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Sandor Katz

Sandor Katz, a self-proclaimed fermentation revivalist, became hooked on fermentation with his first homemade batch of sauerkraut, earning him the nickname “Sandorkraut”. As an AIDS survivor, he considers fermented foods an important part of his health and well-being. His 2003 book, Wild Fermentation, was lauded by Newsweek as the “fermentation bible”, and his 2012 book, The Art of Fermentation, received a James Beard award and was a finalist at the International Association of Culinary Professionals. In 2014, Katz received the Craig Claiborne Lifetime Achievement Award from the Southern Foodways Alliance.

See Sandor Katz May 11, 2016 at “Microbes: From Your Food to Your Brain”

Sandor Katz

What hooked you on cooking?
I’ve always loved eating, and my parents both cooked and we were always expected to help in the kitchen. I got especially interested in cooking from scratch, and understanding and experiencing how the raw products of agriculture are transformed into the foods we love to eat.
The coolest example of science in your food?
Our food is all biology and chemistry. Of course, I am most tuned into the biological processes, though at a certain level they break down to chemistry. One question that I have thought a lot about is: Why is fermentation practiced everywhere? I do not know this to be absolute fact, but I have been unable to find any counter-example. And the reason that we now understand is that all of the plants and animal products that make up our food are populated by elaborate microbial communities. Microbial transformation of our food is an inevitability and the question is how do we deal with that fact.
The food you find most fascinating?
I’m endlessly fascinated by kefir, a fermented milk, or rather by the culture that produces it, undulating rubbery masses known as kefir grains. These symbiotic communities of bacteria and yeast (SCOBIES) are incredibly complex, with more than 30 distinct organisms that have been identified.
What scientific concept–food related or otherwise–do you find most fascinating?
Co-evolution. How we have evolved with plants and microorganisms and how they have influenced what we are and how we have influenced what they are, and how each of these organisms has influenced the others. All the foods that’ve been interested in come about as a result of these co-evolutionary relationships.
Your best example of a food that is better because of science?
Certainly fermentation is better understood because of science, and it is possible thanks to science to replicate particular ferments in environments other than those in which they emerged as spontaneous outcomes. However, it is important to note that science has had negative effects on fermentation practices as well as positive ones. The presumption that large undefined communities of organisms are dangerous has led to the replacement of traditional starter cultures with pure culture starters that cannot easily be perpetuated, thus diminishing the ability of home, village, or small-scale producers to perpetuate cultures and thereby breeding dependence on starters purchased from a lab for each batch.
How do you think science will impact your world of food in the next 5 years?
I’m very excited by all the new findings in microbiology, especially our emerging understandings of microbial communities in different environments and their complex interactions. My hope is that our growing understandings of the functional importance of microbial communities will help us move beyond the war on bacteria, and embrace bacteria as our ancestors, allies, and greatest protection.
One kitchen tool you could not live without?
My crocks! Vessels are the most basic of kitchen tools.
Five things most likely to be found in your fridge?
Milk, yogurt, starter cultures, beer, miso. Kraut and kimchi might be in the fridge, or might be on the counter.
Your all-time favorite ingredient? Favorite cookbook?
Brussels sprouts, along with almost any cruciferous vegetable. They are so delicious and versatile! I like to check out cookbooks and explore recipes from diverse sources, but Joy of Cooking is my enduring go-to.
Your standard breakfast?
I love to use my sourdough starter to make savory vegetable sourdough pancakes, incorporating almost any vegetables, leftover grains if I have them, and cheese, topped off with fried eggs and yogurt-hot sauce.

Inside the Experimental Cuisine Collective

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Robert Margolskee, Mitchell Davis, Florence Fabricant, Wylie Dufresne, and Hervé This at the Experimental Cuisine Collective’s launch workshop on April 11, 2007. Photo credit: Antoinette Bruno (Star Chefs)

 

Launched in 2007, the Experimental Cuisine Collective (ECC) has proven itself as an invaluable resource for those interested in learning about the scientific principles behind food. Founded by Drs. Kent Kirshenbaum and Amy Bentley of New York University in collaboration with Chef Will Goldfarb of WillPowder, the ECC hosts workshops approximately five times per year, each featuring different topics and/or speakers. ECC’s current Director is Anne McBride, a PhD candidate in Food Studies at NYU and Culinary Program/Editorial Director for the Culinary Institute of America. Widely recognized for her ability in establishing connections between scientists and chefs, McBride has been instrumental in developing ECC’s programs. ECC’s workshops have gained nationwide acclaim, featured in media outlets such as Serious Eats, New York Observer, and even the Food Network!

The impressive roster of past ECC speakers include renowned chefs and scientific minds such as Dan Barber, Wylie Dufresne, Rachel Dutton, and Mark Bomford. The topics of ECC workshops are also interestingly diverse, covering topics from soda politics with Marion Nestle to cooking insects with the Yale Sustainable Food Project to the New York Academy of Medicine’s Eating Through Time conference.

Our recent Science & Food public event featured Dr. Kent Kirshenbaum , who stopped to answer a few questions for us about the ECC:

What motivated you to start the Experimental Cuisine Collective?
I was asked by the National Science Foundation to consider establishing a science outreach program as part of their emphasis on “Broader Impacts” of scientific research. I’ve always been eager to establish connections between scientists and experts from other disciplines, so exploring the terrain between chemistry and cuisine came about very naturally.
What has been one of your most memorable experiences since founding the site?
The Experimental Cuisine Collective has always been more about direct engagement rather than as a web-based portal for information. One of my most memorable experiences with the ECC was preparing an alginate-based mango-juice pearl with a 4th grade student at a science fair.  I asked her if we were doing science or cooking. After a moment’s careful thought she replied, “I guess it’s both!” That was a very satisfying moment.

Another memorable experience was giving a lecture series about the ECC throughout New Zealand during the “International Year of Chemistry”. The director of the ECC, Anne McBride, and I got the chance to prepare what we believe were the world’s first vegan pavlovas for our audiences throughout New Zealand. We love Kiwis!

What do you hope the Experimental Cuisine Collective’s readers take away from the website?
I think they are excited about the lecture programs we are offering at NYU, and the opportunity to learn what science can contribute to cooking — along with how chefs can advance scientific objectives. Plus, I hope readers are quick to appreciate that we have been offering our programs for almost 10 years, and all of it has been completely free of charge!
Are there any upcoming projects you would like people to know about?
Our upcoming meeting will be devoted to hydroponic farming, in partnership with the Institute of Culinary Education. We will be meeting at ICE’s indoor 540-square-foot farm in lower Manhattan, designed by Boswyck Farms, which has 3,000 plant sites and in which 22 crops are currently growing. The amazing thing about this farm is that it is literally across the street from the tallest building in the Western Hemisphere. Science can help us grow in so many ways and places!

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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Kent Kirshenbaum

Dr. Kent Kirshenbaum received his PhD in Pharmaceutical Chemistry at UCSF, is an NSF Career Award recipient, and is currently a professor of Chemistry at NYU. His research focuses on the creation of new peptide-based macromolecules that can be used as research tools or therapeutic strategies. In 2012, he filed a patent for a foaming agent which acts as a vegan substitute for egg whites, making vegan meringues a delicious possibility.

See Kent Kirshenbaum March 8, 2016 at “The Impact of What We Eat: From Science & Technology, To Eating Local”

Kent Kirshenbaum

What hooked you on cooking?
Spending time with my mom got me hooked on cooking. She exemplified the “slow food” concept, and she’d take days to make a pasta sauce. I grew up in a drafty house in San Francisco that was cold all year around, and being near her at the stove was the warmest place to be. Once my wife and I had kids, I realized how satisfying it was for me to provide my family with sustenance through cooking and culture through cuisine.
My dad got me hooked on science. He studied metallurgy and worked for a mining company. He would go on business trips and bring me back samples of different minerals to play with. It was kind of like the situation described in the book “Uncle Tungsten” by Oliver Sachs.
The coolest example of science in your food?
Mayonnaise. You take two immiscible liquids – oil and water, and find a way to get them to mix. How do they do that?? Add an emulsifier, provide some energy and voila! It’s just a shame the product itself is so repugnant.
The food you find most fascinating?
Fermented butters. Such as smen, the fermented butter of North Africa and “bog butter” from the British Isles.
What scientific concept–food related or otherwise–do you find most fascinating?
I’m fascinated by the relationship between the sequence, structure and function of proteins.
In the kitchen, transglutaminase — also known as meat glue — is a compelling example of enzymology. Nixtamilization is an amazing concept, and the word “nixtamilization” itself is like a really short poem.
Your best example of a food that is better because of science?
Either Pop Rocks or the clean water that comes out of my home faucet. Although I’m not sure either of them really qualify as a foodstuff.
We love comparing the gluten in bread to a network of springs. Are there any analogies you like to use to explain difficult or counter-intuitive food science concepts?
When explaining specificity in the sensory perception of food, I use the “lock in key” analogy to describe how ligands engage protein receptors. Although the analogy is imperfect, it begins to get the idea across.
How does your scientific knowledge or training impact the way you cook? Do you conduct science experiments in the kitchen?
Because I am trained as a chemist, I am fastidious about following a published protocol (recipe) and I tend to be absurdly precise about volumes. I love experimenting with food – we filed a patent application on new way to make vegan meringues. But when it comes to cooking at home I tend to be a traditionalist.
One kitchen tool you could not live without?
My home water carbonation system. I love sparkling water that I can generate from the New York City public water supply and doesn’t need to be shipped from a European spring.
Five things most likely to be found in your fridge?
Harissa, capers, preserved sour cherries, home-made stock and parmesan cheese. I get anxious if my supply of Reggiano is running low.
Your all-time favorite ingredient? Favorite cookbook?
I’m a spice guy. Right now I’m fixated on sumac and cardamom. My favorite cookbooks is “Where Flavor Was Born” by Andreas Viestad which explores how spices are used across the region of the Indian Ocean. It inspired me to visit a cardamom plantation in Kerala, India.
Other favorites include “In Nonna’s Kitchen” and “Cucina Ebraica”, because these books connect me to the memories of my mother and her mother.
Your standard breakfast?
A cup of black coffee and a baked good that I enjoy on my walk from home to my lab. New Yorkers have a bad habit of walking and eating. On the weekends, bagels and smoked salmon. No doughnuts. Never a doughnut. Maybe a beignet. But only in New Orleans.

Maple Syrup

Photo credits: flickr/Doug

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.

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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

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

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

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

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

  1. “Learn about the Science of Maple Syrup.” Cary Institute of Ecosystem Studies. N.p., 24 Mar. 2013. Web. 25 Nov. 2015.
  2. 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.
  3. “Viscosity Comparison Chart.” Viscosity Comparison Chart. The Composites Store, n.d. Web. 25 Nov. 2015.

Elsbeth SitesAbout 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.

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Deep-fried Turkey: Delicious or Dangerous?

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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?

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[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.

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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

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

Vince ReyesAbout 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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Structural Changes in Chocolate Blooming

Is there anything more disappointing than finding a chocolate bar in the back of the desk drawer, anticipating a tasty treat, then unwrapping the bar only to find a dull, grey haze has overtaken your dear candy? Seeing as bloomed chocolate is still edible, yes, there are many things more disappointing than that. But surely you’re curious about how chocolate that was once shiny and perfect came to be filmy and rough. Chocolate blooming, the process that produces the white-grey film that appears on the surface of an old chocolate, is due to molecular migration. More specifically, this imperfection is caused by the movement of fats to the surface of the chocolate followed by a subsequent recrystallization. In a paper published by Applied Materials & Interfaces, a team of researchers dedicated to keeping our chocolates blemish-free has clarified the precise mechanisms that cause chocolate blooming.

The main fat in chocolate is cocoa butter, which is solid at room temperature and melts at 37 degrees Celsius. The proportion of solid to liquid cocoa butter depends on the lipid composition, which depends on which specific triglycerides are present. The solid to liquid proportion also varies with the storage conditions of the chocolate.

As proposed by Aguilera et al, scientists who study this chocolate blooming, consider chocolate as a particulate medium of fat-coated particles such as cocoa solids, sucrose, and milk powder, all suspended in a fat phase with the aid of an emulsifier, which helps to mix fats and oils with water, which usually repel each other. There are six crystallographic polymorphs of cocoa butter molecules, that is, there are six ways the molecules can organize themselves. The structural stability of these polymorphs increases from 1- 6; form 1 is the best at forming solid butter at room temperature, while form 6 tends to arrange in the loose bonds of a liquid. Form 5 is the main form in chocolate, as it possesses the most aesthetically desirable properties. While the phenomenon of blooming is well known to result from melting and recrystallization of chocolate into a less desirable polymorph, it has been unclear how fat moves through the chocolate particle network: Does it move along the fat-particle interface? Does it diffuse through the fat phase (cocoa butter), or through the matrix of assorted particles?

Possible lipid migration pathways in chocolate - Reinke et al

Possible lipid migration pathways in chocolate – Reinke et al

In this experiment, researchers used synchrotron microfocus small-angle X-ray scattering to determine the preferential migration pathway of the cocoa butter molecules surrounded by three different soild components (cocoa solids, skim milk, and sucrose). This technique allows researchers to record the scattering of x-rays through a sample with defects in the nanometer range. They can then extrapolate information about the material’s macromolecules, their shapes and sizes up to 125 nanometers, and distances between partially ordered materials, such as pore sizes. For this experiment, this method is better than more traditional macroscopic techniques as the sample does not need to be dissected in order to examine it, therefore the same sample can be continually analyzed.

Sketch of the experimental setup - Reink et al

Sketch of the experimental setup – Reink et al

The researchers prepared and tempered four different chocolate samples. An initial scattering of x-rays and data collection was performed before the addition of sunflower oil, then 10 uL of oil was pipetted onto the chocolate surface, and a second scan was performed. Images of the droplet were captured through a high-speed camera. These scans were repeated at 5, 10, and 30 minutes after oil addition, and again after 1, 2, 5, and 24 hours.

The results obtained suggest that oil is migrating through pores and cracks in the solid structure driven by capillarity within seconds. This means that the oil can flow in narrow spaces in opposition to gravity. Then chemical migration through the fat phase occurs. The oil doesn’t traverse the fat-particle interface, nor does it move through the matrix of solid particles. This migration disrupts the crystalline cocoa butter, which induces softening.

Because the most immediate migration of oils occurs through the material porous structure, the formation of chocolate bloom could be prevented by minimizing pores and defects in the chocolate matrix. To prevent the longer-term effects of chemical migration of lipids, one must minimize the content of non-crystallized liquid cocoa butter. Tempering chocolate lends to crystalline structures that resist migration, as will reducing the liquid fat content. However, to ensure that you never encounter a sad hazy chocolate again, we recommend eating all chocolate goods expeditiously.

Works Cited

  1. Tracking Structural Changes in Lipid-based Multicomponent Food Materials due to Oil Migration by Microfocus Small-Angle X-ray Scattering. Svenja K. Reinke, Stephan V. Roth, Gonzalo Santoro, Josélio Vieira, Stefan Heinrich, and Stefan Palzer. ACS Applied Materials & Interfaces 2015 7 (18), 9929-9936. DOI:10.1021/acsami.5b02092
  2. Aguilera, J. M.; Michel, M.; Mayor, G.Fat Migration in Chocolate: Diffusion or Capillary Flow in a Particulate Solid?—A Hypothesis PaperJ. Food Sci. 2004, 69, 167–174

 


Elsbeth SitesAbout 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.

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Freezer Burnt Meat

Photo credit: flickr/Steven Depolo

Photo credit: flickr/Steven Depolo

Freezing is an indispensable tool in modern cooking and eating. The biochemical processes that typically occur in meats cause decay, fat oxidation, and rancidity; the higher the temperature, the faster these reactions occur. Thus, we can largely thwart off these undesirable processes by keeping meat chilled. But tossing meat into the freezer rarely results in rainbows, sunshine, or perfect burger patties, because strangely enough we can also accelerate meat decay with cold. Freezer burn can take a beautiful filet mignon and turn its surface into a leathered, unappetizing slab.

Freezer burn is caused by water sublimation from ice crystals at the meat’s surface into the dry freezer air. Sublimation occurs when a solid substance undergoes a phase change and becomes a vapor without first passing through the liquid phase. The ice crystals on the meat surface sublimate, and leave behind tiny cavities. These tiny yet numerous cavities increase the surface area of the meat and expose more tissue to the air. This accelerates oxidation of fats, which causes the rancid flavors of old spoiled meat. We usually describe oxidized fats as simply tasting “off,” which is a vague term but seems apt if you’ve ever tasted lipids past their prime, perhaps by using shortening that has been in the pantry since you were a toddler.

Photo Credit: flickr/Marcus Ward

Here, solid ice crystals directly vaporize without first passing through the liquid phase. Photo Credit: flickr/Marcus Ward

In addition to the surface area increase caused by sublimation, the freezing process itself lends itself to fat oxidation. When the liquid water in meats crystallize in the cold, the concentrations of oxidizing salts and trace metals in the tissues increases. Unfortunately, oxidation can occur over time even in wrapped and frozen meats. Some oxygen will inevitably remain in contact with the meat, unless we create a vacuum seal.

Once meat has been damaged by the cold, there’s no undoing the oxidation. So either we plan our meals so that meats are cooked immediately after purchase, or we learn to prevent the sublimation that ruins both our pork chops and our days. We simply need to keep water crystals inside the meat and keep oxygen out. Using a vacuum sealer is our best bet for avoiding freezer burn, but for cheapskates like me who won’t shell out the $30 for the sealing device, a water-impermeable plastic wrapped tightly around the meat works well enough for most home chefs.

Thus meat is sealed away happily in plastic, free from villainous oxygen. Photo credits: flickr/Mike

Thus meat is sealed away happily in plastic, free from villainous oxygen. Photo credits: flickr/Mike

References cited

  1. McGee, Harold. “Meats.” McGee on Food & Cooking: An Encyclopedia of Kitchen Science, History and Culture. London: Hodder & Stoughton, 2004. N. pag. Print.
  2. “Sublimation.” The Columbia Electronic Encyclopedia. Columbia University Press, 2012. Web. 20 July 2015.

 


Elsbeth SitesAbout 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.

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Physiology of Foie Gras

Photo Credits: (flickr/Ulterior Epiculture)

Photo Credits: (flickr/Ulterior Epicure)

Decadent, diseased, silky, sinful. The adjectives that follow foie gras range from the disgusting to the luxurious. The fattened liver of a duck or goose polarizes people, and there seems to be no middle ground wherein a person can both enjoy foie gras and ethically question it. Because it is such a controversial food, the discourse surrounding it is often steeped in emotion, but the best way to make an informed, fact-based decision is through science. Here we will examine physiology, pathology, and a bit of genetics regarding waterfowl and foie gras in an attempt to promote overall awareness of what we eat (or don’t eat).

Foie gras is French for fatty liver, and that is exactly what it is. The liver of a bird, usually a duck or sometimes a goose, that has been force-fed to the point of having a fat, enlarged liver. The liver must weigh more than 300g for ducks, and 400g for geese to legally bear the name foie gras in France. [1] Force-feeding is typically done through a practice called gavage, wherein a long tube is inserted into the bird’s mouth and throat up to three times a day for 3-10 days. French rural code L654-27-1 states that “Foie gras belongs to the protected cultural and gastronomical heritage of France.”[2] Currently, the farming of animals to produce foie gras is banned in 22 EU nations, but not its sale or import. In California, the sale of foie gras was banned in 2004, the ban was lifted in early 2015 by a federal court, and the lifting of that ban is currently being appealed. [3] Needless to say, it’s a very complicated issue.

Photo Credits: (flickr/Pickled newt)

Photo Credits: (flickr/Pickled newt)

Foie Gras Physiology

Many bird species, including ducks and geese, eat prey much wider than the diameter of their esophagus. Consequently, the inner diameter of the upper part of the esophagus is comparatively larger than in mammals. [4] Also unlike mammals, the upper esophagus is not circled by cartilaginous rings, which explains how birds swallow whole, live fish with ease. In humans, the upper esophageal sphincter is a high-pressure zone situated between the pharynx and the cervical esophagus. The sphincter is composed of muscle, cartilage, and bone, [5] and thus is much more rigid than the upper esophagus of a waterfowl. Most birds species posses an “outpouching” of the esophagus, known as the crop. It also allows the birds to store large amounts of food before sending it along to the stomach for digestion. [4]

Another important difference in human and duck anatomy is the trachea. In humans, food and air start along the same path in the mouth, then the trachea (or windpipe) branches off at the back of the throat where the epiglottis prevents food from entering the trachea and channels swallowed food along its proper route, the esophagus. Try to force something past the epiglottis, and you trigger the unpleasant pharyngeal reflex, or gag reflex. Certainly a gavage would trigger this in a human, which is one reason why images of force fed birds make us so uncomfortable. Foie producers say if the procedure is carried under proper conditions, the gavage does not block the upper respiratory tract as the birds’ tracheas and esophaguses are completely separate, [6] and thus they do not gag or feel discomfort as a human would. However, foie gras critics rebuke that this is a ridiculous excuse, and that the birds are clearly harmed by the gavage.

Ducks and geese are sometimes reported to be panting when observed in a foie-farm. But before we assume they do so because they’re in distress, we should keep in mind that like a dog, panting in birds is a thermo-regulatory reflex. [4] Humans have sudoriferous glands (sweat glands) that discharge sweat to take care of latent heat, but birds do not. They regulate body temperature by opening their beaks and panting to cool down. Researchers have examined whether other avian behaviors are indicators of distress, like avoidance behavior, elevated heart rate, or elevated cortisol (stress hormone) levels. They report that force-feeding does not stress the birds more than typical capture and handling does. [1] [Side note: Most of this research was conducted by the same group of scientists from the French National Institute for Agricultural Research, so it would be helpful to have experiments performed by more organizations.]

Photo Credits: (flickr/Jeremy Couture)

Photo Credits: (flickr/Jeremy Couture)

Pathology

In mammals, hepatic steatosis (fatty liver) is a pathological condition. Human fatty liver occurs when there is an imbalance of fat uptake and export in the liver, most often caused by alcoholism, malnutrition, obesity, or diabetes. On its own, hepatic steatosis is not harmful and can be reversed, but if not addressed with dietary and lifestyle change it can develop into cirrhosis, wherein the healthy liver tissue is replaced by scar tissue, or necrosis (tissue death). Indeed, foie gras in a human is a disease. [7]

Certain metabolic adaptations in migratory birds and fish cause a natural hepatic steatosis, and proponents of foie gras use this observation to argue that the condition is not pathological in those species. These animals must compile large energy stores for their migrations, and they do so by ingesting carbohydrates and storing the energy as fat, a process called lipogenesis. [8] Foie producers posit that they are simply exploiting the incredible lipogenetic abilities of the fowl liver. The human liver does no more than 30% of our entire bodies’ lipogenesis, as our adipose tissue carries most of the workload. [9] By contrast, the avian liver performs the vast majority of their lipogenesis, up to 96% of it in some species. [10] To further their argument that their birds are not diseased, foie farmers assert that it is in their best interest to avoid producing diseased livers, as they are of no commercial value.

Photo Credits: (flickr/Jay Tong)

Photo Credits: (flickr/Jay Tong)

Genetics of the Muscovy Duck

In addition to the anatomical and physiological aspects of waterfowl that may make the production of foie gras seem less cruel, a look into the breed may provide further insight. Foie gras is made from the liver of the Moulard duck, which is the product of a female Pekin artificially inseminated with the sperm of a male Muscovy duck. [1]The Moulard, or “mule duck” genotype is not present in the wild, and like other hybrid species, it is sterile. Therefore, the animals themselves cannot breed more baby Moulards.

Muscovies are non-migratory, [11] so unlike migratory species, in natural settings they do not gorge themselves to put on extra fat to carry them through long periods of physical exertion with no breaks to replenish energy. It might seem like they would be a poor choice for duck farming, but they are prized for their well-flavored, lean meat.

Pekin ducks on the other hand have many of the characteristics of migratory species. They are naturally gregarious and clump themselves together whether or not they have space to roam. [11] Years of breeding have made them very plump and small-winged, and thus they no longer migrate. However, their inner organs and basic metabolism still maintain characteristics of migratory waterfowl. The moulard thus exhibits the more desirable behavioral features of the two species. Like muscovies, they have no migratory instincts, so they are easy to farm-raise. But they retain all of the anatomy and metabolism of Pekins that naturally make them want to gorge and store energy as fat.

Photo Credits: (flickr/Taylor149)

Photo Credits: (flickr/Taylor149)

In this physiological context, gavage and foie gras might not be as tortuous as some imagine it to be. Even with this information, some people may still feel uncomfortable with the idea of force-feeding, and that is perfectly reasonable. If we want to eat foie gras entirely guilt-free, perhaps we should support the production of “humane” foie gras, where the animal is left to gorge on its own as if it were preparing for migration. Examining foie gras through a scientific lens teaches us to evaluate the animal body for its natural capabilities, but science does not always give us clear answers as to what is morally right. Regarding foie gras, the jury is literally still out.

References Cited

  1. Guémené, Daniel, Gérard Guy, Jérôme Noirault, Nicolas Destombes, and Jean-Michel Faure. “Rearing Conditions during the Force-feeding Period in Male Mule Ducks and Their Impact upon Stress and Welfare.” Animal Research 55.5 (2006): 443-58. Web.
  2. “Legifrance – Le Service Public De L’accès Au Droit.” Code Rural Et De La Pêche Maritime. N.p., n.d. Web. 19 Feb. 2015
  3. McClurg, Lesley. “The Legal Battle Over Foie Gras Continues.” – Capradio.org. Capital Public Radio, 9 Feb. 2015. Web. 19 Feb. 2015.
  4. Guémené, Daniel, Gérard Guy, Jacques Servière, and Jean-Michel Faure. “Force Feeding: An Examination of Available Scientific Evidence.” Artisan Farmers Alliance (n.d.): n. pag. Artisanfarmers.org. Web.
  5. Kuo, Braden, and Daniela Urma. “Esophagus – Anatomy and Development.” GI Motility Online (2006): n. pag. Web.
  6. http://onlinelibrary.wiley.com/store/10.1111/j.1740-8261.1991.tb00087.x/asset/j.1740-8261.1991.tb00087.x.pdf?v=1&t=i5inm4hl&s=a129cb6b04b350dfd5778a83eaaea1f2f0fb02a0
  7. Jaeschke, Hartmut, Jaspreet S. Gujral, and Mary Lynn Bajt. “Apoptosis and Necrosis in Liver Disease.” Liver International 24.2 (2004): 85-89. Web.
  8. Pilo, B., and J.c. George. “Diurnal and Seasonal Variation in Liver Glycogen and Fat in Relation to Metabolic Status of Liver and M. Pectoralis in the Migratory Starling, Sturnus Roseus, Wintering in India.” Comparative Biochemistry and Physiology Part A: Physiology 74.3 (1983): 601-04. Web.
  9. Timlin, Maureen T., and Elizabeth J. Parks. “Temporal Patterns of De Novo Lipogenesis in the Postprandial State in Healthy Men.” The American Journal of Clinical Nutrition 18.1 (2005): 35-42. Web.
  10. Desmeth, M., M. Messeyne, G. Schuermans, J. Vandeputte-Poma, and F. Vandergeynst. “Effect of Age and Diet on the Fatty Acid Composition of Triglycéridesand Phospholipids from Liver, Adipose Tissue and Crop of the Pigeon.” The Journal of Nutrition 111 (1980): n. pag. Web.
  11. Lopez, Kenji. “The Physiology of Foie: Why Foie Gras Is Not Unethical.” Serious Eats. N.p., 16 Dec. 2007. Web. 18 Feb. 2015.

Elsbeth SitesAbout the author: Elsbeth Sites is pursuing 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.

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Bar Stools and Molecules: Buttery Nipple Science

[Photo Credit: Vince C Reyes]

[Photo Credit: Vince C Reyes]

You may think a buttery nipple is just a fun shot to buy a friend on his or her birthday, but it’s more complex than that. It’s got layers… specifically two. For those not familiar with the bar classic, the buttery nipple is composed of a layer of Irish cream sitting on top of butterscotch schnapps.

Buttery Nipple Shot Recipe

½ oz. Irish cream
1 oz. Butterscotch schnapps

  1. Pour 1 oz. of Butterscotch schnapps into a chilled shot glass.
  2. Carefully pour ½ oz. of Irish cream onto the back of a downturned spoon so it rolls from the spoon and floats on the surface of the schnapps.
  3. Enjoy!

This and other layered shots like the American flag, the B-52, and the Alien Brain Hemorrhage, take advantage of the slight differences in density among spirits. As density, a substance’s mass per unit volume (Density = mass / volume), dictates the layering in these drinks; the most dense liquid is placed at the bottom followed by progressively less dense liquids. In the case of the buttery nipple, the less dense Irish cream floats on the more dense butterscotch schnapps. If you were to reverse the order with the butterscotch schnapps poured on the Irish cream, the layers would not form. The more dense butterscotch schnapps would sink to the bottom of the glass and result in a mixture of the two spirits.

For the home bartender looking to make new layered drinks, the absolute density of a spirit is not always easy to measure. However, a different quantity, specific gravity, is often available online1. Specific gravity is the ratio of the density of substance to water (specific gravity = density of a substance / density of water). Water has a specific gravity of 1.0. More dense liquids have specific gravities greater than 1.0 and less dense liquids have specific gravities less than 1.0. In the case of the buttery nipple shot, butterscotch schnapps (Dekyper’s ButterShots) has a specific gravity of 1.12 while Irish cream (Bailey’s) has a specific gravity of 1.06.1 The specific gravity is often available online for alcoholic beverages because it is important in the fermentation and distillation process, and different beers, wines, and spirits have characteristic specific gravities.

If the specific gravity of an alcoholic beverage cannot be found, some recommend using proof or alcohol by volume (ABV) to layer drinks. Both are mandated on all alcoholic beverages sold and therefore easy to find. In general, proof is the amount of alcohol in a beverage. Specifically in the US, proof is defined as twice the percentage of the alcohol by volume. The alcohol in any beverage you drink is ethyl alcohol, also called ethanol (C2H6O).

Figure 1: Molecular Formula of Ethanol [Image Credit: Vince C Reyes]

Figure 1: Molecular Formula of Ethanol [Image Credit: Vince C Reyes]

At room temperature (77°F or 25°C), ethanol has an absolute density of 789.00 kg/m3 and a specific gravity of 0.7872. As many alcoholic spirits are primarily a mixture of ethanol and water, which has an absolute density of 999.97 kg/m3 and specific gravity 1.0, greater alcohol content can often correspond to a smaller density. For example in the case of the buttery nipple, Irish cream (Baily’s) is 17% ABV, while Butterscotch schnapps is 14.8% ABV. Therefore, the higher alcohol content and corresponding lower density of the Baily’s Irish cream allows it to sit on top of butterscotch schnapps. This shortcut, however, is not always correct as many spirits have ingredients other than water and ethanol. Many spirits contain cream, sugars, or other flavoring agents, which can change their densities, making alcohol content an imperfect proxy for density. For example, Smirnoff’s flavored vodkas all have 35% ABV, but have varying specific gravities: citrus vodka has a specific gravity of 0.96, while the more dense watermelon vodka has a specific gravity of 0.981.

Figure 2: Layering in a Buttery Nipple.  *ABV is not always an indicator of density. [Image Credit: Vince C Reyes]

Figure 2: Layering in a Buttery Nipple.
*ABV is not always an indicator of density. [Image Credit: Vince C Reyes]

Lastly although other factors such as altitude affect density, temperature is the other most relevant factor for an aspiring bartender. Liquids are denser when cold. Temperature is an indicator of the speed of molecules within a substance. At low temperatures, liquids have slower moving molecules that pack closer together resulting in greater mass per volume. In contrast, at higher temperatures, molecules in liquids move around more quickly and take up less space resulting in a reduced density. For example, water near room temperature (70°F [21°C]) is less dense (0.998 g/cm3), than water near freezing (1.000 g/cm3 at 39.2 °F [4.0 °C])3. This is why using chilled spirits, glass wear, and spoons when making a layered shot can ensure that spirits remain at their densest and form layers.

Ultimately, a great layered shot is one that is not only effectively layered, but also delicious. If you don’t enjoy the buttery nipple, you now have the scientific knowledge to experiment with your own concoctions!

Learn more

  1. Specific Gravity of Different Spirits from GoodCocktails.com
  2. Specific Gravity of Other Liquids from Engineering Tool Box
  3. The Density of Water at Different Temperatures from the US Geological Survey

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

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5 Things About Taste

At our 2014 public lecture How We Taste, Chef Wylie Dufresne, Dr. Dana Small, and Peter Meehan explored the tantalizingly complex concept of flavor. The evening was full of scientific discovery, childhood memories, and culinary innovation. In honor of this enlightening event, here are 5 things you might not know about our sense of taste:

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