A greek yoghurt and a method for preparing the same

Abstract

The present application belongs to the technical field of fermented dairy product processing, and particularly relates to a Greek yogurt and a preparation method thereof. Through cooperation between various steps, especially limitation of protein content in the first two steps and intermittent ultrasonic treatment after fermentation to remove whey, the present application can avoid problems such as product powder astringency, strong paste mouth, strong granular feeling, poor tissue state, too low viscosity, water separation during shelf life and the like of high-protein yogurt. In the present application, intermittent ultrasonic treatment is used to remove whey, increase protein content and improve product viscosity. Since whey is discharged, whey separation during shelf life is avoided, and the stability during shelf life is ensured. Compared with centrifugal separation or membrane filtration to remove whey, ultrasonic treatment effectively reduces the shear caused by product whey separation over the pump, improves the water holding capacity of the product, and thus stabilizes the shelf life. In addition, ultrasonic waves can reduce the average particle size of the system, narrow the particle size distribution range, reduce the granular feeling of the product and improve the smoothness.

Description

Technical Field

[0001] This invention belongs to the field of fermented dairy product processing technology, specifically relating to a Greek yogurt and its preparation method. Background Technology

[0002] Greek yogurt, also known as whey-free yogurt, is characterized by its high protein content, thick texture, delicate and rich flavor, and taste that is somewhere between yogurt and cheese. Greek yogurt is highly regarded for its unique sensory appeal and nutritional value, and has been a hit in the yogurt market for the past decade.

[0003] Currently, there are three common methods in existing technologies to increase the protein content of Greek yogurt: (1) pre-concentration, including flash evaporation, nanofiltration, microfiltration, ultrafiltration, reverse osmosis, etc.; (2) adding exogenous protein powder, including whey protein, milk protein, whole milk powder, skim milk powder, etc.; (3) whey separation method, including membrane concentration (nanofiltration, microfiltration, ultrafiltration, reverse osmosis, etc.) or centrifugation after fermentation to remove whey.

[0004] However, when using the above three methods to produce Greek yogurt with a protein content higher than 6.0g / 100mL, various problems arise, including powdery and astringent products, strong stickiness, a grainy texture, poor consistency, low viscosity, and water separation during shelf life. For example, using pre-concentration, a protein index higher than 6.0g / 100mL due to membrane concentration will affect fermentation time and flavor due to excessively high ion concentration, while also resulting in larger particle size and a noticeable astringency. Adding exogenous protein limits the protein content of yogurt products; adding too much protein powder leads to severe powdery and astringent taste and poor mouthfeel. Using whey separation and post-membrane concentration after fermentation subjectes the material to significant pressure during membrane processing, disrupting the original structure and network, leading to unstable shelf life and low viscosity. Centrifugation after fermentation to remove whey is also problematic; insufficient centrifugal force will not achieve the target protein content, while excessive force will damage the product system, making it prone to poor consistency and water separation during shelf life. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problems that occur in the prior art when the protein content of Greek yogurt is higher than 6.0g / 100mL, such as varying degrees of powderiness, strong stickiness, strong graininess, poor texture, low viscosity, and water separation during shelf life. The present invention provides a Greek yogurt and its preparation method.

[0006] Therefore, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing Greek yogurt, comprising the following steps:

[0008] S1, concentrate the liquid milk to control its protein content at 2.4-4.0g / 100mL;

[0009] S2, mix the concentrated liquid milk with protein powder to obtain a fermentation base, and control the protein content in the fermentation base to be 2.4-6.0g / 100mL;

[0010] S3 involves homogenizing the fermentation substrate, sterilizing it once, and then fermenting it.

[0011] S4. The fermented material is subjected to intermittent ultrasonic treatment for 10-60 minutes to remove whey and undergo secondary sterilization to obtain the Greek yogurt.

[0012] The ultrasonic intermittent treatment includes ultrasonic treatment for 4-30 seconds, followed by an interval of 4-30 seconds. The frequency of the ultrasonic treatment is 20-40KHz, and the power is 20-60W.

[0013] Optionally, during the intermittent ultrasonic treatment, the ultrasonic probe is located in the fermented material, and the whey is slowly discharged during the intermittent ultrasonic treatment. The separated whey is discharged through a small hole at the bottom of the fermentation tank.

[0014] Optionally, the temperature for the first sterilization is 75-145℃, and the time is 200-300s;

[0015] And / or, the secondary sterilization temperature is 60-105℃ and the time is 2-40s.

[0016] Optionally, the fermentation process includes inoculating the material after primary sterilization with a yogurt starter culture, fermenting at a temperature of 25-45°C for 5-20 hours, and achieving a final pH of 4.3-4.6.

[0017] Optionally, the homogenization temperature is 45-75°C, and the total homogenization pressure is 120-200 bar;

[0018] And / or, the concentration method in step S1 is at least one of flash evaporation, falling membrane, nanofiltration, microfiltration, ultrafiltration, and reverse osmosis.

[0019] Optionally, step S2 may also include adding conventional yogurt ingredients to the concentrated liquid milk;

[0020] Optionally, the conventional yogurt ingredients include at least one of sweeteners, protein powder, heavy cream, and stabilizers.

[0021] Optionally, the Greek yogurt comprises the following ingredients in parts by weight:

[0022] Concentrated liquid milk 75-95 parts; protein powder 0.2-6 parts; light cream 0.2-1 part; sweetener 5-10 parts; yogurt starter 0.2-1 part; stabilizer 2-5 parts.

[0023] Optionally, at least one of the following (1)-(6) must be satisfied:

[0024] (1) The liquid milk is at least one of cow's milk, goat's milk, camel's milk or reconstituted milk;

[0025] (2) The liquid milk is skimmed, whole, or semi-skimmed liquid milk;

[0026] (3) The protein powder is at least one of whey protein powder, milk protein powder, skim milk powder, and whole milk powder;

[0027] (4) The yogurt starter is at least one of Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus plantarum, Lactobacillus casei, Lactococcus lactis subsp. lactis, and Lactococcus lactis subsp. milk fat.

[0028] (5) The sweetener is at least one of white sugar, fructose syrup, maltose, erythritol and stevia;

[0029] (6) The stabilizer is at least one of agar, pectin, gelatin, gellan gum, and starch.

[0030] All the raw materials selected in this invention are conventional raw materials used in the yogurt preparation process, and the addition of each component complies with the requirements of relevant laws, regulations or standards.

[0031] The present invention also provides a Greek yogurt prepared by the above-described preparation method.

[0032] Optionally, the Greek yogurt has a protein content of 4-15g / 100mL; preferably, the Greek yogurt has a protein content of 6-15g / 100mL.

[0033] The technical solution of this invention has the following advantages:

[0034] 1. The method for preparing Greek yogurt provided by this invention includes the following steps: S1, concentrating liquid milk to control its protein content at 2.4-4.0 g / 100 mL; S2, mixing the concentrated liquid milk with protein powder to obtain a fermentation base, controlling the protein content in the fermentation base at 2.4-6.0 g / 100 mL; S3, homogenizing the fermentation base, sterilizing it once, and fermenting it; S4, subjecting the fermented material to intermittent ultrasonic treatment for 10-60 min to remove whey, sterilizing it a second time, and obtaining the Greek yogurt; wherein, the intermittent ultrasonic treatment includes ultrasonic treatment for 4-30 s, with an interval of 4-30 s, the frequency of the ultrasonic treatment being 20-40 kHz, and the power being 20-60 W. This invention, through the coordination between the various steps, especially the limitation of the protein content in the first two steps and the application of intermittent ultrasonic treatment after fermentation, can avoid problems such as varying degrees of powderiness, strong stickiness, strong graininess, poor texture, excessively low viscosity, and water separation during shelf life. The use of intermittent ultrasonic treatment to remove whey increases protein content. Compared to applying ultrasound during fermentation, this method shortens fermentation time, saves on industrial production costs, increases product viscosity, and balances the viscosity loss during the subsequent secondary pasteurization of room-temperature yogurt. Furthermore, by removing whey, it prevents whey separation during the shelf life, ensuring stable shelf-life. Compared to centrifugation or membrane filtration for whey removal, ultrasonic treatment effectively reduces the structural damage caused by shearing after dewhey removal and membrane filtration, improving the product's water-holding capacity and thus stabilizing shelf life. Additionally, ultrasound can reduce the average particle size of the system, narrow the particle size distribution range, reduce the product's graininess, and improve smoothness.

[0035] In addition, secondary sterilization can produce room-temperature Greek yogurt, which is convenient to store and has a long shelf life.

[0036] 2. The Greek yogurt provided by the present invention is prepared using the specific preparation method provided by the present invention, and the protein content can be as high as 4-15g / 100mL; preferably, the protein content of the Greek yogurt is as high as 6-15g / 100mL, and there will be no problems such as powdery texture, strong stickiness, strong graininess, poor texture, low viscosity, or water separation during shelf life. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is the clarification index result of an embodiment of the present invention;

[0039] Figure 2 These are the clarification index results of Embodiment 2 and the comparative example of the present invention. Detailed Implementation

[0040] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0041] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0042] Example 1

[0043] This embodiment provides a Greek yogurt, the preparation method of which includes the following steps:

[0044] (1) After passing milk through a reverse osmosis membrane (RO), the protein content of concentrated milk is controlled at 2.6±0.2g / 100ml. When the temperature is raised to 25℃, the raw materials are stirred. 1kg whey protein powder, 1kg light cream, 50kg white sugar, and 20kg stabilizer are added to the milk in sequence. The stabilizer includes 1.8kg agar, 1.8kg pectin, 5kg gelatin, 0.3kg gellan gum, and 11.1kg starch. The stirring speed is 40 rpm and the stirring is carried out for 20 minutes to allow the raw materials to dissolve fully. The protein content of the system is 3.6g / 100ml.

[0045] (2) The mixture obtained in step (1) is homogenized, wherein the homogenization temperature is 55°C and the total homogenization pressure is 160 bar, to obtain a homogenized product.

[0046] (3) Sterilize the homogenized product at 85°C for 300s, and then cool the sterilized product to 43°C.

[0047] (4) Add 0.2 kg of yogurt starter to the cooled sterilized product. The yogurt starter is Chr. Hansen, model MN01. Ferment in a horizontal fermenter at 43°C until the acidity of the fermentation liquid is >70° and the pH is 4.4-4.5. At the same time, break the emulsion and stir. Simultaneously, lower the temperature of the yogurt to 15°C.

[0048] (5) Apply high-intensity ultrasonic intermittent treatment to the fermented yogurt in step (4) to remove whey. The frequency of the ultrasonic device is 20KHz and the power is 30W. The ultrasonic treatment lasts for 8s, with an interval of 12s. Each cycle lasts for 20s. The total time for ultrasonic intermittent treatment is 30min.

[0049] (6) Sterilize the yogurt obtained in step (5) at 75°C for 6 seconds to obtain Greek yogurt with a protein content of 6.2g / 100ml.

[0050] Example 2

[0051] This embodiment provides a Greek yogurt, the preparation method of which includes the following steps:

[0052] (1) After the milk is passed through an ultrafiltration membrane (UF), the protein content of the concentrated milk is controlled at 3.0±0.2g / 100ml. When the temperature is raised to 45℃, the raw materials are stirred. 10kg whey protein powder, 5kg light cream, 60kg white sugar, and 25kg stabilizer are added to the milk in sequence. The stabilizer includes 1.7kg agar, 1.8kg pectin, 6kg gelatin, 0.5kg gellan gum, and 15kg starch. The stirring speed is 40 rpm and the stirring is carried out for 30 minutes to allow the raw materials to dissolve fully. The protein content of the system is 5.1g / 100ml.

[0053] (2) The mixture obtained in step (1) is homogenized, wherein the homogenization temperature is 62°C and the total homogenization pressure is 140 bar, to obtain a homogenized product.

[0054] (3) Sterilize the homogenized product at 85°C for 300s, and then cool the sterilized product to 43°C.

[0055] (4) Add 0.2 kg of yogurt starter to the cooled sterilized product. The yogurt starter is Chr. Hansen, model MN01. Ferment in a horizontal fermenter at 43°C until the acidity of the fermentation liquid is >70° and the pH is 4.4-4.5. At the same time, break the emulsion and stir. Simultaneously, lower the temperature of the yogurt to 15°C.

[0056] (5) Apply high-intensity ultrasonic intermittent treatment to the fermented yogurt in step (4) to remove whey. The frequency of the ultrasonic device is 30KHz and the power is 50W. The ultrasonic treatment lasts for 10s, followed by an interval of 10s. Each cycle lasts for 20s. The total time for ultrasonic intermittent treatment is 30min.

[0057] (6) The yogurt obtained in step (5) is sterilized at 75°C for 6 seconds to obtain high-protein Greek yogurt with a protein content of 8.1g / 100ml.

[0058] Example 3

[0059] This embodiment provides a Greek yogurt, the preparation method of which includes the following steps:

[0060] (1) After the milk is flash-electrolyzed, the protein content of the concentrated milk is controlled at 3.8±0.2g / 100ml. When the temperature is raised to 55℃, the milk is stirred to start the process. 30kg whey protein powder, 10kg light cream, 80kg white sugar, and 30kg stabilizer are added to the milk in sequence. The stabilizer includes 2.0kg agar, 1.7kg pectin, 6kg gelatin, 0.3kg gellan gum, and 20kg starch. The stirring speed is 40 rpm and the mixture is stirred for 30 minutes to allow the raw materials to dissolve fully. The protein content of the system is 6.0g / 100ml.

[0061] (2) The mixture obtained in step (1) is homogenized, wherein the homogenization temperature is 65°C and the total homogenization pressure is 160 bar, to obtain a homogenized product.

[0062] (3) Sterilize the homogenized product at 85°C for 300s, and then cool the sterilized product to 43°C.

[0063] (4) Add 0.2 kg of yogurt starter to the cooled sterilized product. The yogurt starter is Chr. Hansen, model MN01. Ferment in a horizontal fermenter at 43°C until the acidity of the fermentation liquid is >70° and the pH is 4.4-4.5. At the same time, break the emulsion and stir. At the same time, lower the temperature of the yogurt to 15°C.

[0064] (5) Apply high-intensity ultrasonic intermittent treatment to the fermented yogurt in step (4) to remove whey. The frequency of the ultrasonic device is 40KHz and the power is 40W. The ultrasonic treatment lasts for 15s, followed by an interval of 15s. Each cycle lasts for 30s. The total time for ultrasonic intermittent treatment is 40min.

[0065] (6) Sterilize the yogurt obtained in step (5) at 75°C for 6 seconds to obtain Greek yogurt with a protein content of 15.1g / 100ml.

[0066] Example 4

[0067] This embodiment provides a Greek yogurt, the preparation method of which includes the following steps:

[0068] (1) After the milk is passed through an ultrafiltration membrane (UF), the protein content of the concentrated milk is controlled at 3.0±0.2g / 100ml. When the temperature is raised to 45℃, the raw materials are stirred. 10kg whey protein powder, 5kg light cream, 60kg white sugar, and 25kg stabilizer are added to the milk in sequence. The stabilizer includes 1.7kg agar, 1.8kg pectin, 6kg gelatin, 0.5kg gellan gum, and 15kg starch. The stirring speed is 40 rpm and the stirring is carried out for 30 minutes to allow the raw materials to dissolve fully. The protein content of the system is 5.1g / 100ml.

[0069] (2) The mixture obtained in step (1) is homogenized, wherein the homogenization temperature is 75°C and the total homogenization pressure is 120 bar, to obtain a homogenized product.

[0070] (3) Sterilize the homogenized product at 105°C for 200s, and then cool the sterilized product to 38°C.

[0071] (4) Add 0.2 kg of yogurt starter to the cooled sterilized product. The yogurt starter is Chr. Hansen, model MN01. Ferment in a horizontal fermenter at 38°C until the acidity of the fermentation liquid is >70° and the pH is 4.4-4.5. At the same time, break the emulsion and stir. At the same time, lower the temperature of the yogurt to 15°C.

[0072] (5) Apply high-intensity ultrasonic intermittent treatment to the fermented yogurt in step (4) to remove whey. The frequency of the ultrasonic device is 30KHz and the power is 50W. The ultrasonic treatment lasts for 10s, followed by an interval of 10s. Each cycle lasts for 20s. The total time for ultrasonic intermittent treatment is 30min.

[0073] (6) The yogurt obtained in step (5) was sterilized at 105℃ for 2 seconds to obtain high-protein Greek yogurt with a protein content of 8.0g / 100ml. This indicates that changes in sterilization, homogenization, and fermentation temperature do not significantly affect the protein content, but do affect the fermentation time and stability. Low homogenization pressure results in large product particles, long sterilization time, and poor product shelf-life stability.

[0074] Example 5

[0075] This embodiment provides a Greek yogurt, the preparation method of which includes the following steps:

[0076] (1) After the milk is passed through an ultrafiltration membrane (UF), the protein content of the concentrated milk is controlled at 3.0±0.2g / 100ml. When the temperature is raised to 45℃, the raw materials are stirred. 10kg whey protein powder, 5kg light cream, 60kg white sugar, and 25kg stabilizer are added to the milk in sequence. The stabilizer includes 1.7kg agar, 1.8kg pectin, 6kg gelatin, 0.5kg gellan gum, and 15kg starch. The stirring speed is 40 rpm and the stirring is carried out for 30 minutes to allow the raw materials to dissolve fully. The protein content of the system is 5.1g / 100ml.

[0077] (2) The mixture obtained in step (1) is homogenized, wherein the homogenization temperature is 62°C and the total homogenization pressure is 140 bar, to obtain a homogenized product.

[0078] (3) Sterilize the homogenized product at 85°C for 300s, and then cool the sterilized product to 43°C.

[0079] (4) Add 0.2 kg of yogurt starter to the cooled sterilized product. The yogurt starter is Chr. Hansen, model MN01. Ferment in a horizontal fermenter at 43°C until the acidity of the fermentation liquid is >70° and the pH is 4.4-4.5. At the same time, break the emulsion and stir. At the same time, lower the temperature of the yogurt to 15°C.

[0080] (5) Apply high-intensity ultrasonic intermittent treatment to the fermented yogurt in step (4) to remove whey. The frequency of the ultrasonic device is 20KHz and the power is 20W. The ultrasonic treatment lasts for 5s, followed by an interval of 5s. Each cycle lasts for 10s. The total time for ultrasonic intermittent treatment is 10min.

[0081] (6) The yogurt obtained in step (5) is sterilized at 75°C for 6 seconds to obtain high-protein Greek yogurt with a protein content of 6.1g / 100ml.

[0082] Example 6

[0083] This embodiment provides a Greek yogurt, the preparation method of which includes the following steps:

[0084] (1) After the milk is passed through an ultrafiltration membrane (UF), the protein content of the concentrated milk is controlled at 3.0±0.2g / 100ml. When the temperature is raised to 45℃, the raw materials are stirred. 10kg whey protein powder, 5kg light cream, 60kg white sugar, and 25kg stabilizer are added to the milk in sequence. The stabilizer includes 1.7kg agar, 1.8kg pectin, 6kg gelatin, 0.5kg gellan gum, and 15kg starch. The stirring speed is 40 rpm and the stirring is carried out for 30 minutes to allow the raw materials to dissolve fully. The protein content of the system is 5.1g / 100ml.

[0085] (2) The mixture obtained in step (1) is homogenized, wherein the homogenization temperature is 62°C and the total homogenization pressure is 140 bar, to obtain a homogenized product.

[0086] (3) Sterilize the homogenized product at 85°C for 300s, and then cool the sterilized product to 43°C.

[0087] (4) Add 0.2 kg of yogurt starter to the cooled sterilized product. The yogurt starter is Chr. Hansen, model MN01. Ferment in a horizontal fermenter at 43°C until the acidity of the fermentation liquid is >70° and the pH is 4.4-4.5. At the same time, break the emulsion and stir. Simultaneously, lower the temperature of the yogurt to 15°C.

[0088] (5) Apply high-intensity ultrasonic intermittent treatment to the fermented yogurt in step (4) to remove whey. The frequency of the ultrasonic device is 40KHz and the power is 60W. The ultrasonic treatment lasts for 30s, followed by an interval of 30s. Each cycle lasts for 60s. The total time for ultrasonic intermittent treatment is 60min.

[0089] (6) The yogurt obtained in step (5) is sterilized at 75°C for 6 seconds to obtain high-protein Greek yogurt with a protein content of 14.9g / 100ml.

[0090] Comparative Example 1

[0091] The mixture was prepared according to the method of Example 2, with the following differences: (1) no exogenous protein powder was added, and the protein content was controlled at 8.0±0.2g / 100ml after passing through an ultrafiltration membrane in the milk stage; (5) whey was not removed by ultrasonic treatment, and the mixture was directly sterilized at 75℃ for 6s in (6). The protein content of the final product was controlled to be 8.0±0.2g / 100ml.

[0092] Comparative Example 2

[0093] The mixture was prepared according to the method of Example 2, with the following differences: (1) the milk was not subjected to ultrafiltration membrane to regulate protein content, and exogenous whey protein powder was added regardless of the protein content, with the protein content controlled at 8.0±0.2g / 100ml; (5) the whey was not removed by ultrasonic treatment, and the mixture was directly sterilized at 75℃ for 6s as in (6). The final product protein content was controlled at 8.0±0.2g / 100ml.

[0094] Comparative Example 3

[0095] The mixture was prepared according to the method of Example 2, with the following differences: (1) the milk was not subjected to ultrafiltration membrane and no protein powder was added; (5) the whey was not removed by ultrasonic treatment, but was concentrated by membrane, that is, the fermented yogurt was subjected to ultrafiltration membrane (UF) to remove whey and then sterilized at 75°C for 6 seconds in (6). The protein content of the final product was controlled to be 8.0±0.2g / 100ml.

[0096] Comparative Example 4

[0097] The mixture was prepared according to the method of Example 2, with the following differences: (1) the milk was not subjected to ultrafiltration membrane and no protein powder was added; (5) the whey was not removed by ultrasonic treatment, but by centrifugation, that is, the fermented yogurt was centrifuged to remove whey and then sterilized at 75°C for 6 seconds in (6). The protein content of the final product was controlled to be 8.0±0.2g / 100ml.

[0098] Comparative Example 5

[0099] The mixture was prepared according to the method of Example 2, except that: (5) the yogurt after fermentation in step (4) was subjected to high-intensity ultrasonic intermittent treatment to remove whey. The frequency of the ultrasonic device was 60KHz and the power was 70W. The ultrasonic treatment lasted for 40s, followed by an interval of 40s. Each cycle lasted for 80s, and the total time for ultrasonic intermittent treatment was 80min. The resulting yogurt product had a protein content of 15.6g / 100ml. Although the protein content was high, the product viscosity was also high, and it could not be pumped by diba. The high protein content of the product resulted in a bitter taste.

[0100] Comparative Example 6

[0101] The mixture was prepared according to the method of Example 2, except that: after adding the bacterial strain in step (4), high-intensity ultrasonic intermittent treatment was applied during the fermentation process to remove whey, with the same parameters as in Example 2, and the protein content of the final product was controlled to be 8.0±0.2g / 100ml.

[0102] Experimental Example

[0103] 1. Product stability analysis

[0104] The stability analyzer measures the distribution of a sample by detecting the transmittance of light, enabling performance analysis of the sample, including dispersibility, shelf life, and stratification stability. The clarification index characterizes the likelihood of instability phenomena such as water separation and sedimentation; a lower value indicates a more stable system, while a higher value indicates a less stable system. The stability of the yogurts obtained in Examples 1-6 and Comparative Examples 1-6 was analyzed using a LUMiSizer X65 stability analyzer.

[0105] The results are as follows Figure 1 , Figure 2 As shown, the clarification indices of Examples 1-6 are relatively small, all below 0.5, and the clarification index of Example 2 is 0.476, all of which are smaller than the clarification indices of Comparative Examples 1-6. This indicates that the pre-concentration index and a small amount of exogenous protein were limited before fermentation, and the whey was removed by intermittent ultrasonic treatment after fermentation. Compared with a single method to increase protein content, or membrane concentration and centrifugation to remove whey after fermentation, the former system is more stable and less prone to water separation during shelf life.

[0106] 2. Product particle size analysis

[0107] The particle size of the suspension (the products obtained in the examples and comparative examples were diluted with 9 times their mass of water) was determined using an LA 960 laser particle size analyzer. The particle size of the yogurts obtained in Examples 1-6 and Comparative Examples 1-6 was also determined using this method.

[0108] As shown in Table 1, the particle size of Examples 1-6 ranges from 50.46688 μm to 53.07591 μm. Compared with the comparative examples, the particles in each example are smaller, with a finer and smoother texture, stronger melting properties, and less powdery feel.

[0109] Table 1 Particle size analysis of Examples 1-6

[0110]

[0111] The data above shows that the particle size of Example 2 is 52.37555 μm, while that of Comparative Example 1 is 128.25420 μm. This is because a single pre-membrane concentration was used. If the protein concentration index of the membrane exceeds 6.0 g / 100 mL, the product particle size will be too large due to the excessively high ion concentration in the system, resulting in a noticeable powdery and astringent taste. The particle size of Comparative Example 2 is 75.88946 μm, which is higher than that of Example 2. This indicates that adding exogenous protein to make the final product protein content exceed 6.0 g / 100 mL will result in larger particles, a severe powdery and astringent taste, and a poor mouthfeel. The comparison of particle size between Example 2 and Comparative Examples 3 and 4 shows that the use of intermittent ultrasonic treatment to remove whey effectively reduces the particle size. The final product obtained by post-membrane concentration and centrifugation to remove whey has a smaller particle size, resulting in a smoother and more delicate mouthfeel. Comparative Example 5 had a particle size of 69.94211 μm. The ultrasonic treatment parameters were too high, and the treatment time was too long, resulting in significant whey removal and a protein content >15.0 g / 100 mL. The product had large particle size and a powdery texture. Comparative Example 6 had a particle size of 54.40914 μm, also higher than Example 2. The ultrasonic treatment during fermentation and the long fermentation time affected the casein gelation effect, resulting in larger particles and consequently impacting the texture.

[0112] 3. Product viscosity analysis

[0113] The viscosity of the yogurts obtained in Examples 1-6 and Comparative Examples 1-6 was analyzed by measuring the viscosity at 25°C and a shear rate of 751 l / s using an Anton Paar MCR302 rheometer.

[0114] The data in the table below show that the rheological viscosity of Example 2 is 0.70074 Pa·s, and the viscosities of Examples 1-6 are all within the acceptable range, which meets the viscosity design for Greek-style high-protein yogurt. Comparative Examples 3 and 4 have lower viscosities compared to Example 2. This indicates that using intermittent ultrasonic treatment to remove whey results in minimal viscosity loss, allowing the product to achieve a high viscosity suitable for eating with a spoon. Simultaneously, the high viscosity provides a certain water-retention effect and good stability.

[0115] Table 2 Rheological Viscosities of Examples 1-6 and Comparative Examples 1-6

[0116]

[0117] 4. Sensory evaluation of the product

[0118] Sensory evaluations were performed on the high-protein Greek-style room-temperature yogurts prepared in Examples 1-6 and Comparative Examples 1-6, using the following methods:

[0119] The product underwent sensory evaluation (also known as "taste testing") by 20 randomly selected tasters. The sensory evaluation used a scoring method: this method evaluates the product or its characteristics using numerical scores, with the average score determining the quality. Decimal numbers were rounded off. The scoring rules used a 0-10 range, with 0-2 considered poor, 3-5 considered average, 6-8 considered good, and 9-10 considered excellent. Evaluation items included: texture, aftertaste, body, and smoothness. The scoring criteria are shown in the table below.

[0120] Table 3 Product Sensory Evaluation Scoring Standards

[0121]

[0122] The sensory evaluation results are shown in Table 4. The results show that, compared with the comparative example, the example has a better curd texture, rich milky aroma, thick and mellow taste, and better aftertaste. The yogurt texture is noticeably thick, delicate and smooth.

[0123] Table 4. Sensory Evaluation Results of Products

[0124]

[0125] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing Greek yogurt, characterized in that, Includes the following steps: S1, concentrate the liquid milk to control its protein content at 2.4-4.0g / 100mL; S2, mix the concentrated liquid milk with protein powder to obtain a fermentation base, and control the protein content in the fermentation base to be 4.0-6.0g / 100mL; S3 involves homogenizing the fermentation substrate, sterilizing it once, and then fermenting it. S4. The fermented material is subjected to intermittent ultrasonic treatment for 10-60 minutes to remove whey and obtain the Greek yogurt. Among them, the intermittent ultrasonic treatment includes ultrasonic treatment for 4-30 seconds, intermittent treatment for 4-30 seconds, ultrasonic treatment frequency of 20-40KHz, and power of 20-60W. The process includes a second sterilization step after the whey removal process.

2. The method for preparing Greek yogurt according to claim 1, characterized in that, During the intermittent ultrasonic treatment, the ultrasonic probe is located in the fermented material.

3. The method for preparing Greek yogurt according to claim 1, characterized in that, The temperature for the first sterilization is 75-145℃, and the time is 200-300 seconds; And / or, the secondary sterilization temperature is 60-105℃ and the time is 2-40s.

4. The method for preparing Greek yogurt according to claim 1, characterized in that, The fermentation process includes inoculating the sterilized material with a yogurt starter culture, fermenting at a temperature of 25-45°C, and setting the final pH value at 4.3-4.

6.

5. The method for preparing Greek yogurt according to any one of claims 1-4, characterized in that, The temperature of the homogenization is 45-75℃, and the total pressure of the homogenization is 120-200 bar. And / or, the concentration method in step S1 is at least one of flash evaporation, falling membrane, nanofiltration, microfiltration, ultrafiltration, and reverse osmosis.

6. The method for preparing Greek yogurt according to claim 1, characterized in that, Step S2 also includes adding regular yogurt ingredients to the concentrated liquid milk.

7. The method for preparing Greek yogurt according to claim 6, characterized in that, The ingredients of the conventional yogurt include at least one of sweeteners, cream, and stabilizers.

8. The method for preparing Greek yogurt according to claim 7, characterized in that, The Greek yogurt comprises the following ingredients in parts by weight: Concentrated liquid milk 75-95 parts; protein powder 0.2-6 parts; light cream 0.2-1 part; sweetener 5-10 parts; yogurt starter 0.2-1 part; stabilizer 2-5 parts.

9. The method for preparing Greek yogurt according to claim 8, characterized in that, Satisfy at least one of the following (1)-(6): (1) The liquid milk is at least one of cow's milk, goat's milk, camel's milk or reconstituted milk; (2) The liquid milk is skimmed, whole, or semi-skimmed liquid milk; (3) The protein powder is at least one of whey protein powder, milk protein powder, skim milk powder, and whole milk powder; (4) The yogurt starter is at least one of Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus plantarum, Lactobacillus casei, Lactococcus lactis subsp. lactis, and Lactococcus lactis subsp. milk fat. (5) The sweetener is at least one of white sugar, fructose syrup, maltose, erythritol and stevia; (6) The stabilizer is at least one of agar, pectin, gelatin, gellan gum, and starch.

10. A Greek yogurt prepared by the preparation method according to any one of claims 1-9.

11. The Greek yogurt according to claim 10, characterized in that, The protein content of the Greek yogurt is 4-15g / 100mL.

12. The Greek yogurt according to claim 11, characterized in that, The protein content of the Greek yogurt is 6-15g / 100mL.

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