Apparatus and method for assessing the condition of packaged foods

Abstract

To evaluate the state of food in a container-packed state.SOLUTION: An evaluation device 1 for the state of container-packed food comprises: one set of electrode plates 13 configured to have container-packed food as an object to be measured arranged therebetween and facing each other; an LCR meter 30 configured to measure impedance between the electrode plates at a predetermined measurement frequency of 8,300 to 1.2 MHz; and an analysis device 40 which acquires information on relation between real-number elements of impedance measured at the measurement frequency and the state of the food, and evaluates the state of the food as the object to be measured based upon the relation between the real number element of impedance obtained based upon the output of the LCR meter 30 and the relation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for assessing the condition of packaged food products. [Background technology]

[0002] Generally, packaged foods are known. For example, such packaged foods are produced in an integrated manufacturing facility where human intervention is not possible from cooking to sealing. Therefore, the condition of the food, such as the hardness or softness of the food, cannot be confirmed during production. Therefore, for example, random inspection is performed after the product is completed.

[0003] For example, in the case of cooked rice, the difference in hardness or softness due to the degree of cooking has a relatively large effect on the taste. For example, Patent Document 1 discloses that the condition of cooked rice can be evaluated by irradiating the cooked rice with light and measuring the amount of reflected light and transmitted light at specific wavelengths. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-270312 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, if the technology described in Patent Document 1 is applied to the evaluation of packaged foods, the containers must be opened before measurements can be performed. In contrast, it would be convenient to be able to evaluate the state of food while it is still packaged.

[0006] The present invention aims to evaluate the condition of food while it is packed in a container. [Means for solving the problem]

[0007] According to one aspect of the present invention, an apparatus for evaluating the condition of a containerized food comprises a pair of opposing electrode plates configured to place the containerized food being measured between them, an LCR meter configured to measure the impedance between the electrode plates at a predetermined measurement frequency of 8,300 Hz or more and 1.2 MHz or less, and an analysis device that acquires information on the relationship between the real component of the impedance measured at the measurement frequency and the state of the food, and evaluates the state of the food being measured based on the relationship and the real component of the impedance obtained based on the output of the LCR meter. Effect of the Invention

[0008] According to the present invention, the condition of food can be evaluated while it is packed in a container. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an outline of a configuration example of an evaluation device according to an embodiment. [Diagram 2] FIG. 2 is a flowchart for explaining an example of a method for measuring and evaluating a packaged food. [Diagram 3] FIG. 3 is a schematic diagram showing an example of the configuration of a tray-shaped retort container. [Figure 4] FIG. 4 is a schematic diagram showing an outline of an instrument used for measuring the hardness of cooked rice samples. [Diagram 5] FIG. 5 shows the relationship between the real component Rs value and the measurement frequency obtained by impedance measurement for cooked rice samples each having a different target water absorption capacity upon heating. [Figure 6] FIG. 6 shows the relationship between the real component Rs of the impedance and the actual thermal water absorption capacity when the measurement frequency is 1,023 Hz (low frequency region). [Figure 7] FIG. 7 shows the relationship between the real component Rs of the impedance and the actual thermal water absorption capacity when the measurement frequency is 10,120 Hz (medium frequency region). [Figure 8]FIG. 8 shows the relationship between the real component Rs of the impedance and the actual thermal water absorption capacity when the measurement frequency is 29,670 Hz (high frequency region). [Figure 9] FIG. 9 shows the relationship between the hardness of cooked rice measured by a compression test and the actual water absorption capacity upon heating. [Figure 10] FIG. 10 shows the relationship between the hardness of cooked rice and the real component Rs of the impedance when the measurement frequency was 29,670 Hz. [Figure 11] FIG. 11 shows the relationship between the coefficient of determination (R2) of the relationship between the hardness of cooked rice and the real component Rs of the measured impedance and the measurement frequency. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment will be described with reference to the drawings. The embodiment relates to an evaluation device and an evaluation method for evaluating the state of food, such as the hardness of food, with a packaged food as a measurement object. In particular, the embodiment relates to an evaluation device and an evaluation method for evaluating the hardness of food non-destructively using an electrical impedance method.

[0011] [Evaluation device configuration] 1 is a diagram showing an outline of a configuration example of an evaluation device 1 according to an embodiment. As shown in FIG. 1, the evaluation device 1 includes a measurement unit 10, an LCR meter 30, and an analysis device 40.

[0012] The measurement unit 10 includes a set of electrode plates 13 including a first electrode plate 11 and a second electrode plate 12 opposed to each other, and an electromagnetic shielding box 18 surrounding the set of electrode plates 13. In the evaluation device 1, a measurement target 90 is placed between the set of opposed electrode plates 13 in the electromagnetic shielding box 18, and its impedance is measured. The first electrode plate 11 and the second electrode plate 12 are each connected to an LCR meter 30 via a cable 21 such as a coaxial cable. In addition, the electromagnetic shielding box 18 and the LCR meter 30 are grounded as shown typically by a cable 23 in the figure.

[0013] The LCR meter 30 applies an AC signal of a predetermined frequency to the pair of electrode plates 13, and obtains an AC response from the pair of electrode plates 13. The LCR meter 30 determines the impedance between the pair of electrode plates 13 based on the obtained response signal. In this embodiment, the LCR meter 30 performs impedance measurement using a predetermined measurement frequency of 8,300 Hz to 1.2 MHz. In this embodiment, the impedance measurement may be performed at a plurality of measurement frequencies, or may be performed at a single measurement frequency. The measurement frequency is more preferably 9,300 Hz to 1,040 kHz, more preferably 10,400 Hz to 860 kHz, more preferably 14 kHz to 680 kHz, more preferably 20 kHz to 460 kHz, and more preferably 30 kHz to 320 kHz. The LCR meter 30 outputs the measurement result to the analysis device 40.

[0014] The analysis device 40 is, for example, a general computer. That is, the analysis device 40 includes a central processing unit (CPU) 41, a memory 42, a storage 43, and the like. The storage 43 stores information on the relationship between the real component Rs of the impedance measured by the LCR meter 30 using the measurement frequency and a value indicating the state of the food, such as the hardness of the food, which information has been acquired in advance. This relationship may be stored, for example, as a function or as a look-up table. In addition, this relationship does not have to be stored in the storage 43, and for example, the analysis device 40 may refer to the relationship stored outside the analysis device 40 via a network.

[0015] The analysis device 40 determines the real component Rs of the obtained impedance based on the measurement result obtained from the LCR meter 30. The analysis device 40 determines and evaluates the state of the food, which is the measurement object 90, such as hardness, based on the determined real component Rs of the impedance and the relationship recorded in the storage 43.

[0016] The measurement object 90 of the evaluation device 1 as described above is, for example, as follows. Food may include, for example, cooked rice. That is, packaged food may include packaged cooked rice. Packaged cooked rice may include not only white rice, but also red rice, sticky rice, and other foods cooked using rice as an ingredient in general. The container may be made mainly of synthetic resin. The container may have a multi-layer structure. The container may include, for example, an oxygen barrier layer for blocking oxygen, and an oxygen absorbing layer for absorbing oxygen. The oxygen absorbing layer may include those using synthetic resin as well as those utilizing the oxidation reaction of iron powder.

[0017] [Evaluation method] A description will be given of a method for evaluating the hardness of a packaged food according to this embodiment using the evaluation device 1. Fig. 2 is a flow chart for explaining an example of the measurement and evaluation of a packaged food.

[0018] In step S1, the measurement object 90 is carried into the measurement unit 10 and inserted between the first electrode plate 11 and the second electrode plate 12 of the pair of electrode plates 13.

[0019] In step S2, the evaluation device 1 performs impedance measurement on the measurement object 90 at a predetermined measurement frequency. That is, with the measurement object 90 placed between a pair of electrode plates 13, the LCR meter 30 applies an AC signal of a predetermined measurement frequency between the pair of electrode plates 13 and acquires a response signal between the pair of electrode plates 13. The LCR meter 30 determines the impedance based on the acquired response signal.

[0020] In step S3, evaluation device 1 determines the value of real component Rs of the impedance. That is, analysis device 40 determines the value of the real component Rs based on the impedance obtained in step S2.

[0021] In step S4, the evaluation device 1 evaluates the hardness of the measurement object 90. That is, the analysis device 40 compares the real component Rs of the impedance obtained in step S3 with the relationship between the real component Rs and the hardness of the food, etc., recorded in the storage 43, specifies the hardness, etc., of the food of the measurement object 90, and performs a predetermined evaluation.

[0022] In step S5, the measurement object 90 is carried out from the measurement unit 10.

[0023] The evaluation in step S4 will be further explained. There may be various kinds of information on the hardness of the foodstuffs, etc., associated with the real component Rs of the impedance described above. For example, when the foodstuff is cooked rice, this information may be information on the hardness of the cooked rice measured by a compression test. In this case, in order to prepare this information, for example, a plurality of types of cooked rice cooked under different conditions are prepared as samples. The cooking conditions may include various conditions such as the amount of water absorbed by the raw rice, the ratio of the amount of raw rice to water, and the cooking time. For each of these samples, impedance measurement is performed in a containerized state using an apparatus including a measuring unit 10 and an LCR meter 30 similar to the evaluation apparatus 1, and then the hardness of the cooked rice taken out of each container is measured using a compression tester.

[0024] The above information may not be a value directly indicating hardness, but may be a value expressed by, for example, a water absorption ratio expressed by the weight of raw rice relative to the total weight after cooking. The above information may also be a value indicating other states of cooked rice.

[0025] Based on such information indicating hardness, etc., the hardness, etc. of the food of the measurement object 90 is determined, and the state of the food's hardness, etc. may be evaluated based on whether it is within a specified range, for example, and a judgment may be made as to whether the containerized food is good or bad.

[0026] Alternatively, the real component Rs of the impedance may be directly associated with whether the containerized food is good or bad, and based on this relationship, a judgment of whether the containerized food is good or bad may be made based on the real component Rs of the impedance, which is directly related to the hardness of the containerized food.

[0027] According to the evaluation device 1 of the present embodiment and the evaluation method using the same as described above, the hardness of a packaged food can be evaluated non-destructively. Generally, packaged foods are sterilized after sealing the container or sealed in a container in a sterile state, so it is difficult to check the state of the food after cooking. Quality control can be performed by destructive inspection by sampling. According to the evaluation device 1 of the present embodiment and the evaluation method using the same, not only sampling inspection but also non-destructive inspection is possible. Therefore, for example, when the food is cooked rice, it becomes possible to inspect and reject even sudden defects in the hardness and quality of cooked rice that may occur especially in the commonly performed individual cooking.

[0028] In this embodiment, since it is possible to evaluate the hardness of food by impedance measurement at a predetermined frequency, the impedance measurement can be performed in a short time compared to impedance measurement while changing the frequency, etc. Therefore, according to this embodiment, it is also possible to perform 100% inspection in the production process of containerized foods.

[0029] For example, evaluation device 1 is incorporated in a production line, a carry-in device carries the produced containerized food between a pair of electrode plates 13, and an unloading device carries the containerized food whose impedance has been measured out from between the pair of electrode plates 13. Here, the carry-in device and the unloading device are, for example, conveyors that transport containerized foods, and the conveyor may carry the containerized food into measuring unit 10 in step S1 and carry it out from measuring unit 10 in step S5 described above. In this way, the impedance associated with the containerized food inserted between a pair of electrode plates 13 is measured continuously or intermittently, and the hardness, etc. of the containerized food can be determined. EXAMPLES

[0030] Cooked rice was used as the food to be measured. Impedance measurements were performed on containerized cooked rice cooked under different cooking conditions, and it was clarified that there is a certain relationship between the real component Rs of the measured impedance and the cooking conditions or the hardness of the cooked rice.

[0031] [method] 1. Sample The sample was prepared as follows. Non-glutinous rice (multiple raw materials produced in 2019, no-rinse rice, Food Association, Hiroshima City) was used. Raw rice was soaked in tap water at room temperature for 3 hours to prepare absorbed rice. The weight of the obtained absorbed rice was about 1.3 times that of raw rice.

[0032] Tap water was placed in the inner pot of an electric rice cooker (Zojirushi, NP-RM05, Osaka City) together with absorbed rice, and the rice was cooked according to the instruction manual. The target water absorption ratio, which indicates how many times the weight of raw rice will be after cooking, was defined as (target water absorption ratio) = (total weight before cooking) / (weight of raw rice). In the rice cooking operation, tap water was added and the rice was cooked with the target water absorption ratios set to 1.6, 1.9, 2.1, 2.6, 3.1, and 3.6. After the rice cooking operation was completed, the cooked rice was thoroughly loosened and then the weight of the cooked rice was measured. The weight measured here was defined as the "total weight after cooking."

[0033] The container used was a tray-shaped retort container 110 having an enclosure 111 with dimensions of 110 mm×73 mm×depth 33 mm and a seal portion 112 with dimensions of 127 mm×90 mm, as shown in Fig. 3. A transparent lid was used as the lid.

[0034] 120 g of cooked rice was packed into the container. The container was sealed with a lid by heat and pressure using a special sealer. Five samples were prepared for each water absorption ratio.

[0035] The prepared sample was kept upright (with the lid facing up) in a thermostatic chamber at 20°C for at least one hour. The sample whose temperature had become constant was used for measuring the electrical properties.

[0036] 2. Electrical property measurements A measuring device having the same configuration as the evaluation device 1 shown in FIG. 1 was used to measure the impedance of the container-packed cooked rice. The LCR meter was 3522-50 manufactured by HIOKI (Ueda City) or IM3536 manufactured by HIOKI. A box made of polystyrene foam with dimensions of 320 mm × 390 mm × 170 mm and aluminum foil attached to the outside was used as the electromagnetic wave shielding box. Two electrode plates with dimensions of 120 mm length × 160 mm width × 2 mm thickness were placed facing each other in this electromagnetic wave shielding box. A fluororesin spacer was inserted between the electrode plates, and the electrode plates were fixed with a distance of 36 mm between the electrode plates. These electrode plates were placed on silicone rubber legs so that each electrode plate was horizontal. Each electrode plate and the LCR meter were connected via a coaxial cable. Noise was blocked by connecting the aluminum foil of the electromagnetic wave shielding box to the earth terminal of the LCR meter.

[0037] The above-mentioned sample was placed on the lower electrode plate in an upright position (with the lid side facing up) and placed between the two electrode plates. Impedance measurements were performed at 200 frequencies between 100 Hz and 100 kHz in logarithmic intervals using an LCR meter (3522-50). Impedance measurements were also performed at 300 frequencies between 100 Hz and 8 MHz in logarithmic intervals using an LCR meter (IM3536). The measurement temperature was 20°C.

[0038] The measured values ​​were recorded and analyzed using a computer. The impedance measurements yielded the complex impedance Z, the real component Rs of the impedance, the imaginary component X, and the phase angle θ.

[0039] 3. Hardness measurement A small benchtop compression tester (Shimadzu Corporation, EZ-SX, Kyoto City) was used to measure the hardness of the cooked rice samples. A jig 121 for fixing the measurement container, as shown in FIG. 4, was attached to the lower stage of the small benchtop compression tester. A PTFE plunger 122 with a diameter of the compression part of 20 mm was attached to the upper movable part via a load cell.

[0040] The container-packed cooked rice sample after the impedance measurement was opened, and the cooked rice was filled into an aluminum cup-shaped measuring container 123 having an inner diameter of 40 mm and a height of 15 mm. At this time, the height of the cooked rice was set to 15 mm. The measuring container filled with the cooked rice was fixed to a small tabletop compression tester using a measuring container fixing jig, and a compression test was performed using a plunger at a compression speed of 1 mm / sec up to a strain of 67%. Three or four measurements were performed for each cooked rice sample.

[0041] The measured data (load-displacement curves of cooked rice samples) were analyzed using software (TRAPEZIUMX, Shimadzu Corporation). In the analysis, hardness was determined based on the maximum load.

[0042] [Results and Discussion] 1. Actual water absorption rate of cooked rice samples The (total weight after cooking) / (weight of raw rice) of each cooked rice sample with a different target water absorption ratio was defined as the "actual water absorption ratio." The actual water absorption ratios of cooked rice with target water absorption ratios of 1.6, 1.9, 2.1, 2.6, 3.1, and 3.6 were 1.55, 1.82, 1.97, 2.40, 2.66, and 3.17, respectively.

[0043] 2. Relationship between real component of impedance Rs and measurement frequency Figure 5 shows the relationship between the real component Rs value and the measurement frequency obtained by impedance measurement at 100 Hz-100 kHz for cooked rice samples with different target water absorption rates. Below approximately 10,000 Hz, a linear relationship with almost the same slope was obtained for all samples, although the absolute values ​​differed. The slope changed around 10,000 Hz, and above 10,000 Hz, a linear relationship with a different slope for each sample's water absorption rate was obtained.

[0044] From the results shown in Fig. 5, it was deemed necessary to separate the frequency range into three regions: the low frequency range below 10,000 Hz, the mid-frequency range around 10,000 Hz, and the high frequency range above 10,000 Hz.

[0045] 3. Relationship between the real component of impedance Rs and the actual thermal water absorption FIG. 6 shows the relationship between the real component Rs of the impedance and the actual thermal water absorption when the measurement frequency is 1,023 Hz (low frequency region). FIG. 7 shows the relationship between the real component Rs of the impedance and the actual thermal water absorption when the measurement frequency is 10,120 Hz (medium frequency region). FIG. 8 shows the relationship between the real component Rs of the impedance and the actual thermal water absorption when the measurement frequency is 29,670 Hz (high frequency region). The error bars in each figure indicate the maximum and minimum values ​​of the measurement results for each sample.

[0046] When the measurement frequency was 1,023 Hz, the Rs value increased with increasing water absorption. However, no difference in Rs value was observed between samples with low water absorption. When the measurement frequency was 10,120 Hz, the Rs value gradually increased with increasing water absorption, except when the water absorption was 1.6 times. When the measurement frequency was 29,670 Hz, the Rs value decreased with increasing water absorption. However, no difference in Rs value was observed between samples with high water absorption.

[0047] From the above results, it became clear that the difference in water absorption capacity of cooked rice can be evaluated based on the real component Rs of the impedance measured non-destructively. Furthermore, it became clear that measurement in the low frequency range is effective for evaluating samples with high water absorption capacity, and measurement in the high frequency range is effective for evaluating samples with low water absorption capacity.

[0048] 4. Relationship between hardness and actual water absorption rate Figure 9 shows the relationship between the hardness of cooked rice measured by the compression test and the actual water absorption capacity. The hardness of cooked rice decreased as the water absorption capacity increased, and there was a high correlation between the hardness of cooked rice and the actual water absorption capacity (R 2= 0.945). The harder the cooked rice sample, the lower the water absorption ratio, the greater the change in hardness. As mentioned above, measurements in the high frequency range are effective for evaluating samples with low water absorption ratios.

[0049] Figure 10 shows the relationship between the hardness of cooked rice and the real component Rs of the impedance when the measurement frequency was set to 29,670 Hz. A high positive correlation was observed between the hardness of cooked rice and the real component Rs of the impedance when the measurement frequency was set to 29,670 Hz, and the coefficient of determination (R 2 ) was 0.878.

[0050] As described above, it has been shown that the hardness of containerized cooked rice can be measured non-destructively by impedance measurement in the high frequency range.

[0051] We investigated the measurement frequency at which the hardness of packaged cooked rice can be evaluated non-destructively by impedance measurement. Measurements were performed at frequencies from 100 Hz to 8 MHz for each sample with a target heat absorption ratio of 1.5 to 3.6 times, and the relationship between the hardness of the cooked rice and the real component Rs of the measured impedance was plotted as shown in Figure 10. Based on the results, the coefficient of determination (R 2 ) was identified. Figure 11 shows the coefficient of determination (R 2 ) and the measurement frequency.

[0052] When the measurement frequency is 8,300 Hz or more and 1.2 MHz or less, the coefficient of determination (R 2 ) was 0.5 or more. Therefore, it was clarified that the measurement frequency is preferably 8,300 Hz or more and 1.2 MHz or less for the packaged cooked rice sample with the target heat absorption ratio of 1.5 times or more and 3.6 times or less. Furthermore, when the measurement frequency is 9,300 Hz or more and 1,040 kHz or less, the coefficient of determination (R 2 ) is 0.6 or more and the measurement frequency is 10,400 Hz or more and 860 kHz or less, the coefficient of determination (R 2 ) is 0.7 or more and the measurement frequency is 14 kHz or more and 680 kHz or less, the coefficient of determination (R2 ) is 0.8 or more and the measurement frequency is 20 kHz or more and 460 kHz or less, the coefficient of determination (R 2 ) is 0.9 or more and the measurement frequency is 30 kHz or more and 320 kHz or less, the coefficient of determination (R 2 ) was 0.95 or more. Therefore, for the container-packed cooked rice sample with a target heat absorption ratio of 1.5 times or more and 3.6 times or less, it is more preferable that the measurement frequency is 9,300 Hz or more and 1,040 kHz or less, more preferably that the measurement frequency is 10,400 Hz or more and 860 kHz or less, more preferably that the measurement frequency is 14 kHz or more and 680 kHz or less, more preferably that the measurement frequency is 20 kHz or more and 460 kHz or less, and more preferably that the measurement frequency is 30 kHz or more and 320 kHz or less.

[0053] Although the present invention has been described above by showing preferred embodiments, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. [Explanation of symbols]

[0054] 1. Evaluation device 10. Measurement section 11 First electrode plate 12 Second electrode plate 13 A set of electrode plates 18 Electromagnetic wave shielding box 21 Cable 30 LCR Meter 40 Analyzer 41 CPU 42 Memory 43 Storage 90 Measurement Object

Claims

1. A pair of electrode plates facing each other, configured so that a containerized food to be measured is placed therebetween; an LCR meter configured to measure the impedance between the electrode plates at a predetermined measurement frequency between 8300 Hz and 1.2 MHz, inclusive; an analysis device that acquires information on a relationship between a real component of impedance measured at the measurement frequency and a state of food, and evaluates the state of the food, which is a measurement object, based on the relationship and the real component of impedance obtained based on an output of the LCR meter; Equipped with The food product is cooked rice, The relationship is the relationship between the real component of the impedance of cooked rice having a heat absorption rate of 1.5 times or more and 3.6 times or less and the state related to the hardness of the cooked rice. A device for assessing the condition of packaged foods.

2. The evaluation device according to claim 1 , wherein the measurement frequency is a single frequency.

3. The state regarding the hardness of the cooked rice is the hardness of the cooked rice determined by a compression test. The evaluation device according to claim 1 .

4. The state regarding the hardness of the cooked rice is the heating water absorption ratio of the cooked rice. The evaluation device according to claim 1 .

5. A loading device that is a part of a production line for packaged food and that loads the packaged food produced between the electrode plates; a discharge device which is a part of a production line for packaged food and which discharges the packaged food, the impedance of which has been measured, from between the electrode plates; The evaluation device according to claim 1 , further comprising:

6. Placing a packaged food as a measurement target between a pair of opposing electrode plates and measuring the impedance between the electrode plates at a predetermined measurement frequency of 8300 Hz or more and 1.2 MHz or less using an LCR meter; evaluating, by an analysis device, the state of the food whose impedance has been measured based on a real component of the impedance obtained based on the output of the LCR meter and a relationship between the real component of the impedance measured at the measurement frequency prepared in advance and the state of the food; Including, The food product is cooked rice, The relationship is the relationship between the real component of the impedance of cooked rice having a heat absorption rate of 1.5 times or more and 3.6 times or less and the state related to the hardness of the cooked rice. Methods for assessing the condition of packaged foods.

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