Flavor-enhanced fermented milk tea and preparation method thereof

Abstract

The invention provides flavor-enhanced fermented milk tea and a preparation method thereof, and the flavor-enhanced fermented milk tea is prepared by fermenting a milk tea matrix by adopting lactobacillus casei and kluyveromyces marxianus based on plasma activated water (PAW) combined with an oil-water interface fermentation technology. According to the present invention, the plasma activated water (PAW) is combined with the oil-water interface fermentation technology, such that the efficient enrichment of the fermentation flora on the oil-water interface can be achieved, the growth of the infectious microbes can be inhibited, the fermentation efficiency and the milk tea flavor can be significantly improved, the addition of the synthetic emulsifier is not required, and the centrifugal precipitation rate and the fat floating rate of the product can be substantially reduced. The invention provides a green solution with high safety, excellent stability and excellent sensory quality for the industrial production of the fermented milk tea, and has important value for promoting the upgrading of the traditional dairy product industry.

Description

Technical Field

[0001] This invention belongs to the field of milk tea technology, specifically relating to a flavor-enhanced fermented milk tea and its preparation method. Background Technology

[0002] The current milk tea and fermented milk tea industry faces several pressing technical challenges, primarily manifested in low fermentation efficiency, limited flavor profiles, poor product stability, and short shelf life. Traditional fermented milk tea production processes mainly rely on the natural metabolic processes of natural microorganisms or commercial starter cultures. However, the antibacterial properties of tea polyphenols significantly inhibit microbial activity, leading to prolonged fermentation cycles and insufficient viable cell counts. Furthermore, oil-water separation occurs during fermentation, necessitating the use of synthetic emulsifiers to maintain system stability. Additionally, traditional high-temperature sterilization techniques destroy active ingredients such as tea polyphenols and vitamins, while low-temperature sterilization struggles to balance microbial safety with the retention rate of active ingredients. To ensure product shelf life, the only options are to add chemical preservatives or rely on cold chain transportation, increasing costs and reducing health benefits, thus failing to meet commercial requirements.

[0003] Based on the aforementioned technical bottlenecks, the industry urgently needs to develop an innovative solution that can simultaneously improve fermentation efficiency, product stability, health attributes, and flavor quality. The flavor-enhanced fermented milk tea and its preparation method provided by this invention offer a new paradigm for the industrialization of fermented milk tea. It not only solves the technical bottlenecks of traditional processes in terms of efficiency, stability, and health attributes, but also meets the current consumer demand for additive-free beverages and naturally mellow flavors, thus possessing significant market application prospects and industrialization promotion value. Summary of the Invention

[0004] Technical problem to be solved: In view of the above-mentioned technical problems, the first objective of the present invention is to provide a flavor-enhanced fermented milk tea.

[0005] A second objective of this invention is to provide a method for preparing the flavor-enhanced fermented milk tea.

[0006] Technical solution: A flavor-enhanced fermented milk tea is prepared by fermenting a milk tea matrix using plasma-activated water (PAW) combined with oil-water interface fermentation technology and a compound fermentation agent.

[0007] Preferably, the compound fermentation agent includes Lactobacillus casei and Kluyveromyces martensii; the Lactobacillus casei was purchased from Xi'an Xihai Biotechnology Co., Ltd., catalog number XH177; the Kluyveromyces martensii was purchased from Anhui Xinsheng Biotechnology Co., Ltd., catalog number 241224.

[0008] Preferably, the milk tea base includes whole milk powder, tea powder, sucrose, and fructooligosaccharides.

[0009] A method for preparing flavor-enhanced fermented milk tea includes the following steps:

[0010] S1. Preparation of plasma activated water (PAW): PAW is prepared by treating production water using an atmospheric pressure plasma jet (APPJ) multi-nozzle system.

[0011] S2. Preparation of milk tea base: Add tea powder, whole milk powder, sucrose and fructooligosaccharides to PAW, stir until completely dissolved, and pasteurize to obtain aseptic milk tea base;

[0012] S3. Constructing an oil-water interface fermentation system: Coconut oil is heated, added to aseptic milk tea base and stirred evenly. After cooling, vitamin E is added, and after high-speed shearing and high-pressure homogenization, a microemulsion is obtained.

[0013] S4. Fermentation: Lactobacillus casei and Kluyveromyces martensii are combined to prepare a compound fermentation agent, which is then inoculated into a microemulsion and fermented at low speed. After fermentation, the mixture is pasteurized at low temperature to produce flavor-enhanced fermented milk tea.

[0014] S5. Post-processing: Pectin is added to the fermented milk tea, and after homogenization and vacuum degassing, it is cooled and filled into sterile containers under aseptic conditions.

[0015] Preferably, the active components of PAW in step S1 include reactive oxygen species and reactive nitrogen species, including but not limited to hydroxyl radicals, H2O2, and NO3. - .

[0016] Preferably, the voltage of the APPJ multi-nozzle system in step S1 is 5~10 kV.

[0017] Preferably, the power of the APPJ multi-nozzle system in step S1 is 20~40 W.

[0018] Preferably, the processing time of the APPJ multi-nozzle system in step S1 is 1 to 4 minutes.

[0019] Preferably, the gas in the APPJ multi-nozzle system in step S1 is an N2 / O2 mixture, and the volume ratio of N2 to O2 is 5~10:2~4.

[0020] Preferably, the total gas flow rate of the APPJ multi-nozzle system in step S1 is 5~10 L / min.

[0021] Preferably, the solid-liquid ratio in the aseptic milk tea matrix in step S2 is 0.15~0.4:1.

[0022] Preferably, the mass ratio of tea powder to whole milk powder in step S2 is 1:4~8.

[0023] Preferably, the total amount of sucrose and fructooligosaccharides added in step S2 is 2-8 wt%.

[0024] Preferably, in step S2, the pasteurization temperature is 70-80℃ and the pasteurization time is 10-15 seconds.

[0025] Preferably, the volume ratio of aseptic milk tea base to coconut oil in step S3 is 1:0.2~0.28.

[0026] Preferably, the amount of vitamin E added in step S3 is 0.005~0.007 wt%.

[0027] Preferably, the viable count of Lactobacillus casei in the compound fermentation agent in step S4 is 4.2~5.7×10⁻⁶. 6 CFU / mL.

[0028] Preferably, the viable count of *Kluyveromyces martensii* in the compound fermentation agent in step S4 is 3.3~6.5 × 10⁻⁶. 5 CFU / mL.

[0029] Preferably, the volume ratio of the compound fermentation agent to the microemulsion in step S4 is 1~1.5:4~7.

[0030] Preferably, the amount of pectin added in step S5 is 0.1~0.35%.

[0031] Beneficial effects:

[0032] 1. Ordinary water, as a solvent, has no effect on promoting the activity of fermentation microorganisms and cannot regulate the fermentation pathway. This invention uses low-temperature plasma to treat production water to generate PAW with a high redox potential. PAW is rich in hydroxyl radicals, H2O2, and NO3. - The active ingredients can regulate the metabolic process of the fermentation microbial community. By combining with the oil-water interface, they form micron-sized oil droplets in the fermentation system, which enriches the fermentation microbial communities of Lactobacillus casei (strong hydrophobicity) and Kluyveromyces martensii (whose cell wall mannose protein can anchor oil droplets) at the oil-water interface. The active particles in PAW can not only reduce the interfacial tension of oil and water to form a more stable microemulsion system, expand the contact area of ​​the fermentation microbial community and improve the fermentation efficiency, but also activate the metabolic pathways of the fermentation microbial community and promote the synthesis of flavor substances such as ketones and aldehydes. This makes the flavor-enhanced fermented milk tea product prepared by this invention more flavorful and improves the sensory score by 22.9~48.2%.

[0033] 2. Hydrophilic bacteria (such as Escherichia coli) tend to grow in the aqueous phase, while the hydrophobic layer (oil phase) at the oil-water interface hinders their migration to the nutrient-rich aqueous phase regions such as milk proteins and sugars, thus limiting their proliferation. Molds usually depend on the surface of the aqueous or solid phase for growth. The physical barrier formed at the oil-water interface can reduce their attachment points and decrease the probability of colony formation. At the same time, H2O2 in PAW can also inhibit other bacteria, creating a favorable environment for the fermentation community, which can improve fermentation efficiency and avoid contamination by other bacteria.

[0034] 3. The active components (reactive oxygen / reactive nitrogen) in PAW can reduce interfacial tension. During fermentation, the fermentation microorganisms colonize the oil-water interface and secrete natural bio-emulsifiers (such as polysaccharides, proteins, and biosurfactants). These metabolites synergistically form a dense interfacial film structure with PAW, which can effectively prevent fat globule aggregation and phase separation. PAW can also promote the covalent cross-linking of milk proteins and tea polyphenols, improving emulsion stability. The fatty acids produced by the fermentation microorganisms can reduce interfacial tension, increase the interfacial viscoelastic modulus, effectively resist oil droplet collision and coalescence, and maintain the homogeneity of the system. The flavor-enhanced fermented milk tea product prepared by this invention did not show stratification after standing at room temperature for 30 days. A stable emulsion system was constructed without adding synthetic emulsifiers, thus improving the stability of the product. Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments:

[0036] Example 1

[0037] This embodiment describes the preparation of flavor-enhanced fermented milk tea, including the following steps:

[0038] S1. Preparation of PAW: An atmospheric pressure plasma jet (APPJ) multi-nozzle system was used to treat production water to generate active oxygen and active nitrogen. Process parameters: voltage 8 kV, power 30 W, N2 / O2 mixed gas (8:2, v / v), total gas flow rate 8 L / min, treatment time 3 min, yielding a pH of 6.5–7.5, H2O2 concentration of 30 mg / L, and NO3-. - PAW at a concentration of 8 mg / L and an oxidation-reduction potential (ORP) of 420 mV;

[0039] S2. Preparation of milk tea base: Dissolve 0.35 kg of tea powder and 2.1 kg of whole milk powder in 15 L of PAW, stir at 50℃ for 20 min, add 0.3 kg of sucrose and 0.15 kg of oligofructose, stir evenly, and pasteurize at 75℃ for 15 s to obtain aseptic milk tea base.

[0040] S3. Constructing an oil-water interface fermentation system: 3.3 L of coconut oil was heated to 60℃, added to aseptic milk tea matrix, stirred evenly, cooled to 40℃, 344.5 mg of mixed tocopherol concentrate was added, high-speed shearing at 10000 rpm for 2 min, and then homogenized twice under high pressure at 50 MPa to obtain a microemulsion.

[0041] S4. Preparation of compound fermentation inoculum: Lactobacillus casei and Kluyveromyces martensii were combined to prepare a compound fermentation inoculum. The viable count of Lactobacillus casei in the compound fermentation inoculum was 5.3 × 10⁻⁶. 6 The viable count of *Kluyveromyces martensii* was 4.8 × 10⁻⁶ CFU / mL. 5 CFU / mL;

[0042] S5. Fermentation: The compound fermentation agent was inoculated into the microemulsion at a volume ratio of 1.2:5.6, and fermented at 32℃ and 50 rpm with low stirring. Fermentation was terminated when the pH dropped to 4.3±0.2, and pasteurized at 50℃ for 25 min. The lactic acid content was ≥8 g / L and the ethanol content was ≤0.5%.

[0043] S6. Post-processing: Add 0.1% pectin to the fermented milk tea, homogenize once at 20 MPa, degas under vacuum at -0.05 MPa and 20°C, cool to ≤25°C in a sterile environment (cleanliness ≥ ISO 8 level), and fill into sterile containers.

[0044] Example 2

[0045] The difference between this embodiment and Embodiment 1 is that the volume ratio of N2 to O2 in this embodiment is 6:4.

[0046] Example 3

[0047] The difference between this embodiment and Embodiment 1 is that the amount of coconut oil added in this embodiment is 3.9 L.

[0048] Example 4

[0049] The difference between this embodiment and Embodiment 1 is that the viable count of Lactobacillus casei in this embodiment is 4.5 × 10⁻⁶. 6 CFU / mL, viable count of Kluyveromyces maculae was 6.2 × 10⁻⁶. 5 CFU / mL.

[0050] Example 5

[0051] The difference between this embodiment and Embodiment 1 is that the volume ratio of the compound fermentation agent and the microemulsion in this embodiment is 1.2:4.

[0052] To further illustrate the technical effects of the present invention, a comparative example is also provided, as follows:

[0053] Comparative Example 1

[0054] The difference between this comparative example and Example 1 is that this comparative example uses ordinary water fermentation.

[0055] Comparative Example 2

[0056] The difference between this comparative example and Example 1 is that this comparative example is a common water-oil interface fermentation.

[0057] Comparative Example 3

[0058] The difference between this comparative example and Example 1 is that this comparative example involves PAW fermentation alone.

[0059] Comparative Example 4

[0060] The difference between this comparative example and Example 1 is that the oil-water interface fermentation technology in this comparative example is replaced by the addition of an emulsifier, namely sucrose ester and sodium carboxymethyl cellulose, wherein the amount of sucrose ester added is 30 g and the amount of sodium carboxymethyl cellulose added is 15 g.

[0061] Table 1 Physicochemical properties of Examples 1-5 and Comparative Examples 1-4

[0062]

[0063] As shown in Table 1, compared with ordinary water fermentation (Comparative Example 1), ordinary water combined with oil-water interface fermentation (Comparative Example 2), PAW fermentation alone (Comparative Example 3), and PAW combined with emulsifier (Comparative Example 4), the protein, fat, tea polyphenol, and caffeine content and the bacterial concentration at the oil-water interface during fermentation in Examples 1-5 of this invention are all higher than in all comparative examples. This indicates that PAW combined with the oil-water interface (Examples 1-5) forms a more stable microenvironment, which is more conducive to the metabolic activities of microorganisms on the one hand, and promotes the enrichment of microorganisms at the interface on the other hand, promotes the decomposition or transformation of milk protein and fat, and forms small molecule peptides, free amino acids, or emulsified fats that are easier to retain. In addition, the active ingredients (reactive oxygen and reactive nitrogen) in PAW degrade the cell wall of tea leaves, promote the dissolution of tea polyphenols and caffeine, and the oil-water interface may prevent these components from excessively binding and precipitating with milk protein through adsorption, thus reducing component loss to a certain extent.

[0064] Table 2. Microbial detection of Examples 1-5 and Comparative Examples 1-4

[0065]

[0066] As shown in Table 2, compared with ordinary water fermentation (Comparative Example 1), ordinary water combined with oil-water interface fermentation (Comparative Example 2), PAW fermentation alone (Comparative Example 3), and PAW combined with emulsifier (Comparative Example 4), the colony counts of *E. coli* and *Mold* in Examples 1-5 of this invention were significantly lower than those in the comparative examples. The active ingredients (reactive oxygen and reactive nitrogen) in PAW can destroy the cell membrane of microorganisms, oxidize proteins and nucleic acids, thereby inhibiting the growth of *E. coli*, *Mold*, and other miscellaneous bacteria. The hydrophobic-hydrophilic cross-linking structure formed at the oil-water interface restricts the migration and colonization of miscellaneous bacteria, especially inhibiting the adsorption of highly hydrophilic *E. coli* and *Mold*. In addition, lactic acid bacteria also further inhibit the growth of miscellaneous bacteria by competing for nutrients and secreting substances such as bacteriocins.

[0067] Table 3. Stability of Examples 1-5 and Comparative Examples 1-4

[0068]

[0069] As shown in Table 3, compared with ordinary water fermentation (Comparative Example 1), ordinary water combined with oil-water interface fermentation (Comparative Example 2), PAW fermentation alone (Comparative Example 3), and PAW combined with emulsifier (Comparative Example 4), the centrifugal sedimentation rate and fat flotation rate in Examples 1-5 of this invention were significantly lower than those in the comparative examples, and the product homogeneity was better, with no stratification observed after standing at room temperature for 30 days. In contrast, due to poor stability, Comparative Examples 1-4 all showed obvious solution stratification after standing at room temperature for 30 days, accompanied by fat flotation and flocculent precipitation.

[0070] Table 4 Sensory Scoring Details

[0071]

[0072] Table 5. Flavor compound content and sensory scores of Examples 1-5 and Comparative Examples 1-4

[0073]

[0074] As shown in Table 5, compared with ordinary water fermentation (Comparative Example 1), ordinary water combined with oil-water interface fermentation (Comparative Example 2), PAW fermentation alone (Comparative Example 3), and PAW combined with emulsifier (Comparative Example 4), the relative contents of ketones and aldehydes in Examples 1-5 of the present invention are significantly higher than those in Comparative Examples 1-4. The sensory scores are 90.06-92.65 points, which shows that the taste is mellow, the flavor is rich and balanced, the mouthfeel is delicate and smooth, and the aftertaste is long and lasting. The overall flavor characteristics are significantly better than those of the comparative examples.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A flavor-enhanced fermented milk tea, characterized in that: The flavor-enhanced fermented milk tea is prepared by fermenting a milk tea base with a compound fermentation agent, which includes Lactobacillus casei and Kluyveromyces martensii. The milk tea base includes whole milk powder, tea powder, sucrose, and fructooligosaccharides.

2. The method for preparing a flavor-enhanced fermented milk tea according to claim 1, characterized in that, Includes the following steps: S1. Preparation of plasma-activated water: Production water is treated using an atmospheric pressure plasma jet multi-nozzle system to obtain plasma-activated water; S2. Preparation of milk tea base: Add tea powder, whole milk powder, sucrose and fructooligosaccharides to plasma-activated water, stir until completely dissolved, and pasteurize to obtain aseptic milk tea base; S3. Constructing an oil-water interface fermentation system: Coconut oil is heated, added to aseptic milk tea base and stirred evenly. After cooling, vitamin E is added, and after high-speed shearing and high-pressure homogenization, a microemulsion is obtained. S4. Fermentation: Lactobacillus casei and Kluyveromyces martensii are combined to prepare a compound fermentation agent, which is then inoculated into a microemulsion and fermented at low speed. After fermentation, the mixture is pasteurized at low temperature to produce flavor-enhanced fermented milk tea. S5. Post-processing: Pectin is added to the fermented milk tea, and after homogenization and vacuum degassing, it is cooled and filled into sterile containers under aseptic conditions.

3. The preparation method according to claim 2, characterized in that: The active components in the plasma-activated water during step S1 include reactive oxygen species and reactive nitrogen species, including but not limited to hydroxyl radicals, H2O2, and NO. 3- .

4. The preparation method according to claim 2, characterized in that: In step S2, the solid-liquid ratio of the aseptic milk tea matrix is ​​0.15~0.4:1; the mass ratio of tea powder to whole milk powder is 1:4~8; and the total amount of sucrose and fructooligosaccharides added is 2~8 wt%.

5. The preparation method according to claim 2, characterized in that: In step S3, the volume ratio of aseptic milk tea base to coconut oil is 1:0.2~0.28; the amount of vitamin E added is 0.005~0.007 wt%.

6. The preparation method according to claim 2, characterized in that: In step S4, the viable count of Lactobacillus casei in the compound fermentation agent is 4.2~5.7×10⁻⁶. 6 The viable count of *Kluyveromyces martensii* was 3.3–6.5 × 10⁻⁶ CFU / mL. 5 CFU / mL; the volume ratio of the compound fermentation agent to the microemulsion is 1~1.5:4~7.

7. The preparation method according to claim 2, characterized in that: The amount of pectin added in step S5 is 0.1~0.35 wt%.

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