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December 17, 2013 at 10:38 am

Food Science 101: The Miracle of Salt

Salt – the delicious alchemy between explosive sodium and the toxic green gas chlorine – is an essential mineral for biological life and an all-purpose tool for deliciousness.

Kosher Salt

The Great Seasoning

To understand the role salt plays in our perception of food, we need to trek to the start of the alimentary canal – the passage food takes to get to your stomach –starting with your mouth. Lining the surface of each human tongue are thousands of anemone-like structures called papillae or taste buds, each with chemical sensors that detect the five basic tastes. (The idea that the tongue is divided into different sections by taste is a myth).

When you chew food, an array of chemicals and flavor compounds triggers a chemical reaction in the papillae that is transmitted to your brain. Ta-da, taste!

While saltiness is itself one of the five flavors, it also modifies our perception of the other four.

Inside the taste bud, atomic mechanisms for producing salty, sweet, sour and umami flavors are pretty similar; a complicated biological process called depolarization creates an electrical charge that’s sent off to the brain. Salt acts as an amplifier for these flavors by increasing the charge.

Bitterness works differently. Instead of generating an electrical charge, the taste bud releases a calcium ion (Ca2+ for you chemistry majors) that creates a signal for the brain. For reasons not entirely understood, salt overrides this reaction in the taste buds, effectively masking the bitter sensation.

Enough science. Test this yourself by dissolving a pinch of salt in a cup of coffee, gin and tonic, or cut grapefruit – all of which have bitter flavor compounds – and see if you notice a difference. Without tasting overtly salty, the flavor profile will sweeten and mellow.

Chefs will tell you that the way to achieve restaurant-quality results at home is with salt. The pros season early and often, aiming for the bliss point where the natural flavors are accentuated but not yet noticeably salty. In practice, this means salting (just a pinch at a time) during each step of a recipe, rather than right at the end. 

Note that taste sensitivity varies from person to person, you’ll get the most mileage out of your salt if you constantly sample and adjust on the fly.

(Source: Flickr)

(Source: Flickr)

Salt & Protein, A Match Made in Heaven

The earliest evidence of humans consciously salting food goes back 10,000 years. Then, salt was essential as a preservative for ingredients that were scarce or seasonal, particularly proteins. Fast forward a few millennia and the practice survives in the field of charcuterie, a French word meaning “cooked flesh” that refers to the salting, curing, and fermentation that produce ham, bacon, sausage, pâtés and more.

Salt and meat, you see, have a very special relationship.

Sprinkle salt on a steak or piece of fish and within a minute or so moisture will start to bead on its surface. This is osmosis, the same process you learned about in seventh grade science, but with an elevated purpose. Because the interior of the meat is essentially salt-free, the flavorful salt ions gradually migrate across its surface, seasoning the steak from inside.

Dehydration, a second benefit of salting meat, occurs simultaneously.  The exchange between H2O and NaCl molecules leaves the outer surface of the steak with less moisture, a boon to the caramelization that produce a golden, crackling crust.

When a cut of meat (or really anything) hits a hot pan, the sizzling sound you hear is water near its surface boiling off into the air. Pre-salting your ingredients and patting them dry before cooking accelerates the process, which happens before browning can start.

The most impressive of salt’s many spectacular traits (according to me), happens on a microscopic scale. It is the reaction between salt ions and the long strands of amino acids that are called proteins. These strands, generally coiled into tight balls like yarn, unfold in the presence of heat during cooking to form long networks of interconnected strings – like a meaty spider web.

Salt’s unusual chemistry forces the protein yarn balls to uncoil similarly, creating an effect very similar to cooking with heat. The next time you eat a nice cured salami or piece of smoked salmon, thank salt’s amazing chemical gifts for the firm, luxurious texture.

(Source: Flickr)

(Source: Flickr)

Recipe: Salt in Action

The key difference in this chicken recipe is that the bird is salted heavily one or two days before it’s cooked and left completely uncovered in the refrigerator. During that time the skin will dehydrate and tense from the interaction between proteins in its surface and salt. The end product is a perfectly seasoned bird with staggeringly crisp skin.

Salted, Dried, Whole Roasted Chicken

Adapted from Thomas Keller’s internet-famous Roast Chicken Recipe

Ingredients:

  • One chicken, roughly 4 pounds (preferably free-range/organic)
  • Kosher salt & black pepper
  • 3 garlic cloves, peeled and crushed
  • 5 thyme sprigs (or other fresh herbs)
  • 2 Tablespoons olive or canola oil
  • 4 tablespoons unsalted butter, sliced

Directions:

  1. Rub the chicken with oil and generously season the skin of the chicken with at least a tablespoon of salt. You can see Thomas Keller making it rain here. Rub some salt inside the cavity as well. Add black pepper to taste.
  2. Put the garlic and thyme inside the cavity and truss the bird, if you know how. At least tie the legs together.
  3. Let your seasoned chicken rest in the refrigerator uncovered (preferably on a rack of some sort) for a day or two. Its skin will tighten and discolor – this is ok.
  4. At least an hour before you start cooking, take the bird out and let it rest at room temperature. You can place it breast side up on a rack or a bed of root vegetables to maximize the airflow around it.
  5. Preheat the oven to 475°F.
  6. Place the slices of butter on the breast of the chicken and roast it for 25 minutes.
  7. Reduce the heat to 400°F and roast an additional 40 minutes.
  8. Check the temperature every 5 minutes until a thermometer reads 160°F in the inside of the thigh and the juices are clear.
  9. Rest for 15 minutes at room temperature. Behold the magic of salt.

-Lloyd Ellman

7 Comments

  1. Pingback: Food Science 101 - The Perfect Steak | Food Politic

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  5. Stefanie Ellman Getnick says:

    Wow! I really enjoyed your article and learned so much about this substance that
    I happen to love.. I was so happy that you weren’t going to be saying that salt was baaaaad for me. When I was in the hospital this past year, at first they were serving me all my food with no salt at all. I told them there was absolutely no reason for me to have to forego the latter AND until they rectified the situation I would not eat anything. They checked my records, apologized and I was a whole lot happier. KUDOS to you cuz! Feel free to e-mail me any more articles of yours in the future. Happy holidays–I love you—-Stefie

  6. Great read! What a terrific blend of chemistry and culinary history! You must have had one terrific science teacher. I am going to make it required reading for my AP Chem students.

  7. very interesting! and thanks for making all the science around it ‘accessible’ and easy to understand!

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