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SOME PROPERTIES OF
FOAM SPRAY DRIED
IVE‘EOLE EGGS:

Thesis for the Degree of M . S .
MICHIGAN STATE UNIVERSITY
JOHN G. REAGAN
1967

ABSTRACT

SOME PROPERTIES OF FOAM SPRAY DRIED WHOLE EGGS

by John G. Reagan

Frozen liquid whole eggs were thawed and spray dried
using two different nozzle sizes and two different levels
of injected nitrogen in addition to a non-nitrogen injected
treatment. Some of the whole egg powder was put through
instantizing equipment. Total solids, solubility index,
pH, dispersibility, bulk density, filtration rate and
particle size distribution were determined on the egg
powder from each drying method and instantizing procedure.
The particle size distribution was determined through the
use of the Coulter Counter, model B.

"Flowability" was not measurably improved by foam
spray drying or by instantizing. The instantizing proce-
dure following spray drying did not appear to be effective
in this study since both solubility and dispersibility de-
creased. Instantizing the whole egg powder had little
effect on the particle size distribution and bulk density.
It appeared instantization did not occur.

Foam spray dried whole egg powder has increased
solubility, larger particles, decreased bulk density and
is slightly more dispersible than the conventional (non-

nitrogen injected) spray dried whole egg powder.

SOME PROPERTIES OF FOAM SPRAY DRIED WHOLE EGGS

by

John G. Reagan

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Food Science

1967

AC KN OWLE DGMENT

The author wishes to express his appreciation to
Dr. L. E. Dawson for his guidance, assistance and helpful
criticism throughout the course of study.

He is also grateful to Dr. W. M. Breene, Professor
of Food Science, and to Dr. T. I. Irmiter, Professor of
Foods and Nutrition, for their critical review of the manu-
script.

The author wishes to thank Dr. B. S. Schweigert and
the members of the faculty of the Department of Food Science
for making facilities available and the interest shown
during the preparation of this manuscript. His sincere
thanks go also to Mr. Victor Armitage, Mr. Lee Blakely
and Mr. Dale Finch for their assistance in spray drying
the eggs used in this study.

The author is deeply indebted to his wife, Anne,
for her assistance in typing, encouragement and under-

standing throughout a trying period.

ii

TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . ii
LIST OF TABLES. . . . . . . . . . . . . . . . . . . . iv
INTRODUCTION. . . . . . . . . . . . . . . . . . . . . 1

LITERATURE REVIEW . . . . . . . . . . . . . . . . . .

Us)

Particle Size. . . . . . . . . . . . . . . . . . 3
Solubility . . . . . . . . . . . . . . . . . . . 4
Dispersibility . . . . . . . . . . . . . . . . . 4
Flowability. . . . . . . . . . . . . . . . . . . 5
Foam Drying. . . . . . . . . . . . . . . . . . . 6
Total Solids . . . . . . . . . . . . . . . . . . 7
Functional Properties. . . . . . . . . . . . . . 7

EXPERIMENTAL PROCEDURE. . . . . . . . . . . . . . . .

oo

Spray Drying . . . . . . . . .

Total Solids . . . . . . . . . . . . . . . . . . ll
Solubility . . . . . . . . . . . . . . . . . . . 11
Time of Filtration . . . . . . . . . . . . . . 12
pH . . . . . . . . . . . . . . . . . . . . . . . 12
Dispersibility . . . . . . . . . . . . . . . . . 13
Particle Size Analysis . . . . . . . . . . . . . 14
Bulk Density . . . . . . . . . . . . . . . . . . 18
Visual Observations of Dispersibility. . . . . . 19

RESULTS 0 O O O O O O O O O O 0 O O O O O O O O O 0 O 20

Total Solids . . . . . . 20

Solubility . . . . . . . . . . . . . . . . . . . 20
pH . . . . . . . . . . . . . . . . . . . . . . . 23
Dispersibility . . . . . . . . . . . . . . . . . 23
Bulk Density . . . . . . . . . . . . . . . . . . 23
Filtration Rate. . . . . . . . . . . . . . . . . 27
Particle Size. . . . . . . . . . . . . . . . . . 29
Observed Dispersibility. . . . . . . . . . . . . 29

DISCUSSION. 0 O O O O O O O O O O O O O O O O O O O O 32

LITERATURE CITED. 0 O O O O O O O O O O O O O O O O O 35

iii

LIST OF TABLES

Table
1 Conditions of spray drying . . . . .
2 Total solids of egg samples spray
dried and treated by different
procedures . . . . . . . . . . . . .
3 Solubility index of egg samples
spray dried and treated by
different procedures . . . . . . . .
4 pH of egg samples spray dried and
treated by different procedures. . .
5 Dispersibility of egg samples spray
dried and treated by different
procedures 0 O O O O O O O O O O O O
6 Bulk density of egg samples spray
dried and treated by different
procedures . . . . . . . . . . . . .
7 Time to collect 10 ml filtrate of
egg samples spray dried and treated
by different procedures. . . . . . .
8 Particle size distribution of egg

samples spray dried and treated by
different procedures . . . . . . . .

iv

INTRODUCTION

Eggs and egg products are very perishable unless
frozen, dried or refrigerated (shell eggs) until utilized.
Dehydration not only offers a means of preserving quality,
but also reduces the packaging, handling, storing and trans-
portation costs.

Koudele and Heinshon (1960) reviewed the history of
the egg drying industry. They reported that in the United
States, the idea of drying eggs was conceived in the late
1800's. However, the first successful commercial egg drying
Operation apparently took place in China, where German en-
gineers introduced dried eggs in the early 1900's. Stauf
was credited with the invention of the spray dryer in 1901.
The belt type dryer for "flake" whole egg and yolk was in-
troduced by Keith and Hussey in 1907, and in 1913 Gray and
Jensen produced a cyclonic type spray dryer (Berquist 1964).

During the early 1930's the drying industry for
albumen and yolk was re-established in the United States.
However, with the outbreak of World War II, the production
of dried whole eggs dwarfed that of albumen and yolk.

Drying of whole eggs reached a peak in the United States
during 1944 when over 300 million pounds of dried whole

egg were produced.

The introduction of gas into the liquid feed line
is not a new idea as it was done in 1922 by Heath and
Washburn when they introduced a somewhat soluble inert
gas such as carbon dioxide or nitrogen under pressure dur-
ing the spray drying of milk. The most successful modifi-
cation of this method was introduced by Hanrahan and Webb
(1961). This method of gas injection under pressure into
the liquid feed line is currently known as foam spray drying.

Physical, chemical and functional properties of eggs
may be altered during a drying process. Thus advances in
drying techniques are sought to produce products which will
perform as well or better than the fresh egg. Foam spray
drying was introduced by Heath and Washburn (1922) in an
attempt to improve some of the physical properties of the
dried product. Normal spray dried eggs lack "flowability"
and "instantizing" characteristics desired in the product.

This research was conducted to evaluate some of the
physical and chemical prOperties of foam spray dried whole
eggs, and to relate these prOperties to possible improve-
ments in functional characteristics of the resulting pro-
ducts. At the present time there is a general lack of
information in the literature concerning the properties
of foam spray dried eggs in comparison with conventional

spray dried products.

LITERATURE REVIEW

Particle Size

 

Pearce gt_§l. (1946) reported using a “RoTap Shaker"
with an assortment of sieves to separate dried whole egg
powder into portions according to particle sizes. This
machine shakes the dried food continuously and taps the
tOp cover of the sieves frequently during the operation.

In this study, powder of particle size small enough to pass
through an 80 mesh (U.S.) screen or sieve appeared to have
better baking properties than coarser material. Mori
(1964) used the RoTap Shaker and the Coulter Counter to
determine the particle size analysis of dried milk. Parti-
cles which passed through a #60 sieve (U.S.) (screen) were
subjected to the Coulter Counter analysis. The Coulter
Counter counts particles electronically. Particles are
suspended in a solution through which an electrical current
can pass. As the particles pass through an Opening in a
tube the electrical current is disrupted and the impulse

is registered and counted automatically when the particle
size exceeds the limits as set on the machine. Mori found
he needed both the shaker and Coulter Counter for Optimum
analysis of instantized milk powders because of the wide

range in particle size.

Lightbody and Fevold (1948) reported that spray
dried egg particles were hollow spheres from 7 to 120 microns
in diameter. The atomization conditions, nozzle orifice
size, liquid line pressure, liquid viscosity and solids
content are among factors known to affect particle size.

The Coulter Counter (Anon 1965a) reportedly can be
used for determining numbers of particles as well as a
particle size distribution for materials which can be sus-
pended in a solution condusive to the passage of an electri-
cal current. Several other workers have reported other
means of determining particle size or surface areas in milk
powders, Fox gt_al. (1963), Janzen gt_al. (1953), Berlin

25 g. (1964) and Shaw 3:; El.- (1946).

Solubility

 

The Institute of American Poultry Industries (1962)
recommended Stuart's Solubility Index for evaluating dried
egg solids and for a possible purchase specification. The
amount of protein precipitate is measured from a 1.5 gram
sample of egg powder and 5 ml of the subsequent filtrate.
Bishov and Mitchell (1964) described their method for a

similar solubility study.

Dispersibility

 

Sugihara gt 31. (1962) reported that fluff drying,
agglomeration or gas impregnation prior to spray drying

of liquid whole egg, to which corn syrup solids had been

added, improved the dispersibility strikingly over conven-
tional spray dried whole egg powder. Two methods for
determining dispersibility of whole egg powder were found
(Downs 1966 and Miller gt_§l. 1959). In Down's method the
egg powder is reconstituted to a known total solids content.
After mixing, a 5 gram sample of the reconstituted egg is
dried and the resulting total solids content compared with

the known total solids content.

Flowability

 

Several methods for improving the flowability of
dried egg and yolk powders have been attempted. The usual
reason given for the clumping, sticking or clinging together
of whole egg and yolk powder is the relative high fat con-
tent. Whole egg powder is usually 40+ per cent lipid ma-
terial and yolk powder is around 65 per cent lipid material.
Among the methods tried to improve flowability of egg powders
have been 1) coating the egg particle, 2) agglomeration or
instantizing and 3) foam drying.

Forsythe gt 31. (1964) reported the use of a colloidal
silica gel preparation in dried egg yolk powders. The col-
loidal silica gel was used to coat the individual yolk
particles or clusters of yolk particles so the fat does
not come in contact between the yolk particles or clusters.
This method was found to be effective as measured by a

standard screen test.

Agglomeration or instantizing has been used primarily
for dried milk prepared for home use in the past several
years. These processes can include agglomeration by wetting

and then redrying or by coating, Mori (1964).

Foam Drying

 

Foam drying can be divided into two principal methods:
1) foam mat drying and 2) foam spray drying. The foam mat
drying is also called film drying or "puff" drying. The
principle is drying under high vacuum at low temperature
with the incorporation of nitrogen before the concentrate
goes through the final homogenizer. Dried milk, tomato
juice, egg albumin and other liquids and purees have been
produced in this manner, Mori (1964), Ginnette 22 El! (1963)
and COpley and VanArsdel (1964).

Foam spray drying involves injection of a gas such
as nitrogen or air under pressure into the liquid feed line
between the pressure pump and the Spray nozzle by means of
a mixing chamber in the liquid feed line. Heath and Wash-
burn (1922) first reported this method and the modifications
by Hanrahan and Webb (1961) have been the most successful
when used for drying high acidity whey. The process has
also been tried with cheese (Finch 1966) and milk (Hanrahan

gt El. 1962 and Bell et El‘ 1963).

Total Solids

 

Low moisture levels in dried egg products are essen-
tial for Optimum quality stability. The military specifica-
tions for dried whole egg (AnOn 19650) establishes a minimum
of 97.5 per cent total solids and the military specifications
for a dehydrated egg mix (Anon 1965b) sets a minimum of 98
per cent total solids content. The minimum total solids
recommended for commercial purposes is 95 per cent, Forsythe
and Miyahara (1959), Miyahara and Berquist (1961) and

Forsythe (1964).

Functional Properties

 

Wolfe (1967) obtained representative samples of the
same whole egg powders as used by this author. She reported
no differences in functional properties of the whole egg

powders when used in custards.

EXPERIMENTAL PROCEDURE

Frozen whole eggs, adjusted to 26 per cent total
solids, were obtained from a commercial source. Sixty
pounds of liquid whole eggs were Spray dried for each

treatment.

Spray Drying

The frozen whole eggs in 30 pound tin containers
were thawed under cold running tap water for approximately
16 hours and then placed in 10 gallon stainless steel milk
cans. The milk cans were placed in a water bath at 60°C
and the liquid egg temperature brought up to 57°C prior to
the drying process. All liquid eggs to be foam spray dried
required nitrogen injection at a constant rate into the
liquid egg immediately after passing through the homogenizer
and prior to spraying.

The spray dryer and supporting equipment consisted
of the following:

1. Waukesha positive pump - fed liquid whole egg
into the high pressure pump (homogenizer).

2. Cherry Burrell high pressure pump variable speed

drive (homogenizer).

3. Nitrogen injection chamber with source of nitrogen
under pressure.

4. C. E. Roger horizontal spray dryer. Capacity of
250 pounds N.F.D.M. per hour, three nozzles, gas fired and
cyclone separator.

5. Taylor instrumentation panel to record inlet and
outlet air temperature.

6. Nozzles. The SX 69 and SK 64 with number 17 core
from the Spraying Systems Company were used.

The samples of eggs were spray dried as shown in
Table l. The foam spray treatments were a modification of
the method suggested by Hanrahan and Webb (1961). The
nitrogen pressure exceeded the homogenization pressure by
approximately 100 psi. A Brooks Rotameter metered the
nitrogen into the stream of liquid whole egg as the egg
passed through the injection chamber.

The egg powder was then collected from the dryer
and placed in Cryovac bags which were evacuated, sealed,
and stored at 3°C for further testing.

Approximately one-half of the dried egg powder from
each treatment was instantized using a Blaw-Knox Instantizer,
Series A-20 at 6-7 psi steam. Intake temperature was 143°C
and the exhaust temperature was 82°C. After instantizing
once, half of the instantized product was instantized a

second time under the same conditions.

10

TABLE 1. Conditions of spray drying

 

 

 

 

Homogeni-

Spray dry- Nozzle/ Nozzle zation Nitrogen Inlet Outlet
ing method core diameter pressure per gal. temp. temp.
No. Inches PSI Cu. ft. °C °C

Conven- l

tional 64-17 .036 2500 none 140 93
I 64-17 .036 1050 0.3 117 81
II 64-17 .036 1050 2.0 117 80
III 69-17 .0292 900 0.3 116 80
IV 69-17 .0292 900 2.0 118 80

 

lAn homogenization pressure of 2500 psi is recommended
for this machine. However, the nitrogen available only had
1000-1150 psi, the nitrogen injected spray drying methods had
homogenization pressures approximately 100 psi less than the
available nitrogen supply.

11
Total Solids

The total solids content of the dried egg products
was determined by the method prOposed by the Institute of
American Poultry Industries (1962). Two grams of a well
mixed sample were placed in a previously dried and tared
aluminum moisture dish with cover. The cover was loosened
and placed in a vacuum oven at 100°C for 5 hours. The
sample was removed from the oven, placed in a desiccator
to cool to room temperature and then weighed. The results

were reported as per cent total solids.

Solubility

Stuart's Solubility Method was used as outlined by
the Institute of American Poultry Industries (1962).

One and one-half grams of dried whole egg powder
were added to 50 ml of distilled water in a 250 ml Erlen-
meyer flask with a screw cap tOp. The temperature of the
water was 21-24°C. The contents of the flask were thoroughly
agitated to obtain a uniform dispersion. The flask and
contents were allowed to stand for 30 minutes at room tem-
perature. The contents of the flask were agitated vigor-
ously and filtered through a Whatman #12 fluted filter
paper. The first 10 ml of filtrate were collected in a
10 ml volumetric flask. Five m1 of the 10 m1 filtrate
were transferred, using a volumetric pipette, to a 15 m1

tapered centrifuge tube which was graduated in 0.1 ml

12

subdivisions. Five m1 of 0.1M sodium acetate buffer (pH
4.6) were added to the centrifuge tube. The sodium acetate
buffer was made with 102 m1 of 0.1N acetic acid and 98 ml
of 0.1 N sodium acetate. The pH was adjusted to 4.6.

After the buffer was added, sufficient water was added to
bring the contents to a final volume of 15 ml. The centri-
fuge tube was transferred to a water bath at 100°C for two
minutes, cooled to approximately room temperature in a
second water bath and then centrifuged at 2,000 rpm for 6
minutes. The volume of centrifuged precipitate was read to
the nearest 0.1 m1 graduation. The number obtained was

recorded as Stuart's Solubility Index.

Time of Filtration

 

An estimate of filtration rate was determined as the
total time elapsed between the addition of the egg suSpen-
sion to the filter paper and the collection of the first

10 m1 of the filtrate in the volumetric flask.

Pli

Five grams of dried egg powder from each treatment
were mixed with 30 m1 of deionized water in a beaker. The
pH of the egg suspension was determined by placing the
electrodes in the beaker containing the egg sample. A
Beckman Zeromatic pH meter was used, and all pH measure-

ments recorded to the nearest 0.1 of a unit.

13

Dispersibility

 

A modification Of the method suggested by Downs (1966)
was used. The following is used to determine how much water
is needed for reconstitution of a 60 gram sample of dried
egg powder to a desired total solids content of 30.6 per cent:

1. Determine the total solids content of the whole
egg powder as outlined previously.

2. Multiply 60 grams by total solids (l) to deter-
mine total solids content of the 60 gram sample.

3. Multiply (2) by 100 and divide by 30.6 (the de-
sired per cent total solids when reconstituted) to deter-
mine the total amount of reconstituted egg desired (grams).

4. From (3) subtract the weight of the sample of
whole egg powder (60 grams) to determine the grams of water
which must be added to have a total solids content of 30.6
per cent.

Before mixing the egg samples, the vacuum oven and
forced air drying oven (to be used later) were preheated
to 100°C. A Kitchen Aid model K5-A mixer with paddle was
allowed to warm up for 10 minutes and the speed of the
paddle was adjusted to 130 planetary rpm. Water was divided
equally between two beakers after the pH was adjusted to
7.0. The egg powder was weighed into the mixing bowl and
the bowl placed on the mixer. One-half of the water was
added to the mixing bowl and the paddle attached to the
mixer. The egg and water were mixed for 30 seconds. The

sides of the bowl and paddle were scraped and the slurry

14

was mixed an additional 30 seconds. The bowl and paddle
were scraped a second time. The remaining water was added
and the slurry mixed for an additional 30 seconds. The
paddle was scraped and the bowl was removed from the mixer.
The slurry was strained immediately through an 8 inch num-
ber 20 sieve into an 8 inch collection pan. The slurry

was allowed to drain 5 minutes and the contents of the
collecting pan were transferred to a 500 m1 beaker. Five
gram portions of the strained slurry were weighed into dry
and previously tared aluminum moisture dishes with covers.
The slurry was mixed before the weighing process to Obtain

a uniform sample. The samples were placed in the forced

air oven at 100°C to evaporate the excess moisture until

the slurry thickened. The samples were then transferred

to the vacuum oven and dried at 98-100°C under 30 inches

of vacuum for 5 hours or until a constant weight was obtained.
Dry air was released into the vacuum oven, the samples re-
moved and placed in a desiccator, cooled to room temperature
and then weighed. The weight of the residue divided by the
weight of the liquid sample determined total solids content
of the sample. The total solids content of the reconstituted
sample divided by the total solids content representing com-
plete dispersion (.306) multiplied by 100 determined per

cent dispersibility.
Particle Size Analysis

Several attempts were made to separate the dried

whole egg powder according to size by use of a RoTap shaker.

15

Placing the egg powder on the tOp sieve and then shaking
resulted in the egg powder forming little balls about the
size of peas on the top two sieves. Very little powder
went past the second sieve (number 20). To eliminate the
effect of moisture the sieves (a total of six), the bottom
collection pan and the top lid were dried in an oven, re-
moved after drying and the sieves taped together with 2
inch masking tape, the egg sample added, the lid placed on
the top sieve and sealed with the masking tape. The result
was a closed system so air could not get in, however the
separation did not improve. Next the whole egg powder was
dried in an oven before shaking in the closed system but
again there was no improvement in separation. Dried rice
was added to the tOp of each sieve and the sieves taped.
This increased separation somewhat but was not entirely
satisfactory. The shaking time was varied but increased
separation did not take place after 2 hours when compared
with 15 minutes.

Since the particles tended to cling together and
would not pass through the sieves without the use of an
external force, the Coulter Counter (Anon 1965a) Model B
was used to evaluate the particle size distribution. The
Coulter Counter consisted of a sample stand, an amplifying
unit and a small vacuum pump. A beaker containing the
sample suspended in a solution containing 10 grams ammonium
thiocyanate per liter of isopropyl alcohol (vehicle) was

placed on the sample stand in such a manner that a tube

16

with a 400 micron diameter Opening was immersed in it.
Previously the ammonium thiocyanate-iSOprOpyl alcohol solu-
tion was filtered through a Millipore filter with a 0.45
micron pore size disc. A 4 per cent ammonium thiocyanate-
iSOprOpyl alcohol solution is recommended by the manufac-
turer but no difference could be found using 10, 20, 30 or
40 grams ammonium thiocyanate per liter isoprOpyl alcohol,
thus the lowest concentration of ammonium thiocyanate was
used.

The aperture filled with the vehicle was connected
to a vacuum system which provided a flow of a measured volume
of vehicle, 2,000 microliters for the 400 micron diameter
aperture tube, through the aperture in the tube. Platinum
electrodes were located within and without the aperture
tube and a constant voltage was maintained between them.

The vehicle flowing through the aperture exhibited
a resistance which was changed when a particle passed through
the sensing zone. This change in resistance was amplified
and counted. The size of particles was reflected by the
magnitude of change in resistance which was manifested as
pulse height on an oscillosc0pe. The number of particles
passing through the aperture tube Opening was counted elec-
tronically. An adjustable threshold setting permitted the
counting of only those pulses which exceeded a given height
on the oscilloscope. In this manner the minimum size of
the particles was regulated. To increase the range of

pulse height, and thus the range of particle size measured,

17

it was possible to decrease the resistance across the elec-
trodes and to increase the amplification gain. The volume
of vehicle passing through the counting aperture was regu-
lated by the vacuum system provided with a traveling mercury
column which activated starting and stOpping probes preset
for known volume displacements.

The apparatus was standardized by determining the
half count of a sample of uniform size particles with known
diameter in microns (ragweed pollen). The settings of
amplification gain, threshold and resistance across the
platinum electrodes were adjusted in order to calculate a
calibration factor (k) for each aperture tube. This factor,
which corresponded to the known diameter of the standard,
was in turn used to calculate settings to give other parti-
cle diameters.

Counting of particles was then made on an unknown
sample at pre-determined settings, starting with the largest
particles. Counts were taken at 10 micron intervals down
to the 10 micron level which was the lowest useable reading
using the 400 micron diameter aperture tube. Smaller
diameter aperture tubes were tried but became clogged by
the larger egg particles. No method was found which would
separate the larger particles from the smaller particles.
Coincidence of particles passing through the aperture at
high counts was compensated for by using a coincidence
factor which was a function of the number Of particles

actually counted, size of the aperture diameter opening

18

and volume of vehicle passing through the aperture opening.
The adjusted counts were corrected for each interval in
diameter. The summation of these factors comprised the
total volume of particles in a given volume of vehicle.
From these data, the percentage weight distribution was
calculated, assuming a uniform density for all particles
and a spherical shape.

A stirrer located on the sample stand kept the parti-
cles in a uniform suspension during counting. Counts did
not change for the same settings during the counting period.
Therefore, it was assumed the particle size did not change

nor were the particles dissolved in the vehicle medium.

Bulk Density

 

A modification of the bulk density method reported
by Mori (1964) for milk powder was used to evaluate dried
whole egg powders. Sufficient egg powder was sifted through
a #10 sieve to loosely fill a previously weighed 100 ml
graduated cylinder. A loose pack bulk density was not
determined since the whole egg powder was not free flowing
enough to eliminate large air pockets when placed in the
cylinder without tapping the cylinder. The cylinder was
tapped gently for approximately 3 minutes using a ball
point pen which had been inserted inside a 1/4 inch diameter
rubber tubing 4 inches long. A 3 minute tapping period
was sufficient to give a constant volume reading. The

volume of packed whole egg powder was read to the nearest

19

m1 and the cylinder and egg powder were weighed. The re-

sults were reported as grams/m1.

Visual Observations of Dispersibility

To estimate, by visual means, the relative dispers-
ibility of whole egg powders, a series of observation tests
were carried out on the egg powder from each treatment. A
250 ml volume of distilled water was placed in each of
several 400 ml beakers. A 0.25 and a 0.50 gram sample of
egg powder from each treatment were separately sieved through
a 4 inch #10 sieve into separate beakers. The 0.25 gram
sample was allowed to sit quiescently to see how rapidly
the particles would sink without any mixing. The final
observation was made after the solution stood for 4 hours.
The second sample (0.50 gram) was sieved in similar manner
then stirred for approximately 30 seconds and observed for
clusters of particles which did not disperse but remained

floating.

RESULTS

Total Solids

 

All of the dried egg products in this study had
total solids exceeding 95 per cent (Table 2). No apparent
differences in total solids content were noted between con-
trol samples and those foam spray dried.

In these dried egg products, the samples instantized
once contained an average of only .29 per cent less total
solids than the controls and those instantized twice which
contained .60 per cent less total solids. These minor dif-
ferences in total solids content would probably not affect
the other factors evaluated. Mori and Hedrick (1965) re-
ported moisture increases of 1.16 to 1.72 per cent for dry
non-fat milk powders passing once through the same type of
instantizer used in this study. They also reported that
higher inlet temperatures of the instantizer resulted in

lower increases in moisture uptake.

Solubility

 

The foam spray dried egg powder appeared to be more
soluble than the conventional Spray dried egg product (Table

3). A slight decrease in solubility was noted when the egg

20

21

TABLE 2. Total solids of egg samples spray dried and
treated by different procedures

 

 

 

 

Spray drying Number of times instantized
method
0 l 2
Per cent total solids1

% - range % - range % - range
Conventional 96.9 i .04 96.5 i .03 95.9 i .03
I 97.0 i .06 96.7 i.°02 96.6 i .10
II 97.1 i .05 97.0 i .04 96.8 i .06
III 96.8 i .10 96.6 i .07 96.4 i .05
IV 96.8 i_.10 96.3 i .05 96.0 i .09

 

 

lEach figure is the mean value from 3 samples

I "'1. ur- «1.3.:

TABLE 3. Solubility index of egg samples spray dried and

22

treated by different procedures

 

 

Spray drying

Number of times instantized

 

 

 

method 1
ml of precipitatel
ml - range m1 — range m1 - range
Conventional .9 i .l .7 i .1 .8 i .1
I 1.7 i .1 1.1 i .1 1.0 i .1
II 1.5 i .1 .9 i .1 .9 i .1
III 1.6 i .1 1.0 :~.1 .9 i .1
IV 1.2 i .1 1.2 i .l 1.0 i .l
1

Each figure is

the mean value from 3 samples

23

products were instantized. The non-instantized low nitrogen
foam spray dried egg products (spray drying methods I and
III) were slightly more soluble than the high nitrogen egg
products of the same nozzle size (spray drying methods II

and IV).

PE

Table 4 shows the foam spray dried products usually
had a slightly higher pH than the conventional spray dried
products. There was also a tendency for pH to decrease
slightly when the egg powder had been instantized. None of
the egg powders showed an increase in pH after the whole

egg powders had been instantized.

Dispersibility

The foam spray dried egg products usually showed a
slight increase in dispersibility over the conventional
spray dried egg products (Table 5). The instantized whole
egg products for all spray drying methods had a lower dis—
persibility than the non—instantized egg products. The
second instantizing treatment did not appear to affect

dispersibility.

Bulk Density

 

A very marked difference in bulk density was noted
between the conventional spray dried and the foam spray

dried egg products as shown in Table 6, with the foam spray

24

TABLE 4. pH of egg samples spray dried and treated by

different procedures

 

 

 

 

Spray drying method Number of times instantized
0 l 2
pH
Conventional 8.6 8.5 8.6
I 8.8 8.6 8.6
II 8.8 8.4 8.5
III 8.8 8.7 8.6
IV 8.8 8.8 8.8

 

25

TABLE 5. Dispersibility of egg samples spray dried and
treated by different procedures

 

 

 

 

Spray drying Number of times instantized
method 0 l 2
Per cent dispersed1
% - range % - range % - range
Conventional 93.5 i 0.9 92.9 i 0.3 92.4 i 0.8
I 96.1 i 1.0 94.7 i 0.9 95.6 i 0.9
II 97.0 i 1.0 94.3 i 1.0 95.4 i 0.5
III 96.3 i 1.2 94.2 i 0.9 92.0 i 1.0
IV 96.6 i 1.0 96.1 i 0.9 92.5 i 0.2

 

Each figure is the mean value from 3 samples

 

26

TABLE 6. Bulk density of egg samples spray dried and
treated by different procedures

 

 

Spray drying

Number of times instantized

 

 

 

method 0 l 2
gram/m1l
g/ml - range g/ml - range g/ml - range
Conventional .27 i .006 .30 i .003 .31 i .005
I .12 i .002 .12 :_.003 .12 i .003
II .11 i .002 .13 i .005 .14 i .005
III .13 i .005 .14 i .005 .14 :_.005
IV .09 i .004 .10 i .002 .10 i .002
1

Each figure is

the mean value from 3 samples

27

dried product having a much lower bulk density. All spray
dried treatments increased in bulk density when the pro-
ducts were instantized. The treatment resulting in the
lowest bulk density was that in which high nitrogen and a
0.0292 inch orifice Opening was used (spray drying method
IV). The products foam dried under low nitrogen exhibited
a slightly higher bulk density than those dried under high

nitrogen and using either nozzle size.

Filtration Rate

 

Preliminary observations indicated considerable dif— A w
ferences in filtration times between samples. Actual rates,
as measured by the time required for the first 10 ml of
filtrate to pass through the filter paper in the solubility
test, indicated great differences among the samples as shown
in Table 7. The filtration times varied markedly frOm 7 to
164 minutes. The shortest times were noted when the non-
instantized egg products were filtered. The four foam spray
dried egg treatments had filtration times of about 10 min-
utes in comparison with an average of 68 minutes for the
conventional spray dried egg product. The filtration times
for the foam spray dried instantized egg products increased
up to 1100 per cent over the corresponding non-instantized
foam spray dried egg powder. The greatest increases were
recorded for the low nitrogen samples (spray drying methods
I and III). Instantizing twice appeared to further increase

the filtration times for all spray drying methods. The

 

28

TABLE 7. Time to collect 10 ml filtrate of egg samples
spray dried and treated by different procedures

 

 

 

 

 

Spray drying Number of times instantized
method 0 l 2
Minutes1
Min - range Min - range Min - range
Conventional 68 i 5 78 i 7 81 :j 7
I 10 1.1 95 1’ 8 150 i 10
II 10 i_l 45 1' 4 54 i 5
III 10 :,2 124 i 10 164 1’13
IV 7 i l 43 i 5 72 i 6
1

Each figure is the mean value from 3 samples

29

smallest per cent increase in the filtration time when com-
paring the instantized products with the non-instantized
egg products was found in the conventional spray dried egg

products.

Particle Size

 

Particle sizes of the dried egg products, as calcu-
lated from the Coulter Counter data, were categorized as
follows: weight per cent 1) 90 microns and above, 2) be-
tween 60 and 89 microns, 3) between 30 and 59 microns and
4) less than 30 microns. The majority of the conventional
spray dried product measured in the 30-59 micron range with
very little of the product above 90 microns as is shown in
Table 8. When the whole eggs were foam spray dried there
was a noticeable decrease in the 30-59 micron range with
the increase coming in the above 60 micron range. That
portion of the product measuring less than 30 microns did
not vary greatly due to treatment. Instantizing did not
appear to affect the particle size distribution in any of
the spray dried products obtained in this study, thus it
appears little, if any, instantizing (agglomeration) took

place.

Observed Dispersibility

The percentage of foam spray dried non-instantized
egg products dispersed (as measured by this method) was

higher than that of the instantized foam spray dried egg

30

TABLE 8. Particle size distribution of egg samples spray
dried and treated by different procedures

 

 

Spray drying Number of times instantized
method 0 1 2

 

Weight per cent less than 30 micronsl/
Wt.% - range Wt.% - range Wt.% - range

 

 

 

 

Conventional 12 i l 14 i 1 l6 :_1»
I 14 i l 15 i 1 14 i 1
II 10 1 1 15 i’l 11 i.1
III 9 i l 13 :_1 9 1’1
IV 11 i.1 12 i 1 9‘: 1
Weight per cent from 30-59 micronsl/
Conventional 69 i 2 68 i 2 65 i 2
I 39 i 1 37 i l 39 :_1
II 37 i.1 44 i 1 41 i 1
III 40 i 2 38 i.1 38 i 1
IV 37 i 1 37 i l 33 i 1
Weight per cent from 60-89 micronsi/
Conventional 18 i 1 16 1’1 15 i l
I 30 i.1 31 i l 29 i 1
II 34 i l 27 i 1 30 i 1
III 37 1,1 31 i 1 33 i 1
IV 37 i l 33 1’1 35 i 1
Weight per cent 90 microns and abovelf
. 2/ 2/ 2/
Conventional l :.—- 2 i — 4 i_-
I 17 i’l 17 :_1 18 :,1
II 19 i’l 14 i l 18 i 1
III 14 i 1 17 i 1 20 :.1
IV 15 i 1 18 i 1 23 i 1
i/Each figure is the mean value from 3 samples
2/

— Less than 1 per cent

31

products. A few lumps of the instantized dried egg products
remained on the surface of the water after stirring, but
these lumps or clusters of egg particles became dispersed

in the solution when they were stirred again after standing
several minutes.

The conventional spray dried egg products sank the
fastest with the foam spray dried non-instantized egg powders
second but much slower than the conventional spray dried
egg powders. At the end of 4 hours, nearly all of the con-
ventional spray dried egg product had sunk below the surface
of the water. Dried egg from all foam spray drying methods
except for method III showed the non-instantized powder with
greater sinkability prOperties than the instantized foam
spray dried egg powders. Product from spray drying method
III appeared to have the same sinkability characteristics

regardless of the number of times instantized.

DISCUSSION

One of the major problems encountered in handling
dried egg products is related to their lack of "flowability."
The treatments used in this study (foam spray drying and
instantizing) were believed to affect this product
characteristic.

Foam spray drying has been reported as increasing
particle size, which should improve flowing properties of
the dried product. In this study, the desired flowability
was not achieved as was shown by a failure to sieve the
whole egg powder using the RoTap Shaker.

It was felt that foam spray drying and instantizing
should increase particle size. However, in this study
instantizing whole egg powder under the conditions used
did not appear to increase particle size, as shown by the
results from the Coulter Counter analysis. Perhaps the
conditions for instantizing whole egg powder should differ
from the conditions used for milk powders. In view of the
observation that the total solids content decreased only
slightly, perhaps more steam or.a wetting agent-should be
tried, or the colloidal silica gel method as suggested by

Forsythe (1964).

32

 

33

The decrease in total solids after instantizing was
not as great as had been reported by Mori and Hedrick (1965)
using dry milk solids. It is possible the higher fat con-
tent Of the spray dried whole egg product did not allow as
much moisture to penetrate the egg particles in comparison
with the milk powders. If the egg particles did not become
very wettable this could account for the little difference
in particle size before and after instantizing.

The reason the solubility of egg powder was decreased
after instantizing as shown in spray drying methods I, II
and III, is not known. Comparisons among the total solids
content, particle size distribution, bulk density and dis-
persibility do not appear to provide an answer. The de-
crease in pH is more apparent between the non-instantized
and instantized products in all the spray drying methods
although the differences are slight.

The great variation in time required to collect the
first 10 ml of filtrate in the solubility study is appar-
ently not related to other results, including the egg powder
solubility. There did not appear to be any clumps of parti-
cles remaining on the filter paper after filtering.

The results in the dispersibility tests were rela-
tively high, although Miller 35 31. (1959) reported results
greater than 95 per cent dispersed using a slightly differ-
ent method and only using conventional spray dried egg
powders. Downs (1966) reported that on several occasions

results were obtained in excess of 100 per cent. Mori

 

34

(1964) reported a maximum of 48 per cent dispersibility
when testing instantized milk powders using another method.

The decrease in bulk density of products foam spray
dried was expected, since the nitrogen was incorporated into
the liquid whole egg before drying. The increase in bulk
density after instantizing was also expected since total
solids content normally decreases when the egg powder is
instantized.

The instantizing procedure used in this experiment
following the spray drying Operation for whole eggs does
not appear to be worth-while, since both solubility and
dispersibility decreased. Instantizing the whole egg powder
had little effect on the particle size distribution, bulk
density or the apparent flowability of the egg powder.

Based on review of all data obtained, foam spray
dried whole egg powder has increased solubility, larger
particles, decreased bulk density and is slightly more
dispersible than the conventional spray dried whole egg
powder.

It would also appear that a powder with a high fat
content such as whole egg powder, needs further research
before the desired flowability characteristics can be im-
proved without the addition of such products as a colloidal

silica gel preparation.

 

10.

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"IIIIIIIIIIIIIIIIII