Method for determining optimal harvesting time of Laifeng ginger based on texture characteristics and cell wall polysaccharide

Abstract

The invention relates to the technical field of Laifeng ginger planting, and specifically provides a Laifeng ginger optimal harvesting time determination method based on texture characteristics and cell wall polysaccharides, and the method comprises the following steps: S1, time node determination: starting harvesting from the 60th day after sowing, then harvesting for one period every 30-60 days, and at least harvesting for four periods; s2, detection: selecting tender ginger of Laifeng ginger harvested at different periods in the step S1, and detecting the brittleness value, the moisture content, the transverse relaxation time of bound water, the total pectin content and the cellulose content; s3, single score conversion: converting the detection values into corresponding single scores according to a preset five-level segmentation scoring rule; and S4, comprehensively judging different brittleness harvesting periods by adopting a weighted scoring function. According to the method, a three-in-one harvesting standard of time nodes, quantitative indexes and visual characteristics is formed, traditional experience dependence is broken, technical support is provided for large-scale and standardized planting, and standardized development of the Laifeng ginger industry is promoted.

Description

Technical Field

[0001] This invention relates to the field of Laifeng ginger cultivation technology, and in particular to a method for determining the optimal harvesting period of Laifeng ginger based on its textural properties and cell wall polysaccharides. Background Technology

[0002] Laifeng ginger is a unique Chinese ginger variety that is both used in medicine and food. It is known for its tender flesh and unique flavor. Its crisp and tender texture is the core quality indicator for making processed products such as crispy slices and crispy ginger.

[0003] Currently, farmers rely primarily on traditional experience to harvest Laifeng ginger, using the number of days since sowing and tuber size as intuitive criteria, lacking scientifically quantifiable indicators related to crispness. This extensive harvesting method often leads to deviations in harvesting timing: harvesting too early results in underdeveloped tubers, low yield, and insufficient crispness; harvesting too late intensifies cell wall lignification, pectin degradation, and increased cellulose content, further reducing crispness and severely impacting the taste and quality of processed products, causing raw material waste and economic losses. Therefore, there is an urgent need to establish a scientific method for determining the harvesting period based on the high crispness characteristics of the developmental stage, enabling precise control of the high crispness quality of Laifeng ginger. Summary of the Invention

[0004] In view of this, the present invention proposes a method for determining the optimal harvesting period of Laifeng ginger based on its textural properties and cell wall polysaccharides. This method constructs a five-index comprehensive scoring system to achieve an objective and quantitative evaluation of the crispness quality of ginger, thereby guiding farmers to concentrate on harvesting during this period for use in crispy slices and crispy ginger products.

[0005] The technical solution of this invention is implemented as follows: a method for determining the optimal harvesting period of Laifeng ginger based on its textural properties and cell wall polysaccharides, comprising the following steps: S1, Determine the time nodes: Start harvesting from the 60th day after sowing, and then harvest once every 30-60 days, for a minimum of 4 harvests; S2, Detection: Select young ginger from Laifeng ginger harvested at different times in step S1, and test its crispness value, moisture content, bound water lateral relaxation time, total pectin content and cellulose content. The crispness value directly reflects the density of ginger tissue structure and its crisp texture. The cellulose content determines the cell wall strength and mechanical properties and is highly correlated with the crispness value. The total pectin content affects the cell wall softness and tissue hardness and is significantly correlated with the crispness value. The lateral relaxation time of bound water reflects the binding state of water with the cell wall, and the water content affects the overall texture characteristics of the tissue. S3, Single-item score conversion: Based on the preset five-level segmented scoring rules, the detection value is converted into the corresponding single-item score: 100 points, 80 points, 60 points, 40 points and 20 points respectively; S4, Comprehensive Judgment: The following weighted scoring function is used for comprehensive judgment: ; In the formula, S—comprehensive score, S t — Brittleness is worth classifying, S m —Moisture content score, S r —Combining the water transverse relaxation time score, S p —Total pectin content score, S c —Cellulose content score; S≥85 indicates an extremely brittle harvesting period; 75≤S<85 indicates a highly brittle harvesting period; 65≤S<75 indicates a moderately brittle harvesting period; 55≤S<65 indicates a moderately low brittle harvesting period; and S≤55 indicates a low brittle harvesting period.

[0006] Based on the above technical solutions, the preferred options are as follows: in the individual score, 100 points correspond to a fragility value ≥52 (Peakcounting), cellulose content 220-226 mg / g DW, total pectin content 29-33 mg / g DW, water-bound lateral relaxation time 12-14.5 ms, and moisture content 94.5%-95.5%.

[0007] Secondly, this invention provides a rapid method for determining the optimal harvesting period of Laifeng ginger: when at least 3 of the following 5 conditions are met simultaneously, it can be determined as a suitable harvesting period for high brittleness: brittleness value ≥52 Peak counting, moisture content 94.5-95.5%, transverse relaxation time (T2) of bound water 12-14.5ms; total pectin content 29-33mg / gDW, and cellulose content 220-226mg / gDW.

[0008] Based on the above technical solutions, preferably, the total pectin content includes the content of water-soluble pectin, ion-soluble pectin, and covalently soluble pectin.

[0009] Based on the above technical solutions, preferably, the brittleness value is determined by the puncture method of a texture analyzer.

[0010] Based on the above technical solutions, preferably, the transverse relaxation time (T2) of the bound water is determined using a nuclear magnetic resonance analyzer.

[0011] Based on the above technical solutions, preferably, the total pectin and cellulose are extracted from the cell walls of young ginger.

[0012] The method for determining the optimal harvesting period of Laifeng ginger based on textural properties and cell wall polysaccharides, as proposed in this invention, has the following advantages over existing technologies: (1) Accurately identify the high-brittle harvest window: By identifying the key time node of about 120 days after sowing, and combining brittleness parameters, moisture content, NMR determination of bound water relaxation time, pectin and cellulose content, the high-brittle quality of Laifeng ginger can be accurately determined, effectively avoiding quality decline caused by improper harvesting time.

[0013] (2) Establish a standardized harvesting system: Combine scientific indicators such as texture characteristics, moisture status and cell wall polysaccharide composition with field growth conditions to form a three-in-one harvesting standard of "time nodes + quantitative indicators + intuitive characteristics", break the reliance on traditional experience, provide technical support for large-scale and standardized planting, and promote the standardized development of Laifeng ginger industry. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 The crispness values ​​of young ginger at different harvesting periods; Figure 2 Moisture content of young ginger at different harvesting periods; Figure 3 The transverse relaxation time (T2) of bound water in ginger at different harvesting periods. Figure 4 The total pectin content of young ginger at different harvesting periods; Figure 5 The cellulose content of young ginger at different harvesting periods.

[0016] Figure 1-5 The data in the middle are the mean ± SEM, and the error bars are SEM. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] The Laifeng ginger materials used in this invention all come from the ginger nursery of the planting base in Lushui Town, Laifeng County, Hubei Province. The planting conditions for Laifeng ginger are consistent, and the same cultivation conditions (including soil, fertilization, water quality and pest and disease control measures) are adopted, with a plant spacing of 30cm.

[0019] Example 1

[0020] This embodiment provides a method for determining the optimal harvesting period of Laifeng ginger based on its textural properties and cell wall polysaccharides, including the following steps: S1, Determine the time point: Harvesting should begin 60 days after sowing; S2, Detection indicators: Select young ginger leaves from Laifeng ginger harvested at different times and test the following indicators: Peak counting, moisture content (%), transverse relaxation time of bound water (ms), total pectin content (mg / g DW), and cellulose content (mg / g DW) are shown in the table below. Figure 1-5 .

[0021] Example 2

[0022] This embodiment provides a method for determining the optimal harvesting period of Laifeng ginger based on its textural properties and cell wall polysaccharides, including the following steps: S1, Determine the time point: Harvesting should begin 90 days after sowing; S2, Detection indicators: Select young ginger leaves from Laifeng ginger harvested at different times and test the following indicators: Peak counting, moisture content (%), transverse relaxation time of bound water (ms), total pectin content (mg / g DW), and cellulose content (mg / g DW) are shown in the table below. Figure 1-5 .

[0023] Example 3

[0024] This embodiment provides a method for determining the optimal harvesting period of Laifeng ginger based on its textural properties and cell wall polysaccharides, including the following steps: S1, Determine the time point: Harvesting should begin 120 days after sowing; S2, Detection indicators: Select young ginger leaves from Laifeng ginger harvested at different times and test the following indicators: Peak counting, moisture content (%), transverse relaxation time of bound water (ms), total pectin content (mg / g DW), and cellulose content (mg / g DW) are shown in the table below. Figure 1-5 .

[0025] Example 4

[0026] This embodiment provides a method for determining the optimal harvesting period of Laifeng ginger based on its textural properties and cell wall polysaccharides, including the following steps: S1, Determine the time point: Harvesting should begin 180 days after sowing; S2, Detection indicators: Select young ginger leaves from Laifeng ginger harvested at different times and test the following indicators: Peak counting, moisture content (%), transverse relaxation time of bound water (ms), total pectin content (mg / g DW), and cellulose content (mg / g DW) are shown in the table below. Figure 1-5 .

[0027] The following are the testing methods for each indicator: 1 Brittleness value The crispness value of ginger was determined by a texture analyzer. Three uniformly sized pieces of young ginger were randomly selected and puncture tests were performed using a 2mm diameter cylindrical probe (P / 2) of the texture analyzer. The initial velocity was 1mm / s, the penetration velocity was 1mm / s, the velocity after the test was 5mm / s, the test distance was 6mm, and the trigger force was 10g. The surface of the ginger was randomly selected, the ginger was fixed, and the test was performed. Each sample was tested 3 times, and the average value was taken.

[0028] 2. Moisture content Six uniformly sized pieces of ginger were randomly selected and dried using a freeze dryer. The weights of the samples were recorded before and after drying.

[0029] 3. Transverse relaxation time of bound water (T2) Three uniformly sized ginger samples were randomly selected, and the transverse relaxation time (T2) of the samples was measured using the CPMG pulse sequence in the Numai nuclear magnetic resonance analyzer.

[0030] The CPMG pulse sequence parameters were set as follows: main frequency: 12 MHz; offset frequency: 290236.41 kHz; 90° pulse time: 7.52 μs; 180° pulse time: 14 μs; number of sampling points: 1050022; repetition time: 6000 ms; number of accumulations: 4; number of echoes: 18000. Finally, the T2 inversion spectrum was obtained using low-field nuclear magnetic resonance T2 inversion software.

[0031] 4. Cell polysaccharide index 4.1 Sample Pretreatment 4.1.1 Preparation of cell wall material Three uniformly sized pieces of young ginger were randomly selected, chopped, and freeze-dried to constant weight in a freeze dryer. The freeze-dried sample was then placed in a grinding jar, ground, mixed thoroughly, and bagged. The bag was then sealed and stored at -20°C.

[0032] Preheat a water bath to 95°C. Weigh 0.06g of the ground sample and place it in a 10mL test tube. Add 7mL of 75% ethanol solution to the test tube. Incubate in a 95°C water bath for 30min. After the test tube has cooled to room temperature, centrifuge at 8000rpm for 10min and discard the supernatant.

[0033] Rinse repeatedly about twice with 7 mL of 75% ethanol (to remove sugar).

[0034] This component is then mixed with 7 mL of a methanol:chloroform (trichloromethane) = 1:1 solution (to remove proteins and protein complexes), inverted and mixed thoroughly, left to stand horizontally for 10 min, centrifuged at 8000 rpm for 10 min to remove the supernatant, and the extraction is repeated twice.

[0035] Add 7 mL of pure acetone (to remove fats and pigments), mix by inverting, centrifuge at 8000 rpm for 10 min, and rinse repeatedly about twice until the color turns white to obtain coarse cell walls.

[0036] The sample was then soaked in 7 mL of 90% dimethyl sulfoxide (to remove starch) for 15 hours, and centrifuged at 8000 rpm for 10 minutes to remove the supernatant.

[0037] Finally, the filter residue was rinsed twice with 7 mL of 75% ethanol.

[0038] Place in a 45°C oven until the weight remains constant to obtain cell wall material (CWM). Store in a vacuum desiccator or sealed centrifuge tubes at -20°C for later use.

[0039] 4.1.2 Extraction and fractionation of cell wall polysaccharides Weigh 0.006g of dried cell wall material (CWM), flatten and mix well before weighing; Extract with 1 mL of 50 mmol / L sodium acetate in a water bath at 25°C and shake at 160 rpm for 6 hours. Centrifuge at 8000 rpm for 10 minutes and discard the supernatant. The extract is water-soluble pectin (WSP). The insoluble matter was extracted with 1 mL of 50 mmol / L sodium acetate buffer (containing 50 mmol / L EDTA-2Na) in a 25°C water bath shaker (160 rpm) for 12 hours. The supernatant was removed by centrifugation at 8000 rpm for 10 min, and ionic pectin (ISP) was obtained by centrifugation. The insoluble matter was extracted with 1 mL of 50 mmol / L Na2CO3 in a water bath at 25 °C for 24 hours. The supernatant was removed by centrifugation at 8000 rpm for 10 min to obtain covalently bound pectin (CSP). The insoluble matter after removing pectin was extracted with 1 mL of 1M KOH by shaking for 5 h, and the supernatant was removed by centrifugation at 8000 rpm for 10 min to obtain hemicellulose 1; The insoluble matter after removing pectin was extracted with 1 mL of 3M KOH by shaking for 5 h, and the supernatant was removed by centrifugation at 8000 rpm for 10 min to obtain hemicellulose 2; Combine the two solutions to obtain a hemicellulose liquid. Finally, wash twice with deionized water, centrifuge at 8000 rpm for 10 min, and the remaining precipitate is cellulose.

[0040] 1 mL of 60% sulfuric acid was slowly added to the cellulose precipitate and left at room temperature for 1 h to obtain a cellulose solution.

[0041] 4.2 Determination of pectin content Add 2.5 mL of sulfuric acid to a 10 mL test tube, cool to 4°C in an ice bath, then add 0.3 mL of the test sample solution (the sample obtained in steps 2-4 of 4.1.2) to the sulfuric acid layer, stopper the tube, and gently shake to mix. Heat the test tube in a boiling water bath for 10 min, and after cooling to room temperature, continue cooling to 4°C in an ice bath. Slowly add 0.1 mL of 0.15% carbazole ethanol solution (carbazole reagent), and gently place the test tube in a boiling water bath for 5 min. Remove the tube, mix well, and continue heating for 10 min. Cool to room temperature, and measure the absorbance at 530 nm. Record the absorbance value. Using galacturonic acid as a standard, determine and plot the standard curve using the carbazole-ethanol method, and calculate the pectin content.

[0042] 4.3 Determination of cellulose content Take 0.3 mL of the cellulose solution (the sample obtained in step 8 of 4.1.2) and add it to a 10 mL graduated test tube. Then add 2 mL of anthrone reagent to each test tube. After all the tubes have been added, place them together in a boiling water bath and cap the tubes to prevent evaporation. Boil for 10 minutes, then remove and cool under running water. Once the solutions in each tube have reached room temperature, quickly measure the absorbance of the remaining tubes at 620 nm. Using glucose as a standard, determine and plot the standard curve using the sulfuric acid-anthrone method, and calculate the cellulose content.

[0043] I. Scoring Criteria and Weighting According to the preset five-level segmented scoring rules, the above detection values ​​are converted into corresponding single-item scores: 100 points, 80 points, 60 points, 40 points and 20 points, as shown in Table 1.

[0044] Table 1. Rating Levels and Standards

[0045] II. Comprehensive Discriminant Function The following weighted scoring function is used for comprehensive judgment:

[0046] In the formula, S—comprehensive score, S t — Brittleness is worth classifying, S c —Cellulose content score, S p —Pectin content score, S r —Combining the water relaxation time score, S m —Moisture content score.

[0047] Note: Each item is scored out of 100, then multiplied by the corresponding weighting coefficient, and the sum is the overall score, with a maximum score of 100.

[0048] III. Threshold for Determination and Harvesting Recommendations Table 2 Correspondence between Overall Score and Harvesting Recommendations

[0049] IV. Quick Judgment Rules To facilitate rapid field assessment, this invention also provides simplified assessment rules: The optimal harvesting period for high brittleness can be determined when at least 3 of the following 5 conditions are met simultaneously: The brittleness value is ≥52 peak counting, the moisture content is 94.5-95.5%, the transverse relaxation time (T2) of bound water is 12-14.5 ms, the total pectin content is 29-33 mg / g DW, and the cellulose content is 220-226 mg / g DW.

[0050] V. Determining the Optimal Harvest Period Table 3. Detection results of various indicators of Ginger of the Wild at different growth stages

[0051] from Figure 1-5 The results in Table 3 show that the crispness value first decreases and then increases with the extension of growth days, reaching its maximum value (53 Peak Counting) at 120 days, at which point the crispness and tenderness are optimal. The moisture content decreases continuously with the extension of growth days, reaching 93.73% at 120 days, which ensures both crispness and supports metabolism. The bound water relaxation time (T2) gradually shortens with the increase of days, reaching 16.85 ms at 120 days, reflecting the matching between the bound water state and texture. The total pectin content decreases significantly with growth, but still retains sufficient gelatinous structure at 120 days (30.55 mg / g DW). The cellulose content increases significantly with growth, but does not become excessively lignified at 120 days (221.94 mg / g DW).

[0052] Overall scoring trend: Example 1 (60 days) had a low overall score (high pectin, low cellulose, insufficient crispness); Example 2 (90 days) showed an increase in crispness, but the overall score was moderate; Example 3 (120 days) had the best coordination among the five indicators, with an overall score ≥85 points; Example 4 (180 days) showed a significant decrease in crispness, excessive cellulose, and a lower overall score.

[0053] In summary, the optimal harvest time for Laifeng ginger is 120 days after planting. At this time, the textural characteristics (brittleness value), moisture state (moisture content and bound water), and cell wall polysaccharide composition (pectin / cellulose ratio) of Laifeng ginger synergistically form a "high-brittleness quality window," which is the core time node and indicator basis for scientifically determining the harvest period. Harvesting too early results in underdeveloped tubers with a brittleness value below 53 Peak Counting, leading to insufficient crispness and tenderness. Harvesting too late intensifies cell wall lignification (cellulose content above 221.94 mg / g DW), excessive pectin degradation (total pectin content below 30.55 mg / g DW), and a brittleness value below 53 Peak Counting, resulting in a coarse and hard texture in the tubers, severely affecting the quality of processed products, causing raw material waste and economic losses.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the optimal harvesting period of Laifeng ginger based on its textural properties and cell wall polysaccharides, characterized in that, Includes the following steps: S1, Determine the time nodes: Start harvesting from the 60th day after sowing, and then harvest once every 30-60 days, for a minimum of 4 harvests; S2, Detection: Select young ginger from Laifeng ginger harvested at different times in step S1, and test its crispness value, moisture content, bound water lateral relaxation time, total pectin content and cellulose content. S3, Single-item score conversion: Based on the preset five-level segmented scoring rules, the detection value is converted into the corresponding single-item score: 100 points, 80 points, 60 points, 40 points and 20 points respectively; S4, Comprehensive Judgment: The following weighted scoring function is used for comprehensive judgment: ； In the formula, S—comprehensive score, S t — Brittleness is worth classifying, S m —Moisture content score, S r —Combining the water transverse relaxation time score, S p —Total pectin content score, S c —Cellulose content score; S≥85 indicates an extremely brittle harvesting period; 75≤S<85 indicates a highly brittle harvesting period; 65≤S<75 indicates a moderately brittle harvesting period; 55≤S<65 indicates a moderately low brittle harvesting period; and S≤55 indicates a low brittle harvesting period.

2. The method for determining the optimal harvesting period of Laifeng ginger based on textural properties and cell wall polysaccharides as described in claim 1, wherein in the individual score, 100 points correspond to a fragility value ≥52 Peak counting, cellulose content 220-226 mg / g DW, total pectin content 29-33 mg / g DW, bound water transverse relaxation time 12-14.5 ms, and moisture content 94.5%-95.5%.

3. The method for determining the optimal harvesting period of Laifeng ginger based on textural properties and cell wall polysaccharides as described in claim 1, characterized in that, The total pectin content includes the content of water-soluble pectin, ion-soluble pectin, and covalently soluble pectin.

4. The method for determining the optimal harvesting period of Laifeng ginger based on textural properties and cell wall polysaccharides as described in claim 1, characterized in that, The brittleness value was determined using a texture analyzer puncture method.

5. The method for determining the optimal harvesting period of Laifeng ginger based on textural properties and cell wall polysaccharides as described in claim 1, characterized in that, The transverse relaxation time of the bound water was determined using a nuclear magnetic resonance analyzer.

6. The method for determining the optimal harvesting period of Laifeng ginger based on textural properties and cell wall polysaccharides as described in claim 1, characterized in that, The total pectin and cellulose were extracted from the cell walls of young ginger.

Images