EP1692188A1

EP1692188A1 - Apparatus and method for processing meal and water to batter for recovering starch and/or protein therefrom, and batter produced with this apparatus and/or method

Info

Publication number: EP1692188A1
Application number: EP04808704A
Authority: EP
Inventors: Johan Pieter Marseille; Robert Jan Hamer
Original assignee: Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
Current assignee: Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
Priority date: 2003-11-11
Filing date: 2004-11-11
Publication date: 2006-08-23
Also published as: WO2005044860A1; NL1024760C2

Abstract

The invention relates to an apparatus and method for processing meal and water to a batter from which starch and/or protein can be recovered. The apparatus comprises a kneading trough which is subdivided into multiple kneading zones successive in feeding direction, in particular a pre-mixing, reduction and final processing zone. Each zone is provided with individually controllable kneading means, so that optimal kneading conditions can be set per zone. Control of the kneading speed takes place on the basis of the morphological condition of the batter, in particular the size and shape of protein particles present therein. This condition can be monitored with, for instance, ultrasonically reflective measuring means. The kneading is stopped when the protein particles have reached a particular target size, where coherent protein networks can be formed. These protein networks can then be rid of the enclosed starch in a separation device, preferably a roller device.

Description

Title: Apparatus and method for processing meal and water to batter for recovering starch and/or protein therefrom, and batter produced with this apparatus and/or method

The invention relates to an apparatus for processing meal (including wheat meal) and water to batter, from which batter starch and/or protein (in the case of wheat meal: gluten protein) can then be recovered. Such an apparatus is known, for instance from the starch industry. The known apparatus comprises a kneading trough, supply means for the supply of meal, water and any additives, as well as kneading means for kneading these ingredients to batter. During the preparation of the batter, the following process takes place on a nano and micro scale. Meal consists of many flour particles which each comprise starch and protein. The protein consists of relatively long, crumpled protein molecules. By addition of water, the flour particles are hydrated so that the protein molecules swell and unfold. A part of the protein dissolves in the water. The non-water-soluble protein particles (in wheat: glutenin particles) form small weak protein networks (protein units of some tenths of millimeters) which are continuously decomposed during kneading. During and as a result of this composition and decomposition process of protein networks (on micro and millimeter scale), protein particles are deformed and reduced on a nano scale, so that they can form increasingly stronger and larger protein networks. When the protein networks are sufficiently large (in wheat, this is called gluten aggregation), the batter is ready to separate protein and starch therefrom, for instance by washing the starch from the protein networks. This separation process proceeds more easily as the formed protein networks are larger, stronger and purer (that is, contain less enclosed starch). The known kneading apparatus has a number of disadvantages. For instance, it can react to varying process conditions in a limited manner, such as variations in the meal composition resulting from varying harvests, use of other types of grain or variations within a grain variety. Such variations require adjustment of the kneading conditions to guarantee the yield and quality of the protein and/or starch. An important kneading condition is the kneading speed (rotational speed) of the kneading means. The maximum kneading speed is determined by the maximum acceptable forces on the kneading means. With the known kneading apparatus, these forces are relatively high, especially as the kneading process and the associated composing and decomposing of protein networks has already advanced further. As a result, the kneading speed can hardly be increased, so that the variations can insufficiently effectively be anticipated, which may result in considerable (regulation) losses and/or a final product of inferior quality. It is an object of the invention to provide an apparatus of the above-described type, where the disadvantages of the known apparatuses are obviated, while preserving their advantages. For this purpose, an apparatus according to the invention is characterized by the measures according to claim 1. By dividing the apparatus into at least two kneading zones which are successive in feeding direction, in which the kneading conditions such as the kneading speed, temperature and/or the dosing of the water, meal and any additives are individually settable, the kneading conditions can always be optimally adjusted to the development of the batter and changing process conditions can be reacted to in a flexible manner. For instance, the kneading trough may be divided into a pre -mixing zone and a reduction zone. In the pre-mixing zone, meal and water are combined and kneaded to a homogenous batter, whereby the flour particles are hydrated and the protein molecules present therein unfold. In the reduction zone, the batter is then kneaded further, whereby insoluble protein particles (with wheat meal: glutenin particles) are deformed and reduced by means of an above-described composition and decomposition process, until sufficiently large, coherent protein networks can form. The kneading in the pre-mixing zone requires relatively little energy and can therefore take place using relatively low kneading speeds and relatively small forces. By contrast, the kneading in the reduction zone requires much energy, using relatively high kneading speeds and great forces. Due to the division into separate kneading zones, per zone, the most suitable kneading conditions can be set and kneading can take place in an energy -conscious manner. In addition, thus, in the less heavily loaded kneading zones, such as the pre-mixing zones, sufficient reserves are available to be able to quickly and adequately react to varying process conditions. The division into kneading zones further has the advantage that successive stages in the development of the batter can take place in parallel in successive kneading zones. This allows continuous production of batter. In an advantageous embodiment, an apparatus according to the invention is characterized by the measure according to claim 7. In such a final processing zone, the kneading conditions may be set such that further reduction of the protein particles is stopped and the protein and the smaller protein networks already formed have the opportunity to aggregate to relatively large, strong networks (gluten networks in the case of wheat meal). The reduction can be stopped by decreasing the energy transfer to the batter. For this purpose, the final processing zone is preferably provided with water supply means for diluting the batter, so that the viscosity decreases and the energy transfer decreases. In addition, in an advantageous embodiment, the final processing zone can be provided with supply means for additives according to the measures according to claim 9. It is known per se to add additives, particularly enzymes, to the batter in order to neutralize negative influences of fibers present in the batter on the formation and quality of the protein networks. Usually, such additives are added at the start of the kneading process. A disadvantage of this is that, then, the batter still has a crumbly, little homogenous structure and the kneading speeds are, moreover, low. As a result, a relatively large amount of additives is needed to still obtain a homogenous mixing. This is costly and increases the risk of undesired side effects. By not adding the additives until the final processing zone, as proposed in the present invention, much fewer additives are sufficient. Further, this can reduce the water consumption in the final processing zone, in that the additives prevent the fibers present in the batter from binding to the water and undermining the diluting action thereof. Further, it has experimentally been found that the addition of additives at the end of the kneading process is favorable to both the protein yield and the purity of the recovered starch. In a further advantageous embodiment, an apparatus according to the invention is characterized by the measures according to claim 13. Due to such an exchangeable design, successive kneading zones can at least temporarily take over one another's tasks and thus even more flexibly anticipate unexpected deviations in the development of the batter. Thus, the kneading means in the final processing zone are preferably dimensioned such that, therewith, sufficient energy can be transferred to the batter to reduce protein particles present therein, should this have been done insufficiently in the preceding reduction zone. Thus, the final processing zone can function as a continuation of the reduction zone. Likewise, the reduction zone can function as a continuation of the pre-mixing zone. The different kneading zones are preferably designed as modular, couplable parts so that the number of zones per kneading apparatus and/or the length thereof can be extended as needed, depending on, for instance, the type of meal to be processed. In a further advantageous elaboration, an apparatus according to the invention is characterized by the measures according to claim 14. A great problem with known kneading apparatuses is that the batter therein is often kneaded too long ('overkneaded') or too short ('underkneaded'). With overkneading, the above-mentioned protein particles (glutenin particles) are reduced too strongly and, moreover, during the composition and decomposition process, formed protein units can become irreparably damaged. As a result, the final protein yield decreases and the quality declines. With underkneading, the protein particles (glutenin particles) are, conversely, not sufficiently reduced, so that they can contribute insufficiently to the formation of strong protein networks. Consequently, the separation of the protein and starch becomes considerably more difficult, the risk that the starch becomes polluted is higher and the final protein and starch yields will be lower. In an apparatus according to the invention, in an advantageous manner, use is made of the insight that, for each type of meal (wheat, rye, legumes, etc.), there is a particular size of the protein particles where network formation proceeds optimally, regardless of the exact composition or quality of the respective type of meal. For wheat meal, this has been demonstrated in "Understanding the link between GMP and dough: from glutenin particles in flour towards developed dough" of Clyde Don et al., published in Journal of Cereal Science 38 (2003), pp. 157-165. According to this article, glutenin particles with a size distribution between about 5 and 100 μm form ideal building blocks for the composition of gluten protein networks. This target size is reached by kneading. By controlling the kneading means on the basis of the momentary size of the protein particles (glutenin particles), kneading can simply take place until a majority of the protein particles, for instance 80% or more, has an average size which corresponds to the target size. Here, the shearing forces caused during the kneading ensure that the relative (chemical) equilibrium between the protein particles changes, both on a micro scale and on a nano scale, such that the glutenin particles obtain a size at which glutenin formation proceeds optimally. Then, the kneading is stopped. By thus timely stopping the kneading, underkneading and overkneading can be avoided and strong protein networks can be formed in the batter. The result of this is that the protein and starch can relatively simply be separated, resulting in a high starch and protein yield, with a high degree of purity. In a particularly advantageous embodiment, an apparatus according to the invention is characterized by the measures according to claim 15. For a good operation of the above-described apparatus, it is important that the size of the protein particles can accurately and quickly be estimated or measured. It is known from practice to estimate the condition of the batter on the basis of the amount of energy supplied to the kneading means. This is considered a measure for the amount of energy transferred to the batter. With this information, it is then estimated, on the basis of empirical data from previous kneading sessions, how "far" the batter has been developed. Such a measurement method does not yield an accurate picture, inter alia because it is uncertain how much of the energy supplied has been actually transferred to the batter. This is a further cause why batter is often overkneaded or underkneaded in the known kneading processes. Further, a measurement method is known where, at regular intervals, batter samples are taken, which are analyzed in a laboratory. Such a measurement method yields accurate information, but is time-consuming and therefore unsuitable for use in a continuous production process. Experiments of applicant have shown that, with ultrasonically reflective sensors, morphological changes in the batter, particularly changes in the average particle size and/or shape can accurately and momentarily be monitored. Thus, stages in the development of the batter corresponding with these morphological changes can be made visible and kneading conditions can be adjusted accordingly. In addition, with such an ultrasonically reflective measurement technique, the moment when the majority of the protein/glutenin particles reaches an optimal size and deformation can accurately be determined, so that the reduction process can be stopped timely. Preferably, the reduction zone is provided with multiple ultrasonically reflective sensors placed one behind the other in feeding direction, so that the batter development can be monitored from the beginning to the end and the kneading conditions can be controlled such that the protein particles have the desired size and shape at the end of the reduction zone. Of course, the other kneading zones may also be provided with one or more ultrasonically reflective sensors or other measuring means. The sensors are preferably provided in the kneading trough with the aid of special, detachable coupling pieces. Such coupling pieces can help to protect sensitive parts of the sensors against harmful influences from outside or of the batter, flour or water. Further, this allows the sensors to be replaced in a simple manner, for the benefit of, for instance, cleaning, calibration or similar maintenance activities. It is noted that the ultrasonically reflective measurement technique can also advantageously be used in a kneading device without the limitative measures of the preceding claims, for instance in a kneading apparatus which is not subdivided into different kneading zones. Experiments of applicant have shown that, when the batter is prepared as described hereinabove and the protein particles thus have the desired size and deformation at the end of the reduction zone, virtually complete aggregation can take place in the subsequent final processing zone when the energy transfer is decreased, for instance by diluting the batter or decreasing the kneading speed. This causes the protein network (gluten protein) to 'spontaneously' separate from the bulk of starch, without large amounts of washing and/or diluting water needing to be supplied for the purpose. In addition, this 'spontaneous' separation is found to take place even more completely when the kneading temperature is decreased to below the conventional temperatures of 30° to 40°C, for instance to below 27°C, in particular below 23°C and preferably to about 20°C or lower. In this manner, much energy can be saved. Moreover, the final protein yield is found to be higher than is conventional. The batter prepared from wheat flower with an apparatus according to the invention contained protein networks with a protein content between about 60 and 68% (on a dry matter basis), whereas percentages between 40 and 50% are conventional with protein networks prepared with the known kneading apparatuses. In a particularly advantageous embodiment, the prepared batter is then separated in an apparatus according to claim 23. With the known apparatuses, the ready batter is conventionally intensively mixed with water in a so-called 'siever' and then led to a separation device, for instance a series of shaking sieves. In the siever, the protein networks are reduced to millimeter size between two rotating disks provided with knives, so that enclosed starch is released and can be washed away with water. A disadvantage of this manner of separating is that, thereby, relatively much washing water is consumed and the protein networks are irreparably reduced and damaged. In an apparatus according to the invention, it is possible, due to the strong and pure protein networks, to make use of a completely new separation technique, where the batter with the diluting water is led from the final processing zone between a set of rollers. Here, still enclosed starch is expressed from the networks and discharged together with the diluting water. This roller cycle can be repeated a few times if desired, either by repeatedly leading the protein along the same set of rollers or by setting up multiple pairs of rollers one behind the other. Especially in a continuous production process, the latter set up is preferred. Experiments of applicant have shown that good results can be obtained with three pairs of rollers set up one behind the other. The diluting water can optionally be collected and recycled. The separation device needs much less water compared to the known separation method. In addition, the protein networks remain largely intact. It is noted that the measures discussed hereinabove (use of rollers as separation device and decrease of the process temperature to promote spontaneous aggregation) can also advantageously be used in kneading apparatuses where the kneading trough is not subdivided into kneading zones. It is only important that the batter is kneaded such that the protein particles undergo the desired reduction and can thus aggregate to strong, pure protein networks. The invention further relates to a method for recovering starch and/or protein from meal and batter produced with this method or an apparatus according to the invention. In the further claims, further advantageous embodiments of an apparatus and method according to the invention are described. In explanation, an exemplary embodiment of an apparatus for recovering protein and/or starch from meal will be elucidated in more detail with reference to the drawing, in which: Fig. 1 diagrammatically shows a kneading apparatus according to the invention, with three successive kneading zones; Fig. 2 shows a cross section of the kneading apparatus along line II-II in Fig. 1, in which the kneading means are visible in more detail; Fig. 3 diagrammatically shows an ultrasonic reflection sensor and a coupling piece for this, for installation of the sensor in the kneading apparatus according to Fig. 1; Fig. 4 shows an example of a measurement result of an ultrasonically reflective measurement; and Fig. 5 diagrammatically shows a separation device according to the invention, for separating protein and starch from batter, prepared in a kneading apparatus according to Fig. 1. In this description, same or corresponding parts have same or corresponding reference numerals. The terms meal and flour will be used interchangeably. In this description, the term meal or flour is to be understood to mean at least ground grain (for instance wheat, rye, oat, barley, spelt, etc.) or legumes with a protein content of at least 3 wt.% (on a dry matter basis, that is, dry protein in relation to dry flour). A continuous process is understood to mean a production process with a continuous input (here: flour, water and any additives) and a continuous output (here: batter). The term ultrasonic reflection is understood to mean a measurement method where a measuring object is exposed to an ultrasonic vibration (with a frequency of, for instance, 5 MHz) and where a response signal reflected by the measuring object is received by a sensor and converted to a value, curve or pattern, representative for the size and/or composition of the respective object. In this description, the term inline measurement is understood to mean a measurement which takes place directly on or to the process, where the measurement results are obtained directly, at least without any appreciable delay. In the following description, the invention will be elucidated in more detail on the basis of an apparatus and method for recovering gluten protein and starch from wheat meal. Gluten protein or gluten for short is the water-insoluble part of protein which is found in wheat. It is explicitly noted that the apparatus and method according to the invention are also applicable for recovering starch and protein from other types of grain or legumes. Fig. 1 diagrammatically shows an apparatus 1 according to the invention for preparing batter 20 from flour 2, water 15 and any additives 17. The kneading apparatus 1 comprises a cyHndrical kneading trough 3, which is subdivided into kneading zones 3A-C, in the exemplary embodiment shown three zones, namely a pre-mixing zone A, a reduction zone B and a final processing zone C. These zones 3A-C correspond with three preparation stages of the batter 20, to be described hereinbelow. Each zone 3A-C is provided with kneading means 5A-C. In the exemplary embodiment shown, these each comprise a drive shaft 4A-C bearing-mounted centrally in the respective kneading zone 3A-C, which shaft is provided with blades 6. The blades 6 extend to near an inner wall of the kneading zone 3A-C are provided around the drive shafts 4A-C in a spiral-shaped manner, where successive blades have been rotated over 120° relative to one another. The blades 6 are each built up from three bar-shaped arms 21, 22, 23, which are, by their first ends, attached to the drive shafts 4A-C and are, by their other ends, mutually connected by a cross blade 24. Here, the middle arm 22 extends in radial direction from the drive shaft 4A, while the two outer arms 21, 23 include a smaller, positive and negative angle α, respectively, with the middle arm 22, as can clearly be seen in Fig. 2. The blade 6 thus has a somewhat twisted shape. As a result, mixing chiefly takes place in radial direction. The large number of arms 21-23 ensures intensive kneading. In addition, the twisted shape provides a good propelling action in feeding direction (indicated by arrow A in Fig. 1). The drive shafts 4A-C are each individually drivable by a drive means 7A-C known per se, for instance a servomotor, which is coupled to a control device 16. Here, the coupling between the drive means 7A-C and the different drive shafts 4A-C is preferably constructed such that the feed- through between the different kneading zones 3A-C is not, at least as little as possible, hampered thereby. This may, for instance, be realized by designing the outer drive shafts 4A,C so as to be hollow and having the middle drive shaft 4B continue with extended (and preferably reduced) ends to outside the kneading trough 3, through the hollow drive shafts 4A,C. On one or both projecting ends of the drive shaft 4B, a drive means 7B can then engage, without disturbing the feed-through in the kneading trough 3. Depending on the distances to be covered, the extended ends may be supported by one or more bearings in the hollow drive shafts 4A,C. Of course, many other constructions are possible. The pre-mixing zone 3A is, near a first end 8, provided with first supply means 11 for the supply of flour 2 and provided, in feeding direction A, with a series of second supply means 12 placed one behind the other at regular intervals for stepwise supply of water 15. The first and second supply means 11, 12 are connected to the above-mentioned control device 16 with which a desired flow can be supplied to meal 2 and water 15 at all times. The final processing zone 3C is provided with third supply means 13 for the supply of water and fourth supply means 14 for the supply of additives 17, which are, just like the preceding supply means 11, 12, connected to the control device 16. Further, the final processing zone 3C is, near an end 9, provided with discharge means 18 for the discharge of ready batter 20 to a separation device to be described in more detail hereinbelow, with which gluten 28 and/or starch 29 can be recovered from the batter 20. All kneading zones 3A-C further comprise a number of ultrasonically reflective measuring means 10 (to be described hereinbelow in more detail with reference to Fig. 3) with which developments in the batter 20, particularly morphological developments of glutenin particles present in the batter 20 (reduction, deformation) can accurately be monitored inline, during the passing through of the different kneading zones 3A-C. The signals measured are fed back to the control device 16. Via suitable signal-processing means 19, this is provided with a control algorithm which compares the development measured with a desired development path and adjusts the kneading conditions (speed of the kneading means 5A-C, dosing of the supply means 11-14) in the different kneading zones 3A-C in case of an observed deviation. Of course, in the kneading trough 3, further measuring means may be provided for measuring further process parameters, such as for instance the temperature, the viscosity of and/or the percentage of dry matter in the batter, the energy supplied to the kneading means and/or kneading resistance experienced by these kneading means 5A-C. These measurement data may also be used by the control unit 16 and the control algorithm included therein for control of the kneading conditions. Fig. 3 shows, in partly exploded cross section, an ultrasonically reflective measuring means 10 according to the invention which can be screwed down in the wall of the kneading trough 3 in a detachable manner via a coupling piece 25. The measuring means 10 comprises a housing 30, inside which a vibration source 26, for instance a piezoelectric element, is included with which an ultrasonic vibration can be transmitted. The measuring means 10 further comprises a signal detector 27 with which a response signal reflected by the batter 20 can be received and conveyed to above-mentioned signal-processing means 19. The reflected signal comprises information regarding the morphological development of the batter. This information is inter alia included in the intensity of the response signal (determined by the extent of either reflection or absorption) and the phase shift with respect to the transmitted vibration signal. With the signal-processing means 19 such as filters, this information is analyzed and presented in suitable graphical form, an example of which is shown in Fig. 4. In this, a number of successive measurement results can be seen, which clearly show how the location of the peak value Mi shifts and smaller, secondary peaks M2 arise. With suitable caHbration, from the shift of the peak value Mi, information regarding the average particle size can be deduced. Further information can be deduced from the shape of the curve and the absence or presence of the secondary peaks M2. Preferably, per kneading zone 3A-C, multiple measuring means 10 are provided, as shown in Fig. 1, so that the development of the batter 20 can accurately be monitored and, on the basis thereof, adjustments can timely be made. The coupling piece 25 is designed such that, in mounted condition, an inwardly directed side thereof connects virtually seamlessly to the inner waU of the kneading trough 3, to avoid seams and cracks in which batter 20 and/or flour 2 can remain behind. Further, the coupling piece 25 has such a design that the more sensitive parts of the measuring means 10, in particular the vibration source 26 and the signal detector 27, do not directly contact the batter 20 but are screened therefrom by a more robust intermediate part 31. Further, the coupling piece 25 is simply detachable due to the screwed connection, so that the measuring means 10 can simply be replaced. The operation of the kneading apparatus 1 shown in Fig. 1 is as follows. In the pre-mixing zone 3A, the first stage of the batter preparation process takes place, in which meal 2 supplied by the first supply means 11 is mixed "into the crumb" with gradual supply of water 15 via the second supply means 12. Here, flour particles present in the meal are hydrated, whereby the protein particles in these flour particles swell and unfold. With the aid of the control device 16, the proportion of meal, water is preferably dosed such that the percentage of dry matter in the batter 20 is approximately 63% near the start of the pre-mixing zone 3A, that is, at the start of the "mixing into the crumb", and then gradually decreases to a lower percentage, for instance about 45%, near the end of the pre-mixing zone 3A (or the beginning of the next zone). Preferably, the batter 20 is then homogenous. The desired dry matter percentages, particularly the percentage at the end of the pre-mixing zone 3A, depend on inter alia the type of grain used and the kneading temperature, and the values mentioned are therefore to be taken to be illustrative. With the values given hereinabove, wheat flour was used as flour and the kneading temperature was about 20°C. For this development stage of the batter 20, relatively little energy is needed. The kneading means 5A are therefore controUed using a moderate rotational speed, for instance 15 revolutions per minute. The residence time in the pre-mixing zone 3A is, for instance, about 5 minutes. It is noted that aU above-mentioned values and the values foUowing hereinbelow only serve as an illustration and depend on inter alia the size of the kneading trough 3 used. The values are therefore by no means to be taken as being limitative. Then, the batter 20 is kneaded further in the reduction zone 3B, where the energy transfer is considerably increased by driving the kneading means 5B using a higher rotational speed of, for instance, about

40 revolutions per minute. This causes the insoluble glutenin particles to be deformed and reduced, during a process where protein networks are continuously formed, decomposed and formed again, whereby the size of the protein networks gradually increases and accordingly the viscosity of the batter 20. The deformation and reduction of the glutenin particles are monitored using the above-described ultrasonically reflective measuring means 10 and compared with a desired reduction and deformation, respectively, by the control device 16. Depending on the outcome of this comparison, the rotational speed of the kneading means 5B is adjusted if needed, and such that the glutenin particles have the desired size at the end of the reduction zone 3B, that is, at the transition to the final processing zone 3C. On the one hand, the residence time of the batter 20 in the reduction zone 3B needs to be sufficiently long so that the energy needed for reducing the glutenin particles can be transferred to the batter 20 but, on the other hand, it is preferably as short as possible, with a view to the transit time and production rate. In practice, it is found that, with a residence time of between about 2 to 4 minutes, good results can be achieved. In the final processing zone 3C, the third stage of the batter preparation process then takes place. Here, the energy transfer to the batter 20 is decreased by reducing the rotational speed of the kneading means 5C, for instance to 20 revolutions per minute, so that further reduction of the glutenin particles is stopped and aggregation of the gluten network can take place. Additionally or alternatively, such a 'spontaneous' aggregation can be promoted by setting a lower temperature than the conventional kneading temperatures of 30° to 40° in the final processing zone 3C (or in all kneading zones). Preferably, the temperature is around 20°C or lower. Additionally or alternatively, via the third supply means 13, a small amount of water 15 can be added. As a result, the viscosity of the batter 20 decreases and the shearing forces decrease so that the reduction is stopped and aggregation of the gluten network can take place. The dilution is preferably small, so that the percentage of dry matter in the batter 20 remains at least higher than 40%. Further, in this final processing zone 3C, additives 17 may be supplied via the fourth^' supply means 14. With these additives, interference of fibers (inter alia soluble pentosans, water-insoluble residues of endosperm cell wall, bran, brush hairs and pericarp) present in the batter 20 with the formation of gluten networks is minimized. Suitable additives 17 comprise inter alia pH-regulating chemicals, oxidative and reductive substances and enzymes to decompose pentosans or to cut protein molecules in particular places. In addition, the additives 17 can prevent fibers present in the batter 20 from preventing the desired viscosity decrease by bonding with water. Consequently, in the final processing zone 3C, finally, less diluting water is sufficient than would be the case without addition of additives. Just Hke in the two preceding zones 3A,B, in this zone 3C, use can be made of ultrasonically reflective measuring means 10 to monitor the condition of the batter 20, in particular the aggregation of gluten networks, and to adjust, for instance, the dosing of water 15, additives 17 or the rotational speed of the kneading means 5C on the basis thereof. If the glutenin particles should not have reached their target size at the end of the second zone 3B, then the final processing zone 3C can function as continuation of the reduction 3B by choosing the rotational speed of the third kneading means 5C so as to be equal to that of the reduction zone 3B and postponing the supply of water 15 and additives 17. At the end of the final processing zone 3C, the batter 20 is ready to recover the gluten protein 28 and starch 29 therefrom. This may take place in a conventional manner, for instance by washing, filtering, centrifuging or a combination thereof. Preferably, however, use is made of a separation device 40 as shown in Fig. 5. This device 40 comprises an input opening 41 and three pairs of rollers 42A-C placed on below the other. Above each pair of rollers 42A-C, supply means 46 for washing water are provided, below each pair of rollers 42A-C, a declining sieve 43 is arranged. On this, batter and water led between the rollers are coUected. This batter consists of gluten networks 28 and water with starch 29 suspended therein. During the feed-through between the rollers 42A-C, a part of the starch 29 enclosed in the gluten 28 is expressed from this and taken along by the (washing) water. The washing water with the starch 29 suspended therein falls through the sieve 43 on an inclining collecting screen 44 arranged below this and is fed, via this screen 44, to further separation means where the starch is filtered from the water. This water can then be pumped back to the water supply means 46 for reuse. The (partly) expressed gluten remains on the sieve 43 and is led, via an overflow 45 and feeding means 47 arranged therebelow, to the second pair of rollers 42B located therebelow, where the same process is repeated, after which the then remaining gluten is led to the third pair of rollers 42C for a last pressing. Of course, depending on, for instance, the starting grain, more or fewer pairs of rollers may be provided. In a particularly advantageous embodiment, the roUers are profiled. This increases the grip on the suppHed batter 20 so that the risk of accumulation is reduced. In addition, this increases the pressing surface so that a still better pressing action is obtained. This is the more advantageous because (gluten) protein is difficult to stretch. By providing the rollers with, for instance, corrugations, the protein is alternately stretched, each time in different pressing directions. This promotes the separation of starch. The above-described separation device 40 offers the advantage that it is less destructive to the protein networks than the known separation devices and leaves the gluten networks largely intact. In addition, the device consumes little water, which can, in addition, easily be recycled. Although the above-described roller separation device 40 is particularly intended for separating batter 20 which has been prepared with a kneading apparatus 1 according to the invention and which is therefore 'well separable' due to the relatively large, strong, pure protein networks, the roller separation device 40 is not limited to such a use, but can also be deployed for separating protein and starch from batter which has been prepared in a conventional apparatus. The above-described apparatus according to the invention has many advantages. For instance, due to the subdivision of the kneading process into successive kneading zones with individually settable kneading conditions as well as the improved measurement method based on ultrasonic reflection, kneading can take place more energy -consciously, while the supply of energy can better be adapted to the momentary need of the batter. Moreover, this allows the development of the batter, in particular the reduction of protein particles present therein, to be controlled such that strong protein networks can be formed, irrespective of the composition of the meal. This aUows a good separation of protein and starch with a high yield and high purity at all times. In addition, this separation can take place with relatively little water when use is made of a roUer device according to the invention. In addition, the kneading process as described hereinabove is found to produce stiH better results at a relatively low kneading temperature, in particular around room temperature, so that energy can be saved. The water consumption can be reduced still further by not adding fiber-neutralizing additives until the end of the kneading process. The invention is by no means limited to the exemplary embodiments shown in the description and the drawing. It is explicitly noted that combinations of (parts of) exemplary embodiments shown are understood to be within the inventive concept. In addition, many variations are possible within the scope of the invention set forth in the claims. For instance, the kneading process may be divided into more stages than shown in the exemplary embodiments. The kneading means may be designed differently, for instance as a rotatably arranged spiral or screw spindle, whose windings extend to near the jacket of the kneading cylinder. Further, in addition to or instead of the (ultrasonic) measuring means mentioned, other measuring means may be used for monitoring batter parameters, for instance one or more temperature sensors, flow meters, viscosity meters, camera with suitable pattern recognition programs, etc. The nozzles for dosing water and/or additives may be placed around the circumferential wall of the kneading trough, in order to bring about a still more uniform supply. These and many other variations are understood to be within the scope of the invention as set forth in the following claims.

Claims

1. An apparatus for processing meal and water to such a batter that starch and/or protein can be recovered therefrom, comprising: a. a kneading trough (3); b. first and second supply means (11; 12) connecting to the kneading trough (3) for the supply of meal and water, respectively; c. kneading means (5) arranged in the kneading trough (3) for mixing meal (2) and water (5) to batter (20) and for kneading this batter (20) so that protein particles present in the meal (2) reduce and thus form protein networks (28); and d. discharge means (18) for discharge of the ready batter (20) to a separation device for separating the protein networks (28) and starch (29), characterized in that the kneading trough (3) comprises at least two kneading zones (3A-C) successive in feeding direction, with individually settable kneading conditions per kneading zone (3A-C).

2. An apparatus according to claim 1, wherein a control device (16) is provided for controlling the different kneading conditions in the different kneading zones (3A-C) on the basis of a desired development path for the batter (20) and protein particles present therein during the passing through of the different kneading zones (3A-C).

3. An apparatus according to claim 1 or 2, wherein each kneading zone (3A-C) is provided with measuring means (10) for infine measuring and monitoring at least one parameter representative for the development of the batter (20).

4. An apparatus according to any one of the preceding claims, wherein one of the kneading zones (3A-C) is arranged as a pre-mixing zone (3A) for kneading the batter (20) to a homogenous mixture wherein protein molecules present in the meal (2) are hydrated, unfold and are separated from one another. 5. An apparatus according to claim 4, wherein the pre-mixing zone (3A) comprises a series of second supply means (12) placed one behind the other

5 in feeding direction (a), preferably over the whole feeding length, for dosed supply of water (15) and any additives (17), wherein the proportion of dry matter (%ds) in the batter (20) gradually decreases in feeding direction (A).

6. An apparatus according to claim 4 or 5, wherein one of the kneading zones (3A-C) following the pre-mixing zone (3A) is arranged as reduction0 zone (3B) for further kneading the batter (20) and reducing protein particles present therein.

7. An apparatus according to claim 6, wherein one of the kneading zones (3A-C) following the reduction zone (3B) is arranged as final processing zone (3C) for stopping, at least inhibiting further reduction of the5 protein particles and for allowing these protein particles to aggregate to relatively large, strong protein networks (28).

8. An apparatus according to claim 7, wherein the final processing zone (3C) comprises third supply means (13) for the supply of water (15), for diluting the batter (20) and thus stopping the reduction.0

9. An apparatus according to claim 7 or 8, wherein the final processing zone (3C) comprises fourth supply means (14) for the supply of additives (17), in particular enzymes, for neutralizing fibers present in the batter (20) in order to prevent bonding of these fibers with water (15).

10. An apparatus according to any one of the preceding claims, wherein5 each kneading zone (3A-C) comprises kneading means (5A-C), of which at least the kneading speeds are individually controllable so that a desired kneading speed and corresponding energy transfer to the batter (20) is settable per kneading zone (3A-C).

11. An apparatus according to claim 10, wherein the amount of energy o transferred in the reduction zone (3B) is considerably higher than in the other kneading zone(s) (3A,C), in particular the pre-mixing zone (3A) and a possible final processing zone (3C).

12. An apparatus according to any one of claims 6-11, wherein the residence time of the batter (20) in the reduction zone (3B) is shorter than 4 minutes, is in particular shorter than 3 minutes and is preferably about 2 minutes.

13. An apparatus according to any one of the preceding claims, wherein successive kneading zones (3A-C) are arranged such that they can at least temporarily take over one another's kneading conditions , so that a kneading zone (3A-C) can function as a continuation of an adjacent kneading zone (3A,B).

14. An apparatus for processing meal (2) and water (15) to such a batter (20) that starch (29) and/or protein (28) can be recovered therefrom, comprising a kneading trough (3), first and second supply means (11, 12) connecting thereto for the supply of meal (2) and water (15), respectively, kneading means (5) arranged in the kneading trough (3) for mixing meal (2) and water (15) to batter (20) and for kneading this batter (20) so that protein particles present in this meal (2) reduce and thus form protein networks, and discharge means (18) for discharge of the ready batter (20) to a separation device for separating the protein networks (28) and starch (29), possibly according to any one of the preceding claims, characterized in that the control of the kneading means (5), in particular the kneading speed, takes place on the basis of the morphological condition of the protein particles, in particular the momentary size and shape thereof, compared to a predetermined desired morphology.

15. An apparatus according to claim 14, wherein the kneading trough (3) comprises ultrasonically reflective measuring means (190 for measuring the morphological condition of the protein particles, in particular an average size thereof.

16. An apparatus according to claim 15, wherein the ultrasonically reflective measuring means (10) have been provided in a wall of the of the kneading trough (3) in a detachable manner with the aid of a coupling piece (25), wherein the coupling piece (25) protects sensitive parts of the measuring means (10) against batter (20) present in the kneading trough (3) in use.

17. An apparatus according to any one of claims 6-16, wherein a majority, preferably more than about 80%, of the protein particles has a target size between about 5 and 100 μm and more in particular between about 20 and 80 μm at the end of the reduction zone (3B).

18. An apparatus according to any one of the preceding claims, wherein the kneading trough (3) is designed as a cyHndrical tube, and the kneading means (5A-C) comprise a drive shaft (4A-C) arranged centrally in the tube, which drive shaft (4A-C) is provided with blades (6) which have been provided around the drive shaft (4A-C) in a spiral-shaped manner, preferably relatively rotated over 120°, and which, with a free end, extend substantially radially to near an inner wall of the kneading trough (3).

19. An apparatus according to claim 18, wherein each blade (6) is built up from at least three bar-shaped arms (21, 22, 23), wherein a centrally located arm (22) of these arms (21-23) extends substantially radially from the drive shaft (4A-C) and wherein the arms (21, 23) located on both sides of this central arm (22) include an positive and negative angle (α), respectively, with the central arm (22), which angle (α) is between about 5° and 20°; aU this such that the blade (6) has a somewhat twisted shape with a propeUing action in feeding direction (A) of the kneading trough (3).

20. An apparatus according to any one of the preceding claims, wherein the preparation of the batter (20) takes place in a continuous process.

21. An apparatus according to any one of the preceding claims, wherein the production capacity is larger than 20 tons per hour, is in particular larger than 40 tons per hour and is preferably about 60 tons per hour.

22. An apparatus according to any one of the preceding claims, wherein the meal (2) is wheat meal, the protein (28) to be recovered is gluten and the protein particles are glutenin particles.

23. An apparatus according to any one of the preceding claims, wherein a 5 separation device (40) is connected to the discharge means (18), which separation device (40) comprises at least one pair and preferably multiple pairs of rollers (42A-C0 arranged one behind the other in feeding direction, for expressing water (15) and starch (29) suspended therein from the protein networks (28).0

24. An apparatus according to claim 23, wherein the separation device (40) comprises filter means for filtering starch (29) from the expressed water (15), and recycling means for reuse of the filtered water in any subsequent roller cycles, for washing and expressing remaining starch (29) from the protein networks (28).5

25. A method for continuous recovery of starch (29) and/or protein (28) from meal (2), in particular starch and/or gluten protein from wheat meal, wherein meal (2) and water (15) are combined to a batter (20) and wherein this batter (20) is kneaded so that particular water-insoluble protein particles present in the meal (2) (glutenin particles in wheat meal) are o reduced and can thus form coherent protein networks (28), which protein networks (28) can then be separated from starch (29) present among them, characterized in that the kneading of the batter (20) is controUed on the basis of the morphological condition of the respective protein particles, in particular the average size thereof compared to a predetermined target size.5

26. A method according to claim 25, wherein the morphological condition of the protein particles, in particular the momentary size thereof can be monitored inline with the aid of ultrasonic measurement techniques, in particular ultrasonic reflection measurements.

27. A method according to claim 25 or 26, wherein, as soon as the o majority of the protein particles has reached a predetermined target size, further reduction of the protein particles is stopped by diluting the batter (20) with water (15).

28. A method according to claim 27, wherein, prior to or during the dilution of the batter (20), additives (17) can be added, in particular enzymes, which can neutralize the fibers present in the batter (20) so that these fibers cannot, or can at least to a lesser extent, bond with water.

29. A method according to claim 27 or 28, wherein, after dilution, the weight percentage of dry matter is at least 25 wt.% ds, preferably more than 30 wt.% ds and in particular about 35wt.% ds or more.

30. A method according to any one of claims 25-29, wherein the preparation temperature of the batter (20) is lower than 27°C, is in particular lower than 23°C and is preferably equal to or lower than 20°C.

31. A method according to any one of claims 25-30, wherein the protein networks (28) and the protein (29) present among them are separated from one another by roUers, wherein the starch is expressed from the networks (28).

32. A batter, manufactured in an apparatus according to any one of claims 1-24 or with a method according to any one of claims 25-30, wherein the protein networks (28) formed in this batter (20) are relatively large, have a strong coherence and a protein content higher than 60%, preferably higher than 65% (based on dry matter measurements).