Science & Food – Page 2 – Science and Food

Black Sesame Seeds on Heavy Metal Cleanup

February 2, 2016/in News & Views/by Grant Alkin

Black sesame seeds: more than just a tasty garnish on sushi rolls and rice. Photo credit: Arnold Gatilao (arndog/Flickr)

Black sesame seeds: more than just a tasty garnish on rice. Photo credit: Arnold Gatilao (arndog/Flickr)

Heavy metals, such as cadmium, lead, and mercury, leach into our food supply through the air and water; these undesirable additives come from industrial processes such as mining, smelting, battery manufacture, electroplating, and pesticide production. Cadmium and lead are the chief contaminants of rice, wheat, and foods containing these cereals [1]. Mercury is often found in seafood, but cadmium and lead can also be present in smaller amounts [2]. Even trace amounts of these heavy metals can be extremely toxic to human health, since they have extremely long biological half-lives, or time required for half the absorbed metals to leave the body: 10 years for cadmium [3], 30 days for lead [4], and 60 days for mercury [5]. Thus, there is an increased risk of chronic poisoning due to heavy metal accumulation in tissues and organs, which can lead to impairment of the immune and central nervous system [6].

Current protective measures against dietary exposure to heavy metals involve chelating agents, which are compounds that can bind to metal ions. Chelating agents include cereal fibers from wheat, rice, and oat bran, as well as polyglutamic acid, which is the main constituent of nattō, Japanese fermented soybeans [7]. Although edible, the efficacy of these particular chelating agents has so far only been evaluated for removing heavy metals from water and soil.

What about the heavy metals we’ve already ingested? In a collaboration among researchers in Italy and Austria, ground black sesame seeds (Sesamum indicum L.) were shown to effectively bind to cadmium, lead, and mercury under simulated physiological conditions.

A major challenge in using chelating agents is that they also bind to many essential ions in the body, such as calcium (Ca²⁺), zinc (Zn²⁺), and iron (Fe²⁺); this can result in deficiencies, which can have negative health effects. Unlike other chelating agents used for heavy metal detoxification, which cannot differentiate between essential metal ions and toxic heavy metal ions (cadmium (Cd²⁺), lead (Pb²⁺), and mercury (Hg²⁺)), black sesame seeds exhibited selectivity towards the heavy metals. In mixtures that contain heavy metals plus essential metal ions, the ground black sesame seeds bound to far more heavy metals than essential metals. Interestingly, low levels of iron increased the amount of cadmium and lead bound to the sesame seeds. While other chelating agents, such as thiamine and becozinc, risk deficiencies in essential metals [8], the preference of black sesame seeds to bind to toxic heavy metals make it a favorable dietary supplement for heavy metal detoxification.

The ability of black sesame seeds to bind to toxic heavy metals may be attributed to lignans, a type of phytochemical commonly found in plants and a major component of sesame seeds. To determine how the heavy metals were binding to the ground black sesame seeds, the study compared the binding abilities of ground black sesame seeds against model phytochemicals, caffeic acid, ferulic acid, and coniferyl acid, which represented sesame seed lignans after digestion in the stomach. Of the three model pigments, caffeic acid was observed to remove the most heavy metals, suggesting that digested sesame seed lignans may have a similar chemical structure to caffeic acid.

Lignans in black sesame seeds are responsible for heavy metal binding. Left: Model pigments representing digested lignans were compared to ground black sesame seeds (BSP) for heavy metal removal. Right: Caffeic acid and the suggested binding sites for cadmum (Cd²⁺), lead (Pb²⁺), and mercury (Hg²⁺)

There are additional benefits to lignans in sesame seeds! As a major category of phytoestrogens, lignans are known to be effective antioxidants. Moreover, sesame seeds specifically contain the lignans, sesamin and sesamolin, which studies have shown to also contain pharmacological benefits such as antihypertensive, anti-inflammatory, and anticarcinogenic properties [9].

For those worried about chronic dietary exposure to heavy metals, prevention may be as tasty as black sesame seeds sprinkled on sushi rolls.

Read the paper: Manini P., Panzella L., Eidenberger T., Giarra A., Cerruti P., Trifuoggi M., Nappolitano A. (2016) Efficient Binding of Heavy Metals by Black Sesame Pigment: Toward Innovative Dietary Strategies to Prevent Bioaccumulation. J Agric Food Chem.

References cited

Cuadrado C., Kumpulainen J., Carbajal A., Moreiras O. Cereals contribution to the total dietary intake of heavy metals in Madrid, Spain. Journal of Food Composition and Analysis, 2013; 13: 495-503.
Falcó G., Llobet J., Bocio A., Domingo J. Daily intake of arsenic, cadmium, mercury, and lead by consumption of edible marine species. Journal of Agricultural and Food Chemistry, 2006; 54: 6106-6112.
Godt J., Scheidig F., Grosse-Siestrup C., Esche, V., Bradenburg P., Reich A., Groneberg D. A. The toxicity of cadmium and resulting hazards for human health. Journal of Occupational Medicine and Toxicology, 2006; 1: 22.
Gulson B., Stable lead isotopes in environmental health with emphasis on human investigations. Science of the Total Environment, 2008; 400: 75-92.
Yaginuma-Sakurai K., Murata K., Iwai-Shimada M., Kurokawa N., Tatsuta N., Satoh H. Hair-to-blood ratio and biological half-life of mercury: experimental study of methylmercury exposure through fish consumption in humans. Journal of Toxicological Sciences, Feb 2012; 37(1): 123-130.
Woimant F. Trocello J. M., Disorders of heavy metals. Handbook of Clinical Neurology, 2014; 120: 851-864.
Siao, F. Y., Lu J. F., Wang J. S., Inbaraj B. S. Chen B. H. In vitro binding of heavy metals by an edible biopolymer poly(γ-glutamic acid). Journal of Agricultural and Food Chemistry, 2009; 57: 777-784.
Tandon S. K., Singh S. Role of Vitamins in Treatment of Lead Intoxication. The Journal of Trace Elements in Experimental Medicine, 2000; 13: 305-315.
Kim J. H., Seo W. D., Lee Y. B., Park C. H., Ryu H. W., Lee J. H. Comparative assessment of compositional components, antioxidant effects, and lignan extractions from Korean white and black sesame (Sesamum indicum L.) seeds for different crop years. Journal of Functional Foods, 2014; 7: 495-505.

About the author: Alice Phung once had her sights set on an English degree, but eventually switched over to chemistry and hasn’t looked back since.

Read more by Alice Phung

Blood Orange

January 19, 2016/in Flavor of the Month/by Grant Alkin

While traditional oranges are available at your local supermarket all year long, the best time to enjoy the juicy, crimson flesh of blood oranges is during these winter months. So while you venture out for some delicious blood oranges, consider these fascinating tidbits. How do they get their characteristic color? How are they different from everyday oranges?

About the author: Eunice Liu is studying Linguistics at UCLA. She attributes her love of food science to an obsession with watching bread rise in the oven.

Read more by Eunice Liu

Sanshool Seduction: The Science of Spiciness

January 13, 2016/in Science & Food/by Grant Alkin

One of the most aggressive flavors we can experience is spiciness. Imagine a bright red chili pepper whose color gives us fair warning of its propensity to ignite a fire. In fact, a common physiological response to eating spicy food is analogous to the way our body responds to an elevation in internal body temperature. You can feel the burn. The consumption of spicy ingredients triggers our exocrine (sweat) glands to secrete fluid at the skin’s surface to promote cooling through the evaporation of our perspiration.

So how is it that spicy food can make us sweat?

Red Chili Peppers [Photo Credit: The Paleo Diet]

Chemical Structure of Capsaicin [Photo Credit: Dartmouth]

The answer lies in our head. Our body’s reaction to spiciness is a result of input delivered from receptors in our mouth to our central nervous system. A compound found in many spicy ingredients such as chili peppers is called capsaicin. This molecule activates sensory neurons in our mouth called thermal nociceptors [1,2]. The activation of these thermal pain receptors in turn stimulates our sympathetic nervous system [3], which is associated with our body’s “flight-or-flight” responses. Therefore, the characteristic increase in heart rate and sweat production due to the consumption of capsaicin-rich ingredients is due in part to the capsaicin’s role in adrenaline secretion [4].

If you decide to brave the spice, here’s some advice: When it comes to relieving the pain of the capsaicin burn, your best bet is to have a glass of cold milk or better yet, a bowl of ice cream. The compound, casein, is a hydrophobic substance found in milk that operates to “absorb” the lipid-rich capsaicin molecules making it easier to cleanse your mouth of the spicy chemical [5].

However, capsaicin isn’t the only fiery compound that can elicit unique physiological responses. On the other end of the spectrum is a compound known as hydroxyl-alpha sanshool, commonly found in Z. Bungaenum peppercorns. This variety of peppercorn is commonly grown in the Sichuan province of China, and is referred to as the Sichuan peppercorn. The characteristic “flavor sensation” one might experience when eating Sichuan cuisine is a mind-numbing spiciness.

Here’s how that happens.

Sichuan Peppercorns [Photo Credit: Serious Eats]

Chemical Structure of Hydroxy-Alpha Sanshool [Photo Credit: Hong Kong University]

Hydro-alpha sanshool activates somatosensory neurons that are responsible for detecting innocuous stimuli such as a gentle touch. This is opposite of the nociceptors that detect capsaicin which primarily detect noxious or painful stimuli. The stimulation of somatosensory neurons by hydro-alpha sanshool produces a similar effect to local anesthetics used to moderate pain in surgery. The compound found in Sichuan peppercorns trigger somatosensory neurons to prevent the influx and efflux of electrolytes, Na⁺ and K⁺, through ion channels [6,7]. The resulting effect of hydro-alpha sanshool is to cease the propagation of neuronal action potential through the nervous system’s pain pathways. So, when you enjoy a delicious dish of Liang Fen (Cold Mung Bean Noodles with Sichuan Peppercorn/Chili Vinegar), or Suan Cai Yu (Poached Fish in Green Sichuan Peppercorn Sauce) you can experience thrilling mouth numbness. Your first instinct after eating these dishes will be to grab the closest glass of water available to you. Interestingly, a sip of flat water after eating these dishes will produce a surprising fizziness like you might experience while drinking sparkling water.

Liang Fen: Cold Mung Bean Noodles with Sichuan Peppercorn/Chili Vinegar [Photo Credit: Serious Eats]

References cited

Caterina, M., Schumacher, M., Tominaga, M., Rosen, T., Levine, J., Julius, D. “The capsaicin receptor: a heat-activated ion channel in the pain pathway”. Nature. 389 (1997): 816-824.
Liu, M., Max, M., Parada, S., Rowan, J., Bennett, G. “The Sympathetic Nervous System Contributes to Capsaicin-Evoked Mechanical Allodynia But Not Pinprick Hyperalgesia in Humans” The Journal of Neuroscience. 16.22 (1996): 7331-7335.
Ohnuki, K., Moritani, T., Ishihara, K., Fushiki, T. “Capsaicin Increases Modulation of Sympathetic Nerve Activity in Rats: Measurement Using Power Spectral Analysis of Heart Rate Fluctuations”. Bioscience, Biotechnology, and Biochemistry. 65.3 (2001): 638-643.
Watanabe, T., Sakurada, N., Kobata, K. “Capsaicin-, Resiniferatoxin-, and Olvanil-Induced Adrenaline Secretions in Rats Via the Vanilloid Receptor” Bioscience, Biotechnology, and Biochemistry. 65.11 (2001): 2443-2447.
Fire and Spice. General Chemistry Online!.
Tsunozaki, M., Lennertz, RC., Vilceanu, D., Katta, S., Stucky, CL., Bautista, DM. “A ‘Toothache Tree’ Alkylamide Inhibits AD Mechanonociceptors to Alleviate Mechanical Pain” Journal of Physiology. 591 (2013) 3325-3340.
Bautista, DM., Sigal, YM., Milstein, AD., Garrison, JL., Zorn, JA., Tsuruda, PR., Nicoll, RA., Julius, D. “Pungent Agents from Szechuan Peppers Excite Sensory Neurons by Inhibiting Two-Pore Potassium Channels” Nature Neuroscience. 11.7 (2011): 772-779.

About 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.

Read more by Anthony Martin

Anatomy of a hot chocolate

December 15, 2015/in Science & Food/by Grant Alkin

Photo credit: Flickr/louish

Hot chocolate: it’s a winter staple. Amidst falling temperatures and dreary skies, there’s nothing quite like taking a swig of this sumptuous beverage and seeking warm refuge in the delights of a steaming mug. Hot chocolate is as straightforward as drinks go: at its core, it’s milk, cocoa powder, and sugar. Despite its simplicity, this cold-weather classic is swirling with science.

The backbone of any decent hot chocolate is milk. Beyond water, milk is perhaps the most basic and familiar substance to humans. We’re all born drinking some form of it, but how often do we stop and think about its underlying science? Milk is an emulsion, which is a mixture of two immiscible liquids—in this case, water and fat. The water-based component of milk is loaded with vitamins, minerals, and protein and contains immiscible fat globules suspended throughout. How do water and fat coexist peacefully in solution together? The answer lies in emulsifiers, which are molecules that are both water- and fat-soluble. Milk contains proteins, namely casein, that attract and unite the fluids that would otherwise separate. Rich, silky, and chemically intriguing, this dairy product serves as the perfect vehicle for chocolate (1).

Photo credit: Flickr/chocolatereviews

Chocolate serves as the heart of the beverage. Some recipes call for it in the form of cocoa powder. Cocoa powder mixed in with your milk is a colloid—a type of mixture in which solid particles are dispersed throughout a fluid. Another popular culinary colloid you may recognize is coffee, which contains small coffee particles dispersed in water.

Photo credit: Flickr/csb13

A glass of hot chocolate simply isn’t complete with a dollop of whipped cream plopped on top. Lauded for its decadent mouthfeel, cream is an emulsion of butterfat and water, similar to milk but with a higher fat content. Fresh milk left undisturbed will separate into two layers; the top becomes enriched with fat globules that can be skimmed off as cream, leaving behind a relatively fat-free layer—skim milk. Cream and milk have remarkably different fat contents, as cream is required to have at least 30% milk fat compared to whole milk which is a mere 3%.

With some simple agitation, willpower, and a whisk, we can transform heavy cream into whipped cream, a culinary foam. Similar to emulsions, foams combine two immiscible substances, but instead of water and fat, air or gas is entrapped within a fluid or solid. Whisking incorporates air into the cream, and the newly introduced bubbles are held captive by the structure of the foam. Fluids and gases have very different properties, so how does agitation keep them together? Agitation disorients the fat globules and strips away their protective membranes, forcing them to cling to other fat molecules or aggregate around air bubbles—anything to avoid having to be in contact with water. Agitate your cream enough and you’ll wind up with stiff peaks when these fat-encapsulated air bubbles begin to form a stable network (2).

Photo credit: Flickr/knitsteel

Whether they’re being roasted over a campfire or floating lazily on the surface of your hot chocolate, marshmallows are a surefire way to please and are another way to enhance your chocolate-drinking experience. Marshmallows were originally made as a meringue (yet another culinary foam!) consisting of whipped eggs and sugar flavored with the juice from roots of the marsh mallow plant. The making of marshmallows has since evolved so that now they are created by aerating a mixture of simple sugar syrup and gelatin to form a foam that stabilizes once the gelatin sets. Whipping incorporates air bubbles that are trapped in the solid matrix, forming these springy and sugary confections that pair exceptionally well with chocolate (1).

Hot chocolate is the ultimate winter beverage. It’s creamy, decadent and versatile. Drink it plain or spice it up with some chili powder, orange, or peppermint and you’ll surely find a style that will leave you positively foaming at the mouth.

References cited

McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. New York: Scribner, 2004. Print.
Lower, Claire. Cream Science: On Whipping, Butter, and Beyond. Serious Eats. 2014.

About the author: Mai Nguyen is an aspiring food scientist who received her B.S. in biochemistry from the University of Virginia.

Read more by Mai Nguyen

Stinky Tofu

December 8, 2015/in Science & Food/by Grant Alkin

You may be familiar with stinky tofu’s strong, pungent odor that makes you wrinkle your nose in disgust. Although this dish certainly lives up to its name, taking a bite into its crunchy, deep-fried exterior that gives way to warm, firm tofu might just make you a stinky tofu convert. A popular street food in Taiwan, Hong Kong, and parts of China, stinky tofu is a fermented tofu dish that is often deep-fried, drizzled with a salty sauce, and served with a side of pickled vegetables. This dish can also be found simmered in spicy hot pot, grilled on skewers, and mixed into rice porridge. So what is the secret to its stink?

Stinky tofu from Luodong township in Yilan, Taiwan.

It starts with the brine used to ferment the tofu. The conventional process involves adding shelled shrimp and vegetables such as bamboo shoots and Chinese green cabbage to salt water in wide mouth jars. These jars are then exposed to air for several months to allow the brine to undergo natural microbial fermentation that results in its unique stinky smell. Bricks of tofu are then soaked in the liquid for 4-6 hours to develop its flavor [1].

The major bacteria strains that that contribute to the fermentation process include Bacillus sphaericus, Enterococcus gallinarum, Acinetobacter spp., and Corynebacterium spp. [1]. Microbes of the Bacillus genus secrete proteases that hydrolyze, or break down, the tofu proteins into their constituent amino acids (aka the building blocks of proteins) and peptides (molecules made of multiple amino acids) [2]. Two important sulfur-containing amino acids, cysteine and methionine, degrade during the fermentation process and form various sulfides that are responsible for those sulfurous, meaty, and onion odors [3].

Stinky tofu that have been marinated and are ready for deep-frying

If that is not stinky enough, the volatile flavor compound that contributes most to stinky tofu’s smell is indole, which is associated with fecal and animal odors. Less potent flavor compounds include esters, alcohols, aldehydes and ketones, which confer sweet and fruity odors. In fact, a research study analyzing volatile flavor compounds in a sample of fermented stinky tofu identified a total of 39 compounds that contribute to its smell [3]. Considering how molecules become even more volatile when heated (diffusion speeds up with higher temperatures), helps to further explain why you get a burst of stinky odor when stinky tofu is deep-fried [4].

Stinky tofu definitely lives up to its name, but don’t let the smell deter you from trying the dish. After all, if you end up loving it you will never have trouble finding a stinky tofu stand if you just follow your nose!

References cited

Chang, H., Wang, S., Chen, J., & Hsu, L. “Mutagenic Analysis of Fermenting Strains and Fermented Brine for Stinky Tofu.” Journal of Food and Drug Analysis. 9.1 (2001): 45-49. Web.
Stinky tofu. Microbe Wiki.
Liu, Y., Miao, Z., Guan, W., Sun, B. “Analysis of Organic Volatile Flavor Compounds in Fermented Stinky Tofu Using SPME with Different Fiber Coatings.” 17 (2012): 3708-3722. Web.
Hui, Y.H. (2007). Handbook of Food Science, Technology, and Engineering (Vol. 4). Hoboken, NJ: Wiley & Sons, Inc.

About the author: Catherine Hu received 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.

Read more by Catherine Hu

Maple Syrup

December 1, 2015/in Science & Food/by Grant Alkin

Photo credits: flickr/Doug

Nothing sets the tone for a drowsy Sunday afternoon like a breakfast that features maple syrup. This sticky and wonderful syrup fills the nooks and crannies of our nation’s waffles with the taste of autumn and the smell of Canada. Let’s take a moment to appreciate the science that makes maple syrup and its confectionery relatives the crown jewel of breakfast condiments.

Generally, syrups are made by extracting sap from plants and boiling them down so they become a more concentrated and viscous liquid. The sugar maple tree, Acer saccharum produces the sap that can eventually become maple syrup, as it produces sap in greater quantities than other maple varieties.

Optimal conditions for sap harvesting involve extreme temperature fluctuations from day to night. The northeastern United States and eastern Canada, of course, have just the night-day temperature shifts to produce quality maple sap. The traditional sap-seeker drills a small hole into the cambium, or woody tissue, of a maple tree, and inserts a spout. On warm days when temperatures are above freezing, the liquid sap expands and creates positive pressure in the xylem – the plant version of veins; this pressure pushes sap out of the tap hole and into the collection vessel. When night falls and temperatures drop below freezing, sap contracts as all liquids do when chilled. As the sap contracts, this creates negative pressure, which sucks water from the soil into the roots and the tree; this replenishes the sap that has bled out of the tap hole.

Photo Credits: flickr/Chiot’s Run

After harvesting, the harvested sap is boiled down until it has a viscosity of about 150-200 centipoises – a viscosity very similar to that of motor oil. When the liquid has reached this consistency, it has undergone a 40x reduction in volume. The resulting syrup is approximately 62% sucrose, 34% water, 3% glucose and fructose, and 0.5% malic acid, other acids, and traces amounts of amino acids. The distinct and lovely aromatic notes of maple come from wood byproducts like vanillin, other products of sucrose caramelization, and products of Maillard reactions between the plant sugars and the amino acids.

Photo Credits: flickr/LadyDragonflyCC

Another delectable treat from Northern climates is maple sugar. Maple sugar is made by boiling maple syrup (which has a boiling temperature 25-40°F above the boiling point of water, but varies with altitude) to increase sucrose concentration, then letting the syrup cool. Left alone, the sucrose accumulates into coarse crystals that are thinly coated with the remainder of the syrup. Simply put, maple sugar is plain table sugar with a natural coating of maple flavor.

Photo Credits: flickr/cdn-pix

A luxury to smear on your toast or pancake, maple cream is surprisingly simple to make, and despite its name, doesn’t contain any dairy. This delicious creamy spread is a malleable mixture of very fine crystals that are dispersed in a small amount of syrup. Maple cream is made by cooling maple syrup rapidly to 70°F by immersing its container in ice water, then beating it continuously until it becomes very stiff; thereafter it is warmed until it becomes smooth and has the texture and viscosity of a runny buttercream frosting.

Photo credits: flickr/ Anne White

One last note on maple syrup – beware of imposters! If the bottle doesn’t say maple syrup, it is not maple syrup. Breakfast or pancake syrup disappointingly consists of corn syrup and artificial flavors.

Works Cited

“Learn about the Science of Maple Syrup.” Cary Institute of Ecosystem Studies. N.p., 24 Mar. 2013. Web. 25 Nov. 2015.
McGee, Harold. “Sugars and Syrups.” On Food and Cooking: The Science and Lore of the Kitchen. 1st ed. New York: Scribner, 2004. N. pag. Print.
“Viscosity Comparison Chart.” Viscosity Comparison Chart. The Composites Store, n.d. Web. 25 Nov. 2015.

About the author: Elsbeth Sites received 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

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.

Read more by Vince Reyes

Cranberry

November 17, 2015/in Flavor of the Month/by Grant Alkin

Cranberries are harvested in late autumn, just in time to celebrate the holidays. Whether you prefer to enjoy cranberries in a jam, as a sauce from the can, juiced, dried, or fresh, there’s no denying that cranberries are festive. They’re tart, dark red, and pair really well with a turkey dinner (according to science). Read more

Bologna

October 27, 2015/in Science & Food/by Grant Alkin

Photo Credit: flickr/Jazz Guy

Around autumn, students, teachers, and parents may have some big decisions to make. Private school or public? AP calculus or Art History? What to pack for lunch? Often, the answer to that last question is a bologna sandwich. Bologna is the archetypal American sandwich meat – salty, moist, and a bit mysterious.

Bologna is a semisolid meat product made from one or more livestock sources, most commonly beef or pork, and may contain poultry meat. According to the Food and Drug Administration, “[Bologna] may not contain more than 30% fat or no more than 10% water, or a combination of 40% fat and added water. Up to 3.5% non-meat binders and extenders (such as nonfat dry milk, cereal, or dried whole milk) or 2% isolated soy protein may be used, but must be shown in the ingredients statement on the product’s label by its common name.”^[1] In all, you can be sure that at least 45.5% of a given bologna is meat.

Photo Credit: flickr/Anne Mair Valentine

In most other deli meats, the source animal is somewhat apparent through the texture and flavor of the meat (think roast turkey or ham). This is not so for bologna, because the FDA requires that all bologna ingredients be comminuted, or reduced to minute particles so that no lard, collagen, or spices are detectable on the tongue.^[1] Essentially, the result of comminution is a “meat batter”^[1] Most bologna producers don’t reveal the particular spice blend they use, but typical pickling spices like black pepper, coriander, and celery seed will most likely be included, as well as myrtle berries.

A package labeled “Bologna with Variety Meats” can consist of no less than 15% of raw skeletal muscle meat with raw meat byproducts.^[1] Byproducts in this case refer to non-skeletal muscle organs, like heart, kidney, or liver. Bologna of this nature must name the animal species said byproducts were sourced from, and be individually named in the ingredients list.

“Mechanically Separated” means that the meat product contains more than 150 milligrams of calcium per 100 grams of product, whereas a product that falls below this threshold can list the ingredient as “pork trimmings” or “ground pork”, for example.^[1] Some calcium inevitably joins the meat via machinery that separates meat from bone, with incredible efficiency, called Advanced Meat Recovery (AMR). Bones contain both calcium carbonate and calcium phosphate, so the 150mg calcium maximum is intended to ensure bone particulate and dust are not present in the bologna. Through AMR, the bone is to remain intact while meat is scraped, shaved, or forced off through a sieve at high pressure. Pork and poultry may be processed in this way, but regulations do not permit human food to include mechanically separated beef — a precaution against Bovine Spongiform Encephalopathy, or Mad Cow disease.

Principles of Meat Science. 4th ed. Dubuque, IA: Kendall/Hunt

The resulting pulverized/ground up, comminuted meat product is encased in a thin cellulose tube, ranging from about 0.025 mm to about 0.076 mm in thickness^[3], which is manufactured from wood pulp.^[2] They are engineered to have elastic properties similar to natural intestinal casings used for more traditional sausages. The inner surfaces can be coated with dye and smoke flavor that diffuses into the meat product, and antibiotics may incorporated into the casing to stifle bacterial growth.^[2]

We can sing songs of our bologna’s names, we can contemplate the silliness of its pronunciation, but without some research it is difficult to discuss exactly what bologna is. Despite its enigmatic status, I hear it’s quite good when fried.

Works Cited

United States. United States Department of Agriculture. Food Safety and Inspection Service. Hot Dogs and Food Safety. Web. 20 Oct. 2015.

Aberle, Elton David. “Principles of Meat Processing.” Principles of Meat Science. 4th ed. Dubuque, IA: Kendall/Hunt, 2001.

Nicholson, Myron D. Method of Making a Cellulose Food Casing. Viskase Corporation, Courtaulds Fibres Limited, assignee. Patent US 5277857 A. 11 Jan. 1994. Print.

About the author: Elsbeth Sites received 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

Nutmeg

October 21, 2015/in Flavor of the Month/by Grant Alkin

Nutmeg is a key note in October comfort favorites such as pumpkin spice lattes and spiced bread. The spice is warm, sweet, and spicy, perfect for the gradually colder days of autumn. Take a closer look at nutmeg, however, and you might find a disquieting surprise. Are you prepared to take a whiff of nutmeg science? Read more