AU778710B2 - Process and apparatus for de-hulling and splitting lentils - Google Patents

Description

WO 01/28686 PCT/CA00/01203 1 PROCESS AND APPARATUS FOR DE-HULLING 2 AND SPLITTING LENTILS 3 4 FIELD OF THE INVENTION 6 The present invention relates to a process and apparatus for de-hulling 7 and splitting lentils.

8 9 BACKGROUND OF THE INVENTION A lentil is a form of pea which comprises an interal kernel having an 11 external, thin, fibrous hull or husk. The kernel is generally shaped like a 12 football and has a plane of weakness along its midline so that it may be 13 separated down the middle into two halves. In the trade, the hulled kernels 14 are commonly referred to as "wholes" or "footballs" and the separated kernel halves are referred to as "splits".

16 Hulled splits provide a widely marketed food source. They are rich in 17 proteins and can be quickly cooked by boiling in water. It is desirable to split 18 the wholes to conserve energy used in cooking the lentils.

19 In Western Canada lentils are commonly de-hulled and split using a sequence of two machines referred to as a "huller" and a "splitter".

WO 01/28686 PCT/CA00/01203 1 The huller comprises a stack of disc-shaped stones, slightly spaced 2 apart vertically and contained in a dose-fitting drum or housing. The stones 3 are rotated within the drum by a common drive. The bottom outlet from the 4 drum is choked as required to control the retention time. The ientiis are fed in at the top of the drum. As they slowly work their way down to the outlet, the 6 hulls are loosened and removed by frictional contact with the stones, drum 7 wall and other lentils.

8 The cleaned or hulled wholes are then fed into the splitter. This unit 9 comprises a pair of stacked, conically-shaped stones, slightly spaced apart vertically, contained in a close-fitting housing. The stones are rotated at 11 different speeds. In reaction to the regime of frictional forces to which they 12 are subjected as they pass through the splitter, the wholes are sub-divided 13 into splits.

14 This commercially applied equipment and procedure is characterized by certain shortcomings. More particularly: 16 Too many of the lentils may be insufficiently de-hulled. This is 17 particularly a problem with large lentils having flat or irregular 18 surfaces. As a result, the end product of hulled splits may be 19 contaminated with too high a proportion of hull material; Too many of the hulled kernels may become chipped, with the 21 result that part of the kernel is lost as fragments with the chaff; and 22 Too many of the splits may be chipped with consequent losses of 23 valuable kernel material.

22-11-2001 CA000120: 1 Typically, these prior art commercial operations will have losses of kernel 2 material in the order of 20 30% and contamination of the end product with 3 huul material will ofen exceed the intemationai standard of 1.5% maximum 4 hull content.

The present invention has as objectives: 6 reducing fragmentation or chipping of the wholes and splits; 7 improving the efficiency of removing hulls to thereby reduce the 8 proportion of hull material in the final product; 9 increasing the production of splits as the final product; and providing a system which is able to successfully process a variety of 11 lentil types, particularly large lentils having irregular surfaces.

12 The published prior art is represented most relevantly by EPO patent 13 application 820814 Al (Satake et al). This reference teaches that it is know to 14 use gapped, contra-rotating rubber rolls, operated at different rotation speeds, to de-hull feed such as rice.

16 17 SUMMARY OF THE INVENTION 18 In accordance with the invention, I have combined apparatus and 19 process steps and conditions to achieve improved recovery and purity of hulled splits. More particularly, the invention involves: 21 Providing a pair of opposed, cylindrical, slightly gapped, 22 downwardly rotating rollers referred to as 'chaffers'. Each chaffer 23 has a rubber-like or elastic, resilient, circumferential surface layer.

24 The rubber-like layer is preferably formed of polymer or elastomer j i J,10 I ,1.

AMENDED SHEET 22-11-2001 CA000120: 1 and preferably has a Shore A durometer hardness of about 60 2 more preferably about 65 85. This range has been found to 3 provide gouu auldherence Ito te null. if the hardness is less than 4 about Shore A 60, the feed submerges too deeply in the chaffer surface layer and de-hulling suffers. If the hardness is greater than 6 about Shore A 85, increased chipping of the lentils results. The 7 chaffer surfaces are spaced apart, preferably to form a gap just less 8 than one split in width. Preferably the gap spacing is about 20 9 30/1000 of an inch, optimally about 24/1000" for large calibre lentil.

The gap spacing provides minimal chipping during splitting. The 11 chaffers are rotated at different speeds to provide a frictional 12 shearing effect adequate to remove the hull when de-hulling and to 13 split the kernels when splitting. In addition the chaffers are rotated 14 at speeds selected to provide adequate retention time to achieve the desired quality of de-hulling and splitting. Preferably the 16 chaffers are operated at a rotational speed differential in the range 17 of about 56 61%, more preferably 58 61%. If the differential is 18 lower than about 56%, shearing is less adequate for de-hulling and 19 splitting. If it is higher than 61%, retention time is short and dehulling and splitting results suffer. In addition, the feed exit velocity 21 from the chaffers becomes excessive and further chipping occurs.

22 Optimally, I operate a pair of 15" diameter chaffers at 675 685 23 rpm for one chaffer and 1060 1090 rpm, for the other, respectively; ncI I. 1/-A AMENDED SHEET I I UU I UMUUU I u 1 Preferably providing a feed means for supplying the lentils or 2 kernels to the top end of the chaffer gap in the form of a laterally 3 extending sheet of sing ntis or kemels that is, the sheet is only 4 one lentil or kernel in thickness) if the feed is stacked in layers during feeding, chipping is increased; 6 Preferably providing.an exit chute, at the bottom of the chaffer gap, 7 which is adapted to direct the product into a container with a 8 minimum of chipping. More particularly the chute may be a flat, 9 curved tube that has top and bottom walls that are closely spaced to contain and guide the emitted product while minimizing zig-zag 11 movements that can lead to chipping. The kernels leave the 12 differentially rotating chaffers at high velocity and at an angle. It is 13 therefore desirable to channel and guide them to the container with 14 a chute designed to minimize fragmentation; and Preferably passing the lentils and whole kernels in sequence 16 through chaffers in a two stage process of de-hulling and splitting at 17 controlled temperatures. Preferably the same pair of chaffers are 18 used for each of the two stages. In the first stage, the lentils, at 19 ambient temperature, preferably at a temperature of about -10°C to +27 0 C, most preferably -10 to 20 0 C, are passed through the 21 chaffers to remove about 80 90% of the hull material and produce 22 about 97% cleaned wholes and about 3% splits. If the temperature 23 of the feed in the first stage is less than about minus 10°C, hull 24 separation deteriorates. If the temperature is greater than about {EM195031.DOC:1)5 AMENDED SHEET 22-11-2001 CA000120" 1 270C, de-hulling suffers and a greater quantity of splits is produced.

2 The product is then dried and heated, for example in a grain dryer, 3 preferab!y to about 30 A41 to waakn th adhesiveness of t 4 splits forming the wholes. If the temperature of the wholes fed to splitting is less than about 30 0 C, there is a decrease in the yield of 6 splits. If the temperature of the wholes is greater than about 41 0

C,

7 the meat of the kemels is degraded. The heated wholes are then 8 passed through the chaffers for splitting.

9 As a result of processing the lentils in this way, one can recover 85 88% of the original kernel material or meat in the form of splits with a hull content less 11 than The purity of the splits product is in the order of 99%. The losses 12 of kerel material has been reduced to about 12 14%, compared to the prior 13 art system losses of about 20 14 In one aspect, the invention is directed to a process comprising: de-hulling lentils at a temperature of about -10 0 C to 27 0 C by 16 feeding them through the gap of a pair of spaced apart, opposed, 17 downwardly rotating chaffers having elastomeric surface layers and 18 being rotated at different speeds so that they are operative to apply 19 adequate frictional shearing to de-hull substantially all of the lentils to produce substantially clean "wholes" or kerels; 21 drying and heating the cleaned wholes to a temperature of about 22 30 OC to 41 0 C; and 23 splitting the dried heated wholes by feeding them through the gap of 24 a pair of spaced apart, opposed, downwardly rotating chaffers (EM195031.DOC:11 6 AMENDED SHEET 22-11-2001 CA000120; 1 having elastomeric surface layers and being rotated at different 2 speeds so that they are operative to apply adequate frictional 3 shearing so as to split substantially aii of the whoies to produce 4 substantially clean splits.

In another aspect, the invention is directed to an assembly comprising: 6 a pair of cylindrical, driven, gapped, downwardly rotating rollers 7 having elastomer or polymer surface layers having a Shore A 8 durometer hardness of about 60 85, the rollers being rotated at 9 different speeds so that the differential is about 58 61%, the rollers being spaced apart about 20 30/1000"; 11 flat means for feeding lentils or lentil wholes to the gap between the 12 rollers as a single unit layer that is, the layer is formed of lentils 13 (or wholes) that are not stacked one on another; and 14 curved flat tube means for receiving hulled lentil wholes or splits issuing from the gap and closely containing them while delivering 16 them to storage container means.

17 Broadly stated the invention in one form comprises a method for de- 18 hulling lentils, each comprising a kernel covered by a hull, the kernel 19 consisting of a pair of united halves or splits, to produce whole kernels comprising: passing lentils, at ambient temperature through a pair of 21 opposed, cylindrical, gapped, downwardly rotating, driven rollers, the rollers 22 being gapped to provide a gap spacing in the range 20/1000 to 30/1000 of an 23 inch, each having an elastic, resilient circumferential surface layer formed of 24 material having a Shore A durometer hardness in the range 60 to 85, the {EMIO! l 5 DOC:!;^ AMENDED SHEET 22-11-2001 1 rollers being rotated at different speeds selected to provide sufficient frictional 2 shearing so that the major portion of the lentil hulls is removed to produce 3 hulled whole kernls.

4 Broadly stated, the invention in another form comprises a method for de-hulling lentils, each comprising a kernel covered by a hull, the kernel 6 consisting of a pair of united halves or 'splits', and splitting the hulled kernel 7 into splits, comprising: passing lentils at ambient temperature through a pair 8 of opposed, cylindrical, gapped, downwardly rotating, driven rollers, each 9 having an elastic, resilient circumferential surface layer, the rollers being rotated at different speeds, the Shore A durometer hardness of the roller 11 surface layers, the gap between the rollers, the roller speeds and their 12 differential in speed being collectively operative so as to substantially remove 13 the lentil hulls and produce hulled kernels; heating and drying the kernels to at 14 least 30 0 C to produce kernels amenable to splitting; and passing the produced kernels through a pair of opposed, cylindrical, gapped, downwardly rotating, 16 driven rollers, each having an elastic, resilient circumferential surface layer,.

17 the rollers being rotated at different speeds; the Shore A durometer hardness 18 of the roller surface layers, the gap between the rollers, the roller speeds and 19 their differential in speed being collectively operative so as to split the kernel into splits.

21 And in another form the invention comprises apparatus for de-hulling 22 lentils, each comprising a kernel covered by a hull, to produce whole kemrnels, 23 comprising a pair of opposed, cylindrical, gapped, downwardly rotatable 24 rollers; each roller having an elastic, resilient circumferential surface layer Iu.!FoA0.. OC::.

CA000120: AMENDED SHEET 22-11-2001 1 formed of material having a Shore A durometer hardness in the range of 60 2 85; the rollers having a gap spacing in the range 20/1000 to 30/1000 of an 3 inch; and means for indiidua!!y rotating each rller so that the rollers may be jl J. VI .I La L I uIIe 1 I may uM 4 operated at a rotational speed differential.

DESCRIPTION OF THE DRAWINGS 6 Figure 1 is a schematic side view showing the feed hopper and tray, 7 chaffers, exit tube and product container; 8 Figure 2 is an expanded view of part of Figure 1; 9 Figure 3 is a top plan view of the chaffers and their drive assemblies; and 11 Figure 4 is a perspective view of the assembly.

12 DESCRIPTION OF THE PREFERRED EMBODIMENT 13 The invention will now be described in connection with a test run at 14 optimum conditions.

In accordance with the Figures, a feed hopper 1 was-provided for 16 feeding lentils (in a first stage) and hulled wholes (in a second stage) onto a 17 wide, downwardly angled tray 2. The tray 2 comprised a bottom wall 3 and 18 side walls 4. A plurality of upstanding dividers 5 sub-divided the upper end of 19 the tray 2 into parallel channels 6 extending part of the length of the tray. The upper end of the tray 2 was open but its lower end was closed in by a top wall 21 7 to form a flat tube. The tray 2 extended between the hopper 1 and the gap 22 8 formed between the chaffers 9. The widths of the hopper 1 and tray 2 were 23 substantially equal to the length of the gap 8. The hopper fed the lentils to the 24 tray as a train or sheet of feed, one feed unit thick, moving down the channels {EM!195031. DOC:}9 CA000120: AMENDED SHEET WO 01/28686 PCT/CA00/01203 1 6. Otherwise stated, a feed means, comprising the hopper 1 and tray 2, was 2 provided for feeding feed in the form of a sheet, substantially one feed unit 3 thick, to the chaffer gap 8 along its length.

4 The chaffers 9 were a pair of cylindrical hollow steel drums 11, each coated with an elastomeric surface layer 12. The steel drums 11 had an O.D.

6 of 15" and length of 24". Each was coated with a layer 12 of polyurethane, 7 about 0.5 inches thick. The polymer was obtained from Rubberworld 8 Industries Inc. of Edmonton, Alberta, Canada. The elastomer was bonded to 9 the steel. It had a Shore A hardness of about 65. The chaffers 9 were evenly spaced apart .024" to form the gap 8. The chaffers 9 were horizontally and 11 rotatably mounted in a frame 14. Conventional belt and sprocket assemblies 12 15, driven by hydraulic motors 16, separately rotated each of the chaffers 9 at 13 a variable selected speed. The chaffers were operated at 675-685 and 1060 14 1090 rpm respectively to provide a speed differential of about 59.5%.

An exit chute 20 extended along and downwardly from the gap 8 to the 16 storage container 21 or other delivery point. The exit chute 20 was a flat tube 17 extending the length of the gap 8. It comprised top, bottom and side walls 22, 18 23 and 24. The top and bottom walls 22, 23 were spaced apart 5/8 inches.

19 The chute 20 was curved and had a length of about 14".

In the first stage or pass of the process, de-hulling, the lentils, at a 21 temperature of 19 22 0 C, were supplied to the gap 8 as a feed layer with the 22 lentils close together but only one unit thick. After passing through the 23 chaffers 9, the chaff and kernel chips were separated by screening. The 24 product, hulled wholes, was then heated in a grain dryer (not shown) to raise SUBSTITUTE SHEET (RULE 26) WO 01/28686 PCT/CA00/01203 1 the feed temperature to 38 40°C. The heated feed was then fed through the 2 same chaffers 9 in the same way as the original lentils. Following are the 3 results of the run: 4 De-hulling: yield of hulled whole kernels 75.1% 6 yield of unhulled whole kernels 17.9% 7 yield of hulled splits 0.68% 8 yield of unhulled splits 0.05% 9 losses (hulls and chips) 6.22% Splitting: 11 yield of hulled wholes 17.1% 12 yield of unhulled wholes -4.3% 13 yield of hulled splits 72% 14 yield of unhulled splits 0.9% losses (hulls and chips) 5.7%.

16 A number of runs using the assembly shown have been carried out at 17 varying conditions. The following observations have been made, comparing 18 them to the optimum run described: 19 In de-hulling, with increasing temperature of the feed, the recovery of hulled wholes decreased and the recovery and purity of splits 21 decreased; 22 When the speed differential was 55% the percentage of hulled 23 wholes was less and when the speed differential was 65% the 24 percentage of hulled wholes decreased; 11 SUBSTITUTE SHEET (RULE 26) 1 If the gap was 0.022", hull and chip losses increased, if the gap was 2 0.030", purity of the final product decreased; 3 If the splitting temperature was 30'C, split yield decreased and if the 4 temperature was greater than 41 C, kernel degradation was noted.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge in Australia.

oo

Claims (1)

1. 22-11-2001 CA000120: 1 THE EMBODIMENTS OF THE INVENTION IN WHICH AN 2 EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS 3 FOLLOWS: 4 1. A method for de-hulling lentils, each comprising a kernel covered by a hull, the kernel consisting of a pair of united halves or splits, to produce 6 whole kernels comprising: 7 passing lentils, at ambient temperature, through a pair of opposed, 8 cylindrical, gapped, downwardly rotating, driven rollers, the rollers being 9 gapped to provide a gap spacing in the range 20/1000 to 30/1000 of an inch, each having an elastic, resilient circumferential surface layer formed of 11 material having a Shore A durometer hardness in the range 60 to 85, the 12 rollers being rotated at different speeds selected to provide sufficient frictional 13 shearing so that the major portion of the lentil hulls is removed to produce 14 hulled whole kernels. 16 2. The method as set forth in claim 1 wherein: 17 the rollers are operated at a rotational speed differential in the range 56 18 to 61%. 19 3. The method as set forth in claim 2 wherein: 21 the lentils are at a temperature in the range minus 10°C to 270C. 22 23 24 M1ii031.DOc;1}1i3 AMENDED SHEET 1 4. The method as set forth in claim 3 comprising: 2 passing the produced kernels through a pair of opposed, cylindrical, 3 gapped, downwardly rotating, driven rollers, each having an elastic, resilient 4 circumferential surface layer, the rollers being rotated at different speeds, the Shore A durometer hardness of the roller surface layers, the gap between the 6 rollers, the roller speeds and their differential in speed being collectively 7 operative so as to split the kernels into splits. 8 9 5. The method as set forth in claim 4 wherein: the surface layers of the rollers doing the splitting have a Shore A 11 durometer hardness in the range 60 to 12 the rollers are gapped to provide a gap spacing in the range 20/1000 to o 13 30/1000 of an inch; and 14 the rollers are operated at a rotational speed differential in the range 56 to 61%. 16 17 6. The method as set forth in claim 5 wherein: 18 the roller surface layer Shore A durometer hardness is in the range S" 19 to 21 7. The method as set forth in claim 5 wherein: 22 the lentils are at a temperature in the range 10°C to 20 0 C; and 23 the roller surface layer Shore A durometer hardness is in the range 24 to fENO l3.O)4 ;1,114 22-11-2001 CA000120 I 1 2 8. A method for de-hulling lentils, each comprising a kernel covered by 3 a the kerne coLnsistUing f a pair of uliiteLU halves or spins', and spitting 4 the hulled kernel into splits, comprising: passing lentils at ambient temperature through a pair of opposed, 6 cylindrical, gapped, downwardly rotating, driven rollers, each having an 7 elastic, resilient circumferential surface layer, the rollers being rotated at 8 different speeds, the Shore A durometer hardness of the roller surface layers, 9 the gap between the rollers, the roller speeds and their differential in speed being collectively operative so as to substantially remove the lentil hulls and 11 produce hulled kernels; 12 heating and drying the kernels to at least 30"C, to produce kernels 13 amenable to splitting; and 14 passing the produced kernels through a pair of opposed, cylindrical, gapped, downwardly rotating, driven rollers, each having an elastic, resilient 16 circumferential surface layer, the rollers being rotated at different speeds, the 17 Shore A durometer hardness of the roller surface layers, the gap between the 18 rollers, the roller speeds and their differential in speed being collectively 19 operative so as to split the kernels into splits. 21 9. The method as set forth in claim 8 wherein the kemels are heated 22 and dried to a temperature in the range 30*C 41 0 C and, while at that 23 temperature, are split. 24 {EM19531 nn.DOC;115 AMENDED SHEET 22-11-2001 CA000120: 1 10. The method as set forth in claim 9 comprising: 2 feeding the lentils to the gap between the rollers in the form of a sheet l3 of lentils, said sheet bei y onl ly Iione reltil thick, andI 4 feeding the hulled kernels to the gap between the rollers in the form of a sheet of kernels, said sheet being only one kernel thick. 6 7 11. The method as set forth in claim 10 wherein: 8 the rollers have a Shore A durometer hardness in the range 60 to 9 the rollers are gapped to provide a gap spacing in the range 20/1000 to 30/1000 of an inch; and 11 the rollers are operated at a rotational speed differential in the range 56 12 to 61%. 13 14 12. Apparatus for de-hulling lentils, each comprising a kernel covered by a hull, to produce whole kernels, comprising: 16 a pair of opposed, cylindrical, gapped, downwardly rotatable rollers; 17 each roller having an elastic, resilient circumferential surface layer 18 formed of material having a Shore A durometer hardness in the range of 60 19 the rollers having a gap in the range 20/1000 to 30/1000 of an inch; 21 and 22 means for individually rotating each roller so that the rollers may be 23 operated at a rotational speed differential. 24 {eMssnai AMENDED SHEET 1 13. The apparatus as set forthin claim 12 comprising: 2 means for feeding lentils along the length of the roller gap at its upper 3 end in the form of a layer of lentils, one lentil in thickness. 4 14. The apparatus as set forth in claim 13 comprising: 6 a curved, flat chute, having top, bottom and side walls and extending 7 along the length of the gap at its lower end, for receiving hulled kernels and 8 conveying them to a delivery point. A method for de-hulling lentils, each comprising a kernel covered by a hull, the kernel consisting of a pair of united halves or splits, to produce whole kernels substantially as herein described with reference to the drawings. 16. A method for de-hulling lentils, each comprising a kernel covered by a hull, the kernel consisting of a pair of united halves or 'splits', and splitting the hulled kernel into splits substantially as herein described with reference to the *9 drawings. 17. Apparatus for de-hulling lentils, each comprising a kernel covered /by a hull, to produce whole kernels substantially as herein described with reference to the drawings. r fE!~419o31? .DO117 I- ~-17