From the blog December 17, 2015 Modernist Cuisine Team

Good Eating in An Exoskeleton

The winter holidays are often celebrated with glorious roasts. But there’s another staple of Christmas and New Year’s fare: crustaceans. From country to country and coast to coast, it’s all about seafood.

In Australia, barbecued or steamed prawns (referred to as shrimp in the US), Australian crayfish, and marron take center stage on the table for Christmas dinner, a trend that is being echoed in the United Kingdom, where more and more families are replacing traditional turkey with large lobsters. Seafood is staple Christmas Eve fare, but most notably in Italy where the night is known as la Vigilia. Also referred to as the Eve of Seven Fishes in the United States, the night culminates around the kitchen table, which is set with course after course of dishes laden with a variety of fresh fish and crustaceans. Lobster, in particular, has become a Christmas Eve and New Year’s Eve tradition (despite some cultural superstitions) for many families throughout the world and, along with crab and prawn, is a staple of Réveillon, celebrated in France, Belgium, Brazil, Portugal, Quebec, New Orleans, and other areas with French or Portuguese influence. The food at réveillons, long dinner parties preceding both Christmas and New Year’s Day, is luxurious, extravagant, and comforting—a mix that is well suited for delectable crustaceans.

Lobster Disrobed

Selecting crustaceans

Although cooking crustaceans isn’t terribly complex, picking the right ones for the pot can be a challenge. You’ll do better armed with the knowledge that when crustaceans grow, they periodically shed their exoskeletons; that is, they molt. Many cooks know to avoid crustaceans that are getting ready to molt, but you may not know when to chase after those that have already molted.

Timing is important here because prior to molting, lobsters and crabs shed a large amount of muscle mass. They literally shrink inside their shells. After the exoskeleton weakens, they break out of it, living briefly without any protective covering at all. Just after molting, they pump up, adding 50%–100% to their body weight by absorbing water. You don’t generally want to eat a crustacean that is about to molt or that has just molted and is taking on a lot of ballast. The exception is soft-shelled crab, which is cooked just after having molted.

Once their new shells begin to harden, crustaceans are perhaps at their best for the table. Many say that a lobster with a new exoskeleton is exceptionally sweet and firm. Likely, this is because the creature ate voraciously after molting to replenish its protein and energy stores in order to rebuild its protective armor.

What to look for

1. Look at shell color and firmness:

When crustaceans are at their prime for eating, their topsides will be deeply colored, and their bellies will take on a stained or dirty look. The shell should be firm to the touch. Crustaceans are primed for cooking when their shells will have become very hard.

2. Compare size to weight:

Crustaceans will feel heavy for their size because they are filled with dense muscle tissue, not tissue that is bloated with absorbed water. Crustaceans that are about to molt feel the lightest because their shells are partly empty.

3. The shell will also give you clues that tell you when it’s better to pass on a particular animal:

Recently molted crabs and lobsters have shells with a grayish-to-green cast on their topsides and a lustrous white abdomen. That’s because the pigmentation of the shell comes from the animal’s diet, and they haven’t yet eaten enough to color the shells more richly.

Sometimes you will see a pinkish tinge, commonly referred to as rust, on the bottom of the crabs, which can indicate that they are getting close to molting. Before they do, they will reabsorb calcium from the shell, softening it. A telltale sign is that the shell will begin to appear slightly green again. They will bloat with water to loosen the shell and then will shed muscle mass to become small enough to squeeze out of it. Such crabs do not make for good eating.

MEAT4_Lobster bare_IMG_3393

 

So pick it right, and you’ll enjoy the aroma of cooked crustaceans, which is unique. The chemistry responsible for this redolence turns out to be the Maillard reaction, which normally requires a very high cooking temperature. But because the flesh of crustaceans contains a lot of sugars and amino acids (such as glycine, which tastes sweet) to counteract the salinity of seawater, the Maillard reaction occurs at an unusually low temperature. After you’re done feasting, save your crustacean shells. Collect them in the freezer until you have enough to make Pressure-Cooked Crustacean Stock. If you don’t have any shells, use whole shrimp (with heads on), which are relatively inexpensive and easy to find.

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