Preparation method of jackfruit-based postbiotic coffee

Abstract

The application discloses a preparation method of a jackfruit-based postbiotic coffee and belongs to the technical field of food. Jackfruit is used as a substrate, is inactivated after being fermented by lactobacillus plantarum HNU531, 10%-40% (w / w) of beta-cyclodextrin and maltodextrin are added as drying aids, vacuum freeze-drying is carried out to obtain postbiotic freeze-dried powder, and then the postbiotic freeze-dried powder is compounded with coffee at a mass ratio of 1:10. The results show that the flavonoid content and total sugar content of the product are significantly improved, the total sugar content is increased by 220% compared with coffee, the acidity and sweetness are 1.4 times and 2 times of coffee respectively. Under the premise that no exogenous sweetener and acidity regulator is added, the coffee bitterness is effectively improved, a coordinated taste of "slightly sour-sweet-fresh" is formed, and the product is endowed with unique jackfruit flavor. The research provides a new idea and processing technology reference for the development of functional flavor coffee.

Description

Technical Field

[0001] This invention relates to a method for preparing durian-based post-biotic coffee, belonging to the field of food technology. Background Technology

[0002] Coffee, a widely consumed non-alcoholic beverage globally, presents a multi-dimensional sensory experience encompassing bitterness, acidity, and sweetness. Consumer expectations for "low-irritant, harmonious flavors, and added health benefits" continue to rise. Therefore, how to reduce bitterness and enhance sweetness while preserving coffee's distinctive character has become a key focus for the entire industry. Current methods primarily address this through green bean selection, roasting curves, extraction parameters, or the addition of auxiliary ingredients. Microbial fermentation is considered the most promising pathway—reshaping the flavor profile by altering the ratio of organic acids to glycoside precursors. However, current fermentation methods are concentrated in the fresh fruit or green bean stage, resulting in significant batch-to-batch variations, a narrow controllable window, and insufficient ability to directly influence the final cup's bitterness and sweetness levels.

[0003] To add a health label, some studies have attempted to introduce live probiotics into coffee systems. However, the bacteria are extremely sensitive to high temperatures, low pH, and high-pressure extraction environments, resulting in fluctuating survival rates. Furthermore, metabolic byproducts can easily conflict with the original aroma of coffee, causing uncertainty in flavor. In contrast, metabiotics—the bacterial fragments and metabolites retained at the end of fermentation—possess advantages such as heat resistance, acid resistance, and shear resistance, and can remain stable in the food processing chain. However, they have long been limited to milk-based or fruit and vegetable juice carriers, rarely venturing into the coffee scenario, and lacking a practical solution that simultaneously addresses both flavor modification and functional expression.

[0004] Durian pulp is rich in lipids, polysaccharides, and fermentable substrates, possessing a naturally smooth sweetness and mellow aroma, making it an ideal substrate for post-fermentation. Unfortunately, current applications of durian are mostly limited to the physical mixing level of "pulverizing the pulp and directly flavoring," failing to utilize microbial methods to transform it into active components with targeted flavor-modifying capabilities, nor has a processing paradigm deeply integrated with coffee been established. Therefore, developing a new route using durian juice as a fermentation base to prepare highly stable post-fermenters and introducing them into the coffee chain, which can reduce bitterness and enhance sweetness and acidity within the tolerance limits of the processing, while also endowing the product with a functional narrative, has become an urgent issue to fill the current technological gap. Summary of the Invention

[0005] Given the shortcomings of existing technologies, this invention aims to propose a post-fermentation coffee preparation process based on durian: first, durian juice is fermented using a specific Lactobacillus plantarum, then post-fermentation is obtained at high temperatures, which is then added to coffee powder to reduce bitterness, enhance acidity, freshness, and sweetness, thereby comprehensively improving the sensory experience. To achieve the above objectives, this invention adopts the following technical solution: This invention provides a method for preparing durian-based post-biotics, comprising the following steps: (1) The third generation of Lactobacillus plantarum HNU531 was inoculated into durian juice for fermentation culture. After the fermentation was completed, the fermentation liquid was inactivated to obtain durian-based post-biotic fermentation product. (2) Add a drying agent to the fermentation product described in step (1) and freeze dry to obtain durian-based post-biotic powder; (3) Mix the durian-based post-biotic powder with coffee powder and brew to obtain durian-based post-biotic coffee.

[0006] In one embodiment, the Lactobacillus plantarum HNU531 was deposited at the Guangdong Provincial Center for Microbial Culture Collection on December 15, 2025, with the accession number GDMCC No: 67494.

[0007] Preferably, Lactobacillus plantarum is first added to the Lactobacillus plantarum. HNU531 The culture was inoculated into MRS liquid medium and incubated statically at 37°C for 24 h. Subsequently, the culture was passaged twice with 200 µL of bacterial solution, each passage lasting 24 h, to obtain the third generation. The third generation culture was centrifuged at 4000 rpm for 5 min, the supernatant was discarded, and the culture was resuspended in sterile physiological saline. The culture was then directly inoculated into durian juice and fermented at 37°C for 24 h.

[0008] After fermentation, 10% to 40% of β-cyclodextrin or maltodextrin is added as a drying agent, and then freeze-dried to obtain durian-based post-biotic powder.

[0009] Preferably, the durian-based post-biotic ferment is inactivated by incubation at 90°C for 10 minutes.

[0010] Preferably, durian-based post-biotics are evenly mixed with coffee powder at a ratio of 5% to 20% to prepare durian-based post-biotic coffee.

[0011] Preferably, the coffee is brewed with hot water at 90-95°C.

[0012] The present invention also provides durian-based post-biotic coffee prepared by the method.

[0013] In one embodiment, the durian-based post-biotic coffee retains its original flavor while significantly reducing bitterness and enhancing acidity, umami, and sweetness, thus optimizing the overall sensory experience.

[0014] This invention also provides a method for improving the sensory flavor of coffee, by incorporating *Lactobacillus plantarum* (… Lactiplantibacillus plantarumHNU531 was inoculated into durian juice for fermentation, and the fermentation product was mixed with coffee powder for brewing; the Lactobacillus plantarum HNU531 was deposited at the Guangdong Provincial Center for Microbial Culture Collection on December 15, 2025, with the culture collection number: GDMCC No: 67494.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention uses durian pulp as a fermentation substrate to prepare postbiotics. Durian pulp is rich in reducing sugars, free amino acids, and minerals such as potassium and magnesium, which can serve as a natural nutrient reservoir for Lactobacillus plantarum, thus facilitating the preparation of stable postbiotic fermentation products.

[0016] This invention introduces post-biotics rather than live bacteria into coffee, completely avoiding the defects of live probiotics that are easily inactivated during roasting, extraction and shelf life. With the excellent heat resistance and process compatibility of post-biotics, it ensures a high degree of consistency in product quality between batches.

[0017] When the durian-based post-biotic obtained by this invention is added to coffee at 10%, it can significantly reduce bitterness while preserving the original flavor structure of coffee, and simultaneously enhance acidity and sweetness, making the overall flavor more balanced and significantly improving the sensory score.

[0018] Preservation of biological materials: Lactobacillus plantarum ( Lactiplantibacillus plantarum HNU531, taxonomically named Lactiplantibacillus plantarum It was deposited on December 15, 2025 at the Guangdong Provincial Center for Microbial Culture Collection, located at 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, with accession number GDMCC No: 67494. Attached Figure Description

[0019] Figure 1 Sensory evaluation charts for coffee and durian-based post-biotic coffee.

[0020] Figure 2 The total sugars (A), pH (B), ABTS (C), and flavonoids (D) of coffee and durian-based post-biotic coffee.

[0021] Figure 3 Electronic tongue diagrams of coffee and durian-based post-biotic coffee.

[0022] Figure 4 Volcano plot (A) of differential metabolites in coffee and durian-based post-biotic coffee, volatile component analysis (B) and LC-VIP (C) during fermentation.

[0023] Figure 5 GC-VIP image for coffee and durian-based post-biotic coffee. Detailed Implementation

[0024] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0025] The coffee powder used in the following examples was purchased from Hainan Nongken Mushan Coffee Co., Ltd. Other commercially available coffee powders or coffee powder obtained by grinding commercially available coffee beans can also achieve the effects of the present invention.

[0026] Example 1: Lactobacillus plantarum ( Lactiplantibacillus plantarum Screening and identification of HNU531 This study collected fecal samples from 50-year-old men in Chang'an Village, Changfeng Town, Wanning City, Hainan Province, and prepared 10-fold dilution gradients using a 10-fold dilution method. -1 -10 -5 100 μL of each diluted sample solution was spread onto MRS agar medium and anaerobically incubated at 37°C for 48 h. After multiple isolation, purification, and culture cycles, and after identifying the morphology of Gram-stained bacteria under a microscope, samples with a single morphology were retained, and samples containing other bacteria were discarded.

[0027] Identification of isolates: DNA was extracted from the isolates according to the kit. PCR was then performed to amplify the 16S rRNA gene of each sample. The amplified products were then electrophoresed using 0.8% agarose gel electrophoresis. Sequencing was performed by Qingdao Pengxiang Biotechnology.

[0028] The sequence of the isolate was compared with NCBI, and the highest Query cover and Ident information in the output results were selected as the species-level identification result of the isolate, which was identified as Lactobacillus plantarum and later named Lactobacillus plantarum HNU531.

[0029] The plant lactobacillus ( Lactiplantibacillus plantarum HNU531 colonies were incubated on agar medium at 37°C for 24 h. The colonies were milky white, 0.1-0.2 cm in diameter, with a smooth, moist, raised surface and neat edges. Under an optical microscope, they appeared as rods.

[0030] The method for determining the acid tolerance of the strain is as follows: Adjust the pH of the MRS broth medium to 2.0 and 3.0 respectively using 1 mol / L HCl. Then, the activated strain is added at a ratio of 10... 10CFU / mL inoculum was inoculated into MRS broth medium at different pH values ​​and incubated at 37℃ for 4 h. After 10-fold serial dilutions, the inoculum was plated onto MRS agar medium, and the viable cell count was determined to calculate the survival rate and characterize the strain's tolerance. The method for determining the strain's bile salt tolerance is as follows: the activated strain was inoculated at 10... 10 Inoculated at a CFU / mL inoculum into MRS broth containing 0.3% ox bile salts, incubated at 37°C for 4 h, and then serially diluted 10-fold before being plated onto MRS agar. The viable bacterial count was determined, and the survival rate was calculated to characterize the strain's tolerance. Experiments revealed that *Lactobacillus plantarum* (… Lactiplantibacillus plantarum HNU531 exhibits good tolerance, with 38% tolerance at pH 2, 83% tolerance at pH 3, and 14% tolerance to bile salts.

[0031] Example 2: Preparation of Durian-Based Post-Generogenic Coffee The third generation of Lactobacillus plantarum HNU531 was inoculated into durian juice for fermentation culture. After fermentation, the fermentation broth was inactivated to obtain durian-based post-biotic fermentation product.

[0032] Lactobacillus plantarum HNU531 was inoculated into MRS liquid medium and cultured at 37℃ for 24 h to obtain the first-generation bacterial culture. 200 µL of the first-generation culture was inoculated into fresh MRS liquid medium and cultured at 37℃ for 24 h to obtain the second-generation bacterial culture. Another 200 µL of the second-generation culture was inoculated into fresh MRS liquid medium and cultured at 37℃ for 24 h to obtain the third-generation bacterial culture, which was then used for further processing. Fresh durian was pulped and filtered through gauze to remove impurities, yielding clear durian juice. The third-generation Lactobacillus plantarum HNU531 bacterial culture was centrifuged at 4000 r / min for 5 min, the supernatant was discarded, and the bacterial cells were resuspended in physiological saline.

[0033] The third-generation bacterial culture was centrifuged at 4000 r / min for 5 min, the supernatant was discarded, and the culture was resuspended in sterile physiological saline. The culture was then directly inoculated into durian juice. The initial inoculation concentration of *Lactobacillus plantarum* HNU531 was 10. 9 Fermentation was carried out at CFU / mL at 37℃ for 24 h. After fermentation, the durian fermentation broth was incubated at 90℃ for 10 min to inactivate the fermentation broth, yielding durian-based post-biotics. 10%–40% (w / w) of β-cyclodextrin or maltodextrin was added as a drying agent, followed by freeze-drying to obtain durian-based post-biotic powder. The durian-based post-biotic powder was then uniformly mixed with coffee powder at a ratio of 5%–20% (w / w) to prepare durian-based post-biotic coffee powder.

[0034] Table 1. Moisture content and solubility of durian-based post-biotics with added maltodextrin and β-cyclodextrin (10%-40%)

[0035] Table 1 shows the changes in moisture content and solubility of durian-based post-biotic freeze-dried products prepared with maltodextrin and β-cyclodextrin at different addition ratios (10%~40%). Overall, the moisture content shows a decreasing trend in residual moisture as the addition of β-cyclodextrin increases from 10% to 40%, while no specific trend is observed when the addition of maltodextrin increases from 10% to 40%, indicating that these two excipients have limited impact on the dryness of the final product. Specifically, the solubility of the maltodextrin group increases with increasing addition, while the solubility of the β-cyclodextrin group decreases with increasing addition. In short, increasing the amount of maltodextrin can simultaneously achieve lower moisture content and higher solubility, while increasing β-cyclodextrin only reduces solubility and has a limited impact on moisture content. In summary, the lowest moisture content was found in "30% maltodextrin" at 5.58%, while the highest solubility was found in "40% maltodextrin" at 95.38%. Considering both moisture content and solubility, subsequent experiments were conducted using the groups corresponding to 10% β-cyclodextrin and 20% maltodextrin added to durian.

[0036] Example 3: Analysis of Durian-Based Post-Generogenic Coffee Durian-based post-biotic coffee was prepared according to the method in Example 2. 10% by mass of β-cyclodextrin was added to the durian-based post-biotic, followed by freeze-drying to obtain durian-based post-biotic powder. The durian-based post-biotic powder was then uniformly mixed with coffee powder at a 1:10 ratio to obtain durian-based post-biotic coffee powder, named durian-based post-biotic coffee (β-10%). 20% by mass of maltodextrin was added to the durian-based post-biotic, followed by freeze-drying to obtain durian-based post-biotic powder. The durian-based post-biotic powder was then uniformly mixed with coffee powder at a 1:10 ratio to obtain durian-based post-biotic coffee powder, named durian-based post-biotic coffee (maltodextrin-20%). Pure coffee powder was named coffee. The coffee powders from each group were brewed with hot water at 90-95℃ using a slow pouring method, and then sensory evaluation was conducted. The sensory evaluation review panel consisted of 20 members. The research team consisted of 15 sensory members aged 30 and above. The evaluation criteria included: mouthfeel, flavor, body, aftertaste, texture, and acidity. Each coffee sample was evaluated in five copies according to SCAA standards.

[0037] Table 2 Sensory Evaluation Scoring Table

[0038] Table 2 is the sensory evaluation rating table. Figure 1This is a radar chart of sensory evaluation, with five dimensions: acidity, flavor, texture, body, and aftertaste. Higher scores indicate better performance. Coffee: Scores for all five dimensions were between 10 and 12, with "flavor" and "aftertaste" scoring the highest at 12. Overall, acidity was low and body was high. Durian-based post-biotic coffee (β-10%): Acidity was high, body was lower than coffee, and aftertaste was moderate. Durian-based post-biotic coffee (maltodextrin-20%): Scores for all five dimensions were 8-10, with similar texture and body values. Summary: The overall taste of coffee was slightly lower than the two durian samples. In the durian group, the difference in taste between adding 20% ​​maltodextrin and 10% β-cyclodextrin was minimal. Based on the analysis of moisture content and solubility combined with sensory evaluation, durian-based post-biotic coffee (maltodextrin-20%) was ultimately selected for subsequent physicochemical index determination.

[0039] Example 4: Analysis of Durian-Based Post-Activated Coffee Durian-based post-biotic coffee (malt-20%) was prepared according to the method in Example 3, and coffee prepared from pure coffee powder was used as a control for subsequent analysis.

[0040] This experiment used the sulfuric acid-phenol method to determine the total sugar content in coffee. Figure 2 As shown in Figure A, the total sugar content in coffee is 0.5 mg / mL, while the total sugar content in durian-based post-biotic coffee is 1.6 mg / mL, which is 3.2 times higher. The sugar content is increased after adding freeze-dried powder fermented with durian. The total sugar content of durian-based post-biotic coffee is significantly higher than that of coffee, which not only provides more sweetness to the flavor but also has a higher Maillard reaction potential.

[0041] Use a pH meter to measure the pH value of coffee, such as Figure 2 As shown in B. Both are weakly acidic, but the pH of durian-based post-biotic coffee (5.17) is lower than that of coffee (5.29), showing a significant difference.

[0042] ABTS determination method: Dissolve ABTS powder and K2S2O8 in purified water at a volume ratio of 1:1, mix thoroughly, and let stand at room temperature for 16 hours in the dark. Then, dilute the mixture with purified water until the absorbance at 734 nm reaches 0.70 ± 0.02, thus obtaining the ABTS stock solution. For measurement, measure 0.3 mL of the sample solution, add 2 mL of ABTS stock solution, mix thoroughly, and react at room temperature in the dark for 30 minutes. Then measure the absorbance at 734 nm. Calculate the ABTS radical scavenging rate using the following formula: ABTS radical scavenging rate (%) = [1 - ] × 100%. Where Ai is the absorbance of the sample solution mixed with ABTS reagent, Aj is the absorbance of the sample solution mixed with ultrapure water (sample control), and Ac is the absorbance of ultrapure water mixed with ABTS solution (blank control). For example... Figure 2 C stands for ABTS: As shown in the image, the ABTS value of durian-based post-biotic coffee is higher than that of regular coffee. This indicates that the antioxidant activity of coffee is enhanced after the durian-based post-biotic compounding treatment. The introduction of durian-based post-biotics not only did not weaken the antioxidant properties of coffee, but also significantly improved its ABTS free radical scavenging ability, giving the product stronger functional attributes. This has positive significance in the development of health-oriented coffee products.

[0043] The total flavonoid content was determined using the aluminum chloride colorimetric method, with rutin as the standard. 50 μL of sample solution was added to 50 μL of 5% sodium nitrite solution and allowed to stand at room temperature for 6 minutes. Then, 50 μL of 10% aluminum chloride solution was added, and the reaction was continued for another 6 minutes. Next, 400 μL of 1 mol / L sodium hydroxide solution and 300 μL of water were added, and the mixture was allowed to stand for 15 minutes. Finally, 200 μL of the reaction solution was transferred to a 96-well plate, and the absorbance was measured at 510 nm. A blank control was prepared by adding 950 μL of water to 50 μL of sample. The final result is expressed as milligrams of rutin equivalents per gram of dry weight (DW) of sample. Figure 2 D represents the flavonoid content in coffee: The bar chart comparison shows that the flavonoid content in coffee is approximately 14.1 μM Fe(II) / g DW, while that in durian-based post-biotic coffee is approximately 15.5 μM Fe(II) / g DW. Durian-based post-biotic coffee has about 9% more flavonoids than coffee, and is richer in flavonoids, which contributes to the neuroprotective effect and anti-cancer potential of coffee.

[0044] Electronic tongue analysis of coffee. Figure 3 This is an electronic tongue radar chart. The six axes correspond to seven taste sensors: acid, bitter, compound-1, sweet, salty, compound-2, and umami. Response values ​​are expressed as relative voltage differences (%). From the scale readings, the maximum response for each sensor is 9%, and the minimum is 3%. Coffee: Bitterness 7%, acidity 5%, umami around 5.8%, sweetness 4%, compound-2 and compound-1 both around 6%, with bitterness significantly higher than durian-based post-fermented coffee. Durian-based post-fermented coffee: Sweetness 8%, acidity 7%, umami around 6.8%, bitterness only 15%; sweetness and acidity are higher than coffee. Overall, coffee is predominantly "bitter-acid," while durian-based post-fermented coffee is predominantly "sweet-acid," showing a clear difference in taste between the two.

[0045] Using metabolomics analysis, such as Figure 4As shown in Figure A, compared to the coffee group, durian-based post-biotic coffee showed 258 upregulated substances, more than the total number of downregulated substances (217), while most substances (2490) showed no significant difference. Among the metabolites, (-)-Epigallocatechin 3-glucuronide, a slightly bitter, slightly sweet and sour secondary metabolite found in paulownia plants, was increased in durian coffee. Maltohexaose, a functional oligosaccharide with very low sweetness, contributes mainly to texture, sweetness, and balance in food, and its content was increased in durian-based post-biotic coffee. Glu and Ala contribute to a fresh, slightly bitter-sweet taste. Ala provides a mild aftertaste, while high concentrations bring noticeable bitterness and astringency, synergistically enhancing freshness; these were also increased in durian-based post-biotic coffee. Therefore, durian-based post-biotic coffee presents a more fresh-sweet taste.

[0046] Figure 5 The study showed an increase in the content of sucrose and asparagine (Asn) in durian-based post-biotic coffee. Sucrose influences sweetness in taste, reshaping aroma release, flavor balance, and mouthfeel; it not only provides sweetness but also masks flavors and compensates for aroma. Asparagine's effect on food flavor and taste is "weakly sweet - slightly umami - no bitterness," primarily through enhancing sweetness and umami, buffering saltiness and bitterness, and indirectly enhancing aroma as a Maillard precursor. The high abundance of free amino acids and polysaccharides in durian-based post-biotic coffee significantly differentiates it from traditional coffee in terms of aroma concentration, sweet flavor, and body texture, creating a novel beverage with a differentiated sensory experience that combines tropical fruit aromas with a rich, sweet, and umami flavor.

[0047] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing durian-based post-biotic coffee, characterized in that, Includes the following steps: (1) Bacterium plantarum ( Lactiplantibacillus plantarum HNU531 was inoculated into durian juice for fermentation to obtain fermentation broth; (2) Add a drying agent to the fermentation liquid in step (1) and freeze dry to obtain durian-based post-biotic powder; (3) Mix the durian-based post-biotic powder with coffee powder and brew to obtain durian-based post-biotic coffee.

2. The method according to claim 1, characterized in that, The Lactobacillus plantarum HNU531 was deposited at the Guangdong Provincial Center for Microbial Culture Collection on December 15, 2025, with the accession number GDMCC No: 67494.

3. The method according to claim 2, characterized in that, In step (1), the initial inoculum size of *Lactobacillus plantarum* HNU531 in the durian juice is 10 g / L. 8 -10 10 CFU / mL.

4. The method according to claim 3, characterized in that, The fermentation conditions described in step (1) are: fermentation at 35-42 ℃ for at least 24 h.

5. The method according to claim 4, characterized in that, The drying agent in step (2) includes β-cyclodextrin or maltodextrin.

6. The method according to claim 5, characterized in that, The amount of the drying agent added in step (2) is 10%-40% m / m of the fermentation broth.

7. The method according to claim 6, characterized in that, Step (3) Add the durian-based post-biotic powder to the coffee powder at a mass ratio of 5%-20%.

8. The method according to claim 7, characterized in that, In step (3), brew with hot water at 90-95℃.

9. Durian-based post-biotic coffee prepared by any one of claims 1 to 8.

10. A method for improving the sensory flavor of coffee, characterized in that, Lactobacillus plantarum ( Lactiplantibacillus plantarum HNU531 was inoculated into durian juice for fermentation, and the fermentation product was mixed with coffee powder for brewing; the Lactobacillus plantarum HNU531 was deposited at the Guangdong Provincial Center for Microbial Culture Collection on December 15, 2025, with the culture collection number: GDMCC No:67494.

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