阅读说明：本技术 一种新鲜母乳的长期冷藏方法 (Long-term refrigeration method of fresh breast milk ) 是由 姚卫蓉 陈宇伦 施思倩 苏莹 池可心 谢云飞 于航 杨方威 于 2021-08-20 设计创作，主要内容包括：本发明公开了一种新鲜母乳的长期冷藏方法,属于食品保鲜领域。本发明向母乳中添加乳化剂并采用均质手段辅助冰箱冷藏母乳。分别测定了母乳冷藏期间酸臭味、pH、可滴定酸度和游离脂肪酸四个指标,结果发现采用该法冷藏的母乳达到3天以上,脂肪酸相关指标才出现突变,并且所有指标劣变延缓率均在40％以上,平均延缓率在70％以上。因此,本发明可以将冷藏母乳时间提升至3天以上,为新鲜母乳保藏提供了一种操作简单、成本低廉的新方法。(The invention discloses a long-term cold storage method of fresh breast milk, belonging to the field of food preservation. The invention adds the emulsifier into the breast milk and adopts a homogenizing method to assist the refrigerator to refrigerate the breast milk. Four indexes of acid odor, pH, titratable acidity and free fatty acid in the breast milk refrigeration period are respectively measured, and the result shows that when the breast milk refrigerated by the method is refrigerated for more than 3 days, the indexes related to the fatty acid are mutated, the degradation delay rate of all the indexes is more than 40%, and the average delay rate is more than 70%. Therefore, the invention can prolong the time for refrigerating the breast milk to more than 3 days, and provides a novel method with simple operation and low cost for preserving the fresh breast milk.)

1. A method for long-term refrigeration of fresh breast milk, comprising the steps of: uniformly heating fresh breast milk to 45-65 ℃, adding a food-grade emulsifier with the mass fraction of 0.02-0.10%, uniformly mixing, homogenizing, cooling to room temperature, sealing, and refrigerating at-1-10 ℃;

wherein the fresh breast milk refers to the breast milk which is preserved in an environment of-1-10 ℃ immediately after being extruded, and the maximum time interval from the subsequent heating treatment is 2 h.

2. Method for the long-term cold storage of fresh breast milk according to claim 1, characterized in that the fresh breast milk is uniformly heated, in particular by means of water bath heating.

3. The method of claim 1, wherein the fresh breast milk is heated and mixed with the food grade emulsifier by stirring.

4. A method for the long-term refrigeration of fresh breast milk as claimed in claim 1, wherein the cooling is by running tap water.

5. The method of claim 1, wherein the refrigerator provides a refrigeration environment of-1 to 10 ℃.

6. The method for the long-term refrigeration of fresh breast milk according to claim 1, wherein the food-grade emulsifier comprises at least one of soy phospholipids, egg phospholipids, mono/diglycerol fatty acid esters, carrageenan, and citric acid fatty acid glycerides.

7. Method for the long-term cold storage of fresh breast milk according to claim 1, characterized in that the conditions of homogenization are: the homogenizing speed is 10000-.

8. The method for the long-term refrigeration of fresh breast milk according to claim 1, comprising the steps of:

(1) uniformly heating fresh breast milk to 45-65 ℃, adding a food-grade emulsifier with the mass fraction of 0.02-0.10%, and uniformly mixing;

(2) homogenizing the breast milk obtained in the step (1), cooling to room temperature, sealing, and refrigerating at-1-10 deg.C; monitoring fatty acid related indexes in the refrigeration process: acid odor, pH, titratable acidity and free fatty acid content; and (3) stopping refrigeration when the fatty acid related index is mutated, and determining the refrigerated shelf life of the breast milk according to the mutation of the acid odor, the pH value, the titratable acidity or the free fatty acid, wherein the mutation is determined according to the statistical significance difference of the p <0.05 level.

9. Use of the long term refrigeration method of any one of claims 1-8 for the refrigerated storage of human breast milk or fresh animal milk.

10. Fresh breast milk prepared by the long term refrigeration process of any one of claims 1-8; the refrigerated shelf life of the fresh breast milk is not less than 3 days.

Technical Field

The invention relates to a long-term cold storage method of fresh breast milk, belonging to the field of food preservation.

Background

The breast milk is the best nutrient source for the infants, and is characterized by proper components, easy digestion, immunoregulation performance and certain anti-infection function, thereby providing nutrition and protection for the infants. In recent years, driven by the pressure of the home, work and social environment, many young women have begun to attempt to replace traditional parental feeding with extruded milk feeding. In the process, the problem of family preservation of fresh breast milk is more prominent, the quality of the breast milk is sharply reduced due to fat deterioration, and the phenomenon that infants refuse to accept feeding frequently occurs, so that a great amount of breast milk is wasted.

The pH of breast milk refers to the ratio of the total number of hydrogen ions in the milk to the amount of total substances. Titratable acidity refers to the total amount of all acidic components, i.e., total acidity, including the concentration of undissociated acid and the concentration of dissociated acid. The lipids in breast milk can be roughly classified into cholesterol, neutral fat, phospholipid, free fatty acid, and the like. Free Fatty Acid (FFA), also known as non-esterified fatty Acid (NEFA), is one of the products of lipolysis. Thus, pH, titratable acidity and free fatty acids constitute three indicators for monitoring fatty acid changes during breast milk refrigeration.

At present, methods for preserving fresh breast milk include a heating method, a freezing method and a refrigerating method, and other auxiliary treatment modes are not available temporarily. The heating method ensures the safety of breast milk by killing microorganisms, but it accelerates the hydrolysis of proteins and fats and inactivates certain biofunctional components (e.g., enzymes). Ice crystals formed by freezing can disrupt the integrity of the fat globule membrane of breast milk. The refrigeration method can effectively maintain the nutrition and the biological activity of the breast milk in a short time, but the method is easy to generate fat stratification and sour odor after 24 hours, so that the quality of the breast milk is rapidly deteriorated, the infant is difficult to accept, and a large amount of breast milk is wasted. Therefore, it is urgent to adopt a simple method which can satisfy the requirement that the ordinary family can not only keep the flavor but also maintain the freshness during the process of refrigerating the breast milk.

Disclosure of Invention

[ problem ] to

Provides a simple method which can satisfy the requirements of common families on flavor preservation and freshness maintenance in the process of breast milk refrigeration.

[ solution ]

In order to solve the problems, the invention provides a method for assisting the refrigeration of breast milk by adding an emulsifier and adopting a homogenizing means, the method has simple operation and low cost, obviously improves indexes such as acid odor, pH, acidity and free fatty acid during the refrigeration of the breast milk, and prolongs the refrigerated shelf life of the breast milk.

The invention has the technical idea that food-grade emulsifiers such as soybean lecithin, yolk lecithin, mono/diglycerol fatty acid ester, carrageenan and citric acid fatty glyceride are added into breast milk, so that the risks of fat oxidation and fat globule aggregation caused by the fact that an interface membrane of a milk fat globule cannot be repaired in the subsequent homogenization process can be reduced to a certain extent, and further the fat deterioration process is slowed down. In addition, part of the food-grade emulsifier can properly supplement the phospholipid content in the breast milk, and the nutritional value of the breast milk is improved. Homogenizing is used as an auxiliary means to finely break milk fat globules, reduce the diameter of the fat globules, and the dispersion effect of Brownian motion can partially overcome the tendency of fat globule aggregation, so that the floating speed of the fat globules is reduced, the fat oxidation deterioration is improved, the casein content adsorbed on the surface of the fat globules is increased, the viscosity is improved, the digestibility of protein is improved, the luster is increased, and the like.

A first object of the present invention is to provide a method for long-term refrigeration of fresh breast milk, comprising the steps of: firstly, uniformly heating fresh breast milk to 45-65 ℃, adding a food-grade emulsifier with the mass fraction of 0.02-0.10%, uniformly mixing, homogenizing, cooling to room temperature, sealing, and refrigerating in an environment of-1-10 ℃. The refrigerated shelf life of the breast milk treated by the method is not less than 3 days.

Wherein the fresh breast milk refers to the breast milk which is preserved in an environment of-1-10 ℃ immediately after being extruded, and the maximum time interval from the subsequent heating treatment is 2 h. Preferably, the refrigeration temperature is from-1 ℃ to 4 ℃.

As a specific embodiment of the invention, fresh breast milk is uniformly heated, specifically, a water bath heating mode is adopted.

As a specific embodiment of the invention, the fresh breast milk is uniformly heated, added with the food-grade emulsifier and uniformly mixed by stirring.

In one embodiment of the present invention, the cooling is performed by running tap water.

As a specific embodiment of the invention, a refrigerator provides a refrigerated environment of-1-10 ℃.

In a specific embodiment of the present invention, the food-grade emulsifier includes at least one of soybean lecithin, egg yolk lecithin, mono/diglycerol fatty acid ester, carrageenan, and citric acid fatty acid glyceride.

As a specific embodiment of the present invention, the conditions of homogenization: the homogenizing speed is 10000-.

As an embodiment of the invention, the equipment used for homogenization is a small household homogenizer.

As a specific embodiment of the invention, the method comprises the following steps:

(1) uniformly heating fresh breast milk to 45-65 ℃, adding a food-grade emulsifier with the mass fraction of 0.02-0.10%, and uniformly mixing;

(2) homogenizing the breast milk obtained in the step (1), cooling to room temperature, sealing, and refrigerating at-1-10 deg.C; monitoring fatty acid related indexes in the refrigeration process: acid odor, pH, titratable acidity and free fatty acid content; and (3) stopping refrigeration when the fatty acid related index is mutated, and determining the refrigerated shelf life of the breast milk according to the mutation of the acid odor, the pH value, the titratable acidity or the free fatty acid, wherein the mutation is determined according to the statistical significance difference of the p <0.05 level.

A second object of the present invention is to provide the use of the aforementioned long-term cold storage method for the cold storage of human breast milk or fresh animal milk.

A third object of the present invention is to provide fresh breast milk prepared by the aforementioned long-term refrigeration method; the refrigerated shelf life of the fresh breast milk is not less than 3 days.

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the invention, a treatment method of adding a food-grade emulsifier in combination with homogenization is adopted, and the fat deterioration can be remarkably delayed through the synergistic effect of the food-grade emulsifier and the homogenization, so that the indexes such as acid odor, pH, acidity and free fatty acid in the breast milk refrigeration period are remarkably improved, the quality guarantee period of the breast milk is prolonged, and the refrigeration freshness of the breast milk can be well maintained; meanwhile, the refrigerated breast milk can also keep the flavor and the nutritional value.

(2) According to the long-term cold storage method for the fresh breast milk, the food-grade emulsifier is added and the homogenization treatment is combined, and the combined technical scheme has the advantages that the technical effects of delaying fat deterioration and prolonging the cold storage quality guarantee period of the breast milk are superior to the sum of cold storage effects which can be achieved by the cold storage treatment method with the food-grade emulsifier added and the homogenization treatment added separately.

(3) According to the method, the food-grade emulsifier is added into the breast milk, the homogenization method is adopted to assist the refrigerator to refrigerate the breast milk, four indexes of acid odor, pH, titratable acidity and free fatty acid during the breast milk refrigeration are respectively measured, and the result shows that the breast milk refrigerated by the method is more than 3 days, the indexes related to the fatty acid are mutated, the degradation delay rate of all indexes is more than 40%, and the average delay rate is more than 70%. Therefore, the invention can prolong the time for refrigerating breast milk to more than 3 days.

(4) The invention provides a new method for family preservation of fresh breast milk, and the method is simple and convenient to operate and low in cost.

Drawings

FIG. 1 shows sensory evaluation scores of sour odor during the preservation of breast milk in example 1 and comparative example 1.

FIG. 2 is a line graph showing the fitting trend of the sensory evaluation score of sour odor during the preservation of breast milk in example 1 and comparative example 1.

Fig. 3 is a graph showing changes in pH during the preservation of breast milk in example 1 and comparative example 1.

Fig. 4 is a graph showing a trend of a pH change during the process of preserving breast milk according to example 1 and comparative example 1.

Fig. 5 shows changes in acidity during the preservation of breast milk in example 1 and comparative example 1.

Fig. 6 is a graph showing a trend of the acidity change during the process of preserving breast milk in example 1 and comparative example 1.

Fig. 7 shows the change of free fatty acid during the process of preserving breast milk in example 1 and comparative example 1.

Fig. 8 is a line graph showing the fitted trend of free fatty acid changes during the process of preserving breast milk of example 1 and comparative example 1.

Note: the capital letters in the above figures 1, 5, 7 indicate significant differences between different samples at the same time (intra-group differences), the lower case letters indicate differences between the same samples at different times (inter-group differences), p < 0.05; the homogeneous + emulsifier group in FIGS. 1 to 8 above shows the results of example 1, and the untreated group shows the results of comparative example 1.

Detailed Description

The following description of the preferred embodiments of the present invention is provided for the purpose of better illustrating the invention and is not intended to limit the invention thereto.

The test methods involved in the examples of the invention and the comparative examples are as follows:

sour and stink smellThe index is obtained by scoring the sour and odorous degree of the breast milk in the cold storage process by 12 sensory panel judges, wherein the total score is 0-5 (the sour and odorous degree increases along with the score), the score interval is 1, and the final score is the score after the average value is obtained.

pH valueThe measurement was performed by a pH meter.

Titratable acidityThe determination is carried out by adopting a phenolphthalein indicator method which is the first method in GB5009.239-2016 (determination of food safety national standard food acidity).

Free fatty acid contentFree fatty acid (NEFA) assay kit (colorimetric method) was used for the assay.

Content of volatile flavor componentDetermination of breast milk by headspace solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS)And (3) taking a proper amount of liquid breast milk into a 20mL screw glass bottle, inserting a solid phase extraction head for adsorption balance, extracting at 40 ℃ for 20min, and finally analyzing at a GC sample injection port. GC-MS parameter conditions: the chromatographic column is a capillary chromatographic column (TRWAXMS 30m × 0.25mm × 0.25 mm); temperature rising procedure: the initial column temperature was 40 deg.C, held for 3min, ramped up to 120 deg.C at 4 deg.C/min, ramped up to 240 deg.C at 10 deg.C/min, and held for 8 min. The carrier gas is high-purity helium, and the flow rate is 1.0 mL/min; in a non-shunting mode, the temperature of a sample inlet is 250 ℃, and the temperature of a transmission line is 240 ℃; mass spectrometry conditions Electron Impact (EI) ion source: electron energy 70 eV; the ion source temperature was 240 ℃; filament current 50 muA; mass scan range (m/z): 33 to 450 u. The qualitative method comprises the following steps: and (4) analyzing the identification result by software retrieval and combining the matching degree of NIST library. The quantitative method comprises the following steps: and (4) performing normalization calculation according to the peak area.

Example 1

A method for long-term refrigeration of fresh breast milk, comprising the steps of:

(1) the lactating volunteers provided fresh breast milk for 2h (fresh breast milk means that the breast milk was kept in an environment of-1 deg.C-10 deg.C immediately after expression, and the maximum time interval to the subsequent heat treatment was 2 h).

(2) And (3) preheating the obtained fresh breast milk in a water bath at 60 ℃, and maintaining the constant temperature of 60 ℃ to obtain the constant-temperature breast milk.

(3) Adding 0.05% soybean phospholipid (food-grade emulsifier) into constant temperature breast milk, and stirring.

(4) Homogenizing the breast milk obtained in the step (3) by using a small household homogenizer (specification 800w, model HB8020S, sold on the market) to obtain homogenized breast milk: the homogenizing speed of the small household homogenizer is 25000rpm/min, and the homogenizing time is 8 min.

(5) And (4) cooling the homogenized breast milk obtained in the step (4) to room temperature by using running tap water, and sealing.

(6) And (5) refrigerating the breast milk obtained in the step (5) in a refrigerator at 4 ℃.

(7) Fatty acid related indices were monitored during the cold storage, all of which determined the time points of 0, 16, 24, 40, 48, 64, 72, 88 and 96h of breast milk cold storage.

(8) And determining the time point of the mutation of the fatty acid related index.

Comparative example 1 (untreated)

The traditional refrigeration method of fresh breast milk comprises the following steps:

(1) the lactating volunteers provided fresh breast milk for 2h (fresh breast milk means that the breast milk was kept in an environment of-1 ℃ to 10 ℃ immediately after expression, with a maximum time interval of 2h to subsequent treatment).

(2) And (3) refrigerating the breast milk obtained in the step (1) in a refrigerator at 4 ℃.

(3) Fatty acid related indices were monitored during the cold storage, all of which determined the time points of 0, 16, 24, 40, 48, 64, 72, 88 and 96h of breast milk cold storage.

(4) And determining the time point of the mutation of the fatty acid related index.

Soybean lecithin is used as a food emulsifier, breast milk (recorded as homogenizing plus emulsifier) obtained by combining food-grade emulsifier in embodiment 1 of the invention with homogenizing treatment and fatty acid related indexes of the breast milk (recorded as untreated) obtained by directly refrigerating untreated breast milk in comparative example 1 are monitored, and the test results are shown in figures 1-8.

Comparative example 1: referring to fig. 1-2, the sour odor of breast milk of comparative example 1 begins to mutate when refrigerated for 16h, generating sour odor; from the pH, referring to FIGS. 3-4, the breast milk of comparative example 1 was significantly reduced in pH after 24h of refrigeration, to about 6.5 at 40h, and then continued to maintain the downward trend; from the titratable acidity, referring to fig. 5-6, the acidity of the breast milk of the comparative example 1 is always much higher than that of the breast milk treated by the example 1 within 96h of refrigeration; referring to FIGS. 7 to 8, the initial value of free fatty acid in breast milk of comparative example 1 was low in the initial stage of cold storage (0 to 40 hours), but after 16 hours, the content of free fatty acid began to rise significantly, reaching a maximum of 3900. mu. mol/L at 72 hours, at which point significant deterioration of breast milk had occurred. The refrigerated shelf life of the breast milk of comparative example 1 was 16h by comprehensive analysis.

Example 1: as shown in figures 1-2, the human milk sour odor of example 1 of the present invention began to mutate at 72h of refrigeration, resulting in a slight sour odor; as shown in fig. 3-4, the pH of the breast milk treated with the homogenized emulsifier in example 1 decreased more slowly during the cold storage than the breast milk not treated and directly cooled in comparative example 1, and remained at about 7 at 72h of cold storage; as shown in FIGS. 5-6, from the titratable acidity, the acidity of the homogenized and emulsifier treated breast milk of example 1 of the present invention was very low and began to mutate at 88 h; as shown in FIGS. 7-8, the initial value of free fatty acid in breast milk treated with the homogenized emulsifier of example 1 of the present invention was higher than that of comparative example 1, but the free fatty acid began to change significantly only after being refrigerated for 40h, but was stable in both the time periods of 0-24h and 48-96h, and the free fatty acid content at 96h was comparable to that of comparative example 1 when being refrigerated for 64 h. The breast milk of example 1, on a comprehensive analysis, had a refrigerated shelf life of at least 72 hours (3 days).

It is shown that the refrigerated shelf life of the breast milk treated in example 1 of the present invention is significantly extended compared to the breast milk refrigerated without treatment.

The data monitored for fatty acid related indicators of breast milk cold storage of example 1 and control 1 were analyzed by linear fit and summarized in table 1, wherein the data for the fit of example 1 to control 1 are shown in fig. 2, 4, 6 and 8.

As is clear from the analysis of Table 1, the deterioration delay ratios of all the indexes of the method of example 1 are 40% or more, and the average delay ratio is 70% or more. Therefore, the invention can prolong the time for refrigerating breast milk to more than 3 days.

TABLE 1 Change in Key index of quality deterioration in Breast milk at 4 ℃ in comparative example 1 and example 1

Note: the degradation reduction rate (%) was (control slope-homogeneous + emulsifier slope)/control slope × 100.

The change in the content of flavor components (ug/kg) in breast milk during the cold storage at 4 ℃ of the breast milk of comparative example 1 and example 1 was monitored.

Table 2 comparison of the change in the content of flavor ingredient (ug/kg) in breast milk during the cold storage at 4 ℃ in the breast milk of comparative example 1 and example 1

From the data analysis in Table 2 and the combination of the sour odor results (FIGS. 1-2), it is clear that the main flavor changes in breast milk are a sharp increase in the contents of butyric acid and caproic acid, and an increase in the contents of acetic acid, myristic acid and nonanal. In the cold storage process, the acetic acid content generally has a trend of increasing firstly and then decreasing, and reaches a maximum of 1.54ug/kg at 24h in example 1, while the acetic acid content in comparative example 1 is 5.97uk/kg, which is decreased by 74.20%; and at 96h, the acetic acid content of comparative example 1 was also higher than the maximum value of example 1 during refrigeration. The butyric acid content and the caproic acid content are always increased in the refrigeration process, but the slope of the butyric acid increase curve obtained by experimental fitting in example 1 is 0.0415, while the slope of the butyric acid increase curve in comparative example 1 is 0.097, and the slope of the butyric acid increase curve in example 1 is reduced by 57.22% compared with that in comparative example 1; the slope of the curve for the caproic acid increase in example 1 was 0.1749, compared to 0.4574 for comparative example 1, which is a 61.76% slower increase in example 1 compared to comparative example 1; the total of pelargonic acid, benzoic acid, myristic acid, capric acid and pelargonic acid remained virtually unchanged or decreased in example 1, whereas the contents of myristic acid and pelargonic acid increased in comparative example 1. The taste difference of the breast milk in the cold storage process is greatly related to the content of the medium-short chain free fatty acid, the medium-short chain fatty acid is volatile, the contribution to the flavor of the breast milk is the largest, such as butyric acid and caproic acid, along with the prolonging of the storage time, triglyceride is hydrolyzed, and the chain breakage of the long-chain fatty acid is possible, so that the content of the butyric acid and the caproic acid is higher and higher, and the milk is an important reason for causing the sour and the stink of the breast milk. This shows that the breast milk of example 1 has not been significantly deteriorated within 3 days of cold storage and has a good shelf life. Illustrating that the method of the present invention is useful for maintaining refrigerated freshness of breast milk; meanwhile, the refrigerated breast milk can also keep the flavor and the nutritional value. Table 2 the data can further demonstrate that the refrigerated shelf life of the breast milk of example 1 of the present invention is at least 3 days.

Example 2

A method of long term refrigeration of fresh breast milk, with reference to example 1, the only difference being that the food emulsifier is replaced by soya lecithin for egg lecithin. Specifically, the method comprises the following steps:

a method for long-term refrigeration of fresh breast milk, comprising the steps of:

(1) the lactating volunteers provided fresh breast milk for 2h (fresh breast milk means that the breast milk was kept in an environment of-1 deg.C-10 deg.C immediately after expression, and the maximum time interval to the subsequent heat treatment was 2 h).

(2) And (3) preheating the obtained fresh breast milk in a water bath at 60 ℃, and maintaining the constant temperature of 60 ℃ to obtain the constant-temperature breast milk.

(3) Adding 0.05% yolk phospholipid (food-grade emulsifier) into constant temperature breast milk, and stirring.

(4) Homogenizing the breast milk obtained in the step (3) by using a small household homogenizer (specification 800w, model HB8020S, sold on the market) to obtain homogenized breast milk: the homogenizing speed of the small household homogenizer is 25000rpm/min, and the homogenizing time is 8 min.

(5) And (4) cooling the homogenized breast milk obtained in the step (4) to room temperature by using running tap water, and sealing.

(6) And (5) refrigerating the breast milk obtained in the step (5) in a refrigerator at 4 ℃.

(7) Fatty acid related indices were monitored during the cold storage, all of which determined the time points of 0, 16, 24, 40, 48, 64, 72, 88 and 96h of breast milk cold storage.

(8) And determining the time point of the mutation of the fatty acid related index.

The yolk phospholipid is adopted as the food emulsifier, and the fatty acid related index of the breast milk obtained by the food-grade emulsifier combined homogenization treatment in the embodiment 2 of the invention in the refrigeration process is monitored, and the result shows that:

the breast milk sour odor of the embodiment 2 of the invention begins to mutate when being refrigerated for 72h, and generates a slight sour odor; the breast milk treated with the homogenized emulsifier in example 2 had a pH value which decreased slowly compared to the control during cold storage, and remained at about 6.9 during 72 hours of cold storage; from the titratable acidity, the acidity of the breast milk treated by the homogenizing and emulsifying agent in the embodiment 2 of the invention is extremely low and the breast milk begins to mutate after 72 hours; the initial value of the free fatty acid of the breast milk treated by the homogenizing emulsifier in the embodiment 2 is higher than that of the control group, but the free fatty acid begins to change significantly only after being refrigerated for 48 hours, but slowly increases from the whole and is more stable. As a general analysis, the breast milk of example 2 of the present invention had a refrigerated shelf life of at least 3 days.

Example 3

A method of long term refrigeration of fresh breast milk, with reference to example 1, the only difference being that the food emulsifier is replaced by soya lecithin to glyceryl citrate fatty acid ester. Specifically, the method comprises the following steps:

a method for long-term refrigeration of fresh breast milk, comprising the steps of:

(1) the lactating volunteers provided fresh breast milk for 2h (fresh breast milk means that the breast milk was kept in an environment of-1 deg.C-10 deg.C immediately after expression, and the maximum time interval to the subsequent heat treatment was 2 h).

(2) And (3) preheating the obtained fresh breast milk in a water bath at 60 ℃, and maintaining the constant temperature of 60 ℃ to obtain the constant-temperature breast milk.

(3) Adding 0.05% citric acid fatty glyceride (food-grade emulsifier) into constant temperature breast milk, and stirring.

(4) Homogenizing the breast milk obtained in the step (3) by using a small household homogenizer (specification 800w, model HB8020S, sold on the market) to obtain homogenized breast milk: the homogenizing speed of the small household homogenizer is 25000rpm/min, and the homogenizing time is 8 min.

(5) And (4) cooling the homogenized breast milk obtained in the step (4) to room temperature by using running tap water, and sealing.

(6) And (5) refrigerating the breast milk obtained in the step (5) in a refrigerator at 4 ℃.

(7) Fatty acid related indices were monitored during the cold storage, all of which determined the time points of 0, 16, 24, 40, 48, 64, 72, 88 and 96h of breast milk cold storage.

(8) Determining the time point of the mutation of the fatty acid related index

The fatty acid glyceride citrate is used as a food emulsifier, and the fatty acid related index of the breast milk obtained by the food-grade emulsifier combined homogenization treatment in the embodiment 3 of the invention in the refrigeration process is monitored, and the result shows that:

the breast milk sour odor of the embodiment 3 of the invention begins to mutate when being refrigerated for 72h, and generates a slight sour odor; the breast milk treated with the homogenized emulsifier of example 3 had a pH value that decreased slowly during cold storage compared to the control, and remained at about 7 at 64 h; from the titratable acidity, the acidity of the breast milk treated by the homogenizing and emulsifying agent in the embodiment 3 of the invention is extremely low and the mutation begins to occur at 64 h; the initial value of the free fatty acid of the breast milk treated by the homogenizing emulsifier in the embodiment 3 is higher than that of the control group, but the free fatty acid begins to change significantly only after being refrigerated for 40 hours, but is stable before and after 40 hours. Thus, the refrigerated shelf life of the breast milk of example 3 of the present invention was at least 3 days.

Example 4

A method for the long-term refrigeration of fresh breast milk, with reference to example 1, with the only difference that the bath temperature is adjusted to 55 ℃.

Specifically, the method comprises the following steps:

a method for long-term refrigeration of fresh breast milk, comprising the steps of:

(1) the lactating volunteers provided fresh breast milk for 2h (fresh breast milk means that the breast milk was kept in an environment of-1 deg.C-10 deg.C immediately after expression, and the maximum time interval to the subsequent heat treatment was 2 h).

(2) And (3) preheating the obtained fresh breast milk in a water bath at 55 ℃, and maintaining the constant temperature of 60 ℃ to obtain the constant-temperature breast milk.

(3) Adding 0.05% soybean phospholipid (food-grade emulsifier) into constant temperature breast milk, and stirring.

(4) Homogenizing the breast milk obtained in the step (3) by using a small household homogenizer (specification 800w, model HB8020S, sold on the market) to obtain homogenized breast milk: the homogenizing speed of the small household homogenizer is 25000rpm/min, and the homogenizing time is 8 min.

(5) And (4) cooling the homogenized breast milk obtained in the step (4) to room temperature by using running tap water, and sealing.

(6) And (5) refrigerating the breast milk obtained in the step (5) in a refrigerator at 4 ℃.

(7) Fatty acid related indices were monitored during the cold storage, all of which determined the time points of 0, 16, 24, 40, 48, 64, 72, 88 and 96h of breast milk cold storage.

(8) Determining the time point of the mutation of the fatty acid related index

By monitoring the fatty acid related index of the breast milk obtained by the food-grade emulsifier combined homogenization treatment in the embodiment 4 of the invention in the refrigeration process, the result shows that:

the breast milk sour odor of the embodiment 4 of the invention begins to mutate when being refrigerated for 72h, and generates a slight sour odor; the breast milk treated with the homogenized and emulsifier of example 4 had a pH value that decreased slowly during cold storage compared to the control, and remained at about 7 at 72h of cold storage; from the titratable acidity, the acidity of the breast milk treated by the homogenizing and emulsifying agent in the embodiment 4 of the invention is extremely low and the breast milk begins to mutate after 72 hours; the initial value of the free fatty acid of the breast milk treated by the homogenizing emulsifier in the embodiment 4 of the invention is higher than that of the control group, but the free fatty acid begins to change significantly only after being refrigerated for 40h, but is stable before and after 40 h. In summary, the refrigerated shelf life of the breast milk of example 4 of the present invention was at least 3 days.

Example 5

A method for long-term cold storage of fresh breast milk, with reference to example 1, except that the homogenization time was adjusted to 5 min.

By monitoring the fatty acid related index of the breast milk obtained by the food-grade emulsifier combined homogenization treatment in the embodiment 5 of the invention in the refrigeration process, the result shows that:

the breast milk sour odor of the embodiment 5 of the invention begins to mutate when being refrigerated for 72h, and generates a slight sour odor; the breast milk treated with the homogenized and emulsifier of example 5 had a pH value that decreased slowly during cold storage compared to the control, and remained at about 7 at 64 h; from the titratable acidity, the acidity of the breast milk treated by the homogenizing and emulsifying agent in the embodiment 5 of the invention is extremely low and the mutation begins to appear at 64 h; the initial value of the free fatty acid of the breast milk treated by the homogenizing emulsifier in the embodiment 5 of the invention is higher than that of the control group, but the free fatty acid begins to change significantly only after being refrigerated for 40h, but is stable before and after 40 h. In summary, the refrigerated shelf life of the breast milk of example 5 of the present invention was at least 3 days.

Example 6

A method for long-term cold storage of fresh breast milk, as described in example 1, except that the homogenization rate was adjusted to 20000rpm/min and the homogenization time was adjusted to 10 min.

By monitoring the fatty acid related index of the breast milk obtained by the food-grade emulsifier combined homogenization treatment in the embodiment 6 of the invention in the refrigeration process, the results show that:

the breast milk sour odor of the embodiment 6 of the invention begins to mutate when being refrigerated for 72h, and generates a slight sour odor; the breast milk treated with the homogenized and emulsifier of example 6 had a pH value that decreased slowly during cold storage compared to the control, and remained at about 7 at 64 h; from the titratable acidity, the acidity of the breast milk treated by the homogenizing and emulsifying agent in the embodiment 6 of the invention is extremely low and the mutation begins to appear at 64 h; the initial value of the free fatty acid of the breast milk treated by the homogenizing emulsifier in the embodiment 6 of the invention is higher than that of the control group, but the free fatty acid begins to change significantly only after being refrigerated for 40h, but is stable before and after 40 h. In summary, the refrigerated shelf life of the breast milk of example 6 of the present invention was at least 3 days.

Example 7

A method for long-term storage of fresh breast milk, which is different from example 1 only in that the relative amount of soybean phospholipids added is adjusted to 0.1%.

By monitoring the fatty acid related index of the breast milk obtained by the food-grade emulsifier combined homogenization treatment in the embodiment 8 of the invention in the refrigeration process, the results show that:

the breast milk sour odor of the embodiment 8 of the invention begins to mutate when being refrigerated for 72h, and generates a slight sour odor; the breast milk treated with the homogenized and emulsifier of example 8 had a pH value that decreased slowly during refrigeration compared to the control, and remained at about 7 at 88h of refrigeration; from the titratable acidity, the acidity of the breast milk treated by the homogenizing and emulsifying agent in the embodiment 8 of the invention is extremely low and the mutation begins to occur at 88 h; the initial value of the free fatty acid of the breast milk treated by the homogenizing emulsifier in the embodiment 8 of the invention is higher than that of the control group, but the free fatty acid begins to change significantly only after being refrigerated for 48 hours, but is stable before and after 48 hours. In summary, the refrigerated shelf life of the breast milk of example 8 of the present invention was at least 3 days.

Example 8

A method for long-term storage of fresh breast milk, which is different from that of example 1 only in that the refrigerator storage temperature in step (6) is adjusted to 0 ℃ and 10 ℃.

By monitoring the fatty acid related index of the breast milk obtained by the food-grade emulsifier combined homogenization treatment in the embodiment 9 of the invention in the refrigeration process, the results show that:

when the refrigerating temperature of the refrigerator in the step (6) is adjusted to be 0 ℃, the breast milk sour odor of the embodiment 9 of the invention begins to mutate when being refrigerated for 72 hours, and slight sour odor is generated; the breast milk treated with the homogenized and emulsifier of example 9 had a pH value that decreased slowly during refrigeration compared to the control, and remained at about 7 at 88h of refrigeration; from the titratable acidity, the acidity of the breast milk treated by the homogenizing and emulsifying agent in the embodiment 9 of the invention is extremely low and the mutation begins to occur at 88 h; the initial value of the free fatty acid of the breast milk treated by the homogenizing emulsifier in the embodiment 9 is higher than that of the control group, but the free fatty acid begins to change significantly only after being refrigerated for 48 hours, but is stable before and after 48 hours. Thus, the refrigerated shelf life of the breast milk of example 8 of the present invention was at least 3 days.

Comparative example 2 (homogeneous alone)

A method of long term refrigeration of fresh breast milk, with reference to example 1, the only difference being that the addition of a food emulsifier in step (3) is omitted.

Comparative example 3 (emulsifier only)

A method for long-term refrigeration of fresh breast milk, with reference to example 1, with the only difference that the homogenization process of steps (2), (4) and (5) is omitted, comprising the following steps:

(1) the lactating volunteers provided fresh breast milk for 2h (fresh breast milk means that the breast milk was kept in an environment of-1 ℃ to 10 ℃ immediately after expression, with a maximum time interval of 2h to subsequent treatment).

(2) Adding 0.05% soybean phospholipid (food grade emulsifier) into breast milk, and stirring.

(3) And (3) refrigerating the breast milk obtained in the step (2) in a refrigerator at 4 ℃.

(4) Fatty acid related indices were monitored during the cold storage, all of which determined the time points of 0, 16, 24, 40, 48, 64, 72, 88 and 96h of breast milk cold storage.

(5) And determining the time point of the mutation of the fatty acid related index.

The data monitored for the fatty acid related indicators of breast milk cold storage of control examples 2-3 and example 1 were analyzed by linear fit and summarized in table 3.

TABLE 3 Change in Key index of quality deterioration in Cold storage at 4 ℃ of breast milk of comparative examples 2-3 and example 1

Analysis of table 3 shows that the three indexes of sour odor, pH and acidity in example 1 are significantly improved as compared with those of comparative examples 2 and 3. The experiment process shows that the acid odor of the comparative example 3 has mutation at 16h, which is equivalent to that of the comparative example 1, and the acid odor of the comparative example 2 begins to have mutation at 40 h. Analysis of the data in tables 1 and 3 shows that the milk quality is improved significantly by the homogenization treatment, but when the homogenization treatment is combined with the addition of the emulsifier, the degradation rate of the acid odor is 85.27%, the degradation rate of the pH is 61.71%, the degradation rate of the acidity is 88.63%, and the free fatty acids are closer to those of comparative example 2. Therefore, the long-term refrigeration method for fresh breast milk provided by the invention has the advantages that the food-grade emulsifier is added and combined with homogenization treatment, and the combined technical scheme has the technical effects of delaying fat deterioration and prolonging the refrigeration quality guarantee period of the breast milk, and is superior to the sum of refrigeration effects which can be achieved by the method of singly homogenizing treatment and singly adding the food-grade emulsifier.

In conclusion, the processing method of adding the food-grade emulsifier and homogenizing is adopted, and the fat degradation can be remarkably delayed through the synergistic effect of the food-grade emulsifier and the homogenizing, so that the indexes of acid odor, pH, acidity, free fatty acid and the like in the breast milk refrigeration period are remarkably improved, the quality guarantee period of the breast milk is prolonged, and the refrigeration freshness of the breast milk can be well maintained; meanwhile, the refrigerated breast milk can also keep the flavor and the nutritional value.

Example 9

The use of the long-term refrigeration method of examples 1-8 for the refrigerated storage of human breast milk or fresh animal milk. The shelf life of human breast milk or animal fresh milk in a refrigeration environment can be remarkably prolonged, and the flavor and the nutritional value of the breast milk can be kept after refrigeration.

Finally, it should be noted that: the above embodiments are only used to help understand the technical solution and core idea of the present invention, and the scope is not limited thereto; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: it is possible to modify the solutions described in the embodiments or to substitute some or all of the technical features of the embodiments, and these modifications or substitutions also fall within the scope of the claims of the present invention.