Method for producing smoked food having reduced polycyclic aromatic hydrocarbon content, method for reducing polycyclic aromatic hydrocarbon content in smoked food, and smoked food having reduced polycyclic aromatic hydrocarbon content

Abstract

The present invention relates to a method for producing smoked food, the method comprising: a step for generating smoke by heating wood; a step for filtering the smoke generated in the preceding step through a filtration section heated to 80°C or higher; and a step for smoking a food item by exposing the food item to the smoke filtered in the preceding step.　According to the present invention, it is possible to provide a method for producing smoked food having a reduced content of polycyclic aromatic hydrocarbon such as benzo[a]pyrene and having a pleasant smoky aroma, and to provide smoked food that achieves both a reduction in polycyclic aromatic hydrocarbon content and a pleasant smoky aroma.

Description

Method for producing smoked foods with reduced polycyclic aromatic hydrocarbon content, method for reducing the polycyclic aromatic hydrocarbon content in smoked foods, and smoked foods with reduced polycyclic aromatic hydrocarbon content

[0001] The present invention relates to a method for producing a smoked food product having a reduced polycyclic aromatic hydrocarbon content and a good smoked aroma, a method for reducing the polycyclic aromatic hydrocarbon content in a smoked food product while favorably retaining smoked aroma components, and a smoked food product having a reduced polycyclic aromatic hydrocarbon content and a good smoked aroma.

[0002] Smoked foods are traditionally preserved foods made by salting or pickling dried bonito flakes, as well as meat, seafood, and eggs, seasoning them, drying them, and then exposing them to smoke to enhance their flavor. In smoked foods, the antibacterial properties of the smoke penetrate the food. Prolonged exposure to smoke reduces the moisture content of the food, lowering its water activity and improving its shelf life. Smoking is a food processing technique that involves heating hardwoods (such as zelkova, oak, konara oak, teak, beech, and sawtooth oak), fragrant cherry, sawdust, apple, and hickory, to high temperatures, exposing the food to smoke, thereby enhancing flavor and allowing the antibacterial and antiseptic properties of the smoke to penetrate the food. Complete combustion of wood produces carbon dioxide and water vapor, resulting in little smoke. Therefore, an incomplete combustion environment is intentionally created to produce smoke. However, incomplete combustion of wood produces polycyclic aromatic hydrocarbons such as benzo[a]pyrene, benzo[a]anthracene, benzo[b]fluoranthene, and chrysene. Many of these polycyclic aromatic hydrocarbons have been reported to be carcinogenic, mutagenic, and teratogenic, and restrictions on them are being considered or strengthened in many countries, including Europe and the United States.

[0003] Therefore, efforts have been made to reduce the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene in smoked foods. For example, dried fish is produced in two stages: a drying process in which unnecessary parts (head, internal organs, etc.) are removed from the raw fish, washed with water, cut into pieces (raw cut), and then boiled and dried with hot air, followed by repeated drying and steaming; and a smoking process in which plant materials are burned, burned incompletely, or thermally decomposed to generate smoke, and the smoke components are attached to or brought into contact with the dried fish. In the smoking process, a direct current or alternating current voltage is applied to the dried and shaped fish or smoke, causing the smoke components to attach to the dried and shaped fish in a short period of time, thereby producing dried fish with a smoky or smoky aroma and a benzo[a]pyrene content of 5. Proposed technologies include a technique for producing dried fish with a controlled concentration of 0 ppb by mass or less (Patent Document 1), and a technique for using an edible coating material that can be reversibly dissolved or eluted by exposure to hot water or steam at 30°C or higher and then formed into a film by cooling and / or drying, dissolving or eluting the coating material to coat the surface of a food material, forming a temporary film that is then fixed, and then smoking the food material to attach harmful components contained in the smoke to the film, and after the smoking process, exposing the film to hot water or steam at 30°C or higher to dissolve or elute the film and remove it from the surface of the food material (Patent Document 2). Another proposed technology involves filtering smoke through a filter made of zeolite before smoking, and it has been reported that 93% or more of the polycyclic aromatic hydrocarbons in the smoke were removed (Non-Patent Document 1).

[0004] However, it has been observed that when the polycyclic aromatic hydrocarbon content in smoked foods is reduced, the smoked aroma components used for smoking are also reduced at the same time, and it has not been possible to achieve both a reduction in polycyclic aromatic hydrocarbons and a satisfactory and sufficient smoked aroma in the smoked foods. Therefore, there is a need for a smoked food that achieves both a reduction in the polycyclic aromatic hydrocarbon content and a satisfactory and sufficient smoked aroma in the smoked foods.

[0005] JP 2016-171777 A JP 2020-110071 A

[0006] Smoked foods are tastier, less harmful with a tip from the auto industry, Science Daily, March 20, 2018, American Chemical Society; https: / / www.sciencedaily.com / releases / 2018 / 03 / 180320084409.htm

[0007] Therefore, the present invention aims to provide a method for producing a smoked food product in which the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene is sufficiently reduced and which has a good smoked aroma, and to provide a smoked food product in which both the content of polycyclic aromatic hydrocarbons and the good smoked aroma are reduced.

[0008] As a result of extensive research aimed at solving the above-mentioned problems, the inventors of the present invention have discovered that by filtering smoke generated by heating wood through a heated filtration section so as to suppress condensation, and then exposing food materials to the filtered smoke to smoke them, it is possible to reduce the polycyclic aromatic hydrocarbon content in smoked foods while still allowing the smoky aroma components to remain satisfactorily. Further research led to the completion of the present invention. The inventors also discovered that it is possible to reduce the polycyclic aromatic hydrocarbon content in smoked foods while still retaining the smoke aroma components by passing smoke generated by, for example, heating wood through a filtration section heated to suppress condensation, or by passing smoke generated by, for example, heating wood through a flow path heated to suppress condensation and filtering the smoke through the filtration section, and then exposing food materials to the filtered smoke for smoking; or by passing smoke generated by, for example, heating wood through a filtration section and then introducing the filtered smoke into a smoking section through a flow path heated to suppress condensation and then exposing food materials to the smoke for smoking; and further investigation led to the completion of the present invention.

[0009] Accordingly, the present invention relates to the following: [1] A method for producing smoked foods, comprising the steps of heating wood to generate smoke, filtering the smoke generated in the aforementioned step by passing it through a filtration section heated to 80°C or higher, and exposing food materials to the smoke filtered in the aforementioned step to smoke them. [2] The method according to [1], wherein the filtration section is constructed by placing, attaching to, or filling a porous filter medium in a filter. [3] The method according to [1] or [2], wherein the filtration section is heated to 100°C or higher. [4] The method according to [1] or [2], wherein the filtration section is heated to prevent condensation from forming in the filtration section. [5] The method according to any one of [2] to [4], wherein the porous filter medium is one or more types of porous particles selected from the group consisting of diatomaceous earth, cellulose, and perlite, each having an average particle size of 114 μm or less, and zeolite, each having an average particle size of 1.9 mm or less. [6] The manufacturing method according to any one of [1] to [5], wherein the polycyclic aromatic hydrocarbon content in the smoked food is 50% or less of the polycyclic aromatic hydrocarbon content in a smoked food smoked by exposure to unfiltered smoke. [7] The manufacturing method according to any one of [1] to [6], wherein the residual rate of smoky aroma components indicated by guaiacol, 2-methylphenol, and phenol in the smoked food is 40% or more of the content of said smoky aroma components in the smoked food smoked by exposure to unfiltered smoke. [8] The manufacturing method according to any one of [1] to [5], wherein the polycyclic aromatic hydrocarbon content in the smoked food is 50% or less of the polycyclic aromatic hydrocarbon content in a smoked food smoked by exposure to unfiltered smoke, and the residual rate of smoky aroma components indicated by guaiacol, 2-methylphenol, and phenol in the smoked food is 40% or more of the content of said smoky aroma components in the smoked food smoked by exposure to unfiltered smoke. [9] The manufacturing method according to any one of [1] to [8], wherein the smoked food is dried fish flakes.

[10] A method for reducing the content of polycyclic aromatic hydrocarbons in smoked foods while retaining the smoky aroma components, comprising: filtering smoke generated by heating wood through a filtration section heated to 80°C or higher; and exposing food materials to the filtered smoke to smoke them.

[11] The method according to

[10] , wherein the filtration section is constructed by installing, attaching, or filling a porous filter medium in a filter.

[12] The method according to

[10] or

[11] , wherein the filtration unit is heated to 100°C or higher.

[13] The method according to any one of

[10] to

[12] , wherein the filtration unit is heated so as not to cause condensation in the filtration unit.

[14] The method according to any one of

[11] to

[13] , wherein the porous filter medium is one or more types of porous particles selected from the group consisting of diatomaceous earth, cellulose, and perlite, each having an average particle size of 114 μm or less, and zeolite, each having an average particle size of 1.9 mm or less.

[15] The method according to any one of

[10] to

[14] , wherein the polycyclic aromatic hydrocarbon content is reduced to 50% or less of the polycyclic aromatic hydrocarbon content in a smoked food smoked by exposure to unfiltered smoke.

[16] The method according to any one of

[10] to

[15] , wherein the residual rate of smoke aroma components, indicated by guaiacol, 2-methylphenol, and phenol, in a smoked food is 40% or more of the smoke aroma component content in a smoked food smoked by exposure to unfiltered smoke.

[17] The method according to any one of

[10] to

[14] , wherein the polycyclic aromatic hydrocarbon content is reduced to 50% or less of the polycyclic aromatic hydrocarbon content in a smoked food smoked by exposure to unfiltered smoke, and the residual rate of smoky aroma components, indicated by guaiacol, 2-methylphenol, and phenol, in the smoked food is 40% or more of the content of said smoky aroma components in the smoked food smoked by exposure to unfiltered smoke.

[18] The method according to any one of

[10] to

[17] , wherein the smoked food is dried fish.

[19] A smoked food, wherein the polycyclic aromatic hydrocarbon content is reduced to 50% or less of the polycyclic aromatic hydrocarbon content in a smoked food smoked by exposure to unfiltered smoke, and the residual rate of smoky aroma components, indicated by guaiacol, 2-methylphenol, and phenol, is 40% or more of the content of said smoky aroma components in the smoked food smoked by exposure to unfiltered smoke.

[20] The smoked food according to

[19] , wherein the smoked food is dried fish.

[21] A method for producing smoked foods, comprising the steps of generating smoke, passing the smoke generated in the generating step through a filtration section heated to suppress condensation, or passing the smoke generated in the generating step through a filtration section via a flow path heated or heated to suppress condensation, and filtering the smoke, and exposing food materials to the smoke filtered in the generating step to smoked food; or the method comprises the steps of generating smoke, passing the smoke generated in the generating step through a filtration section to filter the smoke, and introducing the smoke filtered in the generating step into a smoking section via a flow path heated or heated to suppress condensation, and exposing food materials to the smoke to smoked food.

[22] The method according to

[21] , wherein the filtration section is heated to 80°C or higher.

[23] The method according to

[21] or

[22] , wherein the flow path is heated or heated to 30°C to 250°C.

[24] The method according to any of

[21] to

[23] , wherein the filtration section comprises a filter and a filter medium.

[25] The manufacturing method according to any one of

[21] to

[24] , wherein the smoked food is dried fish.

[26] A method for reducing the polycyclic aromatic hydrocarbon content in a smoked food while retaining smoky aroma components, comprising: passing generated smoke through a filtration section heated to suppress condensation, or passing through a flow path heated or heated to suppress condensation through the filtration section, and then filtering the smoked smoke; and exposing food materials to the filtered smoke for smoking; or filtering the generated smoke through a filtration section, and introducing the filtered smoked smoke into a smoking section through a flow path heated or heated to suppress condensation, and then exposing food materials to the smoke for smoking.

[27] The method according to

[26] , wherein the filtration section is heated to 80°C or higher.

[28] The method according to

[26] or

[27] , wherein the flow path is heated or heated to 30°C to 250°C.

[29] The method according to any one of

[26] to

[28] , wherein the filtration section comprises a filter and a filter medium.

[30] The method according to any one of

[26] to

[29] , wherein the smoked food is dried fish.

[0010] The present invention provides a method for producing a smoked food product in which the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene is sufficiently reduced and which has a good smoked aroma. The present invention also provides a method for reducing the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene while maintaining good smoked aroma components in a smoked food product. Furthermore, the present invention provides a smoked food product in which the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene is sufficiently reduced and which has a good smoked aroma.

[0011] Fig. 1 is a diagram showing the effect of the heating temperature of the filtration section on the respective residual rates of guaiacol, 2-methylphenol, and phenol, which are used as indicators of smoke aroma components, in Test Example 3. Fig. 2 is a diagram showing the effect of the material of the porous filter medium of the filtration section on the respective residual rates of guaiacol, 2-methylphenol, and phenol, which are used as indicators of smoke aroma components, in Test Example 4. Fig. 3 is a diagram showing an outline of the apparatus used in producing dried bonito flakes in Examples 1 to 5 and Comparative Examples 1 to 3. Fig. 4 is a diagram showing an outline of the roasting and drying apparatus used in producing smoked foods in Examples 6 to 15 and Comparative Examples 4 to 13.

[0012] The present invention provides a method for producing smoked foods (hereinafter also referred to as the "production method of the present invention"), which includes the steps of heating wood to generate smoke, filtering the smoke generated in the above step through a heated filter section to suppress condensation, and exposing food materials to the smoke filtered in the above step to smoke them.

[0013] In another aspect, the manufacturing method of the present invention includes a step of generating smoke, a step of passing the smoke generated in the step through a filtration section that is heated to suppress condensation or through a flow path that is heated or warmed to suppress condensation and filtering the smoke, and a step of exposing food materials to the smoke filtered in the step. Alternatively, the manufacturing method of the present invention includes a step of generating smoke, a step of passing the smoke generated in the step through a filtration section and filtering the smoke, and a step of introducing the smoke filtered in the step into a smoking section through a flow path that is heated or warmed to suppress condensation and exposing food materials to the smoke.

[0014] Smoked foods produced by the production method of the present invention are not particularly limited as long as they are produced by exposing ingredients to smoke generated by heating wood or the like, and are foods that have improved shelf life and a unique flavor, and examples include dried fish such as bonito flakes, dried bonito flakes, tuna flakes, mackerel flakes, sardines flakes, and horse mackerel flakes, smoked seafood products such as dried scallops, smoked salmon, smoked oyster products, seasoned smoked squid products, and smoked kamaboko, smoked meat products such as ham, sausage, and bacon, smoked dairy products such as smoked cheese, and smoked eggs. The production method of the present invention is particularly preferably applied to the production of dried fish such as bonito flakes, dried bonito flakes, tuna flakes, mackerel flakes, sardines, and horse mackerel flakes.

[0015] In the "smoke-generating step" included in the manufacturing method of the present invention, wood used to generate smoke can be wood commonly used in the manufacture of smoked foods. Preferably, chipped wood from hardwoods (such as zelkova, oak, konara oak, oak, teak, beech, and sawtooth oak), cherry, walnut, apple, and hickory is used. Commercially available smoking materials can be used as such wood. The wood needs only to be heated to a temperature sufficient to generate smoke. For the manufacture of dried fish, the temperature is typically about 200°C to 650°C, preferably about 350°C to 600°C, and more preferably about 400°C to 550°C. For other smoked foods, the temperature is typically about 100°C to 600°C, preferably about 200°C to 550°C, more preferably about 200°C to 400°C, and even more preferably about 200°C to 300°C. Methods for heating wood include igniting the wood, heating the wood using radiant heat from a high-temperature electric heating coil, electric heater, iron plate, etc., heating the wood with a gas such as superheated steam, and rubbing the wood against metal. Wood can also be heated using a commercially available smoke generator or carbonization device.

[0016] In addition, the "smoke-generating step" included in another embodiment of the manufacturing method of the present invention includes generating smoke by heating wood, as well as by means other than heating wood. In this embodiment, the "smoke-generating step" also includes generating smoke by heating non-wood combustion materials such as bagasse (a plant material derived from sugarcane), corn cobs, or coconut husks, or by heating food residues such as tea leaves, coffee, or coffee grounds. Methods similar to those used to heat wood can be used to heat non-wood combustion materials, tea leaves, coffee, or food residues, as long as they are heated to a temperature sufficient to generate smoke. For the production of dried fish, heating is typically performed at about 200°C to 650°C, preferably about 350°C to 600°C, and more preferably about 400°C to 550°C. For other smoked foods, heating is typically performed at about 100°C to 600°C, preferably about 200°C to 550°C, more preferably about 200°C to 400°C, and even more preferably about 200°C to 300°C.

[0017] In the "filtering step" included in the manufacturing method of the present invention, filtering methods commonly used in gas filtration, such as filtration / dust removal, gravity settling, inertial separation, centrifugal force dedusting (vortex type, axial flow type), washing dedusting, and electrostatic precipitator, can be used, but from the viewpoint of the efficiency of removing polycyclic aromatic hydrocarbons, a filtering / dust removal method in which a filter medium is packed in a filter is preferably used. Therefore, in the "filtering step" included in the manufacturing method of the present invention, the filtration section through which the smoke generated in the above step passes for filtration comprises a filter and a filter medium, and is preferably constructed by installing, attaching, or packing a filter medium in a tank-, box-, or disk-shaped filter made of metal, glass, highly heat-resistant resin, or the like. In the production method of the present invention, examples of the filter material constituting the filtration section include porous particles such as inorganic porous particles and organic porous particles; filters made of glass fiber or highly heat-resistant resin, such as bag filters, prefilters, ULPA filters (ultra-high performance filters), HEPA filters (high performance filters), quasi-HEPA filters, and MEPA filters (medium performance filters); and nonwoven fabric filters made of metal or glass wool. In the present invention, a filtration section constructed by installing or attaching porous filter material, such as a glass fiber filter, nonwoven fabric filter, or porous particles, or by filling the metal filter is more preferably used. In the production method of the present invention, commercially available products can be used as the porous filter material preferably used to constitute the filtration section. The size of the filter can be set depending on the amount of smoke to be filtered, but for example, in small-scale production of smoked foods at a laboratory level, a filter size of 17 cm is preferred. ２ ~50cm ２ In the production of smoked foods at the concept / performance test (CP test) level, a filter having a filtration area of ​​about 34 m is preferably used. ２ ~111m ２ A filter having a filtering area of ​​about this size is used.

[0018] In the manufacturing method of the present invention, porous particles can be more preferably used as a porous filter medium. Examples of porous particles that can be used include those commonly used as filter media, filter aids, adsorbents, etc., such as inorganic porous particles such as diatomaceous earth, perlite, and zeolite, and organic porous particles such as cellulose. Diatomaceous earth is a porous deposit (sedimentary rock) composed primarily of silicon dioxide, which is formed from fossilized diatom shells, and is primarily used as a filter aid. In the present invention, commercially available products such as "Radiolite" (Showa Chemical Industry Co., Ltd.) can be used. Perlite is a general term for glassy volcanic rock that expands upon heating and is classified as perlite, obsidian, and rosinite. Porous materials obtained by crushing and separating foamed perlite are used as filter aids. In the present invention, commercially available products such as "Topco Perlite" (Tohko Perlite Industry Co., Ltd.) can be used. Zeolites are microporous crystalline aluminosilicates, and are divided into natural zeolites and synthetic zeolites. They are used as molecular sieves, ion exchange materials, catalysts, adsorbents, etc. In the present invention, commercially available products such as "Shimane Prefecture Natural Zeolite" (Shinsei Co., Ltd.) and "Nitto Zeolite" (Nitto Funka Kogyo Co., Ltd.) can be used. Cellulose is the main component that constitutes the cell walls and fibers of trees and plants, and is a polysaccharide in which glucose is bonded β-1,4. In the present invention, commercially available products offered as cellulose filter aids (for example, "VITACEL" (Rettenmeyer), etc.) can be used.

[0019] When the porous filter medium is a porous particle having physical adsorption ability, such as diatomaceous earth, perlite, or cellulose, the average particle diameter measured by laser diffraction / scattering is preferably 114 μm or less, more preferably 14 μm to 114 μm, and even more preferably 25 μm to 114 μm. When the porous filter medium is a porous particle having chemical adsorption ability, such as zeolite, the average particle diameter measured by laser diffraction / scattering is preferably 1.9 mm or less, more preferably 16 μm to 1.9 mm. In this specification, the term "average particle diameter" refers to the average particle diameter corresponding to 50% of the cumulative volume distribution curve obtained by measuring particle diameters by laser diffraction / scattering.

[0020] Considering the adsorption of the smoky aroma components in smoke in addition to the adsorption and removal effect of polycyclic aromatic hydrocarbons, porous particles with physical adsorption ability, such as diatomaceous earth, perlite, and cellulose, are preferably used rather than porous particles with chemical adsorption ability, such as zeolite.

[0021] The thickness (layer thickness) of the porous particle layer packed in the filtration section is usually 0.3 mm to 10 mm, preferably 3 mm to 6 mm, and more preferably 4 mm to 6 mm.

[0022] In the "filtering step" included in the manufacturing method of the present invention, the filtration section must be heated to suppress condensation. Here, "condensation" refers to the phenomenon of condensation of water vapor in the air. The presence or absence of condensation can be evaluated visually or using a commercially available dew meter, and the amount of condensation can be measured using a commercially available dew meter. The heating temperature of the filtration section can be determined as a temperature that can suppress condensation in the filtration section depending on the thermal conductivity of the filter material and the heating method, but is usually 80°C or higher, preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, even more preferably 130°C or higher, and even more preferably 140°C or higher. In addition, considering the heat resistance of the filter and the effect of suppressing condensation, the heating temperature of the filtration section is usually 250°C or lower, preferably 200°C or lower. In one embodiment of the present invention, the heating temperature of the filtration section is usually 80°C to 250°C, preferably 100°C to 200°C, more preferably 110°C to 200°C, even more preferably 130°C to 200°C, and even more preferably 140°C to 200°C. The filtration section is preferably heated so as not to cause condensation in the filtration section. The filtration section is preferably heated indirectly using a heating or heat-retaining device (e.g., a mantle heater, ribbon heater, etc.) that can encase and heat the entire filter in which a filter medium is installed, attached, or filled.

[0023] The smoke is sucked by a vacuum pump or the like from a sampling port provided in the location where the smoke is generated (smokehouse), and introduced into the filtration section via a hose, tube, pipe, metal piping, or the like, and filtered through the filtration section. The flow rate at which the smoke is introduced into the filtration section and filtered can be set appropriately depending on the amount of smoke and the production scale of the smoked food, but for example, in the production of small-scale smoked foods at the laboratory level, it is preferably 5 L / min to 35 L / min, and more preferably 10 L / min to 15 L / min. Furthermore, in the production of smoked foods at the CP test level, it is preferably 8,600 m ３ / hour ~ 12,000m ３ / hour. The smoke filtered through the filtration unit is sent to and introduced into the smoking unit using hoses, tubes, pipes, metal piping, etc., by suction with a vacuum pump or air blown by a pump, etc. The flow path (hoses, tubes, pipes, metal piping, etc.) for introducing the smoke into the filtration unit and the flow path (hoses, tubes, pipes, metal piping, etc.) for introducing the smoke that has passed through the filtration unit into the smoking unit are also preferably heated or warmed to suppress the occurrence of condensation. The flow path for introducing the smoke into the filtration unit is preferably heated or warmed to about 30°C to 250°C, more preferably to about 70°C to 250°C, even more preferably to about 100°C to 250°C, even more preferably to about 110°C to 200°C, and even more preferably to about 110°C to 150°C. Furthermore, the flow path for introducing the smoke that has passed through the filtration unit into the smoking unit is preferably heated or warmed to about 30°C to 250°C, more preferably to about 30°C to 200°C, even more preferably to about 30°C to 150°C, and even more preferably to about 30°C to 100°C. The hoses, tubes, pipes, metal piping, etc. can be heated using a tube cover heater. The hoses, tubes, pipes, metal piping, etc. that constitute the flow path for introducing smoke into the filtration unit, and the hoses, tubes, pipes, metal piping, etc. that constitute the flow path for introducing the smoke that has passed through the filtration unit into the smoking unit, can be heat-resistant to withstand the above-mentioned heating or warming, and can be made of resin or rubber, or metal piping such as stainless steel, which do not deteriorate or corrode when in contact with the smoke. However, it is preferable to use hoses, tubes, pipes, etc. made of silicone resin or silicone rubber, or stainless steel piping.

[0024] In the "smoking step" included in the manufacturing method of the present invention, the smoke filtered through the heated filtration section in the above-mentioned "filtering step" is introduced into the smoking section, and food materials are exposed to the smoke in the smoking section to smoke. The flow rate when the smoke filtered through the heated filtration section is introduced into the smoking section can be appropriately set depending on the amount of smoke and the production scale of the smoked food, but for example, in the production of small-scale smoked foods at the laboratory level, it is preferably 5 L / min to 35 L / min, more preferably 10 L / min to 15 L / min. Furthermore, in the production of smoked foods at the CP test level, it is preferably 8,600 m ３ / hour ~ 12,000m ３ In addition, in one example of a roasting and drying device, the opening area of ​​the slits provided to introduce smoke into the smoking section is 1.2 m in total. ２ The flow rate of the smoke as it passes through the slit is 2 m / sec. The time for which the food material is exposed to the smoke is set appropriately depending on the type and condition of the food material, the desired degree of smoking, etc., but is preferably 120 to 360 minutes, more preferably 180 to 240 minutes, when producing dried fish, and preferably 1 to 10 minutes, more preferably 5 to 10 minutes, when producing other smoked foods.

[0025] In another embodiment of the manufacturing method of the present invention, the generated smoke may be filtered by passing it through a filtration section heated to suppress condensation, or it may be passed through a flow path heated or heated to suppress condensation and then filtered by passing it through the filtration section. Alternatively, the smoke filtered through the filtration section may be introduced into a smoking section through a flow path heated or heated to suppress condensation, and the food material may be exposed to the smoke to perform smoking. In this embodiment of the manufacturing method, the filter and filter material included in the filtration section, the heating temperature of the filtration section, the hoses, tubes, pipes, metal piping, etc. that constitute the flow path for introducing the smoked smoke into the filtration section and their heating or heating temperatures, and the hoses, tubes, pipes, metal piping, etc. that constitute the flow path for introducing the smoked smoke that has passed through the filtration section into the smoking section and their heating or heating temperatures are as described above for the manufacturing methods of the other embodiments of the present invention.

[0026] The production method of the present invention may include, as necessary, steps that are typically employed in the production of smoked foods, such as preparation and conditioning of ingredients to be smoked (e.g., removing unnecessary parts from meat, seafood, etc. and cutting as appropriate), boiling, roasting, seasoning (e.g., salting, marinating in pickling liquid), mold-grown, drying, etc., before or after the smoking step.

[0027] In smoked foods produced by the production method of the present invention, the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene is reduced, for example, by 50% or less, preferably 30% or less, more preferably 20% or less, even more preferably 10% or less, even more preferably 5% or less, and even more preferably 3% or less, compared to smoked foods produced by smoking through exposure to unfiltered smoke, and a good smoke aroma is retained. The smoke aroma retained in smoked foods produced by the production method of the present invention contains, as main smoke aroma components, phenols such as syringol, guaiacol, 4-ethylguaiacol, 2-methylphenol, phenol, and 3-methylphenol. Among these smoke aroma components, guaiacol, 2-methylphenol, and phenol are used as indicators of smoke aroma components. Smoked foods produced by the method of the present invention retain more of these smoke aroma components than conventional polycyclic aromatic hydrocarbon-reduced products, with the remaining amount being 40% or more, preferably 60% or more, more preferably 80% or more, even more preferably 90% or more, even more preferably 94% or more, and even more preferably 95% or more of the amount in smoked foods produced by exposure to unfiltered smoke. The remaining amounts of the smoke aroma components used as indicators, i.e., guaiacol, 2-methylphenol, and phenol, are expressed as the sum of the remaining amounts of each of these smoke aroma components. The content of polycyclic aromatic hydrocarbons, such as benzo[a]pyrene, in smoked foods can be determined by high-performance liquid chromatography, as described below. Furthermore, the remaining amount of the smoke flavor components used as the index in the smoked food can be determined by quantitative analysis using gas chromatography mass spectrometry (GCMS), as described below.

[0028] The present invention also provides a method for reducing the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene in smoked foods while maintaining a good level of smoke aroma components (hereinafter also referred to as the "reduction method of the present invention"). The reduction method of the present invention comprises filtering smoke generated by heating wood through a filtration unit heated to suppress condensation, and exposing food materials to the filtered smoke for smoking. The smoked food, wood used to generate the smoke, heating temperature and heating method for generating the smoke, filter and filter media included in the filtration unit, heating temperature and heating method for the filtration unit, filtration conditions, smoking conditions, and the like used in the reduction method of the present invention are as described above for the production method of the present invention. Furthermore, the hoses, tubes, pipes, metal piping, etc. that constitute the flow path for introducing smoke components into the filtration section in the reduction method of the present invention, and the hoses, tubes, pipes, metal piping, etc. that constitute the flow path for sending the smoke that has passed through the filtration section to the smoking section are as described above in the production method of the present invention, and the heating or warming temperatures and heating or warming methods for the hoses, tubes, pipes, metal piping, etc. that constitute the flow path are also as described above in the production method of the present invention. The reduction method of the present invention can be particularly preferably applied to reducing the polycyclic aromatic hydrocarbon content in dried fish such as bonito flakes, dried bonito flakes, tuna flakes, mackerel flakes, sardine flakes, and horse mackerel flakes.

[0029] In another aspect, the reduction method of the present invention includes passing the generated smoke through a filtration section that is heated to suppress condensation, or passing the generated smoke through a filtration section via a flow path that is heated or warmed to suppress condensation, and then filtering the smoke, and exposing food materials to the filtered smoke to smoke. Alternatively, the reduction method of the present invention includes filtering the generated smoke through a filtration section, and then introducing the filtered smoke into a smoking section via a flow path that is heated or warmed to suppress condensation, and then exposing food materials to the smoke to smoke. In the reduction method of this aspect, the means for generating smoke is as described above for the production methods of other aspects of this aspect. In addition, in the reduction method of this embodiment, the filter and filter material provided in the filtration section, their heating temperature and heating means, the hoses, tubes, pipes, metal piping, etc. that constitute the flow path for introducing the smoke into the filtration section, their heating or heating temperature and heating or heating means, and the hoses, tubes, pipes, metal piping, etc. that constitute the flow path for introducing the smoke that has passed through the filtration section into the smoking section, their heating or heating temperature and heating or heating means are as described above in the manufacturing methods of other embodiments of this embodiment.

[0030] The reduction method of the present invention makes it possible to reduce the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene in smoked foods while favorably retaining the smoke flavor components in the smoked foods. The reduction method of the present invention reduces the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene in smoked foods compared to smoked foods produced by exposing the foods to unfiltered smoke and smoking them, and reduces the polycyclic aromatic hydrocarbon content in the smoked foods to, for example, 50% or less, preferably 30% or less, more preferably 20% or less, even more preferably 10% or less, even more preferably 5% or less, and even more preferably 3% or less. On the other hand, in the reduction method of the present invention, the smoke aroma components in smoked foods remain well, and the smoke aroma components (guaiacol, 2-methylphenol, and phenol) that are used as indicators of smoke aroma components remain at 40% or more, preferably 60% or more, more preferably 80% or more, even more preferably 90% or more, even more preferably 94% or more, and even more preferably 95% or more of the content of the smoke aroma components in smoked foods produced by exposing the foods to unfiltered smoke and smoking them. Note that, as described above in the production method of the present invention, the remaining amount of the indicator smoke aroma components is expressed as the sum of the remaining amounts of these smoke aroma components. The method for quantifying the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene in smoked foods and the remaining amount of the indicator smoke aroma components are also as described above in the production method of the present invention.

[0031] Furthermore, the present invention provides a smoked food product having a reduced content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene and having a good smoked aroma (hereinafter also referred to as the "smoked food product of the present invention" in this specification). The smoked food of the present invention has a polycyclic aromatic hydrocarbon content such as benzo[a]pyrene reduced to 50% or less, preferably 30% or less, more preferably 20% or less, even more preferably 10% or less, even more preferably 5% or less, and even more preferably 3% or less of the polycyclic aromatic hydrocarbon content in a smoked food produced by exposure to unfiltered smoke and smoking, and contains smoke aroma components (guaiacol, 2-methylphenol, and phenol) that are used as indicators of smoke aroma components, at 40% or more, preferably 60% or more, more preferably 80% or more, even more preferably 90% or more, even more preferably 94% or more, and even more preferably 95% or more of the smoke aroma component content in a smoked food produced by exposure to unfiltered smoke and smoking. The content of the smoke aroma components used as the indicators, i.e., guaiacol, 2-methylphenol, and phenol, is represented by the total content of these smoke aroma components. The method for quantifying the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene in smoked foods and the remaining amount of the smoke aroma components used as indicators is as described above in the production method of the present invention.

[0032] The smoked food of the present invention is produced by the above-described production method of the present invention. Here, the "smoked food" is as defined above in the production method of the present invention. The smoked food of the present invention can be particularly preferably provided as dried fish such as dried bonito, dried bonito flakes, dried tuna, dried mackerel, dried sardines, and dried horse mackerel.

[0033] The present invention will now be described in more detail with reference to test examples and examples.

[0034] Test Example 1: Examination of the effect of the average particle size of the porous particles constituting the porous filter medium in the filtration section on the removal rate of benzo[a]pyrene. A high-temperature bag filter ("PS6555", Nakao Filter Industry Co., Ltd. (outer diameter = 90 mm, inner diameter = 76 mm)), porous particles, and a prefilter (inner diameter = 76 mm) were placed in a stainless steel disc filter holder ("Multi-purpose disc filter holder", ADVANTEC Co., Ltd.) to form the filtration section. Diatomaceous earth ("Radiolite", Showa Chemical Industry Co., Ltd.) was packed in a layer thickness of 5 mm as the porous particles. The filtration section was indirectly heated to 150°C using a mantle heater. Firewood (Quercus serrata) was burned in a smokehouse to generate smoke. The generated smoke was aspirated at 10 L / min and filtered through the filtration section. Next, food materials were exposed to the smoke filtered as described above for 30 minutes. For comparison, food materials were exposed to unfiltered smoke without passing through the filtration section for 30 minutes. Smoke inhalation was initiated when the hydrocarbon concentration in the smokehouse reached 250 ppm or higher. Bonito was boiled, dried, and finely ground in an ultracentrifugal grinder (Retsch ZM200) (Retsch) at 1 mm mesh size and 10,000 rpm (hereinafter referred to as "dried perilla powder"). The benzo[a]pyrene content of the dried perilla powder after the end of the smoke exposure was measured using high-performance liquid chromatography as follows. <Measurement Method> (1) After the end of the exposure, 1 g of the dried perilla powder was mixed with 100 mL of hexane, stirred, and the benzo[a]pyrene was extracted three times. The mixture was then dehydrated with anhydrous sodium sulfate and filtered. The filtrate was concentrated using an evaporator to prepare the sample. (2) Measurement conditions: (i) Instrument: 1260 Infinity LC System (Agilent Technologies, Inc.) (ii) Column: Mightysil RP-18 GP (inner diameter = 4.6 mm, length = 250 mm, particle size = 5 μm) (Kanto Chemical Co., Inc.) (iii) Column temperature: 35°C (iv) Flow rate: 1 mL / min (v) Mobile phase: acetonitrile / distilled water (volume ratio before mixing = 80 / 20) As the diatomaceous earth, products with average particle sizes of 114 μm, 39 μm, 27 μm, and 14 μm, respectively, were used as porous particles to form the filtration section.The benzo[a]pyrene removal rate was determined by comparing the benzo[a]pyrene content in the dried raw powder exposed to smoke that passed through each filter with the benzo[a]pyrene content in the dried raw powder exposed to smoke that did not pass through the filter. The benzo[a]pyrene removal rate was determined by subtracting the benzo[a]pyrene content (5 ppb) in the dried raw powder before exposure to smoke from the measured benzo[a]pyrene content values ​​for the cases exposed to smoke that passed through the filter and the case exposed to smoke that did not pass through the filter. The results are shown in Table 1.

[0035]

[0036] As shown in Table 1, by exposing the dried raw material powder to smoke filtered through a filtration section constructed using diatomaceous earth with an average particle size of 114 μm or less as porous particles, more than 97% of the benzo[a]pyrene contained in the dried raw material powder was removed.

[0037] Test Example 2: Examination of the effect of the material of the porous particles constituting the porous filter medium in the filtration section on the removal rate of benzo[a]pyrene As the porous particles constituting the porous filter medium in the filtration section, cellulose filter aids ("VITACEL L10" (average particle size = 18.0 μm) and "VITACEL L600-30" (average particle size = 28.6 μm), Rettenmeyer), perlite ("TOPCO PERLITE No. 31" (average particle size = 25.4 μm) and "TOPCO PERLITE No. 34" (average particle size = 27.6 μm), Toko Perlite Industry Co., Ltd.), and zeolite ("Shimane Prefecture Natural Zeolite No. 2" (average particle size = 59.1 μm) and "Shimane Prefecture Natural Zeolite No. 3" (average particle size = 37.5 μm), Shinsei Co., Ltd.) were used. The removal rate of benzo[a]pyrene in the dried raw powder was calculated when the powder was exposed to smoke filtered through a filter unit made of each porous particle in the same manner as in Test Example 1. The results are shown in Table 2.

[0038]

[0039] As shown in Table 2, in all cases where the filtration section was constructed using porous particles of cellulose, perlite, or zeolite, the dried raw powder exposed to smoke that passed through the filtration section removed more than 99% of the benzo[a]pyrene contained in the dried raw powder exposed to smoke that did not pass through the filtration section.

[0040] Test Example 3: Study of the effect of heating temperature of the filtration section on the retention rate of smoke-flavored components. Diatomaceous earth ("Radiolite," Showa Chemical Industry Co., Ltd.) (average particle size = 27 μm) was used as the porous particles constituting the porous filter medium in the filtration section, and dried perilla powder was exposed to smoke that had passed through the filtration section in the same manner as in Test Example 1 above. Boiling water was added to the smoke-exposed dried perilla powder so that the dried perilla powder content was 5 wt %, mixed well, and allowed to stand for 3 minutes. The mixture was then filtered through a coffee filter and allowed to cool to room temperature. 1 mL of the filtrate was accurately weighed into a 20 mL gas chromatographic vial to prepare a 5 wt % dried bonito stock. Guaiacol, 2-methylphenol, and phenol were selected as indicators of the smoke-flavored components contained in the dried bonito stock, and the dried bonito stock was analyzed for smoke-flavored components. The content of each smoke aroma component in the dried perilla powder exposed to smoke that had passed through the filter was compared with the content of each smoke aroma component in the dried perilla powder exposed to smoke that had not passed through the filter, and the residual rate of each smoke aroma component was calculated. The content of each smoke aroma component was measured by gas chromatography-mass spectrometry (GC-MS) as follows.(1) Equipment used: (i) Gas chromatograph (GC): Agilent 7890A GC system (Agilent Technologies, Inc.) (ii) Mass spectrograph (MS): Agilent 5975C series (Agilent Technologies, Inc.) (iii) Solid phase microextraction (SPME) fiber: SPME fiber assembly, divinylbenzene / carboxene / polydimethylsiloxane (DVB / CAR / PDMS), fiber diameter: DVB layer / CAR·PDMS layer=50 μm / 30 μm (iv) Column: DB-WAX (inner diameter=0.25 mm, length=60 m, film thickness=0.25 μm) (Agilent Technologies, Inc.) (2) Sample collection: (i) Extraction temperature: 50° C. (ii) Collection time: 30 minutes (3) GC conditions: (i) Gas used: Helium (ii) Oven temperature: Hold at 40°C for 3 minutes, then increase to 230°C at 4°C / min, and hold at 230°C for 4 minutes (iii) Injection port pressure: 110.91 kPa (iv) Mode: Splitless (v) Flow rate: 1 mL / min (vi) Average linear velocity: 25.641 cm / sec (4) MS conditions: (i) Measurement mode: Scan (ii) Mass range: 35-350 (iii) Ion source temperature: 230°C (iv) Quadrupole temperature: 150°C The residual rate of each smoke aroma component was calculated when the filtration section was not heated and when the filtration section was heated to temperatures of 100°C, 110°C, 120°C, 130°C, and 150°C, and the effect of the heating temperature of the filtration section on the residual rate of the smoke aroma component was examined. The results are shown in Figure 1.

[0041] As shown in Figure 1, when the filtration section was not heated, the residual rate of smoke aroma components in the dried perilla powder exposed to smoke that had passed through the filtration section significantly decreased to about 20%. On the other hand, the residual rate of smoke aroma components in the dried perilla powder exposed to smoke that had passed through the heated filtration section exceeded 40% when the filtration section was heated to 100°C, exceeded 94% when the filtration section was heated to 110°C, exceeded 97% when the filtration section was heated to 120°C, and exceeded 100% when the filtration section was heated to 130°C or higher. These results suggest that heating the filtration section to 100°C or higher can suppress condensation on the filtration section and effectively prevent smoke aroma components from being captured and removed by the condensed water. It was observed that this effect is significantly improved by heating the filtration section to 110°C or higher.

[0042] Test Example 4: Examination of the effect of the material of the porous particles constituting the porous filter medium in the filtration section on the survival rate of smoke-flavored components The cellulose filter aid, perlite, and zeolite used in Test Example 2 were used as the porous particles constituting the porous filter medium in the filtration section, and dried perilla powder was exposed to smoke that had passed through a filtration section indirectly heated to 150°C, as in Test Example 1. As in Test Example 3, guaiacol, 2-methylphenol, and phenol were selected as indicators of the smoke-flavored components contained in the smoke aroma. The content of each smoke-flavored component in the dried perilla powder exposed to smoke that had passed through the filtration section was compared with the content of each smoke-flavored component in the dried perilla powder exposed to smoke that had not passed through the filtration section, and the survival rate of each smoke-flavored component was calculated to examine the effect of the material of the porous particles constituting the porous filter medium in the filtration section on the survival rate of the smoke-flavored components. The content of smoke flavor components in the dried perilla powder was measured for 5 wt % dried bonito stock prepared from each dried perilla powder in the same manner as in Test Example 3. The results are shown in Figure 2. In Figure 2, the average particle size of the porous particle material in the filtration section is shown in parentheses.

[0043] As shown in Figure 2, when cellulose and perlite were used as porous particles, it was confirmed that nearly 100% or more of the smoke aroma components remained. On the other hand, when zeolite was used as porous particles, the retention rate of the smoke aroma components was lower than when cellulose and perlite were used as porous particles, but a retention rate of 60% or more was still confirmed. Because zeolite has chemical adsorption ability, it was suggested that it may have a stronger ability to capture smoke aroma components than diatomaceous earth, cellulose, perlite, etc., which have physical adsorption ability.

[0044] The above results of Test Examples 1 to 4 suggest that in order to achieve both a high removal rate of benzo[a]pyrene and a high retention rate of smoke-flavor components, it is more preferable to use a porous material with physical adsorption ability, such as diatomaceous earth, cellulose, or perlite, as a porous filter medium in the form of particles with an average particle size of 114 μm or less.

[0045] [Test Example 5] Study on the effect of the average particle size of zeolite on the removal rate of benzo[a]pyrene The results of Test Example 4 suggest that when zeolite with chemical adsorption ability is used as a porous filter medium, it may exhibit different adsorption behavior than when diatomaceous earth, cellulose, perlite, etc. with physical adsorption ability are used as a porous filter medium. Therefore, zeolites with different average particle sizes were used as porous filter medium to study the effect of the average particle size of zeolite on the removal rate of benzo[a]pyrene. Various zeolites shown in Table 3 were used as porous particles constituting the porous filter medium, and dried raw powder was exposed to smoke passed through a filtration section indirectly heated to 150 ° C., as in the case of Test Example 1 above, and the benzo[a]pyrene removal rate was determined when each zeolite was used as porous particles constituting the porous filter medium. Nitto Zeolite No. 2, Nitto Zeolite No. 1, and Nitto Zeolite #70 shown in Table 3 are products of Nitto Funka Kogyo Co., Ltd., and Shimane Prefecture Natural Zeolite No. 3 is a product of Shinsei Corporation.

[0046]

[0047] As shown in Table 3, unlike porous filter media such as diatomaceous earth, cellulose, and perlite, which have physical adsorption capabilities, zeolite, which has chemical adsorption capabilities, showed a very good benzo[a]pyrene removal rate even when its average particle size exceeded 114 μm.

[0048] [Examples 1 to 5, Comparative Examples 1 to 3] Production of Dried Bonito Dried Bonito was produced as follows using the apparatus outlined in Figure 3. In Figure 3, firewood (oak) was burned in a smokehouse to generate smoke, and when the hydrocarbon concentration in the smokehouse was 250 ppm or higher, the smoke was sucked in at 10 L / min using a vacuum pump and introduced into the smoking section, and 15 pieces of dried raw fish (approximately 50 g) were exposed to the smoke to produce dried bonito. In Figure 3, the filtration section had the same configuration as in Test Example 1 above, and the porous particles constituting the porous filter medium were diatomaceous earth ("Radiolite #600" (average particle size = 27 μm), Showa Chemical Industry Co., Ltd.), cellulose filter aid ("Vitacel L600-30" (average particle size = 28.6 μm), Rettenmeyer), and zeolite ("Nitto Zeolite No. 1" (average particle size = 500 μm), Nitto Funka Kogyo Co., Ltd.), each packed in a layer thickness of 5 mm. Also, in Figure 3, a vacuum filtration filter holder KGS-47 (Advantec) was used as the smoking section. In Figure 3, smoke was passed through the filtration section and then introduced into the smoking section, and dried raw fish was exposed to smoke under the conditions shown in Table 4 to produce the dried bonito flakes of Examples 1 to 5. The filtration section was indirectly heated at 150°C using a mantle heater, and the silicone tubes for introducing smoke from the smokehouse to the filtration section and from the filtration section to the smoking section were heated at 100°C using a tube cover heater. Dried bonito flakes were produced in the same manner as in Example 2, except that the filtration section and the silicone tubes for introducing smoke from the smokehouse to the filtration section and from the filtration section to the smoking section were not heated. This was used as Comparative Example 1. The smoke was not passed through the filtration section, but was introduced directly into the smoking section through a silicone tube heated at 100°C using a tube cover heater, and the dried bonito was exposed to the smoke for 4 hours. The smoke was not passed through the filtration section, but was introduced directly into the smoking section without heating the silicone tube. These were used as Comparative Examples 2 and 3, respectively.

[0049] A sensory evaluation was conducted by four panelists on the intensity of the smoky aroma of each of the dried bonito flakes in Examples 1 to 5 and Comparative Examples 1 to 3. The sensory evaluation was conducted by having each panelist score the intensity of the smoky aroma compared to the control dried bonito flakes according to the following evaluation criteria, with the intensity of the smoky aroma of the control being set at 4.0 points, and the average score of the four panelists was calculated. The evaluation results are also shown in Table 4. <Sensory evaluation criteria> No smoky aroma detected: 0 points; Very weak smoky aroma compared to the control: 1.0 points; Weak smoky aroma compared to the control: 2.0 points; Slightly weak smoky aroma compared to the control: 3.0 points; Smoky aroma equivalent to the control: 4.0 points; Slightly stronger smoky aroma compared to the control: 5.0 points

[0050]

[0051] As shown in Table 4, the dried bonito flakes of Examples 2 and 4 were produced by exposing dried bonito to smoke passed through a filter section for 4 hours under conditions in which the filter section, which was constructed using diatomaceous earth and cellulose as porous particles constituting the porous filter media, and the silicone tubes for introducing smoke from the smokehouse to the filter section and from the filter section to the smoking section, respectively, were heated. These dried bonito flakes had a slightly weaker smoky aroma than the control dried bonito flakes produced by exposing dried bonito to smoke without passing through a filter section for 4 hours under conditions in which the silicone tubes for introducing smoke from the smokehouse to the filter section and from the filter section to the smoking section, respectively, were heated. The dried bonito flakes of Example 5 were produced by exposing dried bonito to smoke passed through a filter section for 4 hours under conditions in which the filter section and the silicone tubes for introducing smoke from the smokehouse to the filter section and from the filter section to the smoking section, respectively, were heated, but the porous particles filled in the filter section were zeolite. The dried bonito flakes of this Example were perceived to have a weaker smoke aroma than the dried bonito flakes of Examples 2 and 4. The dried bonito flakes of Examples 1 to 3 were produced by exposing dried bonito to smoke passed through a filtration section composed of porous particles filled with diatomaceous earth, and the smoke aroma was perceived as stronger depending on the exposure time to smoke. On the other hand, the dried bonito flakes of Comparative Example 1 were produced by exposing dried bonito to smoke passed through a filtration section under conditions in which the filtration section and the silicone tubes for introducing smoke from the smokehouse to the filtration section and from the filtration section to the smoking section were not heated. The dried bonito flakes of this Comparative Example had a much weaker smoke aroma than the control. The dried bonito flakes of Comparative Example 2 were produced by exposing dried bonito to smoke not passed through a filtration section for 4 hours under conditions in which the silicone tubes for introducing smoke from the smokehouse to the smoking section were not heated. The dried bonito flakes of this Comparative Example had a much weaker smoke aroma than the control. The dried bonito flakes of Comparative Example 3 were produced by exposing dried raw bonito to smoke that had not passed through a filter for 8 hours under the same conditions as those for the dried bonito flakes of Comparative Example 2. The dried bonito flakes of this Comparative Example had a slightly stronger smoky aroma than the control dried bonito flakes, and it was expected that the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene would increase due to long-term exposure to smoke that had not passed through a filter.

[0052] Examples 6 to 15, Comparative Examples 4 to 13: Production of Smoked Foods Smoked foods were produced as follows using the roasting / drying apparatus shown in Figure 4. Specifically, smoke generated by indirectly heating cherry chips in a carbonization apparatus in Figure 4 was sucked using a vacuum pump. The smoke that passed through the smoking chamber was collected at 10 L / min from the secondary side (outlet side) of the smoking chamber and passed through a filtration section (using diatomaceous earth ("Radiolite #600" (average particle size = 27 μm), Showa Chemical Industry Co., Ltd.) as the porous particles constituting the porous filter material) with the same configuration as in Test Example 1 above. The collected smoke was then introduced into a vacuum desiccator installed as a smoking section on the secondary side (outlet side) of the filtration section. The food materials shown in Table 5 were placed in the vacuum desiccator and smoked for 5 to 10 minutes. The food materials were then dried in a constant temperature dryer at 80°C for 40 to 60 minutes to produce the smoked foods of Examples 6 to 10. In Figure 4, the carbonization layer in the carbonizer was set to 525°C, and the chip input amount was 5 kg. The circulation fan and exhaust fan were set to 35 Hz and 15 Hz, respectively, and the flange heater was set to a voltage of 160 V using a transformer. The differential pressure was measured from the hydrocarbon measurement sample collection port, and the damper opening was adjusted to be between -50 kPa and 0 kPa. The silicone tube used to introduce smoke collected from the smoke collection port into the filtration section was heated to approximately 100°C using a tube cover heater, and the filtration section was heated to 150°C using a mantle heater. Furthermore, smoked foods of Examples 11 to 15 were produced in the same manner as in Examples 6 to 10 above, except that hickory chips were used instead of cherry chips. In Examples 6 to 15 above, the smoke collected from the smoke collection port in Figure 4 was not passed through the filtration section, but rather branched into two branches and introduced into a vacuum desiccator installed as a smoking section via an unheated tube.The food materials placed in the vacuum desiccator were smoked in the same manner as in Examples 6 to 15, to produce the smoked foods of Comparative Examples 4 to 13.

[0053] The strength of the smoky aroma was evaluated for each of the smoked foods of Examples 6 to 15 and Comparative Examples 4 to 13. The strength of the smoky aroma was evaluated by sensory evaluation by 15 panelists, who rated the smoky aroma of each food ingredient that had not been smoked as "very weak (--)" and evaluated according to the following evaluation criteria. The evaluation results were determined by discussion among the 15 panelists. The results of the sensory evaluation are also shown in Table 5. <Sensory evaluation criteria> Very weak: -- Weak: - Average: ± Strong: + Very strong: ++

[0054]

[0055] As shown in Table 5, regardless of whether eggs, seafood, dairy products, meat, or processed foods thereof were used as ingredients, smoking with smoke passed through the filtration section under conditions in which both the tube for introducing smoke from the smoke collection port into the filtration section and the filtration section were heated resulted in a strong or very strong smoke aroma. On the other hand, the smoked foods of the Comparative Examples, which were smoked with smoke introduced into the smoking chamber via an unheated tube from the branching section to the filtration section without passing through the filtration section, exhibited a stronger smoke aroma than the non-smoked ingredients, but the intensity was weaker than that of the smoked foods of the Examples. When producing the smoked foods of Examples 6 to 15, the smoke collected from the smoke collection port was introduced into the heated filtration section through a heated tube and then into the vacuum desiccator installed as the smoking section. This is thought to have caused a temperature drop in the tube from the secondary side (outlet side) of the filtration section to the vacuum desiccator, resulting in significant condensation within the vacuum desiccator, which resulted in significant smoke-aroma components adhering to the foods being smoked. On the other hand, when producing the smoked foods of Comparative Examples 4 to 13, the tube from the branching point to the filtration section to the vacuum desiccator installed as the smoking section was not heated. As a result, condensation occurred inside the tube before the smoke collected from the smoke collection port was introduced into the vacuum desiccator, and the smoke aroma components were absorbed into the condensed water, which is thought to have reduced the amount of smoke aroma components introduced into the vacuum desiccator.

[0056] As described above in detail, the present invention can provide a method for producing smoked foods in which the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene is sufficiently reduced and which have a good smoked aroma. The present invention can also provide a method for reducing the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene while maintaining a good smoked aroma component in smoked foods. Furthermore, the present invention can provide smoked foods in which the content of polycyclic aromatic hydrocarbons such as benzo[a]pyrene is sufficiently reduced and which have a good smoked aroma.

[0057] This application is based on patent application No. 2024-055041 filed in Japan, the contents of which are incorporated in their entirety herein.

Claims

1. A method for producing smoked foods, comprising the steps of heating wood to generate smoke, filtering the smoke generated in the aforementioned step through a filter section heated to 80°C or higher, and exposing food materials to the smoke filtered in the aforementioned step to smoke them.

2. The manufacturing method according to claim 1, wherein the filtering section is constructed by placing, attaching or filling a porous filter medium in a filter.

3. The method according to claim 1 or 2, wherein the filtration section is heated to 100°C or higher.

4. The method according to claim 1 or 2, wherein the filtration section is heated so as to prevent condensation from forming in the filtration section.

5. The manufacturing method according to claim 2, wherein the porous filter medium is one or more types of porous particles selected from the group consisting of diatomaceous earth, cellulose, and perlite having an average particle size of 114 μm or less, and zeolite having an average particle size of 1.9 mm or less.

6. The method of claim 1 or 2, wherein the polycyclic aromatic hydrocarbon content in the smoked food is 50% or less of the polycyclic aromatic hydrocarbon content in a smoked food smoked by exposure to unfiltered smoke.

7. The production method according to claim 1 or 2, wherein the remaining rate of smoky aroma components, indicated by guaiacol, 2-methylphenol, and phenol, in the smoked food is 40% or more of the content of said smoky aroma components in a smoked food smoked by exposure to unfiltered smoke.

8. The production method according to claim 1 or 2, wherein the polycyclic aromatic hydrocarbon content in the smoked food is 50% or less of the polycyclic aromatic hydrocarbon content in a smoked food exposed to unfiltered smoke and smoked, and the remaining rate of smoky aroma components, indicated by guaiacol, 2-methylphenol, and phenol, in the smoked food is 40% or more of the content of said smoky aroma components in a smoked food exposed to unfiltered smoke and smoked.

9. The method according to claim 1 or 2, wherein the smoked food is dried fish.

10. A method for reducing the polycyclic aromatic hydrocarbon content in smoked foods while retaining the smoky aroma components, comprising filtering smoke generated by heating wood through a filter section heated to 80°C or higher, and exposing food materials to the filtered smoke to smoke them.

11. The method according to claim 10, wherein the filtering section is constructed by placing, attaching or filling a porous filter medium in a filter.

12. The method according to claim 10 or 11, wherein the filtration section is heated to 100°C or higher.

13. The method according to claim 10 or 11, wherein the filtration section is heated so as to prevent condensation from forming in the filtration section.

14. The method according to claim 11, wherein the porous filter medium is one or more types of porous particles selected from the group consisting of diatomaceous earth, cellulose, and perlite having an average particle size of 114 μm or less, and zeolite having an average particle size of 1.9 mm or less.

15. The method of claim 10 or 11, wherein the polycyclic aromatic hydrocarbon content is reduced to 50% or less of the polycyclic aromatic hydrocarbon content in a smoked food smoked by exposure to unfiltered smoke.

16. The method according to claim 10 or 11, wherein the remaining rate of smoky aroma components, indicated by guaiacol, 2-methylphenol, and phenol, in a smoked food is 40% or more of the content of said smoky aroma components in a smoked food smoked by exposure to unfiltered smoke.

17. The method according to claim 10 or 11, wherein the polycyclic aromatic hydrocarbon content is reduced to 50% or less of the polycyclic aromatic hydrocarbon content in a smoked food smoked by exposure to unfiltered smoke, and the remaining rate of smoky aroma components, indicated by guaiacol, 2-methylphenol, and phenol, in the smoked food is 40% or more of the content of said smoky aroma components in a smoked food smoked by exposure to unfiltered smoke.

18. The method according to claim 10 or 11, wherein the smoked food is dried fish.

19. A smoked food in which the polycyclic aromatic hydrocarbon content has been reduced to 50% or less of the polycyclic aromatic hydrocarbon content in a smoked food exposed to unfiltered smoke, and the remaining rate of smoky aroma components, indicated by guaiacol, 2-methylphenol, and phenol, is 40% or more of the content of said smoky aroma components in a smoked food exposed to unfiltered smoke.

20. The smoked food product according to claim 19, which is dried fish.

21. A method for producing smoked foods, comprising the steps of generating smoke, passing the smoke generated in the step through a filtration section that is heated to prevent condensation, or passing the smoke generated in the step through a filtration section via a flow path that is heated or warmed to prevent condensation, and filtering it, and exposing food materials to the smoke filtered in the step to smoke them; alternatively comprising the steps of generating smoke, passing the smoke generated in the step through a filtration section to filter it, and introducing the smoke filtered in the step into a smoking section via a flow path that is heated or warmed to prevent condensation, and exposing food materials to the smoke to smoke them.

22. The method of claim 21, wherein the filtration section is heated to 80°C or higher.

23. The method of claim 21 or 22, wherein the flow path is heated or warmed to 30°C to 250°C.

24. The manufacturing method according to claim 21 or 22, wherein the filtration section comprises a filter and a filter medium.

25. The method of claim 21 or 22, wherein the smoked food is dried fish.

26. A method for reducing the polycyclic aromatic hydrocarbon content in smoked foods while retaining smoky aroma components, comprising: passing the generated smoke through a filtration section that is heated to prevent condensation, or passing the generated smoke through a filtration section via a flow path that is heated or warmed to prevent condensation, and then filtering the smoke; and exposing food materials to the filtered smoke for smoking; alternatively, filtering the generated smoke through a filtration section, introducing the filtered smoke into a smoking section via a flow path that is heated or warmed to prevent condensation, and then exposing food materials to the smoke for smoking.

27. The method of claim 26, wherein the filtration section is heated to 80°C or higher.

28. The method of claim 26 or 27, wherein the flow path is heated or warmed to between 30°C and 250°C.

29. The method according to claim 26 or 27, wherein the filtration section comprises a filter and a filter medium.

30. The method of claim 26 or 27, wherein the smoked food is dried fish.

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