阅读说明：本技术 一种褐色常温酸奶及其制备方法 (Brown normal-temperature yoghourt and preparation method thereof ) 是由 孙颜君 刘振民 苏米亚 徐致远 王磊 莫蓓红 于 2020-12-29 设计创作，主要内容包括：本发明公开了一种褐色常温酸奶及其制备方法,该常温酸奶包括以下质量百分比的原料：无抗奶81.255～87.755％、乳糖酶0.016～0.052％、甜味剂4～8％、乳蛋白强化物0～0.3％、淀粉8～10％、果胶0.08～0.12％、琼脂0.10～0.15％、结冷胶0.01～0.05％、食用香精0～0.1％和发酵剂0.003～0.009％。制备方法包括：先将无抗奶预热,离心分离,制得脱脂乳,将脱脂乳预热后均质、杀菌、冷却；再添加乳糖酶,搅拌,酶解,待酶解完成后,升温褐变,将乳糖酶灭活,冷却；将其预热,添加甜味剂、乳蛋白强化物、淀粉、果胶、琼脂、结冷胶,搅拌；再均质、杀菌、冷却,添加食用香精、接种发酵剂进行发酵,得到酸奶基料,将其破乳后杀菌,冷却,灌装。本发明的常温酸奶葡糖糖含量低,质地细腻顺滑,制备方法简单,常温下可放置6～9个月。(The invention discloses brown normal-temperature yoghourt and a preparation method thereof, wherein the normal-temperature yoghourt comprises the following raw materials in percentage by mass: the milk beverage comprises, by weight, 81.255-87.755% of non-resistant milk, 0.016-0.052% of lactase, 4-8% of a sweetener, 0-0.3% of a lactoprotein reinforcement, 8-10% of starch, 0.08-0.12% of pectin, 0.10-0.15% of agar, 0.01-0.05% of gellan gum, 0-0.1% of flavoring essence and 0.003-0.009% of a leavening agent. The preparation method comprises the following steps: preheating nonreactive milk, performing centrifugal separation to obtain skim milk, preheating the skim milk, homogenizing, sterilizing, and cooling; adding lactase, stirring, performing enzymolysis, heating to brown after the enzymolysis is finished, inactivating the lactase, and cooling; preheating, adding sweetener, lactoprotein reinforcer, starch, pectin, agar, and gellan gum, and stirring; homogenizing, sterilizing, cooling, adding edible essence and inoculating starter, fermenting to obtain yogurt base material, demulsifying, sterilizing, cooling, and packaging. The normal-temperature yoghourt disclosed by the invention is low in glucose content, fine and smooth in texture, simple in preparation method and capable of being placed for 6-9 months at normal temperature.)

1. The brown normal-temperature yoghourt is characterized by comprising the following raw materials in percentage by mass: the milk beverage comprises, by weight, 81.255-87.755% of non-resistant milk, 0.016-0.052% of lactase, 4-8% of a sweetener, 0-0.3% of a lactoprotein reinforcement, 8-10% of starch, 0.08-0.12% of pectin, 0.10-0.15% of agar, 0.01-0.05% of gellan gum, 0-0.1% of flavoring essence and 0.003-0.009% of a leavening agent.

2. The brown normal-temperature yoghourt as claimed in claim 1, wherein the nonreactive milk is one or two of cow milk and goat milk;

the protein content in the non-antibiotic milk is more than or equal to 2.8 wt%, the lactose content is more than or equal to 3.0 wt%, the solid content of the non-fat milk is more than or equal to 8.1 wt%, and the titration acidity is less than or equal to 18 DEG T.

3. The brown room temperature yogurt of claim 1, wherein the starch is one or more of corn starch, waxy corn starch, tapioca starch, and potato starch;

the milk protein fortifier is one or more of casein powder, whey protein powder and milk protein powder;

the leavening agent comprises Lactobacillus bulgaricus and Streptococcus thermophilus.

4. A method of preparing a brown room temperature yoghurt as claimed in any one of claims 1 to 3, characterized in that the method comprises the following steps:

s1: preheating nonreactive milk, performing centrifugal separation to obtain skim milk, preheating the skim milk, homogenizing, sterilizing, and cooling to obtain feed liquid A;

s2: preheating the feed liquid A in the S1, adding lactase, uniformly stirring, controlling the enzymolysis temperature and time, heating to the browning temperature for browning after enzymolysis is finished, inactivating the lactase, and cooling to obtain feed liquid B;

s3: preheating the material liquid B in the step S2, adding a sweetening agent, a lactoprotein reinforcement, starch, pectin, agar and gellan gum, and fully and uniformly stirring to obtain a material liquid C;

s4: homogenizing, sterilizing and cooling the feed liquid C in the step S3, adding edible essence, inoculating a starter, and fermenting to obtain a yogurt base material;

s5: demulsifying the yogurt base material obtained in the step S4, sterilizing, cooling and filling to obtain the yogurt base material.

5. The preparation method of the brown room-temperature yogurt as claimed in claim 4, wherein in S1, the temperature of non-resistant milk preheating is 50-60 ℃, and the fat content of skim milk is less than 0.5%;

the preheating temperature of the skim milk is 55-65 ℃, and the homogenizing pressure is 150-250 bar;

the sterilization temperature of the skim milk is 115-125 ℃, the sterilization time is 10-30 s, and the skim milk is cooled to be below 10 ℃.

6. The preparation method of the brown room-temperature yogurt as claimed in claim 4, wherein in the S2, the feed liquid A is preheated at 35-50 ℃, the enzymolysis temperature is 35-50 ℃, the enzymolysis time is 1.5-3 h, and the stirring speed is 5-15 rpm.

7. The preparation method of the brown room-temperature yogurt as claimed in claim 4, wherein in S2, after the enzymolysis is completed, the temperature is raised to 85-95 ℃ for browning, the browning time is 100-200 min, and the temperature is cooled to below 10 ℃.

8. The preparation method of the brown room-temperature yogurt as claimed in claim 4, wherein the preheating temperature of the feed liquid B in the S3 is 50-60 ℃.

9. The preparation method of the brown room-temperature yogurt as claimed in claim 4, wherein in S4, the homogenization temperature is 50-65 ℃, and the homogenization pressure is 150-250 bar;

the sterilization temperature is 90-95 ℃, and the sterilization time is 3-7 min;

the cooling temperature is 42-45 ℃;

the fermentation time is 4-7 h, and the acidity at the fermentation end point is 70-90 DEG T.

10. The preparation method of the brown room-temperature yogurt as claimed in claim 4, wherein in S5, the sterilization temperature is 70-80 ℃ and the sterilization time is 10-40S;

cooling to 25-30 ℃.

Technical Field

The invention belongs to the technical field of fermented foods, and particularly relates to brown normal-temperature yogurt and a preparation method thereof.

Background

Brown yogurt is a new product in the yogurt family, brown dairy products are favored by consumers due to unique flavors in recent years, and the sales volume is increased year by year. The domestic market has seen the yogurt with the taste of roasted yogurt, cooked yogurt, Russian flavor yogurt and charcoal roasted yogurt. The unique color and flavor of brown yogurt are derived from Maillard reaction, mainly refer to the process of generating brown or black polymers through crossing, decomposing, condensing and polymerizing between amino compounds and carbonyl compounds, so the brown yogurt is also called carbonyl ammonia reaction and is a non-enzymatic browning reaction which may occur in all food processing. At present, reducing sugar such as glucose, high fructose syrup and the like are additionally added into cow milk in a commercial mode, or the cow milk is fermented by lactic acid bacteria and then lactose is decomposed to generate glucose so as to react with amino compounds in the cow milk to carry out Maillard reaction. In recent years, with the increase of health consciousness of consumers, low-sugar and sugar-free products are gradually popular, and glucose is taken as a main representative of high GI, so that the low-sugar and sugar-free products are not suitable for diabetics, fitness people and the like. Dairy products are representative of health foods, and there is an increasing demand for products with low sugar and reduced sugar. The brown yoghourt is used as an important product of the special fermented dairy product, does not additionally add reducing sugar, can ensure that the product has better brown color and luster and flavor, and has certain technical difficulty and barrier.

Disclosure of Invention

The invention aims to solve the technical problem that reducing sugar needs to be additionally added to the existing brown normal-temperature yoghourt product to perform Maillard reaction browning, so that consumers incapable of eating the reducing sugar cannot eat the product. According to the invention, a lactase enzymolysis technology is innovatively used, accurate lactase enzymolysis is carried out before milk fermentation, and a normal-temperature brown yoghourt product with low glucose content, fine and smooth texture and attractive color is prepared by controlling the enzymolysis degree, the generated reducing sugar amount and the subsequent Maillard reaction proceeding degree. The preparation method is simple and can be used for industrial production. The prepared product can be placed for 6-9 months at normal temperature, the sensory test of the product is excellent, the product microorganism meets the national standard in the quality guarantee period, the product property is stable, and the phenomena of layered whey precipitation and the like are avoided.

On one hand, the invention provides brown normal-temperature yoghourt which comprises the following raw materials in percentage by mass: the milk beverage comprises, by weight, 81.255-87.755% of non-resistant milk, 0.016-0.052% of lactase, 4-8% of a sweetener, 0-0.3% of a lactoprotein reinforcement, 8-10% of starch, 0.08-0.12% of pectin, 0.10-0.15% of agar, 0.01-0.05% of gellan gum, 0-0.1% of flavoring essence and 0.003-0.009% of a leavening agent.

Further, the nonreactive milk is one or two of cow milk and goat milk;

the protein content in the non-antibiotic milk is more than or equal to 2.8 wt%, the lactose content is more than or equal to 3.0 wt%, the solid content of the non-fat milk is more than or equal to 8.1 wt%, and the titration acidity is less than or equal to 18 DEG T.

Further, the starch is one or more of corn starch, waxy corn starch, cassava starch and potato starch;

the milk protein fortifier is one or more of casein powder, whey protein powder and milk protein powder;

the leavening agent comprises Lactobacillus bulgaricus and Streptococcus thermophilus.

On the other hand, the invention also provides a preparation method of the brown normal-temperature yoghourt, which comprises the following steps:

s1: preheating nonreactive milk, performing centrifugal separation to obtain skim milk, preheating the skim milk, homogenizing, sterilizing, and cooling to obtain feed liquid A;

s2: preheating the feed liquid A in the S1, adding lactase, uniformly stirring, controlling the enzymolysis temperature and time, heating to the browning temperature for browning after enzymolysis is finished, inactivating the lactase, and cooling to obtain feed liquid B;

s3: preheating the material liquid B in the step S2, adding a sweetening agent, a lactoprotein reinforcement, starch, pectin, agar and gellan gum, and fully and uniformly stirring to obtain a material liquid C;

s4: homogenizing, sterilizing and cooling the feed liquid C in the step S3, adding edible essence and an inoculated leavening agent, and fermenting to obtain a yoghourt base material;

s5: demulsifying the yogurt base material obtained in the step S4, sterilizing, cooling and filling to obtain the yogurt base material.

Further, in S1, the temperature for preheating the non-antibiotic milk is 50-60 ℃, and the fat content of the skim milk is less than 0.5%;

the preheating temperature of the skim milk is 55-65 ℃, and the homogenizing pressure is 150-250 bar;

the sterilization temperature of the skim milk is 115-125 ℃, the sterilization time is 10-30 s, and the skim milk is cooled to be below 10 ℃.

Further, in S2, the preheating temperature of the feed liquid A is 35-50 ℃, the enzymolysis temperature is 35-50 ℃, the enzymolysis time is 1.5-3 h, and the stirring speed is 5-15 rpm.

Further, in S2, after the enzymolysis is finished, heating to 85-95 ℃ for browning, wherein the browning time is 100-200 min, and cooling to below 10 ℃ after browning.

Further, in S3, the preheating temperature of the feed liquid B is 50-60 ℃.

Further, in S4, the homogenizing temperature is 50-65 ℃, and the homogenizing pressure is 150-250 bar;

the sterilization temperature is 90-95 ℃, and the sterilization time is 3-7 min;

the cooling temperature is 42-45 ℃;

the fermentation time is 4-7 h, and the acidity at the fermentation end point is 70-90 DEG T.

Further, in S5, the sterilization temperature is 70-80 ℃ and the time is 10-40S;

cooling to 25-30 ℃.

The positive progress effects of the invention are as follows:

the invention provides a pure plant sucrose-free oat coffee beverage, which breaks the traditional concept of adding milk and coffee for consumers. The additive is reduced as much as possible to ensure the stability of the product. Enzymes are relied upon to degrade the sticky starch in oats into sugars that can serve to increase sweetness in the final product.

Detailed Description

In order to more clearly illustrate the technical solution of the present invention, the technical solution of the present invention will be further illustrated with reference to the following specific embodiments:

one of the technical schemes provided by the invention is as follows:

the invention provides brown normal-temperature yoghourt which comprises the following raw materials in percentage by mass: the milk beverage comprises, by weight, 81.255-87.755% of non-resistant milk, 0.016-0.052% of lactase, 4-8% of a sweetener, 0-0.3% of a lactoprotein reinforcement, 8-10% of starch, 0.08-0.12% of pectin, 0.10-0.15% of agar, 0.01-0.05% of gellan gum, 0-0.1% of flavoring essence and 0.003-0.009% of a leavening agent.

The nonreactive milk is one or two of cow milk and sheep milk.

The protein content in the non-antibiotic milk is more than or equal to 2.8 wt%, the lactose content is more than or equal to 3.0 wt%, the solid content of the non-fat milk is more than or equal to 8.1 wt%, and the titration acidity is less than or equal to 18 DEG T.

The starch is one or more of corn starch, waxy corn starch, tapioca starch, and potato starch.

The milk protein fortifier is one or more of casein powder, whey protein powder and milk protein powder.

The leavening agent comprises Lactobacillus bulgaricus and Streptococcus thermophilus.

Sweetener refers to an additive that imparts sweetness to the food product, preferably sucrose and/or sugar substitutes. The sugar substitute is a substance capable of generating sweet taste or enhancing sweet taste and has much lower calorie than sucrose, preferably one or more of aspartame, acesulfame potassium, sucralose, lactitol, xylitol and erythritol. The addition amount of the sucrose is 4-8%; the addition amount of the sucrose substitute is 0.005-0.015%.

The second technical scheme provided by the invention is as follows:

a preparation method of brown normal-temperature yoghourt comprises the following steps:

s1: preheating nonreactive milk, performing centrifugal separation to obtain skim milk, preheating the skim milk, homogenizing, sterilizing, and cooling to obtain feed liquid A;

s2: preheating the feed liquid A in the S1, adding lactase, uniformly stirring, controlling the enzymolysis temperature and time, heating to the browning temperature for browning after enzymolysis is finished, inactivating the lactase, and cooling to obtain feed liquid B;

s3: preheating the material liquid B in the step S2, adding a sweetening agent, a lactoprotein reinforcement, starch, pectin, agar and gellan gum, and fully and uniformly stirring to obtain a material liquid C;

s4: homogenizing, sterilizing and cooling the feed liquid C in the step S3, adding edible essence and an inoculated leavening agent, and fermenting to obtain a yoghourt base material;

s5: demulsifying the yogurt base material obtained in the step S4, sterilizing, cooling and filling to obtain the yogurt base material.

Specifically, in S1, the temperature for preheating the non-antibiotic milk is 50-60 ℃, and the fat content of the skim milk is less than 0.5%.

The preheating temperature of the skim milk is 55-65 ℃, and the homogenizing pressure is 150-250 bar.

The sterilization temperature of the skim milk is 115-125 ℃, the sterilization time is 10-30 s, and the skim milk is cooled to be below 10 ℃.

Preferably, the nonreactive milk used in step S1 is cow milk, goat milk or other animal milk used alone or mixed, wherein the mixed milk has a protein content of not less than 2.8 wt%, a lactose content of not less than 3.0 wt%, a non-fat milk Solid (SNF) content of not less than 8.1 wt%, and a titer acidity of not more than 18 ° T, wherein the contents are mass percentages of the components in the raw milk.

Specifically, in S2, the preheating temperature of the feed liquid A is 35-50 ℃, the enzymolysis temperature is 35-50 ℃, the enzymolysis time is 1.5-3 h, the stirring speed is 5-15 rpm, the lactose hydrolysis rate is 70-80%, and the contents of lactose and glucose after hydrolysis are 3.5-4%.

Specifically, in S2, after enzymolysis is completed, the temperature is raised to 85-95 ℃ for browning, the browning time is 100-200 min, the content of glucose and galactose used for browning is 4.75-6%, after the browning is completed, the content of glucose is 1.25-2%, galactose cannot be detected, and after the browning is completed, the product is cooled to less than 10 ℃ for standby.

Specifically, in S3, the preheating temperature of the feed liquid B is 50-60 ℃.

Specifically, in S4, the homogenizing temperature is 50-65 ℃, and the homogenizing pressure is 150-250 bar.

The sterilization is pasteurization, a tubular sterilization mode is adopted, the sterilization temperature is 90-95 ℃, and the sterilization time is 3-7 min.

The cooling temperature is 42-45 ℃.

The fermentation time is 4-7 h, and the acidity at the fermentation end point is 70-90 DEG T.

Specifically, in S5, pasteurization is carried out by adopting a plate-type sterilization mode, wherein the sterilization temperature is 70-80 ℃, and the sterilization time is 10-40S.

And S5, cooling to 25-30 ℃, and then carrying out aseptic filling.

The brown normal-temperature yoghourt prepared by the method has the protein content of 2.63-2.92%, the fat content of 2.44-2.75%, the carbohydrate content of 12.13-21.26%, the viscosity of 200-250 cP, the titrated acidity of 70-90 DEG T and the glucose content of 0.45-1.0%, wherein the contents refer to the mass percentage of the components in the yoghourt.

The viscosity of the product after being placed at normal temperature is 200-250 cP, the viscosity fluctuation of the upper layer and the lower layer of the product is small in the process of being placed at normal temperature for 6-9 months, the phenomena of layering and whey precipitation are avoided, the product state is good, and the product flavor is good in the quality guarantee period.

Aiming at the problem that in the prior art, 1-3% of reducing sugar (such as glucose) needs to be additionally added into common brown yoghourt for Maillard reaction browning, so that consumers incapable of eating the reducing sugar cannot eat the product. According to the invention, a lactase enzymolysis technology is innovatively used, accurate lactase enzymolysis is carried out before milk fermentation, and a normal-temperature brown yoghourt product with low glucose content, fine and smooth texture and attractive color is prepared by controlling the enzymolysis degree, the generated reducing sugar amount and the subsequent Maillard reaction proceeding degree. The preparation method is simple and can be used for industrial production. The prepared product can be placed for 6-9 months at normal temperature, the sensory test of the product is excellent, the product microorganism meets the national standard in the quality guarantee period, the product property is stable, and the phenomena of layered whey precipitation and the like are avoided.

According to the invention, lactose in the cow milk is hydrolyzed by lactase, the lactose is decomposed into galactose and glucose, the galactose and the glucose are reducing sugars, and the lactose hydrolysis rate is 70-80%. Wherein the content of galactose and reducing sugar is 3.5-4%, galactose is preferably completely utilized for browning, 1.25-2% of glucose is then utilized, 1.25-2% of glucose left after browning is preferably utilized in the subsequent fermentation process, about 0.8-1.2% of glucose is utilized, and the content of glucose in the final product is 0.45-1%.

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

On the basis of the common knowledge in the field, the preferred conditions can be combined randomly to obtain the preferred embodiments of the invention. On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention. On the basis of the common knowledge in the field, the preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

The performance indexes of the raw materials meet the requirements of relevant quality standards. Other materials and equipment not specifically described are commercially available.

Example 1

A brown normal-temperature yoghourt and a preparation method thereof are disclosed, wherein the raw material formula is shown in table 1, and the preparation method comprises the following steps:

(1) preheating non-antibiotic milk to 50 ℃, then degreasing, continuously heating the skim milk to 55 ℃, and homogenizing under the condition of 150 bar; homogenizing, sterilizing (115 deg.C/10 s) the skimmed milk, and cooling to below 10 deg.C;

(2) preheating skim milk to 35 ℃, adding 0.052% lactase, carrying out heat preservation and enzymolysis at 35 ℃ for 1.5h, wherein the stirring speed is 5r/min, the lactose hydrolysis rate is 70%, and the contents of half lactose and glucose after hydrolysis are both 3.5%;

(3) heating the defatted milk after enzymolysis to 85 ℃ to perform browning reaction for 30min, wherein the content of glucose after browning is 1.25%, the content of galactose cannot be detected, and cooling to less than 10 ℃ after browning for later use;

(4) and (3) uniformly mixing the browned cow milk with other ingredients except the leavening agent (added after sterilization at 90 ℃/3 min) and lactase (added in the step 2) and separated cream to obtain a mixed solution.

Table 1 raw material recipe of example 1

In the ingredients, the protein content in the raw milk is 3.0 wt%, the fat content is 3.0 wt%, the lactose content is 4.5 wt%, and the titration acidity is less than or equal to 18 DEG T. The material preparation temperature is 50 deg.C, and two-stage homogenization is carried out at 50 deg.C, the first stage pressure is 50bar, and the second stage pressure is 150 bar. Continuously heating to 90 deg.C for sterilization, cooling to 42 deg.C after sterilization for 3min, adding 0.003% for fermentation, fermenting for 7 hr, cooling to 70 deg.C, and stopping fermentation.

And (3) performing plate-type sterilization treatment on the yogurt base material after fermentation and cooling, wherein the sterilization condition is 70 ℃ for 10s, and filling at 25 ℃.

The viscosity of the product is 230cP after the product is placed at normal temperature for a period of time, and the product has little viscosity fluctuation and has no phenomena of layering, whey precipitation and the like in the process of placing the product at normal temperature for 6 months.

The basic indexes of the normal-temperature fermented milk prepared by the method are as follows:

TABLE 2 Normal temperature yogurt indexes of example 1

Example 2

A brown normal-temperature yoghourt and a preparation method thereof are disclosed, wherein the raw material formula is shown in table 3, and the preparation method comprises the following steps:

(1) preheating the nonreactive milk to 55 ℃, then degreasing, continuously heating the skim milk to 60 ℃, and homogenizing under the condition of 200 bar; homogenizing, sterilizing (120 deg.C/20 s), cooling to below 10 deg.C

(2) Preheating skim milk to 45 ℃, adding 0.016% lactase, carrying out heat preservation and enzymolysis at 45 ℃ for 2.3h, wherein the stirring speed is 10 r/min, the lactose hydrolysis rate is 75%, and the half lactose and glucose content after hydrolysis are both 3.75%;

(3) heating the defatted milk after enzymolysis to 90 ℃ to perform browning reaction for 60min, wherein the content of glucose after browning is 1.75%, the content of galactose cannot be detected, and cooling to less than 10 ℃ after browning for later use;

(4) and (3) uniformly mixing the browned cow milk with other ingredients and removed cream except the leavening agent, edible essence (added after sterilization at 93 ℃/5 min) and lactase (added in the step 2) to obtain a mixed solution.

Table 3 raw material recipe of example 1

Raw materials	Addition amount (%)
		Raw milk	81.255
Pectin	0.12
		Agar-agar	0.15
Gellan gum	0.05
		Starch	10
White granulated sugar	8
		Edible essence	0.1
Whey protein powder	0.3
		Leaven	0.009
Lactase	0.016
		Total up to	100

In the ingredients, the protein content in the raw milk is 3.0 wt%, the fat content is 3.0 wt%, the lactose content is 4.5 wt%, and the titration acidity is less than or equal to 18 DEG T. The material preparation temperature is 55 deg.C, and two-stage homogenization is carried out at 60 deg.C, the first stage pressure is 60bar, and the second stage pressure is 120 bar. And continuously heating to 93 ℃ for sterilization, cooling to 43 ℃ after the sterilization time is 5min, adding 0.009% of streptococcus thermophilus and lactobacillus bulgaricus for fermentation, fermenting for 4h, then cooling to 80 ℃ and stopping fermentation.

And (3) performing plate-type sterilization treatment on the yogurt base material after fermentation and cooling, wherein the sterilization conditions are 75 ℃ and 25s, and filling at 27 ℃.

The viscosity of the product is 200cP after being placed at normal temperature for a period of time, and the product has little viscosity fluctuation and no phenomena of layering, whey precipitation and the like during being placed for 9 months at normal temperature.

The basic indexes of the normal-temperature yoghourt prepared by the method are as follows:

TABLE 4 ambient yogurt indices for example 2

Example 3

A brown normal-temperature yoghourt and a preparation method thereof are disclosed, wherein the raw material formula is shown in table 5, and the preparation method comprises the following steps:

(1) preheating the nonreactive milk to 60 ℃, degreasing, continuously heating the skim milk to 65 ℃, and homogenizing under the condition of 250 bar; homogenizing, sterilizing (125 deg.C/30 s), cooling to below 10 deg.C for use

(2) Preheating skim milk to 50 ℃, adding 0.034% lactase, performing enzymolysis at 50 ℃ for 3h while keeping the temperature, wherein the stirring speed is 15 r/min, the lactose hydrolysis rate is 80%, and the contents of half lactose and glucose after hydrolysis are both 4%;

(3) heating the skim milk after enzymolysis to 95 ℃ to perform browning reaction for 70min, wherein the content of glucose after browning is 2%, the content of galactose cannot be detected, and cooling to less than 10 ℃ after browning for later use;

(4) and (3) uniformly mixing the browned cow milk with other ingredients except the leavening agent, the edible essence (added after sterilization at 95 ℃/7 min) and the lactase (added in the step (2)) and the separated cream in the following table to obtain a mixed solution.

Table 5 raw material recipe of example 3

Raw materials	Addition amount (%)
		Raw milk	84.000
Pectin	0.1
		Agar-agar	0.13
Gellan gum	0.03
		Starch	9
White granulated sugar	6.5
		Lactase	0.034
Edible essence	0.05
		Whey protein powder	0.15
Leaven	0.006
		Total up to	100

In the ingredients, the protein content in the raw milk is 3.0 wt%, the fat content is 3.0 wt%, the lactose content is 4.5 wt%, and the titration acidity is less than or equal to 18 DEG T. The temperature of the mixture is 60 ℃, and the mixture is homogenized at the second stage at 65 ℃, the first stage pressure is 50bar, and the second stage pressure is 200 bar. Continuously heating to 95 deg.C for sterilization, cooling to 43 deg.C after sterilization for 7min, adding 0.006% Streptococcus thermophilus and Lactobacillus bulgaricus, fermenting for 4 hr, then cooling to 90 deg.C to terminate fermentation.

And (3) performing plate-type sterilization treatment on the yogurt base material after fermentation and cooling, wherein the sterilization conditions are 80 ℃ and 40s, and filling at 30 ℃.

The viscosity of the product is 250cP after the product is placed at normal temperature for a period of time, and the product has little viscosity fluctuation and has no phenomena of layering, whey precipitation and the like in the process of being placed at normal temperature for 8 months.

The basic indexes of the normal-temperature fermented milk prepared by the method are as follows:

TABLE 6 Normal temperature yogurt indexes of example 3

Comparative example 1

The same as example 1, except that the temperature of the defatted milk enzymolysis is 30 ℃, the enzymolysis is carried out for 1h, the hydrolysis rate of the lactose is 55%, other processes are the same as example 1, the acidity reaches 70 DEG T after 10h of fermentation after the leaven is added, and the glucose content is 1.55%.

Comparative example 2

In the same example 1, the enzymolysis reaction time of skim milk is 5h, the hydrolysis rate of lactose is 95%, and other processes are the same as in the example 1, and the glucose content is 3.0%.

Comparative example 3

The same as example 2, except that the browning time is 90min, the other processes are the same as example 2, after the leavening agent is added, the acidity reaches 70 DEG T after 15h of fermentation, and the viscosity of the product is 128 cp.

Comparative example 4

The same as example 2, only the browning time is 30min, the other processes are the same as example 2, and after the leavening agent is added, the acidity is 70 DEG T after fermentation for 4 h.

Comparative example 5

Refer to patent CN 108056165 a "application of lactase in shortening fermentation time of brown fermented dairy products" process flow:

preheating whole milk to 55 deg.C, adding 2% anhydrous glucose, heating to 90 deg.C, keeping the temperature for 2 hr, cooling browned milk to 60 deg.C, adding stabilizer, sweetener, edible essence and protein powder according to reference example 3, except for leavening agent and edible essence (added after sterilizing at 95 deg.C/5 min) and lactase (added after cooling to 41 deg.C), mixing with other ingredients, and removed dilute butter

The ingredients are circularly stirred for 25 min:

TABLE 7 raw material formulation of comparative example 5

Raw materials	Addition amount (%)
		Raw milk	84.024
Pectin	0.1
		Agar-agar	0.13
Gellan gum	0.03
		Starch	9
Leaven	0.006
		White granulated sugar	6.5
Edible essence	0.05
		Whey protein powder	0.15
Lactase	0.01
		Total up to	100

Homogenizing the prepared feed liquid at 65 deg.C and 15MPa, sterilizing at 95 deg.C for 5min, cooling to 41 deg.C, adding 0.01% lactase, 0.006% Streptococcus thermophilus and Lactobacillus bulgaricus, and fermenting for 11 hr until acidity reaches 70 ° T;

the subsequent operation was the same as in example 3, and the viscosity of the resulting yogurt was 159 cp.

Effect example 1

And (3) carrying out a heat preservation test on the yoghourt finished product, namely placing the yoghourt finished product at 25 ℃ and 37 ℃ for 1 month respectively, unpacking 3 bags of samples each time, and observing the state of the yoghourt. The yogurt was cut from the bottom and top, and the upper and lower layer viscosities were measured (measurement temperature: 25 ℃) by observing whether whey was deposited. The test results are as follows:

TABLE 8 Heat preservation test results

As can be seen from the above results, after being left at 25 ℃ and 37 ℃ for 1 month, the products of the examples have no bleeding phenomenon in both the upper layer and the lower layer, and the difference in viscosity between the upper layer and the lower layer is small. Comparative example 3 the product had a viscosity difference of 17cp when placed at 25 ℃ and the whey was seriously separated from the top of the sample when placed at 37 ℃; comparative example 5 the product had more severe demixing and severe whey separation at the top, and no viscosity could be measured, regardless of whether the product was left at 25 ℃ or 37 ℃.

Effect example 2

Sensory evaluation method

10 dairy researchers with relevant backgrounds were selected for sensory training and 5 of them were randomly selected as sensory assessors. The scoring criteria are shown in table 9 below:

TABLE 9 sensory evaluation criteria

Counting the scoring data of the sensory evaluator and taking an average value, adding the scores of all indexes to calculate a total score, wherein the higher the score is, the better the product quality is, and the determination result is shown in the following table:

TABLE 10 sensory evaluation results

From the above results, examples 1, 2 and 3 had better flavor, color and texture; comparative examples 1, 2, 3 and 4 had insufficient flavor and color.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.