Avocado evaluation method and evaluation device

Abstract

To provide a method for more accurate non-destructive evaluation of avocados. [Solution] The method includes an excitation step S10 in which excitation light EL is irradiated onto an avocado FV to excite autofluorescent substances contained in the avocado FV, a measurement step S20 in which fluorescence FL emitted from the excited autofluorescent substance is measured, and an evaluation step S30 in which the avocado is evaluated based on the fluorescence intensity in a first wavelength range and the fluorescence intensity in a second wavelength range of the fluorescence FL, wherein the first wavelength range includes the fluorescence region of chlorophyll and the second wavelength range includes the fluorescence region of carotenoids.

Description

[Technical field]

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

[0002] It is desirable to evaluate the freshness (ripeness) and taste of fruits and vegetables in advance before setting appropriate prices and distributing them. However, once the fruits and vegetables are invaded or destroyed for tasting or sampling inspection, their commercial value drops significantly, and this method does not allow for 100% 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 as seen by the human eye, the sensation when touched or held, the sound made when lightly tapped, the smell given off, etc.

[0004] While the above-mentioned methods are extremely useful for a consumer to make purchasing decisions regarding fruits and vegetables, they are heavily dependent on personal skill and are therefore insufficient for making more precise evaluations of the freshness, taste, etc. of fruits and vegetables.

[0005] In view of these circumstances, methods and devices for evaluating and inspecting the freshness, taste, etc. of fruits and vegetables non-invasively and quantitatively, 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 indices 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 capable of detecting 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] JP 2023-109722 A [Patent Document 2] JP 2023-180924 A Summary of the Invention [Problem to be solved by the invention]

[0009] As mentioned above, there are techniques for non-destructively evaluating fruits and vegetables by examining their concentration and content based on the fluorescence emitted by exciting the chlorophyll contained in them. However, there are some fruits and vegetables that are difficult to accurately evaluate when chlorophyll is the only indicator.

[0010] For example, avocados are one type of fruit or vegetable that is difficult to accurately evaluate non-destructively. Unlike common fruits such as grapes and mangoes, which have a thin, soft skin, avocados are covered with a thick, hard skin. In other words, for fruits with soft skin, it is possible to obtain a lot of internal information by letting the light from the light source enter the interior, but for fruits with thick, hard skin such as avocados, the light from the light source cannot enter the interior and internal information cannot 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 for solving the above problems is based on the technical ideas set forth in the following [1] to

[13] . [1] A method for evaluating an avocado, comprising: an excitation step of irradiating an avocado epidermis with excitation light to excite an autofluorescent substance contained in the avocado epidermis; a measurement step of measuring fluorescence emitted from the excited autofluorescent substance; 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 a fluorescence region of chlorophyll and the second wavelength range includes a 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 described in [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 method for evaluating an avocado described in any of [1] to [3], 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] 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 fluorescence intensity in a first wavelength range including a chlorophyll fluorescence range and fluorescence intensity in a second wavelength range including a carotenoid fluorescence range, the evaluation unit is configured to be capable of calculating an evaluation result of an 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 multiple 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 up the light projection 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 central 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 central 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 described in [7], wherein the inclination angle of the projection axis of the excitation light source is 10° or more and less than 20°, and the length of the light-shielding member is 25 mm or more and less than 35 mm.

[0013] Using a method such as [1], it is possible to perform a more accurate non-destructive evaluation of avocados by using the fluorescence derived from chlorophyll and carotenoids contained in the avocado skin as a composite evaluation index. In particular, it is difficult to penetrate light from a light source into fruits with thick, hard skin such as avocados. However, a method such as [1] makes it possible to 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 exposed to long-term ultraviolet light, and can distinguish between the fluorescence originating from chlorophyll and carotenoids and the excitation light, while providing chlorophyll and carotenoids with sufficient energy for excitation.

[0015] Methods such as [3] allow for the simultaneous detection of chlorophyll-derived fluorescence and carotenoid-derived fluorescence with relative ease.

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

[0017] An 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, thereby enabling 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 applied 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] Devices such as [9] can relatively easily detect chlorophyll-derived fluorescence and carotenoid-derived fluorescence 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 well suited for the non-destructive evaluation of large quantities of avocados because they can provide rapid visual 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 due to the change in fatty acid ratio that occurs with ripeness.

[0025] In devices such as

[13] , the light from the light source is concentrated directly under the spectrometer, making it possible to obtain fluorescence intensity with high efficiency even from the skin of fruits such as avocados, where the light from the light source has difficulty penetrating. Effect of the Invention

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

[0027] [Figure 1] 1 is a flowchart illustrating an evaluation method according to an embodiment of the present invention. [Diagram 2] 1 is a diagram illustrating an excitation light source wavelength and a long-pass filter according to the present invention. FIG. [Diagram 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. 1 is a diagram illustrating the correlation between the fluorescence intensity ratio and the ripeness of avocado. [Diagram 5] FIG. 2 is a diagram illustrating a functional configuration of an evaluation device according to an embodiment of the present invention. [Figure 6] FIG. 1 is a diagram illustrating an evaluation device according to an embodiment of the present invention. [Figure 7] FIG. 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 evaluated. [Figure 11] FIG. 1 is a scatter plot based on the fluorescence intensity ratio in the avocados evaluated. [Figure 12] 1 is a conceptual diagram for comparing a conventional evaluation device with the evaluation device of the present invention. [Figure 13]11A and 11B are diagrams illustrating adjustment of the angle of an excitation light source and the length of a light blocking member. [Figure 14] This is a photograph of the appearance of the avocado that was the subject of fluorescence spectrum analysis and GC / FID. [Figure 15] 15 shows three-dimensional fluorescence spectra of each avocado shown in FIG. 14. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, the avocado evaluation method and evaluation device according to the 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. Also, 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 (such as chlorophyll and carotenoids) contained in the epidermis of the avocado FV.

[0031] In the excitation step S10, in order to simultaneously excite the chlorophyll and carotenoid contained in the epidermis of the avocado FV with excitation light EL having a similar 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 this 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 order to discriminate 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 FIG. 2 and FIG.

[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 near a wavelength of 500 nm (510 nm, 550 nm), but does not detect peaks derived from chlorophyll near 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 shows that the chlorophyll-derived peaks at a wavelength of around 700 nm (688 nm, 740 nm) can be detected, but the carotenoid-derived peaks at a wavelength of around 500 nm (510 nm, 550 nm) are indistinguishable from the excitation light peaks.

[0035] FIG. 3 is a graph comparing the epidermal fluorescence profile (500 to 800 nm) of an avocado 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 using a long-pass filter, the chlorophyll-derived peak at a wavelength of approximately 700 nm was detectable, but the carotenoid-derived peak at a wavelength of approximately 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, and the overall sensitivity is reduced. In addition, 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 near a wavelength of 520 nm, and a fluorescence peak due to carotenoids is observed near 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 an equivalent 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 discriminate 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 targeted, etc.

[0038] The specific evaluation method will be described 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 (based on the methods of the excitation step S10 and the measurement step S20). Also, based on the obtained fluorescence intensity, for each of the immature, mature, 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 mature group, and 1.11 in the overripe group, respectively. It can be seen that there is a tendency for the chlorophyll content to be less at maturity compared to when immature and overripe, in terms of the relationship between the degree of ripeness and the chlorophyll amount.

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

[0043] According to Fig. 4(B), the fluorescence intensity ratio A2 shows values of 0.02 in the immature group, 0.07 in the mature group, and 0.11 in the overripe group, respectively. It can be seen that there is a positive correlation between the degree of ripeness and the carotenoid amount.

[0044] Therefore, for the immature, mature, and overripe groups, by creating an evaluation criterion that sets 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), the evaluation criterion can be set as follows: when A2 < 0.05, it is immature; when 0.05 ≤ A2 ≤ 0.09, it is mature; when 0.09 < A2, it is overripe.

[0046] Regarding avocados classified as ripe, threshold values 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: unripe when A2 < 0.05, shipment ripeness when 0.05 ≤ A2 ≤ 0.07, purchase ripeness when 0.07 < A2 ≤ 0.09, and overripe when 0.09 < A2. By doing so, appropriate evaluations can be made 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 avocado 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 avocado to be evaluated with that determination criterion.

[0049] As the consumption of chlorophyll 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, with reference to Figs. 5 to 7, an avocado evaluation device according to an embodiment of the present invention will be described in detail.

[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 multiple excitation light sources 1 are monochromatic LEDs each having a light source central wavelength of 410 nm or more and less than 480 nm. In particular, a blue LED having a light source central wavelength of about 450 nm is preferably used.

[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 about 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 result including the fluorescence intensity in the first wavelength region and the fluorescence intensity in the second wavelength region. The evaluation result can be a quantitative result such as a numerical value, or a qualitative result such as "unripe, ripe (suitable for shipping, ripe for purchase), overripe, etc.

[0056] Examples of the evaluation unit 3 include circuits including a central processing unit (CPU), a microprocessing unit (MPU), a digital signal processor (DSP), and a field programmable gate array (FPGA).

[0057] The evaluation unit 3 may further include a storage unit (not shown). Examples of the storage unit include a random access memory (RAM), a read only memory (ROM), a solid state drive (SSD), and a hard disk drive (HDD). When 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 includes a liquid crystal screen 41 and a color display unit .

[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 numerical values ​​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 it is "ripe," and red if it is "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 it is “ripe for shipping,” yellow if it is “ripe for purchase,” and red if it is “overripe.”

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

[0064] A method for evaluating avocado FV using the evaluation device X will be described with reference to FIG. First, the epidermis of the avocado FV is irradiated with excitation light EL from the excitation light source 1, exciting autofluorescent substances (such as chlorophyll and carotenoids) contained in the epidermis of the avocado FV (excitation step S10). In the excited autofluorescent substance, fluorescence FL is emitted when excited state electrons return to the ground state, and this fluorescence FL is received by the light receiving section 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 region and the fluorescence intensity in the second wavelength region, the evaluation unit 3 calculates an evaluation result of the avocado FV (evaluation step S30). When the avocado FV is evaluated using the evaluation device X, the evaluation result can be displayed on the liquid crystal screen 41 or the color display unit 42 of the display unit 4, or both, in a quantitative (e.g., numerical) or qualitative (e.g., unripe, ripe (ripe for shipping, ripe for purchase), overripe) form.

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

[0066] As shown in FIG. 6(C), the multiple excitation light sources 1 are provided so as to surround the light receiving section 2. Further, the light blocking member 5 is provided so as to cover the multiple 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 and the technical significance of the arrangement of the excitation light source 1 and 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 multiple 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 of them is inclined toward the light receiving section 2, a sufficient amount of light can be ensured when irradiating excitation light at a short distance. 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 multiple excitation light sources 1 and the light receiving section 2 so as to open the light projection direction as seen from the multiple excitation light sources 1 and the light receiving direction as seen from the light receiving section 2 . In other words, the light blocking member 5, located between the excitation light source 1 and the avocado FV to be evaluated, can concentrate the excitation light EL on the epidermis of the avocado FV and suppress 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 a value between 25 and 35 mm, and preferably to 30 mm.

[0071] <Optimization of excitation light source angle θ and light shielding member length L> 12 is a diagram for explaining the difference between a conventional optical device and the evaluation device X of the present invention. The upper and lower diagrams are diagrams conceptually showing the design of the light source and the light blocking member, and the corresponding position distribution of the fluorescence intensity. As shown in Fig. 12(a), conventional optical devices are designed to have a wide integration region by arranging multiple light sources 1', and to homogenize the fluorescence intensity within the integration region. Also, the light shielding member 5' is intended simply 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, where the light from the light source has difficulty entering.

[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 luminance 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 FIG. 13(b1) and FIG. 13(b2). In this luminance 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 them.

[0073] [Example] 360 avocados including avocados P, Q, and R shown in Fig. 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> As the excitation light source 1, four blue LED light sources (wavelength 450 nm) each having an output of about 200 mW were used, 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 a wavelength 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 the values (Fig. 10). As shown in Fig. 10, when the evaluation criteria were set such that the avocado was evaluated as unripe when A2 < 0.05, ripe when 0.05 ≤ A2 ≤ 0.09, and overripe when 0.09 < A2, as shown in Fig. 10, each avocado was evaluated as P: unripe, Q: ripe, and 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 by simply 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 excitation step S10 and the measurement step S20 similar to those in the example, avocados P, Q, and R were respectively 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 ripe; if 1.10 < A1, it is considered unripe or overripe. By setting such evaluation criteria, each avocado can be tentatively evaluated as P: unripe or overripe, Q: ripe, and R: unripe or overripe. However, if it is impossible to distinguish between unripe and overripe for the evaluation targets such as avocados P and R, the evaluator cannot determine whether the evaluation target is unripe and should be allowed to ripen 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 using both fluorescence derived from carotenoid and fluorescence derived from chlorophyll as evaluation indices determines unripe, ripe, and overripe based on the fluorescence derived from carotenoid, and can determine ripe, unripe, or overripe based on the fluorescence derived from chlorophyll. Therefore, the reliability of the ripe 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 various modifications are possible based on design requirements, actual circumstances, etc.

[0079] <Relationship between the ratio of fatty acids contained in avocado and fluorescence intensity> The present inventors 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 (unripe to overripe) shown in Fig. 14 under the following measurement conditions. (Measurement conditions) Measuring device: Fluorolog 3-22 (HORIBA Jobin Yvon) Light source: Xenon lamp Detector: Photomultiplier tube (PMT) Excitation wavelength: 250-750 nm (10 nm intervals) Observation wavelength: ~850 nm (2 nm intervals) Slit width: 2 nm on both the excitation and observation sides Time constant: 0.02 s

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

[0081] Table 1 shows the numerical 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 the luminescent component L1 is derived from aromatic amino acids and proteins, the luminescent component L2 from vitamins and carotene, and the luminescent components L4 to L7 from chlorophyll. Furthermore, from FIG. 15 and Table 1, in ripe avocado E, luminescence components L4 to L7, which are believed 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 some changes in luminescence characteristics other than a simple increase in chlorophyll content.

[0085] Furthermore, the present inventors performed GC / FID analysis under the conditions described below for avocados A and E (unripe and overripe) shown in FIG. 14, and quantified the amounts of fatty acids contained therein (palmitic acid, oleic acid, linoleic acid). (Measurement conditions) Palmitic acid standard: Fujifilm Wako Pure Chemicals, 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℃ Heating program (standard solution): 170 ℃ → 230 ℃ Heating program (sample solution): 170 ℃ → 320 ℃ Split ratio: 20 Injection gas flow rate: 2 mL / min (helium, constant flow mode) Injection volume: 1 μL Detector temperature: 300℃

[0086] Table 2 shows the analytical conditions and the sample concentrations of each fatty acid 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 ripeness of avocados A and E and the results of GC / FID analysis suggested that as the avocado ripened, the proportion of oleic acid tended to decrease and the proportion of palmitic acid tended to increase. 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 change in the luminescence characteristics of avocado predicted from the changes in luminescence components L4 to L7 (especially luminescence components L4 and L5) in the three-dimensional fluorescence spectrum is expected, based on the above considerations, to be related to changes in components accompanied by a decrease in oleic acid and / or an increase in palmitic acid.

[0093] The decrease in the oleic acid ratio and the increase in the palmitic acid ratio are difficult to detect as a change in a single wavelength, but by analyzing the correlation between the change in the fluorescence spectrum and the change in the fatty acid ratio, the ripeness of the avocado can be grasped more accurately.

[0094] Furthermore, the excitation wavelengths and fluorescence wavelengths 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). Therefore, it is estimated that changes in fluorescence intensity in the first wavelength region reflect, to a certain 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 an avocado-specific factor, namely the fatty acid ratio, 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 Filters 3. Evaluation section 4 Display section 41 LCD screen 42 Color display section 5. Light-shielding material FV Avocado EL excitation light FL Fluorescence

Claims

1. an excitation step of irradiating an avocado skin with excitation light to excite an autofluorescent substance contained in the avocado skin; a measuring step of measuring fluorescence emitted from the excited autofluorescent substance; and evaluating the avocado based on the fluorescence intensity in a first wavelength range and the fluorescence intensity in a second wavelength range, the first wavelength range includes a chlorophyll fluorescence range and the second wavelength range includes a carotenoid fluorescence range; In the evaluation step, the avocado is evaluated by calculating a first fluorescence intensity ratio calculated based on two or more fluorescence peaks derived from chlorophyll in the first wavelength range, and a second fluorescence intensity ratio calculated based on the fluorescence peaks derived from chlorophyll in the first wavelength range and the fluorescence peak derived from carotenoid in the second wavelength range.

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. The apparatus includes 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 capable of measuring 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 calculate a first fluorescence intensity ratio calculated based on two or more fluorescence peaks derived from chlorophyll in the first wavelength range, and a second fluorescence intensity ratio calculated based on the fluorescence peak derived from chlorophyll in the first wavelength range and the fluorescence peak derived from carotenoid in the second wavelength range, to calculate an evaluation result of the avocado; The display unit is configured to be able to display the evaluation result.

5. The evaluation device according to claim 4 , wherein the plurality of excitation light sources are arranged so as to surround the light receiving section and so that a projection axis of each of the excitation light sources is inclined toward the light receiving section.

6. 6. The evaluation device according to claim 5, 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 projection direction seen from the plurality of excitation light sources and a light-receiving direction seen from the light-receiving unit.

7. The evaluation device according to claim 4 , wherein the excitation light source has a light source central wavelength of 410 nm or more and less than 480 nm.

8. 8. The evaluation device according to claim 7, wherein the light receiving section has an optical filter, the optical filter including a long-pass filter that transmits light having a wavelength that is 10 nm or longer than a central wavelength of the excitation light source.

9. The evaluation device according to claim 4 , wherein the display unit is capable of displaying peak intensities in the first wavelength range and the second wavelength range as the evaluation result.

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

11. The inclination 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 6 , 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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