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The Science of Sous Vide

“Sous vide,” or “under vacuum,” refers to a style of cooking in which food is sealed in a plastic bag and submerged in a water bath that is held at a controlled temperature [1]. This technique originated in ancient times when humans wrapped their food in salt, fat, animal leaves, and animal bladders before cooking [2]. Sous vide in its fully realized form began in the 1960s as NASA scientists began to incorporate this concept into creating astronauts’ sealed-bag meals [2]. In the 1970s, French chefs (who had already popularized cooking en papillote or in paper), adopted the sous vide technique of cooking in plastic [3]. From here, sous vide spread to professional kitchens across the world, but it was not until the 1990s that food scientists began to study the deeper science behind sous vide processing. By the mid-2000s, sous vide became widely known and the past decade has seen a massive increase in its popularity [1] where it is heralded as “the most important technological advance in the kitchen since the microwave.” [3] Before sous vide machines were accessible to the home chef, a common method was using an ice chest, which keeps water hot long enough to effectively sous vide food [4]. Although this is still a popular and inexpensive technique, sous vide machines are now available from many brands for under $200.

Traditionally cooked steak (left) vs. sous vide steak (right). The gradation is very visible in the traditionally cooked steak. Photo credit: Nathan Myhrvold/Modernist Cuisine

Traditionally cooked steak (left) vs. sous vide steak (right). The gradation is
very visible in the traditionally cooked steak. [Photo credit: Modernist Cuisine]

The appeal of sous vide comes with its ease and ability to precisely control the temperature at which the food is cooked. By targeting a specific minimum temperature at which proteins denature, it is virtually impossible to overcook your food. When food is cooked by traditional methods such as on the stovetop or in the oven, the outside of the food rises to temperatures that are much higher than the final desired temperature of the food. This increases the risk of overcooking the outside (and inside) of the food in an attempt to reach the correct internal temperature. By using sous vide, food is cooked for a longer period of time and at a lower temperature than usual and is raised uniformly to the same temperature [5]. This prevents evaporative loss of moisture (Fig. 1) and enables tough cuts of meat to be made tender while still cooking them medium/medium-rare [1].

Figure 1: The weight loss (moisture loss) from New York strip steak at varying temperatures ranging from 120-160°F [6].

Figure 1: The weight loss (moisture loss) from New York strip steak at varying temperatures ranging from 120-160°F [6].

Another advantage to sous vide is from a nutritional standpoint. Sous-vided vegetables retain their vitamins and trace elements; by contrast, boiling removes 60% or more of these nutrients [3]. Sous vide also requires little added fat (oils, butter, etc. are usually added solely for flavor). Additionally, because the food is sealed in a plastic pouch, this largely reduces oxidation and therefore preserves the nutritional qualities of polyunsaturated fatty acids [7]. Lastly, because food can be cooked at lower temperatures, the vitamins that are normally destabilized at the high temperatures of traditional cooking methods are preserved [8].

While this effective technique was formerly limited to professional kitchens, it is now accessible for the home cook! Companies such as Anova, Nomiku, and Sansaire have recently developed sous vide machines at an attractive price point. Fascinated by the attention around this rapidly popularized method, I purchased my own Anova and set out to test to see if these sous vide machines lived up to the stories.

At-home immersion circulators from different popular brands. Photo credit: Modernist Cooking Made Easy

At-home immersion circulators from different popular brands. [Photo credit: Modernist Cooking Made Easy]

The first beast I tackled was the one I have always had a penchant for overcooking – the New York Steak. No matter what technique I tried to use, I always end up oversearing and getting a ring of medium-well steak around my perfectly medium-rare center. Using one of my favorite sites for recipes, Chef Steps, I attempted their Simple Sous Vide Steak with Red Wine Sauce. I pre-seared my steaks (this gives you a better crust at the end of the cooking process), placed them in a Ziploc bag with some butter, and popped them into my preheated 135°F water bath. After an hour I removed the steaks and quickly seared them again to get a delicious golden brown crust. Result? Mouthwatering, juicy, tender steak with unbelievable flavor and a beautiful medium-rare interior that extended from edge to edge. Absolute gastronomic perfection.

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Results from my sous-vided New York steak. [Photo credit: Ashton Yoon]

Thrilled with the results of my first experiment, I tackled a variety of other proteins and the results of these attempts are shown below. Salmon was so simple: a quick 20 minutes at 126°F yielded the most buttery salmon I had ever tasted, with a compelling sashimi-like texture.

Photo credit: Ashton Yoon

Salmon in brine (left) and finished sous vide salmon with lemon wasabi aioli, recipe from Sous Vide Supreme (right). [Photo credit: Ashton Yoon]

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Pork belly immersed in the water bath (left). Honey sriracha pork belly with carrot purée, salsa verde, and pickled radishes. Recipe inspired from the 2014 movie “Chef” (right). [Photo credit: Ashton Yoon.]

New Zealand rack of lamb with herb crust during the cooking process (left). Final product, lamb recipe from Epicurious and Hasselback potato recipe from The Kitchn. Photo credit: Ashton Yoon.

New Zealand rack of lamb with herb crust during the cooking process (left). Final product, lamb recipe from Epicurious and Hasselback potato recipe from The Kitchn. [Photo credit: Ashton Yoon.]

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Eggs during the sous vide process, no plastic sealing needed (left). Egg cooked at 155°F, recipe from Serious Eats (right). [Photo credit: Ashton Yoon.]

My impression of at-home sous vide? Stellar. Not only was the entire cooking process easy, but I was guaranteed to get perfect results every time. The flavors and moisture retention were incredible. And the added nutritional value is just the cherry on top of the already sweet, sweet cake.

References cited

  1. Baldwin, Douglas. “Sous Vide Cooking: A Review.” International Journal of Gastronomy and Food Science 2012: 15-30. Print.
  2. Myhrvold, Nathan. “Why Cook Sous Vide?Modernist Cuisine. Cima Creative, 2013. Web. 24 November 2015.
  3. Renton, Alex. “Sous Vide: The Chef’s Secret Coming to Your Kitchen.The Guardian. Media Limited, 2014. Web. 25 November 2015.
  4. López-Alt, J. Kenji. “Cook Your Meat in a Beer Cooler: The World’s Best (and Cheapest) Sous Vide Hack.Serious Eats. Serious Eats, 2010. Web. 2 January 2015.
  5. Suchy, Sara. “Testing Cooking Temperatures of Sous Vide.” Inside Science. American Institute of Physics, 2013. Web. 25 November 2015.
  6. López-Alt, J. Kenji. “How to Sous Vide Steak.” Serious Eats. Serious Eats, 2010. Web. 2 January 2015.
  7. Sasson, L. (2006). Functions of Fat Lecture, New York University.
  8. Buckley, C. (1987). “Storage stability of vitamin C in a simulated sous vide process.” Hotel and Catering Research Centre Laboratory Report 238: 2.

Ashton YoonAbout the author: Ashton Yoon received her B.S. in Environmental Science at UCLA and is currently pursuing a graduate degree in food science. Her favorite pastime is experimenting in the kitchen with new recipes and cooking techniques.

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Marcel Vigneron

Chef Marcel Vigneron was first introduced to the public eye as the runner-up of season two’s Top Chef. Known on the show for his molecular gastronomy techniques, Vigneron has since then built upon his specialty with his own reality TV show in 2010, Marcel’s Quantum Kitchen, and competing on Iron Chef and later seasons of Top Chef.

Marcel Vigneron

What hooked you on cooking?
I love a good challenge and cooking is one of the only occupations that I can think of that requires you to utilize every single one of your senses while simultaneously challenging you not only physically, but mentally and creatively. It pretty much provides me with everything I would ever want out of a career and you get to perform a good deed for society and provide people with not only nourishment but also experience.
The coolest example of science in your food?
Science is always in our food whether we know it or not but if I had to choose one, I would say I thoroughly enjoy working with eggs! Whether it be by whipping whites to peaks, yolks to sabayon, making a hollandaise or whatever the case may be, eggs allow for so many fascinating scientific processes to take place through emulsification, aeration, coagulation and many more…
The food you find most fascinating?
Rather than say “eggs” again, which would probably be my first choice, I will venture to say that I find olive oil to be quite fascinating. It’s amazing how something when raw can taste so disgusting but through brining and pressing one can yield such an amazingly diverse and healthy product that goes with just about anything…
What scientific concept–food related or otherwise–do you find most fascinating?
Brining and curing have always fascinated me. Originally used as means of preservation, they have now become a staple technique in the kitchen for so many things.
Your best example of a food that is better because of science?
Vinaigrettes!!! A simple combination of oil and vinegar becomes so much more practical when emulsified temporarily or permanently with the addition of xanthan gum.
How do you think science will impact your world of food in the next 5 years?
I think science will make a positive impact on the world of food in the next 5 years through education. Every phenomenon that takes place during cooking and even in agriculture can be explained through science. The more we understand these activities and happenings the more prepared we will be to make conscious decisions regarding the future of our food.
One kitchen tool you could not live without?
ALL I NEED IS 1 KNIFE!!!!
Five things most likely to be found in your fridge?
Yuzu juice, miso paste, tofu, almond milk, fish on ice.
Your all-time favorite ingredient?
Salt because it brings out the flavor in everything.
Favorite cookbook?
Thomas Keller’s The French Laundry.
Your standard breakfast?
Chia seeds hydrated in almond milk with berries and nuts.

Vinny Dotolo

Vinny Dotolo is one half of the culinary duo dubbed as “Kings of Dude Food”. Alongside John Shook, the pair opened Animal, a meat-centric restaurant located in L.A.’s Fairfax Village. Following the success of Animal, the duo have since opened the equally acclaimed Son of a GunTrois Mec, and Petit Trois.

Vinny Dotolo

What hooked you on cooking?
Mainly the kitchen culture and obviously the delicious food and the never-ending learning process.
The coolest example of science in your food?
I guess science happens every day in our kitchens. Looking at it from a scientific perspective, I think the transformation and cooking of proteins.
The food you find most fascinating?
Eggs have always kept my mind racing.
What scientific concept–food related or otherwise–do you find most fascinating?
Emulsifications.
Your best example of a food that is better because of science?
Fermented foods.
How do you think science will impact your world of food in the next 5 years?
In general, I think understanding food and how and why things happen in the kitchen. Different techniques seem to be popping up constantly.
One kitchen tool you could not live without?
Vita prep.
Five things most likely to be found in your fridge?
Pickles
Cheese
Lemonade
Jam of some kind
The baby’s food
Your all-time favorite ingredient? Favorite cookbook?
Lemons are my favorite ingredient, they brighten everything up! Favorite cook book is tough. I have such a diverse collection but the one that changed my life and perspective and appreciation for food is the French Laundry.
Your standard breakfast?
Toast and coffee.

Ramen and the Perfect Egg

The arrival of autumn comes with the promise of changing leaves and chillier climates, often cueing our urge to prepare warmer meals aimed at combatting the frigid weather. One foolproof method that guarantees victory against the cold is a hot bowl of soup, such as ramen.  There are many variations of ramen but one dear to many hearts (and mouths) is tonkotsu ramen.  This style of ramen involves the boiling of pork bones for extended periods of time to produce a deliciously fatty and hearty pork broth that has an incredible depth of flavor.  The broth alone is what makes the ramen but the accoutrements that dress the soup are just as important.  Tonkotsu ramen is often served with slices of marinated, slow-cooked pork loin (chashu), enoki and wood ear mushroom, dried seaweed (nori), and green onions.  However, one of my favorite ramen toppings is the soy-marinated soft-boiled egg known as ajitsuke tamago.

Photo credit: Anne Regalado (My Bare Cupboard)

Photo credit: Anne Regalado (My Bare Cupboard)

Perfectly prepared ajitsuke tamago has a set outer layer of egg white with a delicate, intact silky egg yolk. However, achieving the ideal soft-boiled egg isn’t a trivial task.  The preparation of both hard and soft-boiled eggs culminates in the process known as protein denaturation.  Eggs themselves are nothing more than protein reservoirs and their exposure to heat disrupts the chemical and ionic bonds involved in maintaining their secondary and tertiary configurations causing them to unfold into linearized structures [1].   The unfolding of complex proteins into strings of amino acid chains through thermal energy transfer allows for the formation of new bonds between molecules that facilitate the transition of a raw, liquid egg into a cooked, solid egg [1]. Ovotransferrin and ovalbumin and are the most abundant proteins found in egg whites and their denaturation causes them to form tightly associated protein clumps that result in the solidification of the egg whites at 140°F and 180°F, respectively. [2,3]. Furthermore, the egg yolks will also become solid once they reach a sustained temperature of 160°F. Therefore, one must consider the balance of temperature and time to attain the characteristics of a perfectly soft-boiled egg.

Heat causes the phase transition of the egg from a liquid state to a water-insoluble state that's ready for eating! Photo Credit: SPIE

Heat causes the phase transition of the egg from a liquid state to a water-insoluble state that’s ready for eating! Photo Credit: SPIE

Timothy Ferriss, author of The 4-Hour Chef [4], conducted an experiment to dispel our egg boiling anxieties. He placed four eggs in a pot of water and brought it to boiling temperature (212°F); after 6 minutes he removed each of them in 2-minute increments.  His verdict? The sweet spot to achieve the perfect ajitsuke tamago egg consistency is somewhere between 6-7 minutes (see image below). I’d err between 5-6 minutes, as the salt from the soy-marinated will continue to “cook” the outer egg white layer.

Photo Credit: The 4-Hour Chef

Photo Credit: The 4-Hour Chef

If you enjoy the challenge of making dishes at home, check out this tutorial on how to make your own tonkotsu ramen!

Tonkotsu Ramen Broth

Ingredients

  • 3 pounds pig trotters, split lengthwise or cut crosswise into 1-inch disks (as your butcher to do this for you)
  • 2 pounds chicken backs and carcasses, skin and excess fat removed
  • 2 tablespoons vegetable oil
  • 1 large onion, skin on, roughly chopped
  • 12 garlic cloves
  • One 3-inch knob ginger, roughly chopped
  • 2 whole leeks, washed and roughly chopped
  • 2 dozen scallions, white parts only (reserve greens and light green parts for garnishing finished soup)
  • 6 ounces whole mushrooms or mushroom scraps
  • 1 pound slab pork fat back

Full recipe at Food Lab.

References cited

  1. Nelson, D; Cox, M (2012). Lehninger Principles of Biochemistry. 4th Ed. New York: W.H. Freeman
  2. Huntington JA; Stein PE (2001). Structure and properties of ovalbumin. Journal of Chromatography B 756 (1-2): 189–198
  3. Wu, J, Acero-Lopez, A (2012). Ovotransferrin: Structure, bioactivities, and preparation. Food Research Int 46: 480-487
  4. Ferriss, T (2012). The 4-Hour Chef. Boston: New Harvest

Anthony MartinAbout the author: Anthony Martin received his Ph.D. in Genetic, Cellular and Molecular Biology at USC and is self-publishing a cookbook of his favorite Filipino dishes.

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5 Things About Baking

At our 2013 Science of Pie event, Christina Tosi, Zoe Nathan, and the fantastic students from the Science & Food undergraduate course taught us all about pies, baking, creativity, and the scientific process. We just can’t get enough pie science, so here are 5 fun facts related to baking and some of our favorite baking ingredients:

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Baking1


Baking2


Baking3


Baking4


Liz Roth-JohnsonAbout the author: Liz Roth-Johnson is a Ph.D. candidate in Molecular Biology at UCLA. If she’s not in the lab, you can usually find her experimenting in the kitchen.

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The Science of Cookies

How would you describe your perfect chocolate chip cookie? Thin and chewy? Ultra-crispy? Thick and cakey? Whatever your preference, knowing how to manipulate the ingredients in a basic cookie recipe is the first step toward chocolate chip cookie bliss. At last week’s “Science of Cookies” student event, graduate student Kendra Nyberg showed us how to achieve two very different cookie textures by riffing off of the classic Toll House chocolate chip cookie recipe.

ScienceofCookies

Cookies wait to be tasted (left) while Kendra explains how gluten makes cookies chewy (right)

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Thin, chewy cookies (left) and thick, soft cookies (right)

Thin, Chewy Cookies from Smitten Kitchen
These cookies are all about moisture. A wetter cookie dough spreads more during baking, creating a much thinner cookie. Extra moisture also promotes gluten development in the cookie dough, creating a slightly denser, chewier cookie. This recipe from Smitten Kitchen maximizes moisture content by using melted butter, less flour, less egg white (which can dry out cookies), and a higher brown-to-white sugar ratio (brown sugar can help retain moisture) than the classic Toll House Recipe.

ThinChewyCookieRecipe

Thick, Soft Cookies from My Baking Addiction
Where the previous cookies craved moisture, this recipe from My Baking Addiction removes extra moisture to create thicker, less chewy cookies. Increasing the flour content and using extra cold butter creates a drier dough that spreads less easily in the oven; adding baking powder to the dough lends extra fluffing power. The reduced moisture in this dough also limits gluten formation for a slightly softer (less chewy) cookie.

ThickSoftCookieRecipe

Of course, this is barely the tip of the cookie engineering iceberg. There are so many ways to tweak a cookie recipe to achieve different textures. In addition to this brief introduction, the internet is full of great resources for cookie hacking. This particularly handy guide from Handle the Heat clearly show some of the ingredient manipulations described above. If you end up experimenting with your favorite cookie recipes, be sure to tell us about it in the comments below!


Liz Roth-JohnsonAbout the author: Liz Roth-Johnson is a Ph.D. candidate in Molecular Biology at UCLA. If she’s not in the lab, you can usually find her experimenting in the kitchen.

Read more by Liz Roth-Johnson


Reinventing the Egg

Even if you’re not watching your cholesterol, there are plenty of reasons to avoid eating eggs. Ethical issues aside, industrial eggs provide only about 20% of the energy it takes to produce them. And while some egg substitutes do exist, they often pale in comparison to the real thing. Josh Tetrick, the CEO of Hampton Creek Foods, thinks we can do better. Read more

Baking Without Eggs

With the Science of Pie coming up in just a few weeks, we’ve been spending a lot of time thinking about baked goods. And one ingredient in particular has really captured our imagination—the egg! In the realm of baked goods, eggs are highly revered for their binding and leavening abilities. The fats and proteins within an egg can also contribute to important properties like moisture, texture, and mouthfeel [1]. Read more