Drinking type fermented milk and preparation method thereof

Abstract

The invention belongs to the technical field of fermented products, and particularly relates to drinking type fermented milk and a preparation method thereof. The preparation method comprises the following steps: (1) adding a fermented milk base material into compound protease for enzymolysis to obtain an enzymolysis mixture; the compound protease consists of papain and acid protease; the fermented milk base material at least comprises an emulsion; (2) carrying out enzyme deactivation on the enzymolysis mixture, inoculating strains and fermenting to obtain fermented milk; and (3) demulsifying the fermented milk to obtain the low-temperature drinking type fermented milk. Compared with the existing preparation method of the drinking type fermented milk, the preparation method has the advantages that homogenization is not needed after demulsification, so that the steps are simplified; and the rheological property of the prepared fermented milk is slightly different from that of the fermented milk which is demulsified and then homogenized by a conventional process, and the thermal stability is better.

Description

Technical Field

[0001] The invention belongs to the technical field of fermented products, and particularly relates to drinkable fermented milk and a preparation method thereof. Background Art

[0002] Fermented milk is a dairy product made from milk through fermentation with lactic acid bacteria. Fermented milk is generally divided into coagulated fermented milk and stirred fermented milk according to its form. Among them, stirred fermented milk can be divided into different types of stirred fermented milk according to different states. Drinking fermented milk, as a type of stirred fermented milk with higher fluidity, is popular among consumers because of its convenience to drink, thin texture, easy swallowing and digestion, and unique taste.

[0003] At present, drinking fermented milk is obtained by demulsifying stirred yogurt and then homogenizing it. The process is relatively cumbersome and can easily damage the yogurt curd stabilization system. For example, the existing patent CN109730149A discloses a room temperature drinking fermented milk and a preparation method thereof. The preparation method comprises the following steps: S1: pre-sterilizing antibiotic-free milk and uniformly mixing it with a sweetener, starch, a stabilizer and amylase, and performing enzymolysis in stages to obtain a mixed solution; S2: homogenizing the mixed solution obtained in step S1, sterilizing it, cooling it, adding edible essence, inoculating a starter and fermenting it to the end point to obtain a fermented milk base; S3: demulsifying the fermented milk base obtained in step S2, homogenizing it, sterilizing it, cooling it, and filling it The room temperature drinkable fermented milk can be obtained by packaging; for example, the existing patent CN114073270A discloses a method for preparing drinkable fermented milk and drinkable fermented milk, and the method for preparing drinkable fermented milk comprises the following steps: mixing raw milk, condensed milk, dietary fiber, protein powder, egg yolk product and a portion of sugar, performing a first homogenization treatment and sterilizing to form a milk base; adding a starter to the milk base, fermenting it, and subjecting it to a first chilling; mixing the remaining sugar and stabilizer to obtain a sugar solution, and subjecting it to a second chilling; mixing the milk base subjected to the first chilling and the sugar solution subjected to the second chilling, and subjecting them to a second homogenization (homogenization after demulsification), and a third chilling to obtain the drinkable fermented milk. Summary of the Invention

[0004] The purpose of the present invention is to develop a preparation method for drinkable fermented milk based on protease hydrolysis. In this preparation method, the emulsion is first enzymatically hydrolyzed with protease, and after the enzyme is inactivated, the drinkable fermented milk can be obtained by fermentation. No homogenization is required after fermentation and emulsion breaking, and the prepared drinkable fermented milk has strong fluidity and good thermal stability.

[0005] In order to achieve the purpose of the present invention, the present invention provides a method for preparing drinkable fermented milk, comprising: (1) adding a composite protease to a fermented milk base for enzymatic hydrolysis to obtain an enzymatic hydrolysis mixture; the composite protease is composed of papain and acidic protease; and the fermented milk base includes at least an emulsion; (2) inactivating the enzymatic hydrolysis mixture, inoculating a bacterial strain, and fermenting to obtain fermented milk; and (3) demulsifying the fermented milk to obtain a low-temperature drinkable fermented milk.

[0006] Furthermore, in the above step (3), the fermented milk is demulsified and then sterilized to obtain the fermented milk that can be drunk at room temperature.

[0007] Furthermore, in the above step (3), the fermented milk is demulsified and then sterilized to obtain the fermented milk for drinking at room temperature, and the sterilization includes: treating at 95° C. for 20 minutes.

[0008] Furthermore, in the above step (1), the mass fraction of the composite protease in the emulsion is greater than 0.8%, and the ratio of papain to acid protease is greater than 2:3.

[0009] Furthermore, in the above step (1), the mass fraction of the composite protease in the emulsion is 1% or 1.2%, and the ratio of papain to acid protease is 1:1.

[0010] Furthermore, in the above step (1), the mass fraction of the composite protease in the emulsion is 1%, and the ratio of papain to acid protease is 3:2.

[0011] Furthermore, in the above step (1), the enzymatic hydrolysis includes: stirring at a constant temperature of 45° C. for 1 hour.

[0012] Another aspect of the present invention provides a drinkable fermented milk prepared by the method for preparing drinkable fermented milk of the present invention.

[0013] The beneficial effects of the present invention include at least: compared with the existing preparation method of drinkable fermented milk, the preparation method of the drinkable fermented milk provided by the present invention does not require homogenization after demulsification, which simplifies the steps; and the rheological properties of the prepared fermented milk are not much different from those of the fermented milk prepared by demulsification and then homogenization in the conventional process, and the thermal stability is better. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The results of protein hydrolysis in mixed solution A by different proteases are shown as follows: 1: blank group; 2: 0.1% alkaline protease group; 3: 0.1% neutral protease group; 4: 0.05% acid protease + 0.05% trypsin group; 5: 0.05% papain + 0.05% acid protease group; 6: 0.1% trypsin group; 7: 0.1% acid protease group; 8: 0.1% papain group;

[0015] Figure 2 Storage modulus of fermented milk prepared with different protease groups; 1: blank group; 2: 0.05% acid protease + 0.05% trypsin group; 3: 0.05% papain + 0.05% acid protease group; 4: 0.1% papain group; 5: 0.1% acid protease group; 6: 0.1% trypsin group; 7: 0.1% neutral protease group; 8: 0.1% alkaline protease group; 9: conventional process group;

[0016] Figure 3 The loss modulus of fermented milk prepared with different protease groups: 1: blank group; 2: 0.05% acid protease + 0.05% trypsin group; 3: 0.05% papain + 0.05% acid protease group; 4: 0.1% papain group; 5: 0.1% acid protease group; 6: 0.1% trypsin group; 7: 0.1% neutral protease group; 8: 0.1% alkaline protease group; 9: conventional homogenization process group after demulsification;

[0017] Figure 4 The effects of different preferred proteases on the thermal stability of fermented milk are shown in Figure 1. 1: blank group; 2: 0.05% papain + 0.05% acid protease group; 3: 0.05% papain + 0.05% acid protease enzymatic hydrolysis followed by demulsification and homogenization group.

[0018] Figure 5 The storage modulus of fermented milk prepared by different preferred protease groups, including: 1: 0.04% papain + 0.04% acid protease group; 2: 0.06% papain + 0.04% acid protease group; 3: 0.04% papain + 0.06% acid protease group; 4: 0.05% papain + 0.05% acid protease group; 5: 0.06% papain + 0.06% acid protease group; 6: conventional process group;

[0019] Figure 6 The loss modulus of fermented milk prepared by different preferred protease groups, including: 1: 0.04% papain + 0.04% acid protease group; 2: 0.06% papain + 0.04% acid protease group; 3: 0.04% papain + 0.06% acid protease group; 4: 0.05% papain + 0.05% acid protease group; 5: 0.06% papain + 0.06% acid protease group; 6: conventional process group;

[0020] Figure 7The clarity index of fermented milk prepared with different preferred protease groups is shown in FIG1 , wherein: 1: 0.04% papain + 0.04% acid protease group; 2: 0.06% papain + 0.04% acid protease group; 3: 0.04% papain + 0.06% acid protease group; 4: 0.05% papain + 0.05% acid protease group; 5: 0.06% papain + 0.06% acid protease group; and 6: conventional process group. DETAILED DESCRIPTION

[0021] The examples are provided to better illustrate the present invention, but are not intended to limit the present invention to the examples. Therefore, non-essential improvements and adjustments to the embodiments made by those skilled in the art based on the above-mentioned invention still fall within the scope of protection of the present invention.

[0022] The terms used herein are only used to describe specific embodiments and are not intended to limit the present disclosure. Unless the context clearly has a different meaning, expressions in the singular include expressions in the plural. As used herein, it should be understood that terms such as "include", "have", "comprise" and the like are intended to indicate the presence of features, numbers, operations, materials or combinations. The terms of the present invention are disclosed in the specification and are not intended to exclude the possibility that one or more other features, numbers, operations, materials or combinations thereof may exist or may be added. As used herein, " / " may be interpreted as "and" or "or", depending on the circumstances.

[0023] An embodiment of the present invention provides a method for preparing drinkable fermented milk, comprising: (1) adding a composite protease to a fermented milk base for enzymatic hydrolysis to obtain an enzymatic hydrolysis mixture; the composite protease comprises papain and acidic protease; and the fermented milk base comprises at least an emulsion; (2) inactivating the enzymatic hydrolysis mixture, inoculating a bacterial strain and fermenting to obtain fermented milk; and (3) demulsifying the fermented milk to obtain a low-temperature drinkable fermented milk.

[0024] It should be noted that the coagulation process of fermented milk primarily involves casein, a milk protein. First, during fermentation, the pH drops from 6.6 to 5.8, causing casein dissociation. This reduces electrostatic interactions, allowing minerals to escape from micelles and destabilize the system. Subsequently, when the pH drops to 5.2, casein phosphopeptides are released, forming a calcium-containing precipitate. Subsequently, as the pH continues to drop to 4.6, a large amount of calcium ions detach from the precipitate, forming a network structure. Finally, when the pH drops below 4.6, a gel forms.

[0025] In addition, the molecular weight of casein has a significant impact on the thermal stability of the gel. High-molecular-weight casein has stronger intermolecular interactions, and the gel structure it forms is relatively strong, but it is prone to thermal denaturation under high temperature conditions. Moderate-molecular-weight casein strikes a balance between water solubility and gel stability, and is relatively stable to temperature changes. Low-molecular-weight casein has good water solubility, but the gel it forms is prone to dissociation and loss of stability at high temperatures. Therefore, in the food industry, by rationally controlling the molecular weight of casein, the thermal stability of the product's gel can be adjusted to meet different processing and storage conditions.

[0026] In the present invention, the purpose of controlling the molecular weight of casein is achieved by enzymatic hydrolysis of protein by protease, wherein alkaline protease, acidic protease, trypsin, papain and neutral protease and their combination have different effects on the hydrolysis of casein; wherein, alkaline protease and acidic protease hydrolyze casein into smaller peptide chains and amino acids within their active pH range, producing relatively small hydrolyzates; trypsin, due to its deep hydrolysis, generates hydrolyzates containing smaller peptide chains and amino acids; papain also hydrolyzes casein to produce smaller peptide chains and amino acids; neutral protease is active under conditions close to neutral pH, hydrolyzes casein to produce medium-sized peptide chains and free amino acids; the molecular weight of these differential hydrolyzates affects the application and function of casein. In the present invention, it is found that the combined enzymatic hydrolysis of acidic protease and papain can obtain small molecules with appropriate molecular weight, so that the prepared drinking fermented milk has better thermal stability.

[0027] It should also be noted that the fermented milk base refers to the basic raw material for preparing fermented milk, including at least emulsion. It at least includes emulsion and may also include additives for preparing fermented milk, such as sweeteners and stabilizers. In addition, the emulsion includes raw milk or a compound milk compounded with milk powder, and the choice can be based on specific circumstances.

[0028] In some specific embodiments, in the above step (3), the fermented milk is demulsified and then sterilized to obtain a fermented milk that can be drunk at room temperature. It should be noted that the fermented milk can be demulsified and then sterilized. After the fermented milk is demulsified and sterilized, the product obtained is a fermented milk without live bacteria. Compared with the fermented milk with live bacteria, the fermented milk without live bacteria has the advantages of high stability (product quality and taste are not easily affected by environmental factors such as temperature and humidity), long shelf life (generally 3-6 months), and suitability for specific groups of people (people who are lactose intolerant or need to avoid the intake of live bacteria). However, since it does not have live bacteria, its nutritional value is relatively low and the taste will be slightly monotonous. In addition, the purpose of sterilization is mainly to kill the lactic acid bacteria produced by inoculation and fermentation in the fermented milk and some residual bacteria, so as to prevent the fermented milk from continuing to ferment under normal temperature conditions.

[0029] In some specific embodiments, in step (3), the fermented milk is demulsified and then sterilized to obtain room temperature drinkable fermented milk, and the sterilization comprises treating the milk at 95°C for 20 minutes. It should be noted that the sterilization method can be any known method in the art, preferably treating the milk at 95°C for 20 minutes. Under these conditions, the best sterilization effect can be achieved in the shortest time.

[0030] In some specific embodiments, in the above step (1), the mass fraction of the composite protease in the emulsion is greater than 0.8%, and the ratio of papain to acid protease is greater than 2:3.

[0031] It should be noted that experiments conducted in the present invention have shown that when the mass fraction of the composite protease in the emulsion is greater than 0.8% and the ratio of papain to acid protease is greater than 2:3, the resulting fermented drinkable milk has better rheological properties and stability. On the other hand, if the mass fraction of the composite protease is too low, the fluidity is poor. From the perspective of fluidity and stability, a higher mass fraction, within a reasonable addition range, is better.

[0032] In some specific embodiments, in the above step (1), the mass fraction of the composite protease in the emulsion is preferably 1% or 1.2%, and the ratio of papain to acid protease is 1:1. At this ratio, the prepared drinkable fermented milk has good fluidity and stability; further, more preferably, the mass fraction of the composite protease in the emulsion is preferably 1%, and the ratio of papain to acid protease is 1:1. At this ratio, the prepared drinkable fermented milk has better fluidity and stability than other ratios, and also has good thermal stability.

[0033] In some specific embodiments, in the above step (1), the mass fraction of the composite protease in the emulsion can be 1%, and the ratio of papain to acidic protease can be 3:2. In addition, when the composite protease, papain, and acidic protease are in the above ratios, the fluidity and stability of the prepared drinkable fermented milk are not as good as the above "the mass fraction of the composite protease in the emulsion is preferably 1%, and the ratio of papain to acidic protease is 1:1", but are also good.

[0034] In some specific embodiments, in step (1), the enzymatic hydrolysis may include: stirring at a constant temperature of 45°C for 1 hour. It should be noted that the enzymatic hydrolysis procedure can be selected according to the type of enzyme selected. The enzymatic hydrolysis condition of the papain and acid protease combination in the present invention can preferably be stirring at a constant temperature of 45°C for 1 hour. Under this condition, the best enzymatic hydrolysis effect can be obtained in the shortest time.

[0035] Another embodiment of the present invention provides a drinkable fermented milk prepared by the method for preparing drinkable fermented milk of the present invention. It should be noted that the method for preparing drinkable fermented milk of the present invention can produce drinkable fermented milk with good thermal stability and strong fluidity.

[0036] In order to better understand the present invention, the content of the present invention is further explained below with reference to specific examples, but the content of the present invention is not limited to the following examples.

[0037] In the following examples, papain was derived from papaya, trypsin was derived from pancreas of cattle, acidic protease was derived from Aspergillus niger, alkaline protease was derived from Bacillus subtilis, and neutral protease was derived from Bacillus subtilis. All of the above proteases were purchased from Xiasheng Food Co., Ltd.

[0038] 1. Preparation of Drinkable Fermented Milk

[0039] (1) 8 portions of 400 g of pre-pasteurized milk were heated to 45°C in a water bath. Different proteases (see Table 1, with no protease added as a control) were added to each portion and stirred at 45°C for 1 h to obtain different mixtures A.

[0040] (2) Immediately heat different mixtures A to 90°C and inactivate the enzyme for 10 minutes to obtain different mixtures B;

[0041] (3) Cool the mixture B to 42°C and add 1*10 7 cfu / g bacterial strain (commercial starter (Streptococcus thermophilus and Lactobacillus bulgaricus), Danisco (China) Co., Ltd.), and placed in a 42 °C incubator for 6 h and then cooled to obtain different mixtures C;

[0042] (4) Mixture C was demulsified at 100 r / min for 30 min and then heat-treated at 95°C for 20 min to obtain different room temperature drinkable fermented milks.

[0043] Table 1 Grouping of different proteases

[0044] serial number Protease addition 1 No protease added 2 0.1% papain 3 0.1% trypsin 4 0.1% acid protease 5 0.1% alkaline protease 6 0.1% neutral protease 7 0.05% acid protease + 0.05% trypsin 8 0.05% acid protease + 0.05% papain

[0045] 2. Analysis of protein hydrolysis

[0046] A certain amount of the above different mixtures A were taken, SDS loading buffer was added, and the samples were loaded onto 10% polyacrylamide gels. Electrophoresis was performed at room temperature at constant current (300mA) and constant voltage (80V) for 90min. The agar gel was removed, stained with Coomassie brilliant blue solution, and destained in decolorizing solution. The gel was photographed and analyzed using a gel imager. A standard protein marker (10KD-180KD) was used as a control. The results are shown in FIG. Figure 1As shown in the figure, from the perspective of protein hydrolysis in mixture A, compared with the blank group, the 0.1% alkaline protease group and the 0.1% neutral protease group completely hydrolyzed casein into small molecular polypeptides, the hydrolysis degree of the 0.1% papain group and the 0.1% trypsin group was relatively weak, the hydrolysis degree of the 0.05% acid protease + 0.05% trypsin group was relatively good, and the combination of 0.1% acid protease group and 0.05% papain + 0.05% acid protease had the best hydrolysis effect, which could make the casein hydrolyzed polypeptides evenly distributed between the molecular weights of 17KD and 43KD.

[0047] Effects of protease hydrolysis on pH, acidity and viable cell count of fermented milk

[0048] The pH value, titratable acidity, and counts of Lactobacillus bulgaricus and Streptococcus thermophilus of different mixtures C were determined using the pH meter method, acid-base titration method, and lactic acid bacteria counting method (all referring to the relevant methods of GB19302-2010 National Food Safety Standard Fermented Milk); the results are shown in Table 2.

[0049] Table 2 Effects of different proteases on the fermentation of mixture C

[0050]

[0051]

[0052] It can be seen from Table 2 above that after 6 hours of unified fermentation, compared with the blank group, the pH of the 0.1% alkaline protease group, 0.05% acid protease + 0.05% trypsin group, 0.05% papain group + 0.05% acid protease, 0.1% trypsin group and 0.1% acid protease group was lower than that of the blank group, and the acidity was higher than that of the control group; in addition, except for the 0.1% acid protease group and 0.1% papain group, the number of thermophilic Streptococcus in other groups was higher than or equal to that of the blank group; the 0.1% alkaline protease group, 0.05% acid protease + 0.05% trypsin group, 0.05% The number of Lactobacillus bulgaricus in the papain + 0.05% acid protease group, the 0.1% acid protease group and the 0.1% papain group was lower than that in the blank group. From the above, it can be seen that the 0.1% alkaline protease group, the 0.05% acid protease + 0.05% trypsin group and the 0.05% papain + 0.05% acid protease group can simultaneously meet the conditions that the pH is lower than that of the blank group, the acidity is higher than that of the blank group, the number of live Lactobacillus bulgaricus (the post-acidity of fermented milk is mainly caused by Lactobacillus bulgaricus, and reducing the number of live Lactobacillus bulgaricus can weaken the post-acidity) is lower than that of the blank group, and the number of thermophilic Streptococcus is higher than that of the blank group.

[0053] Combining the protein hydrolysis of the above-mentioned different mixtures A and the pH values, titrated acidities, and the numbers of Lactobacillus bulgaricus and Streptococcus thermophilus of the above-mentioned different mixtures C, it can be seen that in the present invention, a 0.05% acid protease + 0.05% trypsin group and a 0.05% papain + 0.05% acid protease group can be selected. The protease hydrolysis of this group can increase the number of viable bacteria of Streptococcus thermophilus and reduce the number of viable bacteria of Lactobacillus bulgaricus, shorten the fermentation time, and delay the acidification of fermented milk.

[0054] 4. Rheological test

[0055] In this test, the conventional drinking fermented milk prepared by the homogenization process after demulsification was used as a comparison. The specific process is as follows: 1 portion of 400g of pre-sterilized milk was taken, heated to 42℃ in a water bath, and 1*10 7 cfu / g bacteria, and placed in a constant temperature box at 42℃ for 6 hours, then demulsified. After demulsification, homogenized under 10 bar conditions, and a conventional process control sample was obtained after homogenization.

[0056] The demulsified solutions of the different mixtures C prepared above and the control samples of the conventional process were scanned at 4°C in the frequency range of 0.1Hz-10 Hz, and the corresponding storage modulus (G') and loss modulus (G") were recorded; the results are shown in Figure 2 and Figure 3 .

[0057] The results showed that the rheological properties, i.e., the consistency, of the blank group were significantly higher than those of the other groups. The consistency of the 0.1% trypsin group, 0.1% papain group, and 0.05% papain + 0.05% acid protease group was moderate, and the consistency was not much different from that of the drinking fermented milk samples produced by conventional processes, that is, the 0.1% trypsin group, 0.1% papain group, and 0.05% papain + 0.05% acid protease group could make the samples have a refreshing and smooth taste, while the 0.1% acid protease, 0.1% neutral protease, 0.1% alkaline protease, and 0.05% acid protease + 0.05% trypsin groups had too low a consistency.

[0058] Combined with the protein hydrolysis of the above-mentioned different mixtures A, the pH value, titrated acidity, the number of Lactobacillus bulgaricus and Streptococcus thermophilus of the above-mentioned different mixtures C, and the above-mentioned rheological test results, the 0.05% papain + 0.05% acid protease group had the best effect, with more uniform protein molecular weight and more suitable rheological properties.

[0059] 5. Observation on thermal stability of fermented milk

[0060] The tissue states of the different drinking fermented milks prepared above (blank group, 0.05% papain + 0.05% acid protease group, 0.05% papain + 0.05% acid protease enzymatic hydrolysis followed by demulsification and homogenization (10 bar homogenization)) were observed. Figure 4 As shown by Figure 4 It can be seen that the blank group showed obvious flocculation after heating, while the 0.05% papain + 0.05% acid protease group and the 0.05% papain + 0.05% acid protease enzymatic hydrolysis followed by demulsification and homogenization group did not show any protein flocculation or stratification during the entire heating process.

[0061] The above results show that the drinking fermented milk prepared by the 0.05% acid protease + 0.05% papain combination can achieve a refreshing and smooth taste, strong fluidity, and good thermal stability without additional post-emulsification homogenization, and contains a variety of small molecule bioactive peptides with multiple biological activities.

[0062] 6. Screening of different ratios of papain + acid protease

[0063] (1) Rheological test

[0064] Different drinking fermented milks were prepared by adding papain and acidic protease in different ratios (see Table 3) and following the above-mentioned preparation method.

[0065] Table 3 Different papain + acid protease ratios

[0066] serial number Different proportions 1 0.04% papain + 0.04% acid protease 2 0.06% papain + 0.04% acid protease 3 0.04% papain + 0.06% acid protease 4 0.05% papain + 0.05% acid protease 5 0.06% papain + 0.06% acid protease 6 Conventional homogenization process after demulsification (same as above)

[0067] The rheological properties of the different fermented milks prepared above were tested, namely, the rheological properties were scanned in the frequency range of 0.1 Hz to 10 Hz at 4 ° C, and the corresponding storage modulus (G') and loss modulus (G") were recorded. The results are shown in Figure 5 and Figure 6 As shown, the results showed that except for the 0.04% papain + 0.04% acid protease group with higher consistency, there was no significant difference in the rheological properties of the other groups, and all were within the rheological range of moderate consistency.

[0068] (2) Stability analysis

[0069] The stability of the different drinking fermented milks was analyzed using a Lumisizer analyzer under the following test conditions: a rotation speed of 1500 rpm, a time of 130 min, and a temperature of 4°C.

[0070] The results are as follows Figure 7As shown in the results, the clarification index of the group with the highest clarification index was 0.04% papain + 0.06% acid protease, indicating that the stability of the fermented milk prepared by this protease group was poor, even worse than that of the conventional process group; while the stability of the other four protease groups was better than that of the conventional process group, among which the clarification index of the group with the lowest clarification index was the best.

[0071] Based on the above rheological test and stability analysis results, it can be seen that the consistency of the 0.04% papain + 0.04% acid protease group is poor, and the 0.04% papain + 0.06% acid protease group has the highest clarity index and poor stability; therefore, in the present invention, the total enzyme content of papain and acid protease is greater than 0.8%, wherein the ratio of papain to acid protease is greater than (2:3); preferably, the total enzyme content of papain and acid protease is 1%, and the ratio of papain to acid protease is 1:1.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be covered by the scope of the claims of the present invention.

Claims

1. A method for preparing drinkable fermented milk, characterized in that: include: (1) adding a composite protease to a fermented milk base for enzymatic hydrolysis to obtain an enzymatic hydrolysis mixture; the composite protease is composed of papain and acidic protease; the fermented milk base includes at least an emulsion; (2) inactivating the enzyme in the enzymatic hydrolysis mixture, inoculating a bacterial strain for fermentation to obtain fermented milk; (3) demulsifying the fermented milk to obtain a low-temperature drinking type fermented milk.

2. The preparation method according to claim 1, characterized in that In step (3), the fermented milk is demulsified and then sterilized to obtain fermented milk that can be drunk at room temperature.

3. The preparation method according to claim 2, characterized in that In step (3), sterilization includes: treating at 95°C for 20 minutes.

4. The method for preparing drinkable fermented milk according to claims 1 to 3, characterized in that: In step (1), the mass fraction of the composite protease in the emulsion is greater than 0.8%, and the ratio of papain to acid protease is greater than 2:

3.

5. The method for preparing drinkable fermented milk according to claim 4, wherein: In step (1), the mass fraction of the composite protease in the emulsion is 1% or 1.2%, and the ratio of papain to acid protease is 1:

1.

6. The method for preparing drinkable fermented milk according to claim 4, wherein: In step (1), the mass fraction of the composite protease in the emulsion is 1%, and the ratio of papain to acid protease is 3:

2.

7. The method for preparing drinkable fermented milk according to claim 1, 2, 3, 5 or 6, characterized in that: In step (1), the enzymatic hydrolysis includes: stirring at a constant temperature of 45° C. for 1 hour.

8. The method for preparing drinkable fermented milk according to claim 4, wherein: In step (1), the enzymatic hydrolysis includes: stirring at a constant temperature of 45° C. for 1 hour.

9. Drinkable fermented milk produced by the method for producing drinkable fermented milk according to any one of claims 1 to 8.

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