Tips & Tricks

Why Does Food Stick To My Knife? (And How To Make It Stop.)

The food! It sticks to my knife!

The food! It sticks to my knife!

One of the reasons why I love to cook is one I have in common with people who knit: it is involving enough to keep your mind off world peace issues, but leaves enough mental space that you can wander, hold imaginary conversations, turn sentences around in your mind (everyone does that, right?), and generally putter about in the coziness of your own head.

Prepping vegetables launches me into such inner monologues, and in recent months they have been dominated by this nagging question: why does food stick to my knife, and how do I make it stop?

You know the phenomenon, I’m sure, but let me describe it for you: whenever I slice something (say, an onion or a zucchini), the pieces I’ve just cut tend to stick to the right side of the blade (I’m right-handed), so that when I’m cutting the next slice, the pieces that are stuck on there get pushed up and off by the new slice, and fall either to the right of my blade (unruly, but fine), or tumble off the cutting board and possibly onto the floor (messy), or fall to the left side of my blade, in which case I’m likely to cut into them again moments later (extra annoying).

After composing an imaginary email in my head over a few zucchini-slicing sessions (I eat a lot of zucchini), I finally sat down and wrote to Peter Hertzmann, the spectacularly knowledgeable creator of the à la carte website and associated blog, cooking instructor, and author of the must-own Knife Skills Illustrated, of which he kindly offered me a copy when we met in San Francisco a few years ago (more details about the book)*. And naturally Peter had answers, which I’m sharing below, mixed in with a few more tips I gathered in my research.

So, why does food stick to my knife?

The main reason is surface tension, a physical phenomenon that makes the surface of liquids resist an external force. In this case, it means that foods with a high water content (and many vegetables are more than 90% water) create slices with a moist surface that clings to the flat of the blade.

And how do I make it stop?

You could decide to subsist on low-water foods — I’m sure a diet of beef jerky and rice crackers will do you a world of good — or you could adopt one or more of these three strategies:

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How To Roast Hazelnuts and Remove Hazelnut Skin

How to Roast Hazelnuts

Few nuts are as notably improved by roasting as the hazelnut.

Most raw hazelnuts you find at the store are, in truth, a little chewy and a little bland, like a draft version of themselves. But a healthy roasting fixes that, boosting the flavor and allowing the excess water to evaporate, thereby leaving you with wonderfully crisp nuggets of pure nuttiness.

The bonus advantage when you roast hazelnuts is that it gives you the opportunity to skin them while you’re at it, rubbing them in a kitchen towel as the bitter husk easily detaches into a million little flakes you do not want to accidentally spill on your kitchen floor, trust me.

How to Roast Hazelnuts In Five Steps


I roast my hazelnuts by the 500 grams (about 4 cups, a little over one pound) because that’s the amount that fits nicely in a single layer on my rimmed baking sheet, leaving the nuts a little — but not too much — wiggle room.


I insert the baking sheet in the oven preheated to 180°C (360°F), and leave the nuts in for 15 minutes, stirring them every 5 minutes or so. They are done when they are fragrant, their skin cracked and glistening. Because the husk is pretty dark, it can be hard to tell if it’s starting to turn black and burn, so if you’re unsure, it’s best to err on the side of under-roasted.

Note: To make optimal use of the now heated oven, I may roast a batch of almonds or pumpkin seeds to follow, or schedule the roasting when I have another dish to bake.


I pour the nuts into a clean kitchen towel (they may over-roast if left on the baking sheet) and let cool. I then close the towel up into a bundle, and give it an energetic massage so the hazelnuts will rub against one another and the skin will come off in little flakes. Not all of it will, and that’s okay.


I transfer the hazelnuts to a big jar, collecting them delicately from the towel with my cupped hands and making sure as little of the skin flakes come with. How long the roasted hazelnuts will keep before going rancid depends on how fresh they were to begin with — in most cases, you should be good for a couple of months.


I confess that most of the hazelnuts I roast and skin in this fashion, I end up snacking on with dried fruit such as prunes, figs, pears, or dates, as mentioned in this post about food gifts. But I also love to eat them on Roasted Cauliflower à la Mary Celeste, use them for a Hazelnut and Nectarine Gratin, or grind them to make Dukkah, this fantastic spice mix from Egypt. (More hazelnut recipes?)

How to Roast Hazelnuts

Join the conversation!

Do you usually roast and skin the nuts you cook and bake with? And what’s your favorite way to enjoy hazelnuts?

PS: Have you ever stopped to wonder why the skin comes off hazelnuts more easily after roasting? Well, let me tell you why. It’s because water, this incredible, magical element, expands when heated. This means that hazelnuts, which are partly made of water, become slightly bigger when heated. But their papery brown skin isn’t as elastic, so it is soon forced to loosen its grip on the surface of the nut. Once cooled, the hazelnuts return to their original size but the skin doesn’t stretch back down, remaining cracked, loose, and easy to rub off. Neat, huh?

I only learned this recently as the owner of U Salognu described this very process to explain how he skinned the chestnuts for his chestnut flour.

Grated Carrots, Three Ways

Grated carrots, three ways

We seem to have skipped spring altogether to jump directly into the thick of summer. And with the near-canicule* temperatures we’ve been experiencing, our menus have been all about cold foods and crudités.

I’ve long been a fan of grated carrot salads — when I was a child, this was the only way I would eat carrots at all — and I’ve recently become interested in the different ways one can grate the carrots for it.

I seldom use the grating attachment on my food processor; for small quantities, I find it too bothersome to take out, clean and put away.

For a while, I used the large holes of a box grater (such as this one), and was fairly pleased with the results, though the larger, tougher carrots were a bit of a workout, and any carrot that had become limp from too much time in the fridge was a pain to handle**.

Carrots grated with a box grater.

Carrots grated with a box grater.

Then one day, I tired of the box grater and moved on to the brute force approach of simply chopping raw carrots in my mini food processor. It’s noisy, but it takes about a minute, and you get a couscous-like texture — coarse or fine, as you prefer — that is quite lovely.

Carrots chopped in the food processor.

Carrots chopped in the food processor.

But lately, I’ve switched to what is now my preferred method: I use my mandoline slicer with the comb-like blade attachment. This produces super neat little flecks of carrot with a perfect square section, which is not only attractive, but also optimally crunchy.

Carrots cut with a mandoline slicer.

Carrots cut with a mandoline slicer.

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140 Recipe Ideas In 5 Ingredients or Less

Spaghetti with sardine tomato sauce

Two weeks ago, I wrote about Jules Clancy’s fantastic new book, 5 Ingredients, 10 Minutes, and offered to give away three copies as prizes in a 5-ingredient recipe contest.

You collectively submitted nearly 140 five-ingredient recipes, all of which sound fantastic and provide a fascinating glimpse into your personal tastes and appetites. It’s been very difficult to pick just three — why, oh why do I put myself in these situations? — but I had to, so I elected Ms. C’s pan-fried tofu with kale and noodles, Rakhi’s mujaddara, and Pierre Pozi’s sardine boulettes (submitted in the French version of the contest). Congratulations! You will soon be receiving your copy of 5 Ingredients, 10 Minutes.

And to thank you all for your invaluable contributions, I’ve collated your recipe formulas into a masterlist we can all dip into; recipe details can be found in the comment section of the original post. (If you read French, you’ll find even more 5-ingredient suggestions in the French masterlist.)

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How To Peel Onions Without Crying

Red Onion

Of all the kitchen inconveniences the cook has to live with, the one that generates the highest number of defensive strategies is no doubt the chopping of onions, and the associated teargas effect.

The reason why it makes you cry is explained in detail here, and if you like to read about enzymes and syn-propanethial-S-oxide, as do I, it is worth a read.

But to put it more simply, chopping onions causes the release of an irritant gas in the air, which, upon reaching your eyes, triggers a blinking and tearing reflex designed to wash it away. Yet another illustration, albeit an annoying one, of what a nifty machine the ol’ human body is.

Such an unusual tip could not go untested, so I soon tried it, using the butt end of a loaf of pain au levain and feeling both experimental and silly, but I am happy and amazed to report it worked perfectly.

Not all onions are created equal (the fresher the onion, the less you cry) and not all cooks are as sensitive, but this phenomenon explains the volume of tips and tricks floating about — some of them amusingly contradictory — designed to either hinder the release of said gas, or prevent it from reaching the eyes.

Some people rinse the onions in cold water after peeling, or chop them underwater. Some recommend keeping onions in the fridge, or plopping them in the freezer for a few minutes before chopping. Some chop from the stem end down, others from the root end up. Some recommend breathing through the nose, others only through the mouth, while others still hold a sip of water in their mouth, and try not to laugh and spit it out.

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