Guest post by Steven Du
Paste, the Latin Late antiquity translation for the word Pasta.  Eating spaghetti and meatballs today typically involves boiling some dried spaghetti pasta and pouring on some pasta sauce from a jar. But have you ever wondered how to make these golden silky strands? To start off, we have to sail to China with Marco Polo and learn about the origins of Bing.
Bing is Chinese for wheat products and dumplings.  W’re starting off in China because that’s actually where noodles come from. Despite wheat being grown in the Mediterranean long before arriving to China, the northern Chinese were the first to develop the art of making noodles with it.  As the great age of exploration got underway, many of the noodles from China were brought to the Mediterranean and Middle East by the explorer Marco Polo. Yes, Marco Polo brought the art of noodle making to European nations!
The art and science of noodle making isn’t as complex as it seems, considering that dried noodles can be found in many kitchen cupboards around the country. To knead our way into noodle heaven, we must a start off with gathering our raw materials. The essential ingredient in noodles is flour, which can come in varying forms like rice flour and durum flour (used to make pasta). Each of these flours are special in their own way; for instance, rice flour lacks the gluten proteins that are abundant in wheat, but rather relies on amylose as a binding agent. Proteins like gluten are essential for pasta because they provide the foundation of the pasta’s unique texture and elasticity. Specifically, durum pasta dough is elastic and stretchy because of the gluten protein networks that are formed in the dough. Gluten is a protein complex made of glutenin and gliadin and is found in many wheat products; this protein network gives flour its ability to stick together and form a unified structure that’s up to the task of being boiled without falling apart. 
In comparison, starches lack the proteins that form pasta. Instead, the polysaccharides amylose and amylopectin provide the structure in things like rice noodles. These compounds function like to gluten and gliadin to provide networks of structure in noodles. Specifically, when the starches are combined with water, they form a paste like durum pasta, and when boiled in water the starches form a crystalline continuous network like pasta. However, unlike pasta, starch noodles can be translucent because of the lack of insoluble proteins or intact starch granules to scatter light.  Rice noodles, like starch noodles, are gluten-less, but they do contain cell walls and proteins that create a white noodle. The structure of rice noodles is due to amylose and amylopectin as well. The raw materials necessary for noodle/pasta making are amylose or starch, water, and maybe some protein or fat. With such ingredients available anyone can make pasta/noodles at home.
Key ingredients for making pasta:
Flour, Rice Flour, or Starch: Produced by the process of milling, whereby the grinding and turning of wheat grains, rice, or starches converts them into fine particulates . There are many variations of wheat flours, but enriched and refined flours are the result of filtering of the germs of wheat grains to leave the white flour . In addition to pasta, flours create multitudes of pastas and pastries.
Water: The hydration solvent needed to bring together all the flour and other ingredients. Water hydrates the flour and makes up about 30-40% of the pasta. When the flour is combined with the water, it forms a homogenous mass that is malleable enough to be shaped into strands of pasta/noodles. After the mixture is combined, we have to allow the mixture to rest to hydrate the gluten and form a gluten network that provides the pasta its elasticity and structure to be shaped into pasta/noodles.
Egg: The amazing binding abilities of eggs also contribute to pasta texture. What makes egg pasta different from just regular wheat flour pasta and water? To start off, the golden color and silky texture outshine any regular pasta. While gluten supplies a small percentage of protein, egg provides additional proteins in the mixture that contribute to an even more tender and delicate texture. Within the protein-rich yolk is beta-carotene which provides the yellow hue we see in all our pasta in the kitchen. Alternatively, you can omit the eggs, and just do water and flour as this has enough of the binding mechanisms needed to form the cohesive mass, but it is recommended to add eggs for the decadence and taste.
To begin making fresh pasta, one must form a paste with flour. To allow the gluten proteins to reabsorb water, the paste should rest for about 30 minutes, enough for the mass to be malleable to be shaped into sheets.  The dough is then rolled out and formed into sheets to create long strands of pasta or shaped into your preferred pasta shape. Could be flat noodles, round noodles or flat pieces that are shaped into ears or butterflies.
While the process of making fresh pasta is very simple, dried pasta provides a convenient and tasty alternative. Dried pasta is simply made by dehydrating fresh pasta – in other words, removing the water that was added to the paste to create fresh pasta. Dehydration occurs once the gluten networks formed in the paste have been ‘set’ in the dough and are interconnected from kneading the dough and water together. Removing the water leaves the gluten networks intact, but removes the moisture that allows the starch granules to be flexible and malleable; the resultant pasta is hard and brittle and can conveniently be stored for long periods of time in the cupboard.
All in all, pasta provides a simple way to restructure and reconstitute a grain that has been turned into a flour and cooked to create a soft and chewy byproduct that we can add to sauces and dishes. By milling grains and rice, we unlock the potential of molecules like gluten and amylose, that impart structural stability to pasta and noodles so they can hold their shape. Historically, the Chinese and Italian have worshipped noodles/pasta for their silky characteristics and convenience, and as such we should commemorate noodles/ pasta like our predecessors; and enjoy fresh made noodles.pasta and the simplicity behind the art itself. 
Guest post by Steven Du
Creamistry – n. the science of creating ice cream using Liquid Nitrogen and not to be confused with the ice cream shop of the same name . Ice cream does not seem complicated to make, but contrary to popular belief it’s not as simple as just freezing cream and sugar. Rather, this complex process requires slowly freezing cream to allow small ice crystals to form, creating a creamy texture. The process can be long and arduous, but there’s a secret ingredient for much speedier ice cream: liquid nitrogen.
Liquid nitrogen is a chemical that boils at a very low temperature, -312 F to be precise. This means that at room temperature, nitrogen is a gas, while at very cold temperatures below -312F, it’s a liquid. In its liquid form, nitrogen provides a handy way to make ice cream fast: it can be poured over the ice cream base mixture—which is mostly heavy cream and sugar— to reduce the temperature of your ice cream mixture very quickly.
The drop-in temperature reduces the motion of all the molecules and water molecules begin to form small seed crystals and nucleation sites. As you stir, the mechanical energy breaks up the crystals into tiny pieces. By contrast, if you place your ice cream mixture into the freezer, there are no external forces to interrupt the growth of the ice crystals, and the resultant ice cream will feel grainy and coarse.
We mention crystals a lot, but in the ultimate ice cream, we never want to feel the texture of crystals in our mouths; ideally, they are much smaller than the particle size that our taste buds can detect: about 20 μm . If the water crystals are too large they can have an adverse effect on the texture, resulting in an ‘icy’ texture that is not so smooth and creamy.
The formation of ice crystals starts with nucleation sites or seed crystals that are frozen in the solution of cream and sugar. The more nucleation sites, the more ice crystals. If frozen too quickly, the initial nucleation sites may develop into much larger crystals and have adverse effects on the overall ice cream texture . But with rapid stirring, large ice crystals are prevented from forming and you get a creamy and smooth texture that can even rival the smoothness of store bought ice cream.
Most ice cream shops centrifuge bowls filled with ice cream mixtures with a mixer to prevent the formation of large ice crystals, but flash freezing with liquid nitrogen circumvents that. A speedy freeze doesn’t allow enough time for large ice crystals above 100mm to develop and creates more seed crystals . Creamier ice creams contain minute ice crystals ranging around 10- 20 μm, when churned slowly or frozen quickly.
Using liquid nitrogen as a freezing agent isn’t new; it’s used in other industries to preserve samples of cells and tissues, as well as to flash freeze food products for preservation. It’s also been used in a plethora of restaurants and dishes in the recent age of modernist cuisine. For example, creating powder from flash frozen herbs with fresh picked herbs, or even creating a foie gras flower from frozen duck liver.
Additionally, cryocooking — primarily cryo ‘frying’ — is utilized as a technique to freeze a food product and allow it to fry without becoming overcooked. For example, a burger patty may be flash frozen with liquid nitrogen, and deep fried to allow for a perfectly medium rare burger patty. By contrast, if the burger was pre-frozen, it could slowly develop ice crystals in the freezer, resulting in an undesirable texture.
Safety is something we should always discuss with working with chemicals. As liquid nitrogen is a very cold liquid, it should always be handled with gloves and protective eyewear. If liquid nitrogen gets in contact with your skin it can result in severe frost bite.
Overall, liquid nitrogen provides a fun and unique method to develop dishes that have unique textures. Cold and refreshing new dishes have inundated the food world, everything from frozen caviar pearls to frozen cereal balls called “Dragon Breath”. Check out your local Creamistry ice cream shop for a quick display of this science in action!
Guest post by Steven Du
The flavor reaction. What makes bread crust brown and tasty? What makes the smell of searing meat so savory and delicious? How can grill marks and black crust on meats supply such a flavor punch?
Three words: the Maillard reaction. This simple reaction creates thousands of flavonoids that impart food with flavors that make us come back for more every time. The essential components of the Maillard reaction are protein and sugars that lead to flavonoids that make food delicious.
Several factors are important for the Maillard reaction, the most important, however, is heat. From what was likely a simple mistake thousands of years ago, humans have continued to refine the relationship between flames and food. . Simple roasting led to an explosion of culinary techniques and a quest to find flavors to satisfy our desires of delicious foods.
The Maillard reaction requires two other important factors though: protein and sugars. To kick-start the reaction, you first need to heat the components to above 300 degrees Fahrenheit, necessary to evaporate the moisture on the surface of the proteins. The temperature is also crucial because the reaction isn’t helped along by enzymes.
Advice for a budding chef attempting to make a delicious steak dinner: Salt for 30 minutes prior to release more moisture and dry the steak out.  By drying the meat, the proteins are exposed to higher temperatures earlier enabling the tasty Maillard reaction to take place.
Be careful of an abundance of sugar, though. Too much can lead to caramelization as opposed to a Maillard reaction due to the relative lack of proteins and amino groups. Caramelization leads to a sweet nutty flavor and brown coloring. By contrast, Maillard reactions result in the development of additional flavors with the addition of the amino groups from proteins, creating a multitude of flavonoids and aromas that blend together together to form a sweet or savory dish.
The basic chemistry in this reaction happens between amino acids and reducing sugars. The carbonyl group of the sugar reacts with the amino group of the amino acid and produces water and other intermediates, which undergo multiple rearrangements . These rearrangements can be from the amadori rearrangement to short-chain hydrolitic fission,1 which leads to deoxyhexodiulose and other aroma, flavor, and color compounds as seen in figure 1. The more we “brown” the item, the more diverse the flavonoids that come out. However, overdoing the reaction can also lead to toxic byproducts, such as those found in black and burnt foods . Melanoidins are common byproducts from the Maillard reaction, which are the browning pigments seen on meats and breads.
From the basic meat we cook on the stove, to the browning of bread, there are a variety of recipes that utilize the complex, yet pleasuring and delectable Maillard reactions to create delicious foods. The Maillard reaction not only shaped the development of food, it also revolutionized how we look at food.
If you’re living in Los Angeles, there is no doubt that you’ve noticed the surging popularity of plant-based foods in the dining landscape. Not only are restaurants blooming with new vegan menu options, but plant-based food products are increasingly emerging in the food industry. Notable newcomers include veggie burgers and dairy-free products including milk, yogurt, and even cheese! We are now welcoming the age of the plant butchers: a group of creative and enterprising culinary geniuses and food scientists who are passionate about developing healthier and more sustainable forms of meat by exploring the world of plant proteins. A new generation of cheesemakers is also on the rise, experimenting with bacteria to develop plant-based ‘dairy’ products. Let’s explore how these passionate individuals come up with such creative food innovations.
A Plant-Based Burger that Bleeds
Patrick Brown, a biochemistry professor from Stanford University, has spent the the last five years trying to investigate at a molecular level why beef tastes, smells, and cooks the way it does. He’s the CEO of Impossible Foods, a California-based company, that has successfully innovated new methods and ingredients to naturally recreate the sights, sounds, aromas, textures and flavors of a meat burger — their creation is called the “Impossible Burger” — which uses 95% less land, 74% less water, and creates 87% less greenhouse gas emissions (Elliott). A key feature of the Impossible Burger is heme, a molecule that is found in high concentrations in beef. Heme is an iron-containing molecule in blood that carries oxygen. It’s heme that makes our blood red and makes meat look pink and taste slightly metallic (Hoshaw). However, harvesting sufficient amounts of heme for a commercially available burger was challenging and required innovative scientific techniques.
Luckily, there is a plant-based version of heme called leghemoglobin, which is a nitrogen/oxygen carrier hemoprotein found in the nitrogen-fixing root nodules of leguminous plants such as soybeans. When nitrogen-fixing bacteria called rhizobia colonize the roots of legumes as part of a symbiotic interaction between plant and bacterium, the legumes will begin synthesizing leghemoglobin. Leghemoglobin, which has a high affinity for oxygen, is able to buffer the concentration of free oxygen in the cytoplasm of the infected plant cells to ensure proper function of the oxygen-sensitive nitrogenase, the enzyme responsible for fixing atmospheric nitrogen.
However, extracting leghemoglobin from mass production of soybeans would be expensive, time consuming, and would release large amounts of carbon into the atmosphere from unearthing the plants. A more efficient strategy is to use yeast! Genetic modification of the common yeast, S. cerevisiae, is a powerful way to produce desired molecules such as leghemoglobin. Using genetic engineering and molecular biology techniques, the Impossible team took the gene in soybean which encodes for the heme protein and transferred it into yeast, which enabled the production of vast quantities of the blood-like compound. To replicate how beef feels in the mouth, the Impossible Burger contains a combination of protein from wheat and potatoes, and coconut oil. The wheat and potato proteins result in a firm exterior when the meat is seared, while coconut oil is essential for the juiciness. Among all plant oils, coconut oil has a higher melting point, meaning that it melts above temperatures of 37 degrees Celsius; so the burger becomes juicy when the patty hits the frying pan and has a good mouthfeel, similar to lard when you eat it. While Impossible Burger is headquartered in Redwood City, California, it has recently partnered with fast food chain Umami Burger to offer the meat-free option at 14 locations in California.
Impossible burgers are also found locally at the Crossroads restaurant! Listen to our recent tasting of the impossible burger with UCLA Science & Food’s Amy Rowat and Evan Kleiman of KCRW’s Good Food found at this link: https://soundcloud.com/kcrws-good-food/01-gf-071517-impossible-burger
Cheese Without The Milk
Cheese is another animal-based product that is now available in a plant-based version. They call it “vegan cheese”, and it gives a surprisingly rich and creamy mouthfeel with a tangy flavor as the normal dairy version. Keeping the essence of what makes cheese cheese, the new generation of vegan cheeses are also made through fermentation and aging. The base ingredient used to make vegan cheese is typically tree nuts such as cashews, Brazil nuts, macadamia nuts, hazelnuts, or almonds. The approach is to first soak the raw nuts, blending them with a little water to make a slurry texture. This slurry mixture will be the media used to inoculate the bacterial cultures, which will ferment the sugars from the nuts into acids, which is what creates the cheese’s tangy flavor. Similar to the art of cheesemaking, vegan cheese makers can create different tasting vegan cheeses using various bacterial blends to acidify the cheese to different extents and produce different flavor compounds. The inoculated slurry is then left to ferment for approximately 36 hours.
To solidify milk into cheese, rennet is commonly added to curdle the protein in milk: this complex of enzymes is produced in the stomachs of ruminant mammals. The key component of rennet is a protease enzyme called chymosin . To make a vegan-version of chymosin that does not require emptying animal stomachs, cheesemakers rely on the development of genetic engineering: the gene encoding chymosin is transformed into bacteria, fungi or yeast so they can produce chymosin during their natural fermentation (Harris TJ). The resulting chymosin is called FPC, which stands for “fermentation-produced chymosin.” To ensure that the vegan cheese does not contain any GM (genetically modified) ingredients, the chymosin produced by the genetically modified organisms is isolated from the fermentation broth and the organisms are killed. In addition to rennet, oil, emulsifiers and thickeners are often also added to produce firmer types of vegan cheeses.
Aging, also called ripening, is the last and most crucial stage in cheese making. During the process of aging, microbes and enzymes transform the texture and the flavor intensity of the cheese, which contribute to the distinct flavor of cheeses. The three primary reactions that define cheese ripening are glycolysis, proteolysis, and lipolysis. The role of glycolysis is to acidify the curd or cheese, which produces many downstream effects including the regulation of flavor, texture, and melting point of the cheese. The role of proteolysis and amino acid catabolism is to: (1) develop the cheese texture by increasing the water binding capacity of the curd, and indirectly through an increase in pH due to the release of ammonia during breakdown of amino acids; and (2) develop the flavor of cheese through the production of short-medium peptides and free amino acids, which when broken down into simpler compounds, generate many important volatile flavor compounds, and also the release of strong, flavorful compounds from the cheese matrix during chewing (Eskin, p342). Low levels of lipid degradation contribute to the ripening of cheeses such as Cheddar, Gouda, and Swiss Cheese by breaking down fat into short fatty acids (which are 4 to 10 carbons long) and are highly flavored. However, excessive levels of lipolysis could lead to a rancid taste (McSweeney and Sousa 2000; Collins et al. 2003b).
Although vegan foods may invoke the image of a healthier diet, it is important to note that some varieties of vegan alternatives can also be highly processed to get the flavors and texture just right. Trying to make your own vegan meat in your kitchen may be a challenge, but making your own vegan cheese is definitely worth to try! Here is a delicious recipe to make vegan cheese using cashew nuts: http://www.thebuddhistchef.com/recipe/vegan-cheese/
With the increased awareness on the positive impacts of enjoying vegan foods (REF) and increased evidences on the health risks of consuming meat (“Meat Consumption and Cancer Risk.”), together with the inspiring and delicious vegan food creations posted on Instagram (currently, #vegan is posted 2.47 million times per hour), the future is bright for scientists seeking to learn how to create new, funky, and delicious vegan food products. It is also a perfect time for curious individuals who are seeking try and experience new vegan food options!
Harris TJ, Lowe PA, Lyons A, Thomas PG, Eaton MA, Millican TA, Patel TP, Bose CC, Carey NH, Doel MT (April 1982). “Molecular cloning and nucleotide sequence of cDNA coding for calf preprochymosin”. Nucleic Acids Res. 10 (7): 2177–87. PMC 320601 . PMID 6283469. doi:10.1093/nar/10.7.2177.
Elliott, Farley. “Some vegans are up in arms about Umami’s new meatless Impossible Burger.” Eater LA. Eater LA, 19 May 2017. Web. 08 Aug. 2017.
ESKIN, N.A MICHAEL. BIOCHEMISTRY OF FOODS. S.l.: ELSEVIER ACADEMIC PRESS, 2016. Print.
Hoshaw, Lindsey. “Silicon Valley’s Bloody Plant Burger Smells, Tastes And Sizzles Like Meat.” NPR. NPR, 21 June 2016. Web. 05 Aug. 2017.
McSweeney, Paul L.H., and Maria José Sousa. “Biochemical pathways for the production of flavour compounds in cheeses during ripening: A review.” Le Lait, EDP Sciences, 1 May 2000, lait.dairy-journal.org/articles/lait/abs/2000/03/l0301/l0301.html. Accessed 8 Sept. 2017.
Collins Y F, McSweeney P L H and Wilkinson M G (2004), Lipolysis and catabolism of fatty acids in cheese. In Cheese: Chemistry, Physics and Microbiology, Vol 1: General Aspects, 3rd edn, pp 373–389. Fox P F, McSweeney P L H, Cogan T M and Guinee T P, eds. London: Elsevier. Considine T, Healy A,
“Meat Consumption and Cancer Risk.” The Physicians Committee, 2 Nov. 2015, www.pcrm.org/health/cancer-resources/diet-cancer/facts/meat-consumption-and-cancer-risk. Accessed 8 Sept. 2017.
As the peak of summer approaches, we here at Science & Food love to reach for one of our favorite frosty treats: the ice cream sandwich. Being true Science & Foodies, we started to wonder about this amazing composite material- how do you get the coexisting chewy cookie yet firm ice cream? We began to search for answers by turning to Natasha Case, founder of the Los Angeles favorite “Coolhaus” which serves gourmet ice cream and ice cream sandwiches. Trained as an architect at both UC Berkeley and UCLA, Natasha merged her experience as an architect with her passion for food in the ideation of Coolhaus. Starting with food trucks and storefronts in LA, Coolhaus is now sold in nationwide grocery stores such as Whole Foods.
We asked Natasha what the main factor is that contributes to the science of ice cream. Her response? Surprisingly, it is air! The amount of air incorporated into ice cream is referred to as overrun  and is calculated by this equation :
% Overrun = [(Volume of ice cream produced-Volume of mix used)/Volume of mix used] x 100%
For example, if we started with 10 gallons of ice cream mix and had 15 gallons of finished ice cream at the end, the overrun calculations would be as such: 15-10 = 5 and 5/10 = 0.5. 0.5 x 100% = 50%, meaning there is 50% volume, or the volume has increased by 50% as a result of the addition of air . Air is crucial in ice cream: air bubbles contribute to ice cream mouthfeel in addition to the use of butterfat. The texture of frozen desserts such as gelato and ice cream depends on this interplay between fat and air. Gelato typically has about 10% butterfat and 20-30% overrun  while ice cream can have up to 16% butterfat and 30-50% overrun . With 12-14% butterfat and a low overrun, Coolhaus technically produces “gelato style” ice creams ; this is one of the key components to the success of the Coolhaus ice cream sandwich.
While air content contributes to ice cream texture, it also affects how quickly ice cream melts. Typically, more air results in ice cream that melts more quickly . Ever notice how when you buy the budget brand ice cream it starts melting almost instantly? This is because budget brands of ice cream typically increase their overrun to decrease ingredient costs – it’s cheaper to fill a half gallon tub with more air than cream! So how does increased air content result in a faster meltdown rate? To answer this question, we need to consider the small-scale structure of ice cream. Ice cream is a colloid, or a solution that is comprised of two insoluble materials with one dispersed throughout the other. When ice cream is churned, it breaks up the ice crystals formed by water to give the ice cream a smooth texture. Churning also causes the fat globules in the milk and cream coalesce and allow for the dispersion and stabilization of air throughout the ice cream. Because fat is hydrophobic, it prefers to align itself closer to the air bubbles rather than the ice crystals. Therefore, the texture of ice cream is a result of the interplay between these air bubbles, ice crystals, and fat globules . Now, let’s consider what happens when ice cream melts.
Melting involves factors such as air cells, ice crystals, and fat globules and the stability of these air cells is one of the largest factors that affect meltdown rate . Air cells are formed in ice cream due to shear stress during churning. Fat globules partially coalesce and form a network around the air cells (Figure 1) that prevent agglomeration and disperse the serum phase around the ice crystals, thus preventing ice crystal collisions that would lead to accelerated melting . Therefore, the ratio of fat : air must be sufficient to prevent the agglomeration, and lower amounts of air will allow for this. Thus, by decreasing the overrun, you can achieve a slower-melting ice cream that stays in your sandwich longer.
So we’ve solved the mystery of the filling, but what about the oh-so-chewy cookie that gives the extra oomph to Coolhaus’ sammies? Natasha gave us the scoop – Coolhaus uses pectin. Though the precise combination of ingredients is proprietary, we postulate that the pectin serves as a thickening and stabilizing agent that allows the cookie to remain chewy despite sub-zero temperatures. Pectin is a polysaccharide contained in plant tissue . As the pectin binds water, it causes freezing point depression, a phenomenon that occurs when a solute is dissolved in a solvent. As a solute is dissolved, it interacts with water molecules, thus interfering with the attractive forces between water molecules that cause them to interact and become a solid (Figure 2). Thus, in order to achieve an ordered state, the freezing point must be lowered even further to decrease particles’ kinetic energy enough that they can no longer overcome the interparticle attractive forces and become frozen . In this manner, pectin lowers the freezing point of the water in the cookie, preventing the formation of ice’s crystalline structure that leads to hardness.
For more about pectin, check out a previous S&F article on Citrus Suprême.
In her search for confection perfection, Natasha has one goal in mind with the science behind her ice cream sandwich: to evoke emotional reactions that link to memories and nostalgia.
“Flavor is generally conceived to be an instinctual or emotional aspect of taste, but when you can also get into the understanding of it from a scientific standpoint you can actually, to an even further degree, elevate that emotional or instinctual side by knowing what is actually creating those sensations on your palate, mind, and in your soul.” –Natasha Case
Dave Arnold set up his own experiments to mix the perfect Manhattan, explaining, “A dose of science will do you good. Think like a scientist and you will make better drinks.” In his first experiment, he used different sized ice to make his drinks. His conclusion: different ice, different stir, same Manhattan. James Scott, a mycologist who runs the business Sporometrics, was called upon by the Hiram Walker Distillery to investigate a mysterious black fungus plaguing the warehouses and the surrounding neighborhood. Also using the scientific method, Scott discovered a new fungal species which grows preferably on the angel’s share of whiskey. An identical fungal growth is also found outside the Rémy Martin distillery in Cognac, France.
Guest post by Earlene Mulyawan
Yogurt is an ancient food that has been around for several millennia. One theory of the discovery of yogurt is that during 10,000 – 5,000 BC, when Herdsmen began the practice of milking their animals, they stored their milk in bags made of the intestinal gut of the animals. The intestines contain natural enzymes that cause the milk to curdle and sour. The herdsmen noticed that this method of storing milk extends its shelf life and preserves it. When they consumed the fermented milk, they enjoyed it and so they continued making it. Whether or not this theory is true, the consumption of fermented milk has survived into modern times, and spread throughout the world. The word “yogurt” is believed to have come from the Turkish word “yogurmak,” which means to thicken coagulate, or curdle. Today, the FDA defines yogurt as a milk product fermented by two bacterial strains: a lactic acid producing bacteria: Lactobacillus bulgaricus and Streptococcus thermophiles.
To make yogurt, milk is first heated to 180 degrees Fahrenheit for 30 minutes to denature the whey proteins; this allows the proteins to form a more stable gel. The yogurt is pasteurized before adding the cultures. The pasteurization process kills any pathogens that can spoil milk as well as to eliminate potential competitors of the active cultures. After milk pasteurization, the milk is cooled down to 108 degrees Fahrenheit, the temperature for optimal growth of yogurt starter cultures. Last, the yogurt starter cultures (probiotics) is added into the cooled milk and incubated until a pH of below 5 is obtained. This is called the fermentation process, whereby lactose in the milk is converted to lactic acid, which lowers the pH. When the pH drops below pH 5, micelles of caseins, which are amphiphilic proteins, loses its tertiary structure due to the protonation of its amino acid residues. The denatured casein proteins reassemble by interacting with other casein proteins, and these intermolecular interactions result in a network of molecules that provides the semisolid texture of yogurt (Zourari, Accolas, & Desmazeaud).
The fermentation process is also essential for the tangy flavor of yogurt: the production of lactic acid by Lactobacillus bulgaricus imparts a sour acidic and refreshing taste. A mixture of various carbonyl compounds like acetone, diacetyl and acetaldehyde are also major contributors to the tarty yogurt flavor. Yogurt has a high concentration of acetaldehyde due to the low utilization of this metabolite by yogurt bacteria, which lack alcohol dehydrogenase, the main enzyme needed to convert acetaldehyde into ethanol (Lees, G. J., and G. R. Jago). During fermentation, acetaldehyde is produced directly from lactose metabolism as a result of pyruvate decarboxylation. However, lactic acid bacteria also have alternative metabolic pathways that can produce acetaldehyde (Figure 1):
Yogurt may provide potential health benefits by enhancing nutrient absorption and digestion (Fernandez). However, most commercialized yogurts that are sold in grocery stores contain added sugars, artificial ingredients and fillers, and only a marginal amount of probiotics. (Mercola). Homemade yogurt is an excellent way of getting probiotics into your system without the unnecessary chemicals and flavorings found in commercialized yogurts. All you need is a high quality starter culture and milk! Epicurious‘ step by step on how you can make yogurt at home can help you get started. Or you can check out The White Moustache, the website of Homa Dashtaki, a guest lecturer during the Spring 2017 Science and Food undergraduate course.
A Zourari, Jp Accolas, Mj Desmazeaud. Metabolism and biochemical characteristics of yogurt bacteria. A review. Le Lait, INRA Editions, 1992, 72 (1), pp.1-34.
Fernandez, M. A., and A. Marette. “Potential Health Benefits of Combining Yogurt and Fruits Based on Their Probiotic and Prebiotic Properties.” Advances in nutrition (Bethesda, Md.). U.S. National Library of Medicine, 17 Jan. 2017. Web. 03 July 2017.
Lees, G. J., and G. R. Jago. “Formation of acetaldehyde from threonine by lactic acid bacteria.” The Journal of dairy research. U.S. National Library of Medicine, Feb. 1976. Web. 11 Apr. 2017.
Mercola, Joseph. “Benefits of Homemade Yogurt Versus Commercial.” Organic Consumers Association. N.p., n.d. Web. 03 July 2017.
We all know that feeling: the burning sensation as we slice into a fresh onion, eyes watering and wincing to relieve the stinging. There are claims that home remedies can solve this problem, including burning a candle, putting the onion in the freezer before chopping, or cutting the onion underwater. In this article we will investigate the culprit behind our onion tears and a possible scientific resolution that has emerged in the 21st century.
The teary-eyed response to cutting an onion is due to the chemical syn-propanethial-S-oxide, which the onion has evolved as a defense mechanism against predators. Each cell inside the onion contains a vacuole filled with enzymes  called allinases that convert amino acid sulfoxides that are present in the onion cell to sulfenic acids  (namely 1-propenyl-L-cysteine sulphoxide, or PRENSCO); these are then transformed by another enzyme into syn-propanethial-S-oxide  (Fig 1).When the onion cell structure is broken during chopping, the enzymes are released and are then able to interact with other chemicals inside the onion cell, thus catalyzing the chemical reactions that produce syn-propanethial-S-oxide  (Fig 1).
The strong, spicy odor that onions emit when chopped are surprisingly not the culprit chemical that makes your eyes water. This odor is formed by the condensation of syn-propanethial-S-oxide to form odorous thiosulfanates . Because syn-propanethial-S-oxide is a volatile sulfur compound, it easily diffuses into the air . Your cornea contains nerves that relay information to the larger nerves responsible for touch, temperature, and pain detection on your face . The nerves on your cornea detect the presence of syn-propanethial-S-oxide and send the signal to your central nervous system (Fig 2), which then stimulate the autonomic nerve fibers on the lachrymal glands to produce tears  in order to dilute the syn-propanethial-S-oxide. This is why referred to as lachrymatory compound or lachrymator, which can be defined as “an irritant that causes the eyes to fill with tears without damaging them” .
Whereas previously it was thought that a generic allinase could produce syn-propanethial-S-oxide, recent research has shown that it is synthesized by a specific enzyme called ‘lachrymatory factor synthase’ . In fact, scientists succeeded in producing onions in 2015 with suppressed lachrymatory-factor synthase genes that contained 7.5 times less syn-propanethial-S-oxide as well as eliminated the lachrymatory response among sensory panelists . Additionally, scientists have found that when they mixed only generic allinases and PRENSCO in vitro, the production of thiosulphinate – the chemical responsible for onion’s flavor – increased . No more tears & more flavor? Sounds like a tasty treat we would be down for!
Nothing welcomes spring as deliciously as an asparagus dish. But are you a little lost which is the freshest bunch on the shelf? How to best store them? Other ways to cook them besides oven roasting? City Kitchen’s got you covered. Where asparagus is a springtime treat, bananas are a year-round breakfast luxury. Unfortunately, its perennial availability puts it at risk for extinction.
Guest post by Panisa Sundravorakul
Instant noodles are delicious, cheap, and easy to prepare. This combination of traits make instant noodles a seemingly perfect solution for college students’ hectic schedules and depleted bank accounts. Let us take a moment to appreciate what made instant noodles possible — let us savor the science behind this culinary delicacy.
Instant noodles are truly a technological marvel – they can last for up to 12 months on the shelf, and a tiny little packet of seasoning makes the noodles taste so good. You can thank science for making this all possible. The shelf life of instant noodles ranges from 4 to 12 months, depending on environmental factors. Finding ingredients that are stable for this long, especially fats and oils that are prone to oxidation, is a culinary challenge.
Antioxidants like tertiary-butyl hydroquinone (TBHQ) can extend the shelf life of instant noodles by preventing the oxidation of fats and oils; this happens by donating electrons to neutralize free radicals, which stabilize the radical’s instability . The texture of instant noodles is preserved by propylene glycol, which is found in the noodles mixture, and helps them retain moisture and prevent them from drying .
Monosodium L-glutamate (MSG) is a common additive used to enhance the flavor of instant noodles. This molecule adds a robust and savory flavor to food, which is commonly described as umami, the fifth flavor after salt, sweet, sour, and bitter. Recent studies have found L-glutamate (Glu) receptors and transduction molecules in the gut mucosa, as well as the oral cavity (REF). The gastric infusion of MSG activates several brain areas, such as the insular cortex that is linked to the regulation of homeostasis; the limbic system is linked to olfaction; and hypothalamus is linked to certain metabolic processes and hunger control. This suggests that Glu signaling via the gustatory and visceral pathway plays a crucial role in digestion, absorption, and metabolism. 
While noodles might be tasty, convenient, and save you money and time, they do not contain sufficient nutrients that fulfill the body’s daily nutritional needs. Instant noodles are relatively high in sodium, carbohydrates and fat, and quite low in protein, fiber, vitamins, and minerals . Figure 1 compares the daily nutrition intake as recommended by The National Institute of Health to the nutritional content in one package of instant noodles (Figure 1) . Instant noodles account for too much of daily sodium intake, and not enough for fiber, vitamin A and C, calcium, and iron daily intake.
There is no doubt that instant noodles are a fascinating food science innovation. Health-wise, instant noodles are certainly safe to eat, but if you are thinking about consuming them regularly, think again about how your health could benefit from eating more nutrient-rich foods.