Potato harvest 2009 in most of North Western Europe was
characterised by hot and dry weather during the second part
of the season, resulting in a high dry matter content of the
potatoes. For french fry processing, a high dry matter
content is typically desirable as it has positive effects on
product texture and yield. High dry matter content is also
generally linked to a mature crop and therefore a good
However, there is one major disadvantage of potatoes with
a very high dry
matter content: increased blackspot susceptibility.
Unfavourable harvesting conditions further exacerbated the
problems. Waste percentage as high as 20% have been
consists of dark coloured spots below the surface resulting
from tissue damage. The dark spots are only visible after
peeling. As for the exact colour: the Dutch call
this defect "blauw" (Blue), while other languages
refer to black: German
("Schwarzfleckigkeit"), English ("blackspot") and Spanish
("mancha negra"). In order to not to offend the
Dutch, let's say that "greyish" is probably the
How much black spots actually develop depends on two
- blackspot susceptibility of the
potatoes: how easy do the potatoes get
damaged and develop this discoloration
- The actual forces applied to the potatoes
Factors influencing blackspot susceptibility:
- higher dry matter content --> higher
- higher temperatures during handling --->
- Fertilisation: a low potassium content
--> increased blackspot suspceptability,
Nitrogen fertilisation postpones maturity
---> lower dry matter content, hence
Forces influencing the forces applied to the potato
- how rough you handle your potatoes (e.g.
also dependent on conditions during harvest)
- size and shape of the potato
- storage height in potato storage
So you can get away with a high blackspot susceptibility to
some extent as long as you "treat your potatoes like eggs".
It is important to realize that the damage to the potato
tissue is not immediately visible. The initial damage starts a
range of biochemical processes in the potato, including a colour reaction
involving PolyPhenol Oxidase (PPO). In 10-20 hours the first
discoloration becomes visible and it typically takes several
days before the colour has fully developed. You can take
advantage of this fact by immediately processing potatoes
after they have been exposed to potential mechanical damage. Colour
development is strongly temperature dependent, faster at
higher temperatures and could occur - even during the
process - until the responsible enzymes are inactivated.
If you have potatoes in storage with very high dry
matter, it is important to know that black spot issues
typically increase during storage, especially if a lot of
additional water is lost during storage. So minimize water
losses, don't store too long and process immediately after
removal from storage.
For processors, trying to "peel away" black spots is
probably not the way to go, since black spots are located
fairly deep in the tuber. This is more a job for electronic
sorters and ADR's. Especially lucky are french fry
manufacturers who have installed (additional) optical
sorters at the end of the line. Under these challenging
circumstances these end of line sorters can help stay within
specifications without sorting out too much good material.
Paul van Eijck
The potato hotbox is the ideal tool to achieve overnight
assessment of potato bruising.
The hotbox allows evaluation of the quality ahead of time
and provides support in decisions on what lots need to be
processed right away and what lots can be stored. The Hotbox
is also ideal for blackspot susceptability testing.
The Hot Box indicates bruise levels after just 12 hours. It
has an integral heavy duty fan, thermostatically controlled
heater, water reservoir and timer. Separate trays allow periodic
sampling throughout the work period. Different models are available
to suit different size operations.
indicated in todays editorial, blackspot and bruising
results from the combination of blackspot susceptability and
the actual forces applied to the potato. The Smart Spud
helps you measure the actual forces applied to the potato.
Just add the Smartspud sensor to the flow of potatoes and
follow the forces applied to the "potato" sensor as it moves
with the real potatoes on the screen in real time. Within
seconds you see exactly how your harvester, windrowers,
grading, washing and packing facilities are causing damage
to your crop.
Stop guessing, start measuring.
Order a SmartSpud...
French Fries and Potato Specialties
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Oolannin is a Finnish manufacturer of frozen potato
products and meals. Oolannin is a subsidiary of
Estrella Maarud Holding A/S
Estrella Maarud manufactures and markets salted snacks
in the Nordic and Baltic countries under the brands
of Estrella, Maarud and Taffel.
Estrella Maarud is owned by
Herkules Capital, who acquired this business from
Kraft in october 2008.
OK-Snacks is a Danish manufacturer of savory snacks.
Brand names include: OK Snacks factories are located
in Ejstrupholm and Søndersø.
Crispo Denmark AS
Crispo Denmark A/S is a small potato chips manufacturer
in Denmark. Crispo produces handmade kettle chips
and sells them in Denmark and throughout Europe.
Brands include "Grov" and "Best Bite".
National Restaurant Association (NRA)
The National Restaurant Association (NRA) is the
leading business association for the restaurant
industry in the United States.