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Deep-fried Turkey: Delicious or Dangerous?

November 24, 2015/in DIY Kitchen Science, Science & Food/by Grant Alkin

Is a Deep-Fried Turkey your Destiny [Photo Credit: Jinx!]

While you may think the most dangerous thing you can do during the holidays is talk politics with your uncle, starting a kitchen fire is a more realistic threat to your safety. According to the United States Fire Administration (USFA), the number of structure fires double on Thanksgiving, causing on average $28 million in property damage¹. Cooking causes the majority of these blazes, with grease and oil as the main culprits in ignition². Despite the astonishingly large number of holiday mishaps, home cooks continue using fats. A select few even engage in one of the most daring of food adventures: deep-frying a turkey.

A quick Internet search for “deep-fried turkey” reveals how dangerous this culinary practice can be. There are plenty of videos and pictures that document the aftermath of a deep-fried turkey fire. A careless and unprepared chef can turn a deep-fried turkey into a deep-fried disaster within minutes. The bird quickly becomes engulfed in a fireball that can be seen from the rest of the neighborhood. So then, what makes deep-frying more appealing than roasting? More importantly, can it be done safely?

[Photo credit: State Farm]

The key to effectively deep-frying a turkey is oil. Oil makes the bird both delicious and dangerous. Oil’s interaction with the poultry causes the characteristic crispy golden brown crust that draws people to deep-frying. This same oil, however, can ignite and cause a fire. To effectively and safely deep-fry a turkey, you must understand the science underlying deep-frying.

Oil is the key to a Deep-Fried Turkey [photo credit: Joe]

The main appeal of a deep-fried turkey is the texture created by oil interacting with the bird’s skin. In deep-frying, hot oil completely engulfs the food. Put an uncooked turkey in hot oil and bubbles immediately start forming. The bubbles are not from the oil, but from the water within the surface of the bird that escapes as tiny pockets of steam. Water boils at 212 °F, but the temperature of oil in a deep fryer is typically around 350 °F or greater. Because of these high temperatures, the water in the turkey skin rapidly evaporates. This dehydration at the surface combined with the high temperature make conditions perfect for the Maillard reaction.

Maillard reactions create the characteristic deep browning and appealing aromas that you may have experienced when you deep-fry a turkey. These reactions typically occur when proteins and sugars in foods are exposed to high heat (284 – 329 °F): the amino acid building blocks of proteins react with sugars at high heat to create a complex set of flavor molecules. This is why a deep-fried turkey may evoke similar flavors and aromas as seared steak, roasted coffee, or toasted bread. As heat continues to vaporize the water on the bird’s skin, the reaction speeds up and the resulting flavor molecules become more and more concentrated.

While Maillard reactions can also be achieved through roasting a turkey, deep-frying avoids some of the pitfalls of oven roasting. First, because the hot oil completely envelops the bird, the outside gets an even brown coat. The temperature of the oil remains relatively constant as it spreads into every crevice. Such uniformity can be harder to achieve in traditional oven roasting, because of differences in air temperature within the oven. Moreover, poor heat circulation can result in uneven cooking. In extreme cases, you might find one side of the turkey charred, while the other is still undercooked.

Next, because the oil can transfer more heat than air per unit volume and time, deep-frying can allow the bird’s surface to get hot quickly enough so that the inside does not overcook. In deep-frying, oil acts as the workhorse transferring heat to food. By contrast, ovens rely on air to transfer heat. Compared to air, cooking oil has a much higher rate of heat conduction. Heat transfers between substances when the molecules collide and transfer energy. Because a liquid such as oil is more dense then air, its molecules are more closely packed; there are more molecules per volume to transfer energy. As a result, the high heat needed for the Maillard reactions develops much faster in a deep fryer than in the oven. In general, oven roasting generally takes about 2-4 hours, while deep-frying can take as little as 30 minutes. Slower increases in surface temperature, as in the case of the oven, allow for more time for the high heat to spread to the center of the turkey and overcook the inside.

Many deep-frying fans claim that the practice “seals in the juices”, however, internal temperature has a larger impact on moisture. If you’ve ever bit into a dry piece of fried chicken, you know, that deep-frying does not guarantee juicy poultry. Fans claim that oil creates a barrier to lock in moisture, but as previously highlighted, hot oil causes it to vaporize and escape. Even water near the interior can escape if it reaches the boiling point because the crust remains porous. The meat on the inside cooks in the same way as in roasting, but only faster because the oil transfers more heat. Thus, regardless of whether you deep-fry or roast the bird, you need to watch the internal temperature to get a juicy turkey.

While hot oil is essential for transforming your turkey into a delicious brown and crispy treat, properly controlling the oil will keep you safe. The first step is having the proper equipment. While a turkey can be deep fried in any number of large pots you already have, none of them are specifically designed to safely handle 3 gallons or more of hot oil and a giant turkey. Having a deep fryer specific for turkeys ensures that when you use the right amount of oil, the turkey is completely submerged and the oil won’t overflow. Also you can cook with a turkey deep fryer outside; this keeps the hot oil safely away from anything flammable in your home. So if you do make a mistake, it’s far away from anything that can spread a fire.

Next, to avoid turning the turkey into a giant fireball, it must be properly dried. This means checking that the bird is completely thawed and free of excess water. If too much ice or water remain, either can quickly vaporize causing oil to spray into the air. You may have seen a similar reaction occur when you throw drops of water into hot oil to test if it’s reached frying temperature. Sudden vaporization results in tiny droplets of oil spewing out in a fine mist. As microscopic droplets, the oil increases its chances of contacting the burner and reaching its flash point, or the temperature at which a material can ignite. (The flash point is around 600-700°F for many cooking oils.) In the deep fryer, oil won’t get as hot, but as droplets, oil can reach this temperature because of their small size and increased surface area. The ignition of a few small oil droplets can set off a chain reaction that engulfs the entire bird. This is why a seemingly innocent icy turkey can turn into a fireball.

Finally, you may want to consider that deep-frying adds a significant amount of fat to your bird compared to roasting it. The entire surface of the turkey is covered in oil and some may seep into the interior. In general, deep-frying can result in as much as 5 to 40% of a food’s weight in oil³. If you are concerned about your fat intake you might want to avoid this deep-fried treat. However, eating a deep-fried bird only on Thanksgiving likely won’t jeopardize your health too much.

Deep-frying a turkey requires significant culinary effort. Although this cooking method is potentially dangerous, your fowl can develop delicious flavors and aromas that cannot be achieved as quickly in the oven. Whether or not you want to make the investment ultimately depends on what you like about eating turkey. If you only care about juicy meat, then using an oven and monitoring the temperature can be easier. However, if you crave a truly unique treat encased in a crispy brown crust, then deep-frying a turkey may be your next gastronomic adventure.

References cited

USFA. Thanksgiving Day Fires in Residential Buildings (2009-2011) http://www.usfa.fema.gov/downloads/pdf/statistics/snapshot_thanksgiving.pdf
USFA. Cooking Fires in Residential Buildings (2008-2010) http://www.usfa.fema.gov/downloads/pdf/statistics/v13i12.pdf
Owen R. Fennema, editor, Food Chemistry, 2nd Edition (New York: Marcel Dekker, Inc, 1985), 210-221

About the author: Vince Reyes earned his Ph.D. in Civil Engineering at UCLA. Vince loves to explore the deliciousness of all things edible.

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The Science of Steamed Milk: Understanding Your Latte Art

July 21, 2015/in Science & Food/by Grant Alkin

Guest post by Christina Jayson

Photo credit: Dan Lacher (journeyscoffee/Flickr)

Watch a barista at work and you will observe the art of preparing a perfect café au lait, cappuccino, macchiato, or mocha – all of which involve different quantities of steamed milk. Behind the artistic foam hearts and milk mustaches lies a science to steamed milk.

Students of UCLA’s SPINLab (Simulated Planetary Interiors Lab) team developed an app that allows you to “calculate the power output of your steamer” and predict the “steaming time for optimal milk temperature based on amount, type and starting temperature of your milk”. Samuel May of SPINlab explains the calculations the app takes into account that allows it to predict the temperature of milk at a given time. They show that the temperature increase of milk over time is linear, allowing them to make these predictions based on a Linear Heating Model.

But what exactly happens when you steam milk? Steaming involves introducing hot water vapor (T = 250-255 °F) into cold milk (T = 40 °F) until it reaches the ideal temperature for a “perfectly steamed latte.”

While the process sounds simple enough there are a host of variables that need to be considered. Most importantly, different milks require different amounts of steaming time. As SPINLab expert, Sam warned, too high a temperature can scald the milk: scalding kills bacteria and denatures enzymes; this inactivates the enzymes and causes curdling as denatured milk proteins clump together. Since different types of milk and dairy alternatives have different molecular compositions, this means they have different steaming temperatures. This difference all boils down to the composition of milk.

Figure 1. Milk broken down into its molecular constituents. Modified from Properties of Milk and Its Components. [3]

Milk is composed of three main components: of proteins, carbohydrates, and fat (Figure 1).

Milk is 3.3% total protein, including all nine essential amino acids; the protein content can be broken down into two main types, casein and serum. Serum, or whey proteins, contain the majority of the essential amino acids. Whey proteins can be coagulated by heat and denaturation of some of these proteins with heat; this gives cooked milk a distinct flavor. Caseins form spherical micelles that are dispersed in the water phase of milk [1]. When steaming milk, the injected air bubbles disrupt the micelles. The protein molecules then encompass the air bubbles, protecting them from bursting and leading to the formation of foam. The take away: The different protein content of different milks consequently affects each milk’s ability to maintain that frothy foam decorating your latte [2]. Whole milk results in a thicker, creamier foam and skim milk results in more foam and larger air bubbles, while almond milk is able to hold a light and long-lasting foam [2].

Table 1: Percent of protein in different types of milk and non-dairy alternative [2]

Milk	% Protein
Skim milk	3.4
1% milk	3.4
2% milk	3.3
Whole milk	3.2
Soy milk	2.7
Almond milk	0.4

Lactose is the carbohydrate component of milk – a disaccharide composed of D-glucose and D-galactose. There are two forms of lactose present in an equilibrium mixture due to mutarotation, α-lactose and β-lactose. β-lactose is the more stable form, and also the sweeter form of the two [3]. When you steam milk past a temperature of 100 °C, this causes a “browning reaction,” or the Maillard reaction, in which the lactose and milk proteins – mostly caseins – react to form what is know as an Amadori product [4]. The colorless Amadori product is a molecular complex between the lysine residues of protein molecules and the lactose molecules. As the reaction continues with heating, the Amadori product can undergo dehydration and oxidation reactions, or rearrangements that lead to a loss of nutritional value and the formation of unappealing flavor compounds in milk that Sam warned could result from over-steaming.

The last main constituent of milk is the milkfat that exists as globules in the milk. Over 98% of milkfat is made up of fatty acids of different types, including saturated, monounsaturated, and polyunsaturated fatty acids. These fat molecules can also stabilize the formation of foam by surround the air and entrapping it in a bubble. While higher fat content leads to stable foam at temperatures below room temperature, milks with lower fat contents (like skim milk) are better at stabilizing foam at higher temperatures [3]. This could be due to the reduced surface tension of the fat along the air bubble surface that is a result of an increase in fat percentage. Heating up these fat molecules not only affects foam texture; when heated or steamed, the fatty acids also participate in chemical reactions, such as oxidation reactions, that can give rise to an undesirable flavor [5].

For the lactose intolerant and fans of non-dairy alternatives, you may be wondering how lactose free options such as soy or almond milk compare. Their steaming temperatures differ mildly due to their distinct properties – for example, almond milk has a lower protein content (Figure 2). According to the experience and experimentation of expert baristas, certain brands of soy or almond milk can hold a foam better than others; the science underlying this phenomenon still remains to be determined.

Table 2: Ideal steaming temperatures for milk and non-dairy alternatives [6]

Milk	Soy Milk	Almond Milk	Coconut
150 °F	140 °F	130 °F	160 °F

The moral of the story is that each component of milk contributes to its ability to froth and foam, and steaming influences each of these components. With this knowledge, you can wisely choose your milk at Starbucks depending upon your foaming desires, or simply download Sam’s app and perfectly steam your milk at home.

References cited

O’Mahony, F. Milk constituents. Rural dairy technology: Experiences in Ethiopia, Manual No.4; International Livestock Centre for Africa Dairy Technology Unit, 1988.
Blais, C. The Facts About Milk Foam. Ricardo, [Online] November 2014;
Chandan, R. Properties of Milk and Its Components. Dairy-Based Ingredients.; Amer Assn Of Cereal Chemists, 1997; pp 1-10.
van Boekel, M.A.J.S. Effect of heating on Maillard reactions in milk. Food Chemistry. 1998, 62:4, 403-414.
Walstra, P. Dairy Technology: Principles of Milk Properties and Processes; CRC Press, 2013.
Dairy Alternatives – Soy, Almond, Coconut, Hazel, Cashew. Espresso Planet. [Online] April 2013;

Christina Jayson is a recent UCLA Biochemistry graduate about to embark on her Ph.D. journey at Harvard.

Lobsters: A Crustacean Sensation

May 19, 2015/in Science & Food/by Grant Alkin

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

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.

References cited

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

About 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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The Science of Bacon

April 7, 2015/in Science & Food/by Grant Alkin

Photo Credit: Mai Nguyen

Imagine rolling out of bed on a Saturday morning, shuffling into your kitchen, and tossing a few strips of streaky bacon into a skillet. After a few minutes, you’ll hear a delightful crackling and sizzling, soon followed by a complex and savory aroma that could lure even the most resolute of vegetarians to the kitchen. As time passes, you peek into the skillet and notice the bacon begin to brown and bubble. After an agonizing wait, the bacon has finally reached a desired color and crispness and is ready to be consumed. You eagerly bite into a strip of bacon and are met with a pleasantly smoky taste, crunch, and a melt-in-your-mouth sensation. Bacon is a delight to eat, but it’s even better when you understand the science of why it’s so delicious.

There are two major factors that can explain why bacon has such a devoted fan base, with the first and more obvious factor being its aroma. Scientists have identified over 150 compounds responsible for bacon’s distinctive smell. As bacon cooks, there are a couple of different things going on. The Maillard reaction, the browning that results when amino acids in the bacon react with reducing sugars present in bacon fat, produces several desirable flavor compounds. This same browning reaction is also what forms the darkened and crunchy exterior on a pretzel or provides a stout beer with its characteristic color and taste.

During this process, bacon fat also melts and degrades into flavor compounds of its own. The compounds produced from the Maillard reaction and from the thermal degradation of bacon fat combine to form even more aroma compounds. In one study, scientists used gas chromatography and mass spectroscopy and revealed many of these aroma compounds to be pyridines, pyrazines, and furans, which were also found in the aroma of a fried pork loin that was tested. Pyridines, pyrazines, and furans are known to impart meaty flavors, so what actually sets bacon apart from the fried pork loin is the presence of nitrites. Nitrites are introduced into bacon during the curing process and are believed to react with aroma compounds in such a way that dramatically increases the presence of other nitrogen-forming compounds, including those meaty pyridine and pyrazine molecules. Ultimately, we can thank the high presence of nitrogen compounds as well as the interplay of fat, protein, sugars, and heat for bacon’s savory and unique aroma [1].

Now imagine that you’re eating breakfast. You alternate between bites of fluffy pancake drenched in maple syrup and mouthfuls crispy bacon, and maybe you’ll also have a side of velvety scrambled eggs. Here, you have a variety of textures on your plate –which brings us to our next concept to explain why bacon is so revered—mouthfeel.

Mouthfeel is described as the physical sensations felt in the mouth when eating certain foods. Bacon delivers a crunchy contrast to the softer textures found in scrambled eggs or pancakes in a mouthfeel phenomenon known as dynamic contrast. The brain craves novelty, and sensory contrasts will often increase the amount of pleasure that the brain derives from food, which is why you can find bacon as a textural accompaniment in many classic, creative, or sometimes questionable combinations. In a strip of bacon, you’ll see that it consists of lean meat that is heavily marbled with fat. During the cooking process, fat renders off leaving behind a product that simultaneously crisps and melts in your mouth when consumed, a texture combination that is rivaled by few other foods.

The melt-in-your-mouth phenomenon of bacon illustrates another nuance of mouthfeel, which is vanishing caloric density. Vanishing caloric density can be blamed for why it’s so easy to mindlessly consume massive amounts of popcorn, cotton candy, or other foods that seem to melt in your mouth. Upon ingestion of these foods, it is believed that the brain is tricked into thinking that you’re eating fewer calories than you actually are. Foods with vanishing caloric density have low satiating power but high oral impact, so your brain urges you to consume more, as it finds them more rewarding [2].

Between its tantalizing aroma and its delectable mouthfeel, it’s no surprise why bacon mania has so aggressively swept the nation.

Now you can use science to justify eating an entire package of bacon in one sitting. Photo credit: Mai Nguyen

References cited

Timón, M., Carrapiso, A., Jurado, A., van de Lagemaat, J. A study of the aroma of fried bacon and fried pork loin. Journal of the Science of Food and Agriculture, 2004; 84:825-831.
Witherly S. Why Humans Like Junk Food. iUniverse, Inc.; 2007.

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