CN106912605A - A kind of acidified milk preparation method for suppressing post-acidification of yoghurt - Google Patents

Abstract

The invention discloses a kind of acidified milk preparation method for suppressing post-acidification of yoghurt.Preparation method of the invention, as raw material, is obtained with matrimony vine and fresh high-quality breast through Bifidobacterium, bacillus bulgaricus and streptococcus thermophilus fermentation.The inventive method can suppress the rear acidifying of fermented yoghourt, extend the shelf-life of Yoghourt, the inducible Bifidobacterium secreting bacteria element of matrimony vine, and bacteriocin can suppress the rear acidifying in storage after Yoghourt fermentation.The inventive method prepare Yoghourt milk is pure, lacteous uniform, comfortable acid, delicate mouthfeel, stick-slip is agreeable to the taste, be of high nutritive value, with health-care tonic effect.

Description

A method for preparing fermented milk capable of suppressing post-acidification of yogurt

technical field

The invention relates to the technical field of fermented milk, in particular to a method for preparing fermented milk for inhibiting post-acidification of yoghurt and its application.

Background technique

In recent years, with the improvement of people's consumption level and civilized quality in our country, the output of yogurt has grown at an average annual rate of 25%, and has become the largest fermented dairy product in my country. People's demand for yogurt has increased year by year, and the quality of yogurt has been improved. It has been greatly improved, and varieties of designs and colors emerge in endlessly, but the shelf life of yogurt has not been significantly improved.

Wolfberry (Lycium barbarum) belongs to the deciduous shrub of Solanaceae. It is used as a traditional Chinese medicine and functional food in Asian countries. It is widely used in brewing wine, tea, water, soup, porridge, etc. The fruit, leaves, seedlings and roots of wolfberry can be used as medicine, which is an important component of traditional Chinese medicine formula. Lycium barbarum is a traditional precious Chinese medicinal material in my country. It has the functions of "moistening the lungs, clearing the liver, nourishing the kidneys, replenishing qi, replenishing fatigue, expelling wind, and rejuvenating the name". It is called a first-class medicinal material.

Post-acidification of yogurt can be divided into three stages: (1) acid production during cooling; (2) acid production after cooling; (3) acid production during refrigeration. Studies have shown that the acidic substances after acidification are mainly lactic acid produced by lactic acid bacteria metabolizing sugars, and lactase, which is related to metabolism, is its key enzyme and is an intracellular enzyme. The cell wall or cell membrane of Lactobacillus bulgaricus has a protective effect on the activity of lactase, which leads to greater activity of lactase in yogurt products under acidic conditions during storage, and the continued fermentation of lactose to produce lactic acid leads to post-acidification. Therefore, Lactobacillus bulgaricus is post-acidification. Acidification of the main acid-producing strains. Adjusting the ratio of cocci and bacilli during the inoculation process will help the two bacteria to ferment better, shorten the fermentation time, and reduce the degree of post-acidification. It is also possible to control the acid production of lactic acid bacteria by changing the composition of the starter and utilizing the inhibitory effect of its metabolites (such as bacteriocin) on lactic acid bacteria, so as to control post-acidification is also a direction of current research. The bacteriocin-producing Bifidobacterium was selected to be fermented with the mixed starter of Lactobacillus bulgaricus and Streptococcus thermophilus to produce yogurt. It was found that the addition of Bifidobacterium could effectively inhibit the post-acidification of yogurt. In this study, the yogurt starter with strong activity of bacteriocin-producing Bifidobacterium was prepared using Lycium barbarum skimmed emulsion as the medium, and the post-acidification of yogurt was inhibited by changing the composition and ratio of the starter.

Although there are many studies and applications on inhibiting post-acidification of yogurt, there are no reports on the technology that can effectively inhibit the post-acidification of yogurt at each stage by using wolfberry skim milk as the medium for the preparation of starter and fermenting yogurt with wolfberry as raw material.

Contents of the invention

The technical problem to be solved by the present invention is to suppress post-acidification of yogurt, prolong the shelf life of yogurt, and provide a kind of wolfberry yogurt with health-care and nourishing effects, which has pure milk flavor, uniform milk color, suitable sweet and sour, delicate taste, sticky and smooth palatability, and high nutritional value .

In order to solve the above technical problems, the present invention adopts the following technical solutions.

A method for preparing fermented milk for inhibiting post-acidification of yoghurt, comprising the steps of:

(1) In the fermentation container, add fresh milk, then add water, wolfberry slurry, compound stabilizer, white sugar and skimmed milk powder in sequence, and mix evenly to obtain a mixed fermentation material;

(2) After preheating the mixed fermentation material, place it in high-pressure homogenization medium and high-pressure homogenization, sterilize, cool, inoculate the starter, and carry out fermentation; through homogenization, the fine and smooth taste of yogurt can be improved, and the stability of yogurt can be improved;

(3) After the fermentation is over, the fermented product is air-cooled or water-cooled and refrigerated.

Further, in step (1), according to the mass percentage of fresh milk, the addition amount of each component is: water 5%~10%, wolfberry slurry 10%~15%, stabilizer 0.1%~0.2%, white Sugar 2%~10%, skimmed milk powder 2%~10%.

Further, in step (1), the wolfberry slurry is prepared through the following steps:

Select high-quality wolfberry, wash it with warm water at 50°C for 3 to 4 times, wash off dust and impurities, drain the water, add 3 to 5 times as much water as wolfberry, cook at 100°C for 30 minutes, and beat to obtain wolfberry pulp. The Lycium barbarum slurry was homogenized to obtain the Lycium barbarum slurry for subsequent use.

The addition of wolfberry can inhibit the post-acidification of yogurt during storage after fermentation, prolong the shelf life of yogurt, and also increase the nutritional and health components of yogurt.

Furthermore, the wolfberry is common edible or medicinal wolfberry, including Ningxia wolfberry, Tianjin wolfberry and Xinjiang wolfberry.

Further, in step (1), the fresh milk does not contain impurities, antibiotics and antibacterial substances, the total dry matter content in the milk is not less than 11.5wt.%, the milk fat percentage is greater than 3wt.%, and the acidity does not exceed 19° T, and other indicators meet the procurement standards for fresh milk in my country.

Further, in step (1), the compound stabilizer is a mixture of propylene glycol alginate solution, xanthan gum solution and pectin solution.

Furthermore, in step (1), the mass concentration of the propylene glycol alginate solution is 0.10%-0.50%.

Furthermore, in step (1), the mass concentration of the xanthan gum solution is 0.1%~1.0%.

Furthermore, in step (1), the mass concentration of the pectin solution is 0.1%-0.2%.

Furthermore, in step (1), the propylene glycol alginate solution, the xanthan gum solution and the pectin solution are mixed at a mass ratio of 1~2:1~2:1~2.

Further, in step (2), the preheating is at 60-70° C. for 20-40 minutes.

Further, in step (2), the pressure of the high-pressure homogenization is 20-30 MPa.

Further, in step (2), the sterilization is heating at 90-95° C. for 5-10 minutes.

Further, in step (2), the cooling is to cool to 42°C.

Further, in step (2), the starter is obtained from strains that are cultured on the sterilized Lycium barbarum skim emulsion through activation and subculture; the strains include Bifidobacterium, Lactobacillus bulgaricus and thermophilic Streptococcus lactis;

Under aseptic conditions, a small amount of strains of Bifidobacterium, Lactobacillus bulgaricus, and Streptococcus thermophilic lactis were inoculated into the sterilized Lycium barbarum skim emulsion with an inoculation loop. Activation and subculture once, so that the activity of the bacteria is basically normal, and then the bacteria that have recovered the normal activity are activated and cultured in the wolfberry skim milk liquid medium, and the culture is continuously expanded, and finally the working starter is produced.

Lycium barbarum skimmed milk liquid culture medium was selected to prepare the starter. Lycium barbarum can induce bifidobacteria to secrete bacteriocins, which can inhibit the post-acidification of yogurt during storage after fermentation.

Further, in step (2), according to the ratio of the mixed fermented material, the inoculum amount of the Bifidobacterium is 5U~10U/250L, the inoculum amount of the Lactobacillus bulgaricus is 15U~30U/250L, and the The inoculation volume of Streptococcus lactis is 20U~40U/250L;

Too much inoculum will easily lead to too fast acid production, which will easily cause syneresis of the protein in the curd, and cause more whey to precipitate.

Further, in step (2), the temperature of the fermentation is 40-45° C., and the fermentation time is 3-5 hours.

Further, in step (2), the fermentation is terminated when the acidity reaches 70°T to 75°T by measuring the acidity of the material in the later stage of fermentation.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The method for preparing yogurt of the present invention uses wolfberry as raw material, which can inhibit post-acidification of yogurt and prolong the shelf life of yogurt;

(2) The yoghurt prepared by the method of the present invention has pure fragrance, uniform milk color, suitable sweet and sour taste, delicate taste, sticky and smooth taste, high nutritional value, and has health-care and nourishing effects.

detailed description

The scheme of the present invention will be further elaborated below in conjunction with the examples, but the present invention is not limited to the following examples.

Example 1

A wolfberry yoghurt, which is prepared through the following steps:

(1) Preparation of wolfberry raw materials

Select high-quality wolfberry and wash it with warm water at 50°C for 3 times to wash off dust and impurities, drain the water, add 3 times the water of wolfberry, cook at 100°C for 30 minutes, beat to obtain wolfberry pulp, and homogenize the prepared wolfberry pulp ,spare.

(2) Selection of raw milk

Select fresh and high-quality milk, which does not contain impurities, antibiotics and antibacterial substances, the total dry matter content of the milk is not less than 11.5wt.%, the milk fat rate is greater than 3wt.%, the acidity does not exceed 19°T, and other indicators meet the requirements of my country's national production line. Purchasing standards for fresh milk.

(3) Preparation of starter

Under aseptic conditions, a small amount of strains of Bifidobacterium, Lactobacillus bulgaricus, and Streptococcus thermophilic lactis were inoculated into the sterilized Lycium barbarum skim emulsion with an inoculation loop. Activation and subculture once, so that the activity of the bacteria is basically normal, and then the bacteria that have recovered the normal activity are activated and cultured in the wolfberry skim milk liquid medium, and the culture is continuously expanded, and finally the working starter is produced.

(4) Preparation of compound stabilizer

Prepare a propylene glycol alginate (PGA) solution with a mass concentration of 0.10%, prepare a xanthan gum solution with a mass concentration of 0.1%, and prepare a pectin solution with a mass concentration of 0.1%. : 1:1 mass ratio mix.

(5) Ingredients

Add 1000g of fresh milk in step (2) as raw material, add 5% of water according to the mass ratio of fresh milk, add 10% of wolfberry slurry prepared in step (1), add 0.1% of compound stabilizer, add white Add 2% granulated sugar and 2% skimmed milk powder, mix evenly to prevent agglomeration, and obtain a mixed fermentation material.

(6) Homogenization and sterilization

Preheat the mixed fermented material at 60°C for 40 minutes, then put the mixed fermented material into a homogenizer, homogenize at 20MPa to improve the delicate and lubricated taste of the yogurt, improve the stability of the yogurt, and heat at 95°C for 5 minutes to sterilize.

(7) Cooling, inoculation and fermentation of milk

After sterilization, the mixed fermentation material is cooled to the inoculation temperature of 42°C, and the inoculation amount of Bifidobacterium is 5U/250L, the inoculum amount of Lactobacillus bulgaricus is 15U/250L, and the inoculum amount of Streptococcus thermophilic lactis is 20U/250L Ferment for 5 hours at a fermentation temperature of 40°C, measure the acidity in the later stage of fermentation, and stop the fermentation when the acidity reaches 70°T.

(8) Cold treatment and refrigeration

The product fermented in step (7) is air-cooled, and refrigerated to obtain the finished product.

(9) Sensory evaluation

According to the sensory evaluation, the wolfberry yoghurt has pure aroma, uniform milk color, rich wolfberry flavor, sticky and smooth palatability, high nutritional value, significantly inhibits post-acidification of yogurt, and prolongs the shelf life by 3 days.

Example 2

A wolfberry yoghurt, which is prepared through the following steps:

(1) Preparation of wolfberry raw materials

Select high-quality wolfberry and wash it with warm water at 50°C for 4 times, wash off dust and impurities, drain the water, add 4 times the water of wolfberry, cook at 100°C for 30 minutes, beat to obtain wolfberry pulp, and homogenize the prepared wolfberry pulp ,spare.

(2) Selection of raw milk

Select fresh and high-quality milk, which does not contain impurities, antibiotics and antibacterial substances, the total dry matter content of the milk is not less than 11.5wt.%, the milk fat rate is greater than 3wt.%, the acidity does not exceed 19°T, and other indicators meet the requirements of my country's national production line. Purchasing standards for fresh milk.

(3) Preparation of starter

Under aseptic conditions, a small amount of strains of Bifidobacterium, Lactobacillus bulgaricus, and Streptococcus thermophilic lactis were inoculated into the sterilized Lycium barbarum skim emulsion with an inoculation loop. Activation and subculture once, so that the activity of the bacteria is basically normal, and then the bacteria that have recovered the normal activity are activated and cultured in the wolfberry skim milk liquid medium, and the culture is continuously expanded, and finally the working starter is produced.

(4) Preparation of compound stabilizer

Prepare a propylene glycol alginate (PGA) solution with a mass concentration of 0.20%, prepare a xanthan gum solution with a mass concentration of 0.3%, and prepare a pectin solution with a mass concentration of 0.15%. : 1:1 mass ratio mix.

(5) Ingredients

Add 2000g of fresh milk in step (2) as raw material, add 8% of water according to the mass ratio of fresh milk, add 12% of wolfberry slurry prepared in step (1), add 0.15% of stabilizer, and add white sugar 5%, add 5% skimmed milk powder, mix evenly to prevent agglomeration, and obtain a mixed fermented material.

(6) Homogenization and sterilization

Preheat the mixed material at 65°C for 30 minutes, then put the mixed fermented material into a homogenizer, and homogenize it at 25MPa to improve the delicate and lubricated taste of the yogurt, improve the stability of the yogurt, and heat at 93°C for 8 minutes to sterilize.

(7) Cooling, inoculation and fermentation of milk

After sterilization, cool down to the inoculation temperature of 42°C, strictly operate, the inoculum amount of Bifidobacterium is 8U/250L, the inoculum amount of Lactobacillus bulgaricus is 18U/250L, and the inoculum amount of Streptococcus thermophilic lactis is 36U/250L; Ferment at 42°C for 4 hours, measure the acidity at the later stage of fermentation, and stop the fermentation when the acidity reaches 72°T.

(8) Cold treatment and refrigeration

The product fermented in step (7) is water-cooled and refrigerated to obtain the finished product.

(9) Sensory evaluation

According to the sensory evaluation, the wolfberry yoghurt has pure aroma, uniform milk color, strong wolfberry flavor, sweet and sour taste, sticky taste, delicate taste, high nutritional value, significantly inhibits post-acidification of yogurt, and prolongs the shelf life by 5 days.

Example 3

A wolfberry yoghurt, which is prepared through the following steps:

(1) Preparation of wolfberry raw materials

Select high-quality wolfberry and wash it with warm water at 50°C for 3 times to wash off dust and impurities, drain the water, add 5 times the water of wolfberry, cook at 100°C for 30 minutes, beat to obtain wolfberry pulp, and homogenize the prepared wolfberry pulp ,spare.

(2) Selection of raw milk

Select fresh and high-quality milk, which does not contain impurities, antibiotics and antibacterial substances, the total dry matter content of the milk is not less than 11.5wt.%, the milk fat rate is greater than 3wt.%, the acidity does not exceed 19°T, and other indicators meet the requirements of my country's national production line. Purchasing standards for fresh milk.

(3) Preparation of starter

Under aseptic conditions, a small amount of strains of Bifidobacterium, Lactobacillus bulgaricus, and Streptococcus thermophilic lactis were inoculated into the sterilized Lycium barbarum skim emulsion with an inoculation loop. Activation and subculture once, so that the activity of the bacteria is basically normal, and then the bacteria that have recovered the normal activity are activated and cultured in the wolfberry skim milk liquid medium, and the culture is continuously expanded, and finally the working starter is produced.

(4) Preparation of compound stabilizer

Prepare a propylene glycol alginate (PGA) solution with a mass concentration of 0.50%, prepare a xanthan gum solution with a mass concentration of 1.0%, and prepare a pectin solution with a mass concentration of 0.2%. : 1:2 mass ratio mixing.

(5) Ingredients

Add 3000g of fresh milk in step (2) as raw material, add 10% water according to the mass ratio of fresh milk, add 15% of wolfberry raw material prepared in step (1), add 0.2% stabilizer, add 10% white sugar , add 10% skimmed milk powder, mix well to prevent agglomeration.

(6) Homogenization and sterilization

Preheat the mixed material at 70°C for 20 minutes, then put the mixed fermented material into a homogenizer, homogenize at 30MPa to improve the delicate and lubricated taste of the yogurt, improve the stability of the yogurt, and heat at 90°C for 10 minutes to sterilize.

(7) Cooling, inoculation and fermentation of milk

After sterilization, cool down to the inoculation temperature of 42°C, strictly operate, the inoculum amount of Bifidobacterium is 10U/250L, the inoculum amount of Lactobacillus bulgaricus is 30U/250L, and the inoculum amount of Streptococcus thermophilic lactis is 40U/250L; fermentation temperature Ferment at 45°C for 3 hours, measure the acidity at the later stage of fermentation, and stop the fermentation when the acidity reaches 75°T.

(8) Cold treatment and refrigeration

The product fermented in step (7) is air-cooled, and refrigerated to obtain the finished product.

(9) Sensory evaluation

According to the sensory evaluation, the wolfberry yoghurt has pure aroma, uniform milk color, rich wolfberry flavor, sweet and sour taste, high nutritional value and good taste, and can obviously inhibit post-acidification of yogurt, prolonging the shelf life by 4 days.

Claims (10)

1. a method for preparing fermented milk that suppresses post-yogurt acidification, is characterized in that, comprises the steps: (1) In the fermentation container, add fresh milk, then add water, wolfberry slurry, compound stabilizer, white sugar and skimmed milk powder in sequence, and mix evenly to obtain a mixed fermentation material; (2) After preheating the mixed fermentation material, put it in a high-pressure homogenization medium and high-pressure homogenization, sterilize, cool, inoculate the starter, and carry out fermentation; (3) After the fermentation is over, the fermented product is air-cooled or water-cooled and refrigerated. 2. A method for preparing fermented milk that inhibits post-acidification of yogurt according to claim 1, characterized in that in step (1), according to the mass percentage of fresh milk, the amount of each component added is: water 5% ~10%, wolfberry pulp 10%~15%, compound stabilizer 0.1%~0.2%, white sugar 2%~10%, skimmed milk powder 2%~10%. 3. A method for preparing fermented milk that inhibits post-acidification of yogurt according to claim 1, characterized in that, in step (1), the wolfberry slurry is prepared through the following steps: Select high-quality wolfberry, wash it with warm water at 50°C for 3 to 4 times, wash off dust and impurities, drain the water, add 3 to 5 times as much water as wolfberry, cook at 100°C for 30 minutes, and beat to obtain wolfberry pulp. The Lycium barbarum slurry was homogenized to obtain the Lycium barbarum slurry for subsequent use. 4. A method for preparing fermented milk that inhibits post-acidification of yogurt according to claim 1, characterized in that in step (1), the fresh milk does not contain impurities, antibiotics and antibacterial substances, and the total dryness of the milk is The substance content is not less than 11.5wt.%, the milk fat rate is more than 3wt.%, the acidity is not more than 19°T, and other indicators meet the procurement standards of fresh milk in my country. 5. A method for preparing fermented milk that inhibits post-acidification of yogurt according to claim 1, characterized in that in step (1), the compound stabilizer is: propylene glycol alginate solution, xanthan gum solution and A mixture of pectin solutions; the mass concentration of the propylene glycol alginate solution is 0.10% to 0.50%; the mass concentration of the xanthan gum solution is 0.1% to 1.0%; the mass concentration of the pectin solution is 0.1% ~0.2%; the propylene glycol alginate solution, xanthan gum solution and pectin solution are mixed according to the mass ratio of 1~2:1~2:1~2. 6. A method for preparing fermented milk that inhibits post-acidification of yogurt according to claim 1, characterized in that in step (2), the preheating is at 60-70°C for 20-40 minutes; the high-pressure The homogeneous pressure is 20~30MPa; the sterilization is heating at 90~95°C for 5~10min; the cooling is cooling to 42°C. 7. A method for preparing fermented milk that inhibits post-acidification of yogurt according to claim 1, characterized in that in step (2), the starter is prepared by using sterilized Lycium barbarum skim emulsion as a medium It is obtained by activating subculture and activating culture; the strains include Bifidobacterium, Lactobacillus bulgaricus and Streptococcus thermophilic lactis. 8. A method for preparing fermented milk that suppresses post-acidification of yogurt according to claim 7, characterized in that, in step (2), according to the ratio of the mixed fermented material, the inoculation amount of the bifidobacteria is 5U~ 10U/250L, the inoculum size of the Lactobacillus bulgaricus is 15U~30U/250L, and the inoculum size of the Streptococcus thermophilic lactis is 20U~40U/250L. 9 . The method for preparing fermented milk that inhibits post-acidification of yogurt according to claim 1 , wherein in step (2), the fermentation temperature is 40-45° C., and the fermentation time is 3-5 hours. 10. A method for preparing fermented milk that inhibits post-acidification of yogurt according to claim 1, characterized in that in step (2), by measuring the acidity of the material in the late stage of fermentation, when the acidity reaches 70°T ~ 75°T, Stop fermentation.