Every year I have to deep fry last year‘s Idaho potatoes, they come out very very dark and sometimes they’re not even done. How can I remedy this problem?

First of all, Idaho like every long-term storage potato-growing state only harvests once per year, beginning in late summer. So sometimes the difference between ‘this year’ and ‘last year’ can be confusing. We typically just say, this year’s storage crop, as most of the harvest goes into multiple, giant sheds and shipped out as the months progress until new crop begins in late August and the cycle begins anew.

One likely reason you are seeing the issue described, is when potatoes are held too cold (below 42°F for too long a period-which can range from a couple days to a week) anyplace along the way, in transit or storage. Then, what occurs is the starches within the potato convert to sugar, changing the cooking chemistry. In fries, the outside cut surface will caramelize and discolor too soon, while the inside of the potato is undercooked.

Most of the time, cold-affected potatoes can be reconditioned, that is to say, left at ambient (room) temperature for about a week or so and the excess sugars within will naturally burn off.  In the meantime, a short-term solution is to leach the fresh-cut fries with very hot water and allowed to drain in bus tubs just prior to use. This will help remove the surface sugars. Also, in the blanch stage lower the oil temperature from 350°F down to 325°F (I’ve heard some chefs say they drop the temperature down to 275°F) – it may take some trial-and-error in your case. This will allow for a more even blanching in oil, then follow at the final-fry stage at the usual 350°F oil temperature.