Cooking Issues

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They’re Going to Put Me in the Movies

June 11th, 2010 · Uncategorized

Howdy Readers!

If you get back from the bar in time, we’re going to be mixing drinks on Late Night with Jimmy Fallon tonight at 12:35am EST on NBC.  We’ll have the video up on the blog tomorrow.

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Anytime it Rains it Rains… Manna From Heaven

June 9th, 2010 · Uncategorized

by Dave Arnold

Today I had my first article published in the New York Times, and it’s on  manna.  Yes, like manna from heaven.  Here is the link. Below is a short  post  with some additional information. The first part is (mostly) a quote from the article.  For the full skinny go to the NY times website. The second part of the post has some info I couldn’t fit into the article.

Left: shir-khesht manna; Center: hedysarum manna; Right: Chios Mastic (not a manna, but a resin that is also a tree sap)

From the article (mostly):

After a couple months of wandering around the Sinai after their exodus from Egypt, the Israelites got hungry and started grumbling. God conjured up two things for them –quails in the evening, and manna in the morning.  “In the morning there was a layer of dew around the camp. When the layer of dew evaporated, behold, on the surface of the wilderness there was a fine flake like thing, fine as frost on the ground. When the sons of Israel saw it, they said to one another, “What is it?” (Exodus 16:13-15)” “What is it,” in ancient Hebrew, is mân-hû –the probable derivation for the word manna.  As for its description: “It was like coriander seed, white, and its taste was like wafers with honey (Exodus 16:31).”

Turns out, manna is real. There are dozens of varieties, and they have been used for millennia.  The defining features of all mannas are 1) they are sweet, and 2) they appear as if from nowhere, delivered by Providence, without cultivation. Most manna is either dried plant sap or the honeydew excreted by bugs that eat the sap. Rarer are the non-sap mannas, including Trehala manna, the sweet-tasting cocoon of the Larinus maculates beetle, and  manna-lichen (Lecanora esculenta), which dries up and blows around to form semi-sweet clouds out of which manna settles into drifts – a literal windfall.  Biblical manna was almost certainly a sap manna –the favored theory says the Israelites’ came from a tamarisk tree (Tamarix gallica).  Every continent has sap mannas.  They form best in extremely dry climates –like the middle east’s  – where sap oozes during the night and dries up in the morning.

Additional info (mostly):

Some people believe that manna can simply drip spontaneously from a tree or bush. Unlikely – most tree species, even those with an extremely wide geographical range, only produce manna in very specific regions and at very specific times. This production pattern points to the intervention of bugs. Ravenous insects puncture holes in the stems, leaves and roots of the plant, causing sap to run. Sometimes the bugs eat the sap and poop it out as sweet honeydew.  Like the familiar aphids that produce honeydew here, manna-producing bugs, like the Coccus manniparu responsible for Tamarisk manna, are very small and can go unnoticed even by the gatherers and casual studiers of manna.  People aren’t the only manna enjoyers: ants and other insects collect it, too. Exodus warns us that if we leave our manna sitting around it will attract maggots.

I have not been able to locate the biblical Tamarisk manna here in the United States.

There are two types of manna available here in the US from Behroush Sharifi the Saffron King, dealer in rare spices and dried foods from ancient Silk Road: Hedysarum and Shir-Khesht.  Both are products of Iran and are imported from the bazaar in the town of Yazd.  They are some of the most unprocessed foods you can get. They contain bits of leaves and twigs and who knows what else.

Hedysarum is the dried sap of the camelthorn bush. It looks like this:

Hedysarum (Alhagi) manna. From the camelthorn bush. And look --there is a thorn on the left.

It tastes like a combination of maple syrup, brown sugar, blackstrap molasses, honey, and nuts –  delicious. My wife detected a note of clams –not like eating clams, but like the aftertaste.  Upon re-tasting the manna, I detected that flavor as well; it wouldn’t stop me from using it in a dessert.  Her response to the Hedysarum  supports Mr. Sharifi’s claim that manna tastes different to different people and has a wide range of nuanced flavors.  According to the most recent work I have found – which dates from the 1880’s — Hedysarum contains melezitose.  Melezitose is a trisaccharide sugar associated with honeydew in aphids, which points to Hedysarum’s  bug-derivation.

Shir-Khesht manna is the dried sap of the cotoneaster nummilaria shrub.  It looks like this:

Shir Khesht manna. Check out the leaves in the stuff!

Shir-khesht (which means “dried-milk” in Persian) is whiter than hedysarum manna. It is sweet, with some gumminess that eventually dissolves in the mouth. Shir-khesht has a tongue-cooling effect that comes from mannitol, a sugar alcohol in this and many other mannas; the sensation is similar to menthol, without the menthol taste. Mannitol is tolerated by diabetics and is reputed to have other medical benefits. It also has notes of honey and herb, and a faint bit of citrus peel.

Wylie Dufresne (my brother in law) sprinkles Shir-Khesht on foie gras.  At the FCI we make a drink with it.  Traditionally, manna was boiled into syrups to purify it for medicinal preparations. We heat two parts water to one part Shir-Khesht manna, strain it, and add the syrup to bourbon.  Consume this drink neat, at room temperature.  As with the raw manna, the drink changes as you sip it.  It is sweet, but not overly so. It is cooling, complex and satisfying.

We made a simple syrup out of the shir-khesht manna. It didn't all dissolve. Left overs on the right --twigs, leaves, etc.

Maker's Mark and manna --served room temp and sipped slowly. A pricey drink.

Oh. Don’t eat too much manna at once. Its indigestible sugars make it act as a laxative. The $28 an ounce price tag will help you avoid this problem.

For a gentle non-habit forming sleep inducer, check out Manna: An Historical Geography, By R.A. Donkin, published by Junk (no joke), 1980.

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Stretchy Chewy Ice Cream 2: The Rise of Chewbacca, Steamed Potatoes, and an Equipment Review

May 27th, 2010 · Uncategorized

posted by Dave Arnold

It stretches, it snaps, it is made from potatoes!

Salep dondurma is a variety of Turkish ice cream prized for its stretchy, chewy nature. The stretch and chew comes courtesy of  salep, the powdered root of a rare Turkish orchid. It is illegal to export the powder from Turkey, so folks (including us) have come up with fake salep recipes with legal ingredients. We posted on it here: Fake Fryable, Brûlée-able Salep Dondurma Ice Cream.

Yesterday, by accident, we came up with our easiest and favorite chewy ice cream yet. We like it better than the real salep. Plus, it is made from potatoes! The story includes an equipment review, some luck, and some celebration. Chewbacca isn’t really in the post.

This post was supposed to be an equipment review of the Beater Blade

The BeaterBlade

The Equipment Review:

The Beater Blade is a hard plastic paddle with rubber scrapers on its sides — so you don’t need to scrape the the bowl while you are using a stand mixer. Our pastry department loves it; they even claim it makes their cakes rise higher. I just wanted to know whether it would make a better liquid nitrogen ice cream.

When making liquid nitrogen ice cream in a Kitchen-Aid it’s very easy to partially over-freeze, to bad effect. A crust of frozen ice cream forms on the inside surface of the bowl and isn’t removed by the standard paddle –you have to scrape it off by hand. You are left with ice cream that is too hard in some places and too soft in others. I figured the BeaterBlade would either solve that problem entirely or shatter into tiny pieces because liquid nitrogen, plastic, and rubber don’t always play nicely together. We tried it yesterday and it works beautifully:

LN ice cream with the BeaterBlade. Notice the ice cream on the side of the bowl isn't over-frozen and the whole batch has a uniform consistency.

We haven’t broken the paddle yet. Someday we will.

Dumb Luck:

We were done with the equipment review. We were cleaning up. Sitting on the table were some leftover potatoes that we had steamed for another experiment.  Just big old hunks of cold steamed russet potatoes –dry, fluffy, mealy.

Potato chunks

We were in a bit of a silly mood, so I said, “hey, blend some of those potatoes into the ice cream base.” We Vita-Prepped enough potatoes into the vanilla ice cream base to make a gluey batter. We put the batter into a Kitchen-aid fitted with the BeaterBlade, hit it with LN and, to our great surprise, it became super-stretchy, super-chewy, super-smooth, super-easy ice cream.

Stretchy potato ice cream.

Stretchy potato ice cream

In case you want to know what happens around here when we discover something new:

Discovery time with Fabulous, A.J., Nastassia (taking the pictures), and me.

I did my happy dance, which wasn’t appreciated because the students next door were taking a final. I just couldn’t help myself.

I don’t have an exact recipe yet. Just make sure the ice cream base has a lot of flavor and a lot of sugar, because you will add a lot of potato. You don’t need the LN either, just make this  however you normally make ice cream.

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Head to Tail Drinking: Breaking up Distillations in the Rotovap

May 19th, 2010 · Uncategorized

posted by Dave Arnold

A Thai basil distillation broken up into 27 pieces based on volatility

We’ve been working hard over the past four years to make the best possible hooch. I thought we were doing a top-notch job, but yesterday I discovered I was wrong.  That’s because yesterday we split a distillation run into 27 distinct parts based on volatility, nosed and tasted them all, and blended the best of them back together:  super-hooch.  This test was done with home-made Thai basil eau de vie, and it was truly excellent.

As many of our readers know, the rotary evaporator (rotovap) is perhaps my favorite piece of equipment.  It allows us to distill at very low temperatures, with very complete flavor recovery.  For example, the aforementioned eau de vie never went above room temperature.  For more on how a rotovap accomplishes these miracles, see the rotovap primer.

Our distillations are more akin to gin than to traditional distillation –they are re-distillations of already purified spirits, with the intention of capturing flavor. Traditional distillation’s primary purpose is to concentrate ethanol.  You start with a lower proof alcohol (such as whiskey mash, or fermented potatoes) with some impurities. When you distill, you concentrate these impurities as well as the ethanol. The first liquid to leave the still is referred to as the heads, and it is full of nasty stuff.  After the heads come the heart –the good stuff you want to drink.  Lastly, the tails – no good.  Too much heads or tails makes for popskull moonshine that can make you sick.  Distillation enthusiasts often ask me if I cut the heads and tails out of our rotovap distillate.  With re-distillation there is no need to remove heads and tails  for safety, though it is typical to remove them for taste.  At the school, we usually don’t separate the heads from the heart — I like the heads. But we do cut off the tails –we just stop the distillation when the flavor tapers off. Then  it occurred to me: What if some phases of the distillation process produce better flavors than others?  In  alcohol-concentration distillation the breakdown into heads heart and tails makes sense, but in flavor-based distillation there isn’t any reason to assume that the best flavors should be concentrated in the center of the run, or that undesirable flavors will only occur in the beginning or end. I pride myself on getting the maximum flavor out of my distillations, but what if some of the flavors I’ve been collecting are not so good?

Because different aroma and flavor compounds have different volatilities, they distill at different times — and so the flavor of the distillate changes  over the course of a run.  What if  I separated the entire distillation into small samples of slightly different volatility and checked their flavor individually? Most people with rotovaps can’t taste the distillate as they go.  Rotovaps are sealed systems under vacuum –that’s how they work. To taste the distillate, you have to stop the distillation, break the vacuum, pour off the distillate, and restart. Years ago, I addressed this limitation by building a pump system that connects to the output of my rotovap (see  picture below).  To this pump system I added a bunch of luer-lock stopcocks that allow me to divert the flow of distillate into any one of four small graduated cylinders, or into a larger collection beaker.

How we separate the distillation samples: The peristaltic pump pumps the distillate out of the vacuum into the manifold. The pump’s other –arguably more important-- function is to save flavor that would otherwise be lost –see the primer

Closeup of the manifold

Thai Basil Eau De Vie

We blended 750 mls of vodka with 82.5 grams of Thai basil leaves, put them into the rotovap and distilled with a bath temperature of 40°C and a condenser temperature of -17°C. In a rotovap, the product you’re distilling is a good 15-20°C cooler than the water bath, so the Thai basil was never heated above room temperature.  With the new stopcock system we easily separated the distillation into 20ml samples. We collected every 20 mls that came off the rotovap, then capped and labeled them.  Some samples were a little more, or a little less than 20 mls, so we recorded the actual number of mls of each sample, accurate to 0.5 ml. After we collected 542 mls of distillate (27 samples), we shut down the rotovap and got to tasting.

Tasting and mixing.

We checked every sample for alcohol content with a refractometer.  The first two samples read lower in alcohol than the second two did.  I don’t know if they were actually lower in alcohol, or if impurities made them read lower.   We smelled each sample in order, then tasted them.  We organized the samples into four groups:

  • Green: everybody liked these
  • Yellow: everyone thought these were OK
  • Orange: some people hated these, some thought they were OK
  • Red: everyone hated these

The samples were tasted by 6 people –we will do tastings with larger groups very soon. Here’s the tasting chart, with abbreviated notes:

As I had hypothesized, there were samples right in the heart of the distillation that we all hated –I had hoped there wouldn’t be; because diverting the distillate at precise times isn’t the easiest thing to do.

Blending spirits is a complex problem.  Sometimes, small additions of flavors you don’t like can actually make the drink as a whole taste better –counter-intuitive, but true.  We had to test whether removing the parts of the distillation run that we didn’t like improved the taste of the whole distillate. We did some blending and made four different eau de vies:

  • 3 mls from every vial in the green group: “Green”
  • 3 mls from every vial in the green group AND the yellow group: “Yellow”
  • 3 mls from every vial in the green group, the yellow group and the orange group: “Orange”
  • 3 mls from every vial: “Red”

I thought Green would be the hands-down winner, but three of the six people at the tasting preferred Yellow.  Everyone chose Green and Yellow as their favorite two liquors.  The people who chose Green had a strong preference for Green, while Yellow lovers tended to like both. Half the tasters preferred the Red liquor to the Orange one.  I was surprised that the Orange liquor would score lower on some people’s ratings than the red because the red samples were unanimously disliked on their own –goes to show the whole isn’t just the sum of its parts.  One fact is certain: selectively removing portions of the distillate that occur in the “heart” of the run can improve the flavor of the hooch you make.

We ran two more Thai basil distillations using the same amount of liquor and basil as the first test: one we did the old way, and one we did by diverting the distillate according to the recipe for “Yellow” above.  The one made like Yellow was better than the one made the old way, showing that the same flavors come out of the distillation at the same point in the run from batch to batch.

Now we have a problem:  how do we distill this way on a regular basis?  How are we going to get our yield up? Is there a way to re-use the red and orange part of the distillation, the way a pro distiller does?

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The Quest for French Fry Supremacy 2: Blanching Armageddon

May 12th, 2010 · Uncategorized

by Dave Arnold

Strap yourself in and get ready to keep track of many tastings. For some French Fry background, see the previous post FF Supremacy Part 1. We use a blanch-dry-fry-fry technique; this post investigates the ins and outs of pre-blanching, blanching, and drying.

Spoiler alert: here’s the final answer … Soak the cut fries for one hour in a room temperature solution of Pectinex SP-L (a pectolytic and hemicellulolytic enzyme mix), blanch in boiling water (don’t overload your blanching container) for 14 minutes 30 seconds (assuming your water takes 1:30 to get back to boil), do not dry before frying.

A couple notes: one of the developers of the Cook’s Illustrated recipe, which we discussed in our previous post, sent us an email reply. We are publishing his response, with permission, at the end of this piece. Our next French Fry post will deal with potato types, oil types, and freezing between first and second fry. Don’t look for it right away. My interns are really, really sick of making fries.

What Is the Ideal Fry?

The sixty-plus, side-by-side blind tests we conducted in the past week and a half have changed my ideal fry. Prior to this marathon I posited that the crunchiest fry would be the best fry. Not true. We aim for crunchiness because we think it’s the opposite of sogginess, that most dreaded of French fry attributes. The truth is, a fry just needs to be somewhat crunchy, with no signs of sogginess.  Too much crunch becomes hardness –a turn-off. We produced some specimens that were basically potato chips shaped like fries, and they weren’t good. What is good? A fry you want to keep eating even after it has gone cold.

Our ideal fry:

  1. tastes delicious right out of the fryer with a crunchy crust and hearty, cooked potato interior texture
  2. is salty on the interior and  exterior
  3. avoids “hollow fry” (see the previous post for more explanation)
  4. is still desirable after it gets cold
  5. doesn’t get soggy while cooling, and doesn’t taste dry after cooling
  6. isn’t greasy. Note that greasiness does not necessarily correlate to the oil content of the fry.

4 and 5 are especially important. A monkey can make a French fry that tastes good right out of the oil –but he needs your help to make one that stays good as it cools down.

Blanching Theory:

Blanching fries does a lot for you  – such as:

  • killing the enzymes that make the potatoes turn purpley-brown. Blanching is always necessary if the potatoes will be air-dried before frying.
  • gelatinizing the starch. During frying, pre-cooked fries form a crust faster than raw ones, and they can be cooked at higher oil temperatures than raw fries  – which is easier for workflow.
  • pre-salting the interior of the fries. We blanched two batches of fries, one in boiling 3% salt water, one in boiling plain water. The plain-water fries tasted like crap next to the salt-water ones.  All subsequent tests fries were blanched in a 3% salt solution.  So here’s your First Rule: Use salt water to blanch.  And remember, the potatoes absorb salt.  If you re-use your blanching water, add more salt.  Potatoes properly blanched in a 3% salt solution need very little additional surface salt.
  • getting rid of the excess sugar  that leads to overly dark fries.  If you re-use your blanch water, the sugars will equilibrate and you’ll lose this advantage.
  • altering the texture of the finished fry. This effect is the hardest to sort out. How does blanching change the texture? Keep with me:

Many people advocate blanching fries until they “almost fall apart.” To test this advice we blanched fries in boiling water with 3% salt for different lengths of time.  We boiled a large amount of water and added all the potatoes at once. The water never went below 85°C and it returned to a boil in 1 minute 30 seconds. We pulled some fries at 5 minutes 20 seconds, when the potatoes were done.  We overcooked the rest, pulling some at 7 minutes 11 seconds, 9 minutes 11 seconds, 11 minutes 11 seconds, 14 minutes 30 seconds and 20 minutes zero seconds.

We blanched fries for 6 lengths of time: between 5 minutes 20 seconds and 20 minutes.

We dried all the fries in a convection oven with door open and the fan set to cool; fried them in 170°C oil until they formed a crust but were still blond; then fried in 190°C oil until crispy and golden brown.  The internal texture of the fries remained fairly consistent, but the crusts became progressively crunchier as the cooking time increased.  The 14:30 fries were unanimously voted first place.  The 20 minute fries didn’t brown well and were overly salty; nobody liked them.  A strange phenomenon occurred with the 11:11 fries –they were saltier than the 9:11 fries and the 14:30 fries.  Weird, because they were all cooked in the same pot. I think I know why:  aside from being too salty, the 11:11 fries also seemed a bit hollow.  I think they dried out a little more in the convection, which would lower their moisture content, making them seem saltier –and, as we shall see – leading to a hollow fry. Second Rule: Blanch fries for a long time –like 14 minutes and 30 seconds, in boiling water.

Some like it Rough:

Many people assume that long blanching times make a better crust because overcooked potatoes have a rough surface that gets crunchier than the smoother surface of a less-done potato.  To test this hypothesis, we made 3 batches of fries:

  1. Blanched until done –the control.
  2. Blanched until done, and scraped with coarse sandpaper to make a rough surface.
  3. Cut oversized, blanched to death, cooled and cut down to size by hand with a sharp knife to create a smooth surface.

We took oversize fries; blanched the hell out of them; then cut them down with a sharp knife. We were testing whether surface-rougness=crunch or overcooking=crunch --so wewanted to create an overcooked fry with a smooth surface.

I sanded some non-overcooked fries to see if roughing up the surface made the fries crunchier.

Top Row: French fries blanched till done. Bottom Row: French fries blanched till done and sanded. Left to right: blanched; first fry; second fry exterior; second fry interior. Notice the surface of the sanded one is significantly rougher.

The sandpaper batch was a little crunchier than the control, but not nearly as crunchy as the overcooked batch that we cut smooth.  I don’t think this test is conclusive, but I do think that surface roughness is a minor, not major, player in crunchiness.  If you look at the pictures of the fries blanched at various times, only parts of the surface of the overcooked fries appear any more beat-up than the normal ones, yet the whole fry is crunchier.

Blanching fries for a long time makes them curnchier and crunchier, but even at 20 minutes, the french fry still has patches that are very smooth --yet these areas are also crunchy. I don't think it is increased roughness which is causing the fries to get crunchy.

Porosity and surface fissures may play a big role, but I don’t think macroscopic roughness does.

Starting With Cold Water, and Pre-Blanch Tricks: Pectin vs Starch:

Potatoes are made up of cells filled with starch granules glued together by pectin, hemicellulose, cellulose, and other junk referred to in the biz as Non-Starch Polysaccharides (NSP).  Blanching at temperatures above 75°C cause starch granules to swell. The longer and hotter the blanch, the more the granules swell, until they finally break. Destruction of starch granules doesn’t necessarily mean destruction of potato cells. –research indicates that the cells stay mostly intact during long cooking, even though starch leaks out of them. Long blanching at high temperatures also breaks down pectin, making French fries softer. Blanching or pre-blanching at temperatures below 75°C –or blanching slowly so the fries stay between 60 and 75 degrees C for several minutes — activates an enzyme called pectin methylesterase (PME). In the presence of calcium, PME strengthens pectin and allows it to withstand the rigors of cooking without breaking down,  producing a fry that is stiffer and has more structure than the same fry without the low-temperature blanch. Even though PME is active at temperatures  below 60-70°C, the calcium the enzyme needs to work remains locked in the starch granules at lower temperatures.  Above 75°C, PME is denatured too rapidly to make a difference.   The two basic techniques for PME activation are:

  1. Pre-blanch the fries in a temperature-controlled water bath between 60 and 70 degrees C for several minutes, up to an hour. We call this “the Steingarten” in honor of Jeffrey Steingarten, who uses this technique on mashed potatoes.  We did this procedure for one hour, then blanched in boiling water till overcooked.
  2. Start the blanch with cold water, or allow the temperature of the blanch water to dip below 70°C when you add the potatoes to the water.  Even a couple of minutes below 70-75°C is enough to get some PME effect.  For our test, we started from cold and blanched for 25 minutes (it took about 15 minutes to boil).

I have a bottle of straight PME enzyme called NovoShape.  It is made by the same folks who bring you Pectinex SP-L and Pectinex Smash XXL, and it is intended to firm up fruits.  If you add a pinch of calcium and some NovoShape to raspberries ,  you can boil those raspberries and they won’t fall apart.  Your blueberries won’t bleed into muffins. You get it. To really test out PME activation, I decided to use NovoShape on two additional batches:

  1. Soak fries in a 0.4% PME/0.5 % calcium gluconate solution kept at 25°C (I kept the temperature low so I wouldn’t activate the native PME) for two hours, then blanch in boiling water till overcooked.  This treatment should harden the surface only.
  2. Vacuum- infuse fries with a 0.4% PME/0.5 % calcium gluconate solution and then keep at 55°C (higher temps aren’t necessary because I am adding the calcium) for an hour, then blanch in boiling water until overcooked.  This treatment should harden the whole fry.

Compared to the control (blanched in boiling water till overcooked), the Steingarten fry was hard, and the inside hollow.  It stayed hard as it cooled, but we didn’t find it pleasant.  Perhaps in another circumstance (other than tasting a zillion fries side by side) we might have interpreted this fry as crunchy in a good way.  But the multiple tests have shown us a difference between hard (bad) and crunchy (good).  Likewise, the fries that had the PME injected into them were hard and hollow –no good.  The fries that had been soaked in the PME were hard on the outside, a bit hollow, and also greasy.  The ones blanched from cold were crunchier than the control, and looked really good; but didn’t have as much potato flavor as the control.  The control was the best of the lot –even though it wasn’t the crunchiest.

Third Rule: Make sure your blanching water is boiling, and don’t let the water temperature get below 80°C. The best internal texture and flavor for French fries is possible only when PME is not activated. We figure the best way to do this in a restaurant situation is to use a pasta cooker for blanching.

While researching enzymes and French fries in the scientific literature, I came across an article on Pectinex SP-L in fries (The Effects of Enzymes on Fat Content and Texture of French Fries, G. Lisinska, et al. Food Chemistry, vol 102 (2007) 1055-1060). Pectinex SP-L is the exact opposite of Novoshape –it breaks pectin down.  The theory of the article is that pectin and starch are antagonistic –the starch wants to swell, and the pectin wants to hold it back. As the potato is fried, the starch swells and eventually dehydrates, forming a crust on the fry.  If the pectin at the surface is not degraded, fissures appear in the crust as it dries, leading to more oil penetration (the main focus of the article is preventing oil penetration, because people are obsessed with fat content – and because oil is more expensive than potatoes).  Using SP-L breaks down the pectin at the surface, allowing major starch expansion and preventing fissures and cracks in the crust. Here are the SEM pictures from the article borrowed without permission:

Left to Right: Cut fries soaked in water without SP-L (300x); Cut Fries soaked in water with SPL (300x); No SP-L after first fry (150x) --note the fissures and cracks; With SP-L after first fry (150x) --smooth. These pictures reprinted without permission from "The Effects of Enzymes on Fat Content and Texture of French Fries", G. Lisinska, et al. N.B. The technique used in that paper isn't the same one we use --they soak after an initial blanch, we soak before we blanch.

OK –more tests.

  1. French fries soaked in a 0.4% SPL solution at 25°C for 1 hour and then blanched for 14:30 in boiling water.  This should soften the surface.
  2. French fries vacuum injected with a 0.4% SPL solution at 25°C for 1 hour and then blanched for 14:30 in boiling water.  This should soften the whole fry.
  3. French Fries vacuum infused with a 0.4% PME/0.5 % calcium gluconate solution and then soaked in a 0.4% SPL solution kept at 55°C for an hour and then blanched for 14:30 in boiling water.  This should soften the outside of the fry but harden the inside.  We did this one just for giggles, even though we were skeptical about using PME. We were rooting against this technique, because it is a pain in the rear.

The SP-L injected fries were a complete disaster. They wouldn’t brown properly and were hard like rocks. The PME-injected SPL -soaked fries were good, but they didn’t have as much potato flavor as the control, and they seemed hard. As they cooled they got dry.  The SP-L soaked fries were a huge winner.  They had a great potato flavor and a great crust.  The crust lasted much longer than the crust in the control, but wasn’t hard or dry.  This was a fry you could eat cold.

PS: You can get Pectinex SP-L from us if you can’t get a sample from Novozymes or Gusmer.

Fourth Rule: Soak your fries in a 0.4% solution of Pectinex SP-L at 25°C for about an hour before you blanch.

To Dry or Not To Dry:

Our standard practice has been to dry out our fries after the blanch, but before the first fry.  We scoop the fries out of the blanching water, carefully put them on cooling racks, and put them in a convection oven with the cooling fan on and the door ajar.  Sometimes, if the fries don’t get dried off right away, I’ll put the convection on low (60 or 70°C) to dry them out faster.  At home I use a three-speed fan or a hair dryer. The reasoning behind drying: after frying, the potatoes will stay crunchier, longer, because they have less internal moisture.  The fries form a better crust because their surface is dry before they go into the fryer.  The literature (see bibliography at the end of the previous post) says that dried French fries absorb less oil than fries that haven’t been dried (although there is some confusion about how oil content is measured –see the article Understanding Oil Absorption During Deep Fat Frying, by Pedro Bouchon, which is chapter 5 in Advances in Food and Nutrition Research, vol 57 2009).  The amount of oil a fry absorbs is roughly proportional to the amount of water that is boiled out, because the oil gets injected into the voids left by the water as the fry cools.  Dried fries are compacted more and have a denser surface, so they absorb less oil.  But…. do they taste better?

In the informal side-by-side tests I have run over the years, dried fries have always won.  But now that I was more focused on internal texture, I wasn’t sure how the tests would pan out.  We blanched a bunch of fries using several techniques: SP-L soak, PME soak, boiling blanch, blanch from cold, etc. We dried half of each batch in the convection oven with the door ajar, and fried the other half without drying.

In general, dried fries were crunchier than non-dried fries, but they tended to be hollower, and they tended to taste hard and dry when cold.  The fries that had had not been dried, although not as crunchy as their dried brethren, always had a better internal texture and potato flavor, and remained pleasant even when cold –sometimes they even seemed to get better.  For instance, in blanched-from-cold French fries (with some PME activation),  tasters preferred the dried fries straight out of the fryer, but after 10 minutes, the un-dried fries were surprisingly pleasant.  Not super crunchy –but not soggy.

This over-dried Novoshape PME soaked fry has a super hard exterior crust (like a fried wonton) but the inside, which wasn't hardened, has gone completely hollow.

Our favorite blanching technique, SP-L soaking, and the runner-up, straight boiling, responded slightly differently to drying.  The standard boil wasn’t quite crunchy enough when fried without drying.  The dried, standard-boil guys were crunchy –but a bit hollow.  I think we had over-dried them.  In the case of regular boiling, I think a happy medium between no-dry and really-dry would be best.  On the other hand, the SP-L soaked fries were crunchy enough straight out of the fryer, had a great potato flavor, and tasted not good, but great, when cold.  The cold fries were not soggy, not dry, and not hard.  Not super-crunchy, but crisp and pleasant.  I could eat them all day.

Notice the difference between the crust on the dried fry vs the non-dried one. This is typical of the differnece between dried and non dried fries. Notice the dried fry on top is hollow, but the bottom one is not.

The winning fry: SP-L soaked, not dried.

Fifth Rule: Don’t dry your fries too much –they will turn hard and hollow.  Some fries, like the SP-l soaked, shouldn’t be force dried at all.

The current technique in a nutshell: Peel potatoes, cut into fries and rinse.  Soak in a 0.4% solution of Pectinex SP-L and water for 1 hour at room temperature. Blanch fries in boiling water with 3% salt added (or to taste).  Make sure the water temperature doesn’t drop below 80°C.  Blanch for 14.5 minutes.  Drain fries on a cooling rack, but don’t force dry them.  Fry them at 170°C till they form a crust but are still blond.  Fry a second time in 190°C oil till crispy and golden brown. Eat.

The French Fry Crew: Naz, Nick Wong, A.J., Piper, Adam, Jeremie, Jason (King LN), Wipop "Bam" Suppipat, Stazi, and two idiots.


We took our magnified pictures with this rig:

Cheap stereomicroscope with a home-made PVC lens adapter.

Vinegar Fries

We make a lot of vinegar fries.   We inject vinegar into raw fries and then blanch those fries in vinegar.  It takes a long time to cook potatoes in vinegar.  The acid makes it more difficult to break down the pectin.  We tested our vinegar blanching technique against our new favorite blanching technique.  They tasted like vinegar –which is good, but they were hard –which is bad.  We had always liked them –because they are super-crunchy, but now we were a little disappointed by the texture.

Weird Enzyme Thingy

One of our tests (not reviewed) involved blanching fries starting with cold water and pulling them out when they reached 70°C.  Those fries turned a weird purple –just like they hadn’t been blanched at all.  The ones that were pulled at 60°C didn’t change color –neither did the ones pulled at 80°C.  Any ideas?

Fries blanched from cold and pulled at 70C oxidized, but those cooked to 60C and 80 C did not. We don't know why.

A Response from a Former Cooks Illustrated Tester on Frying in Cold Oil:

“We didn’t have the same problem that you guys did with the fries – they were slightly greasier than normal but by no means unacceptably so, and they stayed crisp for longer as well. Granted, our focus with the recipe was more on hassle and less on quality – we would never be able to publish a three-stage fry. From looking at the pictures accompanying the post, I think that the burner you were using was considerably more powerful than the ones we tested on – we don’t use restaurant-grade stoves here, really. With a lower oil temperature, the fry spends more time cooking through, and presumably loses more moisture as well. We had an ancillary problem that we think had to do with the relative age of the potatoes – some fries would come out incredibly crispy, but others would just be tough. We think that this tendency had to do with the relative sugar content of  the potatoes, as we had no way to control for the age of the potatoes and so some were doubtlessly stored longer than others, and we had no idea which were which. I’d be interested to see if we can find a way to control for that.”

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The Quest For French Fry Supremacy Part 1

April 27th, 2010 · Uncategorized

by Dave Arnold

I consider myself a fry-expert, and I believe almost anything can be fried to good or great effect. I deep fry steak, bacon, bones for stock, as well as the obvious stuff – like French fries.

A fry-cook can be judged by their fries. At the FCI we make really good ones– but we want to make the best. Our technique is basically Blanch, Dry, Fry, Fry. We are currently exploring these phases in excruciating detail in our search for the perfect fry. Today, I’ll walk you through our current recipe –and explore a simple alternative. Next Time, the first serious FF investigation: blanching.

The Perfect Fry:

Perfect French fries are super crunchy on the outside with a good cooked-potato texture and flavor on the inside.  They shouldn’t taste too greasy.  They should be salty.  They should stay crispy for at least 10 minutes.  Easy, right?

The Current Technique

  1. Select a variety of potato.
    I use Idaho russets (there are several varieties of russeted potatoes; we usually get Burbanks). Nils, being from Sweden, thinks we should use other potatoes. We’ll find out.
  2. Peel potatoes and keep submerged in water.
    While the peel has vitamins and flavor, it does not produce as nice a crust as the rest of the potato, plus it can hide rot and blemishes. Away it goes.
  3. Cut the potatoes with a French fry cutter and place in water to prevent oxidation.
    The cutter we use is 3/8” square. We like this size, or slightly larger. Smaller fries have a very high crust-to-core ratio; shoestring fries are almost all crust. Super-thick fries are like baked potatoes with a French-fry crust. We go for a middle ground. I have some evidence that hand-cut fries may be better. I don’t know if the slight irregularity makes them better or if the sharp knife produces a better fry than the relatively dull French fry cutter.
  4. Optional: inject the French fries with a flavor –like vinegar—or a texture-modifying enzyme like Novoshape (a pectin methyl esterase that strengthens the structure of the potato) using a vacuum machine; or soak them in a texture-modifying enzyme like Pectinex SP-L (an enzyme that breaks down pectin structure –some studies indicate that breaking down pectin at the surface of the fry can decrease oil absorption in increase consumer preference). Note that the two enzymes above do exactly opposite things, yet both can contribute to a better fried potato. Confusing.
  5. Optional: pre-blanch French fries in 55 C ( 131 F) water for 40 minutes.
    Potatoes naturally contain the enzyme Pectin Methyl Esterase (see the previous cook-step). This pre-blanch activates that enzyme and strengthens the structure of the fry, but also changes it. This technique was discussed in depth by Jeffrey Steingarten in his first book The Man Who Ate Everything , so we call it the Steingarten technique. Steingarten used it for mashed potatoes. Heston Blumenthal picked it up and made it popular with chefs. It doesn’t just work on mashed potatoes — it works for any potato preparation, and other vegetables too. Some people love this technique; some hate it. Nils and I don’t enjoy the mashed potatoes– the texture reminds us of a very fine hominy grit or tiny, tiny bb’s. Nils also dislikes the Steingarten technique for French fries because he’s looking for a creamy interior. The ST emphasizes the crust; the fry’s inside can lose its potato texture (creamy or fluffy, depending) and, at the extreme, can exhibit the phenomenon we call “hollow fry”: a crust with no internal potato structure. Nils cannot tolerate hollow fry. I am OK with the occasional hollow fry because, for me, crust is paramount.
  6. Rinse off fries and blanch in salty water until they are cooked through.
    We blanch for many reasons: blanching with salt improves flavor by salting the inside of the fry;  leaches out sugar, which reduces premature browning; kills enzymes (important if you can’t fry right away or are planning a pre-fry drying step); pre-cooks the potato so the first fry can be high-temp and short duration; and, lastly, blanching pre-pastes and pre-gelatinizes the starch, purportedly creating a barrier at the surface of the fry to prevent excess oil intrusion.
  7. Dry the fries with a convection oven, fan, or hair drier until the surface is leathery.
    The drying step helps form the crust and dehydrate the potato. Studies show that partially dehydrating the fries reduces oil uptake when frying. Other studies show that overall dehydration isn’t important, but the leathery surface formed by drying reduces oil uptake and forms a nice crust. Removing surface moisture also saves your oil from excess-water abuse.
  8. Choose an oil or fat for frying.
    Finished French fries are up to 10 percent oil, so this choice makes a real difference. We normally use industrial fry oil because we are working on the stovetop and this oil can withstand the temperature abuse.
  9. Fry in hot oil (roughly 170 C, 340 F) until a crust forms (to test, we pull the fries out of the oil and tap on them) but the fries are still blond.
    The oil temperature is high because we have already cooked the potatoes – we are only working on crust formation.   This step should be fast.

    The first fry should leave the fries blond. When they come out of the oil they should be almost white. They dry down to this yellow color.

  10. Shake the hell out of the fries as they come out of the oil, and allow them to cool.
    Studies show that most oil absorption takes place after the fries are removed from the oil, as they are cooling down (see bibliography).
  11. Optional: freeze the French fry.
    Freezing acts like partial dehydration. When the frozen fries are finished, they liberate water freely, leading to rapid dehydration and good crust formation with a porous interior. Pre-frozen fries are crunchier than fresh and stay crisper longer after they are fried, but they tend toward hollow fry. Nils hates this step; I like it.
  12. Finish-fry in very hot oil, 195 C (385 F), till crispy and golden brown.
  13. Shake the hell out of the fries.
  14. Eat.

I have been told our fry technique is complicated.  I don’t think so.  It is easy to do –especially in bulk. In our last Harold McGee class someone asked us about a technique published in the July 2009 Cooks Illustrated, which advocates throwing raw potatoes in cold oil and cooking them in one step by heating the oil.  We tried it.

Frying in cold oil.

Fried from cold. Didn't stay crispy long.

Here is a magnified view of the interior and crust of the French fry.

Magnified image of the interior and crust of the cold oil French fry.

We didn’t like the results.  The fries had a fantastic crust –right out of the fryer.  Unfortunately, they wilted quickly compared to our normal fry.  Within a couple of minutes, we didn’t want to eat them at all.  Our standard fries are good even when cold. I think the cold-cooked French fries wilted because they were too high in moisture.  The Cooks Illustrated folks solve this problem by using a thinner fry – just 1/4 inch. Less interior means less moisture. Less moisture means less wilting.  Less interior also means less textural difference and less potato flavor. Another problem with this technique:  the interior of the fry isn’t salted.  Once you taste a fry that’s salted from the inside, you won’t go back.

Cooks Illustrated claims their technique makes a less oily fry than their control double fry, and they have lab results to prove it.  Their photo of  twice-fried fries looks terrible; super greasy.  They stacked the deck in their favor by using a crummy double-fry technique.

A Partial French Fry Bibliography

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Citrus Lunacy on Gene Lester’s Ranch: Attack of the Acid-Eaters

April 16th, 2010 · Uncategorized

by Dave Arnold:

Flying Dragon Trifoliate Orange. Cool branches, no fruit.

I believe in building your taste memory. A good taste memory makes you a better cook and a better eater.  One of my favorite techniques is to try a zillion varieties of something all at once – to quickly see the whole range of possibilities. A couple years ago Harold McGee and I charged through a 2 day apple-eating marathon at the world’s largest collection of apples. A life changing experience.  Lucky for us, McGee arranged a similar experience with citrus last month.  Here is the story:

Gene Lester is a collector.  At his ranch in Watsonville, CA he collects wood specimens, classical music recordings, pre-war Fords, avocado trees, and citrus.  At over 200 varieties, his private collection of citrus tree is the most impressive in the US.  Every March, Mr. Lester invites the California Rare Fruit Growers Association out for a day of discussion and tasting. McGee scored invitations for the Cooking Issues team. Then, disaster struck – two days before the tasting we were told that the Rare Fruit folks would need to exclude us for insurance reasons.  Ever gracious, Gene Lester invited us to a private tasting with a small group of his friends the day before the big event. We prepared for a citrus feeding frenzy.

Some dangers lurk in the eat-it-all, shotgun-tasting approach. Gastrointestinal distress is one.  Not a big deterrent for me –physical comfort isn’t my priority, and I have a cast iron stomach. Ditto for McGee and Nastassia.  Then there’s palate fatigue:  marathon liquor tastings (even if you’re spitting) can bring this on. The danger that concerns me most is information overload.  When tasting unfamiliar food families (an example for me is pu-erh teas, which I’ll write about in an upcoming post) it’s best to focus on thoughtful tasting of a few distinct examples.  But, if you are very familiar with the basics of a food family – I’ve been a citrus fanatic since I can remember – overload is much less likely. I know how to taste citrus – and I wanted to rack up the variety count.

It took a while for Mr. Lester to figure out that we wanted to taste not just a lot of citrus, but a preposterous amount of citrus.  It took us a little while to figure out if he would let us.  In the end, it all worked out.  Some highlights from the tasting, and from Mr. Lester:

Gene Lester on Oranges vs. Mandarins:

“All sweet oranges, with the exception of some blood oranges, taste pretty much like an orange.  Every mandarin has its own unique taste.”

I was surprised to hear him say that, but after a couple-dozen types of mandarins and tens of oranges, I couldn’t argue.  Some oranges are really pretty, like the pink fleshed Cara Cara that is becoming a popular premium commercial crop.

Gene Lester about to cut into a Cara Cara orange with his badass fruit testing knife. Don't worry, we brought one too.

Some oranges have better or worse juice (the juice of Navels and some other citrus have high concentration of limonoate A-ring lactone (LARL) which is enzymatically converted to the extremely bitter substance limonin after juicing: see here). Some are better for eating out-of-hand. But all the oranges tasted pretty orange-y.  Each mandarin, by contrast, had its own perfume and taste. One of the mandarins, Armstrong, tasted exactly like canned mandarin oranges (although I don’t think it is a prominent variety for canning). Man, did I eat a lot of those growing up, and I thought it was the canning process that gave them that tinny note.

A note on Citrus Color:

The Peel:

All the ripe limes in Lester’s collection have yellow skin, including the Bearss (or Persian) lime familiar to us from U.S. supermarkets –California climate does that to limes.  Perversely, though we import a lot of limes from Mexico, the Mexican lime – which we call the key lime – isn’t what we import.  We import the Bearss limes.  Lester said he believes the dark green limes in our stores are painted.  I wasn’t sure if he was joking.

All of Lester’s citrus peels were beautiful and highly colored –California peels look great.  It is a strange citrus fact that the more tropical the climate, the more poorly colored and raggedy the peels look –sorry Florida.

Left: California peel. Right: Florida peel. Sorry Florida.

Unfortunately, on many types of citrus, California climate also makes peels very thick.  Lester explained that his climate wasn’t quite hot enough to do perfect grapefruits and pomelos. Oh well.

Thong Dee Pummelo. Look Ma, no fruit!

The Fruit:

The blood oranges don’t get too bloody on Lester’s ranch, because they don’t get the significant hot day/cool night temperature swing that they thrive on. But we had some fairly dark Morros.

Moro blood orange

Blood oranges are dark because of anthocyanin pigments that develop in them; pink and red fleshed citrus, on the other hand, are pigmented by lycopene.  Little known fact: The lycopene in pink grapefruit juice is removed by gelatin freeze-thaw clarification (maybe I’ll post on that some day).


While many varieties were beautiful, like this Variegated Eureka Lemon with pink flesh:

Variegated Eureka Lemon

…and many had such crazy names that we were compelled to try them –think Eustis Limequat, Nippon Mandarinquat, and Sinton Citrangequat


Nippon Mandarinquat

…and many look famously bonkers, like this Buddha’s Hand citron flipping you the bird:

Rude Buddha. Buddha's Hand Citrus flipping us off.

…a few stuck out in our minds as fruits with potential.  Much of the time, when I say, “potential,” I mean “potentially great for cocktails” –bear that in mind. Our tastes run to the acid. Not included in this list is anything which we can already source –like Australian finger limes, yuzucalamondin (calamansi), or kieffer lime (note that Gene Lester prefers the spelling kieffer  lime to the more usual kaffir lime because in South Africa, the latter word is a pejorative racial epithet.  We have banished k*ffir lime from our vocabulary).

1. Australian Finger lime. 2. Cut it open. 3. Squeeze it out. 4. Zero-hydrocolloid lime caviar.

Poorman Orange, aka New Zealand Grapefruit: Simply put: delicious. It doesn’t taste quite like a grapefruit – it is a little less bitter and perhaps more complex, but it definitely does not taste like an orange. Citrus Varieties of the World states, “When mature, the flavor is unique among citrus varieties, having some of the characteristics of the grapefruit combined with the slightest trace of lime and lemon, somewhat resembling a ‘bitter lemon’ soft drink.” Nastassia’s notes just say, “amazing.” I think the poorman orange could be very popular in the US.  It is primarily grown in New Zealand, where there isn’t enough heat to grow excellent quality proper grapefruits.  I bet some parts of California are perfect for it (like Gene Lester’s ranch). New Zealand is allowed to import some citrus into the US, but I don’t know if Poorman orange can be shipped.  I’ve never seen it in any market.

Poorman Orange, aka New Zealand Grapefruit

Kusaie, and Rangpur Lime: Both of these are “mandarin limes” (a mandarin crossed with lemon that taste like limes –go figure).  Both are great for cocktails (or marmalade).  Rangpur lime is sometimes used as a rootstock, and also as an ornamental citrus. Think of it as a tiny, seedy fruit with a nice flavored peel and a taste between a sour orange, a lime, and a lemon.  Kusaie is primarily grown as an ornamental  in Hawaii.  I think the peel of the kusaie is even better than the rangpur, but the taste is somewhat similar.  Kusaie would make some killer cocktails.

Kusaie and McGee

Ginger Lime: The name is pretty accurate –this guy is a lime with a gingery tasting peel.   Pretty darned good.  Most citrus leaves are not aromatic –kieffer lime leaves (aka lime leaves) are the notable exception—but ginger lime leaves are. They have a great gingery aroma.  We want to throw some ginger lime leaves into soups.

Ginger lime posing with Nastassia

Natsudaidai:  The natsudadai is a Japanese citrus that, according to some, is an acquired taste.  If so, we acquired that taste pretty quick.  It is a super-refreshing mix of sour and bitter with some sweet to back it up.  It is almost a ready-made beverage. Just add bubbles.  Better yet, add gin and bubbles.  We really, really want to find a source for natsudaidai.

Super-tasty Natsudaidai

Allspice: An interesting little tangelo (mandarin crossed with grapefruit) that has a full, orange-y-mandarin flavor but really does have an allspice note.  A winner.

Allspice. Tastes like..... allspice.

The problem with many of these fruits is they are impossible to source.  David Kinch, of Manresa, in Los Gatos, CA, is fortunate enough to have a working relationship with Mr. Lester, and sometimes features rare citrus from Lester’s ranch at the restaurant. FoodPlayerLinda from Playing With Fire and Water, one of our favorite blogs, received a Gene Lester care package from Kinch and wrote a characteristically beautiful post on it here (how do we get on Kinch’s citrus mailing list!).  She also published a cool recipe using ginger limes here.  Weird citrus is hard to source because import rules are very strict –there is a looming and ever-present danger of plant pests destroying our domestic citrus industry.  Even countries that are allowed to send citrus to the US do so only with permits and special inspections (the rules).  Even Florida is not allowed to ship citrus to other citrus producing states (check this).

If you can grow your own citrus, a good place to source trees is Four Winds Growers, which has an amazing array of dwarf citrus trees to choose from.

If you are looking for the most comprehensive guide to citrus on the net, Gene Lester recommends the Citrus Pages, created and maintained by Jorma Koskinen.  Look there for a exhaustive list of varieties with photos, tasting notes, history, and lineage.

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Announcing Cooking Issues Forums!

April 13th, 2010 · Uncategorized

We love our readers. You are a smart bunch of folks, and we want to know what’s on your mind –so we’re launching Cooking Issues Forums.
Some of the most enlightening information on our blog has come from reader comments. Unfortunately, we have to approve each comment before it goes up, and the subject matter is limited to what we are posting about. We want the exchange to be faster, and we want to take on a broader range of subjects – so we all get to learn more.


Cooking Issues is a niche blog. We have a point of view, and a pretty narrow range of topics that it makes sense for us to address. So we have some guidelines:
Stick to food –specifically, an analytical approach to cooking and eating, with or without the use of technology. We love blind tastings. We love careful observation. We love inquisitive people.
Where we ate brunch this weekend isn’t germane. There are plenty of sites better suited to discussions of where to eat and what to eat there.
The Cooking Issues forum content needs to stay rich and specific. We don’t want just another food forum.

The Rules:

  • Browse the primers before asking a question.
  • No ad hominum or personal attacks (Nastassia is the forum’s hammer. She can’t wait to ban someone).
  • Don’t make negative comments about another chef’s work. This is not the place.
  • Don’t bad-mouth other blogs.
  • Don’t be prissy about other people’s posts. No need to point out that they misspelled teh internetz. Remember, some of our readers use English as a second language. And Dave can’t spell either.
  • We have disabled personal messages on these forums because we want the discussions to be public. The Cooking Issues team will respond to open messages in the forum only.
  • Networking is fine. Talking about products is great. Don’t make us the shills for a corporation.

Getting Started:

Click the forums link at the top of the blog and register. The registration is mandatory to post. Without registration we will be inundated with spam –who needs another Viagra ad? Posts will go up in real time.
We have populated the forums with some subject headings we think are important; we will change them as you tell us to.

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Skoal Party Aftermath

April 13th, 2010 · Uncategorized

posted by Nastassia Lopez

This weekend we had a Skoal party – which served as a great excuse to celebrate Dave and Nils’ birthdays.

Skoals to come, but this photo about sums up the night:

*Photography thanks to Dave’s brother-in-law, Travis Huggett.

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Sous-Vide and Low Temp Primer Part II: Cooking Without a Vacuum.

April 7th, 2010 · low temperature cooking, sous vide, Uncategorized

posted by Dave Arnold

For part one of the primer, an introduction to low-temperature cooking and sous vide –including some funky charts– see here.

I got a bit long winded again.  I  intended to have Part II of this primer cover all forms of packing and preparing for low temperature cooking.  It was getting way too long – so here’s today’s installment.

II. Low Temperature Cooking Without a Vacuum.

… in which we’ll discuss preparing foods for low-temperature cooking without using a vacuum machine; we’ll look at zip-loc bags, plastic wrap, and cooking in oil/stock/humid air.

Before We Start: A Note from New York City:

New York City + No HACCP plan = no vacuum machines.

In New York City, a restaurant cannot use a vacuum machine without developing a HACCP plan.  HACCP (Hazard Analysis Critical Control Points) is a system designed to ensure food safety.  It was developed by large corporations who were making food for space missions –giving an astronaut food poisoning can be catastrophic. Creating your own HACCP plan (explained in the upcoming safety section of the primer), even if you don’t implement it fully, is a great way to help yourself ensure food safety. HACCP plans administered by the Board of Health, on the other hand, are a pain in the rear. They entail extra inspections, log books, lots of time, and possibly spending money on consultants. Look here for the Board of Health guidelines.  Low temperature techniques that do not require a vacuum machine have a major advantage for New Yorkers: no HACCP plan required. 

Even If You Don’t Cook in New York City:

While I love a commercial vacuum machine, about 90% of what a cook wants to accomplish with low temperature cooking can be achieved without a vacuum machine.  When Nils was at restaurant Aquavit he did a lot of low-temperature work with a circulator, but didn’t have a vacuum machine.  Back then restaurants weren’t required to have a HACCP plan;  he didn’t have a commerical vacuum because they cost too much.

Today many home cooks use the Food Saver vacuum for low temp.  I don’t use my Food Saver any more. I use Ziploc bags, without a vacuum.  I find Ziplocs easier than the Food Saver – I don’t have to hunt down the special bags, I can easily bag sauces (a pain with the Food Saver), I can bag hot foods (foods to be vacuumed need to be cold – more on that in the next primer installment).  My Food Saver has been relegated to potato-chip-bag-resealer.

To Review:  

Low temperature cooking is defined as any cooking procedure where the cooking temperature is at, or close, to the desired final internal temperature. There are two requirements for low-temperature cooking:

  • precise and accurate temperature control
  • a cooking medium which conducts heat more efficiently and accurately than dry air. Water and water vapor are typical; oil, stock, or any other liquid will work.

The Basics: To Pack or Not To Pack

There are two basic approaches to low temperature cooking:

  • Expose the food to the cooking environment – includes cooking in temperature controlled poaching liquids, oil, 100% humid air. I call this “unprotected” low temp.
  • Protect the food from the cooking environment – includes vacuum bagging (covered in the next installment of the primer), Ziploc bagging, plastic wrapping.

Unprotected Cooking Techniques:

100% Humid Air

You can’t cook low-temperature in dry air; for example, don’t try it in your oven. Dry air is a poor heat conductor and causes evaporative cooling at the surface of your food – making accurate temperature control impossible. 100% humid environments, like you can achieve in a combi oven, don’t conduct heat as well as straight water, but they can be very accurate. This kind of cooking is simple. Food goes into the cooker and gets pulled when it’s done; no wrapping required. The workflow is very intuitive for most cooks. But there are some disadvantages to 100% humid cooking; if you’re doing a cook-chill procedure the food isn’t protected from recontamination (it would be if it was wrapped); and during long cooking times (like several hours) the food’s surface tends to degrade.

Combi ovens and CVap ovens provide a 100% humid environment:

Combi Ovens

Combi oven.

Combi ovens are combination steam/convection ovens; modern ones can operate at low temperatures. The main advantage of combi ovens: they can  handle large amounts of food without getting bogged down by overloading, or by repeated opening and closing. Unfortunately, the ovens expend an enormous amount of energy to maintain this stability. Combis are also expensive and difficult to retrofit into many kitchens. And perhaps their biggest problem: they aren’t very accurate. Studies by Chris Young and Nathan Myhrvold show that while a combi oven’s average temperature can be accurate to within a couple of degrees centigrade, at any one moment it can be tens of degrees off. Combis should only be used to cook large items , like roasts, that won’t overcook in the ten minutes or so that it takes  the combi to swing back and forth around its target temperature.

CVap Ovens

CVap technology was originally developed for Kentucky Fried Chicken. Colonel Sanders needed something that would hold his chicken in perfect condition; he asked his friend and fryer guru, Winston L. Shelton, for help. In response, Shelton invented  CVap (Controlled Vapor) technology. CVap ovens are basically food holding cabinets with a bain marie in the bottom. Both the oven cavity and the bain marie are heated and temperature controlled. The cook can control the humidity inside the oven by adjusting the difference in temperature between the bain marie and the oven air. The core temperature of the food will not rise above the temperature of the bain marie. The surface texture of the food is controlled by the humidity of the oven air. You set the temperature of the oven air much higher than the water for crispy foods, like fried chicken, and you set it the same temperature for low temp cooking. For a detailed discussion of why the CVap works, see here.

CVaps come in many shapes and sizes, from very large down to single drawers like this one.

The inside of a CVap.

The Cvap comes in a range of sizes, is much cheaper than a combi, doesn’t require a lot of power, doesn’t require a water supply or a drain, and is extremely easy to retrofit. Many restaurants in New York City bought CVaps immediately after the Health Department  instituted HAACP control for sous-vide cooking. It is difficult to get a HAACP plan approved for sous-vide fish, and it is impossible to get one approved for fish below pasteurization temperatures (which is where we usually want to cook it). Since the possibilities of low temperature fish attracted many chefs to low temperature cooking in the first place, many took up the CVap.  It was basically unheard of in chef circles prior to the health department crack down. The disadvantage of the CVap:  it can start sucking wind if overloaded, or if the door is frequently opened and closed.

Cooking Directly in Water/Fat/Stock/Poaching Liquid

The immersion circulator is many cooks’ instrument of choice for low temperature cooking;  most cooks only use their immersion circulator with water. Take note: you can circulate any liquid you want –stock, beer, oil, duck fat, lard, apple cider, whatever. I am often asked if the circulator will be damaged by liquids other than water.  Happily, the answer is No.   If you ask Philip Preston from Polyscience (whose circulators we use) he will tell you the machines  aren’t NSF rated for direct food contact. It isn’t because the circulators aren’t safe for direct food contact, it’s just that getting the NSF rating would cost a lot more money than it is worth.  Here are the rules for unprotected cooking in the circulator:

  • Make sure the circulator is clean.  Circulate detergent to clean it.  Scrub the heating coils with a toothbrush.  We use the oven cleaning tablets from our combi oven manufacturer to clean ours.  Those tablets eat everything.  Other people use CLR (calcium, lime, rust) remover.  Do what you like, but keep those circulators clean.
  • Make sure you aren’t going to suck small items into your circulator pump. Any time you add herbs, burnt wood chips, crushed lobster shells, or any other flavoring to your bath, wrap it in cheesecloth first.
  • Be careful, especially with oil and fat, to get good circulation.  Bad circulation = bad temperature control and could = safety problem. The cooking liquid should be moving around all sides of the food at all times.
  • Never cook unprotected in a liquid that isn’t hot enough to kill bacteria.  We always keep our liquids above 54.4˚C (130˚F).

Tips for using a circulator to cook unprotected food. All of the parts that touch the cooking liquid are food-grade; but the machine isn't NSF rated for direct food contact because the rating would be too costly to obtain.

Unprotected Cooking in Liquid

Eggs are one of the few foods that we circulate directly in water. The whisk is just to keep them from rattling around in the circulated bath.

Eggs in their shells are cooked low temperature in plain water without any further protection –after all, they come pre-wrapped.  Most foods will have their flavors leached out if cooked in water (that’s how broth is made) but some foods benefit from cooking in stock or other flavorful liquid. These foods are prime candidates for unprotected low temperature cooking in liquid.  Fish can be cooked in a temperature -controlled court-bouillon.  Ham can be cooked in temperature-controlled apple cider. Bratwurst can be poached in temperature-controlled beer.  Most of the time, you are better off putting a small amount of your flavorful liquid in a bag with your food and doing protected low temperature cooking  — cooking directly in the liquid requires a lot of it.  Here are some cases where cooking directly in liquid makes sense:

  • If you have an item too big to bag easily, like a whole ham, that could also benefit from some added moisture and some mellowing (many hams are salty)
  • If you are cooking many of the same item over a period of time –like sausages:

 Let’s say you cook a couple hundred sausages a day. Start with a stock that complements your sausage. Use an immersion circulator to keep that stock at 60˚C (140˚F). Throw raw sausages into the stock to cook as you need them and pull out the cooked ones to finish on the grill. After a couple of hours your stock will take on a taste almost identical to your sausage.  The stock will taste like liquid sausage. I verified this phenomenon by paying five bucks to drink a cup of cooking water from a New York City hot dog vendor. After your stock has reached the liquid-sausage stage it is no longer changing the flavor of your sausages. The stock and the sausages are in equilibrium.  At the end of the day, throw some ice into your stock to cool it down and put it in the fridge.  The next day, bring your stock back to the boil to kill bacteria and start again.  If you added the right amount of ice the day before (determined by trial and error), you should be able to maintain a constant amount of stock indefinitely. In China, stocks have been continuously maintained this way for hundreds of years.

Getting liquid hot dog: cooking liquid in equilibrium with meat. Our intern Clifford scoped out the hot dog guy across the street, negotiated for a cup of precious hot-dog water, and got some.

Clifford with liquid hod dogs. This liquid smells and tastes exactly like a hot dog. It doesn't add or detract from the taste of the sausage. After hundreds of hot dogs were cooked in it, it is in equilibrium with the meat.

Unprotected Cooking in Fat

Circulating lamb directly in fat.

You can also cook directly in temperature controlled fat.  Fat doesn’t leach the flavors out of food and often provides a beneficial unctuousness. It is expensive to fill a whole circulating bath with fat, so use this technique in  circumstances like these:

  • Some chefs and customers attach a stigma to cooking in plastic bags; fat poaching, however,  has an aura of tradition and wholesomeness
  • If you are cooking a lot of the same item, it can be convenient to cook directly in fat.  No time is required for bagging. It’s  much faster to pull items directly out of a fat bath than to un-bag them.  The cost of the fat is less significant over a large number of items
  • Very large items –like a 36 inch striped bass –can be difficult to bag, and you might not want their flavor altered by a stock.  Cook them directly in oil or fat.

36 inch striper circulating in fat. All of the containers and other stuff in the bath is to minimize the amount of oil needed.

Protected Low Temperature Cooking

Most low temperature cooking work involves protecting the food from the cooking medium with some sort of impervious cover, which is almost invariably made of plastic.  The advantages of protected cooking are:

  • There is no loss of flavor to the cooking medium.
  • There is a reduced risk of contamination. 
  • Different types of foods can be cooked in the same vessel at the same time.
  • Protected foods are very easy to chill quickly after they are cooked.

The main disadvantages to protected cooking are the time it takes to wrap or bag the food, and some people’s trepidation about cooking in plastic.

Cooking in Plastic:

Many people are concerned about the possibility of chemicals from plastics leaching into foods during cooking.  I haven’t been able to get any firm data on the migration of plastic materials from bags and plastic wraps into food, but I’m fairly certain that at least a small amount of migration is likely to occur. Whether or not that degree of migration is harmful is up for debate.  

Many people are currently worried about the plasticizer Bisphenol A (BPA).  Here is what the US government has to say about it.  BPA is used primarily in polycarbonate.  While we don’t wrap foods in polycarbonate, low temperature cooking is often done in polycarbonate containers (eg Lexans or Cambros).

Polyvinyl Chloride, another commonly used kitchen plastic , contains a whole mess of plasticizers –usually a group of chemicals called phthalates.  As far as the PVC industry is concerned, phthalates cause tumors in rodents but not in primates –even in larger than normal doses. Other people are not so sure. Who knows? Many commercial plastic wraps are made of PVC.  Often, these wraps smell bad –indicative of residual solvents and whatever is was used to make them.  Aside from any purported health issues, bad smelling plastic wrap can most definitely make your food taste bad. Fatty foods like cheese are more likely to pick up bad odors from plastic wrap. Don’t use plastic wrap that smells bad.  On the positive side, PVC is a pretty good vapor and moisture barrier and can have pretty good heat resistance.

 Polyethylene, in its many guises, is another major plastic used to wrap foods. Most supermarket plastic wrap is made from polyethylene (PE).  Polyethylene is usually plasticizer free –which is good news.  Polyethylene wraps usually have some chemicals added to increase cling –often ethyl vinyl acetate (EVA) and polybutene (PIB).  I haven’t found any health concerns on these two ingredients.  The bad news about polyethylene is that it doesn’t tolerate very high temperatures and it is not a very good gas barrier. Plastic wrap is an especially bad gas barrier because it is made from low density polyethylene (LDPE).  Food wrapped in LDPE will still oxidize.  Odors might also be able to penetrate LDPE. Use several layers.  Ziploc bags, as far as I can determine, are usually made of polyethylene.  The freezer Ziplocs are better gas barriers than standard Ziplocs, both of which seem better than plastic wrap.  Perhaps Ziplocs are just thicker than plastic wrap, maybe they contain some other type of polyethylene.  I don’t know.

Packing Without the Vacuum:

Ziploc Bagging:

Ziploc bags are excellent cook-chill tools.  At the school we always call out Ziploc, rather than re-sealable bags, because many off-brands don’t work.  The seals fail, the bags come apart when cooking, etc.  Do not purchase the Ziploc with the sliding do-dad.  Get the regular double-seal type.  We buy the freezer storage bags because they are supposed to act as a better vapor barrier than the regular type, and they are rated for re-heating in the microwave.  We stock quart and gallon size bags.  If you learn the proper technique for bagging, Ziploc bags can get almost as tight as a vacuumed bag.

The Technique:

  1. Fill a container with water deep enough to easily submerge your food and bag.
  2. Always add some sort of liquid to the bag –fat, stock, sauce, etc.  The liquid is necessary to fill the gaps around your food and expel the air from the bag. 
  3. Add your food item.  A significant advantage of Ziplocs over vacuum bags is that the food can be added to the bag hot.  All vacuum bagging procedures require your food to be cold (more on that in the upcoming vacuum section of the primer).  If you are searing meat and adding it directly to the Ziploc bag make sure the surface of the meat is below 100˚C (212˚F) or the bag will melt.  Be especially careful to not touch the bag with a hot set of tongs or spatula.
  4. Close the seal of the bag almost to the edge, leaving the last portion of the seal open –make sure you have correctly sealed the bag.  Put your finger in the corner to make sure that part of the seal is open.
  5. Carefully immerse the bag in the water starting with the  closed corner, not the open one. Make sure you do this step carefully,  allowing  air to escape up and out of the open corner.
  6. Just as the open part of the seal is about to go under the water, close it up.

1. Fill a container with enough water to submerge your product. 2. Make sure there is liquid or oil in the bag. Add your product and seal the bag except for one corner. Put your finger in the open corner and start submerging your bag like it shows in the picture. Submerging as shown will minimize the amount of trapped air.

1 and 2. Submerge the bag and work out all the air. 3. Just before the last corner goes underwater, remove your finger and seal the bag completely.

Finished Ziploc. No air bubbles. Almost as good as a vacuum.

The advantages of the Ziploc are:

  • you don’t need to buy a vacuum
  • food can be bagged hot
  • food can be removed from the bag and re-bagged easily
  • the process is very gentle on foods and doesn’t change food textures the way vacuum bagging can
  • it’s just as effective for cooking as vacuum bagging for most items

The disadvantages of the Ziploc are:

  • not as convenient for bagging a lot of items as the vacuum machine
  • Ziplocs cost more than vacuum bags
  • doesn’t provide some vacuum benefits –fast marination, extended storage, oxygen removal.

Wrapping in Plastic Wrap:

Rolling foods in plastic wrap is an excellent preparation technique for low temperature cooking. Rolls cook evenly and are easy to portion.  We often combine rolling with some meat glue (see the transglutaminase primer).  Properly rolled roulades in plastic wrap will not allow water to penetrate.  Really good rolls are dense –they will sink.  Here is the technique in pictures, borrowed from our transglutaminase primer.  Remember –making good rolls isn’t as easy as it looks.

Another option for plastic wrapping: the cannon ball.  Place the food to be cooked in a square of plastic wrap and twist to form a ball.  Tie up the loose end.  The part of the cannonball near this loose end isn’t going to be very pretty –serve it face down on the plate.

1. Mis en place for the cannonball. Plastic wrap and either butchers twine or a length of twisted plastic wrap to tie off the ball. 2. Put your product in the center of the plastic. Normally, we would add some meat glue.

1. Gather up the meat. 2. Use your hand to squeeze out most of the air and form the ball. 3. Make sure to get out the air at the point where the plastic wrap comes together.

1. Twist the cannonball to form the shape. 2. What your cannonball should look like.

If there are large air bubbles in the ball you can poke them with a skewer and they will go away. If you poke the wrap with a skewer you'll need a second layer of plastic.

1. Place the cannonball in another piece of plastic wrap. 2. Squeeze the air out and reinforce the ball shape. 3. Twist to lock.

1. Tie the cannonball off. If you use string as pictured, be careful to not rip the plastic. Tying with plastic minimizes this risk. 2. The finished cannonball.

The underside of the cannonball looks a little wonky. Serve this side down.

Whenever you use plastic wrap, use a brand that doesn’t smell bad.  If you are worried about phthalates, use polyethylene  instead of PVC.

Next installment: the vacuum machine. 

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