Method for evaluating quality of liquid milk

Abstract

The invention provides a method for evaluating the quality of liquid milk. The method comprises the following steps: acquiring the content of active substances and the content of microbial markers of the liquid milk; obtaining an activity index F of the liquid milk according to the content of the active substances; obtaining a safety index S of the liquid milk according to the content of the microbial marker; and evaluating the quality of the liquid milk according to the activity index F and the safety index S. The liquid milk quality evaluation method provided by the invention has the characteristics that the nutritional quality and the safety quality of the liquid milk can be objectively evaluated, and the accuracy is relatively high.

Description

Technical Field

[0001] The invention relates to an evaluation method, in particular to an evaluation method for liquid milk quality, and belongs to the field of food engineering. Background Art

[0002] Liquid milk contains active substances that are beneficial to the human body. These active substances are easily inactivated when the liquid milk is sterilized at high temperatures or ultra-high temperatures. However, to ensure safety, sterilization or disinfection is required to reduce the content of microorganisms in the liquid milk.

[0003] Therefore, liquid milk with higher quality should contain fewer microorganisms while retaining more active substances. The content of active substances and microorganisms are both indicators for evaluating the quality of liquid milk.

[0004] At present, there is no evaluation method for the above qualities of liquid milk. Therefore, developing a method for evaluating the quality of liquid milk has become the current research direction. Summary of the invention

[0005] The invention provides a method for evaluating the quality of liquid milk, which has the characteristics of being able to objectively evaluate the nutritional quality and microbial safety quality of liquid milk.

[0006] The present invention provides a method for evaluating the quality of liquid milk, wherein the evaluation method comprises the following steps:

[0007] 1) obtaining the content of active substances and the content of microbial markers in the liquid milk;

[0008] 2) obtaining an activity index F of the liquid milk according to the content of the active substance;

[0009] 3) obtaining a safety index S of the liquid milk according to the content of the microbial marker;

[0010] 4) evaluating the quality of the liquid milk according to the activity index F and the safety index S.

[0011] The evaluation method as described above, wherein the active substances include lactoperoxidase, lactoferrin, immunoglobulin, protease and lipase.

[0012] In the above evaluation method, the step of obtaining the activity index F of the liquid milk according to the content of the active substance comprises:

[0013] The activity index F is calculated according to Formula 1:

[0014] F = (0.004F1 + 0.11F2 + 0.02F3 - 0.02F4 - 0.32F5) / P Formula 1;

[0015] in:

[0016] F1 is the lactoperoxidase content of liquid milk, U / L;

[0017] F2 is the lactoferrin content of liquid milk, mg / L;

[0018] F3 is the immunoglobulin content of liquid milk, mg / L;

[0019] F4 is the protease content of liquid milk, U / 100mL;

[0020] F5 is the lipase content of liquid milk, mg / g;

[0021] P is the total protein content of liquid milk, g / 100mL.

[0022] In the evaluation method as described above, the microbial markers include total colony count, thermotolerant psychrophilic bacteria, and endotoxin.

[0023] The evaluation method as described above, wherein the step of obtaining the safety index S of the liquid milk according to the content of the microbial marker comprises:

[0024] The safety index S is calculated according to Formula 2:

[0025]

[0026] in:

[0027] S1 is the total colony count of liquid milk, CFU / mL;

[0028] S2 is the content of thermotolerant psychrophilic bacteria in liquid milk, CFU / mL;

[0029] S3 is the endotoxin content of liquid milk, logEU / mL;

[0030] d is the number of days between the production date and the inspection date, d.

[0031] The evaluation method as described above, wherein the quality of the liquid milk is evaluated according to the activity index F and the safety index S, comprises:

[0032] Evaluating the nutritional quality of the liquid milk according to the first corresponding relationship between the activity index F, the preset activity index and the nutritional quality grade of the liquid milk; and / or,

[0033] The safety quality of the liquid milk is evaluated according to the second corresponding relationship among the safety index S, the preset safety index and the safety quality grade of the liquid milk.

[0034] In the evaluation method as described above, the first corresponding relationship includes:

[0035] If the preset activity index is ≥ 0, the nutritional quality of the liquid milk is level one;

[0036] If the preset activity index is less than 0, the nutritional quality of the liquid milk is level 2;

[0037] The second corresponding relationship includes:

[0038] If the safety index S is ≥ 0, the biosafety quality of the liquid milk is level one;

[0039] If the safety index S is less than 0, the biosafety quality of the liquid milk is level 2.

[0040] The evaluation method as described above, wherein the method further comprises:

[0041] Respectively obtain the activity index F and the safety index S of N different liquid milks, N≥2;

[0042] Obtaining N quality indexes A according to the N activity indexes F and safety indexes S;

[0043] According to the N quality indexes A, the quality differences of N different liquid milks are evaluated.

[0044] In the above evaluation method, the step of obtaining N quality indexes A according to the N activity indexes F and safety index S comprises:

[0045] The quality index A is calculated according to formula 3;

[0046] A=F+S Formula 3.

[0047] In the evaluation method as described above, wherein the step of evaluating the quality differences of N different liquid milks according to the N quality indexes A comprises:

[0048] The first quality index A1>the second quality index A2, then the quality of the first liquid milk is better than the quality of the second liquid milk;

[0049] The first liquid emulsion and the second liquid emulsion are any two of N different liquid emulsions, and the first quality index A1 is the quality index of the first liquid emulsion, and the second quality index A2 is the quality index of the second liquid emulsion.

[0050] The method for evaluating the quality of liquid milk provided by the present invention evaluates the quality of liquid milk by detecting the content of active substances and the content of microbial markers in the liquid milk, and has the characteristics of being able to objectively evaluate the nutritional quality and microbial safety quality of liquid milk. DETAILED DESCRIPTION

[0051] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0052] The present invention provides a method for evaluating the quality of liquid milk, comprising the following steps:

[0053] 1) Obtaining the content of active substances and microbial markers in liquid milk;

[0054] 2) obtaining the activity index F of the liquid milk according to the content of the active substance;

[0055] 3) Obtaining the safety index S of the liquid milk according to the content of the microbial marker;

[0056] 4) Evaluate the quality of liquid milk based on the activity index F and safety index S.

[0057] Liquid milk is a liquid dairy product, including at least one of sterilized milk, sterilized milk, reconstituted milk, and formula milk. The present invention does not limit the specific selection of liquid milk, as long as it can be sampled and the evaluation method provided by the present invention can be completed. For example, liquid milk can be selected from at least one of fresh cow's milk, fresh goat's milk, fresh deer's milk, fresh camel's milk, pasteurized cow's milk, pasteurized goat's milk, pasteurized deer's milk, pasteurized camel's milk, reconstituted cow's milk, reconstituted goat's milk, reconstituted deer's milk, and reconstituted camel's milk. In one embodiment, the liquid milk is commercially available low-temperature milk.

[0058] Active substances are nutrients with biological activity that exist naturally in liquid milk, including active proteins, phosphopeptides, oligosaccharides, conjugated linoleic acid, gangliosides, sphingolipids, milk minerals, growth factors and nucleotides. After entering the human body, the above-mentioned active substances have the functions of resisting the invasion of pathogens such as bacteria, activating the body's immune response, and maintaining the health of the body. Therefore, the content of the above-mentioned active substances can be used as one of the factors to be considered when evaluating the quality of liquid milk. The evaluation method provided by the present invention does not limit the specific types of active substances for content detection, and it is sufficient to select active substances that are beneficial to the human body for content detection. For example, in one embodiment, active protein substances are detected.

[0059] The activity index F is an evaluation index obtained by detecting the content of active substances in liquid milk. The activity index represents the content of active substances in the liquid milk processing process, and can further reflect the nutritional quality of the liquid milk. The present invention does not specifically limit the correspondence between the content of active substances and the activity index. The activity index can reflect the content of active substances in the liquid milk. In one embodiment, the higher the content of active substances, the higher the activity index; the present invention does not specifically limit the specific calculation method of the activity index. For example, in one embodiment, the detected active substance content can be weighted and then weighted calculation can be performed to obtain the activity index.

[0060] Microbial markers are substances in liquid milk that can represent living microorganisms or microbial decomposition residues in liquid milk. Since microorganisms and their metabolites will have a negative impact on human health after entering the human body, it is reasonable to use the content of microbial markers to evaluate the quality of liquid milk. The evaluation method provided by the present invention does not limit the specific types of microbial markers for content detection, and representative microbial markers can be selected for content detection. For example, in one embodiment, the total number of colonies is selected as a microbial marker for detection.

[0061] The safety index S is an evaluation index obtained by detecting the content of microbial markers in liquid milk. The safety index represents the growth trend and reproduction of microorganisms in liquid milk, and can further reflect the safety quality of liquid milk. The present invention does not specifically limit the correspondence between the content of microbial markers and the safety index. The safety index can reflect the content of microbial markers in liquid milk. For example, in one embodiment, the higher the content of microbial markers, the lower the safety index. The present invention does not specifically limit the specific calculation method of the safety index. For example, in one embodiment, the detected microbial marker content can be weighted and then weighted calculation can be performed to obtain the safety index.

[0062] The inventors found that due to differences in sterilization processes, the quality of low-temperature milk currently on the market is uneven. Specifically, in addition to pasteurized milk that really needs to be refrigerated, some high-temperature sterilized milk and ultra-high temperature sterilized milk also promote the concept of needing refrigeration, confusing consumers' cognition; at the same time, even for low-temperature milk that implements the pasteurized milk product standards, its active substance retention rate and microbial safety level are not the same, and the freshness of the products varies greatly. In addition, there are some products with high sterilization intensity or poor raw milk quality that cover up the defect of low active substance retention rate by concentrating the products. Traditional sterilization evaluation methods, such as F value, D value, Z value, C value, etc., although they can reflect the impact of sterilization treatment on microorganisms and heat-sensitive substances, are only applicable to thermal sterilization methods, and require clear sterilization parameters and index detection values ​​for evaluation, and are not applicable to commercially available products, especially products that have been treated by non-thermal sterilization methods.

[0063] Therefore, the present invention provides a method for evaluating the quality of liquid milk by combining product-related indicators such as the thermosensitive active ingredients and total bacterial count of the product. On the one hand, the method can objectively evaluate the sterilization effect of the product, thereby providing suggestions for improving the quality of raw milk and microbial safety of low-temperature milk products. On the other hand, it can also objectively evaluate the freshness of the product and provide a reference direction for product optimization and upgrading.

[0064] Since the activity index F can reflect the nutritional quality of liquid milk, and the safety index S can reflect the safety quality of liquid milk, the use of the activity index F and the safety index S can more objectively and accurately evaluate the quality of liquid milk from the two aspects of nutrition and safety. It is easy to understand that the present invention does not specifically limit the implementation order of step 2), step 3), and step 4). For example, in one embodiment, the nutritional quality of liquid milk can be evaluated according to the activity index F after obtaining the activity index F of liquid milk, and the safety quality of liquid milk can be evaluated according to the safety index S after obtaining the safety index S of liquid milk, without having to evaluate the nutritional quality and safety quality of liquid milk according to the activity index F and the safety index S after obtaining the activity index F and the safety index S. The present invention does not specifically limit the method for evaluating the quality of liquid milk using the activity index F and the safety index S, and it is sufficient to meet the requirements of using the activity index and the safety index to reflect the quality of liquid milk.

[0065] The method of evaluating the quality of liquid milk using the activity index F and the safety index S is closely related to the calculation method of the activity index F and the safety index S. For example, in one embodiment, when the value of the activity index F increases with the increase of the active substance content, the safety index S decreases with the content of the microbial marker, and the values ​​of F and S are not less than 0, the quality of the liquid milk can be reflected by the product of the activity index F and the safety index S. The larger the product value of the activity index F and the safety index S, the higher the quality of the liquid milk.

[0066] The method for evaluating the quality of liquid milk provided by the present invention realizes an objective evaluation of the quality of liquid milk by detecting the content of active substances such as active proteins and the content of microbial markers such as the total colony count in the liquid milk, and has the characteristic of being able to objectively evaluate the nutritional quality and safety quality of liquid milk.

[0067] In one embodiment, the active substances include lactoperoxidase, lactoferrin, immunoglobulins, proteases and lipases.

[0068] Peroxidase, lactoferrin, immunoglobulin, α-lactalbumin and β-lactoglobulin are widely recognized functional active proteins in liquid milk. The above active substances have different thermal stabilities. During the processing of liquid milk, as the intensity of heat treatment increases, the above active substances will suffer different degrees of loss. Generally, the thermal sensitivity is ranked as follows: lactoperoxidase>immunoglobulin>lactoferrin>β-lactoglobulin>α-lactalbumin. Among them, lactoperoxidase is the most sensitive to heat. When the sterilization temperature is less than 70°C, the content slowly decreases with time. When the sterilization temperature is higher, it will denature rapidly and the content will be greatly reduced. However, α-lactalbumin and β-lactoglobulin are relatively insensitive to heat and have less loss during heat sterilization. Therefore, the selection of lactoperoxidase, lactoferrin and immunoglobulin with higher thermal sensitivity as active substances for content detection can more objectively reflect the nutritional quality of liquid milk. The higher the content of active substances with higher thermal sensitivity, the higher the nutritional quality of liquid milk.

[0069] Protease and lipase can decompose the protein and fat contained in liquid milk, causing the quality of liquid milk to deteriorate. Therefore, the presence of protease and lipase is one of the main reasons for the quality deterioration of liquid milk during its shelf life. The higher the content of protease and lipase in liquid milk, the faster the quality of liquid milk deteriorates. Therefore, testing the content of protease and lipase in liquid milk can also reflect the nutritional quality of liquid milk.

[0070] Therefore, taking lactoperoxidase, lactoferrin, immunoglobulin, protease and lipase as active substances and detecting their contents can better reflect the degree of retention of beneficial active ingredients (lactoperoxidase, lactoferrin, immunoglobulin) and the degree of inactivation of harmful active ingredients (protease, lipase) during the processing of liquid milk, thereby making the evaluation method provided by the present invention more accurate.

[0071] Further, in one embodiment, obtaining the activity index F of the liquid milk according to the content of the active substance includes:

[0072] The activity index F was calculated according to formula 1:

[0073] F = (0.004F1 + 0.11F2 + 0.02F3 - 0.02F4 - 0.32F5) / P Formula 1;

[0074] in:

[0075] F1 is the lactoperoxidase content of liquid milk, U / L;

[0076] F2 is the lactoferrin content of liquid milk, mg / L;

[0077] F3 is the immunoglobulin content of liquid milk, mg / L;

[0078] F4 is the protease content of liquid milk, U / 100mL;

[0079] F5 is the lipase content of liquid milk, mg / g;

[0080] P is the total protein content of liquid milk, g / 100mL.

[0081] Formula 1 is used to calculate the activity index F of liquid milk. According to Formula 1, the activity index F of liquid milk is positively correlated with the lactoperoxidase content F1 of liquid milk, the lactoferrin content F2 of liquid milk, and the immunoglobulin content F3 of liquid milk, respectively, and negatively correlated with the protease content F4 of liquid milk and the lipase content F5 of liquid milk, that is, when the lactoperoxidase content F1, the lactoferrin content F2 of liquid milk, and the immunoglobulin content F3 of liquid milk are higher, the activity index F of liquid milk is higher; and when the protease content F4 of liquid milk and the lipase content F5 of liquid milk are higher, the activity index F of liquid milk is lower.

[0082] The inconsistency of basic indicators in existing liquid milk products will bring difficulties to the quality evaluation of liquid milk. In particular, the content of active protein in concentrated liquid milk often increases significantly, making it difficult to evaluate objectively. Therefore, Formula 1 refers to the protein content of liquid milk products on the market, standardizes various indicators, converts them into the content corresponding to every 3.2g of protein, and introduces the total protein content P as a calculation parameter.

[0083] At the same time, based on a large number of studies, the inventors preliminarily set the weighting coefficients for each parameter in Formula 1 according to the thermal stability of different components and their impact on product quality as follows: lactoperoxidase: lactoferrin: immunoglobulin: protease: lipase = 5:3:2:0.5:0.5; in addition, the inventors determined the benchmark values ​​of each indicator through analysis of relevant indicators of commercially available liquid milk products: protein content is 3.2g / 100ml, lactoperoxidase is about 3700U / L, lactoferrin is 85mg / L, immunoglobulin is 360mg / L, protease is 80U / 100ml, and lipase is 5mg / g. Finally, the weighting coefficients are combined with indicator standardization to obtain the coefficients of each item in Formula 1.

[0084] Since Formula 1 fully considers the thermal stability of each active substance, its influence on product quality and product index standardization factors, when the activity index F of the liquid milk is calculated using Formula 1, the evaluation method provided by the present invention has the characteristic of higher accuracy.

[0085] In one embodiment, the microbial markers include total colony count, thermotolerant psychrophilic bacteria, and endotoxin.

[0086] Both the total colony count and thermotolerant psychrophilic bacteria can directly reflect the microbial safety of liquid milk products after processing, but the evaluation conditions are different. Compared with the total colony count, thermotolerant psychrophilic bacteria can better reflect the microbial proliferation of liquid milk under refrigerated sales conditions. Endotoxins are derived from microbial lysis products and can directly reflect the level of microorganisms in raw milk, thereby evaluating the quality of raw milk used to make liquid milk.

[0087] Therefore, using total colony count, thermotolerant psychrophilic bacteria, and endotoxin as microbial markers to obtain the safety index S of liquid milk can evaluate the survival of microorganisms and the residual status of inactivated microorganisms in liquid milk products, and further evaluate the safety quality of liquid milk, so that the evaluation method provided by the present invention has higher accuracy.

[0088] Furthermore, according to the content of the microbial marker, the safety index S of the liquid milk is obtained, including:

[0089] Calculate the safety index S according to formula 2:

[0090]

[0091] in:

[0092] S1 is the total colony count of liquid milk, CFU / mL;

[0093] S2 is the content of thermotolerant psychrophilic bacteria in liquid milk, CFU / mL;

[0094] S3 is the endotoxin content of liquid milk, logEU / mL;

[0095] d is the number of days between the production date and the inspection date, d.

[0096] Formula 2 is used to calculate the safety index S of liquid milk. According to Formula 2, the safety index S of liquid milk is negatively correlated with the total colony count S1 of liquid milk and the content of thermotolerant psychrophilic bacteria S2 of liquid milk, and positively correlated with the endotoxin content S3 of liquid milk. That is, when the total colony count S1 and the content of thermotolerant psychrophilic bacteria S2 are lower, the safety index S of liquid milk is higher; when the endotoxin content S3 of liquid milk and the lipase content of liquid milk are higher, the safety index S of liquid milk is higher.

[0097] At the same time, based on a large number of studies, the inventors preliminarily set the weighting coefficients for each parameter in Formula 2 according to the impact of different biomarkers on product quality as follows: total colony count: thermotolerant psychrophilic bacteria: endotoxin = 3:6:1; in addition, the inventors analyzed the relevant indicators of commercially available liquid milk products and determined the benchmark values ​​of each indicator as: total colony count 500CFU / ml, thermotolerant psychrophilic bacteria 10CFU / ml, endotoxin 2Log EU / ml. Finally, the weighting coefficients and indicator standardization were combined to obtain the coefficients in Formula 2.

[0098] Since Formula 2 fully considers the influence of each microbial marker on product quality and the product index standardization factor, when the safety index S of liquid milk is calculated using Formula 2, the evaluation method provided by the present invention has the characteristic of higher accuracy.

[0099] In one embodiment, the quality of the liquid milk is evaluated according to the activity index F and the safety index S, comprising:

[0100] The nutritional quality of the liquid milk is evaluated according to a first correspondence between the activity index F, a preset activity index and the nutritional quality grade of the liquid milk; and / or the safety quality of the liquid milk is evaluated according to a second correspondence between the safety index S, a preset safety index and the safety quality grade of the liquid milk.

[0101] The first correspondence may include at least one preset activity index range and a liquid milk nutritional quality level corresponding to the at least one preset activity index range, and each preset activity index range corresponds to a liquid milk nutritional quality level. After obtaining the activity index F, if the activity index F is within a preset activity index range in the correspondence, the liquid milk nutritional quality level corresponding to the preset activity index range is the nutritional quality level of the liquid milk.

[0102] Similarly, the second corresponding relationship may include at least one preset safety index range and the liquid milk safety quality level corresponding to the at least one preset safety index range, and each preset safety index range corresponds to a liquid milk safety quality level. After obtaining the safety index S, if the safety index S is within a preset safety index range in the corresponding relationship, the liquid milk safety quality level corresponding to the preset safety index range is the safety quality level of the liquid milk.

[0103] Exemplarily, the corresponding relationship includes:

[0104] First correspondence: if the preset activity index is ≥ 0, the nutritional quality of liquid milk is level one;

[0105] If the preset activity index is less than 0, the nutritional quality of the liquid milk is level 2;

[0106] The second corresponding relationship: if the safety index S ≥ 0, the biosafety quality of liquid milk is level 1;

[0107] If the safety index S is less than 0, the biosafety quality of the liquid milk is level 2.

[0108] Therefore, when the activity index F≥0, it falls within the preset activity index range in the first corresponding relationship, the nutritional quality of the liquid milk is the nutritional quality evaluation level corresponding to the preset activity index range, and the nutritional quality evaluation level of the liquid milk is level one; when the activity index F<0, it falls within the preset activity index range in the first corresponding relationship, the nutritional quality of the liquid milk is the nutritional quality evaluation level corresponding to the preset activity index range, and the nutritional quality evaluation level of the liquid milk is level two.

[0109] Similarly, when the safety index S ≥ 0, it falls within the preset safety index range in the second corresponding relationship, the biosafety quality of the liquid milk is the biosafety quality evaluation level corresponding to the preset safety index range, and the biosafety quality evaluation level of the liquid milk is level one; when the safety index S < 0, it falls within the preset safety index range in the second corresponding relationship, the biosafety quality of the liquid milk is the biosafety quality evaluation level corresponding to the preset safety index range, and the biosafety quality evaluation level of the liquid milk is level two.

[0110] Among them, the first-level nutritional quality means that the liquid milk retains more active substances due to the mild sterilization or sterilization conditions during the processing; the second-level nutritional quality means that the liquid milk contains less active substances. The reason may be that the raw milk used to prepare the liquid milk is of poor quality and has a low content of active substances, or it may be that the sterilization or sterilization conditions during the processing of the liquid milk are too harsh, resulting in the inactivation of the active substances contained in the raw milk.

[0111] Biosafety quality level 1 means that the content of microbial markers in liquid milk is relatively low, which indicates that the sterilization or sterilization treatment during the processing of liquid milk is effective; biosafety quality level 2 means that the content of microbial markers in liquid milk is relatively high, and the liquid milk may be a food safety hazard. The reason may be that the effect of sterilization or sterilization treatment during the processing of liquid milk needs to be improved, or it may be that the raw milk is contaminated by microorganisms.

[0112] Furthermore, guidance can be provided for the improvement of the liquid milk production process based on the combination of F value and S value. Specifically, when F>0 and S>0, we can try to further improve the product quality from the two aspects of raw milk quality and processing method; when F≥0 and S≤0, at least one of the raw milk quality and processing method needs to be improved; when F<0 and S>0, the product is not real low-temperature milk, and the processing method must be improved; when F<0 and S<0, there are great problems with the raw milk quality, which must be improved.

[0113] In one embodiment, the evaluation method provided by the present invention further comprises:

[0114] Obtain the activity index F and safety index S of N different liquid milks respectively, N≥2;

[0115] According to N activity indexes F and safety index S, N quality indexes A are obtained;

[0116] According to N quality indexes A, the quality differences of N different liquid milks are evaluated.

[0117] Furthermore, the evaluation method provided by the present invention also includes: evaluating the nutritional quality differences of N different liquid milks according to N activity indexes F, and evaluating the biological safety quality differences of N different liquid milks according to N safety indexes S.

[0118] Sampling multiple liquid milks and comparing the quality differences between the liquid milks by using the activity index F, the safety index S, and the quality index A helps to objectively evaluate multiple liquid milks from different sources with unified standards, making the evaluation method provided by the present invention more objective.

[0119] Furthermore, according to the N activity indexes F and the safety index S, N quality indexes A are obtained, including:

[0120] The quality index A is calculated according to formula 3;

[0121] A=F+S Formula 3.

[0122] By using the sum of the activity index F and the safety index S as the quality index A for evaluating the quality of liquid milk, the nutritional quality and biosafety quality reflected by the activity index F and the safety index S can be combined to jointly evaluate the quality of liquid milk, while avoiding errors caused by F or S having a value less than 0 when using the product of the activity index F and the safety index S to evaluate the quality of liquid milk, so that the evaluation method provided by the present invention has higher accuracy.

[0123] Furthermore, evaluating the quality differences of N different liquid milks according to N quality indexes A also includes: if the first quality index A1>the second quality index A2, the quality of the first liquid milk is better than the quality of the second liquid milk; wherein the first liquid milk and the second liquid milk are any two of the N different liquid milks, and the first quality index A1 is the quality index of the first liquid milk, and the second quality index A2 is the quality index of the second liquid milk.

[0124] The above content shows that the evaluation method provided by the present invention can be used to compare the quality difference of any two liquid milks among N different liquid milks. It is easy to understand that the evaluation method provided by the present invention can also be used to compare the quality of any two or more liquid milks among N different liquid milks, and the quality of the liquid milks involved in the comparison can be ranked in a specific order.

[0125] Exemplarily, the first liquid milk, the second liquid milk, and the third liquid milk are selected from N different liquid milks and evaluated using the evaluation method provided by the present invention to obtain a first quality index A1, a second quality index A2, and a third quality index A3, wherein the first quality index A1 is the quality index of the first liquid milk, the second quality index A2 is the quality index of the second liquid milk, and the third quality index A3 is the quality index of the third liquid milk. If the first quality index A1> the second quality index A2> the third quality index A3, the quality of the first liquid milk, the second liquid milk, and the third liquid milk can be ranked from high to low as: first liquid milk, second liquid milk, and third liquid milk.

[0126] Furthermore, based on N activity indices F, evaluating the nutritional quality differences of N different liquid milks also includes: if the first activity index F1> the second activity index F2, the nutritional quality of the first liquid milk is better than the nutritional quality of the second liquid milk; wherein the first liquid milk and the second liquid milk are any two of the N different liquid milks, and the first activity index F1 is the activity index of the first liquid milk, and the second activity index F2 is the activity index of the second liquid milk.

[0127] The above content shows that the evaluation method provided by the present invention can be used to compare the nutritional quality differences of any two liquid milks among N different liquid milks. It is easy to understand that the evaluation method provided by the present invention can also be used to compare the nutritional quality of any two or more liquid milks among N different liquid milks, and the nutritional quality of the liquid milks involved in the comparison can be ranked in a specific order.

[0128] Exemplarily, the first liquid milk, the second liquid milk, and the third liquid milk are selected from N different liquid milks and evaluated using the evaluation method provided by the present invention to obtain a first activity index F1, a second activity index F2, and a third activity index F3, wherein the first activity index F1 is the activity index of the first liquid milk, the second activity index F2 is the activity index of the second liquid milk, and the third activity index F3 is the activity index of the third liquid milk. If the first activity index F1> the second activity index F2> the third activity index F3, the nutritional quality of the first liquid milk, the second liquid milk, and the third liquid milk can be ranked from high to low as: first liquid milk, second liquid milk, and third liquid milk.

[0129] Similarly, according to N safety indexes S, the difference in biosafety quality of N different liquid milks is evaluated, including: the first safety index S1> the second safety index S2, then the biosafety quality of the first liquid milk is better than the biosafety quality of the second liquid milk; wherein the first liquid milk and the second liquid milk are any two of the N different liquid milks, and the first safety index S1 is the safety index of the first liquid milk, and the second safety index S2 is the safety index of the second liquid milk.

[0130] The above content shows that the evaluation method provided by the present invention can be used to compare the safety quality differences of any two liquid milks among N different liquid milks. It is easy to understand that the evaluation method provided by the present invention can also be used to compare the safety quality of any two or more liquid milks among N different liquid milks, and the safety quality of the liquid milks involved in the comparison can be ranked in a specific order.

[0131] Exemplarily, the first liquid milk, the second liquid milk, and the third liquid milk are selected from N different liquid milks and evaluated using the evaluation method provided by the present invention to obtain a safety index S1, a second safety index S2, and a third safety index S3, wherein the first safety index S1 is the safety index of the first liquid milk, the second safety index S2 is the safety index of the second liquid milk, and the third activity index F3 is the nutritional quality index of the third liquid milk. If the first activity index F1> the second activity index F2> the third activity index F3, the biological safety quality of the first liquid milk, the second liquid milk, and the third liquid milk can be ranked from high to low as: the first liquid milk, the second liquid milk, and the third liquid milk.

[0132] The method for evaluating the quality of liquid milk provided by the present invention is further described below through examples.

[0133] Example 1

[0134] Commercially available low-temperature milk was used as liquid milk 1 for evaluation. The protein content of the liquid milk was labeled as 3.2 g / 100 mL. The low-temperature milk was produced by physical sterilization + pasteurization process.

[0135] Example 2

[0136] This embodiment is basically the same as the embodiment 1, except that this embodiment uses the same type of commercially available low-temperature cow milk with a different production date from that in the embodiment 1 as the liquid milk 2 for evaluation.

[0137] Example 3

[0138] This embodiment is basically the same as the embodiment 1, except that this embodiment uses the same type of commercially available low-temperature cow milk with a production date different from that of the embodiment 1 and the embodiment 2 as the liquid milk 3 for evaluation.

[0139] Example 4

[0140] Commercially available low-temperature milk was used as liquid milk 4 for evaluation. The protein content of the liquid milk was labeled as 3.8 g / 100 mL. The low-temperature milk was produced by physical sterilization + pasteurization process.

[0141] Example 5

[0142] Commercially available low-temperature milk was used as liquid milk 5 for evaluation. The protein content of the liquid milk was labeled as 3.4 g / 100 mL. The low-temperature milk was prepared by a pasteurization process.

[0143] Example 6

[0144] Commercially available low-temperature milk was used as liquid milk 6 for evaluation, and its protein content was marked as 3.2 g / 100 mL. The low-temperature milk was produced by ultra-high temperature pasteurization process, wherein the ultra-high temperature pasteurization sterilization temperature was 129-131° C. and the sterilization time was 2 s.

[0145] Example 7

[0146] Commercially available low-temperature milk was used as liquid milk 7 for evaluation, and its protein content was marked as 4.0 g / 100 mL. The low-temperature milk was produced by ultra-high temperature pasteurization process, wherein the sterilization temperature of the ultra-high temperature pasteurization process was 129-131° C. and the sterilization time was 2 s.

[0147] Example 8

[0148] Commercially available low-temperature milk was used as liquid milk 8 for evaluation, and its protein content was marked as 3.3 g / 100 mL. The low-temperature milk was produced by an INF sterilization process, wherein the sterilization temperature of the INF sterilization process was 155-159° C. and the sterilization time was 0.09 s.

[0149] Example 9

[0150] Commercially available low-temperature milk was used as liquid milk 9 for evaluation. The protein content of the liquid milk was labeled as 3.6 g / 100 mL. The low-temperature milk was produced by physical sterilization + pasteurization process.

[0151] Example 10

[0152] Raw milk was sequentially subjected to milk purification treatment (treatment temperature of 10°C, treatment centrifugal force of 4500g), degassing treatment (treatment pressure of -0.05bar, treatment time of 0.1s), homogenization treatment (treatment temperature of 55°C, treatment pressure of 180bar), and sterilization treatment (treatment temperature of 72°C, treatment time of 15s) to obtain liquid milk 10 for evaluation.

[0153] Embodiment 11

[0154] This embodiment is basically the same as Embodiment 10, except that the raw cow milk used in this embodiment and the raw cow milk used in Embodiment 10 are selected from different pastures, and liquid milk 11 is prepared for evaluation.

[0155] Example 12

[0156] This embodiment is basically the same as embodiment 10, except that the treatment temperature of the sterilization treatment is 85° C., the treatment time is 15 s, and liquid milk 12 is obtained for evaluation.

[0157] Example 13

[0158] This embodiment is basically the same as embodiment 10, except that the treatment temperature of the sterilization treatment is 137° C., the treatment time is 4 s, and liquid milk 13 is obtained for evaluation.

[0159] Test example

[0160] 1. Detect the lactoperoxidase content, lactoferrin content, immunoglobulin content, protease content, lipase content, total protein content, total bacterial count, thermotolerant psychrophilic bacteria content, endotoxin content, and the number of days between the production date and the test date in the liquid milks 1-13 according to the following methods:

[0161] Lactoperoxidase: Detected by enzyme-linked immunosorbent assay according to standard T / TDSTIA 001-2021;

[0162] Lactoferrin: Detected by high performance liquid chromatography, referring to standard T / TDSTIA 006-2019;

[0163] Immunoglobulin: Detected by enzyme-linked immunosorbent assay according to standard T / TDSTIA 003-2021;

[0164] Protease: Tested according to GB / T 28715-2012;

[0165] Lipase: tested according to GB / T 5523-2008;

[0166] Total protein: tested according to GB 5009.5-2016;

[0167] Total colony count: tested in accordance with NY / T 939-2016;

[0168] Thermotolerant and psychrophilic bacteria: tested in accordance with GB 4789.2-2016;

[0169] Endotoxin: Use Toxinsensor TM LAL kit was used for detection.

[0170] According to the above test results, the activity index F of each liquid milk is calculated according to formula 1, the safety index S of each liquid milk is calculated according to formula 2, and the quality index A of each liquid milk is calculated according to formula 3, and filled in Table 1.

[0171] Table 1 Liquid milk evaluation data record table

[0172]

[0173] According to the data in Table 1:

[0174] 1) It is known from common knowledge in the art that liquid milk produced by pasteurization and physical sterilization has lower microbial marker content than liquid milk produced by pasteurization alone. Therefore, liquid milk produced by pasteurization and physical sterilization has higher biosafety quality than liquid milk produced by pasteurization alone. It can be seen from Table 1 that the S values ​​of liquid milk 1, liquid milk 2, liquid milk 3, liquid milk 4, and liquid milk 9 prepared by both pasteurization and physical sterilization processes are significantly different from the S values ​​of liquid milk 5 and liquid milk 10 prepared only by pasteurization. Specifically, by comparing the S values ​​of liquid milk 1, liquid milk 2, liquid milk 3, liquid milk 4, and liquid milk 9 prepared by both pasteurization and physical sterilization processes with the S values ​​of liquid milk 5 and liquid milk 10 prepared only by pasteurization, it can be seen that the S values ​​of liquid milk 1, liquid milk 2, liquid milk 3, liquid milk 4, and liquid milk 9 prepared by both pasteurization and physical sterilization processes are significantly higher than the S values ​​of liquid milk 5 and liquid milk 10 prepared only by pasteurization, which is consistent with the logic that "compared with liquid milk prepared only by pasteurization, liquid milk prepared by both pasteurization and physical sterilization processes has higher biosafety quality". This indicates that the method provided by the present invention for obtaining the safety index S of liquid milk according to the content of microbial markers and then evaluating the quality of liquid milk according to the safety index S is objective.

[0175] 2) It is known from the common knowledge in the art that compared with liquid milk prepared by pasteurization, liquid milk prepared by ultra-high temperature pasteurization or INF sterilization has a lower content of microbial markers. Therefore, compared with liquid milk prepared by pasteurization, liquid milk prepared by ultra-high temperature pasteurization or INF sterilization has higher biosafety quality. As shown in Table 1, the S values ​​of liquid milk 5 and liquid milk 10 prepared by pasteurization are significantly lower than the S values ​​of liquid milk 6, liquid milk 7, and liquid milk 8 prepared by ultra-high temperature pasteurization or INF sterilization. This is consistent with the logic of "compared with liquid milk prepared by pasteurization, liquid milk prepared by ultra-high temperature pasteurization or INF sterilization has a lower content of microbial markers". This also shows that the method provided by the present invention for obtaining the safety index S of liquid milk according to the content of microbial markers, and then evaluating the quality of liquid milk according to the safety index S is objective.

[0176] 3) According to common knowledge in the art, liquid milk produced by a pasteurization process with a higher treatment temperature has a lower content of active substances than liquid milk produced by a pasteurization process alone or by a pasteurization process and a physical sterilization process. Therefore, liquid milk produced by a pasteurization process with a higher treatment temperature has a lower nutritional quality than liquid milk produced by a pasteurization process alone or by a pasteurization process and a physical sterilization process. As can be seen from Table 1, the F values ​​of liquid milk 1, liquid milk 2, liquid milk 3, liquid milk 4, liquid milk 9, liquid milk 5, and liquid milk 10 prepared by using only pasteurization technology or using both pasteurization technology and physical sterilization technology are significantly different from the F values ​​of liquid milk 6, liquid milk 7, and liquid milk 8 prepared by using a sterilization technology with a higher treatment temperature. Specifically, the F values ​​of liquid milk 1, liquid milk 2, liquid milk 3, liquid milk 4, liquid milk 9, liquid milk 5, and liquid milk 10 prepared by using only pasteurization technology or using both pasteurization technology and physical sterilization technology are significantly different from the F values ​​of liquid milk 6, liquid milk 7, and liquid milk 8 prepared by using a sterilization technology with a higher treatment temperature. From the F values ​​of liquid milk 6, liquid milk 7, and liquid milk 8, it can be seen that the F values ​​of liquid milk 1, liquid milk 2, liquid milk 3, liquid milk 4, liquid milk 9, liquid milk 5, and liquid milk 10 obtained by using only pasteurization technology or using both pasteurization technology and physical sterilization technology are significantly higher than the F values ​​of liquid milk 6, liquid milk 7, and liquid milk 8 obtained by using a sterilization technology with a higher treatment temperature, which is consistent with the logic that "compared with liquid milk obtained by using only pasteurization technology or using both pasteurization technology and physical sterilization technology, liquid milk obtained by using a sterilization technology with a higher treatment temperature has lower nutritional quality". This shows that the method provided by the present invention for obtaining the activity index F of liquid milk according to the content of active substances and then evaluating the quality of liquid milk according to the activity index F is objective.

[0177] 4) Although liquid milk 3 is the same product as liquid milks 1 and 2 but produced on different dates, its F value is significantly lower than that of liquid milks 1 and 2. This may be related to the unstable control of raw milk quality or processing, and targeted improvements need to be made after the cause is identified.

[0178] 5) Comparing liquid milk 10 and liquid milk 11, it can be seen that under the premise of the same sterilization process, the two have similar F values, but there is a significant difference in S value. This may be due to the different sources of raw milk for the two. Liquid milk 11 needs to improve the quality of raw milk.

[0179] 6) The F value of liquid milk 13 is less than 0 and the S value is greater than 0. According to the evaluation principle, liquid milk 13 is not real low-temperature milk. This is consistent with the common knowledge in the art that liquid milk obtained by high-temperature sterilization has higher biosafety quality and lower nutritional quality.

[0180] 7) Comparing liquid milk 10, liquid milk 12, and liquid milk 13, the sterilization temperatures of the three liquid milks are liquid milk 10, liquid milk 12, and liquid milk 13 from low to high. The F values ​​of the three liquid milks are liquid milk 10, liquid milk 12, and liquid milk 13 from high to low; the S values ​​of the three liquid milks are liquid milk 13, liquid milk 12, and liquid milk 10 from high to low, which is also consistent with the common knowledge in the art that liquid milk obtained by high temperature sterilization has higher biosafety quality and lower nutritional quality.

[0181] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the quality of liquid milk, characterized in that: The following steps are involved: 1) obtaining the content of active substances and the content of microbial markers in the liquid milk; 2) obtaining an activity index F of the liquid milk according to the content of the active substance; 3) obtaining a safety index S of the liquid milk according to the content of the microbial marker; 4) evaluating the quality of the liquid milk according to the activity index F and the safety index S.

2. The evaluation method according to claim 1, characterized in that: The active substances include lactoperoxidase, lactoferrin, immunoglobulin, protease and lipase.

3. The evaluation method according to claim 2, characterized in that: The step of obtaining the activity index F of the liquid milk according to the content of the active substance comprises: The activity index F is calculated according to Formula 1: F = (0.004F1 + 0.11F2 + 0.02F3 - 0.02F4 - 0.32F5) / P Formula 1; in: F1 is the lactoperoxidase content of liquid milk, U / L; F2 is the lactoferrin content of liquid milk, mg / L; F3 is the immunoglobulin content of liquid milk, mg / L; F4 is the protease content of liquid milk, U / 100mL; F5 is the lipase content of liquid milk, mg / g; P is the total protein content of liquid milk, g / 100mL.

4. The evaluation method according to any one of claims 1 to 3, characterized in that: The microbial markers include total colony count, thermotolerant psychrophilic bacteria, and endotoxin.

5. The evaluation method according to claim 4, characterized in that: The step of obtaining the safety index S of the liquid milk according to the content of the microbial marker comprises: The safety index S is calculated according to Formula 2: in: S1 is the total colony count of liquid milk, CFU / mL; S2 is the content of thermotolerant psychrophilic bacteria in liquid milk, CFU / mL; S3 is the endotoxin content of liquid milk, logEU / mL; d is the number of days between the production date and the inspection date, d.

6. The evaluation method according to any one of claims 1 to 5, characterized in that: The step of evaluating the quality of the liquid milk according to the activity index F and the safety index S comprises: Evaluating the nutritional quality of the liquid milk according to the first corresponding relationship between the activity index F, the preset activity index and the nutritional quality grade of the liquid milk; and / or, The safety quality of the liquid milk is evaluated according to the second corresponding relationship among the safety index S, the preset safety index and the safety quality grade of the liquid milk.

7. The evaluation method according to claim 6, characterized in that: The first corresponding relationship includes: If the preset activity index is ≥ 0, the nutritional quality of the liquid milk is level one; If the preset activity index is less than 0, the nutritional quality of the liquid milk is level 2; The second corresponding relationship includes: If the safety index S is ≥ 0, the biosafety quality of the liquid milk is level one; If the safety index S is less than 0, the biosafety quality of the liquid milk is level 2.

8. The evaluation method according to any one of claims 1 to 7, characterized in that: Also includes: Respectively obtain the activity index F and the safety index S of N different liquid milks, N≥2; Obtaining N quality indexes A according to the N activity indexes F and safety indexes S; According to the N quality indexes A, the quality differences of N different liquid milks are evaluated.

9. The evaluation method according to claim 8, characterized in that: The obtaining of N quality indexes A according to the N activity indexes F and the safety index S comprises: The quality index A is calculated according to formula 3; A=F+S Formula 3.

10. The evaluation method according to claim 8 or 9, characterized in that: The step of evaluating the quality differences of N different liquid milks according to the N quality indexes A comprises: The first quality index A1>the second quality index A2, then the quality of the first liquid milk is better than the quality of the second liquid milk; The first liquid emulsion and the second liquid emulsion are any two of N different liquid emulsions, and the first quality index A1 is the quality index of the first liquid emulsion, and the second quality index A2 is the quality index of the second liquid emulsion.

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