Method and apparatus for evaluation of avocado

Abstract

To provide a method for performing more accurate non-destructive evaluation of avocado.SOLUTION: The method includes: an excitation step S10 of irradiating excitation light EL onto an avocado FV to excite autofluorescent substances contained in the avocado FV; a measurement step S20 of measuring fluorescence FL emitted from the excited autofluorescent substances; and an evaluation step S30 of evaluating the avocado on the basis of fluorescence intensities in a first wavelength region and a second wavelength region in the fluorescence FL, the first wavelength region including a fluorescence region of chlorophyll, and the second wavelength region including a fluorescence region of carotenoid.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for non-invasively and non-destructively evaluating and inspecting fruits and vegetables primarily by optical techniques, and an apparatus therefor. [Background technology]

[0002] It is desirable to price and distribute fresh produce appropriately after evaluating its freshness (ripeness), taste, etc. in advance. However, once the produce is invaded or destroyed for tasting or sampling inspection, the commercial value of the produce drops significantly, and this method does not allow for full inspection.

[0003] For this reason, the freshness and taste of fruits and vegetables have traditionally been evaluated and estimated non-invasively and simply based on their appearance to the human eye, the feel of the fruit when touched or held, the sound it makes when lightly tapped, the smell it emits, etc.

[0004] While the above-mentioned methods are very useful for consumers to make purchasing decisions about fruits and vegetables, they are heavily dependent on personal skill and are therefore insufficient for more rigorous evaluation of the freshness and taste of fruits and vegetables.

[0005] In view of this situation, methods and devices for non-invasively and quantitatively evaluating and inspecting the freshness and taste of fruits and vegetables, mainly by optical techniques, have been proposed.

[0006] For example, Patent Document 1 describes an evaluation device and evaluation method for determining characteristic values ​​such as sugar content, color chart value, and chlorophyll concentration from indicators based on fluorescence when grapes are irradiated with excitation light, and for determining the shipping time.

[0007] Furthermore, Patent Document 2 describes a food storage cabinet (refrigerator) equipped with a freshness detection unit that can detect the freshness and ripeness of vegetables based on the fluorescence emitted when the chlorophyll contained in the vegetables is excited. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2023-109722 [Patent Document 2] Japanese Patent Application Publication No. 2023-180924 Summary of the Invention [Problem to be solved by the invention]

[0009] As mentioned above, there are methods for non-destructively evaluating produce by examining the concentration and content of chlorophyll based on the fluorescence emitted by exciting the chlorophyll contained in the produce. However, there are some produce that are difficult to accurately evaluate when chlorophyll alone is used as an indicator.

[0010] For example, avocados are one type of fruit and vegetable that are difficult to accurately evaluate non-destructively. While the skin of common fruits such as grapes and mangoes is thin and soft, avocados are characterized by being covered with a thick, hard skin. That is, for fruits with soft skin, it is possible to obtain a lot of internal information by letting the light source light penetrate the interior, whereas for fruits with thick, hard skin such as avocados, it is not possible to let the light source light penetrate the interior, and therefore no internal information can be obtained.

[0011] The present invention has been made in consideration of the above-mentioned problems, and provides a method for more accurate non-destructive evaluation of avocados. [Means for solving the problem]

[0012] The present invention, which aims to solve the above problems, is based on the technical ideas set out in the following [1] to

[13] . [1] A method for evaluating avocados, comprising: an excitation step of irradiating excitation light onto the avocado skin to excite autofluorescent substances contained in the avocado skin; a measurement step of measuring the fluorescence emitted from the excited autofluorescent substances; and an evaluation step of evaluating the avocado based on the fluorescence intensity in a first wavelength range and the fluorescence intensity in a second wavelength range of the fluorescence, wherein the first wavelength range includes the fluorescence region of chlorophyll and the second wavelength range includes the fluorescence region of carotenoids. [2] The avocado evaluation method described in [1], wherein the excitation light has a central wavelength of 410 nm or more and less than 480 nm. [3] The avocado evaluation method according to [1] or [2], wherein the measurement step is a step of measuring fluorescence having a wavelength that is 10 nm or more longer than the central wavelength of the excitation light. [4] The avocado evaluation method according to any one of [1] to [3], wherein in the evaluation step, the avocado is evaluated based on the fluorescence intensity ratio between the fluorescence peak in the first wavelength range and the fluorescence peak in the second wavelength range. [5] An avocado evaluation device comprising a plurality of excitation light sources, a light receiving unit, an evaluation unit, and a display unit, wherein the light receiving unit is configured to be capable of measuring the fluorescence intensity in a first wavelength range including the fluorescence range of chlorophyll and the fluorescence intensity in a second wavelength range including the fluorescence range of carotenoids, the evaluation unit is configured to be capable of calculating an evaluation result of the avocado based on the fluorescence intensity in the first wavelength range and the fluorescence intensity in the second wavelength range, and the display unit is configured to be capable of displaying the evaluation result. [6] The evaluation device described in [5], wherein the plurality of excitation light sources are arranged to surround the light receiving unit and the projection axis of each excitation light source is inclined toward the light receiving unit. [7] The evaluation device described in [5] or [6], further comprising a light-shielding member arranged to cover the plurality of excitation light sources and the light-receiving unit, the light-shielding member being arranged to open the light-projecting direction as seen from the plurality of excitation light sources and the light-receiving direction as seen from the light-receiving unit. [8] The evaluation device according to any one of [5] to [7], wherein the excitation light source has a light source center wavelength of 410 nm or more and less than 480 nm. [9] The evaluation device described in any one of [5] to [8], wherein the light receiving unit has an optical filter, and the optical filter includes a long-pass filter that transmits light having a wavelength that is 10 nm or more longer than the light source center wavelength of the excitation light source.

[10] The evaluation device according to any one of [5] to [9], wherein the display unit is capable of displaying peak intensities in the first wavelength range and the second wavelength range as the evaluation result.

[11] The evaluation device according to any one of [5] to

[10] , wherein the display unit is capable of displaying a predetermined color based on the evaluation result as the evaluation result.

[12] The avocado evaluation method described in [2], wherein the first wavelength range is 680 nm or more and less than 750 nm.

[13] The evaluation device according to [7], wherein the tilt angle of the projection axis of the excitation light source is 10° or more and less than 20°, and the length of the light blocking member is 25 mm or more and less than 35 mm.

[0013] By using a method such as [1], the fluorescence from the chlorophyll and carotenoids contained in the avocado skin can be used as a composite evaluation index, allowing for more accurate non-destructive evaluation of avocados. In particular, it is difficult to penetrate light from a light source into fruits with thick, hard skins such as avocados. However, methods such as [1] can more accurately evaluate the ripeness of the inside of an avocado based on information obtained from the skin.

[0014] The method of using light in the wavelength range described in [2] as excitation light reduces the risk of irreversible damage to avocados, as occurs when ultraviolet light is irradiated for a long period of time, and can distinguish between the fluorescence derived from chlorophyll and carotenoids and the excitation light, while providing chlorophyll and carotenoids with sufficient energy for excitation.

[0015] The method described in [3] allows for the simultaneous detection of chlorophyll-derived fluorescence and carotenoid-derived fluorescence relatively easily.

[0016] By using a method such as [4], it is possible to perform more accurate evaluation based on the fluorescence intensity derived from carotenoids, using the fluorescence intensity derived from chlorophyll as a reference.

[0017] The apparatus such as [5] can easily carry out the avocado evaluation method of the present invention.

[0018] The arrangement of the excitation light source described in [6] is advantageous in that a sufficient amount of light can be ensured when irradiating excitation light at a short distance.

[0019] A device such as [7] can concentrate excitation light on the evaluation object between the light source and the evaluation object, while suppressing the influence of natural light, allowing for highly accurate evaluation.

[0020] [8] An apparatus that uses light in the wavelength range described above as an excitation light source reduces the risk of irreversible damage to avocados, as occurs when ultraviolet light is irradiated for a long period of time, and can relatively easily distinguish between the fluorescence originating from chlorophyll and carotenoids and the excitation light, while providing chlorophyll and carotenoids with sufficient energy for excitation.

[0021] An apparatus such as [9] can relatively easily detect the fluorescence derived from chlorophyll and the fluorescence derived from carotenoids simultaneously.

[0022] A user of a device such as

[10] can verify the evaluation results obtained by the device based on the peak intensities in the first and second wavelength ranges displayed on the display unit.

[0023] Devices such as

[11] are suitable for non-destructive evaluation of large quantities of avocados because they can quickly obtain visual evaluation results.

[0024] Methods such as

[12] can more accurately assess the ripeness of avocados by taking into account not only the fluorescence derived from chlorophyll but also the change in fluorescence intensity resulting from the change in fatty acid ratio with ripeness.

[0025] In a device like

[13] , the light from the light source is concentrated directly under the spectrometer, so it is possible to obtain fluorescence intensity with high efficiency even from the skin of fruits such as avocados, where the light from the light source is difficult to penetrate. [Effects of the Invention]

[0026] According to the present invention, an evaluation method and evaluation device are provided that can perform more accurate non-destructive evaluation of avocados by including not only fluorescence derived from chlorophyll but also fluorescence derived from carotenoids as evaluation indices. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a flowchart illustrating an evaluation method according to an embodiment of the present invention. [Figure 2] 1 is a diagram illustrating an excitation light source wavelength and a long-pass filter according to the present invention. FIG. [Figure 3] 1 is a diagram illustrating an excitation light source wavelength and a long-pass filter according to the present invention. FIG. [Figure 4] FIG. 10 is a diagram illustrating the correlation between the fluorescence intensity ratio and the ripeness of avocados. [Figure 5] FIG. 2 is a diagram illustrating a functional configuration of an evaluation device according to an embodiment of the present invention. [Figure 6] 1 is a diagram illustrating an evaluation device according to an embodiment of the present invention. [Figure 7] 1 is a diagram illustrating an evaluation device according to an embodiment of the present invention. [Figure 8] 1 is a photograph showing the appearance of an avocado according to an embodiment of the present invention. [Figure 9] 1 is a diagram illustrating a usage mode of an evaluation device according to an embodiment of the present invention. [Figure 10] FIG. 1 is a scatter plot based on the fluorescence intensity ratio in the avocados to be evaluated. [Figure 11] FIG. 1 is a scatter plot based on the fluorescence intensity ratio in the avocados to be evaluated. [Figure 12] 1 is a conceptual diagram comparing a conventional evaluation device and an evaluation device of the present invention. [Figure 13]10A and 10B are diagrams illustrating adjustment of the angle of the excitation light source and the length of the light blocking member. [Figure 14] This is a photograph of the appearance of the avocados subjected to fluorescence spectrum analysis and GC / FID. [Figure 15] The three-dimensional fluorescence spectrum of each avocado shown in Figure 14. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, an avocado evaluation method and evaluation device according to an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the embodiment shown below is an example of the present invention, and the present invention is not limited to the following embodiment. The evaluation device according to the embodiment of the present invention is indicated by the symbol X.

[0029] [How to evaluate avocados] Hereinafter, the avocado evaluation method according to the embodiment of the present invention will be described in detail with reference to FIGS.

[0030] <Excitation process> The excitation step S10 is a step of irradiating the epidermis of the avocado FV with excitation light EL to excite autofluorescent substances (chlorophyll, carotenoids, etc.) contained in the epidermis of the avocado FV.

[0031] In the excitation step S10, in order to simultaneously excite the chlorophyll and carotenoids contained in the epidermis of the avocado FV with excitation light EL having the same central wavelength, excitation light EL having a central wavelength of 410 nm or more and less than 480 nm is preferably used, the reason for which will be described later.

[0032] <Measurement process> The measuring step S20 is a step of measuring the fluorescence FL emitted from the autofluorescent material excited in the exciting step S10. In the measurement step S20, in particular, in order to distinguish between the excitation light EL and the fluorescence FL derived from carotenoids, the fluorescence FL having a wavelength 10 nm or longer than the central wavelength of the excitation light EL is preferably measured. Such a measurement step S20 can be realized by fluorescence measurement using a long-pass filter that transmits light having a wavelength 10 nm or longer than the central wavelength of the excitation light EL.

[0033] The selection of the excitation light source wavelength and the long-pass filter will be explained below with reference to FIGS.

[0034] FIG. 2 compares the reflectance fluorescence profiles of avocado (Avocado FV) measured using a UV light source (wavelength 365 nm) and a blue visible light source (wavelength 450 nm). As shown in Figure 2(A), the reflectance fluorescence profile excited by a UV light source detects peaks derived from carotenoids around a wavelength of 500 nm (510 nm, 550 nm), but does not detect peaks derived from chlorophyll around a wavelength of 700 nm (688 nm, 740 nm). On the other hand, as shown in Figure 2(B), the reflectance fluorescence profile obtained by excitation with a blue visible light source detects peaks originating from chlorophyll at wavelengths around 700 nm (688 nm, 740 nm), but the peaks originating from carotenoids at wavelengths around 500 nm (510 nm, 550 nm) are indistinguishable from the peaks of the excitation light.

[0035] FIG. 3 is a graph comparing the avocado epidermal fluorescence profile (500 to 800 nm) measured using a blue visible light source (wavelength 450 nm) with and without a long-pass filter (which transmits light with wavelengths of 460 nm or longer). As shown in Figure 3(A), in measurements without a long-pass filter, the chlorophyll-derived peak at a wavelength of around 700 nm was detected, but the carotenoid-derived peak at a wavelength of around 500 nm was indistinguishable from the excitation light peak (corresponding to Figure 2(B)). On the other hand, as shown in Figure 3(B), when a long-pass filter that transmits light with wavelengths of 460 nm or more is used, the background intensity is reduced to about half, reducing the overall sensitivity, and the profile in the wavelength range of 500 to 600 nm changes significantly. Specifically, the influence of excitation light is suppressed, a valley due to the light absorption of carotenoids is observed around a wavelength of 520 nm, and a fluorescence peak due to carotenoids is observed around a wavelength of 550 nm.

[0036] As described above, in order to simultaneously excite the chlorophyll and carotenoids contained in the epidermis of avocado FV with excitation light having the same central wavelength, excitation light EL having a central wavelength of 410 nm or more and less than 480 nm is preferably used. Furthermore, in order to distinguish between the excitation light EL and the fluorescence FL derived from carotenoids, the fluorescence FL having a wavelength 10 nm or more longer than the central wavelength of the excitation light EL is preferably measured.

[0037] <Evaluation process> The evaluation step S30 is a step of evaluating the avocado FV based on the fluorescence intensity in the first wavelength range and the fluorescence intensity in the second wavelength range of the fluorescence FL measured in the measurement step S20. In this embodiment, the first wavelength range is set to 680 to 750 nm, and the second wavelength range is set to 480 to 550 nm. The fluorescence intensity in the first wavelength range and the second wavelength range may be set to wavelength ranges different from those described above depending on the experimental environment, the type of avocado FV being tested, etc.

[0038] The specific evaluation method will be explained below.

[0039] The present inventors performed a sensory test on ripeness of 600 avocados by an expert and measured the fluorescence intensity in the first wavelength region and the second wavelength region (according to the methods of the excitation step S10 and the measurement step S20). Also, based on the obtained fluorescence intensities, for each of the immature, ripe, and overripe groups, the fluorescence intensity ratio A1 of the fluorescence peak derived from chlorophyll (wavelength 740 nm) to the fluorescence peak derived from chlorophyll (wavelength 685 nm), and the fluorescence intensity ratio A2 of the fluorescence peak derived from carotenoid (wavelength 550 nm) to the fluorescence peak derived from chlorophyll (wavelength 685 nm) were calculated, and based on these, the chlorophyll content and carotenoid content were calculated. The summary of these results is shown in Fig. 4.

[0040] According to Fig. 4(A), the fluorescence intensity ratio A1 shows values of 1.12 in the immature group, 1.01 in the ripe group, and 1.11 in the overripe group, respectively. It can be seen that there is a tendency for the chlorophyll amount to be less at the ripe stage compared to the immature and overripe stages in terms of the maturity and chlorophyll amount.

[0041] Therefore, in the classification evaluation of the immature, ripe, and overripe groups of avocados, when only the fluorescence intensity ratio A1 derived from chlorophyll is used as an index, it is possible to evaluate only whether it is ripe immediately.

[0042] On the other hand, when evaluating immaturity or overripeness, it is推测 that it is necessary to measure an individual over time and it is difficult to evaluate immediately. <0_{000}0211> According to Fig. 4(B), the fluorescence intensity ratio A2 shows values of 0.02 in the immature group, 0.07 in the ripe group, and 0.11 in the overripe group, respectively. It can be seen that there is a positive correlation between the maturity and the carotenoid amount.

[0044] <000_{00}215>Therefore, for the immature, ripe, and overripe groups, by creating evaluation criteria that set the threshold value and reference range of A2 based on the above-mentioned respective values, it is possible to classify and evaluate the avocado to be evaluated into each group.

[0045] For example, based on the results shown in Fig. 4(B), evaluation criteria can be set such that when A2 < 0.05, it is immature, when 0.05 ≤ A2 ≤ 0.09, it is ripe, and when 0.09 < A2, it is overripe.

[0046] Regarding avocados classified as ripe, thresholds and reference ranges for ripeness at the time of shipment (shipment ripeness) considering post-shipment ripening and ripeness at the time of purchase (purchase ripeness) assuming consumption after purchase may be further included as evaluation criteria.

[0047] For example, based on the results shown in Fig. 4(B), evaluation criteria can be set as follows: when A2 < 0.05, it is unripe; when 0.05 ≤ A2 ≤ 0.07, it is at shipment ripeness; when 0.07 < A2 ≤ 0.09, it is at purchase ripeness; and when 0.09 < A2, it is overripe. By doing so, appropriate evaluations can be performed in both the shipment and purchase scenarios.

[0048] That is, the evaluation step S30 uses a determination criterion that associates the ratio of the fluorescence peak intensity in the first wavelength range to the fluorescence peak intensity in the second wavelength range for a group of avocados to be evaluated with sensory indicators such as unripe, ripe, and overripe, and evaluates the avocados to be evaluated by comparing the ratio of the fluorescence peak intensity in the first wavelength range to the fluorescence peak intensity in the second wavelength range measured for the avocados to be evaluated with that determination criterion.

[0049] As chlorophyll consumption progresses (as the avocado ripens), the relative ratio of the fluorescence peak intensity of carotenoids increases, so it becomes possible to estimate and evaluate the internal ripeness from the ratio of the fluorescence peak intensities of chlorophyll and carotenoids in the epidermis.

[0050] [Avocado Evaluation Device] Hereinafter, the avocado evaluation device according to an embodiment of the present invention will be described in detail with reference to Figs. 5 to 7.

[0051] Fig. 5 is a block diagram showing the functional configuration of the evaluation device X. As shown in Fig. 5, the evaluation device X includes an excitation light source 1, a light receiving unit 2, an evaluation unit 3, and a display unit 4.

[0052] The plurality of excitation light sources 1 are monochromatic LEDs each having a light source central wavelength of 410 nm or more and less than 480 nm, and are particularly preferably blue LEDs having a light source central wavelength of around 450 nm.

[0053] The light receiving unit 2 is a spectrometer having an optical filter 21, and is capable of measuring the fluorescence intensity in the fluorescence region of chlorophyll and the fluorescence intensity in a second wavelength region which is the fluorescence region of carotenoids.

[0054] The optical filter 21 is a long-pass filter that transmits light having a wavelength that is 10 nm or longer than the central wavelength of the excitation light source 1 . In the evaluation device X, a blue LED with a light source central wavelength of around 450 nm is preferably used as the excitation light source 1, and therefore a long-pass filter that transmits light with a wavelength of 460 nm or more is preferably used as the optical filter 21.

[0055] The evaluation unit 3 can calculate an evaluation result of the avocado FV based on the spectroscopic measurement results including the fluorescence intensity in the first wavelength range and the fluorescence intensity in the second wavelength range. The evaluation result can be a quantitative result such as a numerical value, or a qualitative result such as "unripe, ripe (suitable for shipping, suitable for purchase), overripe, etc.

[0056] Examples of the evaluation unit 3 include circuits including a CPU (Central Processing Unit), an MPU (Microprocessing Unit), a DSP (Digital Signal Processor), and an FPGA (Field Programmable Gate Array).

[0057] The evaluation unit 3 may further include a storage unit (not shown). Examples of the storage unit include a RAM (Random Access Memory), a ROM (Read Only Memory), an SSD (Solid State Drive), and an HDD (Hard Disk Drive). If the evaluation unit 3 has a storage unit, it can store a predetermined number of evaluation results, evaluation conditions, and the like.

[0058] The display unit 4 has a liquid crystal screen 41 and a color display unit 42.

[0059] The liquid crystal screen 41 can display the fluorescence peak intensity in the first wavelength range and the fluorescence peak intensity in the second wavelength range as the evaluation result of the avocado FV by the evaluation device X.

[0060] As the liquid crystal screen 41, an organic EL display called an OLED (Organic Light Emitting Diode) is preferably used, but any element capable of drawing and displaying characters and numbers can be used.

[0061] The color display unit 42 can display a predetermined color based on the evaluation result of the avocado FV by the evaluation device X. For example, the color display unit 42 can display colors such as green if the evaluation result of the avocado FV by the evaluation device X is "unripe," blue if "ripe," and red if "overripe."

[0062] Alternatively, the color display unit 42 can display colors such as green if the evaluation result of the avocado FV by the evaluation device X is "unripe," blue if "ripe for shipping," yellow if "ripe for purchase," and red if "overripe."

[0063] The color display unit 42 is preferably realized by a combination of multicolor LEDs or single-color LEDs, but any element other than an LED can be used as long as it can display a predetermined color based on the evaluation results of avocado FV by the evaluation device X. The color display unit 42 may also be included in the liquid crystal screen 41 .

[0064] The method for evaluating avocado FV using the evaluation device X will be described with reference to FIG. First, the excitation light source 1 irradiates the epidermis of the avocado FV with excitation light EL, exciting the autofluorescent substances (chlorophyll, carotenoids, etc.) contained in the epidermis of the avocado FV (excitation step S10). When excited electrons in the excited autofluorescent substance return to the ground state, fluorescence FL is emitted, and this fluorescence FL is received by the light receiving unit 2 through the optical filter 21 and subjected to spectroscopic measurement (measurement step S20). Based on the results of the spectroscopic measurement, particularly the fluorescence intensity in the first wavelength range and the fluorescence intensity in the second wavelength range, the evaluation unit 3 calculates the evaluation result of the avocado FV (evaluation step S30). When the evaluation of avocado FV is performed using the evaluation device X, the evaluation results can be displayed quantitatively (e.g., numerically) or qualitatively (e.g., immature, ripe (ripe for shipping, ripe for purchase), overripe), or both, on the liquid crystal screen 41 or color display unit 42 of the display unit 4.

[0065] 6A, 6B, and 6C are a perspective view, a plan view, and a bottom view, respectively, of the evaluation device X. As shown in FIG. 6, the evaluation device X includes an excitation light source 1, a light receiving unit 2, a display unit 4, a light blocking member 5, and an evaluation unit 3 as an internal component not shown in FIG.

[0066] As shown in FIG. 6(C), the plurality of excitation light sources 1 are provided so as to surround the light receiving section 2. The light-shielding member 5 is provided so as to cover the plurality of excitation light sources 1 and the light-receiving section 2.

[0067] The evaluation device X may further include an optional start-up switch S and an optional port P used for power supply, data transmission and reception, and the like.

[0068] 7 is a diagram for explaining the inside of the evaluation device X, the arrangement of the excitation light source 1, the technical significance of the light blocking member 5, etc. In FIG. 7, the optical axis is indicated by a straight arrow.

[0069] As shown in FIG. 7, the plurality of excitation light sources 1 are provided so that the light projection axis of each of them is inclined toward the light receiving section 2 side. By providing the plurality of excitation light sources 1 surrounding the light receiving section 2 so that the light projection axis of each is inclined toward the light receiving section 2, a sufficient amount of light can be ensured when irradiating excitation light at short distances. In this embodiment, the angle θ of the excitation light source 1 is set to 10° to 20°.

[0070] The light-shielding member 5 covers the plurality of excitation light sources 1 and the light-receiving section 2 so as to open the light-emitting direction seen from the plurality of excitation light sources 1 and the light-receiving direction seen from the light-receiving section 2 . In other words, the light-shielding member 5, located between the excitation light source 1 and the avocado FV to be evaluated, concentrates the excitation light EL on the epidermis of the avocado FV, while suppressing the influence of natural light, thereby assisting in accurate evaluation. In this embodiment, the length L of the light blocking member 5 is set to between 25 and 35 mm, preferably 30 mm.

[0071] <Optimization of excitation light source angle θ and light-shielding member length L> 12 is a diagram illustrating the difference between a conventional optical device and the evaluation device X of the present invention. The upper and lower figures are diagrams conceptually illustrating the design of the light source and the light-shielding member, and the corresponding positional distribution of the fluorescence intensity. As shown in Figure 12(a), conventional optical devices are designed to uniform the fluorescence intensity within a wide integration region by arranging multiple light sources 1'. Furthermore, the light-shielding member 5' is simply intended to block external light, and its length has not been optimized. On the other hand, as shown in FIG. 12(b), the evaluation device X of the present invention has a narrow integral region, but the length of the light-shielding member 5 and the angle of the excitation light source 1 are optimized to concentrate the light from multiple light sources directly below the spectrometer so that the fluorescence intensity directly below the spectrometer is maximized. In other words, the angle θ of the excitation light source 1 and the length L of the light-shielding member 5 are optimized to obtain fluorescent intensity with high efficiency even from fruits such as avocados, which are difficult for light from the light source to penetrate.

[0072] For example, in the evaluation device X of the present invention, the excitation light source angle θ and the light blocking member length L are adjusted and optimized as follows. First, an evaluation tool is prepared, in which an optical sensor such as a camera is installed under a white acrylic plate, as shown in FIG. 13(a). Next, when the end of the light-shielding member 5 of the evaluation device X is aligned with the acrylic plate portion of the tool and the excitation light source 1 is turned on, a brightness pattern corresponding to the angle θ of the excitation light source 1 and the length L of the light-shielding member 5 is obtained, as shown in Figure 13(b1) and Figure 13(b2). In this brightness pattern, the excitation light source angle θ and the light blocking member length L can be adjusted so that the focus of the multiple excitation light sources 1 is uniform and more centralized, thereby optimizing these.

[0073] [Example] 360 avocados including avocados P, Q, and R shown in Figure 8 were evaluated using the following methods (Examples and Comparative Examples). After the evaluation in this example, a sensory test was conducted, and the results were as follows: P: unripe, Q: ripe, R: overripe.

[0074] <Example> Four blue LED light sources (wavelength 450 nm) each having an output of about 200 mW were used as the excitation light source 1, and excitation light EL was irradiated onto the epidermis of the avocado (FV) (excitation step S10). Next, the fluorescence FL emitted from the avocado skin was passed through a long-pass filter that transmits light with wavelengths of 460 nm or more, and then the fluorescence profile was measured using the light receiving unit 2 (spectroscope) (measurement step S20). FIG. 9 is a diagram showing how the excitation step S10 and the measurement step S20 are performed using the evaluation device X. Next, the avocados were evaluated based on the peak intensities in the first wavelength range: 680 to 750 nm and the second wavelength range: 480 to 550 nm in the obtained fluorescence profiles (evaluation step S30). Specifically, based on the fluorescence intensity obtained in the measurement step S20, the fluorescence intensity ratio A1 of the fluorescence peak derived from chlorophyll (wavelength 740 nm) to the fluorescence peak derived from chlorophyll (wavelength 685 nm), and the fluorescence intensity ratio A2 of the fluorescence peak derived from carotenoid (wavelength 550 nm) to the fluorescence peak derived from chlorophyll (wavelength 685 nm) were calculated, and the avocados were classified and evaluated based on these values (Fig. 10). As shown in Fig. 10, when the evaluation criteria were set such that if A2 < 0.05, it was unripe; if 0.05 ≤ A2 ≤ 0.09, it was properly ripe; if A2 > 0.09, it was overripe, as shown in Fig. 10, each avocado was evaluated as P: unripe, Q: properly ripe, R: overripe, which was consistent with the subsequent sensory test results. For example, when using the evaluation device X, the user can perform the evaluation method of the present invention including the excitation step S10, the measurement step S20, and the evaluation step S30 performed by the evaluation unit 3, just by turning on the activation switch S with the excitation light source 1 and the light receiving unit 2 facing the skin of the avocado FV. In addition, when the activation switch S of the evaluation device X is turned on, the evaluation device X can automatically perform a series of processes up to displaying the evaluation result on the display unit 4 after the excitation step S10, the measurement step S20, and the evaluation step S30.

[0075] Thus, according to the method of the present invention, for the ripeness of an avocado (avocado FV) that is difficult to judge from its appearance, chlorophyll content, etc., a more accurate evaluation can be performed using an index including fluorescence derived from carotenoid.

[0076] <Comparative Example> In the comparative example, after the same excitation step S10 and measurement step S20 as in the example, avocados P, Q, and R were each evaluated based on the peak intensity in the first wavelength range: 680 - 750 nm in the obtained fluorescence profile (evaluation step S30). Specifically, based on the fluorescence intensity obtained in the measurement step S20, the avocados were classified and evaluated based on the fluorescence intensity ratio A1 of the fluorescence peak derived from chlorophyll (wavelength 740 nm) to the fluorescence peak derived from chlorophyll (wavelength 685 nm) (Fig. 11). As shown in Fig. 11, when using A1 as an evaluation index, if A1 ≤ 1.10, it is considered mature, and if 1.10 < A1, it is considered immature or overripe. By setting evaluation criteria like this, each avocado can be roughly evaluated as P: immature or overripe, Q: mature, R: immature or overripe. However, if it is impossible to distinguish between immaturity and overripeness of the evaluation targets like avocados P and R, the evaluator cannot determine whether the evaluation target is immature and should be ripened further, or overripe and should be disposed of before spoilage.

[0077] Therefore, compared with the conventional method using fluorescence derived from chlorophyll as an index, according to the method of the present invention using an index including fluorescence derived from carotenoid, a more accurate evaluation can be performed on the ripeness of avocados (avocado FV) that are difficult to judge from appearance, chlorophyll content, etc. In addition, the evaluation method of the present invention that uses both fluorescence derived from carotenoid and fluorescence derived from chlorophyll as evaluation indices determines immaturity, maturity, and overripeness based on the fluorescence derived from carotenoid, and can determine maturity, immaturity, or overripeness based on the fluorescence derived from chlorophyll. Therefore, the reliability of the maturity determination is higher than when only the fluorescence derived from carotenoid is used as an index.

[0078] Note that each configuration and function shown in the above embodiments, examples, etc. are merely examples, and can be variously modified based on design requirements, actual circumstances, etc.

[0079] <Relationship between the ratio of fatty acids contained in avocado and fluorescence intensity> The inventors of the present invention performed three-dimensional fluorescence spectrum analysis on the shoulder portions (within the solid line frames) and body portions (within the broken line frames) of avocados A to E (immature to overripe) shown in Fig. 14 under the following measurement conditions. (Measurement conditions) Measurement device: Fluorolog 3 - 22 (HORIBA Jobin Yvon) Light source: Xenon lamp Detector: Photomultiplier tube (PMT) Excitation wavelength: 250 to 750 nm (in 10 nm increments) Observation wavelength: up to 850 nm (2 nm intervals) Slit width: 2 nm on both the excitation and observation sides Time constant: 0.02 s

[0080] FIG. 15 shows three-dimensional fluorescence spectra for each of avocados A to E, with the excitation wavelength on the vertical axis and the fluorescence wavelength on the horizontal axis, and the corresponding fluorescence intensity shown in a heat map format.

[0081] Table 1 shows the numerical values ​​of the emission intensities of luminescent components L1 to L6 classified by excitation wavelength and fluorescence wavelength in the three-dimensional fluorescence spectrum analysis of avocados A to E.

[0082] [Table 1]

[0083] Here, it is believed that luminescent component L1 is derived from aromatic amino acids and proteins, luminescent component L2 from vitamins and carotene, and luminescent components L4 to L7 from chlorophyll. Furthermore, from Figure 15 and Table 1, in ripe avocado E, luminescence components L4 to L7, which are thought to be derived from chlorophyll, tend to be slightly higher than the others, and luminescence components L4 and L5 in particular show relatively high intensities.

[0084] Therefore, the changes in luminescence components L4 to L7 suggested that some changes in luminescence characteristics were occurring, rather than simply an increase in chlorophyll content.

[0085] Furthermore, the inventors performed GC / FID analysis on avocados A and E (unripe and overripe) shown in FIG. 14 under the following conditions to quantify the fatty acids contained therein (palmitic acid, oleic acid, linoleic acid). (Measurement conditions) Palmitic acid standard: Fujifilm Wako Pure Chemical Industries, special grade reagent (purity 98.2%) Oleic acid standard: Fujifilm Wako Pure Chemical Industries, Biochemical grade (purity 99.1%) Linoleic acid standard: Fujifilm Wako Pure Chemical Industries, Wako Grade 1 (purity 89.4%) Measurement equipment: GC6890 (Agilent technologies) Analytical column: TG-5SILMS (Thermo Fisher Scientific) Inlet temperature: 300℃ Temperature program (standard solution): 170 °C → 230 °C Temperature program (sample solution): 170 °C → 320 °C Split ratio: 20 Injection gas flow rate: 2 mL / min (helium, constant flow mode) Injection volume: 1 μL Detector temperature: 300 °C

[0086] Table 2 shows the analytical conditions and the concentrations of each fatty acid in the samples for the GC / FID analysis of palmitic acid, oleic acid, and linoleic acid in avocados A and E.

[0087] [Table 2]

[0088] Table 3 also shows the approximate quantitative values ​​of palmitic acid, oleic acid, and linoleic acid in avocados A and E based on GC / FID analysis, expressed as mass percent concentrations.

[0089] [Table 3]

[0090] Based on the values ​​in Table 3, the approximate composition ratio of the three fatty acid components in avocados A and E is as follows. A: Palmitic acid 14%, Oleic acid 76%, Linoleic acid 12% E: Palmitic acid 24%, Oleic acid 62%, Linoleic acid 14%

[0091] In other words, the results of the ripeness and GC / FID analysis of avocados A and E suggested that the proportion of oleic acid tends to decrease and the proportion of palmitic acid tends to increase as the avocado ripens. As avocados ripen, oleic acid is thought to decrease through hydrolysis, liberation, oxidation, and decomposition, becoming part of the volatile components. In addition, the accompanying increase in the proportion of palmitic acid is thought to bring the avocado closer to a high-oil ripe state.

[0092] Here, the changes in the luminescence properties of avocado predicted from the changes in luminescence components L4 to L7 (especially luminescence components L4 and L5) in the three-dimensional fluorescence spectrum are expected to be related to changes in components accompanied by a decrease in oleic acid and / or an increase in palmitic acid, based on the above considerations.

[0093] The decrease in the proportion of oleic acid and the increase in the proportion of palmitic acid are difficult to detect from a change in a single wavelength, but by analyzing the correlation between changes in the fluorescence spectrum and changes in the proportion of fatty acids, it is possible to grasp the ripeness of avocados more accurately.

[0094] Furthermore, the excitation wavelength and fluorescence wavelength of the luminescent components L4 and L5, which clearly show changes due to the fatty acid ratio, overlap with the excitation fluorescence region of chlorophyll in the present invention (first wavelength region: excitation wavelength 410 to 480 nm, fluorescence wavelength 680 to 750 nm), so it is estimated that changes in fluorescence intensity in the first wavelength region reflect to a large extent changes in the fatty acid ratio of avocado.

[0095] In addition to the fact that direct prediction of ripeness based on fluorescence from chlorophyll and carotenoids is possible (Figure 4, etc.), it was estimated as described above that changes in the fluorescence intensity in the first wavelength range reflect, to a certain extent, changes in the fatty acid ratio of the avocado. Therefore, the present invention, which evaluates avocados based on fluorescence in a first wavelength range (derived from chlorophyll) and fluorescence in a second wavelength range (derived from carotenoids), also takes into account the fatty acid ratio, an element unique to avocados, and can provide a more accurate avocado evaluation method than evaluation methods based on changes in a single wavelength. [Explanation of symbols]

[0096] X evaluation device 1. Excitation light source 2 Light receiving section 21 Optical Filter 3 Evaluation section 4 Display section 41 LCD screen 42 Color display section 5 Light blocking material FV Avocado EL excitation light FL fluorescence

Claims

1. an excitation step of irradiating excitation light onto the avocado skin to excite an autofluorescent substance contained in the avocado skin; a measuring step of measuring fluorescence emitted from the excited autofluorescent substance; an evaluation step of evaluating the avocado based on the fluorescence intensity in a first wavelength range and the fluorescence intensity in a second wavelength range of the fluorescence, The method for evaluating avocados, wherein the first wavelength range includes a fluorescence range of chlorophyll and the second wavelength range includes a fluorescence range of carotenoids.

2. The avocado evaluation method according to claim 1 , wherein the excitation light has a central wavelength of 410 nm or more and less than 480 nm.

3. The avocado evaluation method according to claim 2 , wherein the measuring step is a step of measuring fluorescence having a wavelength that is 10 nm or more longer than the central wavelength of the excitation light.

4. 4. The avocado evaluation method according to claim 1, wherein in the evaluation step, the avocado is evaluated based on a fluorescence intensity ratio between a fluorescence peak in the first wavelength range and a fluorescence peak in the second wavelength range.

5. a plurality of excitation light sources, a light receiving unit, an evaluation unit, and a display unit; the light receiving unit is configured to be able to measure a fluorescence intensity in a first wavelength range including a fluorescence range of chlorophyll and a fluorescence intensity in a second wavelength range including a fluorescence range of carotenoid, the evaluation unit is configured to be able to calculate an evaluation result of the avocado based on the fluorescence intensity in the first wavelength range and the fluorescence intensity in the second wavelength range; The display unit is configured to be able to display the evaluation result.

6. 6. The evaluation device according to claim 5, wherein the plurality of excitation light sources are arranged so as to surround the light receiving section and so that the light projection axis of each excitation light source is inclined toward the light receiving section.

7. 7. The evaluation device according to claim 6, further comprising a light-shielding member arranged to cover the plurality of excitation light sources and the light-receiving unit, the light-shielding member being arranged to open a light-projecting direction seen from the plurality of excitation light sources and a light-receiving direction seen from the light-receiving unit.

8. The evaluation device according to claim 5 , wherein the excitation light source has a light source center wavelength of 410 nm or more and less than 480 nm.

9. 9. The evaluation device according to claim 8, wherein the light receiving section has an optical filter, and the optical filter includes a long-pass filter that transmits light having a wavelength that is 10 nm or longer than the central wavelength of the excitation light source.

10. The evaluation device according to claim 5 , wherein the display unit is capable of displaying peak intensities in the first wavelength range and the second wavelength range as the evaluation result.

11. 11. The evaluation device according to claim 5, wherein the display unit is capable of displaying a predetermined color based on the evaluation result as the evaluation result.

12. The avocado evaluation method according to claim 2 , wherein the first wavelength range is equal to or greater than 680 nm and less than 750 nm.

13. the tilt angle of the projection axis of the excitation light source is equal to or greater than 10° and less than 20°; The evaluation device according to claim 7 , wherein the length of the light blocking member is equal to or greater than 25 mm and less than 35 mm.

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