For making crisps you need a potato which behaves as follows:
1. It must fry well, so it needs low water content and high dry matter.
2. The crisps must have the right 'snap' after frying.
3.The crisps must have a good flavour.
4. They crisps must fry to the correct colour (as decided by the marketing men) - pale golden brown.
5. In addition to this you need a potato which will give a reliable yield and which has reasonable resistance to the main potato pests.
All of the criteria must be met, and not many potatoes qualify.
It is interesting to note that nearly all crisps are made from white potatoes of very dry character.
WHY ARE MOST CRISPING POTATOES WHITE?
There are three main sorts of potato, if we classify by skin colour: red, white and russet.
Starch / dry matter is highest for whites and lowest for reds. ( # - see footnote)
Glucose content is highest for reds and lowest for whites.
Russets are somewhere in the middle.
The colour of crisps depends on the glucose content. At about 340-380F, the glucose 'browning' reaction occurs, forming poly-cyclamen. At higher temperatures, glucose forms dark-coloured caramel. Either of these reactions leads to dark crisps.
Immature tubers, high in glucose, also make dark crisps.
Crisps are dehydrated to about 2% water. A typical red potato could be crisped, but its lower dry matter content means that it would absorb more oil, make fewer crisps of darker colour, and the crisps would have less 'snap'.
Chips (french fries) are not cooked as thoroughly as crisps, so the intermediate glucose content of russets is acceptable. Slightly darker chips are OK.
# There are some exceptions; for example, the red-skinned ROOSTER has very high dry matter and can be used for crisps, and some white varieties contain a lot more water, but the generalisations above are not too far from the truth.
Nigel Deacon / Diversity website / 2010
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