Note: Descriptions are shown in the official language in which they were submitted.
t~
Back~round of the I_vention
The pre~ent invention relates to edible protein
products derived from fibrous fungal material obtained ~rom
a fermenter. When such a material is mechanically worked and
then directly air dried, it becomes very hard and tough-
textured, Similarly, products made from the material by
reductlon of nucleic acid content and direc-t air drying of
the filter cake also have an undeslrable texture.
The use o~ dielectric heating ln the production o~
edible proteinaceous materials made ~rom substances such as
soy flour/soy protein isolate is disclosed in U.S. Patent
Nos. 3,622,673 and 3~810,764.
Summary of the Invention
The present invention relates to a heat t;reatment
and drying process and re~ultant product. More speci~ically,
the process involves a rapid heat treatment and partial
drying o~ a fibrou~ fungal mass u~ing dlelectric heating to
puf~ and heat-set the material which generally is followed
by a slow ~inal drying such as by hot air. Pre~erably the
fibrous mass is mechanically worked prlor to the dielectric
heating treatment. me process can produce a range of
products which closely resemble various meats in te~ture.
Brief Descri tion of the Drawin s
- ~ _ g
Fig. 1 is a schematic drawing of the extrusion,
dielectric drying and cutting apparatus used to perform the
process of the present invention.
Figs. 2 tQ 5 are photomicrographs of the product
.~ ~
of the present invention.
Det~iled ~escri~tion
me starting material for use ln the present
inventlcn i5 generally prepared by fermentation o~ a non-
toxic microfungu~ on an assimllable carbohydrate. The
re~ultant product has a substantial protein content and is
use~ul a~ food ~or both humans and animals. Various micro-
fungl may be used to prepare the starting materl~l. The
pre~erred micro~ungus is Fusarium ~ Schwabe
deposited with the Commonwealth Mycological Institute and
assigned the number I.M.I. 145,425. Suitable variant~ o~
this micro~un~us also deposited with the Commonwealth
Mycological Institute include I.M.I. 154,209; I.M.I. 154,2103
I.M~I. 154,211; I.M.I. 154,212 and 154,213. Other suitable
nontoxlc mlcro~ungi incl~de, but are not limlted to, FU rlum
oxysporum (I~MoI~ 154,214), ~usarium solani (I.M.I. 154~217)J
and Pen~cillium nota~um ~r~ (I.M.I. 142~383; I~MoI~
,
142,3843 I.M.I. 142~385~ I.M.I. 142,386), with the identiPying
numbers o~ strains thereof which have been deposited with the
20 Commonwealth MycQlogical Inst~tute glven ~n parenthesis.
typ~cal prepar~tion o~ the starting material i~ as ~ollows:
A continuous 8-liter fermenter ls sterilized and
continuously charged with a sterlle med~um consistlng Or
r lOO 11ter~
M~;S04 L~o. 5 ::
Zrl504~ 7H20 O, 83
CuS04~ 5H20 01~167
Mnso4~. lH20 O. 63
FeS04~ 7H20 O. 83
3 K2S4 10. 0
~ 3 ~
~r ~ t~
(~H4)2S4 144. 0
NaM4 2H2 o.o83
CoC12.6H20 0~17
NaCl 10
CaC12 8.0
KH2P4 379.0
Biotin . ooo6
Dextrose .H20 85ooo.o
Ammonium citrate 4.0
Water to 100 liters
Boric acid 0.05
The rate o~ charging the sterile medium is 1.18
liters per hour. The medium in the fermenter i~ initially
inoculated with a spore suspen~ion of the desired organism
~uch as Piusarlum ~ Schwabe I.M.I. 145,425 and then
stirred wlth a 6-bladed dlsc turbine operated ~t 850 rpm.
Air is flowed through the fermenter ~t a rate o~ 3~6 liters
per minute. Additlonal oxygen ~low 1~ 2.0 liters per
minute. me ~ermenter temperature ls 29.2C~, and the pH
1~ 4~8. Ammonia i~ added to control the pH. The ~ermenter
produ~tivlty 1~ 5.45 gram~ per liter hsur. The product,
fugal myceliwm, is continuou ly dr~wn off ~rom the
~ermenter and collected in a product receiver and held at
8C. A~ter 185 hours o~ operationJ the pooled product,
whlch was collected and cooled during the ~inal 10 hour
period, i9 then harve~ted and fllteredO The resultant
~ilter cake is then suspended in 8.o liters of flltra~e
which ha~ a7read~ been preheated to 72C and ad~usted to
pH 6.o ~th ~aOH. Addition o~ the cake to the ~lurry
.
decreases the slurry temperature to 64C which i~ then
maintained for 20 minutes. This treatment serves to
reduce the nucleic acld content o~ the ~ilter cake so that
higher levels o~ ingestion of the material by humans will
be permisslbl~, but i8 unneces~ary if the product ls to be
fed to animals ~uch as ruminants. me slurry i8 then
filtered and washed on the filter bed with one-half the bed
volume of distilled water. me fi~ter cake is next dewatered
with a vacuum to a solids content of 27.6 weight percent. At
this point the wet filter cake comprises an entangled mass
o~ limp ~lexible mycelial filament~. It is an open network
with strands in random orientation except in regions where
they have been drawn into some order by mech~nlcal work.
Since the strands are flexlble, interfllament cont,act~ are
frequent and involve relatlvely large areas of sur~ace contact.
If mechanical work is done on the filter cake in a d$rected
~ashion, the filaments become ordered in direction by slid~ng
over each other ~hile the area of weak inter-filament contac~s
increases. The rapid heat setting o~ these contacts serves
to increase the strength of the product even after rehydration
50 that a marked increase ~n cookability and chewabllity of
the product is observed.
De~criptlon o~ the Drawin~
Re~erring now to Fig. 1, the filter cake o~ mycel~wm
is fed to feed hopper 10 of meat grlnder 12~ Meat grinder 12
is fitted with a screw auger whlch forces the mycelial ma~
through die 14 to ~orm an extruded m~celial mass 13 onto
conveyor 15. Generally the die of the meat grlnd~r will be
fitted with a foraminous member ~uch a~ a mesh ~hlch ~erves
to orient the mycelia within the ma~s in the machine direction
-- 5 ~
followed by a compaction zone which serves to press the
mycelia into contact with each other. Conveyor 15 transports
the e~truded mycelial mass 13 through dielectric heater 16.
Dlelectric heater 16 consists of a grounded electrode plate 17,
and electrode plate 18 which is activated by radio frequency
generator 19. After passing through dielectric heater 16~ the
mycella are cut lnto chunks 20 by knife 21 which alternately
may be placed as shown at 21a. The chunks 20 are collected
in vessel 22.
me mycelium in the filter cake contain substantial
amo~nts of water. Generally the filter cake will contain
from 15 to 40 welght percent solids with a more usual range
of from 20 to 33 weight percent solids. me weight percent
solid~ as used herein is determined by weighing a sample,
drying the material for 16 hours at 60C in a vented oven to
completely dry the material, and then weighing the resulting
dried sample.
The dielectric heating step will generally rapidly
dry the filter cake to increase the solids content thereof
by ~rom 8 to 40 weight percent as based on the total original
filter cake composition to contain from 30 to 70 weight
percent solids with from 40 to 60 weight percent solids being
the preferred r~nge. It has been found that when the RNA
reduced product is dried rapidly to less than 40 and
e~pecially less than 30 weight percent solids, -the final
dried product upon rehydration is tough textured and undesirably
- hard. It has also be observed that when the RNA reduced
product is dielectrically dried rapidly to greater than 60
weight percent solids, and especially when dried dielectrically
rapidly to greater than 70 weight percent solids, the ultimate
-- 6 --
i~7~5~
rehydrated product exhibits poor chewability and poor integrity
and on rehydration and cooking is soft in texture. Further-
more it i8 dif~icult to avoid burnin~ and degradation of the
protein when the material is rapidly dielectrically dried
~eyond 70 weight percent solids~ Thus the unexpected result
has been found that when dried dielectrically rapidly to within
this preferred range of from 40 - 60 weight percent sollds,
and then further dr~ed at a much slower rate by conventional
means such as hot air, the dried RNA reduced product can be
rehydrated to absorb from 1 to 5 and preferably 1~5 to 3.0 times
its welght o~ water. For when the untreated filter cake is
dried entirely by hot air, the dried product will only take
up about 0.2 to 0.5 times the solids weight of water on rehy-
dration. Further when the product is dielectrically dried
rapidly ln excess of that provided by the present invention
the rehydrated product does not retain its shape and its
texture well on cooking~
Although puffing is normally associated with a
large expansion in the overall dimensions of the product during
the heating step, in this case~ pu~fing refers to the resistance
of the material during heating to the shrivelling up or
collapse and hardening which take place on slow drying. The
rapid heating CRn expand the product but any excessive
expansion of the overall dimensions of the product is generally
undesirable slnce it results ln a product which on rehydrat~on
has an apparent density less than meat and a texture, strength,
and other physical characteriskics unlike meat. Thus,
expansion of the material is generally needed only when pro-
ducing a mince type product. Generally the product will not
change more than about 20~ in volume during the rapid drying
-- 7 --
step. The rapid drying apparently serves to heatset the
product. The heat-setting then evidently serves to cau~e
the cells to retain their physical dimensions and resist
further shrinkage. The apparent bulk density o~ slowly air
dried fungal materlal grown as described above is about
o.85 to 0.95 g/cc, whereas the apparent bulk density of
the same material dried in accordance with the present
invention generally is ~rom 0.52 to 0.73 g/cc (both cases
dried to essential dryness). Thus the pu~fing heat-setting
step serves to retain pores and to cross-link the material so
that it can be easily rehydrated. The pore size between the
relatively coarse fibers of the product can be controlled by
varying the rate of dielectric drying. Generally from 2 to 13
kilowatt (k~)-seconds, kilojoules (kJ), o~ dielectric energy
per gram of solids in the filter cake is used with about 2 to
9 kW-seconds (kJ) per gram being preferred. In order to achieve
the proper pore size, this amount of energy should be applied
for 5 to 300 seconds covering cross-sectional dimensions o~
1/8 inch (.32 cm) diameters to 1~1/2 inch (3.81 cm) by 2-1/2
inch (6.35 cm). Larger sizes take correspondingly longer~ For
instance, a 5-1/2 x 5-1/2 x 3 inch (14 x 14 x 7.6 cm) thick chunk
takes about 20 minutes. To achieve 3 kW-seconds per gram in
120 second~, 25 watts per gram are needed to be applied to the
material. Watt per gram value can be calculated by di~iding the
energy input in Watt-seconds per gram with the heatlng tlme in
seconds~ We have ~ound that ~or a mince-type product the
energy is applied ~or 5 to 60 seconds with about 15 seconds
being the optimum~ whereas for a 1/2 x 1/2 inch (1.27 cm by
1.27 cm )chunk-type product the energy should be appl ed
for 30 to 180 seconds to reach the 30 to 70 weight percent
-- 8 --
solids level with the optimum being about 130 seconds. For
1-1/2 x 2-1/2 inch (3.8 x 6.~ cm) ribbons about 200 to 300 seconds
are used with 250 seconds being optimum. The dielectric heating
is generally performed at a frequency o~ from 1 to 3,000
Megahertz. Higher frequencies than 3,000 ~z can be used but
are more expensive to produc~ and control and do not appear
to offer any advantage. Frequencies about 13 to 90 MHz are
preferred for ease of control, product uniformity, lower cost
per kilowatt, equipment life, etc. However, frequencies into
the microwave range can be used. In particular 915 to 2450
MHz frequencies have been used satisfactorily.
The dewatered filter cake may be mechanically worked
prior to the dielectric heating. When this is done, it is
generally preferred that the high frequency electric field of
the dielectric heater be applled at right angles to the
orientation of the fibers developed in mechanically working
the material being treated. It has been discovered that the
direction in which the high frequency electric field is applied
has a significant influence on the structure of the finished
product, and the best chewability in the final rehydrated
product is obtained when the electric field is applied at
right angles to the direction of the fibers~ Thus a vertical
field is preferred for continuous strip production. However,
when the voltage across the air gap is large it may be desirable
to use a disperse field.
In order for -the water vapor created by the dielectric
heating to expand and heat-set the product properly, the
thickness of the material being dried should be between 0.2
to 15.0 cm. Below this thickness the water vapor can
escape without adequate puffing and heat~settlng of the
_ g _
~ 6~'7~
product and tne pore size i~ difficult to control. When
heating material greater than 15.0 cm in thickness, it is
difficult to control voids in the product which are un
desirable for some end uses. For products of about 1.25 by
1.25 cm cross-sections, void formation can be minimized by
feedin~ continuous lengths of product through the dielectric
oven and using 130 to 180 second drying times to partially
dry and heat-set the product (up to 300 second~ for larger
cross sections).
If de-slred, minor amounts of a binder such as gluten
may be incorporated in the material prior to drylng. In cer-
tain instances it is desirable to dry the material in a steam
atmosphere in order to avoid skin formation on the product.
The dielectric heating step also reduces the odor of
the product as compared with that of the product obtained by
hot air drying only.
The dielectrically heat-set and partially dried
material can be frozen wet. When th~wed, and optionally
rehydrated, it retains its puffed heat~set structure~ improved
cookability, chewability, etc.
After the rapid dielectric heating step, the produc-t
i8 ~urther dried to a moisture content of less than 10 weight
percent in order to improve the shelf life and texture of the
product. Generally this step is carried out at from 50C to
150C~ At 50C adequate drying generally takes about 20 hours.
At 150C adequate drying generally takes about 20 minutesO
After drying, the fungal produc-t is stored until it
is formulated into a food produc-t. Upon formulation, the
dried fungal product is rehydrated with water. me pre*erred
products of the present invention will take up from 1 to 5
-- 10 --
~7~
times their weight ~as ba~ed on the actual solids content
thereof prior to rehydration) o~ water. m e rehydration
mea~urement i~ made by lmmer~ing the dried product in boil~ng
water at standard atmospheric pressure ~or 20 minutes
followed by draining and blotting ~ith paper towel6.
The mechanlcal worl~ing ætep is not essential and~ if
desired, may be o~itted for ~ome end uses in order to provide
a bread-like product that may ~e u~ed as a ground meat
ex-tender. However J in the pre~erred aspect o~ the lnvention,
it i5 deslred to produce a chunky product wh~ch resemble~ meat
in texture after cooklng, and therefore, it i~ necessary to
per~orm some mechanical working on the product prlor to the
dielectrlc heating ~tepc In order for the best re~ults to be
obtained ln a texturlzed product, the ~ungal hyphae ~hould
have their turgor reduced~ m e original cell~ a~ grown are
relatively rlgid and when mechanically worked they tend to
dewater and due to thelr rigidit~ the resultant product has
an undesirably ~ew number of contact point~ between individual
hyphae resulting in poor mechanical ~trength. The nuclelc
acid reductlon ~tep described aboYe in the descriptlon of
growlng the Yungal ~ibers adequatelg reduce~ the turgor oP
the flbers for th~ purpose. Alternatlvely the fiber~ may be
wa~hed with a dilute salt solution to remove water ~rom wlthin
the cells thereby reducing the turgor of ~he hyphae. The
mechanical working serves to all~n the hyphae and to pre3~
them together to form larger fibers or flber bundles made up
o~ many hyphae. The larger fibers are lnterconnected by many
hyphae giving a meat-like texture to the product. To prepare
a mince-t M e product, the filter cake which pre~erably
contains 20-33 weight percent ~olids i~ extruded through a
plate about 1/4~ (o.64 cm) thick provided with holes from
1/8" (.32 cm) to 7/16" (1~11 cm) in diameter~ with about
3/16" (o,48 cm) being optimum, to form strands which are
then dried by dielectrical heating ~or 5 to 60 minutes to
a 30 to 70 weight percent solids level. The material may be
cut, ground, or chopped into lengths of 1/8" ~.32 cm)
- to 7/16" (1.11 cm) with about 1/4" (o.64 cm) being pre-
~erred either be~ore or after the final drying. me dielectric
heating in this case causes some expansion and puffing as well
as heat-setting o~ the product. The product is then further
dried to below 10 weight percent moisture over a period of
20 minutes to 20 hours to improve texture and the shelf li~e
thereof.
Another type of product which can be produced by the
process o~ the present invention closely simulates a pork-
loin slice. mis is prepared by extruding the filter cake as
described in the example below to ~orm a 1.27 cm square strip.
The s-trip is then cut into lengths of about 1 to 1 1/2 feet
(30.48 to 45.72 cm)~ The lengths are then bundled up with
about 6 to 15 strips to a bundle. The bundle is wrapped
with cheese cloth or plastlc film and then hand worked
using a mot~on similar to that used to milk a cow to ext~nd
the length of the bundle 1~5 to 3 times with about 2 times
being preferred. me resulting extended bundle is then sliced
at 1/2" (1.27 cm) intervals giving a 1/2" (1.27 cm) ~lice
with a 1/4" ~o.64 cm) to 3/4" ~1.90 cm) slice being typical.
Using the dielec-tric apparatus de.scribed in the example below
with its electrode in a disperse ~ield con~iguration and
1 slice in the oven at a time, an 88 second residence time
and the distance be-tween the plane or upper electrode tips and
- 12 -
~L~7~
the plane of the lower electrode tips of 1-3/8" t3.49 cm)
results in a product containing 40 weight percent solids.
Production rate can be increased by simultaneously processing
a higher number of slices equally spaced along the belt as
long as the rated power of the dielectric heater is not
exceeded. Alternakely, applicants have used a 2450 MHz
multimode cavlty oven to hea~ four slices at a time. Using
a power ~etting of 1 kilowatt and 150 seconds residence
tlme, the resultant product contained 50 weight percent solids.
The pork loin sllce is further dried to below 10 weight percent
moisture over a period of 20 minutes to 20 hours to improve
the shelf life thereof.
The preferred product to which the process of the
present invention is applicable is chunks as described in the
example below. ~he extrusion process described therein is not
a part of the present invention. However, the heat setting and
drying o~ the extruded product so as to retain its texturized
structure, yet provldlng a drled rehydratable product is part
o~ this in~ention.
Description of the Preferred Embodiments
- Example 1 ; ..
A filter cAke of mycelium prepared ~rom Fusarium
~raminearum Schwabe I.M.I. 145,425, prepared as descrlbed aboYe,
is fed lnto a small electrically drlven meat grinder. The
~llter cake contains 27.6 weight percent solids. The
f~lter cake is extruded through a 5 cm diameter dle ~itted
wi~h a 0.6 mm square mesh screen and then through a 4 to 1
compaction die a~ a ra~e o~ 2.5 feet per minu~e (76 cm per
minute) onto a Teflon~ ~synthetic fluorocarbon polymer
manufactured by E. I. du Pont de Nemol-rs and Co.) coated
- 13 -
mesh conveyor belt 3" (7.6 cm) wide driven at 2.5 feet
(76 cm) per minute. The belt is passed between two flat
rectangular dielectric heater electrodes 15" (38 cm)~wide
by 18" (45.7 cm) long, by l/4" (o.63 cm) thick. The electrodes
are spaced 2-3/8" (6 cm) apart. A l/2" (1.27 cm) thick Teflon~
belt ~uide 3-1/2" (8.9 cm) wide is set on the lower electrode,
which electrode is grounded. The conveyor belt i~ in~contact
with the top of this belt guide. me presence of this belt
guide serves to pOBitiOn the product in the field such that
the heating intensity tends to be uniform throughout the
product cross-section. This eliminates a tendency of the
product to over pu~f at the bottom and under puf~ at the top.
me upper electrode which is covered wlth l/8'l (.32 cm) thick
Teflo ~ æheet is connected to an 85 MHz tuneable 8 kilowa-tt
ad~ustable radio frequency generator unit manufactured by
W. T. La Rose Associates of Cahoes, N~Y. This unit is tuned
to 85 MHz and is operated at a power output up to 8 ~ilowatts.
me product coming of~ the dielectric heater contains 50.7 weight
percent ~ollds and is cut into l/2" to l'' (1.27 cm to 2.54 cm)
length chunks. The chunks are then collected and dried in an
air oven at 50C for 20 hours to achieve a moisture content
of less than l weight percent~ On boillng in water for 15 min-
utes at atmospheric pressure the chunks take up 1.8 times their
dry weight of water.
Photomicrographs showing a freeze fractured product
chunk magnified 60X, lOOX, 300X3 and 1JOOOX are presented as
Fig. 2, 3, 4 and 5 respectively. It will be noted that the pro-
duct is made up of relatively coarse fibers having an average
diameter of about 0.5 mm and a length to diameter ratio of
greater than 20. These fibers have been found to vary from
- 14 ~
~L~7~ L59
O.2 to 1.O mm in diameter in the various meat-like products
Applicants have prepared, and are interconnected with hyphae
which have an average diameter of about 0. oo8 mm and an
average length to diameter ratio of about 100. Generally,
these hyphae in the various meat-like products applicants
have prepared, have been found to vary from 0.004 to 0.01 mm
in diameter and to have length to diame~er ratios of from 10
to 1,000. In additlon, the fibers have been found to be con-
nected by at leas~ one hypha ln each 0.1 to 1.O mm of each
~iber length.
The product shown in Figs. 2-5 contains about 55
weight percent protein. Generally the product will contain
from 45 to 60 weight percent protein.
Example 2
A filter cake containing 34 ~eight percent solids
ls extruded into a 1.27 cm by 1.27 cm cross-section rope uslng
the die described in Example 1 at a rate o~ 4.6 ~eet per minute
~140 cm per minute) onto a Teflon~ coated mesh conyeyor
belt 3" (7.5 cm) wide driven at 4.6 feet (140 cm) per minute.
The ~elt is passed between two sets of electrode arrays
(1.9 cm diameter aluminum rods spaced 20.3 cm apart in each set~
O~ 3zt- effective heater length in a dispersed ~leld config-
uratlon. The distance between the plane o~ the upper electrode
~ips and the plane of the lower electrode tips is 3.75"
(9.5 cm). The conveying belt is positioned 1.125" (2.86 cm)
aboYe ~he plane o~ the lower electrode ~ips so that the
hea~lng intenslty tends to be uni~orm throughout ~he product
cros~-sectlon. The lower electrode is connected to a 27 MHz
tunable 6 kllowatt adjustable radio frequency generator unit
manufactured by Fitchburg Industrial Products Company of Fitchburg,
- 15 ~
~7~
Massachusetts. Thls uni~ is tuned to 27.5 MHz and is operated
at a power output to extrudate of 4.7 kilowatts. The product
coming of~ the dielectric heater is cut into 1/2" (1.27 cm) to
1" ~2.54 cm) length chunks. The chunk3 contain 47.4 weight
percent solids. The chunks are then collected and dried in an
alr oven at 50C for 20 hours. This dried product has a moisture
content of less than 1 weight percent. On boiling in water for
20 minutes at atmospherlc pressure andblotting with paper towels,
pieces o~ this dried product take up 1.5 times their dry weight
of water-
Example 3
A filter cake of mycelium of Fusarium ~raminearum
Schwabe I.M.I. 145,425, prepared as described above, is fed
to a hydraulic ram type extruder. The filter cake containing
30 weight percent solids is forced through an oval die
measuring 3.8 cm by 6.35 cm fitted with a o.6 mm mesh screen
over a 19 strand breaker plate. There is a 4 to 1 reduction
.in filter cake size as t~e material passes from the screen
through the breaker plate and a further 1.3 to 1 reduction in
filter c~ke size as the merged strands pass from the 19 strand
breaker pla~e to the oval die outlet. The extrudate is dis-
charged through the ova~ die at a rate of 414 cm per minute
onto a conveyor belt. The extrudate is cut to 150 cm
len~ths, which are removed ~rom the conveyor belt and placed
on trays. A~ter a brief time ~he 150 cm lengths are lndivi-
dually placed on a ~eflon~ coated mesh conveyor belt 7.5 cm
wide driven at 24 cm per minu~e. The belt is passed through
two flat rectangular dielectric hea~er electrodes 38 cm wide
by 72 cm long, by o.63 cm thick. This provides for a residence
time o~ 180 seconds in the dlelectr:Lc heater. The electrodes
16 -
are spaced 15.5 cm apart~ A 1.25 cm thick Teflon~ belt guide
8.9 cm wide is set on the lower electrode, which electrode is
grounded. m e conveyor belt is in contact with the top of the
belt guider The presence of the belt guide serves to position
the product in the ~ield such that the heatlng intensity tends
to be uniform throughout the product cross-section. The upper
electrode which is covered with a .32 cm thick Teflon~ sheet
is connected to an 85 MHz tuneable 12~5 kW ad~ustable radlo
frequency generator unit manufactured by W. T. La Rose
Associates of Cahoes, N.Y. This unit is operated at a power
output of 5.4 kilowatts to the extrudate. me product coming
off the dielectric heater contains 40.3~ solids. The product
is further broken into chunks of 1.9 cm x 1.9 cm x 2.5 cm and
dried in an air oven at 90C for 4 hours. This dried product
has a molsture content of less than 1 percent. On boiling in
water for 20 minutes at atmospheric pressure~ pieces of this
dried product take up 1.6 times their dry weight of water. ~hen
fractured at liquid nitrogen temperature in the direction of
the f^tbers, the material is very similar in structure to the
product shown in Fig,s. 2-5.
Exa~ple 4
Example 3 is repeated using the same extruded
material and equipment, etc. except that the electrodes of
the dielectric heater are spaced 13.9 cm apartg the conveyor
is operated at 43.2 cm per minute and the power is set at
8.4 k~ to the extrudate~ Three passes through the dielectric
heater are used for each piece being dried. The solids
content of the dielectrically dried product is 50'~. m e
product is then cut into pieces which are then dried in an
air oven at 90C ~or four hours. m is dry product has a
- 17 -
~17~
moisture of less than 1%. After boiling in water for
20 minutes at atmospheric pressure, pieces of this product
take up 1.6 times their dry weight of water.
- 18
