I therefore thought it might be useful to summarize my results to date, particularly with the starch-infused ultrasonic fries in MC. I've been trying to improve on that recipe, or at least simplify it.
Now, I've made the traditional double-cooked fries on and off for 40-50 years, and earlier this year I experimented with Heston Blumenthal's triple-cooked Pommes Pont-Neuf, which uses water, sugar, salt, and baking soda to blanch the fries for 20 minutes, until very tender, followed by vacuum cooling (or air drying), frying at 150C/300F about 7 minutes, cooled again, and then frying at 22C/430F until crisp.
Those were a substantial improvement over my older technique, although I found that 20 minutes was too long -- too many of the fries fell apart. 15 minutes seems about right, at least with Idaho Russets.
After reading the starch-infused ultrasonic French fries recipes from MC, I ordered a Branson B5510 2-1/2 gallon ultrasonic machine, and followed the recipe. My wife and I agreed that they were absolutely the best we had ever eaten, bar none! They were deliciously crunchy on the outside, and soft and succulent, rather like a good baked potato, on the inside.
These were hand cut into 1/2" or 1.5 cm square-cut fries.
Because I don't have a combi oven (which the MC video suggests using), I cooked three potatoes (750 g, divided onto two bags, after brining them with 15g of salt in 750 ml of water) in a big pan in water on the stove, in two SV bags.
I then drained them and let them cool in the freezer for about 20 minutes, while I made up the potato starch mixture.
I transferred the potatoes to two new bags, and added the potato starch mixture, then put them in the Branson ultrasonic cleaner, which had been degassed and brought up to 64C. After 20 minutes, I flipped the two bags over, and gave them another 20 minutes. (The recipe calls for 45 minutes per side, but I misread or misremembered it.)
I then put the fries on a rack, and put them in my JennAire oven on the dryer function at 100F for about 20 minutes. After that, I transferred the fries to a rack, and put them in my chamber vacuum and ran it it five times at maximum vacuum. Several times it timed out, unable to reach 99% vacuum, so I had to stop and restart it.
Then I put them in my Krups Professional Deep Fryer at 330F for three minutes using Crisco vegetable oil, and afterwards put them on rack in my cool garage, with an electric fan blowing on them to cool them.
Then finally back in the deep fryer at the maximum setting (375F), but unfortunately this isn't quite hot enough. So instead of merely 3 minutes, I had to give the fries closer to 6 minutes to reach a nice goldren-brown color
Served with ketchup and Boar's Head Creole mustard, together with two SV lamb shoulder chops, with rosemary and garlic confit for Valentine's Day, the results were absolutely worth the effort!
Now, some have questioned whether this was worth the time and expense.
But as someone said, even a monkey ought to be able to make hot, fresh, French fries that taste good right out of the fryer -- the real question is what happens after they cool a bit, and what they "feel" like. Certainly there are lots of fast food joints that fall down in that regard.
To my mind, taste isn't the only important factor -- auditory and other sensory "crunch" factors are also important to the overall dining experience. And it was the extra delicious crunch, plus the soft, mealy interior that made those fries so appealing.
Since that initial, successful result, I've tried a couple of variations.
The first was to simply boil the potatoes in a pan, rather than bagging them. That didn't work too well -- the potatoes tended to fall apart, while bagging them under vacuum seemed to hold them together better.
Cooking the bags in a pot of the stove didn't work too well -- I don't have a deep enough pan.
But I do have an immersion circulator, so I cranked it up to 95C -- whereupon it started to boil at my altitude (7000ft.) So I turned it down to 90C, and cooked two bags containing a total of 750 g of cut fries for 15 minutes. I could easily have done four or more bags at the same time.
In a misguided effort to save time, I tried boiling the fries along with the potato starch. Big mistake! The starch made a very gloppy mess down at the bottom of the bag. Start over.
After boiling the fries, I cooled them in room temperature water before draining them. I think that was a mistake as well. Draining them, then putting them in the freezer briefly seemed to work better.
Then I added the potato starch mixture (150 g water, 75 g of potato starch, divided across two bags), pulled vacuum until the starch mixture started to boil, and sealed them.
Then into the Branson ultrasonic for 45 minutes, then flipped the bags over for another 45 minutes. The bags were submersed in plain water, in a perforated rack to keep them off the bottom of the unit.
(BTW, there is a considerably less expensive ultrasonic machine, the Samson GBW-300 Ultrasonic Fruit and Vegetable Washer, that is around $250. I wish I had seen that one before buying the much more expensive Branson.)
I've done this twice, now, once with the Branson heater on and set at 62C, and once in just room temperature water. I didn't measure the final temperature in that case, but the ultrasonic warmed up the water -- I would guess to about 50C.
I then put the fries on a rack and put them in my cool garage with a fan blowing on them to cool and dry the fries, followed by vacuum cooling. I now think that my convection dehydrator function on the oven (set at 100F) worked better, followed by vacuum cooling them further.
Then into the deep fryer, set at 162C/330F for about 7 minutes, per MC.
Then back to the garage and fan again. In the future, I think I'll try refrigerating or even freezing the fries on a rack at this point. Others have said that 24 hours in the fridge helps considerably.
Heston Blumenthal recommends 220C/430F for the final fry. Unfortunately, no deep fryer I know of will go that high, and I don't like stinking up the kitchen with a Le Creuset or wok pan, so I had to use 190C/375F for about five minutes. (I might think about opening up my Krups Professional and seeing if I could recalibrate the setting to get it hotter, even though that would probably void the warranty.)
In general, this second go-round, although excellent, wasn't quite as superlative as the first, so I'll go back to that method next time, perhaps with some added refrigeration between the first and second frying.
A little added salt might have helped -- perhaps some hickory-smoked sea salt, and some pepper.
Next time, I'll try using a salad spinner to drain the fries after boiling them, before dehydrating and cooling them. I just hope it wouldn't break them. This could also be used after the first frying step.
Other changes that might be worth trying would be to try adding the sugar and baking soda that Heston uses during the initial blanching. (I'm not sure what effect the baking soda has -- I guess it makes it more alkaline, but to what end?)
And I might skip the ultrasonic cavitation, to see how much difference that makes. It would certainly speed up the process. And I'm not sure I could tell the difference between 20 minutes a side and 45 minutes -- another variable that would be worth exploring.
Sorry for the length of this post, but I wanted to summarize my experiments, and invite others to contribute as well.
Edited by Robert Jueneman, 20 February 2012 - 12:52 PM.