WO2025145717A1 - Additive-free normal temperature yogurt and preparation method therefor - Google Patents

Abstract

An additive-free normal temperature yogurt and a preparation method therefor. A slime-producing bacterium is used as a fermentation strain, and same is used in combination with a stabilizer, such as citrus fiber, seaweed powder and glutinous rice starch. The preparation method for the additive-free normal temperature yogurt comprises: adding white granulated sugar, citrus fiber, seaweed powder and glutinous rice starch into milk at 18°C-25°C for material dissolution, performing homogenization and sterilization after the material dissolution to obtain a mixed material liquid, inoculating and fermenting the mixed material liquid to obtain fermented milk, and performing pasteurization on the fermented milk to obtain the normal temperature yogurt, wherein the citrus fiber is citrus fiber after performing freezing and grinding.

Description

A kind of zero-additive room-temperature yogurt and preparation method thereof Technical Field

The invention relates to the technical field of dairy products, and specifically provides a zero-additive room-temperature yogurt and a preparation method thereof.

Background Art

There are endless types of yogurt on the market, and most yogurts need to add food additives to maintain the stability of the yogurt system. Due to the different sources of food additives, they can be divided into: natural yogurt stabilizers and artificial yogurt stabilizers. For zero-additive yogurt, natural yogurt stabilizers are preferred.

Natural yogurt stabilizers generally affect the flavor and taste of zero-additive yogurt due to their own characteristics or flavors. In addition, it is difficult for natural yogurt stabilizers to ensure long-lasting stability throughout the shelf life of zero-additive room-temperature yogurt. Therefore, in the research on natural yogurt stabilizers, the focus is on optimizing the compounding effect of yogurt stabilizers and optimizing the addition method of yogurt stabilizers.

Natural yogurt stabilizers such as citrus fiber are a type of dietary fiber extracted from citrus peels that has the property of swelling when it absorbs water. When citrus fiber combines with water, it forms a viscous substance that increases the viscosity of the yogurt. Since citrus fiber or other natural yogurt stabilizers can serve as fermentation substrates for starters, it is not clear what role natural yogurt stabilizers play during the shelf life of room temperature yogurt as storage time increases.

Summary of the invention

The existing technology adds citrus fiber, seaweed powder and physical starch to the yogurt system, mainly to obtain yogurt with high stability and no water precipitation during the shelf life. However, as the storage time increases, the use of citrus fiber will cause the viscosity of the yogurt to increase significantly, seriously affecting the taste and stability of the yogurt.

In order to overcome the defects of the prior art, the present invention provides a zero-additive room-temperature yogurt and a preparation method thereof.

In a first aspect, the zero-additive room-temperature yogurt provided by the present invention uses slime-producing mold as the fermentation strain, and the addition amount of the fermentation strain is 200 dcu/ton; the stabilizer of the zero-additive room-temperature yogurt includes: citrus fiber, seaweed powder and glutinous rice starch, and the citrus fiber is citrus fiber after freeze-grinding, and the conditions of the freeze-grinding are: soaking the coarsely ground citrus fiber in liquid nitrogen for 3-5 minutes, so that a layer of ice layer is formed on its surface, and then grinding until the fineness is 150-220 mesh.

The present invention adopts a new idea to solve the problem of the viscosity of room temperature yogurt products using citrus fiber, seaweed powder and glutinous rice starch as stabilizers increasing during the shelf life. Specifically, the present invention starts from the citrus fiber itself, uses citrus fiber with greatly improved fineness as raw material, and uses the improved citrus fiber in combination with seaweed powder and glutinous rice starch, which significantly improves the viscosity of room temperature yogurt during the shelf life.

The present invention freeze-grinds citrus fiber to significantly improve the fineness of citrus fiber, and obtains citrus fiber with significantly improved fluidity, dispersibility and hydration as a stabilizer for yogurt preparation. Compared with other grinding methods, citrus fiber obtained by liquid nitrogen freeze-grinding can significantly improve the yogurt sticking defect caused by citrus fiber, and has a beneficial effect on maintaining the stability of room temperature yogurt during the shelf life and improving the taste.

As a zero-additive room-temperature yogurt, the raw materials used in the invention are only composed of milk, frozen and ground citrus fiber, seaweed powder, glutinous rice starch, white sugar and slime-producing fungi.

Specifically, in the zero-additive room temperature yogurt provided by the present invention, the ratio of frozen-ground citrus fiber, seaweed powder, and glutinous rice starch is (1-4):(2-6):(14-20) by mass.

More specifically, the ratio of citrus fiber, seaweed powder and glutinous rice starch after freeze-grinding is 1:2:14 or 4:6:20 by mass.

The zero-additive room-temperature yogurt provided by the invention comprises 871-903 parts by weight of milk, 1-4 parts by weight of frozen and ground citrus fiber, 2-6 parts by weight of seaweed powder, 12-20 parts by weight of glutinous rice starch and 70-90 parts by weight of white granulated sugar.

In a second aspect, the present invention provides a method for preparing the above-mentioned zero-additive room-temperature yogurt, comprising: adding white sugar, frozen and ground citrus fiber, seaweed powder, and glutinous rice starch to pretreated milk in sequence to obtain a mixed liquid, and fermenting the mixed liquid using slime-producing fungi to obtain the zero-additive room-temperature yogurt.

The pretreatment is to heat the milk to 55-60° C. to facilitate the mixing of the materials.

The invention is based on the combination of specific citrus fiber, seaweed powder and glutinous rice starch, which effectively simplifies the preparation method, and the yogurt stabilizer with natural ingredients and white sugar can be mixed at one time.

More specifically, the method for preparing the zero-additive room temperature yogurt of the present invention comprises:

(1) heating the milk to 55-60° C., sequentially adding white sugar, frozen and ground citrus fiber, seaweed powder, and glutinous rice starch to the heated milk, and then homogenizing and sterilizing to obtain a mixed liquid;

(2) cooling the mixed liquid of step (1) to 40-42° C., adding Lactobacillus bulgaricus and Streptococcus thermophilus to ferment until the pH value reaches 4-4.3, breaking the emulsion, stirring and cooling to obtain fermented milk;

(3) pasteurizing and cooling the fermented milk obtained in step (2) to obtain the zero-additive room-temperature yogurt.

In the preparation method provided by the present invention, the homogenization conditions in step (1) are: primary pressure 110-150 bar, secondary pressure 50-80 bar; the sterilization conditions in step (1) are: 130-135° C., 3-5 s.

In the preparation method provided by the present invention, the rotation speed of the demulsification stirring in step (2) is 35-40 revolutions per minute, and the stirring time is 10-12 minutes.

As a specific embodiment of the present invention, a method for preparing zero-additive room temperature yogurt comprises:

(1) After the milk is adjusted from the milk silo, it is directly pumped into the hot plate at a pressure of 10-15 bar to heat the milk to 45-60°C in a cycle. After the heating is completed, the milk is directly pumped into the batching tank to add raw materials. During the process of adding raw materials, the milk is not circulated and heated, which reduces the shearing of the product stabilizer and improves the product stability.

The raw materials added are white sugar, citrus fiber, seaweed powder and glutinous rice starch in sequence. After the feeding is completed, the product is homogenized and the homogenization pressure is: the first-level pressure is 110-150 bar, and the second-level pressure is 50-80 bar. After the homogenization is completed, it is sterilized at a sterilization temperature of 130-135°C and a sterilization time of 3-5s to obtain a mixed liquid.

(2) The mixed liquid is cooled to 40° C., Lactobacillus bulgaricus and Streptococcus thermophilus are added, and fermented in a fermenter. When the pH value reaches 4-4.3, the mixture is stirred to break the emulsion. The stirring speed is 35-40 revolutions per minute. The stirring is carried out for 10-12 minutes. After the stirring is completed, the mixture is quickly cooled in the fermenter to 20-25° C. to obtain cooled fermented milk.

(3) The cooled fermented milk is pasteurized at 95°C for 200-300 seconds and cooled to 20-25°C to obtain zero-additive room temperature yogurt.

In addition, the inventors found that the problem of citrus fiber and seaweed powder sticking to the tube still exists during the ultra-high temperature instantaneous sterilization stage. To solve this problem, the present invention further provides the following technical solutions.

In one aspect, the present invention provides a method for preparing room temperature yogurt, comprising: adding white sugar, citrus fiber, seaweed powder and glutinous rice starch to milk at 18-25° C. for mixing, homogenizing and sterilizing after mixing to obtain a mixed liquid, inoculating and fermenting the mixed liquid to obtain fermented milk, and pasteurizing to obtain the room temperature yogurt;

The citrus fiber is frozen and ground citrus fiber, and the processing method is as described above.

As mentioned above, freezing and grinding citrus fiber can improve the re-adhesion defect of yogurt caused by citrus fiber during the shelf life. However, in industrial production, during the ultra-high temperature instantaneous sterilization stage, there is a problem of citrus fiber and seaweed powder sticking to the tube. This may be caused by the re-adhesion characteristics of citrus fiber, a natural raw material. Therefore, faced with this problem, the inventor first thought of replacing citrus fiber or further modifying citrus fiber, but after a series of attempts, no ideal effect was obtained. However, after studying During the process, it was unexpectedly discovered that the problem of citrus fiber and seaweed powder sticking to the tube during the ultra-high temperature instantaneous sterilization stage can be effectively solved by using low-temperature (18-25°C) chemical processing instead of 55-60°C as mentioned above, without any obvious negative impact on the stability and taste of the final product.

Here, the fermentation bacteria are Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus (ie, Lactobacillus bulgaricus and Streptococcus thermophilus), and the addition amount of the fermentation bacteria is 200 dcu/ton.

Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus are slime-producing fungi. Using them in fermentation substrates containing specific citrus fiber, seaweed powder and glutinous rice starch is beneficial to obtaining good fermentation effects and product stability.

In some embodiments of the present invention, the mass ratio of citrus fiber, seaweed powder and glutinous rice starch after freeze-grinding is (1-4):(2-6):(10-20).

The frozen ground citrus fiber, seaweed powder and glutinous rice starch are controlled within the above ratio range, which is conducive to improving the yogurt stickiness defect and maintaining the stability and taste of the yogurt during the shelf life. In addition, the present invention has found that after the improvement to the cold material, the amount of glutinous rice starch can be reduced to a certain extent without obvious influence on the final result.

According to the preparation method of room temperature yogurt provided by the present invention, in addition to the fermentation bacteria, the raw materials of the room temperature yogurt are: 880-917 parts of milk, 1-4 parts of frozen and ground citrus fiber, 2-6 parts of seaweed powder, 10-20 parts of glutinous rice starch and 70-90 parts of white sugar.

In some embodiments of the present invention, the method for preparing the room temperature yogurt comprises:

(1) heating the milk to 18-25° C., adding white sugar, citrus fiber, seaweed powder and glutinous rice starch to homogenize and sterilize the milk to obtain a mixed liquid;

(2) After the mixed liquid is cooled to 40-42° C., Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus are added to ferment until the pH value reaches 4-4.3, the mixture is stirred and cooled to obtain fermented milk;

(3) pasteurizing the cooled fermented milk and cooling it to obtain the room temperature yogurt.

Furthermore, in step (1), the homogenization conditions are: primary pressure 110-150 bar, secondary pressure 50-80 bar; the sterilization conditions are: 125-135°C, 3-5s.

Furthermore, in step (2), the rotation speed of the demulsification stirring is 35-40 revolutions per minute, and the stirring time is 10-12 minutes.

Furthermore, in step (3), the pasteurization conditions are: 95° C., 200-300 s, optionally 300 s.

In a specific embodiment of the present invention, the method for preparing the room temperature yogurt comprises:

After the milk is adjusted from the milk silo, it is heated to 20°C on a hot plate and then directly poured into the batching tank. White sugar, citrus fiber (frozen ground citrus fiber), seaweed powder and glutinous rice starch are added. After the feeding is completed, the product is homogenized: the first-level homogenization pressure is 110 bar, and the second-level pressure is 70 bar. After the homogenization is completed, it is sterilized at a temperature of 130 degrees Celsius and a sterilization time of 5 seconds. The liquid is cooled to 40-42 degrees Celsius and the strains are added. The strains are Lactobacillus delbrueckii subspecies Bulgaria and Streptococcus salivarius thermophilic subspecies. Fermentation is carried out in a fermentation tank. When the pH value reaches 4.3, the milk is broken and stirred. The stirring speed is 35 revolutions per minute and stirred for 10 minutes. After stirring, it is quickly cooled in the fermentation tank to 20 degrees Celsius to obtain the cooled fermented milk. The cooled fermented milk is pasteurized at a temperature of 95°C and a time of 300 seconds. Cool to 25 degrees Celsius and can it.

On the other hand, the present invention provides a room temperature yogurt, which is prepared by the above preparation method. The raw materials of the room temperature yogurt are: 880-917 parts of milk, 1-4 parts of frozen and ground citrus fiber, 2-6 parts of seaweed powder, 10-20 parts of glutinous rice starch and 70-90 parts of white sugar, and fermentation strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus.

Furthermore, the raw materials of the room temperature yogurt are as follows: 888.1-917 parts of milk, 1-4 parts of frozen and ground citrus fiber, 2-6 parts of seaweed powder, 10-11.9 parts of glutinous rice starch and 70-90 parts of white sugar, as well as fermentation strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus.

The present invention not only provides a room-temperature yogurt without adding food additives and which completely utilizes raw materials to build a stable system of the product, but also uses low-temperature materials so that the amount of glutinous rice starch in the product of the present invention can be reduced.

The room temperature yogurt of the present invention does not separate out water when placed at 38° C. for 6 months.

Beneficial effects of the present invention:

The present invention provides room temperature yogurt without any food additives, and completely utilizes raw materials to build a stable system of the product. The present invention pre-treats citrus fiber to obtain liquid nitrogen frozen and ground citrus fiber, and uses seaweed powder and glutinous rice starch as stabilizers. Under the premise of maintaining the stability of the yogurt system, the re-adhesion defect of room temperature yogurt caused by citrus fiber during the shelf life is improved.

In the present invention, fermentation bacteria Lactobacillus bulgaricus and Streptococcus thermophilus are used in a fermentation substrate containing specific citrus fiber, seaweed powder and glutinous rice starch, thereby obtaining a good yogurt fermentation effect, simplifying the adding method of the yogurt stabilizer, and further simplifying the yogurt preparation method.

In addition, the present invention unexpectedly discovered that the use of 18-25°C low-temperature cooling materials can effectively solve the problem of citrus fiber and seaweed powder sticking to the tube during ultra-high temperature instantaneous sterilization and pasteurization, and has no obvious negative impact on the stability and taste of the final product. Furthermore, under the condition of cooling materials, the room temperature yogurt of the present invention can also reduce the amount of glutinous rice starch, so that the formula is cleaner.

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

The term "include" or "comprising" in the present invention is an open description containing the specified components or steps described, and other specified components or steps that will not be substantially affected.

The endpoints and any values of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

Example 1

This embodiment provides a formula and preparation method of zero-additive yogurt, as follows:

The formula of zero-additive yogurt is:

903 parts by weight of milk, 1 part by weight of frozen and ground citrus fiber, 2 parts by weight of seaweed powder, 14 parts by weight of glutinous rice starch and 80 parts by weight of white sugar; the added amount of fermentation bacteria is 200 dcu/ton.

The method of freezing and grinding citrus fiber is liquid nitrogen treatment: the coarsely ground 60-mesh citrus fiber is immersed in liquid nitrogen for 3-5 minutes to form a layer of ice on its surface, and then continued to grind to a fineness of 200 mesh.

The preparation method of zero-additive yogurt is as follows: (1) after the milk is adjusted from the milk silo, the milk is directly beaten into a hot plate using a pressure of 10 bar to heat the milk to 55° C. in a circulation manner, and after the heating is completed, the milk is directly beaten into a batching tank; raw materials are added, and the milk is not circulated and heated during the process of adding raw materials, so as to reduce the shear of the product stabilizer and thus improve the product stability.

The raw materials added are white sugar, citrus fiber, seaweed powder, and glutinous rice starch. After the feeding is completed, the product is homogenized. The first-level homogenization pressure is 110 bar, and the second-level pressure is 70 bar.

After homogenization, sterilization is carried out at a temperature of 130°C and a sterilization time of 5 seconds.

(2) The feed liquid of step (1) is cooled to 40° C., Lactobacillus bulgaricus and Streptococcus thermophilus are added to ferment in a fermenter, and when the pH value reaches 4.3, the emulsion is broken and stirred at a stirring speed of 35 revolutions per minute for 10 minutes. After stirring, the feed liquid is quickly cooled in the fermenter to 20° C. to obtain cooled fermented milk.

(3) The cooled fermented milk is pasteurized at 95°C for 300 seconds and cooled to 25°C to obtain zero-additive room temperature yogurt.

Example 2

This embodiment provides a formula and preparation method of zero-additive yogurt, as follows:

The formula of zero-additive yogurt is:

888 parts by weight of milk, 4 parts by weight of frozen and ground citrus fiber, 6 parts by weight of seaweed powder, 20 parts by weight of glutinous rice starch and 82 parts by weight of white sugar; the added amount of fermentation bacteria is 200 dcu/ton.

The method of liquid nitrogen rapid freezing and grinding of citrus fiber is the same as that in Example 1, and the fineness of the citrus fiber used is 180 mesh.

The preparation method is as follows: (1) after the milk is adjusted from the milk silo, the milk is directly beaten into a hot plate (hot plate temperature) at a pressure of 15 bar to heat the milk to 60°C in a circulating manner. After the heating is completed, the milk is directly beaten into a batching tank and raw materials are added. During the process of adding raw materials, the milk is not circulated and heated to reduce the shear of the product stabilizer, thereby improving the product stability.

The added raw materials are white sugar, citrus fiber, seaweed powder and glutinous rice starch in sequence. After the feeding is completed, the product is homogenized with a first-level homogenization pressure of 120 bar and a second-level pressure of 50 bar. After the homogenization is completed, it is sterilized with a sterilization temperature of 130°C and a sterilization time of 5 seconds to obtain a mixed liquid.

(2) The mixed liquid is cooled to 40° C., and Lactobacillus bulgaricus and Streptococcus thermophilus are added to ferment in a fermenter. When the pH value reaches 4.3, the mixture is demulsified and stirred at a stirring speed of 35 revolutions per minute for 10 minutes. After stirring, the mixture is quickly cooled in the fermenter to 20° C. to obtain cooled fermented milk.

(3) The cooled fermented milk is pasteurized at 95°C for 300 seconds and cooled to 25°C to obtain zero-additive room temperature yogurt.

Example 3

This embodiment provides a formula and preparation method of zero-additive room temperature yogurt, as follows:

The formula used in this embodiment is the same as that in embodiment 2. The method of liquid nitrogen rapid freezing and grinding of citrus fiber is the same as that in embodiment 1. The fineness of the citrus fiber used is 150 mesh. The preparation method of citrus fiber used is the same as that in embodiment 1.

Example 4

This embodiment is the same as embodiment 2, except that the fineness of the citrus fiber used is 220 mesh.

Example 5

This embodiment provides a room temperature yogurt, and its formula is as follows:

900.1 parts by weight of milk, 85 parts by weight of granulated sugar, 1 part by weight of citrus fiber, 2 parts by weight of seaweed powder, and 11.9 parts by weight of glutinous rice starch; the fermentation bacteria are Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus, with a total addition amount of 200 dcu/ton.

The preparation method is as follows:

After the milk is adjusted from the milk silo, the milk hot plate is heated to 20℃ and then directly poured into the mixing tank. White sugar, citrus fiber, seaweed powder and glutinous rice starch are added. After the feeding is completed, the product is homogenized. The first-level homogenization pressure is 110bar and the second-level pressure is 70bar. After the homogenization is completed, it is sterilized at a temperature of 130 degrees Celsius and a sterilization time of 5s. The liquid is cooled to 40 degrees Celsius and the bacteria are added. Lactobacillus delbrueckii subspecies Bulgarian and Streptococcus salivarius thermophilus subspecies are fermented in a fermentation tank. When the pH value reaches 4.3, the milk is broken and stirred at a stirring speed of 35 revolutions per minute for 10 minutes. After stirring, the milk is quickly cooled in the fermentation tank to 20 degrees Celsius to obtain cooled fermented milk. The cooled fermented milk is pasteurized at a sterilization temperature of 95 degrees Celsius for 300 seconds. It is cooled to 25 degrees Celsius and canned.

Example 6

This embodiment provides a room temperature yogurt, and its formula is as follows:

898.1 parts by weight of milk, 85 parts by weight of granulated sugar, 3 parts by weight of citrus fiber, 3 parts by weight of seaweed powder, and 10.9 parts by weight of glutinous rice starch; the fermentation bacteria are Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus, with a total addition amount of 200 dcu/ton.

The preparation method is as follows:

After the milk is adjusted from the milk silo, the milk hot plate is heated to 20℃ and then directly poured into the batching tank, and white sugar, citrus fiber, seaweed powder and glutinous rice starch are added. After the feeding is completed, the product is homogenized, and the homogenization pressure is 110bar at the first level and 70bar at the second level. After the homogenization is completed, it is sterilized at a temperature of 125 degrees Celsius and a sterilization time of 5s. The liquid is cooled to 40 degrees Celsius and the strains of Lactobacillus delbrueckii subspecies Bulgaria and Streptococcus salivarius thermophilus subspecies are added to ferment in the fermentation tank. When the pH value reaches 4.3, the milk is broken and stirred at a stirring speed of 35 revolutions per minute for 10 minutes. After stirring, it is quickly cooled in the fermentation tank to 20 degrees Celsius to obtain the cooled fermented milk. The cooled fermented milk is pasteurized at a temperature of 95℃ for 300s. Cool to 25 degrees Celsius and canned.

Example 7

This embodiment provides a room temperature yogurt, and its formula is as follows:

899 parts by weight of milk, 85 parts by weight of granulated sugar, 2 parts by weight of citrus fiber, 4 parts by weight of seaweed powder, and 10 parts by weight of glutinous rice starch; the fermentation bacteria are Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus, with a total addition amount of 200 dcu/ton.

The preparation method is as follows:

After the milk is adjusted from the milk silo, the milk hot plate is heated to 20℃ and then directly poured into the batching tank, and raw materials are added. The order of raw material addition is white sugar, citrus fiber, seaweed powder, and glutinous rice starch. After the feeding is completed, the product is homogenized. The first-level homogenization pressure is 110bar and the second-level pressure is 70bar. After homogenization, it is sterilized at a temperature of 130 degrees Celsius and a sterilization time of 5s. The liquid is cooled to 40 degrees Celsius and the strains of Lactobacillus delbrueckii subspecies Bulgaria and Streptococcus salivarius thermophilus subspecies are added. Fermentation is carried out in a fermentation tank. When the pH value reaches 4.3, the milk is broken and stirred. The stirring speed is 35 revolutions per minute and stirred for 10 minutes. After stirring, it is quickly cooled in the fermentation tank to 20 degrees Celsius to obtain the cooled fermented milk. The cooled fermented milk is pasteurized at a temperature of 95℃ and a time of 300s. Cool to 25 degrees Celsius and can it.

Comparative Example 1

This comparative example is the same as Example 4, except that in step (2) of this comparative example, the feed liquid of step (1) is cooled to 40° C. and Lactobacillus bulgaricus and Streptococcus thermophilus are added as fermentation strains in an amount of 300 dcu/ton.

Comparative Examples 2-5

In Comparative Example 2, other ingredients and preparation methods are the same as those in Example 4, except that seaweed powder is not used in the formula of this comparative example.

In Comparative Example 3, other ingredients and preparation methods are the same as those in Example 4, except that: citrus fiber is not used in this comparative example.

In Comparative Example 4, other ingredients and preparation methods are the same as those in Example 4, except that: this comparative example uses citrus fiber that has not been frozen and ground by liquid nitrogen and has a fineness of 220 meshes.

In Comparative Example 5, other ingredients and preparation methods are the same as those in Example 4, except that corn starch is used instead of glutinous rice starch in this comparative example.

Comparative Example 6

This comparative example provides a room temperature yogurt, the formula of which is the same as that of Example 5, and the preparation method adopts a common heating material process, which is as follows:

(1) After the milk is adjusted from the milk silo, it is directly pumped into the hot plate (hot plate temperature) at a pressure of 15 bar to heat the milk to 60°C in a circulation cycle. After the heating is completed, it is directly pumped into the batching tank and the raw materials are added. During the process of adding the raw materials, the milk is not circulated and heated, which reduces the shear of the product stabilizer and improves the product stability.

The added raw materials are white sugar, citrus fiber, seaweed powder and glutinous rice starch in sequence. After the feeding is completed, the product is homogenized with a first-level homogenization pressure of 120 bar and a second-level pressure of 50 bar. After the homogenization is completed, it is sterilized with a sterilization temperature of 130°C and a sterilization time of 5 seconds to obtain a mixed liquid.

(2) The mixed liquid is cooled to 40° C., and Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus are added to ferment in a fermenter. When the pH value reaches 4.3, the mixture is demulsified and stirred at a stirring speed of 35 revolutions per minute for 10 minutes. After stirring, the mixture is quickly cooled in the fermenter to 20° C. to obtain cooled fermented milk.

(3) The cooled fermented milk is pasteurized at 95°C for 300 seconds and cooled to 25°C to obtain room temperature yogurt.

Comparative Example 7

This comparative example provides a room temperature yogurt, and its formula is as follows:

900.1 parts by weight of milk, 85 parts by weight of white sugar, 3 parts by weight of seaweed powder, 11.9 parts by weight of glutinous rice starch; fermentation bacteria Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus, with a total addition amount of 200 dcu/ton. The preparation method is the same as that of Example 5.

Comparative Example 8

This comparative example provides a room temperature yogurt, and its formula is as follows:

899 parts by weight of milk, 85 parts by weight of white sugar, 2 parts by weight of citrus fiber, 4 parts by weight of seaweed powder, 10 parts by weight of corn starch; fermentation bacteria Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus, the total addition amount is 200 dcu/ton. The preparation method is the same as that of Example 7.

Experimental Example 1 Comparison of product viscosity of Examples 1-4 and Comparative Examples 1-5

In this experimental example, the viscosity (unit: mPa.s) of the products of Examples 1-4 and Comparative Examples 1-5 was measured by a rheometer at 25°C, using a CC27 probe and a ramp rate of 75 seconds, as shown in Table 1. The target viscosity range is 220-380.

Table 1 Viscosity of products of Examples 1-4 and Comparative Examples 1-5

Experimental Example 2 Comparison of the stability of the products of Examples 1-4 and Comparative Examples 1-5 during the shelf life

The products of Examples 1-4 and Comparative Examples 1-5 were placed at 38°C for heat preservation observation. The stability results of the products during the shelf life are shown in Table 2.

Table 2 Stability results of products in Examples 1-4 and Comparative Examples 1-5 during shelf life

Experimental Example 3 Comparison of product preferences of Examples 1-4 and Comparative Examples 1-5

This experimental example tests the likeability of the products of Examples 1-4 and Comparative Examples 1-5.

20 tasters were randomly selected to conduct a product flavor test (also known as a "taste test"). The flavor test uses a scoring method: the scoring method is a method of using numerical scores to evaluate products or product characteristics, and finally the average score is used to determine the quality. The scoring rule is based on a range of 0-10 points, 0-2 points are considered poor, 3-5 points are considered fair, 6-8 points are considered good, and 9-10 points are considered excellent. The evaluation items include: color, flavor, and taste. The flavor test results are shown in Table 3.

Table 3 Product preference rating results of Examples 1-4 and Comparative Examples 1-5

It can be seen from Tables 1-3 that compared with Example 4, after omitting or replacing the type of stabilizer (citrus fiber, seaweed powder, glutinous rice starch) in Comparative Examples 2, 3 and 5, although the room temperature yogurt basically does not have a re-viscosity defect during the shelf life, the initial viscosity and stability of the room temperature yogurt prepared in Comparative Examples 2, 3 and 5 do not meet the requirements.

For example, the product obtained in Comparative Example 2 without using seaweed powder developed patterns within one month and began to precipitate water from the second month, and its stability during the shelf life was poor, which shows that seaweed powder is an indispensable stabilizer, and the absence of seaweed powder will greatly affect the stability of the product during the shelf life.

The product obtained in Comparative Example 3 without using citrus fiber showed slight water precipitation starting from the second month, and its stability during the shelf life was poor. The viscosity remained at a low level throughout the shelf life. This shows that citrus fiber is an important factor affecting viscosity and is also the main reason for the viscosity rebound during the shelf life. To solve the problem of viscosity rebound during the shelf life, in-depth research on citrus fiber is needed.

The product obtained by using corn starch instead of glutinous rice starch in Comparative Example 5 also showed slight water precipitation in the second month, and its stability during the shelf life was poor, which also shows that the product of the present invention needs to use glutinous rice starch with higher viscosity, and cannot use corn starch with lower viscosity. Maintaining the viscosity of the product is also a key reason for maintaining the stability of the product. In other words, the product of the present invention must have a certain viscosity to maintain stability, and avoid the phenomenon of viscosity rebound during the shelf life.

Compared with Example 4, after increasing the amount of starter in Comparative Example 1, the initial viscosity and stability of the room temperature yogurt prepared did not meet the requirements. It was confirmed that in the yogurt system with citrus fiber, seaweed powder and glutinous rice starch as stabilizers, changing the amount of starter would seriously affect the fermentation effect and stability effect of room temperature yogurt.

Compared with Example 4, Comparative Example 4 provides ordinary citrus fiber with the same fineness of 220 mesh but not ground by liquid nitrogen (the liquid nitrogen ground product will not produce agglomeration, thermal denaturation and other problems due to high temperature grinding). It is found that even if the fineness is the same, since the citrus fiber has not been pretreated, it will still cause the yogurt system to stick back after being used as a stabilizer, and due to the simplification of the preparation method, the 220 mesh citrus fiber that has not been treated with liquid nitrogen is used together with seaweed powder and glutinous rice starch as a stabilizer, and the stability effect played is very limited. As shown in Table 1, the viscosity of Comparative Example 4 is 30%, 41%, 54% and 78% higher than that of Example 4 at one month, two months, three months, four months and five months, respectively, which shows that the viscosity of the comparative example increases month by month, and the rate of viscosity increase increases month by month relative to Example 4; as shown in Table 2, the product prepared by Comparative Example 4 has patterns at two months and water separation at the third month; and as shown in Table 3, its mouthfeel is significantly lower than that of Example 4.

Experimental Example 4

In this experimental example, a rheometer was used at 25°C, using a CC27 probe and a ramp rate of 75 seconds to measure the viscosity (unit: mPa.s) of the products of Examples 5-7 and Comparative Examples 6-8. The results are shown in Table 4.

Table 4

Experimental Example 5

The product formulations of Examples 5-7 and Comparative Examples 6-8 were sterilized for the first time (ultra-high temperature instantaneous sterilization) and the tubes were dismantled to observe whether there was tube sticking. The results are shown in Table 5.

Table 5

Experimental Example 6

The products of Examples 5-7 and Comparative Examples 6-8 were placed at 38°C for heat preservation observation. The stability results of the products during the shelf life are shown in Table 6.

Table 6

Experimental Example 7

This experimental example tests the likeability of the products of Examples 5-7 and Comparative Examples 6-8.

20 tasters were randomly selected to conduct a product flavor test (also known as a "taste test"). The flavor test uses a scoring method: the scoring method is a method of using numerical scores to evaluate products or product characteristics, and finally the average score is used to determine the quality. The scoring rule is based on a range of 0-10 points, 0-2 points are considered poor, 3-5 points are considered fair, 6-8 points are considered good, and 9-10 points are considered excellent. The evaluation items include: color, flavor, and taste. The flavor test results are shown in Table 7.

Table 7

As can be seen from Table 4-7, only appropriate raw materials and processes can ensure the stability and taste of the product. Improvements in product processing can greatly improve the tube sticking phenomenon during product production and significantly reduce the amount of starch added to the product. Starch from different sources will affect the viscosity, stability and taste of the product.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the above embodiments can still be applied to the present invention. The technical solutions described in the above embodiments are modified, or some of the technical features are replaced by equivalents; however, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (17)

A zero-additive room-temperature yogurt, characterized in that the zero-additive room-temperature yogurt uses slime-producing fungi as fermentation strains, and the addition amount of the fermentation strains is 200 dcu/ton; the stabilizer of the zero-additive room-temperature yogurt comprises: citrus fiber, seaweed powder and glutinous rice starch, the citrus fiber is citrus fiber after freeze-grinding, and the freeze-grinding conditions are: soaking the coarsely ground citrus fiber in liquid nitrogen, forming a layer of ice on its surface, and then grinding until the fineness is 150-220 meshes, and optionally, the slime-producing fungi are Lactobacillus bulgaricus and Streptococcus thermophilus. The zero-additive room-temperature yogurt according to claim 1 is characterized in that the raw materials of the zero-additive room-temperature yogurt are composed of milk, frozen and ground citrus fiber, seaweed powder, glutinous rice starch, white sugar and slime-producing fungi. The zero-additive room temperature yogurt according to claim 2 is characterized in that, in the zero-additive room temperature yogurt, the ratio of frozen-ground citrus fiber, seaweed powder and glutinous rice starch is (1-4):(2-6):(14-20) by mass. The zero-additive room-temperature yogurt according to claim 3 is characterized in that, in the zero-additive room-temperature yogurt, the ratio of frozen-ground citrus fiber, seaweed powder, and glutinous rice starch is 1:2:14 or 4:6:20 by mass. The zero-additive room temperature yogurt according to claim 4 is characterized in that the zero-additive room temperature yogurt comprises 871-903 parts by weight of milk, 1-4 parts by weight of frozen and ground citrus fiber, 2-6 parts by weight of seaweed powder, 12-20 parts by weight of glutinous rice starch and 70-90 parts by weight of white granulated sugar. The method for preparing the zero-addition room temperature yogurt according to any one of claims 1 to 5 is characterized in that it comprises: adding white sugar, frozen and ground citrus fiber, seaweed powder, and glutinous rice starch to the pretreated milk in sequence to obtain a mixed liquid, and fermenting the mixed liquid with slime-producing fungi to obtain zero-addition room temperature yogurt, optionally, the slime-producing fungi are Lactobacillus bulgaricus and Streptococcus thermophilus, optionally, the pretreatment is to heat the milk to 55-60°C, optionally, after the milk is adjusted from the milk warehouse, the milk is beaten into a hot plate by pressure to circulate and heat the milk to 55-60°C, and optionally, the pressure is 10-15 bar. The method for preparing zero-additive room temperature yogurt according to claim 6, characterized in that it comprises: (1) heating the milk to 55-60° C., sequentially adding white sugar, frozen and ground citrus fiber, seaweed powder and glutinous rice starch to the heated milk for homogenization and sterilization to obtain a mixed liquid; (2) cooling the mixed liquid of step (1) to 40-42° C., adding slime-producing fungi for fermentation, and fermenting until the pH value reaches 4-4.3, breaking the emulsion, stirring and cooling to obtain fermented milk, and optionally cooling to 20-25° C.; (3) pasteurizing and cooling the fermented milk obtained in step (2) to obtain the zero-additive room temperature yogurt, and optionally cooling it to 20-25°C. The method for preparing zero-additive room temperature yogurt according to claim 7 is characterized in that the homogenization conditions in step (1) are: primary pressure 110-150 bar, secondary pressure 50-80 bar; the sterilization conditions in step (1) are: 130-135°C, 3-5s. The method for preparing zero-additive room temperature yogurt according to claim 7 is characterized in that the rotation speed of the demulsification stirring in step (2) is 35-40 revolutions per minute, and the stirring time is 10-12 minutes. The method for preparing zero-additive room temperature yogurt according to claim 7 is characterized in that the pasteurization temperature in step (3) is 95° C. and the time is 200-300 seconds. A method for preparing room temperature yogurt, characterized in that it comprises: adding white sugar, citrus fiber, seaweed powder and glutinous rice starch to milk at 18-25° C. to make a mixture, homogenizing and sterilizing the mixture to obtain a mixed liquid, inoculating and fermenting the mixed liquid to obtain fermented milk, and pasteurizing the mixture to obtain the room temperature yogurt, wherein the fermentation bacteria are Lactobacillus delbrueckii subspecies bulgaricus and Streptococcus salivarius subspecies thermophilic; The citrus fiber is freeze-ground citrus fiber, and the freeze-ground conditions are: soaking the coarsely ground citrus fiber in liquid nitrogen to form a layer of ice on its surface and then grinding it until the fineness is 150-220 meshes, Optionally, the mass ratio of citrus fiber, seaweed powder and glutinous rice starch after freeze-grinding is (1-4):(2-6):(10-20). The method for preparing room temperature yogurt according to claim 11 is characterized in that, in parts by weight, in addition to the fermentation bacteria, the raw materials of the room temperature yogurt are: 880-917 parts of milk, 1-4 parts of frozen and ground citrus fiber, 2-6 parts of seaweed powder, 10-20 parts of glutinous rice starch and 70-90 parts of white sugar. The method for preparing room temperature yogurt according to claim 11 or 12, characterized in that the preparation method comprises: (1) heating the milk to 18-25° C., adding white sugar, citrus fiber, seaweed powder and glutinous rice starch to homogenize and sterilize the milk to obtain a mixed liquid; (2) After cooling the mixed liquid to 40-42° C., adding Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus to carry out fermentation until the pH value reaches 4.3, breaking the emulsion, stirring, and cooling to obtain fermented milk; (3) pasteurizing the cooled fermented milk and cooling it to obtain the room temperature yogurt. The method for preparing room temperature yogurt according to claim 13 is characterized in that, in step (1), the homogenization conditions are: primary pressure 110-150 bar, secondary pressure 50-80 bar; the sterilization conditions are: 125-135°C, 3-5s. The method for preparing room temperature yogurt according to claim 13, characterized in that, in step (2), the rotation speed of the demulsification stirring is 35-40 revolutions per minute, and the stirring time is 10-12 minutes. The method for preparing room temperature yogurt according to claim 13, characterized in that in step (3), the pasteurization conditions are: 95°C, 200-300s, optionally 300s. A room temperature yogurt, characterized in that it is prepared by the preparation method according to any one of claims 11 to 16, wherein the raw materials of the room temperature yogurt are composed of: 888.1 to 917 parts of milk, 1 to 4 parts of frozen and ground citrus fiber, 2 to 6 parts of seaweed powder, 10 to 11.9 parts of glutinous rice starch and 70 to 90 parts of white sugar, and fermented bacteria Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus, and optionally, the room temperature yogurt is placed at 38° C. for 6 months without decomposition.