This invention relates to a novel process for treating grain to improve its baking properties.

The enzyme alpha amylase is present at varying levels in all wheat grains. One form of it is known as green alpha and is active in the building up of starch in the period of crop growth when the grain is filling. Once the grain matures to a state of ripeness the level of alpha amylase normally reduces to a low level. There then follows a short period varying from one to several days when the wheat is ready for harvesting. Once this short period is over the level of alpha amylase increases to a high level as the process of germination of the wheat grain proceeds. This latter type of the alpha amylase enzyme is known as germination alpha and its build up is very considerably accelerated by wet or humid weather at or preceding the harvesting of the crop. The effect of these high levels of this enzyme is to break down the starch into soluble sugars which precedes and is an integral part of the germination process. In severely wet harvesting conditions the wheat grains can actually start to sprout especially if the crop is laid.

Where wheat is used for the production of flour for any baking process there is a preferred upper limit to the level of alpha amylase activity present in the flour. This is particularly so where the flour is being used for baking bread. This aspect of the suitability of wheat of flour for baking is normally measured using the Hagberg test method. High levels of alpha amylase together with the associated changing of the wheat starch into sugars result in bread having a weak, sticky and totally unacceptable crumb structure. Loaves baked from flour containing a high level of alpha amylase tend to fall apart and are almost impossible to slice.

It has long been known that the alpha amylase present in wheat could be inactivated by heat. However, the amount of heat required to inactivate this enzyme has disastrous effects on the gluten content which thus renders the wheat unsuitable for baking and bread making purposes.

The present invention seeks to inactivate the alpha amylase enzyme without the use of heat thus preserving the other essential constituents of the wheat grain.

Accordingly, the present invention provides a method of improving the baking properties of grain, flour or dough comprising causing an electrical field to be established in or across it or causing an electric current to flow through it. It has been found that the alpha amylase enzyme can be deactivated by the use of electric fields and/or currents.

Preferably, in its application to grain or flour, the method further comprises subjecting the grain or flour to an impulse. Although the following is speculative, it is thought that the electrical effects or the electrical effects coupled with the impact and acceleration caused by the impulse may destroy certain cells specifically associated with the action of the alpha amylase enzyme. It is thought that the lysosomes within these cells may be being destroyed.

The impulse may be provided by physical contact with a moving impeller and if the impeller is selected from an appropriate material, such as elastomeric polyurethane with a hardness between 80 and 85 degrees A, the motion of the impeller through grain may itself electrically charge the grain, which is subsequently discharged. Simultaneously, the grain may also be subjected to an electric field, either alternating or static.

The impeller may comprises one or more blades mounted for rotation about an axis. Preferably, the impeller rotates above a metallic pan and causes the grain to pass across

the pan. The clearance between the impeller blades and the pan is preferably up to 5 mm, most preferably between 1 and 2 mm.

The impeller may be insulated from the pan and the pan insulated from earth.

The method of the invention may comprise causing an applied electric field of between 10 and 25 kV/cm to be established across the grain, flour or dough. Such a field is preferably applied for a period of up to 10s. The grain, flour or dough may be conveyed between a pair of electrodes, between which said electric field is established.

The method according to the invention may comprise applying a corona discharge to the grain, flour or dough, e.g. by passing the grain, flour or dough through a corona discharge. The discharge is preferably applied to the grain, flour or dough for a period of up to 0.1s. and it current density is preferably between 0.0001 and 0.01 mA/cm ² , most preferably between 0.0005 and 0.001 mA/cm ² .

The present invention also extends to apparatus for improving the baking properties of grain or flour comprising means for causing an electric field to be established across or in or for causing a current to pass through the grain or flour and means for subjecting the grain or flour to an impulse.

The wheat grains may be subject to a charge of electricity, e.g for only a fraction of a second, and subsequently discharged. A static charge may be employed. The grains may concurrently be subjected to impact and rapid acceleration. For an enhanced effect in inactivating the alpha amylase enzyme, the grains are preferably subjected to an electric field during their charging and subsequent discharging.

Alternatively, the electrical current may be passed through the grains by simply conveying the grains between a pair of electrodes so as to complete an electrical connection between the two, thus allowing the flow of electrical current through the grains.

The invention will now be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic view in cross section of a grain pre-cleaner and separator;

Figure 2 shows detail of the impeller blade and chamber;

Figure 3 shows an alternative impeller blade; and

Figure 4 is a view in the product direction of the impeller and chamber of figure 3.

The invention may be embodied in a modification of the grain separation machine disclosed in UK patent no. 2213079. The machine comprises a hopper 21 containing an inclined rotary screen or drum 22 of perforated steel which is revolved in the hopper 21 by chain drives 23 via sprockets 24, 25, 26 from an electric motor 28 mounted in an accessible place on a sub-frame 29 outside the enclosed frame 31 of the machine. The frame 31 is stiffened and plated as necessary to support the necessary fixing shafts and bearings and is in the form of a casing which encloses most of the components of the machine.

Under the screen 22 a levelling auger 32 is located centrally in the hopper 21 for levelling the grain upstream of a feed roller 33 to ensure a regular and steady flow of grain to the feed roller 33. The amount of grain passing to the feed roller 33 is regulated by a gate 34. The gate is moveable across the grain path between the auger 32 and the roller 33 by adjustment of a handle 35. The roller 33

comprises a set of four longitudinal vanes 36 mounted on a shaft 37 and rotation of the shaft causes the vanes 36 to sweep the grain over a lip 38 into a chute 39 in a regular stream. The lip 38 is formed from angle material welded on the frame 31 at 25° to the horizontal. The frame is also strengthened by a box section 41 which forms a rigid bottom to the hopper 21.

In a further embodiment (not illustrated) the feed roller 33 is dispensed with. Instead the grain enters a wide downward chute to a distribution roller (not shown) which allows it to pass evenly into an intermediate chamber through which it falls to the impeller 51 described hereafter.

A sheet of wire mesh 42 on the side of the hopper 21 arranged between the hopper 21 and the chute 39 enables an operator to view the feed roller 33 in safety.

The system of sprockets and drives for the rotating elements from the motor 28 are as follows: the motor 28 drives pulley 17a via a "v" belt 43. A smaller pulley 17b coaxial with 17a transmits the drive via a single or twin belt 44 to auger 32 and pulley 26a using a moveable tension roller 45. The pulley 26a is coaxial with and fixed to a sprocket 26b which drives the cleaning screen 22 via chains 23 and sprockets 24, 25. Also mounted coaxially with pulley 26a and fixed to rotate therewith is a gear wheel 46 which, with gear wheel 47 and chain 48, provides a variable speed drive to the feed roller 33.

The chute 39 is a rectangular section U-shaped passage open to the top with the centre line angled at approximately 45* to the horizontal. At the apex and mounted eccentrically in an impeller chamber 49 is a grain impeller 51, the construction of which is indicated in Figure 2. The four impeller blades 52 are made of a flexible and resilient material and are bolted to the square shaft 53 at a trailing tangent supported by respective plates 54. The

blades 52 are made from a material which produces static electricity when in high speed frictional contact with the wheat grains. One suitable material is elastomeric polyurethane with a hardness between 80 and 85 degrees A. The blades 52 may, for example, be 1400mm long, 136mm wide and 16mm thick. The impeller 51 has as an integral part a shaft 53 which forms its axis. This shaft 53 is mounted in bearings the housing of which is fully insulated by an electrical non-conductor. The drive is by way of a pulley fixed to the shaft and driven by belts which are also non¬ conductors to achieve impeller speeds of about 2050 rpm.

The impeller 51 is mounted with its shaft 53 parallel to the plane of the chute 39, the part 50 of the chute which passes under the impeller being in the shape of an arc of a circle and forming the lower wall of the impeller chamber. The radius of the circle arc forming the lower wall is greater than the radius of the impeller 51. The chute 39 guides grain/seed through the impeller chamber tangentially past the impeller 51. Rotation of the shaft 53 from an impeller motor 55 and belt 56 causes the blades 52 to sweep the bottom 50 of the chute 39. As the blade returns to its natural position it assists in shooting the grain up the inclined outlet arm 60 of the chute 39. The outlet arm 60 of the chute includes an adjustable wall 57 for altering the choke of the chute 39. When in operation there is a small gap of about 1/16th inch between the impeller blades 52 and the bottom or pan 50 of the impeller chamber. The pan 50 is fabricated from mild or stainless steel for example and is insulated from earth. This may be achieved by standing the machine on rubber wheels. The pan 50 is not connected to adjacent feed and recovery apparatus, to ensure its isolation from earth. Thus the impeller 51 is totally insulated from the machine in which it is housed and the housing is also isolated from earth.

The relative geometry of the wall 50 and the impeller are as follows: a vertical line drawn through the centre 70 of the circle 50 is nearer to the outlet arm 60 of the chute

39 than a vertical line through the impeller centre. Moreover a line drawn through both the centre 70 of the circle arc 50 and through the impeller centre is at 20° to the vertical.

The motor 55a for the impeller is positioned on slide rails (not shown) on a sub-frame (not shown). Adjustment of the position of the motor on the rails can be used to alter the speed of rotation of the impeller 51 in conjunction with an automatic variable speed drive pulley 55b. Angle pieces 58 help constrain the shape of the impeller chamber 49 and the chute 39 and impeller chamber 49 are fixed to the frame 31 via brackets 59. The impeller acts purely mechanically to impel the grain and not as a fan.

The outlet arm 60 of the chute 39 opens into a separation chamber 61 into and through which a stream of air is drawn from an intake 62 by a centrifugal extractor and blower fan 63 for aspirated cleaning. The air stream forms a counter flow which pneumatically modifies the grain trajectories by slowing the grain down. The air intake may be regulated by a butterfly valve 64 located in the intake conduit 62.

There are three outlets from the separation chamber, a first outlet 65 for selected grain or head corn, a second outlet 66 for rejected grain or tailings and a third outlet 67 via the fan 63 through which dust and chaff is drawn on the air stream. The first and second outlets each include respective grain collection chambers 68, 69 having an open end out of which the grain is delivered by respective augers 71, 72 driven by respective belts 81, 82 from a pulley 17b on the same shaft as the pulley 17a. If required conduits can be fitted to the outlets to convey the grain to a different location.

A slidable mounted grain pan 73 is angled approximately 45 ^β to the horizontal and includes at the upper end a divider 74. The grain pan 73 forms a catching site for lower density grain. The grain pan is attached to the inner of

telescopically mounted threaded members 75 which extends and recedes in response to the turning of a handle 76. Rotation of the handle 76 moves simultaneously the divider 74 and the grain pan 73.

Underneath the grain pan is a conduit 77 leading directly down to the first chamber or collecting bin 68 access to which is above the divider 74. At the lower end the grain pan 73 extends partially across a door 78 to which it is parallel and which is hinged at the lower end, the door forming a roof to the first chamber 68 as well as functioning as an extension to the grain pan when closed. The second chamber or collecting bin 69 is disposed adjacent the first chamber 68 and at the bottom of the grain pan 73 and grain pan door 78. Underneath the grain collecting chambers 68, 69, but not connected to them, is a conduit 83 leading directly from the separation chamber 61 via a chaff and dust collecting chamber 84.

The machine is susceptible of use as a gravity separator. The grain pan door is first closed and then the handle 76 is turned to move the divider and grain pan downwardly by a pre-determined amount. The position of the divider will have been determined in advance depending on what grain is to be collected and can subsequently be adjusted according to the output sample required. With the first and second chamber 68, 69 open and the conduit to the first chamber opening to the separation chamber grain is fed to the hopper 21. The rotating screen 22 operates as before removing any trash. Grain is levelled by the auger 32 and moved by the feed roller 33 down the chute to the impeller. Grain shot into the separation chamber travels along a trajectory dependent on its own individual properties landing either above or below the divider 74. That grain reaching above the divider falls into the conduit 77 and travels to the first chamber 68 to be conveyed out of the machine by the auger 71. That grain not reaching the divider lands into the second chamber to be conveyed from the machine by the auger 72. For this operation the air

flow through the intake is drawn into the separation chamber above the divider against the grain movement thus removing the dust and chaff on its stream via the dust and chaff collecting chamber 84.

Enclosing the machine and operating under a partial vacuum has the added advantage of rendering the environment of the machine substantially dust free thus easing the common problem of "farmer's lung" that is often encountered.

The grain is fed into the machine at an accurately controlled rate in a thin stream into the impeller chamber The rate of introduction of material depends to an extent on the dimensions of the machine, but currently about 13.8 tonnes per hour per metre of width of the machine is fed in.

The speed of travel of the grain entering the impeller chamber is relatively slow as they only have to fall a short distance by gravity. Upon entering the chamber they are brought into contact with the plastic impeller blades 52 which are set at a trailing tangent so that their angle of approach causes the grains to run along the face of the blades as the grain is rapidly accelerated to a speed of about 1,600 metres per minute in a distance of about 150mm.

The friction of the wheat grains on the plastic produces a static electrical charge which, it is thought, passes through the wheat grains and is given up to the housing the wheat grains progress at high speed along the curved bottom 50 of the chamber. This discharge of static electricity is considerably assisted because centrifugal force causes the wheat grains to be pressed tightly against the curved metal bottom 50 of the impeller chamber once they have lost contact with the impeller blades 52.

The effect of the charging and discharging of the wheat grains, together perhaps with the impact of the impeller blades 52, is to inactivate, at least partially, the alpha

amylase enzyme. This results in an increase in "falling time" of the Hagberg test as well as an improvement in the baking properties of the flour produced from this wheat. Increases in Hagberg "falling times" in the region of 40s have been observed.

It has been found that the effectiveness of the charging and discharging of the wheat grains can be considerably enhanced by subjecting the grains to an alternating electric field during their charging and subsequent discharging. This can relatively easily be achieved by passing, for example, 420V 50Hz cables 100 under the bottom 50 of the impeller chamber. The closer the cables 100 are to the chamber, the better. The cables 100 are preferably arranged transversely to the machine and correspond in position the point at which the impeller blades 52 approach most closely the bottom 50 of the chamber. It is believed that the alternating electric field imposed by the cables 100 causes oscillating currents within the charged wheat grains, thereby increasing the effect of this static charge on the alpha amylase enzyme.

In addition or alternatively, a high tension supply may be connected to the insulated impeller 51, the wheat grains completing a circuit between the impeller 51 and the pan 50 during use of the machine. Current then flows between the impeller 51 and the pan 50 through the wheat grains, following the line of least resistance. A conductor, such as a perforated aluminium mesh, may be embedded in the blades to take the current to the tips of the blades. Again, further improvements in Hagberg "falling times" are found with these modifications.

Where it is required to attain even more marked improvements in the Hagberg "falling times" or the baking properties of the wheat the process can be repeated several times. This can be done by either passing the wheat through the machine again or by arranging other such units to operate in tandem as part of the same machine.

The machine provides a full range of adjustment for the process of gravity separation by using only a simple screw handle adjuster 76, throughput being adjustable by feed shaft speed changes and the position of the feed hopper slide 24 which can also be safely adjusted with the machine in motion.

The machine can be installed in situ in a grain handling area or fitted to a trailer chassis or to the chassis of a goods vehicle for use at different locations.

All the belts are "v" belts mounted outside bearings so that they can be replaced without dismantling the machine. Chains are encased inside the frame to protect the belts and pulleys from oil.

The present invention can be applied in other ways. For example, grain, flour or dough can be treated solely with an electric field. A 30kV, 5mA power supply is connected to a large base plate as one electrode and to a circular top electrode of 250mm diameter, a "spinning" for anti- corona measures. The plates are held at a separation of 10mm. Grain, flour or dough is either spread between the plates in a single layer or conveyed between the plates on an insulated conveyor. The field is applied for up to 10s either in bursts if no conveyor is used or continuously, with the width of the plates and the conveyor speed determining the length of time the field is applied. Field strengths of 10, 20 and 25 kV/cm may be used.

A modification of this method allows for a movable top plate, which is brought down into contact with the grain, flour or dough when energised, to allow a current to flow through the product. Again, up to 10s. of current flow duration may be allowed, but the field strength may be limited by unwanted heating effects etc.

A further alternative subjects grain, flour or wheat to a corona discharge for a period of up to 0.1s. The grain,

flour or wheat is conveyed or allowed to fall through the corona discharge, the current density of which is maintained at between 0.0001 and 0.01 mA/cm ² , preferably between 0.0005 and 0.001 mA/cm ² . The treated product is gathered and discharged either immediately or after some time.