阅读说明：本技术 一种采用脱脂奶粉制备发酵剂的工艺 (Process for preparing leavening agent by using skimmed milk powder ) 是由 杨成龙 陈慎 黄颖颖 陆东和 于 2020-06-12 设计创作，主要内容包括：本发明公开了一种采用脱脂奶粉制备发酵剂的工艺,包括以下步骤：1)复原乳制备、2)灭菌、3)冷却、4)接种、5)保温发酵、6)破乳、7)离心、8)冻干、9)分装。本发明通过采用脱脂乳粉作为主要发酵原料,同时利用添加破乳剂提升水乳分离的效果,克服以脱脂乳粉作为发酵原料时易产生的水乳分离现象,同在保证离心效果的前体下缩短离心时间、降低离心强度,降低因离心强度过大造成的菌体破坏或菌体胞外多糖层的破坏,同时大幅缩短冻干时间,减少因冻干周期过长导致的活菌数损失,最大限度保持发酵酸奶的活菌数,提高了冻干效率和发酵菌剂产品品质,提高了生产效率的同时降低了能耗。(The invention discloses a process for preparing a leavening agent by using skim milk powder, which comprises the following steps: 1) preparing reconstituted milk, 2) sterilizing, 3) cooling, 4) inoculating, 5) preserving heat and fermenting, 6) demulsifying, 7) centrifuging, 8) freeze-drying and 9) subpackaging. The invention adopts the skim milk powder as the main fermentation raw material, and simultaneously improves the effect of water-milk separation by adding the demulsifier, overcomes the phenomenon of water-milk separation which is easily generated when the skim milk powder is used as the fermentation raw material, shortens the centrifugal time and reduces the centrifugal strength under the condition of ensuring the precursor of the centrifugal effect, reduces the damage of thalli or extracellular polysaccharide layers of thalli caused by overlarge centrifugal strength, greatly shortens the freeze-drying time, reduces the loss of viable count caused by overlong freeze-drying period, keeps the viable count of fermented yoghourt to the maximum extent, improves the freeze-drying efficiency and the quality of fermentation microbial inoculum products, improves the production efficiency and reduces the energy consumption.)

1. A process for preparing a leavening agent by using skim milk powder is characterized in that: which comprises the following steps:

1) preparing reconstituted milk: adding skimmed milk powder and sucrose into 55-60 deg.C water, dissolving completely, and making into reconstituted milk;

2) and (3) sterilization: sterilizing the reconstituted milk;

3) and (3) cooling: cooling the sterilized feed liquid to 35-45 ℃;

4) inoculation: inoculating passage type microbial inoculum activated in advance, wherein the microbial inoculum contains viable bacteria of Streptococcus thermophilus and Lactobacillus bulgaricus, and the viable bacteria number is not less than 10⁸CFU/g, the usage amount of the microbial inoculum is 0.05-0.1 percent of the total weight of the feed liquid;

5) and (3) heat preservation fermentation: after uniformly stirring the inoculated feed liquid, culturing and fermenting in a constant temperature and humidity box, and stopping fermentation when the inoculated feed liquid reaches a solidification state;

6) demulsifying: adding a demulsifier accounting for 0.05-0.1 percent of the total weight of the feed liquid into the feed liquid, and reacting for 30-60min at 40-50 ℃;

7) centrifuging: centrifuging the feed liquid, collecting bacterial sludge, adding freeze-drying protective agent, mixing, and packaging;

8) freeze-drying: putting the bacterial sludge into a freeze dryer, laying a plate, pre-freezing at the temperature of minus 40 ℃ to minus 30 ℃ for 2h-4h, and then freeze-drying in four stages:

9) subpackaging: and (4) crushing the powder cake obtained after freeze-drying, and subpackaging to obtain the leavening agent.

2. The process for preparing a starter culture using skim milk powder according to claim 1, wherein: in the step 1), the mass percentage of each component in the reconstituted milk is as follows: 12-25% of skimmed milk powder, 5-15% of cane sugar and 70-80% of water.

3. The process for preparing a starter culture using skim milk powder according to claim 1, wherein: in the step 2), the sterilization mode is pasteurization, high-temperature sterilization or ultrahigh-temperature instantaneous sterilization.

4. The process for preparing a starter culture using skim milk powder according to claim 1, wherein: in the step 5), the culture conditions in the constant temperature and humidity chamber are as follows: culturing at 37-42 deg.C for 3-5 h.

5. The process for preparing a starter culture using skim milk powder according to claim 1, wherein: in the step 6), the demulsifier is sodium chloride, sodium sulfate, calcium carbonate or potassium carbonate.

6. The process for preparing a starter culture using skim milk powder according to claim 1, wherein: in the step 7), a horizontal centrifuge or a disc type separator is adopted for centrifugation, the centrifugal speed is 3000-5000 r/min, and the centrifugation time is 5-15 min.

7. The process for preparing a starter culture using skim milk powder according to claim 1, wherein: in the step 7), the components and the mass percentage of the freeze-drying protective agent are as follows: 3-6% of glycerin, 1-2% of sodium glutamate, 0.5-1% of sorbitol and the balance of water, wherein the total amount of all the components is 100%.

8. The process for preparing a starter culture using skim milk powder according to claim 1, wherein: in the step 7), the volume ratio of the freeze-drying protective agent to the bacterial sludge is 4: 1.

9. The process for preparing a starter culture using skim milk powder according to claim 1, wherein: in the step 8), the thickness of the paving disc is 20mm-40 mm.

10. The process for preparing a starter culture using skim milk powder according to claim 1, wherein: in the step 8), after pre-freezing, freeze-drying is carried out according to the following four stages:

a first freeze-drying stage, wherein the temperature is controlled to be between 30 ℃ below zero and 20 ℃ below zero, the freeze-drying time is 2 to 4 hours, and the vacuum degree is 30 to 40 Pa;

freeze-drying for 2-4 h at-20 deg.C to-15 deg.C under vacuum degree of 20-30 Pa;

a third freeze-drying stage, wherein the temperature is controlled to be between 10 ℃ below zero and 5 ℃ below zero, the freeze-drying time is 10h to 15h, and the vacuum degree is 15Pa to 20 Pa;

freeze-drying at 5-15 deg.C for 4-8 hr under 10-15 Pa.

Technical Field

The invention belongs to the technical field of food processing, and particularly relates to a process for preparing a leavening agent by using skim milk powder.

Background

The method mainly comprises the steps of preparing concentrated bacterial suspension of high-concentration bacteria from lactic acid bacteria by means of concentrated culture, centrifugal collection and the like, adding an anti-freezing protective agent, and carrying out sublimation drying on water under the conditions of vacuum and low temperature to prepare a dry powdery solid starter culture, which is also called a direct vat set starter. The method is researched in the aspects of centrifugation, protective agents and the like, most of direct vat set starter adopts full-cream milk or full-cream milk powder as a raw material, skim milk powder is used as a freeze-drying protective agent in most cases, and is added as a small amount of additive in the freeze drying process to achieve the purpose of protecting the number of viable bacteria, and a preparation method of a microbial inoculum which completely adopts skim milk as a fermentation raw material is not mentioned.

Because the fat content in the skim milk powder is generally not more than 2%, the fat is not used as an emulsifier in the process of fermenting the yoghourt, the separation of water and milk is easy to occur, and meanwhile, the low fat content has certain influence on the mouthfeel of the yoghourt prepared by fermentation, so the fermented milk is less used as the main raw material for preparing the yoghourt. In the traditional process, only a centrifugal method is adopted in the fermentation process, and residual thalli in the supernatant are excessive under low centrifugal strength; the shearing action of cells is enhanced by high centrifugal force intensity and long-time centrifugation, the mutual pressure among thalli in pressure sedimentation is increased, the phenomena of cell shrinkage, collapse, extracellular substance dispersion, cell wall and cell membrane damage and the like can be caused, and the viable bacteria retention rate of the microbial inoculum is influenced to a certain extent; the poor centrifugal effect can further prolong the time of the freeze-drying process, improve the energy consumption and further reduce the viable bacteria retention rate of the freeze-dried microbial inoculum.

Disclosure of Invention

The invention aims to provide a process for preparing a leavening agent by using skim milk powder.

In order to achieve the purpose, the invention adopts the following technical scheme:

a process for preparing a leavening agent by using skim milk powder comprises the following steps:

1) preparing reconstituted milk: adding skimmed milk powder and sucrose into 55-60 deg.C water, and dissolving with high speed stirring device to obtain reconstituted milk;

2) and (3) sterilization: sterilizing the reconstituted milk;

3) and (3) cooling: cooling the sterilized feed liquid to 35-45 ℃;

4) inoculation: inoculating passage type microbial inoculum activated in advance, wherein the microbial inoculum contains viable bacteria of Streptococcus thermophilus and Lactobacillus bulgaricus, and the viable bacteria number is not less than 10⁸CFU/g, the usage amount of the microbial inoculum is 0.05-0.1 percent of the total weight of the feed liquid, and the process keeps sterility to avoid the pollution of mixed bacteria;

5) and (3) heat preservation fermentation: stirring the inoculated feed liquid uniformly, culturing and fermenting in a constant temperature and humidity chamber, stopping fermentation when the feed liquid reaches a solidification state, wherein the number of viable bacteria can reach 10 when the fermentation is stopped¹⁰CFU/g；

6) Demulsifying: adding a demulsifier accounting for 0.05-0.1 percent of the total weight of the feed liquid into the feed liquid, and reacting for 30-60min at 40-50 ℃;

7) centrifuging: centrifuging the feed liquid, collecting bacterial sludge, adding freeze-drying protective agent, mixing, and packaging;

8) freeze-drying: putting the bacterial sludge into a freeze dryer, laying a plate, pre-freezing at the temperature of minus 40 ℃ to minus 30 ℃ for 2h-4h, and then freeze-drying in four stages:

9) subpackaging: and (3) crushing the powder cake obtained after freeze-drying, crushing to the fineness of 40-80 meshes, and subpackaging to obtain the leaven.

In the step 1), the mass percentage of each component in the reconstituted milk is as follows: 12-25% of skimmed milk powder, 5-15% of cane sugar and 70-80% of water.

In the step 2), the sterilization mode is pasteurization, high-temperature sterilization or ultrahigh-temperature instantaneous sterilization.

In the step 5), the culture conditions in the constant temperature and humidity chamber are as follows: culturing at 37-42 deg.C for 3-5 h.

In the step 6), the demulsifier is sodium chloride, sodium sulfate, calcium carbonate or potassium carbonate.

In the step 7), a horizontal centrifuge or a disc type separator is adopted for centrifugation, the centrifugal speed is 3000-5000 r/min, and the centrifugation time is 5-15 min.

In the step 7), the components and the mass percentage of the freeze-drying protective agent are as follows: 3-6% of glycerin, 1-2% of sodium glutamate, 0.5-1% of sorbitol and the balance of water, wherein the total amount of all the components is 100%.

In the step 7), the volume ratio of the freeze-drying protective agent to the bacterial sludge is 4: 1.

In the step 8), the thickness of the paving disc is 20mm-40 mm.

In the step 8), after pre-freezing, freeze-drying is carried out according to the following four stages:

a first freeze-drying stage, wherein the temperature is controlled to be between 30 ℃ below zero and 20 ℃ below zero, the freeze-drying time is 2 to 4 hours, and the vacuum degree is 30 to 40 Pa;

freeze-drying for 2-4 h at-20 deg.C to-15 deg.C under vacuum degree of 20-30 Pa;

a third freeze-drying stage, wherein the temperature is controlled to be between 10 ℃ below zero and 5 ℃ below zero, the freeze-drying time is 10h to 15h, and the vacuum degree is 15Pa to 20 Pa;

freeze-drying at 5-15 deg.C for 4-8 hr under 10-15 Pa.

The invention adopts the skim milk powder as the main fermentation raw material, and simultaneously improves the effect of water-milk separation by adding the demulsifier, thereby overcoming the phenomenon of water-milk separation which is easily generated when the skim milk powder is used as the fermentation raw material, simultaneously, the demulsifier is added, the centrifugal time is shortened under the condition of ensuring the precursor of the centrifugal effect, the centrifugal strength is reduced, the thallus damage or the damage of the thallus extracellular polysaccharide layer caused by overlarge centrifugal strength is reduced, simultaneously, the freeze-drying time is greatly shortened, the loss of the viable count caused by overlong freeze-drying period is reduced, the viable count retention rate of the fermented yoghourt (the viable count retention rate of the product containing streptococcus thermophilus and lactobacillus bulgaricus can reach 60 to 70 percent) is maximally maintained, the freeze-drying efficiency and the quality of the fermentation microbial inoculum are improved, the production efficiency is improved.

Compared with the leaven prepared by the conventional process, the product of the invention has obvious advantages, the retention rate of viable count reaches 90.3 +/-0.5%, the freeze-drying time is shortened to 12-24h, and the water content of the microbial inoculum is reduced to 1.2 +/-0.2%.

The leaven prepared by the invention can be used as a microbial inoculum to be applied to the production of yoghourt, can be used as a solid beverage product to be sold separately, and can also be used as an auxiliary material additive of various dried leisure foods and liquid concocted beverages.

Detailed Description

A process for preparing a leavening agent by using skim milk powder comprises the following steps:

1) preparing reconstituted milk: adding skimmed milk powder and sucrose into water of 55-60 deg.C according to the proportion of skimmed milk powder 12-25%, sucrose 5-15%, and water 70-80%, and dissolving with high speed stirring device to obtain reconstituted milk;

2) and (3) sterilization: sterilizing the reconstituted milk by pasteurization, high-temperature sterilization or ultrahigh-temperature instantaneous sterilization;

3) and (3) cooling: cooling the sterilized feed liquid to 35-45 ℃;

4) inoculation: inoculating passage type microbial inoculum activated in advance, wherein the microbial inoculum contains viable bacteria of Streptococcus thermophilus and Lactobacillus bulgaricus, and the viable bacteria number is not less than 10⁸CFU/g, the usage amount of the microbial inoculum is 0.05-0.1 percent of the total weight of the feed liquid, and the process keeps sterility to avoid the pollution of mixed bacteria;

5) and (3) heat preservation fermentation: stirring the inoculated material liquid, culturing at 37-42 deg.C in constant temperature and humidity chamber for about 3-5 h, stopping fermentation when the material liquid reaches solidification state, and stopping fermentation until viable count reaches 10¹⁰CFU/g；

6) Demulsifying: adding a demulsifier accounting for 0.05-0.1 percent of the total weight of the feed liquid into the feed liquid, and reacting for 30-60min at 40-50 ℃;

the demulsifier is sodium chloride, sodium sulfate, calcium carbonate or potassium carbonate;

7) centrifuging: centrifuging by adopting a horizontal centrifuge or a disc type separator, wherein the centrifuging conditions are as follows: rotating at 3000rpm-5000rpm for 5-15 min; centrifuging, collecting bacterial sludge, adding a freeze-drying protective agent, uniformly mixing the freeze-drying protective agent and the bacterial sludge according to the volume ratio of the freeze-drying protective agent to the bacterial sludge of 4: 1, and subpackaging;

the freeze-drying protective agent comprises the following components in percentage by mass: 3-6% of glycerin, 1-2% of sodium glutamate, 0.5-1% of sorbitol and the balance of water, wherein the total amount of all the components is 100%;

8) freeze-drying: placing the bacterial sludge into a freeze dryer, and paving the bacterial sludge to be 20-40 mm thick; pre-freezing at the temperature of minus 40 ℃ to minus 30 ℃ for 2h to 4h after the laying of the plate is finished; lyophilization was then performed in four stages:

a first freeze-drying stage, wherein the temperature is controlled to be between 30 ℃ below zero and 20 ℃ below zero, the freeze-drying time is 2 to 4 hours, and the vacuum degree is 30 to 40 Pa;

freeze-drying for 2-4 h at-20 deg.C to-15 deg.C under vacuum degree of 20-30 Pa;

a third freeze-drying stage, wherein the temperature is controlled to be between 10 ℃ below zero and 5 ℃ below zero, the freeze-drying time is 10h to 15h, and the vacuum degree is 15Pa to 20 Pa;

freeze-drying at 5-15 deg.C for 4-8 h under 10-15 Pa;

9) subpackaging: and (3) crushing the powder cake obtained after freeze-drying, crushing to the fineness of 40-80 meshes, and subpackaging to obtain the leaven.