| DENSE MEDIUM SEPARATION -> AGRIC: POTATOES | CARROTS SUGAR |
Control of Potato Processing
Why does the grower bring
stones and other trash to market? Why does the processor
have to deal with defective, undesirable, diseased or
improperly stored potatoes? Why is he forced at times to
reject an entire load of potatoes simply because a small
percentage of them do not meet specification? Why does the
fry market process potatoes that are too high in reducing
sugars? Why does the fry market process potatoes that vary
too much in moisture content? Why does the canning market
process potatoes that should never be put in a can?
Clear &
Faultless Separation
Back in 1985 ESR
International designed a unique bi-directional dense medium
barrel for the sorting of a variety of root vegetables such
as carrots, potatoes, salsifies and beets. Not only did
this separator remove stones and other high-density debris
from the root vegetables, but it also removed near-gravity
extraneous material such as corn stubble, fly ash and bits
of plastic.
Eventually it was discovered
that this drum could be used to separate a good vegetable
from a bad vegetable, and although the difference in
density between a good and bad might be but a few points to
the second or third decimal place, a clear and faultless
separation took place. Here was a separator that performed
20 to 35 times more accurately than the best vegetable
separators on the market at the time. Not only were the
maintenance costs associated with the processing of trash
drastically reduced, but also issues regarding the quality,
taste or texture of the vegetable fell for the first time
within the processor’s control.
Potato Dirt
is the Key
In this revolutionary
sorting process, the suspension fines needed to change the
density of water are obtained nowhere else but from the
dirt that mechanical harvesters extract along with the
potatoes. Two stages of classifying cyclones isolate
ultra-fine sand from the scrub and rinse water of the
pre-processing and cleaning line. By using these natural
suspension-creating fines, one avoids the dreadful health
issues associated with the use of clay or sand contaminated
with dioxins or heavy metals, and one avoids as well the
thorny environmental and maintenance issues associated with
the use of salt and the disposal of brine.
The Most
Successful Separator in Europe
Eventually sixteen
bi-directional dense medium separators were sold in Belgium
and France. The leading vegetable processor in Europe,
Bonduelle, with a colossal 30% share of the European
vegetable market, bought five separators. Their fifth
separator, recently installed in August 2004 in Renescure,
France, is the first vegetable separator designed by ESR
International that does not employ vibratory screens. The
food giant, Nestle (Sitpa), bought two 60 TPH potato
separators which were installed at its dehydrating facility
in Rosiere, France. With sixteen separators in continuous
operation in Europe, some for almost 20 years, it is truly
remarkable that no one to this day has ever been able to
establish a single separation error in the finished
product.
Fry Color
& Canning
This technology can push the
potato industry in places it would never dream of going.
Never again does the fry market have to process high sugar
content potatoes that discolor and burn when fried, and
never again does the canning market have to process high
starch content potatoes that slough or disintegrate in a
can. Since only those potatoes that pass the density test
are allowed to be processed, most of the elaborate,
sophisticated and costly equipment needed to identify and
eliminate defects after processing is itself eliminated.
Imagine the money that is saved by not having to fry or can
a bad potato, and exciting possibilities open up of
eliminating an entire range of diseased, bruised, damaged,
stressed or improperly stored potatoes.
Uniformity in
Frying
But if the potato processor
can control tuber density to within a few points to the
third decimal place, he can also apply a level of control
far beyond simply eliminating stones and undesirable
potatoes. In frying chip potatoes, for example, the
operator can process at a given time only those potatoes of
a narrow and limited moisture range. In this way potatoes
pass through a frying line at a speed that precisely
matches their moisture content and therefore, the entire
batch fries in a thoroughly uniform manner. By creating two
or more categories of low moisture content potatoes, as
shown in the following diagram, all the potatoes exiting a
frying line are cooked to the same moisture content and
crispiness. Nothing is undercooked, and nothing is burned.
Likewise, in canning
potatoes, the processor should not be satisfied with
eliminating stones and undesirable potatoes of a high
solids content. The operator now has the means of making
distinctions between what cans best as whole potatoes
(<1.072 density) and what cans best as sliced or diced
potatoes (from 1.072 to 1.080). As the density of a potato
increases, the amount of time it can be cooked in a can
decreases. Since, due to their relatively large surface
area, sliced and diced potatoes can be cooked more quickly,
they will not slough even though their density might be
relatively high. In this way the cannery has a lot more
options at its disposal, and is, therefore, confronted with
a lot less reject.
An Average
Underwater Weight is No Longer Acceptable
Both in the frying and
canning of potatoes specifications regarding quality should
no longer measured in terms of an average specific gravity.
An average gravity says nothing about the presence or
extent of the low- or high-density tails of a distribution
curve. Current practice dictates that quality control has
to adjust average specific gravity numbers at times too far
to the left or too far to the right to make sure that truly
undesirable potatoes of a high or low gravity do not appear
within the processing line. How wasteful such a practice
proves to be, especially when an entire load or even
harvest might be rejected based on a relatively small
percentage of bad potatoes! With ESR technology, the grower
or processor is assured that not a single potato of the
wrong density can appear within a processing line. This
allows him to chop off the undesirable tail of a
distribution curve, and in so doing, he is confronted with
lot less reject.
Conclusion
In conclusion, this dense medium separator employing fine sand in suspension can make an enormous difference to both the grower and processor of potatoes. Why bring trash to market? Why process undesirable potatoes? Why reject large quantities of good potatoes? Why bring the right potato to the wrong market? Why process the right potato at the wrong speed or temperature? With this simple and inexpensive dense medium technology, ESR International can put the potato grower or processor firmly in control of the science and art of bringing to a chip, French fry, table, flake, granule or canning market exactly what it demands.