CN116076568A - Fermented milk with long shelf life and processing method thereof - Google Patents

Abstract

The invention relates to the technical field of fermented milk, in particular to fermented milk with a long shelf life and a processing method thereof. The processing method comprises the following steps: aseptically inoculating the sterile lactic acid bacteria starter into sterilized raw milk or raw milk products, aseptically filling and fermenting; the processing method of the sterile lactic acid bacteria starter comprises the following steps: inoculating the pure culture of lactobacillus strain into a sterile culture medium for culturing to obtain a sterile lactobacillus starter; the raw material components of the sterile culture medium comprise: 5-10% of dairy products, 0-1% of yeast extract, 0-8% of carbohydrate, 0-1% of nutrients and the balance of water; alternatively, the sterile medium may comprise: 0-1% of yeast extract, 0-8% of carbohydrate, 0-1% of nutrient and the balance of one or more of whey or dairy permeate. The prepared fermented milk product can be preserved for a long time at normal temperature or low temperature without deterioration while maintaining high amount of active lactobacillus.

Description

Fermented milk with long shelf life and processing method thereof

Technical Field

The invention relates to the technical field of fermented milk, in particular to fermented milk with a long shelf life and a processing method thereof.

Background

At present, the fermented milk is mainly of two types, one is a low-temperature active fermented milk product, mainly low-temperature yoghourt, takes raw cow (sheep) milk or milk powder as raw materials, and is prepared into a product with reduced pH value after sterilization and fermentation, wherein the quantity of active lactobacillus in the product is kept to be more than or equal to 10 ⁶ CFU/g. The shelf life is generally varied from 15 to 21 days under the condition of low-temperature refrigeration. The other is normal temperature fermented milk product, which is prepared from raw cow (sheep) milk or milk powderThe raw materials are sterilized, fermented and then subjected to heat treatment to obtain heat-treated fermented milk, wherein active lactobacillus is killed in the heat treatment. The heat-treated fermented milk product can be stored at normal temperature, and the shelf life is generally 3-6 months.

In the prior art, the fermented milk product obtained by fermenting active lactobacillus inevitably has other miscellaneous bacteria except lactobacillus remained in the product due to the limitation of production and processing technical conditions, so the active lactobacillus product must be kept refrigerated, and the shelf life is usually not more than 21 days, otherwise, the risk of deterioration exists. The heat treatment of fermented milk can realize long shelf life under normal temperature storage condition, but the active lactobacillus in the fermented milk is almost completely killed, and the stability of the fermented milk is destroyed by the heat treatment process after fermentation, and proper viscosity and stability of the fermented milk must be maintained by adding an emulsifying thickener. In order to solve the problems, a processing technology of active bacteria yoghourt with long shelf life is developed, so that the obtained fermented milk product keeps high quantity of active lactic acid bacteria and is kept at normal temperature or low temperature for a long time without deterioration, and the processing technology is an important subject to be solved in the industry.

Disclosure of Invention

The invention provides fermented milk with a long shelf life and a processing method thereof, which are used for solving the defect that a low-temperature active fermented milk product cannot be stored for a long time in the prior art, and provides a processing method of the fermented milk, which can be stored for a long time at normal temperature or low temperature without deterioration while keeping the high number of active lactobacillus.

The invention provides a processing method of fermented milk, which comprises the following steps: aseptically inoculating the sterile lactic acid bacteria starter into sterilized raw milk or raw milk products, aseptically filling and fermenting;

the processing method of the sterile lactic acid bacteria starter comprises the following steps: inoculating the pure culture of lactobacillus strain into a sterile culture medium for culturing to obtain a sterile lactobacillus starter;

the raw material components of the sterile culture medium comprise: 5-10% of dairy products (comprising one or more of milk powder, whey powder and dairy product permeate powder), 0-1% of yeast extract, 0-8% of carbohydrate (which can be one or more of monosaccharide, disaccharide and oligosaccharide), 0-1% of nutrients (comprising one or more of vitamins, phosphate and mineral raw materials) and the balance of water;

alternatively, the sterile medium may comprise: 0-1% of yeast extract, 0-8% of carbohydrate (one or more of monosaccharide, disaccharide and oligosaccharide), 0-1% of nutrient (one or more of vitamin, phosphate and mineral raw materials) and the balance of whey or one or more of dairy product permeate;

the processing method of the ferment also comprises sterilizing the culture medium, and can adopt a microporous filter membrane with the pore diameter not more than 0.45 micrometer to filter, or adopt a method of sterilizing at the temperature of 115-121 ℃ for 7-20 min for sterilization, thus obtaining the sterile culture medium.

The invention can realize natural fermented milk products with long shelf life by fermenting raw milk with lactobacillus without using emulsifying agent and thickening agent. The preparation method is simple and has wide applicability.

According to the method for processing the fermented milk provided by the invention, in the method for processing the sterile lactic acid bacteria starter, the culture condition is 25-43 ℃ for 3-16 h.

More preferably, the culture conditions are 41 to 43℃for 5 to 13 hours.

And/or the Lactobacillus is one or more of streptococcus thermophilus (Streptococcus salivarius subsp. Thermophilus), lactobacillus bulgaricus (Lactobacillus delbrueckii subsp. Bulgarica), bifidobacterium (bifidobacteria), lactobacillus (Lactobacillus), lactobacillus casei (Lactobacillus casei), lactobacillus mucilaginosa (Lactobacillus mucilaginosa), lactobacillus plantarum (Lactobacillus plantarum), lactococcus lactis (Lactobacillus), and leuconostoc mesenteroides (Leuconostoc mesenteroides).

In some embodiments, the dairy permeate is a dairy permeate powder or a dairy permeate.

Preferably, when the lactic acid bacteria are streptococcus thermophilus (Streptococcus thermophilus) and lactobacillus bulgaricus (Lactobacillus bulgaricus), the dairy product is whey or cow milk permeate in the raw material components of the sterile culture medium.

More preferably, the raw material components of the sterile medium include: 4-7% of whey powder, 0.4-0.6% of yeast extract and the balance of water.

Or, the raw material components of the sterile culture medium comprise: 6-8% of whey powder and the balance of water.

Or, the raw material components of the sterile culture medium comprise: 0.4 to 0.6 percent of yeast extract and the balance of cow milk penetrating fluid.

In some preferred embodiments of the invention, the raw material components of the sterile medium include: whey powder or whey permeate powder 5-7%, yeast extract 0.4-0.6%, and water in balance.

The invention is suitable for culturing different species of preferred lactobacillus strains or strains by expanding and developing the formula and the preparation technology of the preferred lactobacillus liquid culture medium, is suitable for further improving the lactobacillus culture effect and obtains the non-mixed lactobacillus starter with better performance.

According to the processing method of the fermented milk provided by the invention, the raw milk is raw milk, and the raw milk comprises full-fat raw milk, defatted raw milk or partially defatted raw milk;

and/or the raw milk product is reconstituted milk or a mixture of raw milk and partially reconstituted milk.

According to the processing method of the fermented milk, the raw milk or the raw milk product can be selectively blended or not blended, and the blending comprises the addition of one or more of other food raw materials, sweetening agents, thickening agents, emulsifying agents, essence and spices.

The processing method of the fermented milk provided by the invention further comprises the step of homogenizing raw milk, raw milk products, blended raw milk or blended raw milk products;

preferably, the homogenizing step is as follows: preheating the raw materials to 50-80 ℃, and homogenizing at 10-30 MPa. By utilizing the homogenizing step, the produced fermented milk has better quality.

Further preferably, the homogenized raw material is prepared as a sterile raw material, preferably by ultra-high temperature or high pressure sterilization.

According to the processing method of the fermented milk, the addition amount of the sterile lactic acid bacteria starter is 0.1-5.0% during aseptic inoculation;

preferably, the sterile on-line addition system is used to add the sterile lactic acid bacteria starter.

According to the processing method of the fermented milk, provided by the invention, the raw milk or the raw milk product inoculated with the sterile lactic acid bacteria starter is filled into a sterile packaging material by adopting sterile filling equipment under a sterile environment.

Preferably, the aseptic filling equipment and aseptic packaging materials herein may be selected from those currently commercially available from manufacturers of packaging machines such as the rile or medium and sub-grade packaging machines and corresponding packaging materials.

According to the processing method of the fermented milk provided by the invention, the fermentation conditions of the fermented milk are as follows: fermenting for 4-72 h at 25-43 ℃.

The invention also provides a fermented dairy product, which is prepared by the method. The fermented milk formula developed by the invention can more effectively protect the activity of the lactic acid bacteria and improve the survival rate and survival time of the active lactic acid bacteria in the yoghurt.

The invention has the beneficial effects that:

(1) The processing method of the fermented milk provided by the invention is suitable for preparing the fermented milk with or without food additives. In the production process, lactobacillus naturally ferments the curd to form the special quality of fermented milk, and mechanical treatment procedures such as filling, heat treatment and the like for destroying the naturally fermented curd are not needed after fermentation, so that the quality of the naturally fermented curd is still maintained for the finished product. The quality guarantee period of the fermented milk can be prolonged and the special quality of the fermented milk of the natural fermented curd can be maintained through the control of the processing technology on the basis of not additionally adding food additives.

(2) The invention prepares the pure culture starter for lactic acid bacteria suitable for aseptic adding and inoculating process, adopts an aseptic adding and inoculating mode, adds the starter into sterilized commercial aseptic raw milk, and ferments in a package after aseptic filling to obtain a fermented milk product. The method has the advantages that the pollution of various production links of starter preparation, material sterilization, inoculation, filling and fermentation is strictly avoided, and the produced fermented milk products are guaranteed to be free of mixed bacteria pollution in the whole process from production, packaging to storage and transportation, so that the products can be kept to keep good quality of the fermented milk for a long time in the environment of normal temperature and low temperature, and the spoilage and deterioration of the products caused by foreign bacteria can not occur.

Drawings

In order to more clearly illustrate the invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic flow chart of the method for processing the fermented milk with long shelf life.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the present invention, "%" means mass percent.

The invention provides a processing method of a liquid fermented milk product, which comprises the following steps:

1.1 preparation of the sterile lactic acid bacteria starter

1.1.1 lactic acid bacteria species: including all lactic acid bacteria suitable for use in fermented milk, including but not limited to one or more of the species of dairy starter cultures such as Streptococcus thermophilus (Streptococcus thermophilus), lactobacillus bulgaricus (Lactobacillus bulgaricus), lactococcus lactis (Lactococcus lactis), leuconostoc mesenteroides (Leuconostoc mesenteroides)

Streptococcus thermophilus and Lactobacillus bulgaricus are preferred.

1.1.2 preparation of sterile Medium

(1) The culture medium solution is prepared by taking milk powder, whey or dairy product permeate as a main raw material, and adding or not adding other food raw materials, food additives and nutrition enhancer components. For example: 5-10% of whey powder, 0-1% of yeast extract and 0-5% of glucose, and adding water and fully stirring for dissolution.

(2) The culture medium solution is sterilized at high temperature and high pressure or micro-filtration to obtain the sterile culture medium solution.

1.1.3 activating the pure culture of the lactobacillus strain by a liquid culture medium for 1-2 generations to obtain a pure culture solution of the lactobacillus, inoculating the pure culture solution of the lactobacillus strain into the sterile culture solution under a sterile environment, and culturing for 3-16 hours under a proper temperature environment to obtain the sterile lactobacillus starter.

1.2 preparation of fermented milk with long shelf-Life

1.2.1 raw milk: may be fresh raw milk, including whole, defatted or partially defatted; or mixing reconstituted milk or raw milk with partially reconstituted milk

1.2.2 blending: the preparation comprises adding one or more of sweetener, thickener, emulsifier, essence, spice, other food raw materials, etc., and mixing to obtain the mixture.

The raw milk can be mixed with other raw materials and auxiliary materials to prepare yoghourt or flavored fermented milk products with different flavors; or may be formulated to produce yogurt or fermented milk.

1.2.3 homogenization sterilization: the raw milk or the blended material is preheated to 50-80 ℃, then homogenized under 10-30 MPa, and then sterilized under ultra-high temperature or high pressure to obtain the commercial sterile material.

1.2.4 aseptic inoculation of starter: under aseptic conditions, a liquid leavening agent is added to the sterilized sterile material. The addition amount of the liquid leavening agent is controlled to be 0.1-5.0%.

Preferably, the starter is added using a sterile in-line addition system.

1.2.5 aseptic filling: filling the material inoculated with the fermenting agent into a sterile closed packaging container by adopting sterile filling equipment under a sterile environment

1.2.6 heat preservation fermentation: and (3) placing the sterilized and filled product in a proper temperature environment within the range of 25-42 ℃, and fermenting for 4-72 h to obtain a fermented milk product with the pH value below 4.6.

Example one

Whey permeate powder 6%, yeast extract 0.5% and purified water 93.5% are mixed and dissolved to prepare a whey culture medium, and the whey culture medium is sterilized by micro-filtration and aseptically filled in an asepsis closed container. Then adding the streptococcus thermophilus bacterial pure culture under the aseptic condition, and then preserving the heat and fermenting for 8 hours at 42 ℃ to obtain the streptococcus thermophilus starter.

Mixing whey permeate powder 6%, yeast extract 0.5%, and purified water 93.5%, dissolving to obtain whey culture medium, sterilizing by micro-filtration, and aseptically packaging in an aseptic closed container. Then adding the pure culture of the lactobacillus bulgaricus strain under the aseptic condition, and then preserving the heat and fermenting for 10 hours at 42 ℃ to obtain the lactobacillus bulgaricus starter.

Preheating raw milk to 65 ℃ for homogenization, then 138 ℃ for 3 seconds, sterilizing, adding 0.5% of streptococcus thermophilus starter and 0.5% of lactobacillus bulgaricus starter into the sterilized raw milk by adopting a sterile on-line adding mode, adding the starter, filling the mixture into sterile sealed packages in a sterile way, preserving the temperature at 42.5 ℃ for more than 4 hours, until the pH value is reduced to below 4.6, stopping fermentation, and cooling to normal temperature or refrigerating for preservation.

Example one indicator Change during storage of fermented milk

Example two

7% of whey powder and 93% of purified water are mixed and dissolved to prepare a culture medium, and the culture medium is sterilized by micro filtration and then aseptically filled in an asepsis closed container. Then adding the streptococcus thermophilus bacterial pure culture under the aseptic condition, and then preserving the heat and fermenting for 8 hours at 42 ℃ to obtain the streptococcus thermophilus starter.

7% of whey powder and 93% of purified water are mixed and dissolved to prepare a culture medium, and the culture medium is sterilized by micro filtration and then aseptically filled in an asepsis closed container. Then adding the pure culture of the lactobacillus bulgaricus strain under the aseptic condition, and then preserving the heat and fermenting for 10 hours at 42 ℃ to obtain the lactobacillus bulgaricus starter.

Mixing raw milk with adjuvants such as white sugar, skimmed milk powder, pectin, etc., homogenizing at 60deg.C, sterilizing at 180deg.C for 3s, adding 1% Streptococcus thermophilus starter and 0.5% Lactobacillus bulgaricus starter into sterilized raw milk by aseptic on-line adding, aseptic packaging, incubating at 42deg.C for more than 4 hr, stopping fermentation until pH is reduced below 4.6, and cooling to normal temperature or cold storage.

Example three

99.5% of cow milk penetrating fluid, 0.5% of yeast extract is added for mixing and dissolving to prepare a culture medium, and after micro-filtration and sterilization, the culture medium is aseptically filled in an asepsis closed container. Then adding the streptococcus thermophilus bacterial pure culture under the aseptic condition, and then preserving the heat and fermenting for 8 hours at 42 ℃ to obtain the streptococcus thermophilus starter.

99.5% of cow milk penetrating fluid, 0.5% of yeast extract is added for mixing and dissolving to prepare a culture medium, and after micro-filtration and sterilization, the culture medium is aseptically filled in an asepsis closed container. Then adding the pure culture of the lactobacillus bulgaricus strain under the aseptic condition, and then preserving the heat and fermenting for 10 hours at 42 ℃ to obtain the lactobacillus bulgaricus starter.

Mixing raw milk with 6% white granulated sugar, 0.5% skim milk powder and 0.02% pectin, homogenizing at 65deg.C, sterilizing at 38deg.C, adding 1% Streptococcus thermophilus starter and 0.5% Lactobacillus bulgaricus starter into sterilized raw milk by aseptic on-line method, aseptic packaging, incubating at 42deg.C for more than 4 hr until pH is reduced below 4.6, stopping fermentation, and cooling to normal temperature or cold storage.

Example index Change during storage of fermented milk

Example four

Mixing whey permeate powder 6%, yeast extract 0.5% and purified water 93.5%, dissolving to obtain culture medium, sterilizing with micro-filter, and aseptically packaging in an asepsis closed container. Then adding the streptococcus thermophilus bacterial pure culture under the aseptic condition, and then preserving the heat and fermenting for 8 hours at 42 ℃ to obtain the streptococcus thermophilus starter.

Mixing whey permeate powder 6%, yeast extract 0.5% and purified water 83.5%, dissolving to obtain culture medium, sterilizing with micro-filter, and aseptically packaging in an asepsis closed container. Then adding the pure culture of the lactobacillus bulgaricus strain under the aseptic condition, and then preserving the heat and fermenting for 10 hours at 42 ℃ to obtain the lactobacillus bulgaricus starter.

Mixing reconstituted milk with adjuvants such as 6% white sugar and 0.02% pectin, homogenizing at 65deg.C, sterilizing at 138 deg.C for 3s, adding 1% Streptococcus thermophilus starter and 0.5% Lactobacillus bulgaricus starter into sterilized raw milk by aseptic on-line adding, aseptic packaging, incubating at 42+ -1deg.C for more than 4 hr until pH is reduced to below 4.6, stopping fermentation, and cooling to normal temperature or cold storage.

The fermented dairy product obtained by the invention has a shelf life of more than 45 days under the normal temperature preservation condition, and the quantity of active lactobacillus in the product is not less than 10 ⁶ CFU/g, (meeting the limit standard of the number of active lactobacillus in national standard fermented milk). After 60 days of normal temperature preservation, the fermented milk can still maintain good quality for 4 to 6 months despite the reduction of the quantity of active lactobacillus.

The fermented dairy product obtained by the invention has a shelf life under the condition of low-temperature refrigeration (4 ℃) preservationFor more than 2 months, the amount of active lactobacillus in the product is not less than 10 ⁶ CFU/g, (meeting the limit standard of the number of active lactobacillus in national standard fermented milk). After 3 months of low-temperature preservation, the quantity of active lactobacillus is reduced, but the fermented milk can still keep good quality for more than 5 months.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A method for processing fermented milk, comprising: aseptically inoculating the sterile lactic acid bacteria starter into sterilized raw milk or raw milk products, aseptically filling and fermenting;

the processing method of the sterile lactic acid bacteria starter comprises the following steps: inoculating the pure culture of lactobacillus strain into a sterile culture medium for culturing to obtain a sterile lactobacillus starter;

the raw material components of the sterile culture medium comprise: 5-10% of dairy products (comprising one or more of milk powder, whey powder and dairy product permeate powder), 0-1% of yeast extract, 0-8% of carbohydrate (which can be one or more of monosaccharide, disaccharide and oligosaccharide), 0-1% of nutrients (comprising one or more of vitamins, phosphate and mineral raw materials) and the balance of water;

alternatively, the sterile medium may comprise: 0-1% of yeast extract, 0-8% of carbohydrate (one or more of monosaccharide, disaccharide and oligosaccharide), 0-1% of nutrient (one or more of vitamin, phosphate and mineral raw materials) and the balance of whey or one or more of dairy product permeate;

the processing method of the ferment also comprises sterilizing the culture medium, and can adopt a microporous filter membrane with the pore diameter not more than 0.45 micrometer to filter, or adopt a method of sterilizing at the temperature of 115-121 ℃ for 7-20 min for sterilization, thus obtaining the sterile culture medium.

2. The method for processing fermented milk according to claim 1, wherein the cultivation conditions in the method for processing the non-microbial lactic acid bacteria starter are 25 to 43 ℃ for 3 to 16 hours;

and/or the Lactobacillus is one or more of streptococcus thermophilus (Streptococcus salivarius subsp. Thermophilus), lactobacillus bulgaricus (Lactobacillus delbrueckii subsp. Bulgarica), bifidobacterium (bifidobacteria), lactobacillus (Lactobacillus), lactobacillus casei (Lactobacillus casei), lactobacillus mucilaginosa (Lactobacillus mucilaginosa), lactobacillus plantarum (Lactobacillus plantarum), lactococcus lactis (Lactobacillus), and leuconostoc mesenteroides (Leuconostoc mesenteroides).

3. The method of processing fermented milk according to any one of claims 1 to 2, wherein the raw milk is raw milk, the raw milk including whole raw milk, skim raw milk or partially skim raw milk;

and/or the raw milk product is reconstituted milk or a mixture of raw milk and partially reconstituted milk.

4. A method of processing fermented milk according to any one of claims 1 to 3, wherein the step of formulating or not formulating the raw milk or raw milk product is selected, the formulating comprising adding one or more of other food materials, sweeteners, thickeners, emulsifiers, fragrances, flavours.

5. The method for processing fermented milk according to any one of claims 1 to 4, further comprising a step of homogenizing raw milk, raw milk product, prepared raw milk or prepared raw milk product;

preferably, the homogenizing step is as follows: preheating the raw materials to 50-80 ℃, and homogenizing at 10-30 MPa.

6. The method of processing fermented milk according to any one of claims 1 to 5, further comprising preparing a sterile raw material from the homogenized raw material, preferably by ultra-high temperature or autoclaving.

7. The method for processing fermented milk according to any one of claims 1 to 6, wherein the amount of the non-microbial lactic acid bacteria starter to be added is 0.1 to 5.0% at the time of aseptic inoculation;

preferably, the sterile on-line addition system is used to add the sterile lactic acid bacteria starter.

8. The method of processing fermented milk according to any one of claims 1 to 7, wherein the raw milk or the raw milk product inoculated with the sterile lactic acid bacteria starter is filled into a sterile packaging material in a sterile environment by using a sterile filling device;

preferably, the aseptic filling equipment and aseptic packaging materials herein may be selected from those currently commercially available from manufacturers of packaging machines such as the rile or medium and sub-grade packaging machines and corresponding packaging materials.

9. The method for processing a fermented milk according to any one of claims 1 to 8, wherein the fermentation conditions of the fermented milk are: fermenting for 4-72 h at 25-43 ℃.

10. A fermented dairy product prepared according to the method of any one of claims 1 to 9.

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