WO 2007/010238 PCT/GB2006/002661
Apparatus, system and method
Technical field
This invention relates generally to an apparatus and systems for simulating digestion and
methods for using the same, for example for physiologically relevant investigations into
food and pharmaceutical digestion by vertebrates using real foods and pharmaceutical
preparations.
Background art
While humans have achieved the seemingly impossible feat of putting humans into outer
space and on the moon, there remains an incredible lack of information on the most basic
of all functions - ingestion and digestion of foodstuffs. How the alimentary canal
achieves the critical life-perpetuating function of receiving whole food-stuffs, the physico-
chemical process by which critical nutrients are extracted, and excess or unnecessary
components are eliminated, is understood very well in some respects, and very poorly in
other respects. The general addition of various chemicals at various stages of the
digestive process and the extraction of certain nutrients has been studied extensively.
However, the models available for the actual physical manipulation of food-stuffs remain
relatively crude.
Some of the most sophisticated models that are available to date include that described
in US Patent No. 5,525,305, issued on June 11, 1996, for an "In Vitro Model of an In Vivo
Digestive Tract". In that model, a relevant set of questions may be asked with respect to
the digestive process as applied to a relatively limited subset of test foodstuffs. The
system consists essentially of at least one unit including at least two pressure chambers
into which a fluid may be introduced, passed back and forth between the two pressure
chambers, into which may be added various chemicals, enzymes, and pH modulators.
U.S. Patent No. 6,022,733, issued on February 8, 2000, relates to a "Simulated Biological
Dissolution and Absorption System", including a cell monolayer in contact with a medium
in which pharmaceutical formulations may be dissolved, and analyzed, and an effluent
from said cell monolayer to permit analysis of uptake of the dissolved pharmaceutical
composition.
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U.S. Patent No. 6,379,619, issued April 30, 2002, relates to an "Artificial Gut", which
includes a series of hollow fibers lined with selected biological components, including
enterocytes, and perfusing the series of hollow fibers thus coated with biological
components, including under oxygenation.
In none of these systems is there a concerted focus on the actual physical forces and
handling of the materials introduced to ensure that, as much as possible, the system
reflects actual physiological processes, from both a chemical point of view, but also a
mechanical perspective. Accordingly, it is believed that there remains a long felt need for
a system that incorporates these parameters, which may be used in conjunction with or to
supersede the systems already known in the art, including but not limited to those
mentioned above, for seeking to model digestion of foods, Pharmaceuticals, and specific
nutrients.
A brief discussion of a "model gut" devised by the present inventors was made in
"Science and Innovation" Issue 2:05 released by the Institute of Food Research, Norwich,
UK (www.ifr.ac.uk). However that discussion did not teach or suggest the structure of the
model gut.
Thus it can be seen that the disclosure of novel apparatus, systems and methods for
improved simulation of digestion would provide a contribution to the art.
Summary of the invention
Novel apparatus, systems and methods are provided which incorporate physical,
mechanical and biochemical environments elucidated to exist in the in vivo lumen of the
vertebrate digestive tract.
In preferred embodiments the system includes an holistic stomach and, preferably, at
least a portion of the small intestine, capable of handling complex foods, real meals and
pharmaceutical preparations.
Thus the model may include at least three distinct stages of very different physical and
environmental conditions, as reflected by state of the art investigation into the operation
of the human gut during different stages of meal processing.
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Stage 1 simulates the main body of the stomach (the upper part of the stomach), a region
with inhomogeneous mixing behaviour, distinct acid and enzyme additions and a unique,
physiologically relevant emptying routine into Stage Two. This may be provided by (a) an
outer containment vessel into which fluid can be introduced and removed via at least one
orifice, and (b) an inner digestion chamber comprising a rigid portion through which the
foodstuff can be introduced and a flexible portion which tapers from the rigid portion to an
aperture from which the foodstuff can be removed, wherein said inner chamber is
securable within the outer vessel such that reversible alteration of fluid pressure within
the outer vessel causes reversible partial compression of the flexible portion for mixing
foodstuff present therein.
Stage 2 simulates the antrum (the lower part of the stomach), where the digesta from
Stage 1 is subjected to physiologically relevant shear forces to break down the food
structure, prior to emptying into Stage 3. Stage 2 may be provided by:
(a) an outer cylinder including in a first end wall an entry port through which the foodstuff
can be introduced, and at the opposite second end an opening for receiving an inner
cylinder, and in the side wall proximal to the first end wall an exit port from which the
foodstuff can be removed, (b) an inner cylinder slidably mounted within the outer cylinder
and including in a first end wall an aperture through which the foodstuff can be reversibly
forced between the inner and outer cylinders, and at the opposite second end an opening
for receiving a plunger, (c) a plunger slidably mounted within the inner cylinder for
drawing the foodstuff through the entry port and aperture into the inner cylinder, wherein
the aperture is within a resilient diaphragm secured within the end wall of the inner
cylinder, and wherein the volume of the inner cylinder is between 20 and 200 ml
Stage 3 simulates conditions found in the duodenum (the first section of the small
intestine).
Novel systems and methods are also provided which combinations of stages and\or steps
further provide for improved modelling of in vivo digestion.
Preferably the stages described above may be in modular form and may be integrated
together to provide model gut systems according to the invention. Preferably the systems
may be computer controlled, for example by software running on a computer system, and
monitoring of all parts of the systems may be performed in real time.
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Detailed disclosure of preferred embodiments
In developing the apparatus, systems and methods according to this invention, the
present inventors have been mindful to develop and incorporate state of the art scientific
information relevant to the in vivo vertebrate, including but not limited to, human digestion
of real foodstuffs. Thus, the inventors have undertaken magnetic resonance imaging
(MRI), and specifically, Echo Planar Imaging (EPI), studies in human volunteers during
the digestive process. The inventors observed meals within the body of the stomach and
discovered that the stomach pulses gently after ingestion of a meal, resulting in only mild
mixing. It was noted that gastric secretions released from the stomach wall during this
phase penetrate into the meal bolus by only a few millimeters around the outer surface,
following which a sloughing of the now hydrated outer surface of the bolus occurs. The
"sloughate" is emptied into the antrum. It was found that this secretion, diffusion and
sloughing cycle reiterates until the entire meal bolus is cleared from the body of the
stomach. Thus, Stage 1 of the present system incorporates this physiological process,
by providing a flexible vessel of appropriate geometry. Preferably, a non-porous, easily
cleaned, oil, water, acid and enzyme resistant (at physiological temperatures) and robust
material is selected for mimicking the walls of the body of the stomach. Ideally, the
material is also permissive of MRI, such that direct comparison of MRI images of
"digestion" in this stage of the model with MRI images obtained in vivo is facilitated.
Appropriate materials and construction geometries include those shown in the figures and
equivalents thereof. For example, therefore, for Stage 1, the main body of the stomach,
the outer digestion vessel and non flexible components of the inner digestion chamber
are preferably constructed from Perspex. The flexible part of the inner digestion chamber
is preferably constructed from polyurethane. All o-rings are preferably nitrile rubber and
the screws and bolts are preferably nylon. All other parts of this stage of the model are
preferably constructed from Delrin. Where compatibility with MRI is not required,
naturally, other materials including metal, such as stainless steel, titanium, and the like,
may be used for the rigid portions of the apparatus. Flexible portions of the apparatus
may likewise be constructed from latex or other appropriate materials.
PRE-STAGE 1 TREATMENT OF MATERIAL - MASTICATION OF FOODSTUFFS.
To ensure reproducibility in size reduction of food material prior to processing at stage 1
(the model of the main body of the stomach) a precision cutting device was designed.
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This apparatus was used to produce material resulting from a 'standard chew' within the
bucal cavity of vertebrates prior to simulated digestions within the stomach and small
intestines. The designed piece of apparatus cuts food material into cubes of
approximately 3mm2 dimensions, representing the approximate size of food produced by
human chewing prior to swallowing. The apparatus consists of double-edged razor blades
aligned 3mm apart on a metal frame. The apparatus is used to first cut 3mm wide strips
from food material and then turned 90° to cut these strips into cubes. The resulting cubes
are pushed out of the device by a pivoted array of rods. Once cut, the food material is
subjected to low levels of α-amylase "digestion" at 37°C for a period of time ranging
between 10-60 seconds. This pre-treatment technology optionally further includes a
mechanical crushing/breakdown of the food material/structure with parallel addition and
mixing of a 'model saliva' (aqueous mix of mucins and digestive enzymes). This pre-
treated food material is then fed into Stage 1, a simulation of the main body of the
stomach.
STAGE 1 - THE MAIN BODY OF THE STOMACH
Thus the invention provides an apparatus for simulating digestion of a foodstuff, which
apparatus comprises:
(a) an outer containment vessel into which fluid can be introduced and removed via at
least one orifice, and
(b) an inner digestion chamber comprising a rigid portion through which the foodstuff can
be introduced and a flexible portion which tapers from the rigid portion to an aperture from
which the foodstuff can be removed
wherein said inner chamber is securable within the outer vessel such that reversible
alteration of fluid pressure within the outer vessel causes reversible partial compression
of the flexible portion for mixing foodstuff present therein.
The foodstuff can be any material which it is desired to model the digestion of, including
complex foods, real meals or model meals, pharmaceutical or nutraceutical preparations
or formulae including slow release formulations. Optionally the food-stuff used in the
process may include added active materials (e.g. pro- or pre-biotics; pathogenic or non-
pathogenic bacteria etc.) which it is desired to study within the in vitro system.
Typically the volume of the inner chamber is between 500 and 1000 ml.
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Preferably the rigid portion is annular and the flexible portion is conical or frustoconical
and is connected at its upper extremity to the rigid portion and at its lower extremity to a
resilient annular member which is of smaller diameter than the rigid annular portion and
which defines the aperture.
The flexible portion may comprise a moulded flexible sheet material secured around each
of the rigid annular portion and the resilient annular member by an O-ring.
The mixing achieved by Stage 1of the apparatus is inhomogeneous mixing. The gentle
pulsing produced by the addition and removal of fluid from the outer containment vessel
facilitates the penetration of digestive additives (which correspond to gastric secretions)
into the peripheral of the foodstuff bolus.
Preferably the apparatus further comprises a valve for controlling flow from the aperture
in the resilient annular member. The novel structure of part-flexible, part-rigid inner
digestion vessel and the continued pulsing produced by the outer chamber will result in
the preferential emptying of the now hydrated outer region of the foodstuff bolus through
the aperture when the isolating valve between Stage 1 and Stage 2 is opened. This
sequence of events will repeat until Stage 1 is empty resulting in a continued cycle of
hydration around the outside of the foodstuff bolus followed by preferential emptying of
this now hydrated portion (an 'onion pealing' effect).
Thus the invention provides the ability to accurately mimic both the biochemical and
physical processes of dilution and mixing of meals within the stomach. Contrary to the
traditional idea of rapid and complete homogenization of a meal within the main body of
the stomach, gastric contents appear to be rather poorly mixed. Long after ingestion the
meal remains heterogeneous, with gastric secretions only penetrating around the outside
of the food bolus. MRI investigation suggest that the centre of the meal bolus is not
diluted by secretions for an appreciable time. The data also suggested that the stomach
selectively emptied into the lower part of the stomach (the antrum) the more dilute,
peripheral components of the meal bolus, which are closest to the contractile activity. This
suggests that food leaves the bolus by a process of elution.
The inner chamber may be held within a cassette which can be demountably secured
within the outer vessel, for example to facilitate removal for cleaning or decontamination
purposes. Thus the outer vessel may comprise a top plate, a bottom plate, an annular
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chamber wall extending between and sealingly affixed to each of said top plate and said
bottom plate wherein apertures in said top plate in said bottom plate permit the cassette
to be demountably secured therein. Preferably the cassette comprises a top sealable
plate rigidly disposed apart from, a bottom sealable plate, each of which respectively
sealably mate to an aperture in said top plate and an aperture in said bottom plate of
said containment means, wherein the rigid portion of the inner chamber is sealably
mounted within the top sealable plate of the cassette.
All structural components are preferably composed of materials which permit real-time
MRI, echo-planar MRI, or other on-line monitoring and analysis of ongoing processes to
occur. Such materials include, but are not limited to, Delrin for rigid structural
components, and polyurethane for pliable components. Preferably all or part of the inner
chamber and outer vessel are composed of a material permissive of MRI such that any
foodstuff within the inner chamber can be visualised using MRI
In use, to simulate the gentle mixing and squeezing of foodstuffs introduced into the body
of the stomach, a "simulated stomach" according to this invention comprises a sealed
outer containment vessel, and an inner digestion chamber contained within the outer
containment vessel. The outer containment vessel is filled completely with a fluid,
including but not limited to water. A known, controlled quantity of water is introduced into
and cyclically removed from this containment vessel at a definable and controllable rate,
which creates a gentle squeezing and relaxing ('massaging') of the flexible part of the
inner digestion chamber. In one embodiment of this invention, a pneumatic actuator, a
stepper motor to drive the actuator and an intelligent controller are coupled to control the
introduction and removal of fluid from the containment vessel.
Preferably the inner chamber has a plurality of pH electrodes disposed within it, wherein
each pH electrode optionally contains its own reference electrode. In addition to
simulating the mechanical mixing that occurs in the body of the stomach in vivo, the
apparatus of this invention this provides online monitoring of the mixing of digesta within
the stomach. Acid diffusion and resulting pH changes can be monitored by the series of
pH electrodes (Figure 4), designed and positioned to minimally interfere with mixing,
distributed throughout the inner digestion chamber. Preferably, the electrodes are small,
soft and robust enough to sustain the physical and chemical environment to which they
are exposed. Due to inhomogeneous mixing in the body of the stomach, both pH and
diffusion gradients are measured throughout the body of the meal. Accordingly, each pH
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electrode preferably contains its own reference electrode. Each electrode is preferably
interfaced with a central processing unit, such as a personal computer, to permit
simultaneous monitoring of all electrodes in real time and control of the rate of delivery of
hydrochloric acid to the digestion chamber as shown in figure 4.
Preferably the inner chamber includes an applicator for introducing digestive additives
from respective digestive additive reservoirs, wherein the applicator is optionally arranged
within the inner chamber so as to float upon any foodstuff present therein and deliver said
digestive additives onto the interior walls of said inner chamber and\or the foodstuff. The
additives may be conducted from the reservoirs to the applicator by hoses passing
through the outer vessel such that the temperatures of the additives are modified by fluid
in the outer vessel. The additives will generally be one or more of acid, alkali, enzymes
(particularly digestive enzymes, which are well known to those skilled in the art). Other
additives may include phospholipids and bile. Acid and enzymes will typically be stored in
temperature controlled reservoirs. The acid reservoir is held at room temperature
whereas the reservoirs containing the enzymes are held at between 1-4°C. Both the acid
and the enzymes are drawn with the use of computer controlled peristaltic pumps from
their respecting storage reservoirs through narrow bore silicone rubber hoses. The rate of
enzyme and acid additions are controlled and monitored in real time by appropriate
process control software (figure 4). The hoses carrying the additions are looped into the
main containment vessel where the acid and enzymes contained within the hoses are
rapidly warmed from their native temperatures to 37°C. The hoses then feed into a device
that floats on top of the meal contained within the digestion chamber. This device rises
and falls with the movement of the meal within the digestion chamber. The acid and
enzymes are deposited from their respective hoses into this device where they are mixed
and then evenly secreted on top of the meal around the wall of the digestion chamber.
The rate at which the acid is secreted onto the meal within the digestion chamber is
controlled via a feedback mechanism as shown in figure 4.
As noted above, the pH at specific points within the digestion chamber is measured with
the use of pH electrodes as described previously. These pH electrodes may be interfaced
with a central processing unit. Software is implemented that relates measured pH with the
rate and amount of acid added into the digestion chamber. The software, in real time,
measures pH, calculates required acid and then controls the peristaltic acid pump and
hence the rate and amount of acid delivered to the digestion chamber. This system is
discussed in more detail below.
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Preferably the outer vessel has at least one temperature sensor within it. Temperature
throughout the simulation of the main body of the stomach is controlled via an external
temperature controller. This temperature controller heats and circulates the fluid
contained within the outer containment vessel. Thermocouples or like temperature
sensors are positioned throughout the containment vessel and on the outside of the
flexible portion of the digestion chamber. These temperature sensors are connected to a
central processing unit that monitors the measured values in real time. The temperature
output of the temperature controller is then adjusted by the central processing unit (figure
4) to ensure the temperature of the fluid circulated within the containment vessel is
maintained at pre-determined desired values during processing
With reference to figure 1 A, there is provided a schematic representation of one
embodiment of the main body of the stomach portion of an apparatus according to the
present invention. This portion of the apparatus is represented in left-to-right cross-
section, as a chamber 100, comprising a top plate 110, a bottom plate 120, an annular
chamber wall 130 extending between and sealingly affixed to each of said top plate 110
and said bottom plate 120 to create a closed compartment volume 101. Said closed
compartment volume 101 defined between said top plate 110, said bottom plate 120 and
said annular chamber wall 130 represents a first structural element 140 shown in isolation
in figures 2A, as a side cross sectional view, and figure 2B, as a top cross-sectional view.
Said structural element 140 is a sealed compartment, forming a containment means for
various ports for mass transport into and out of said compartment volume 101 through
said top plate 110 and said bottom plate 120. Affixing said top plate 110 to said bottom
plate 120 and clamping said annular chamber wall 130 therebetween, are provided a
series of support rods 131 fixed between the underside of said top plate 110 and the
topside of said bottom plate 120.
Primary to the function of this aspect of the invention is a removable cassette 200 which
is detachably and sealably inserted into and removed from said structural element 140 via
apertures 111 in said top plate 110 and 121 in said bottom plate 120. Said removable
cassette 200 is shown in isolated cross-sectional detail in figure 3A. This preferably
detachable cassette 200 defines the internal working volume, in which initial processing
of foodstuffs occurs, by analogy to a vertebrate, and in a preferred embodiment, human,
stomach. Said cassette 200 shown in figure 3A comprises a top sealable plate 210 and a
bottom sealable plate 220 each of which respectively sealably mate to said aperture 111
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in said top plate 110 and said aperture 121 in said bottom plate 120 of said containment
means 140. Gaskets 211 and 221 are provided at the mating edge of said top plate 210
where it meets said aperture 111 and the edge of said lower plate 220 where it meets the
said aperture 121. Handles 212 are provided affixed to said top plate 210 to facilitate
transport of said cassette. Retaining clips lock said cassette insert into place within said
chamber 200. Keeping said top plate 210 and said bottom plate 220 rigidly spaced apart
are a series of rods 230. These rods 230 while rigidly maintaining said top plate 210 and
said bottom plate 220 in spaced apart relationship to each other, provide open-access to
structures disposed between said top plate 210 and said bottom plate 220 and spatially,
within a circumference circumscribing said rigid rods 230. In this manner, fluid pressure,
air pressure, or the like, and changes thereof within said volume 101 are not impeded by
said rods 230 in the way that a solid annulus, such as 130 employed for defining the
chamber 140 would do. Of course, rather than the rods 230, an annulus similar to 130
could be used, wherein a plurality of holes in the walls thereof could permit transmission
of fluid pressure and changes thereof to the volume included within the circumference of
said annulus. Other equivalent variations achieving the function of rigidly spacing said
top plate 210 and said bottom plate 220 while permitting transmission of fluid pressures
and variations thereof may be utilized for this purpose.
As a part of said cassette 200, there is provided an annular structure 240 for receiving
foodstuffs for analysis and processing according to the invention. Said annular structure
240 is sealably affixed within an orifice 241 in said upper plate 210. Sealably affixed to
the lower extremity of said annular structure 240 is a pliable membrane 250, affixed via
gasket 251, or by equivalent means known in the art, including, but not limited to, for
example, crimping wire, a screw-clamp, or the like. Said pliable membrane 250 is affixed
at its lower extremity to the upper extremity of a valve structure 260, via gasket 252. Said
valve structure 260 is rigidly and sealably affixed through an orifice in said lower plate
220. Said valve structure may be manually actuated or it may be under computer control
for regulating passage of mass there through. Preferably, the pliable membrane 250
tapers from the lower extremity of said annular structure 240 toward its own terminus
affixed to said valve structure 260. In this way, a volume 242 is defined by the internal
space confined by the inside of said annular structure 240 and said tapered pliable
membrane 250. Foodstuff is included within the volume 242 to which is added metered,
known quantities of selected additives, including but not limited to digestive enzymes,
acids, bases and the like. Thus, for example, lipases, dilute hydrochloric acid and the
like, may be added to the foodstuff included within said volume 242. As the food thus
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included and treated is broken down, the "digesta" thus produced is permitted to traverse
via said valve structure 260 into the next discrete digestive compartment of the model
digestive system.
From the foregoing, it will be appreciated that the main body of the stomach is composed
of the element 100 in combination with the element 200. It will also be appreciated by
those skilled in the art that enhancements in the physiological relevance of this apparatus
may be achieved by, for example, collagen coating of surfaces brought into contact with
foodstuff. Furthermore, such surfaces may be seeded as a growth surface for endothelial
cells, fibroblasts, or the like, as appropriate, depending on the degree to which it is
desired to mimic the physiologic milieu encountered by foodstuffs in vivo. It should be
borne in mind, however, that enhancements of this nature, while coming within the scope
of the invention contemplated herein, will significantly increase the maintenance and care
needed to maintain the apparatus in proper working order. It will also be appreciated
that, in the first instance, where simulation of physical and chemical processing of
foodstuffs is desired, such an exquisite degree of physiologic mimicry may not be
necessary or even desirable.
Because data obtained, as discussed herein above, utilizing in vivo MRI, echo-planar
MRI, and the like, indicates that food is digested from the outside inward, enzymes, acids,
bases, and the like are added to the outside of a bolus of foodstuff included in said
volume 242. This is accomplished via applicator 300 comprising hoses 301 through
which enzymes, acids, bases and the like are transmitted to nozzles 302 which deliver
said enzymes, acids, bases and the like to the periphery of said annular structure 240 by
secreting a fine stream of these materials onto the interior walls of said annular structure
240 as well as onto the exterior surface of the foodstuff included in said volume 242. The
applicator 300 floats on top of the volume 242 as it delivers enzymes, acids, bases
moving both up and down as the level of volume 242 changes, thereby achieving a
uniform delivery of these digestive components to the exterior of the foodstuff within the
volume 242. To gently mimic what has been observed via in vivo MRI utilizing echo-
planar MRI, a liquid, such as water, is introduced and removed rhythmically, into and out
of the volume 101 once the cassette 200 containing the foodstuff has been locked into
place in orifices 111 and 121 within said chamber 100. As fluid is introduced and
removed, a gentle massaging of the flexible membrane 250 is induced, which assists in
admixture of added digestive components with the exterior layers of the foodstuff, as well
as inducing gentle sloughing of layers of the foodstuff toward said valve mechanism 260,
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ready for passage into the next phase of the simulated digestive tract. Fluid is added to
and removed from the volume 101 by means of fluid addition and removal ports 102 and
103. To bleed the volume 101 of air, an air bleed port 104 is provided. To permit
regulation of the temperature of the enzymes, acids, and bases in hoses 301 prior to
addition to volume 242 hoses 301 are looped 105 into and immersed in volume 101. The
temperature regulation, rate of fluid ingress and egress via ports 102 and 103, rate and
composition of mass addition via applicator 300 and nozzles 302, and rate at which mass
is permitted to flow through valve 260 from the simulated main body of the stomach
compartment of the simulated digestive system into the antrum compartment, are all
amenable to computerized control.
STAGE 2 - THE ANTRUM
Stage 2 of the Model provides a simulation of the antrum (the lower region of the
stomach).
Thus in another aspect the invention further provides an apparatus for simulating
mechanical digestion of a foodstuff, which apparatus comprises:
(a) an outer cylinder including in a first end wall an entry port through which the foodstuff
can be introduced, and at the opposite second end an opening for receiving an inner
cylinder, and in the side wall proximal to the first end wall an exit port from which the
foodstuff can be removed,
(b) an inner cylinder slidably mounted within the outer cylinder and including in a first end
wall an aperture through which the foodstuff can be reversibly forced between the inner
and outer cylinders, and at the opposite second end an opening for receiving a plunger,
(c) a plunger slidably mounted within the inner cylinder for drawing the foodstuff through
the entry port and aperture into the inner cylinder,
wherein the aperture is within a resilient diaphragm secured within the end wall of
the inner cylinder,
and wherein the volume of the inner cylinder is between 20 and 200 ml.
Using EPI the inventors have measured the breakdown forces experienced by the food
bolus within the antrum and the frequency of antral contractions. Within Stage 2 they
have simulated this region of high shear, mimicking both the rate and strength of
contractions experienced by the food bolus in vivo.
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Stage 2 in this aspect of the invention comprises a system of nested cylinders, which
permits dead-spaces between Stages 1 and 2 and optionally Stage 3 to be minimised.
The aperture in the inner cylinder through which the foodstuff can be reversibly forced
creates a shearing force. Preferably it is present within a resilient diaphragm secured
within the end wall of the inner cylinder - for example consisting of a flat polyurethane
rubber 'ring' sealably mounted at or near the terminus of the inner cylinder (e.g. of
diameter 25 to 40 mm e.g. 30 or 32 mm), and incorporating an orifice of between 5 and
15 mm e.g. 6, 8, or 10 mm).
The apparatus may comprise a stand having a base plate and a vertical support member,
which support member provides a clamp for securing the outer cylinder and a guide
through which the arm of the plunger passes for ensuring true movement of the plunger
within the inner cylinder.
The outer cylinder and the second end of the inner cylinder may each comprise at least
one collar, said collars having a plurality of apertures aligned between said collars and
said apparatus further comprises a plurality of guide rods passing through said aligned
apertures for ensuring true movement of the inner cylinder within the outer cylinder
Stage 2 can be oriented vertically or horizontally. In the former case, gravitational forces
help to achieve optimal sieving of the foodstuff prior to passing to Stage 3 if present, with
larger pieces of sheared foodstuff material being preferentially retained in Stage 2, and in
particular in the inner cylinder. Additionally a vertical orientation permits degassing of
Stage 2 into Stage 1 via the valve between the two.
The removable cassette facilitates its sterilisation e.g. by autoclaving. This is particularly
useful where pathogenic bacteria may have been part of the tested foodstuff.
Preferably the apparatus further comprises means for heating the foodstuff. For example
the apparatus could be heated by providing a heated water jacket, which may preferably
be fed by heated water from the heating system of Stage 1. Alternatively heating may be
directly via a heating block. Preferably the apparatus is heated so as to maintain the
processed foodstuff at a temperature of 37°C.
Accordingly, with reference to figures 5A-5D, there is provided a schematic
representation of one embodiment of Stage 2, the antrum 500, portion of the apparatus
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according to this invention. The sequence of figures 5A through 5D represent one cycle,
sequentially, of actions that occur in the simulated antrum. Figure 6 represents a
schematic diagram of one complete antrum cycle.
At the top end of the antrum 500, there is provided a port 510 which interlocks with the
bottom end 260 of Stage 1, the main body of the simulated stomach, (comprised by 200
and 300). The port 510 is preferably valved, said valve being either manually or
automatically opened or closed. Set off at 90 degrees to said port 510 is another port
520. The port 520 permits the headspace of the system to be bled, and permits for
foodstuffs processed by the antrum 500 to be transmitted to the next stage, simulative of
the duodenum, Stage 3, for further processing. Operationally, foodstuff processed from
Stage 1, comprised by 200 and 300 is drawn into a chamber via port 510, with port 520
closed. During the first initial charge of the antrum only, there will be a small amount of
air contained within the antrum, which may be displaced by bubbling up through the main
body of the stomach (Stage 1) (automatic de-gassing). To assist in drawing foodstuff into
the antrum, a plunger 530 is drawn downward, thereby creating a volume 531 defined by
a piston 532, at the head of the plunger 530, and the internal walls of a chamber 533.
Said chamber, 533, sealingly mates with an external chamber 534. At the head of said
chamber 533, there is provided an aperture, 535. As a result, once the plunger 530 has
been drawn down to a sufficient, pre-set level, and the volume 531 has been filled with
foodstuff from Stage 1, the valve 510 is closed, and the plunger 530 is locked in position.
Said chamber 533 is then drawn down, forcing foodstuff from volume 531 through said
aperture 535 and into volume 536, defined now by the inner walls of chamber 534, and
the upper portion of said chamber 533. At maximum displacement of the chamber 533,
the end wall of chamber 533 preferably remains a pre-determined distance, preferably of
about 10-20mm, from the piston 532, defining a 'dead' volume 537. This volume
compensation avoids physical crushing of particles between the piston 532 and the end
internal wall of the chamber 533. The chamber 533 is then raised within said chamber
534, thereby forcing foodstuff back through aperture 535, thereby recreating/refilling
volume 531, while concomitantly diminishing volume 536.
By repeated strokes of chamber 533 forcing foodstuff through aperture 535, the foodstuff
is subjected to sufficient shear to break the foodstuff down. When sufficiently broken
down to mimic physiologic processes and foodstuff size, port 520 is opened and plunger
530 is pushed upward to urge the processed food into Stage 3 of the simulated digestion
model of this invention. Preferably, the whole of the antrum contents is not displaced and
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the plunger stops at a pre-determined point, providing a 'dead' volume 538 between the
piston 532 and chamber 533, to trap larger particles. The pre-determined point may be
set by the user either before or after the main body of the stomach (stage 1) is filled and
the chamber allowed to charge under gravity. The larger particles stay in the system and
undergo several cycles of 'fluid shearing' as described above, until they become more
easily flushed out.
Over subsequent cycles, the 'recharging' plunger stroke is preferably the same as the
initial charging stroke, and a fixed amount of material is therefore retained in the antrum
on each charge. The stroke length of the plunger and of the chamber may therefore
advantageously remain constant throughout the processing of the sample and no further
user inputs are required.
It will be appreciated that each of the steps and components described above may be
accomplished manually. Thus, at the appropriate junctures, the plunger 530 may be
manually drawn down, after manually closing port 520 and opening port 510. Chamber
533 may be manually moved up and down for as many cycles as necessary to achieve
the breakdown of foodstuffs to desired degree of particle size reduction. Alternatively,
and preferably, all of these actions may be automated. The plunger 530 and chamber
533 may be driven by means including, but not limited to, motors, pneumatic or hydraulic
means. In some preferred embodiments, when used in conjunction with the first stage
apparatus (main body of the stomach) described above, the stepper motor used in the
'massaging' step in the first stage may be suitable for incorporation into the present
second stage apparatus.
Preferably the driving means provides flexibility in the movement of the plunger and
chamber and is suitable for use with the control systems described herein. Preferably the
driving means of the plunger 530 includes a spring 539 with fixed travel; this allows for
changes in the volume of the cylinder caused by displacement of the inner chamber 533
to be compensated. Preferably the plunger and the chamber are each able to move at
between 5-50 mm/second. Valves may be solenoids which are programmed to open or
close at the right time in relation to the other actions in the system. Preferably the valves
(510, 520) are computer controlled (open or shut), have minimal dead volume and are
acid and surfactant resistant.
With respect to this embodiment of the antrum, reference is made to figure 5E, in which
there is provided not only the operative components as described above, there is also
WO 2007/010238 PCT/GB2006/002661
provided a stand 540 comprising a base plate 541 and a vertical support member 542.
Affixed to said vertical support member 542 there is provided a lockable guide 543 which
ensures straight and true movement of said plunger 530. Also affixed to said vertical
support member 542 are two additional guides, 544 and 545. Running through guides
544 and 545 are rods 546 and 547 which also run through an horizontal member 548 by
means of which said chamber 533 is moved up and down to breakdown foodstuff, as
described above. Said guides 544 and 545 also provide a means by which the entire
antrum 500 is oriented in mating contact with the lower portion of the main body of the
stomach, at point 260 as described herein-above.
The materials used for the construction of the apparatus are preferably resistant to acid
(pH 2.0), biological surfactants (phospholipids, bile salts, fatty acids, amphilic proteins
etc) and are also preferably resistant to degradation by standard cleaning detergents.
Preferably the design of the apparatus allows easy disassembly for cleaning or
replacement of parts. The end plate of the chamber is preferably interchangeable to
provide various sized holes to suit differing mechanical requirements. The Stage 2
(antrum) apparatus is preferably suitable for mounting directly beneath the base plate of
Stage 1 (main body of the stomach) of the apparatus, to reduce the dead volume
between the two stages to a minimum.
The movement of the plunger and of the chamber may preferably be monitored and
controlled by a control system, preferably a computer controlled system, as shown in
Figure 7.
STAGE 3-DUODENUM, INTESTINES, NUTRIENT ABSORPTION AND EXCRETION
Having described in some detail the processing of foodstuffs according to this invention,
through Stage 1 (the main body of the stomach) and Stage 2 (the antrum), duodenal and
intestinal processing, nutrient absorption and finally excretion may then optionally be
studied. These functions are achieved by purpose-built elements that interface with the
above described Stages 1 and 2 of the present invention. When incorporated, such
further components would come within the scope of the present invention, and may take
the form, for example, of the system of U.S. Patent No. 6,022,733, issued on February 8,
2000, which relates to a "Simulated Biological Dissolution and Absorption System". That
system includes a cell monolayer in contact with a medium in which pharmaceutical
WO 2007/010238 PCT/GB2006/002661
formulations may be dissolved, and analyzed, including in an effluent from said cell
monolayer, to permit analysis of uptake of the dissolved pharmaceutical composition.
Such a system may optionally be juxtaposed distal to Stages 1 and 2 of the present
invention. Likewise for the system of U.S. Patent No. 6,379,619, issued April 30, 2002,
which relates to an "Artificial Gut", which includes a series of hollow fibers lined with
selected biological components, including enterocytes, wherein perfusing the series of
hollow fibers thus coated with biological components occurs, including under
oxygenation. In the event such a system is incorporated distal to Stages 1 and 2 of the
present invention, a filtration system is incorporated to ensure that fouling and blockage
of the fibers does not ensue.
SYSTEMS
In a further aspect of the present invention there is provided a system for simulating
digestion of a foodstuff, which system comprises a first stage having:
(a) an outer containment vessel into which fluid can be introduced and removed via at
least one orifice, and
(b) an inner digestion chamber comprising a rigid portion through which the foodstuff can
be introduced and a flexible portion having an aperture from which the foodstuff can be
removed
wherein said inner chamber is securable within the outer vessel such that
reversible alteration of fluid pressure within the outer vessel causes reversible partial
compression of the flexible portion for inhomogeneously mixing foodstuff present therein,
wherein the apparatus further comprises a second stage connected to said first
stage,
the second stage comprising means for mechanically shearing foodstuff
introduced from the inner digestion chamber of the first stage,
and wherein the apparatus optionally further comprises a third stage connected to
said second stage,
the third sage comprising means for preferential absorption of material from the
foodstuff removed from the second stage.
Preferably the first and second stages are connected via a valve for controlling flow
between the first and second stages.
Preferably the means for mechanically shearing foodstuff comprise:
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WO 2007/010238 PCT/GB2006/002661
(a) an outer cylinder including in a first end wall an entry port through which the foodstuff
can be introduced from the inner digestions chamber of the first stage, and at the
opposite second end an opening for receiving an inner cylinder, and in the side wall
adjacent the first end wall an exit port from which the foodstuff can be removed,
(b) an inner cylinder slidably mounted within the outer cylinder and including in a first end
wall an aperture through which the foodstuff can be reversibly forced between the inner
and outer cylinders, and at the opposite second end an opening for receiving a plunger,
(c) a plunger slidably mounted within the inner cylinder for drawing the foodstuff through
the entry port and aperture into the inner cylinder,
Most preferably the first stage and second stage are Stage 1 and Stage 2 respectively as
described in the preceding aspects. Preferably these stages are integrated and function
as a synchronised unit.
In preferred embodiments of the systems of the invention control systems are present.
The following factors are among those which may be controlled:
(i) synchronisation of the plunger and the chamber movement in the second
stage
(ii) sequencing of inlet and outlet valves
(iii) volume measurement and 'dead volume' in the second stage
(iv) internal temperature in the system
(v) pH calibration
Other factors may also be controlled, as described in more detail below.
As noted hereinabove, the apparatus and systems of the present invention are
particularly susceptible to automation. Thus a system of the present invention may
comprise:
(a) additive controlling means for introduction of acid or alkali additives from respective
additive reservoirs into the first stage, and
(b) a central processing unit (CPU), which processor is able to:
(i) input pH values from pH electrodes disposed within the inner chamber,
(ii) compare the pH values inputs with a predetermined value
(iii) provide a control signal to said additive controlling means in accordance with the
result of the comparison at (ii).
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WO 2007/010238 PCT/GB2006/002661
The means for introduction of digestive additives may be a peristaltic pump which acts on
a flexible hose connecting the storage reservoir to the applicator
In another embodiment the system comprises:
(a) temperature controlling means for adjusting the temperature of fluid introduced into
the outer vessel, and
(b) a CPU, which processor is able to:
(i) input temperature values from a temperature sensor within the outer vessel,
(ii) compare the temperature values with a predetermined value
(iii) provide a control signal to said temperature controlling means in accordance with the
result of the comparison at (ii).
The system may comprise:
(a) pumping means for introduction and removal of fluid from the outer vessel such as to
alter the fluid pressure therein,
(b) a central processing unit (CPU), which processor is able to provide a control signal to
said pumping means in accordance with predetermined values relating to preferred
volume and flow rate of the fluid introduced and removed from the outer vessel.
The predetermined values may be calculated by the CPU on the basis of values
corresponding to the physical and\or biochemical composition of the foodstuff input to the
CPU by a user.
The pumping means for introduction and removal of fluid from the outer vessel may be a
pneumatic actuator and a stepper motor to drive the actuator.
The system may comprise a CPU which is able to provide a control signal to valves
controlling any one or more of:
(i) introduction of foodstuff into the first stage,
(ii) batch delivery of foodstuff from the first stage to the second stage, or
(iii) batch delivery of foodstuff from the second stage to the optional third stage
The system may comprise a CPU which is able to provide a control signal to means
driving the plunger and chamber in the antrum (second stage), for controlling any of the
following:
(i) the level at which the plunger is locked after charging the apparatus
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WO 2007/010238 PCT/GB2006/002661
(ii) the maximum displacement of the chamber (defining the first 'dead
volume')
(iii) the point at which the plunger stops during discharge (defining the second
'dead volume')
(iv) the number of strokes of the chamber in each shearing cycle and the
number of shearing cycles
(v) the rate of movement of the chamber and/or of the plunger
(vi) the delay between each emptying and filling cycle.
The level and position of the plunger and chamber in steps (i), (ii) and/or (iii) above may
be pre-determined by the user and inputted to the CPU. This sets the 'dead volume' and
can be done either before or after the main body of the stomach is filled. Preferably the
user input is locked to prohibit entry of values which would cause the end of the plunger
and the end of the chamber to collide.
Any of the CPUs mentioned above may form part of a computing device, for example a
standard personal computer (PC), which may additionally comprise other known
components such as a keyboard, monitor, operating system, system memory, memory
storage devices, cache memory, data backup unit, GUI controller and input-output
controllers, all of which typically communicate in accordance with known techniques such
as via a system bus. As will be understood by one skilled in the relevant art, there are
many possible configurations of these components, and many further optional
components may also be present.
User input of the variables described above for Stage 1 and Stage 2 of the apparatus, to
the CPU may preferably be via a graphical user interface (GUI). The graphical user
interface controller may comprise any software program capable of providing graphical
input and output interfaces between the computer/CPU and a user, and for processing
inputs from the user. As is well known in the relevant art, a user may provide input
information using a GUI by selecting, pointing, typing, speaking, and/or otherwise
operating or providing information into one or more input devices in a known manner.
Figure 8 shows a computing device that is suitable for use in the invention. Computing
device 600 may include many more components than those shown. The components
shown, however, are sufficient to disclose an illustrative embodiment for practicing the
invention.
WO 2007/010238 PCT/GB2006/002661
Computing device 600 includes processing unit (CPU) 612, video display adapter 614,
and a mass memory 602, all in communication with each other via bus 622. The mass
memory generally includes RAM 616, ROM 632, and one or more permanent mass
storage devices, such as hard disk drive 628, tape drive, optical drive, and/or floppy disk
drive. The mass memory stores operating system 620 for controlling the operation of
computing device 600. Any general-purpose operating system may be employed. Basic
input/output system ("BIOS") 618 is also provided for controlling the low-level operation of
network device 600. As illustrated in Figure 8, computing device 600 can communicate
with other devices e.g. using a communications network, via interface unit 610. Interface
unit 610 can be constructed for use with various communication protocols e.g. the TCP/IP
protocol. Interface unit 610 is sometimes known as a transceiver, transceiving device, or
network interface card (NIC).
The mass memory as described above illustrates another type of computer-readable
media, namely computer storage media. Computer storage media may include volatile,
nonvolatile, removable, and non-removable media implemented in any method or
technology for storage of information, such as computer readable instructions, data
structures, program modules, or other data. Examples of computer storage media
include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM,
digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape,
magnetic disk storage or other magnetic storage devices, or any other medium which can
be used to store the desired information and which can be accessed by a computing
device.
The mass memory also stores program code and data. One or more applications 650 are
loaded into mass memory and run on operating system 620. Applications 650 may
include computer executable instructions which, when executed by computing device
600, transmit, receive, and/or otherwise process data and/or enable communication with
another device.
A typical operating environment is shown in Figure 9.
The CPUs may be the same or different. Preferably the control systems of the first stage,
second stage and third stage may be integrated with each other to provide an overall
control system.
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As noted above, the system may further comprise a pre-first stage apparatus for cutting
the foodstuff into portions having desired dimensions and optionally exposing it to one or
more digestive enzymes
METHODS OF USE
The invention further provides use of any of the above described apparatus or systems
for modelling digestions e.g. for modelling any one or more of: the digestibility of the
foodstuff; the release or presence of an active agent from the foodstuff; the interactions of
dietary components of the foodstuff; the survival of an organism within the foodstuff.
Such methods find utility in food safety, oral drug development, novel, functional, and
specialist food characterisation, screening of active components, food structure studies
etc.
A typical method may comprise:
(a) providing an apparatus or system as described above,
(b) providing the foodstuff in portions having desired dimensions,
(c) optionally incubating the portions with a-amylase and\or mucins,
(d) introducing the portions into the inner chamber,
(e) introducing known amounts of digestive additives into the inner chamber,
(f) inhomogeneously mixing the foodstuffs by cyclically introducing and removing fluid
such as to squeeze and relax the flexible portion of the inner chamber while maintaining
preferred temperature, pH and enzymatic composition of the foodstuff.
Preferably the method comprises:
(a) providing the apparatus or system,
(i) introducing a preferred volume of foodstuff into the inner cylinder by drawing down the
plunger
(ii) withdrawing the inner cylinder such as to force foodstuff through the aperture of the
inner cylinder into the outer cylinder,
(iii) depressing the inner cylinder thereby forcing foodstuff back through aperture from the
outer cylinder into the inner cylinder,
(iv) optionally repeating steps (ii) to (iii) for as many cycles as necessary to achieve the
breakdown of foodstuffs to desired degree of particle size reduction,
(v) removing a preferred volume of foodstuff from the exit port, which volume is
optionally less than the volume of foodstuff introduced in step (i)
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(vi) optionally repeating steps (i) to (v).
As noted above, the foodstuff may be sampled from the inner chamber and\or inner
cylinder at intervals (in real time) to assess its composition and\or state of digestion.
Having generally described this invention with respect to its mode of operation, (including
its best mode), those skilled in the art are provided the following exemplary disclosure to
ensure that they are fully enabled to practice this invention, and that the written
description thereof is fully adequate so as to advise those wishing to practice this
invention of its many advantages. However, it should be understood that this invention is
not limited in its scope to the specifics of this exemplary support. Reference is made for
this purpose to the claims appended to this invention disclosure, including the equivalents
thereof, as a definition of the scope of this invention.
The disclosure of all references cited herein, inasmuch as it may be used by those skilled
in the art to carry out the invention, is hereby specifically incorporated herein by cross-
reference.
Figures
FIGURE 1A provides a cross-sectional view of a first embodiment of Stage one, the main
stomach body portion of the simulated digestive tract of this invention; Figure 1B provides
a bottom view, Figure 1C provides a top view and figure 1D provides a second cross-
sectional view rotated ninety degrees with respect to the Figure 1A view.
FIGURE 2A provides a cross-sectional view of the containment vessel of the body of the
stomach, while Figure 2B provides a top view of the chamber.
FIGURE 3A provides a detailed cross-sectional view of the stomach cassette; Figure 3B
provides an external side view of the stomach cassette.
FIGURE 4A-E provides detailed logic block diagrams of the software/hardware control
systems for Stage 1.
FIGURE 5A-E provide schematic representations of Stage 2, the antrum, of the invention.
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FIGURE 6 provides a representation of the stages of the charging, shearing and
discharging cycle of the antrum, the second stage of the apparatus of the invention. Dead
volume (piston B-C) and fill volume (piston C-E) can be used to set point (D) to maintain
dead volume at maximum barrel movement.
The closing of the fiil valve (RED) may be optional to allow 'reflux' into the main body of
the stomach (stage 1) i.e. the opening and closing of the fill valve can be synchronised
with the cycle or not, as needed. Additionally, if fill valve is open during the
'homogenisation' cycle then 'reflux1 can accommodate volume changes due to the
displacement of the barrel.
FIGURE 7 provides a logic block diagram of the software/hardware control systems for
Stage 2.
FIGURE 8 provides a schematic representation of a computing device suitable for use in
the control systems of the invention.
FIGURE 9 provides a representation of a typical operating environment.
Examples
EXAMPLE 1:
Validation of hvdration, mixing and emptying profiles of gastric additions within
Stage 1 of The Model.
Model meals (solutions of locust bean gum (LBG) in water of varying viscosity and at
37°C) were subjected to simulated gastric processing within Stage 1 of The Model and
data on hydration, diffusion rates of gastric secretions containing visible dyes and
subsequent emptying profiles were measured and compared to data collected from
previous in vivo studies.
EXAMPLE 2:
Validation of overall function of Stage 1.
Echo-planar magnetic resonance imaging (EPI) of the Model to assess mixing dynamics
and hydration profiles of meals during processing. Stage 1 has been constructed entirely
24
WO 2007/010238 PCT/GB2006/002661
out of materials that can be placed safely in the very high magnetic field of a magnetic
resonance imaging (MRI) scanner. In vitro EPI utilizing the apparatus according to this
invention confirms that physical handling of a test meal mirrors in vivo EPI in human
volunteers using comparable, simple LBG test meals.
EXAMPLE 3:
Validation of digestion of food material within Stage 1.
Model meals containing raw and processed vegetable material are prepared. These
meals are subjected to simulated digestions and samples are collected at varying time
points. The resulting digestion samples are compared under microscopy to previously
collected in vivo gastric aspirates of identical meals.
EXAMPLE 4:
Validation of breakdown forces experienced in Stage 2.
Agar beads of differing fracture strength were produced and fed to human volunteers
during in an EPI study, enabling the measurement of the breakdown forces experienced
within the antrum. The physical breakdown forces thus measured are incorporated into
the antrum portion of the model according to this invention. The same protocols are used
to validate the shear experienced within the simulated antrum (Stage 2 of the model).
EXAMPLE 5:
Validation of mixing and homogenisation in Stages 1+2.
The physical behaviour of high fat meals, as observed in vivo using EPI and naso-gastric
aspiration of digesta is replicated in the model system of this invention. The amount and
spatial distribution of fat within the gastric lumen are critical factors influencing delivery to
the small intestines. In vivo (human), two emulsion meals were produced that were of
similar physical characteristics but showed very different behaviour within the stomach,
resulting in different gastric emptying profiles. The same emulsion meals are produced
and used in the validation of lipid handling within this invention.
EXAMPLE 6:
Validation of Model as a whole system (Stages 1,2 + 3).
WO 2007/010238 PCT/GB2006/002661
The model is tested for ability to replicate the rate of digestion of allergenic proteins from
peanuts and milk and the creation of similar patterns of protein fragmentation as found in
gastric and duodenal aspirates from in vivo studies. Meals containing either milk or
peanuts are produced and fed to the whole model. Samples of both gastric and duodenal
digesta are collected at the same time points as those within the in vivo study. SDS-page
and microscopy of each sample are performed and protein fragment profiles are
compared to those from the in vivo samples.
EXAMPLE 7:
Validation of the Model as a whole system.
The model is tested for ability to replicate in vivo digestibility data for carotenoids from
fresh and processed fruit and vegetables collected from ileostemy patients. Here the
persistence of food material within the gut lumen and the rate of particle size reduction of
the food matrix by both biochemical and physical processing is assessed. From collection
of digesta at various key areas within the model the stability of the gut colloidal phases is
assessed and the digestion products of the major nutrients, including protein and lipid, is
extracted and analysed and compared to the data collected from the in vivo human
digestion studies.
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CLAIMS
1 An apparatus for simulating digestion of a foodstuff, which apparatus comprises:
(a) an outer containment vessel into which fluid can be introduced and removed via at
least one orifice, and
(b) an inner digestion chamber comprising a rigid portion through which the foodstuff can
be introduced and a flexible portion which tapers from the rigid portion to an aperture from
which the foodstuff can be removed
wherein said inner chamber is securable within the outer vessel such that
reversible alteration of fluid pressure within the outer vessel causes reversible partial
compression of the flexible portion for mixing foodstuff present therein.
2 An apparatus as claimed in claim 1 wherein the rigid portion is annular and the
flexible portion is conical or frustoconical and is connected at its upper extremity to the
rigid portion and at its lower extremity to a resilient annular member which is of smaller
diameter than the rigid annular portion and which defines the aperture.
3 An apparatus as claimed in claim 3 wherein the flexible portion comprises a
moulded flexible sheet material secured around each of the rigid annular portion and the
resilient annular member by an O-ring.
4 An apparatus as claimed in any one of the preceding claims wherein the inner
chamber is held within a cassette which can be demountably secured within the outer
vessel.
5 An apparatus as claimed in claim 4 wherein the outer vessel comprises a top
plate, a bottom plate, an annular chamber wall extending between and sealingly affixed to
each of said top plate and said bottom plate wherein apertures in said top plate in said
bottom plate permit the cassette to be demountably secured therein.
6 An apparatus as claimed in claim 5 wherein the cassette comprises a top sealable
plate rigidly disposed apart from a bottom sealable plate, each of which respectively
sealably mate to an aperture in said top plate and an aperture in said bottom plate of
said containment means,
wherein the rigid portion of the inner chamber is sealably mounted within the top
sealable plate of the cassette.
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7 An apparatus as claimed in any one of claims 2 to 6 wherein the apparatus further
comprises a valve for controlling flow from the aperture in the resilient annular member.
8 An apparatus as claimed in any one of the preceding claims wherein the volume
of the inner chamber is between 500 and 1000 ml.
9 An apparatus as claimed in any one of the preceding claims wherein the inner
chamber has a plurality of pH electrodes disposed within it, wherein each pH electrode
optionally contains its own reference electrode.
10 An apparatus as claimed in any one of the preceding claims wherein the inner
chamber includes an applicator for introducing digestive additives from respective
digestive additive reservoirs, wherein the applicator is optionally arranged within the inner
chamber so as to float upon any foodstuff present therein and deliver said digestive
additives onto the interior walls of said inner chamber and\or the foodstuff.
11 An apparatus as claimed in claim 10 wherein the additives are conducted from the
reservoirs to the applicator by hoses passing through the outer vessel such that the
temperatures of the additives are modified by fluid in the outer vessel.
12 An apparatus as claimed in claim 10 or claim 11 where the additives are selected
from: acid, alkali, enzymes.
13 An apparatus as claimed in any one of the preceding claims wherein the outer
vessel has at least one temperature sensor within it.
14 An apparatus as claimed in any one of the preceding claims wherein all or part of
the inner chamber and outer vessel are composed of a material permissive of MRI such
that any foodstuff within the inner chamber can be visualised using MRI.
15 An apparatus for simulating mechanical digestion of a foodstuff, which apparatus
comprises:
(a) an outer cylinder including in a first end wall an entry port through which the foodstuff
can be introduced, and at the opposite second end an opening for receiving an inner
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cylinder, and in the side wall proximal to the first end wall an exit port from which the
foodstuff can be removed,
(b) an inner cylinder slidably mounted within the outer cylinder and including in a first end
wall an aperture through which the foodstuff can be reversibly forced between the inner
and outer cylinders, and at the opposite second end an opening for receiving a plunger,
(c) a plunger slidably mounted within the inner cylinder for drawing the foodstuff through
the entry port and aperture into the inner cylinder,
wherein the aperture is within a resilient diaphragm secured within the end wall of
the inner cylinder,
and wherein the volume of the inner cylinder is between 20 and 200 ml.
16 An apparatus as claimed in claim 15 wherein the apparatus comprises a stand
having a base plate and a vertical support member, which support member provides a
clamp for securing the outer cylinder and a guide through which the arm of the plunger
passes for ensuring true movement of the plunger within the inner cylinder.
17 An apparatus as claimed in claim 16 wherein the outer cylinder and the second
end of the inner cylinder each comprise at least one collar, said collars having a plurality
of apertures aligned between said collars and said apparatus further comprises a plurality
of guide rods passing through said aligned apertures for ensuring true movement of the
inner cylinder within the outer cylinder.
18 An apparatus as claimed in any one of claims 15 to 17 wherein the outer cylinder
is vertically orientated.
19 An apparatus as claimed in any one of claims 15 to 18 wherein the apparatus
further comprises means for heating the foodstuff.
20 A system for simulating digestion of a foodstuff, which apparatus comprises a first
stage having:
(a) an outer containment vessel into which fluid can be introduced and removed via at
least one orifice, and
(b) an inner digestion chamber comprising a rigid portion through which the foodstuff can
be introduced and a flexible portion having an aperture from which the foodstuff can be
removed
WO 2007/010238 PCT/GB2006/002661
wherein said inner chamber is securable within the outer vessel such that
reversible alteration of fluid pressure within the outer vessel causes reversible partial
compression of the flexible portion for inhomogeneously mixing foodstuff present therein,
wherein the apparatus further comprises a second stage connected to said first
stage,
the second stage comprising means for mechanically shearing foodstuff
introduced from the inner digestion chamber of the first stage,
and wherein the apparatus optionally further comprises a third stage connected to
said second stage,
the third stage comprising means for preferential absorption of material from the
foodstuff removed from the second stage.
21 A system as claimed in claim 20 wherein the first and second stages are
connected via a valve for controlling flow between the first and second stages.
22 A system as claimed in claim 20 or claim 21 wherein the means for mechanically
shearing foodstuff comprise:
(a) an outer cylinder including in a first end wall an entry port through which the foodstuff
can be introduced from the inner digestions chamber of the first stage, and at the
opposite second end an opening for receiving an inner cylinder, and in the side wall
adjacent the first end wall an exit port from which the foodstuff can be removed,
(b) an inner cylinder slidably mounted within the outer cylinder and including in a first end
wall an aperture through which the foodstuff can be reversibly forced between the inner
and outer cylinders, and at the opposite second end an opening for receiving a plunger,
(c) a plunger slidably mounted within the inner cylinder for drawing the foodstuff through
the entry port and aperture into the inner cylinder.
23 A system as claimed in any one of claims 20 to claim 22 wherein the first stage
comprises an apparatus as claimed in any one of claims 1 to 14, and the second stage
comprises an apparatus as claimed in any one of claims 15 to 19.
24 A system as claimed in any one of claims 20 to claim 23, which system
comprises:
(a) additive controlling means for introduction of acid or alkali additives from respective
additive reservoirs into the first stage, and
(b) a central processing unit (CPU), which processor is able to:
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(i) input pH values from pH electrodes disposed within the inner chamber,
(ii) compare the pH values inputs with a predetermined value
(iii) provide a control signal to said additive controlling means in accordance with the
result of the comparison at (ii).
25 A system as claimed in claim 24 wherein the means for introduction of digestive
additives is a peristaltic pump which acts on a flexible hose connecting the storage
reservoir to the applicator.
26 A system as claimed in any one of claims 20 to claim 25, which system
comprises:
(a) temperature controlling means for adjusting the temperature of fluid introduced into
the outer vessel, and
(b) a central processing unit (CPU), which processor is able to:
(i) input temperature values from a temperature sensor within the outer vessel,
(ii) compare the temperature values with a predetermined value
(iii) provide a control signal to said temperature controlling means in accordance with the
result of the comparison at (ii).
27 A system as claimed in any one of claims 20 to claim 26, which system
comprises:
(a) pumping means for introduction and removal of fluid from the outer vessel such as to
alter the fluid pressure therein,
(b) a central processing unit (CPU), which processor is able to provide a control signal to
said pumping means in accordance with predetermined values relating to preferred
volume and flow rate of the fluid introduced and removed from the outer vessel.
28 A system as claimed in claim 27 wherein the predetermined values are calculated
by the CPU on the basis of values corresponding to the physical and\or biochemical
composition of the foodstuff input to the CPU by a user.
29 A system as claimed in claim 27 or claim 28 wherein the pumping means for
introduction and removal of fluid from the outer vessel is a pneumatic actuator and a
stepper motor to drive the actuator.
WO 2007/010238 PCT/GB2006/002661
30 A system as claimed in any one of claims 20 to 29, wherein the second stage
comprises an apparatus according to any one of claims 15 to 19, further comprising:
a) drive means for driving movement of said inner cylinder
b) drive means for driving movement of said plunger, which may be the same or different
to the drive means of part a),
b) a central processing unit (CPU), which processor is able to provide a control signal to
said means driving the plunger and cylinder, for controlling any of the following:
(i) the level at which the plunger is locked after charging the apparatus
(ii) the maximum displacement of the cylinder
(iii) the point at which the plunger stops during discharge
(iv) the number of strokes of the cylinder in a shearing cycle and the
number of said shearing cycles
(v) the rate of movement of the cylinder and/or of the plunger
(vii) the delay between each emptying and filling cycle.
31 A system as claimed in any one of claims 20 to claim 30, which system comprises
a central processing unit CPU which is able to provide a control signal to valves
controlling any one or more of:
(i) introduction of foodstuff into the first stage,
(ii) batch delivery of foodstuff from the first stage to the second stage, or
(iii) batch delivery of foodstuff from the second stage to the optional third stage.
32 A system as claimed in any one of claims 20 to claim 31 further comprising a pre-
first stage apparatus for cutting the foodstuff into portions having desired dimensions and
optionally exposing it to one or more digestive enzymes.
33 A method of simulating digestion of a foodstuff, which method comprises:
(a) providing an apparatus as claimed in any one of claims 1 to 14 or a system as claimed
in any one of claims 20 to 32,
(b) providing the foodstuff in portions having desired dimensions,
(c) optionally incubating the portions with α-amylase and\or mucins,
(d) introducing the portions into the inner chamber,
(e) introducing known amounts of digestive additives into the inner chamber,
(f) inhomogeneously mixing the foodstuffs by cyclically introducing and removing fluid
such as to squeeze and relax the flexible portion of the inner chamber while maintaining
preferred temperature, pH and enzymatic composition of the foodstuff.
32
WO 2007/010238 PCT/GB2006/002661
34 A method of simulating digestion of a foodstuff, which method comprises:
(a) providing an apparatus as claimed in any one of claims 15 to 19 or a system as
claimed in claim 22 or claims 23 to 32 as dependent on claim 22,
(i) introducing a preferred volume of foodstuff into the inner cylinder by drawing down the
plunger
(ii) withdrawing the inner cylinder such as to force foodstuff through the aperture of the
inner cylinder into the outer cylinder,
(iii) depressing the inner cylinder thereby forcing foodstuff back through aperture from the
outer cylinder into the inner cylinder,
(iv) optionally repeating steps (ii) to (iii) for as many cycles as necessary to achieve the
breakdown of foodstuffs to desired degree of particle size reduction,
(v) removing a preferred volume of foodstuff from the exit port, which volume is
optionally less than the volume of foodstuff introduced in step (i)
(vi) optionally repeating steps (i) to (v).
35 A method as claimed in claim 33 or claim 34 wherein the foodstuff is sampled
from the inner chamber and\or inner cylinder at intervals to assess its composition and\or
state of digestion.
36 A method as claimed in any one of claims 33 to 35 for modeling any one or more
of: the digestibility of the foodstuff; the release or presence of an active agent from the
foodstuff; the interactions of dietary components of the foodstuff; the survival of an
organism within the foodstuff.

The invention provides an apparatus for simulating digestion of a foodstuff, which
apparatus comprises : (a) an outer containment vessel into which fluid can be introduced and removed via at least one orifice, and (b) an inner digestion chamber comprising a rigid portion (240) through which he foodstuff can be introduced and a flexible portion (250) which tapers from the rigid portion to an aperture (260) from which the foodstuff can be removed wherein said inner chambers is seλurable within
the outer vessel such that reversible alteration of fluid pressure within the outer vessel
such the reversible alteration of fluid pressure within the outer vessel causes reversible
partial compression of the flexible portion for mixing foodstuff present therein. Also provided is an apparatus for simulating mechanical digestion of a foodstuff, which apparatus comprises: (a) an outer cylinder (534) including in a first end wall an entry port through which the foodstuff can be introduced, and at the opposite second end an opening for receiving an inner cylinder (532), and in the side wall proximal to the first end wall an exit port from which the foodstuff can be removed, (b) an inner cylinder (533) slidably mounted within the outer cylinder can including in a first end wall an
aperture through which the foodstuff can be reversible forced between the inner and
outer cylinders, and at the opposite second end an opening for receiving a plunger, and
(c) a plunger slidably (530) mounted within the inner cylinder for drawing the foodstuff
through the entry port and aperture into the inner cylinder, wherein the aperture is
within a resilient diaphragm secured within the end wall of the inner cylinder, and wherein the volume of the inner cylinder is between 20 and 200 ml. The invention also provides systems and methods for simulating digestion of a foodstuff.