Patent Publication Number: US-2022232882-A1

Title: Baked item, method for preparing baked item, and microwave heating method for baked item

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/CN2020/114540, filed on Sep. 10, 2020, which claims priority to Chinese Patent Application No. 201910899623.X, filed on Sep. 23, 2019. The disclosures of the aforementioned applications are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     This application relates to the field of microwave heating, and in particular, to a baked item, a method for preparing the baked item, and a microwave heating method for the baked item. 
     BACKGROUND 
     A heat not burn technology refers to a method of baking a specific baked item (for example, a cigarette) through low-temperature heating without burning to generate vapor for a user to inhale. 
     Conventional low-temperature baking apparatuses mainly energize a heating element, the heating element generates heat through the Joule effect, and the heating element is in direct contact with the baked item (tobacco) to transfer the heat to the tobacco for baking. This method has problems such as a long preheating time and non-uniform cigarette baking, and the utilization efficiency of the tobacco is low. 
     Microwave heating is a process of utilizing continuous polarization of a heated material in a microwave electromagnetic field, and heating the material by using a dielectric loss (similar to internal friction) generated due to high-frequency reciprocating movement of dipoles inside the heated material. This method is characterized by a high heating speed and being capable of heating various parts of the baked item, so that the problems of a long preheating time and poor cigarette baking uniformity of the conventional electric heating method may be resolved. However, when heating a conventional cigarette, general microwave heating apparatuses cannot effectively heat the baked item to a target temperature, so it is difficult to effectively bake a tobacco to obtain a good taste. 
     SUMMARY 
     According to various embodiments of this application, a baked item is provided, including a tobacco and a microwave absorbing agent, where the tobacco and the microwave absorbing agent are both capable of absorbing microwaves to generate heat, the microwave absorbing agent is made of a non-volatile solid material with a stable dielectric loss constant, the dielectric loss constant of the microwave absorbing agent does not change along with temperature, the dielectric loss constant of the microwave absorbing agent is higher than a dielectric loss constant of lignocellulose in the tobacco, and the microwave absorbing agent is capable of stably absorbing microwaves to generate heat to heat the tobacco through thermal conduction. 
     In an embodiment, the microwave absorbing agent is one of or any combination of ceramic powder, an inorganic non-metal element, a ferrite absorbing agent, or metal powder. 
     In an embodiment, the ceramic powder includes one of or any combination of silicon carbide, silicon nitride, or aluminum nitride; the inorganic non-metal element includes one of or any combination of coke, carbon powder, or graphite powder; the ferrite absorbing agent includes Fe 3 O 4 ; and the metal powder includes one of or any combination of Ti powder, Fe powder, or Ni powder. 
     In an embodiment, the microwave absorbing agent is uniformly distributed in the tobacco, and a particle size of the microwave absorbing agent ranges from 2 μm to 200 μm. 
     In an embodiment, a ratio of a volume of the microwave absorbing agent to a volume of the tobacco ranges from 1% to 30%. 
     In an embodiment, a thermal conductivity of the microwave absorbing agent is higher than a thermal conductivity of the tobacco. 
     In an embodiment, the baked item is a cigarette, and the cigarette includes a tobacco portion, a filter portion, and a microwave filter membrane, where the tobacco portion includes the tobacco and the microwave absorbing agent; and the microwave filter membrane is disposed in the filter portion or between the filter portion and the tobacco portion. 
     In an embodiment, the microwave filter membrane is a metal foil, the metal foil is provided with a first through hole, airflow is capable of circulating from the first through hole, the metal foil is configured to reflect microwaves to prevent microwave leakage, and the first through hole is configured to intercept transmission of the microwaves. 
     This application further provides a method for preparing the foregoing baked item, including the following steps: 
     S 110 : pulverizing a tobacco raw material into a first component; 
     S 120 : adding an additive to the first component to obtain a second component through uniform mixing, and adding powder of the microwave absorbing agent into the second component and uniformly mixing to obtain a third component; or adding the microwave absorbing agent and the additive to the first component and uniformly mixing to obtain a fourth component through uniform mixing; and 
     S 130 : shaping the third component or the fourth component. 
     In an embodiment, the additive in step S 120  includes one of or any combination of an acidity regulator, a bulking agent, a humectant, a stabilization agent/coagulating agent, a thickening agent, or a natural flavoring agent. 
     In an embodiment, a manner for shaping the third component or the fourth component in step S 130  includes at least one of coating, die-casting, or thermoforming. 
     This application further provides a microwave heating method for the foregoing baked item, including the following steps: 
     S 210 : generating, by a microwave generator, microwaves to heat the baked item; and 
     S 220 : absorbing, by the tobacco and the microwave absorbing agent, the microwaves to generate heat, and further heating, by the microwave absorbing agent, the tobacco through thermal conduction. 
     In an embodiment, the microwave heating method for the baked item further includes a temperature control step S 230 : detecting, by a temperature detection unit, a temperature of the baked item, and transmitting a result of the detection to a circuit control unit, so that the circuit control unit controls a heating temperature of the baked item by controlling a working power of the microwave generator. In an embodiment, a manner in which the temperature detection unit detects the temperature of the baked item in step S 230  includes at least one of thermocouple temperature measurement, optical pyrometer temperature measurement, or infrared optical fiber temperature measurement. 
     In an embodiment, a manner in which the temperature detection unit detects the temperature of the baked item in step S 230  includes at least one of calculating a temperature of a cigarette according to a variation of a physical parameter of the cigarette or calculating a temperature of a cigarette according to a working power of the microwave generator. 
     Details of one or more embodiments of this application are provided in the accompanying drawings and descriptions below. Other features, objectives, and advantages of this application will become apparent from the specification, the accompanying drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic structural diagram of a cigarette according to an embodiment of this application; 
         FIG. 2  is a schematic structural diagram of a microwave heating apparatus according to an embodiment of this application; 
         FIG. 3  is a schematic diagram of an electrical connection relationship among electronic components in a microwave heating apparatus according to an embodiment of this application; 
         FIG. 4  is a flowchart of a method for preparing a baked item according to an embodiment of this application; and 
         FIG. 5  is a flowchart of a microwave heating method for a baked item according to an embodiment of this application. 
     
    
    
     To better describe and illustrate embodiments and/or examples in this application disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of any of the disclosed application, currently described embodiments and/or examples, and the best modes of this application currently understood. 
     DETAILED DESCRIPTION 
     To help understand this application, the following describes this application more comprehensively with reference to the related accompanying drawings. The accompanying drawings show exemplary implementations of this application. However, this application may be implemented in many different forms, and is not limited to the implementations described in this specification. On the contrary, the implementations are provided to make understanding of the disclosed content of this application more comprehensive. 
     It should be noted that, when a component is referred to as “being fixed to” another component, the component may be directly on the component, or an intervening component may be present. When a component is considered to be “connected to” another component, the component may be directly connected to the other component, or an intervening component may also be present. The terms “inter”, “outer”, “left”, “right” and similar expressions used in this specification are only for purposes of illustration but do not indicate a unique implementation. 
     When a baked item such as a conventional cigarette is heated by microwaves, the cigarette can hardly be effectively heated to a target temperature, so it is difficult to obtain a good taste. It is found through research that a specific reason mainly lies in that, general microwave heating frequency is 2.45 GHz, and a heating power of a material of a unit volume under action of a microwave field is P=2πf·ε 0 ε′ tan δ·/E/ 2 , where f is microwave frequency, ε′ tan δ is a dielectric loss constant of the material, ε 0  is a vacuum dielectric constant, and E is an intensity of a microwave electric field, so that the microwave heating is closely related to the dielectric loss constant of the material and the intensity of the microwave electric field. Main components of a cigarette include lignocellulose, some water, and additives such as glycerol and flavoring agent. A tobacco baking process mainly includes volatilization of the water, the glycerol, nicotine, and a plant volatile substance and thermolysis of some cellulose and lignin. In a microwave heating early stage of the cigarette, dielectric loss constants of the water (the dielectric loss constant is 10 to 20) and the glycerol are relatively high, so that the temperature of the tobacco can rise quickly. However, along with volatilization of the water and the glycerol, and a dielectric loss constant of the lignocellulose being relatively small, a temperature-rising rate of the tobacco may decrease quickly. Therefore, when a baked item such as a conventional cigarette is heated by microwaves, the baked item cannot be effectively heated to a target temperature, and according to a design of the cigarette, the target temperature is generally 250° C. to 400° C. 
     In an embodiment, the baked item is a cigarette  100 . As shown in  FIG. 1 , the cigarette  100  includes a filter portion  110 , a microwave filter membrane  120 , and a tobacco portion  130 . The tobacco portion  130  includes a tobacco  131  and a microwave absorbing agent  132 . The tobacco  131  is the same as a tobacco  131  in a common low-temperature baking cigarette. The tobacco  131  and the microwave absorbing agent  132  are both capable of absorbing microwaves to generate heat. The microwave absorbing agent  132  is made of a non-volatile solid material with a stable dielectric loss constant. The microwave absorbing agent  132  is capable of stably absorbing microwaves to generate heat to heat the tobacco  131  through thermal conduction. Under double heating of microwave radiation and thermal conduction, the temperature of the tobacco  131  can rise to an effective baking temperature. 
     The microwave absorbing agent  132  has a relatively stable dielectric loss constant. It should be noted that, the relatively stable dielectric loss constant of the microwave absorbing agent described herein refers to that the microwave absorbing agent is generally in a solid state and may not be volatilized or undergo a chemical reaction, so that the dielectric loss constant thereof may not change along with temperature, and the microwave absorbing agent can stably absorb microwaves to generate heat. The microwave absorbing agent  132  may be granular or sheet ceramic powder (for example, silicon carbide, silicon nitride, or aluminum nitride), an inorganic non-metal element (for example, coke, carbon powder, or graphite powder), a ferrite absorbing agent (for example, Fe 3 O 4 ), or even metal powder (for example, Ti, Fe, or Ni). The microwave absorbing agent  132  is added in a reproduction process of the tobacco, so that the microwave absorbing agent is uniformly distributed in the tobacco  131 . The microwave absorbing agent  132  may be one of or any combination of the foregoing ceramic powder, the inorganic non-metal element, the ferrite absorbing agent, or the metal powder. The dielectric loss constant of the microwave absorbing agent is generally higher than a dielectric loss constant of lignocellulose in the tobacco. For example, a dielectric loss constant of the silicon carbide is generally 0.02 to 0.2, a dielectric loss constant of graphite ranges from 0.01 to 0.2, and a dielectric loss constant of lignocellulose is generally lower than 1*10 −3 . 
     Mixing of the microwave absorbing agent  132  and the tobacco  131  is not common mechanical mixing, but is to dope the microwave absorbing agent  132  in the reproduction process of the tobacco  131 . In an embodiment, and with reference to  FIG. 4 , a method for preparing a tobacco  131  product mainly includes the following steps: 
     S 110 : pulverizing a tobacco raw material into a first component; 
     S 120 : adding a required additive to the first component obtained in step S 110  and uniformly mixing to form a second component, the required additive mainly including an acidity regulator, a bulking agent, a humectant, a stabilization agent/coagulating agent, a thickening agent, or a natural flavoring agent; and adding powder of the microwave absorbing agent  132  into the second component and uniformly mixing to obtain a third component; or adding the microwave absorbing agent  132  and the additive to the first component and uniformly mixing to obtain a fourth component; and 
     S 130 : shaping the third component or the fourth component by coating, die-casting, or thermoforming. According to the foregoing method for preparing the tobacco  131  product, the microwave absorbing agent  132  can be mixed in the tobacco  131  quite uniformly, to heat to the tobacco  131  through thermal conduction subsequently. 
     For a particle size of the microwave absorbing agent  132 , the portability of being mixed into the tobacco  131  is mainly considered, and it is difficult to mix the microwave absorbing agent into the tobacco when the particle size is too large. Therefore, in an embodiment, the particle size of the microwave absorbing agent  132  ranges from 2 μm to 200 μm. In another embodiment, the particle size of the microwave absorbing agent  132  ranges from 2 μm to 50 μm, and a ratio of a volume of the microwave absorbing agent  132  to a volume of the tobacco  131  ranges from 1% to 30%. In addition, generally, a thermal conductivity of the powder of the microwave absorbing agent  132  is higher than a thermal conductivity of the tobacco  131 . Therefore, adding the microwave absorbing agent  132  into the tobacco  131  can further improve the thermal conductivity of the entire cigarette  100 , to further improve the temperature uniformity of the cigarette  100  after being heated. 
     After the cigarette  100  including the microwave absorbing agent  132  is placed into a microwave heating apparatus, in addition to absorbing microwaves to generate heat, the tobacco  131  of the tobacco portion  130  may be further heated by the microwave absorbing agent  132  through thermal conduction, and temperature rising of the tobacco  131  is more stable and uniform under a double heating mechanism of microwave radiation and thermal conduction. In a volatilization process of materials such as water and glycerol in the tobacco  131 , the microwave absorbing agent  132  can provide stable heating through thermal conduction, to enable the temperature of the tobacco  131  to continue to rise to an effective baking temperature and produce unique smoked incense through thermolysis, thereby obtaining a good taste. 
     A main function of the microwave filter membrane  120  is to prevent microwaves from being leaked out from the filter portion  110 , and the microwave filter membrane may be located in the middle of the filter portion  110  or may be located at a boundary of the filter portion  110  and the tobacco portion  130 . In the embodiment shown in  FIG. 1 , the microwave filter membrane  120  is located in the filter portion  110 . In an embodiment, as shown in  FIG. 1 , the microwave filter membrane  120  is a metal foil or a metal sheet. The metal foil or the metal sheet is provided with a plurality of first through holes  121 , and airflow can flow normally at the first through hole  121  when the cigarette  100  is smoked. The metal material can reflect microwaves to prevent microwave leakage, and the first through hole  121  can intercept transmission of microwaves to play a role of shielding. 
     In an embodiment,  FIG. 2  shows a structure of the microwave heating apparatus configured to heat the cigarette  100 , the apparatus mainly includes a housing  210 , and a power supply  220 , a circuit control unit  230 , a microwave generator  240 , and an accommodation cavity  250  located in the housing  210 . The accommodation cavity  250  is configured to place the cigarette  100  including the microwave absorbing agent  132 ; and the microwave generator  240  is configured to generate microwaves to further heat the cigarette  100  in the accommodation cavity  250 .  FIG. 3  shows an electrical connection relationship among the electronic components in the microwave heating apparatus. As can be seen from  FIG. 3 , the circuit control unit  230  is electrically connected to the microwave generator  240  to control the microwave generator  240  to work; and the power supply  220  is electrically connected to the circuit control unit  230  to supply power to the microwave heating apparatus. 
     In an embodiment, as shown in  FIG. 2 , the microwave heating apparatus is further provided with a smoking set main control switch  260 , a display screen  270 , a microwave power control button  280 , a temperature detection unit (not shown in  FIG. 2 ), a charging interface  212 , and an airway hole  211  on the housing  210 , and the airway hole  211  is in communication with the accommodation cavity  250 . The electrical connection relationship among the electronic components in the microwave heating apparatus is shown in  FIG. 3 , the smoking set main control switch  260  is electrically connected to the power supply  220  or the circuit control unit  230  to turn on the microwave generator  240  to work; the display screen  270  is electrically connected to the circuit control unit  230 , to display a working power of the microwave generator  240  and/or a temperature in the accommodation cavity  250 ; the microwave power control button  280  is electrically connected to the circuit control unit  230  to adjust and control working frequency of the microwave generator  240 ; the temperature detection unit  400  is electrically connected to the circuit control unit  230  to detect a temperature of the cigarette  100  in the accommodation cavity  250  and transmit a detected temperature to the circuit control unit  230 ; and the charging interface  212  is electrically connected to the power supply  220  to charge the power supply  220  in the microwave heating apparatus. 
     In a specific embodiment, as shown in  FIG. 2 , the microwave generator  240  is a magnetron tube and can generate microwaves whose frequency is 2.45 GHz; and a microwave transmission channel  290  is further disposed between the microwave generator  240  and the accommodation cavity  250 , and the microwave transmission channel  290  is configured to transmit the microwaves generated by the microwave generator  240  to the accommodation cavity  250 . The accommodation cavity  250  is a cylindrical microwave resonator, the accommodation cavity  250  may be a metal material or may be a high-temperature-resistant organic material such as ceramic or teflon, but an inner side of the accommodation cavity  250  needs to include a metal reflecting layer, to enable microwaves to be vibrated and propagated inside the accommodation cavity  250 . A bottom of the accommodation cavity  250  is provided with a plurality of second through holes  251  facilitating entrance of airflow in an inhaling process and adjustment of inhaling resistance, and the airway hole  211  on the housing  210  of the microwave heating apparatus is in communication with the accommodation cavity  250  through the second through holes  251 . After the cigarette  100  is inserted into the accommodation cavity  250  of the microwave heating apparatus, the accommodation cavity  250  and the microwave filter membrane  120  in the cigarette  100  can form a microwave sealing cavity. Once the microwave generator  240  is turned on, microwaves are vibrated inside the accommodation cavity  250  to heat the tobacco portion  130  (including the tobacco  131  and the microwave absorbing agent  132 ) in the cigarette  100 , to increase the temperature of the tobacco portion of the cigarette  100  to a suitable temperature, thereby baking suitable vapor through thermolysis for a user to inhale. 
     In the embodiment shown in  FIG. 2 , the baked item is the cigarette  100 , and the cigarette  100  is provided with the microwave filter membrane  120 . It may be understood that, in some other embodiments, if the baked item only includes the tobacco  131  and the microwave absorbing agent  132 , and the baked item is not provided with the microwave filter membrane  120 , the microwave filter membrane  120  needs to be disposed at an airflow outlet of the accommodation cavity  250  on the microwave heating apparatus heating the baked item, to prevent microwaves inside the accommodation cavity  250  from being leaked out. 
     In an embodiment, and with reference to  FIG. 5 , the microwave heating method for the cigarette  100  includes the following steps: 
     S 210 : generating, by the microwave generator  240 , microwaves to heat the cigarette  100 ; and 
     S 220 : absorbing, by the tobacco  131  and the microwave absorbing agent  132  in the cigarette  100 , the microwaves to generate heat, and further heating, by the microwave absorbing agent  132 , the tobacco  131  through thermal conduction. The temperature of the tobacco  131  rising to an effective baking temperature under a dual heating mechanism of microwave radiation and thermal conduction. In some other embodiments, the microwave heating method for the cigarette  100  further includes a temperature control step S 230 : detecting, by the temperature detection unit  400 , a temperature of the cigarette  100 , and transmitting a result of the detection to the circuit control unit  230 , so that the circuit control unit  230  controls a heating temperature of the cigarette  100  by controlling a working power of the microwave generator  240 . 
     The temperature detection unit  400  can directly or indirectly detect the temperature of the cigarette  100 . A direct temperature measurement manner includes thermocouple temperature measurement, optical pyrometer temperature measurement, and infrared optical fiber temperature measurement, where the infrared optical fiber temperature measurement is performed according to infrared electromagnetic waves radiated on a surface of the cigarette. An indirect temperature measurement manner mainly includes calculating according to experience, for example, calculating the temperature of the cigarette according to a variation of a physical parameter of the cigarette or calculating the temperature of the cigarette according to the working power of the microwave generator. A temperature control manner of the cigarette may be power feedback-type temperature control, namely, the heating temperature of the cigarette is controlled by the circuit control unit by controlling working frequency of the microwave generator. The microwave power control button  280  includes a certain quantity of adjustment grades. For example, in an embodiment, the microwave power control button includes six grades, which indicates that the cigarette includes six different balance temperatures, and generally, the balance temperatures range from 250° C. to 400° C. with 20° C. as a stage. 
     According to the baked item in this application, the microwave absorbing agent  132  is added into the tobacco  131 , the microwave absorbing agent  132  is made of a non-volatile solid material with a stable dielectric loss constant, and the microwave absorbing agent  132  is capable of stably absorbing microwaves to generate heat to heat the tobacco  131  through thermal conduction. After the baked item of this application is placed into a microwave heating apparatus, in addition to absorbing microwaves to generate heat, the tobacco  131  of the tobacco portion  130  may be further heated by the microwave absorbing agent  132  through thermal conduction, and temperature rising of the tobacco  131  is more stable and uniform under a double heating mechanism of microwave radiation and thermal conduction. In a volatilization process of materials such as water and glycerol in the tobacco  131 , the microwave absorbing agent  132  can provide stable heating through thermal conduction, to enable the temperature of the tobacco  131  to continue to rise to an effective baking temperature and produce unique smoked incense through thermolysis, thereby obtaining a good taste. 
     In an embodiment, silicon carbide ceramic powder, carbon powder, Fe 3 O 4 , and a composite additive of silicon carbide and carbon powder (a weight proportion is 1:1) are used as the microwave absorbing agent, to measure a temperature-rising rate of the cigarette under action of microwaves in different particle sizes and mixture ratios. A working power of the microwave generator is 30 W, frequency of microwaves generated by the microwave generator is 2.45 GHz, an internal temperature of the cigarette is measured through thermocouple temperature measurement, and the temperature is controlled to be around 300° C. in the power feedback-type temperature control manner. As shown in Table 1, D50 in Table 1 refers to a median of the particle sizes. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Particle  
                   
                   
                   
                   
               
               
                   
                 size 
                 Ratio  
                   
                   
                   
               
               
                 Microwave 
                 of the  
                 of the 
                   
                   
                 t = 3 min 
               
               
                 absorbing  
                 absorbing  
                 absorbing 
                   
                   
                 (balanced  
               
               
                 agent 
                 agent/D50 
                 agent/% 
                 t = 5 s 
                 t = 10 s 
                 state) 
               
               
                   
               
             
            
               
                 None (common 
                 / 
                 / 
                  68° C. 
                  83° C. 
                  95° C. 
               
               
                 cigarette) 
                   
                   
                   
                   
                   
               
               
                 SiC 
                  5 μm 
                 10% 
                 104° C. 
                 165° C. 
                 296° C. 
               
               
                 SiC 
                 15 μm 
                 20% 
                 158° C. 
                 246° C. 
                 295° C. 
               
               
                 SiC 
                 15 μm 
                 30% 
                 235° C. 
                 298° C. 
                 295° C. 
               
               
                 SiC 
                 25 μm 
                 30% 
                 240° C. 
                 296° C. 
                 298° C. 
               
               
                 Carbon powder 
                 15 μm 
                 20% 
                 180° C. 
                 265° C. 
                 296° C. 
               
               
                 Carbon powder 
                 25 μm 
                 30% 
                 275° C. 
                 295° C. 
                 298° C. 
               
               
                 Fe 3 O 4  powder 
                 15 μm 
                 20% 
                  82° C. 
                 128° C. 
                 296° C. 
               
               
                 Fe 3 O 4  powder 
                 25 μm 
                 30% 
                 125° C. 
                 163° C. 
                 295° C. 
               
               
                 Sic/C powder  
                 15 μm 
                 20% 
                 235° C. 
                 298° C. 
                 298° C. 
               
               
                 (1:1) 
               
               
                   
               
            
           
         
       
     
     As can be seen from the data in Table 1, after the temperature of the common cigarette rises to about 80° C., it is difficult for the temperature to continue to rise. Addition of the microwave absorbing agent can increase the temperature-rising rate of the cigarette, to raise the temperature of the cigarette to a temperature designed by temperature control. As the content of the microwave absorbing agent increases, the temperature-rising rate of the cigarette may be increased, and the particle size of the microwave absorbing agent has no apparent impact on the temperature-rising rate. 
     The technical features in the foregoing embodiments may be combined. For concise description, not all possible combinations of the technical features in the embodiments are described. However, provided that combinations of the technical features do not conflict with each other, the combinations of the technical features are considered as falling within the scope described in this specification. 
     The foregoing embodiments merely express several implementations of this application. The descriptions thereof are relatively specific and detailed, but should not be understood as limitations to the scope of this application. It should be noted that for a person of ordinary skill in the art, several transformations and improvements can be made without departing from the idea of this application. These transformations and improvements belong to the protection scope of this application. Therefore, the protection scope of the patent of this application shall be subject to the appended claims.