Process and apparatus for making meat analogs

There is provided a method and apparatus for forming meat analog products and for texturizing a doughmass wherein the ingredients are mixed, passed through a conduit having a decreasing cross-sectional area while the doughmass is heated therein, the heating being done such that a greater heat intensity is applied to the center of the doughmass than to the doughmass adjacent the walls of the conduit.

BACKGROUND OF THE INVENTION 
The present invention relates to meat analogs and more particularly, 
relates to a method and apparatus for forming meat analog products. 
Meat analog products are well known in the art and there have been various 
methods and apparati proposed for preparing such products. The meat analog 
products are frequently used as substitutes for natural meat products as 
they consist of all-vegetable materials, may contain fewer fat calories 
and have a lower cholesterol content. However, in order to obtain consumer 
acceptance, the visual appearance and the texture of the products must 
meet certain standards. To date, this has been difficult to do leading to 
the situation that, although one can manufacture products which have 
certain superior properties such as nutritional value, the various sensory 
properties desired have not been achieved for a product which can be 
manufactured on a commercial scale. 
Originally, the formation of meat analog products relied on the use of 
fiber spinning wherein a spinning dope is formed from alkali treated 
protein with the dope subsequently being extruded through a die or 
membrane into an aqueous precipitant bath which sets the filaments or 
fibers. Also known in the art are thermoplastic extrusion techniques to 
form certain products where a mixture of protein, water and flavor 
ingredients is fed into a cooker extruder and subsequently released into 
the atmosphere. 
Various attempts have been made in the past years to arrive at a more 
consumer acceptable product and techniques have included the forming of a 
dough which is then subjected to stretching and heat to provide 
uni-directional parallel meat like fibers. Although such processes have 
been described since the 1960's, applicant is not aware of products being 
produced on a commercial scale utilizing this technology. Such technology 
has been described, for example, in U.S. Pat. Nos. 3,693,533; 3,814,823; 
4,125,635; and 4,910,040. In the last mentioned patent, the patentee 
discloses a method for preparing food products having aligned fibers 
wherein a protein source and a carbohydrate source are mixed, forced 
through a first passageway having a constant cross-sectional area, pushed 
through a second passageway having a decreasing cross-sectional area, and 
then pushed through a third passageway with a constant cross-sectional 
area, and heating the fibers in the third section to fix or set the fibers 
in a linearly aligned configuration. 
While there are different theories as to how and why the fibers form, it 
has been well established that there does indeed exist fiber formation as 
a result of mixing the required ingredients along with the application of 
heat and stretching. However, the methods and apparatuses for the 
production of such meat analog products have generally tended to exist 
only in laboratory type apparatuses and to date, to the best of 
applicant's knowledge, there does not exist a system capable of sufficient 
throughput to become commercially viable. It is believed that this lack of 
commercial success is due to the inability to scale up from laboratory 
type of systems to systems which are capable of producing commercial 
quantities. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a method and 
apparatus for the production of meat analog products, which method and 
apparatus can operate on a commercial scale. 
It is a further object of the present invention to provide a method and 
apparatus for the production of meat analog products wherein novel means 
of heating the dough are provided to overcome the limitations inherent in 
methods taught in the prior art and to thereby make it possible to 
increase throughput, without compromising product quality, in a manner 
sufficient for the process to become commercially viable. 
It is a further object of the present invention to provide a method and 
apparatus for the formation of meat analog products wherein microwave 
heating is utilized. 
It is a still further object of the present invention to provide a method 
and apparatus suitable for the preparation of meat analog products wherein 
ohmic heating is utilized to heat the doughmass. 
It is a further object of the present invention to provide methods and 
apparati for the manufacture of meat analog products wherein greater 
uniformity of fiber formation in the product is provided. 
According to one aspect of the present invention, there is provided an 
apparatus suitable for the manufacture of meat analog products, the 
apparatus comprising means for mixing the ingredients, means for passing 
the ingredients through a conduit having a decreasing cross-sectional area 
in the direction of product flow, a substantially constant cross-sectional 
area exit tube, and means for heating the doughmass inside conduit with 
the decreasing cross-sectional area, the heating means comprising 
microwaves transported to the doughmass through a coaxial waveguide 
extending along the exit tube. 
There is also provided a method of producing a food product having fibers 
formed therein, the method including the steps of forming a doughmass, 
passing the doughmass through a conduit having a decreasing 
cross-sectional area in the direction of doughmass flow, subjecting the 
doughmass to a thermal treatment while in the conduit such that a greater 
heat intensity is supplied to the interior portion of the dough compared 
to the doughmass adjacent the conduit walls, and thereafter passing the 
doughmass through an exit pipe having a substantially constant 
cross-sectional area. 
There is also provided a method of producing a food product having fibers 
formed therein, comprising the steps of forming a doughmass, passing the 
doughmass through a conduit having a decreasing cross-sectional area in 
the direction of doughmass flow, subjecting the doughmass to microwave 
energy having a standing wave pattern such that more power is applied to 
the central part of the doughmass inside the conduit with the decreasing 
cross-sectional area compared to the doughmass adjacent the conduit walls, 
and thereafter passing the heated doughmass through an exit conduit having 
a substantially constant cross-sectional area. 
In another aspect, there is provided an apparatus suitable for producing a 
food product having fibers formed therein, the apparatus comprising means 
for mixing ingredients to form a doughmass, means for passing the 
doughmass through a conduit having a decreasing cross-sectional area in 
the direction of product flow, a substantially constant cross-sectional 
area exit tube connected to a smaller end of the conduit, thermal 
treatment means adapted to subject the doughmass in the conduit to a 
thermal treatment such that the doughmass in the interior portion of the 
conduit is subjected to a greater heat intensity than the doughmass 
adjacent the conduit walls. 
There is also provided an apparatus for producing a food product having 
fibers formed therein, the apparatus comprising means for mixing 
ingredients to form a doughmass, means for passing the doughmass through a 
conduit having a decreasing cross-sectional area in the direction of 
product flow, a substantially constant cross-sectional area exit tube 
connected to the smaller end of the conduit, microwave heating means 
adapted to subject the doughmass to microwave energy having a standing 
wave pattern such that more power is applied to the central part of the 
doughmass compared to the doughmass adjacent the conduit walls. 
There is also provided a method of producing a food product having fibers 
formed therein, the method including the steps of forming a doughmass, 
passing the doughmass through a conduit having a decreasing 
cross-sectional area in the direction of doughmass flow, subsequently 
passing the doughmass through an exit pipe having a substantially constant 
cross-sectional area, and heating the doughmass while in the decreasing 
cross-sectional area conduit by guiding microwaves through a coaxial 
waveguide formed between an exterior of the exit pipe and housing 
thereabouts such that microwave energy passes through a wall of the 
conduit in order to heat the doughmass product therein. 
There is also a method of producing a food product having fibers formed 
therein, the method comprising the steps of forming a doughmass, passing 
the doughmass through a conduit having a decreasing cross-sectional area 
in the direction of doughmass flow, thereafter passing the heated 
doughmass through an exit pipe having a substantially constant 
cross-sectional area, and heating the doughmass while in the conduit by 
passing current through the doughmass to thereby heat the doughmass, 
generally referred to herein as ohmic heating. 
There is also provided an apparatus suitable for producing a food product 
having fibers formed therein, the apparatus including a feed pipe, a 
conduit having a decreasing cross-sectional area extending from the feed 
pipe, an exit pipe connected to the narrower end of the conduit having the 
decreasing cross-sectional area, a first electrode located in the conduit, 
a second electrode associated with the feed pipe or conduit, and means for 
connecting the electrodes to a source of energy such that current will 
pass between the electrodes when a doughmass is in the conduit. 
The dough used in the present invention can be formed of known ingredients 
as has been amply discussed in the art. Thus, the dough may include a 
variety of different protein containing ingredients, which, in a preferred 
embodiment may include a mixture of wheat gluten and a soya protein 
isolate. The dough may also contain a number of different additives or 
dough conditioners along with blends of cereal, oil seed and vegetable 
proteins, and optionally including fish proteins, dairy proteins as well 
as emulsions of meat and/or poultry. Carbohydrates in the dough may be 
specifically added or alternatively, carbohydrates may be present in the 
particular protein containing ingredient which is utilized. 
Even further, other materials may be added to or comprise the doughmass. 
Thus, materials such as lentils, chick-peas, algae and insect proteins 
could be utilized. It would also be possible to incorporate certain animal 
derived materials within the doughmass to provide a desired engineered 
product. 
As will be appreciated by those knowledgeable in the art, various ratios of 
protein to carbohydrate to water may be utilized depending upon the final 
product desired. In preferred embodiments, the protein preferably 
comprises between 30% and 80% of the doughmass on a dry basis and more 
preferably, between 40% and 70%. The water content preferably is between 
20% and 70% of the moist doughmass and more preferably, between 30% and 
60%. 
Conventional additives including lubricating agents, flavoring materials, 
salt, sweetening agents, and the like can also be added to the dough. The 
use of these additives is conventional and the process of the present 
invention is not limited thereto; it is understood that one skilled in the 
art is able to arrive at formulations in which fibers will be formed. It 
is also understood that certain formulations may either enhance or 
diminish the degree of fiber formation and again, it is well within the 
skill of one knowledgeable in the art to vary the formulation depending 
upon the final product desired. It will be understood that the use of the 
term "meat analog products" herein includes all those products which are 
of a fibrous nature and formed from a dough. 
The general design of an apparatus for forming meat analog products is well 
known in the art and thus, a typical system includes means for mixing, 
wetting and kneading the various ingredients for a period of time 
sufficient to provide a dough like material. The means of mixing and 
kneading the dough are well known in the art and the mixing may either be 
done on a batch or a continuous basis. 
The dough is then passed through a conduit or passageway which has a 
decreasing cross-sectional area in the direction of the doughmass flow. In 
order to feed the conduit or passageway having the decreasing 
cross-sectional area, there may conveniently be provided a feed pipe as is 
well known in the art. As the dough is passed through the conduit, it is 
subjected to a heating step to heat the dough sufficiently to form and 
substantially set the fibers. In most embodiments of the present 
invention, it is preferred that the dough be subjected to a thermal 
treatment such that the doughmass at the center of the conduit is 
subjected to a greater heating intensity than the doughmass adjacent the 
conduit walls. In other words, it is preferred that the center of the 
doughmass be heated at a greater rate (more energy) since the velocity 
profile of the doughmass is such that the dough at the center of the 
conduit moves at a greater speed than the dough which is closer to the 
walls of the conduit. This increasingly parabolically shaped velocity 
profile of the doughmass through the conduit with the decreasing 
cross-sectional area means that if uniform heating is attempted, the 
doughmass adjacent the walls will be heated to a greater extent than that 
in the interior. Accordingly, according to the present invention steps are 
taken to ensure that a greater heat intensity is applied to the interior 
of the doughmass compared to that adjacent the conduit walls. 
The means of effecting the greater heating at the center of the doughmass 
may include several different arrangements. Thus, for example, one may 
elect to cool the outer layers of the doughmass to attempt to equalize the 
temperature distribution. Alternatively, one may use certain 
configurations of microwave heating such that there is greater microwave 
energy intensity at the center. Still further, one may employ ohmic 
heating for such purposes as will be discussed in greater detail 
hereinbelow. 
As mentioned above, the present invention contemplates the use of microwave 
heating as one of the means of heating the doughmass inside the conduit 
having the decreasing cross-sectional area. 
As will be described in greater detail, different applicators may be used 
for the microwave heating. In the description herein, the conduit having a 
decreasing cross-sectional area will generally be referred to as having a 
conical configuration (it may also be referred to as conical section or 
cone) since a truncated cone is one of the easier configurations to work 
with. It will be understood that different configurations can also be 
used, i.e. a rectangular tapered section or other geometric 
configurations. Thus, in one embodiment, one may use, as a means of 
microwave heating the doughmass inside the conical section, a rigid 
coaxial microwave applicator with single cone-end feed. Such design 
permits the microwave energy to be transported from an exterior power 
source to inside the conical section and thus permits heating the 
doughmass inside the conical section while at the same time permitting 
construction with a steel enclosure thereby making the device resistant to 
the very high pressures resulting from moving the doughmass through it at 
large flow rates. Alternative applicators with contoured heating can also 
be used as will be described in greater detail hereinbelow. 
While at the present time both the 2450 MHz and the 915 MHz microwave 
frequency (895 MHz in the United Kingdom) can be used, where allowed by 
the regulations governing radio communications and other communications in 
various countries, it has generally been preferred to use 915 MHz 
microwave energy in view of its greater heat penetrating ability allowing 
to uniformly heat samples with a greater diameter. This can be important 
in the design of applicators for a device that needs to permit commercial 
scale output flowrates. Naturally, other frequencies could be used. 
The conical section is preferably constructed with an inner layer of FDA 
approved non-metallic material that is microwave transparent, i.e. 
material that has a low dielectric loss factor. The microwaves flow 
through the non-metallic material which then stays relatively cool. An 
outer steel shell encasing the inner layer of non-metallic material 
provides the necessary strength and prevents the escape of the microwave 
radiation. 
As is understood by those knowledgeable in the art, the optimum 
transmission and absorption of microwave power is dependant on the shape 
and dimensions of the components. A smooth surface finish is essential in 
the microwave carrying parts and rounded corners help to prevent arc-over. 
The air space in the coaxial waveguide must be neither too small nor too 
large--i.e. if the space is too small, there is a danger of arc-over and 
if it is too large, there is the possibility of the formation of a TE 11 
mode which would likely introduce uneven power distribution around the 
cone circumference. The dimensions of the various parts are 
interdependent; for optimum power transfer and symmetry, the coaxial 
waveguide dimensions and the transition cylinder shape must be adjusted to 
each other and the cone size. Again, this is within the capability of 
those knowledgeable in the art. 
Prior to the conduit of decreasing cross-sectional area, there may be 
provided a preheat section wherein the doughmass is subjected to a 
preheating step as is well known in the art. Typically, the preheat 
section raises the dough to a temperature in the range of between 
60.degree. to 80.degree. C. while in the conical section, the doughmass is 
raised to a heat of between 90.degree. and 140.degree. C. 
In another embodiment of the present invention, ohmic heating may be 
utilized to heat the doughmass. In the ohmic heating, a current is passed 
through the doughmass and several different arrangements may be utilized. 
Thus, one can arrange configurations to provide a greater concentration at 
the center of the product and thus, at high flow rates, when the material 
in the cone moves more slowly at the outer edges than at the center, the 
contoured heat input having lower heating power input at the outer edge 
would reduce or prevent overheating and hardening of the product at the 
outer edges. Thus, one can produce different heat inputs at the center and 
outer edge. 
Having thus generally described the invention, reference will be made to 
the accompanying drawings illustrating embodiments thereof, in which:

DETAILED DESCRIPTION OF THE INVENTION 
Referring to the drawings in greater detail, and by reference characters 
thereto, in FIG. 1 there is a block diagram of a typical apparatus for 
forming meat analog products and this apparatus would include a first 
section which functions as a feed section 10; a section 12 having a 
conduit of a decreasing cross-sectional area in the direction of product 
flow as indicated by arrow 18; and an exit pipe section 14. Box 16 
indicates typical system controls which would be utilized. 
Turning to FIG. 2, there is illustrated therein the flow of the product 
within the apparatus. In feed section 10, as indicated by lines 20, there 
exists what could be termed "plug flow" wherein the majority of the 
product advances at an even velocity with a slight slowing adjacent the 
walls of the conduit. Once the product enters conical section 12, as 
indicated by line 22, the rate of flow at the center tends to increase 
visa vis the flow closer to the walls of the conduit. As the 
cross-sectional area continues to decrease, the velocity profile becomes 
increasingly parabolic as shown by line 24. Subsequently, in exit zone 14, 
as shown by profile lines 26, the product flow reverts to a plug type 
flow. 
One embodiment of an apparatus using microwave energy for heating of the 
dough is shown in FIG. 3 wherein microwave energy (arrows 28), generated 
from a suitable microwave power source, is propagated in a conventional 
rectangular waveguide 30 in the usual transverse electric TE.sub.10 mode 
with the electric field parallel to the short walls of the waveguide 30. 
The electromagnetic field follows the 45 degree bend generally designated 
by reference numeral 32 and then strikes adjustable rectangular aperture 
34 with most of the energy passing through the aperture 34. A shaft 35 
made of dielectric material is connected to a suitable drive. Some of the 
microwaves impinge on a transition cylinder 36 while others go around 
transition cylinder 36 and are reflected back by a sliding short 38. 
Sliding short 38 has a drive shaft 39 associated therewith. The 
interaction of the microwaves, flowing in opposite directions, sets up a 
standing wave within the waveguide section between aperture 34 and sliding 
short 38. Adjustment of sliding aperture 34 and sliding short 38 by 
suitable motors (not shown) will position a wave peak at the center of 
transition cylinder 36. 
Transition cylinder 36 is formed of a metallic material and is shaped to 
guide the microwaves into a space between the outer surface of exit pipe 
42 and the inner surface of a metallic outer tube 44. This thus forms a 
coaxial space 40 which becomes the coaxial waveguide. Thus, the field 
propagates along coaxial waveguide 40 in the usual transverse 
electromagnetic TEM mode. There may be some asymmetry of power levels on 
opposite sides of the transition cylinder 36 and on opposite sides of the 
coaxial waveguide 40 especially near the transition. A certain length of 
coaxial waveguide of at least 3 feet (or about 3 wavelengths at 915 MHz) 
permits considerable dissipation and equalization of the asymmetric field 
and currents. In addition, there are provided a pair of probes 46 mounted 
through outer tube 44 to monitor the balance of the microwave field 
intensity on both sides of the transition cylinder 36. This data, and 
forward and reflected power measurements, are the inputs to a feedback 
control (not shown) which can then adjust the positions of sliding 
aperture 34 and sliding short 38. This thus provides maximum power flow to 
the doughmass in the conical section 12 and optimizes the uniformity of 
current distribution around the walls of the coaxial waveguide. The 
electromagnetic field thus flows through coaxial waveguide 40 towards 
conical section 12 and then through the inner layer 48 of non-metallic 
microwave transparent material of the conical section to the doughmass 
inside of it. With the configuration shown in FIG. 3 the microwave 
electromagnetic field contacts and penetrates the doughmass in the narrow 
part of the conical section. If so desired, means can be provided to have 
the microwave power penetrate the doughmass inside the cone not in its 
narrow part but somewhere further upstream. For example, by replacing part 
of the inner non-metallic cone layer, adjacent the metallic exit tube, 
with metal, the microwave power will not penetrate the doughmass in the 
narrow part of the cone but further upstream. Microwave power is absorbed 
by the doughmass inside the conical section in view of the relatively high 
loss factor or dissipation factor of the doughmass. Power is absorbed 
uniformly and instantaneously through to the center of the doughmass. One 
can employ thermocouples (not shown) embedded in the cone-end of exit pipe 
42 as a means to monitor the temperature. 
FIG. 4 illustrates a symbolic representation of the electric field in the 
waveguide and cone and there is illustrated the standing waves which are 
set up between aperture 34 and short 38. Thus, as shown in FIG. 5, there 
would be a standing wave of three half wave lengths if there were no 
transition cylinder. As seen in FIG. 4, the waves strike the transition 
cylinder 36 and then flow along the coaxial waveguide 40 as travelling 
waves. Three half wave lengths is a preferred number; one or two half wave 
lengths would not allow sufficient space between the transition cylinder 
36 and moveable aperture 34 and sliding short 38 to permit adjustment 
while the possibility of perturbation or arcing would be increased. The 
arrows in the cone symbolize the penetration of microwave energy into the 
doughmass. There is progressively less microwave energy in the cone as the 
waves progress towards the wide end. 
Referring to FIGS. 6, 7 and 7A, these Figures illustrate a microwave single 
mode cavity. As previously described, there is a feed section 10, a 
conical section 12, and an exit section 14. As previously discussed, at 
higher product flow rates, there is a greater differential of product 
velocity between the product at the center of the doughmass and the 
product adjacent the wall of the conduit. In this embodiment, there is 
provided a microwave single mode cavity which is a microwave resonant 
cavity which sets up a single microwave mode which has one or more peaks 
of electric field intensity. 
The microwaves are propagated along a rectangular waveguide 80 in a manner 
similar to that previously described. However, the transition from the 
waveguide 80 to the circular cavity 82 is through an iris or aperture 84 
which is cut into the shorting wall on the end of the waveguide. The 
cylindrical cavity is attached to this end wall and the same iris is cut 
into the round wall of the cylindrical cavity. This cavity is filled with 
a plastic or ceramic dielectric which supports a cone liner and provides 
an environment where the wavelength is somewhat shorter than in air. This 
shortening of the wavelength is dependant on the dielectric constant of 
the material which fills the cavity and which material may be selected to 
provide an optimum wavelength for positioning the contour of the central 
heating effect desired. 
One may refer to FIG. 9 which symbolically shows the electric field 
intensity distribution wherein a standing wave is created with the broad 
peak of power density on the cone axis providing a greater central heating 
of the doughmass. 
FIG. 8 shows a combination of two applicators; a single mode cavity 
applicator as described with reference to FIG. 6 and the rigid coaxial 
applicator with the single cone-end feed of FIG. 3. In this embodiment, 
the microwave power from the generator flows along rectangular waveguide 
30 in which there is provided variable depth probes 48 each having a 
waveguide to coax transition. Power then flows along flexible coaxial 
cables 52 and is coupled into a single mode cavity by means of small 
coupling loops 54. 
The insertion depth of probes 48 in rectangular waveguide 30 are variable 
so that power levels are the same. Suitable motorized actuators may be 
utilized and controlled by feedback from sensors (not shown) which are 
near coupling loops 54. 
After contacting probes 48, microwaves continue along the rectangular 
waveguide in the manner described with respect to FIG. 3, strike the 
transition cylinder 36, then are propagated through coaxial waveguide 40 
to be absorbed by the doughmass inside conical section 12. 
In this way, the degree of heat contouring in the narrow part of the cone 
may be varied and which can be advantageous for different flow rates 
and/or product formulations. One could use thermocouples at the narrow end 
of the cone to provide a feedback control of the temperature. 
FIG. 9 illustrates the principles of using standing waves. It is a symbolic 
representation of a cross-sectional view of the electric field intensity 
in a single mode cavity. In this case, three half wavelengths across a 
diameter are induced in the cavity with a central peak surrounded by an 
annular ridge of high intensity. The wave patterns are symmetrical about 
the center-line of the conical section. The standing waves would be 
analogous to the standing waves set up in the rectangular waveguide of the 
applicator described in the embodiment shown in FIG. 3. In this case, the 
standing wave would impart more power to the central part of the cone so 
that the edges of the product in the cone would receive less power. In 
other words, the slower moving dough at the cone edges would therefore 
heat up to a temperature similar to that achieved in the faster moving 
center. 
The diameter of the cylindrical cavity as described would vary depending 
upon the non-metallic dielectric material used to fill it. Thus, if one 
were to use plastic material such as, for example, Lexan or Ultem, the 
diameter would be approximately 12 inches. A cavity made of a ceramic 
material with a dielectric constant higher than that of the plastic 
materials, would naturally have a much smaller diameter. Thus, one may 
optimize the apparatus depending upon the particular dielectric material 
used. Also, one must take into account the dielectric constant of the 
doughmass and the choice of frequency. For example, one could achieve a 
sharper peak at 2450 MHz, but in order to ensure adequate penetration to 
the center of the doughmass, the cavity should then be located at the 
narrower end of the cone. 
In yet another embodiment of the invention, shown in FIG. 10, there is 
again provided a feed section 102, a conical section 104 and an exit 
section 106. For ease of illustration, there is illustrated a single 
structure having an inner non-conductive layer 108 and an outer 
reinforcing layer 110. It will be understood that distinct and separate 
components would normally be utilized. 
A piston 112 is operated in the direction of arrow 114 to push doughmass 
115 towards the exit section 106. 
Mounted interiorly are three ring electrodes 116, 118 and 120 operatively 
connected to an electric circuit powered by two transformers 126 and 127. 
In this embodiment, using 60 Hertz ohmic heating, current passes from ring 
electrode 116 which is located in the feed section proximate the wider end 
of the conical section to ring electrode 118, as indicated by arrows 122, 
to preheat the doughmass passing therethrough. Current will also flow 
through the conductive doughmass 115 from ring electrode 116 to ring 
electrode 120, as indicated by arrows 124, to heat the doughmass, while it 
is going through the conical section, to a temperature above the heat 
coagulation temperature of the heat coaguable proteins contained therein. 
As a result, a fibrous texture is created and heat set and one obtains a 
product with a high quality texture. 
Utilizing this arrangement, one could also vary the configuration of the 
electrodes to achieve a center heating effect similar to that discussed 
with respect to the embodiment utilizing microwaves. 
In FIG. 11 there is illustrated a modified version of an ohmic heating 
apparatus. In this version, for illustration purposes, the electrodes 130 
shown are those used for preheating inside the feed section; a similar 
principle could be used in the conical section 12. 
Thus, there are provided a plurality of electrodes 130 which, in FIG. 11a, 
are shown as three electrode pairs (A1, A2), (B1, B2), (C1, C2). 
As previously discussed, the material in the cone tends to move more slowly 
proximate the walls of the cone then at the center. A voltage would be 
applied to the electrodes arranged in pairs opposite each other on the 
circumference. Each electrode pair would be connected to a separate 
transformer through a solid state relay. When the voltage is applied to 
the electrodes, a current flows through the doughmass, which is conductive 
in view of its water and salt components. Accordingly, this would result 
in heating of the doughmass. The current would preferably be controlled 
with sequential time-sharing so that only one electrode pair is on at a 
given time. The current flow between the electrodes spreads across the 
dough. However, the current path is longer around the circumference than 
across the diameter so that more power is absorbed in the center. The 
addition of current from three electrode pairs helps produce a relatively 
uniform temperature gradient between the center and edge of the doughmass. 
FIG. 12 illustrates current flow between the longitudinal electrodes as 
described in FIG. 11. Thus, if one were to consider the flow of current 
between two electrodes 130 and analyze its two paths with one across the 
diameter of the doughmass and the other path around half of the 
circumference. Squares 132 represent elements of unit resistance in 
alternative paths of current flow. Although the discussion will be limited 
to current flowing in the plane of the paper, the ratios of current are 
similar in a three-dimensional analysis. For present purposes, one will 
assume that the current flows in a path 0.5 inches wide and the diameter 
of the conduit is 4.5 inches with the path following the half 
circumference being 7 inches. Comparing the two paths, one may see that 
the resistance across the diameter would be a unit of 9 with the 
resistance around a circumferential path being a unit of 14. If one were 
to analyze the power density, one would arrive at a power ratio of 0.4:1 
such that there is 21/2 times more power in the path across the diameter 
than in the circumferential path. If one were to utilize a number of pairs 
of electrodes, it will be seen that there would be more heat generated in 
the center of the doughmass. The heating intensity follows Poisson's laws 
for static magnetic and electric fields and thus can be calculated. 
FIG. 13 illustrates a variation of the ohmic heating embodiment, and in 
this Figure, it will be seen that there are a plurality of electrodes 
which may be installed on the inner surface of the conduit. The electrodes 
have a somewhat spiral configuration and utilizing this arrangement, one 
is able to provide a more even distribution of the heat concentration 
which otherwise would tend to occur near the electrodes. 
It will be understood that the heating intensity on the outer diameter of 
the dough would be relatively high directly under the active electrodes 
and decrease rapidly on either side of it. When the power switches to the 
next pair of electrodes, this heating pattern would also move. The average 
heating under the electrodes would therefore become fairly uniform; 
however, there would be a minimum average heating intensity between 
adjacent electrodes. 
The use of spiral or curved electrodes would function to "smear" the 
heating pattern to produce nearly uniform average heating intensity on the 
surface of the dough diameter. Because of the smearing of this heating 
pattern, the average heating intensity would actually be one-half of the 
value under the electrode. 
It is preferred that the upper heating intensity level be monitored so that 
undesired heating effects do not occur. Particularly, it would be 
undesirable to have the generation of high temperature steam which tends 
to insulate the dough from the electrode and make the heating unstable. 
One means of minimizing this problem is to increase the surface area of 
the electrodes. Also, one could change the rate at which the switching of 
the electrodes is accomplished. Thus, by using solid state relays, one can 
apply pulses of energy before switching to another pair of electrodes. 
This procedure would allow any steam bubble to reach equilibrium with the 
temperature of the surrounding dough before additional power is induced at 
that point. 
In one arrangement using ohmic heating, one may operate the system such 
that the electrodes may be considered as forming an electrode cage about 
the doughmass. Each electrode could be connected to either side of the 
line through a relay controlled by a computer and appropriate software 
such that only one pair of electrodes may operate at a time, but any two 
electrodes may form an electrode pair. Thus, the electrode cage can be 
operated in modes which would provide a variety of heating patterns. One 
could, as above mentioned, provide maximum center heating by exciting 
electrodes 180.degree. apart. However, if adjacent electrodes were 
excited, the current flow would be confined to the outer volume of the 
dough cylinder. It would thus be possible to provide different heating 
patterns adjusted for a particular dough velocity and/or dough 
formulation. Furthermore, one could utilize sensors along with suitable 
control software to vary the heating pattern as required. 
Still further, it is possible to combine various of the methods described 
herein. One could, for example, provide ohmic heating in a certain region 
where required such as at the exit end of the conical section. A plastic 
cone section would still be compatible with a single mode cavity microwave 
applicator. 
It will be understood that the above described embodiments are for purposes 
of illustration only and that changes and modifications may be made 
thereto without departing from the spirit and scope of the invention.