Starch-Infused French Fry Perfection

[EnriqueB]

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?

In Heston words (from his last book HB at Home):

The purpose of the first session in the fryer, at a gentler temperature, is to make any stach left in the surface cells dissolve and combine to create a rigid outer layer that can withstand the higher temperature of the final frying, which will colour the chips golden. Skipping this can undo all the trouble you've taken to dry out the potatoes and drive off moisture.

(...)

Although this first, low temperature frying might seem a time-consuming process, once the chips have had it, they can be stored in the fridge for up to three days before their second, high-temperature frying.

[EnriqueB]

I have explained my tests with more detail on my blog (in Spanish, I'm afraid): first a survey/summary of the technique and variations, then the tests that I summarized above, with some more pictures and explanations.

[adey73]

Can I ask 2 stupid questions?

1)The ultrasonic wave is coming from the bottom of the bath, so that's why you can't lay the fries in vertically?

2) if you dispensed with the starch could you put the potato strips in the bath without the bag or would they explode?

[Robert Jueneman]

Not stupid questions, but I'm afraid I don't know the answer for certain.

I THINK that the ultrasonic cavitation extends pretty much throughout the liquid, so it should matter which direction the fries are loaded, although you wouldn't want to pack them too densely.

I think you could put the potatoes in the bath with or without the startch. They shouldn't explode, but of course you would ned more starch, an it would be a bit of a mess to clean up afterwards.

Try it and see!

[dachickenfarmer]

Tried the Heston fries (per his cooking show on YouTube ) today. Did per video's instructions, adding freezing step between steps 2 & 3 (per his book, I hear). Very good - Thinking this one through, the freezing seems key - between steps 1/2 and 2/3 - not for direct drying, but for indirect, as a frozen baton of potato will take more time in the oil to get to the cusp of browning in step 2, and browning, in step 3, if frozen. This gives the water on the outer portion of the baton more time to boil (or sublimate, in the beginnning of 3) away before being "done". Either way, yummy. It also explains at least part of why frozen pre-cooked store bought fries are quite yummy.

[ePressureCooker]

Sorry for resurrecting a somewhat older post, but I found this thread completely by accident when researching something completely different, and since I had tried some of the methods mentioned above (in a slightly different fashion), I thought I would add some additional information in case anyone who posted here is still interested (or for anyone else who finds it). Wish I had found this thread months and months ago, would have saved me a lot of experimentation!

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.

I had actually tried the vinegar solution method in a variety of different ways (soaking the fries in a water and vinegar solution, steaming them in a water and vinegar solution or both) and the vinegar does in fact strengthen the pectin in the cell walls, reinforcing the cellular structure of the potato. When I make cubed hash browns, I'll use a slightly vinegar water solution to pressure cook the potatoes (essentially parboiling them, or par-steaming them, if you are precise, since I have them raised above the water with a vegetable steamer). That makes them more firm and less crumbly when I go to do the quick fry for hash browns or hash. But it did nothing as far as I could achieve as far as making crispier french fries. I considered it a bust, at least as far as either presoaking or pre-cooking the potatoes in the pressure cooker.

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.

Saw Cooks Illustrated mention this on one of their TV programs this season, that's what gave me the idea for trying baking soda on french fries. But I've also done some experimentation with different fats to make french fries and other fried foods, and "How to Read a French Fry" is right, any fat that is highly saturated (like animal fats) will make crispier fried foods.

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.

I didn't try using yukons, but two things I can say about potatoes. One is that its better to use potatoes that have been in storage for a few weeks or more, than fresh. Even if I just keep them in the bag for a week before making fries, they're better. Another is that using smaller Russets, rather than the larger baking ones, also works better on the crispiness issue. In both cases, it seems that water loss explains the better results.

I concur, you'll get limper fries with the baking soda solution because of the chemical reaction, whereas vinegar will strengthen. However, as I learned from my experimentations, which were not consistent until I consulted a chemist friend of mine, there is another important ingredient that should be included for optimal results (I'll discuss that below.)

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.

I don't think HB wants limp potatoes per se, that is the side effect of the chemical reaction that takes place. To compensate for that, I started cutting thicker steak cut size fries, so they wouldn't break, but the chain reaction could take place on the surface without weakening it so much that it went limp or was prone to breakage. I also steamed the potatoes, not boiled them in the solution.

I don't know about the sugar, I'll have to try that now that I've seen this thread, but I suspect it might aid in browning, perhaps? As for the baking soda, you just need a little bit, but what you absolutely should add to the solution is salt. At least on the TV program I saw, ATK didn't say anything about salt in the boiling solution (perhaps it mentioned it in the article referenced, but I haven't seen that). My chemist friend explains the chain reaction as such: the small amount of baking soda (a base) starts the chain reaction where a base comes in contact with the surface of the potato, meets the cell wall, which is composed of, among other things, pectin, and essentially breaks a cell, releasing both a second base and the starch inside the cell. This second base has trouble remaining soluble, and that's where the salt comes in, it helps it remain soluble in the water so the chain reaction continues. The second base very quickly meets an adjacent cell, breaks it, releasing more starch and more of the second base. Oddly enough, in researching what the second base was, I found out that its actually a food additive added to improve flavor, and that its actually put in vinegar potato chips of all things to add flavor (even though it has nothing to do with vinegar). The physical effect on the french fry surface (at least to the naked eye, I don't have a microscope) is a very tacky, sticky coating, which I suspect is the released starch.

They were definitely the crispiest french fries I've ever made with a single fry (as opposed to double frying), and even without saturated fats.

[philie]

concerning the intensive discussion maybe its worth putting up these two recipes for someone who is eager to try yet another way of making (quite delicious?) fries?

http://www.chefsteps.com/activities/thin-cut-french-fries

http://www.chefsteps.com/activities/thick-cut-french-fries

[Robert Jueneman]

concerning the intensive discussion maybe its worth putting up these two recipes for someone who is eager to try yet another way of making (quite delicious?) fries?

http://www.chefsteps.com/activities/thin-cut-french-fries

http://www.chefsteps.com/activities/thick-cut-french-fries

Interesting! Unfortunately, they didn't comment on the thin vs. thich cut fries, but their technique of determining the specific gravity (and presumably, the wetness or dryness) was certainly interesting -- one more variable to eliminate. And this might account for the earlier recommendation to use one to two week old potatoes, rather than fresh ones -- presumably they are somewhat dryer.

Unfortunately, at the moment I am recovering from a nasty fall that severely dislocated my left ankle and broke the fibula in four places, requiring a 10" plate and a bunch of screws to hold everything together. So I won't be standing up and cooking fries anytime soon, but maybe somone else can try some of these techniques, and post their results.

[ePressureCooker]

concerning the intensive discussion maybe its worth putting up these two recipes for someone who is eager to try yet another way of making (quite delicious?) fries?

http://www.chefsteps.com/activities/thin-cut-french-fries

http://www.chefsteps.com/activities/thick-cut-french-fries

Interesting! Unfortunately, they didn't comment on the thin vs. thich cut fries, but their technique of determining the specific gravity (and presumably, the wetness or dryness) was certainly interesting -- one more variable to eliminate. And this might account for the earlier recommendation to use one to two week old potatoes, rather than fresh ones -- presumably they are somewhat dryer.

Unfortunately, at the moment I am recovering from a nasty fall that severely dislocated my left ankle and broke the fibula in four places, requiring a 10" plate and a bunch of screws to hold everything together. So I won't be standing up and cooking fries anytime soon, but maybe somone else can try some of these techniques, and post their results.

As an additional piece of information, as someone who has actually home grown their own potatoes, fresh potatoes, like corn, have a lot more sugar than the ones you get even in the farmer's market. That sugar starts converting to starch the minute you harvest them, and I would assume that conversion continues, albeit more slowly, when they are in proper storage. So it may also be a matter of maximizing starch, as well as minimizing water. ;D

[&roid]

I made the chefsteps thick cut fries last weekend and they were amazing. Have to say I was skeptical about the benefits of triple cooking prior to doing these, no longer! Well, well worth the effort (it's not that much in reality, just an extra step in the sous vide). They were far an away the best fries I've ever had.

[Paul Bacino]

https://vimeo.com/32758577

 

It appears, bag sous vide or combi-oven or convection cook..

 

Ultrasonic the fries in the  bag (  I have one of those )

 

Then double fry!!

 

Anyone done  this?

 

If I get some free time soon it might be work experimenting

[Kerry Beal]

I did - I'm sure I posted about it somewhere on here - but not sure where I'd start to look.

 

Found it.

Edited February 19, 2015 by Kerry Beal (log)