About potato dry matter content
Dry matter content of potatoes is of key importance for the texture of the
final product. Also Yield and fat content are affected by potato dry matter
content.
Dry matter content of potatoes
can be expressed in three different
ways. They can be converted into
each other:
- percentage dry matter
- specific gravity
- weight in water (w.i.w.)
Table of the relation between weight in water, dry matter
content and specific gravity
The following table provides
guidance on the dry matter content
required for various potato
products:
Dry Matter Content
|
Product |
Minimum Weight in Water (%dm) |
Optimum Weight in Water (%dm) |
Maximum Weight in Water (%dm) |
|
French Fries |
360 (19.7%)
|
400 (21.7%)
|
450 (24.1%)
|
|
Potato Chips |
400 (21.7%)
|
420 (22.7%) |
470 (25.1%) |
|
Dehydrated Products |
380 (20.7%)
|
400 (21.7%)
|
450 (24.1%)
|
Methods to assess potato dry matter content
In association with Martin Lishman, we offer you the following tools to
measure dry matter content of potatoes:
Measuring the dry matter content of potatoes by the weight in water is
the standard method in Europe and is gaining ground in North America due to its
precision. This digital balance makes it even easier:
- A digital balance that calculates potato dry matter
content and specific gravity.
- Any weight of potatoes can be measured.
- Records weight in water and weight in air, and
calculates dry matter automatically.
- For use in the QC laboratory or in the field.
Requires a container with just a 40cm depth of water
- Portable, simple to use and robust. Stores data for
PC download.
Digital Balance for Weight in Water Product Description...
When recommended: We strongly recommend
weight in water as the preferred method for assessment of
dry matter of potatoes.
The Hydrometer has long been the industry standard in the
North American Potato Industry:
- Suitable for static applications, requires large
water bin (45 gal/175 liter)
- Potato weight needs to be exact.
- Available in different dry matter ranges from 17 to
27 %
Hydrometer Product Description...
When recommended: this method is more
cumbersome than a weight in water assessment: you need a
larger bin, the weight has to be exact, it is less precise
and that is why we do not recommend this method. Why would
you still consider this method: a hydrometer is less
expensive than a weight in water balance.
This portable unit is specifically designed for use in
the field and provides information on dry matter
distribution:
- Tests individual tubers for dry matter
- An alternative to the potato hydrometer, avoids the need for a
45gal drum of water
- Ideal for measuring dry matter quickly, simply and accurately in
the field
This tool comes in two versions: the regular version and
the salad potato version. The salad potato version contains
next to the regular corer a smaller corer, so smaller
potatoes can be tested.
Dry matter Field Kit Product Description...
When recommended: for in field use, for
testing tuber to tuber dry matter distribution
Tips on measuring potato dry matter content
Applicable to hydrometer, digital balance for weight in
water:
- Increasing the total potato weight (through repeats, up to 15 kg) will
increase the accuracy.
- Removing hollow or glassy potatoes with a salt bath prior to measuring
average dry matter, delivers most precise results. A single hollow or glassy
potato can seriously skew results. Hollow or glassy potatoes typically float
in a solution with a specific gravity of 1060 kg/m3, which can be prepared
by dissolving 153 g of NaCl per liter in water.
|
