Savor the Science: Denatured Proteins Edition (w/ Ceviche Recipe!)

Welcome to Savor the Science! In each Savor the Science, RENDER’s resident chemist, Claire Lower, will explore culinary questions through a scientific lens, perfecting recipes and demystifying techniques. Theories and reactions will be discussed and experiments will be performed; it’s like your high school chemistry class, only edible. Twice a month, Claire will take a scientific concept (such as the acid-base reactions in baking, macerating, or Maillard browning), explain it in a way that would make Bill Nye proud (hopefully), and then provide an edible experiment which allows you to demonstrate your new scientific food knowledge. 

It’s science you can eat!

Do you love Claire Lower's Savor the Science? Then make sure you subscribe to our print magazine so you can read Claire's essay in our second issue, the Roots Issue.


Ceviche is an ideal summer dish.

     Who wouldn't want this?

     Who wouldn't want this?

Requiring nothing more than a citrus marinade and the freshest of fish, this dish is always light, refreshing, and cold; all things that are good when the temperature gets above 80 degrees. And, not only is it delicious and super easy to make, it is impressive. By soaking seafood in citrus juice, you can produce a restaurant-quality dish with about ten minutes of work and thirty minutes of drinking margaritas while you let the acid do its thing.

Ceviche isn’t quite raw, but it’s not exactly cooked either. “What is this fish paradox?” you ask, “How can something be “not raw” without ever being exposed to heat? What is this, some sort Schrödinger’s fish?”

Not exactly.

Though it is never “cooked” in the traditional sense, ceviche goes through a chemical process that effectively rearranges or “denatures” the fish’s proteins, much like the application of heat.

Proteins are large, complex biological molecules made up of long chains of atoms that twist and fold in on themselves in unique, three dimensional structures. These unique arrangements are the proteins “native form.”

Myoglobin – a protein found in the muscle of vertebrates – in its native form.

Myoglobin – a protein found in the muscle of vertebrates – in its native form.

When a protein is exposed to a situation that is “stressful” for it, like heat or an acidic environment, it loses its unique structure, and can become thick and dense. When you denature a protein, you are destroying its native form. The change is purely structural; no atoms are gained or lost, they are simply rearranged.

Imagine a wad of rubber bands, all twisted and tangled together. Now imagine someone comes in with scissors and snips a couple of them. You still have the same amount of rubber band; none has been removed, but that wad is never going back to the shape it was in.

       Just try to put it back in its “native form.”

       Just try to put it back in its “native form.”

Denaturing proteins is a similar process. Proteins are held together by bonds. Heat or acidic substances break some of those bonds, and the protein is forever changed. This is why high fevers are dangerous; once your proteins are scrambled, there’s no folding them back together.

For food, this usually results in coagulation, a process which causes proteins to develop a sort of delicate density, like cooked egg whites.  Recall our rubber band: now that it has been unraveled, more of its long chains are exposed, allowing the atoms on these changes to interact with previously unexposed areas, forming new bonds throughout the chains that hold the various lengths of protein close together (McGee, 1984). This new closeness between molecules creates a denser configuration, driving out water and increasing toughness.

In the case of ceviche, lime juice (which has a pH of about 2) denatures the proteins in the fish, freeing the long chains of amino acids from its native form, allowing them to rearrange in a formation that is similar to that of traditionally cooked seafood.

Because of the delicate nature of fish, this process can occur quite rapidly; leave it too long and your ceviche will become tough and rubbery. Just look at the change in color and consistency that occurred in tilapia after being exposed to lime juice for ten minutes.

But what of pesky pathogens? Isn’t heat required to make seafood safe for consumption?

Lucky for us, acid takes care of that as well. Vibrio cholera, a seafood-borne pathogen, cannot exist in an environment that has a pH of less than 4.5 (Potter, 2010) even at room temperature, so marinating seafood in lemon or lime juice should take care of it.

Phew! Now that we don’t have to worry about pathogens and possible death, let’s denature some tilapia!


Deliciously Denatured Tilapia Ceviche

You will need:

·       2 tilapia filets (about 1 lb.) [Note: Partially freeze fish for easy and neat chopping.]

·       The juice of 4 limes

·       ½ cup of peeled, de-seeded chopped cucumber

·       ¼ finely chopped purple onion

·       2 tablespoons fresh cilantro leaves

·       ½ cup soy sauce

·       1 tablespoon Sriracha

·       A couple of dashes of Worcestershire sauce

·       1 teaspoon chopped ginger

·       1 teaspoon chopped garlic


Instructions:

1.     Combine cucumber, onion, and cilantro in a small bowl. Sprinkle with salt to get ‘em sweaty; cover and chill in the refrigerator.

2.     Combine soy sauce, Worcestershire sauce, ginger, garlic, and Sriracha in a food processor until smooth. Cover and chill.

3.     Cut fish into half-inch cube-esque pieces. Place in a nonreactive bowl and pour lime juice over. Stir around to make sure all the fish pieces are submerged in the juice.

4.     Cover and chill until fish is completely opaque (20-30 minutes).

5.     Drain lime juice from fish, gently squeezing fish with your hands before transferring to a bowl.

6.     Add soy sauce mixture to taste (I used about half of the mixture). It is quite salty, so I like to err on the side of less soy sauce, letting guests add more if they desire.

7.     Stir in vegetable mixture and serve with toasted baguette or Cuban bread.

 

Further reading: 

Jeff Potter. 2010. Cooking for Geeks. (Sebastopol: O’Reilly), 286

Harold McGee. 1984. On Food and Cooking: The Science and Lore of the Kitchen. (New York: Scribner), 808-809

 

 

 

Savor the Science: Molecular Gastronomy Library Edition

Welcome to Savor the Science! In each Savor the Science, RENDER’s resident chemist, Claire Lower, will explore culinary questions through a scientific lens, perfecting recipes and demystifying techniques. Theories and reactions will be discussed and experiments will be performed; it’s like your high school chemistry class, only edible. Twice a month, Claire will take a scientific concept (such as the acid-base reactions in baking, macerating, or Maillard browning), explain it in a way that would make Bill Nye proud (hopefully), and then provide an edible experiment which allows you to demonstrate your new scientific food knowledge. 

It’s science you can eat!

 

There are few things I love more in this world than accessible, fun, scientific explanations of food, cooking, and flavor. You already know that I’m a big fan of Harold McGee’s On Food and Cooking, but there is a wealth of information outside of that amazing tome, and we’re discovering more and more each day.

Not every book is a good fit for every reader, so we here at RENDER have reviewed three of varying levels of accessibility. Hopefully one of them will find its way on to your bookshelf or into your kitchen.

The Classic: Molecular Gastronomy: Exploring the Science of Flavor by Hervé This

When people think “molecular gastronomy,” they usually think of spherified juices and cocktails you inhale; not a perfectly cooked egg. At its core, molecular gastronomy is less about making ice cream with liquid nitrogen and olive oil powder with maltodextrin; it’s about understanding food and cooking on a molecular level, allowing us to perfect techniques and debunk old myths.

(Fancy maltodextrin powders never win Chopped anyway, the judges are always kind of like “Uh, this is kinda gross.”)

Known by most as the “father of molecular gastronomy” and the man who unboiled an egg,” Hervé This wrote Molecular Gastronomy in 2005, years after coining the term with fellow scientist Nicholas Kurti.

Though physical chemists aren’t usually known for their elegant prose, This manages to be almost poetic in describing egg coagulation, flat globules in milk, and bacteria in hard sausages.

The Pros: This thought of food in terms of chemical mixtures (which it is) but that doesn’t make him a cold and calculating chemist. His love for food and cooking is apparent in each concise chapter (This manages to bestow a wealth of information in each 3-4 page chapter); his goal of educating and enlightening clear in every paragraph.

This does not drone on for pages, boring the reader with dry, emotionless facts and graphs. He is able to communicate scientific concepts succinctly and never loses sight of the matter at hand: FOOD. After explaining that the old spoon in the bottle trick does not, in fact, keep champagne from going flat, he negates the need of such a discussion by declaring that “Once you’ve opened a bottle, finish it off!”

The Cons: Molecular Gastronomy may not appeal to those who hated every moment of every science class they ever took. Though This describes the molecular aspects of food in an accessible and engaging way, basic scientific nomenclature is still employed.

Highlight: Chapter 3, which is all about hard-boiled eggs, makes one truly appreciate how complex the seemingly simple act of boiling an egg can be.

 

 

The Compilation: The Kitchen as Laboratory: Reflections on the Science of Food and Cooking

 

I was really excited about this book. It has a really cool looking beaker on the cover, in which appears to be some shrimp and thinly-sliced zucchini. It’s pretty sleek looking, really.

Compiled by César Vega, Jobb Ubbink and Erik van der Linden, this book reads like a compilation of slightly informal journal articles, which may be good or bad, depending on who you are. Containing a variety of essays and recipes from various artists, it’s a bit of a grab bag in terms of accessibility.

The Pros: The science within The Kitchen as Laboratory is legit. If you are a lover of graphs and the scientific method, this is the book for you. The essays are thorough and the language precise and the recipes are surprisingly easy to follow.

Also, there are poems.

Cons: Parts of this book are oh so boring. I like science, but even I had a hard time with some of the chapters. Since it is a compilation, the level of accessibility varies from essay to essay, but it is clear that the book was written by scientists and not science communicators. This isn’t to say that every essay is completely inaccessible, but some authors are more engaging than others and there’s no way to tell before reading the essay.

Highlight: The chapter entitled “Ice Cream Unlimited” (Chapter 17), which features recipes for Cherry-Kriek Sorbet and Tzatziki Ice Cream.

 

The Showstopper: Heston Blumenthal at Home

Though Blumenthal dislikes his work being characterized as “molecular gastronomy” explaining in a feature on The Guardian that “Molecular makes it sound complicated, and gastronomy makes it sound elitist.”  In spite of his preference, Heston and his restaurant – The Fat Duck – are firmly associated with the term; the dude loves liquid nitrogen and sous-vide. Loves it.

At Home features some adapted Fat Duck favorites (such as the Bacon and Egg Ice Cream) but also includes recipes for staples such as compound butters, stocks, and mayonnaises. Don’t be fooled by the seemingly “simpler” recipes; this is not a simple cookbook.

This is a beautiful, informative, ever so slightly pedantic tome perfect for the home chef who wants to take it up a notch.

The Pros: First of all, the images alone make the book worth picking up. The photo accompanying a recipe for Pea and Ham Soup somehow manages to look elegant and slightly sinister while the cheese-centric photos are downright erotic.

Each chapter begins with a short historical/scientific treatise concerning the subject at hand. The chapter on cheese explains the process of cheese making, offers tips on how to cook cheese to perfection, and finally explains what those little white crystals on parmesan are. (Surprise! It’s MSG!)

Though some may be initially annoyed by this, Blumenthal supplies most measurements by mass and – be still my chemist’s heart – the metric system. This eliminates the tiny amount of guesswork that is involved when dealing with volume, and helps the reader produce consistently good dishes each time; 100 grams is always 100 grams.

In addition to beautiful photos, educational prologues, and a superior system of measurement, the recipes are just plain fun. Whether through presentation or flavor Blumenthal’s dishes are truly creative. His Garden Salad with Sauce Gribiche looks like an actual vegetable garden, finely walking the line between “utterly charming” and “maybe a little too whimsical.”

The Cons: These recipes are not of the budget variety. Whether through specialty equipment (pressure cooker, blow torch, a sous-vide constant temperature water circulator) or specialty ingredients (dry ice, smoking chips, all of those British foods that are hard to find this side of the pond) one can end up spending quite a bit per recipe. And never let it be said that Blumenthal skimps on quality; vanilla extract is never suggested, only the bean, though it’s hardly fair to call that a “con.” I’ll take mild fussiness over Sandra Lee –style shenanigans any day.

Highlight: Whiskey Ice Cream. BECAUSE WHISKEY AND ICE CREAM.

I leave you with a recipe. Because July 4th is fast approaching, I thought it appropriate to give you something you could take to a BBQ. Let others bring plebeian chips and dip. Let lesser ones bring watermelon. You are bringing Choucroûte, sauerkraut’s more sophisticated cousin.

Choucroûte

Choucroûte is a savory, slightly less pungent variety of pickled cabbage, elevated with butter-sauteed onions and Gewürztraminer wine. Toss it with potatoes for a potato salad that is light or heavy on flavor (and vitamin C) or use it to top grilled sausages. Everyone will be very impressed by your worldliness and culinary skill.

Choucroûte (adapted from Heston Blumenthal at home)

You will need:

100 g unsalted butter

400 g peeled and finely sliced onions

1 clove of garlic, smashed and chopped

1 tsp juniper berries, wrapped in a muslin bag

300 g Gewürztraminer wine

50 g white wine vinegar

Salt and pepper

1 cabbage (Savoy is suggested, but I could only find green)

1 tbsp groundnut or grapeseed oil (I omitted this and used the residual bacon grease)

30 g smoked bacon lardons

1. Melt the butter over medium heat and sweat the garlic, onions, and juniper berries until onions are soft and lightly colored (about 20 minutes). Discard juniper berries.

2. Add wine and reduce by about a third. Add vinegar and reduce for 5 minutes. Season with salt and pepper and remove from heat. Strain onions and reserve both liquid and onions. (I’m not sure why, as you add them all back together in the end.)

3. Cut cabbage in half and remove tough core. Slice leaves into thin strips (5 mm, to be exact).

4. If you are using oil, heat and add bacon. Cook bacon until lightly colored and drain on paper towels. Cook cabbage in oil and bacon grease for about 7 minutes. Mix in onions, liquid, and bacon and cook for an additional 5 minutes.

5. Season with salt and pepper to taste before serving.

Be the hit of your respective 4th of July party.