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Issued November 22, 1907.



United States Department of Agriculture,

BUREAU OF CHEMISTRY Circular No. 37.
H. W. WILEY, Chief of Bureau.



GENERAL RESULTS OF THE INVESTIGATIONS SHOWING THE EFFECT OF
SULPHUROUS ACID AND SULPHITES UPON DIGESTION AND HEALTHS



INTRODUCTION.

The relations of sulphurous acid to health are perhaps of greater
importance than those of the preservatives already studied namely,
boron compounds and salicylic acid and its salts. The reason of this
is found in the fact that the use of sulphurous acid at the present time
is more general, and in certain classes of food products, according to
the statements of manufacturers, more nearly approaches a necessity
than is the case with boron or salicylic acid compounds.

Sulphurous acid in some form is extensively employed in many
technical operations in the preparation of foods. This is especially
true in the production of wine, in the preparation of evaporated or
desiccated fruits, and in the manufacture of molasses. The problem
presents itself under two aspects namely, the use of sulphurous acid
or its compounds for technical purposes in the preparation of foods
and its application to the finished products as a preservative.

In the preparation of foods, sulphurous acid is chiefly employed in
the form of the fumes of burning sulphur, applied either to the food
products themselves in the course of manufacture or to the con-
tainers in which the food products are held. In the ripening of the
wines in cellars it is customary to fumigate the barrels with burning
sulphur each time the wines are racked. In this manner it often
happens that the wine before it is finally ready for sale on the market
may have been placed in five or more freshly sulphured containers.
By this treatment the wine absorbs a varying quantity of the sulphur-

By reason of the restrictions placed by law upon the printing and distribu-
tion of bulletins exceeding 100 pages, it is not possible to supply the demand for
Bulletin 84, Influence of Food Preservatives and Artificial Colors on Digestion
and Health, from the regular edition. In order to give as wide a circulation as
possible to the results of the experimental work, it has been deemed advisable, in
the case of Part III, on Sulphurous Acid and Sulphites, as in the case of Part I,
on Boric Acid and Borates, and Part II, on Salicylic Acid and Salicylates (Cir-
culars 15 and 31), to publish the results in the form of a circular for general
distribution.

16108 No. 3707 1




ous acid, depending to some extent upon the amount of sulphur used
in fumigating.

When sulphurous acid is used as a preservative for food products
after the manufacture has been completed, it is usually employed in
the form of bisulphite of lime or some similar preparation. Sulphur-
ous acid has the property of uniting with certain organic radicals, such
as aldehydes and some sugars, to form compounds which are more or
less stable, and in this form it is known as combined sulphurous acid.
When it exists in the form of an absorbed gas or in combination with
an ordinary metallic base, such as soda, potash, or lime, it is said to
be in a free state. Combined sulphurous acid is set free from the or-
ganic combination by treatment with an acid with the aid of heat or
with a dilute alkali in the cold.

In the accompanying report the effects of the combined sulphurous
acid are not to be considered, except in so far as the combination
takes place with the foods with which the sulphurous acid may be
mixed after entering the stomach. The purpose of the investigation
is, therefore, to determine practically the effect of free sulphurous
acid that is, sulphurous acid in a gaseous state absorbed by water or
united with a base rather than the effects of combined sulphurous
acid. In no case has any question been considered in these investi-
gations relating to the food value of the organic sulphur existing in
proteids and other foods.

i It is true that probably in the process of digestion complete saponi-
fication of the combined sulphur compounds takes place, so that
finally they appear in the small intestines in a free state that is, as
sulphurous acid or sulphites and are then oxidized to sulphuric acid,
as is the free sulphurous acid, during the metabolic processes.

Practically, in the technical use of sulphurous acid in the manu-
facture of food products only the fumes of burning sulphur are
employed. Desiccated fruits, pared or unpared, are subjected, after
the removal of the pit or core, to the fumes of burning sulphur in
what is known as a " sulphur box." In the manufacture of wines
a piece of so-called " sulphur candle " that is, a piece of cloth which
has been dipped in melted sulphur is burned. This candle is
attached to a wire, ignited, placed in the barrel, the bung inserted,
and the candle allowed to burn until the whole of the sulphur is con-
sumed. Previous to the sulphuring it is the custom to thoroughly
wash the barrel so that the interior thereof at the time of sulphuring
is moist. The moist surface of the wood absorbs the sulphurous acid
more freely than does the dry wood. The ostensible object of the
sulphuring is to keep the barrels sweet; in other words, to destroy
any yeasts or other ferments which may adhere to the surface of the

[Cir. 37]



wood or be present within it. The barrels are often sulphured some
days, or even weeks, before they are filled ; at other times the filling
of the barrel with wine takes place immediately after the sulphuring.
In both, cases notable quantities of sulphurous acid become diffused
throughout the wine itself. It is evident that some care must be
exercised in the use of sulphur in wine making for two very impor-
tant reasons. In the first place, if too much sulphur be used, red
wines would to a certain extent be bleached. In the second place,
if the wines become entirely saturated with sulphurous acid the sec-
ondary fermentations which produce the ripening of the wine would
not take place. In such cases the wines apparently appear to be per-
fectly mature within one or two years, whereas the proper maturation
of a wine requires a much longer time. In the manufacture of non-
fortified sweet wines much larger amounts of sulphur are used than in
the manufacture of dry wines. This is an important fact, since it
shows that the large quantities of sulphur are not necessary for the
preservation of dry wines, because it is well known that red wines,
which are generally very dry, are quite as well preserved as white,
although containing much less sulphurous acid. It is claimed that
in the manufacture of sweet wines that is, those in which the natural
sugars coming from the juice of the grape are not entirely fer-
mented larger quantities of sulphur are necessary to prevent fer-
mentation after the wine is mature. If the sweet wine be made
from a suitable kind of grape that is, one which is so rich in sugar
that it gives a certain maximum quantity of alcohol and still leaves
some unfermented sugar it is evident that no excess of sulphurous
acid will be necessary. In such a case the wine would be preserved
by its natural alcoholic content. If, on the other hand, a sweet wine
be made from a must so poor in sugar that it is necessary to add an
additional quantity, the product can not be regarded as a natural
wine, and hence there seems to be no necessity for providing for its
manufacture.

In the manufacture of sirups and molasses it is quite customary to
expose the freshly expressed juices of the cane to the fumes of burn-
ing sulphur. The " sulphur box " used in this case is so constructed
that the juice, falling over shelves by gravity, absorbs the fumes of
the burning sulphur rising from the box, which to this extent serves
as a chimney. The sulphur dioxid becomes incorporated with the
components of the juice, forming more or less stable compounds which
are not entirely broken up by subsequent boiling. The sulphur in
this form, as well as that which may still be present in the free state
that is, either as an absorbed gas or in combination with metallic
bases passes into the finished product. When sugar is made the
sulphur compounds are concentrated in the molasses and this con-

[Cir. 37]



centration becomes greater in proportion to the number of crops of
sugar crystals removed. In very low grade molasses the sulphur
naturally occurs in extraordinarily large quantities.

In the preparation of evaporated apricots, peaches, pears, and man-
darins sulphuring is practiced for the following reasons :

1. To produce as clear and intense a yellow color as possible.

2. To conceal decayed portions of the fruit which have been over-
looked in trimming.

3. To prevent fermentation and decay during the drying of {he
fruit.

4. To protect the fruit during drying from flies and other insects
the larva? of which would otherwise develop after the fruit was
stored.

5. To kill the cells of the fruit and thus make the texture more
porous, which expedites drying.

In the application of the fumes of burning sulphur in the prepara-
tion of evaporated apples the principal object appears to be the pres-
ervation of the color of the finished product. Fruits which have been
sulphured before evaporation seem to have a lighter color than
those which are dried without sulphuring. At the same time it is
well known that highly sulphured fruits are preserved with a lower
degree of desiccation than those not sulphured, and for this reason
a greater weight of fruit is produced from a given weight of the raw
material when sulphur is used. It is not difficult to preserve a water
content of 30 per cent or over in the finished product when liberal
sulphuring is practiced. The use of sulphurous acid also makes it
easier to protect the finished product from mold and fungous growths
in general after manufacture. That excessive quantities of sulphur
are not necessary for the production of evaporated fruits of pleasing
appearance is well attested by analytical data obtained by the exam-
ination of fruits purchased in the open market having a light and
pleasing color and at the same time containing only a small quantity
of sulphurous acid. On the other hand, it is quite easy by certain
forms of treatment during the process of manufacture to obtain a
product in which sulphurous acid is present in excessively large
quantities. The analytical data also show that a portion of the
sulphurous acid used in the preparation of such products becomes
oxidized into sulphuric acid after a certain time, thus artificially
increasing the small amount of sulphates naturally present in some
food products, which does not appear to be a desirable practice.

As sulphurous acid in some form is almost universally employed in
the manufacture of wines, molasses, and sirups, and in the prepara-

[Cir. 37]



tion of desiccated fruits, it is evident that the prohibition of its use
would necessitate a radical change in methods of manufacture. This
fact, however, it might be stated, has nothing whatever to do with
the purposes of the present investigation. Assuming that in the
manufacturing processes certain added bodies are used which are
found on investigation to be injurious to health, the rational conclu-
sion of such an investigation would be not to excuse or overlook the
use of such bodies, but to institute investigations looking to their sup-
pression. If, therefore, the results of the present study indicate that
sulphurous acid, even in small quantities, is a deleterious substance
when added to foods, it would be reasonable to expect that manufac-
turers, as well as investigators, would immediately take steps looking
to the early suppression of the injurious substance. While it is not
likely that such an event could be accomplished within a year or two,
it is reasonable to suppose that it could be eventually brought about
without any disturbance to manufacture and without any diminution
in the output of the article.

In matters of this kind it is advisable to proceed when possible
with conservative steps and to avoid any attempt at sudden and
revolutionary changes in methods of manufacture. In all such cases,
however, it will be found not only possible and desirable to make the
food product in question without the use of the deleterious substance,
but there is evidence to show that the products thus manufactured
will be more palatable, more wholesome, and more valuable than
those made according to the methods commonly used at present.
Practical experiments have shown, for instance, the possibility of pro-
ducing a high grade sirup from cane juice and other saccharine saps
without the use of the fumes of burning sulphur. Analytical data
show the presence on the market of considerable quantities of desic-
cated fruits of good appearance in which the quantity of sulphur is
so small as to be ascribed rather to the conversion of the natural sul-
phur content of the product than to the addition of the sulphur in
its manufacture. At the present time considerable quantities of wine
are made without the addition of sulphur of any description, and
these wines are of fine appearance, excellent flavor, and of noted
purity and wholesomeness.

In so far as the mere tint of the food product is concerned, it is
not a difficult matter to familiarize the public with a tint of a dif-
ferent kind from that which would be produced by the use of sul-
phur. The only arguments of any force favoring the use of sul-
phurous acid in food products are those which relate either to the
preservation of the food product or to its color. As the preservation
of the product can be easily secured, and a slight change in color

[Cir. 37]



rendered familiar without working any hardship, these arguments
seem to have no force whatever in justifying the continuation of the
use of sulphurous acid in foods. It may be the part of wisdom in
the administration of food laws to tolerate existing methods of manu-
facture for a certain length of time looking to their amelioration or
change, but that is a question with which this investigation is not
concerned.

There is reason to believe, therefore, as a result of the present
studies, which have shown that the use of sulphurous acid in foods is
deleterious, that a rapid change will be made in the processes of manu-
facture, looking to the complete and somewhat speedy suppression of
its employment. The use of sulphurous acid and sulphites never
adds anything to the flavor or quality of a food, but renders it
both less palatable and less healthful. Every fact which has been
brought out, therefore, in the investigation tends to accentuate the
justness of the conclusion, namely, that the use of sulphurous acid in
foods should be suppressed.

ORGANIZATION OF THE EXPERIMENT.

The organization of the work in general was practically identical
with that of the previous investigations as reported in Parts I and II
of Bulletin 84 and summarized in Circulars 15 and 31.

The experiments were conducted on twelve young men from the
Department of Agriculture and a local medical school, who voluntarily
assumed the obligations imposed by work of this kind. They pledged
themselves to abide by the rules and regulations guiding their conduct
during the period of the observation, to indulge in no unusual exer-
cise or study, to pursue the ordinary tenor of their daily lives without
any more variation than is incident to regular habits. They further
undertook to eat only the food which was given them at the hygienic
table, to collect and deliver for analysis the excreta of their bodies,
to observe regular hours respecting sleep and work, and to report
the quantity of water which was drunk away from the hygienic table.
The young men were not placed under surveillance, but simply were
trusted with their pledge that they would not violate any of the rules
of conduct prescribed. The diet was varied so as to give a choice of
meats, vegetables, fruits, and cereals, with bread, butter, milk, and
coffee. Food of the best quality was purchased, free of any added
preservative or coloring matter and in a perfect state of preservation,
and every precaution was used to have the food and all the appurte-
nances of the table perfectly sanitary.

[Cir. 37]



ADMINISTRATION OF THE PRESERVATIVE.



SCHEDULE OF ADMINISTRATION.

The fore period in Series VII began on February 1, 1904, and the
after period closed on March 11. The fore period extended over a
period of ten days, the preservative period lasted twenty days, and the
after period ten days, a total of forty days under observation. The
divisions of the periods are shown in Table I.

Table I. Dates of periods and suoperiods, Series VII.



Periods and subperiods.



Date of
begin-
ning.



Date of
ending.



Fore period

First subperiod . . .

Second subperiod .
Preservative period. . .

First subperiod . . .

Second subperiod .

Third subperiod . .

Fourth subperiod .
After period

First subperiod . . .

Second subperiod .



1904.
Feb. 1

....do...
Feb. 6
Feb. 11

....do...
Feb. 16
Feb. 21
Feb. 26
Mar. 2

....do...
Mar. 7



1904.
Feb. 10
Feb. 5
Feb. 10
Mar. 1
Feb. 15
Feb. 20
Feb. 25
Mar. 1
Mar. 11
Mar. 6
Mar. 11



Series XI and XIII, mentioned in the following pages, are special
studies conducted at a later date. The purpose of these studies was to
develop certain points in regard to the effect of the preservative on
the blood and the distribution of the nitrogenous elements of the
urine, to which the results obtained in Series VII had pointed as
being of special interest and calling for further elaboration.

The salt used for the administration of the sulphurous acid was
sodium sulphite, and the quantity of S0 2 contained therein was cal-
culated. About one-fourth of the weight of crystallized sulphite
(Na 2 S0 3 7 H 2 0) is composed of sulphurous acid (S0 2 ). The total
and average amounts of the preservative administered and all indi-
vidual variations in the quantities taken may be found in Table II.

Table II. Schedule of administration of preservative, Series VII.



Period and date.


Sodium sulphite as S0 2 (capsules). -


Sulphurous acid as S0 2 (aqueous solu-
tion).




No. 1.-


No. 2.


No. 3.


No. 4.


No. 5.


No. 6.


No. 7.


No. 8.


No. 9.


No. 10.


No. 11.


No. 12.


1904.

First subperiod:
Feb. 11


gms.

6.113
.240
.254
.254
.254


gms.

6.113
.240
.254
.254
.254


gms.
0.113
.240
.254
.254
.254


gms.

0.113
.24C
.254
.254
.254


gms.
0.113
.240
.254
.254
.254


gms.

0.113
.240
.254
.254
.254


gms.

0.078
.178
.200
.200
.200


gms.

6.078
.178
.200
.200
.200


gms.

0.078
.178
.200
.200
.200


gms.

0.078
.178
.200
.200
.200


gms.

0.078
.178
.200
.200
.200


gms.
078


12


178


13


200


14.

15


.200
200






Total


1.115
.223


1.115
.223


1.115
.223


1.115
.223


1.115
.223


1.115
.223


.856
.171


.856
.171


.856
.171


.856
.171


.856
.171


856


Average


.171


[Cir. 37]



























Table II. Schedule of administration of preservative, Series VII. Cont'd.



Period and date.


Sodium sulphite as S0 2 (capsules).


Sulphurous acid as S0 2 (aqueous solu-
tion).




No. 1.


No. 2.


No. 3.


No. 4.


No. 5.


No. 6.


No. 7.


No. 8.


No. 9.


No. 10.


No. 11.


No. 12.


1904.

Second subperiod:
Feb. 16


gms.

0.508
.508
.508
.508
.508


gms.

0.508
.508
.508
.508
.508


gms.
0.508


gms.

0. 508


qms.
0.508
.508
.508
.508
.508


gms.

0.508
.508
.508
.508
.508


qms.
0.400
.400
.400

.400


qms.
0.400
.400
.400
.400
.400


qms.
0.400
.400
.400
.400
.400


gms.

0.400
.400
.400
.400
.400


gms.

0.400
.400
.400
.400
.400


gms.
400


17


.508 I .508
.508 ! .508
.508 .508
.508 ! .508


.400
400


18


19


.400
.400


20


Total


2.540
.508


2.540 2 run


2.540

.508


2.540 9" 540


1 600


2. 000
.400


2.000
.400


2.000
.400


2.000
.400


2 000


Average


.508


.508
760


.508


.508


.320


.400


Third subperiod:
Feb. 21


.762
.762
.762
.762
.762


.762


.762
.762
.762
.762
.762


.762
.762
.762
.254



.762
.762
.762
.762
.762


.400
.400
.400
.400
.200


.400
.400
.400
.400
.400


.400
.400
.400
.400
400


.400
.400
.400
.400
.400


.400
.400
.400
.400
.400


400


22


.762
.762
.762
.762


.762
.762
.762
.762


400


23


400


24

.25


.400















Total


3.810
.762


3.810
.762


3.810 ! 3.810
.762 | .762


2.540
.508


3.810
.762


1.800
.360


2 000 9 nno


2.000
.400


2.000
.400


1 600


Average


.400


.400


.320


Fourth subperiod:
Feb. 26


.762
.762
.762
.762
.762


.762
.762
.762
.762
.762


.381






1.020
1.020
1.020
1. 020
1.020


ooooo
ooooo
ooooo


.400
.400
.100
.400
,400


.400
.400
.400
.400
.400


.400
.400
.400
.400
.400


.400
.400
.400
.400
.400


o


27

28




o


29


o


Mar. 1


o






Total


3.810
.762


3.810
.762


.381
.076


5. 100
1.020














2. 000
.400


2. 000
.400


2.000
.400


2.000
.400


o


Average





Entire preservative
period:

Total

Average


11. 275
.564


11. 275
.564


7.846
.392


12. 565
.628


6. 195
.310


7.465
.373


4.256
.213


6.856
.343


6.856
.343


6.856
.343


6.856
.343


4.456
.223



METHOD OF ADMINISTRATION.

A slight variation in the administration of the preservative was
introduced by the fact that it was deemed important that the investi-
gation should include sulphurous acid in a gaseous state as well as in
combination as sulphites. The most convenient method for the
administration of the gaseous sulphurous acid was found to be by the
preparation of an aqueous solution of the acid of standard strength
taken, after dilution with water, as an ordinary drink. Water
proved to be a more convenient vehicle than milk or other beverages
for this purpose.

In the form of sulphites the method of administration in capsules
was practiced. This method, as in the previous investigations, was
found not only to be the most convenient, but also, all things con-
sidered, the most desirable form in which to administer a substance
of this kind.

Attention has been called in the previous reports to the distaste
which the subject would acquire for a food product in which he knew
the preservative had been mixed, and therefore less disturbance of
the mental equilibrium was caused by the administration of the cap-
sule, the envelope of which is itself a food product and would be soon

[Cir. 37]



dissolved in the acid digestive juices of the stomach. Moreover, in
the solution of this capsule the whole of the preservative is not dis-
charged at once into the contents of the stomach, but the capsule dis-
solving at different points presents gradually increasing surfaces at
which solution of its contents may take place, and this, in connection
with the peristaltic action of the stomach, results in a complete incor-
poration of the preservative with the food in the stomach in a
reasonable period of time. Thus, in substances which do not possess
any active escharotic action, no possible damage can be done to the
walls of the stomach by this method of administration. The objec-
tions which have been made to this form of administration are un-
doubtedly of a merely captious character, for the purpose, if pos-
sible, of prejudicing the public against the conclusions reached.
Inasmuch as the capsule is a common method of administering solid
remedies at the present time the practice of the medical profession
approves unanimously this method of exhibition.



SUMMARY OF RESULTS.
MEDICAL AND CLINICAL DATA.

These data clearly show that the administration of sulphites and of
sulphurous acid in a free state in the quantities employed produces
harmful effects. A tendency is manifested in practically every case
to produce headache and digestive disturbances. In some cases these
symptoms are not clearly marked, while in others they are extremely
well denned. In many cases uneasy sensations and even pain were
developed in the stomach and intestines, and there were complaints
of " heartburn." The occurrence of this class of symptoms during
the administration of the preservative and their gradual disappear-
ance during the after period seem to be conclusive evidence that they
could have been due only to the effect of the preservative itself. There


1

Online LibraryUnited States. Bureau of ChemistryGeneral results of the investigations showing the effect of sulphurous acid and sulphited upon digestion and health → online text (page 1 of 2)