Milk skin flavored fermented milk and preparation method thereof

Abstract

The invention discloses milk skin flavored fermented milk and a preparation method thereof. The preparation method comprises the following steps: 1) inoculating a base material with a strain to obtain a mixed base material; sterilizing the single cream to obtain sterilized single cream; (2) mixing the mixed base material with the sterilized single cream, and fermenting to obtain the fermented milk with the milk skin flavor, the base material comprises raw milk and a sweetening agent. The raw milk, the single cream and the lactic acid bacteria are used as raw materials, and the fermented single cream can suspend on the surface layer of the solidified fermented milk through a process of mixing the skimmed milk and the bacteria and fermenting the sterilized single cream, so that the fermented milk with the milk skin flavor, which is excellent in texture and flavor, is obtained.

Description

Technical Field

[0001] The invention relates to the field of fermented dairy products, in particular to a milk skin flavored fermented milk and a preparation method thereof. Background Art

[0002] With the development of the dairy industry and the improvement of consumers' demand for dairy product quality, dairy products are showing a trend of diversification, personalization and high-end development. Yogurt is loved by many consumers for its rich taste. As the domestic yogurt market continues to expand, in addition to strain research and development, flavor and taste innovation, texture innovation has always been an important direction for yogurt product innovation. Texture innovation includes thickness adjustment, fruit and nut addition, gelation, low-fat or fat-free yogurt, protein enhancement, new fermentation agents, heat treatment and cold treatment, etc.

[0003] Lactic acid bacteria grow and multiply in milk, ferment and decompose lactose to produce organic acids such as lactic acid, which causes the pH value of milk to drop, causing casein to agglutinate near its isoelectric point. We call this kind of curdled yogurt coagulated yogurt. Coagulated yogurt has a strong natural fermented aroma, is delicate and smooth, has a thick texture, is sweet and sour, and has an endless aftertaste. It can effectively relieve lactose intolerance. Coagulated yogurt is a good natural source of calcium. Every 100 grams of coagulated yogurt contains about 120 mg of calcium. It is also rich in B vitamins, choline, etc., so it has a strong competitive advantage.

[0004] In recent years, specialty yogurts such as milk skin yogurt have also received much attention. They are popular among consumers because of their sticky taste and rich milk flavor. Milk skin yogurt is made by boiling fresh milk and letting it stand, combining a thin film (i.e. milk skin) formed by the milk fat and protein floating up with yogurt. Its production process is: the raw materials are filled into containers, and then lactic acid bacteria are inoculated in the containers for fermentation to form a coagulated yogurt, and finally sold directly with the containers, that is, filling first and then fermenting. The containers are generally traditional glass bottles and porcelain bottles. Due to its special texture, it is still in the handmade stage and cannot be industrialized and mass-produced.

[0005] CN109730147A discloses a method for making layered flavored fermented milk and a product thereof, wherein skim milk and cream are mixed, preheated, homogenized, sterilized, cooled once, inoculated and fermented, concentrated, smoothed, cooled twice, and filled into a can filled with flavored sauce to obtain layered fermented milk with a clear interface between jam and yogurt, but it is a stirred yogurt. Stirred yogurt is a yogurt product obtained by stirring and mixing jam or other auxiliary materials with yogurt gel after milk fermentation, then filling into a container, and then cooling and ripening. Its production process is to ferment first and then fill, and the finished product is in a viscous and uniform semi-fluid state. CN115530236A discloses a coagulated yogurt and a preparation method thereof, wherein a coagulated yogurt with a three-layered structure is made by a one-step filling process, wherein the upper and lower layers are jam layers containing fruit particles, and the middle layer is a yogurt layer. Although it belongs to a coagulated yogurt, it does not have milk skin. CN118415237 discloses a fermented milk with milk skin flavor and a preparation method thereof, which comprises mixing raw cow (sheep) milk, sweetened condensed milk, white sugar, cream, stabilizer and agar, stirring, heating and sterilizing, then inoculating a starter and continuing to stir, dispensing into cups, fermenting at 40-42°C to 70-75°F, and cooling to obtain fermented milk with milk skin flavor. It is stirred continuously during the production process, and the fat is broken up and fully floated by stirring to obtain a coagulated yogurt with milk skin on the upper layer and fermented milk on the lower layer. The patent stirs whole milk containing about 3% fat during the batching process to make the fat float up to form milk skin. The requirements for raw milk are strict, and skim milk powder and reconstituted milk cannot be used as raw materials; and a certain proportion of stabilizer needs to be added at the same time. Too high a stabilizer leads to a decrease in the water separation rate and thus a decrease in smoothness, while too low a stabilizer leads to an increase in the water separation rate, increased fluidity, and inability to coagulate; in addition, the fat globules in unhomogenized whole milk have a larger diameter, which may cause the texture of milk skin yogurt to be rough. Although the patent omits the homogenization step, when this method is used for industrial production, the existing fermented milk production line needs to be modified, resulting in increased costs.

[0006] Therefore, a method for producing milk skin yogurt with simple steps without changing the original fermented milk production line is needed. Summary of the invention

[0007] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a milk skin flavored fermented milk and a preparation method thereof.

[0008] To achieve the above objectives and other related objectives, the present invention is achieved through the following technical solutions.

[0009] The first aspect of the present invention provides a method for preparing milk-flavored fermented milk, comprising the following steps:

[0010] 1) inoculating the base material with bacteria to obtain a mixed base material; sterilizing the cream to obtain sterilized cream;

[0011] 2) mixing the mixed base and the sterilized cream and fermenting them to obtain the milk skin flavored fermented milk;

[0012] The base comprises raw milk and a sweetener.

[0013] In some embodiments, the fat content of the raw milk is 0.01% to 1.5 wt%. The method for detecting fat in raw milk in this application is carried out with reference to the first method in GB 5413.3-2010 National Food Safety Standard Determination of Fat in Infant Food and Dairy Products.

[0014] In certain embodiments, based on the total weight of the base and the cream, the raw milk accounts for 80-90 wt %.

[0015] In certain embodiments, the sweetener is selected from one or more of white sugar, erythritol, aspartame, steviol glycosides and sucralose.

[0016] In certain embodiments, based on the total weight of the base and the cream, the sweetener accounts for 0.01 to 10.0 wt %.

[0017] In certain embodiments, based on the total weight of the base and the cream, the cream accounts for 5 to 15 wt %.

[0018] In certain embodiments, the base further comprises one or more of whey protein powder, a thickener, a flavoring agent, and a coloring agent.

[0019] In certain specific embodiments, based on the total weight of the base and the cream, the whey protein powder accounts for 0.4-2.0 wt %.

[0020] In certain specific embodiments, the thickener is selected from one or more of pectin, gelatin, agar, propylene glycol alginate, lactitol, diacetyl tartaric acid mono- and diglycerides, natural starch and modified starch.

[0021] Preferably, based on the total mass of the base and the cream, the thickener accounts for 0.3-2.0 wt %.

[0022] In certain specific embodiments, the flavoring substance is selected from one or two of spices and taste improvers.

[0023] Preferably, based on the total mass of the base and the cream, the flavoring substance accounts for 0.01 to 0.1 wt %.

[0024] In some specific embodiments, the colorant is selected from natural colorants or synthetic colorants.

[0025] Preferably, based on the total mass of the base and the cream, the colorant accounts for 0.01 to 0.1 wt %.

[0026] In certain embodiments, in 1), the bacterial species is selected from one or more of Bifidobacterium animalis subsp. lactis, Bifidobacterium bifidum, Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus.

[0027] In certain embodiments, in 1), based on the total mass of the base and the cream, the inoculation amount of the strain is 0.02-0.2 g / kg.

[0028] In certain embodiments, in 1), the sterilization temperature is 90-95°C.

[0029] In certain embodiments, in 1), the sterilization time is 5 to 10 minutes.

[0030] In certain embodiments, in 1), the inoculation temperature is 42°C to 45°C.

[0031] In certain embodiments, in 1), the base material is pre-treated, and the pre-treatment is selected from one or more of mixing, homogenization and sterilization.

[0032] In some specific embodiments, the mixing temperature is 40-55°C.

[0033] In some specific embodiments, the mixing time is 15 to 30 minutes.

[0034] In some specific embodiments, the homogenization temperature is 60-65°C.

[0035] In some specific embodiments, the homogenization pressure is 18-20 MPa.

[0036] In some specific embodiments, the sterilization temperature is 90-95°C.

[0037] In some specific embodiments, the sterilization time is 5 to 10 minutes.

[0038] In certain embodiments, in 2), the fermentation temperature is 42-45°C.

[0039] In certain embodiments, in 2), the end point acidity of the fermentation is 65-75°T.

[0040] In certain embodiments, in 2), the fermentation time is 4 to 7 hours.

[0041] In certain embodiments, in 2), the mixed base may be added to the container first, and then the sterilized cream may be added. Alternatively, the sterilized cream may be added to the container first, and then the mixed base may be added.

[0042] The second aspect of the present invention protects the fermented milk with milk skin flavor obtained by the preparation method as described above.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The fermented milk with milk skin flavor of the present invention is made of raw milk, cream and lactic acid bacteria, and skim milk and bacteria are mixed with sterilized cream for fermentation, so that the fermented cream can be suspended on the surface of the coagulated fermented milk, thereby obtaining a fermented milk with milk skin flavor with excellent texture and flavor. The preparation method of the present invention is simple in process, and large-scale industrial production can be realized by step-by-step filling using the original fermented milk production line, thereby reducing the cost increase caused by the transformation of the production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A flow chart showing the method for preparing milk skin flavored fermented milk in the present application.

[0046] Figure 2 Shows actual photos of the finished products obtained in Example 1, Example 2, Example 4 and Comparative Example 3 of the present application.

[0047] Figure 3 Shows actual photos of the finished products obtained in Example 3, Example 5, and Comparative Example 1 and Comparative Example 2 of the present application.

[0048] Figure 4 The finished products obtained in Comparative Examples 1 and 2 of the present application are shown in a top view after opening the cover.

[0049] Figure 5 The finished products obtained in Example 3 and Example 5 of the present application are shown in a top view after opening the cover.

[0050] Figure 6 The finished products obtained in Example 1 and Example 4 of the present application are shown in a top view after the cover is opened.

[0051] Figure 7 The finished products obtained in Example 2 and Comparative Example 3 of the present application are shown in a top view after opening the cover.

[0052] Figure 8 Shows actual photos of the finished products obtained in Comparative Examples 4, 5, and 6 of this application.

[0053] Fig. 9The finished products obtained in Comparative Examples 4, 5 and 6 of the present application are shown in a top view after opening the cover.

[0054] Fig.10 The cross-sectional view shows the finished products obtained in Example 3 and Comparative Examples 1 and 2 of the present application.

[0055] Fig.11 Shows the cross-sectional views of the finished products obtained in Example 1, Example 4, and Example 5 of the present application.

[0056] Fig.12 The cross-sectional view of the finished products obtained in Example 2 and Comparative Example 3 of the present application is shown.

[0057] Fig.13 Shows the cross-sectional views of the finished products obtained in Comparative Examples 4, 5, and 6 of the present application.

[0058] Fig.14 A cross-sectional view showing the finished product obtained in Comparative Example 7 of the present application. DETAILED DESCRIPTION

[0059] Traditional milk skin is made by pouring fresh milk into a pot and simmering it over a slow fire, stirring it with a spoon, whipping it to form bubbles, and keeping it warm over a slow fire to form a film. After it cools naturally, use a knife to cut it along the edge of the pot, pick it up with chopsticks and hang it in a ventilated place to dry. This is fresh milk skin. Traditional fermented milk skin is made by putting the fresh milk skin taken out of the pot into a container for fermentation for 3-5 months to mature. The production process of traditional fermented milk skin is: raw milk → heating to a slight boil (90℃) → stirring and stirring (25cm-40cm) → forming foam → keeping warm to form a film → cooling to form skin → picking milk skin → putting it into a container → fermenting in a cool place → finished product. However, the processing of fermented milk skin is still in the traditional manual production stage, with low production efficiency, uneven product quality, and no unified standards and technical operation specifications.

[0060] The first aspect of the present invention provides a method for preparing milk-flavored fermented milk, comprising the following steps:

[0061] 1) inoculating the base material with bacteria to obtain a mixed base material; sterilizing the cream to obtain sterilized cream;

[0062] 2) mixing the mixed base and the sterilized cream and fermenting them to obtain the milk skin flavored fermented milk;

[0063] The base comprises raw milk and a sweetener.

[0064] The term flavored fermented milk refers to a product made from more than 80% cow (sheep) milk or milk powder, with other raw materials added, the pH value is reduced after sterilization and fermentation, and food additives, nutritional enhancers, fruits, vegetables, grains, etc. are added or not added before or after fermentation.

[0065] The applicant has used whole-fat raw cow's milk or whole-fat raw goat's milk as the object, and used the method of the present application to prepare milk skin yogurt. As a result, it was found that although the flavored fermented milk had milk skin, it was particularly thin, with no obvious stratification and no obvious cross section; in addition, the milk skin was not firm, and obvious cracks appeared in the milk skin after shaking; it was also tried to mix and homogenize low-fat raw milk and cream, sterilize, and inoculate bacteria for fermentation. As a result, it was found that although the yogurt obtained was solid and had a cross section, it had no stratification, that is, no milk skin flavored fermented milk was obtained. It was accidentally discovered that using low-fat raw milk as the object, by homogenizing it and forming a mixed base with bacteria, and then co-fermenting it with sterilized cream, a milk skin yogurt with a milk skin thickness of more than 2mm was obtained. The homogenizer is an indispensable part of the existing yogurt production line. The present application uses low-fat raw milk as the object to prepare milk skin yogurt, which can use the original yogurt production line to avoid the defect of increased cost caused by the transformation of the production line. Even without adding a thickener, a milk skin having a thickness exceeding 2 mm can be obtained in the present application.

[0066] The mixing time after the base material is inoculated with the bacteria in the present application is 2 to 10 minutes. The mixing time should not be too long or too short. If it is too long, it will cause curd, and the curd and the sterilized cream will ferment together, which is not conducive to the formation of milk skin; if it is too short, it will cause uneven mixing of the base material and the bacteria, which is not conducive to the subsequent fermentation to obtain bottle yogurt.

[0067] In certain embodiments, based on the sum of the mass of the base and the cream, the proportion of the cream is 5-15wt%, also 5-9wt%, also 8-12wt%, also 9-15wt%, also 5wt%, 8wt%, 10wt%, 12wt%, 15wt%. The cream can be any cream suitable for preparing yogurt in the art, for example, it can comply with relevant standards such as GB 19646-2010 National Food Safety Standard for Cream, Butter and Anhydrous Butter. The proportion of cream should not be too low or too high. When it is lower than 5%, the thickness of the cream is less than 2mm. For example, when the proportion of cream is 1wt%, the thickness of the cream is only 1mm. When it is higher than 15%, although the thickness of the cream increases, obvious yellow pores are generated on the surface of the cream. This may be because the fat in the cream is at high temperature for a long time, causing the color to turn yellow and the texture to become rough, resulting in a decrease in the appearance and taste of the cream yogurt.

[0068] In some embodiments, the fat content of the raw milk is 0.01% to 1.5wt%. Raw milk refers to skimmed raw milk or skimmed reconstituted milk. Raw milk may comply with relevant standards such as GB 19301 National Food Safety Standard for Raw Milk; reconstituted milk may comply with relevant standards such as GB 19644 National Food Safety Standard for Milk Powder. Reconstituted milk is preferably skimmed milk powder. The raw milk may preferably come from cows and / or sheep, such as one or more of cow milk, goat milk and buffalo milk.

[0069] In certain embodiments, based on the total mass of the base and the cream, the raw milk accounts for 80-90wt%, also known as 80-85wt%, also known as 84-90wt%, also known as 80wt%, 90wt%, or 84%.

[0070] In some specific embodiments, the sweetener is selected from one or more of white sugar, erythritol, aspartame, steviol glycosides and sucralose. The white sugar is generally various edible sugars suitable for preparing yogurt in the food field. For example, it can comply with relevant standards such as "GB / T 317-2018 White Sugar".

[0071] In some specific embodiments, based on the total mass of the base and the cream, the proportion of the sweetener is 0.01-10.0wt%, also known as 0.01-1.8wt%, 1-5wt%, 4-10.0wt%, 8wt%, 4wt%, 4.5wt%, or 10wt%.

[0072] In certain embodiments, the base comprises 80-84 wt % of skim milk, 6-8 wt % of a sweetener, and 10-12 wt % of cream.

[0073] In certain embodiments, the base further comprises one or more of whey protein powder, a thickener, a flavoring agent, and a coloring agent.

[0074] In some specific embodiments, based on the total mass of the base and the cream, the whey protein powder accounts for 0.4-2.0wt%, 0.4-0.8wt%, 0.7-1.2wt%, 1.1-2wt%, 0.4wt%, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt% and 2wt%. The whey protein powder is generally various whey protein powders suitable for preparing yogurt in the food field, for example, it can meet the relevant standards such as GB11674-2010 National Food Safety Standard Whey Powder and Whey Protein Powder.

[0075] In certain specific embodiments, the thickener is selected from one or more of pectin, gelatin, agar, propylene glycol alginate, lactitol, diacetyl tartaric acid mono- and diglycerides, and starch. Preferably, it is gelatin or starch.

[0076] In some specific embodiments, based on the total mass of the base and the cream, the thickener accounts for 0.3-2.0wt%, or 0.3-0.88wt%, or 0.6-1.26wt%, or 1.15-2wt%, or 0.3wt%, 0.4wt%, 0.5wt%, 0.7wt%, 1wt%, 1.2wt%, 1.5wt% and 2wt%.

[0077] In certain specific embodiments, the flavoring substances are selected from one or more of spices and taste improvers. The spices are selected from one or more of propylene glycol, lactic acid and diacetyl. The taste improver is selected from fruit juice or plant extract. The spices in this application all comply with the provisions on pigments in the "GB 2760-2024 National Food Safety Standard for the Use of Food Additives".

[0078] In some specific embodiments, based on the total mass of the base and the cream, the flavor substance accounts for 0.01-0.1wt%, or 0.01-0.06wt%, or 0.03-0.08wt%, or 0.06-0.1wt%, or 0.01wt%, 0.02wt%, 0.04wt%, 0.06wt%, 0.09wt% and 0.1wt%.

[0079] In some specific embodiments, the pigment is selected from natural colorants or synthetic colorants. The natural colorant is selected from one or more of beetroot red, carmine, annatto, capsicum red, turmeric, lutein, natural carotene, copper chlorophyll, vegetable carbon black and caramel color. The synthetic colorant is selected from carmine. The colorants in this application all comply with the provisions of the colorant in the "GB2760-2024 National Food Safety Standard Food Additives Usage Standard".

[0080] In some specific embodiments, based on the total mass of the base and the cream, the proportion of the colorant can be 0.01-0.1wt%, 0.01-0.06wt%, 0.03-0.08wt%, 0.06-0.1wt%, or 0.01wt%, 0.02wt%, 0.04wt%, 0.06wt%, 0.09wt% and 0.1wt%.

[0081] In certain embodiments, in 1), the bacterial species is selected from one or more of Bifidobacterium animalis subsp. lactis, Bifidobacterium bifidum, Lactobacillus acidophilus, Lactobacillus casei, Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.

[0082] In certain embodiments, in 1), based on the total mass of the base and the cream, the inoculation amount of the bacteria is 0.02-0.2 g / kg, preferably 0.05-0.1 g / kg.

[0083] In certain embodiments, in 1), the cream is sterilized at a temperature of 90-95° C., 90-93° C., 92-95° C., 95° C. or 90° C. The sterilization time is 5-10 min, 5-6 min, 5 min, 5.3 min, 5.5 min, 5.8 min or 6 min.

[0084] In certain embodiments, in 1), during the inoculation, the temperature of the base material is 42°C to 45°C, or 40°C to 48°C, or 46°C to 55°C, or 55°C, 45°C, 55°C, or 40°C.

[0085] In certain embodiments, in 1), the base material is pre-treated, and the pre-treatment includes one or more of mixing, homogenization and sterilization.

[0086] In certain specific embodiments, the pre-treatment is selected from mixing, homogenizing and sterilizing.

[0087] In some specific embodiments, the mixing temperature is 40-55° C., or 40-48° C., or 46-55° C., or 55° C., 45° C., 55° C., or 40° C. The mixing time is 15-30 min, or 15-24 min, or 20-30 min, or 30 min, 20 min, 25 min, or 15 min. The mixing method is stirring.

[0088] In some specific embodiments, the homogenization method can be a conventional homogenization method in the art, such as the homogenization temperature is 60-65° C., or 60-63° C., or 62-65° C., or 65° C., 62° C., or 60° C. The homogenization pressure is 18-20 MPa, or 18 MPa, 18.5 MPa, 19 MPa, or 20 MPa.

[0089] In some specific embodiments, the sterilization method can be a conventional dairy product sterilization method in the art, such as a sterilization temperature of 90-95° C., 90-93° C., 92-95° C., 95° C., or 90° C. The sterilization time is 5-10 min, 5-8 min, 7-10 min, or 5 min.

[0090] In some more specific embodiments, the sterilization further includes cooling, and the cooling method is a conventional cooling method in the art.

[0091] In certain embodiments, in 2), the fermentation temperature is 42-45°C, or 42, 45°C, or 43°C. Fermentation generally refers to the process of preparing microbial cells themselves, or direct metabolites or secondary metabolites by means of the life activities of microorganisms under aerobic or anaerobic conditions, and the fermentation process is performed to provide fermentation products. Preferably, the fermentation process can be an aerobic fermentation process, which can usually be carried out under air conditions. Specifically, the sterilized material can be canned and then fermented.

[0092] In certain embodiments, in 2), the end point acidity of the fermentation is 65-75°T, or 65-75°T, or 65-75°T, or 70°T, 65°T, 72°T, or 75°T.

[0093] In certain embodiments, in 2), the fermentation time is 4 to 7 hours, or 4 to 6.5 hours, or 5.5 to 7 hours, or 7 hours, 6 hours, 4 hours, or 5 hours.

[0094] In certain embodiments, in 2), the mixed base is added first, and then the sterilized cream is added.

[0095] In certain embodiments, in 2), after fermentation, the method further comprises cooling the fermentation product to 4-10°C, 4-8°C, 6-10°C, or 9-12°C to terminate the fermentation.

[0096] The second aspect of the present invention protects the fermented milk with milk skin flavor obtained by the preparation method as described above.

[0097] In certain embodiments, the thickness of the milk skin in the milk skin flavored fermented milk is greater than 2 mm, and may be 2 to 10 mm, 2 to 5 mm, or 2.5 mm, 3.0 mm, 3.5 mm, 4.5 mm, or 4 mm.

[0098] The milk skin flavored fermented milk obtained in the present application is in a solid state, with milk skin having a thickness greater than 2 mm on the upper layer and fermented milk on the lower layer, and there is obvious stratification between the upper and lower layers; at the same time, the milk skin flavored fermented milk of the present application is stored for 3 weeks and the stratification is still obvious, indicating that the milk skin flavored fermented milk of the present application is stable in nature.

[0099] The applicant shook the fermented milk with milk skin flavor at 6°C and 200 r / min for 5 hours, and the stratification was still obvious. In addition, the stratification was still obvious after refrigerating at 2-6°C for 3 weeks, indicating that the fermented milk with milk skin flavor of the present application can be stably stratified.

[0100] The invention adopts the method of mixing the strain and the base material, adding sterilized cream for co-fermentation during packaging, realizing the production of fermented milk with milk skin flavor on an assembly line, breaking the barrier of manual production of fermented milk with milk skin flavor. The fermented milk with milk skin flavor of the invention has excellent texture and meets consumers' expectations for fermented milk with milk skin flavor.

[0101] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0102] Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are for describing the specific embodiments rather than for limiting the scope of protection of the present invention; in the present specification and claims, unless otherwise expressly stated herein, the singular forms "a", "an" and "the" include plural forms.

[0103] When the embodiments give numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the grasp of the prior art by those skilled in the art and the record of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention can also be used to realize the present invention.

[0104] In the examples of this application, the material information used is as follows:

[0105]

[0106] Example 1

[0107] According to the recipe in Table 1, fermented milk with milk skin flavor was prepared, wherein the fat content of the raw milk was 0.5 wt %.

[0108] Table 1 Raw material formula (by mass percentage)

[0109] Raw milk 80.0％ Lactic acid bacteria 0.1g / kg white sugar 8.0％ Cream 12.0％

[0110] The preparation method of milk skin flavored fermented milk comprises the following steps:

[0111] 1) Mix white sugar and raw milk according to the formula in Table 1, stir at 40°C for 15 minutes; homogenize at 60°C and 20MPa; then sterilize at 95°C for 5 minutes, cool to 42°C, inoculate lactic acid bacteria starter, stir and mix for 5 minutes until uniform, and record it as material A (mixed base).

[0112] According to the weight proportion of the cream in Table 1, sterilize at 95°C for 5 min, cool to 42°C, and record it as material B (sterilized cream).

[0113] 2) In a 100 mL plastic cup, first fill material A and then fill material B, seal the cup, and ferment at 42° C. for about 5 h to an end point acidity of 70° T, cool to 8° C., and ripen to obtain fermented milk with milk skin flavor.

[0114] The fermented milk with milk skin flavor that has been refrigerated and matured has a layer of creamy yellow milk skin on the surface, which has a smooth and delicate taste and a rich milky aroma; the lower layer of yogurt has a silky and delicate taste, and is sweet and sour. The combination of the two makes the taste richer.

[0115] The actual picture of the finished product obtained in this embodiment is shown in Figure 2 ; See the actual photo after opening the cover Figure 6 .

[0116] Example 2

[0117] According to the recipe in Table 2, fermented milk with milk skin flavor was prepared, wherein the fat content of the raw milk was 1.5 wt %.

[0118] Table 2 Raw material formula (by mass percentage)

[0119] Raw milk 80.52％ Lactic acid bacteria 0.2g / kg Sucralose 0.08％ Cream 15.0％ Erythritol 4.0％ Whey protein powder 0.4％

[0120] The preparation method of milk skin flavored fermented milk comprises the following steps:

[0121] 1) Whey protein powder, erythritol, sucralose and raw milk were mixed according to the formula in Table 2, stirred at 55° C. for 25 min, homogenized at 65° C. and 18 MPa, sterilized at 95° C. for 5 min, cooled to 45° C., inoculated with lactic acid bacteria starter, and stirred for 10 min until uniform, which was recorded as material A.

[0122] According to the weight of the cream in Table 2, sterilize it separately at 90°C for 6 minutes, cool it to 45°C, and record it as material B.

[0123] 2) First fill material A, then fill material B, seal and ferment at 45°C for about 4 hours to the end point acidity of 65°T, cool to 10°C, and then ripen.

[0124] The fermented milk with milk skin flavor that has been refrigerated and matured has a layer of creamy yellow milk skin on the surface, which has a smooth and delicate taste and a rich milky aroma. The yogurt on the bottom has a silky and delicate taste, and is sweet and sour. The combination of the two makes the taste richer.

[0125] The actual picture of the finished product obtained in this embodiment is shown in Figure 2 ; See the actual photo after opening the cover Figure 7 .

[0126] Example 3

[0127] According to the recipe in Table 3, fermented milk with milk skin flavor was prepared, wherein the fat content of the raw milk was 1 wt %.

[0128] Table 3 Raw material formula (by mass percentage)

[0129] Raw milk 90.0％ Lactic acid bacteria 0.02g / kg Stevioside 0.01％ Cream 5.0％ white sugar 4.49％ Natural starch 0.5％

[0130] The preparation method of milk skin flavored fermented milk comprises the following steps:

[0131] 1) Starch, white sugar, steviol glycoside and raw milk were mixed according to the formula in Table 3, stirred at 45°C for 20 minutes, homogenized at 62°C and 19 MPa, sterilized at 90°C for 5 minutes, cooled to 43°C, inoculated with lactic acid bacteria starter, and stirred for 8 minutes until uniform, which was recorded as material A.

[0132] According to the weight of the cream in Table 3, sterilize it separately at 90°C for 5 minutes, cool it to 43°C, and record it as material B.

[0133] 2) First fill material B, then fill material A, seal and ferment at 43°C for about 6 hours to the end point acidity of 72°T, cool to 2°C, and then ripen.

[0134] The fermented milk with milk skin flavor that has been refrigerated and matured has a layer of creamy yellow milk skin on the surface, which has a smooth and delicate taste and a rich milky aroma. The yogurt on the bottom has a silky and delicate taste, and is sweet and sour. The combination of the two makes the taste richer.

[0135] The actual picture of the finished product obtained in this embodiment is shown in Figure 3 ; See the actual photo after opening the cover Figure 5 .

[0136] Example 4

[0137] According to the recipe in Table 4, fermented milk with milk skin flavor was prepared, wherein the fat content of the raw milk was 0.3 wt %.

[0138] Table 4 Raw material formula (by mass percentage)

[0139] Raw milk 80.0％ Lactic acid bacteria 0.2g / kg Erythritol 4.0％ Cream 10.0％ white sugar 6.0％ / /

[0140] The preparation method of milk skin fermented milk comprises the following steps:

[0141] 1) White sugar, steviol glycoside and raw milk were mixed according to the formula in Table 4, stirred at 55°C for 20 minutes, homogenized at 62°C and 19 MPa, sterilized at 90°C for 5 minutes, cooled to 43°C, inoculated with lactic acid bacteria starter, and stirred for 8 minutes until uniform, which was recorded as material A.

[0142] According to the weight proportion of the cream in Table 4, sterilize it separately at 90°C for 5 minutes, cool it to 43°C, and record it as material B.

[0143] 2) First fill material B, then fill material A, seal and ferment at 43°C for about 7 hours to the end point acidity of 75°T, cool to 4°C, and then ripen.

[0144] The fermented milk with milk skin flavor that has been refrigerated and matured has a layer of creamy yellow milk skin on the surface, which has a smooth and delicate taste and a rich milky aroma. The yogurt on the bottom has a silky and delicate taste, and is sweet and sour. The combination of the two makes the taste richer.

[0145] The actual picture of the finished product obtained in this embodiment is shown in Figure 2 ; See the actual photo after opening the cover Figure 6 .

[0146] Example 5

[0147] According to the recipe in Table 5, fermented milk with milk skin flavor was prepared, wherein the fat content of the raw milk was 0.8 wt %.

[0148] Table 5 Raw material formula (by mass percentage)

[0149] Raw milk 84.0％ Lactic acid bacteria 0.05g / kg white sugar 7.6％ Cream 8.0％ gelatin 0.3％ essence 0.1％

[0150] The preparation method of milk skin flavored fermented milk comprises the following steps:

[0151] 1) Mix gelatin, white sugar and raw milk according to the formula in Table 5, stir at 55°C for 30 minutes; homogenize at 65°C and 20MPa; then sterilize at 90°C for 5 minutes, cool to 42°C, inoculate lactic acid bacteria starter, and stir for 8 minutes until uniform, which is recorded as material A.

[0152] According to the weight of the cream in Table 5, sterilize it separately at 90°C for 5 minutes, cool it to 42°C, and record it as material B.

[0153] 2) First fill material B, then fill material A, seal and ferment at 42°C for about 7 hours to the end point acidity of 75°T, cool to 2°C, and then ripen.

[0154] The fermented milk with milk skin flavor that has been refrigerated and matured has a layer of creamy yellow milk skin on the surface, which has a smooth and delicate taste and a rich milky aroma. The yogurt on the bottom has a silky and delicate taste, and is sweet and sour. The combination of the two makes the taste richer.

[0155] The actual picture of the finished product obtained in this embodiment is shown in Figure 3 ; See the actual photo after opening the cover Figure 5 .

[0156] Example 6

[0157] The difference between Example 6 and Example 1 is that skimmed milk powder reconstituted milk is used instead of skimmed raw milk, and the rest is the same as Example 1.

[0158] Comparative Example 1

[0159] The difference between Comparative Example 1 and Example 1 is that no cream is added, and the rest is the same as Example 1.

[0160] The actual picture of the finished product obtained in this comparative example 1 is shown in Figure 3 ; See the actual photo after opening the cover Figure 4 .

[0161] Comparative Example 2

[0162] The difference between Comparative Example 2 and Example 1 is that the amount of cream added is 2%, and the rest is the same as Example 1.

[0163] The actual picture of the finished product obtained in this comparative example 2 is shown in Figure 3 ; See the actual photo after opening the cover Figure 4 .

[0164] Comparative Example 3

[0165] The difference between Comparative Example 3 and Example 1 is that the amount of cream added is 18%, and the rest is the same as Example 1.

[0166] The actual picture of the finished product obtained in this comparative example 3 is shown in Figure 2 ; See the actual photo after opening the cover Figure 7 .

[0167] Comparative Example 4

[0168] The difference between Comparative Example 4 and Example 1 is that the cream is not added separately, but mixed with the base material, homogenized, sterilized, inoculated and fermented.

[0169] The actual picture of the finished product obtained in this comparative example 4 is shown in Figure 8; See the actual photo after opening the cover Fig. 9 .

[0170] Comparative Example 5

[0171] The method of CN109730147A is adopted, and 5% of light cream is added to form a stirred flavored yogurt.

[0172] The specific method is as follows: preheat the raw milk and white sugar of Example 1 to 40°C and stir for 15 minutes; homogenize at 60°C and 20MPa; then sterilize at 95°C for 5 minutes, cool to 42°C, inoculate lactic acid bacteria starter, stir for 5 minutes until uniform, ferment at 42°C to a pH of 4.50, concentrate to a concentrated fermented milk with a protein content of 8.5% and a fat content of 5.0% by a centrifuge, smoothen at 600rpm, cool to 16°C, and the viscosity of the concentrated flavored fermented milk is 3150mPas; then add cream with a final concentration of 5wt%.

[0173] The actual picture obtained in this comparative example 5 is shown in Figure 8 ; See the picture after opening the cover Fig. 9 .

[0174] Comparative Example 6

[0175] The method of CN109730147A was adopted, and 15 wt% of cream was added later to form a stirred flavored yogurt, which is the same as the preparation method of comparative example 5, except that the final concentration of the cream was 15 wt%.

[0176] The actual picture obtained in this comparative example 6 is shown in Figure 8 , see the picture after opening the cover Fig. 9 .

[0177] Comparative Example 7

[0178] The difference between Comparative Example 7 and Example 1 is that whole milk is used instead of skim milk, and the fat content of whole milk is 3.1 wt%. The rest is the same as Example 1.

[0179] 1) Testing

[0180] 20 professional tasters were invited to conduct sensory inspection and taste samples, score the sensory and tasting results, and calculate the average value. The higher the average value, the better the effect and the higher the evaluation. The sensory evaluation results are shown in Table 6 below.

[0181] The full score for tissue status is 5, and the scoring criteria are no whey precipitation, fine texture, and no roughness;

[0182] The flavor score is 5 points, and the scoring criteria are moderate sweetness and sourness, smooth taste, and appropriate aroma.

[0183] Table 6

[0184] sample Flavor Organization Status Example 1 4.2 4.1 Example 2 4.1 4.1 Example 3 4.2 4.2 Example 4 4.3 4.2 Example 5 4.5 4.5 Example 6 4.0 4.0 Comparative Example 1 4.0 4.0 Comparative Example 2 4.2 4.1 Comparative Example 3 3.8 3.2 Comparative Example 4 4.1 4.0 Comparative Example 5 3.9 3.8 Comparative Example 6 3.8 3.7 Comparative Example 7 4.1 4.1

[0185] As can be seen from Table 6, the texture of the coagulated fermented milk of Examples 1-6 of the present invention and Comparative Examples 1-2 and Comparative Example 4 is smooth, delicate and natural, and the cream has a richer taste after fermentation, which improves the overall flavor of the fermented milk. The coagulated fermented milk of Comparative Example 3 is not so good, because the amount of cream added is too high, resulting in a rough texture and obvious yellow pores on the surface, which also affects the taste. Comparative Examples 5 and 6 add cream to stirred yogurt, and both are liquid and interpenetrate each other. The cream does not have the unique thick taste after fermentation without fermentation, which affects the sensory organs and taste.

[0186] 2) Statistics of stratification on the second day after ripening

[0187] The finished products of Examples 1-6 and Comparative Examples 1-7 were recorded for stratification. The specific results are shown in Table 7 and Figure 2-9 shown.

[0188] Table 7 Stratification results

[0189]

[0190] As can be seen from Table 7, the fermented milk with milk skin flavor of Examples 1-6 of the present invention is a coagulated fermented milk with a smooth and delicate texture, obvious stratification and better effect, which can reach more than 2 mm; and as the cream content increases, the thickness of the upper layer increases.

[0191] The effects of Comparative Examples 1-7 are poor, and Comparative Examples 1 and 4 cannot achieve the delamination effect.

[0192] In Comparative Example 1, no cream was added, and the components in the base material were uniform, so that the density difference could not be used to achieve the desired stratification after packaging.

[0193] Comparative Example 4 adjusts the production process to the existing conventional coagulated fermented milk process, that is, the cream is mixed, homogenized, sterilized, etc. with other ingredients simultaneously, and is not sterilized separately before mixing during packaging, so that stratification cannot be achieved. This is because in the conventional process, the cream will be fully dispersed in the milk like other components and distributed evenly, so the stratification effect cannot be achieved.

[0194] In Comparative Example 2, because the amount of cream added was too little, the entire surface could not be evenly filled, and the layering effect was not ideal.

[0195] Although the thickness of the upper layer in the product of Comparative Example 3 is relatively high, due to the excessive amount of cream added, the surface of the milk skin is rough, with obvious yellow pores, poor sensory perception, and poor taste.

[0196] Comparative Examples 5 and 6 both fail to cover the entire surface layer, and the layer boundaries are unclear and penetrate each other.

[0197] The upper layer of the product of Comparative Example 7 is particularly thin, and there are cracks between the milk skins even without shaking.

[0198] 3) Statistics of stratification after shaking on a shaker at 6°C and 200 r / min for 5 hours

[0199] The finished products of Examples 1-6 and Comparative Examples 1-7 were shaken at 6°C and 200 r / min for 5 hours and then the stratification was recorded. The specific results are shown in Table 8 and Figure 10-13 shown.

[0200] Upper layer thickness: Use a ruler to measure the distance from the surface to the delamination.

[0201] Cross-section observation: Use a spoon to dig out the yogurt of each embodiment and comparative example. If it is a solidified yogurt, there will be a cross-section at the place dug out by the spoon, and if it is a stirred yogurt, there will be no cross-section; in addition, if the cross-section of the solidified yogurt is uneven after shaking, it also indicates that the preparation method of the solidified yogurt is not good.

[0202] Table 8 Stratification results

[0203]

[0204]

[0205] comprehensive Figures 10 to 14 As shown in Table 8, after shaking on a shaker at 6°C and 200 r / min for 5 h, the fermented milk with milk skin flavor of Examples 1-6 of the present invention did not change significantly, indicating that the fermented milk could maintain a layered state for a long time.

[0206] from Fig.10 It can be seen that although Comparative Example 1 has a cut surface, there is no stratification (milk skin), that is, the product obtained by directly fermenting the base material without adding cream is not milk skin yogurt.

[0207] from Fig.11 and Fig.12 It can be seen that the amount of cream added to the base cannot be too little or too much. Too little will result in the milk skin not being able to cover the entire upper layer, and the thickness of the milk skin will be reduced; while too much will result in obvious yellow pores on the surface, and the surface will be unsmooth and slightly rough.

[0208] from Fig.13 It can be seen that before shaking, the cream in Comparative Examples 5 and 6 was dispersed on the surface of the yogurt due to its low density, but was in a flowing state, and the yogurt on the lower layer was also in a flowing state; after being shaken on the shaker, the change was more obvious, the flowing upper layer of cream and the lower layer of yogurt penetrated each other, the original thin layer of cream on the surface also disappeared, and the whole was a thick liquid.

[0209] from Fig.14 It can be seen that after the comparative example 7 was shaken on the shaking table, cracks appeared on the surface and the milk skin was not firm.

[0210] 4) Statistics of stratification after refrigeration at 2-6℃ for 3 weeks

[0211] After refrigeration for 3 weeks, the stratification of the final products of Examples 1-5 and Comparative Examples 1-7 was recorded. The specific effects are shown in Table 9.

[0212] Table 9 Stratification results

[0213]

[0214]

[0215] As can be seen from Table 9, even after being refrigerated for 3 weeks, Examples 1-5 of the present invention still have obvious stratification, which indicates that the fermented milk with milk skin flavor obtained in the present application has high stability and a long storage time.

[0216] The above examples are for the purpose of illustrating the embodiments disclosed by the present invention and are not to be construed as limitations of the present invention. In addition, the various modifications listed herein and the variations of methods and compositions in the invention are obvious to those skilled in the art without departing from the scope and spirit of the present invention. Although the present invention has been specifically described in conjunction with various specific preferred embodiments of the present invention, it should be understood that the present invention should not be limited to these specific embodiments. In fact, various modifications obvious to those skilled in the art as described above to obtain the invention should be included within the scope of the present invention.

Claims

1. A method for preparing milk-flavored fermented milk, characterized in that: The steps include: 1) inoculating the base material with bacteria to obtain a mixed base material; sterilizing the cream to obtain sterilized cream; 2) mixing the mixed base and the sterilized cream and fermenting them to obtain the milk skin flavored fermented milk; The base comprises raw milk and a sweetener.

2. The preparation method according to claim 1, characterized in that: The sweetener is selected from one or more of white sugar, erythritol, aspartame, steviol glycoside and sucralose; And / or, the fat content of the raw milk is 0.01% to 1.5wt%; And / or, in step 2), based on the total mass of the base material and the cream, the cream accounts for 5.0 to 15.0 wt%.

3. The preparation method according to claim 2, characterized in that: Based on the total weight of the base material and the cream, the raw milk accounts for 80-90 wt%; And / or, based on the total weight of the base and the cream, the sweetener accounts for 0.01% to 1.5wt%; And / or, the base further comprises one or more of whey protein powder, a thickener, a flavoring agent and a coloring agent.

4. The preparation method according to claim 3, characterized in that: The thickener is selected from one or more of pectin, gelatin, agar, propylene glycol alginate, lactitol, diacetyl tartaric acid mono- and diglycerides, natural starch and modified starch; And / or, the flavoring substance is selected from one or more of spices and taste improvers; And / or, the colorant is selected from natural colorants or synthetic colorants.

5. The preparation method according to claim 3, characterized in that: Based on the total weight of the base material and the cream, the whey protein powder accounts for 0.4-2.0 wt%; and / or, based on the total mass of the base and the cream, the thickener accounts for 0.3 to 2.0 wt%; and / or, based on the total weight of the base and the cream, the flavoring substance accounts for 0.01 to 0.1 wt %; And / or, based on the total weight of the base material and the cream, the colorant accounts for 0.01 to 0.1 wt %.

6. The preparation method according to claim 1, characterized in that: The bacterial species is selected from one or more of Bifidobacterium animalis subsp. lactis, Bifidobacterium bifidum, Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus; And / or, based on the total mass of the base material and the cream, the inoculation amount of the strain is 0.02-0.2 g / kg.

7. The preparation method according to claim 1, characterized in that: 1), the inoculation temperature is 42°C to 45°C; And / or, in 1), the sterilization temperature is 90-95°C; And / or, in 1), the sterilization time is 5 to 10 minutes; And / or, in 1), the base material is pre-treated, and the pre-treatment is selected from one or more of mixing, homogenization and sterilization.

8. The preparation method according to claim 7, characterized in that: The homogenization temperature is 60-65°C; And / or, the homogenization pressure is 18-20 MPa; And / or, the sterilization temperature is 90-95°C; And / or, the sterilization time is 5 to 10 minutes.

9. The preparation method according to claim 1, characterized in that: 2), the fermentation temperature is 42-45°C; And / or, in 2), the fermentation time is 4 to 7 hours; And / or, in 2), the end point acidity of the fermentation is 65-75°T.

10. The fermented milk with milk skin flavor obtained by the preparation method according to any one of claims 1 to 9.

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