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Lobsters: A Crustacean Sensation

Photo credit: Flickr/Stacylynn

Photo credit: Flickr/Stacylynn

They lurk in the depths of the ocean, feasting on the remains of their fallen neighbors. With stalked eyes, muddy coloring, and large predatory claws, they’re reminiscent of insects and are admittedly neither cute nor cuddly. They’re ancient, they’re cannibalistic, and they’re delicious dipped in lemon and butter. They’re the beloved lobsters, a crustacean sensation.

Lobsters have spent decades clawing their way up social and culinary ranks, rising from their status of an aquatic beach pest to the iconic culinary symbol of New England as we know them today. In early America, lobsters would wash up on Boston beaches after storms and litter the shores with their decomposing bodies. Piles of carcasses would collect and rot, prompting frustrated New Englanders to put them to good use. The festering carcasses were harvested and ground into a slurry, which was then used as fertilizer or fed to prisoners and peasants as a high-protein fuel [1]. Clearly, lobsters were hardly symbolic of fine dining and affluence. Lobsters were so reviled that indentured servants in Massachusetts often signed contracts refusing to eat them more than three times a week, deeming such treatment as being cruel and unusual.

In the mid-1800s, railways overtook America as the dominant mode of transportation and led the lobster on its journey to popularity. Train managers exploited the low cost of small lobsters and fed them whole to unsuspecting inland customers, touting them as a rare and exotic delicacy. Satisfied customers quickly spread word of this new luxury food, and thus began the rise of the lobster. With the help of this clever rebranding, lobster meat began appearing in restaurants alongside salad bar toppings and gained wide recognition not only as a viable source of protein, but also as a respected food item. By World War II, lobsters became integrated into American society as a luxury [2].

Whether they’re plucked straight from the sea or from a tank at the grocery store, there are few foods that beat a freshly cooked lobster. Many of us squirm at the prospect of plunging a live lobster into a bubbling vat of doom, viewing the act as a cruel, but necessary sacrifice we must make in order to eat it. So what is it that compels us to cook them live in the first place? A major turning point in its culinary standing was when chefs realized that lobsters taste better when cooked alive. Cooking live shellfish preserves the structural integrity of the meat and gives a sweeter and cleaner taste, in stark contrast to the putrid flavors that can develop in the mushy flesh of deceased lobsters [1]. The biochemistry of death accounts for this change.

The inside of a dead lobster serves two purposes: it’s a hub for several enzymatic reactions, and it’s a breeding ground for rogue bacteria. Upon death, proteolytic enzymes are activated and attack the lobster’s internal organs. Once under attack, these organs release another wave of enzymes into the lobster’s muscle tissue. A major player here is the liver, which houses a multitude of proteases reserved for digesting food. These digestive proteases, along with the first wave of enzymes, leak out and begin degrading muscle tissue, by breaking collagen and other proteins down into smaller peptides, polypeptides, and amino acids. Given how rapidly these enzymes work, it’s only a matter of time before the lobster’s flesh turns to mush.

Additionally, many nutrient-producing enzymes are also activated upon death. These newly-produced nutrients cause trouble by encouraging bacterial proliferation. As bacteria begin multiplying inside of the lobster, they produce metabolic waste products along with their own brand of proteases, many of which lend to the off-flavors and textural defects found in deceased lobsters. To save the lobster meat from succumbing to textural degradation or bacterial contamination, iced storage or evisceration are often recommended to minimize enzymatic activity. Rapid heating via boiling or steaming, however, still remains the best-known way of rapidly deactivating these enzymes. Bacterial contamination in shellfish can also lead to food poisoning and other complications, so not only does freshly killed seafood taste better, but it’s also much safer to eat. Cooking live lobsters allows us to minimize the ill-effects between death and consumption and spares us from suffering any gastric mishaps [5].

You’ve tossed the lobsters into the pot now—what’s actually going on under that furiously clanking lid? Maybe you’ll hear them thrashing around or a hissing sound as steam escapes from their shells. One thing you’ll also notice as the lobster cooks is its color change—from a blue-black to a brilliant red-orange. A lobster’s muted coloring provides camouflage when it’s prowling around in the sea. Uncooked, a lobster’s shell contains α-crustacyanin, a complex formed when a protein binds with pigmented carotenoids derived the crustacean’s plankton-heavy diet [3]. On their own, carotenoids are richly colored and can range from yellow to red, and they’re also credited with providing sweet potatoes, carrots, and tomatoes with their vibrant colors. When bound to proteins inside a lobster shell, they’re blue. As heat is applied, the α-crustacyanin protein complex denatures and releases free carotenoids. Astaxanthin, the main pigment molecule, is now exposed and provides cooked lobsters with their characteristic red hue [6].

Artwork credit: Michael Kim

Artwork credit: Michael Kim

Within the shell, a lobster’s meat acquires those sweet and nutty aromas we’ve come to associate with seafood and summer. There are more than just cultural influences that have made lobsters desirable; it’s the very chemistry of lobster meat that sets it apart from others. When was the last time you invited company over for dinner and decided to serve boiled steaks? You probably never have. There’s a reason you fired up your grill—and that’s because grilling produces a far more flavorful steak. Cooking at higher temperatures associated with roasting or grilling triggers the beloved browning/Maillard reaction known to impart complex flavors onto your food. A unique feature of lobster meat that it undergoes the Maillard reaction at much lower temperatures than other meats like beef, chicken, or pork. As it turns out, lobsters actually have an unusually high concentration of free amino acids and sugars in their muscle tissue. This abundance of free amino acids more readily undergo these flavor-producing reactions at much lower temperatures than would be re-quired in other types of meat. This is why you can get away with boiling lobsters and shell-fish and still manage to produce incredible flavors (3).

Lobsters are a delight to the masses. They’ve amused countless children at the grocery store in their tanks and they’ve satisfied hungry adults alike. Whether you’re considering its history, culinary uses, or chemistry, the lobster truly is a sensation.

Lobsters3

References cited

  1. Wallace, David Foster. “Consider the Lobster.” Consider the Lobster And Other Essays. New York: Little, Brown, 2005.
  2. Daniel Luzer. “How Lobster Got Fancy“. Pacific-Standard.
  3. McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. New York: Scribner, 2004. Print.
  4. Vieira, Ernest R., and Louis J. Ronsivalli. Elementary food science. New York: Chapman & Hall, 1996. Print.
  5. Proteases in fish and shellfish: Role on muscle softening and prevention. International Food Research Journal 21(1):433-445. Sriket, C. 2014.
  6. Begum, S., et al. 2015. On the origin and variation of colors in lobsters carapace. Phys. Chem. Chem. Phys.

Mai NguyenAbout the author: Mai Nguyen is an aspiring food scientist who received her B.S. in biochemistry from the University of Virginia. She hopes to soon escape the bench in pursuit of a more creative and fulfilling career.

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Texture and Color of Sashimi

photo credits (sake puppets/flickr)

Whether or not you like eating sashimi, such a fine specimen of fish is undeniably an incredibly beautiful food. The subtle flavors, delicate texture and vivid colors make sushi and sashimi such a unique eating experience. To whet your appetite for The Science of Sushi at UCLA, here are some bits of sashimi science we learned from Ole G. Mouritsen’s book, Sushi: Food for the Eye, the Body, and the Soul.

Sashim刺身

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Salmon and Tuna Sashimi – Photo Credits: (avlxyz/flickr)

Why are fish muscles soft?

If you used your finger to poke a raw filet of a bony fish like salmon or tuna, then tried this on meat from a terrestrial animal like beef or pork, you would notice that fish muscle is significantly softer than terrestrial meat. On a very fresh piece of fish, you could poke your finger through the muscle. From a basic understanding of meat texture, it seems strange that the meat of a fast-swimming predator is soft while the flesh of a slow-moving grazer is firm; typically the more an animal uses its muscles, the tougher its muscles.

Yet fish tend to have the same density as the water in which they live, so they do not use their muscles to bear their own weight; fish need only to exert their muscles when they want to move. By contrast, terrestrial animals frequently use their muscles to counter gravity and remain upright. Fish simply have less work to do, and so their muscles do not develop the same chewy texture that land animals do. But not all fish have smooth and tender muscles; some species like shark have tougher meat. Why? Sharks’ bodies happen to have a specific gravity greater than the water they inhabit, so they must exert their muscles at all times to keep afloat, and thus their muscles more closely resemble a ruminant’s in firmness.

Fresh is best

About six hours after the fish is killed a phenomenon common to all animals, rigor mortis, sets in. During rigor mortis calcium ions of the proteins embedded in the muscle fibers are released, causing the muscle fibers to contract and become stiff.

To delay rigor mortis for up to a few days, fish can be deep-frozen immediately after they are caught. Once the process of rigor mortis has run its course, the fish begins to decompose, the muscle fibers separate, and the connective tissue loosens. At this point it is ideal to consume the fish, as it is at its peak of softness and freshness. This type of sushi is called nojime, the type made from fish that are not kept alive after being caught. The opposite is ikijime sushi, prepared from fish with firmer muscles as they are kept alive until the last moment and prepared before rigor mortis can set in.

A rainbow of fish

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Orange, pink, red, white; there is remarkable variation in fish meat color. Photo Credit: Kake Pugh (kake/flickr)

Orange and pink

The muscles of wild salmon and sea trout are typically orange-pink in color. The origins of this distinct shade of salmon begins at the bottom of food chain, with plankton. These little organisms contain a pigment astaxanthin. It belongs to the family of pigments called carotenoids, which includes the pigment that makes carrots orange. Tiny crustaceans eat plankton, and thus ingest astaxanthin, whereupon it is bound to proteins called crustacyanins in the animals’ tough shell. While bound to these proteins, the pigment is blue-green or a dark red-brown. This will seem familiar if you have ever seen live crab or lobster. When a fish comes along and eats the crustacean, the crustacyanins are denatured and they release the pigment, allowing its own red-orange color to become visible. The color change that occurs upon cooking crustacean shells is caused by the same protein-denaturation and pigment-release process that occurs in fishes’ digestion systems.

Red Fish

Although the proteins that form the muscles themselves are colorless, a lot of fish meat is deep red, like tuna. These colored muscles are classified as slow muscles, as they take care of work that has to be carried out on an on-going basis, namely, continuous swimming. Since they require a continuous oxygen supply to produce energy, they contain myoglobin. Myoglobin is responsible for the transport of oxygen within muscle tissues. Each myoglobin molecule can bind one oxygen molecule to form oxy-myoglobin, which is bright red.

White fish

In contrast to slow muscles, fast muscles undertake smaller and more rapid movements like the slapping of fins and tail. These muscles do not contain myoglobin; instead they use the colorless starch glycogen to supply energy. No myoglobin means that these muscles stay colorless or white.

Interested in learning more sushi science from the experts? UCLA Science & Food’s public lecture, The Science of Sushi, is on April 23rd. In this lecture, Dr. Ole Mouritsen will illuminate the science underlying sashimi, nori, sushi rice, umami, and more.  He will be joined by Chef Morihiro Onodera who will share his approach to sushi as well as an inside look into his partnership with a rice farm in Uruguay.

References:

  1. Mouritsen, Ole G. Sushi: Food for the Eye, the Body & the Soul. New York: Springer, 2009. Print.

 


Elsbeth SitesAbout the author: Elsbeth Sites is pursuing her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

Read more by Elsbeth Sites