The record-union., 1897-11-19
THE ANALYSIS OF JELL|Es.
HOW CHEMISTS KNOW WHAT
THEY CONTAIN.
Essay Of DIR. WenzeI, Chemist of
the San Francisco Board
of Health.

yesterday IN the Fruit growers con-
ventlon, on the analysis OF jellies.
| he said that, since he had started
IN on this work he had been ap-
preached by a number of persons who
told him that no chemist could tell by
analysis whether or not curranr,
blackberry or strawb berry jellias had
been adulterated, if they were mixed
with apple jelly. He had therefore
prepared his paper to show how jellies
are analyZed.
Following is his essay:
The chemical analysis of fruit pro-
duets has been a source of frequent
inquiries as TO the methods used and
how an analyst can ascertain if any
| particular kind of jelly, for instance
jelly labeled currant jelly. was made
from currants or from apples.
Before entering upon this subject it
is proper TO first consider the compo-
sition of fruit Juices, their general
properties, and the changes some of
their components undergo during the
process of making jellies. Of an inn
portant constituent of fruit juices we
shall particularize the so-called pectin
bodies, organic substances to which
the geiatinizing properties of the fruit
juices depend.
All fruits contain a certain insoluble
substance called pectose. 1t exists in
the fieshy pulp of unripe fruit which
under the influence of acids is trans
formed into soluble pectin a sub
stance which imparts to fruit juices
the property of gelatinfzing when
boiled
When fruits are heated in contact
with water, the acids contained in
them. which is usually a mixture of
malic and citric acids, the former pre-
dominating, these first act upon the
pectose, converting it into pectin. In
the next place a substance named pee
tare, which is peculiar ferment also
existing ready formed in fruits acts
upon the pectin, producing pectoric
acid which gelatinizes on cooling.
Green fruits do not contain pectin
performed but only pectose. AS the
ripening advances, the juice then con-
tains pectin and parapectin. Lastly,
fruits in the over-ripe state no longer
contain trace of pectin, this sub
stance being converted into metapectic
acid which does not possess gelatiniz
ing properties.
From these considerations it will be
seen that the all-important essential
for producing a first-class fruit jelly is
the selection of fruit not over-ripe. The
same difficulty will also be met when
the fruit has passed into state of de-
composition whereby the pectin also
changed into metapectin thereby losing
the gelatinizing effect. 1t is on this
account that manufacturers use apple
juice, which is rich in pectfn bodies
to fruit when over-ripe or rotten fruit,
apple juice containing from three
eighths per cent of pectin bodies
against currant raspberry, and straw
berry juice which contains only from
3 to l per cent
The next important factor to con-
slider is the free acid contained in
fruits, which varies with different
fruits Currant juice has an acid per-
centage of II to %, whilst apple juice
contains from 3 to 1 per cent. Of free
acid.
Regarding the coloring matter of
such fruits as currants, Strawberries,
raspberries and blackberries, these
coloring principles are readily trans
ferred to alcohol, to which they COM
municate a rich purple color.
Apples, ON the contrary, do not COM
municate any but straw color to the
jellies, and the red color of the apple
is completely destroyed in the jelly
making process, so that in the case of q
currant jelly made from apples, the use
of artificial coloring matters are
requisite in order to initiate the nat
ural color of this fruit, and in all cases
where colors foreign to the natural
fruit We're used, the colors were those
derived from coal tar.
In order to arrive conclusively as to
the purity of a fruit jelly the following
course will have to be considered:
First-The amount of pectin bodies
in which are embraced: Pectose, pac-
tose, pectin, parapectin, meta-pectic
and pectosic acids. These being insol-
uble in alcohol are then precipitated
and are weighed in the analysis as
pectin bodies.
Second-A quantitative estimation Of
malic and citric acids is made, the re-
suit being usually given as malic acid
as this acid is usually present in fruit
juices by far the largest quantity.
Third-The coloring principles con-
tained in these jellies furnish sufficient
aid to distinguish between colored jel-
lies whether natural or artificial. Cur
rants, blackberries, raspberries and
strawberries contain a red coloring
principle which produces a solution OF
acetate Of lead when added to liquid
preparation whether made from the
fruit or jelly BLUSH green precipitate.
Apple juice or apple jelly when treat
ed with acetate of lead gives yellow
ish white precipitate, and the coal-tar
colors of artifcially colored iellies are
not precipitated at all by acetate of
lead
Then again the tinctures obtained by
treating the jellies with alcohol give
liquids possessing certain depths of
color. according to the kind of berry
used; the blackberry giving the dark
est red, next the currant then followed
by the raspberry and strawberry.
On preparing standard tinctures from
pure fruit jellies and comparing tinct-
ures made similarly from fruit jellies
to be analyzed, by this so-called color
imetTic test, the purity or adulteration
with apple juice may be approximately
ascert aimed.
Lastly, the presence of coal tar colors
may be demonstrated by depriving the
tincture made from the jellies of the
alcohof by heating, calculating with
suiphuric acid and adding an equal
volume of amylic alcohol On shak-
ing the mixture thoroughly allowing
the mixture to separate into two lay
ers, the upper layer will contain the
coal-tar color. Pure jellies will COM
municate no color to amyl alcohol,
The following present the analysis
of three ieIlies renn1.fed to the San