When choosing the type of potato to make the perfect French fries there were certain factors that had to be looked at. First, the percent of dry matter (starch) and the percent of water that was in the potato. Also, the sugar content played a role into the decision of what type of potato to use. The average percentage of starch to water in a potato is 17 % starch to 78 % water. The other 5 % of the potato is irrelevant to making French fries. Heston Blumenthal of the Fat Duck discovered that to make the perfect French fry the percent of starch would be 22.5% of the potato. If the potato had more than 22.5 % starch it had a tough, leathery exterior when fried and if the potato had less than 22.5 % starch the potato tasted bland and did not crisp up well. The potatoes that were consistently closest to this percentage were the Maris Piper and the Arron Victory potato. Some other potatoes that are good for French fries are Russet potatoes, Idaho potatoes, King Edward potatoes, and Sante potatoes. If there is too much sugar content in the potato it prevents the fries from crisping. The extra sugar makes the potatoes brown before they crisp so if you wanted to have crisp potatoes you would have to “burn” them if the potato had high sugar contents. The sugar content in the potato increases after the potato has been harvested or if the potato is kept in a chill place like a refrigerator. To make sure that your potato does not have a high sugar content either get potatoes that have just been harvested and that have not been sitting in a factory garage for months or you can get potatoes that were frozen the day they were harvested (I do not know if they have these). Potatoes are typically harvested in September, so that would be the prime time to use the very fresh potatoes.
When choosing the fat in which you want to fry you potatoes there are a few things to consider. What is the smoke rate of the fat? Does the fat impart any pleasant or unpleasant flavors? Do you want the potato to not get any flavor from the fat at all? A high smoke rate for frying is key because if the smoke rate of the fat is below 400 degrees the fat will break down and cause the fries to taste burnt and fishy. Some oils that have high smoke rates are canola (486 degrees), peanut (448 degrees), safflower (509 degrees), and beef tallow (420 degrees), and horse tallow (475 degrees). Horse tallow is used by Alain Passard, owner of L’Arpege, to make his French fries. In America I believe a lot of people would consider using horse tallow unethical. Beef Tallow gives a great flavor to fries that can only be matched by horse tallow. Also let’s say you had extra duck fat around you can use that to make fries, but duck fat would impart a good flavor, but that might not be wanted in the end result of the French fries. Oils like canola, safflower, and peanut do not give of much flavor because they usually have Vitamin E. Vitamin E prohibits the transfer of flavors between the oils and the potatoes being fried. There is no best fat for frying, but if you want your fries to have an extraordinary flavor that most fries don’t have use beef tallow. McDonalds was using beef tallow in America up to 1983 for their fries, but McDonalds stopped using it because people did not like how the fries were so unhealthy. If you want fries with neutral flavor use canola oil, safflower oil, our peanut oil. Just make sure whatever fat you are using that it is very clean.
I think everyone agrees that perfect fries are crisp on the outside and fluffy and tender on the inside. To achieve this there are numerous steps that need to be made. When cutting the potato for French fries the knife you are using or whatever you are using to cut your potatoes has to be extremely sharp. If the knife is not extremely sharp when it cuts through the potato it creates a rigid cut (whenever you have a sharp knife and you cut something the surface that you cut should be very smooth). When this rigid cut goes into the fat that you are frying in it will cause oil to get stuck in the crevices on the surface resulting in greasy fries. All of your fries have to be uniform in size so there is equal browning throughout. If you cut your fries too thin the whole fry will be crispy but there will be no fluffy interior. If you cut your potatoes too thick the crust will be cooked before the inside of the fry gets cooked. Once fries are cut to ¼ inch slices put them in salted cold water for at least an hour. There are many reasons to do this. One reason is that the salted water prevents the potatoes from oxidizing. Secondly, if there is too much water content in your potato the water will leach out of the potato to form equilibrium with the salted water (osmosis). Thirdly, putting the potatoes in the salted water will remove the excess starch that is on the surface of the potatoes. If the excess starch is not removed from the potato when the potato is frying the steam will get trapped inside of the potato which will make the potato have an unpleasant gummy texture. Also, if the steam gets trapped inside of the potato it cannot “block” the oil from coming into the potato. If the oil is not stopped from reaching the inside of the potato, the potato will be very greasy. Then blanch the fries in salted water for 14 minutes and 30 seconds until they are slightly overcooked. Fries need to be cooked twice in a big vat of oil and in small batches of potatoes so the fat does not lower drastically in temperature and so the fries do not stick together. The potatoes must be extremely dry before put into fryer. Some ways to dry the potatoes completely are using a dissactor, a cyrovac, or a salad spinner (the most practical way). There is an initial par cook in the fat at a temperature of 275 degrees to develop the crust of the potato and then there is a second fry at 375 degrees that crisps the outside of the potato. You must initially par cook the potatoes in the fat because the starch in the potato has time to dissolve and glue to the outer cell walls to make them thicker and has a more robust flavor. Also, potato cells have granules of starch, which swell when the cellular water is heated, which forms a “puree” inside of the potato that gives the fries there fluffy texture. After the first period of frying the potatoes should be cooked through but not crispy. If the fat for the pre cook is too hot the potatoes will not get cooked all the way through on the inside and if the fat is too cold the fries will turn out to be too greasy. Once all of the fries have been precooked again in small batches, crisp the fries up in the same fat that was used to precook them, but instead at a much higher temperature. Make sure not to puncture the fries because that will make the inside of the fry collapse, like a soufflé, and the fry would not be as fluffy. The second the fries come out of the fryer drain them and then season them with good sea salt and any other flavorings you wish to impart in the fries. You season right after the fries come out of the fryer because the remaining fat that is still on the fries will make the seasonings stick to the fries. Serve the fries to the diners as quickly as possible. Maybe serve with some sort of vinegar sauce because vinegar (malt vinegar) pairs great with fries.