WO2019095168A1 - Method for preparing set-style normal temperature yogurt and specialized stabilizer therefor - Google Patents

Abstract

Disclosed are a method for preparing a set-style normal temperature yogurt, and a specialized stabilizer therefor. The specialized stabilizer comprises 0.15%-0.3% of agar, 0.4%-1% of a high-ester pectin, 0.1%-0.2% of a low-ester pectin, 0.5%-2% of starch or modified starch, and 0.01%-0.1% of a low-acyl gellan gum in percentage based on the weight of the final product. Fermented yogurt is sterilized at an ultra-high temperature to kill active lactic acid bacteria therein, such that the shelf life of the yogurt can be effectively prolonged and may be up to 8-10 months. The specialized stabilizer therein can ensure that the product is capable of withstanding an ultra-high temperature sterilization treatment, is prevented from protein dehydration shrinkage that causes a large amount of whey to separate out, and is imparted with a solid and bright appearance, characteristically possessed by set-style yogurts, after cooling.

Description

Method for preparing solidified normal temperature yoghurt and special stabilizer thereof Technical field

The invention belongs to the field of processing of fermented dairy products, and particularly relates to a method for preparing a solidified room temperature yogurt and a special stabilizer thereof.

Background technique

Yogurt is a milk product that uses milk as a raw material, pasteurized and then added beneficial bacteria (fermenting agent) to the milk, and then cooled and then filled. The history of yoghurt can be traced back more than 7,000 years ago. Today, fermented milk is increasingly favored by consumers for its rich nutritional value and good health care functions, making it the world's largest dairy product. In China, fermented milk production has increased at an average annual rate of 20% in the past five years, and it is the most profitable and promising product in the dairy industry.

The short shelf life of yoghurt has always been a problem that plagues yoghurt producers and consumers. In addition, transportation, storage and sales require a whole process of cold chain, which causes a series of quality problems such as acidification after market terminal products. In order to cope with and solve this problem, normal temperature came into being. Normal temperature yogurt, also known as long-acting yogurt, is a fermented yogurt that has been aseptically packaged after heat treatment. Its biggest feature is that it can be stored for 100-180 days under normal temperature, and the taste and flavor are basically the same as low-temperature yogurt. In addition to meeting the consumer groups that are required to reserve as much life as possible, the room temperature yoghurt can satisfy the long-term advantage of its long shelf life in addition to satisfying the increasingly fierce social competition and the accelerating pace of life. Remote areas with remote transportation and inconvenient transportation. As a result, the yogurt at room temperature quickly became popular in the market, and it is the fastest growing product among yogurt products.

At present, the process of normal temperature yoghurt is mostly secondary sterilization after fermentation, and then refilled. The existing process at room temperature is realized through sterilization pipeline. Therefore, the normal temperature yoghurt produced is stirred yoghurt, generally using pasteurized Sterilization, the longest storage time can be 6 months. However, due to the limitations of the prior art, it is impossible to use a heat treatment method in the production of a normal temperature yogurt.

In order to produce a solidified room temperature yoghurt, Chinese Patent Application No. 201510673249.3 discloses a room temperature solidified yoghurt and a preparation method thereof, which adopts an ultrahigh pressure treatment of 300-600 MPa to realize secondary sterilization of the product. However, the ultra-high pressure treatment has high requirements on the equipment, the equipment investment is large, and the treatment is Objects are also required to limit industrialized mass production applications. Chinese patent application 201510595832.7 discloses a room temperature solidification type yoghurt and a preparation method thereof, the method adopts secondary compounding, and after the fermentation of the material liquid A is finished, the agar, gelatin and konjac gum are mixed for secondary compounding, and then secondary sterilization. After standing, it is allowed to stand until the liquid solidifies. However, the secondary batching process is cumbersome and is subject to certain restrictions in the promotion of the factory.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the current conflict between the normal temperature operation process of yoghurt and the solidified yoghurt production process, and to disclose a method for preparing a long shelf life solidified yoghurt and a special stabilizer thereof. It is characterized by using a special yogurt stabilizer to stabilize its texture, preventing a large amount of whey from being precipitated by protein dehydration and shrinkage, secondary ultra-high temperature sterilization after fermentation, and cooling to form a solidified yogurt after filling to a package material, greatly extending the shelf life. It can be stored for 8-10 months at room temperature.

In order to extend the shelf life of the product, the production of normal temperature yogurt requires high temperature treatment of the yogurt. However, this step of yoghurt heat treatment, especially at higher temperatures (over 100 ° C), because physical shear will destroy the texture of yogurt and even stabilizers, it is easy to cause water precipitation, so special stabilizers are needed to protect proteins and maintain system stability. . Therefore, the inventors have conducted extensive research and repeated experiments to prepare a novel yoghurt stabilizer by a compounding process of a stabilizer, which can maintain its structural stability under ultra-high temperature treatment. Hot filling is cooled to form a solidified yogurt.

The present invention provides the following technical solutions to solve the above technical problems.

The invention provides a special stabilizer for preparing solidified room temperature yoghurt, which is characterized in that the obtained finished product is calculated by weight percentage, including agar: 0.15-0.3%, high ester pectin: 0.4-1%, Low ester pectin: 0.1-0.2%, starch or modified starch: 0.5-2%, low acyl gellan gum: 0.01-0.1%. The invention also provides a preparation method of a solidified long shelf life normal temperature yoghurt, the raw material comprising a raw material milk, a stabilizer, a sweetener and a starter, the preparation method comprising the following steps:

(1) mixing raw material milk, special stabilizer and sweetener, homogenizing, sterilizing and cooling to obtain a mixed liquid;

(2) inoculating the starter solution in the mixed solution obtained in the step (1), fermenting to the end of the fermentation, demulsification, and cooling;

(3) The fermented milk obtained in the step (2) is subjected to ultra-high temperature instantaneous heat treatment, and after cooling, it is filled to obtain a final product, and the ultra-high temperature treatment condition is 105-121 ° C, 5-30 s.

Wherein, the raw material milk refers to a raw material milk conventionally used in the art, preferably fresh milk and/or treated milk; the fresh milk is whole milk, the treated milk is skim milk and/or reconstituted Milk, the reconstituted milk is prepared according to the routine operation in the art, and is prepared by mixing milk powder and water, preferably prepared by mixing milk powder and water at a mass ratio of 12:88; the content of the raw milk is 80%. Above, it is preferably 83 to 98%, more preferably 85 to 92%, most preferably 90%, and the percentage is a mass percentage based on the total mass of the mixed liquor.

The starter is as long as a starter conventionally used in the art, including Streptococcus thermophilus and Lactobacillus bulgaricus, and the amount added is a conventional addition amount in the art, preferably 2 × 10 ⁶ - 2.4 × 10 ⁸ cfu / mL, more preferably 1.2 × 10 ^{7 -} 1.2 × 10 ⁸ cfu / mL; the amount of addition is calculated as the number of viable cells per ml of the mixed liquor.

The sweetener is, for example, a sweetener conventional in the art, preferably one or more of white granulated sugar, xylitol, fructose, fructose syrup, more preferably in white granulated sugar and fructose syrup. One or more; the sweetener is added in an amount conventionally added in the art, preferably 4-10%, more preferably 5-8%, and the sweetener meets the national standard The provisions in GB-2760-2011; the percentages stated are percentages of the total mass of the mixed liquor.

In the step (1), the temperature of the mixing is a temperature conventional in the art, preferably 40 to 55 ° C, more preferably 43 to 48 ° C; the mixing time is a conventional time in the art, preferably. And the homogenization is conventionally homogenized in the art, and the homogenized temperature is a conventional temperature in the art, preferably 54-66 ° C, more preferably 58. - 62 ° C; said homogenization is secondary homogenization, wherein the first homogeneous pressure is a conventional pressure in the art, preferably 15-19 MPa. The secondary homogeneous pressure is a conventional pressure in the art, preferably 2-5 MPa. And/or, the sterilization is conventional sterilization in the art, generally pasteurization or ultra-high temperature sterilization (UHT sterilization); the pasteurization temperature is a conventional temperature in the art, preferably It is 90-95 ° C; the pasteurization time is a routine time in the art, preferably 5-10 min; the cooling temperature is a conventional temperature in the art, preferably 37-45 ° C, More preferably 39-43 ° C;

In the step (2), the temperature of the fermentation is a temperature conventional in the art, preferably 37-45 ° C, more preferably 39-43 ° C; the end point of the fermentation is a conventional end point in the art. Preferably, the acidity is 70-80 °T, more preferably the acidity is 73-78 °T, the fermentation time is a time conventional in the art, and the fermentation time is actually determined according to the acidity of the fermentation; and/or Cooling temperature-based The conventional temperature in the field is preferably from 15 to 30 ° C, more preferably from 25 to 30 ° C.

In the step (3), the ultra-high temperature instantaneous heating temperature is a conventional temperature in the art, preferably 105-121 ° C, more preferably 115-121 ° C; the processing time is preferably 5-30 s, more preferably The ground temperature is 10-20 s; the cooling temperature is a conventional temperature in the art, preferably 37-50 ° C, more preferably 40-45 ° C; the filled package is preferably deformed. Packaging, more preferably paper cups, PET pre-formed bottles, Tetra Pak packaging; filling volume is 95%-98%.

Based on the common knowledge in the art, the above various preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention.

The reagents and starting materials used in the present invention are commercially available.

The positive progress of the present invention is that the preparation method of the present invention is to super-high temperature sterilize the yoghurt after fermentation to kill the active lactic acid bacteria, which can effectively extend the shelf life of the yoghurt for up to 8-10 months. The special stabilizer can ensure the product can withstand the ultra-high temperature sterilization treatment through the screening and reasonable combination of the colloid, and overcome the ordinary texture of the solidified yogurt after the second heat sterilization, the protein denaturation has a rough taste, aroma weakening and analysis. Defects such as water, after cooling, give the product a firm, shiny appearance that is unique to solidified yogurt.

Detailed ways

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. Unless otherwise stated, the percentages used in the following examples are the mass percentage of each component to the total mass of the mixed liquor.

Example 1

The raw materials are shown in Table 1.

Table 1

(1) According to the raw milk, sweetener, stabilizer, starter and water, the ingredients are mixed and stirred at 40 ° C for 30 min, then homogenized, the first homogenization pressure is 15Mpa, the second homogenization pressure is 5Mpa, homogenization The temperature is 54 ° C, and then sterilized at 90 ° C for 10 min, and then cooled to 37 ° C to obtain a mixed liquid;

(2) Adding a starter to the mixed liquor, wherein Lactobacillus bulgaricus 1×10 ⁶ cfu/mL, Streptococcus thermophilus 1×10 ⁶ cfu/mL, and then fermenting at 37° C., the acidity reaches 70° after 11 hours. T, terminate the fermentation, and cool to 15 ° C;

(3) The fermented milk is demulsified, subjected to ultra-high temperature instantaneous heat treatment at 121 ° C for 5 seconds, cooled to 37 ° C, and then filled with paper cup, filling volume packaging volume of 95%, that is, solidified type normal temperature yogurt, after treatment Store at room temperature.

Example 2

The raw materials are shown in Table 2.

Table 2

(1) According to the raw milk, sweetener, stabilizer, starter and water, the ingredients are mixed and stirred at 43 ° C for 25 min, then homogenized, the first homogenization pressure is 16Mpa, the second homogenization pressure is 4Mpa, and the homogenization temperature After being sterilized at 58 ° C, then 91 ° C for 9 min, and then cooled to 39 ° C to obtain a mixed liquid;

(2) Adding a starter to the mixed liquor, wherein Lactobacillus bulgaricus 1.2×10 ⁸ cfu/mL, Streptococcus thermophilus 1.2×10 ⁸ cfu/mL, and then fermenting at 39° C., the acidity reaches 73° after 10 hours. T, terminate the fermentation, and cool to 25 ° C;

(3) The fermented milk is demulsified, subjected to ultra-high temperature instantaneous heat treatment at 105 ° C for 30 seconds, cooled to 40 ° C, and then filled in a PET preset bottle, and the volume of the package volume is 96%, that is, the solidified type of normal temperature is obtained. Yogurt, stored at room temperature after treatment.

Example 3

The raw materials are shown in Table 3.

table 3

(1) According to the raw milk, sweetener, stabilizer, starter and water, the ingredients are mixed and homogenized at 48 ° C for 20 min, the first homogenization pressure is 17Mpa, the second homogenization pressure is 3Mpa, and the homogenization temperature After being sterilized at 62 ° C, then 92 ° C for 8 min, and then cooled to 43 ° C to obtain a mixed liquid;

(2) Adding a starter to the mixed liquor, wherein Lactobacillus bulgaricus 6×10 ⁶ cfu/mL, Streptococcus thermophilus 6×10 ⁶ cfu/mL, and then fermenting at 43° C., the acidity reaches 78° after 6 hours. T, terminate the fermentation, and cool to 30 ° C;

(3) The fermented milk is demulsified, subjected to ultra-high temperature instantaneous heat treatment at 115 ° C for 20 seconds, cooled to 45 ° C, and then filled in a PET pre-formed bottle, filling the volume of the packaging volume of 97%, that is, the solidified type of normal temperature yogurt Store at room temperature after treatment.

Example 4

The raw materials are shown in Table 4.

Table 4

(1) According to the raw milk, sweetener, stabilizer, starter and water, the ingredients are mixed and stirred at 55 ° C for 15 min, then homogenized, the first homogenization pressure is 19Mpa, the second homogenization pressure is 2Mpa, and the homogenization temperature It is 66 ° C, then sterilized at 95 ° C for 5 min, and then cooled to 45 ° C to obtain a mixed liquid;

(2) Adding a starter to the mixed liquor, wherein Lactobacillus bulgaricus is 6×10 ⁷ cfu/mL, Streptococcus thermophilus 6×10 ⁷ cfu/mL, then fermentation is carried out at 45° C., and the acidity reaches 80° after 5.1 hours. T, terminate the fermentation, and cool to 27 ° C;

(3) The fermented milk is demulsified, subjected to ultra-high temperature instantaneous heat treatment at 118 ° C for 10 seconds, cooled to 50 ° C, and then packaged in a Tetra masonry package, filling the volume of the package by 98%, that is, coagulation Solid type yoghurt at room temperature, stored at room temperature after treatment.

Comparative example 1

The raw material was the same as that of Example 3 except that the step (3) was subjected to a pasteurization method for heating after fermentation, and the sterilization temperature was 75 ° C, and the sterilization time was 20 S.

Comparative example 2

The raw material was the same as that of Example 3 except that a stabilizer commonly used for yoghurt was used, and the following raw materials were compounded, as shown in Table 5.

table 5

The preparation method is the same as in Example 3.

Comparative example 3

The raw material was the same as in Example 3 except that a stabilizer commonly used for yoghurt was used, which was compounded by the following materials, as shown in Table 6.

Table 6

The preparation method is the same as in Example 3.

Effect example 1

Microbial Detection

Methods: In accordance with GB4789.1 "General Principles of Food Microbiology Inspection" and GB4789.18 "Food Microbiology Inspection of Milk and Dairy Products Inspection".

The results of the above-described examples and comparative examples of the room temperature solidified yoghurt which were just prepared were examined as shown in Table 7 below.

Table 7

The room temperature solidified yoghurt obtained in the above examples and comparative examples was stored at room temperature (25 ° C) for 10 months, and then subjected to microbial detection. The results are shown in Table 8.

Table 8

It is indicated that the product prepared by the invention is stored at room temperature for 10 months, and the microbiological related indicators meet the requirements and requirements of GB19302-2010. Comparative Example 1 due to the low sterilization temperature used, normal temperature After storage for 10 months at (25 ° C), the total number of bacteria is 12 CFU / g, there is a certain risk.

Effect example 2

Quality evaluation of solidified yogurt gel

According to the analysis method of "Preparation and Quality Evaluation of Solidified Yogurt" published by Li Lihua and Wang Hongye in the "China Dairy Industry" No. 12, 2010, the water holding capacity and gel strength of the prepared solidified yogurt were evaluated.

The results of the above-described examples and comparative examples of the room temperature solidified yoghurt which were just prepared were as shown in Table 9 below.

Table 9 Quality evaluation of yogurt gel

project	Water holding capacity (%)	Gel strength (g)
Example 1	77.4	twenty four
Example 2	76.1	twenty three
Example 3	80.2	29
Example 4	75.3	33
Comparative example 1	76.4	18
Comparative example 2	60.1	20
Comparative example 3	58.2	twenty one

According to the conclusion of "Preparation and Quality Evaluation of Solidified Yogurt", only when the gel strength of the solidified yogurt reaches 23g and the water holding capacity is 75%, it can resist the bumpy damage during transportation and meet the requirements of quality stability. A combination of the above water holding capacity and gel strength results indicates that the product prepared by the present invention has a better gel quality effect.

Effect example 3

Sensory evaluation experiment:

The experimental sensory evaluation team consists of professional evaluation teams, that is, those who have received professional sensory training. A total of 8 people describe the texture, tissue state, taste, viscoelasticity and other related indicators of the room temperature solidified yogurt product, and make a comprehensive sense of the sample. The results are shown in Table 10.

Table 10 Sensory evaluation of yogurt

From the results of sensory evaluation experiments, the products prepared by the invention can maintain the texture characteristics of the solidified yogurt, and have good taste and taste; while using ordinary yogurt stabilizer, the structure of the protein is destroyed after ultra-high temperature sterilization, so that it is at a high temperature. Gathering underneath causes the final product to form water and has a certain sense of gritty.

Effect example 4

In order to further investigate the quality stability of the yogurt of the invention, we placed the yoghurt products of the examples and the comparative examples at room temperature for 7-10 months, and observed whether the samples had whey precipitation and texture state. The results are shown in Table 11.

Table 11 Quality stability evaluation during yogurt storage period

It can be seen from the above experimental results that the special stabilizer in the present invention is compounded by agar, high ester pectin, low ester pectin, modified starch, and the percentage ratio of the four is adjusted to ensure that the yogurt can withstand super High temperature sterilization to prevent protein hydration and shrinkage caused by a large amount of whey. In the shelf life of 8-10 months, the product basically maintains the firm and bright appearance unique to the solidified yogurt, and no whey is precipitated.

The above are only the preferred embodiments of the present invention, and are not intended to limit the scope of the claims, and other substantially equivalent alternatives that can be considered by those skilled in the art are within the scope of the present invention.

Claims (15)

1. A special stabilizer for preparing yoghurt, characterized in that the special stabilizer comprises agar, high ester pectin, low ester pectin, starch or modified starch, gellan gum.
2. The special stabilizer according to claim 1, wherein the obtained final product is calculated by weight percentage, including agar: 0.15-0.3%, high ester pectin: 0.4-1%, low ester pectin. : 0.1-0.2%, starch or modified starch: 0.5-2%, low acyl gellan gum: 0.01-0.1%.
3. A method for preparing a solidified long shelf life normal temperature yoghurt, characterized in that the raw material comprises a raw material milk, a special stabilizer according to claim 1 or 2, a sweetener and a starter, and the preparation method comprises the following steps:

   (1) mixing raw material milk, special stabilizer and sweetener, homogenizing, sterilizing and cooling to obtain a mixed liquid;

   (2) inoculating the fermenting agent into the mixed liquid obtained in the step (1), fermenting to the end of the fermentation, demulsification, and cooling to obtain fermented milk;

   (3) The fermented milk obtained in the step (2) is subjected to ultra-high temperature instantaneous heat treatment, and is cooled and then filled to obtain a final product, and the ultra-high temperature instantaneous heat treatment condition is 105-121 ° C, 5-30 s.
4. The preparation method according to claim 3, wherein the raw material milk is fresh milk and/or treated milk.
5. The method according to claim 4, wherein the fresh milk is whole milk, and the treated milk is skim milk and/or reconstituted milk.
6. The method according to claim 5, wherein the reconstituted milk is prepared by mixing milk powder and water at a mass ratio of 12:88.
7. The preparation method according to claim 4, wherein the raw milk content is 80% or more, and the percentage is a mass percentage based on the total mass of the mixed liquid.
8. The process according to claim 7, wherein the raw material milk content is from 83 to 94%.
9. The process according to claim 8, wherein the raw material milk content is 90%.
10. The production method according to claim 3, wherein in the step (1), the mixing temperature is 40 to 55 ° C, the mixing time is 15 to 30 minutes, and the homogeneous temperature is 54 to 66 ° C.
11. The preparation method according to claim 3, wherein the starter comprises Streptococcus thermophilus and Lactobacillus bulgaricus in an amount of 2 × 10 ^{6 -} 2.4 × 10 ⁸ cfu. /mL, the added amount is calculated as the number of viable cells per ml of the mixed liquor.
12. The production method according to claim 11, wherein the starter is added in an amount of from 2 × 10 ^{7 to} 1.2 × 10 ⁸ cfu/mL.
13. The preparation method according to claim 3, wherein in the step (2), the temperature of the fermentation is 37 to 45 ° C, and the temperature of the cooling is 15 to 30 ° C.
14. The preparation method according to claim 3, wherein the sweetener is one or more of white granulated sugar, xylitol, fructose, and fructose syrup.
15. The preparation method according to claim 14, wherein the sweetener is added in an amount of from 5 to 8%, the percentage being a percentage of the total mass of the mixed liquor.