Note: Descriptions are shown in the official language in which they were submitted.
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COFFEE BEAN PARTICLES
Field of the invention
The present invention relates to coffee bean particles, methods of producing
coffee bean
particles by de-oiling and milling of coffee beans, and use of coffee bean
particles.
Background
Despite progress in aroma preservation technologies, soluble (or instant)
coffee
products are perceived by some consumers as lacking in freshness and fresh
brewed
coffee aroma as compared to home brewed coffee. To overcome this gap in aroma,
products have been marketed which incorporate finely ground (micronized) roast
coffee
into the soluble coffee to enhance the taste and aroma. Coffee particles in
the beverage
prepared from soluble coffee can be give an unpleasant sandy sensation during
consumption. The sensory perception of the particles can be reduced by
decreasing the
particles size and it is thus desired to obtain a particle size below about 50
microns
since particles below this size are hardly perceived in the mouth.
However, due to their natural oil content, coffee particles get sticky when
ground as
liquid coffee oil is squeezed out of pores during grinding and moves to the
particle
surface. As a consequence, the energy put on those particles in a grinder is
absorbed to
a large extend by plastic deformation and viscous flow in the oil, whereas
sticky
particles form lumps and build up along the walls of the equipment. Dry
grinding
techniques at ambient temperature are therefore limited in terms of the
obtainable
particle size reduction and are normally not able to obtain particle sizes
below 50
microns.
Milling in oil has been disclosed in US1716323, EP0560609 and JP2005312319.
Making use of oil as carrier medium in a continuous bead mill was shown to be
efficient
to overcome adhesive particle interactions, allowing a particle size reduction
well below
the target of 50 microns. In order to process a suspension of coffee particles
in oil,
however, the solid particle content is limited to approximately 50%. At higher
coffee
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particle load the suspension becomes too viscous and can no longer be pumped
in a
reliable manner. Significant amounts of oil are therefore required, which are
complicated to separate from the micronized coffee particles afterwards.
Cryogenic milling is disclosed in US3261689, GB2022394 and CA1110104. This
technology makes use of the fact that coffee oil becomes completely solid
below
temperatures of ca. -20 C. Solid oil does not affect the mechanical properties
and
breakage conditions of roasted coffee particles negatively. On the contrary,
frozen oil is
brittle and hard. On the processing side, the high throughput of liquid
nitrogen in
cryogenic milling is unfavourable in terms of process economics, however.
Depending
on the mill type used, significant amounts of oversize particles need to be
separated by
cryogenic sieving and recycled into the grinder. Furthermore it was observed
that
cryogenically milled coffee tends to aggregate and sediment to the bottom of
the cup,
once reconstituted by the consumer with a coffee beverage. This effect can
again be
attributed to coffee oil which is released once the temperature of the
micronized
particles rising to ambient levels. Free oil is leaking out of the coffee
particles, forming
unsightly "fish eyes" on top of the beverage.
Wet processing of micronized roasted coffee (MRC) in aqueous media performed
in
line with pure soluble coffee (PSC) production is disclosed in U53652292,
U53697288,
GB1489166 and DE3130346. Continuous bead milling in aqueous phase is proposed
to
micronize coffee particles to sizes below 50 gm. The resulting product shows
less
aggregation and sedimentation of coffee particles in the final cup, but
flocculation of
MRC particles is frequently observed as hydrophobic coffee particles interact
to form
floating colloidal structures. This effect can either be accepted or fought
against with
the help of stabilizer additives or pH adjustments. Such additives add cost
and may be
perceived negatively by consumers.
Co-grinding of roasted coffee particles in a jet mill using pure soluble
coffee powder as
carrier is disclosed in U51214875 and EP2659783. By adding a carrier (pure
soluble
coffee powder) that absorbs coffee oil from the particle surfaces, stickiness
of the
product in the mill is avoided and very fine coffee particles are obtained.
Aggregation in
the final cup is reduced. Sedimentation in the cup is still a critical issue,
though. The
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required carrier mass fraction to allow a stable operation of the jet mill is
significant
(order of 50 % by weight, which negatively impacts throughput and process
efficiency
as well as final cup sensory profile.
Accordingly, there is a need for improved methods for obtaining small coffee
bean
particles that do not stick during processing and do not sediment or create
unpleasant
sensory sensations in a food or beverage prepared with the particles.
Summary of the invention
The inventors have found that de-oiling coffee beans allows milling of coffee
to small
particle sizes avoiding some of the drawbacks of the prior art, accordingly
the present
invention relates to coffee bean particles with a D00 particle size of 50
microns or less
and an oil content of 8% (weight/weight) or less. Furthermore, the invention
relates to a
method of producing coffee bean particles comprising: a) removing oil from
coffee
beans to produce de-oiled coffee beans; and b) grinding the coffee beans to a
D90
particles size of 50 microns or less. In still further aspects the invention
relates to
products comprising the coffee bean particles of the invention and uses of the
coffee
bean particles of the invention.
Brief description of the figures
Figure 1 shows a milling chamber of a jet mill blocked with powder according
to
composition 1. Burnt granules (dark color) are found inside the milling
chamber, while
the outlet is blocked with cohesive powder (lighter color, in the center).
Details are in
example 1.
Figure 2 shows a milling chamber of a jet mill containing powder according to
composition 3 after 4 hours of stable operation. Only loose holdup (light
color) is found
in the milling chamber and free outlet tube. Details are in example 1.
Figure 3 shows particle size distribution of roast and ground coffee de-oiled
by
mechanical pressing in two passes (composition 3) before and after milling
(black lines)
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and of a 50/50 mixture of roast and ground coffee and pure soluble coffee
(composition
4) before and after milling (grey lines). Details are in example 1.
Figure 4 shows particle size distribution of roast and ground coffee de-oiled
by
extraction with supercritical CO2 (composition 6) before and after milling
(black lines)
and of a 50/50 mixture of roast and ground coffee and pure soluble coffee
(composition
7) before and after milling (grey lines). Details are in example 2.
Figure 5 shows particle size distribution of roast and ground coffee de-oiled
by
extraction with hexane (composition 9) before and after milling (black lines)
and of a
50/50 mixture of roast and ground coffee and pure soluble coffee (composition
10)
before and after milling (grey lines). Details are in example 3.
Detailed description of the invention
The present invention relates to coffee bean particles with a D90 particle
size of 50
microns or less and an oil content of 8% (weight/weight) or less.
By coffee bean is meant bean, or seed, from any variety of the coffee plant,
e.g. from
Coffea Arabica and/or Coffea canephora. Coffee beans may be green, or raw, or
the
may be roast. Roast coffee beans may be produced by roasting of green coffee
beans in
any suitable way to produce aroma notes associated with roast coffee. Suitable
roasting
methods are well known in the art. By coffee bean particles are meant
particles
produced from coffee beans by breaking the coffee beans into smaller pieces in
any
suitable way, e.g. by crushing, milling, grinding, or the like.
By Arabica coffee bean particles is meant particles of beans of the Coffea
arabica
variety, also called Arabica coffee; and by Robusta coffee bean particles is
meant
particles of beans of the Coffea canephora variety, also called Robusta
coffee.
The coffee bean particles of the invention can be characterized by their size
distribution.
The particle size may e.g. be measured by laser diffraction methods, and can
e.g. be
characterised by its volume distribution, e.g. using the parameter D50,
(volume median
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diameter) the diameter which 50% (based on volume) of the particle population
is
below, and/or D90, the diameter which 90% (based on volume) of the particle
population volume is below. The coffee bean particles of the invention are
characterized
by having a D90 particle size of 50 microns or less, preferably 40 microns or
less, more
preferably 30 microns or less.
Coffee beans naturally comprise oil, roasted Coffea arabica beans normally
comprise
about 15% and roasted Coffea canephora coffee beans about 10% coffee oil by
weight.
The coffee bean particles of the present invention has an oil content which is
reduced
compared to the natural oil content of coffee beans. The coffee bean particles
of the
present invention are characterized by having an oil content of 8% by weight
or less,
preferably 7% or less, more preferably 6% or less. If the coffee bean
particles are
Arabica coffee bean particles, they preferably have an oil content of 7% or
less, more
preferably 6% or less. If the coffee bean particles are Robusta coffee bean
particles,
they preferably have an oil content of 6% or less, more preferably 5% or less.
In a preferred embodiment, the invention relates to Arabica coffee bean
particles with a
D90 particle size of 50 microns or less and an oil content of 8%
(weight/weight) or less.
In another preferred embodiment, the inventions relates to Robusta coffee bean
particles with a D90 particle size of 50 microns or less and an oil content of
6%
(weight/weight) or less. In a further preferred embodiment the invention
relates to a
mixture of i) Arabica coffee bean particles with a D90 particle size of 50
microns or less
and an oil content of 8% (weight/weight) or less, and ii) Robusta coffee bean
particles
with a D90 particle size of 50 microns or less and an oil content of 6%
(weight/weight)
or less. For example, the mixture may comprise between 10% and 90%
(weight/weight)
of Arabica coffee bean particles and between 10% and 90% (weight/weight) of
Robusta
coffee bean particles.
The coffee bean particles of the invention may be green, or raw, coffee bean
particles,
or they may be roast coffee bean particles. Green coffee bean particles are
particles
produced from green coffee beans. Roast coffee particles may be produced from
roast
coffee beans in any suitable way, e.g. by crushing, milling, grinding, or the
like; or they
may be produced by breaking green coffee beans into smaller pieces and
roasting the
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resulting green coffee bean particles to produce roast coffee bean particles.
The present invention further relates to a coffee composition comprising
coffee bean
particles of the invention, and soluble coffee solids, wherein the coffee bean
particles
are present in an amount of 1-100% (weight/weight) of the amount of soluble
coffee
solids, preferably in an amount of 2-50% (weight/weight) of the amount of
soluble
coffee solids, such as in an amount of 3-20% (weight/weight) of the amount of
soluble
coffee solids. By soluble coffee solids is meant water soluble coffee
compounds,
excluding water, which have been extracted from coffee beans, e.g. using water
and/or
steam. Methods for extraction of soluble solids from coffee beans are well
known in the
art of soluble coffee production and any suitable method may be used. Soluble
coffee
solids may be extracted from green or roast coffee beans.
A coffee composition of the invention may e.g. be in the form of a liquid
composition
wherein the soluble coffee solids are dissolved in water and the coffee bean
particles
dispersed therein; in dry form, e.g. as a powder, tablet or the like, wherein
the coffee
bean particle are mixed with dry soluble coffee solids. A liquid coffee
composition may
be in a form suitable for direct consumption as a coffee beverage, e.g. a so
called RTD
(ready to drink) coffee beverage, or it may e.g. be in the form of a
concentrate which
.. can be used for preparing a coffee beverage by dilution with water, milk,
or any other
suitable liquid. A dry coffee composition according to the invention may e.g.
be in the
form of an instant coffee product which is suitable for preparation of a
coffee beverage
by dissolution of the dry composition in water, milk, or any other suitable
liquid. A
coffee composition according to the invention may also be useful as an
ingredient, e.g.
.. for production of other food or beverage products wherein the presence of
coffee solids
is desired, e.g., to impart coffee taste or flavour.
In another embodiment, the present invention relates to a food or beverage
composition comprising coffee bean particles according to the invention, and
soluble
coffee solids, wherein the coffee bean particles are present in an amount of 1-
100%
(weight/weight) of the amount of soluble coffee solids, preferably in an
amount of 2-
50% (weight/weight) of the amount of soluble coffee solids. A food or beverage
composition according to the invention may further comprise protein, e.g. milk
and/or
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plant protein in an amount of 2-50% by weight of dry solids. A food or
beverage
composition according to the invention may e.g. be a so called coffee mix
product
which comprises coffee solids, creamer components and optionally sugar and/or
sweetener. Such a product may be in liquid form, e.g. directly suitable for
consumption
as an RTD coffee beverage such as coffee with milk, café latte, cappuccino,
café
macchiato, or the like, or as a liquid concentrate suitable for preparation of
a coffee
beverage by dilution with water or any other suitable liquid. Such a product
may also be
in dry form, e.g. as an instant coffee mix product suitable for preparation of
coffee
beverage such as coffee with milk, café latte, cappuccino, café macchiato, or
the like, by
.. dissolution of the dry product in water or any other suitable liquid.
The present invention also relates to a method of producing coffee bean
particles of the
invention, accordingly the invention relates to a method of producing coffee
bean
particles, the method comprising a) removing oil from coffee beans to produce
de-oiled
.. coffee beans; and b) grinding the coffee beans to a D90 particles size of
50 microns or
less.
In one embodiment of the invention, step a) is performed before step b), i.e.
oil is
removed from coffee beans before they are ground to produce coffee bean
particles. In
.. another embodiment, step b) I performed before step a), i.e. coffee beans
are ground to
produce coffee bean particles and oil is subsequently removed from the coffee
bean
particles. In a further embodiment of the invention, step a) and b) are
performed, at
least partly, simultaneously, i.e. oil removal and grinding is performed in
one step. In a
preferred embodiment of the invention, coffee beans are subjected to a pre-
grinding,
e.g. using conventional methods for grinding coffee beans, before oil removal
in step a),
and then subsequently subjected to the grinding of step b) further reducing
the particle
size to obtain coffee bean particles of the desired particle size.
Oil removal may be performed by any suitable method, e.g. by pressing or
extraction,
e.g. by liquid carbon dioxide and/or organic solvent. In a preferred
embodiment 30% by
weight of the oil content is removed in step a), such as preferably 50% by
weight. In
another preferred embodiment, oil is removed to reach a desired oil content,
e.g. such
that the oil content after oil removal in step a) is 8% by weight or less,
preferably 7% or
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less, more preferably 6% or less. If the coffee bean particles are Arabica
coffee bean
particles, oil is preferably removed to reach an oil content of 7% or less,
more
preferably 6% or less. If the coffee bean particles are Robusta coffee bean
particles, oil
is preferably removed to reach an oil content of 6% or less, more preferably
5% or less.
By grinding is meant any kind of breaking coffee beans into smaller pieces in
any
suitable way and includes e.g. crushing and milling. Grinding may e.g. be
performed by
jet milling, cryo milling, etc. Grinding may include a step to remove
oversized particles,
e.g. by sieving, to obtain the desired particle size distribution.
The coffee beans subjected to the method of the invention may be green or
roasted
coffee beans. If roasting is performed, it may be performed before, after
and/or during
oil removal in step a); and/or before, after and/or during grinding in step
b). In one
embodiment, green coffee beans are roasted before being subjected to step a)
and b) of
the method of the invention. In another embodiment, green coffee beans are
subjected
to oil removal of step a) and then roasted before being subjected to grinding
of step b).
In a further embodiment, green coffee beans are subjected to step a) and step
b), and
the resulting green coffee bean particles are subsequently roast.
The present invention further relates to use of the coffee bean particles of
the invention
in the preparation of a soluble coffee product. By a soluble coffee product is
meant a
product based on soluble coffee extract which is useful for preparing a coffee
beverages
by reconstitution of the product in water, milk or any other suitable liquid.
A soluble
coffee product may e.g. be in the form of a powder, e.g. a freeze dried or
spray dried
powder of coffee extract. Methods for producing soluble coffee products are
well
known in the art. The coffee bean particles of the present intention may be
used in the
preparation of a soluble coffee product by mixing the coffee bean particles
with coffee
extract. The coffee bean particles may e.g. be mixed with liquid coffee
extract and the
mixture may then be dried, e.g. by freeze drying or spray drying, to produce a
soluble
coffee powder which contains the coffee bean particles of the invention. In a
preferred
embodiment, coffee bean particles of the invention are agglomerated with
soluble coffee
powder to produce a soluble coffee product containing the coffee bean
particles.
Methods for agglomerating soluble coffee powders, e.g. spray dried coffee
powders,
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are well known in the art, and coffee bean particles of the invention may be
agglomerated with soluble coffee powder by introducing the coffee bean
particles into a
conventional agglomeration process. For example, coffee bean particles of the
invention
may be introduced into the agglomeration zone of a spray dying tower during
drying of
coffee extract. In a preferred embodiment, coffee bean particles of the
invention are
transported directly from the grinding process, e.g. performed in a jet mill,
and into the
agglomeration zone of a spray drying tower.
EXAMPLES
All particle sizes and distributions mentioned in the following examples were
measured
by laser diffraction (Malvern Mastersizer 2000, Fraunhofer algorithm,
dispersion in
MCT (medium chain triglyceride) oil).
Example 1
Soluble coffee beverage powder containing 15% micronized roast and ground
coffee particles was de-oiled by mechanical pressing
Arabica coffee (origin Colombia) was roasted to a CTN of 115 and ground. The
coffee,
which was characterized by an oil content of 15 % is referred to as
composition 1 in the
following. It was fed to a continuous expeller press (KOMET, DD85G) at a rate
of 6
kg/h. After one pass through the press, partially de-oiled coffee powder was
obtained
with a residual oil content of 9 % (composition 2). Part of the powder was
treated by
the same press at 6 kg/h throughput in a second pass, resulting in further de-
oiling.
After two passes a powder with residual oil content of 6 % is achieved
(composition 3).
For comparison the powder according to composition 1 was mixed with pure
soluble
coffee powder (PSC, soluble coffee solids obtained by water extraction of
coffee beans)
(type 100% Robusta) in a 1:1 weight ratio. The obtained mix is referred to as
composition 4.
The powders according to composition 1 and 2 were further processed with a jet
mill
(Technologia Meccanica Fluid Jet Mill J-70). The throughput was adjusted by a
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vibrational feeder to 1 kg/h, jet pressure was set to 9 bar. After 30 min of
operation a
decline of the output of the jet mill was observed. Upon opening the milling
chamber,
the outlet tube was found to be blocked by powder adhering to the wall of the
tube.
Furthermore the milling chamber was partially filled with black spherical
coffee granules
(Figure 1). It is assumed that oily coffee particles released free liquid
coffee oil upon
particle collisions inside the jet mill. As the collision energy was
insufficient to
overcome the adhesive forces between those sticky particles, they grew instead
of
breaking apart, forming spherical granules. Over time, these granules grew and
became
denser. Unable to leave the milling chamber through the product outlet tube,
they
accumulated inside the milling chamber. Wall friction and particle-particle
friction
resulted in an increase of the temperature of those granules. A strong burnt
smell was
observed, and the granules were characterized by dark black colour.
The powders according to composition 3 and 4 were further processed with a jet
mill
(Technologia Meccanica Fluid Jet Mill J-70) in the same way as described
above. The
throughput was adjusted by a vibrational feeder to 1 kg/h, jet pressure was
set to 9 bar.
Stable continuous operation of the mill was performed over a period of 4
hours. Only
loose powdery hold-up was found in the mill, where the powder colour was
lighter
rather than darker through the effect of particle size reduction in comparison
to the
respective feed composition (Figure 2). None of the overheating or granule
formation
phenomena that were described above for composition 1 and 2 was observed.
The jet milled products made from compositions 3 and 4 were analyzed by laser
diffraction to measure their particle size distribution. The results are shown
in Figure 3.
.. It can be seen that de-oiling enhanced the efficiency of the jet milling
process. At equal
process conditions a D90 of 44 gm was obtained when jet milling composition 3,
compared to 114 gm for composition 4. While the use of pure soluble coffee
powder as
carrier (composition 4) is successful in enabling jet mill processing of
roasted coffee
particles, the process is more effective when using pure de-oiled roasted
coffee.
a) The micronized coffee powder made from composition 3 was dry mixed
at a
ratio of 15 wt% with spray dried Nescafe powder to obtain a retail coffee
beverage
powder containing 15% MRC. Smooth mouthfeel and absence of sedimentation in
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reconstituted cup was found in a technical tasting session.
b) 64 g of the micronized coffee powder made from composition 3 was mixed
into
900 g of concentrated coffee extract (total solids content: 40 % by weight).
The
resulting suspension of coffee bean particles in coffee extract (total solids
content: 44 %
by weight) was freeze dried in a laboratory freeze drier. After drying for 12
hours at
25 C, 430 g of dry instant coffee beverage powder containing 15 % by weight
MRC
was obtained. Smooth mouthfeel and absence of sedimentation in the
reconstituted cup
was found in a technical tasting session.
c) Analogue to example b) above, a suspension of de-oiled coffee bean
particles
(composition 3) in coffee extract was produced and spray dried using a lab
scale spray
tower (Niro Minor). The obtained dry instant coffee beverage powder containing
15 %
by weight MRC was evaluated as having a smooth mouthfeel and absence of
sedimentation in the reconstituted cup in a technical tasting session.
Example 2
Soluble coffee beverage powder containing 15% micronized roast&ground coffee
particles which was de-oiled by extraction with supercritical carbon dioxide
Arabica coffee (origin Colombia) was roasted to a CTN of 75 and ground. The
coffee,
.. which was characterized by an oil content of 15 % is referred to as
composition 5 in the
following. It was fed into a 5 L supercritical carbon dioxide extractor
composed of a
carbon dioxide inlet, a high pressure pump achieving up to 1000 Bar, two heat
exchangers, an extraction vessel in which the coffee was placed and two
separators to
recover the residues. The coffee was extracted for 3.5h at 50 C at a pressure
of 280
.. Bar with a flow rate of 31kg/h of carbon dioxide. The coffee thus obtained
contained a
residual oil content of 3.1% (composition 6). For comparison the coffee bean
particles
according to composition 6 was mixed with pure soluble coffee powder (type
100%
Robusta) in a 1:1 weight ratio. The obtained mix is referred to as composition
7.
The powders according to composition 6 and 7 were further processed with a jet
mill
(Technologia Meccanica Fluid Jet Mill J-70). The throughput was adjusted by a
vibrational feeder to 1 kg/h, jet pressure was set to 9 bar. Stable continuous
operation
of the mill was performed over a period of 4 hours. Only loose powdery hold-up
was
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found in the mill, where the powder colour was getting lighter rather than
darker
through the effect of particle size reduction in comparison to the respective
feed
composition. None of the overheating or granule formation phenomena that were
described above for composition 1 and 2 was observed.
The coffee bean particles made from compositions 6 and 7 were analyzed by
laser
diffraction to measure their particle size distribution. The results are shown
in Figure 4.
It can be seen that de-oiling enhanced the efficiency of the jet milling
process. At equal
process conditions a D90 of 15.5 gm was obtained when jet milling composition
6,
compared to 27.2 gm for composition 7. While the use of PSC (composition 7) as
carrier was successful in enabling jet mill processing of roasted coffee
particles, the
process was more effective when using pure de-oiled roasted coffee.
Example 3
Soluble coffee beverage powder containing 15% micronized roast&ground coffee
particles which was de-oiled by extraction with hexane
Arabica coffee (origin Colombia) was roasted to a CTN of 75 and ground. The
coffee,
which was characterized by an oil content of 15 % is referred to as
composition 8 in the
following. It was fed into a Soxhlet cartridge and placed in a Soxhlet
extraction vessel.
The coffee was extracted with Petroleum Ether at its reflux temperature for
2hr. The
coffee thus obtained contained a residual oil content of 3% (composition 9).
For
comparison the powder according to composition 8 was mixed with pure soluble
coffee
powder (type 100% Robusta) in a 1:1 weight ratio. The obtained mix is referred
to as
composition 10.
The coffee bean particles according to composition 9 and 10 were further
processed
with a jet mill (Technologia Meccanica Fluid Jet Mill J-70). The throughput
was
adjusted by a vibrational feeder to 1 kg/h, jet pressure was set to 9 bar.
Stable
continuous operation of the mill was performed over a period of 4 hours. Only
loose
powdery hold-up was found in the mill, where the powder colour was getting
lighter
rather than darker through the effect of particle size reduction in comparison
to the
respective feed composition. None of the overheating or granule formation
phenomena
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that were described above for compositions 1 and 2 was observed.
The coffee bean particles made from compositions 9 and 10 were analyzed by
laser
diffraction to measure their particle size distribution. The results are shown
in Figure 5.
It can be seen that de-oiling enhanced the efficiency of the jet milling
process. At equal
process conditions a D90 of 17.1 gm was obtained when jet milling composition
9,
compared to 27.2 gm for composition 10. While the use of PSC as carrier was
successful in enabling jet mill processing of roasted coffee particles
(composition 10),
the process was more effective when using pure de-oiled roasted coffee.
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