MXPA06008146A - Low temperature extrusion process and device for energy optimized and viscosity adapted micro-structuring of frozen aerated masses - Google Patents

Abstract

The invention describes a low temperature extrusion process and a respective device for an energy-optimized and viscosity-adapted micro-structuring of frozen aerated systems like ice cream. Therewith a very finely dispersed microstructure is reached under optimized balance of viscous friction based mechanical energy dissipation (1) and transfer of dissipation heat and additional phase transition (freezing) heat (2) to a refrigerant up to very high frozen water fraction at very low temperatures. With this new process and device aerated masses are continuously frozen and optimally micro-structured under minimized / optimized mechanical energy input. The microstructure of this-like treated masses supports on the one hand preferred rheological properties which lead to improved shaping, portioning and scooping properties, even at very low temperatures, and on the other hand leads to an improved shelf life (heat shock stability) and mouth feel (e.g. creaminess, melting behavior).

Description

- - LOW TEMPERATURE AND DEVICE EXTRUSION PROCEDURE FOR MICROSTRUCTURED WITH OPTIMIZED ENERGY AND VISCOSITY ADAPTED FROM FROZEN AIR MASSES DESCRIPTION The invention comprises a process for the preparation of deep frozen desserts, in particular ice cream, under conditions optimized for the entry of mechanical energy in order to generate a finely dispersed microstructure,. homogeneously, and simultaneously optimized conditions for the transfer of heat dissipated and phase transition (freezing) to a fraction of highly frozen water at low related temperatures as well as a device to carry out this procedure.

BACKGROUND OF THE INVENTION Single and double screw extruders are known as a continuous processing device which are mainly used in the polymer and ceramic materials industry as well as in the food industry, for example, pulp and products are produced from refreshment. Since 1992 (DE 4202231 Cl) extruders have also been suggested to be used for the continuous freezing of frozen desserts such as ice cream.

Processing As described in several publications (see literature review 2-19), a low temperature extruder allows deep freezing of ice cream and other food masses such as yogurt and fruit pulp to a high degree of frozen water fraction (80-90% in relation to the fraction of freezing water) under mechanical stresses that act simultaneously by shear flow. The dissipated heat caused by the viscous friction of the partially frozen and highly viscous systems (dynamic viscosity up to 104 Pas) must be transferred, in addition to the heat of crystallization (freezing) with efficiency, while a balance between the heat generated and transferred is adjusts depending on the heat transfer coefficient k (which describes the transfer of heat through the product layer that adheres to the inner wall of the extruder housing towards and through this steel wall and in a refrigerant that evaporates in contact with the outer wall of the extruder barrel Up to now, maximum heat transfer coefficients are achieved by the proper selection of the extrusion screw geometries with a narrow leakage gap between the tip of the extruder barrel and the inner wall of the barrel extruder in order to effectively replace the frozen material layer close to the extruder barrel network and by using an evaporative coolant (eg ammonia) for the encoding of the extruder housing. The shear velocities generated in the screw channel are narrowly distributed due to the use of screw geometry with a constant and low screw channel height and a slight axial displacement of the distribution of "screws within the double screw extruder systems (EP 0561 118B1). This means that there are no expanded zones with either very high or very low shear rates. At maximum shear rates of approximately 20-30 s "1 for typical ice cream masses, exit temperatures of -12 to -18 ° C are reached at the extruder outlet.The minimum extraction temperature of the mass at the exit of the extruder it depends on the properties of decrease of the freezing point of the mass and the related viscosity of the mass at the respective temperature as well as the dissipation of mechanical energy caused by the viscous friction.In the ice cream mass extrusion (for example according to with EP 0561118, US Pat. No. 5,345,781), only a small pressure gradient is generated over the length of the extruder In general, the total pressure difference between the extruder at the inlet and outlet is <1-5 bars. This guarantees to avoid the separation of the gas-liquid mixture (foam), which is still rather low viscous at the entrance of the extruder, to a large extent.The specific configuration of the extruder screw a yes as the screw distribution (double screw) in the low temperature extruder according to EP 0561118 or US 5,345,781; DE 4202231C1 respectively, in addition to applying an effective and light mixing of the dough. This is obtained in particular by an appropriate flow current distribution in the overlap / intermixed area of screw displacement between the screws in the double screw arrangement.

Product Aspects In addition to the device and procedure described in advance, there are related aspects that are of primary interest in the specific product advantage properties which can be obtained within an ice cream treated with low temperature extrusion. It can generally be stated that such advantageous properties generated by the low extrusion temperature are related to a finer dispersion of the microstructural ice cream components: ice crystals, air bubbles / air cell and agglomerates of fat globules. The degree to which said dispersion is carried out also depends on the ice cream recipe. The following description relates to a typical standard recipe for vanilla ice cream, however, with variations in the fat / milk content of fat (0-16%) and of dry material (35-43%). The advantageous special properties that are obtained for extruded ice creams at low temperature are related to the main structuring dispersed elements in the ice cream which are the granite crystals (1), the air bubbles / air cells (2) and the agglomerates of globules of grease (3) which are all dispersed much finer under high mechanical stresses that act in a laminar shear and elongation flow fields within the extruder flow under low temperature conditions. For ice crystals, secondary nucleation is carried out by crystalline attrition and crystal breakage in addition to the additional primary ice crystal nucleation in the inner barrel wall, nucleation generates a reduction in size by a factor of 2-3 in comparison with a conventional ice cream processing in the freezer and the subsequent hardening tunnel. The average air bubble / air cell size is reduced by a factor of 3-5 compared to conventional procedures due to the increased acting shear stresses that generate bubble / air cell rupture. The intensity of the mechanical treatment in the extruder flow depends strongly on the viscosity of the mass, which is related to the fraction of water frozen at a specific temperature. On the cross section of the extruder screw channel, which forms a narrow annular gap, the shear stresses are distributed rather homogeneously and narrowly (now flow areas with voltage peaks). Over the length of the extruder, the mechanical energy input increases with increasing residence time of the ice cream in the extruder channel as well as an increase in the mass viscosity as a result of an increase in the frozen water fraction. Local destruction of the ice-cream structure by too high energy dissipation and related friction heat generation is avoided with a procedure / device with typically applied shear rates (EP 056118). In cream ice creams containing fat there are fat globules with an atypical main size of approximately 1 micrometer and lower in globule diameter as a result of the liquid ice cream mixing treatment within high pressure homogenizers. Such fat globules also undergo increased mechanical treatment in low temperature extrusion processes. For fat globules this treatment leads to dehusking of the surface of the fat globule from the protein / emulsifier membranes and partially also to a strong deformation of the fat globules by intense shearing acting on the extruder. As a consequence, fat globules treated in this manner are expected to have stronger hydrophobic interactions. Consequently, there is also an increased affinity of the boundary between gas / air bubble. There is an increased interaction between the treated fat globules that leads to the formation of the aggregates of the fat globules. However, the mobility of said fat globules in the highly viscous low temperature loaded ice cream is low and consequently there is no likelihood of aggregate formation of expanded fat globules to a sensibly detectable size (in the mouth). This avoids the generation of a structure that causes a greasy mouthfeel. From a sensory point of view, smaller ice crystals and gas / air bubbles as well as fat globules treated mechanically but not agglomerated to a large extent lead to a perceptible creaminess greatly increased in the product. At the same time, other sensory attributes are also significantly influenced by the low-temperature extrusion of the ice cream, such as the melting behavior, the cold sensation in the mouth and the adaptability (susceptibility to producing ice cream balls). . Due to the increased fine dispersibility of the dispersed components of the ice cream that cause an increase, described in advance in the creamy sensation, the extrusion at low temperature allows to generate a comparable creaminess similar to that of a conventional ice cream processing with a high fat content. less.

Aspects of construction (extruder screws) To generate a homogeneous microstructure of ice cream (1) and at the same time reach very low extruder outlet mass temperatures lower than -12 ° C (2) (Standard vanilla ice cream) The construction of one or more extruder screws with respect to flow conditions related to an adapted rotational speed are of crucial importance.

EP 561118 discloses a twin screw extruder for continuous ice freezing structure using screw geometries, with particularly flat screw channels (ratio of channel height H to channel width of approximately 0.1, ratio of channel height to to external screw diameter of approximately 0.1) and screw angle of approximately 22 to 30 °. EP 713650 relates to a process which also includes a twin screw extruder for the extrusion of frozen products. The screw characteristics are described only by the ratio of extruder length to screw diameter. EP 0808577 describes a comparable process using a single screw extruder with similar screw construction principles, similar to those provided in EP 713650. WO97 / 26800 claims a method and device for the production of frozen ingestible foams as ice cream using also a single screw extruder. The characteristic properties for the geometry of the extruder screw are the proportions: length of the screw with respect to the internal diameter of the extruder housing between 5 and 10, ascending height of the screw with respect to the outlet diameter of the screw between 1 and 2 as well as an external diameter of the screw regarding the internal diameter of the screw between 1.1 and 1.4. The extrusion screw has only one screw displacement. There are also known low temperature extruders (single and double screw extruders) for the treatment of ice cream with 2-6 screw displacements, preferably 2-5 and a screw angle of 28 to 45 °, preferably from 32 to 45 °. Preference is given to a ratio of overall height to general width of less than about 0.2, but greater than 0.1. The preferred ratio of screw channel length to screw inner diameter is set at 2 to 10, preferably 2 to 4. This generates rather short extruders. The basic difficulty in structured continuous freezing of ice cream within low temperature extrusion systems is related to the combination of a mechanical treatment and the simultaneous solidification of the freezing that is carried out. The latter leads to an increase in energy dissipation based on viscous friction proportional to the viscosity and consequently to the need to transfer this dissipated energy in addition to the crystallization enthalpy set free by the freezing process. This coupled heat transfer is limited by a rather low thermal conductivity of the foamed ice cream mass and the relative heat transfer coefficient k related in the ice sheet low temperature extrusion flow. Heat must be transferred from the mass of ice cream flowing through the wall of the unmixed inner barrel to which the ice cream layer adheres, through the wall of the barrel and to the coolant in contact with the outer wall of the barrel . The optimization of the flow conditions in the extruder with respect to the product properties maximally improved, aims at a maximum shear treatment to achieve the finest dispersed microstructure with a minimum extruder outlet temperature. In extruder screw geometries, conventionally described for low temperature extrusion processing with high mechanical treatment, efficient for microstructuring is only achieved in the end area of the low temperature extruder near the extruder outlet. The length of this end zone with an efficient structured generally reaches less than 50% of the total extruder length. Due to the fact that, in general, a pre-frozen ice cream in a conventional ice cream freezer is transferred in the low temperature extruder under inlet conditions of -5 ° C and about 35 to 45% of the freezer water fraction is frozen, this mass experiences only low shear stresses in the extruder inlet zone to approximately 50% of the length of the extruder. The treatment in this extruder domain does not contribute to a finer dispersion of the components of the microstructure (ice crystals, air bubbles / air cells, agglomerates of fat globules). As demonstrated by recent research, there is even an increase in the size of the air bubble / air cell detected in the first 30 to 50% of the length of the extruder. The reason for this is the displacement in the dynamic equilibrium between the dispersion of the air bubble and the coalescence of the air bubble towards an increased contribution of the coalescence due to mechanical stresses that act less compared to the previous treatment of the ice cream in a conventional freezer. Figure 1 shows in an exemplary manner such an effect on the development of air bubble size along the length of the extruder in the first 150 mm of the pilot extruder screw channel (15% of the length of the extruder). In this domain, the average bubble diameter increases by approximately 25% (see also figure 2). Only after 400 to 450 mm (40-45% of the total length 1000 mm, 65 mm external diameter of the extrusion screw and 7 mm height of the screw channel), the efficient fine dispersion starts. The experiments with different screw geometries have confirmed that an increase adapted to the viscosity in the shear treatment in the first 25 to 70% of the length of the extruder channel allows to improve this situation in a remarkable way until an insignificant size increase in the structure in the entrance area and therefore allows a much better use of the extruder volume.

Problem The problem of the invention is to freeze food masses continuously up to the highest possible fractions of frozen water of more than 60 to 65% of the fraction of freezing water under mechanically induced microstructuring of dispersed components such as ice crystals, bubbles air / air cells and aggregates of fat globules / fat globules up to characteristic average diameters of less than about 10 micrometers and smaller diameter distributions (x90 3 / x? o 3 < 10).

A further problem is to provide a device for carrying out said method.

Solution of the problems The problems are corrected by the characteristics that are provided in patent claims 1 and 14.

Additional Solutions Additional inventive modifications of the invention are described in patent claims 2-13 and 15-29.

Advantages With the method of the invention, ice cream masses can be deep frozen continuously and can be optimally and similarly microstructured with a minimized energy / power input which was not possible before. This is permitted by optimized heat transfer conditions from the mass of ice cream to the evaporative coolant to high freeze mass fractions of 80-90% of the fraction of water susceptible to freezing and at very low related temperatures at the outlet of the low temperature extrusion process of the invention of -12 to -18 ° C. The microstructure of these frozen masses treated in this way leads to an advantageous rheology which provides very good conditions of formation, conformation, dosage and adaptability at much lower temperatures than those known above. In addition, ice cream masses extruded at low temperature can be packed and stored without further intensive hardening (deep cooling) which means that conventional hardening tunnels that consume a lot of energy are no longer necessary. Another advantage is related to the possible reduction of the fraction of expensive ingredients, conventionally used (for example milk fats, emulsifiers), to optimize the properties relevant to the consumer as creaminess, necessary in conventionally processed ice creams. The ice cream, which is optimized according to this patent application, shows an improved creaminess with a much lower fat content (reduction of 3-6%) and without the need for emulsifiers. The reduction of fat is of particular nutritional interest. Additional features and advantages may be derived from subsequent drawings in which the invention is partially demonstrated as examples: The following is shown: in Figure 1: the size distribution of the bubble diameters, measured over the length of the extruder; in figure 2: the maximum bubble diameter as a function of temperature over the length of the extruder; in figure 3: a typical temperature profile on the extruder length, measured in a mass of ice cream; in figure 4: the geometric construction of the leakage gap between the screw travel edge and the inner barrel wall; in figure 5: distribution of two screws with a screw channel height that increases over the length of the extruder (example for screws with two screw displacements); in figure 6: distribution of two screws with a constant screw channel height (here exemplary for screws with a screw displacement); in figure 7: distribution of two screws with a constant screw channel height (exemplary for two screw displacements); in figure 8: distribution of two screws with a screw channel height that increases over the length of the extruder and a screw angle that decreases similarly over the length of the extruder (exemplary for extrusion screws with two displacements); in figure 9: exemplary construction of the screw with cuts in the screw displacement (exemplary for two screw displacements); in figure 10: distribution of screw with cuts in the displacement of screw and in the intermingling bolts fixed in the internal barrel wall (exemplary for two screw displacements); in figure 11: cross-sectional view of the distribution of two screws with cuts in the displacement of screw and intermeshing bolts fixed to the inner barrel wall; in figure 12: comparison with the development of maximum bubble size over extrusion length for two different screw configurations (configuration 1: conventional, configuration 2: according to the invention, here with an adapted screw channel height). According to the invention, the input of power or local mechanical energy is adapted to the local heat transfer (rate of heat flow from the ice-cream to the refrigerant) in such a way that a continuous reduction of the temperature in the ice-cream over the extruder length is what results as shown in figure 3 and after that half to two thirds of the length of the extruder an ice cream temperature lower than -11 ° C (standard vanilla ice cream with 10% of milk fat, 36-38% total dry matter content, 100% increase in volume and sugar composition that leads to approximately 55-65% of frozen water fraction at -11 ° C) or a degree of freezing of > 55-60% fraction of frozen water in relation to freezing water is reached. Fine dispersion of air bubbles / air cells (fraction of major number less than 10 μm, maximum bubble size less than 20 μ), aggregates of fat globule / fat globule (fraction of greater number less than 2 μm , maximum size of agglomerate of fat lower than 10 μm) and in particular a reduction of ice crystal cctivity (fraction of major number less than 5 μm, maximum ice crystal diameter less than 50 μ) are generated in the second half to the final third of the length of the extruder at ice-cream temperatures less than < 11 ° C or fractions of frozen water, respectively, of _ > 60% (in relation to the fraction of water susceptible to being frozen) by shear stresses generated in the flow In order to reach said state - finely dispersed microstructure, final, in the extruder, the history of dispersion in the area up to the second third of the length of the extruder are of paramount importance.Extremely effective predispersing is required in this part of the extruder, in particular for air bubbles / air cells.Furthermore, formation should be reduced or avoided of ice crystal aggregates For this purpose, a sufficiently high mechanical energy / power input and related dispersion voltages are required.When increasing the cooling / freezing and an increase related to the viscosity of the ice cream, according to the invention, the power / power input is adapted by variable adjusted screw geometry for crazy optimized heat transfer 1. The variables that influence are the rotational screw speed (1), the thickness of the ice cream layer (2), the ice cream density (3) and the ice cream viscosity (4). For an optimized heat transfer it is necessary to increase 1 and 3 and decrease 2 and 4 as much as possible. Section 3 is mainly influenced by the prediction that acts locally in the extruder screw channel. Item 4 increases along the extruder channel as a consequence of the increase in the frozen water fraction. Sections 1 and 2 are also optimized - locally according to the invention by adapting the screw geometry under given rotational speed conditions, according to the inventive concept of optimized energy and viscosity adapted microstructure (VAM concept). This concept aims to optimize the local flow fields in the extruder in order to minimize the power input and at the same time maximize the dispersion efficiency of the components of dispersed structure of the ice cream and also maximize Xa mixing efficiency in order to optimize the transfer of heat supported by convexión. The constructive implementation of this concept in low temperature extruders can surprisingly be adapted simply as shown from experiments by: minimizing leakage separation between the outer screw travel edge and the barrel housing (1), an optimized screw displacement front edge contour / profile (2) a locally adapted screw channel height H (3) supported by a number of screw displacements (4) adapted locally or by a locally adapted screw angle ( 5) or locally adapted cuts in the displacements of screw (6) or locally adapted bolts interposed with the cuts in the screw displacements, the bolts are fixed to the inner housing of the barrel (7). Based on the experimental investigations using a special measurement and sampling technique, which allows to measure the local temperatures and the microstructure of the ice cream in each length segment of the low temperature extruder (see list of publications: 17-20), derivative subsequent inventive constructions of the screw geometry of the extruder. These constructions go further in comparison with conventionally existing constructions for "extrusion at low temperature. (1) Minimum leakage separation between the screw travel edge and the inner barrel wall The leakage gap between the screw travel edge and the inner barrel wall according to this invention is set to < 0.1 mm, preferably < 0.05 mm (2) Optimized screw displacement for contour / edge profile The flow of ice cream mass at the front edge of the screw displacement is strongly altered by the contour / profile of this edge.

Figure 4 demonstrates an exemplary inventive construction. The flat inclination or the application of a radius allows to generate a compression flow in the front to the trailing edge in such a way that the thickness of a layer of frozen ice that remains in the inner barrel wall is reduced, compared to the Flow in the case of a front edge of abrupt screw displacement. The reduction of ice cream adhering to the barrel wall is indicated as? S and is shown in Figure 4. Even a small reduction of this layer thickness adhering to the wall has been shown to have a strongly positive impact on the transfer of Heat from the ice cream dough to the inner barrel wall. According to the invention for a screw displacement thickness of more than 5 mm, the leakage gap width must be less than 0.1 mm (preferably less than 0.05 mm) and the inclination of the traversing edge must be in the range of -45 ° on the screw displacement thickness of > 2 mm In the case of a radius contour at the front edge of the screw displacement, the related radius must be 2 mm. (3) Locally adapted screw channel height H A reduced screw channel height H (see Figure 5) increases the shear rate proportional to 1 / H at a constant rotational screw speed. This generates an increase related to the dispersion shear stresses. As a consequence, the percentage of mechanical energy introduced dissipated in the viscous friction heat is also reduced. A reduced layer thickness of the ice cream mass in the screw channel according to a reduced screw channel height improves the heat transfer condition. Furthermore, with respect to the flow behavior of the ice cream in the screw channel, the viscosity of the ice cream reduced at an increased shear rate (non-Newtonian shear thinning flow behavior) has not been taken into consideration. The feeding of a pre-frozen ice cream conventionally in a conventional ice cream freezer (standard vanilla ice cream; -5 ° C, approximately 35-40% frozen water fraction, viscosity at a shear rate of 1 s "1 approximately 10 Pas), according to the invention, in the entrance zone of the extruder (I), a proportion of the height of the screw channel and the diameter of the external screw between 0.03 and 0.07, in the middle part of the length of the extruder (II) between 0.1 and 0.15 and the final third of the extruder length (III) between 0.1 and 0.25 is adjusted.

For a double screw extruder used in a feasibility study with an outer screw diameter of 65 mm, this generates absolute heights of the 2-5 mm screw channel in the entrance area (I), from 6.5 to 9 mm in the middle zone (II) of up to 6.5-16.25 mm in the exit zone (III). There may be a gradual change in the screw channel height from one area to the other, but a continuous change is preferred. In the latter case, a preferred range for the angle between the inner barrel wall and the screw root contour () as shown in Fig. 6 is the resultant between 0.4 ° < _ a, < 0.7 ° (figure 5). (4) Number of locally adapted screw displacements An increase in the number of screw displacements reduces the inversely proportional screw channel width and consequently increases the number of screw channels resulting (see Figure 6 and Figure 7). ). The barrel wall, the "sweep frequency" increases proportionally with the number of screw displacements. This improves the heat transfer (i) but in the same way increases the power input / mechanical energy and consequently the heat dissipated (ii). The latter is limited to low temperatures and high viscosities the number of screw displacements. According to the invention, the extruder is divided into three minimum segments along its length. Preferably, in the first third of the length of the extruder there are 3-6 screw displacements, in the second third 2-3 screw movements and in the final third 1-3 screw displacements are preferably installed. (5) Locally adapted screw angle An increase in the screw angle? it increases the axial self-displacement of the mass flow characteristics of the extruder screw and also improves mixing. Mixing can be further increased for larger screw angles, which has a positive impact on convective heat transfer. However, this also has a strong impact on the dissipated heat of viscous friction mechanically induced. Due to this, an increase in the mass viscosity due to a fraction of frozen water increased consequently also limits the increase of the screw angle. According to the invention, screw angles between 45 and 90 ° (preferably 45 to 60 °) are considered in the entrance zone of the extruder. The extreme case of 90 ° means axially oriented "agitated" blades which no longer form a screw (see Figure 8). In the middle zone of the extruder length screw, angles between 30 to 35 ° and in the final third of the length of the extruder are preferably taken into account, between 25 and 30 °. (6) Cuts adapted locally in the screw displacements The local cuts in the screw displacements according to figure 9 allow the transfer of the ice cream mass through these cuts, which improves the mixing and dispersion as well as the transfer of convective heat. At the same time, the viscous friction time and the related dissipated heat increase. Consequently, said treatment only makes sense if the mass viscosity is not too high. According to the invention, the cuts in the screw displacements are applied in the entrance area of the extruder (up to the first approximately 20-30% of the length of the extruder). The width of the cuts can be close or similar to the height of the screw channel. The same rule must be valid for uncut parts of the screw displacement. (7) Intermix bolts adapted locally to the cuts in the screw displacements, the bolts are connected to the inner barrel wall Adaptation of the bolts adapted to the inner barrel wall that intermingle with the cuts in the screw displacements leads to a dispersion flow - more intense in the separation between the screw displacement and the bolt (see figure 10 and 11). This is of particular advantage if the re-coalescence of the air bubbles-air cells in the inlet zone of the extruder under low viscosity conditions should be avoided. In a high viscosity range, the high energy dissipation in such separations is disadvantageous. According to the invention, the intermixing bolts with the cuts in the extruder screw displacements are preferably installed in the first 10-20% of the length of the extruder. Figure 12 shows in an exemplary manner the effect of a screw channel height optimized partially in the development of the average bubble size of an ice cream over the length of the extruder. A reduction in the average bubble size of approximately 20-30% in the final product has a significant improvement in the creaminess and melting behavior as well as in the heat shock stability of the ice cream.

The features described in the summary of the patent claims as well as in the description and in the related drawings may appear separately or in any combination within the embodiment of the invention.

List of abbreviations in Figures 1-12: Figure 1: - Figure 2: - Figure 3: - Figure: YES, S2 = thickness of ice cream layer that adheres to the wall of the inner barrel (SI according to the invention, S2 conventional). ? S = reduction of the adherent layer (= S2-S1) vax = axial velocity component of the thyme displacement n = r.p.m. Sp screw channel width x, y, z = coordinates Figure 5: H (z) = height of the screw channel (here, as a function of the length z coordinate) From (z) = screw inner diameter - (here, as a function of the z-coordinate of length) or i = angle between the inner screw contour line and the inner barrel wall? = screw angle (between a line perpendicular to the screw axis and a projection of the screw displacement in the drawing plane) d = leakage clearance height (radial difference between the inner barrel radius and the outer screw travel radius) ) Figure 6: A = distance from the screw axes Figure 7: see above Figure 8:? A = screw angle at a certain position of coordinate of length? B = screw angle at the screw end of the entrance area Figure 9: bl = length of the projection of a screw displacement section perpendicular to the screw axis Da = outer screw diameter D = inner barrel diameter Figure 10: c radial length of the interlocked bolts connected to the barrel wall interior d = axial length of the intermingling bolts connected to the inner barrel wall a = projection length of the screw displacement section in an even plane allele to the screw shaft Figure 11: f = length of the intermingling bolts on the inner barrel wall in the circumferential direction Figure 12: Config. 1 conventional screw extruder configuration Config. 2 extruder screw configuration according to the invention References Scientific publications: 1. Bolliger S., Windhab E. Prozesstechnologische Beeinsflussung der Eiskristallgrdßenverteilung in Eiskrem ZDS-Band SIE-15, Int. Symposium "INTERICE", ZDS Solingen, 27. -29. eleven . 95 2. Windhab E. Influence of mechanical forces on the dispersing structuring icecream during continous aeration / freezing processes AICHE, Proc. 5th World Congress of Chemical Engineering 1996, 2, 169-175 (1996) 3. Bolliger S.; Windhab E. Structure and Rheology of Multiphase Foods Prozen under Mechanical Energy Input at Low Temperatures Proc. Ist Symp. on Food Rheology and Structure, Zürich; March 16-21, 1997; Edi tor: E. Windhab; B. Wolf; Vincentz Verlag Hannover, 269-274 4. Bolliger S .; Windhab E. The Influence of Mechanical Energy Input During The Freezing of Sorbet on its Structure Engineering & Food; Proc. Int. Conference on Engineering in Foods (ICEF 7); Brighton, England; 14 - 17. 4. 97; Edi tor: R. Jowi tt, Sheffield Academic Press, E 17-21 5. Windhab E. A New Low Temperature Extrusion Process for Ice Cream Int. Dairy Federation Symposium on Ice Cream; Athens, September 18. -20. 1997 6. Windhab E .; Bolliger S. Freezern von Eiskrem ohne Harten Proc. Int. Symp. "inter-ice", ZDS Solingen (1997); 21-33 7. Windhab, E. New Developments in Ice Cream Freezing Technology and Related On-Line Measuring Techniques In "Ice Cream", Int. Dairy Federation, edited by W. Buchheim, ISMN 92 9098 029 3, 112 - 131, (1998) 8. Windhab, E. Neue Produktionskonzepte für Eiskrem auf Basis der Tieftemperaturextrusionstechnik Proc. Int. Eiskrem-Symposium, Interice, ZDS- Solingen, 23.-25. November 1998, Nr. 12, 88-100 '(1998) 9. Windhab, E. Low Temperature Ice Cream Extrusion Technology and related Ice Cream Properties European Dairy Magazine 1, 24-29, (1998) 10. Windhab, EJ New Developments in Crystallization Processing Journal of Thermal Analysis and Heat imetry, Vol 57 (1999), 171-180 11. Bolliger, S., Kombrust, B., Goff, HD, Tharp, B.W. Windhab, E.J. (!!!) Influence of emulsifiers on ice cream produced by conventional freezing and low temperature extrusion processing Internat. Dairy Journal 10, 497-504 (2000) 12. Windhab E. J., H. Wildmoser Tí ef tempera turextrusion Proceedings Int. Seminar "Extrusion", ZDS-Solingen (D); 2. 3 . -24 .10. 2000 13. Wildmoser, H., Windhab E.J. Neue Eiskremstrukturcharakteristika durch Tieftemperaturextrusion Proceedings inter -Eis 2000; SIE 10, 52-62, Solingen (Germany), 13. -fifteen. November 2000 14. Windhab E. J., Wildmoser H. Beitragge von Prozess und Rezeptur zur remigkeit von Eiskrem Proceedings Inter-Eis 2000, SIE-10, 77-86, ZDS-Solingen (Germany), 13. -fifteen. November 2000 15. Wildmoser H, Windhab E Impact of flow geometry and processing parameters in ultra low temperature ice-cream extrusion (ULTICE) on ice-cream microstructure European Dairy Magazine 2001; 5: 26 - 31 16. Wildmoser H and Windhab E.J. Impact of flow geometry and processing parameters in Ultra Low Temperature Ice Cream Extrusion (ULTICE) on ice cream microstructure INTERICE Tagungsband 2001; SIE-10, ZDS-Sollingen 17. Windhab EJ, Wilmoser H.

Extrusion: A Novel Technology for the Manufacture of Ice Cream Proceedings Conference on Emerging technologies, IDF World Dairy Su mi t Auckland, New Zealand, 30 Oct. -l Nov. 2001 18. Windhab E J, Wildmoser H Ultra Low Temperature Ice Cream Extrusion (ULTICE) Proceedings: AITA Congress "II Gelato", Milan (Italy); May 7 (2002) Patent publications WO 9746114, EP 0808577 - EP 0714650 US 8516659 WO 0072697 Al US 3647478 US 3954366 - US 4234259 EP 0438996 A2 EP 0351476 To DE 4202231 Cl EP 0561118 A2 - US 5345781 FR 2717988 To DK 0082/96; WO 9726800 WO 9739637 WO 9817125; US 5713209 - WO 9925537 WO 9924236 CLAIMS 1. Process of extrusion at low temperature for microstructuring adapted in viscosity, with optimized energy, of frozen aerated aerated masses over the length of the extruder screw channel adapted for areas with mechanical treatment of the partially frozen aerated mass, with respect to its local viscosity, it is carried out in such a way that it is obtained, in each of the subsequent zones coming from the dispersion of the air bubbles / air cells and at the same time temperature decrease and related increase of the frozen water fraction. 2. Method as described in claim 1, characterized by a characteristic length of the zones within which the extruder is divided with respect to the adaptation of the mechanical energy input for dispersion as it advances from the air bubbles / cells of the extruder. air and synchronously decreasing the temperature or increasing the frozen water fraction, respectively, which is 1 to 10 times the outer screw diameter, preferably one to two times the external screw diameter. 3. Method as described in claim 1, characterized by a length

Claims (2)

1. characteristic of the zones in which the extruder is divided with respect to the adaptation of the mechanical energy input for dispersion that is carried out of air bubbles / air cells and descending temperature synchronously or increase of the water fraction frozen, respectively, which is one to ten times the outer screw diameter, preferably one to two times the outer screw diameter with a constant length of these zones along the extruder. . Process as described in claim 1, characterized by a characteristic length of the zones in which the extruder is divided with respect to the adaptation of mechanical energy input for dispersion as it advances from the air bubbles / air cells and a decrease synchronous temperature or an increase in the frozen water fraction, respectively, which is one to ten times that of the outer screw diameter, preferably one to two times that of the external screw diameter with a characterizing zone length adapted to the change local mass viscosity. Method as described in claim 1, characterized by an adaptation of the rotational screw speed (1) of processing parameters, mass flow velocity adjusted by a positive replacement pump installed at the extruder inlet (2) and cooling temperature in the inner wall of the extruder housing adjusted by the evaporating pressure of the refrigerant used (3) for a given extruder screw geometry, regulated such that, for a conventional standard vanilla ice cream mass with a temperature of < -ll ° C or greater generally fractions of frozen water mass of about j > 60% relative to the total freeze water fraction are oned within the first 50-75% of the length of the extruder measured from the inlet of the extruder, preferably within 50-65% of the length. Method as described in claims 1 to 5, characterized by an adjustment of the mechanical mass treatment with respect to its viscosity in the related extruder zone by variation adapted by the height of the trough channel. 7. Process as described in claims 1-5, characterized by an adjustment of the mechanical mass treatment with respect to its viscosity in the related extruder zone by variation adapted from the number of screws. 8. Process as described in claims 1-5, characterized by an adjustment of the mechanical mass treatment with respect to its viscosity - in the related extruder zone by variation adapted in the screw angle. 9. Process as described in claims 1-5, characterized by an adjustment of the mechanical mass treatment according to its viscosity in the related extruder zone by varying the width adapted to the cuts in one or more of the screw displacements. 10. Process as described in claims 1-5, characterized by an adjustment of the mechanical mass treatment with respect to the mass viscosity in the related extruder zone by fixed bolts fixed in the inner extruder barrel wall in such a way that they intermingle with the cuts in the screw displacements. 11. Process as described in claims 1-5, characterized by a reduction in the temperature increase and a fraction of frozen water increased along the length of the extruder due to optimized heat transfer to a refrigerant that evaporates in contact with the outer wall of the extruder housing by minimizing the width of the leakage gap between the outer screw travel diameter and the inner extrusion housing diameter. 12. Process as described in claims 1-5, characterized by a decrease in the temperature of the dough, a related increase in the frozen mass fraction and an increase in the dispersion of the microstructure along the length of the extruder due to an optimized heat transfer to a refrigerant which evaporates in contact with the outer wall of the extruder housing by the generation of a flow pattern at the outer front end of the screw displacement, which leads to a reduction in the thickness of the wall layer of frozen material that is not entrained by one or more of the screw shifts smaller than the Leak separation width. 13. Process as described in claims 1-5, characterized by a decreased mass temperature, a related increasing frozen mass fraction and an increase in the dispersion of the microstructure along the length of the extruder due to a transfer of optimized heat to an evaporating coolant in contact with the outer wall of the extruder housing by generating a flow pattern at the outer front end of the screw displacement, leading to a reduction in the thickness of the wall layer of frozen material that it is not eliminated by being dragged by one or several of the screw displacements smaller than the leakage gap width by adjusting the profile of the front edge of screw displacement which is inclined towards the inner barrel wall or rounded with a radius -well defined. Device for extrusion at low temperature under conditions of adapted microstructure without optimized energy viscosity of aerated and frozen systems such as ice cream, according to claim 1, of one or more subsequent claims with a variable screw geometry along the length of the extruder that adjusts locally according to the local viscosity with respect to effective progressive dispersion, simultaneous progressive temperature reduction and related water freezing. Device as described in claim 14, characterized by a leakage gap width between the screw displacement and the inner wall of the barrel of less than 0.1 mm, preferably less than 0.5 m. Device as described in claim 14, characterized by a screw displacement thickness between 2 and 20 mm and 1: inclination of the front edge of screw travel in relation to the inner barrel wall of 10-45 °, preferably 30-35 °, the inclination is preferably applied to the first 2 mm outside of the screw displacement height, or 2: the front edge of rounded screw offset with a radius preferably of >2 mm. Device as described in claim 14, characterized by a channel height of the extruder screw which is adjusted along the length of the extruder to the viscosity of the mass wherein the feed zone (I) of the extruder, the The ratio of the height of screw channel H to the diameter D of the outer screw is preferably adjusted between 0.03 and 0.07, in the area of (length) average (II) between 0.1 and 0.15 and in the final third of the length of the extruder between 0.1 and 0.25. Device as described in claim 14, characterized by a screw channel height that is continuously increased over the length of the extruder so that the non-screwed contour line of the screw root between the mass inlet and the outlet , with the axes of central length of the screws that form an angle of 0.03 to 0.1 °, preferably of 0.05 to 0.07 °. Device as described in claim 14, characterized in that one or more of the screws comprise 3 to 7, preferably 4-5 screw displacements in the first third of the length of the extruder; with 1-4, preferably 2-3 screw displacements in the second third of the extruder length and with 2-3, preferably 1-2 screw displacements in the final third of the extruder length in the vicinity of the extruder outlet. extruder Device as described in claims 14 and 19, characterized by a progressive reduction in the number of screw displacements about 2-3, preferably 3-5 segments of equal or variable length of the extruder while the number of screws -se reduces continuously in 1-2 screw displacements from one segment to another. Device as described in claim 14, characterized in that the screw angles in the entrance zone (I) between 35 and 90 °, preferably between 45 and 60 °, in the middle part of the extruder are between 30 and 45 ° , preferably between 30 and 35 ° and in the final third of the length of the extruder are between 20 and 35 °, preferably between 25 and 30 °. 22. Device as described in claim 14, characterized by a constant or variable screw angle reduction between 45 and 90 °, preferably 45 and 60 ° from the extruder inlet zone (I) a - between 20 and 35 °, preferably 25 to 30 ° in the exit zone (III) of the extruder 23. Device as described in claim 14, characterized by cuts in the displacements of screws on the first of 10 to 30%, preferably 15 a 20% of the length of the extruder 2. Device as described in claims 14 and 21 to 23, characterized by screws having more than one screw displacement and cuts in the respective screw displacements which are displaced axially in such a way that the mass is subjected to scraping / "sweeping" flow in each part of the inner barrel wall 25. Device as described in claims 14 and 23, characterized by cuts in the screw displacements and n where the length of these cuts is 2.5 to 3 times, preferably 1 to 2 times in the screw channel height and where the same dimensions are valid for the uncut portions of the screw displacements. 26. Device as described in claims 14, 23 and 24, characterized by interconstructed elements, for example bolts, connected to the inner barrel wall, interspersed with the cuts in the thyme displacements during the rotation of the screw. - 27. Device as described in claims 14 and 25, characterized by elements, for example bolts, connected to the inner barrel wall at 2-10, preferably 3-5 different positions distributed regularly or irregularly on the perimeter of the inner barrel wall . 28. Device as described in claims 14 and 25 to 27, characterized by more than one of the screw displacements wherein the cuts in these screw displacements have the same axial position to allow intermixing with the interconstructed elements, for example Bolts Device as described in claims 14 and 28, characterized by a single or double screw extruder distribution for low temperature extrusion of aerated and frozen masses, and adapted geometry characteristics, according to one or more of the claims 14 to 28. SUMMARY By this means a very finely dispersed microstructure is achieved under an optimized balance of mechanical energy dissipation based on viscous friction (1) and heat transfer of dissipation and additional phase transition heat (freezing) (2) to a refrigerant to a fraction of highly frozen water at very low temperatures. With this method and device, new aerated masses are continuously frozen and optimally microstructured under a minimized / optimized mechanical energy input. The microstructure of the masses treated in this way supports, on the one hand, preferred rheological properties that lead to improved conformation, dosage and sphericity properties, even at very low temperatures and on the other hand leads to an improved shelf life. (stability to thermal shock) and mouthfeel (for example creaminess, dissolving behavior. Cumulative number distribution QoH zt / t