Patent Publication Number: US-2021166575-A1

Title: Simulated texture presentation device, simulated texture presentation method, and program

Description:
TECHNICAL FIELD 
     The present invention relates to a pseudo-food texture presentation device, a pseudo-food texture presentation method, and a program. 
     BACKGROUND ART 
     Studies on how food texture is presented have been conducted and applications to mastication training, entertainment, food design, and the like have been considered (for example, see NPL 1. Food texture is a physical property of food felt in the mouth. Accordingly, in order to present food texture, it is important to present the hardness and shape of food in the mouth of a user. 
     As a technique of the related art, a scheme of using a physical phenomenon such as a jamming transition to present hardness and a shape can be exemplified. The jamming transition is a physical phenomenon in which a granular material behaves differently depending on the density, and is a phenomenon in which a granular material behaves like a solid when the density is high and behaves like a fluid when the density is low. 
     As an example of a study in which a jamming transition is utilized, a technique applied to a robotic hand has been proposed. For example, NPL 2 proposes a scheme) of deforming a robotic hand in. accordance with the shape of an object by gripping the object which is in a robotic hand which is formed of a granular material and in a soft state so that the robotic hand is familiar with the shape of the object, and thus the object is gripped in a state in which the robotic hand is in a hard state. 
     CITATION LIST 
     Non Patent Literature 
     [NPL 1] Hiroo Iwata, Hiroaki Yano, Takahiro Uemura, and Tetsuro Moriya. 2004. Food Simulator: A Haptic Interface for Biting. In Proc. of VP. &#39;04. 51-57. 
     [NPL 2] Eric Brown, Nicholas Rodenberg, John Amend, Annan Mozeika, Erik Steitz, Mitchell R. Zakin, Hod Lipson, and Heinrich M. Jaeger. 2010. Universal robotic gripper based on the jamming of granular material. Proc. of the National Academy of Sciences 107, 44 (2010), 18809-18814. 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     In the content disclosed in NPL 1, it is difficult to present hardness and a shape in a mouth. 
     On the other hand, NPL 2 discloses a scheme of gripping an object depending on only whether a jamming transition arises or not. However, a technique for controlling hardness of an object in a user&#39;s mouth using the jamming transition has not been disclosed. 
     The present invention has been devised in view of the foregoing problems and an objective of the present invention is to provide a pseudo-food texture presentation device, a pseudo-food texture presentation method, and a program capable of controlling hardness of an object in a user&#39;s mouth using a jamming transition to present food texture by presenting hardness and a shape of the object. 
     Means for Solving the Problem 
     According to a first aspect. of the present invention, a pseudo-food texture presentation device includes: an enclosure body in which a granular material is enclosed; a measurer configured to measure at least one index among a temperature of an ambient environment of the enclosure body, a humidity of the ambient environment of the enclosure body, a temperature of the enclosure body, and a moisture amount on a surface of the enclosure body; and an enclosure body controller configured to control density of the granular material inside the enclosure body in accordance with the measured index. 
     According to a second aspect of the present invention, in the pseudo-food texture presentation device in the first aspect, the enclosure body controller controls the density of the granular material inside the enclosure body when the measured index exceeds a preset threshold. 
     According to a third aspect of the present invention, in the pseudo-food texture presentation device in the first or second aspect, the enclosure body controller controls the density of the granular material inside the enclosure body in accordance with a cumulative value obtained by accumulating the measured index. 
     According to a fourth aspect of the present invention, the pseudo-food texture presentation device in any one of the first to third aspects further includes a determiner configured to determine whether the enclosure body is in a user&#39;s mouth. The enclosure body controller controls the density of the granular material inside the enclosure body in accordance with the measured index when the determiner determines that the enclosure body is in a user&#39;s mouth. 
     Effects of the Invention 
     In the first aspect of the present invention, the density of the granular material inside the enclosure body is controlled in accordance with at least one index among the temperature of the ambient environment of the enclosure body, the humidity of the ambient environment of the enclosure body, the temperature of the enclosure body, and the moisture amount on the surface of the enclosure body. The hardness of the enclosure body is changed by a jamming transition by changing the density of the granular material inside the enclosure body. For example, when the enclosure body is in a user&#39;s mouth, the index is changed over time. In the foregoing configuration, it is possible to change the hardness of the enclosure body in the mouth of the user. As a result, it is possible to present the user with a pseudo-food texture. 
     In the second aspect of the present invention, the hardness of the enclosure body is changed before and after the measured value of the index exceeds the threshold. Thus, it is possible to change the hardness of the enclosure body step by step. When many thresholds are set, the hardness of the enclosure body can be smoothly changed and a diversity of the food textures can be improved. 
     In the third aspect of the present invention, the hardness of the enclosure body is changed in accordance with the cumulative value of the measured index. Thus, it is possible to gradually reduce the hardness of the enclosure body or increase the hardness of the enclosure body reliably. 
     In the fourth aspect of the present invention, the hardness of the enclosure body is changed in accordance with the measured value of the index and when the enclosure body is in the user&#39;s mouth. Thus, the hardness of the enclosure body can be changed by considering not only the measured value of the index but also a time that has passed after the user has put the enclosure body in her or his mouth. As a result, a diversity of food textures can be improved. A time at which the user is determined to have put the enclosure body in her or his mouth can be used as a standard time at which the measured values of the index are accumulated. 
     That is, according to the aspects of the present invention, it is possible to provide a technique capable of controlling hardness of an object in a user&#39;s mouth using a lamming transition. to present food texture by presenting hardness and a shape of the object. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINS 
         FIG. 1  is a perspective view illustrating an outer appearance of a pseudo-food texture presentation device according to First embodiment. 
         FIG. 2  is a block diagram illustrating a configuration of a microcomputer in the pseudo-food texture presentation device illustrated in  FIG. 1 . 
         FIG. 3  is a diagram illustrating an example of a database recorded on a temperature/hardness correspondence recording unit illustrated in  FIG. 2 . 
         FIG. 4  is a diagram illustrating an example of a database recorded on a hardness/atmospheric pressure correspondence recording unit illustrated in  FIG. 2 . 
         FIG. 5  is a diagram illustrating an example of a database recorded on an atmospheric pressure/duty ratio correspondence recording unit illustrated in  FIG. 2 . 
         FIG. 6A  is a diagram illustrating an aspect in which an atmospheric pressure inside a bag illustrated in  FIG. 1  is adjusted to 0 [kPa]. 
         FIG. 6B  is a diagram illustrating an aspect in which an atmospheric pressure inside the bag illustrated in  FIG. 1  is adjusted to −10 [kPa]. 
         FIG. 6C  is a diagram illustrating an aspect in which an atmospheric pressure inside the bag illustrated in  FIG. 1  is adjusted to −30 [kPa]. 
         FIG. 6D  is a diagram illustrating an aspect in which an atmospheric pressure inside the bag illustrated in  FIG. 1  is adjusted to −60 [kPa]. 
         FIG. 7A  is a diagram. illustrating a method of changing the shape of the bag illustrated in  FIG. 1  and presenting the changed shape of the bag to a user. 
         FIG. 7B  is a diagram illustrating a method of changing the shape of the bag illustrated in  FIG. 1  and presenting the changed shape of the bag to the user. 
         FIG. 7C  is a diagram illustrating a method of changing the shape of the bag illustrated in  FIG. 1  and presenting the changed shape of the bag to the user. 
         FIG. 7D  is a diagram illustrating a method of changing the shape of the bag illustrated in  FIG. 1  and presenting the changed shape of the bag to the user. 
         FIG. 8  is a block diagram illustrating pseudo-food texture presentation processing realized by the pseudo-food texture presentation device illustrated in  FIG. 2 . 
         FIG. 9  is a block diagram illustrating a configuration of a pseudo-food texture presentation device according to Second embodiment. 
         FIG. 10  is a block diagram illustrating pseudo-food texture presentation processing realized by the pseudo-food texture presentation device illustrated in  FIG. 9 . 
         FIG. 11  is a block diagram illustrating a configuration of a pseudo-food texture presentation device according to Second embodiment. 
         FIG. 12  is a block diagram illustrating pseudo-food texture presentation processing realized by the pseudo-food texture presentation device illustrated in  FIG. 11 . 
         FIG. 13  is a diagram illustrating a result of hardness sensory evaluation at each stage by a Scheffe&#39;s paired comparison method. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 
     First Embodiment 
     (Configuration) 
       FIG. 1  is a perspective view schematically illustrating an outer appearance of a pseudo-food texture presentation device  1  according to First embodiment. As illustrated in  FIG. 1 , the pseudo-food texture presentation device  1  includes a microcomputer  10 , a vacuum pump  20 , a bag  30  which is an enclosure body, a negative pressure sensor  40 , a plurality of temperature sensors  50 , and a personal computer PC. 
     The vacuum pump  20  includes a suction opening  20   a  used to suck air. The suction opening  20   a  and an air opening  30   a  of the bag  30  are connected by, for example, a flexible tube GT 1  made of polyurethane and a flexible tube GT 2  formed of an acrylic pipe and a silicon hose via a junction JC. The vacuum pump  20  sucks air inside the bag  30  to generate a negative pressure inside the bag  30 . 
     A motor is provided inside the vacuum pump  20 . An air amount sucked from the bag  30  is adjusted (controlled) by controlling a duty ratio of a pulse width modulation (PWM) signal for driving the motor and controlling a revolution speed of the motor. 
     The bag  30  is, for example, formed of a deformable (elastic) substance such as rubber or silicon in a bag shape (in this example, a rubber balloon) and, for example, contains a granular material such as coffee grounds or a starch. The hardness of the bag  30  is chard variously in accordance with an air amount (the degree of vacuum) sucked. by the vacuum pump  20 . When air is sucked by the vacuum pump  20  and the bag  30  is contracted, the density of the granular material increases. Thus, the hardness of the bag  30  increases. Lower atmospheric pressure inside the bag  30  results in higher hardness of the bag  30 . In this way, by controlling the density of the granular material inside the bag  30 , it is possible to control the hardness of the bag  30  by a jamming transition. 
     The negative pressure sensor  40  is connected to the junction JC via, for example, the flexible tube GT 2  and has a function of sensing the atmospheric pressure inside the bag  30 . 
     The plurality of temperature sensors  50  are disposed at a plurality of positions on the surface of the bag  30  (hereinafter also referred to as sensor positions). In this example, the temperature sensors  50  are disposed on the outer surface of the bag  30  and measure the outside temperature of the bag  30  at each sensor position, that is, a temperature of an environment in which the bag  30  is present (hereinafter also referred to as ambient environment of the bag  30 ). Here, the outer surface of the bag  30  is a surface on the outside of the bag  30 . Specifically, the outer surface of the bag  30  is a surface touched by tissues such as the teeth, the tongue, and the like of a user  60  who puts the bag  30  in her or his mouth. 
     The temperature sensors  50  measure the outside temperature of the bag  30  and transmit, to the microcomputer  10 , temperature data including measured values of the temperature and measurement times at which the temperature is measured. The temperature sensors  50  obtain the measured values at predetermined time intervals (for example, intervals of 10 milliseconds) and output the temperature data in real time. 
     It is desirable to provide the plurality of temperature sensors  50  on the bag  30  as in the embodiment, but it is also possible to provide only one temperature sensor  50  on the bag  30 . 
     The microcomputer  10  is connected to the vacuum pump  20  the negative pressure sensor  40 , the plurality of temperature sensors  50 , and the personal computer PC by signal lines S. The present invention is not limited to wired communication and wireless communication may be used. 
     The personal computer PC includes a display unit D such as a liquid crystal display device and has a function of receiving various kinds of measured data (for example, measured data such as atmospheric data and temperature data inside the bag  30 ) from the microcomputer  10  and outputting the measured data or graphs or The like obtained by processing the measured data to the display unit D. 
       FIG. 2  is a block diagram schematically illustrating a configuration of a microcomputer  10  in the pseudo-food texture presentation device  1 . As illustrated in  FIG. 2 , the microcomputer  10  includes a central processing unit (CPU)  11  serving as a control unit, a random access memory (RAM)  12 , a recording unit  13 , a duty ratio output unit  14 , an external device data input unit  15 , and a data output interface (I/F)  16 . The CPU  11  is connected to the random access memory (RAM)  12 , the recording unit  13 , the duty ratio output unit  14 , the external device data input unit  15 , and the data output interface  16  via a system bus BUS. 
     The RAM  12  includes a working area  12   a.    
     The recording unit  13  is configured from a hard disk, a flash memory, or the like and includes a program area in which a pseudo-food texture presentation processing program  13   a  is stored, a temperature recording unit  13   b , a temperature/hardness correspondence recording unit  13   c , a hardness/atmospheric c pressure correspondence recording unit  13   d an atmospheric pressure/duty ratio correspondence recording unit  13   e , and an atmospheric pressure recording unit  13   f .    
     The pseudo-food texture presentation processing program  13   a  is executed by the CPU  11  using the working area  12   a When the pseudo-food texture presentation processing program  13   a  is executed by the CPU  11 , pseudo-food. texture presentation processing to be described below is performed by the CPU  11 . 
     The temperature recording unit  13   b  records temperatures measured by the plurality of temperature sensors  50  in association with measurement times which are times at which the measurement is performed. 
     The temperature/hardness correspondence recording unit  13   c  pre-records a correspondence table (database) in which a temperature corresponds to hardness of the bag  30 . The correspondence table is set such that, for example, the hardness of the bag  30  is lower as the temperature is higher. 
     The hardness of the bag  30  can be set in seven stages in accordance with an atmospheric pressure (0 [kPa] to −60 [kPa]) inside the bag  30  which can be realized by sucking of the vacuum pump  20 . For example, stage 1 is hardness at an atmospheric pressure of 0 [kPa], stage 2 is hardness at an atmospheric pressure of −10 [kPa], stage 3 is hardness at an atmospheric pressure of −20 [kPa], stage 4 sis hardness at an atmospheric pressure of −30 [kPa], stage 5 is hardness at an atmospheric pressure of −40 [kPa], stage 6 is hardness at an atmospheric pressure of −50 [kPa], and stage 7 is hardness at an atmospheric pressure of −60 [kPa]. For example, a lower stage corresponds to lower hardness of the bag  30 , and thus a soft food texture. A higher stage corresponds to higher hardness of the bag  30 , and thus a hard food texture. In other words, the hardness of the bag  30  is the lowest at stage 1. The hardness of the bag  30  becomes higher as the stage increases through stages 2, 3, . . . , and 6. Thus, at stage 7, the hardness of the bag  30  is the highest. 
       FIG. 3  is a diagram illustrating an example of the correspondence table recorded. on the temperature/hardness correspondence recording unit  13   c . As illustrated in  FIG. 3 , when T is a temperature, for example, the hardness is set at stage 7 for T&lt;T 1 , the hardness is set at stage 6 for T 1 ≤T 2 , the hardness is set at stage 5 for T 2 ≤T&lt;T 3 , the hardness is set at stage 4 for T 3 ≤T&lt;T 4 , the hardness is set at stage 3 for T 4 ≤T&lt;T 5 , the hardness is set at stage 2 for T 5 ≤T&lt;T 6 , and the hardness is set at stage 1 for T 6 ≤T. Here, specific temperatures [°C.] are set at T 1  to T 7 . 
     The seven stages described above may not all be used. For example, as will be described below with reference to  FIG. 13 , a combination of the stages at which a difference in hardness can be perceived at the time of mastication may used. For example, the hardness is set at stage 7 for T&lt;T 11 , the hardness is set at stage 4 for T 11 ≤T&lt;T 12 , the hardness is set at stage 2 for T 1   2  ≤T&lt;T 13 , and the hardness is set at stage 1 for T 13 ≤T. Here, specific temperatures [° C.] are set at T 11 , T 12 , and T 13 . 
     The present invention is not limited to the seven stages and the hardness of the bag  30  may be set in fewer or more stages, By setting the hardness of the bag  30  in many stages, it is possible to continuously change the hardness substantially. As a result, it is possible to smoothly change food texture presented to a user. 
     Referring to  FIG. 2 , the hardness/atmospheric pressure correspondence recording unit  13   d  pre-records a correspondence table (database) in which each stage of the hardness of the bag  30  corresponds to an atmospheric pressure at which the hardness at each stage is obtained.  FIG. 4  is a diagram illustrating an example of the correspondence table recorded on the hardness/atmospheric pressure correspondence recording unit  13   d , In the example illustrated in  FIG. 4 , stage 1 corresponds to 0 [kPa], stage 2 corresponds to −10 [kPa], stage 3 corresponds to −20 [kPa], stage 4 corresponds to −30 [kPa], stage 5 corresponds to −40 [kPa], stage 6 corresponds to −50 [kPa], and stage 7 corresponds to −60 [kPa]. 
     Referring to  FIG. 2 , the atmospheric pressure/duty ratio correspondence recording unit  13   e  pre-records a correspondence table (database) in which an atmospheric pressure inside the bag  30  corresponds to a duty ratio of the PWM signal.  FIG. 5  is a diagram illustrating an example of a correspondence table recorded on the atmospheric pressure/duty ratio correspondence recording unit  13   e . As illustrated in  FIG. 5 , an atmospheric pressure inside the bag  30  monotonically decreases with respect to a duty ratio of a PWM signal. 
     Instead of the correspondence table illustrated in  FIG. 5 , the atmospheric pressure/duty ratio correspondence recording unit  13   e  may pre-record a correspondence table in which seven values of duty ratios [%] are described in association with seven pressure values (that is, 0 [kPa], −10 [kPa], . . . , −60 [kPa]) included in the hardness/atmospheric pressure correspondence recording unit  13   d.    
     Referring to  FIG. 2 , the atmospheric pressure recording unit  13   f  records an atmospheric pressure inside The bag  30  measured by the negative: pressure sensor  40  in real time. 
     The duty ratio output unit  14  outputs a PWM signal with the duty ratio set by the CPU  11  to the vacuum pump  20 . Thus, a suction amount (the degree of vacuum) sucked from the bag  30  by the vacuum pump  20  is adjusted (controlled). 
     The external device data input unit  15  receives atmospheric pressure data indicating a measured value of the atmospheric pressure inside the bag  30  from the negative pressure sensor  40  and also receives temperature data indicating a measured value of the temperature from the plurality of temperature sensors  50 . 
     The data output interface  16  outputs, to the personal computer PC, various kinds of data such as data regarding the temperature measured by the temperature sensors  50  in addition to the data regarding the atmospheric pressure inside the bag  30  measured by the negative pressure sensor  40 . Specifically, the CPU  11  outputs, to the personal computer PC via the data output interface  16 , various kinds of data stored in the temperature recording unit  13   b , the temperature/hardness correspondence recording unit  13   c , the hardness/atmospheric pressure correspondence recording unit  13   d , the atmospheric pressure/duty ratio correspondence recording unit  13   e , and the atmospheric pressure recording unit  13   f  included in the recording unit  13 . Thus, not only the various kinds of data but also tables, graphs, or the like obtained by processing the various kinds of data are displayed on the display unit D of the personal computer PC. 
     The pseudo-food texture presentation device  1  that has the foregoing configuration realizes pseudo-food texture presentation processing to be described below when the CPU  11  controls an operation of each constituent element in response to a command described in the pseudo-food texture presentation processing program  13   a.    
     The shape of the bag  30  is not limited to the shape illustrated in  FIG. 1 . The bag  30  can be changed to another shape such as a rectangular parallelepiped. That is, the shape can also be presented as food texture to a user in a pseudo-manner along with the hardness. 
       FIGS. 6A to 6D  are diagrams illustrating aspects in which an atmospheric pressure inside the bag  30  is controlled by the vacuum pump  20 . Specifically,  FIG. 6A  is a diagram illustrating a state of the bag  30  when an atmospheric pressure inside the bag  30  is 0 [kPa].  FIG. 6B  is a diagram illustrating a state of the bag  30  when an atmospheric pressure inside the bag  30  is −10 [kPa].  FIG. 6C  is a diagram illustrating a state of the bag  30  when an atmospheric pressure inside the bag  30  is −30 [kPa].  FIG. 6D  is a diagram illustrating a state of the bag  30  when an atmospheric pressure inside the bag  30  is −60 [kPa]. 
     As illustrated in  FIGS. 6A to 6D , when the atmospheric pressure inside the bag  30  is changed from 0 [kPa], the hardness of the bag  30  is changed and it remains in the same shape as in a state in which the atmospheric pressure inside the bag  30  is 0 [kPa]. 
     In this way, by changing the atmospheric pressure (the stage of hardness) inside the bag  30 , the user  60  can be allowed to perceive another hardness of the bag  30  that has substantially the same shape. 
     A method of changing the shape of the bag  30  and presenting the changed shape to the user will be described with reference to  FIGS. 7A to 7D . 
     First, as illustrated in  FIG. 7A , an atmospheric pressure inside the bag  30  is assumed to be 0 [kPa]. As illustrated in  FIG. 7B , a person who is an operator deforms the shape of the bag  30  with her or his hand in this state. Thereafter, as illustrated in  FIG. 7C , the shape of the bag  30  is kept by causing the vacuum pump  20  to generate a negative pressure (for example, −5 [kPa]) inside the bag  30 . As illustrated in  FIG. 70 , when the user puts the bag  30  in her or his mouth, the atmospheric pressure inside the bag  30  is adjusted to an initial state (for example, −60 [kPa]). 
     In this way, food texture of food in a rectangular parallelepiped of which the hardness is changed with the temperature can be presented to the user  60 . 
     (Operation) 
       FIG. 8  is a diagram schematically illustrating pseudo-food texture presentation. processing according to the Embodiment. The pseudo-food texture presentation processing illustrated in  FIG. 8  is realized. when the CPU  11  in the microcomputer  10  executes the pseudo-food texture presentation processing program  13   a  using the working area  12   a . The pseudo-food texture presentation processing program  13   a  causes the CPU  11  to function as a measured value receiver  13   a   1 , a temperature calculator  13   a   2 , a hardness calculator  13   a   3 , an atmospheric pressure controller  13   a   4 , and an atmospheric pressure control executer  13   a   5 . 
     The measured value receiver  13   a   1  receives the temperature data from the plurality of temperature sensors  50  via the external device data input unit  15  and records the received temperature data on the temperature recording unit  13   b.    
     The temperature calculator  13   a   2  calculates a temperature of the ambient environment of the bag  30  based. on the temperature data received by the measured value receiver  13   a   1 . As an example, the temperature calculator  13   a   2  may calculate an average value obtained by averaging measured values (latest measured values) of the temperatures measured at the plurality of sensor positions as the temperature of the ambient environment of the bag  30 . As another example, the temperature calculator  13   a   2  may calculate a highest measured value among the measured values (latest measured values) of the temperatures measured at the plurality of sensor positions as the temperature of the ambient environment of the bag  30 . 
     The hardness calculator  13   a   3  calculates the hardness of the bag  30  in accordance with the temperature calculated by the temperature calculator  13   a   2  with reference to the correspondence table recorded on the temperature/hardness correspondence recording unit  13   c . For example, when a temperature Tc calculated by the temperature calculator  13   a   2  is in the range of T 3 ≤Tc&lt;T 4 , the hardness calculator  13   a   3  determines stage 4 as the hardness of the bag  30  at the temperature Tc by referring to the correspondence table illustrated in  FIG. 3 . 
     Based on the temperature calculated by the temperature calculator  13   a   2 , the atmospheric pressure controller  13   a   4  calculates an atmospheric pressure at which the hardness of the bag  30  calculated by the hardness calculator  13   a   3  is obtained from the correspondence table recorded in the hardness/atmospheric pressure correspondence recording unit  13   d . Subsequently, the atmospheric pressure controller  13   a   4  sets a duty ratio of the PWM, signal in accordance with the calculated atmospheric pressure at the calculated atmospheric pressure by referring to the correspondence table recorded on the atmospheric pressure/duty ratio correspondence recording unit  13   e . For example, when the hardness calculator  13   a   3  determines stage 4 as the hardness of the bag  30 , the atmospheric pressure controller  13   a   4  determines −30 [kPa] as the atmospheric pressure at which the hardness at stage 4 is obtained by referring the correspondence table illustrated in  FIG. 4  at stage 4. Then, the atmospheric pressure controller  13   a   4  determines 6 [%] as the duty ratio at which the atmospheric pressure inside the bag  30  is set to −30 [kPa] by referring to the correspondence table illustrated in  FIG. 5 . 
     Finally, to adjust (control) the atmospheric pressure inside the bag  30 , the atmospheric pressure control executer  13   a   5  controls a revolution speed of the motor of the vacuum pump  20  based on the duty ratio set by the atmospheric pressure controller  13   a   4 . Specifically, the atmospheric pressure control executer  13   a   5  generates a PWM signal with the duty ratio set by the atmospheric pressure controller  13   a   4  supplies the generated PWM signal to the vacuum pump  20  via the duty ratio output unit  14 . 
     In this way, for example, when. the temperature of the ambient environment of the bag  30  is determined to increase the CPU  11  may reduce the duty ratio of the PWM signal. That is, the CPU  11  may reduce the hardness of the bag  30  with the increase in the temperature of the ambient environment of the bag  30  in the order from stages 7 to 1. Thus, it is possible to present a user with food texture of food (for example, ice cream) which becomes soft with an increase in temperature. 
     The pseudo-food texture presentation processing program  13   a  may cause the CPU  11  to further function as an atmospheric pressure receiver  13   a   6 . In this case, the atmospheric pressure receiver  13   a   6  may receive the measured value of the atmospheric pressure inside the bag  30  from the negative pressure sensor  40  and the atmospheric pressure controller  13   a   4  may adjust the duty ratio based on the measured value received by the atmospheric pressure receiver  13   a   6  so that the atmospheric pressure inside the bag  30  becomes the atmospheric pressure at which the hardness calculated by the hardness calculator  13   a   3  is calculated. 
     (Effects) 
     In this way, the pseudo-food texture presentation device  1  monitors the temperature of the ambient temperature of the bag  30  using the temperature sensors  50  mounted on the bag  30 . The pseudo-food texture presentation device  1  may reduce the density of the granular material inside the bag  30 , for example, as the temperature of the ambient environment of the bag  30  increases. The hardness of the bag  30  is reduced by a jamming transition by reducing the density of the granular material inside the bag  30 . In the embodiment, the density of the granular material inside the bag  30  is controlled by changing the atmospheric pressure inside the bag  30 . Thus, it is possible to present the user with food texture such as overall continuous softening texture, for example, food texture of an ice cream, when the temperature increases. 
     MODIFICATION EXAMPLES 
     In the above-described example, the temperature sensors  50  are disposed on the outer surface of the bag  30 . However, the temperature sensors  50  may be disposed on the inner surface of the bag  30 . Here, the inner surface of the bag  30  is a surface on the inner side of the bag  30 . Specifically, the inner surface of the bag  30  is a surface regulating an inner space in which the granular material is sealed. 
     In an example in which the temperature sensors  50  are disposed on. the inner surface of the bag  30 , the temperature calculator  13   a   2  calculates a temperature of the bag  30  itself. Since a method of calculating the temperature of the bag  30  based on the measured values of the temperatures obtained by the temperature sensors  50  is similar to the method of calculating the temperature of the ambient environment of the bag  30 , as described above, description thereof will be omitted. 
     The correspondence table recorded on the temperature/hardness correspondence recording unit  13   c  may be set so that the higher temperature results in higher hardness of the bag  30 . In this way, it is possible to present the user with food texture of food hardened with an increase in temperature. 
     Instead of the temperature sensor  50 , a humidity sensor maybe used. When the humidity sensor is used, the CPU  11  monitors a humidity of the ambient environment of the bag  30  and controls the density of the granular material inside the bag  30  with a change in humidity of the ambient environment of the bag  30 . 
     In the above-described example, an enclosure body is configured as one bag  30 . However, the enclosure body may be configured as a plurality of bags in which a granular material is sealed. The enclosure bodies maybe formed in a structure in which a plurality of bags are disposed in parallel, for example, so that bunches of citrus fruits or the like are lined up (a first structure) or may be in a multiple structure in which a plurality of bags are disposed in a nesting shape (a second structure). For example, in a multiple structure by two bags, one bag (an outer bag) covers the entire other bag (an inner bag). In the second structure, by controlling the hardness for each bag, it is possible to express food texture of food that has different food textures on outer and inner sides of fondant chocolate, for example. 
     The enclosure body may have a structure in which the first and second structures are combined (a third structure). For example, the enclosure body includes first, second and third bags, the first bag covers the entire second and third bags, and the second and third bags are disposed in parallel in the first bag. In the third structure, for example, it is possible to express food texture in which citrus fruits of lined-up bunches are inside fondant .chocolate 
     When the enclosure body is configured as a plurality of bags, a granular material may be changed for each bag. For example, different granular materials may be used for one bag among the plurality of bags and another bag among the plurality of bags. For example, when the enclosure body includes first and second bags, coffee grounds may be sealed in the first bag and starch may be sealed in the second bag. For example, when the enclosure body includes first, second, and third bags, coffee grounds may be sealed in the first and second bags and starch may be sealed in the third bag. 
     When the enclosure body is configured as a plurality of bags, a material of the bag may be changed for each bag. For example, when the enclosure body includes first and second bags, the first bag may be formed of natural rubber and the second bag may be formed of silicon. For example, when the enclosure body includes first, second, and third bags, the first and second bags may be formed of natural rubber and the third bag may be formed of silicon. 
     When the enclosure body is configured as a plurality of bags, the density of a granular material is controlled for each bag. Thus, it is possible to present a user with food texture with different hardness for each part, specifically, food texture in which only a part with a high temperature is soft. 
     The density of the granular body may be controlled in at least one of the plurality of bags. In other words, the density of the granular body may not be controlled in one bag or several bags among the plurality of bags. 
     Further, by partitioning the bag  30  into a plurality of pieces and controlling the density of the granular material for each piece, it is possible to present a user with food textures with different hardness for each piece. 
     The pseudo-food texture presentation device  1  may further have a density measurement function (a density sensor) of measuring the density of the granular material sealed inside the bag  30 . For example, the density measurement function is capable of measuring the density of the granular material by pre-ascertaining the contents of the granular material inside the bag  30 , a volume (capacity) of the bag  30  in an initial state, and an air amount remaining in the bag  30  and measuring the volume (capacity) of the air discharged from the bag  30  or flowing in the bag  30 . 
     When the granular material flows in and out from the bag  30  with the discharge and inflow of air, the amount of the granular material inside the bag  30  is changed. By considering a change in an amount of air remaining in the bag  30  along with inflow or outflow of the granular material, it is possible to accurately measure the density of the granular material inside the bag  30 . 
     The CPU  11  of the pseudo-food texture presentation device  1  can calculate the hardness of the bag  30  based on the measured density of the granular material. 
     In the above-described example, the density of the granular material inside the bag  30  is changed by controlling the atmospheric pressure inside the bag  30  using the vacuum pump  20 . However, the density of the granular material may be changed by providing a structure in which the granular material flows in the bag  30  or flows out from the bag  30  and controlling the amount of the granular material which is inside the bag  30 . 
     Further, by combining the vacuum pump and the inflow or outflow of the granular material, it is possible to also change an increase or decrease the volume (size) and the shape of the bag  30  while keeping the hardness (or the density of the granular material) of the bag  30  or change the hardness while keeping the shape of the bag  30 . 
     Second Embodiment 
     (Configuration) 
       FIG. 9  is a block diagram schematically illustrating a configuration of a pseudo-food texture presentation device  2  according to Second embodiment. As illustrated in  FIG. 9 , the pseudo-food texture presentation device  2  includes the microcomputer  10 , the vacuum pump  20 , the bag  30 , the negative pressure sensor  40 , and the personal computer PC. In  FIG. 9 , similar reference signs are given to similar constituent elements to the constituent elements illustrated in  FIG. 2  and description of these constituent elements will be omitted. 
     The microcomputer  10  includes the CPU  11 , the RAM  12 , the record unit  13 , the duty ratio output unit  14 , the external device data input unit  15 , the data output interface (I/F)  16 , and the input unit  17 . The CPU  11  is connected to the random access memory (RAM)  12 , the recording unit  13 , the duty ratio output unit  14 , the external device data input unit  15 , the data output interface  16 , and the input unit  17  via the system bus BUS. 
     The recording unit  13  includes a program area in which a pseudo-food texture presentation processing program  13   g  is stored, an elapsed time/hardness correspondence recording unit  13   h , the hardness/atmospheric pressure correspondence recording unit  13   d , the atmospheric pressure/duty ratio correspondence recording unit  13   e , and the atmospheric pressure recording unit  13   f.    
     The pseudo-food texture presentation processing program  13   g  is executed by the CPU ail using the working area  12   a . When the pseudo-food texture presentation processing program  13   g  is executed by the CPU  11 , pseudo-food texture presentation processing to be described below is performed by the CPU  11 . 
     The elapsed time/hardness correspondence recording unit  13   h  pre-records a correspondence table (database) in which an elapsed time which is a time elapsed from a standard time corresponds to the hardness of the bag  30 . In the embodiment, the standard time is a time at which the bag  30  is in the mouth of the user  60 . The correspondence table may be set such that, for example, the hardness of the bag  30  is lower as the elapsed time increases. Since the correspondence table can be generated by a similar method to the method of generating the correspondence table recorded on the temperature/hardness correspondence recording unit  13   c  described in First embodiment, specific description thereof will be omitted. 
     The input unit  17  is, for example, a hardware button and is used for the user  60  to input, to the pseudo-food texture presentation device  2 , the fact that the bag  30  is in the user&#39;s mouth. The user presses the button at a timing at which the bag  30  is in the user&#39;s mouth. The input unit  17  is not limited to the button and may be another input device such as a microphone. When the input unit  17  is a microphone, the user inputs the fact that the bag  30  is in the user&#39;s mouth by voice. 
     The input unit  17  may be provided at a different location from the casing of the microcomputer  10 , for example, in the personal computer PC. 
     The pseudo-food texture presentation device  2  that has the foregoing configuration realizes pseudo-food texture presentation processing to be described subsequently by causing the CPU  11  to control an operation of each constituent element in response to a command described in the pseudo-food texture presentation processing program  13   g.    
     (Operation) 
       FIG. 10  is a diagram schematically illustrating pseudo-food texture presentation processing according to the embodiment. The pseudo-food texture presentation processing illustrated in  FIG. 10  is realized when the CPU  11  executes the pseudo-food texture presentation processing program  13   g . The pseudo-food texture presentation processing program  13   g  causes the CPU  11  to function as a determiner  13   g   1 , an elapsed time calculator  13   g   2 , a hardness calculator  13   g   3 , an atmospheric pressure controller  13   g   4 , and an atmospheric pressure control executer  13   g   5 . 
     The determiner  13   g   1  determines whether the bag  30  is in the mouth of the user  60  in response to an operation performed by the user  60  on the input unit  17 . In an example in which the user  60  presses a button when the bag  30  is in the mouth of the user  60 , it is determined that the bag  30  is in the user&#39;s mouth when the determiner  13   g   1  detects that the button is pressed. When the determiner  13   g   1  detects that the button is pressed again, the determiner  13   g   1  may determine that the bag  30  is taken out from her or his mouth of the user  60 . 
     When the determiner  13   g   1  determines that the bag  30  is in the mouth of the user  60 , the elapsed time calculator  13   g   2  calculates an elapsed time. Specifically, the elapsed time calculator  13   g   2  sets, as a standard time, a time at which the determiner  13   g   1  determines that the bag  30  is in the mouth of the user  60  and calculates the elapsed time from the standard time. 
     The hardness calculator  13   g   3  calculates the hardness of the bag  30  in accordance with the elapsed time calculated by the elapsed time calculator  13   g   2  with reference to the correspondence table recorded on the elapsed time/hardness correspondence recording unit  13   h.    
     The atmospheric pressure controller  13   g   4  and the atmospheric pressure control executer  13   g   5  perform same processing as that of the above-described atmospheric pressure controller  13   a   4  and the atmospheric pressure control executer  13   a   5  (see  FIG. 8 ). Therefore, description of the atmospheric pressure controller  13   g   4  and the atmospheric pressure control executer  13   g   5  will be omitted. 
     The pseudo-food texture presentation processing program  13   g  may cause the CPU  11  to further function as an atmospheric pressure receiver  13   g   6 . The atmospheric pressure receiver  13   g   6  performs the same processing as the above-described atmospheric pressure receiver  13   a   6  (see  FIG. 6 ). Therefore, description of the atmospheric pressure receiver  13   g   6  will be omitted. 
     That is, the processing performed to control the density of the granular material inside the bag  30  to realize the hardness calculated by the hardness calculator  13   g   3  is common between First and Second embodiments. 
     (Effects) 
     As described above, the pseudo-food texture presentation device  2  monitors, as an elapsed time, a time in which the bag  30  is in the mouth of the user  60 . The pseudo-food texture presentation. device  2  may reduce the density of the granular material inside the bag  30 , for example, as the elapsed time is longer. The hardness of the bag  30  is reduced by a jamming transition by reducing the density of the granular material inside the bag  30 . Thus, it is possible to present the user with food texture such as overall continuous softening texture, for example, food texture of an ice cream, when the time is elapsed. 
     MODIFICATION EXAMPLES 
     In the above-described example, based on an input by the user, it is determined that the bag  30  is in the user&#39;s mouth. A method of determining whether the bag  30  is in the user&#39;s mouth is not limited to the foregoing example. 
     For example, a humidity sensor is disposed on the bag  30  and the determiner  13   g   1  may perform the determination based on an outside humidity of the bag  30  measured by the humidity sensor. Specifically, the determiner  13   g   1  determines that the bag  30  is in the user&#39;s mouth when a measured value of humidity is less than a threshold at time t and is equal to or greater than the threshold at time t+. At difference between times t and t+1 is, for example, 10 milliseconds. The determiner  13   g   1  may determine that the bag  30  is taken out from the user&#39;s mouth when the measured value of humidity is equal to or greater than the threshold at time t and is less than the threshold at time t+1. Instead of the humidity sensor, a temperature sensor or a moisture sensor may be used. 
     When it is determined that the bag  30  is in the user&#39;s mouth, the CPU  11  may control the density of the granular material inside the bag  30 , in this example, the atmospheric pressure inside the bag  30 . When the determination is performed using a humidity sensor or a temperature sensor, it is determined that the bag  30  is in the user&#39;s mouth after the bag  30  is in the user&#39;s mouth. Therefore, by controlling the density of the granular material inside the bag  30  when it is determined that the bag  30  is in the user&#39;s mouth, it is possible to change the hardness of the bag  30  immediate after the bag  30  is the mouth of the user  60 . 
     The standard time is not limited to the time at which the bag  30  is in the mouth of the user  60 . The standard time may be a time before the bag  30  is in the mouth of the user  60 . That is, the elapsed time may be included in not only a period in which the bag  30  is in the mouth of the user  60  but also a period in which the bag  30  is not in the mouth of the user  60 . 
     A temperature sensor or a humidity sensor may be provided on the bag  30  and the density of the granular material inside the bag  30  may be controlled based on a cumulative value in accordance with an elapsed time of a temperature or humidity. In this case, the CPU  11  identifies, as the standard time, a time at which the bag  30  is in the mouth of the user  60  by one of the above-described method and calculates a cumulative value (a cumulative value over elapsed time) of measured values of the temperature or humidity from the standard time to a current time. Then, the CPU  11  calculates the hardness of the bag  30  in accordance with the calculated cumulative value of the measured values of the temperature or humidity and controls the density of the granular material inside the bag  30 , as described above. In this way, by controlling the density of the granular material based on two indexes of the elapsed time and the temperature or humidity, it is possible to improve reproduction of overall continuous softening food texture as in an ice cream. 
     For example, when the bag  30  is in the mouth of the user  60  and opens her or his mouth wide, the temperature or humidity of the ambient environment of the bag  30  temporarily decreases in some cases. In this case, the hardness of the bag  30  is temporarily returned (increased). By performing the control based on the cumulative value, it is possible to prevent the hardness of the bag  30  from being temporarily returned. 
     Third Embodiment 
     (Configuration) 
       FIG. 11  is a block diagram schematically illustrating a configuration of a pseudo-food texture presentation device  3  according to Third embodiment. As illustrated in  FIG. 11 , the pseudo-food texture presentation device  3  includes the microcomputer  10 , the vacuum pump  20 , the bag  30 , the negative pressure sensor  40 , a plurality of moisture sensors  52 , and the personal computer PC. In  FIG. 11 , similar reference signs are given to similar constituent elements to the constituent elements illustrated in  FIG. 2  and description of these constituent elements will be omitted. 
     The plurality of moisture sensors  52  are each disposed at a plurality positions (sensor positions) on the surface of the bag  30 . The moisture sensors  52  are disposed on the outer surface of the bag  30 . The moisture sensors  52  measure a moisture amount (a saliva amount) attached to the sensor positions and transmit measured values of the moisture amounts and moisture amount data including measurement times to the microcomputer  10 . The moisture sensors  52  obtains measured values at predetermined time intervals (for example, 10 millisecond intervals) and output the moisture amount data in real time. 
     It is preferable to provide the plurality of moisture sensors  52  according to the embodiment on the bag  30 , but only one moisture sensor  52  may be provided on the bag  30 . 
     The recording unit  13  in the microcomputer  10  includes a program area in which a pseudo-food texture presentation processing program  13   i  is stored, a moisture amount recording unit  13   j , a moisture amount/hardness correspondence recording unit  13   k , a hardness/atmospheric pressure correspondence recording unit  13   d , the atmospheric pressure/duty ratio correspondence recording unit  13   e , and the atmospheric pressure recording unit  13   f.    
     The pseudo-food texture presentation processing program  13   i  is executed by the CPU  11  using the working area  12   a . When the pseudo-food texture presentation processing program  13   i  is executed by the CPU  11 , pseudo-food. texture presentation processing to be described below is performed by the CPU  11 . 
     The moisture amount recording unit  13   j  records the moisture amounts measured by the plurality of moisture sensors  52  in association with measurement times. 
     The moisture amount/hardness correspondence recording unit  13   k  pre-records a correspondence table (database) in which a moisture amount attached to the bag  30  corresponds to the hardness of the bag  30 . The correspondence table may be set such that, for example, the hardiness of the bag  30  is lower as the moisture amount increases. Since the correspondence table can be generated by a similar method to the method of generating the correspondence table recorded on the temperature/hardness correspondence recording unit  13   c  described in First embodiment, specific description thereof will be omitted. 
     (Operation) 
       FIG. 12  is a diagram schematically illustrating pseudo-food texture presentation processing according to the embodiment. The pseudo-food texture presentation processing illustrated in  FIG. 12  is realized when the CPU  11  executes the pseudo-food texture presentation. processing program  13   i . The pseudo-food texture presentation processing program  13   i  causes the CPU  11  to function as a measured value receiver  13   i   1 , a moisture amount calculator  13   i   2 , a hardness calculator  13   i   3 , an atmospheric pressure controller  13   i   4 , and an atmospheric pressure control executer  13   i   5 . 
     The measured value receiver  13   i   1  receives moisture amount data from the plurality of moisture sensors  52  via the external device data input unit  15  and records the received moisture amount data on the moisture amount recording unit  13   j.    
     The moisture amount calculator  13   i   2  calculates a moisture amount attached to the bag  30  based on the moisture amount data received by the measured value receiver  13   i   1 . As an example, the moisture amount calculator  13   i   2  may calculate a sum value obtained by summing measured values (latest measured values) of the moisture amount measured at the plurality of sensor positions as the moisture amount attached to the bag  30 . As another example, the moisture amount calculator  13   i   2  may calculate a highest measured value among the measured values (latest measured values) of the moisture amount measured at the plurality of sensor positions as the moisture amount attached to the bag  30 . 
     The hardness calculator  13   i   3  calculates the hardness of the bag  30  in accordance with the moisture amount calculated by the moisture amount calculator  13   i   2  with reference to the correspondence table recorded on the moisture amount/hardness correspondence recording unit  13   k.    
     The atmospheric pressure controller  13   i   4  and the atmosphere pressure control executer  13   i   5  perform the same processing as the above-described atmospheric pressure controller  13   a   4  and the atmospheric pressure control executer  13   a   5  (see  FIG. 6 ). Therefore, description of the atmospheric pressure controller  13   i   4  and the atmospheric pressure control executer  13   i   5  will be omitted. 
     The pseudo-food texture presentation processing program  13   i  may cause the CPU  11  to further function as an atmospheric pressure receiver  13   i   6 . The atmospheric pressure receiver  13   i   6  perform the same processing as the above-described atmospheric pressure receiver  13   a   6  (see  FIG. 6 ). Therefore, description of the atmospheric pressure receiver  13   i   6  will be omitted. 
     That is, the processing performed to control the density of the granular material inside the bag  30  to realize the hardness calculated by the hardness calculator  13   i   3  is common between First and Third embodiments. 
     (Effects) 
     As described above, the pseudo-food texture presentation device  3  monitors a moisture (saliva) amount attached to the bag  30 . The pseudo-food texture presentation device  3  may reduce the density of the granular material inside the bag  30 , for example, as the moisture amount attached to the bag  30  is larger. The hardness of the bag  30  is reduced by a jamming transition by reducing the density of the granular material inside the bag  30 . Thus, it is possible to present the user with food texture such as overall continuous softening texture as a saliva amount attached to food increases. 
     MODIFICATION EXAMPLES 
     In the above-described example, the enclosure body is configured as one bag  30 . Instead of this, the enclosure body may be configured as the plurality of bags  30 . The enclosure body may have any one structure among the above-described first, second, and third structures. 
     For example, when the enclosure body has the first structure, the plurality of moisture sensors  52  are disposed on the plurality of bags  30 , respectively. The CPU  11  calculates the attached moisture amount for each bag  30  and controls the hardness for each bag  30  based on a calculation result. Thus, it is possible to present the user with food texture such as softening texture in only a part to which much saliva is attached. 
     The moisture amount calculator  13   i   2  may calculate a cumulative value obtained by accumulating the measured values of the moisture amounts from the standard time to the current time, that is, a cumulative value of the moisture amounts over the elapsed time, for each moisture sensor  52  and may calculate a sum of the cumulative values in the moisture sensors  52  per each sensor as a moisture amount attached to the bags  30 . The moisture amount calculator  13   i   2  may calculate a cumulative value obtained by accumulating the measured values of the moisture amounts from the standard time to the current time for each moisture sensor  52  and may calculate the largest value among the cumulative values in the moisture sensors  52  as the moisture amount attached to the bag  30 . 
     As a method of calculating the standard time or the elapsed time, a similar method to the method described in Second embodiment can be used. For example, it may be determined that the bag  30  is in the mouth of the user  60  based on comparison between a threshold and a moisture amount attached to the bag  30  and measured by a moisture sensor provide on the bag  30 , and that time may be set as the standard time. In the embodiment, based on a relative position or the like of the bag  30  to the mouth of the user  60 , it may be determined that the bag  30  is in the rnouth of the user  60 . 
     In the above-described embodiments, the index indicating an environment in which there is the bag  30  is measured, such as the temperature of the ambient environment of the bag  30 , the humidity of the ambient environment of the bag  30 , the temperature of the bag  30 , the moisture amount attached to the bag  30 , and the elapsed time from the time at which the bag  30  is in the mouth of the user  60 . Then, the density of the granular material inside the bag  30  is controlled based on the measured index and the hardness of the bag  30  is controlled using the jamming transition. Thus, it is possible to present a user with food texture in a pseudo-manner. 
     (Others) 
     In First embodiment, the seven stages are used as the hardness of the bag  30 . A method of identifying a combination of stages in which a person can perceive a difference in the hardness between the seven stages when a person masticates the bag  30  will be described. A similar method can also be applied to an operation (for example, an action of putting the bag  30  between a tongue and the upper jaw) of the mouth of a user on the bag  30  other than mastication. 
     First, an experiment (1. Experiment conditions, 2. Experiment method, and 3. Experiment result) in which a subject is allowed to masticate the bag  30  will be described. By referring to a result obtained from this experiment, it is possible to identify whether a person can perceive the difference in the hardness between any two stages in her or his mouth. 
     1. Experiment Conditions 
     The atmospheric pressure inside the bag  30  is changed in the range of 0 [kPa] to −60 [kPa] and the hardness of the bag  30  is changed from stages 1 to 7 by causing the vacuum pump  20  to suck air inside the bag  30 . 
     In an experiment method to be described below, the hardness between two stages (for example, between stages 1 and 2) set by the vacuum pump  20  is compared. In the comparison of the hardness, a Scheffe&#39;s paired comparison method is used. That is, a subject is allowed to masticate the bags  30  with two different types of hardness (for example, the hardness of stage 1 and the hardness of stage 2) in sequence to assess a level and the level is assessed by determining how much the stack is hard. All the stages in which the bags are assessment targets are combined. 
     Two different types of hardness may be generated using one bag  30  and the subject may be allowed to masticate the bag  30  with the two types of hardness in sequence. Two bags  30  with different types of hardness may be prepared and the subject may be allowed to masticate the two bags  30  with the different types of hardness in sequence. 
     Specifically, for example, the hardness at stage 1 and the hardness at stage 2 are compared to assess how much the bags are hard at which stages, for example, levels 1 to 5. When the levels are assessed in combination of stages 1 to 7, the levels are assessed in combination of  7 C 2 =21 in total. 
     That is, the levels are assessed in combination of stages 1 and 2, stages 1 and 3, . . . , and stages 1 to 7. Subsequently, the levels are assessed in combination of stages 2 and 3, stages 2 and 4, . . . , and stages 2 and 7. Further, the levels are assessed in combination of stages 3 and 4, stages 4 and 5, . . . , and stages 5 and 6. Finally, the levels are assessed in combination of stages 6 and 7. 
     Here, the five levels are assumed to be (i) “the first masticated bag is very harder”, (ii) “the first masticated bag is slightly harder”, (iii) “the first and second masticated bags are substantially the same hard”, (iv) “the second masticated bag is slightly harder”, and (v) “the second masticated bag is very harder”. The levels (i) to (v) are converted into scores (numerical values) 
     Specifically, with regard to the score at the first stage, the score i s converted into “4” when (i) is selected, the score is converted into “2” when (ii) is selected. Similarly, the score is converted into “0” when (iii) is selected, the score is converted into “−2” when (iv) is selected, and the score is converted into “−4” when (v) is selected. Conversely, with regard to the score at the second stage, the score is converted into “−4” when (i) is selected, and the score is converted into“−2” when (ii) is selected. Similarly, the score is converted into “0” when (iii) is selected, the score is converted into “2” when (iv) is selected, and the score is converted into “4” when (v) is selected. That i s, when a comparison target is perceived. to be hard, the score at each stage becomes larger. 
     In this way, the level assessment of relative hardness at each stage to a comparison stage is converted into the score. The score conversion is performed on the assessment of the foregoing 21 methods. 
     In This way, a numerical value obtained by averaging the scores at each stage is plotted as the relative score at each stage. A plotting result will be described below with reference to  FIG. 13 . 
     2. Experiment Method 
     In the experiment, the subject practices a job of the following (2-1) to (2-4) once. When the practice ends, steps of (2-1) to (2-4) are performed by the 21 methods. 
     (2-1) The user masticates the bag  30  of which the hardness is kept at the first stage by the vacuum pump  20  so that the following conditions (A) to (C) are satisfied for 10 seconds (this is referred to as first mastication). 
     (A) The mastication is performed between the upper front and back teeth on the right when viewed from the user  60 . 
     (B) The mastication is performed near the middle of the bag  30 . 
     (C) The mastication is performed as usual when the user always eats. 
     (2-2) When the mastication ends, the user waits for 10 seconds. While the user waits, the user equally extends the contents of the bag. 
     (2-3) The user masticates the bag  30  of which the hard is kept at the second stage by the vacuum pump  20  so that the foregoing conditions (A) to (C) are satisfied for 10 seconds (this is referred to as second mastication). 
     (2-4) At the time of ending, k subjects (where k is a natural number) assess the levels (i) to (v) to determine which bag is harder by comparing the first mastication (2-1) with the second mastication (2-3). 
     3. Experiment Result 
       FIG. 5  illustrates an experiment. result.  FIG. 5  is a diagram (a graph) illustrating a result of sensory assessment at each step plotted by the Scheffe&#39;s paired comparison method. The sensory assessment is assessing characteristics of a target (herein, the hardness of the bag  30 ) using the senses of the user. 
     First, a method of reading measured data in the graph will be described. A relative score at each stage is plotted on the horizontal axis (a psychological hardness scale) of the graph. The scores are results obtained when the k subjects assess the level of the relative hardness in combination of the 21 methods. Therefore, the score at each stage is plotted as a relative score on the psychological hardness scale. The horizontal axis of the graph represents the psychological hardness scale, 4 is a relative score indicating that the subject feels the hardest, and −4 is a relative score indicating that the subject feels the softest. 
     That is, for example, when stage 1 is seen from stage 2, the k subjects feel very soft at stage 1. As a result, when seen from stage 2, a difference from stage 1 is about “−1.7” on the psychological scale. 
     On the other hand, when the hardness of the bag  30  is increased at stage 5, stage 6, and stage 7, it can be known that the bags with the hardness at stages 5, 6, and 7 have different hardness from stage 2 when seen from stage 2. However, between stages 5, 6, and 7, the difference in the hardness is not felt so much. As a result, a difference between stages 5 and 6 on the psychological scale is about “0.4” and a difference between stages 6 and 7 is about “0.2” which are small values. 
     Then, for example, the subject feels considerably soft when the subject masticates the bag  30  with the hardness of stage 1 when seen from stage 7 than when the subject masticates the bag  30  of stage 7. As a result, a difference between stages 1 and 7 on the psychological scale is about “−3.8”. 
     Here, “*” or “**” is attached on a solid line between the stages, above the solid line, or below the solid line. The solid line, “*,” and “**” indicate that “there is a certain constant significant difference” between two stages (for example, stages 1to 2). The “significant difference” is not a difference caused by chance or due to an error and is a “meaningful difference”. 
     For example, stages 1 and 2 are connected by a solid line and “** (p&lt;0.01)” is assigned. Further, for example, stages 4 and 7 are connected by a solid line and “* (p&lt;0.05)” is assigned. 
     Here, p is a p value. The p value is an index used to determine whether the significant difference arises. When the p value is a value lower than a significant level (normally, 5%), it is determined that there is a significant difference. Further, the significant level is a probability serving as a standard at which a probability of a certain event arising is determined to be rarely an accident (to be significant). That is, when the p value obtained at the time of occurrence of a certain event (for example, a result that (i) “the first masticated bag is very hard” in the stage assessment at stages 1 and 2) is equal to or less than 5%, a measurement result obtained from the event is rarely considered to be an accident, that is, it is determined that there is a significant difference. 
     In this experiment, in the level assessment in which stage 1 and stages 2 to 7 are combined, stage 2 and stages 4 to 7 are combined, and stage 3 and stages 5 to 7 are combined, the p value=0.01 or less (&lt; significant level=1%) is obtained. Therefore, it is proved that the user  60  can perceive the difference in the hardness in her or his mouth at a probability of 99% or more. 
     In the assessment in which stages 4 and 7 are combined, 0.01&lt;p value&lt;0.05 is obtained. Therefore, it is proved that the user  60  can perceive the difference in the hardness in her or his mouth at a probability of 9% or more. 
     In this way, in this experiment, it is proved that the user  60  can perceive the difference in the hardness between stage 1 and stages 2 to 7, between the stage 2 and stages 4 to 7, between stage 3 and stages 5 to 7, and between stages 4 and 7. 
     A case in which the hardness of the bag  30  is changed from stage 7 to a lower stage will be considered. With reference to  FIG. 13 , there are the following five patterns when the hardness of the bag  30  is changed between. stages at which the subject can perceive the difference in the hardness. 
     (1) Stages 7, 4, 2, and 1 
     (2) Stages 7, 4, and 1 
     (3) Stages 7, 3, and 1 
     (4) Stages 7, 2, and 1 
     (5) Stages 7 and 1 
     When the hardness of the bag  30  is changed in accordance with pattern (1), a change in food texture (hardness) can be presented to the user at the four stages. In patterns (2) to (4), the change i. the food texture can be presented to the user at the three stages. In pattern (5), the change in the food texture can be presented to the user at the two stages. 
     Further, for example, when the hardness of the bag  30  is changed from stage 6 to a lower stage, the change in the food texture can be presented at a maximum of three stages. 
     Accordingly, it is preferable to use pattern (1) above in which the change in the food texture can be expressed at the most stages. 
     Similarly, when the hardness of the bag  30  is changed to a higher stage, it is preferable to use the pattern in which a stage such as stage 1, 2, 4, or 7 is changed. 
     In the above-described embodiments, the density of the granular material inside the bag  30  (the atmospheric pressure inside the bag  30 ) may be controlled so that the hardness of the bag  30  is changed between stages at which the difference in the hardness can be perceived. The density of the granular material inside the bag  30  may be controlled so that the hardness of the bag  30  is changed simply step by step (for example, stages 7, 6, 5, . . . , and 1). 
     The hardness of the bag  30  at each stage depends on a material, a thickness, or a shape of the bag  30 , the granular material, the amount of the granular material, or the like. Therefore, the foregoing combinations are exemplary combinations in which the stages at which the person can perceive the difference in the hardness when the person masticates the bag  30 . 
     Next, a method of generating the database recorded on the atmospheric pressure/duty ratio correspondence recording unit  13   e  will be described. 
     1. Procedure 
     (1) The duty ratio s changed from 0 [%] to 100 [%] (normally turned on). p (2) After each duty ratio is designated and 2 seconds has passed, an atmospheric pressure [kPa] inside the bag  30  is acquired 100 times an total at intervals of 10 [ms]. 
     (3) An average value of an atmospheric pressure [kPa] inside the bag  30  acquired 100 times is calculated. 
     2. Result 
     By performing the foregoing procedure, as illustrated in  FIG. 5 , the database indicating a relation between the duty ratio of the PWM signal for driving the vacuum pump  20  and the atmospheric pressure inside the bag  30  is obtained. 
     The present invention is not limited to the foregoing embodiments and various modifications can be made in execution steps within the scope of the present invention without departing from the gist of the present invention. Further, various inventions can be extracted by appropriately combining the plurality of constituent elements disclosed including the invention of the various steps in the foregoing embodiments. For example, when several constituent elements are deleted from all the constituent elements described in the embodiments or several constituent elements are combined but the problems mentioned in Technical Problem can be solved and the effects described in Effects of the Invention can be obtained, a configuration in which the constituent elements are deleted or combined can be extracted as an invention. 
     REFERENCE SIGNS LIST 
     
         
           1  Pseudo-food texture presentation device 
           10  Microcomputer 
           11  CPU 
           12  RAM 
           12   a  Working Area 
           13  Recording unit 
           13   a  Pseudo-food texture presentation processing program 
           13   a   1  Measured value receiver 
           13   a   2  Temperature calculator 
           13   a   3  Hardness calculator 
           13   a   4  Atmospheric pressure controller 
           13   a   5  Atmospheric pressure control executer 
           13   a   6  Atmospheric pressure receiver 
           13   b  Temperature recording unit 
           13   c  Temperature/hardness correspondence recording unit 
           13   d  Hardness/atmospheric pressure correspondence recording unit 
           13   e  Atmospheric pressure/duty ratio correspondence recording unit 
           13   f  Atmospheric pressure recording unit 
           14  Duty ratio output unit 
           15  External device data input unit 
           16  Data output interface 
           20  Vacuum pump 
           20   a  Suction opening 
           30  Bag 
           30   a  Air opening 
           40  Negative pressure sensor 
           50  Temperature sensor 
           60  User 
         GT 1 , GT 2  Flexible tube 
           2  Pseudo-food texture presentation device 
           13   g  pseudo-food texture presentation processing program. 
           13   g   1  Determiner 
           13   g   2  Elapsed time calculator 
           13   g   3  Hardness calculator 
           13   g   4  Atmospheric pressure controller 
           13   g   5  Atmospheric pressure control executer 
           13   g   6  Atmospheric pressure receiver 
           13   h  Elapsed time/hardness correspondence recording unit 
           17  Input unit 
           3  Pseudo-food texture presentation device 
           13   i  Pseudo-food texture presentation processing program 
           13   i   1  Measured value receiver 
           13   i   2  Moisture amount calculator 
           13   i   3  Hardness calculator 
           13   i   4  Atmospheric pressure controller 
           13   i   5  Atmospheric pressure control executer 
           13   i   6  Atmospheric pressure receiver 
           13   j  Moisture amount recording snit 
           13   k  Moisture amount/hardness correspondence recording unit 
           52  Moisture sensor