Tomato products: pulp, ketchup, and chili sauce.Bigelow, W. D. (Willard Dell)
Science
Tomato products: pulp, ketchup, and chili sauce.
Bigelow, W. D. (Willard Dell)
Tomato products
In using this method the steam is turned off, and as soon as the foam
subsides the cup is sunk well below the surface of the pulp. At this
time the heat in various portions of the kettle is of course uniform,
by reason of the thorough mixture caused by the vigorous boiling. Owing
to the large mass of rather viscous material, and the heat of the
kettle itself, the contents of the kettle cool slowly, and even after
10 minutes the temperature does not decrease more than 1° F., except at
the very surface of the pulp. As a result of several observations, it
was found that a thermometer bulb held 3 inches below the surface of
the pulp showed a lowering of temperature of not more than 1° F. in 10
minutes and a lowering of only 0.5° F. in from 5 to 7 minutes.
The bail employed was about 6½ inches wide and 8 inches long. There
was some difficulty, owing to the pulp spattering on the hands of
the operator because of the air escaping from the cup. This might be
diminished by the use of a longer bail, or by wearing suitable gloves.
When evaporating tanks are used it will probably be necessary to attach
the bail to a stick or support of some kind. In addition to permitting
this method of filling, the bail has the additional advantage that
the cup full of pulp may be handled for washing and conveying to the
balance much more conveniently and with less danger of spilling than
with the handle on the side of the cup. Again, the bail does not heat
when the cup is filled with hot pulp, and for that reason is easier to
handle.
(d) HYDROMETER METHOD
Hydrometers are of little value in determining the specific gravity
of tomato pulp. With cold pulp they cannot be used at all. With hot
pulp a relatively slender hydrometer comes to rest and readings can
be taken with more or less accuracy. The value of the reading is
relative to the specific gravity of the pulp and varies with the shape
of the hydrometer and with the character of the pulp. It is necessary
therefore to obtain the relation between the reading of the hydrometer
in the hot pulp and the specific gravity (obtained by an accurate
method) of the same pulp cooled without evaporation. In the hands of a
careful operator some manufacturers have found hydrometers (used with
hot pulp) helpful in making pulp of uniform specific gravity.
The hydrometer gives much more accurate results with the filtrate of
pulp. As shown on page 31, there is a direct relation between the
specific gravity of tomato pulp and of the liquor obtained by filtering
or straining the same, so that when the specific gravity of the latter
is known that of the former may be ascertained readily by means of
a table. This method is peculiarly applicable to the examination of
cyclone juice and light pulp from which the insoluble solids may be
removed quickly by straining through a cloth, and it therefore affords
the most rapid method that is available to the average factory for
determining the specific gravity of cyclone juice.
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