The Secret Ingredient in Both Meat and Bread: The Maillard Reaction

By Ashton Yoon | October 10, 2017 1:00 pm
Canadian Bacon Donut Complimentary of Portobello Cafe in Whistler, Canada. This donut provides many examples of the Maillard reaction. When frying the donut batter, high temperatures promote browning of the dough and also impart crispiness. Secondly, the bacon!  the flavors in bacon are the result of Maillard reaction products. The browning of the bacon creates and releases flavnoids. Photo Credit: Steven Du

Canadian Bacon Donut Complimentary of Portobello Cafe in Whistler, Canada. This donut provides many examples of the Maillard reaction. When frying the donut batter, high temperatures promote browning of the dough and also impart crispiness. Secondly, the bacon!  the flavors in bacon are the result of Maillard reaction products. The browning of the bacon creates and releases flavnoids. Photo Credit: Steven Du

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. [1]. 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. [3] 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 [1]. 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 [1]. Melanoidins are common byproducts from the Maillard reaction, which are the browning pigments seen on meats and breads.

Figure 1. Maillard Reaction Scheme and possible products. Photo Credit: Compound Interest

Figure 1. Maillard Reaction Scheme and possible products. Photo Credit: Compound Interest

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.

References:

  1. Martins, Sara, et al. “A Review of Maillard Reaction in Food and Implications to Kinetic Modeling.” Food Science and Technology, 2011, www.researchgate.net/profile/Sara_Martins3/publication/222682804_A_review_of_Maillard_reaction_in_food_and_implications_to_kinetic_modelling/links/0fcfd51140ffcf26ff000000.pdf.
  2. Tamanna, Nahid, and Niaz Mahmood. “Food Processing and Maillard Reaction Products: Effect on Human Health and Nutrition.” International Journal of Food Science, Hindawi Publishing Corporation, 2015, www.ncbi.nlm.nih.gov/pmc/articles/PMC4745522/.
  3. Schulze, Eric. “An Introduction to the Maillard Reaction: The Science of Browning, Aroma, and Flavor.” Serious Eats, 13 Apr. 2017, www.seriouseats.com/2017/04/what-is-maillard-reaction-cooking-science.html.
CATEGORIZED UNDER: Science & Food

The Vegan Way

By Ashton Yoon | September 26, 2017 10:00 am
Meatless burger patty. Photo Credit: Impossible Foods

Meatless burger patty. Photo Credit: Impossible Foods

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

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Photo Credit: J. Kenji López-Alt/Serious Eats

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/

Photo Credit: Veg Kitchen

Photo Credit: Veg Kitchen

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!

Sources cited:

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.

CATEGORIZED UNDER: Science & Food

We All Scream for…Ice Cream!

By Ashton Yoon | August 1, 2017 10:00 am

 

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Photo Credit: Coolhaus

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 [1] and is calculated by this equation [2]:

% 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 [2]. 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 [3] while ice cream can have up to 16% butterfat and 30-50% overrun [4]. With 12-14% butterfat and a low overrun, Coolhaus technically produces “gelato style” ice creams [5]; this is one of the key components to the success of the Coolhaus ice cream sandwich.

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igure 1: Stabilization of air cells by fat in ice cream. (Photo Credit: Molecular Recipes)

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 [5]. 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 [4]. 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 [6]. 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 [1]. 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.

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Figure 2: Freezing in pure solvent (A) vs. in a solution. (Photo Credit: Seville International College)

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 [7]. 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 [8]. 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.

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Photo Credit: Coolhaus

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

 

References Cited:

  1. Sofjan, R. P., & Hartel, R. W. (2004). Effects of overrun on structural and physical characteristics of ice cream. International Dairy Journal, 14(3), 255-262. doi:10.1016/j.idairyj.2003.08.005
  2. Goff, H.D. & Hartel, R.W. (2003). Ice cream. New York, New York: Springer US.
  3. Poon, L. (2014). Why scream for gelato instead of ice cream? Here’s the scoop. NPR. Retrieved from http://www.npr.org/sections/thesalt/2015/06/16/413223571/why-scream-for-gelato-instead-of-ice-cream-heres-the-scoop
  4. Compound Chem, (2015). The chemistry of ice cream. Infographic. Retrieved from http://www.compoundchem.com/2015/07/14/ice-cream/
  5. Case, N. (2017, July 11). Personal interview.
  6. Pelan, B. M. C, Watts, K. M., Campbell, I. J., & Lips, A. (1997). The stability of aerated milk protein emulsions in the presence of small molecule surfactants. Journal of Dairy Science, 80, 2631–2638.
  7. Pedrolli, D. B., Monteiro, A. C., Gomes, E., & Carmona, E. C. (2009). Pectin and pectinases: Production, characterization and industrial application of microbial pectinolytic enzymes. The Open Biotechnology Journal, 3(1), 9-18. doi:10.2174/1874070700903010009
  8. University of North Carolina at Chapel Hill. Raoult’s law. Retrieved from https://cssac.unc.edu/programs/learning-center/Resources/Study/Guides/Chemistry%20102/Solutions
CATEGORIZED UNDER: Science & Food

Perfect Manhattans & Mysterious Fungi

By Ashton Yoon | July 13, 2017 10:00 am

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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.
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CATEGORIZED UNDER: What We're Reading

The Science of Yogurt

By Ashton Yoon | July 4, 2017 10:00 am

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.

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Photo Credit: Makeyourownyogurt.com

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):

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Figure 1: Pathways to acetaldehyde production (Chaves, A.C.S.D. et al. 2002)

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.

Enjoy!

 

Sources:

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.

CATEGORIZED UNDER: Science & Food

Why Do Onions Make Us Cry?

By Ashton Yoon | June 6, 2017 10:00 am
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Photo Credit: Tastyart Ltd Rob White/Getty Images

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 [1] called allinases that convert amino acid sulfoxides that are present in the onion cell to sulfenic acids [2] (namely 1-propenyl-L-cysteine sulphoxide, or PRENSCO)[3]; these are then transformed by another enzyme into syn-propanethial-S-oxide [4] (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 [1] (Fig 1).

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Figure 1. Reaction mechanism for the formation of syn-propanethial-S-oxide. (Burnham, P.M. (1996))

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 [2]. Because syn-propanethial-S-oxide is a volatile sulfur compound, it easily diffuses into the air [1]. Your cornea contains nerves that relay information to the larger nerves responsible for touch, temperature, and pain detection on your face [2]. 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 [2] 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” [5].

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Figure 2. The lachrymal response (Tiwari, S., Ali, M.J., and Vemuganti, G.K. (2014)/ScienceDirect)

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’ [3]. 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 [6]. 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 [3]. No more tears & more flavor? Sounds like a tasty treat we would be down for!

References Cited:

  1. Singh, M. (2016). The science of why onions make us cry. NPR. Retrieved from http://www.npr.org/sections/thesalt/2016/06/22/482032913/the-science-of-why-onions-make-us-cry
  2. Scott, Y. Scientific American. What is the chemical process that causes my eyes to tear when I peel an onion? Retrieved from https://www.scientificamerican.com/article/what-is-the-chemical-proc/
  3. Imai, S., Tsuge, N., Tomotake, M., Nagatome, Y., Sawada, H., Nagata, T., Kumagai, H. (2002). An onion enzyme that makes the eyes water. Nature, 419, 685.
  4. American Chemical Society. (2013). Syn-Propanethial S-oxide. Retrieved from https://www.acs.org/content/acs/en/molecule-of-the-week/archive/s/molecule-of-the-week-syn-propanethial-s-oxide.html
  5. Burnham, P.M. (1996). Propanethial s-oxide, the lachrymatory factor in onions. J. American Chemical Society, 118(32), 7492-7501.
  6. Kato, M., Masamura, N., Shono, J., Okamoto, D., Abe, T., & Imai, S. (2016). Production and characterization of tearless and non-pungent onion. Scientific Reports, 6, 23779. doi:10.1038/srep23779.
CATEGORIZED UNDER: Health & Medicine, Top Posts
MORE ABOUT: nutrition

Asparagus Season and Banana Problems

By Ashton Yoon | May 16, 2017 12:38 pm

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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.
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CATEGORIZED UNDER: What We're Reading

The Savory Science of Instant Noodles

By Ashton Yoon | April 25, 2017 12:00 pm
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(Credit: Pornpen Suechaicharoen/Shutterstock)

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 [1]. 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 [2].

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. [3]

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Figure 1. Nutritional content vs. daily recommended intake for various components of instant noodles. (Photo Credit: Panisa Sundravorakul)

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 [4]. 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) [5]. 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.

References Cited:

  1. Toxicology Data Network. “T-Butylhydroquinone”. S. National Library of Medicine. 2013. Web. 21 January 2017.
  2. Agency for Toxic Substances and Disease Registry (ATSDR).”Toxicological profile for Propylene Glycol”. Department of Health and Human Services, Public Health Serv 1997. Web. 7 Jan 2017.
  3. Torii, K. “Brain activation by the umami taste substance monosodium L-glutamate via gustatory and visceral signaling pathways, and its physiological significance due to homeostasis after a meal”. Journal of Oral Biosciences. 54.3 (2012): 144-150. Web. 20 March 2017.
  4. Nissin Foods. “Top Ramen- Nutrition Facts and Ingredients”. Nissin Foods. Web. 21 January 2017. National Institute of Health. “Nutrient Recommendations: Dietary Reference Intakes (DRI)”. U.S. Department of Health & Human Services. 2011. Web. 21 January 2017.
CATEGORIZED UNDER: Science & Food

Science & Food UCLA 2017 Public Lecture Series

By Ashton Yoon | April 13, 2017 10:28 pm

 

Public Lecture

The 2017 UCLA Science & Food public lecture series is here!

FOOD WASTE: Solutions Informed by Science (and what to do with your leftovers)

Tuesday, May 2nd
7:00 pm to 8:30 pm
Freud Playhouse, Macgowan Hall

World-renowned chef Massimo Bottura, UCLA professor Jenny Jay, Zero Waste Consultant and “Waste Warrior” Amy Hammes will participate in a panel discussion moderated by Evan Kleiman on “Food waste: solutions informed by science,” hosted by Dr. Amy Rowat, Science and Food, and the UCLA Healthy Campus Initiative. The discussion will focus on measuring the environmental effects of food waste, how policy influences food waste and its relationship to hunger and the environment.

General admission tickets are available for $25 from the UCLA Central Ticket Office (CTO) . Tickets can be purchased from the UCLA CTO over the phone or in person and will not include additional fees or surcharges. The UCLA CTO is located on-campus and is open Monday–Friday, 10am –4pm. A UCLA CTO representative can be reached during these hours at 310-825-2101. Tickets can also be purchased online from Ticketmaster for $25 plus additional fees. A limited number of $5 student tickets are available to current UCLA students. These must be purchased in person at the UCLA CTO with a valid Bruin Card.

For questions, please email laurah@ucla.edu.

CATEGORIZED UNDER: Public Lectures, Science & Food

To Eat With Your Eyes

By Nessa Riazi | April 13, 2017 10:26 am
anosmia_postcard-r386061700b48463c873726ec0560b87b_vgbaq_8byvr_324

Figure 1: (photocredit: Zazzle)

Interacting with food is an incredibly sensual experience. One might imagine the smell of an oven roast, or picture an oozing chocolate lava cake, maybe even hear the crunch of a stale baguette. But what happens when you lose your sense of smell and taste?

Anosmia is a disorder where one loses their ability to smell. There are various forms of this unfortunate disorder: Congenital anosmia is when someone is unable to smell at birth, and hyposmia describes the diminishing sense of smell that develops over time. Our senses of smell and taste are interdependent, so if you lose one of these senses, you lose the other one too.

Olfaction

Figure 2: (photocredit: Monell Center)

In understanding anosmia, it is critical to first grasp the science of smell. Whenever we breathe air, particles pass through our nose and bind to the olfactory receptors beneath the cribriform plate. The “nerve cells come into direct contact with the air we breathe,” [1] connecting the nose with the brain through the cribriform plate, a structure that resembles a honeycomb. This cribriform plate is crucial to our sense of smell, and any harm done to the plate can in turn damage the neurons that pass through it [3]. Some of the individuals who develop anosmia or hyposmia are either subject to injuries of the head, nasal polyps, inhaling toxic chemicals, or an upper respiratory infection (URI)–such as a cold– that damaged the receptor neurons. Swelling of the nasal tissue as a result of inflammation may “stretch the receptor cells and damage their ability to function properly” [3]. This is one potential factor, but further research is being conducted to understand more about the causes of anosmia.

smellpic

Figure 3: Anatomical representation of the olfactory system depicting how the nerves run directly through the cribriform plate. (Photocredit: Lippincott Williams & Wilkins)

As expressed by Nisha Pradhan, a college student who developed anosmia, her inability to smell is perhaps even affecting her memory, as she cannot recall certain scents from her past [2]. While memories engage with all senses, though primarily with sight, we underestimate the role that smell has in providing a context for us to categorize our everyday life experiences; most importantly though its relevance personal health. Not being able to smell freshly baked cookies is unfortunate, but the inability to detect rotting milk or smoke from a nearby fire is dangerous. While in some cases anosmia can worsen, it is not always a permanent condition and can subside with time as nasal congestion or other issues subside. Scientists are currently conducting research to develop potential treatments for anosmia. The Monell Center—which focuses specifically on research relating to taste and smell– is testing to see if olfactory stem cells can be used to synthesize new olfactory neurons. Olfactory receptor cells have the ability “to regenerate from specialized stem cells across a persons lifetime.” These stem cells would be derived from healthy individuals and then be transplanted into the patient [3].

Though it may slip the crevices of one’s mind, the nose is a vulnerable organ essential in constructing our everyday perceptions of life around us. It allows us to retrace memories, map the physical world around us, and most importantly preserve well-being. Heightening our gastronomic experiences, our ability to smell and taste food is a gateway to more meaningful sensory, social phenomena and life without them could only become incredibly bland.

References Cited:

  1. “What is Anosmia?” http://www.webmd.com/brain/anosmia-loss-of-smell#2-6
  2. Heist, Annette. “With no Sense of Smell, The World Can Be a Grayer, Scarier Place.” http://www.npr.org/sections/health-shots/2016/10/10/496455192/with-no-sense-of-smell-the-world-can-be-a-grayer-scarier-place
  3. “Causes of Anosmia.” Monell Center. https://www.monell.org/research/anosmia/anosmia_causes

 

CATEGORIZED UNDER: Science & Food
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