High-protein liquid yogurt and preparation method thereof

Abstract

The present invention discloses a high-protein liquid yogurt and a preparation method thereof, belonging to the field of dairy product processing. The high-protein liquid yogurt provided by the present invention is fermented with a bird's nest enzymatic hydrolysate, milk powder, and yogurt starter at a mass ratio of 100:(12-14):(0.008-0.012) with a concentration of 4%-6%. The liquid yogurt has a pH value of 4.1≤pH≤4.5 and a lactic acid bacteria count of >1×10 8 CFU / g, protein content>5.0%; the preparation method of the high-protein liquid yogurt provided by the present invention is as follows: after the bird's nest is enzymatically hydrolyzed with a neutral protease, milk powder is added to the bird's nest enzymatic hydrolyzate, the mixture is stirred and homogenized, sterilized, cooled, a starter is added, and fermented for 5-6 hours to obtain the high-protein liquid yogurt; the present invention is based on the fact that the interaction between the hydrolyzed bird's nest protein and the milk protein can hinder the pH drop during the fermentation process to cause protein gelation but does not affect the fermentation of lactic acid bacteria, thereby producing liquid yogurt with a high protein content; the high-protein liquid yogurt prepared by the present invention has good fluidity without homogenization after fermentation, and does not stratify or precipitate after low-temperature storage.

Description

Technical Field

[0001] The present invention relates to the field of dairy product processing, and in particular to a high-protein liquid yogurt and a preparation method thereof. Background Art

[0002] Yogurt is a gel-like dairy product made from raw cow's milk, raw goat's milk, or milk powder through sterilization and fermentation. However, some consumers who prefer a lighter taste have a low tolerance for the gel-like texture of traditional set yogurt. Therefore, the dairy industry stirs and homogenizes the set yogurt after fermentation to produce a flowable stirred yogurt. Compared to set yogurt, stirred yogurt has enhanced fluidity, but also increases production costs. Furthermore, because stirring or homogenization disrupts the protein gel structure in the yogurt, stirred yogurt is prone to whey separation during storage. Currently, most yogurts on the market have similar protein levels. Therefore, there is an urgent need for a high-protein yogurt product that exhibits fluidity without stirring or homogenization, has low viscosity, and does not experience whey separation.

[0003] Bird's nest is a recognized and precious food in my country, with a high protein content and a large amount of bird's nest acid. It is often sold in the form of bird's nest strips, fresh stewed bird's nest, etc. However, the processing of bird's nest produces a large amount of bird's nest fragments. Compared with bird's nest strips, bird's nest fragments are cheaper and have lower added value, but they also contain a large amount of bird's nest acid and have a high nutritional value. In the process of exploring the utilization of bird's nest fragments, this research team unexpectedly discovered that after protease hydrolysis of bird's nest, it can hinder the gelation of milk protein caused by the decrease in pH during milk fermentation without affecting the fermentation of lactic acid bacteria, thereby forming a low-viscosity, flowable liquid yogurt with a high protein content, without the need for homogenization after fermentation. At the same time, it is also rich in bird's nest acid. Therefore, the present invention aims to provide a high-protein liquid yogurt and a method for preparing it. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-protein liquid yogurt and a preparation method thereof, so as to improve the problems in the dairy industry such as the need to stir the solidified yogurt after fermentation to obtain flowable yogurt, the increased production cost, and the easy whey separation during storage of stirred yogurt.

[0005] In one aspect, the present invention provides a method for preparing a bird's nest enzymatic hydrolysate, comprising the following steps:

[0006] Mix the sieved bird's nest crumbs with distilled water to prepare a bird's nest suspension;

[0007] Adding neutral protease to the bird's nest suspension to enzymatically hydrolyze the bird's nest;

[0008] The neutral protease is inactivated and filtered to obtain the bird's nest enzymatic hydrolysate.

[0009] In some embodiments, the sieve has a mesh size of 80-100.

[0010] In some embodiments, the amount of neutral protease added is 300 U / g of bird's nest crumbs.

[0011] Another invention provides a method for preparing high-protein liquid yogurt, comprising the following steps:

[0012] Adding milk powder to the bird's nest enzymatic hydrolysate, stirring evenly, sterilizing, cooling, and then adding yogurt starter to prepare a fermentation raw material;

[0013] The fermentation raw materials are fermented and post-ripened to produce high-protein liquid yogurt.

[0014] Preferably, the milk powder includes at least one of cow milk powder, goat milk powder and camel milk powder.

[0015] Preferably, the mass ratio of the bird's nest enzymatic hydrolysate: milk powder: yogurt starter is 100: (12-14): (0.008-0.012).

[0016] Preferably, the sterilization treatment conditions are: 75-80°C for 25-30 min.

[0017] Preferably, the fermentation conditions are: fermentation at an ambient temperature of 42-44°C for 4-6 hours.

[0018] Preferably, the post-ripening conditions are: lowering the temperature to 3-5°C and then leaving it for 20-28 hours.

[0019] The beneficial effects of the present invention include:

[0020] (1) In the preparation method of high-protein liquid yogurt provided by the present invention, after the bird's nest fragments are enzymatically hydrolyzed by protease, the gelation of milk protein caused by the decrease in pH during milk fermentation can be hindered without affecting the fermentation of lactic acid bacteria, and at the same time, the yogurt is enriched with bird's nest acid;

[0021] (2) The high-protein liquid yogurt provided by the present invention is liquid without stirring after fermentation, has fluidity and low viscosity, and has high protein content, and has no significant difference in pH and total bacterial count compared with traditional gel-type yogurt;

[0022] (3) The high-protein liquid yogurt provided by the present invention has no stratification phenomenon and no precipitation after being stored at low temperature for three months, and the product has a refreshing taste. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The appearance of the yogurt prepared in the embodiment of the present invention (right) and the comparative example (left);

[0024] Figure 2 The microstructure of yogurt prepared in the embodiment of the present invention (right) and the comparative example (left). DETAILED DESCRIPTION

[0025] The present invention will be further described with reference to the accompanying drawings.

[0026] On the one hand, an embodiment of the present invention provides a method for preparing a bird's nest enzymatic hydrolyzate, comprising the following steps:

[0027] S1. Mix the sieved bird's nest fragments with distilled water to prepare a bird's nest suspension;

[0028] S2, adding neutral protease to the bird's nest suspension to enzymatically hydrolyze the bird's nest;

[0029] S3, inactivating the neutral protease, and filtering to obtain the bird's nest enzymatic hydrolysate.

[0030] In some embodiments, the sieve has a mesh size of 80-100.

[0031] In some embodiments, the amount of neutral protease added is 300 U / g of bird's nest crumbs.

[0032] Another invention, an embodiment of the present invention provides a method for preparing high-protein liquid yogurt, comprising the following steps:

[0033] D1. Add milk powder to the bird's nest enzymatic hydrolysate, stir evenly and sterilize.

[0034] At 42-44°C, add yogurt starter to prepare fermentation raw material;

[0035] D2. Fermenting and post-ripening the fermentation raw materials to obtain high-protein liquid yogurt.

[0036] In some embodiments, the milk powder in step D1 includes at least one of cow milk powder, goat milk powder, and camel milk powder.

[0037] Specifically, the mass ratio of the bird's nest enzymatic hydrolysate: milk powder: yogurt starter is 100: (12-14): (0.008-0.012).

[0038] In some embodiments, the sterilization treatment conditions in step D1 are: sterilization at 75-80° C. for 25-30 minutes.

[0039] In some embodiments, the fermentation conditions in step D3 are: fermentation at an ambient temperature of 42-44° C. for 4-6 hours.

[0040] In some embodiments, the post-ripening condition in step D3 is: lowering the temperature to 3-5° C. and then post-ripening for 20-28 hours.

[0041] The yogurt starter involved in the embodiments of the present invention can be a conventional yogurt starter powder available on the market; specifically, the yogurt starter used in the embodiments of the present invention is purchased from Chr. Hansen A / S of Denmark; the bird's nest crumbs used in the embodiments of the present invention are from Xiamen Yanzhiwu Sinong Food Co., Ltd.; the neutral protease used in the embodiments of the present invention is purchased from Henan Wanbang Chemical Technology Co., Ltd.

[0042] Example 1

[0043] Example 1 of the present invention provides a high-protein liquid yogurt and a preparation method thereof

[0044] The preparation method of bird's nest enzymatic hydrolysate comprises the following steps:

[0045] S0, crush the bird's nest and pass it through a 100 mesh sieve:

[0046] S1, 4g of sieved bird's nest crushed was added to 100g of distilled water to prepare a bird's nest suspension;

[0047] S2. Cool the bird's nest suspension to 53°C and place in a boiling water bath for 20 min. After the water bath, cool it to 53°C and add 1200 U of neutral protease to react for 2 h.

[0048] S3, the above solution was placed in a boiling water bath for 2 minutes to inactivate the neutral protease, and filtered to obtain the bird's nest enzymatic hydrolysate:

[0049] After the bird's nest enzymatic hydrolysate is obtained, high-protein liquid yogurt is prepared by the following steps, including:

[0050] D1, 12g of milk powder was mixed with 100g of bird's nest enzymatic hydrolysate, stirred and homogenized, and then heat sterilized at 80°C for 30 min, cooled to 43°C, and 0.012g of yogurt starter was added to obtain a fermentation raw material;

[0051] D2. Ferment the fermented raw materials at 43°C for 5 hours. After fermentation, cool them to 4°C and post-ripen them at 4°C for 24 hours to obtain high-protein liquid yogurt.

[0052] Example 2

[0053] Example 2 of the present invention provides a high-protein liquid yogurt and a preparation method thereof, which is different from Example 1 in that: the amount of bird's nest crumbs added in step S1 is 5 g; the amount of neutral protease added in step S2 is 1500 U; the amount of milk powder added in step D1 is 13 g; and the other conditions and steps are consistent with Example 1.

[0054] Example 3

[0055] Example 3 of the present invention provides a high-protein liquid yogurt and a preparation method thereof, which is different from Example 1 in that: the amount of bird's nest crumbs added in step S1 is 6 g; the amount of neutral protease added in step S2 is 1800 U; the amount of milk powder added in step D1 is 14 g; and the other conditions and steps are consistent with Example 1.

[0056] Comparative Example 1

[0057] The comparative example of the present invention provides a method for preparing yogurt, which is different from that of Example 1 in that: the bird's nest enzymatic hydrolyzate is replaced by water; and the other steps and conditions are consistent with those of Example 1.

[0058] Property detection

[0059] The present invention measured and compared the pH, lactic acid colony count, protein content, etc. of the yogurt prepared in Examples 1, 2, 3 and Comparative Example 1:

[0060] (1) pH is measured using a pH meter;

[0061] (2) The number of lactic acid colonies was determined according to the dilution plate count method specified in GB 4789.35;

[0062] (3) Protein content was determined by Kjeldahl method:

[0063] (4) The yogurts prepared in Examples 1-3 and Comparative Example 1 were stored at 4°C for 3 months to observe whether there was stratification or precipitation; the results are shown in Table 1;

[0064] At the same time, the present invention measured the appearance and microscopic morphology of the yogurt prepared in Example 1 and Comparative Example 1: The appearance and morphology were directly observed visually, and the results were as follows: Figure 1 As shown in the figure, the microstructure of yogurt was observed by using Nile blue to stain milk protein and then using a laser confocal microscope to observe the microstructure of yogurt. Figure 2 As shown;

[0065] Table 1 Comparison of properties of yogurt

[0066]

[0067] Referring to the table, it can be found that the protein content of the yogurt prepared in the embodiments provided by the present invention is higher than that of the comparative example, and the protein content of the yogurt prepared in the embodiments is higher than that of the comparative example; the yogurt prepared in the embodiments of the present invention has fluidity, does not delaminate, and does not precipitate after being stored at ℃ for months, while a slight whey precipitation occurs on the surface of the yogurt in the comparative example; the S+ value and lactic acid colony count of the high-protein liquid yogurt provided by the present invention are not significantly different from those of ordinary yogurt, and both exceed the ×&)8J specified in *%.

[0068] Referring to the figure, it can be found through direct visual observation that the yogurt prepared in the embodiment of the present invention (right) is liquid and flowable; while the yogurt in the comparative example (left) is solid and cannot flow. It can be concluded that the yogurt prepared in the embodiment of the present invention has strong fluidity without stirring after fermentation.

[0069] Referring to the figure, the protein in the yogurt prepared in the comparative example (left) formed a continuous gel network, while the protein in the yogurt prepared in the embodiment of the present invention (right) formed smaller, discontinuous aggregates. Therefore, the yogurt was not gelled but was liquid and had fluidity.

[0070] While the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. A method for preparing high-protein liquid yogurt, characterized in that: The following steps are involved: Adding milk powder to the bird's nest enzymatic hydrolysate, stirring evenly, sterilizing, cooling, and adding yogurt starter to prepare a fermentation raw material; the mass ratio of the bird's nest enzymatic hydrolysate: milk powder: yogurt starter is 100: (12-14): (0.008-0.012); The fermentation raw materials are fermented and post-ripened without stirring after fermentation to obtain a high-protein liquid yogurt with a bird's nest enzymatic hydrolyzate concentration of 4.0%-6.0%; The preparation method of the bird's nest enzymatic hydrolysate comprises the following steps: Mix the sieved bird's nest crumbs with distilled water to prepare a bird's nest suspension; Neutral protease was added to the bird's nest suspension at an addition rate of 300 U / g of bird's nest crumbs to enzymatically hydrolyze the bird's nest; The neutral protease is inactivated and filtered to obtain the bird's nest enzymatic hydrolysate.

2. The method according to claim 1, characterized in that The sieved bird's nest fragments are mixed with distilled water, wherein the sieved sieve has a mesh size of 80-100.

3. The method according to claim 1, characterized in that In the step of adding milk powder to the bird's nest enzymatic hydrolysate, the milk powder includes at least one of cow milk powder, goat milk powder and camel milk powder.

4. The method according to claim 1, wherein After stirring evenly, a sterilization step is performed, wherein the sterilization conditions are: sterilization at 75-80°C for 25-30 minutes.

5. The method according to claim 1, characterized in that The fermentation raw materials are fermented and post-ripened, and the fermentation conditions are: fermentation at an ambient temperature of 42-44°C for 4-6 hours.

6. The method according to claim 1, characterized in that In the step of fermenting and post-ripening the fermentation raw materials, the post-ripening conditions are: lowering the temperature to 3-5°C and then leaving it for 20-28 hours.

7. A high-protein liquid yogurt prepared by the method according to any one of claims 1 to 6.

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