Machines for the food processing industry
Düsseldorf   .  Deutschland

Manual Reworking or Re-Peeling of Mechanically Peeled

Potatoes for the Catering Sector? 

Re-Peeling in Batch Peelers or in Roller Peeling Machines?



The manual reworking of potatoes, already peeled mechanically, for the catering sector requires many personnel, above all if the inspection of the peeled material is done on conveyor inspection beltes. Here, the potato lies statically on the belt, and it is impossible for the human eye to ascertain whether there are damages or foul spots at its lower (hidden) side. To make sure this is not the case the staff have to pick up every potato. - If manual reworking is carried out on roller inspection belts, it'll take slightly less time to do the job: You need not pick up every potato. The peeled potatoes pass the personnel in constant rotation: The "good" potatoes keep moving on immediately and are not touched anymore by hand.

Still, the performance of the personnel appears to be insufficient if after a first peeling process at e.g. a waste percentage of 20 to 25 per cent, when peeling medium-sized or large products, eyes and other foul spots must be removed by hand.

You can achieve an hourly capacity of approximately 40 to 60 kgs per person, at a total waste rate of about 30 per cent (if West European continental potatoes are used).
This is true if the potatoes are to be peeled in an absolutely accurate way – as it is usual for the catering industry - .

Due to high labour costs and normally low potato prices in this regions (in the European Community), the industrial peeling factories have been opting for longer peeling times at higher waste rates.

Moreover, it is now common in such factories to dispense with manual "reworking". Potatoes with dark spots or other damages are sorted out by the personnel at the roller inspection table and put on conveyor belts via feeding chutes. These conveyor belts take the potatoes back to the peeling machine for re-peeling… 

Thus, the waste rate will be higher, i. e. between 5 and 20 per cent more. But: a good worker at the roller inspection table will now have an average output capacity of about 120 to 250 kgs/hr, in case of very big potatoes still more... Compare the throughput capacity under item 3.
  7. The sorting and re-peeling (at higher waste rates) has, therefore, proven successful in the EU...

The more so since the DORNOW roller peeling machines peel without water, and the peel pulp produced can be used for fodder, particularly since it consists at 100 per cent of potato parts.
  9. The method of re-peeling has, however, proved successful above all in roller peeling machines. Reason: See items 10 to 13.

In batch peelers with bottom and side peeling you will frequently find "flat" peeling. Due to the centrifugal forces the potatoes move along the inner wall and are peeled "flat" this way after some time. Thus, waste peel is produced in places where it should not be produced...
11. In DORNOW roller peeling machines this does not occur. Here, potatoes are peeled largely regularly.

Further reasons that suggest not to carry out the after-peeling in carborundum batch peeling machines (with peeling segments at the bottom and at the sides):
a. In machines with bottom discs >600 mm the potato is liable to getting inner damages which may result in colouring and a "second skin".

Most batch peelers must be coated with a more rough granulation. A fine graining gets choked too fast so that the peeling capacity falls off drastically.

Peeling elements coated with a rough graining lead to a product with a rough surface structure which is not very favourable for the catering industry.
Further reasons in favour of after-peeling in DORNOW roller peeling machines:

The first part of the peeling rollers can be coated with rough granulation; here, you remove, fast and thoroughly and without flat peeling, those layers of the potatoes that have to be removed!

The second part of the peeling rollers is coated with a coarser granulation. Smooth potatoes leave the re-peeling machine.- The fine granulation doesn't get choked (see above): the peeling rollers clean themselves. The consumer will enjoy smoothly and accurately peeled potatoes thanks to the micro fine-grain peeling method which can be applied here!
14. The above observations are grounded on many years of experience. Their publication is non-committal for us.

Please see section A!


This paper contains non-committal notes. We do not lay claim to completeness. Alterations reserved. 
Our order confirmation, accepted by our customers, is in effect upon delivery. The presentation of a new edition of this treatise will substitute for any previous versions.
Copyright by DORNOW food technology GmbH, D-40549 Düsseldorf

For more information:       

Q94 E2

Dornow food technology GmbH, Willstätterstr. 12, D-40549 Düsseldorf - Germany, USt-Id.-Nr. DE119264470
Tel. ++49-211-527060, Mobile ++49-172-2614932, Fax ++49-211-596883, email, Internet:

Commerzbank AG, Konto-No. 1452333, BLZ 300 400 00, Managing Director Karl-Dietrich Dornow, Amtsgericht Düsseldorf, HRB 22597