WAGNER, BISSETT, BERRY: FOAM-MAT POWDERS
Table 1.
311
Evidence for identity of compounds separated from extracts of
orange concentrate and foam-mat powders*
Color
UV fluorescence
Rf
Compound
anis-
orig | acid | base
aldehyde
Heptamethoxy-
#80
.80
flavone
Spot #1
Nobiletin
Spot #2
o71
Sinensetin
.63
.63
Spot #3
f
ro
f
ro
v
dy
w
dy
w
by
bw
v
by
bw
Other evidence
y
uWmax. 3*H> 270,253
y
UV max. 333/270,250,209
y
y
UV max. 328,264,240
UV max. 328,265,240
b
b
IR spectrum of known
and unknown identical
y
UV max. 3^0,270,253
y
UV max. 329/269,249,208
f3-sito8terol
glycoside
,23
Spot #5
a/
"~
.23
All UV spectra determined in ethanolo
Fluorescence and color code: f - fluorescent, w - white, ro - red
orange, dy - dark yellow, by - bright yellow, bw - blue white,
y - yellow, b - blueo
2.
Bobbitt,
J.
M.
1963.
Thin-layer
chromatography.
Reinhold Publishing Corp., N. Y. pp. 88.
3.
Bissett, O. W., J. H. Tatum, C. J. Wagner, Jr., and
M. K. Veldhuis.
1963.
Foam-mat dried orange juice.
I.
Time-temperature drying studies. Food Technol. 17:92-95.
4.
Hay, G. W., B. A. Lewis, and F. Smith. 1963. Thinfilm chromatography in the study of carbohydrates.
J.
Chromatog. 11:479-86.
5.
Kagi,
H.,
and
K.
Miescher.
1939.
Steroids.
II.
A
new color reaction in the steroid series. Contribution to its
chemism. Helv. Chim. Acta. 22:683-97.
6.
Lawler, Frank K.
1962.
Foam-mat drying goes to
work. Food Eng. 34(2) : 68-69.
7.
Stahl, E., and U. Kaltenbach.
1961.
Dunnschicht-
chromatographie-spurenanalyse von zuckergemischen auf kieselgur g-schichten. J. Chromatog. 5 :351.
8.
Sjogren, C. N.
1962.
Practical facts of foam-mat.
Food Eng. 34(11) :44-47.
BULK DENSITY AND RECONSTITUTION RATES OF
FOAM-MAT DRIED CITRUS POWDERS1
Charles J. Wagner, Jr., 0. W. Bissett and
Robert E. Berry
U. S. Fruit and Vegetable Products Laboratory2
Winter Haven
The foam-mat process is a dehydration method
which is finding increased usage among proces-
sors for the production of high quality fruit and
vegetable powders.
lemon powders in two plants in California (5, 6).
Processors have shown much interest in its use
for
other products.
culture.
2One of the laboratories of the Southern Utilization Re
search and Development Division, Agricultural Research
Service, U. S. Department of Agriculture.
References to specific products of commercial manufac
ture are for illustration only and do not constitute endorse
ment by the U. S. Department of Agriculture.
One
of the advantages
of
foam-mat dried powders is the reduction in ship
ping weight. Also, shipping and storage requires
no refrigeration.
lCooperative research of the Florida Citrus Commission,
and Southern Utilization Research and Development Division,
Agricultural Research Service, U. S. Department of Agri
It is presently being utilized
commercially for the production of tomato and
If
the bulk
density
of
these
dried powders could be increased, the additional
advantage of reduced shipping volume could be
realized.
In previous
studies
it has been found that
upon reconstitution of juice from these powders,
a milky, unnatural appearance sometimes occurs
FLORIDA
312
STATE
HORTICULTURAL
SOCIETY,
1964
especially with powders made using certain types
heated to the desired temperature.
of foaming agents. The foaming agents which
cause this effect, however, offer considerable ad
vantage in ease of moisture removal from the
foam and thus their use is often desired. This
unnatural appearance is caused by the disper
sion of microscopic bubbles of gases throughout
the solution. These bubbles were included in the
the powder had reached the desired temperature,
powder during the formation of the foam, and
were retained during subsequent dehydration (3).
weighed. From this measurement the final bulk
A method for increasing bulk density would serve
rate was also determined as described below.
to eliminate some of this included gas and thus
improve the appearance of the reconstituted juice.
This report indicates the results of applying
temperature and pressure to foam-mat dried
powders to increase the bulk density and the
effects of this increased density on solution rate
and appearance. Two methods were studied for
applying heat and pressure to the powders. These
were based upon the use of a hydraulic press and
a double drum dryer, respectively. The methods
were studied as applied to both orange and grape
fruit powders prepared on a belt-type foam-mat
dryer. The data derived should serve as a guide
for those interested in processes for increasing
bulk density of powders. This process is appli
cable to the so-called glassy-structured food
stuffs of high sugar content. Obviously, it would
not be very effective for dried products such as
milk and potatoes which do not have a melting or
transition point.
As soon as
it was removed and placed on the hydraulic press
and pressure applied for the desired amount of
time.
was
Upon removal, the
pressed
observed for indications
orange cake
of burning.
and
a
150
density
cc
container
in g/cc
was
Drum Dryer.
of
the
determined.
powder
The
All powders used in this study were prepared
by methods described by Bissett et al. (2) and
Berry et al. (1). Of the powders used in these
experiments, some were prepared using a modi
fied soya albumin foam stabilizer with Methocel
(10 cps) referred to herein as MSA/MC and
some using glyceryl monostearate (GMS) foam
After preliminary experiments
ted for further experimentation according to a
method developed at the Western Regional U. S.
D. A. Laboratory in Albany, California 3, 4). A
laboratory atmospheric
obtained from
double-drum dryer was
Blaw-Knox,
Buffalo,
New York,
and adapted with a controlled temperature circu
lating water-glycol system for heating the rolls.
A hopper with a small roller at the bottom was
positioned to feed a thin curtain of powder into
the nip of the drums. The drums were chromium
plated cylinders 6 inches in diameter and 8 inches
long. For most experiments a release agent was
required and several different devices were tried
for applying it.
Release agents were applied by
hand using a cloth, by saturation of a felt strip
which
contacted
the
drum
surface just behind
the doctor blade, by use of a canvas strip which
was inserted into a small trough of the release
wick feeder and the neoprene wiper blade gave
smooth and uniform application. The wick feeder
worked well with low viscosity release agents, and
the neoprene wiper worked well with those of a
higher viscosity.
The pressure exerted upon the
powder was adjusted by varying the opening be
tween the drums.
Best results were obtained at
Maximum pressure obtainable, i.e., with drums
set at minimum clearance, 0.002 inch.
screen.
rotation
An attempt was made to densify dried
grapefruit in the form of dried "sticks" as it
comes off the belt dryer (1, 2). This was not
successful with either foaming agent.
For
preliminary
solution
with the hydraulic press, a drum dryer was adap
stabilizer. All powders were ground in a labora
tory corn-mill and sieved through a 20-mesh
Press.
was
agent and acted as a wick feeder, and by use of
a thin neoprene rubber wiper blade. Both the
Experimental
Hydraulic
The
cake was then ground in a laboratory corn-mill
determi
nation of the effects of applying pressure and
All data
in Tables were obtained with this setting.
speed
was
4
rpm.
With
Drum
grapefruit
powders the solution time was determined on both
the total
(composite)
ground powder from the
laboratory corn-mill, and on the sieved —20 mesh
fraction. For solution times with orange powder,
because the —20 mesh fraction had required less
heat to foam-mat dried orange powder, a Carver
solution time, all powder was ground to pass 20
hydraulic press was utilized.
mesh sieve.
The orange powder
The through put rate is dependent
was weighed into a shallow pan and a screed was
used to form a layer of the desired depth. The
on the feed rate which was controlled by visual
pan of powder was then placed in an oven and
3-5 lbs. of powder per hour were densified.
observation. In these experiments normally about
WAGNER, BISSETT, BERRY: FOAM-MAT POWDERS
Solution Time.
For the determination of solution time the
juices were reconstituted to the approximate
strength of natural juices as follows: 900 ml of
6° C water were measured into a container and
99 g grapefruit powder, or 126 g orange powder,
were placed into a clean dry beaker. The water
was poured onto the powder with rapid stirring.
A stopwatch was started when the water was
poured and stopped when there appeared to be
no
remaining undissolved particles. After de
termination of solution time, the appearance of
the juice was judged for nearness to the appear
ance of natural juice by three judges.
Results and Conclusions
Generally, it was found possible to increase
bulk density of foam-mat dried citrus powders
both by using the hydraulic press and by using
the double drum dryer. The dryer was more effec-
Table 1.
Conditions for increasing bulk
density of orange powders
using double drum dryer
Drum
temp*
Release agent
64
Myverol 18-00
Bulk density*/
g/cc
0o5^
0.66
0.80
0.57
0.59
0.58
•c
67
69
69
75
70
Ityverol
Myverol
Myverol
Jfyverol
18-00
18-00
18-00
18-00
Atmos 300
-'Original density was 0.307 g/cc.
313
tive for increasing density and did not appear to
alter the quality of the citrus powder to any great
extent. Very little increase in density could be
achieved on the hydraulic press without obvious
darkening. Using the hydraulic press, the tem
perature had to be kept below 70° C and the time
below 4 minutes to prevent burning of the pressed
cake. On the other hand, as is shown in Tables
1 and 2 it was possible to use temperatures above
70° C when densifying was carried out on the
drum dryer. This is probably due to the fact that
the exposure time was shorter. With foam-mat
dried powders which had been prepared using a
GMS stabilizer, no release agent was required
to assist removal from the drums. For those
prepared using MSA/MC foam stabilizers, how
ever, there was considerable tendency to stick
to the rolls and a release agent was required.
The release agent was applied at a level of 0.1%
(solids basis) or less. In Tables 1 and 2 some
of the release agents used are listed. Hydrogenated vegetable oil and cottonseed oil were
also tried and found unsuitable. In almost all
cases the densifying treatment on the double
drum dryer resulted in increase of bulk density
by double or more.
Thus, as seen in Table 1, orange powders were
increased from a bulk density of about .30 to
around .60 g/cc or more, and as indicated in
Table 2 grapefruit powders made from GMS
foams increased from .18 to .67 g/cc, and grape
fruit powders using MSA/MC foams were in
creased from .28 to greater than .60 g/cc. The
difference in bulk density achieved in the two
runs made at 69° C was probably due to a differ
ence in rate of feed which was not rigidly con
trolled.
Table 2.
Conditions for increasing bulk density of grapefruit powders using
double-drum dryer.
Drum
Release
Powde:
temp *C
GMS
71-72
MSA/MC
MSA/MC
MSA/MC
MSA/MC
MSA/MC
agent
None
69-72
Atmos 300
6l
Myvacet 9-^0
72
72
72
Myverol 18-98
Myverol 18-71-E
Myvacet 9-4o
.
Densifying
characteristics
Excellent
Good
Very good
Very good
Very poor
Fair
Bulk£'
density g/cc
"O751
0.60
O.65
0.60
mm
mm
0.6l
-'MSA/MC powders contained 1# foam stabilizer, and GMS powder contained
1.5#, total solids.
-'Original densities: GMS powder .18 (Glyceryl monostearate stabilizer).
MSA/MC powder .28 (Modified soya albumin/Methocel
stabilizer).
314
FLORIDA
STATE
HORTICULTURAL
Table 3 compares the solution times of several
SOCIETY,
1964
ange powders prepared using different foaming
powders densified on the double-drum dryer using
agents.
different
fied powders of each type.
were
release
determined
agents.
These
on
total
the
solution
ground
times
powder
(composite) in some cases and on the sieved —20
mesh
powder
fraction
in
others.
Where
they
Original powders are compared to densi
The appearance of
both the powder and the reconstituted juice was
also judged.
Although the densifying treatment
increased the time for reconstitution somewhat, it
were compared, the —20 mesh fraction required
also resulted in improvement in appearance of
less time for solution than the composite fraction.
both the powder and the reconstituted juice.
The improvement in appearance was more strik
ing with powders made from GMS foams than
with those made from MSA/MC foams. This gen
Whereas the solution times for the undensified
control powders were less than 60 seconds, the
densified samples required from 2 to 3 times this
amount of time for solution.
Table 4 gives a comparison of bulk densities
and reconstitution times for grapefruit and orTable 3.
Solution times of orange and grapefruit
powders densified on double-drum dryer
using different release agents,
Time
Powder^/
Release agent
Not densified
MSA/MC
msa/mc
msa/mc
msa/mc
Not densified
Myverol 18-98
Myverol 18-71-E
Myvacet 9-1*0
7mc
Not densified
Myverol 18-00
Myverol 18-85
msa/mc
MSA/MC
for
solution
(sec;
-20 Mesh
Composite
kQ
53
231
210
121
y
55
no
150
120
AtmoB 300
total solids.
MSA/MC: Modified soya albumin/Methocel stabilizers
used, 1.1$ total Bolide.
Because the -20 fraction of grapefruit powder gave
better solution rates than the composite, all orange
powders were ground to -20 mesh before testing.
Table k.
had a more brilliant orange color and the re
constituted juice was more natural in appearance.
While nondensified powder produced many par
ticles which floated during reconstitution, all par
ticles in the densified powder sank. The densified
powder thus resulted in improved appearance
during reconstitution, as well.
Summary
128
128
2^9
-' (»©€ Glyceryl monostearate stabilizer used, 1<,5#
—'
eral trend has been observed in both grapefruit
and orange powders. The densified orange powder
It has been shown that the appearance of both
orange and grapefruit powders prepared by foam-
mat drying, as well as the appearance of the
juice reconstituted from them, can be improved
by increasing the bulk density of the powders
through the application of heat and pressure.
Using a double-drum dryer adapted for the pur
pose, the bulk density of these powders was more
than doubled. This increase in bulk density would
provide a shipping and storage space advantage.
Comparison of bulk densities and solution rates of densified
and control powders prepared with different foaming agents.
Bulk
^ype
powder
Sample
density
g/cc
Grapefruit
GMS
AMG
Control
• 18
Densified
•73
• 16
.60
.28
Control
Densified
MSA/MC Control
Densified
MSA/MC Control
Densified
GMS:
Reconstitution
time
Appearance
Powder
Recon.juice
sec.
60
V. white
Cloudy, foamy
Light
Pair
89
Light
Light
Fair
SI. milky
Fair
Good
Lt. yellow
Excellent
55
V.lt.yellow Fair
l6l
59
93
.67
123
.31
e66
no
Glyceryl monostearate stabilizer used/
Orange
Excellent
1*0$ total solids*
AMG: Acetylated monoglyceride stabilizer used, 1*0$
total solids*
MSA/MC: Modified soya albumin/Methocel stabilizer used, 1,0$
solids.
total
HAYWARD AND EDWARDS: DIPHENYL RESIDUES
315
Using a drum dryer, temperatures as high as
ing the adaptation and use of the double-drum
70°
dryer.
C can be used for
densifying orange and
grapefruit powders without discoloration.
glyceride
derivatives
are
effective
Mono-
as
release
agents during the densifying operation.
Recon-
stitution time is increased somewhat by the densi
fying operation.
Acknowledgment
The authors would like to thank
Dr. A. I.
Morgan, Jr., and Mr. R. P. Graham of the West
ern Regional Research Laboratory, Albany, Cali
fornia, for their advice and suggestions concern
LITERATURE CITED
1. Berry, R. E., O. W. Bissett, C. J. Wagner, Jr., and
M. K. Veldhuis 1964. Foam-mat dried grapefruit powders.
Food Technol. In press.
2. Bissett, O. W., J. H. Tatum, C. J. Wagner, Jr., M.
K. Veldhuis, R. P. Graham and A. I. Morgan, Jr. 1963.
Foam-mat dried orange juice. I. Time-temperature drying
studies. Food Technol. 17:92-95.
3. Graham, R. P., M. R. Hart and A. I. Morgan, Jr.
1964. Foam-mat drying citrus juices. Abstracts of 24th An
nual Meeting of Institute of Food Technologists, No. 29.
4. Graham, R. P., L. F. Ginnette and A. I. Morgan, Jr.
1963. U. S. Patent No. 3,093,488 Preparation of stable de
hydrated products.
6. Lawler, Frank K.
1962.
Foam-mat drying goes to
work. Food Eng. 34:68-69.
6. Sjogren, C. N.
1962.
Practical facts of foam-mat.
Food Eng. 34:44-47.
SOME FACTORS AFFECTING THE LEVEL AND PERSISTENCE OF
DIPHENYL RESIDUES IN CITRUS FRUITS
F. W. Hayward and G. J. Edwards
Experimental Methods
Florida Citrus Experiment Station
Fruit.—The
periment
The legal tolerance of 110 ppm for diphenyl
in oranges, lemons, and grapefruit
(6)
was ex
tended by the U. S. Food and Drug Administra
tion in 1960 to all citrus fruits
(7).
Previous
work at this Station (2) indicated that prolonged
storage
at
high
temperatures
might
produce
residues of diphenyl in excess of the legal tol
erance in tangerines and a few other citrus va
rieties.
Since the
packer
has
no
control
over
time and temperature of storage after the fruit
is shipped, methods of limiting diphenyl residues
other than by regulating holding conditions are
required.
Rygg et al. (4) found that lemons, placed in
open
trays,
lost
diphenyl
quite
rapidly
while
other citrus fruits lost it more slowly (5). Grierson et al.
(1)
found that decay of Dowicooled
oranges was controlled by the residual effects of
previous diphenyl treatment after the fruit was
removed from the diphenyl pads to open crates.
These experiments were designed to determine
to
what
extent the
diphenyl
residue
levels
in
citrus fruits could be controlled by regulating the
number
of pads
used in
each carton.
Studies
were also made of the effects of a solvent-type
protective coating on the absorption and reten
tion of diphenyl by citrus fruits.
Florida Agricultural
No. 1978.
citrus
fruits
for
these
experi
ments came from the groves of the Citrus Ex
Lake Alfred
Experiment Stations Journal
Station.
Two
series
of
experiments
were made using five citrus varieties;
Hamlin
and Valencia oranges, Duncan and Marsh grape
fruit and Dancy tangerines.
Packinghouse
Treatments.—All
fruit
were
washed, dried, and coated with "Flavorseal 93"
before packing except for certain samples that
were packed without waxing.
Packing.—All fruit were packed in standard
bushel telescope cartons with hand
four-fifths
holes.
The
diphenyl pads used each contained
2.35 grams of diphenyl.
Series A.—This comprised five single-carton
treatments of each of the five varieties, diphenyl
treatments being:
1. Control —no diphenyl pad.
2. One-half diphenyl pad in bottom.
3. One-half pad on top and one-half pad in
bottom.
4. One-half pad on top and one full pad in
bottom.
5. One pad on top and one pad in bottom.
Series B.—This series compared waxed and
unwaxed fruit with replicated samples of a single
diphenyl
treatment.
Single
carton
treatments
were as follows:
1. Unwaxed—control—no diphenyl pads.
Series
2. Unwaxed—one
one in bottom.
diphenyl
pad
on
top
and