METHOD FOR THE COMBINED CONTINUOUS MIXING AND METERING OF DOUGHS OR PASTES ENRICHED WITH GAS UNDER STATIC PRESSURE, CONTROL AND/OR REGULATING DEVICE FOR CARRYING OUT SUCH A METHOD, DEVICE FOR CARRYING OUT THE METHOD AND PRODUCTS OBTAINED BY THIS METHOD, AND USE OF SUCH PRODUCTS

Abstract

The invention relates to a method, a control and/or regulating device, a device and products as well as the use of such products. It is shown how gas-foamed products are manufactured from doughs or from pastes in an elongated process space and how the static pressure required for the gas dissolution is maintained in the process space up to the outlet opening and the foaming in the dough or in the paste is not initiated in a targeted manner under predetermined process conditions until the product exits from a metering valve device connected downstream of the process space and the pressure is reduced.

Claims

1. A method for the combined, continuous mixing and metering of doughs or pastes enriched with gas under static pressure for the manufacture of foamed products, preferably baked goods, more preferably gluten-free baked goods, in which a free-flowing or pourable, dry powder mixture for doughs or pastes with a vegetable protein content in the range from 5 to 70% (W/W), based on the dry substance, is introduced into the elongated process space of a motor-driven extruder in which: (i) fluid is added by a fluid supply device for the manufacture of a high viscosity dough or paste having a dynamic viscosity of h (g.)?10 Pas, measured in a rotational rheometer at a shear rate of g.=100 s.sup.?1, and thereby a dough or paste plug builds up continuously which seals against backflow effects of fluid or gas, (ii) the viscosity of the high-viscosity dough or paste plug is reduced by ?20%, preferably ?50%, by metering an additional fluid component fraction at least one further fluid supply point which is spaced apart in conveying direction from the first fluid supply device, (iii) whereinafter a gas component under pressure is supplied and finely dispersed and/or dissolved in the dough or paste fluid phase by a compressed gas supply device arranged in an axial conveying direction, and (iv) wherein at least one dough or paste discharge and metering element configured as a metering valve device is arranged on the discharge side of the processing space configured as a process space, (v) the outlet opening of which is regulated or controlled in its cross-section in order to maintain the static pressure required for the gas dissolution in the process space, and wherein (vi) a measuring device continuously measures the degree of gas dissolution between the compressed gas supply device and the metering valve device (vii) and due to a pressure control, the gas contained in the dough or paste is kept in solution or fine dispersion until the end of the metering valve device and the foam formation is launched under pressure, lowering only when exiting a valve outlet channel of the metering valve device supported by native starch particles, which particles initiate a secondary, heterogeneous gas bubble nucleation, and (viii) wherein the subsequent dough or paste foam expansion of at least ?20% (V/V), supported by the dough or paste viscosity, occurs only after the dough or paste exits the metering valve device.

2. The method according to claim 1, wherein the dough or the paste is transported in one or a plurality of extruders, each extruder having at least one motor-driven extruder screw equipped zonally in different zones with conveying and/or mixing and/or dispersing elements, wherein the extruders are closed gas-tight at both ends during the conveying process, such that no gas loss occurs in the process space by the addition of gas under pressure into the part of the relevant extruder screw channel configured for gas dispersion and/or gas dissolution, and the gas within this partial area of the extruder screw channel is finely dispersed and/or dissolved completely in the dough or in the paste under increased static pressure in a controlled manner and no foam formation is initiated until immediately before the outlet opening of the metering valve device.

3. The method according to claim 2, wherein a free-flowing, dry powder or a free-flowing powder mixture for the production of a dough or a paste is introduced into the extruder screw channel of at least one or a plurality of motor-driven extruder screws and a water- and/or oil-based fluid system is added to this free-flowing powder mixture or the free-flowing powder at the beginning of the extruder screw channel for the production of a high-viscosity dough or a high-viscosity paste with a dynamic viscosity of h (g.)?10 Pas, measured in a rotational rheometer at a shear rate of g.=100 s.sup.?1, which is used as a fluid- and gas-tight sealing plug in the front area of the extruder screw channel, and at a distance therefrom, in the extruder screw channel, a further portion of a water- and/or oil-based fluid system is added to this to produce a diluted, low-viscosity dough or a low-viscosity paste with a dynamic viscosity reduced by ?20%, and gas is subsequently added under pressure to this low-viscosity dough or this low-viscosity paste, and this gas is converted, under superimposed shear in the extruder screw channel in the gap in thin flow layers produced between co-rotating screw conveyors into a solution or alternatively a microdispersion state with gas bubbles in the diameter range ?10 micrometers, in the dough or paste system, as well as while avoiding foam formation, this solution/dispersion state is maintained until bubble nucleation is specifically initiated and increased in the gas-containing dough or in the gas-containing paste shortly before discharge from one or more discharge/metering devices by secondary, heterogeneous gas bubble nucleation and pressure reduction.

4. The method according to claim 1 wherein the control of the fluid supply at the two or more fluid supply devices in the extruder screw channel is carried out as a function of the viscosity of the dough or the paste, wherein in a mixing zone sealing conditions, against fluid and gas backflows from the fluid supply zone-2 downstream in the flow direction from the mixing zone and the compressed gas supply zone, are implemented by the formation of a dough or paste plug of higher dynamic viscosity of h (g.)?10 Pas, measured in a rotational rheometer at a shear rate of g.=100 s.sup.?1, which dynamically seals the extruder screw channel, and by this dynamic sealing, static pressures between 5 to 100 bar are provided in the gas dispersion and dissolution zone, and thereby gas dissolution and/or micro-dispersion conditions are provided for the gas phase in the dough or in the paste with dwell times in this gas dispersion and dissolution zone between 10 to 120 seconds, preferably between 30 to 60 seconds, wherein the axial distance between the fluid supply devices is continuously adjusted and the fluid supply devices are locked in predetermined positions, positions matched to the dough or paste recipe, and the gas-enriched dough or the paste with ?10% (V/V) based on the relaxed state under atmospheric pressure is discharged in a container, a pouring or baking mold, a package or on a conveyor belt via one or more discharge/dosing elements configured as a metering valve device, wherein a static pressure control/pressure conduction brings about the adjustment of the degree of gas microdispersion and/or gas dissolution in the dough or in the paste, as well as for the dissolved gas portion, the gas bubble nucleation and the initiation of bubble expansion is relocated to the outlet end of the discharge/metering elements configured as the metering valve device and the further bubble expansion and foam formation are carried out at least ?20% in the already metered dough or in the paste, with which a fluidically undisturbed, spatially uniform gas bubble expansion with resulting narrow bubble size distribution is described by SPAN values (SPAN=(x.sub.90.3-x.sub.10.3)/x.sub.50.3,) for the metered, foamed dough or the paste in the range of ?1.5, and foam bubble diameter or pore diameter x.sub.50.3 from 4 to 200 micrometers, for the extruded foamed dough or paste, and from 10 to 250, for the product produced from foamed dough or paste by post-treatment in baking processes, and wherein one or more of the following system parameters are used as control variables for the control of the mean bubble/porous diameters (x50.3) as well as their size distribution width: (a) dough or paste viscosity, (b) number density of bubble nucleation nucleator particles added to the dough system, (c) dough or paste mass flow, (d) total mass-related gas component added, (e) rotational speed of the extruder screw, (f) Opening cross-sectional areas of the metering valves, which, as a function of (a) to (e), define the spatial and temporal pressure relief gradients, wherein the pressure relief gradients directly correlate with the corresponding spatial and temporal gas bubble nucleation and expansion gradients.

5. The method according to claim 1 wherein the supply of a water- and/or oil-based fluid system and gas is adjusted in a controlled or regulated manner as a function of the dough or paste recipe, wherein the first fluid metering takes place by means of the fluid supply device-1 at an axial extruder screw length L, measured in conveying direction, which corresponds to 2 to 8 times the extruder screw diameter D, and in that the second fluid metering is applied by means of the fluid supply device-2 at an axial extruder screw length, measured in conveying direction, which corresponds to at least 10 to 14 times the extruder screw diameter, and wherein the metering of the foaming gas takes place by means of the compressed gas supply device in the form of CO.sub.2 or N.sub.2 or N.sub.2O.sub.2 or air or mixtures thereof under a static pressure of 5 to 100 bar, with a gas volume fraction of between 5 and 70% by volume, based on the pressure-relieved ambient state of the dough or alternatively the paste, in the extruder at an axial extruder screw length, which corresponds to at least 12 to 16 times the extruder screw diameter, whereas for the length range of the gas dispersion and dissolution zone at least 12 L/D<20, when using an extruder with a total length of 28 D applies, whereas this and all previously specified L/D length scales with the factor (L/D).sub.max/28 are multiplied when using an extruder with (L/D).sub.max that is other than 28.

6. The method according to claim 1 wherein the process is carried out at a temperature below 160? C., and the foamed dough or paste after discharge into a container, pouring or baking mold, a packaging means or on a conveyor belt is either baked by means of a convection baking process or a combined microwave-convection baking process or is cooled or frozen in a freshly extruded or partially baked state.

7. A control and/or regulating device performing the method according to claim 1, with one or more motor-driven extruder screws, which are supplied by a powder or bulk material metering device configured as a hopper with a discharge element, wherein in a fluid supply zone-1 a free-flowing dough or paste or powder mixture is supplied by means of fluid supply device-1 with a recipe-specific quantity of a water- and/or oil-based liquid in order to achieve, in a downstream mixing zone, a dough or a paste of a higher dynamic viscosity of h.sub.1 (g.)?10 Pas, measured in a rotational rheometer at a shear rate of g.=100 s.sup.?1 h1, and wherein this dough or this paste is metered, in a recipe-specific manner, in a fluid supply zone-2 by means of fluid supply device-2 with an additional amount of fluid, in order to adjust the dough or the paste at a specific viscosity h.sub.2<h.sub.1 reduced by ?10, and wherein gas is subsequently metered, in a controlled manner, in a compressed gas supply zone by means of a compressed gas supply device that is upstream at an axial distance from the fluid supply device-2 under pressure, in order to achieve a reduced density in the final product through foam formation, wherein the introduced gas is subsequently dissolved or homogeneously microdispersed under a controlled, static pressure between 5 and 100 bar, whereas a sensor measuring the electrical conductivity determines the degree of dissolution or alternatively microdispersion of this gas in the aqueous dough or paste phase, in order to indicate the degree to which an equilibrium value of the gas dissolution/microdispersion is achieved during a predetermined dough or paste dwell time at the end of the gas dispersion and dissolution zone VI in the region of the device designated as gas dissolution measuring and extruder outlet zone VII, wherein based upon this measurement, the controlled adjustment of the proportion of dispersed or alternatively dissolved gas is achieved by means of a feedback loop control using actuators, which are either a back pressure valve device configured as a bypass back pressure valve in a preparation phase of the metering process or at least one metering valve device in the activated metering phase of the process, and wherein the degree of opening of these valves determines the static pressure in the gas dispersion and dissolution zone VI, and thereby controls the dispersion and/or dissolution kinetics and the proportions of the dissolved or microdispersed gas or alternatively gas mixture in the dough or in the paste, which is confirmed by achieving an appropriately measured in-line conductivity value k.

8. The control and/or regulating device according to claim 7, wherein the controlled adjustment of the dough or paste shear viscosity: takes place in the fluid supply zone-1 to a value of 10?h.sub.1<1000 Pas, which ensures sealing upstream by the dough or paste in the extruder screw channel against gas or fluid backflow from fluid supply zone-2 IV or the compressed gas supply zone V, wherein the viscosity h.sub.1 takes into account the non-Newtonian flow behavior of the dough by referring to a representative shear rate of 100 s.sup.?1, which acts in the mixing zone III and wherein the related viscosity function h(g.) is determined offline by dough or paste rheometry, by means of high pressure capillary rheometer or rotational rheometry; and takes place in the fluid supply zone-2 to a value of 1 Pas?h.sub.2<20 Pas, and in the thereby viscosity-reduced fluid dough or paste phase compared to h.sub.1, after the compressed gas supply in the compressed gas supply zone in the gas dispersion and dissolution zone VI arranged downstream of the latter, gas is microdispersed and/or dissolved in the compressed gas supply zone within a dwell time of 30 to 300 s, in order to achieve a degree of foaming in the end product, expressed as the gas volume fraction f.sub.G,v of the total product volume, in the range 10?f.sub.G,v<75% (V/V), and connected therewith a correspondingly reduced density in the final product, wherein the viscosity h.sub.2 takes into account the non-Newtonian flow behavior of the dough or of the paste by relating to a representative shear rate of 200 s.sup.?1 which acts in the gas dispersion and dissolution zone VI, wherein the related viscosity function h(g.) offline is determined by means of high pressure capillary rheometry or rotational rheometry.

9. The control and/or regulating device according to claim 7 wherein the adjustment of the static pressure in the gas dispersion and dissolution zone VI is carried out as a function of the electrical conductivity value k measured in the subsequent gas dissolution measuring and extruder outlet zone VII, wherein the degree of attainment of a pressure-dependent equilibrium value for the electrical conductivity k.sub.equ (p.sub.stat.) is a measure of the degree of gas-dough mass transfer achieved during the dough or paste dwell time in the extruder screw channel within the gas dispersion and dissolution zone VI, and thereby the concentration of the dispersed and/or dissolved gas in the dough or in the paste c.sub.GAS is adjusted in a recipe-specific manner in accordance with the conductivity value k measured in-line, wherein the relevant combination of dwell time t.sub.V(30) or dough or alternatively paste volume flow (dV/dt).sub.Product and static pressure p.sub.stat(30) in the gas dispersion and dissolution zone VI is adjusted on the basis of a calibration function k=f(p.sub.stat(30), tv), which is determined in a preliminary test by means of extruder/back pressure valve device coupling, and wherein the static pressure P.sub.stat(30) at the end of gas dispersion and dissolution zone VI, as well as the electrical conductivity k in of the subsequent gas dissolution measuring and extruder outlet zone VII are determined in this preliminary test, while varying the free cross-sectional flow area A.sub.GDV in the back pressure valve device for a selected rotational speed n.sub.S of the extruder screw and dough or paste mass flow (dm/dt).sub.Product, from which transferable combinations of the variables with continuous metering are derived according to the degree of foaming to be achieved in the metered dough and stored in a database for regular process control.

10. The control and/or regulating device according to claim 7 wherein for a given dough or paste mass flow (dm/dt).sub.Product and recipe-related dough or paste viscosity, a feedback loop control is applied with a given electrical conductivity k.sub.setpoint as reference variable w, wherein the static pressure p.sub.stat(30) in the gas dispersion and dissolution zone VI is integrated as indirect manipulated variable y, and the electrical conductivity k measured in the gas dissolution measuring and extruder outlet zone VII is integrated as a controlled variable, and wherein either a back pressure valve device in a bypass line, or at least one metering valve device, and/or a compressed gas supply device and/or a rotational speed-adjustment apparatus for the rotational speed n.sub.S of the extruder screw coupled to the extruder screw drive motor, are used to adjust the static pressure in the gas dispersion and dissolution zone in a defined manner, wherein a back pressure valve device is used in a bypass line in a preparation run to the regular metering process to determine the static pressure p.sub.stat(30) in the gas dispersion and dissolution zone VI, which is achieved under the process conditions set with regard to dough or paste mass flow (dm/dt).sub.Product, gas mass flow (dm/dt).sub.Gas and rotational speed n.sub.S of the screw under specification of product recipe and screw geometries, and which degree of gas dissolution or microdispersion (dm/dt).sub.Gas(L,D)/(dm/dt).sub.Gas is determined, measured via the electrical conductivity k[(dm/dt).sub.Gas(L,D)/(dm/dt).sub.Gas], which adjusts in the dwell times t.sub.V(30) realized in the gas dispersion and dissolution zone VI, wherein (dm/dt).sub.Gas designates the total mass flow of gas added and (dm/dt).sub.Gas(L,D) designates the mass flow of the dissolved (dm/dt).sub.Gas(L) and the micro-dispersed non-dissolved gas component (dm/dt).sub.Gas(D), wherein the latter two variables additionally depend on the type of gas used, and wherein, when switching over from this preparatory run carried out in bypass mode with back pressure valve device to the regular metering process, in which one or more connected metering valve devices are activated, these ensure, by adjusting the degree of opening of the metering valves, that the static pressure and the thereby set degree of gas dissolution or gas dispersion in the gas dispersion and dissolution zone VI, measured via the electrical conductivity of the dough or of the paste, are at the same level as in the preparation test run using the back pressure valve device in the bypass line, and that, for the regular course of the metering process, 2n metering valve devices with n=1 to 20, n denoting half the number of metering valve devices used, are alternately metering in two groups with n metering valve devices each, and thereby that the level of static pressure in the gas dispersion and dissolution zone VI remains constant when switching between the two metering valve device half-groups, which are configured in a similar manner with respect to flow pressure losses, apart from negligible short-term pressure fluctuations less than 0.5 s during the switching process.

11. A device for carrying out the method according to claim 1 for the combined, continuous mixing and metering of doughs or pastes enriched with gas under static pressure, for the manufacture of foamed products, in particular, preferably baked goods, more preferably gluten-free baked goods, using one or a plurality of motor-driven extruder screws, each with a feed hopper for free-flowing dry powder or for free-flowing dry bulk material mixtures, at least two fluid supply devices arranged in the longitudinal axial direction of the extruder concerned, by means of which different fluid quantities are supplied to the extruder screw channel in a controlled or regulated manner via valves, a compressed gas supply device via which gas is introduced into the extruder screw channel under pressure of 5 to 100 bar and in measuring or sensor devices assigned to the extruder screw channel in process-specific zones I to VII in the conveying direction, which measure the static pressure or alternatively the static pressure development along the extrusion process space and measure the dissolved or microdispersed gas content in the dough or in a paste after the gas dispersion and dissolution zone VI, as well as a dough or paste discharge back pressure valve element arranged in a bypass line and configured as a back pressure valve device, the outlet cross section of which can be continuously varied to build up a static back pressure in the extruder screw channel by using a flexible high pressure hose the cross section of which can be adjusted by means of two adjusting pistons, as well as at least one metering valve device configured as a dough or paste discharge metering valve element, which has one or more metering nozzles, the latter arranged in groups with nozzle end discharge cross sections that can be exchanged or adjusted to metering pressure, fluid viscosity and metering mass flow.

12. The device according to claim 11, wherein at least one metering valve device configured as a discharge metering valve element, which can be closed by an adjusting piston, which, in the open state of this metering valve device, frees the outlet nozzle cross-section and comprises a cross-sectional flow area A1 all the way to the valve outlet chamber as well as subsequently over a length of 1 mm to 40 mm, in the valve outlet channel, which has a distinctly narrowed flow channel cross-section with cross-sectional area A2, wherein A2?0.01 to 0.5 A1, and in the metering case, a back pressure of ?2 bar and further is built up upstream of the metering valve device, which back pressure has an impact all the way into the gas dispersion and dissolution zone, and there achieves a set level of gas dissolution and/or gas microdispersion, as well as a static pressure reduction only takes place in the metering nozzle outlet channel, which reduction leads to gas bubble nucleation and incipient gas bubble expansion, and wherein the outlet cross-section, which can be closed in a sealing manner by means of adjusting pistons, preferably comprises a conically narrowing annular cross-section of the flow channel, wherein the stroke of this adjusting piston is adjustable in a manually or motor-controlled manner and, thereby, with an increased stroke, an annular flow cross-section tapering conically in the cross-sectional area can be released for the dough or paste mass to be metered, wherein the mean cross-sectional flow area of this conical annular channel is variable, preferably continuously adjustable, by a factor of ?2, over the entire range of the adjustable stroke length of the valve plunger.

13. The device for carrying out the method according to claim 11 wherein an extruder screw channel of a co-rotating twin screw extruder, with a length of L/D=14 to 50 (where L=screw channel length and D=screw diameter) is provided for the regulated pressure build-up and the gas dissolution in the dough or in the paste, and the extruder length is subdivided into seven length segment zones of respective segment length between L/D=2 and L/D=10, equipped with screw elements of different geometry with regard to assigned process-technical functions, and the following process-technical functions are assigned to these seven length segment zones: Zone I: powder receiving and compression zone; metering and compression of the powder mixture. Zone II: fluid supply zone-1; first fluid supply. Zone III: mixing zone; mixing/kneading and formation of a high-viscosity dough or paste plug sealing the extruder screw channel against zones IV and V. Zone IV: fluid supply zone-2; fluid mixing and reduction of the dough or paste viscosity. Zone V: compressed gas supply zone; introduction of gas component under static pressure up to 100 bar. Zone VI: gas dispersion and dissolution zone; microdispersion and/or dissolution of the admixed gas component. Zone VII: gas dissolution measuring and extruder outlet zone; approach to gas dispersion and/or gas dissolution equilibrium condition, measurement of static pressure and electrical conductivity as well as inlet into bypass or metering nozzle supply lines. and in accordance with the functional assignments of zones I-VII, the extruder screw is equipped with screw elements which optimally support the assigned functions (i) in terms of flow, (ii) in terms of dwell time and (iii) in terms of power input, wherein, as a function of recipe composition and dough- or paste-system-specific gas dissolution or alternatively dispersion kinetics, a change of the extruder zone lengths (24 to 31) for the aforementioned assigned functions by approximately ?1 to 2 L/D segment lengths takes place in such a way that a state of equilibrium with regard to the micro-gas dispersion and gas dissolution in zone VI is achieved.

14. A product produced according to a method according to claim 1 wherein the product is gluten-free, comprising a non-gluten-containing proportion of plant proteins of between 5 and 70% (W/W), preferably between 5 and 40% (W/W), based on dry substance, and a gas volume fraction in the untreated dough or paste of 0.1 to 0.75, preferably 0.25 to 0.5, and in the post-treated or baked product of 0.2 to 0.9, preferably 0.3 to 0.7, wherein the doughs or alternatively pastes foamed in this way comprise mean foam bubble or alternatively pore diameters x.sub.50.3 of 4 to 200 micrometers, preferably of 20 to 100 micrometers, as well as characteristic SPAN values ((x.sub.90.3?x.sub.10.3)/x.sub.50.3 with x.sub.10.3, x.sub.50.3, x.sub.90.3 as 10%-, 50%-90% percentiles of bubble or alternatively porous diameter volume distribution) for quantification of the bubble or alternatively porous diameter distribution width of ?2, preferably ?1.5, more preferably of ?1, as well as for the foam structures obtained from such dough or paste systems by post-treatment in baking processes, comprise mean bubble or alternatively pore diameters of x.sub.50.3=10 to 250, preferably of 20 to 150 micrometers and resulting SPAN values ?2.5, preferably ?1.5, and more preferably of ?1.

15. The product according to claim 14, comprises a vegetable protein content from 5 to 70% (W/W), preferably from 10 to 50% (W/W), in relation to dry mass, a carbohydrate content from 5 to 70% (W/W), preferably from 10 to 50% (W/W), in relation to dry mass, a dietary fiber/plant fiber content of from 3 to 30% (W/W), preferably from 5 to 15% (W/W), in relation to dry mass, a fat/oil content of from 0 to 30% (W/W), in relation to dry mass, and a native starch content of potato, corn or rice starch of ?1 to 5% (W/W), in relation to dry mass, wherein the native starch content comprises one of native potato, corn or rice starch or mixtures thereof at the same total percentile content pretreated by means of freezing-thawing cycles to equal total percentages and is effective as a gas bubble nucleator.

16. Use of a foamed, dough or paste-based product, which is produced by the method according to claim 1, as a base for long-life baked goods, including ready-to-eat gluten-free long-life or fresh baked goods, as a base for fresh or pre-baked and subsequently frozen baked goods, in baked form or alternatively, as a result of protein denaturation, in other thermally stabilized form, as a chunky inclusion component in a chocolate confectionery, ice cream or in another dessert product or in a vegetable or meat pie product, and/or as a coating, covering or surface decoration component of products in chocolate confectionery, ice cream, other desserts, cheese/fresh cheese, meat products, meat-based/meatless pies.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0083] The invention is illustratedin part in a schematic mannerby way of example, in the diagrams and sketches. Wherein:

[0084] FIG. 1 shows an apparatus according to the invention with a motor-driven screw conveyor configured as a continuous conveyor/extruder, partly in schematic exploded view;

[0085] FIG. 2 shows a valve device from FIG. 1 configured as a back pressure valve, in longitudinal cross-section, on a larger scale;

[0086] FIG. 3 shows a metering valve device from FIG. 1, shown partly in cross-section, partly broken off in a top view, on a larger scale;

[0087] FIG. 4 shows a detail from FIG. 3 shown on a larger scale, partly in cross-section, partly broken off;

[0088] FIG. 5 shows an illustration corresponding to FIG. 3 with a different stroke position of the metering valve piston, likewise shown partly in cross-section, partly in top view, partly broken off;

[0089] FIG. 6 shows a detail from FIG. 5, shown on a larger scale, partly in cross-section, partly broken off;

[0090] FIG. 7 shows a circuit diagram for the control/regulation of the apparatus shown in FIG. 1;

[0091] FIG. 8 shows a diagram representation of the exemplary measured relationship between the electrical conductivity measured in-line of a dough under defined static pressure (here 30 bar) as a function of the metered gas quantity (here CO.sub.2) in the gas dispersion and dissolution zone (30) under equilibrium conditions;

[0092] FIG. 9 shows a schematic representation, in the form of a block diagram, of the feedback control circuit for the defined adjustment of the degree of foaming gas dissolution under the static pressure effective in the gas dispersion and dissolution zone, based on the electrical conductivity k measured in-line in this zone;

[0093] FIG. 10 shows a schematic diagram representation of the temporal relationships between the physical process variables when adjusting the static pressure p.sub.stat in the gas dispersion and dissolution zone during the metering preparation phase using the back pressure valve device acting as an actuator in this phase;

[0094] FIG. 11 shows a schematic diagram representation of the temporal relationships between the physical process variables when switching between the back pressure valve device (metering preparation phase) and the metering valve device (metering phase);

[0095] FIG. 12 shows an external shape/structure of a dough product produced according to the invention (here model cake with 30% (W/W) protein content (recipe M1));

[0096] FIG. 13 shows an external shape/structure of a dough product produced according to the invention (here model cake with 24% (W/W) protein content (recipe M2);

[0097] FIG. 14 shows an internal foam structure of a dough product produced according to the invention (here model cake with 30% (W/W) protein content (recipe M1)) with metering of 0.2% (W/W) CO.sub.2 as foaming gas;

[0098] FIG. 15 shows an internal foam structure of a dough product produced according to the invention (here model cake with 24% (W/W) protein content (recipe M2)) with metering of 0.2% (W/W) CO.sub.2 as foaming gas;

[0099] FIG. 16 shows an internal foam structure of a dough product produced according to the invention (here model cake with 30% (W/W) protein content (recipe M1)) with metering of 0.3% (W/W) CO.sub.2 as foaming gas;

[0100] FIG. 17 shows an internal foam structure of a dough product produced according to the invention (here model cake with 24% (W/W) protein content (recipe M2)) with metering of 0.3% (W/W) CO.sub.2 as foaming gas;

[0101] FIG. 18 shows an internal foam structure of a dough product (here model bread with 10% (W/W) protein content, recipe M3) WITHOUT metering of foaming gas;

[0102] FIG. 19 shows an internal foam structure of a dough product (here model bread with 10% (W/W) protein content, (recipe M3)) with metering of 0.5% (W/W) CO.sub.2 as foaming gas;

[0103] FIG. 20 (identical to FIG. 19, repeated for improved direct structure comparison) shows an internal foam structure of a dough product (here model bread with 10% (W/W) protein content, (recipe M3)) with metering of 0.5% (W/W) CO.sub.2 as foaming gas;

[0104] FIG. 21 shows an internal foam structure of a dough product (here model bread with 10% (W/W) protein content, (recipe M3)) with metering of 0.8% (W/W) CO.sub.2 as foaming gas, and

[0105] FIG. 22 shows the experimentally determined functional relationship between the gas component introduced into a dough/paste system (here gluten-free bread dough) under elevated static pressure and the resulting degree of product foaming.

DETAILED DESCRIPTION

[0106] In the drawing, the invention is shown in use on an apparatus designated overall by the reference sign 1, which comprises at least one continuous conveyor configured as a screw conveyor 2, preferably two co-rotating intermeshing screw conveyors, which are driven by a motor 3 or a plurality of motors, for example, respectively, a controllable servomotor or asynchronous motor, possibly by means of a gearbox or by means of a geared motor. Preferably, several screw conveyors 2 which can be equipped with different screw geometries will be selected, since from a process- and material consistency-specific point of view, these allow not only a steady transport, but also a good mixing and/or mechanical pressure/shear stress of the material to be transported to be ensured.

[0107] The screw conveyor 2 is arranged in a housing 4 and conveys a dough- or paste-forming powder mixture in the direction X. The bulk or pourable powder mixture (for example, dough mixture, not shown) is supplied to a hopper 5 from a source not shown, for example, from a silo. The hopper 5 may be provided with a suitable gravimetric or volumetric control or regulation apparatus to determine the respectively desired powder mass flow.

[0108] The dry bulk or pourable powder mixture or the like is added to the hopper 6 and initially transported in the dry, pourable state by a predetermined amount in the direction X by the conveying screw 2 and thereby compacted in the screw channel (preferably twin screw channel), before a fluid, for example, water and/or a multiphase fluid system, for example, an emulsion, is added to the powder mixture or the like in a controlled or regulated manner via a fluid supply device-1 7 and a line 8, which is conductively connected to a fluid supply device-1 9. The fluid supply device-1 9 is fluidically connected via a line 10 to a fluid supply source, for example, to a water line or, for example, to a tank containing an emulsion. The fluid supply device-1 9 may be a motor-driven, controllable or adjustable pump driven by an electric motor (not shown).

[0109] The amount of fluid supplied via the fluid supply device-1 7 wets or moistens the dry powder mixture or the like and is mixed to it to form a relatively high-viscosity, rubbery dough/paste mass by means of the rotating conveying/extrusion screw(s) 2. This high-viscosity dough or paste mass forms a kind of sealing plug which is constantly degrading in conveying direction X but constantly renewing itself in the direction opposite to the conveying direction X, and which continuously seals the interior 11 of housing 4, which housing substantially corresponds to a screw channel or alternatively to a twin-screw channel, in a gas-tight manner towards hopper 6 and thereby towards the outside.

[0110] A second fluid supply device-2 12 is arranged at an axial distance from the fluid supply device-1 7 and is supplied by a second fluid supply device-2 14 with a predetermined amount of fluid via a line 13.

[0111] The second fluid supply device-2 14 receives a supply of the fluid, just as the first fluid supply device 7, for example, water or another suitable liquid or a fluid multiphase system, for example, an emulsion, by means of a line 13. Like the first fluid supply device 1 9, the fluid supply device 2 14 can be a controllable or adjustable pump which, like 9, is driven by a controllable or adjustable electric motor.

[0112] A compressed gas supply device 15 is arranged at an axial distance from the second fluid supply device-2 12, through which compressed gas supply device a gas, under positive pressure, is introduced into the process space 11 of the housing 4.

[0113] The reference sign 16 denotes a check valve, whereas 17 denotes a compressed gas line to which compressed gas, for example compressed air or another gas, can be supplied via a controllable or adjustable valve device 17a.

[0114] 18 indicates a compressed gas source, which is only indicated schematically.

[0115] A measuring device 19, which is configured, for example, as a conductivity sensor, is arranged in the end area of the housing 4 of the apparatus 1 in order to measure the extent to which the compressed gas introduced into the interior 11 of the housing 4 via the compressed gas line 17 is dissolved in the dough or paste that is conveyed by the screw conveyor 2 in the direction X.

[0116] A pressure sensor is arranged at 20, which measures the pressure in the interior 11 of the housing 4.

[0117] The reference sign 21 designates an outlet nozzle and 22 an end plate, to which the outlet nozzle 21 is connected in a paste/dough-conducting manner.

[0118] A bypass line 23 is connected to the outlet nozzle 21 in a dough/paste-conducting manner, to which a back pressure valve device 24 is assigned, which is configured to be controllable or adjustable.

[0119] The apparatus 1 has several process-defined zones in the conveying direction X.

[0120] The reference sign 25 designates a powder material receiving zone in the form of a compression zone, whereas 26 designates a fluid supply zone-1.

[0121] Reference sign 27 designates a mixing zone and 28 designates a further fluid supply zone-2.

[0122] A zone 29 is formed as a compressed gas supply zone, whereas 30 represents a gas dispersion and dissolution zone.

[0123] The reference sign 31 designates a gas dispersion measuring and extruder outlet zone.

[0124] The reference signs 32 through 36 designate measuring devices in the form of static pressure sensors which measure and continuously display the pressure buildup in the various flow zones along the length of the apparatus 1.

[0125] A line 37 in the form of a metering line, to which a metering valve device 38 is assigned, is also connected to the outlet nozzle 21.

[0126] The back pressure valve device 24 is shown in detail in FIG. 2. The bypass line 23 is configured as a connecting nipple, which is arranged on the outlet nozzle 21, and is, for example, coupled in a sealing, detachable manner to the outlet nozzle 21 by means of a screw connection or the like (not shown).

[0127] The bypass line 23 is equipped with a flange 39 and is detachably connected in a sealed manner by means of screws or the like to a pinch valve device 40. As a central component, the latter contains a flexible high pressure hose 44 which is connected on both sides to high pressure hose connectors 41, 43 and sealed by means of high pressure O-ring seals 42, 45.

[0128] As can be seen from FIG. 2, the bypass line 23, the high pressure hose connectors 41, 43 and the high pressure hose 44 form a flow channel of constant cross-section, to which a cross-sectional adjustment device 47 is arranged orthogonally. This cross-sectional adjustment device 47 comprises diametrically opposed adjusting pistons 48 and 49, which are arranged respectively to be continuously but synchronously adjustable in opposite directions, which is to say in the directions T and V. The adjusting piston 48 and adjusting piston 49 is respectively assigned an adjusting head 50 or alternatively 51. In the embodiment shown, the adjusting heads 50 and 51 are form-fittingly but detachably connected to the assigned adjusting pistons 48 and 49, for example, by means of screw threads, and are thereby functionally one piece.

[0129] As can be seen from FIG. 2, the adjusting heads 50, 51 are domed on their top surfaces 52 and 53 that are facing each other and act on the outer circumferential surface of the flexible high pressure hose 44 against each other, but in a synchronous deforming manner. For this purpose, the adjusting pistons 48 and 49 are respectively adjusted in the direction T or alternatively V by a common drive or also by separate drives, for example, by impinging piston-cylinder units acting alternatingly on both sides in order to accordingly change the flow cross-section through the high-pressure hose 44. The adjusting pistons 48 and 49 can also themselves be part of a piston-cylinder unit, wherein the end sections of which each engage and form a seal in an axially adjustable manner in an assigned cylinder space, wherein a pressure medium, for example, a hydraulic fluid or compressed air, can be supplied under pressure on opposite sides in a controlled manner in order to synchronously and at a constant speed drive the adjusting pistons 48 and 49 in the direction T or alternatively V, either directed away from each other or against each other, in order thereby to either reduce or increase the flow cross section of the high pressure hose 44.

[0130] The domed design of the top surface 52 or alternatively 53 of the adjusting heads 50 and 51 prevents damage to the surface of the high pressure hose 44 and largely eliminates critical multi-axial stress conditions.

[0131] The metering valve device 38 comprises a connecting piece 54 which is part of a housing 55. The dough or paste mass enriched with dissolved/fine-dispersed compressed gas flows through an inlet channel 56 of the connecting piece 54 into a valve chamber 57, in which a metering piston 58 engages and forms a seal orthogonally to the longitudinal axis of the connecting piece 54. The metering piston 58 is arranged with infinitely variable stroke adjustment in direction A or alternatively B and is separated in a liquid and gas-tight manner from a valve outlet chamber 61 and from the valve head space 62 by means of seals 59, 60.

[0132] The valve chamber 57 is configured as a cylindrical annular space, which is delimited circumferentially on one side by the inner wall of the housing 55 and on the other side by the outer lateral surface of the metering piston 58.

[0133] During the stroke in direction B or A of the metering piston 58, the dough or the paste that is in thermodynamic quasi-equilibrium state with regard to gas dispersion/gas dissolution, and which fills the cylindrical valve chamber 57, is transferred from this cylindrical valve chamber into the annular gap 63, which is freed up between the lower end of the metering piston 58 and the annular lower seal 60 configured as a metering piston seal, into the valve outlet chamber 61 and from there further through the valve outlet channel 65 into the environment, for example, into a baking mold. The reference sign 59 designates a seal and 62 designates a valve head space. This is favored in that, when the valve is closed, the lower end of the cylindrical metering piston 58 projects into the valve outlet chamber 61 until the end stop, wherein with the likewise cylindrical valve outlet chamber 61, a narrow annular gap of, for example, ?2 mm is formed, and upon opening of the valve by a relatively small stroke of the metering piston 58, a narrow flow gap of ?2 mm is formed, which generates an inwardly directed radial flow, and the valve outlet channel 65 measuring preferably, for example, ?15 mm and having a diameter of, for example, between ?3 and 5 mm is kept as short and narrow as possible, but is in principle adapted to the dough viscosity, which is to say, in a recipe-specific manner. For this purpose, the relevant component can be exchangeable.

[0134] This adaptation according to the invention of the device is carried out in order to prevent a rupture of the metered dough or paste strand when a supercritical volume expansion rate in relation to the surrounding atmosphere is reached.

[0135] In a particular embodiment of the metering piston 58 according to the invention, the metering piston has a cylindrical projection 66 projecting into the valve outlet channel 65, which keeps the flow cross-section in this channel narrowed until shortly before its end and, in the metering position, forms an annular, relatively small cylindrical expansion chamber at the end of the valve outlet channel. The projection 66 is assigned with the end face 64 of the metering piston 58 and, in the embodiment shown, is functionally or materially connected in a unitary manner to the metering piston 58 and, in the embodiment shown, configured in a more or less needle shape, but may also correspond to another embodiment. Overall, the reference sign 67 denotes a valve nozzle tip or a valve nozzle end.

[0136] FIG. 7 shows a circuit diagram for the system according to FIG. 1. Reference signs 68 through 71 and 73 through 82 denote signal lines that lead to the individual sensors, to the valves, the metering element on hopper 5, the compressed gas source 18 or the screw drive motor 3 of the system.

[0137] The reference sign 72 designates a central data processing system with a control and/or regulation system, for example, a computer unit with data memory, in which data for various recipes, which is to say, baking mixtures, and the respective fluid quantities to be added are also recorded in a recipe-specific manner and can be called up, in particular digitally, for the various dough or paste compositions and dough or paste quantities.

[0138] FIG. 8 shows a measurement characteristic of the measuring device 19 configured as a conductivity sensor, for example, for the use of CO.sub.2 as foaming gas to be supplied to the dough or paste in apparatus 1. For the example of a gluten-free model dough, the conductivity increase of approximately a factor of 3 can be derived between a percentage of zero and 0.7 percent by weight of added and dissolved CO.sub.2. From this, it follows that below this state of equilibrium, which at ambient pressure corresponds to a gas component in the product volume of about 75% and a rising of about 300%, the dissolved gas content can be well measured and controlled with the control apparatus according to the invention beyond the typical measure for gas fractions in foamed food/dough or paste systems.

[0139] FIG. 9 shows the control circuit diagram as a block diagram for a feedback control of the system shown in FIG. 1. The conductivity k of the dough measured by the measuring device 19 is the preferred controlled variable x, which is adjusted at 83 to a reference value w 82, which corresponds to a recipe-specific dispersed/dissolved gas concentration c*.sub.GAS,1 in the paste/dough system, which in quasi-equilibrium adjusts under the correspondingly applicable static pressure p.sub.stat,1 after specific dwell time t.sub.V,1 and specific gas concentration c.sub.GAS in the well-mixed/dispersed fluid-gas system at a specific temperature. In accordance with the invention and the dough recipe, the process temperature is preferably kept constant at a value between 40 and 60? C.

[0140] According to the invention, the corresponding relationship k=f (p.sub.stat,1, t.sub.V,1, c.sub.CO2) is determined in laboratory tests in a high-pressure batch stirred reactor with the corresponding paste/dough system under flow conditions comparable to those prevailing in the gas dispersion and dissolution zone 30 of apparatus 1 (typically twin-screw extruder of specific screw geometry, representative shear rate g..sub.R?200 s.sup.?1). Preferably, sufficiently long dwell times of 30 to 200 s are sought in the gas dispersion and dissolution zone 30 to achieve a gas dispersion/dissolution state of equilibrium. For this case, equilibrium functions k=f(p.sub.stat,1, c.sub.CO2), as shown by way of example in FIG. 8, are worked with directly.

[0141] The static pressure p.sub.stat(30) to be set in the gas dispersion and dissolution zone 30 serves as control variable y 89 (control variable) for a given gas metering mass flow (dm/dt).sub.GAS. According to the invention, the gas metering pressure p.sub.GAS serves as actuator 87 for adjusting p.sub.stat(30) for a specified metered product mass flow (dm/dt).sub.Product and/or the valve opening cross-sections A.sub.Vi of the back pressure valve device 24 during start-up of the process or alternatively of the metering valve device 38 during the regular metering process.

[0142] The controlled variable x in the control unit 85 is compared with the reference value (setpoint value) in the signal line 82 by means of the feedback loop 86 in the input 83 with the reference value (reference variable w) and the control difference e is supplied to the controller (for example, PLC) that is configured as a data processing system 72, which outputs a defined adjustment of the control variable y 89 according to the control algorithm stored in the PLC. Disturbance variables z 88 as well as further possible actuators 87 affect the output of the control section. The reference variable (reference specification, setpoint) is designated by w. The control deviation e determines, via the control algorithm stored in the control unit 72, the intensity of the resulting action(s) taken via the actuator(s) 87 in the controlled process. The comparison of the current inline measurement value x with the reference value (reference variable w=electrical conductivity for achieving a specific degree of dough foaming here) is denoted by 83.

[0143] The disturbance variables z act on the control section 84, and influence a stationary controlled operating state. Typical disturbance variables are (a) raw material fluctuations and (b) metering quantity fluctuations.

[0144] FIG. 10 schematically describes typical temporal characteristics of the physical process parameters during start-up of the process and use of the back pressure valve device 24 in the bypass line 23. The gradual, continuously variable constriction of the high pressure hose 44 in the back pressure valve device causes a correlated increase in the static pressure p.sub.stat(30) in the gas dispersion and dissolution zone 30. A dough and paste system-specific change in the electrical conductivity of the material system follows suit. In the case of increased gas dissolution and dissociation, as in the case of CO.sub.2 as foaming gas, a characteristic increase of the electrical conductivity k occurs. In the case of non-dissociating dissolved or finely dispersed gases, the electrical conductivity is reduced as a rule. Laboratory tests provide quantitative information on this.

[0145] FIG. 11 schematically shows the temporal characteristics of the relevant physical process parameters when switching from the back pressure valve device 24 (start-up process) to the metering valve device(s) 38. During start-up by means of back pressure valve device 24, care is taken to ensure that the static pressure p.sub.stat(30) in the gas dispersion and dissolution zone 30 reaches a value by narrowing the valve cross-section, which value, after switching over to metering operation, corresponds to the stationary pressure value during metering operation by means of metering valve device(s) 38, which is to say, a pressure deviation Dp.sub.V is negligibly small.

[0146] A short-term (<approximately 0.5 s) peak-like increase of p.sub.stat(30) is possible when switching from start-up to metering operation, which, however, decays quickly and is negligible compared to the duration of a metering time interval. Conversely, when switching back from metering to bypass (start-up) operation, a short-term decrease of p.sub.stat(30) is possible. In industrial applications, after completion of a metering cycle of a metering valve device, the system is, as a rule, switched over to a second metering valve device operated in tandem.

[0147] As a result of the short-term pressure fluctuations that occur, fluctuations in the controlled variable electrical conductivity k may occur during the switching processes described above, which must be taken into account or compensated for in the control algorithm, for example, by adjusting the measuring time intervals after switching processes.

[0148] FIG. 12 through FIG. 21 describe examples of foamed dough or paste products produced by the method according to the invention after structure fixation in baking processes.

[0149] FIG. 12 through FIG. 17 demonstrate in tabular form (Table 1) for selected exemplary cake batter recipes with variable protein contents, the possibility of influencing the foam structure by means of the protein content of the recipe, as well as by means of the metering of the CO.sub.2 gas quantity. The corresponding recipe components are listed in Table 2.

[0150] All these recipes have been successfully prepared by the method according to the invention, however with differing results in terms of the resulting product density and foam structures.

[0151] As can be seen in Table 1 (FIG. 12 through FIG. 17), an increased protein content leads to improved stabilization of the microfoam structure with smaller bubble sizes and lowered density (FIG. 14 and FIG. 16). An increase of the foam gas content up to 0.2 g CO.sub.2/100 g product has an ameliorative effect on the foam structure [increased rising=lowered density, small bubble diameters (?100 micrometers), narrow bubble size distribution span (SPAN?1.5)]. The case of a further increase of the foaming gas content (FIG. 16 and FIG. 17 with 0.3 g/100 g) results in coarsening of the foam bubbles and loss of volume fraction (approximately 10 to 15%).

TABLE-US-00001 TABLE 2 Exemplary processed cake products (recipe/processing data) Mass in g/100 g foamed dough product Recipe Protein CO.sub.2 Sugar Gluten Flour Cocoa H.sub.2O 1 30 0.2 11 4 9 3 43 2 30 0.3 11 4 9 3 43 3 24 0.2 11 4 9 3 49 4 24 0.3 11 4 9 3 49

[0152] FIG. 18 through FIG. 21 show the internal foam structure comparison for a gluten-free bread recipe with different metering of gas (here CO.sub.2 with 0, 0.5 and 0.8% (W/W) based on the total product mass). FIG. 18 and FIG. 19 clearly show the particular efficiency of the method according to the invention when applied to gluten-free baked goods. The rising (product volume increase due to stably incorporated gas volume fraction) at 0.5% (W/W) metering of gas (based on total mass) increases by a factor of approximately 3 when compared to the non-foamed product of the same recipe. When the foaming gas quantity is over-metered (in this case 0.8% (W/W) CO.sub.2), a larger quantity of gas pores develop which open to the product surface and are connected with one another inside the product, which leads to partial gas outflow and loss of volume of the product.

[0153] FIG. 22 shows the relationship between the metered gas component and the resulting Overrun (=volume increase share compared to the pure dough fluid volume) after the baking process (end product) with intermediate steps for the gas metering quantity. The measurement values shown correspond to mean values from five analyzed samples. The measurement standard deviations are also shown or alternatively are within the size of the symbols.

[0154] The features described in the claims and in the description, as well as those shown in the drawings can be essential for the realization of the invention both individually and in any combination.