Preparation method and application of deastringency walnut kernels

Abstract

The invention relates to the technical field of walnut kernel treatment, in particular to a preparation method and application of deastringency walnut kernels. The preparation method of the deastringency walnut kernels provided by the invention comprises the following steps: soaking initial walnut kernels in alkali liquor, taking out the soaked walnut kernels, standing, and then carrying out water vapor treatment, cleaning and drying to obtain the deastringency walnut kernels. According to the method provided by the invention, through the synergistic effect of alkali liquor soaking, standing and water vapor treatment, the fiber structure of the seed coats of the walnut kernels is fully destroyed, so that astringent substances of the seed coats of the walnut kernels are fully released, the astringent substances of the walnut kernels are effectively removed, the use amount of alkali liquor in the process is small, and the cost is low. According to the method for preparing the deastringency walnut kernels, the damage and loss of protein and fat in the walnut kernels are small, the period of the process is short, and in conclusion, the method for preparing the deastringency walnut kernels is short in period, accurate in deastringency and low in nutrient substance loss.

Description

Technical Field

[0001] The invention relates to the technical field of walnut kernel processing, and in particular to a preparation method of de-astringent walnut kernel and application thereof. Background Art

[0002] Walnut kernels are an important source of various nutrients due to their rich nutritional value. Studies have shown that walnut kernels are rich in protein, fat, sugar, and bioactive ingredients such as B vitamins and vitamin E. Numerous clinical and experimental studies have shown that moderate intake of walnut kernels can supplement the various nutrients needed by the human body, thereby helping to promote cognitive function, optimize the physiological conditions of the skin and hair, and prevent the occurrence of arteriosclerosis to a certain extent.

[0003] Due to the natural nutritional properties of walnut kernels, walnut kernels and their derivative products have gradually become popular among consumers in recent years, and the industry has also expressed optimism about its market potential. However, in the actual processing of walnut kernel products, there is a long-standing technical challenge: the endocarp of walnut kernels contains astringent substances, which are not easy for consumers to accept. Traditional walnut kernel processing methods, such as hot water soaking, long-term alkali treatment, high-concentration alkali treatment, baking, etc., although they can achieve de-astringency to a certain extent, these methods are not only complicated in operation process, time-consuming and economic cost, but also likely to cause a large loss of walnut kernels. Traditional de-astringency methods often choose to remove the entire outer skin of the walnut kernel, which means that a large amount of nutrients will be lost.

[0004] In the related art, there is an urgent need for a method for preparing de-astringent walnut kernels with a short cycle, accurate de-astringency, and low nutrient loss. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is that the related art lacks a method for preparing de-astringent walnut kernels with a short cycle, precise de-astringency and low nutrient loss, thereby providing a method for preparing de-astringent walnut kernels and its application.

[0006] The present invention discloses a method for preparing de-astringent walnut kernels, comprising the following steps:

[0007] The initial walnut kernels are soaked in an alkali solution, taken out and allowed to stand, and then subjected to steam treatment, washing and drying to obtain the de-astringent walnut kernels.

[0008] It can be understood that the initial walnut kernel refers to the walnut kernel whose walnut inner seed coat has not been removed.

[0009] In the present invention, the initial walnut kernels used are free from mildew, oily smell, insect pests, impurities and full grains.

[0010] The synergistic effect of steam treatment and alkali solution can destroy the fiber structure and density of the endocarp. The alkali solution can soften the endocarp of walnut kernels and partially destroy the fiber structure. The high temperature and high humidity of steam can further destroy the dense structure of the endocarp. The steam heating can expand and loosen the cell tissue, thus cooperating more effectively with the effect of alkali solution.

[0011] The synergistic effect of steam treatment and alkali solution can inhibit the activity of oxidases and reduce the formation of dark polymers. Among them, alkali solution can inhibit the activity of some enzymes (such as polyphenol oxidase), but alkali solution treatment alone may cause partial oxidation of some phenols. Steam treatment can quickly inhibit the activity of polyphenol oxidase through high temperature in a short period of time, reducing the speed of phenolic compounds oxidizing into quinone dark polymers. Used in combination with alkali solution, it can effectively inhibit the oxidation of phenolic substances and protect the color and flavor of walnut kernels.

[0012] The synergistic effect of water vapor treatment and alkali solution increases the solubility and diffusion rate of polyphenols. The alkali solution can increase the solubility of polyphenol compounds, making it easier for these substances to be released into the subsequent cleaning solution; the high temperature of water vapor accelerates the diffusion of polyphenol compounds, making it easier for them to diffuse out of the cells. Under the synergistic effect of alkali solution, the removal of polyphenol compounds is more efficient, thereby reducing the astringency of walnut kernels;

[0013] The synergistic effect of water vapor treatment and alkali solution promotes the breakage of cellulose chains and reduces crystallinity; alkali solution can partially hydrolyze cellulose, break cellulose chains, reduce crystallinity, and enhance the fragility of the endocarp; high temperature treatment with water vapor further reduces the crystallinity of cellulose, making it easier to degrade. The combined effect of alkali solution and water vapor can greatly accelerate the destruction of fiber structure and release more astringent substances such as polyphenols.

[0014] The advantage of the synergistic treatment of steam treatment and alkali solution is that it can significantly improve the efficiency of removing astringency while maximizing the protection of the nutritional and sensory quality of walnut kernels.

[0015] Preferably, the mass ratio of walnuts to alkali solution during the soaking of the initial walnut kernels in alkali solution is 1:(2-8).

[0016] Preferably, the alkali solution is selected from aqueous sodium hydroxide solution;

[0017] Preferably, the concentration of the sodium hydroxide aqueous solution is 0.3-3.0%;

[0018] Preferably, the soaking temperature is 15-35°C, and the soaking time is 30s-2min.

[0019] Preferably, the standing temperature is 20-35°C; and the standing time is 30s-2min.

[0020] In the present invention, if the standing time is too long, for example, 3 minutes, the following adverse effects will occur: 1. The alkali solution penetrates too deeply into the interior of the walnut kernel, resulting in unnecessary chemical reactions, increasing the serious denaturation of proteins and excessive saponification of fats in the walnut kernel, thereby causing the deterioration of the nutritional components, flavor and texture of the walnut kernel; 2. The alkali solution reacts excessively with phenolic substances, producing excessive dark quinone substances, causing the color of the walnut kernel to become dark brown or even black, seriously affecting the color quality of the product;

[0021] In the present invention, if the standing time is less than, for example, 20 seconds, the following adverse effects will occur: insufficient penetration of the alkali solution, insufficient penetration of the alkali solution into the walnut kernel endocarp, and inability to completely destroy the fiber structure of the endocarp, thereby affecting the release and removal of astringent substances. This will result in poor synergy with subsequent steam treatment, making it difficult to completely remove the astringency in the subsequent cleaning process, and the astringency removal effect is poor.

[0022] Preferably, the water vapor temperature during the water vapor treatment process is 95-120°C and the time is 1-5min;

[0023] Preferably, the water vapor pressure is 0-0.2 MPa.

[0024] Optionally, the water vapor pressure is an apparent pressure.

[0025] Preferably, the cleaning process includes rinsing and water soaking;

[0026] Preferably, the rinsing is performed by water rinsing;

[0027] Preferably, the water temperature in the elution is 15-35°C; the elution time is 10-50s;

[0028] Preferably, the water temperature during water immersion is 40-80° C., and the immersion time is 4-21 min.

[0029] Optionally, the water washing process is carried out by a drum washing device.

[0030] Optionally, the pH value of the soaking water after the water soaking process is completed is 6.5-7.5.

[0031] Optionally, the water soaking process includes 2-6 soaking processes, and each soaking time is 2-7 minutes.

[0032] Preferably, the drying process is to use air to flush away the moisture on the surface of the washed walnut kernels;

[0033] Preferably, the air is high-pressure air;

[0034] Preferably, the pressure of the high-pressure air is 0.3-1.2 MPa;

[0035] Preferably, the time for flushing the surface moisture of the washed walnut kernels with air is 10-50s.

[0036] Preferably, the method further comprises a treatment process of standing in a protective gas;

[0037] Preferably, the protective gas is selected from nitrogen;

[0038] Preferably, the concentration of the protective gas is greater than or equal to 95%;

[0039] Preferably, the treatment time in the protective gas is 0.5-4 hours.

[0040] The invention also provides a de-astringent walnut kernel, which is prepared by the above-mentioned preparation method.

[0041] The present invention also provides a de-astringent walnut kernel obtained by the above-mentioned preparation method or a walnut milk prepared from the de-astringent walnut kernel.

[0042] The technical solution of the present invention has the following advantages:

[0043] The invention provides a method for preparing de-astringent walnut kernels, comprising the following steps: soaking initial walnut kernels in alkali solution, taking them out and letting them stand, and then performing steam treatment, washing and drying to obtain the de-astringent walnut kernels.

[0044] Through the method provided by the present invention, the synergistic effects of alkali solution soaking, standing and water vapor treatment fully destroy the fiber structure of the walnut kernel endocarp, so that the astringent substances in the walnut kernel endocarp are fully released, thereby effectively removing the astringent substances in the walnut kernel, and the amount of alkali solution used in the process is small, the protein and fat in the walnut kernel are less damaged and lost, and the process cycle is short. In summary, the present invention provides a method for preparing de-astringent walnut kernel with a short cycle, precise de-astringency and low nutrient loss.

[0045] Furthermore, the de-astringent walnut kernels obtained by the preparation method provided by the present invention are light yellow in color, uniform in color, and free from dullness caused by the deposition of astringent substances; the surface of the de-astringent walnut kernels is smooth, with few gaps and defects; compared with untreated walnut kernels, the de-astringent walnut kernels have a more delicate tissue structure and significantly reduced astringency.

[0046] Furthermore, the alkali solution after soaking can be reused 7-15 times, and the unit amount of alkali solution used is significantly reduced. DETAILED DESCRIPTION

[0047] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0048] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0049] The initial walnut kernels used in the embodiments of the present invention and the comparative examples are free of mildew, oily smell, insect pests, impurities, and full grains. The moisture content of the initial walnut kernels is less than 5%.

[0050] Example 1

[0051] The present embodiment provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0052] 1 kg of initial walnut kernels are placed in 4 kg of 0.3% sodium hydroxide solution, soaked at 25°C for 1 min, taken out, and allowed to stand for 1 min (to ensure that the alkali solution fully enters the walnut endocarp); then treated with steam at a gauge pressure of 0.1 MPa and a temperature of 100°C for 3 min; after steam treatment, rinsed with water at a temperature of 30°C for 30 s through a drum rinsing device (this process can remove phenols, quinones and dark polymer substances remaining on the surface of the walnut endocarp); then soaked in 50°C warm water 3 times, each time for 5 min (the pH value of the soaking water after the last soaking is 6.6); after soaking, the surface of the walnut kernels is rinsed with 0.6 MPa high-pressure air for 30 s (this process reduces the moisture content of the walnut kernels and reduces the rates of enzymatic reactions and fat oxidation reactions); then the obtained walnut kernels are placed in a closed container with a nitrogen atmosphere at a concentration of 95% (nitrogen is prepared by a nitrogen generator) for 2 h to obtain the de-astringent walnut kernels.

[0053] Example 2

[0054] The present embodiment provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0055] 1 kg of initial walnut kernels are placed in 4 kg of 1% sodium hydroxide solution, soaked at 25°C for 1 min, taken out and allowed to stand for 1 min; then treated with steam at a gauge pressure of 0.1 MPa and a temperature of 100°C for 3 min; after steam treatment, rinsed with water at a temperature of 25°C for 30 s through a drum rinsing device; then soaked in 50°C warm water 3 times, each time for 5 min (the pH value of the soaking water after the last soaking was 6.9); after soaking, the surface of the walnut kernels was rinsed with 0.6 MPa high-pressure air for 30 s; then the obtained walnut kernels were placed in a closed container with a nitrogen atmosphere at a concentration of 95% (nitrogen was prepared by a nitrogen generator) for 2 h to obtain the de-astringent walnut kernels.

[0056] Example 3

[0057] The present embodiment provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0058] 1 kg of initial walnut kernels are placed in 4 kg of 1.5% sodium hydroxide solution, soaked at 25°C for 1 min, taken out and allowed to stand for 1 min; then treated with water vapor at a gauge pressure of 0.1 MPa and a temperature of 100°C for 3 min; after water vapor treatment, rinsed with water at a temperature of 28°C for 30 s through a drum rinsing device; then soaked in 50°C warm water 3 times, each time for 5 min (the pH value of the soaking water after the last soaking is 7.1); after soaking, the surface of the walnut kernels is rinsed with 0.6 MPa high-pressure air for 30 s; then the obtained walnut kernels are placed in a closed container with a nitrogen atmosphere at a concentration of 95% (nitrogen is prepared by a nitrogen generator) for 1 h to obtain the de-astringent walnut kernels.

[0059] Example 4

[0060] The present embodiment provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0061] 1 kg of initial walnut kernels are placed in 4 kg of 2.5% sodium hydroxide solution, soaked at 25°C for 1 min, taken out and allowed to stand for 1 min; then treated with water vapor at a gauge pressure of 0.1 MPa and a temperature of 100°C for 3 min; after water vapor treatment, rinsed with water at a temperature of 35°C for 30 s through a drum elution device; then soaked in 50°C warm water 3 times, each time for 5 min (the pH value of the soaking water after the last soaking was 7.3); after soaking, the surface of the walnut kernels was rinsed with 0.6 MPa high-pressure air for 30 s; then the obtained walnut kernels were placed in a closed container with a nitrogen atmosphere at a concentration of 95% (nitrogen was prepared by a nitrogen generator) for 1 h to obtain the de-astringent walnut kernels.

[0062] Example 5

[0063] The present embodiment provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0064] 1 kg of initial walnut kernels are placed in 4 kg of 1% sodium hydroxide solution, soaked at 35°C for 1 min, taken out and allowed to stand for 2 min; then treated with steam at a gauge pressure of 0.2 MPa and a temperature of 120°C for 3 min; after steam treatment, rinsed with water at a temperature of 15°C for 30 s through a drum rinsing device; then soaked in 50°C warm water 4 times, each time for 5 min (the pH value of the soaking water after the last soaking is 7.0); after soaking, the surface of the walnut kernels is rinsed with 0.6 MPa high-pressure air for 30 s; then the obtained walnut kernels are placed in a closed container with a nitrogen atmosphere at a concentration of 95% (nitrogen is prepared by a nitrogen generator) for 3 h to obtain the de-astringent walnut kernels.

[0065] Example 6

[0066] The present embodiment provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0067] 1 kg of initial walnut kernels are placed in 8 kg of 1% sodium hydroxide solution, soaked at 35°C for 1 min, taken out, and allowed to stand for 2 min (to ensure that the alkali solution fully enters the walnut seed coat); then treated with steam at a gauge pressure of 0.01 MPa and a temperature of 95°C for 1 min; after steam treatment, rinsed with water at a temperature of 35°C for 30 s through a drum rinsing device; then soaked in 50°C warm water 4 times, each time for 5 min (the pH value of the soaking water after the last soaking was 7.1); after soaking, the surface of the walnut kernels was rinsed with 1.2 MPa high-pressure air for 50 s; then the obtained walnut kernels were placed in a closed container with a nitrogen atmosphere at a concentration of 95% (nitrogen was prepared by a nitrogen generator) for 4 hours to obtain the de-astringent walnut kernels.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0070] 1 kg of initial walnut kernels are placed in 4 kg of 40% ethanol aqueous solution, extracted with 28 kHz ultrasonic wave at 50°C for 30 min, and then rinsed with water at 25°C for 30 s through a drum elution device; then soaked in 50°C warm water for 3 times, each time for 5 min (the pH value of the soaking water after the last soaking is 6.5); after soaking, the surface of the walnut kernels is rinsed with 0.6 MPa high-pressure air for 30 s; then the obtained walnut kernels are placed in a closed container with a nitrogen atmosphere at a concentration of 95% (nitrogen is prepared by a nitrogen generator) for 2 hours to obtain the de-astringent walnut kernels.

[0071] Comparative Example 2

[0072] This comparative example provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0073] 1 kg of initial walnut kernels are placed in 4 kg of 5% NaHCO3 solution, soaked at 65°C for 60 minutes and then taken out, then placed in 4 kg of 2% citric acid solution, soaked at 65°C for 10 minutes and then taken out; then soaked in 50°C warm water 4 times, each time for 5 minutes (the pH value of the soaking water after the last soaking is 7.4); after soaking, the surface of the walnut kernels is rinsed with 0.6 MPa high-pressure air for 30 seconds; then the obtained walnut kernels are placed in a closed container with a nitrogen atmosphere of 95% (nitrogen is prepared by a nitrogen generator) for 2 hours to obtain the de-astringent walnut kernels.

[0074] Comparative Example 3

[0075] This comparative example provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0076] 1 kg of initial walnut kernels are placed in 4 kg of a solution of a 1% tannase-cellulase complex enzyme preparation, and taken out after being oscillated in a 60W ultrasonic wave at 50°C for 15 minutes; after being treated with water vapor, the kernels are rinsed with water at a temperature of 50°C for 30 seconds through a drum rinsing device; thereafter, the kernels are soaked in 50°C warm water for 4 times, each time for 5 minutes (the pH value of the soaking water after the last soaking is 6.3); after the soaking is completed, the kernels are placed in a centrifuge, dehydrated at a speed of 200 r / min for 2 minutes, and finally baked at 60°C for 10 minutes to obtain the de-astringent walnut kernels.

[0077] Comparative Example 4

[0078] This comparative example provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0079] 1 kg of initial walnut kernels are placed in 4 kg of 1% sodium hydroxide solution, soaked at 25°C for 2 minutes and then taken out; then immediately treated with water vapor with a gauge pressure of 0.1 MPa and a temperature of 100°C for 3 minutes; after the water vapor treatment, rinsed with water at a temperature of 25°C for 30 seconds through a drum elution device; then soaked in 50°C warm water 3 times, each time for 5 minutes (the pH value of the soaking water after the last soaking is 6.7); after the soaking is completed, the surface of the walnut kernels is rinsed with 0.6 MPa high-pressure air for 30 seconds; then the obtained walnut kernels are placed in a closed container with a nitrogen atmosphere at a concentration of 95% (nitrogen is prepared by a nitrogen generator) for 2 hours to obtain the de-astringent walnut kernels.

[0080] Comparative Example 5

[0081] This comparative example provides a method for preparing de-astringent walnut kernels, comprising the following steps:

[0082] 1 kg of initial walnut kernels are placed in 4 kg of 1% sodium hydroxide solution, soaked at 25°C for 1 min, taken out and allowed to stand for 1 min; then treated with air at a gauge pressure of 0.1 MPa and a temperature of 100°C for 3 min; after air treatment, rinsed with water at a temperature of 25°C for 30 s through a drum elution device; then soaked in 50°C warm water 3 times, each time for 5 min (the pH value of the soaking water after the last soaking is 6.6); after soaking, the surface of the walnut kernels is rinsed with 0.6 MPa high-pressure air for 30 s; then the obtained walnut kernels are placed in a closed container with a nitrogen atmosphere at a concentration of 95% (nitrogen is prepared by a nitrogen generator) for 3 hours to obtain the de-astringent walnut kernels.

[0083] Test Case

[0084] 1. Kernel yield:

[0085] When the moisture content of the walnut kernel after de-astringency treatment is dried to the same as that of the raw material, the kernel rate is calculated. The calculation formula (1) is as follows:

[0086]

[0087] In the formula: X is the kernel yield of walnut kernel after drying, %; m is the mass of the de-astringent walnut kernel after drying, kg; M is the mass of the initial walnut kernel, kg. The kernel yield is shown in Table 1.

[0088] 2. Endotheca retention rate:

[0089] The walnut endocarp retention rate was determined using imageJ software. Main steps: High-resolution images of walnut samples before and after endocarp removal were collected, and the images were binarized using ImageJ software to measure the endocarp area and calculate the endocarp retention rate.

[0090] The specific process includes the following steps:

[0091] S1 Image acquisition: Take high-resolution images of the walnut samples before and after endocarp removal to ensure uniform lighting and clear visibility of the endocarp part of the sample.

[0092] S2 Image processing: The collected images were imported into ImageJ software. The “Thresholding” tool in the software was used to binarize the image (separate the endocarp region from other regions in the image). The “AdjustThreshold” function was used to precisely adjust the threshold to accurately distinguish the endocarp region.

[0093] S3 Area measurement: Use the "Analyze Particles" tool or the "Measure" function to measure the area of ​​the endocarp in the binary image. Record the endocarp area of ​​the sample before and after endocarp removal.

[0094] S4 Calculate the endocarp retention rate:

[0095] Endocarp retention rate (%) = (endocarp area after peeling / endocarp area before peeling) × 100%

[0096] At least 20 samples were photographed and the average value was taken. The endocarp retention rate is shown in Table 1.

[0097] Table 1

[0098]

[0099]

[0100] 2. Determination of astringent substances in walnut kernels

[0101] The phenol content of the walnut kernels before and after deastringency in the embodiment and the comparative example was determined by the Folin phenol method, and the average value was taken after 20 repeated tests for a single sample. The change in the phenol content of the walnut kernels before and after deastringency was expressed as gallic acid concentration equivalent. The standard curve is y=0.0088x+0.1948, where x is the gallic acid concentration (mg / g) and y is the absorbance (A).

[0102] Table 2

[0103]

[0104]

[0105] 3. Chromaticity value of walnut milk sample

[0106] The de-astringent walnut kernels prepared in the embodiment and the comparative example are respectively prepared into walnut milk, and the preparation process of the walnut milk is as follows:

[0107] Mix 1kg of de-astringent walnut kernels and 3kg of softened water, then grind at 75°C to obtain walnut slurry; stir and shear at a speed of 1800r / min for 15 minutes, then adjust the volume to 10kg, and then homogenize in sequence at a homogenization temperature of 70°C and a homogenization pressure of 36MPa, and obtain walnut milk after filling.

[0108] Color is one of the important indicators affecting the quality evaluation of walnut milk. The three-dimensional color space has three main coordinates: L*, a*, and b*. The chromaticity of walnut milk was measured using a colorimeter. Among them, L* represents the brightness range between 0 and 100, the a* value represents the position between red (positive value) and green (negative value); b* represents the position between yellow (positive value) and blue (negative value). The total color difference (ΔE) is a standard calculation measure that relates human visual judgments of the difference between two perceived colors. Color differences can be divided into insignificant (ΔE: 0-0.5), slightly significant (ΔE: 0.5-1.5), significant (ΔE: 1.5-3), obvious changes (ΔE: 3-6), and huge changes (ΔE: 6-12).

[0109] The total color difference between the two walnut milks was calculated according to the following formula:

[0110]

[0111] Where ΔL=L2-L1; Δa=a2-a1; Δb=b2-b1

[0112] 3.1 The walnut milk prepared from the deastringent walnut kernels obtained in the examples and comparative examples was subjected to a colorimetric test. The test results are shown in Table 3

[0113] The astringency removal rate of Example 4 is the highest. The colors of the walnut milk prepared by Example 4 are L *

[0114] =74.00, a * =0.97, b * =3.48, with this value as a reference, calculate the total color difference (ΔE) of other samples. The smaller the ΔE, the smaller the color difference, and the closer the color is to Example 4.

[0115] Table 3

[0116]

[0117]

[0118] 3.2 Sensory evaluation

[0119] In order to systematically evaluate the sensory quality of walnut milk, 15 tasters scored from four main aspects: color, aroma, astringency, texture and overall score. The score range for each aspect was 1 to 10, with 1 point indicating very poor and 10 points indicating excellent. The overall score was calculated based on the average of the first four items. The sensory evaluation results of the walnut milk prepared in the embodiment and the comparative example are shown in Table 4.

[0120] Table 4

[0121]

[0122]

[0123] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing deastringent walnut kernels, characterized in that: The steps include: The initial walnut kernels are soaked in an alkali solution, taken out and allowed to stand, and then subjected to steam treatment, washing and drying to obtain the de-astringent walnut kernels.

2. The preparation method according to claim 1, characterized in that: The mass ratio of walnut to alkali solution during the soaking of the initial walnut kernel in alkali solution is 1:(2-8).

3. The preparation method according to claim 1 or 2, characterized in that: The alkali solution is selected from an aqueous sodium hydroxide solution; Preferably, the concentration of the sodium hydroxide aqueous solution is 0.3-3.0%; Preferably, the soaking temperature is 15-35°C, and the soaking time is 30s-2min.

4. The preparation method according to any one of claims 1 to 3, characterized in that The standing temperature is 20-35°C; the standing time is 30s-2min.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The water vapor temperature during the water vapor treatment is 95-120°C and the time is 1-5 minutes; Preferably, the water vapor pressure is 0-0.2 MPa.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The cleaning process includes rinsing and water soaking; Preferably, the rinsing is performed by water rinsing; Preferably, the water temperature in the elution is 15-35°C; the elution time is 10-50s; Preferably, the water temperature during water immersion is 40-80° C., and the immersion time is 4-21 min.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The drying process is to use air to flush away the moisture on the surface of the washed walnut kernels; Preferably, the air is high-pressure air; Preferably, the pressure of the high-pressure air is 0.3-1.2 MPa; Preferably, the time for flushing the surface moisture of the washed walnut kernels with air is 10-50s.

8. The preparation method according to any one of claims 1 to 7, characterized in that: It also includes the treatment process of standing in a protective gas; Preferably, the protective gas is selected from nitrogen; Preferably, the concentration of the protective gas is greater than or equal to 95%; Preferably, the treatment time in the protective gas is 0.5-4 hours.

9. A de-astringent walnut kernel, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. Walnut milk prepared from the de-astringent walnut kernels obtained by the preparation method according to any one of claims 1 to 8 or the de-astringent walnut kernels according to claim 9.

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