Method and device for producing a puffed, dried product based on a food or a food additive

Abstract

A process for producing a puffed, dried product based on a food and / or a food additive, wherein the wet starting product is resistant to an atmospheric evaporation temperature of 100°C and has a starting structure in the form of granules, powder or a viscous mass, the process comprising: Exposure of such a wet starting product for the main drying to microwave radiation at atmospheric pressure in a single-mode operation with a first, in particular average, microwave energy density of more than approximately 80 kW / m 2 , preferably more than approx. 90 kW / m 2 , more preferably more than approximately 100 kW / m 2 , preferably wherein the microwave energy density is not greater than approximately 150 kW / m 2 is, more preferably not greater than approximately 110 kW / m 2wherein the method additionally comprises a final drying of the product, which comprises subjecting the product to microwave radiation at atmospheric pressure in a single-mode operation with a second, in particular averaged, microwave energy density, wherein the second microwave energy density is lower than the first microwave energy density, in particular wherein the second microwave energy density is in the range of 3 kW / m 2 up to 20 kW / m 2 , more preferably in the range of 5 kW / m 2 up to 16 kW / m 2 and a device for producing a puffed, dried product based on a food or a food additive.

Description

[0001] The present invention relates to a process for producing a puffed, dried product based on a food or a food additive. Foods are usually processed into foodstuffs.

[0002] Examples of foods and food additives include dough, pasta, whey, starch- and oil-containing products, sugar slurries with ingredients, and dairy products.

[0003] Microwave drying of food is also used, among other things, for snacks where granules, powders, and viscous masses need to be dried quickly. The desired result is structures that experience a volume increase during drying, which occurs due to air inclusions during the drying process when water boils (puffing).

[0004] It is advantageous for residual moisture to be below 0.5% so that the products are “crunchy, crispy” as snacks and have a good storage life (for example, longer than 6 months).

[0005] In other products, such as food additives, but also in the production of coffee and cocoa, viscous mixtures of substances arise from extraction processes, which also require drying with a higher volume fraction as a porous foam cake. This significantly improves the grindability to powder and the subsequent solubility in water of these products, such as coffee and cocoa.

[0006] The process step of increasing the volume by means of air inclusions can be specifically achieved by vacuum, as the evaporation temperature is reduced and thus at microwave energy densities of 1 kW / m 2The desired structure and surface texture can be created on the irradiated surface. However, this is not economical or not sufficiently economical, and it is also slow.

[0007] WO 94 / 15481 A2 discloses a process for producing a puffed product based on a foodstuff, wherein the wet starting product is resistant to an atmospheric evaporation temperature of 100°C, the process comprising: subjecting such a wet starting product to microwave radiation at atmospheric pressure in a single-mode operation with a first microwave energy density of more than 80 kW / m 2. It also discloses a device for producing a puffed dried product based on a foodstuff, the device comprising: a microwave generator for generating microwaves with a predetermined or predeterminable microwave frequency, a channel-shaped monomode microwave applicator for atmospheric main drying, wherein a microwave coupling element is provided for the monomode microwave applicator in order to feed the microwaves generated by the microwave generator into the monomode microwave applicator, a conveyor extending through the monomode microwave applicator, and a control device for controlling a first microwave energy density of more than 80 kW / m 2 for a main drying.

[0008] DE 196 43 989 A1 and DE 10 2013 009 064 B3 represent further close prior art.

[0009] The present invention is therefore based on the object of enabling more economical drying of such foods and food additives.

[0010] According to the invention, this object is achieved by a method according to claim 1.

[0011] "Resistant to an atmospheric evaporation temperature of 100°C" means that the product will not lose any desired properties at this temperature. Examples would be that it will not melt unintentionally or that nutrients will not be destroyed unintentionally.

[0012] Furthermore, this object is achieved by a device according to claim 7.

[0013] The method can be provided for continuous exposure to microwave radiation. Preferably, the conveying or feeding of the product also takes place continuously. The movement of the conveyor belt continuously feeds new product, ensuring that the fresh product is penetrated first by the microwave radiation. In continuous operation, depending on the product type, moisture content, load quantity (area and volume), and belt speed, a channel area is established in which, for example, 80% of the applied microwave energy is thermally converted into the product.

[0014] Advantageously, the surface coverage is in the range of 1 kg starting product / m 2 up to 20 kg starting product / m 2 , preferably in the range of 2 kg starting product / m 2 up to 6 kg starting product / m 2 .

[0015] Advantageously, the energy density is in the range of approximately 25 kW / kg to approximately 100 kW / kg, preferably in the range of approximately 30 kW / kg to approximately 70 kW / kg of starting product.

[0016] Advantageously, the conveying speed is in the range of approximately 0.3 m / min to approximately 5 m / min, preferably in the range of approximately 0.5 m / min to approximately 3 m / min.

[0017] According to a further particular embodiment of the present invention, it can be provided that the wet starting product has an initial moisture content in the range of 5% to 60%, preferably in the range of approximately 10% to approximately 55%.

[0018] The defined main drying process usually takes place in the first 0.5 - 2.5 meters of the channel-shaped microwave applicator. The total length of the microwave applicator is considered the length of the effective range of the microwaves (MW).

[0019] The defined final drying takes place, for example, on the following 2.5 - 8 meters in the microwave applicator after the main drying.

[0020] Advantageously, 80% of the total microwave power used for drying is used during the main drying and 20% of the total microwave power used for drying is used during the final drying.

[0021] Again advantageously, the residual moisture of the product is in the range of approximately 0.3% to approximately 10%, preferably in the range of approximately 0.5% to approximately 3%.

[0022] In a particular embodiment of the device, the control device is further designed to control the microwave radiation in the final drying section such that a second, in particular averaged, microwave energy density is generated on or in the region of the conveyor, wherein the second microwave energy density is lower than the first microwave energy density, in particular wherein the second microwave energy density is in the range of 3 kW / m 2 up to 20 kW / m 2 and even more preferably in the range of 5 kW / m 2 up to 16 kW / m 2 lies.

[0023] Advantageously, the device is designed so that the microwave radiation in the final drying section is generated independently of the microwave radiation in the main drying section.

[0024] Furthermore, the device can be designed in such a way that 80% of the total microwave power used for drying is radiated in the main drying section.

[0025] The length of the main drying section is 20% of the effective range of the microwaves of the single-mode microwave applicator. This is the area into which the microwaves can penetrate due to the design.

[0026] Finally, it can be provided that the length of the final drying section is 80% of the length of the effective range of the microwaves of the single-mode microwave applicator.

[0027] The present invention is based on the surprising discovery that the above-mentioned structures can also be achieved using atmospheric microwave drying if the microwave energy density is sufficiently high, in particular significantly above the conventional microwave energy density. Atmospheric microwave drying is significantly more economical and faster than microwave vacuum drying.

[0028] This type of microwave drying is particularly suitable for foods and food additives that are resistant to atmospheric evaporation temperature (100°C) and that have an initial structure in the form of granules, powder or a viscous mass.

[0029] In atmospheric microwave drying, water is usually heated selectively and completely in volume due to the high dielectric losses if the penetration depth of the microwaves into the material to be dried is greater than the bed height (typically 1 to 3 cm).

[0030] When microwave irradiated with a microwave energy density of ρ in the range of 1 kW / m 2Slow drying can be achieved on the irradiated surface. Diffusion processes through the macroscopic structure of the product begin at temperatures above approximately 50°C, transporting water from the inside to the outside to the surface via the temperature gradient. The water is transported away from the surface as water vapor by the conditioned warm air. Diffusion of the water on the surface occurs in the slow liquid phase. The partial pressure between the core and the surface of the product is low. As a rule, no or hardly any air pockets form. Drying times are also long, for example, over 60 minutes. No volume expansion occurs.

[0031] If the microwave energy density ρ is now set to, for example, approximately 10 kW / m 2increased, the diffusion processes are still slow on the product's surface due to the macroporous structure. Boiling phenomena occasionally occur in the product at approximately 100°C. Water transitions from the liquid phase to the vapor phase, which is accompanied by an increase in volume due to air inclusions / bubbles in the product. The reason for this is that the water or water vapor cannot escape quickly enough through the diffusion pathways.

[0032] Because the diffusion paths within the product are insufficient to transport the water in the liquid phase to the surfaces, the partial pressure in the product increases. Volume expansion also occurs, particularly when water in the product transforms into water vapor.

[0033] With even further increased microwave energy density ρ to typically 80 to 110 kW, for example approx. 100 kW / m 2Surprisingly, the water is suddenly converted into the vapor phase during microwave irradiation throughout the entire volume, and a sudden volume increase occurs due to the high partial pressure. The water vapor permeates the entire product and also ensures a uniform temperature throughout the product volume. The high partial pressure also increases the diffusion paths because the air inclusions rupture more diffusion channels in the macroporous structure.

[0034] However, the microwave energy density ρ must not be too high. Otherwise, it will tear or destroy the structure. This can happen, for example, at microwave energy densities of more than approximately 150 kW / m 2During the expansion phase, the structure should have a viscosity of approximately 50,000 mPas or less, or even better, approximately 20,000 mPas or less. Typically, it should be below approximately 10,000 mPas to allow for the desired increase in volume, until the texture solidifies and sets due to the removal of water.

[0035] For starch-containing products, such as potato chips, the glass transition temperature of potato starch should be exceeded.

[0036] For protein-containing products, the protein coagulation temperature should be exceeded to fix the texture.

[0037] The expanded structure is then advantageously dried to <0.5% residual moisture by further microwave irradiation at low microwave energy densities in a final drying step.

[0038] The uniformity of the electric field in microwave radiation is of crucial importance. Multimode systems are not capable of providing such uniformity in the electric field distribution. Therefore, monomode or single-mode concepts, in which only one fundamental MW wave is capable of propagation, are primarily considered for implementation.

[0039] Further features and advantages of the invention will become apparent from the appended claims and the following description of an embodiment with reference to the schematic drawings. Herein: Fig. 1 shows an apparatus for producing a puffed, dried product based on a food or a food additive according to a particular embodiment of the present invention; and Fig. 2 a device according to another particular embodiment of the present invention.

[0040] The Fig. The device 10 shown in Figure 1 comprises a microwave generator 12 for generating microwaves with a predetermined or predeterminable microwave frequency, a channel-shaped monomode microwave applicator 14 for the predetermined or predeterminable microwave frequency with a main drying section 14a for atmospheric main drying and an adjoining final drying section 14b for atmospheric final drying, a microwave coupling element 18 for the monomode microwave applicator 14 to feed the microwaves generated by the microwave generator 12 into the monomode microwave applicator 14, a conveyor extending through the monomode microwave applicator 14 in its longitudinal direction, in this example a conveyor belt 20, and a control device (not shown) for controlling the microwave radiation in the main drying section 14a and in the final drying section 14b.The control device can also be designed to control other device components, such as the conveyor belt 20.

[0041] In this example, the main drying section 14a is defined as having a length of 2 m, and the final drying section 14b is defined as having a length of 8 m. The length of the main drying section 14a can generally be, for example, in the range of 0.5 to 2 m. The length of the final drying section 14b can generally be, for example, in the range of 2.5 to 8 m. The total length of the main and final drying sections corresponds to the length 24 of the effective range of the microwaves.

[0042] In this example, the single-mode microwave applicator 14 is an H10 single-mode microwave applicator.

[0043] The conveyor belt 20 is carried by support elements 22 and transports a product to be dried via the microwave coupling point, where the microwave coupling element 18 is located, into the area of ​​ultra-rapid drying, i.e. the main drying section 14a, which in this example represents, for example, 20% of the length of the monomode microwave applicator 14, at a conveying speed of 2 m / min. By means of the microwave coupling point, 80% of the above-mentioned 100 kW / m 2 The microwave power is used for volume expansion and structure fixation during ultra-fast drying. The remaining 20% ​​of microwave energy is used for final drying along the remaining 80% of the length of the single-mode microwave applicator 14.

[0044] In this example, the dwell time in the ultra-fast drying area for volume expansion and fixation is in the range of 20 s to 180 s.

[0045] Products can be dosed onto the conveyor belt as a viscous mixture. Products can also be dosed in their final snack form, in molded containers, or individually onto the conveyor belt.

[0046] A second microwave coupling element can also be used for the final drying to make the final drying more independent of the ultra-fast drying with volume expansion and fixation.

[0047] In the Fig. 1, the product to be dried is continuously fed and transported through the monomode microwave applicator 14, wherein the product is preferably continuously exposed to preferably constant microwave power.

[0048] The Fig. 2 shows a device 10 which differs from the device according to Fig.1 essentially in that the monomode microwave applicator 14 is structurally divided into a main drying section 14a and a final drying section 14b by means of a separating element 23. In addition, a second microwave generator 12 is provided for the final drying section 14b, which can also be controlled independently of the first microwave generator 12 for the main drying section 14a. Preferably, the second microwave generator 12 for the final drying is operated with a lower microwave power than the microwave generator 12 for the main drying.

[0049] The features of the invention disclosed in the above description, in the drawings and in the claims may be essential both individually and in any combination for the realization of the invention in its various embodiments.

Claims

[1] A process for producing a puffed, dried product based on a foodstuff and / or a food additive, wherein the wet starting product is resistant to an atmospheric evaporation temperature of 100°C and has a starting structure in the form of granules, powder or a viscous mass, the process comprising: - Exposing such a wet starting product for the main drying to microwave radiation at atmospheric pressure in a single-mode operation with a first, in particular average, microwave energy density of more than 80 kW / m 2 , preferably more than 90 kW / m 2 , more preferably more than 100 kW / m 2 , preferably wherein the microwave energy density is not greater than 150 kW / m 2 is, more preferably not greater than 110 kW / m 2 is, wherein the method additionally comprises a final drying of the product, which comprises subjecting the product to microwave radiation at atmospheric pressure in a monomode operation with a second, in particular averaged, microwave energy density, wherein the second microwave energy density is lower than the first microwave energy density, in particular wherein the second microwave energy density is in the range of 3 kW / m 2 up to 20 kW / m 2 , more preferably in the range of 5 kW / m 2 up to 16 kW / m 2 lies. [2] Method according to claim 1, wherein the exposure to microwave radiation is continuous. [3] A process according to claim 1 or 2, wherein the surface coverage is in the range of 1 kg starting product / m 2 up to 20 kg starting product / m 2 , preferably in the range of 2 kg starting product / m 2 up to 6 kg starting product / m 2 lies. [4] Process according to one of the preceding claims, wherein the wet starting product has an initial moisture content in the range of 5% to 60%, preferably in the range of 10% to 55%. [5] Method according to one of the preceding claims, wherein 80% of the total microwave power used for drying is used during the main drying and 20% of the total microwave power used for drying is used during the final drying. [6] Process according to one of the preceding claims, wherein the residual moisture of the product is in the range of 0.3% to 10%, preferably in the range of 0.5% to 3%. [7] Device (10) for producing a puffed, dried product based on a food or a food additive, the device (10) comprising: - at least one microwave generator (12) for generating microwaves with a predetermined or predeterminable microwave frequency, - a channel-shaped monomode microwave applicator (14) for the predetermined or predeterminable microwave frequency for the main atmospheric drying and, if appropriate, for the final atmospheric drying, wherein at least one microwave coupling element (18) is provided for the monomode microwave applicator (14) in order to feed the microwaves generated by the at least one microwave generator (12) into the monomode microwave applicator (14), - a conveyor (20) extending through the single-mode microwave applicator (14) and - a control device for controlling a first, in particular average, microwave energy density of more than 80 kW / m 2 , preferably more than 90 kW / m 2 , more preferably more than 100 kW / m 2 for a main drying, preferably wherein the microwave energy density is not greater than 150 kW / m 2 is, more preferably not greater than 110 kW / m 2wherein the length of the main drying section (14a) is 20% of the length (24) of the effective range of the microwaves of the single-mode microwave applicator (14). [8] Device (10) according to claim 7, wherein the control device is further designed to control the microwave radiation for final drying such that a second, in particular averaged, microwave energy density is generated on or in the region of the conveying means (20), wherein the second microwave energy density is lower than the first microwave energy density, in particular wherein the second microwave energy density is in the range of 3 kW / m 2 up to 20 kW / m 2 and more preferably in the range of 5 kW / m 2 up to 16 kW / m 2 lies. [9] Device (10) according to claim 8, wherein the device (10) is designed such that the microwave radiation during the final drying is generated independently of the microwave radiation during the main drying. [10] Device (10) according to one of claims 7 to 9, wherein the device (10) is designed such that 80% of the total microwave power used for drying is radiated during the main drying. [11] Device (10) according to one of claims 7 to 10, wherein the length of the final drying section (14b) is 80% of the length (24) of the effective range of the microwaves of the single-mode microwave applicator (14).

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