitable structure, providing more cross-linking sites for subsequent cross-linking treatment, allowing components such as polyphenol oxidase to act on more sites of the physically modified protein, forming a cross-linked network structure with high stability and high water retention, and cooperating with the subsequent fermentation process to obtain dairy products with the advantages of high water retention and good stability.

[0021] Specifically, the dairy product according to the embodiment of the present invention may be in liquid form, specifically may be yogurt, and in particular may be carbonated yogurt (carbonated fermented milk).

[0022] As mentioned above, carbonated yogurt is more prone to water separation, and the water separation is serious. In the embodiments of the present invention, the protein therein can be modified by first subjecting the raw milk to ultrasonic treatment and microwave radiation treatment in sequence. On the one hand, the protein modification can make it have better emulsification properties, which is beneficial to stabilize the system in carbonated yogurt and alleviate whey precipitation. On the other hand, as mentioned above, more cross-linking sites can be provided for subsequent cross-linking treatment to form a cross-linked network structure with high stability and high water retention, which can be used in conjunction with the subsequent fermentation process to produce carbonated yogurt with high water retention.

[0023] Therefore, the embodiments of the present invention can improve the network structure in the carbonated yogurt, improve the stability and water holding capacity of the carbonated yogurt, and reduce the whey precipitation phenomenon by combining ultrasonic treatment, microwave treatment, and polyphenol oxidase enzyme treatment, so that the carbonated yogurt has a higher water holding capacity, and can optimize the quality of the carbonated yogurt, such as the texture and taste. For example, the carbonated yogurt prepared can have the advantages of good color (milky white), uniform state, uniform texture, no whey precipitation, rich characteristic flavor, coordinated aroma, strong taste, delicate taste, rich milk flavor, moderate sweetness and sourness, and uniform taste, while not affecting the gas content of the carbonated yogurt.

[0024] During the above preparation process, the power of the ultrasonic treatment can be greater than or equal to 100 W, which is conducive to more complete physical modification of the raw milk protein structure, providing more action sites for subsequent cross-linking, forming a highly stable and water-retaining cross-linked network, and further improving the stability and water-retaining quality of the obtained dairy products.

[0025] Generally speaking, the power of ultrasonic treatment can be less than or equal to 400 W, and further can be less than or equal to 300 W. This can reduce energy consumption while fully physically modifying the raw milk protein and avoid excessive damage to the raw milk.

[0026] Therefore, in some preferred embodiments, the power of ultrasonic treatment can be 100-400W, for example, 100W, 130W, 150W, 180W, 200W, 230W, 250W, 280W, 300W, 330W, 350W, 380W, 400W or a range consisting of any two of them, preferably 100-300W.

[0027] In addition, the ultrasonic treatment process may include: intermittent ultrasonic treatment of the raw milk, during which the working time of each time is 1 to 2 seconds, and the intermittent time of each time is 1 to 2 seconds, that is, there is an interval of 1 to 2 seconds between each two adjacent working (ultrasonic) processes (no working during the interval), that is, after each working of 1 to 2 seconds, the working is stopped for 1 to 2 seconds (intermittent time), and then the next working is carried out, and so on. Through intermittent ultrasonic treatment, it is possible to avoid excessive physical modification of the raw milk and to avoid damaging the texture of the raw milk, thereby further improving the stability and water retention properties of the obtained dairy products.

[0028] In addition, the time of ultrasonic treatment will also affect the degree of physical modification of raw milk protein to a certain extent. In some preferred embodiments, the time of ultrasonic treatment can be 8 to 12 minutes, for example, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes or a range composed of any two of them, which can further improve the stability and water retention of the obtained dairy products.

[0029] After further research, it is found that, relatively speaking, if the power of microwave radiation treatment is too low, it will affect the degree of physical modification of raw milk to a certain extent, making its physical modification insufficient and having fewer protein cross-linking sites; and if the power of microwave radiation treatment is too large, it will also affect the texture of raw milk to a certain extent. Therefore, considering these factors comprehensively, it is preferred that the power of microwave radiation treatment is 300-500W, for example, 300W, 330W, 350W, 380W, 400W, 430W, 450W, 480W, 500W or a range composed of any two of them, which is conducive to further improving the stability and water retention properties of the obtained dairy products.

[0030] In addition, the microwave radiation treatment time can be 2 to 6 minutes, such as 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes or a range consisting of any two of them, which can further improve the stability and water retention properties of the prepared dairy product.

[0031] In specific implementation, the container containing the raw milk can be placed in a water bath for ultrasonic treatment, and then placed in a microwave device for microwave radiation treatment. Among them, conventional ultrasonic treatment equipment that meets the above ultrasonic power requirements can be used for ultrasonic treatment, and conventional microwave equipment that meets the above microwave power requirements can be used for microwave radiation treatment. Generally, microwave radiation treatment is carried out continuously, that is, during the microwave radiation treatment process, the microwave device continues to work.

[0032] In the embodiments of the present invention, the raw milk used may be conventional fresh milk that complies with China's fresh milk purchase standard GB6914, and may specifically include milk, for example, one or a combination of two or more of skimmed milk or partially skimmed milk. The milk used may be fresh milk, or a reconstituted product made by reducing milk powder, condensed milk or whey protein, or a combination thereof.

[0033] Generally, the above-mentioned base material may also contain one or more of a sweetener, a stabilizer, an emulsifier and sodium citrate, wherein the sweetener can improve the sweetness and taste of the dairy product, the emulsifier can improve the compatibility between the components, the stabilizer can improve the system stability of the dairy product, and sodium citrate can regulate the acidity of the dairy product and avoid the dairy product from being too acidic. When preparing carbonated yogurt, sodium citrate can also assist the fermentation agent in producing gas.

[0034] In some embodiments, the base may contain sweeteners, stabilizers and emulsifiers, and more preferably also contain sodium citrate, which can further improve the stability, texture and other qualities of the dairy product. For example, by introducing these ingredients, the components work synergistically with each other, which is beneficial to the formation of a cross-linked network structure between components such as proteins during the cross-linking process, thereby improving the stability and water retention of the obtained dairy product. At the same time, after the fermented material is fermented, the acidity of the system increases. By introducing these ingredients, the structure of the obtained dairy product (such as the carbonated yogurt described below) can be stabilized to prevent protein denaturation.

[0035] Specifically, the stabilizer may include a colloidal stabilizer, for example, one or more of carrageenan, konjac gum, gellan gum, xanthan gum, pectin, locust bean gum and guar gum. In this way, during the cross-linking treatment, the physically modified protein in the base material can be cross-linked with the colloidal stabilizer and components such as polyphenol oxidase to form a highly stable and highly water-retaining network structure, thereby further improving the system stability and water-retaining properties of the obtained dairy product.

[0036] In some preferred embodiments, the stabilizer in the base includes gellan gum and pectin. The mass ratio of gellan gum to pectin can be 2:(3-5), for example, 2:3, 2:3.5, 2:4, 2:4.5, 2:5 or a range of any two of them. This is more conducive to synergizing with ingredients such as physically modified proteins to form a network structure with high stability and high water retention, thereby further improving the system stability and water retention of the obtained dairy product.

[0037] Specifically, in the above base material, the mass percentage of the stabilizer can be 0.2-0.5%, for example, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5% or a range consisting of any two thereof.

[0038] Additionally, sweeteners may include granulated sugar.

[0039] In addition, in the above base, the mass percentage of the sweetener can be 5-7%, for example, 5%, 5.3%, 5.5%, 5.8%, 6%, 6.3%, 6.5%, 6.8%, 7% or the range of any two thereof.

[0040] In addition, the emulsifier may include one or more of mono- and di-glycerol fatty acid esters, diacetyl tartaric acid mono- and di-glycerol esters, monostearic acid glyceryl ester, succinic acid monoglyceride, propylene glycol fatty acid esters, and propylene glycol alginate.

[0041] In addition, in the above base material, the mass percentage of the emulsifier can be 0.1% to 0.2%, for example, 0.13%, 0.15%, 0.18%, 0.2% or a range consisting of any two thereof.

[0042] In addition, in the above base material, the mass percentage of sodium citrate can be 0-0.3%, more preferably 0.15-0.3%, for example, 0.15%, 0.18%, 0.2%, 0.23%, 0.25%, 0.28%, 0.3% or the range composed of any two thereof.

[0043] It can be understood that the mass percentage of each component in the base refers to the ratio of the mass of each component to the total mass of the base (i.e. the mass fraction of each component based on the total weight of the base being 100%). For example, the mass percentage of the above-mentioned sweetener is 5-7%, which means that, based on the total weight of the base being 100%, the mass fraction of the sweetener (i.e. the ratio of the mass of the sweetener to the total mass of the base) is 5-7%.

[0044] Among them, the total mass of the base is the sum of the masses of all components that constitute the base. For example, the base is composed of modified raw milk, sweetener, stabilizer, emulsifier and sodium citrate. The total mass of the base = the mass of modified raw milk + the mass of sweetener + the mass of stabilizer + the mass of emulsifier + the mass of sodium citrate.

[0045] It should be noted that, for each of the components such as sweeteners, stabilizers, emulsifiers, etc., when they are of multiple types, their mass refers to the sum of the masses of these types. Taking the stabilizer as an example, when the stabilizers in the base are gellan gum and pectin (that is, there are two types of stabilizers in the base, namely gellan gum and pectin), the mass of the stabilizer is the sum of the mass of the gellan gum and the mass of the pectin.

[0046] In addition, for each of the components such as sweeteners, stabilizers, emulsifiers, etc., when there are multiple types, their mass percentage in the base refers to the sum of the mass percentages of these types in the base. Taking stabilizers as an example, when the base contains multiple stabilizers, the mass percentage of the above stabilizer (0.3-0.5%) is the sum of the mass percentages of these stabilizers. For example, there are two types of stabilizers in the base, namely gellan gum and pectin, then in the above base, the mass percentage of the stabilizer (0.3-0.5%) is the sum of the mass percentage of gellan gum and the mass percentage of pectin (that is, the ratio of the sum of the mass of gellan gum and the mass of pectin to the total mass of the base).

[0047] Specifically, the above-mentioned base material can be obtained by degassing, homogenizing and sterilizing the material containing modified raw milk in sequence. For example, in some embodiments, the preparation process of the base material may include: degassing, homogenizing and sterilizing the mixed material containing the modified raw milk, sweetener, stabilizer and emulsifier (i.e., the material containing modified raw milk) in sequence to obtain the base material.

[0048] In a specific implementation, after the raw milk is subjected to ultrasonic treatment and microwave treatment in sequence, the modified raw milk obtained is heated to 55-60°C and then mixed with components such as sweeteners, emulsifiers, stabilizers and sodium citrate (specifically, sweeteners, emulsifiers, stabilizers and sodium citrate can be added to the modified raw milk, and then stirred evenly at 55-60°C, for example, stirred for 10 to 20 minutes (such as 15 minutes) to ensure that the components are evenly mixed) to obtain a mixed material, which is then subjected to degassing, homogenization and sterilization treatments in sequence.

[0049] Specifically, the degassing pressure may be 18-20 MPa, and the degassing temperature may be 60-70°C, that is, the mixed material may be degassed under the conditions of 18-20 MPa and 60-70°C.

[0050] Exemplarily, the degassing pressure can be 18 MPa, 18.3 MPa, 18.5 MPa, 18.8 MPa, 19 MPa, 19.3 MPa, 19.5 MPa, 19.8 MPa, 20 MPa or a range consisting of any two thereof, and the degassing temperature can be 60°C, 62°C, 64°C, 65°C, 67°C, 68°C, 70°C or a range consisting of any two thereof.

[0051] Specifically, the homogenization pressure can be 200-220 bar (that is, the degassed mixed material can be homogenized at a pressure of 200-220 bar), for example, 200 bar, 203 bar, 205 bar, 208 bar, 210 bar, 213 bar, 215 bar, 218 bar, 220 bar or a range consisting of any two of them.

[0052] Specifically, the sterilization temperature can be 93-95°C (that is, the homogenized material can be sterilized at a temperature of 93-95°C), for example, 93°C, 93.5°C, 94°C, 94.5°C, 95°C or a range consisting of any two of them, and the sterilization time can be 280-300s, for example, 280s, 285s, 290s, 295s, 300s or a range consisting of any two of them.

[0053] According to further research by the inventors, in the above cross-linking process, polyphenol oxidase can promote the cross-linking between components such as proteins in the modified raw milk after ultrasonic treatment and microwave radiation treatment, and components such as stabilizers, and polyphenol oxidase will also cross-link, that is, polyphenol oxidase will also cross-link with these components to form a cross-linked network structure with high stability and high water retention. The cross-linking between these components is generally mainly physical cross-linking. Therefore, before fermentation, the raw milk is physically modified by microwave-assisted ultrasonic treatment, and the subsequent cross-linking process in the presence of polyphenol oxidase can improve the stability and water retention of the obtained dairy products (especially carbonated dairy products such as carbonated yogurt).

[0054] Specifically, the polyphenol oxidase may include catechol oxidase and / or laccase, which is beneficial to further improve the stability and water retention of the prepared dairy product.

[0055] In addition, the dosage of polyphenol oxidase can be 40-80 nkat / g, for example, 40 nkat / g, 45 nkat / g, 50 nkat / g, 55 nkat / g, 60 nkat / g, 65 nkat / g, 70 nkat / g, 75 nkat / g, 80 nkat / g or a range consisting of any two thereof. The dosage of polyphenol oxidase means the ratio of the enzyme activity unit (in nkat) of polyphenol oxidase to the mass of the base material (in g), that is, the average amount of polyphenol oxidase used per gram of base material satisfies 40-80 nkat.

[0056] In specific implementation, the cross-linking treatment can be carried out under suitable conditions such as the enzyme activity temperature and pH of the polyphenol oxidase. For example, the base material can be adjusted to a suitable pH, and then polyphenol oxidase is added thereto, and incubated (left standing) at the enzyme activity temperature of the polyphenol oxidase (the temperature of the cross-linking treatment) for a preset time (the time of the cross-linking treatment) to carry out the cross-linking treatment.

[0057] In some embodiments, the temperature of the cross-linking treatment may be 40 to 42° C., and the time of the cross-linking treatment may be 2 to 2.5 hours.

[0058] Generally, the above preparation process may further include: after the base material is subjected to cross-linking treatment in the presence of polyphenol oxidase, the obtained material system is subjected to enzyme inactivation treatment (or enzyme passivation treatment) to obtain the material to be fermented. The enzyme inactivation treatment can passivate the activity of free polyphenol oxidase (i.e., polyphenol oxidase not involved in cross-linking) in the system, making the entire process controllable and avoiding side effects caused by free polyphenol oxidase, such as preventing browning of dairy products.

[0059] Among them, the temperature of enzyme inactivation treatment can be 75-80°C, for example, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C or a range consisting of any two thereof, and the time can be 2-5min, for example, 2min, 3min, 4min, 5min or a range consisting of any two thereof.

[0060] In specific implementation, the container containing the base material can be placed in a water bath at a preset cross-linking treatment temperature (such as 40-42°C) for cross-linking treatment. After the cross-linking treatment is completed, the water bath temperature is raised to a preset enzyme inactivation treatment temperature (such as 75-80°C) and maintained at this temperature for a preset time (such as 2-5 minutes) to perform enzyme inactivation treatment.

[0061] Generally, the temperature at which the fermentation material is inoculated with the fermentation agent and the fermentation temperature are lower than the temperature of the above-mentioned cross-linking treatment and the temperature of the enzyme inactivation treatment, wherein the temperature at which the fermentation material is inoculated with the fermentation agent may be higher than the fermentation temperature. Therefore, after the enzyme inactivation treatment is completed, the obtained material to be fermented can be cooled to the temperature at which the fermentation agent is inoculated, and then the fermentation agent (i.e., the inoculation fermentation agent) is added thereto, and then fermentation is carried out at the fermentation temperature, thereby improving the preparation efficiency.

[0062] In specific implementation, after the enzyme inactivation treatment is completed, the temperature of the obtained material to be fermented can be cooled to 30-35°C (i.e., the temperature of the inoculated fermentation agent), and then the fermentation agent is added thereto, stirred evenly, and then filled and fermented. Specifically, the material to be fermented can be filled and sealed in an aseptic filling equipment, and then placed at a preset fermentation temperature for constant temperature fermentation, and specifically can be left to ferment.

[0063] In some embodiments, the fermentation temperature may be in the range of 28-32°C, for example, 28°C, 29°C, 30°C, 31°C, 32°C or any two thereof.

[0064] In addition, after the fermentation is completed, the fermentation product can be post-ripened, specifically, it can be refrigerated for post-ripening, and the post-ripening treatment temperature can be less than or equal to 10°C, specifically 4-10°C, that is, the fermentation product can be refrigerated for post-ripening at 4-10°C.

[0065] In specific implementation, when the fermented material reaches the system acidity of 78-82°T, it can be cooled to a preset post-ripening treatment temperature (such as 4-10°C as mentioned above) within 15 minutes to inactivate the activity of the starter bacteria, stop fermentation, and perform post-ripening to obtain a dairy product.

[0066] In the above preparation process, the fermentation agent used may include one or more probiotics, preferably one or more of Lactococcus lactis lactic acid subsp. lactis, Lactococcus lactis cremoris subsp. and Leuconostoc mesenteroides subsp. mesenteroides. The use of the fermentation agent is conducive to the preparation of dairy products such as carbonated yogurt.

[0067] Specifically, the amount of the fermentation agent can satisfy the requirement that the mass of the fermentation agent is 0.001% to 0.002% of the mass of the material to be fermented.

[0068] The dairy products prepared in the embodiment of the present invention can be packaged in conventional forms in the art, such as glass bottle packaging, cup packaging, etc. In the embodiment of the present invention, the processes of batching, degassing, homogenization, sterilization, etc. can be carried out using conventional equipment in the art, and there is no particular limitation on this.

[0069] The dairy product provided by the embodiment of the present invention is prepared according to the aforementioned preparation method. As mentioned above, the embodiment of the present invention can improve the stability and water retention of dairy products and other properties, and can optimize the texture and taste of dairy products and other qualities. For related descriptions, please refer to the aforementioned content and will not be elaborated here.

[0070] As mentioned above, the dairy product of the embodiment of the present invention may be in liquid form, specifically yogurt, for example, aerated dairy products such as aerated yogurt, in which the gas mainly includes carbon dioxide (carbonic acid gas).

[0071] As mentioned above, the dairy product of the embodiment of the present invention contains one or more of a sweetener, a stabilizer, an emulsifier and sodium citrate, etc. The specific type and content of each component can be found in the above content, and will not be described in detail here.

[0072] The present invention is further described below through specific embodiments.

[0073] 1. Implementation

[0074] Example 1

[0075] The preparation process of the gas-containing yogurt of this embodiment 1 is as follows:

[0076] 1. Milk-based pretreatment

[0077] (1-1) Ultrasonic treatment: The milk was subjected to intermittent ultrasonic treatment at an ultrasonic power of 300 W for 10 min, wherein the working time of each intermittent ultrasonic treatment was 1 s and the rest time of each intermittent ultrasonic treatment was 1 s;

[0078] (1-2) Microwave radiation treatment: The milk after ultrasonic treatment is subjected to microwave radiation treatment at a power of 500 W for a treatment time of 4 min to obtain modified raw milk;

[0079] (1-3) Mixing: The modified raw milk is heated to 55° C., and then 65 g of white sugar, 1 g of emulsifier, 2 g of gellan gum, 3 g of pectin, and 2.5 g of sodium citrate are added thereto, and then mixed at 55° C. for 10 min to obtain a mixed material; the mixed material is degassed at 65° C. and 18 MPa, and then homogenized at a pressure of 220 bar, and then sterilized at 95° C. for 300 s to obtain a base material; wherein, based on the total weight of the base material being 100%, the mass fraction of white sugar is 6.5%, the mass fraction of the emulsifier is 0.1%, the mass fraction of gellan gum is 0.2%, the mass fraction of pectin is 0.3%, and the mass fraction of sodium citrate is 0.25%;

[0080] (1-4) Enzyme treatment: The pH of the base material was adjusted to 6.0, 80 nkat / g of catechol oxidase was added thereto, mixed well, and incubated in a 40°C water bath for 2 h to perform a cross-linking treatment; then the temperature was raised to 75°C and maintained for 3 min to perform an enzyme inactivation treatment to obtain a material to be fermented;

[0081] 2. Preparation of carbonated fermented milk (carbonated yogurt)

[0082] (2-1) Inoculating the fermentation agent: Cool the material to be fermented to 30-35° C., add 200 U / t of the fermentation agent (the mass of the fermentation agent is about 0.002% of the mass of the material to be fermented, and the fermentation agent includes about 0.01 g of each of Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris), and stir evenly;

[0083] (2-2) Filling and fermentation: The fermented material is filled and sealed in a closed aseptic filling device, and then kept at a constant temperature of 30°C for static fermentation; fermentation is performed until the acidity of the system reaches about 70°F, and the system is cooled to 10°C within 15 minutes, and then refrigerated and ripened to obtain carbonated yogurt.

[0084] Example 2, Example 3 and Example 4: The difference from Example 1 is that in step (1-1), the power of ultrasonic treatment is different, see Table 1 for details. Except for the difference shown in Table 1, the other conditions are the same.

[0085] Example 5, Example 6 and Example 7: The difference from Example 1 is that in step (1-2), the power of microwave radiation treatment is different, see Table 1 for details. Except for the differences shown in Table 1, the other conditions are the same.

[0086] Example 8: The difference from Example 1 is that the power of the ultrasonic treatment in step (1-1) and the power of the microwave radiation treatment in step (1-2) are different, see Table 1 for details. Except for the differences shown in Table 1, the other conditions are the same.

[0087] Example 9, Example 10 and Example 11: The difference from Example 1 is that the amount of catechol oxidase used in step (1-4) is different, see Table 1 for details. Except for the difference shown in Table 1, the other conditions are the same.

[0088] Example 12: The difference from Example 1 is that in step (1-4), laccase is used to replace catechol oxidase, as shown in Table 1. Except for the difference shown in Table 1, the other conditions are the same.

[0089] Example 13: The difference from Example 2 is that (1) the power of the microwave radiation treatment in step (1-2) is different; (2) the amount of catechol oxidase used in step (1-4) is different; see Table 1 for details. Except for the differences shown in Table 1, the other conditions are the same.

[0090] Comparative Example 1: The difference from Example 1 is that (1) the milk is not subjected to ultrasonic treatment in step (1-1); (2) the power of the microwave radiation treatment in step (1-2) is different; (3) the amount of catechol oxidase used in step (1-4) is different; see Table 1 for details. Except for the differences shown in Table 1, the other conditions are the same.

[0091] Comparative Example 2: The difference from Example 2 is that (1) the milk after ultrasonic treatment is not subjected to microwave radiation treatment in step (1-2); (2) the amount of catechol oxidase used in step (1-4) is different; see Table 1 for details. Except for the differences shown in Table 1, the other conditions are the same.

[0092] Comparative Example 3: The difference from Example 2 is that (1) the power of the microwave radiation treatment in step (1-2) is different; (2) the enzyme treatment in step (1-4) is not performed (i.e., the base material prepared in step (1-3) is directly used as the fermented material for subsequent steps (2-1) and (2-2) and other processes); see Table 1 for details. Except for the differences shown in Table 1, the other conditions are the same.

[0093] Table 1

[0094]

[0095] 2. Sensory evaluation and property testing of carbonated fermented milk

[0096] 1. Sensory evaluation

[0097] The gas-containing fermented milk prepared in each embodiment and comparative example was subjected to sensory evaluation in terms of taste and flavor. The main evaluation items included: tissue state (whey separation, fat floating, viscosity, fineness, texture, etc.), color, flavor (including fat taste), mouthfeel, etc. The sensory scoring standards are shown in Table 2.

[0098] When the sensory evaluation of the carbonated fermented milk prepared in each embodiment or comparative example was conducted, 30 people participated in the experiment, and the average of the scores of the 30 people was taken as the final score result. The experimental record results are shown in Table 3.

[0099] Table 2

[0100]

[0101] Table 3

[0102]

[0103] As can be seen from Table 3, compared with Comparative Example 1 (not subjected to ultrasonic treatment), Comparative Example 2 (not subjected to microwave radiation treatment) and Comparative Example 3 (not subjected to enzyme treatment), Examples 1 to 13 use ultrasonic treatment, microwave treatment and polyphenol oxidase enzyme treatment in combination, which can improve the quality of the obtained carbonated fermented milk, such as the tissue state, taste and flavor. In particular, in Examples 1, 2, 5, 8, 9, 12 and 13, by regulating the physical modification conditions of milk and the amount of polyphenol oxidase used in the enzyme treatment process, the whey precipitation problem of the carbonated fermented milk can be controlled to the maximum extent, and the quality of the texture, flavor and taste of the carbonated fermented milk can be improved, so that the carbonated fermented milk has the advantages of good color (milky white), uniform state, uniform texture, no whey precipitation, rich characteristic flavor, coordinated aroma, strong taste, delicate taste, moderate sweetness and sourness, and uniform taste.

[0104] Specifically, compared with Example 3 (ultrasonic power is too low (<100 W)), the ultrasonic power of Examples 1-2 and Example 4 is in a more suitable range (100-400 W), which can have a better improvement effect on whey precipitation of carbonated fermented milk.

[0105] Specifically, compared with Example 6 (microwave power is too low (<300W)) and Example 7 (microwave power is too high (>500W)), the power of microwave radiation treatment in Example 1 and Example 5 is in a more suitable range (300-500W), which can significantly improve the texture and color of carbonated fermented milk, as well as the quality of taste and flavor, and improve the problem of whey precipitation.

[0106] Specifically, compared with Example 10 (the amount of polyphenol oxidase used is too little (<40 nkat / g)) and Example 11 (the amount of polyphenol oxidase used is too much (>80 nkat / g)), the amount of polyphenol oxidase used in Examples 1 and 9 is within a more suitable range (40-80 nkat / g), which can further improve the organizational morphology and color, taste and flavor of the carbonated fermented milk, and improve the problem of whey precipitation.

[0107] 2. Test of water holding capacity and gas content of carbonated fermented milk

[0108] The water holding capacity and gas content of the carbonated fermented milk prepared in each embodiment and comparative example were measured by centrifugation. The specific test results are shown in Table 4.

[0109] The water holding capacity test process is as follows: record the total weight of the sample; put the sample (carbonated fermented milk) into a centrifuge, centrifuge it at 4000 rpm for 10 minutes, and record the weight of the supernatant; then calculate the water holding capacity according to the following formula: water holding capacity = (total weight of sample - weight of supernatant) / total weight of sample.

[0110] Among them, the pressure and carbon dioxide gas capacity multiples are measured according to the pressure reducer method provided in the standard "GB / T 10792-2008 Carbonated Beverages (Soda)".

[0111] 3. Analysis of viscosity and emulsification stability index of carbonated fermented milk

[0112] The viscosity of the carbonated fermented milk prepared in the examples and comparative examples was analyzed, and the milk-based (base material) protein after mixing was purified to analyze the protein emulsification stability. The results are shown in Table 4.

[0113] The emulsion stability index test process is as follows: after mixing, the milk-based (base material) protein is purified to obtain a sample solution to be tested; 3 mL of rapeseed oil and 9 mL of the sample solution to be tested are homogenized on a high-speed dispersing homogenizer for 1 min, 10 mL of a 0.1% SDS solution is added thereto for dilution, and the absorbance value is measured at a wavelength of 500 nm, which is A 0 ; Then the emulsion (the diluted sample solution to be tested) was allowed to stand for 10 min, and then diluted and measured in the same way to obtain the absorbance value A 10 ; Calculate the stability index (emulsion stability (ES)) according to the following formula: Emulsion stability ES = A 10 / A 0 , where A 0 is the absorbance value at zero time, A 10 is the absorbance value at 10 min.

[0114] Table 4

[0115]

[0116] It can be seen from Table 4 that there is no significant difference in the gas content of the carbonated fermented milk of Examples 1 to 13 and Comparative Examples 1 to 3, indicating that the combination of ultrasonic treatment, microwave radiation treatment, and enzyme treatment with polyphenol oxidase does not substantially affect the gas content of the carbonated fermented milk.

[0117] In addition, compared with Comparative Examples 1 to 3, Examples 1 to 13 can take into account the improvement of the water holding capacity and emulsification stability index of the carbonated fermented milk, especially Examples 1, 2, 5, 8, 9, 12 and 13. By regulating the physical modification conditions of the milk and the amount of polyphenol oxidase used in the enzyme treatment process, the water holding capacity and stability of the carbonated fermented milk can be significantly improved, the whey precipitation of the carbonated fermented milk can be inhibited, and the viscosity and other properties of the carbonated fermented milk can be improved.

[0118] This further illustrates that the combined treatment of ultrasonic treatment, microwave treatment and polyphenol oxidase enzyme treatment can improve the network structure in the carbonated fermented milk, thereby improving its water retention and stability. Among them, the protein emulsification stability index analysis shows that under the combined treatment of ultrasonic treatment, microwave treatment and polyphenol oxidase enzyme treatment, protein modification makes the emulsification performance better, which is beneficial to stabilize the system in high-gas content yogurt and alleviate whey precipitation.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a dairy product, characterized in that: The following steps are involved: The raw milk is subjected to ultrasonic treatment and microwave radiation treatment in sequence to obtain modified raw milk; subjecting the base material containing the modified raw milk to cross-linking treatment in the presence of polyphenol oxidase to obtain a material to be fermented; The material to be fermented is fermented in the presence of a fermentation agent to obtain a dairy product.

2. The method for preparing a dairy product according to claim 1, characterized in that: The power of the ultrasonic treatment is greater than or equal to 100W; And / or, the ultrasonic treatment time is 8 to 12 minutes; And / or, the ultrasonic treatment process includes: performing intermittent ultrasonic treatment on the raw milk, and during the intermittent ultrasonic treatment process, each working time is 1 to 2 seconds, and each intermittent time is 1 to 2 seconds.

3. The method for preparing a dairy product according to claim 2, characterized in that: The power of the ultrasonic treatment is 100-400W.

4. The method for preparing a dairy product according to claim 1, characterized in that: The power of the microwave radiation treatment is 300 to 500W; And / or, the microwave radiation treatment time is 2 to 6 minutes.

5. The method for preparing a dairy product according to claim 1, characterized in that: The base material also contains a sweetener, a stabilizer and an emulsifier; wherein, The sweetener includes white sugar; and / or, the stabilizer comprises one or more of carrageenan, konjac gum, gellan gum, xanthan gum, pectin, locust bean gum and guar gum; And / or, the emulsifier includes one or more of mono- and di-glycerol fatty acid esters, diacetyl tartaric acid mono- and di-glycerides, monostearate glyceryl, succinate monoglyceride, propylene glycol fatty acid esters, and propylene glycol alginate; And / or, in the base material, the mass percentage of the sweetener is 5-7%; And / or, in the base material, the mass percentage of the stabilizer is 0.2-0.5%; And / or, in the base material, the mass percentage of the emulsifier is 0.1% to 0.2%; And / or, the base material further contains sodium citrate, and the mass percentage of the sodium citrate is 0.15-0.3%.

6. The method for preparing a dairy product according to any one of claims 1 to 5, characterized in that: The preparation process of the base material comprises: degassing, homogenizing and sterilizing the mixture containing the modified raw milk, sweetener, stabilizer and emulsifier in sequence to obtain the base material; wherein, The degassing pressure is 18-20 MPa, and the degassing temperature is 60-70°C; And / or, the homogenization pressure is 200-220 bar; And / or, the sterilization temperature is 93-95°C, and the sterilization time is 280-300s; And / or, the mixture further contains sodium citrate.

7. The method for preparing a dairy product according to any one of claims 1 to 5, characterized in that: The polyphenol oxidase comprises catechol oxidase and / or laccase; And / or, the dosage of the polyphenol oxidase is 40-80 nkat / g; And / or, the conditions of the cross-linking treatment are: temperature of 40-42° C., time of 2-2.5 h; And / or, the preparation method further comprises: after subjecting the base material containing the modified raw milk to cross-linking treatment in the presence of polyphenol oxidase, performing enzyme inactivation treatment on the obtained material system to obtain the material to be fermented; wherein the enzyme inactivation treatment is performed at a temperature of 75 to 80° C. for a time of 2 to 5 minutes.

8. The method for preparing a dairy product according to any one of claims 1 to 5, characterized in that: The fermentation agent includes one or more of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, and Leuconostoc mesenteroides subsp. mesenteroides; And / or, the mass of the fermentation agent is 0.001% to 0.002% of the mass of the material to be fermented; And / or, the fermentation temperature is 28-32°C; And / or, the fermentation is carried out until the acidity of the system reaches 78-82°T to obtain the dairy product.

9. The method for preparing a dairy product according to any one of claims 1 to 5, characterized in that: The dairy product is aerated yogurt.

10. A dairy product, characterized in that It is prepared according to the preparation method according to any one of claims 1 to 9.

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