Process for the Treatment of Potato Starch with Chlorine under Heating.
Year: 1895

page_text: Date of Application, 20th Dec., 1895-Accepted, 15th Feb.,
1896
COMPLETE SPECIFICATION.
Process for the Treatment of Potato Starch with Chlorine under
Heating.
I, CARL HELLFRISCH, of Kyritz, Province of Brandenburg, Prussia, Specialist
for the Starch-industry, do hereby declare the nature of this invention and in what
manner the same is to be performed to be particularly described and ascertained in
and by the following statement :-
My invention consists in removing from potato starch the peculiar odour of
ethereal oils possessed thereby, by means of chlorine either in the form of chlorine
gas chlorinated water, or chloride of lime solution, under heating.
Potato starch as heretofore prepared, and existing as crude or bleached com-
mercial starch, possesses a peculiar odour of ethereal oils, which appears in a
penetrating and objectionable manner in the conversion of starch into grape sugar,
and which is the cause of the objectionable flavour and odour of the dextrines that
are produced from commercial starch.
I have discovered that the complete removal of this objectionable odour and
flavour of potato starch can be attained by means of chlorine under heating.
In carrying out the process two different methods may be employed.
1. The one method consists in conveying the potato pulp, coming from the
rasping machines and diluted with water, continuously into preliminary heating
apparatus provided with stirring devices, where it is heated to about 45° Č., and is
treated for a short time with chlorine, chlorinated water, or chloride of lime
solution, after which it is subjected at once to the action of the usual washing
sieves.
By this means, in addition to the deodorisation of the potato oil, the albumen of
the potato pulp is retained from the starch, on the sieves, which albumen would
otherwise pass as a polluting agent into the washing waters, so that by this means
the waste waters of the starch are at the same time freed from the albumen bodies
which subsequently become decomposed.
2. According to the second method the raw potato starch is heated in the form
of a milk-like solution in suitable vessels, having stirrers, to a medium temperature
which may advantageously be raised to about 45° C. (which temperature has not
hitherto been employed in potato starch manufactories) and chlorine, chlorinated
water or chloride of lime solution is then added, whereby a very rapid and
continuing alteration of the starch will be effected already after a short treatment,
in such manner that samples taken, on boiling with sulphuric acid or other acid
will no longer give an objectionable ethereal, dextrine-like odour.
If in the last named process it is not intended to convert the starch into sugar,
the starch is allowed to subside in the stirring vessel, is then washed with water,
and dried in the usual manner, thus obtaining a commercial article which ou being
treated for obtaining other derivatives, gives odourless products.
In carrying out the above processes the strength of the chlorinated water or
equivalent chloride of lime solution employed is preferably made such that one
litre of the liquid contains from 2 to 2.5 grammes of free chlorine. To 1000 kilos.
of starch in the form of a liquid containing one part of starch to 15 parts of water,
are added from 200 to 300 litres of the above mentioned solution, this being
introduced at the bottom of the mixing vat.
In the case where the starch is to form an odourless initial material in the
manufacture of starch sugar, the starch milk treated in the above described manner

page_text: so as to be odourless, is mixed in the usual manner with fixed acids and is boiled
down to form thin juice.
In the above described invention it is not a question of an accelerated action of
the chlorine as a bleaching agent, but it is intended by the use of higher
temperatures to provide for the chlorine conditions under which, irrespective of
the simultaneous coagulating action referred to in the first process, it is rendered
capable of acting destructively or by substitution upon the ethereal oils contained
in the potato starch, and consequently it produces effects which it cannot produce
when used in the potato starch manufacture in economically allowable quantities in
the cold. The bleaching action, which might also be produced by other means,
is of quite secondary consideration.
The chemical action of the chlorine on potato starch under higher temperatures
may be explained in such manner that the chlorine partly converts the starch
cellulose of the warmed starch milk, penetrates into the starch granules and then
chlorinates the unsaturated hydrocarbon groups of the ethereal oil contained
therein (according to Payen 001 to 0.0001 per cent. by weight) either into readily
volatile compounds without odour, or it converts the same into compounds which
are soluble at ordinary or higher temperatures in the water of the starch milk, so
as to be removable by washing.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
A process for removing the unpleasant odour and flavour of potato starch,
whether to be used as such, or for the production of odourless derivatives (soluble
starch, dextrine, starch syrup) which process consists in causing chlorine, chlorinated
water, or chloride of lime solution to act under moderate heating, such as to about
45° C., upon either potato pulp coming from the rasping machines or upon starch
milk, substantially as described.
ABEL & IMRAY,
Agents for the Applicant.