A method for simultaneously degrading total flavonoids and condensed tannins in hickory pericarp

Abstract

The application discloses a method for simultaneously degrading total flavonoids and condensed tannins of hickory kernel. The method comprises the following steps: soaking the hickory kernel in the activated plant lactic acid bacteria solution, and reacting for more than 12 hours at 37 DEG C. The strain can target the degradation of condensed tannins and total flavonoids in the seed coat by secreting specific tannin enzymes and flavonoid oxidases, while most of the active flavonoids and polyphenols in the kernel are retained, and the nutrient loss is significantly reduced. In addition, the method only needs a small amount of sterile water, the wastewater production is greatly reduced compared with the traditional process, and high temperature and high pressure conditions are not needed. The plant lactic acid bacteria strain LP4 can be freeze-dried and stored, and the recovery rate of the resolubility activity is greater than 95%, and is suitable for industrial production. The application has the advantages of efficient de-bittering, environmental protection, energy saving and nutrient retention.

Description

Technical Field

[0001] This invention relates to the field of pecan decolorization processing, specifically to a method for deastringing pecans by simultaneously degrading total flavonoids and condensed tannins in the seed coat. Background Technology

[0002] Hickory (Caryacathayensis), belonging to the genus Carya Nutt. of the family Juglandaceae, is an economically valuable tree species endemic to China. Its kernels are rich in nutrients and highly sought after by consumers, giving it significant economic value. However, the seed coat, tightly bound to the hickory embryo, is rich in various astringent substances, such as phenolic compounds, flavonoids, and tannins. Therefore, hickory nuts must be de-astringent before consumption.

[0003] High-temperature boiling and high-pressure steaming are currently the most common methods for removing astringency from pecan kernels. However, during the process, some high-nutrient substances dissolve in the boiling water and are lost, while high-concentration organic wastewater is generated, causing significant environmental pollution and significantly increasing the costs for processing enterprises. How to improve the technology for removing astringency from pecans is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for deastringing pecans that simultaneously degrades total flavonoids and condensed tannins in the seed coat. This method utilizes plant lactic acid bacteria strain LP4 to process pecans, which can effectively reduce the total flavonoids and condensed tannins in the pecan seed coat.

[0005] This invention is achieved through the following technical solution:

[0006] A method for deastringentizing pecans by simultaneously degrading total flavonoids and condensed tannins in the seed coat involves soaking the pecan kernels in an activated plant lactic acid bacteria solution for a period of time; the plant lactic acid bacteria is strain LP4.

[0007]

[0008] Preferably, the reaction temperature is maintained at 37°C.

[0009] Preferably, the soaking time is 12 hours or more.

[0010] Preferably, the preparation process of the activated plant lactic acid bacteria solution involves dissolving plant lactic acid bacteria powder in deionized water and then activating and culturing it, with the mass-to-volume ratio of plant lactic acid bacteria powder to sterile water being 10 μg: 100 μL.

[0011] Preferably, the activation culture is carried out using MRS medium.

[0012] For activation culture, the initial pH of the MRS medium should be maintained at 6-7.

[0013] The method for removing astringency from pecans in this invention is based on the unique biological characteristics of plant lactic acid bacteria strain LP4. It simultaneously degrades total flavonoids and condensed tannins in the pecan seed coat through microbial fermentation, improving astringency removal efficiency while also offering advantages in environmental friendliness and nutrient retention. Its technical effects are specifically reflected in the following aspects:

[0014] The plant-derived lactic acid bacteria strain LP4, after targeted domestication, exhibits a significant affinity for complex phenolic substances (such as condensed tannins and total flavonoids) in pecan seed coat. This strain can directly cleave the ether bonds of condensed tannins and the hydroxyl groups of flavonoids by secreting specific tanninases and flavonoid oxidases, without relying on exogenous enzymes or chemical additives, thus simplifying the process and reducing costs.

[0015] Unlike traditional high-temperature boiling, which leads to a significant loss of water-soluble flavonoids, this method selectively degrades astringent components in the seed coat through enzymatic reactions by microorganisms, while retaining over 70% of the active flavonoids and polyphenols in the kernel, significantly enhancing the nutritional value of the de-astringent product. The mild reaction conditions at 37℃ prevent the destruction of heat-sensitive components (such as unsaturated fatty acids and vitamins), ensuring the natural flavor and nutritional integrity of the pecan kernels.

[0016] Furthermore, microbial fermentation requires only a small amount of sterile water, significantly reducing wastewater generation compared to traditional processes and substantially lowering wastewater treatment costs. Moreover, the entire process eliminates the need for high-temperature, high-pressure equipment, aligning with green and low-carbon processing trends. The strain cultivation and fermentation process requires no expensive equipment or reagents, and the sensory quality (color, taste) and nutritional indicators of the de-astringent pecan kernels meet industry-leading standards, significantly enhancing the product's added value.

[0017] This invention addresses three major technical bottlenecks in the deastringency process of pecans—low efficiency, nutrient loss, and environmental pollution—through the targeted degradation effect of plant lactic acid bacteria strain LP4, providing an efficient, green, and sustainable solution for the deep processing industry of pecans. Attached Figure Description

[0018] Figure 1 The effect of plant-derived lactic acid bacteria on reducing condensed tannins in pecan kernels.

[0019] Figure 2 The effect of plant-based lactic acid bacteria on reducing total flavonoids in pecan kernels. Detailed Implementation

[0020] The following embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0021] The following examples use hickory nuts as the reaction object of plant lactic acid bacteria. The hickory nuts are from farmers in Lin'an. Plant lactic acid bacteria strain LP4 can be obtained by purchase. After the hickory nuts and the plant lactic acid bacteria of this invention are fermented together at 37°C, the changes in the content of the main astringent substances of hickory nuts, total flavonoids and condensed tannins, are tested after the reaction.

[0022] The high-concentration plant-based lactic acid bacteria solution used in the following examples was prepared using the following steps:

[0023] Step (1): Mix plant lactic acid bacteria strain LP4 freeze-dried powder with deionized water at a ratio of 10μg:100μL, spread it on a solid culture medium plate and activate the plant lactic acid bacteria at 37℃ to awaken the metabolic activity of the strain, repair cell damage and restore its normal physiological function.

[0024] Step (2) involves shaking a small amount of liquid culture medium at 37°C and 200 rpm to propagate plant lactic acid bacteria. This is a key step in connecting strain activation with large-scale culture or downstream experiments.

[0025] Step (3): Inoculate a large amount of liquid culture medium at a volume ratio of 1% of the bacterial count to further expand the proliferation;

[0026] Step (4), 12-16 hours later, collect the bacterial cells of plant lactic acid bacteria and remove the culture medium;

[0027] Step (5): Redissolve the bacterial cells with physiological saline, using 10% of the original volume of liquid culture medium.

[0028] Comparison Example

[0029] Mix 5mL of purified water with 5g of pecan kernels in a fermentation container, keep the temperature at 37℃, and keep stirring constantly to ensure a full reaction. After fermenting overnight, remove the pecan kernels.

[0030] Example 1

[0031] Prepare a high-concentration plant lactic acid bacteria solution. Soak 5g of pecan kernels in 5mL of the solution. Maintain the reaction temperature at 37℃ and keep stirring constantly to ensure a full reaction. After reacting overnight, remove the pecan kernels.

[0032] Application Example 1

[0033] The pecan kernels from the control example and Example 1 were ground into powder, thoroughly degreased and deoiled, and then freeze-dried. 0.02g of the pecan kernel powder from each example and control example was weighed out, and all organic matter was extracted with 80% acetone. The absorbance of condensed tannins, the main astringent compounds in pecans, was tested using an enzyme-linked immunosorbent assay (ELISA) reader to test the changes in total flavonoid and condensed tannin content.

[0034] The results are as follows Figure 1-2 As shown, compared to the control example, the plant-based lactic acid bacteria in Example 1 significantly reduced the content of condensed tannins in the pecan kernels. This indicates that the co-fermentation environment with plant-based lactic acid bacteria has a very good effect on reducing the total flavonoids and condensed tannins in pecan kernels.

Claims

1. A method for deastringentizing pecans by simultaneously degrading total flavonoids and condensed tannins in the seed coat, characterized in that, The method involves soaking pecan kernels in an activated plant lactic acid bacteria solution for a period of time; the plant lactic acid bacteria is strain LP4.

2. The method according to claim 1, characterized in that, The nucleotide sequence of the plant lactic acid bacteria strain LP4 is shown in SEQ NO.

1.

3. The method according to claim 1, characterized in that, The reaction temperature was maintained at 37°C.

4. The method according to claim 1 or 3, characterized in that, The soaking time is 12 hours or more.

5. The method according to claim 1, characterized in that, The preparation process of the activated plant lactic acid bacteria solution involves dissolving plant lactic acid bacteria powder in deionized water and then activating and culturing it. The mass-volume ratio of plant lactic acid bacteria powder to sterile water is 10 μg: 100 μL.

6. The method according to claim 5, characterized in that, The medium used for activation culture was MRS medium.

7. The method according to claim 7, characterized in that, The initial pH of the MRS medium is maintained at 6-7.

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