A STUDY OF NEWER METALS USED
FOR QUANTITY COOKERY UTENSILS

TEENS F‘CE TE! DEGREE U? M. S.

Marcia Slipher
1931

 

 

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.Aag...a.:.4 A)

F 0};

A thesis
State College

ments for the

A STUDX OF NELER LETALS USED

QUAETITY CUOELRY'UTiNSlLS

submitted to the Faculty of Michigan
in partial fulfillxent of the require-

degree of Easter of science.

BY

harcia Slioher
M.-

Department of institution Kanagement

Division of home Economics

1931

Acknowledgements

The writer wishes to acknowledge with grati—
tude the helpful advise and criticisms given by

hrs. habelle Ehlers and Dr. karie Dye.

- b _
103804.

11.

Contents

introduction

A. Object of Study

5. Review of Literature

C. ethods Used in taking the Study
D. bource of information

Letals Used in tte rabr ication of

Cool :ing Utensils

A. l‘IiSl‘ OI’Y
n. Leta ls Used for Institution Cooking
1. Dec crea.se in Use of corm er,
anamel and Retirned Steel
2. Present trends in metals used
for institution cooking
C UL? oarison of Aluminum, Stainless Steel
and onel Letal for Quantity Use
A. Boiling gxneriments
B. Baking Experiments
C. Steaming gxnerinen nts
D. :teamtahle ixperiments
3. Chemical Experiments
Discussion
A. Results of boiling} Xperin ents
B. Results of Baking Exteriments
C. Results of Steaming Exteriments
D. Results of Steamtable Experiments
i. Results of Chemical fixperiments
F. :nrxnary

Conclusions
Bibliography

<o~1< O)NPAFJH

ll

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29

I. INTRODUCTION

A. Object of Study

Of recent years more consideration has been
given the materials used in cooking utensils than
for hundreds of years preceding. There are several
reasons for this sudden interest in the materials
in which our foods are cooked. The standards of
proper food preparation are growing more exacting so
that we are inquiring whether a given metal or com-
bination of metals is deleterious in any respect to
the food cooked in it. Institutions have become
vitally interested in more efficient and hence more
economical production of cooked foods, and have
ceased to accept without question the utensils which
tradition prescribed. If some newer metal or alloy
made a cheaper or a more durable utensil the insti-
tutions have been ready to try it out. some of the
metals which have been tried out in recent years
with a View particularly to their use in cooking
utensils for institutions are: aluminum both cast
and Spun, nickel, stainless steels, and konel ketal.
Many aluminum alloys have been experimented with and
also various modifications of the original stainless
steel.

ihis study was undertaken to determine the com-
parative values of aluminum, one of the stainless
steels, and monel metal first as to the speed of

cooking, second as to discoloration of the utensil,

_ 1 -

third as to discoloration of the food, fourth as to
the effect on the flavor of the food, and fifth as
to the solubility of the metal container in the al-
kalis or acids in the liquor from the boiled foods.
A sixth consideration was a comparative study of
aluminum and stainless steel steamtable jars with
the more usual steamtable jar of earthenware or
vitrified china to determine holding quality. This
study gives consideration only to conductivity of
heat, effect of the container upon the food and the
effect of the food upon the container. The cost and
the durability of aluminum, monel metal, and stain-
less steel would give excellent Opportunity for
further study. Monel metal and stainless steels are
so new in their use as cooking utensils that little
information on their length of life in relation to
their price is to be obtained.

B. Review of Literature.

In reviewing the literature little can be found
which has any direct bearing upon the present in-
vestigation. The materials studied, with the ex-
ception of aluminum, are little used for cooking
purposes outside of institutions. The literature
is chiefly confined to articles published in in-
stitution magazines and advertising booklets of the-
metal manufacturing companies. Numerous metallur-
.§ical books deal with the properties of these metals,
tut have little direct connection with their use in

cooking utensils.

1. Aluminum

”Things you should know about

In the article
aluminum" in The American Restaurant kagazine, July,
1929, the discovery and process of manufacture of
aluminum is discussed in detail ending with the fol—
lowing summary: "From every viewpoint, lightness,
economy in first cost, and economy due to extremely
long life, economy in fuel due to heat-conducting
and heat-retaining qualities, and finally in safety
from all harmful action of food acids, aluminum
utensils for cooking are in keeping with the modern
progressive and scientific spirit of the twentieth
century." (1)

Booklets advertising different makes of aluminum
utensils tell the history of its manufacture (2) and
the qualities which make it give enduring service in
kitchens. There are three main reaons why aluminum
is able to present an attractive argument to buyers:
Its comparative lightness, comparative cheapness and
resistance to attack by fruit and vegetable acids.

2. Stainless Steels

Few magazine articles have been published about
stainless steels because their use in institution
kitchens is so new. The home Economics news, October,
1950 has an article by Doris fl. chray, which de—
scribes AIIegheny metal as a stainless, easily cleaned
ware having no effect upon food cooked or stored in it. (5)

kany booklets published about Allegheny steel

1

and Enduro describe their ”Shiny surfa e, the ease with

_ 5 -

which they can be cleaned and kept clean, and their
immunity to all forms of food and fruit acids.” (4)

5. konel ketal

Two very similar articles describing the manu-
facture of Konel metal by the International tickel
Company were published, one in The American Restau-
rant Kagazine, (5) June, 1929, and the other in The
hotel honthly, (6) August, 1950. ”In the hotel and
restaurant business the name konel ketal has become
synonymous with quality, durability and clean, shining
surfaces for kitchen equipment.” (6) ”Today the
restauranteur point with equal pride to the 'front'
and the 'back' of his house. bright shiny equipment
has made the kitchen a place of beauty, pleasant to
look at and more pleasant to work in, maintenance
and replacement costs have been reduced to a minimum
and the kitchen is no longer eating up the profits." (5)

The International Nickel Company has published
numerous illustrated booklets telling of the manu-
facture and uses of Monel hetal. ”Twenty Years of
konel Metal” by Robert C. Stanley gives the many
improVements made upon the metal since its discovery
in 1905. (7) In "Lodern kitchens” (8) attractive
illustrations of the metal are shown and an article
explaining its desirable characteristics is printed.
lhe unusual combination of properties found in Monel
Letal results in definite economies: saving in

cleaning, repair, replacements, and depreciation. (8)

- 4 -

C. Lethods Used in Raking the Study

The methods used in making this study consisted
of a survey of the common metals used in cooking
utensils, and of observing foods cooked by various
methods in containers made of aluminum, stainless
steels, and monel Letal.

1. Survey of metals used in cooking utensils.

Evidently little has been recorded during the
past few centuries about the utensils used for cock-
ing. Archaeologists tell in some of their writings
about the means of cooking by primitive man. Care-
ful reading of many books on medieval history and on
EurOpean modes of living gave some information on
the use of copper. ancyclopedias were studied as
the best source for information on enamel ware, tin,
iron, andzmfijnned steel, and oldcnok books published
in the latter part of the nineteenth century recom-
mend the use of such containers.

Laterial about the later metals; such as alum-
inum, nickel, stainless steels, and konel metal in
cooking utensils was easily obtained from the manu-
facturing companies and from a few magazine articles.
These were read to determine the methods of manu-
facture and the advantages and disadvantages of each
material.

2. The cooking of foods

Various foods were boiled, steamed or baked in
the metal containers and scored by judges for tender-

ness, texture, color, flavor, and in the case of

creamed foods for the lack of curdling. Aluminum and
stainless steel containers were used for the boiling
of vegetables. Lonel netal was omitted in this

series of experiments as a container of this metal

for boiling foods is not manufactured. Baking and
steaming experiments on these same kinds of vegetables
were carried out using stainless stee , aluminum and
Lonel metal utensils. Cooked foods were placed in
vitrified china, stainless steel and aluminum jars

and kept on the steamtable for two hours to determine

lative time when deterioration sets in and the

1)

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rapidity of such deterioration. Creamed foods and
mashed potatoes were used as they curdled or deteriorated
more rapidly than do others.

5. Chemical tests

Liquor from the foods boiled in aluminum was
tested chemically to determine whether there was a
solvent action upon the metal. samples of the foods
darkened by steaming in nonel Letal were ashed and
tested chemically for the presence of COpper and nickel.
D. source of Information

Little information pertaining directly to the
present investigation could be secured fr m sources
other than advertising books or interviews. Although
experience has taught individuals the effects of these
newer metal containers upon foods, no data has been
collected, organized, and published.

Booklets from the International hickel Company,
allegheny Steel Company, Republican steel Corporation,

_ 6 _

and the Aluminum Cooking Utensil Company give definite
information as to the procedure of manufacture of the
metal, and the proper gages for cooking utensils. The
prOperties which make the different metal containers
desirable were discussed. Illustrations of the
utensils we e used showing its many styles at various
prices. luch reliable information was obtained from
these sources.

an interview with hr. Addison, Chairran of the
board of Directors of the etearnes Company, an insti-
tution equipment firm, furnished further interesting
information. ne has done some experimental cookery
using different kinds of metals for utensils in
steaming foods. £8 was kind enough to give his
results from his study and also sore effects of
cooking foods in metal utensils which had been given
him by his customers.
II. LETALS USLD In Tn;.FALHICATIOA OF COOLIEG UTENSILS
A. history

The earliest cookery was probably accomplished
without the aid of any utensils, the food being roasted
by burying it in hot ashes or cooked by the aid of
heated stones. (9) Later wooden vessels carved from
pieces of cedar logs were used for boiling foods.
Hot stones were put into the vessel to heat the con-

tents. Potterv was made from clay and also used for

U

cooking utensils. ”There were an abundance of seething

pots all over the world compose of wood, grass, clay,

or stone.” (10) Of course utensils of such material

could not be placed over a fire but they could be
filled with water and hot stones thrown into the water
uhich heated it sufficiently to cook any food which
might be placed therein. Seething is a term used

to describe this method since it is not quite the

same as boiling.

During the bronze Age people learned how to
smelt cOpper and tin from ores, but it is doubtful
if any of the metal was used for cooking utensils,
since it is known that they considered them valuable
enough for ornaments.

Iron has been used by man for more than 2000
years. AristOtles (584—522h.0.) described the manu-
facture of Indian steel. (11) In ancient times,

5000 B.C. to A.D. 476, food was roasted over the fire
in pots probably made of wood or c0pper. In assyria
and babylonia very elaborate utensils of gold and
silver were used. In medieval times until the reign
of Charlemagne it is useless to try to trace race
characteristics among the hordes which swept down
from northern Europe upon Home. fioman culture was
lost and for food customs one must turn back to
barbaric peOple. (12)

After the Renaissance elaborate utensils of
c0pper, gold, and silver were again used. During
modern times, 1500 to the present, the restaurants
have been developed, and iron and copper kettles used
for cookery. In 1895 alla hellOgg writes in her book
”Science in the kitchen”, ”Modern cookery necessitates

- 8 _

the use of a greater or less variety of cooking
utensils to facilitate the preparation of food.

host of these utensils are manufactured from some
kind of metal as iron, tin, copper, brass or re-
tined steel." (9) Porcelain or granite ware was
introduced in the form of cooking utensils in the
later part of the nineteenth century and was con-
sidered safe and very desirable. Since 1900 great
changes have been made in the kinds of metals used
for cooking utensils and now aluminum has become a
very pOpular metal for containers. Still newer are
stainless steels and Konel hetal made into containers
for cooking foods. So far the two latter are little
used except in institution kitchens. kickel has
been tried in a few institution kitchens, but has
not been very successful.

B. metals Used for Institution Cooking

1. Decrease in the use of COpper, enamel, re-
tinned Steel, Iron and Tin.

From the early restaurants in 1500 to almost
the present time c0pper has been used for cooking
utensils. Containers made of conper are not to
’be recommended because of the discoloration of som
foods and their metallic flavor, although many cooks
esteem them because COpper is a very good conductor
of heat. Copper is very heavy and nowthat women are
being employed in institution kitchens it is being
discriminated against for that reason. It is also

a well-known fact that copper discolors and turns

_ g -

some food green which means that care must be taken
to keep the c0pper refinished and clean. Regardless
of these facts it is still used in many institution
kitchens especially Where foreign chefs are employed
and most jam kitchens use it exclusively.

Tin and iron have been and are still used for
many purposes in institution kitchens, however, not
to so great an extent as formerly. Jhat is called
tin in kitchen utensils is really a sheet of iron
plated with tin. Retinned steel is the same, except
that steel has been used in place of the iron and an
extra heavy coating of tin placed on the steel. Tin
is still used a great deal for such utensils as:
bread pans, pie pans, muffin pans, cake pans, etc.
lron eSpecially cast iron is used today for deep
frying kettles, frying pans, and griddles, but it
has the disadvantages that it is heavy and rusts easily.

Porcelain, enamel, or granite ware are all
sheet iron containers coated with a hard smooth enamel.
Enamel ware of even the highest grade is likely to
be injured by excessive heat which by making the
iron eXpand faster than the glaze cracks the latter.
lt is also liable to be affected by acids whenever
there is the slightest break in the continuity of the
surface of the enamel. Lhen once acid penetrates
the surface so that it can act on the iron underneath,
it will gradually undermine the glaze so that it
peels off. (15) Care must be taken in handling

enamel ware so that bumps do not cause the enamel

to break off. A chipped enamel pan is dangerous to
cook food because the enamel may break off into the
food at any time. Enamelware when intact is a very
satisfactory material in which to cook since there
is no action on the enamel by food acids or alkalis.
It is inexpensive, light in weight and may be very
attractive in color. Since it does not wear well,
however, it is less and less used by institutions.

Retinned steel is used rather more now than
either c0pper or enamelware. Acids do affect the tin
and care must be taken to keep the utensil well
covered with tin or the steel will rust and corrode,
but it still has its place in the institution kitchen.
It is heaview and more expensive than tin or enamel—
ware, but less so than copper or aluminum.

Recently nickel has been tried for utensils in
institution kitchens, because it is not affected by
food acids and alkalis and because of its great
durability. it is very heavy, however, and so far
few institutions have used it.

2. Present trends in metals used for institudon
cooking.

ihree relatively new matals are being made now
to replace the older c0pper, iron, tin, enamel and
retinned steel utensils use in institutions. Alumiinum
has been known and used for several decades, but it

‘31:

is becoming constantly more pOpular due to improvement§””
in its fabrication. stainless steels are alloys
made by several companies each using a different

per cent of composition of steel and chromium.

Only very lately has it been made into cooking utensils.
Konel metal is an alloy metal made from an ore cone
taining Kickel and COpper and is controlled entirely
by ore company in the United States. some types of
cooking utensils are now being made from honel metal
for institutions. It is heavier than aluminum and
stainless steel so is not so desirable as them for
large kettles which must be lifted often.

a. Aluminum.

Aluminum is never found native, but in the form
of oxides. All the cowmercial supply comes from a
clay called bauxite. Aluminum has a great affinity
for oxygen and is covered almost imnediately with an
oxide. In 1824 it was first produced_when Oersted
succeeded in making it hy heating al minum chloride
with potassium amalgam. It was Charles Hall who first
extracted aluminum in commercial quantities from a
clay-like ore. it was in his mother's woodshed, back
of the rambling old homestead in Oberlin, Ohio that

he set out in 1885 to discover a process for making

U

aluminum cheaply. Up to this time aluminum had been
obtaine only with chemicals, slowly and at a pro-
hibitive cost. in February 1886 hall began his new
series of original experiments, passing a current of
electricity through his liquified mixture of clay and
carbon and so produced aluminum. (2) It cost five
dollars a pound until 1887 when inventions in other
fields were applied to aluminum and the cost fell to

twenty cents a pound. (14)

_ 12 -

Aluminum is fabricated in two forms for cooking
utensils; sheets and cast. ”The sheet aluminum is
cut into shapes, round and rectangular, the sizes
being determined by the sizes of the utensils to be
made from them. ihe pieces of sheet metal are taken
to large presses or stamping machines. lhe machines
are provided with a stationary socket, having the form
of the exterior of the utensil to be shaped in it,
and a solid steel die fastened to a moving piston.
The Operator places a piece of sheet metal over the
socket, presses a lever, and down comes the die with
enormous force, stamping the disk into the socket.
Thus the sides and bott m of a utensil are made
without seam or solder-—are one continuous piece of
metal.” (15) Cast aluminum is said by some manu-
facturers to be superior to sheet, because it is

thicker will not dent and h s
’

D'

0 parts upon which

0.3

there is a strain. Aluminum utensils made from

sheets have a strain where the sides are bent up

from the bottom, but cast aluminum avoids this strain
3y being molded. (16) Cast aluminum has been much
improved in the last few years and has a better finish

than was formerly the case. aluminum alloys are being

‘1
D

eXperimented with and some are a,p arin on the

’4'
(
(k

\.

market in the form of cooking utensils having very
desirable properties.

b. Lonel hetal.
he inadvertent pro

”An interesting example of t

duction of a useful alloy is the smelting of a

_ 15 -

nickel-COpper compound, known to-day as German silver,
that t-as smelted in ancient days from a complex

sulfide ore by he Chinese in Yunnan. They made this
alloy, which was named peitung or paktong meaning

white c0pper, in the time of the tou dynasty from

221 3.0 to A.D. 25. "It contained 16% nickel and

80% c0pper. The percent of composition in Germa

silver is very nearly the reverse of that of honel

etal, however, it is interesting to know that an

alloy of co Jper and nickel was made in ancient times.
Jonel Jetal is made only by the international Eichel

Co pany as they have exclusive ri3hts to tne matte

comi in3 from the Sudbury district, Canaia, the only

place it occurs in large quantities. It is a
natural alloy made from refinin3 a nickel-copper ore
instead of separating the reSpective metals. At

first no attempt was made to regulate the amounts

of each metal which went into the alloy, but now

those are made relatively the same for all the re-

fined alloy, being anproximately two—thirds nickel

and one—third cOpper. fhe ore is shipped from Canada

to the refineries in huntington, Zest Virginia for
manufacture. The first step in refining the ore or
matte is to crush it. The matte is then passed into
furnaces of tremendous heat uhich transforms the sulfide
ore into an oxide ore. this ore is then refined by

the electric furnace or onen hearth process much as iron
ore. It is possible to make Ionel metal syntheticall.
but the process is so expensive that it is not practical.

— l4

T

monel hetal is ductile, f exible, and easily
works , and can be readily soldered or brazed. lhe
combined properties of ease to clean, hard dense
surface, and rust and corrosion resistance have made
honel hetal containers desirable in institutions
ealing with food. It is fabricated into sheets

and then made into cooking utensils from these. since
it is necessary to solder the parts of the utensils
together it has not yet been made into round utensils
as steamtable jars and kettles. The gages of honel
metal vary from twenty-five to ten so that it can
be fabricated for many uses. (8)

c. stainless steels
stainless steels are the newest metal alloy used

for institution equipment. "The production of
chromium steel is not by any means new, in fact the
literature of iron and steel metallur3y durin3 the
nineteenth century and the first ten years of the
present century contains many references to the
preparation of chromium steels and to some of their
properties.” (18) An alloy called ferro-chromium

was made in 1876 by haur a Gernan chemist. Alloys of
this type were first produced commercially by Lr.
benno Strauss, of the Lrupp Lork, Essen, Germany.
They have been extensively used in Germany since their
introduction, particularly the well—known alloy VZA,
but until recently have attracted little or no at-
tention in this country. lhe hnduro ware known as

a

1&2 manifactured by the gepublic Corporation is

_ 15 _

similar to the German alloy used in the Krupp works
except that it contains some nickel which 3ives it
a greater resistance to corrosion. There are now
seven formulas by which stainless steels are made.
Six of these are of German origin and the seventh an
English formula is now used by the Allegheny Steel
Corporation in the United States.
Stainless steel was first introduced to the public
in 1914 in the form of cutlery. however, this use
of stainless steel has not been found satisfactory
for institutions since such knives do not hold an
edge. Since 1919 much progress has been made in the
manufacture of stainless steel kitchen equipment and
utensils.

Table 1 gives in comparative form the properties
and relative prices of aluminum, stainless steel and

Lorel metal.

 

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aClds and al;alis. steel, amt fairlv stainless steels
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metals . Tike nic

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(19, 20, 21, 22)

   

 

III. Comparison of Aluminum, Stainless Steel, and
honel hetal for Quantity Use.

Five series of experiments were carried out to
determine the effect of metals and foods upon each
other. flew containers of aluminum, stainless steel,
and Lonel metal were used for all the studies. In
two of the cases it was necessary to omit honel ietal,
because it was impossible to purchase it in steam-
table jars. All foods were prepared for cooking
under standard conditions, only fresh vegetables
being used. Such vegetables as carrots, potatoes
and rutabagas were peeled in an institution vegetable
peeler. lhe food, with the exception of that boiled,
was prepared in quantities large enough to serve
from 125 to 140 peOple. The foods in each container
were cooked under as nearly the same conditions and
temperature as possible.

The cooked foods were scored by three judges, all
in the college institution management department, The
following score card was used with twenty-eight re-
presenting a perfect product. The score card was
adapted from the grading chart suggested by Marion
D. Sweetman in her article "Scientific Study of
Palatability of Food." (23)

A. Boiling Experiments

An aluminum and a stainless steel steamtable

jar having a diameter of eight inches and a capacity

of four and one half quarts were used as containers

in which to boil the vegetables. The foods were

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cleaned, peeled when necessary, and divided in half,
one half being put into each utensil. The same
amount of soft water, at the same temperature, usually
from 25° to 65° Centigrade was put on each vegetable.
An institution sized gas range was used to cook the
food, care being taken to have both containers receive
as nearly the same amount of heat as possible. The
vegetables were cooked in each container the same
length of time. it was not considered necessary to
boil more vegetables then was needed for good scoring
samples since many vegetables are not cooked by
boiling in most institutions and hotels. Records
were kept of the temperature of the water when the
food was placed on the rarge, the length of time it
took the food in each container to come to a boil, and
the length of cooking time. The boiled foods were
placed on plates immediately after taking from the«
stove and scored by three judges. Any discoloration
of the kettles on the food was noted and the degree
of intensity in either case. The color of the liquor
in which the foods were boiled was also observed. The
following list of vegetables were boiled, scored, and
studied in this manner; potatoes, rice, spinach,
cabbage, cauliflower, rutabagas, asparagus, and
rhubarb.
5. baking Experiments

In the baking of vegetables, pans made from the
three metals, aluminum, stainless steel, and tonal

hetal measuring 12 x 20 were used. The aluminum

_ 18 -

baking pan was cast ware, but the stainless steel and
honel letal ones were made of metal sheets of nearly
the same gage. The foods were prepared by standard
methods, a vegetable peeler being used for the potatoes.
In the case of an gratin foods medium white sauce

and bread crumbs were used. The rice pudding was
made with eggs, sugar, milk, and rice which had been
boiled in an enamel utensil. lhe same amount of

food was put into each container and baked in an
electric oven of even temperature throughout. The
vegetables in each pan were cooked the same length

of time and were judged by the score card used for
boiled foods except that special attention was given
to curdling when milk was used in the preparation of
the food. Records were kept of the baking time,
amount of curdling, discoloration of the food and con-
tainer, and distribution of tenderness throughout

the pan. The foods studied by baking were; escollOped
potatoes, cabbageeu gratin, onions au gratin, sweet
potatoes, rice pudding, and tomatoes.

C. Steaming Experiments

netal steamers 8 1/2 x 8 1/2 x 17 inches made

of aluminum, honel Metal and stainless steel were
used for the series of eXperiments on steamed foods.
All vegetables wer prepared by the standard methods,
some being skinned by the vegetable peeler. The same
mount of food was put into each of the containers
which were placed in a sectional steamer for cooking.
Care was taken to have the same temperature for all

t‘i ; “teamers of food. then the food was done

portions of it were removed and scored by the ju gas
as in the previous experiments. The time necessary
for steaming the food, and the discoloration of both
the food and the wetal was recorded. Potatoes, rice,
cabbage, carrots, onions, Spinach, cauliflower,
and asparagus were steamed in the manner explained
above.
D. Steamtable Experiments

Jars made of vitrified china, aluminum, and
stainless steel having a capacity of four and one
half quarts were used for holding foods on the steam-
table. The foods were prepared by standard methods
in the kitchen. The vegetables were steamed and
seasoned as for usual serving. ledium white sauce.
was used for the creamed vegetables. Fresh spinach,
creamed potatoes and creamed cabbage were allowed to
stand on the steam table for two hours. Lashed
potatoes were tested three times, twice using common
storage potatces of the Green Valley variety, and
the third time using new spring potatoes shipped in
from the south. hilk and salt were added to the
mashed potatoes. Two hours is as long as any one
container of food would be likely to stand on a
steamtable during the serving period, so that was
considered a reasonable time limit for the vegetables
to be kept. The mashed potatoes, however, were held
on the steamtable at least three hours so that more
marked results in the deterioration could be noted.

‘

The foods were scored by the judges every half nour

n

the first hour thev were kept on the steamtable and
every fifteen minutes thereafter. This procedure
for scoring was used because food appears to deteriorate
much faster after the first hour than before.
B. Chemical Tests

1. Aluminum

The liquor from the foods boiled in the alumian
steam table jar was collected and put through a
series of three fluted filters to eliminate the in-
soluble matter. The filtrate was tested for aluminum
as follows. To five cubic centimeters of the filtrate
five cubic centimeters of Normal hydrochloric acid,
five cubic centimeters of three normal ammonium
acetate’and five cubic centimeters of aluminon reagent
or alizarin red was added. After mixing to allow the
lake formation to take place the solution was made
alkaline by the addition of a solution containing equal
parts of ammonium hydroxide and ammonium carbonate.
A bright red precipitate persisting in the alkaline
solution indicated the presence of aluminium. (24)
The liquid from all the boiled vegetables; potatoes,
rice, cabbage, carrots, celery, cauliflower, onions,
rutabagas, spinach, tomatoes, rhubarb, and asparagus
was tested by this method.

2. COpper and hickel.

A sample of all the foods which were discolored
when steamed in honel Letal containers was collected
and a raw sample of each of the foods was also pre—

pared to use as a check. The samples were evaporated

to dryness in a Freas electric oven and ignited in

an electric muffle furnace to a white ash. The ashed
material was dissolved in concentrated nitric acid.
Five cubic centimeters of this solution was neutralized
with ammonium hydroxide, then a slight excess was
added. A blue color at this point indicated the
presence of copper. if a red precipitate appeared

five cubic centimeters of dimethyl glvoxine

VF!.'/‘~
481"

.5

was added,nickel also was present. (24)

IV. Discussion

The cooking of food in aluminum, stainless steel,
and honel Letal showed very definite advantages and
disadvantages in the use of each metal for containers.
ihe score card used was found successful, since in
most cases the judges were in close agreement.

A. Boiling Experiments.

Records of the time it required the vegetables
in aluminum and stainless steel to reach a boil
show very definite results.

A study of Table 3 shows very clearly that foods
in all cases boiled more quickly in aluminum than in
stainless steel. it must be remembered that in
both utensils the water was at the same temperature
when placed on the range, but that the temperatures
were not the same for all kinds of vegetables. During
cooking the vegetables in the stainless steel
utensil boiled more vigorously aroundjthe edge and
burned to the sides of the container. Eothing of the
sort could be noted in the aluminum utensil. Con—
sidering the fact that food boiled more slowly and
that it burned to the sides of the stainless steel
utensil it is evident that it does not conduct the
heat as readily as aluminum.

Table 4 showing the average score of all the
judges for the boiling experiments.indicates that
although in more cases the vegetables cooked in
aluminum received the highest score the differences
were not in most cases verygreat and stainless steel

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evidently does not always affect the vegetables which

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Table 5. Kinutes Required to Reach Boiling Point

Vegetables' Aluminum Stainless Difference
Steel in time
Asparagus ll 15 +2
Cabbafle ll 13 +2
Carrots 5 4 +1
Cauliflowe 5 4 +1
Celery 5 e ' +1
Unions 2 1/2 5 +0.5
Potatoes 12 16 +4
Rice 4 6 +2
Rhubarb 5 4 +1
Rutabagas. 5 4 +
Spinach b 4 +1
Tomatoes 5 4 +1

Total difference +17.5
Average Difference + 1.5

Table 4. Average Scores for boiled Vegetables

Vegetables Aluminum Stainless Difference
Steel in time

Asparagus 27 24 +5
Cabbage 25 28 -5
Carrots 25 21 +2
Cauliflower 2e 25 +5
Celery 25 1/2 22 +5 1/2
Onions 2o 25 1/2 -5 1/2
Potatoes 28 26 +2
Rice 15 14 1/2 -1 1/2
Rhubarb 25 20 1/2 +2 1/2
Rutabagas 15 1/2 15 +1 1/2
Spinach 25 25 1/2 +2 1/2
Tomatoes ’ 28 25 +5

 

Total difference +15
Average difference +1.25

are cooked in it. The scoring of vegetables cooked

in alumin‘m indicates that in nine cases out of the

twelve they had better, flavor, color, texture an

were more tender than those coohed in stadnless steel.
Tee records kept of boiling vegetables in alum-

inum and stainless steel show discoloration of the

utensil in hanv cases. From Table 5 an objection to

coloration

0')

aluminum is evident since it shows di
in more cases and many times in a greater degree
than stainless steel. This darkening of the kettle
is harmless and can easily be taken out by boiling
acid foods in it or vinegar may also be used suc-
essfully. Boods which contain a large amount of
starch as rice and potatoes discolor aluminum much
morereadily than do such acid foods as rhubarb and
tomatoes. Lo like conclusion can be drawn for stain-
less steel since potatoes discolor it intensely, but
rice has no more effect on it than do the acid foods.
8. Baking iXperixents

Results of significance were obtained from baking
foods in aluminum, stainless stee , and honel hetal
pans, although little discoloration of the utensils
was found. The ave age scores for baked vegetables
(Table 5) does five one fairly obvious result; that
foods which we e bahed in an aluminum pan had the best
color, texture, quality, and flavor. It was noted
that foods baked in stainless steel and Lonel getal
pais cooked or even burned around the sides and

remained raw or partially done near the center of the

Table 5. Utensil Discoloration

Vegetable

Asparagus
Cabbage
Carrots
Cauliflower
Celery
Ohions
Potatoes
Rice
Rhubarb
Rutabagas
Spinach

Tomatoes

Aluminum

Ho discoloration
go discoloration

ho discoloration

slight discoloration

slight discoloration

dark discoloration

slight discoloration

fr m Boiled Vegetables

otainless Steel

No discoloration

very dark discoloration

very slight discoloration

slight discoloration

no discoloration

no discoloration

very dark discoloration

very dark discoloration no disaioration

no discoloration
slightly discolored
discoloration

no discoloration

no

no

I10

I10

discoloration
discoloration
discoloration

discoloration

Table 6. Average Scores for baked Vegetables

Vegetables

Escalloped Potatoes
Cabbage Au Gratin
Onions Au Gratin
Sweet Potatoes

nice Pudding

Tomatoes

Aluminum

nless
eel

26
25
26
24
24

24

honel

26

24

{\3 (\3
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{\3
{\3

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hi:

hetal

utensil. lndicating that these n etals did not con—
duct the neat in a suitable tanner for cookinn foods.
The only discoloration noted was in the case of rice
ba ed in lonel Letal.

Table 7 shows the amount of curdllng ch 1nd in
baked foods which contained milk. Then just the word
curdling is used in the table a‘stage between slight and
extreme is meant. lhis curdlinq would not be significant
if the food had not been cooked for the ane length of
time and at the same ten :7erature. It is evident that
foods curdled most in Lonel Letal and least in stainless
steel. Some distinct property of‘a metal cannot be
given as a cause of the curdlin however, the results
would indicate that metals nav have some influence upon

the curdling of foods containing milk.

C. steamin h periments

0Q

Table 8, the averages of the scores for steamed
vegetables shows very clearly that foods cooked by
steaming in aluminum are superior or equal in all
cases studied to those cooked in stainless steel or

onel Letal. In the cases of most of the vegetables
those cooked in the Ionel Metal steamer were much
inferior to those from the other two utensils.

Table 9 shows that much of this inferiority was
due to the decided affect upon the color of the foods.
In no case did aluminum affect the color of the food

and stainless steel did only slightly in two cases.

The Konel :etal steamer was more asilv discolored than
the other two. Lr. Addison of the Stearnes

Table 7. Curdling of fiaked Foods Containing Kilk

x.)

Vegetables Aluminum Stainless Steel Lonel Ietal

Escalloped no no curdling no curdling

Potatoes curdling

Cabbage Au Gratin slight extreme
curdling curdling curdling

Onions '

Au Gratin no curdling no curdling slight

curdling
Rice curdling slight
Pudding curdling- extreme

curdling

Table 8. Average Scores for steamed Vegetables

Potatoes
Rice
Cabbage
Carrots
Onions
Spinach
Cauliflower

Asparagus

Aluminum

26

btainless
Steel
24
22
25
27
26
27

27

gonel

16
10
25
27

24

Ietal

Table 9. Discoloration of Steamed Vegetables by Utensil

Vegetables
Potatoes
Rice
Cabbage
Cauliflower
Spinach
Carrots
Onions

Asparagus

Aluminum Stainless Steel monel fetal

no no discoloration very dark grey

discoloration

no ,

discoloration dark grey no discoloration

no no - light grey

discoloration discoloration

no discoloration no light grey
discoloration

no no no

discoloration discoloration discoloration

no discoloration no no
discoloration discoloration

no no discoloration dark grey

discoloration

no light grey green dark grey

discoloration

Company said that some of his customers reported that
potatoes, rice, and cabbage were discolored when
steamed in honel Letal containers. Table 10 sup—
ports his statement. It was found that rice was the
only food when steamed in aluminum which was dis-
colored and that cabbage was the only one affected
in a like manner by stainless steel.
D. Steamtable Experiments

Spinach, creamed potatoes, and creamed cabbage
w<en kept on the steamtable.two hours in vitrified
china, aluminum and stainless steel jars showed a
marked deterioration in all containers. The color
and flavor deteriorated most and rather rapidly after
he first hour and a half. lhe food in the vitrified
china and stainless steel kept much better than did
that in the aluminum container. Vegetables in the
aluminum jar began deteriorating before foods in the
other containers and cooked to the sides of he
utensil before the end of two hours. lashed potatoes
were tested three times keeping them on the steamtable
three hours. By the end of two hours and a quarter
the food in all cOntainers had discolored and lost
flavor and fluffiness. Lihe the other foods tested
the mashed potatoes cooked to the sides of the aluminum
jar.

Table 11 shows the average scores for the food
kept on the steamtable. It is evident from these
scores that food does not keep well in aluminum on

the steamtable, but that vitrified china does hold it

6...

I
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Table 10.

Vegetable

Potatoes
Rice
Cabbage
Carrots
Onions

Spinach

Utensil discoloration from Steamed Vegetables

Cauliflower no

Asparagus

Aluminum Stainless Steel
no no
discoloration discoloration
very extreme no
discoloration discoloration
no slight
discoloration discoloration
no no
discoloration discoloration
no no
discoloration discoloration
no no
discoloration discoloration
no
discoloration discoloration

mo discolorationno

discoloration

ionel letal

very extreme
discoloration
very extreme
discoloration
very extreme
discoloration
no
discoloration
slightly
discolored

no
discoloration
no
discoloration
no
discoloration

Table 11. Averaae Scores for Steamtable Vegetables

Vegetables Aluninum Stainless

steel
Cabbage (Creamed) 25 25
Potatoes 24 26
(Creamed)
Spinach 25 _ 26
Potatoes 25 24

(lashed)

Vitrified China

27

28

27

well and that stainless steel is rather superior to
aluminum also but not as good as vitrified china.
This should be noted as the first time aluminum did
not come first in the scored foods and in this case
it is not even first in relation to the metal con-
tainer. Further experimental work on holding foods
in metal jars on the steamtable should be carried
out to determine more conclusively the best material
to use for such containers. If possible for use on
the steamtable, metal containers are economical,
because the food can be cooked in them and the jars
transferred from the range to the steamtable with-
out the use of an extra utensil.
3. Chemical Tests

1. Aluminum
The liquid from twelve boiled vegetables cooked
in aluminum was tested for traces of this metal, and
from the results it is evident that aluminum is not
soluble in the liquid from most foods (Table 12).

The fact that potatoes, rice and cabbage gave
positive tests for aluminum does not mean that these
foods when cooked in an aluminum utensil would be
in the least injurious or harmful. The test was so
delicate that one gram of aluminum in four million
liters of water could be detected. lhis means that
the aluminum was present in very minute quantities.
Alum baking powders contain more aluminux than could
be got from foods cooked in aluminum kettles and

0 le use it every day without harmful results. it

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_ 27 _

Table 12. Aluminum test

Vegetables Positive
Potatoes +
nice +
Cabbage +
Celery

Onions

Carrots

Tomatoes

Cauliflower
Rutabagas
Asparagus
Rhubarb

Spinach

Negative

is an erroneous idea that an injurious amount of
aluminum is got from foods cooked in containers of
this metal.

2. Copper and hickel

When foods darkened by steaming in honel Letal
were tested chemically no positive results were ob-
tained although very delicate tests for c0pper and
nickel were used. This would indicate that neither of
these metals cause the discoloration of the vegetable.
F. Summary of the Discussion

In general vegetables cooked in aluminum utensils
had better flavor, color, texture, and were more
tender than those cooked in stainless steels or monel
letal. h wever, many of these vegetables discolored
the aluminum utensil. In baked creamed dishes less
curdling was observed in the aluminum container.

Stainless steel is slightly darkened by cab-
bage, carrots, cauliflower, and potatoes. fihen vege-
tables cooked in stainless steel darken the kettle
they seem to acquire a slight meta lic taste. heat
is not conducted well by the stainless steel con—
tainers and the foods easily burn on the sides while
that in the center remains partially cooked.

Lonel Letal conducts the heat so ewhat better
than stainless steel, but is much inferior in that
respect to aluminum. Starchy foods as rice and
potatoes darken and are darkened when cooked in
honel hetal. Cabbage and onio s are also affected

in the same way, but to a less degree. In baked

_ 23 _

dishes containing milk extreme curdling occurred then
the food was cooked in Ionel hetal.

On the steamtable foods retain their original,
flavor, color, and texture longest if kept in vitri-
fied china. Stainless steel h wever makes a very
acceptable substitute. Aluminum is very poor for
steamtable jars and Xonel ketal cannot be purchased
in this style of utensil.

Rice, potatoes, and cabbage when tested chemically
show very slight amounts of alwminum present after
cooking in a utensil made of that matal. Very deli-
cate nickel and copper tests on foods darkened when
steamed in nonel hetal give no results, indicating
that these metals do not affect the color of the food.

V. Conclusions

A. Aluminum is the best metal for cooking
utensils although it is discolored by some fruits
and vegetables. In the case of steaming foods stain—
less stee may be substituted.

B. Konel Letal and stainless steel do not con-
duct heat readily enough to be used in cooking uten—
sils there heat conductivity is important.

C. Vitrified china jars hold food on the steam-
table better than metal containers, but stainless
steel say be used as a substitute.

D. Rice, potatoes, and cabbage after cooking
in aluminum show a very faint positive test for this
Ketal, however he aluminum present is not in large
enough quantities to be injurious.

-29..

VI. Bibliography
1. ”Things You Should know About Aluminum," American
Restaurant Lagazine, Vol. 12, ho. 7, p. 66.
2. ”The Aluminum Age? deard nott fioolley.
5. “Facts for Food Teachers," Doris mcCray, home
Economics Kews, Cct., 1950, p. 8A.
4. ”Soda Fountains, Refrigerators, Cold beverage,

and Food landling Equipment, Allegheny Steel Corp-

oration.

5. ”Ianufacture and Uses of honel,” American
Restaurant gagazine, Vol. 12, ho. 6, p. 84.

6. ”How tonal Letal is ianufactured,” hotel Lonthly,
Vol. 68, E0. 449, p. 69.

7. "Twenty Years of Konel hetal, Rovert C. Stanley.

8. ”Hodern Kitchens,"

International Lickel Company.
9. “:Cience in the Eitchen," Ella iellogg.
lO. " oman's Share in Primitive Culture," 0. 1. hason.
11. ”Letallurgy," Eatfield.
12. ”Outline on the history of Cookery," Barrow
and Shapleigh.
15. "Encyclopedia Britannica,” Vol. 9.
14. ”anycloped'a Britannica," Vol. 2.

15. "The Story of Iear-Ever,‘ Aluminum Cooking Uten-

811 Company, D. 4.

J.

16. "fiagner Cast Aluminum Hotel Rare,‘ 33899? Al‘

uminum Company, p. 2.
17. "The ;ar1y Use of hetals," Rickard, Journal of
the lnstitute of letals, Vol. 43.
18. ”Stainless Iron and steel," honypenny.

l9. ”Corrosion-Hesis ant, heat—Hesistant. and

-l9
ilectrical-Resistant Alloys,” Aierican Society for
Testing hetals.

20. ”The Letallurgy of Aluminum and Aluminum Alloys,”
Anderson.

21. ”Principles of netallurgy," Fulton.

22. ”The Letallurgy of the Non-Ferrous Metals,”
Gowland.

25. ”Palatability of Food,” harion Sweetnan, Journal
of home Economics, Vol. 26, Lo. 2, p. 165.

24. ”gualitative Analysis,‘ Baskerville and Curtman.

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