Room temperature fermented milk and preparation method thereof
Through the collaborative treatment method of low-temperature plasma combined with pulsed electric field, the adverse effects of traditional thermal sterilization on room-temperature fermented milk are solved, effective sterilization and flavor retention under low voltage and electric field strength are achieved, and the stability and taste of the product are improved.
Patent Information
- Application Number
- CN202411464178.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-21
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2044-10-21
AI Technical Summary
Traditional thermal sterilization technology has an adverse effect on the quality of room temperature fermented milk, resulting in odor, powdery, astringent flavor problems. The existing non-thermal sterilization technology such as low-temperature plasma and pulsed electric field have limitations and is difficult to actually produce. Effectively applied in.
The collaborative treatment method of low-temperature plasma combined with pulsed electric field is adopted. Through the combination of low-temperature plasma and pulsed electric field, the sterilization of room-temperature fermented milk is achieved, the voltage and electric field strength is reduced, the loss of nutrients is reduced, and the original flavor of the food is maintained.
The effective sterilization of fermented milk is achieved at a lower voltage and electric field strength, maintaining the flavor quality, solving the flavor problems caused by traditional thermal sterilization, and improving the stability and taste of the product.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of dairy products, and in particular to room temperature fermented milk and a preparation method thereof. Background Art
[0002] Fermented milk is a milk product made from milk using a fermentation culture. It has a sweet and sour flavor and a delicate and smooth taste, and has high nutritional value, and is deeply loved by consumers. Pleasant flavor quality is an important evaluation indicator of food and the most important consumption driver.
[0003] Traditional long-shelf-life yogurt often adds protein powder, starch and other raw materials to improve the storage stability of the product, which increases production costs and makes the resulting yogurt taste rough and astringent. In addition, traditional fermented milk sterilization methods mainly use heat to kill microorganisms, but heating sterilization will have some adverse effects on the quality of room temperature fermented milk, such as causing the loss of heat-sensitive nutrients and producing odors. As consumers' demand for higher quality and fresher foods increases, non-thermal sterilization technology has emerged.
[0004] Non-thermal food sterilization technology refers to a new sterilization technology that does not use heat to kill microorganisms in food and maximizes the preservation of the original nutrition, texture, color and flavor of food. Cold Atmospheric Plasma (CAP) has the advantages of safety, high efficiency, green environmental protection, and no residue after reaction. It has shown great application potential in food microbial inactivation. However, high-dose CAP treatment can easily lead to a decrease in nutrient content, and a single sterilization technology has certain limitations in actual production applications.
[0005] Pulsed Electric Fields (PEF) has the advantages of low temperature rise, short processing time, low energy consumption, high efficiency and economic sustainability. It is considered to be one of the milestones in the development of food processing technology in the 21st century. However, a higher electric field strength (>30kV / cm) is required to meet the needs of practical applications. Increasing the PEF strength will affect the flavor characteristics and nutritional value of food.
[0006] At present, there is no report on the sterilization technology of room temperature fermented milk using low temperature plasma and pulse electric field. The present invention aims to reduce the external addition, solve the flavor problems of room temperature fermented milk such as odor, powdery and astringent caused by the heat sterilization process, and improve the flavor quality of room temperature fermented milk. Summary of the invention
[0007] In order to solve the defects of the prior art, the present invention provides a method for preparing room temperature fermented milk. In the preparation method provided by the present invention, a new sterilization method is adopted.
[0008] Specifically, the present invention has found that the use of low-temperature plasma combined with pulsed electric field can achieve sterilization of room-temperature fermented milk while reducing the treatment dose of low-temperature plasma and pulsed electric field. In addition, the sterilization method provided by the present invention is conducive to retaining the flavor of the fermented milk raw materials and obtaining room-temperature fermented milk with high flavor quality.
[0009] In a first aspect, the present invention provides a method for preparing room temperature fermented milk, comprising: mixing, homogenizing, first sterilization, adding a starter, fermenting, demulsifying, and second sterilization;
[0010] The first sterilization or the second sterilization is a low-temperature plasma treatment followed by a pulse electric field treatment; the low-temperature plasma treatment time is 1 to 5 minutes, the voltage is 3 to 5 kV, and the frequency is 1 to 3 kHz; the electric field intensity of the pulse electric field treatment is 8 to 15 kV / cm, and the number of pulses is 10 to 30.
[0011] In the prior art, in order to achieve effective sterilization, the voltage used by low-temperature plasma is relatively high, generally greater than 50kV; the electric field strength used by pulsed electric field is also relatively high, generally greater than 30kV / cm. The present invention proposes for the first time that low-temperature plasma combined with pulsed electric field is used for sterilization during the preparation of fermented milk. The combination of these two treatment methods has a synergistic effect, and can achieve effective sterilization of fermented milk at a lower voltage and lower electric field strength.
[0012] At the same time, since low-temperature plasma and pulsed electric field are both non-thermal sterilization with low voltage and electric field strength, they can reduce the loss of nutrients in fermented milk and effectively maintain the flavor of fermented milk.
[0013] More specifically, the sterilization method of the low-temperature plasma and pulsed electric field provided by the present invention is not only suitable for sterilizing the fermented curd, but also for sterilizing the raw milk after mixing.
[0014] In the method for preparing room temperature fermented milk provided by the present invention, during the first sterilization, low-temperature plasma treatment is used for 3 to 5 minutes and then a pulse electric field is performed. The electric field intensity of the pulse electric field treatment is 10 to 15 kV / cm, and the number of pulses is 20 to 30. Specifically, during the first sterilization, the raw milk mixed liquid is sterilized.
[0015] During the second sterilization, low-temperature plasma treatment is used for 1 to 3 minutes and then a pulsed electric field is used, wherein the number of pulses of the pulsed electric field is 8 to 12; specifically, during the second sterilization, the curd after fermentation and demulsification is sterilized.
[0016] In the method for preparing room-temperature fermented milk provided by the present invention, during the mixing, the temperature of the raw milk is raised to 40-50°C.
[0017] In the present invention, fermented cream is used as the fermented milk raw material, and the milk aroma and butter flavor of the fermented cream are fully retained through a sterilization method combining low-temperature plasma and pulse electric field.
[0018] As a specific embodiment of the present invention, the method for preparing room temperature fermented milk provided by the present invention comprises:
[0019] (1) adding other raw materials except the fermentation agent to raw milk to mix the raw materials to obtain a mixed liquid;
[0020] (2) After the mixed liquid is heated and homogenized, a first sterilization treatment is performed to obtain a sterilized mixed liquid;
[0021] (3) adding a fermentation agent to the sterilized mixed liquid, fermenting and demulsifying, and then cooling to obtain curd;
[0022] (4) performing a second sterilization treatment on the curd.
[0023] In the preparation method provided by the present invention, the starter comprises: one or more of Lactobacillus helveticus, Lactobacillus rhamnosus and Bifidobacterium adolescentis in the logarithmic growth phase.
[0024] In a second aspect, the present invention provides room temperature fermented milk, which is prepared by the above-mentioned preparation method.
[0025] In the room temperature fermented milk provided by the present invention, in the raw materials for preparing the room temperature fermented milk, fermented cream accounts for 0.3-0.5% of the raw materials of the room temperature fermented milk, chitosan accounts for 0.3-1% of the raw materials of the room temperature fermented milk, and starch accounts for 0.5-1% of the raw materials of the room temperature fermented milk.
[0026] In this recipe, the cultured cream has a high fat content, which may cause stability issues in the fermented milk. The high fat content may make the product more prone to separation or whey separation, affecting the appearance and taste of the product.
[0027] The present invention finds that the method of using low-temperature plasma and pulse electric field in combination can reduce the stability problem caused by fermented cream, and the prepared room-temperature fermented milk has a significant butter flavor. That is, the preparation method provided by the present invention is suitable for preparing room-temperature fermented milk containing fermented cream, and obtaining room-temperature fermented milk with butter flavor, which further proves that the sterilization method of low-temperature plasma and pulse electric field provided by the present invention is conducive to maintaining the stability of fermented milk while achieving sterilization, and retains the flavor of the raw materials used for fermented milk.
[0028] The raw materials for preparing the room temperature fermented milk provided by the invention include: 930-950 parts by weight of raw cow milk, 30-57 parts by weight of white sugar, 3-5 parts by weight of fermented cream, 3-10 parts by weight of chitosan and 5-10 parts by weight of starch.
[0029] The sterilization method of low-temperature plasma combined with pulse electric field technology provided by the present invention has universal applicability. When preparing room-temperature fermented milk of other formulas, the sterilization method can also achieve good results. Therefore, the present invention also provides room-temperature fermented milk of another formula.
[0030] By weight, among the raw materials for preparing the room temperature fermented milk, pectin accounts for 0.1-0.5% of the raw materials for the room temperature fermented milk, gellan gum accounts for 0.05-0.1% of the raw materials for the room temperature fermented milk, and starch accounts for 0.5-2% of the raw materials for the room temperature fermented milk.
[0031] Specifically, the raw materials for preparing the room temperature fermented milk include: 910-950 parts by weight of raw milk, 50-70 parts by weight of white sugar, 5-20 parts by weight of starch, 1-2 parts by weight of pectin and 0.5-1.5 parts by weight of gellan gum.
[0032] The beneficial effects of the present invention are:
[0033] The present invention sterilizes raw milk by low-temperature plasma combined with pulse electric field technology, and after inoculating the starter for fermentation, the curd is sterilized by low-temperature plasma combined with pulse electric field technology. The obtained finished product has a smooth taste and a pleasant creamy aroma, and solves the flavor quality problems such as odor, powdery feeling, and astringency faced by products produced by traditional thermal sterilization technology. In addition, the product has good stability after being placed at room temperature for 6 months. DETAILED DESCRIPTION
[0034] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0035] The method for activating the strain in the present invention is as follows: 200 μL of the strain stored in the glycerol tube is added to 10 mL of sterile liquid culture medium, and then cultured at 37°C for 16 to 18 hours for activation. After the culture is completed, 200 μL of the bacterial solution is added to a new 10 mL of sterile MRS broth culture medium or bifidobacterium culture medium, and then cultured at 37°C for 16 to 18 hours for activation to obtain the activated strain.
[0036] The inoculum size of activated Lactobacillus helveticus and Lactobacillus rhamnosus is 1% to 2% (v / v), and the inoculum size of activated Bifidobacterium adolescentis is 4% to 6% (v / v).
[0037] The starch used in the present invention is corn starch.
[0038] Example 1
[0039] In this embodiment, the raw materials of room temperature fermented milk are: 930 parts by weight of raw milk, 50 parts by weight of white sugar, 4 parts by weight of fermented cream, 8 parts by weight of chitosan, and 8 parts by weight of starch.
[0040] In this embodiment, the fermentation agent used is 1 part by weight of Lactobacillus helveticus in the logarithmic growth phase, 2 parts by weight of Lactobacillus rhamnosus, and 1 part by weight of Bifidobacterium adolescentis.
[0041] The preparation method of room temperature fermented milk in this embodiment is as follows:
[0042] (1) After heating raw milk to 40°C, add white sugar, fermented cream, chitosan and starch, and stir at 400 rpm for 7 minutes to obtain a mixed liquid.
[0043] (2) The mixed liquid was then heated to 65°C and homogenized at a total pressure of 110 bar and a secondary pressure of 40 bar. It was then treated with low-temperature plasma for 5 min (voltage 5 kV, frequency 2 kHz) and then with a pulsed electric field (electric field strength 12 kV / cm, number of pulses 30) to obtain a sterilized mixed liquid.
[0044] (3) The sterilized mixed liquid was heated to 42°C, and Lactobacillus helveticus, Lactobacillus rhamnosus and Bifidobacterium adolescentis in the logarithmic growth phase were inoculated; after fermentation for 5 hours, the acidity and pH were measured. When the acidity was 80 o When the pH value is 4.3, the mixture is stirred at 200 rpm for 10 min, and then the demulsified liquid is cooled to 25°C to inhibit fermentation, thereby obtaining curd;
[0045] (4) The curd is treated with low-temperature plasma for 2 minutes (voltage 3 kV, frequency 2 kHz) and then with a pulsed electric field (electric field strength 8 kV / cm, pulse number 10). Then, aseptic filling is performed to obtain a room temperature fermented milk product.
[0046] Example 2
[0047] The fermented milk raw materials and starter used in this embodiment are the same as those in Example 1, except that in the preparation method of this embodiment, the electric field strength is 15 kV / cm and the number of pulses is 20; the electric field strength of the pulsed electric field treatment used in step (4) is 9 kV / cm and the number of pulses is 8.
[0048] Example 3
[0049] The fermented milk raw materials and starter culture used in this embodiment are the same as those in Example 1, except that in the preparation method of this embodiment, the number of pulses used in the pulsed electric field treatment in step (2) and step (4) is 12.
[0050] Example 4
[0051] The fermented milk raw materials and fermentation agent used in this embodiment are the same as those in Example 1, except that: in the preparation method of this embodiment, the low-temperature plasma treatment time in step (2) is 6 minutes; and the low-temperature plasma treatment time in step (4) is 3 minutes.
[0052] Example 5
[0053] The fermented milk raw materials used in this embodiment are: 930 parts by weight of raw milk, 55 parts by weight of white sugar, 4 parts by weight of fermented cream, 3 parts by weight of chitosan, and 8 parts by weight of starch.
[0054] The leavening agent and preparation method used in this embodiment are the same as those in Example 1.
[0055] Example 6
[0056] In this embodiment, the fermented milk raw materials are 918.1 parts by weight of raw milk, 70 parts by weight of white sugar, 10 parts by weight of starch, 1.3 parts by weight of pectin and 0.6 parts by weight of gellan gum.
[0057] The leavening agent and preparation method used in this embodiment are the same as those in Example 1.
[0058] Comparative Example 1
[0059] In this comparative example, the fermented milk raw materials are 918.1 parts by weight of raw milk, 70 parts by weight of white sugar, 10 parts by weight of starch, 1.3 parts by weight of pectin and 0.6 parts by weight of gellan gum.
[0060] The fermentation agent used in this comparative example is 4 parts by weight of Lactobacillus helveticus in the logarithmic growth phase.
[0061] The difference between the preparation method of this comparative example and that of Example 1 is that in step (2), sterilization is performed after homogenization, the sterilization temperature is 132° C., and the sterilization time is 3 s.
[0062] The sterilization temperature of the sterilization treatment in step (4) is 75°C and the holding time is 20 s.
[0063] Comparative Example 2
[0064] The raw materials of fermented milk in this comparative example are the same as those in comparative example 1. The starter is the same as that in Example 1, which is 1 part by weight of Lactobacillus helveticus in the logarithmic growth phase, 2 parts by weight of Lactobacillus rhamnosus, and 1 part by weight of Bifidobacterium adolescentis.
[0065] The preparation method of this comparative example is the same as that of comparative example 1.
[0066] Comparative Example 3
[0067] In this comparative example, the fermented milk raw materials are 918.1 parts by weight of raw milk, 60 parts by weight of white sugar, 20 parts by weight of starch, 1.3 parts by weight of pectin and 0.6 parts by weight of gellan gum.
[0068] The leavening agent used in this comparative example is the same as that in comparative example 1. The preparation method of this comparative example is the same as that in comparative example 1.
[0069] Comparative Example 4
[0070] The fermented milk raw materials of this comparative example are the same as those of comparative example 1, and the starter is the same as that of comparative example 1.
[0071] The difference between the preparation method of this comparative example and that of comparative example 1 is:
[0072] In step (2), after homogenization, low-temperature plasma treatment is performed for 5 minutes at a voltage of 5 kV and a frequency of 2 kHz; in step (4), low-temperature plasma treatment is performed for 2 minutes at a voltage of 3 kV and a frequency of 2 kHz.
[0073] Comparative Example 5
[0074] The fermented milk raw materials of this comparative example are the same as those of comparative example 1, and the starter is the same as that of comparative example 1.
[0075] The difference between the preparation method of this comparative example and that of comparative example 1 is:
[0076] In step (2), after homogenization, pulse electric field treatment is performed, the electric field strength is 12 kV / cm, and the number of pulses is 30; in step (4), pulse electric field treatment is performed, the electric field strength is 8 kV / cm, and the number of pulses is 10.
[0077] Comparative Example 6
[0078] The formula and leavening agent of this comparative example are the same as those of Example 1, except that: the sterilization method used in step (2) of this comparative example is: low-temperature plasma treatment for 5 minutes (voltage 5 kV, frequency 2 kHz), followed by ultra-high pressure 620 MPa treatment for 15 minutes; the sterilization method used in step (4) is low-temperature plasma treatment for 2 minutes (voltage 3 kV, frequency 2 kHz), followed by ultra-high pressure 330 MPa treatment for 10 minutes.
[0079] Experimental Example 1 Results of centrifugal water loss during storage
[0080] The storage stability test of the yogurt prepared in the embodiment and the comparative example was carried out, and the centrifugal water loss rate was used as a measurement index. The centrifugal water loss rate of the product was measured after being placed at 25° C. for 3 months. The test conditions were 3500 rpm and the time was 20 min. The results are shown in Table 1.
[0081] Table 1 Centrifugal water loss during storage (%)
[0082]
[0083] It can be seen from Table 1 that, compared with the comparative example, the fermented milk prepared in the example has a lower centrifugal water loss rate during storage and better stability during storage.
[0084] The fermented milk obtained in Comparative Examples 1 and 2 has a high centrifugal water loss rate during storage, indicating that even if stabilizer components are added to the fermented milk raw materials, the stability of the fermented milk is still poor under an inappropriate sterilization method.
[0085] Comparison of the results of Comparative Example 3 with those of Comparative Examples 1-2 shows that simply adjusting the fermented milk formula cannot solve the problem of poor stability of the fermented milk caused by the sterilization method.
[0086] The results of Comparative Examples 4-5 indicate that non-thermal sterilization using only low-temperature plasma or pulsed electric field treatment cannot improve the stability of fermented milk.
[0087] Experimental Example 2 Sensory Evaluation
[0088] The sensory quality of the yogurt prepared in the embodiment and the comparative example was evaluated, and more than 15 professional and technical personnel conducted a sensory quantitative descriptive analysis test on the samples, and the standard of the quantitative descriptive analysis can be set to 0-5 points, with no feeling as 0, a little feeling as 1, a little feeling as 2, feeling as 3, a strong feeling as 4, and a very strong feeling as 5. The results are shown in Table 2.
[0089] Table 2 Sensory tasting results
[0090]
[0091] As can be seen from Table 2, compared with Comparative Examples 1 to 6, professional technicians felt that the room temperature fermented milk prepared in Examples 1 to 6 had stronger creamy taste, fermented taste and smoothness, and weaker astringency.
[0092] Experimental Example 3 Quantitative Results of Flavor Substances
[0093] The yogurt prepared in the embodiment and the comparative embodiment was subjected to a quantitative test of flavor substances. The flavor substances were qualitatively and quantitatively analyzed using the comprehensive two-dimensional gas chromatography-olfaction-mass spectrometry (GC×GC-O-MS) technology. First, the flavor substances in the yogurt were extracted by solid phase microextraction technology, and then analyzed by comprehensive two-dimensional gas chromatography-mass spectrometry and olfactometer. The obtained data were qualitatively analyzed by combining mass spectrometry qualitative analysis, retention index (RI) comparison, olfaction (O) comparison and standard compound (STD) verification. Then, the concentration of the obtained compound was quantitatively determined by the external standard quantitative method. 2-methyl-3-heptanone was used as the external standard. The analysis was performed under the same conditions of GC×GC-O-MS. The standard curve was obtained by plotting the response ratio of the standard and internal standard to their respective concentrations. Finally, the accurate concentration of the qualitative compound was determined according to the peak area and the standard curve. The results are shown in Table 3.
[0094]
[0095] As shown in Table 3, compared with the comparative example, the fermented milk prepared in the example has a higher concentration of substances with creamy and buttery flavors, which is consistent with the sensory tasting results.
[0096] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing room temperature fermented milk, characterized in that: include: Mixing, homogenization, first sterilization, adding starter, fermentation, demulsification, second sterilization; The first sterilization or the second sterilization is a low-temperature plasma treatment followed by a pulse electric field treatment; the low-temperature plasma treatment time is 1 to 5 minutes, the voltage is 3 to 5 kV, and the frequency is 1 to 3 kHz; the electric field intensity of the pulse electric field treatment is 8 to 15 kV / cm, and the number of pulses is 10 to 30; The raw materials for preparing the room temperature fermented milk are: 930-950 parts by weight of raw milk, 30-57 parts by weight of white sugar, 3-5 parts by weight of fermented cream, 3-10 parts by weight of chitosan and 5-10 parts by weight of starch.
2. The preparation method according to claim 1, characterized in that: During the first sterilization, the low-temperature plasma treatment is performed for 3 to 5 minutes and then a pulse electric field is performed. The electric field intensity of the pulse electric field treatment is 10 to 15 kV / cm, and the number of pulses is 20 to 30. During the second sterilization, the low-temperature plasma treatment is performed for 1 to 3 minutes and then the pulse electric field is performed, and the number of pulses of the pulse electric field is 10 to 12.
3. The preparation method according to claim 1, characterized in that: During the mixing, the raw milk is heated to 40-50°C.
4. The preparation method according to any one of claims 1 to 3, characterized in that include: (1) adding other raw materials except the fermentation agent to raw milk to mix the raw materials to obtain a mixed liquid; (2) After the mixed liquid is heated and homogenized, a first sterilization treatment is performed to obtain a sterilized mixed liquid; (3) adding a fermentation agent to the sterilized mixed liquid, fermenting and demulsifying, and then cooling to obtain curd; (4) performing a second sterilization treatment on the curd.
5. The preparation method according to claim 4, characterized in that: Leavening agents include: One or more of Lactobacillus helveticus, Lactobacillus rhamnosus and Bifidobacterium adolescentis in logarithmic growth phase.
6. A room temperature fermented milk, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.
7. The room temperature fermented milk according to claim 6, characterized in that: In terms of weight, among the raw materials for preparing the room temperature fermented milk, fermented cream accounts for 0.3-0.5% of the raw materials for the room temperature fermented milk, chitosan accounts for 0.3-1% of the raw materials for the room temperature fermented milk, and starch accounts for 0.5-1% of the raw materials for the room temperature fermented milk.