Frequently Asked Questions

Q: In terms of the potato (processing) industry, how many ways are there to peel potatoes?

A: Basically, there are two: batch and continuous. In addition to batch and continuous peeling which both employ abrasive peeling there are several other means:

  • Knife peels either by machine or by hand is still used in the world with hand peeling obviously for lower volumes. There are drum shaped mechanized knife peelers in some limited numbers
  • Lye peeling has seen major usage in the past and still has some usage today where the potatoes are bathed with a caustic solution and then the skin and the solution are scrubbed off. Tomatoes still heavily utilize this method for peeling.
  • A widely used method employs steam peeling where the potatoes are filled into a large (250 kg- 500kg) pressure vessel. High temperature steam is introduced under high pressure into the vessel after it is sealed. The vessel rotates so that all surfaces of the potatoes are exposed to the high temperature. After a brief time (approximately 10-40 seconds) the surface of the potatoes may reach 130 degrees C but with the pressure there is no boiling. The container is then explosively depressurized and the water in the superheated surface of the potatoes flash boils literally blowing the skin from the surface. The container is emptied and the potatoes and all of the skin and boiled surface starch are then run through separators that may be Vanmark peelers to leave the potatoes cleaned for the next usage.

Q: Which method, batch or continuous, is better for French fry production and why?

A: Batch and continuous abrasive processes both produce peeled potatoes that work in French fry applications. Neither of these methods efficiently removes 100% of the peel due to the surface imperfections or concave shapes. Most French fry plants are running steam peelers followed by a scrubber to remove the loose peel and starch from the surface. So called “dirty” fries are cooked with some peel left on. Vanmark believes that a continuous peel method better matches up to the production methods of a typical fry line.

Potato chip plants run the product with 5 – 30% of the peel remaining on the potato. They typically use an abrasive process and most typically use a continuous peel process for reasons shown above to match up to the slicer and fryer processes. Even in kettle chip operations, the continuous process seems better suited as the cycles of any batch peelers are not synchronized to the cycles of the fryers.

In a chip plant the steam peeler leaves a typical “cook ring” on the outside of the potato that, after slicing and frying, looks like a discolored ring around the chip. This is usually not a desirable feature and steam peeling is rarely seen in chip applications.

In any large volume operation whether the end product is fries, chips or another product, the use of a non-continuous peeler like a steam or batch abrasive peeler requires that additional storage and feed equipment be added to the lines to make up for the stopping and starting of product flow inherent in those processes. These are often referred to as surge hoppers and even feeders. Their purpose is to store product when it is dumped from the batch process and evenly meter it to the line downstream to supply cutting or cooking equipment with a continuous flow of product. A similar set of equipment must be installed upstream of the batch machinery to collect product waiting for the batch machine to open and then quickly feed it in. A continuous peeler removes the need for that extra equipment.

Q: Why is poly chain drive belting more effective than previous types of belting used (and what were the previous belts called?)

A: Poly chain belting and its associated pulley profiles have significantly stronger reinforcing belting and also a stronger tooth profile. They are a more refined form of timing belt. Together these have made belt failures that occurred after a significant run time in the earlier timing belt applications a very rare occurrence. Vanmark has not replaced a poly chain belt due to normal wear failure in over four years of field exposure. The earlier timing belts were not referred to by a particular trade name.

Q: What are quick slip couplers?

A: Vanmark’s roll couplers allow a roll to engage the drive system with a cushioned urethane square drive coupling. This give some cushion for startup loads and also allows the roll to be easily removed from the machine for cleaning, service or changeover after removing the discharge end fasteners. In our 2420 machine, for instance, this feature allows six rolls to be changed out in less than 30 minutes by an experienced operator.

Q: Vanmark now offers over 90% energy efficient motors as compared to 10-15 years ago. How much more throughput are we are providing by way of developing energy efficient motors and reducing power consumption?

A: Improvements in solid state speed controls for electric motors have made the use of hydraulics to get variable speed nearly obsolete in this application. Nearly all of our peeling machines 15 years ago were powered by hydraulic motors using high pressure fluid generated by an electric motor driving a pump. A given production level using a hydraulic system required a 20 HP pump and electric motor unit powering several hydraulic drive motors for the peel rolls, tumbler and an auger discharge. In today’s machine the same output is achieved using three electric motors totaling 11 HP. Our most recent machine has a throughput 33% higher than the hydraulic machine described above and with similar features is fitted with a total of 16 HP to achieve that.

Q: With all the talk about healthy eating, fibre and food security, consumers are being advised to eat grains and to keep skins on fruit/veggies. Is this something you think about? Do you foresee skin on potatoes becoming the norm? How will this affect peeling manufacturers?

A: Processors will always look for recipes that meet the consumer desire. An increasing percentage of those will target health conscious customers. We have seen an increase in interest in using our machines in a cleaning and scrubbing mode to prepare skin-on products for consumption without peeling. Clearly, root crops that emerge from the ground covered in soil need a vigorous cleaning prior to final consumption. As processors add recipes containing skin-on products they are prioritizing both the cleanliness and appearance of the skin to make the most appealing presentation. We see the same trend in the fresh pack market where polishing of the skin improves not only the cleanliness but also the presentation and attractiveness of the fresh products.