Establishment method of rapid nondestructive detection model for water content of fruits

Abstract

The invention belongs to the technical field of agricultural product quality nondestructive testing, and particularly relates to a method for establishing a fruit water content rapid nondestructive testing model, which is characterized in that accurate and objective evaluation of fruit water loss is realized by establishing a quantitative relation model between a fruit water loss amount and a specific impedance characteristic in a water immersion state. The method has the beneficial effects that the quantitative relation model between the fruit moisture loss amount and the specific impedance characteristic (the impedance integral value changing along with the frequency) is established, so that the accurate and objective evaluation of the fruit moisture loss is realized, the freshness of the fruit is further judged, and finally the high-efficiency screening of the fruit with reduced quality is realized; the testing process is rapid and lossless, and no damage is caused to the fruits; the device can be applied to a large-batch fruit cleaning process to screen out low-quality fruits with low water content; the effectiveness of the detection method in a wet environment is verified through case research, and the feasibility of the detection method is proved through reasonable consistency of prediction and actual measurement results.

Description

Technical Field

[0001] The invention belongs to the technical field of non-destructive detection of agricultural product quality, and in particular relates to a method for establishing a rapid non-destructive detection model for fruit water content. Background Art

[0002] Fruit is an essential component of our daily diet and directly impacts our health and quality of life. Implementing rapid, non-destructive fruit quality testing during harvesting, storage, and processing not only ensures fruit quality and safety, but also improves production efficiency while minimizing losses. Rapid, non-destructive assessment of key fruit indicators facilitates fruit sorting, storage, and quality screening. During storage, non-destructive testing enables timely detection of problems such as rot and spoilage, enabling real-time grading and storage of fruit, thereby extending its shelf life.

[0003] Electrical impedance spectroscopy (EIS) has attracted widespread attention as an invasive or non-invasive method for assessing fruit quality. By measuring the electrical parameters of the fruit, this technology can effectively detect indicators such as rot, mechanical damage, disease, maturity, and moisture content, providing a new approach to fruit quality testing. The principle of impedance spectroscopy is to stimulate the fruit with AC signals of different frequencies. By measuring the electrical response of the fruit, this method can provide insights into its internal structure and quality. Because conditions such as rot and damage can cause changes in the internal electrical properties of the fruit, impedance spectroscopy has become a valuable tool for assessing fruit quality by analyzing these fluctuations. In addition, this technology effectively identifies low-quality fruit, prevents it from being included in production, and ensures the quality and safety of processed products. EIS can provide insights into the different states of the sample.

[0004] Existing fruit quality detection technology based on electrical impedance spectroscopy (EIS) faces challenges: on the one hand, individual differences in agricultural products (such as fruit) make it difficult to achieve completely consistent contact geometry between the electrode and the sample surface during measurement, making it difficult to ensure that each sample is in the same measurement state; on the other hand, its electrical parameters have a nonlinear and separable relationship with the target data set. Direct impedance testing in a dry environment leads to large errors, unstable results, and damage to the fruit peel. These factors limit the widespread application of EIS. Summary of the Invention

[0005] The present invention aims to provide a method for establishing a model for rapid and non-destructive detection of water content in fruit, overcoming the shortcomings of the prior art. The method adopts an impedance method model to quantify the water loss of the fruit by measuring the impedance difference before and after the quality change of the fruit, and then establishes a model relationship between the water loss and the impedance characteristic (such as the comprehensive impedance of a specific frequency or an integral region). The testing process is rapid and non-destructive, and does not cause any damage to the fruit. The method can be applied to the large-volume fruit washing process to screen out low-quality fruits with low water content. At the same time, the method solves the problems of large errors, unstable results, and damage to the fruit peel caused by direct impedance testing in a non-aqueous environment.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for establishing a rapid non-destructive detection model for fruit moisture content, characterized by establishing a quantitative relationship model between the amount of moisture loss in the fruit and a specific impedance characteristic under water immersion, thereby achieving an accurate and objective assessment of the moisture loss in the fruit, specifically comprising the following steps:

[0008] 1) Select fresh, intact fruit samples without rot or physical defects and immerse them in water with the stem facing upward. Six measurement points are evenly selected in three directions around the circumference of the fruit stem.

[0009] 2) The fruit samples were measured using an impedance analyzer, with two contact electrodes corresponding to two measurement points in one direction, until the impedance values ​​of the fruit samples in all three directions were measured. A total of 201 frequency sampling points were selected using the logarithmic method;

[0010] 3) Measure the water impedance alone as a benchmark and compare the impedance differences in the three directions;

[0011] 4) The quantitative relationship model between the water loss of fruit and the specific impedance characteristics is established as follows:

[0012] y=A1*exp(-x / t1)+y0

[0013] Where: y is the impedance integral; x is the water loss of the fruit, in g;

[0014] A1=3969487.60±493355.20~4235150.11±526373.56; t1=1.84±0.29~1.89±0.35;

[0015] y0=3.34E7±359734.25~3.65E7±392613.96.

[0016] Furthermore, the impedance analyzer model is E4990A, the frequency range is 20Hz-20MHz, and the test voltage is set to 1V.

[0017] Furthermore, the specific impedance characteristics refer to frequency and impedance integral.

[0018] Furthermore, the fruit sample is Korla fragrant pear with a mass range of 130-135g, which was cleaned in a standardized manner before the experiment.

[0019] Furthermore, the water is any one of city pipe network tap water, drinking grade purified water, salt water, alkaline water, and vinegar water.

[0020] Furthermore, the standardized cleaning process is as follows: at room temperature, use a soft-bristled brush to gently brush the surface of the fruit under running water to remove sand, dust, and residual wax. Avoid mechanical damage to the peel, and the brushing time is ≤30 seconds per fruit.

[0021] Furthermore, the Korla pear can be replaced by apple, orange, strawberry, cherry, blueberry, plum, peach, prune, mango, or loquat.

[0022] Furthermore, the NaCl concentration in the brine is 0.1-20%.

[0023] Furthermore, the concentration of NaOH in the alkaline water is 0.1-10%.

[0024] Furthermore, the concentration of acetic acid in the vinegar water is 0.1-30%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) The present invention establishes a quantitative relationship model between the amount of water loss in fruit and specific impedance characteristics (frequency variation and integrated value), thereby achieving an accurate and objective assessment of the water loss in fruit, thereby determining the freshness of the fruit and ultimately achieving efficient screening of fruit with deteriorating quality;

[0027] 2) The test process is fast and non-destructive, without causing any damage to the fruit. It can be applied to large-volume fruit washing processes to screen out low-quality fruit with low moisture content. It also solves the problems of large errors, unstable results, and damage to the fruit peel caused by direct impedance testing in non-aqueous environments.

[0028] 3) The effectiveness of the detection method in a wet environment was verified through a case study, and the reasonable consistency between the predicted and measured results demonstrated the feasibility of the detection method. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The detection object selected in Example 1 of the present invention is Korla fragrant pear;

[0030] Figure 2The selected three-direction 1-1, 2-2, 3-3 direction schematic diagram marked on the detection object in Example 1 of the present application;

[0031] Figure 3 The three-direction 1-1, 2-2, 3-3 direction impedance curve diagram of the comparative example of the present application in an air environment;

[0032] Figure 4 The pure water impedance curve diagram of Example 1 of the present application;

[0033] Figure 5 The three-direction 1-1, 2-2, 3-3 direction impedance curve diagram of Example 1 of the present application;

[0034] Figure 6 The three-direction 1-1, 2-2, 3-3 direction impedance of Example 1 of the present application; a. dried for 2h, b. dried for 4h, c. dried for 6h, d. dried for 8h, e. dried for 12h comparative curve diagram;

[0035] Figure 7 The impedance average line (located above the pure water average line) of Example 1 of the present application at different drying times;

[0036] Figure 8 The impedance integral value curve diagram of Example 1 of the present application at each drying time (corresponding to different water dispersion loss amounts);

[0037] Figure 9 The fitting equation of Example 1 of the present application based on the impedance integral value at each drying time. DETAILED DESCRIPTION

[0038] The technical solutions of the present application will be described in detail below with reference to specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, not all.

[0039] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the specific embodiments needed to be used in the description of the specific embodiments or the prior art will be briefly introduced. Obviously, the specific embodiments described below are some embodiments of the present application, and those skilled in the art can obtain other specific embodiments without creative labor on the basis of these specific embodiments.

[0040] The components of the embodiments of the present application described and shown in the specific embodiments herein can be arranged and designed in countless different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the specific embodiments is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application.

[0041] In the following examples, the impedance analyzer model is E4990A, with a frequency range of 20 Hz-20 MHz and a test voltage of 1 V. Fruit samples were selected to be fresh, intact, and free of rot or physical defects. The fruit samples weighed 130-135 g and were cleaned in a standardized manner before the experiment. The standardized cleaning process involves gently brushing the fruit surface with a soft brush under running water at room temperature to remove mud, dust, and residual wax. Mechanical damage to the peel should be avoided, and the brushing time should be ≤ 30 seconds per fruit. The NaCl concentration in the salt water ranged from 0.1-20%, the NaOH concentration in the alkaline water ranged from 0.1-10%, and the acetic acid concentration in the vinegar water ranged from 0.1-30%. The "specific impedance signature" proposed in this invention refers to a set or specific key electrical parameter obtained by impedance measurement techniques (typically multi-frequency or swept frequency) while the fruit is submerged in water. The core of "impedance" refers to the impedance values ​​(e.g., impedance amplitude |Z|, phase angle θ, real part R, and imaginary part X) measured at one or more carefully selected frequency points sensitive to moisture changes. Referring to other literature studies, the general change of the phase angle θ has little effect on the impedance. Therefore, in the experiment of the present invention, the emphasis is on the impedance amplitude |Z|, that is, the impedance value; the specific impedance characteristic refers to the integral value of the electrical parameter obtained by frequency sweep at a frequency of 20Hz-20Mhz (that is, the impedance value obtained in the experiment of the present invention).

[0042] Example 1

[0043] The present invention provides a method for establishing a rapid non-destructive detection model for fruit moisture content. The method establishes a quantitative relationship model between the amount of moisture loss in the fruit and a specific impedance characteristic under water immersion, thereby achieving an accurate and objective assessment of the moisture loss in the fruit. The method specifically comprises the following steps:

[0044] 1) Select a fruit sample - Korla fragrant pear and immerse it in drinking-grade purified water with the stem facing upwards. 6 measurement points are evenly selected in three directions around the circumference of the fruit stem; see Figure 1 、 Figure 2 ;

[0045] 2) The fruit samples were measured using an impedance analyzer. The two contact electrodes of the impedance analyzer corresponded to two measurement points in one direction respectively, until the impedance values ​​of the fruit samples in all three directions were measured. A total of 201 frequency sampling points were selected using the logarithmic method; see Figure 5 ;

[0046] 3) Measure the water impedance alone as a benchmark and compare the impedance differences in the three directions; see Figure 4 ;

[0047] 4) The quantitative relationship model between the water loss of fruit and the specific impedance characteristics is established as follows:

[0048] y=A1*exp(-x / t1)+y0

[0049] Where: y is the impedance integral; x is the water loss of the fruit, in g; A1 = 4235150.11 ± 526373.56; t1 = 1.85 ± 0.56; y0 = 3.57E7 ± 383809.88.

[0050] Example 2

[0051] The present invention provides a method for establishing a rapid non-destructive detection model for fruit moisture content. The method establishes a quantitative relationship model between the amount of moisture loss in the fruit and a specific impedance characteristic under water immersion, thereby achieving an accurate and objective assessment of the moisture loss in the fruit. The method specifically comprises the following steps:

[0052] 1) Select a fruit sample - immerse the apple in salt water with the stem facing up. Six measurement points are evenly selected in three directions around the circumference of the stem.

[0053] 2) The fruit samples were measured using an impedance analyzer, with two contact electrodes corresponding to two measurement points in one direction, until the impedance values ​​of the fruit samples in all three directions were measured. A total of 201 frequency sampling points were selected using the logarithmic method;

[0054] 3) Measure the water impedance alone as a benchmark and compare the impedance differences in the three directions;

[0055] 4) The quantitative relationship model between the water loss of fruit and the specific impedance characteristics is established as follows:

[0056] y=A1*exp(-x / t1)+y0

[0057] Where: y is the impedance integral; x is the water loss of the fruit, in g; A1 = 4050497.56 ± 503423.67; t1 = 1.89 ± 0.35; y0 = 3.41E7 ± 367075.77.

[0058] Example 3

[0059] The present invention provides a method for establishing a rapid non-destructive detection model for fruit moisture content. The method establishes a quantitative relationship model between the amount of moisture loss in the fruit and a specific impedance characteristic under water immersion, thereby achieving an accurate and objective assessment of the moisture loss in the fruit. The method specifically comprises the following steps:

[0060] 1) Select a fruit sample - immerse the citrus fruit in alkaline water with the stem facing up. Six measurement points are evenly selected in three directions around the circumference of the fruit stem.

[0061] 2) The fruit samples were measured using an impedance analyzer, with two contact electrodes corresponding to two measurement points in one direction, until the impedance values ​​of the fruit samples in all three directions were measured. A total of 201 frequency sampling points were selected using the logarithmic method;

[0062] 3) Measure the water impedance alone as a benchmark and compare the impedance differences in the three directions;

[0063] 4) The quantitative relationship model between the water loss of fruit and the specific impedance characteristics is established as follows:

[0064] y=A1*exp(-x / t1)+y0

[0065] Where: y is the impedance integral; x is the water loss of the fruit, in g; A1 = 3969487.60 ± 493355.20; t1 = 1.88 ± 0.51; y0 = 3.34E7 ± 359734.25.

[0066] Example 4

[0067] The present invention provides a method for establishing a rapid non-destructive detection model for fruit moisture content. The method establishes a quantitative relationship model between the amount of moisture loss in the fruit and a specific impedance characteristic under water immersion, thereby achieving an accurate and objective assessment of the moisture loss in the fruit. The method specifically comprises the following steps:

[0068] 1) Select a fruit sample, Korla fragrant pear, and immerse it in vinegar water with the stem facing upward. Six measurement points are evenly selected in three directions around the circumference of the stem.

[0069] 2) The fruit samples were measured using an impedance analyzer, with two contact electrodes corresponding to two measurement points in one direction, until the impedance values ​​of the fruit samples in all three directions were measured. A total of 201 frequency sampling points were selected using the logarithmic method;

[0070] 3) Measure the water impedance alone as a benchmark and compare the impedance differences in the three directions;

[0071] 4) The quantitative relationship model between the water loss of fruit and the specific impedance characteristics is established as follows:

[0072] y=A1*exp(-x / t1)+y0

[0073] Where: y is the impedance integral; x is the water loss of the fruit, in g; A1 = 4332298.77 ± 538447.86; t1 = 1.84 ± 0.29; y0 = 3.65E7 ± 392613.96.

[0074] Example 5

[0075] The present invention provides a method for establishing a rapid non-destructive detection model for fruit moisture content. The method establishes a quantitative relationship model between the amount of moisture loss in the fruit and a specific impedance characteristic under water immersion, thereby achieving an accurate and objective assessment of the moisture loss in the fruit. The method specifically comprises the following steps:

[0076] 1) Select a fruit sample (Korla fragrant pear) and immerse it in salt water with the stem facing up. Six measurement points are evenly selected in three directions around the circumference of the stem.

[0077] 2) The fruit samples were measured using an impedance analyzer, with two contact electrodes corresponding to two measurement points in one direction, until the impedance values ​​of the fruit samples in all three directions were measured. A total of 201 frequency sampling points were selected using the logarithmic method;

[0078] 3) Measure the water impedance alone as a benchmark and compare the impedance differences in the three directions;

[0079] 4) The quantitative relationship model between the water loss of fruit and the specific impedance characteristics is established as follows:

[0080] y=A1*exp(-x / t1)+y0

[0081] Where: y is the impedance integral; x is the water loss of the fruit, in g; A1 = 4029037.86 ± 500756.51; t1 = 1.87 ± 0.76; y0 = 3.39E7 ± 365130.98.

[0082] Comparative Example

[0083] 1) Select a fruit sample, Korla fragrant pear, and accurately weigh the selected pear using an electronic balance. The mass is 133.92 g. The pear is placed with the stem facing up. Six measurement points are evenly selected in three directions around the circumference of the stem. The experimental environment is a dry air medium environment with a relative humidity of less than 15%.

[0084] 2) The fruit samples were measured using an impedance analyzer. The two contact electrodes of the impedance analyzer corresponded to two measurement points in one direction respectively. The three pre-selected directions were measured. A total of 201 frequency sampling points were selected using the logarithmic method until the impedance values ​​of the fruit samples in all three directions were measured. The impedance values ​​in each direction are shown in Figure 3 , the impedance values ​​in the three directions show significant discreteness.

[0085] Fitting verification experiments were performed on the models of Examples 1-5 and the comparative example above.

[0086] The fruit was dried in a constant temperature and humidity drying oven (40°C ± 0.5°C, humidity 30% ± 2%) to simulate water loss. After that, the fruit was removed from the drying oven every 2 hours and impedance spectrum data was collected. (Time points and mass: 2h / 133.01g, 4h / 132.03g, 6h / 130.67g, 8h / 128.71g). After 8h, the degree of blackening of the fruit skin became more serious. In view of the fact that the regularity had emerged, the measurement time was extended to 12h. The mass was 123.47g. No data were collected at the intermediate time points. The measurement results are shown in Fig. Figure 6 .

[0087] Through the above verification experiments, the relationship between fruit water loss and electrical parameters (impedance characteristics) was obtained. The impedance average line below the pure water average line under water immersion is highly fitted, and the data above it are selected for key analysis (see Figure 7 The results show that as the drying time increases, the water loss of the fruit increases, and its impedance value shows a steady downward trend. The test results under water immersion remain stable.

[0088] Based on the impedance average data at different drying times, the impedance value is integrated with the frequency change (see Figure 8 ), the integral value curve of the fruit impedance value changing with the moisture loss under different drying times (corresponding to different moisture loss) was obtained, the curve was fitted, and a quantitative relationship model between the moisture loss of fruit (0h / 0g, 2h / 0.91g, 4h / 1.89g, 6h / 3.25g, 8h / 5.21g, 12h / 10.45g) and the specific impedance characteristics (frequency change response and integral value) was established, and the change law of the fruit impedance characteristics under water immersion was obtained (see Figure 9 ). Achieve accurate and objective assessment of fruit moisture loss, thereby judging the freshness and quality of the fruit, and ultimately achieve efficient screening of fruits with deteriorating quality.

[0089] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for establishing a rapid non-destructive detection model for fruit moisture content, characterized in that: By establishing a quantitative relationship model between the amount of water loss in fruits and specific impedance characteristics under water immersion, an accurate and objective assessment of water loss in fruits can be achieved. Specifically, the following steps are included: 1) Select fresh, intact fruit samples without rot or physical defects and immerse them in water with the stem facing upward. Six measurement points are evenly selected in three directions around the circumference of the fruit stem. 2) The fruit samples were measured using an impedance analyzer, with two contact electrodes corresponding to two measurement points in one direction, until the impedance values ​​of the fruit samples in all three directions were measured. A total of 201 frequency sampling points were selected using the logarithmic method; 3) Measure the water impedance alone as a benchmark and compare the impedance differences in the three directions; 4) The quantitative relationship model between the water loss of fruit and the specific impedance characteristics is established as follows: y=A1*exp(-x / t1)+y0 Where: y is the impedance integral; x is the water loss of the fruit, in g; A1=3969487.60±493355.20~4235150.11±526373.56; t1=1.84±0.29~1.89±0.35; y0=3.34E7±359734.25~3.65E7±392613.

96.

2. the method for establishing a rapid nondestructive detection model of fruit water content according to claim 1, is characterized in that, The impedance analyzer model is E4990A, the frequency range is 20 Hz-20 MHz, and the test voltage is set to 1 V.

3. the method for establishing a rapid nondestructive detection model of fruit water content according to claim 1, is characterized in that, The specific impedance characteristics refer to frequency and impedance integral.

4. the method for establishing a rapid nondestructive detection model of fruit water content according to claim 1, is characterized in that, The fruit samples were Korla fragrant pears with a mass range of 130-135 g, which were cleaned in a standardized manner before the experiment.

5. the method for establishing a rapid nondestructive detection model of fruit water content according to claim 1, is characterized in that, The water is any one of city pipe network tap water, drinking grade purified water, salt water, alkaline water, and vinegar water.

6. a method for establishing a rapid nondestructive detection model of fruit water content according to claim 4, characterized in that, The standardized cleaning process is: at room temperature, use a soft-bristled brush to gently brush the surface of the fruit in running water to remove mud, dust and fruit wax residue. Avoid mechanical damage to the peel, and the scrubbing time should be ≤30 seconds per piece.

7. a method for establishing a rapid nondestructive detection model of fruit water content according to claim 4, characterized in that, The Korla fragrant pear can be replaced by apple, orange, strawberry, cherry, blueberry, plum, peach, prune, mango, and loquat.

8. a method for establishing a rapid nondestructive detection model of fruit water content according to claim 5, characterized in that, The NaCl concentration in the brine is 0.1-20%.

9. a method for establishing a rapid nondestructive detection model of fruit water content according to claim 5, characterized in that, The concentration of NaOH in the alkaline water is 0.1-10%.

10. The method for establishing a rapid nondestructive detection model for water content in fruit according to claim 5, wherein: The concentration of acetic acid in the vinegar water is 0.1-30%.

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