Field of Invention
A dehuUing machine for guar seed is designed and developed for its easy dehulling and better recovery of
endosperm (refined guar gum splits). The guar seed is pretreated in submerged condition into the 0.1-0.5% (less
or even more concentration can also be used) aqueous solution of a specified chemical at a specified temperature
for a predetermined duration. A patent has already been applied for this process of pretreatment (Application
number: 1283/DEL/2007; Publication date: 03/04/2009; Title: Process for Dehulling Guar Seed for Refined Guar
Gum Split Production). After pretreatment the hull becomes soft for a relatively short duration. The excess solution
is drained from the sample immediately after this treatment. The solution present on the surface of the seed is
removed within one minute after draining the excess solution. Then the seed is immediately fed to the developed
guar dehulling machine where dehulling of the pretreated guar seed is done.
The guar dehulling machine consists of two circular rings on which steel wire nets having openings of 0.5x0.5 cm
or less, with a clearance of about 2.0 mm between the rings (depending on the size of seeds) are fixed. The
clearance between the circular rings having wire nets (now called disc) is adjustable. The upper disc is stationary
whereas the lower disc rotates in horizontal plane. On the lower disc, a mild steel plate is also fixed for support.
The pretreated seed is fed to the machine immediately after removing surface solution. The machine works on the
principal of abrasion, fiiction and shear. Dehulling of the seed takes place facilitated by weakening of the bond
between the hull and the cotyledon after pretreatment. The hull is removed from the dehuUed lot using aspirator.
The dehulled and unhuUed seeds are separated using grader. DehuUed seeds are dried using hot air to bring
moisture content to about 10% (dry basis) and also to remove the traces of solution used in pretreatment, if any
remained with the dehulled seed.
Dehulled guar seeds are split in to two halves using burr mill. The cotyledons (guar gum splits) and germ are
separated during splitting. The guar gum splits are then separated using pin mill and grader. Polishing of the guar
gum splits removes traces of germ from cotyledon and refined guar gum splits are obtained.
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4. DESCRIPTION (Description shall start from the next page.)
The guar {Cyamopsis tetragonolobd) is one of the most important commercial crops grown in arid and semiarid
regions of India and contributes to 80% of total world production of guar. The seed contains 30-35%
galactomannan located in endosperm (also called refined guar gum split). The concave shaped endosperm
contains 78-82% galactomannan gimi, which forms viscous gel in cold water. Refined guar gum powder has
various food and industrial applications such as in ice cream, as stabilizer for cheese, instant puddings and
whipped cream substitutes, as meat binder, in paper manufacturing, oil well drilling mud, explosives, ore
floatation etc.
Processing of guar seed is aimed to get endosperm fi-ee of germ and hull (popularly known as refined guar gum
splits). The present process of processing guar seeds involve splitting the seed, separation of germ, dehuUing,
separation of hull, and grinding of the endosperm to different sizes and refining of the gimi powder. Splitting
and dehulling of the seed is done by two processes i.e. dry grinding and wet milling (Gimjal and Kadam, 1991).
For wet milling, Patel (1958) obtained patent for guar gum separation in which guar hull is loosened using
chemical agent and also by cooking the seeds in water. Gunjal and Kadam (1991) also gave a process flow
diagram of this process although no details of the specific unit operations have been reported.
For dry processing, Jiwaji Industrial Research Laboratory, Gwalior obtained Indian patent "The process to
obtain refined guar gum in pin-mill without using chemicals" in 1960. As reported in this process, the guar seed
are split into two halves using mill having two grinding surfaces rotating at different speeds. The unhuUed
endosperms are heated to soften the hull and then fed into hammer mill where the hull is removed by abrasion.
Then endosperm is pulverized to remove residual hull and germ. Gunjal and Kadam (1991) also mentioned dry
milling process for processing guar seed. Recovery in wet processing methods is 8 to 10% higher than that in
dry processing method, but the quality of the guar gum produced is not good (Gimjal and Kadam, 1991).
However, information on type of machines used, processing conditions, efficiency, etc are not reported in the
literature.
Conventional Methods of Industrial Dehulling Process and Machine
In industry, the guar seed is first cleaned and then graded into two to three sizes using cylindrical grader and
then fed at the center of horizontal burr (stone) mill. The upper plate of the burr mill rotates at 500-600 rpm
whereas the lower plate is stationary. The clearance between stone plates is based on size of grain to be fed.
Diameter of the plate is usually 61 cm and the coarse emery (14-18 grades) stone is used. The guar seed is split
in to two halves in this machine (Vishwakarma et al., 2009). The seed is not treated prior to splitting. After
splitting the grains, unsplit seeds and part of germ are separated using cylindrical grader.
The splits are then passed through a germ separator (pin mill), where germ is removed from splits. It consists of
two mild steel plates of 53 cm diameter. One plate is stationary whereas the other plate rotates at 3000 rpm.
Three rows of pins of high carbon steel of rectangular rod shape (length 7.5 cm, width 2.5 cm and thickness 2.0
cm) are mounted on moving plate. The germ is removed from splits through shear, which comes out fi-om the
bottom of screen and carried away using blower. Thereafter the splits are heated in a kiln. It consists of a
hollow mild steel cylinder of 300 cm length placed horizontally and rotates at 30 rpm. Diameter of cylinder
towards discharge side is slightly larger than the diameter of the entry side to form a slope of 1° fi-om
horizontal. The splits are fed inside of the cylinder. Outer surface of the cylinder is heated using oil fired
furnace or firewood. The material remains inside the cylinder around 10-15 minutes and heating takes place
through conduction. Temperature of the cylinder is not controlled, however in some of the units; the
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temperature of splits coming out from cylinder is measured that varies from 120-140°C (Vishwakarma et al,
2009). Heating is said to be completed when change in surface colour of splits starts. Heating is done to loosen
the bond between hull and cotyledon so that dehuUing of splits becomes easy.
After heating, the hot splits are fed to guar dehuUing machine from the top comer of machine. It consists of a
mild steel cylinder of 37 cm diameter on which saw tooth blades of high carbon steel are fixed along the length
of cylinder. The capacity of the machine varies between 300-500 kg/h. A wire mesh screen (made from 3-4 mm
thick galvanized iron wire) covers the cylinder. Clearance between tip of the blade and screen is about 0.4 cm.
The cylinder with blades rotates at 1400-1800 rpm. Since the bond between hull and cotyledon is loosened
slightly during heating, subsequently cutting action, impact and friction between splits and blade as well as
friction between splits results in dehuUing (Vishwakarma et al., 2009). About 75% portion of cotyledon is
dehuUed in single pass. Hence usually two dehuUing machines in series are used and even three machines are
used in some industries. A dehuUing machine of 300-350 kg/h capacity machine requires three phase electric
motor of 75 hp for operation.
After dehuUing, the splits are rapidly cooled. The cooled splits are fed to air screen cleaner where broken, and
hulls are separated and cleaned guar gum splits are then conveyed for packaging.
In the process presently followed by industry, about 18-25% of the total endosperm is crushed to broken and
powder during dehuUing, which is sold at as low price as animal feed. Besides this, the process requires very
high energy to process the guar seed to get refined dehuUed splits. The mixing of germ with cotyledon and hull
powder makes it unfit for animal feed.
The present invention gives a dehuUing machine based on a pretreatment process for dehuUing of guar seed. In
this machine, the pretreated seed is dehuUed first and then the dehuUed seeds are split in to two halves. This
dehuUer system neatly and completely separates the toxic and indigestible hull from the seed. Recovery of
endosperm (the main product for making guar gimi powder) is qualitatively and quantitatively higher with this
process. After splitting, the germ obtained may be better used for animal feed with less effort for detoxification.
References:
1. Gunjal, B.B., and Kadam, S.S. 1991. CRC Hand Book of World Food Legumes, Vol.(l): 289-299.
2. Patel, R.R. 1958. Gum. Indian Patent. 61:005. (Cf Chemical Abstracts 52: 21190c, 1958).
3. Vishwakarma, R.K., Nanda, S.K., Shivhare, U.S. 2009. Process for dehuUing guar seed for refined guar
gum split production. Indian patent application no. 1283/DEL/2007. Publication date: 03/04/2009. Journal
no. 14/2009.
4. Vishwakarma, R.K., Nanda, S.K., Shivhare, U.S., & Patil, R.T. (2009). Status on post harvest technology of
guar {Cyamopsis tetragonoloba) in India. Agricultural Mechanization in Asia, Afiica and Latin America,
40(1), 65-72.
Objective of the Invention
Main objective of this invention is therefore design and development of a dehuUing machine for guar seed
based on wet pretreatment process.
Invention therefore provides a better machine for dehuUing pretreated guar seed which comprise
i) Pretreatment of guar seed with 0.5% aqueous solution of ethanol in a 1.2:1 grain to solution ratio for a
specified time at specified temperature, removing the excess solution from the seed based on the process
of pretreatment applied for patent (Application number: 1283/DEL/2007; Publication date: 03/04/2009).
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ii) Design and development of a completely new dehuUing machine for guar seed based on the pretreatment
given above,
iii) DehuUing of guar seed with the developed dehuUing machine. The hull is separated using blower,
iv) Drying of the seed and removal of traces of ethanol from the dehuUed seed,
v) SpUtting of the dried dehuUed guar seed in to two halves,
vi) Separation of germ from the guar gum splits and polishing of splits.
In earlier method used for dehuUing of pretreated seed, about 40-50% seeds were not dehuUed completely.
The hull remained attached v^th these seeds at some places. Complete removal of hull from the seed was done
using emery machine. The present machine is a promise in eliminating one unit operation (heating of splits) and
dehuUing is done in a single machine. The dehuUing with this machine reduces the losses during dehuUing in
comparison to the machine used earlier. It will provide an easy, better and energy efficient method for dehuUing
of guar seed. The guar seeds to be used for this process should be first cleaned and graded (using any
conventional air screen cleaner and grader). Then the moisture content of the seed is adjusted to 10% dry basis
(by adding moisture or drying depending on the initial moisture content of the seeds) for interim storage, if
necessary, prior to fiirther processing as and when required.
The next step involves treating the guar seeds with 0.1-0.5% (Less or even more concentration can also be
used) aqueous solution of specified chemical in submerged condition with grain to solution ration of 1.2:1 and
more as process of pretreatment applied for patent (Application number: 1283/DEL/2007; Publication date:
03/04/2009). The treatment temperature and time can be taken according to the limits suggested in the earlier
applied patent. This pretreatment softens the hull and loosens it from the rest of the seed contained within.
Immediately after the end of the freatment period, the excess solution is drained and solution present on the
surface of the seed is removed. Thereafter the seed is dehuUed immediately using the developed dehuUing
machine.
Brief Description of drawings
Fig. 1 is a view of guar seed dehuUing machine.
Fig. 2 is front view of upper disc of dehuUing machine with hopper.
Fig. 3 is top view of upper disc with hopper.
Fig. 4 is front view of lower disc assembly.
Fig. 5 is top view of lower disc assembly.
Fig. 6 is front view of blower assembly.
Fig. 7 is side view of blower assembly.
Details of Invention (DehuUing Machine)
The dehuUing machine designed and developed for guar seed dehuUing works on the principal of abrasion,
friction and shear (Fig. 1). The machine consists of three parts as described below.
1. Feed hopper: The feed hopper has capacity of about 30 kg treated guar seed. It is made of mild steel of
trapezoidal shape. The top of feed hopper is 46x46 cm and its height is 38 cm. At the bottom of the feed
hopper the size is 10x10 cm. A circular opening of 10 cm diameter is left for feeding the material
between dehuUing plates. A feed control gate is also provided at the bottom of the feed hopper to control
the feed rate during operation. The feed hopper is attached with the upper dehuUing plate with a feeding
pipe of 10 cm diameter. The details of drawings of the feed hopper are shown in Fig. 2 and 3.
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- 2. DehuUing machine: The main dehulling machine consists of two circular discs of 60 cm diameter. The
diameter of discs may be increased or decreased for wet dehulling of other grains. The upper disc is
stationary whereas the lower disc rotates. Both discs are made of steel wire net (0.5 x 0.5 cm openings
or less). Drawing details are given in Fig. 2, 3,4 and 5.
The upper disc, on which the wire net is fixed, is made of mild steel ring (Fig. 3) an opening of 10 cm is
provided in the centre of the rings on which a pipe of 10 cm diameter is fixed to feed the material. The
diameter of the opening can be changed (5-20 cm) to increase or decrease the feed rate. In order to
support the wire net from sagging during operation, foiir mild steel flats are fixed (Fig. 3). The whole
upper disc is fixed on the main fi-ame of the machine with four mild steel flats of 78 cm length attached
on the top of the upper disc (Fig. 3).
The lower disc of the machine is made of 14 gauge mild steel plate. A shaft of 2.1 cm diameter is fixed
in the centre of the disc. The shaft is mounted on a flange to avoid slip during operation. Steel wire net
(0.5x0.5 cm openings or less) is fixed on the top of the lower disc (Fig. 4). A mild steel ring is attached
at the outer periphery of bottom of the lower disc to hold the wire net at its place. This disc rotates in
horizontal plane. A scraper of 20x10 cm is fixed at the bottom of this disc to convey the material
coming out fi-om the clearance between two discs after dehulling towards outlet of the machine (Fig. 4).
The power to rotate this disc is supplied using belt pulley drive mechanism.
The clearance between both discs varies between 2.0-3.0 mm, which can be adjusted between 1.0-5.0
mm according to the need. The assembly of upper and lower discs is placed in a cylindrical casing of 68
cm diameter and 23 cm height (Fig 4).
Pretreated guar seed is fed fi-om the centre of upper disc. Centrifiigal force cause movement of
pretreated guar seeds towards the periphery of the discs. The seed travels outwards by rolling. Due to
the presence of steel wire net on plates and movement of the seed, abrasion of hull takes place, which
scratches the surface of hull and makes it breakable at several locations. The movement of pre-treated
seed on wire nets generates fiiction force in the direction opposite to the direction of movement of seed
as well as in the tangential direction opposite to the tangent of rotation of lower disc. During the
movement inside the discs, the seed stops for a short time in the openings of the wire mesh. The hull,
which is scratched at several places, breaks along hilum due to shear force generated due to relative
motion of plates. Since the upper disc is fixed and lower disc is rotating, the relative motion of the upper
and lower surfaces of seed generates shear force. This shear force separates the hull fi-om the cotyledons
as the bond between the hull and cotyledons is already loosened due to pre-treatment. Since the
cotyledons are attached together tightly, only hull is separated from the seed. After removal of hull, the
remaining cotyledon dimensions are reduced, which does not come in contact of both discs at the same
time and hence comes out the machine undamaged.
The lower disc rotates at 90-120 rpm. Capacity of the machine can be increased or decreased by
changing the rotation speed. It may affect dehulling efficiency of the machine also.
3. Hull separator: The hull separation unit of the machine consists of a blower and an air channel. The
blower is simple fan having four fins, which rotates at 2000 rpm. The drawing details of hull separator
are given in Fig. 6 and 7. The outlet of blower is attached to the air channel directly (Fig. 6). The
rectangular air channel is of 4 x 30 cm in size with 76.7 cm height (Fig. 7). Both ends of the channel
are open. The upper end of channel is expanded to allow settling of the hull and fall. The direction of
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movement of air inside the channel is upward. After dehuliing the seeds, the mixture of hull and
dehuUed seeds are fed in the channel. The difference in terminal velocity is main reason for separation
of hull from the dehulled or unhuUed seeds. Since the hull is of light weight in comparison to the seed,
the hull is suspended in air and carried away towards the upper side of channel. The dehulled and
unhuUed grains settle down and get collected.
The capacity of the dehuliing machine is about 80 kg/h. It is operated by 1.5 hp electric motor. The
optimum dehuliing efficiency of the machine is about 92% with less than 5% broken. At optimum
condition, the rotational speed of the lower plate is 90 ±5 rpm and clearance between plates is 1.5 mm.
The dehulled material obtained can be separated from unhulled material using screen grader as the size
of dehulled material and that of imhuUed material are different. The dehulled material is dried to about
10% moisture content. The dried dehulled cotyledons are fed to burr mill to split into two halves. More
than 98% dehulled cotyledons split in any burr mill. Polishing of the splits, conventionally by pin mill,
removes traces of germ from cotyledon. The refined guar gimi splits are thus obtained.
The novelty of this machine is that it separates the hull of guar seed without splitting the seed. The
dehuUers used at present in industry can neither dehull the seed without splitting, separating the germ
nor without heating. This machine provides an option to obtain of germ that is free from hull. The germ
may be used as a source of protein for himian consumption after suitable treatment/processing.
The dehuliing of the grain should be done within 12 min after removing the excess solution. The best
results are obtained when dehuliing will be done within 5-10 min after removal of excess solution. Dehuliing of
the grain will not take place after 30 min of removal of solution because the bond between hull and cotyledon is
re-established. In the process, the moisture content of the grain increases to 65-75% (dry basis). The moisture is
not diffused in the grain completely and maximum water remains in the hull and cotyledon only.
The novelty of the process over conventional one are as follows:
1. In this dehuliing machine, the dehuliing of seed is carried out prior to splitting and degerming, whereas
the sequence of operation in the conventional process is splitting, degerming and dehuliing.
2. Heating of guar seeds (up to 140°C is indispensable in the process of dehuliing of guar seeds by the
conventional method. No heating is required for dehuliing in the present machine (being patented).
3. The machine designed for dehuliing is simpler in construction, safer in operation and less energy
consuming compared to the heating/roasting/scrubbing operations adopted in the conventional process
for loosening the hull.
4. Neat removal of the entire hull could be achieved in this process (by abrasion, friction and shearing
actions) as compared to removal of hull as scraps in the conventional process (by scrubbing/cutting).
5. The loss of endosperm is reduced to a very low level (less than 3%) in comparison to the conventional
process wherein the loss of endosperm is as high as 10-15%.
6. Superior quality (purity) of the product (viz. refined endosperm) as well as superior quality (purity) of
the byproduct (viz. germ) in comparison to the conventional process.

We claim
i. Design of a dehuUing machine to facilitate dehulling of guar seeds.
ii. A guar seed dehulling machine based on abrasion, friction and shear to remove hull from seed without
heating and before splitting.
iii. A device for dehulling seeds, particularly guar seeds, comprising (a) a housing to place the said dehuUer;
(b) a means disposed on said housing for entry of seed for dehulling; (c) characterized by the dehuUer
made of two discs of metal wire mesh whereby the lower disc rotates in horizontal plane against upper
stationary disc fixed on the main frame, at an adjustable distance and clearance in the range of 1.0 to 5.0
mm. The metal wire mesh of lower disc is fixed on a mild steel plate; (d) a means to separate hull from
cotyledons; (e) a means to collect the processed material; (f) a means for exit of the dehulled seed to feed
in hull separator.
iv. A dehulling machine suitable for dehulling of guar seeds which have been pretreated by a specified method
(separate patent application filed earlier, Application number: 1283/DEL/2007; Publication date:
03/04/2009; Title: Process for Dehulling Guar Seed for Refined Guar Gum Split Production).
V. A dehulling device to remove the hull completely from the pretreated guar grains.
vi. A specially designed machine which is safer and less energy consuming for removal of hulls/husk/pericarp
from guar seeds in comparison to the conventional process of heating and scrubbing operations.
vii. A guar seed dehulling machine which results in superior quality (purity) of the byproduct (viz. germ).
viii. A guar seed dehulling machine which results in higher recovery of endosperm, owing to a very low level
of its loss (less than 5%) as compared to the conventional process and machinery wherein the loss of
endosperm is relatively high (10-15%).