Machines for the food processing industry
Düsseldorf . Deutschland
During steam peeling the fruits to be peeled are
exposed for a short time to high temperatures in a pressure
vessel. After that, the nearly loose skins are abraded and/or
washed off by means of other machines connected behind. The
surface of the peeled fruit is smooth. However, this surface
layer consists of a "cooking ring" which is more
or less thick, due to the short but intensive heat effect.
This "cooking ring" (appr. 2-4 mm deep) consists
of the parboiled, "half-cooked" layer, i.e. this
layer is not raw anymore.
On mechanical peeling the skins of the fruit are
abraded by means of rough or fine carborundum granulation or
by a blade peeling machine with blades. "Cooking
rings" are avoided. The surface of the peeled fruits
can have - depending on the carborundum granulation - a
rough or very smooth appearance. - Mechanical peeling is
carried out in continuously working "roller peeling
machines" or in so-called "batch peelers". In
case of cutting with blade peeling machines a smooth blade
On account of the high investment costs (a steam
generator is required, too), steam peelers are generally
used in Western Europe, if large quantities of fruits (from
7.5 to 20 tons/hr) have to be peeled, with little floor
space being available. But this method is chosen only in
those cases where the "cooking ring" is irrelevant
for the quality of the final product.
This "cooking ring" is unacceptable for
the potato chips industry (GB: crisps), because it affects
the appearance of the final product. That's why one works
with mechanical peelers in the potato chips industry,
whereas the French fries producers (GB: chips) use steam
peelers if high throughputs are required.
Steam peelers are also preferred for difficult
small and fine products, i.e. for cucumbers, Paris carrots
and finger-thick carrots.
Nowadays there are roller peeling machines with
high capacities available (dimensions inner space abt. 3 m
in length, diameter of screw conveyor up to 1.5 m). With
these machines one can achieve considerable throughputs, up
to 5 tons of raw goods per big machine. Capacities are,
however, lower than those of steam peeling plants.
The following fruit can be excellently peeled in
roller peelers: potatoes, carrots, celery roots, beetroot (cooked
or uncooked), turnips, kohlrabi and other tubers and root
vegetables. Some subtropical and tropical fruits, too, can
be peeled mechanically.
The peeled fruit can have a very smooth
Mechanical peeling technology has to be used, at
any rate, in the following cases: in the potato chips
industry (GB: crisps) and in the catering section, in
industrial potato peeling plants, where potatoes for big
canteens, restaurants etc. are peeled. Here, the "cooking
ring" would cause a hardening of the peeled potatoes,
i.e. a "second skin" which would incur the
displeasure of the end user, e.g. the guest in a restaurant.
Here is a true story regarding this matter: the
social director of a renowned German chemical enterprise
(12.000 servings a day for the personnel) purchased years
ago a steam peeling plant for the big canteen of the factory.
Due to the "second skin" ("cooking
ring"), the guests in the factory-owned restaurant had
difficulties in dividing the potatoes on the plates with
their forks. The fork would not penetrate the "second
skin" as easily as that. It often happened that the
potatoes with the gravy slipped from the plate, smudging
visitors' clothes. This also happened in the factory-owned
restaurant for the high executives of the enterprise and
their guests. - The social director was fired. A
mechanically working peeling plant was installed by our
Very good peeling results are achieved with the
mechanical working Multi-Disc-Peeling Machines (MSS). The
latter can both work with blades and with carborundum
The rate of peeling waste in the efficiently
constructed and more modern mechanically working peeling
plants is not necessarily higher than that of steam peeling
plants. By applying the "micro fine-grain peeling",
the DORNOW peeling machines can work fairly economically.
This method uses a very fine carborundum granulation which
takes off only the outer layer of the skin.
On the other hand it is not always expedient to
talk about "low waste rates": in the end, the
peeled fruit are supposed to reach a certain degree of
cleanness! For that, one has often to put up with more waste!
It is not true to say that steam peeling or the
brushing machine connected behind would also eliminate eyes
and foul spots from steam-peeled tubers and root vegetables!
That steam peeling or the machines connected
behind hardly succeed in doing so, is confirmed by the fact
that many steam peeling plants are connected with mechanical
Here is an episode: years ago I visited with
customers, who were interested in buying our machines, a
renowned south German tinning factory. There, a steam
peeling plant and a DORNOW roller peeling plant were in
operation at the same time. The goods to be peeled were
carrots for industry.
The carrots peeled in the steam peeler still
showed many black spots. A lot of personnel were busy to
remove these spots.
The carrots stemming from the next-door working
DORNOW roller peeling plant had been peeled much more
accurately, and it did not even take one tenth of the
inspection personnel to eliminate the foul spots. Certainly,
the roller peeler produced more waste at that time, but the
peeled products had the cleanness required in a tinning
That DORNOW roller peeling machines can also work
at low waste rates, is demonstrated in the potato chips
industry (GB: crisps): Here, the machines peel with waste
rates of 6 to 10 per cent. Of course, potatoes peeled that
way are not completely clean, but the achieved degree of
cleanness will normally do for the chips industry.
On the other hand there are the celery tubers:
they have deep tears and splits in their skins which have to
be peeled off for the most part. In this case the steam
peeler has its difficulties. The DORNOW roller peeling
machines, the peeling rollers of which one can make rotate
quickly and aggressively, will peel the tubers so fast and
accurately that they can be passed on to further processing
with a good conscience.
But the DORNOW roller peeling machines can also
peel "softly": cooked beetroot (CH: Randen) are
peeled neatly and accurately in no time.
Steam peeling appears to be economically
interesting if high peeling throughputs are to be achieved
with little floor space being available. Moreover, it is
excellently suitable for peeling some difficult and
Mechanical peeling is applied in the low-capacity
sector of up to 5 tons of raw material per hour and in those
places where it is actually indispensable: in the potato
chips industry (GB: crisps) and in the catering sector.
paper contains non-committal notes. We do not lay claim to
completeness. Alterations reserved.
DORNOW total on the Web: www.dornow.de / www.dornow.com
Dornow food technology GmbH,
D-40549 Düsseldorf - Germany, USt-Id.-Nr. DE119264470