Starch-Infused French Fry Perfection

[Robert Jueneman]

There are a number of posts having to do with the "perfect" French fry, but most of them date back to the 2003 to 2006 period, and none provide an adequate discussion of the techniques developed recently by Heston Blumenthal, Dave Arnold, and most importantly, in Modernist Cuisine.

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.

Bob

Edited February 20, 2012 by Robert Jueneman (log)

[gfweb]

Great post.

Re baking soda. It speeds the Maillard rxn and also has effect on pectin. I believe I've read that alkalinity will soften pectin and make potatoes surfaces a little shaggy...which might help starch adhere...or promote a crisp surface after frying.

I'm looking for references.

[Robert Jueneman]

Great post.

Re baking soda. It speeds the Maillard rxn and also has effect on pectin. I believe I've read that alkalinity will soften pectin and make potatoes surfaces a little shaggy...which might help starch adhere...or promote a crisp surface after frying.

I'm looking for references.

Thanks.

Sounds like the baking soda might be worth trying.

[gfweb]

Well, I've found reference to low pH strengthening pectin in potatoes, but not the converse.

It would surprise me if something like this isn't covered in Modernist Cuisine.

[Shalmanese]

High ph dissolves pectins. Cooks Illustrated has started doing alkaline cooking of potatoes for home fries/roasted potatoes. Another variable worth looking at is the fry fat. Beef tallow is what McDonalds used to use with great success, bacon fat and duck fat are also great alternatives. Also, go with the le creuset, deep friers simply don't have the oomph to successfully fry anything worthwhile.

[gfweb]

I have tested the effect of pH on boiled potatoes. Fry-sized yukon gold potatoes were boiled gently for 10 minutes in either 1 cup water, 1 cup water with a tbsp of white vinegar or 1 cup water with a tbsp of baking soda.

Limpness (an inverse measure of pectin strength) was measured gravimetrically as shown in Figure 1. The top fry was acid boiled, the middle boiled in water, the bottom alkaline boiled. Note that the alkaline treated potato not only sags most, but also sags closest to the fixed end.

Conclusion, alkalinity promotes pectin destruction and acidity the opposite.

Figure 1.

[Robert Jueneman]

I have tested the effect of pH on boiled potatoes. Fry-sized yukon gold potatoes were boiled gently for 10 minutes in either 1 cup water, 1 cup water with a tbsp of white vinegar or 1 cup water with a tbsp of baking soda.

Limpness (an inverse measure of pectin strength) was measured gravimetrically as shown in Figure 1. The top fry was acid boiled, the middle boiled in water, the bottom alkaline boiled. Note that the alkaline treated potato not only sags most, but also sags closest to the fixed end.

Conclusion, alkalinity promotes pectin destruction and acidity the opposite.

Very interesting! Now, why would the renowned Heston Blumenthal want limp potatoes?

Could it be that the baking soda penetrates to the core of the potato, making the insides desirably softer, while the double frying step adds stiffness and crunch to the outside?

I think a controlled experiment is in order, boiling the potatoes with water only, vinegar (maybe malt vinegar for taste), and baking soda, with or without sugar. (What does the sugar add?)

I confess that I don't really understand technically what the first, low temperature frying step adds after the fries have been boiled.

What size were those fries -- 3/8"? I'm still waiting for my 1/2" blade for my Weston French fry cutter to arrive, hopefully tomorrow, so I will have a bit more uniformity.

[gfweb]

They were about 3/8".

http://www.seriouseats.com/recipes/2010/05/perfect-french-fries-recipe.html is a link in which Kenji Alt tries to reproduce the McD's fry. Turns out he likes vinegar treating to get durability. Interesting read but clearly not the last word. You may be onto something with your second fry theory. More science is needed!

[Robert Jueneman]

High ph dissolves pectins. Cooks Illustrated has started doing alkaline cooking of potatoes for home fries/roasted potatoes. Another variable worth looking at is the fry fat. Beef tallow is what McDonalds used to use with great success, bacon fat and duck fat are also great alternatives. Also, go with the le creuset, deep friers simply don't have the oomph to successfully fry anything worthwhile.

I'm getting quite an education!

Do you have a reference to the particular Cooks Illustrated discussion regarding alkaline cooking of potatoes? I used to subscribe, but they are so antediluvian with respect to sous vide and other modernist processes that I gave up on them. But maybe I need to reconsider.

Next question, what is the difference, if any, between beef tallow and lard (which I thought came from pork)? If beef tallow is in fact different from lard, where can I buy beef tallow, and how well does it keep? I understand that McDonalds used to use 93% beef tallow and 7% cottonseed oil in their fryers, until the vegetarians made them stop. They may also use some beef flavor in their oil -- any idea what kind?.

The French apparently use horse tallow, but good luck find any of that in the US!

As to the deep fryer vs. Le Creuset, my Krups Professional Deep Fryer holds a little more than a gallon of oil -- far more than my largest Le Creuset pot, so it should be less subject to temperature drop.

And very importantly, at least to me, the charcoal filter and fan keeps the fry oil from stinking up the kitchen and getting oil droplets all over everything. I suppose I could buy a turkey fryer and use it outside, but with a 21F chill factor right now, that isn't very appealing. If I couldn't use that, I would probably stop frying entirely.

As I said, however, I might get inside the fryer and tweak the calibration to allow it to go higher -- I did that with a Waring unit I had, and later got rid of because of the fry oil smell. Most fryers aren't very well calibrated in any case.

Does anyone know why 395F seems to be the highest setting for home fryers? Is it because of the smoke point of some oils, and/or the danger of fire?

[gfweb]

Potato type is an issue too. Yukons are more pectin-y than russets. A russet might well turn to mush in alkaline water while a yukon just wilts.

[gfweb]

I have ditched the electric fryers in favor of a big pot of oil and an instant read thermometer. Bigger oil volume means less drop in temp when food is added and I can fry at whatever temp I want.

[Robert Jueneman]

They were about 3/8".

http://www.seriouseats.com/recipes/2010/05/perfect-french-fries-recipe.html is a link in which Kenji Alt tries to reproduce the McD's fry. Turns out he likes vinegar treating to get durability. Interesting read but clearly not the last word. You may be onto something with your second fry theory. More science is needed!

Kenji's recipe also uses vinegar, vs. baking soda. I am definitely have to do the controlled experiment, with three different variables!. Now, if only I could send all of my time in the kitchen a la Nathan, rathe than working, life would be wonderful (but poorer, certainly)!

[Chris Hennes]

Next question, what is the difference, if any, between beef tallow and lard (which I thought came from pork)? If beef tallow is in fact different from lard, where can I buy beef tallow, and how well does it keep?

Are you asking from a technical perspective, or a general cooking/flavor perspective? I know nothing of the technical makeup of either, but tallow is rendered from beef (technically I believe "tallow" refers specifically to rendered beef suet), whereas lard is rendered pork fat. I've never tried to purchase tallow, I make my own when I've needed it, so I'm no help there. Unflavored lard is easily available, but also worthless. Flavored lard is available from Mexican markets that make things such as chicharones.

[Keith_W]

Next question, what is the difference, if any, between beef tallow and lard (which I thought came from pork)? If beef tallow is in fact different from lard, where can I buy beef tallow, and how well does it keep?

You can buy beef tallow from your local supermarket. It is usually wrapped in foil and sold in the refrigerated section, next to butter.

There is yet another variable to mention - the quality and type of potato. I have found that even with the same type of potatoes, some batches of triple cooked fries fail and some succeed. I suspect that this has something to do with how old the potatoes are (and thus the dry weight of the potato), and how much sugar vs. starch is in the potato.

By the way, have you read this Serious Eats article on replicating McDonalds french fries? Suspend your urge to smack me in the head for a moment for mentioning McDonalds ... but apparently your humble neighbourhood Maccas has been serving up triple cooked fries for years. This is the process used by McDonalds:

- blanch in 77C hot water for 15 minutes in vinegary water

- fry at 180C for 50 seconds

- freeze

- fry at 180C for 3 1/2 minutes

Lacking an ultrasonic machine, I make my ultimate fry via Heston's triple cook method. After reading that article, I added a freezing step. It really worked - the fries turned out noticably better. And then it hit me - why not bypass all the trouble and try the oven fry chips sold frozen in the supermarket? After all - they take careful selection with their potato (if they want a consistent product), and they would have cut, blanched, and performed the initial fry for me before freezing. All I had to do was complete the frying.

I went out and bought a 1kg bag of the stuff for $4 (about the same price as a 1kg bag of gourmet potatoes!!) and fried it up when I got home. Result: as good as Heston's triple cooked fries, much more consistent, and without the trouble.

The article also says that there is no magic in the oil. I tend to agree to a point - after all, the only major differences in oil are the flavouring and the smoke point. If it is texture we are talking about - that depends on your frying temperature. Cooking oils have mostly the same surface tension so that should not affect how well the oil coats your fry. But there is no doubt that cooking your fries in duck fat or tallow results in a tastier fry.

For me, my french fry journey ended up in supermarket oven fry chips, fried in beef tallow or duck fat. Somehow, even admitting this makes me feel dirty and unworthy of being on eGullet - but there you have it.

Edited February 21, 2012 by Keith_W (log)

[Shalmanese]

For me, my french fry journey ended up in supermarket oven fry chips, fried in beef tallow or duck fat. Somehow, even admitting this makes me feel dirty and unworthy of being on eGullet - but there you have it.

Well, you and Thomas Keller.

edit: and Danny Meyer.

Edited February 21, 2012 by Shalmanese (log)

[Mjx]

High ph dissolves pectins. Cooks Illustrated has started doing alkaline cooking of potatoes for home fries/roasted potatoes. . . .

. . . .

Do you have a reference to the particular Cooks Illustrated discussion regarding alkaline cooking of potatoes? . . . .

The issue in question is the January & February 2012 of Cook's Illustrated; the discussion is on p. 15, lower right corner.

One point that emerged was that cooking potatoes in an alkaline solution breaks up the the cut surfaces, making them crisp far more efficiently when fried/oven-fried (increased surface area, I'm guessing).

[Shalmanese]

Cooks Illustrated uses 1/2 tsp of baking soda for 10 cups of water.

In their science section, they say:

How could just 1/2 teaspoon of baking soda added to 10 cups of water be so powerful? It’s because alkaline baking soda triggers a chain reaction that literally unzips the backbone of the pectin molecules and causes them to fall apart. This requires only enough alkali to raise the pH of the water high enough to start the reaction, after which it becomes self-sustaining.

[Shalmanese]

Do you have a reference to the particular Cooks Illustrated discussion regarding alkaline cooking of potatoes? I used to subscribe, but they are so antediluvian with respect to sous vide and other modernist processes that I gave up on them. But maybe I need to reconsider.

They tested and recommended the Sous Vide Supreme in November, 2010 and, if you read between the lines, it's clear they have staff familiar with modernist cooking techniques but they need to present recipes accessible to a home audience.

As to the deep fryer vs. Le Creuset, my Krups Professional Deep Fryer holds a little more than a gallon of oil -- far more than my largest Le Creuset pot, so it should be less subject to temperature drop.

And very importantly, at least to me, the charcoal filter and fan keeps the fry oil from stinking up the kitchen and getting oil droplets all over everything. I suppose I could buy a turkey fryer and use it outside, but with a 21F chill factor right now, that isn't very appealing. If I couldn't use that, I would probably stop frying entirely.

As I said, however, I might get inside the fryer and tweak the calibration to allow it to go higher -- I did that with a Waring unit I had, and later got rid of because of the fry oil smell. Most fryers aren't very well calibrated in any case.

Does anyone know why 395F seems to be the highest setting for home fryers? Is it because of the smoke point of some oils, and/or the danger of fire?

A standard LC dutch oven holds 7 quarts which is more than enough for a gallon of oil. The reason why home deep fryers don't go above 395F is because they're designed for dilettantes who occasionally want to bust it out, there's no real demand to engineer something capable of going higher than 395F. Move into the professional realm and you get deep fryers designed for actual deep frying work and they're a completely different class of machine.

[EnriqueB]

Very useful thread, as a couple of weeks ago I also began experimenting with MC fries.

I made four small batches of 5 fries each, each was cooked with a different recipe:

1. Plain triple-cooked from Heston Blumenthal at Home
   
2. Pommes Pont-Neuf
   
3. Starch-infused
   
4. Ultrasonic
   

Fries after the first frying

I could not follow exactly the recipes, due to my limited means:

• Vacuum-cooling the fries was done with a clamp-type machine, not a chamber machine. The machine is a MagicVac Maxima which according to specs reaches 932 mbar vacuum. I used a canister for vacuum. I kept doing vacuum for 3 minutes by keeping the "vacuumn" key pressed all the time. Can a clamp-type machine get the same effect than a chamber machine? Don't know yet. Next time I want to make a side-by-side test between two batches to verify whether using the machine has a noticeable effect or not
  
• Used the fridge for cooling, while some of the recipes instructs to use the freezer
  
• Used an electric deep fryer whose temperature range is 150ºC-190ºC. Good for all recipes except pont-neuf which demands 130 and 220ºC.
  
• The ultrasonic cleaner is good, it even heats the water up to 85ºC, but pretty small (10 fries maximum). That was one of the reasons for the small batches.
  

Some lessons learn:

All batches were pretty good. We liked the ones in HB at Home the least, they were also the simplest.

We liked the interior of the pommes pont-neuf the most, we found it the most tender and flavorful, and the exterior was pretty good also. So the sugar and soda definitely add something. Not as crunchy as the ultrasonic, but given that it requires less effort, overall was probably the winner.

The ultrasonic were too cooked, and some of the fries fell apart and broke in two. This was probably due to having them too long in the ultrasonic bath (90 minutes, 45 per side), and heating the water (my mistake: I though hot water was suggested but then could not find it in the recipe, so I started with 60ºC but after a few minutes turned the heat down, but still the water was hot after the 90 minutes). They had the most crunchy exterior, but this could also be due to them being so cooked, with more crevices and irregular parts.

Starch-infused were somehow in the middle with respect to crunchiness.

In forthcoming trials I want to find out whether vacuum cooling with a clamp type machine adds something, also try the ultrasonic without heat and shorter time (as I'm making pretty small batches), and try the starch infused+ultrasonic. I also want to try different potato varieties, as here in Spain I cannot find the varieties recommended on the original recipes.

[Robert Jueneman]

EnriqueB (and everyone else), thanks for the fantastic contributions. This has become one of the most interesting forums on eGullet -- reminiscent of the early sous vide thread, before it started to become "Dinner."

Your A-B-C-D comparison between the various fry techniques was revealing. Doing them serially, changing multiple variables each time, and trying to remember just what you did, and how they came out, is obviously not the way to do a proper experiment!

The alkalinity vs. acidity question is very, very interesting. It appears that the baking soda helps to break up the surface, and may also improve the tenderness and flavor of the interior. Probably the sugar helps, as well.

So the next obvious thing to try is to blanch the potatoes in the sugar, salt, and baking soda solution, then starch infuse half of those, and then use the ultrasonic on half of the remaining starch-infused fries. I haven't tried the starch-infused only fry, nor the ultrasonic only technique. Hopefully, the baking soda would open up additional crevices and thus improve the starch infusion, while keeping the interior soft and tender.

On the other hand, if you wanted a simple fry and didn't want to bother with the starch-infusion, much less the cavitation, then a vinegar blanch might help keep the fries from getting too limp.

I don't know what to suggest regarding the temperature of the ultrasonic bath, or the time. The first time I did it I used 62C water bath, but only 20 minutes a side, by mistake. The second time I used room temperature water (maybe 22C) for 45 & 45 minutes, and the water was pretty warm at the end, due to the cavitation. I thought the first batch was better, but there were other variables as well.

I don't know why it should be necessary to flip the bag over midway through, except for the fact that if you had two bags, as I did, they might be touching. Next time, I think I'll separate the bags with my sous vide rack. Then I might remove one bag after 45 minutes, and let the other one sit in the bath for the full 90 minutes.

How long did you boil the fries in the first step? At least with Idaho Russets, I think 20 minutes is too long -- they tend to fall apart unless handled very carefully. I'm going to settle on 15 min at 90C in the circulator, and see how that works.

With regard to the commercial frozen fries, the only ones I've used in the past were the 1/4" to 3/8" size, and I'd prefer a 1/2" 1.5 cm steak fry. But if I could find any, it might be worth trying the starch infusion and ultrasonic cavitation on them, assuming they haven't been fried the first time as well.

Which ultrasonic machine are you using?

[EnriqueB]

Your A-B-C-D comparison between the various fry techniques was revealing. Doing them serially, changing multiple variables each time, and trying to remember just what you did, and how they came out, is obviously not the way to do a proper experiment!

Well, my trial was not a very proper experiment neither! Just a first home comparison, useful to get a grasp of each recipe for further testing. For example, I started in the morning and went batch by batch, which meant that the last batch (ultrasonic) was cooling in the fridge for only one hour while the first batch was cooling for almost 5 hours. I'll soon compile all the details on my blog.

Your tests also give me a lot of ideas of what to try and how to change things!

I don't know what to suggest regarding the temperature of the ultrasonic bath, or the time. The first time I did it I used 62C water bath, but only 20 minutes a side, by mistake. The second time I used room temperature water (maybe 22C) for 45 & 45 minutes, and the water was pretty warm at the end, due to the cavitation. I thought the first batch was better, but there were other variables as well.

I remembered having read in MC that heat was recommended when using the ultrasonic bath, but then I reviewed it and only saw that applied to flavour extraction (e.g. truffle butter or vegetable stock), not for fries. And mine turned out overcooked, so next time I'll likely use room-temperature water.

I don't know why it should be necessary to flip the bag over midway through

I can't see a reason for that neither, especially with small batches.

How long did you boil the fries in the first step?

Twenty minutes, except the ultrasonic which were steamed for 15 minutes. The time was right, they had to be handled carefully but not as much that they fell apart. But sure this depends of the potato variety. I'm not sure which was my variety, as most potatoes here in Spain are sold without that information :-(( My provider is looking it up and will tell me next time I go there.

Which ultrasonic machine are you using?

I'll look it up when I'm at home this evening.

Very interesting discussion!

[EnriqueB]

Which ultrasonic machine are you using?

Back at home: I'm using an Emmi-20, these are the specs.

[Robert Jueneman]

This may sound like heresy, but does anyone understand the purpose of the first of the two fry steps in Heston Blumenthal's Pommes Pont Neuf, or in the various starch-infused recipes?

It seems to me that the boiling step should adequately cook the interior of the fries. What is the point, therefore, of cooling them down, drying them, then cooking them again in relatively low temperature oil, then cooling and drying them once again?

I haven't done a controlled, A-B test yet, but the other night, after the 1/2" cutter for my Weston fry cutter finally arrived, I was a little bit impatient, so I first boiled the fries using the brine, sugar, and baking soda recipe, dried them in a salad shooter, and then fried them at my maximum of 395F. That was without the starch infusion, but I thought they were quite good.

I have some starch-infused fires in the fridge, from Sunday's experimentation, and I'm going to try the three step approach vs. the simpler two step approach, and compare them.

Sunday was a bit of a disaster, but I learned a couple of things:

1. Never try to cook 4.5 kg of potatoes and brine in an immersion circulator, unless you have a huge one. The temperature dropped from 90C down to below 80C, and I had to give the potatoes and extra 10 minutes to cook them adequately.

2. Never scale up the recipe for the starch infusion. I tried to mix 250 g of potato flour and 500 g of water, but it was like mixing plaster. I couldn't make any progress with a whip, burned out my Braun immersion blender, and finally had to add a lot more water and mix it in my Thermomix, which jumped all over the counter in the process.

[EnriqueB]

According to CookingIssues: "The first fry forms the foundation of the crust and dehydrates the potato some more. The second fry does the crisping. I don’t think they will stay crunchy as long if you do it all in one shot."

I also think the triple cooked is a useful technique for prior preparation, it seems they freeze perfectly after the first fry, or can be kept refrigerated for up to 3 days.

A couple of times I was short of time I have also done only two steps like you: boiling with salt, sugar and soda + deep frying only once, and the result is pretty good if you consume inmediately. I don't think it is AS good as the three steps versions, but I find those, according to my first test, only marginally better. Nice for a special day but not worth to prepare often.

[Robert Jueneman]

After reading the Cooks Illustrated article, my head is still spinning from the number of variables.

They suggest boiling the potatoes for only a minute, then draining them and reheating for 2 minutes to dry them. That sounds like it might be sufficient to get a nice mushy exterior, while not allowing the potatoes to fall apart, which my 15-20 minute time often does.

You could then starch infuse them, with or without cavitation, and then dry them again. Then deep fry them, or as they suggest, oven-roast them at 500F.

Last night I tried some of the fires I had left over from Sunday's marathon. They were bolded for about 20 minutes in brine with sugar and baking soda, then starch-infused, then put in the fridge. One batch I put in the ultrasonic machine, and put back the fridge to save, the other I fried twice.

I think the recipe uses too much potato flour. Instead of a nice thin batter, it made sort of a gloppy mess. They tasted good, but maybe not quite as good as the ones with cavitation.

And Cooks is right -- doing this for more than 2 people would be a real challenge.