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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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Making Fake Meat Real: How Scientists are Tricking Your Tongue

Fake meat is often associated with a tough, flavorless texture that is added to dishes to provide protein. However, fake meat is no longer just glutinous balls or tofu hidden beneath sauces. From plant protein derived meats to in vitro preparations, there is much more to synthetic meat than what meets the tongue.

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Veggie Sausage. Photo Credit: (Heather Quintal/Flickr)

Replicating meat texture

Meat texture is very complex. Consider the multiple components from muscle tissue fibers, blood vessels, fat, gristle, to nerves. Each component confers a different texture and flavor profile, so replicating meat is quite a challenging process.

Texture plays a big role in determining whether a product tastes like real meat or not. For example, the satisfyingly stringy texture one gets from pulling apart chicken strips. Fortunately, food scientists have found ways to emulate the fibrous quality in fake meat using soy protein. Soy protein is initially globular, so it must be denatured, or broken down, to make it more fibrous. Soy protein is first exposed to heat, solvent, or acid, before it is reshaped with a food extruder [1]. Extrusion processes are useful as they can form meat analogs with fibrous matrices, which can then be rehydrated into meat like substances [2]. However, this process can sometimes result in a dry product. The rising company Beyond Meat has gone further and found a way to use soy flour, pea flour, carrot fiber, and gluten-free flour to emulate the fibrous quality in their fake meat with a wet extrusion process. The proteins are realigned and then locked in position by crosslinking to get a fibrous chicken imitation that is also moist and juicy [1].

Taste & color of meat

The flavors of meat mostly arise during the cooking process. Maillard reactions between sugar and amino acids produce those familiar meat flavors and aromas [3]. The amino acid glutamate is of utmost importance as it activates the umami taste receptors. Real meats contain glutamate as it is found in proteins, and it is released during proteolysis that occurs during meat aging and cooking [4]. Since most fake meats do not contain glutamate, this taste can be added back with soy sauce, tomatoes, mushroom, and cheese in the form of sauces [5]. Another unique aspect of meat is its color. The myoglobin proteins found in muscle are initially red due to heme pigments, but with the added heat of cooking, protein denaturation results in a brown color associated with cooked meat. For fake meat, food colorings and spices can be used to mask the original color.

In vitro meat: your steak from a petri dish

To minimize the number of animals slaughtered, some scientists are even growing animal tissue in the lab [3]. To do this, they take a small muscle tissue sample and look for skeletal muscle satellite cells, which are essentially individual stem cells that are normally used to create new tissue in case of damage. After these satellite cells are collected, they are bathed in a nutrient serum where they can be coaxed into growing. When large enough, they are shocked with an electric current, which causes the tissue to contract and thicken, resembling small fillets of meat a couple centimeters long and a few millimeters thick [3]. While meat products generated using this process are not available at your local supermarket (or butcher), and this product is not truly “meat-less” for vegetarians or vegans, it could potentially maximize meat production by saving cows from the slaughterhouse.

In vitro meat samples. Photo Credit (Janique Goff/Flickr).

In vitro meat samples. Photo Credit (Janique Goff/Flickr).

Fake meat efforts are attracting big investments from Bill Gates and Silicon Valley entrepreneurs, as the demand for meat increases. In fact, population growth and a boost in meat consumption have increased the global demand for meat threefold in the last 40 years [6]. Not only does this intensify the requirements for raising livestock, but it also increases the greenhouse gas emissions emitted during processing [6]. It is no wonder that the search for the best meat-replication process continues on! Whether from an animal or plant base, synthetic meat is becoming increasingly prevalent and is not just for vegetarians and vegans anymore.

References cited:

  1. How ‘fake meat’ is made. Mother Nature Network.
  2. Riaz, Mian N., Anjum, Faqir M., Khan, Muhammad Issa. “Latest Trends in Food Processing Using Extrusion Technology.” The Pakistan Society of Food Scientists 17.1 (2007): 53-138. Web.
  3. Fake meat: is science fiction on the verge of becoming fact? The Guardian.
  4. The Chemistry of Beef Flavor. BeefResearch.org.
  5. What Foods are Glutamate-Rich? Msgfacts.org.
  6. The Bill Gates-backed company that’s reinventing meat. Fortune.

Catherine HuAbout the author: Catherine Hu is pursuing her B.S. in Psychobiology at UCLA. When she is not writing about food science, she enjoys exploring the city and can often be found enduring long wait times to try new mouthwatering dishes.

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