Science & Food – Page 4 – Science and Food

The Science of Steamed Milk: Understanding Your Latte Art

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

Guest post by Christina Jayson

Photo credit: Dan Lacher (journeyscoffee/Flickr)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

References cited

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

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

Coconut

July 14, 2015/in Flavor of the Month/by Grant Alkin

If you’re itching for a tropical getaway, enjoying a coconut snack could help conjure up images of cool sand, blue waters, and swaying palm trees. The coconut tree (Cocos nucifera) and its fruits may very well be the symbol of paradise, since coconut is an ingredient in many Southeast Asian and Pacific Island cuisines. If you find yourself eager to whip up some curry, puttu, Ginataang Manok, macaroons, a cold glass of piña colada, or just feel like sticking a straw into a coconut, take some time to digest a little bit of coconut science before cracking open a coconut. Read more

Flavor-Changing Chewing Gum

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

Growing up as a chubby kid who tried to convince her parents that candy belonged at every meal (a real life Augustus Gloop, if I may), one of my favorite books was Charlie and the Chocolate Factory. And though I’d dream for a mug of the chocolate river, my favorite of Willy Wonka’s creations was the three-course chewing gum. Tomato soup, roast beef, and blueberry pie in one piece of gum? The possibilities! While you can find some commercial versions of flavor-changing gum at the supermarket today, my fingers are crossed for a three-course meal sometime in the near future.

Image Credit: (stevendepolo/flickr)

To get any sort of flavor in a chewing gum in the first place, a process called microencapsulation is used, in which a core of tiny flavor particles is surrounded by a shell coating to produce minuscule spherical capsules – we’re talking diameters of roughly a couple hundred micrometers in size [1]. Chewing gums contain these little flavor microcapsules; the core of each microcapsule is usually some sort of liquid flavoring, and the shell is made of crosslinked proteins which stabilize the core material, isolate the core from the chewing gum base, and will break apart in response to the shear forces of chewing to release the core flavoring [1].

So let’s say you have a stick of strawberry-flavored chewing gum. The gum will be studded and mixed with microcapsules filled with strawberry flavoring oils; those are the beady dots you sometimes see on the chewing gum surface. The fruity flavor is released once you chew on the gum and break open the shells of the strawberry capsules to release the flavoring oils in your mouth.

While there are various methods for flavor encapsulation, the technique which is used to make the capsules in chewing gum is the chemical process called complex coacervation. [4] This process involves an aqueous solution with two or more oppositely charged polymers – one with positive charge (such as gelatin or agar), and another with negative charge (such as carboxymethylcellulose or gum arabic) [2]. These two polymers are diluted into water and then controlled for both pH and temperature, so that when an oily substance (such as a flavoring oil) is mixed into the solution, the molecules form a chemically crosslinked, shell-like film around each of the oil particles, resulting in the encapsulated flavor beads present in chewing gum!

The coacervation solution then separates into two liquid phases – one called a “coacervate” that contains the many tiny oily droplets that contain the polymers and the other is called the “equilibrium liquid”, which serves as the solvent. Once the shells around the oil droplets are formed, the rest of the solution is washed out and the entire capsules are dried so that they can be incorporated into the chewing gum base [3].

The Coacervation Process: (a) The oily flavor droplets float around in an emulsion of the shell polymer solution, (b) The coacervation solution separates into the coacvervate and the solvent (c) The coacervate surrounds the outside of the flavor core, (d) And forms a continuous crosslinked polymer shell around the core.

So how does the flavor-changing gum work? The secret lies in the fact that the tiny flavor capsules in a chewing gum can be engineered to release at different times. By creating microcapsules with different dissolution times, the release of several different flavor capsules can be staggered to make a chewing gum that “changes flavors”. The first flavor composition in a flavor-changing gum is usually the unencapsulated liquid flavor or a starch sugar coating on the surface of the gum, so that the first flavor can be released on contact with saliva [4].

After the initial flavor perception, the second, third, fourth, and any subsequent flavors will be encapsulated, but with varying materials in the cores and shells, so that each flavor is released at a different time during the gum-chewing experience. The goal for a flavor-changing chewing gum is to have its flavors release quickly and intensely, preferably 15 to 45 seconds after the release of the previous flavor [5]. The release times of the microcapsules can depend on a variety of factors involving both the core flavoring substance and the encapsulating materials:

Solubility of Flavoring Substance
Water-soluble flavoring substances are more soluble in our saliva, so they are released in chewing gum before the oil-soluble flavoring substances. Water-soluble flavors include vanilla, synthetic fruit flavors like cherry and lemon, and plant extracts such as coffee and licorice. Oil-soluble flavors include cinnamon oil, peppermint oil, peanut butter flavor, chocolate, and eucalyptus oil [5].

Hydrophobicity of Capsule Shell
Microcapsule shells made of highly hydrophobic proteins, meaning they have low water-absorption properties, take longer to release the core flavor. Meanwhile, shells that are made with less hydrophobic material, which can absorb more water, release the flavor components earlier and more quickly. For example, if we use ethylene-vinyl acetate as the shell material, the release rate can be controlled with a few adjustments. A higher ratio of ethylene to vinyl acetate creates a more hydrophobic shell, which results in a slower release of flavor. On the other hand, using lower ratio of ethylene would create a less hydrophobic shell and a quicker release of flavors [5].

Tensile Strength in Microcapsules
The maximum amount of stress that the encapsulation shell can withstand from chewing before it breaks and releases the core flavor is called the tensile strength. Changing the tensile strength of each flavor’s shell can determine the order in which the flavors are perceived. Materials that lower the shell’s tensile strength are fats, plasticizers, waxes, and emulsifiers, so adding these materials into the shell of a flavor capsule causes it to break more easily and release flavors more quickly [5]. Meanwhile polymers with high molecular weight tend to increase the tensile strength of the shell, so these flavors are released later, since they require more vigorous chewing.

A combination of these factors from hydrophobicity to tensile strength can be used to determine the order of the flavors released for an entire three-course meal (or more!) in just a stick of gum. Tomato soup, roast beef, and blueberry pie, here I come!

Image Credit: (pinkiepielover63/deviantart)

References Cited:

J. Sris, A. Seethadevi, K. Suria Prabha, P. Muthuprasanna, and P. Pavitra. (2012). Microencapsulation: a review. International Journal of Pharma and Bio Sciences. 3: 509–521.
Feng T., Xiao Z., Tian H. (2009). Recent Patents in Flavor Microencapsulation. Recent Patents on Food, Nutrition, & Agriculture. 1:193–202.
Xiao Z., Liu W., Zhu G., Zhou R., Niu Y. (2014). A review of the preparation and application of flavour and essential oils microcapsules based on complex coacervation technology. Journal of the Science of Food and Agriculture. 94: 1482-1494.
Gaonkar A.G., Vasisht N., Khare A.R., Sobel R. (2014). Microencapsultion in the Food Industry: A Practical Implementation Guide. Academic Press. 421-453.
Lenzi S., Kar S., Michaelidou T.A., and Harvey J.E. (2012). Chewing Gum Compositions Providing Flavor Release Profiles. Kraft Foods Global Brands LLC, assignee. Patent WO2012034012.

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

Read more by Eunice Liu

International Variations of Yogurt: A Cultural Exploration of Milk

June 30, 2015/in Science & Food/by Grant Alkin

Photo credit: Robert Koehler

It’s a dessert, it’s a condiment, it’s a breakfast staple. Yogurt can be consumed in a myriad of ways; there also exist several variations of yogurt around the world that differ dramatically in taste and texture.

It all begins with milk—be it from a cow, sheep, buffalo, donkey, or goat. In standard western forms of yogurt, the art of yogurt-making begins by heating milk to 85°C and holding for 30 minutes or at 90°C for 10 minutes. Applying heat denatures the whey protein, lactoglobulin, and plays a pivotal role in determining the yogurt’s final creamy texture. Without this protein denaturation, the milk proteins won’t set together in an organized matrix, but will instead cluster together and form curds.

In the second phase, fermentation, milk is first cooled to a temperature within the range of 30°C-45°C, a range well tolerated by the microbes that play a role in fermentation. Traditional yogurt-making in the western world relies on bacterial cultures containing Lactobacillus bulgaricus and Streptococcus thermophilus, which can be directly added to milk in the form of a packaged starter (similar to yeast) or taken from a previously-made batch of yogurt. The bacteria then convert the milk sugar, lactose, into lactic acid, which firms the yogurt and provides it with its tart and tangy taste.

Fermentation conditions heavily influence the flavor and consistency of the final product. Different types of bacteria thrive in different temperature ranges and can produce several variations in consistencies, ranging from smooth and creamy to thick and jelly-like. At lower temperatures, bacteria produce lactic acid much more slowly and it can take up to 18 hours for the yogurt to set; by contrast, lactic acid bacteria working at higher temperatures can set the milk proteins in just two or three hours. A rapid, high-temperature gelling will result in a firm yogurt, whereas a low-temperature, slow gelling will produce a more delicate, tightly packed protein network. [1]

Throughout the world, we’ll find several different kinds of yogurt or yogurt-like products. Significant textural or taste changes can be made with simple tweaks in the preparation or fermentation process, and we’ll explore a few of these here.

Greek yogurt

Greek yogurt has become ubiquitous in grocery stores over the past decade and is loved for its rich flavor and thick consistency. The secret behind its popularity lies in the straining step. Straining allows the liquid whey component of milk to drain away and also removes some of the lactose, leaving behind a product with reduced sugar and nearly double the protein when compared to its non-strained counterparts. Although not actually of Greek origin (its origins still remain unclear), this strained yogurt is also popular throughout the Middle East and Central Asia [1,2].

Viili

This slimy dairy product topped with mold may sound like a failed kitchen experiment, but is in fact a yogurt-like product held dear to many Scandinavians. Known as viili to the Finnish, långfil to the Swedes, or tättemjölk to those in Norway, this ropy milk product is so thick that it needs to be cut with a knife when served. The main culprit in viili’s ropiness is a mesophilic strain of lactic acid bacteria called Lactococcus lactis subspecies cremoris. During fermentation, this strain of lactic acid bacteria produces long strands of slimy sugars known as exopolysaccharides that create the characteristic texture and flavor profile of viili. On its surface, you’ll find a velvety layer of mold formed from G. candidum, which lends this dairy product fruity and savory notes. The mold also consumes lactic acid, reducing the acidity of viili, giving it a relatively mild acidic flavor. To make viili, you’ll need milk and a viili starter, which contains both Lactococcus cremorisx and G. candidum [3].

Kefir

Although not technically yogurt, kefir is a bubbly, mildly alcoholic, Russian-derived equivalent. What distinguishes kefir from yogurt is that instead of relying solely on lactic acid bacteria for fermentation, it’s made from kefir grains, which are large cauliflower-like complexes composed of lactobacilli bacteria and yeasts. Kefir also sets itself apart from other fermented milk products in that its fermenting microbes exist in these relatively large, popcorn-sized ‘grains,’ instead of being evenly dispersed throughout the milk. While bacteria are busy converting a portion of the lactose into lactic acid, yeasts from the kefir grains also convert lactose into ethanol and carbon dioxide. The result is a tangy, yeasty, and effervescent beverage [4]. Kefir boasts higher probiotic activity than typical yogurts, making it a fermented dairy product of choice among health enthusiasts.

Kefir grains. Photo credit: Chiot’s Run (chiotsrun/Flickr)

Ayran

This national drink of Turkey is made by diluting natural yogurt with ice water and salt. Throughout Turkey, different regional variations of ayran exist, with the most well-known version originating from a town called Susurluk. In Susurluk, local variations of ayran are made from a mixture of cow, buffalo, and sheep’s milk, giving it a distinctive creamy and foamy quality. A notable feature of Ayran is its lower shelf-life when compared to other fermented milk products. Stabilizers are added to ayran to prevent the water and milk mixture from separating, but salt hinders the effects of stabilization [5].

Yakult

Photo credit: Dezzawong/Wikimedia Commons

Now found all over the world and most notably in vending machines throughout Asia, Yakult is a probiotic drink that was developed in Japan. Japanese microbiologist, Minoru Shirota, was searching for a strain of bacteria that would benefit digestive and overall health. His work led him to Lactobacillus casei Shirota, which he cultivated and used to develop Yakult. Yakult is made from adding this unique bacteria strain to skim milk, water, and sugar, and is often enjoyed for its sweet and fruity natural flavors. As seen above, Yakult can also be found in several flavor variations as well.

Cultured milks are a culinary marvel, especially when you consider how many different forms it can take. Head to the dairy aisle and try a new variation of yogurt, or why not attempt making some at home in your own kitchen? With all the different forms out there, you’ll surely find one you enjoy.

References cited:

McGee, Harold. On Food and Cooking. The Science and Lore of the Kitchen. New York: Scribner, 2004. Print.
Lalime, Jennifer. “How to Make Greek-Style Yogurt“. The Feed.
Salminen, Edith. “There Will be Slime“. Nordic Food Lab.
Farnworth, E. R. Kefir—a complex probiotic. Food Science and Technology Bulletin.
“Fame of Foamy Ayran Goes Beyond Borders“. Hurriyet Daily News.

About the author: Mai Nguyen is an aspiring food scientist who received her B.S. in biochemistry from the University of Virginia. She hopes to soon escape the bench in pursuit of a more creative and fulfilling career.

Read more by Mai Nguyen

Mushrooms on Mortality, Menus, and the Mind

June 23, 2015/in Science & Food/by Grant Alkin

What is neither plant nor animal and whose size can span up to 1,665 football fields [1]? A mushroom! The visible part of a mushroom may seem small, but underneath the ground its’ mycelium, or threadlike reproductive organ, can cover an astounding amount of surface area.

Oyster mushrooms. Photo credit: (Ron Wolf/Flickr)

During the recent “Mushrooms: Fungi as Food” event, undergraduate student Elsbeth Sites discussed the edible, dangerous, and innovative parts of the mushroom. Attendees left with Back to the Roots® mushroom kits to try their hand at growing oyster pearl mushrooms.

Mushroom classification

Belonging to the Fungi Kingdom, mushrooms are part of the Basidiomycetes phylum and have distinctive fruiting bodies (the part we see above ground). There are 16,000 species that make up this phylum and 10,000 are large enough to be food. However, do not get too excited and eat the mushrooms you see on the ground, as 10% of these species are poisonous and 30 types are lethal.

Mushrooms as food

What contributes to a mushroom’s unique texture is the chitin that is contained within its cell walls. This substance is similar to keratin, which is found in crustacean shells. To put things in perspective, chitin from crustacean shells is often made into surgical thread because it is durable and resistant to pancreatic, bile, and urine enzyme degradation. It is also biodegradable as it breaks down naturally overtime [2]. It is no wonder that mushrooms hold up well during cooking! This amazing fungus also boasts nutritional benefit: mushrooms are the only item in the produce aisle that produce their own Vitamin D. They can turn the vitamin D precursor, ergosterol, into vitamin D2 (ergocalciferol, an isomer of ergosterol) with the help of the sun’s UVB rays [3]. In addition, shiitake mushrooms and white button mushrooms produce Interleukin-23, a cytokine that helps protect the host from gut pathogens and increases immunity and inflammatory response [4].

Shiitake mushrooms have been found to increase immunity when ingested [4]. Photo Credit: (Keith Weller/Wikimedia)

Mind-altering mushrooms

Of course, some mushrooms can even produce hallucinations. Those of the genus Psilocybe contain the psychoactive ingredient psilocybin, which is a seritonergically-mediated hallucinogen that can cause sensory overload. This ingredient is so potent that in a research study where 36 participants received psilocybin, 58% reported their experience to be among the five most personally meaningful experiences of their lives [5].

Bog Conocybe that contains hallucinogenic psilocybin compounds. Photo Credit: (Ron Gay/Flickr)

Mushrooms as digesters

Mushrooms have a unique ability to decompose organic matter as well as environmental pollutants via bioremediation [6]. Recently, this ability has been extended to “The Infinity Burial Project,” which is developing a mushroom spore filled suit to decompose dead bodies [7]. Interestingly, the mushroom suit is proposed to remediate toxins in the human tissue, making it eco-friendly [7].

The small size of mushrooms is deceiving as different species have various abilities, such as production of nutrients, mind-altering substances, and/or decomposition factors. Who knows what other unique capabilities mushrooms have in store for the future!

References cited:

Strange but True: The Largest Organism on Earth Is a Fungus. Scientific American™.
Nakajima, M., Atsumi, K., Kifune, K., Miura, K., & Kanamaru, H. “Chitin is an effective material for sutures.” The Japanese Journal of Surgery 16.6 (1986): 418-424. Web.
Vitamin D in Mushrooms. USDA.gov.
Chandra, L.C., Traoré, D., French, C., Marlow, D., D’Offay, J., Clarke, SL., Smith, B.J., & Kuvibidila, S. “White button, portabella, and shiitake mushroom supplementation up-regulates interleukin-23 secretion in acute dextran sodium sulfate colitis C57BL/6 mice and murine macrophage J.744.1 cell line.” Nutrition Research 33.5 (2013): 388-396. Web.
Griffiths, R.R, Richards, W.A., Johnson, M.W., McCann, U.D., & Jesse, R. “Mystical-type experiences occasioned by psilocybin mediate the attribution of personal meaning and spiritual significance 14 months later.” Journal of Psychopharmacology 22.6 (2008): 621-632. Web.
Tortella, G.R., Diez, M.C., & Duran, N. “Fungal diversity and use in decomposition of environmental pollutants.” Critical Reviews in Microbiology 31.4 (2005): 197-212. Web.
The Infinity Burial Project. Infinityburialproject.com

About the author: Catherine Hu is pursuing her B.S. in Psychobiology at UCLA. When she is not writing about food science, she enjoys exploring the city and can often be found enduring long wait times to try new mouthwatering dishes.

Read more by Catherine Hu

Pistachio

June 16, 2015/in Flavor of the Month/by Grant Alkin

They’re green, nutty, and floral, the perfect summer combination. Pistachios are used in many summertime favorites around the world, from can’t-get-enough-of-‘em Turkish delights to the Indian Subcontinent ice cream kulfi to the Italian frozen dessert spumone. They’re even perfect for cracking open for snacking while watching the ballgame. If pistachios aren’t the quintessential summer flavor, here are seven reasons why they should be: Read more

Lard Legacy: Does Your Diet Doom Your Child’s Health?

June 2, 2015/in Science & Food/by Grant Alkin

Cheeseburger with Fries [photo credit: TheCulinaryGeek]

Now you can feel even more guilt about how that greasy cheeseburger might affect your future. A study by the National Institutes of Health suggests eating a high fat diet may also impact your child’s health¹.

Growing evidence links increased caloric and fat consumption to the rise in immune-mediated diseases, like arthritis, food allergies, and inflammatory bowel disease². These diseases result from abnormal swelling and inflammation that occur when the immune system produces exaggerated responses or reacts to false signals. Studies suggest the high fat consumption typical of western diets may be responsible for confusing our immune systems. For example, dietary fats promote inflammation and trigger immune responses specific to bacteria³.

Because much of this evidence is based on short-term or population studies, for this study, Myles and collaborators explored the longer-term effects of increased parental fat consumption on their offspring’s immunity using mice¹. Specifically, scientists fed a high fat “western” diet to one group and a low fat control diet to the other. After giving birth, their pups were fed the control diet and exposed to a battery of tests examining their immune response. Compared to the control diet, the western diet had 10% more calories from fat, twice as many carbohydrates, and a higher ratio (as much as 15:1) of omega 6 to omega 3 fats. While both omega fats are essential, healthy diets contain a close balance (2:1) of the animal-derived omega 6 fats relative to the fish- and vegetable-derived omega 3 fats.

While the mice pups showed no differences in weight or blood sugar, the pups whose parents had western diets surprisingly showed significantly lower immune function: these pups were less resilient to bacterial related disease. They had higher mortality rates from internal infections and more severe skin infections. Furthermore, their skin cells displayed a lower level of bacterial defense proteins. Additionally, their colons and spleens did not work as effectively. The colons of these animals, which are critical sites for developing the immune system, showed exaggerated inflammation when exposed bacterial toxins. Both their colons and spleens showed lower levels of immune cells and proteins.

B0008203 E.coli on the surface of intestinal cells

E.coli on the surface of intestinal cells [Photo Credit: Wellcome Images]

Interestingly, researchers suggest that the diet itself did not directly cause the compromised immunity of these mice. Instead, they conclude that the western diet negatively impacted their gut microbiome—the sum of all bacteria present in their gut. In follow-up experiments, pups fed the western diet showed normal immune function if their parents were fed the control diet. Furthermore, DNA characterization of mouse stool revealed that pups from parents on western diets had less diverse bacteria than control pups. Increased fat consumption may have changed available nutrients and limited the bacteria in the parents on western diets. Because mothers shape their offspring’s microbiomes during the birthing and nursing process, pups of parents on the western diet received less diverse bacteria. Therefore in follow-up experiments, the western diet did not affect the immunity of the pups whose mothers ate control diets, because they already had received diverse microbiomes.

Changes in the microbiome may impact the immunity of the pups because of the “hygiene hypothesis”; this essentially suggests we have become too clean. Because we are not exposed to enough bacteria and other immune system triggers growing up, our immune systems don’t develop as extensively as those exposed to a more diverse range of microorganisms. The ‘hygiene hypothesis’ has been fueled by research showing that children in homes with more bacteria have lower asthma and allergy rates. A similar scenario was recapitulated for the immune compromised pups in this study. Final experiments with the mice showed that when the researchers raised pups from both parental groups in the western and control diet together, they both displayed similar bacterial diversity and immune function. By living with the pups with more diverse bacteria, the immune compromised pups exhibited increased diversity in their microbiome and negated the effects of their parents’ western diet. In other words, this result may suggest that even if you lived on a diet of greasy cheeseburgers, your kid’s may still have healthy immune systems if they are rolling around in the dirt with the kids whose parents stuck to their kale and whole grains!

While this study is promising for the hygiene hypothesis, more research is necessary to understand this effect in people. For example, these mice had simpler microbiomes and diets than the average human. It is unclear how this complexity may change the effect for people. Additionally, while this study only looked at fat consumption, other factors such as genetics can impact microbiome diversity and the respective impact on immunity. In any case, assuming this research translates, it suggests eating a lean turkey burger now, may help save your kids from arthritis, food allergies, or inflammatory bowel disease in the future.

References cited:

Myles, I.A. et al. 2013. Parental Dietary Fat Intake Alters Offspring Microbiome and Immunity. Journal of Immunology. 191 (6) 3200-3209.
Kau, A.L. et al. 2011. Human nutrition, the gut microbiome and the immune system. Nature. 474: 327-336.
Calder, P.C. 2011. Fatty Acids and Inflammation: The Cutting Edge Between Food and Pharma. European Journal of Phamacology. 668 (Suppl. 1): S50-S58
Gereda, J.E. et al. 2000. Relation Between House-dust Endotoxin Exposure, Type 1 T-cell Development, and Allergen Sensitisation in Infants at High Risk of Asthma. Lancet 355: 1680-1683

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

Read more by Vince Reyes

Garlic

May 26, 2015/in Flavor of the Month/by Grant Alkin

Image Credit: Robert Benner (mullica/Flickr)

If you’ve ever made the mistake of devouring three bowls of James Beard’s Garlic Soup a few hours before The Job Interview Of Your Life (I’m not speaking from experience here), you will recognize the frantic moment in which you pray that 1) the handful of mints burning in your mouth have superpower strength, or 2) your interviewers cannot smell, or 3) whoever you’re meeting had four bowls of garlic soup. Ahhh, the allure and woe of garlic. Why do you hate me if I love you so much?

Known for its distinct aroma and taste, Allium sativum – or garlic, as most of us know it – makes dishes sweet and pungent while it turns breaths foul and fetid. But what exactly causes garlic breath? More importantly, how do you get rid of it?

“Dear god, what did this guy have for lunch?” — Image Credit: (fiverlocker/Flickr)

The Breakdown of Garlic Breath

Garlic contains many sulfur compounds, but the ones most responsible for garlic breath are: diallyl disulfide, allyl methyl disulfide, allyl mercaptan, methyl mercaptan, and allyl methyl sulfide (AMS). The gases released by all of these compounds, except forAMS, originate in the oral cavity when we mechanically crush garlic in our mouths, so brushing your teeth and tongue will reduce the presence of the mouth-originated odors. However, good dental hygiene doesn’t usually entirely get rid of the smell because AMS is what causes unwelcome garlic breath, and this can linger for several hours or even days.

Allyl Methyl Sulfide (AMS), the unwanted pungent houseguest that overstays its welcome. — Background Credit: Crispin Semmens (conskeptical/Flickr)

AMS is a sulfur compound formed inside the body from allyl mercaptan, so instead of originating in the mouth, AMS is produced in the microflora of the gut. The resultant gas quickly evaporates into the bloodstream, which then diffuses to the lungs and infuses each breath of air that leaves our bodies with traces of strong-smelling allyl methyl sulfide. And if that isn’t wonderful enough, the compound is also released through pores of the skin, which is why you may notice a lingering body odor after garlic-heavy meals. Unfortunately, AMS does not get metabolized in your gut and liver like many other molecules that we eat, so it takes much longer for AMS to breakdown – which is why the AMS stays in the body for many hours later. [1]

SOLUTIONS: When brushing your teeth (sadly) isn’t enough

Image Credit: Robert Bertholf (robbertholf/Flickr)

EAT THIS: Parsley, Spinach, Mint, Apples, Pears, plus any fruits and veggies that are prone to browning (think avocados, bananas, potatoes, etc.)

WHY: These foods contain an enzyme called polyphenol oxidase. (The same enzyme is what makes your fruit salad look brown!). When this compound is exposed to oxygen, it reacts in a way that reduces both the odors of the volatile compounds and the formation of more AMS. [2]

Image Credit: A Girl With Tea (agirlwithtea/Flickr)

DRINK THIS: Green Tea, Coffee, Ku-Ding-Cha (a bitter-tasting Chinese tea), Prune Juice

WHY: These drinks contain a polyphenolic compound called chlorogenic acid, which is another chemical that works to deodorize garlic-derived sulfur compounds on human breath. [2]

Image Credit: (Unsplash/Pixabay)

ALSO DRINK THIS: Lemon juice, Soft Drinks, Beer, Hot Cocoa (and other acidic foods/beverages)

WHY: When garlic cloves are cut or crushed open, they release an enzyme called alliinase that facilitates the reactions which produce compounds responsible for the smell of garlic. Because these drinks have a pH below 3.6, they quickly destroy alliinase and minimize the formation of garlic volatiles. [2]

Image Credit: Mike Mozart (jeepersmedia/flickr)

DRINK THIS INSTEAD OF WATER: Milk!

WHY: While drinking water works extremely well for reducing garlic breath, milk works even better because of its extra fat, protein, and sugar. Specifically, whole milk is effective in the reduction of the hydrophobic compounds diallyl disulfide and allyl methyl disulfide because of its high fat content. Note that drinking milk during a garlic-heavy meal does a better job of killing garlic breath than drinking milk afterwards, because the milk is able to directly react with the volatile compounds when it is mixed with garlic. [3]

Makes me think garlic ice cream might actually be a genius all-in-one odor-neutralizing dessert!

References Cited:

Suarez, F., Springfield, J., Furne, J., Levitt. M. Differentiation of mouth versus gut as site of origin of odoriferous breath gases after garlic ingestion. Am J Physiol. 1999; 276(2):425–30.[http://ajpgi.physiology.org/content/276/2/G425]
Munch, R., Barringer, S.A. Deodorization of Garlic Breath Volatiles by Food and Food Components. Journal of Food Science. March 2014; 79(4): C536-533.

Hansanugrum, A. Barringer, S.A. Effect of Milk on the Deodorization of Malodorous Breath after Garlic Ingestion. Journal of Food Science. August 2010; 75(6): C549-558.

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

Read more by Eunice Liu

Lobsters: A Crustacean Sensation

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

Photo credit: Flickr/Stacylynn

They lurk in the depths of the ocean, feasting on the remains of their fallen neighbors. With stalked eyes, muddy coloring, and large predatory claws, they’re reminiscent of insects and are admittedly neither cute nor cuddly. They’re ancient, they’re cannibalistic, and they’re delicious dipped in lemon and butter. They’re the beloved lobsters, a crustacean sensation.

Lobsters have spent decades clawing their way up social and culinary ranks, rising from their status of an aquatic beach pest to the iconic culinary symbol of New England as we know them today. In early America, lobsters would wash up on Boston beaches after storms and litter the shores with their decomposing bodies. Piles of carcasses would collect and rot, prompting frustrated New Englanders to put them to good use. The festering carcasses were harvested and ground into a slurry, which was then used as fertilizer or fed to prisoners and peasants as a high-protein fuel [1]. Clearly, lobsters were hardly symbolic of fine dining and affluence. Lobsters were so reviled that indentured servants in Massachusetts often signed contracts refusing to eat them more than three times a week, deeming such treatment as being cruel and unusual.

In the mid-1800s, railways overtook America as the dominant mode of transportation and led the lobster on its journey to popularity. Train managers exploited the low cost of small lobsters and fed them whole to unsuspecting inland customers, touting them as a rare and exotic delicacy. Satisfied customers quickly spread word of this new luxury food, and thus began the rise of the lobster. With the help of this clever rebranding, lobster meat began appearing in restaurants alongside salad bar toppings and gained wide recognition not only as a viable source of protein, but also as a respected food item. By World War II, lobsters became integrated into American society as a luxury [2].

Whether they’re plucked straight from the sea or from a tank at the grocery store, there are few foods that beat a freshly cooked lobster. Many of us squirm at the prospect of plunging a live lobster into a bubbling vat of doom, viewing the act as a cruel, but necessary sacrifice we must make in order to eat it. So what is it that compels us to cook them live in the first place? A major turning point in its culinary standing was when chefs realized that lobsters taste better when cooked alive. Cooking live shellfish preserves the structural integrity of the meat and gives a sweeter and cleaner taste, in stark contrast to the putrid flavors that can develop in the mushy flesh of deceased lobsters [1]. The biochemistry of death accounts for this change.

The inside of a dead lobster serves two purposes: it’s a hub for several enzymatic reactions, and it’s a breeding ground for rogue bacteria. Upon death, proteolytic enzymes are activated and attack the lobster’s internal organs. Once under attack, these organs release another wave of enzymes into the lobster’s muscle tissue. A major player here is the liver, which houses a multitude of proteases reserved for digesting food. These digestive proteases, along with the first wave of enzymes, leak out and begin degrading muscle tissue, by breaking collagen and other proteins down into smaller peptides, polypeptides, and amino acids. Given how rapidly these enzymes work, it’s only a matter of time before the lobster’s flesh turns to mush.

Additionally, many nutrient-producing enzymes are also activated upon death. These newly-produced nutrients cause trouble by encouraging bacterial proliferation. As bacteria begin multiplying inside of the lobster, they produce metabolic waste products along with their own brand of proteases, many of which lend to the off-flavors and textural defects found in deceased lobsters. To save the lobster meat from succumbing to textural degradation or bacterial contamination, iced storage or evisceration are often recommended to minimize enzymatic activity. Rapid heating via boiling or steaming, however, still remains the best-known way of rapidly deactivating these enzymes. Bacterial contamination in shellfish can also lead to food poisoning and other complications, so not only does freshly killed seafood taste better, but it’s also much safer to eat. Cooking live lobsters allows us to minimize the ill-effects between death and consumption and spares us from suffering any gastric mishaps [5].

You’ve tossed the lobsters into the pot now—what’s actually going on under that furiously clanking lid? Maybe you’ll hear them thrashing around or a hissing sound as steam escapes from their shells. One thing you’ll also notice as the lobster cooks is its color change—from a blue-black to a brilliant red-orange. A lobster’s muted coloring provides camouflage when it’s prowling around in the sea. Uncooked, a lobster’s shell contains α-crustacyanin, a complex formed when a protein binds with pigmented carotenoids derived the crustacean’s plankton-heavy diet [3]. On their own, carotenoids are richly colored and can range from yellow to red, and they’re also credited with providing sweet potatoes, carrots, and tomatoes with their vibrant colors. When bound to proteins inside a lobster shell, they’re blue. As heat is applied, the α-crustacyanin protein complex denatures and releases free carotenoids. Astaxanthin, the main pigment molecule, is now exposed and provides cooked lobsters with their characteristic red hue [6].

Artwork credit: Michael Kim

Within the shell, a lobster’s meat acquires those sweet and nutty aromas we’ve come to associate with seafood and summer. There are more than just cultural influences that have made lobsters desirable; it’s the very chemistry of lobster meat that sets it apart from others. When was the last time you invited company over for dinner and decided to serve boiled steaks? You probably never have. There’s a reason you fired up your grill—and that’s because grilling produces a far more flavorful steak. Cooking at higher temperatures associated with roasting or grilling triggers the beloved browning/Maillard reaction known to impart complex flavors onto your food. A unique feature of lobster meat that it undergoes the Maillard reaction at much lower temperatures than other meats like beef, chicken, or pork. As it turns out, lobsters actually have an unusually high concentration of free amino acids and sugars in their muscle tissue. This abundance of free amino acids more readily undergo these flavor-producing reactions at much lower temperatures than would be re-quired in other types of meat. This is why you can get away with boiling lobsters and shell-fish and still manage to produce incredible flavors (3).

Lobsters are a delight to the masses. They’ve amused countless children at the grocery store in their tanks and they’ve satisfied hungry adults alike. Whether you’re considering its history, culinary uses, or chemistry, the lobster truly is a sensation.

References cited

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

Read more by Mai Nguyen

Making Fake Meat Real: How Scientists are Tricking Your Tongue

May 12, 2015/in Science & Food/by Grant Alkin

Fake meat is often associated with a tough, flavorless texture that is added to dishes to provide protein. However, fake meat is no longer just glutinous balls or tofu hidden beneath sauces. From plant protein derived meats to in vitro preparations, there is much more to synthetic meat than what meets the tongue.

Veggie Sausage. Photo Credit: (Heather Quintal/Flickr)

Replicating meat texture

Meat texture is very complex. Consider the multiple components from muscle tissue fibers, blood vessels, fat, gristle, to nerves. Each component confers a different texture and flavor profile, so replicating meat is quite a challenging process.

Texture plays a big role in determining whether a product tastes like real meat or not. For example, the satisfyingly stringy texture one gets from pulling apart chicken strips. Fortunately, food scientists have found ways to emulate the fibrous quality in fake meat using soy protein. Soy protein is initially globular, so it must be denatured, or broken down, to make it more fibrous. Soy protein is first exposed to heat, solvent, or acid, before it is reshaped with a food extruder [1]. Extrusion processes are useful as they can form meat analogs with fibrous matrices, which can then be rehydrated into meat like substances [2]. However, this process can sometimes result in a dry product. The rising company Beyond Meat has gone further and found a way to use soy flour, pea flour, carrot fiber, and gluten-free flour to emulate the fibrous quality in their fake meat with a wet extrusion process. The proteins are realigned and then locked in position by crosslinking to get a fibrous chicken imitation that is also moist and juicy [1].

Taste & color of meat

The flavors of meat mostly arise during the cooking process. Maillard reactions between sugar and amino acids produce those familiar meat flavors and aromas [3]. The amino acid glutamate is of utmost importance as it activates the umami taste receptors. Real meats contain glutamate as it is found in proteins, and it is released during proteolysis that occurs during meat aging and cooking [4]. Since most fake meats do not contain glutamate, this taste can be added back with soy sauce, tomatoes, mushroom, and cheese in the form of sauces [5]. Another unique aspect of meat is its color. The myoglobin proteins found in muscle are initially red due to heme pigments, but with the added heat of cooking, protein denaturation results in a brown color associated with cooked meat. For fake meat, food colorings and spices can be used to mask the original color.

In vitro meat: your steak from a petri dish

To minimize the number of animals slaughtered, some scientists are even growing animal tissue in the lab [3]. To do this, they take a small muscle tissue sample and look for skeletal muscle satellite cells, which are essentially individual stem cells that are normally used to create new tissue in case of damage. After these satellite cells are collected, they are bathed in a nutrient serum where they can be coaxed into growing. When large enough, they are shocked with an electric current, which causes the tissue to contract and thicken, resembling small fillets of meat a couple centimeters long and a few millimeters thick [3]. While meat products generated using this process are not available at your local supermarket (or butcher), and this product is not truly “meat-less” for vegetarians or vegans, it could potentially maximize meat production by saving cows from the slaughterhouse.

In vitro meat samples. Photo Credit (Janique Goff/Flickr).

Fake meat efforts are attracting big investments from Bill Gates and Silicon Valley entrepreneurs, as the demand for meat increases. In fact, population growth and a boost in meat consumption have increased the global demand for meat threefold in the last 40 years [6]. Not only does this intensify the requirements for raising livestock, but it also increases the greenhouse gas emissions emitted during processing [6]. It is no wonder that the search for the best meat-replication process continues on! Whether from an animal or plant base, synthetic meat is becoming increasingly prevalent and is not just for vegetarians and vegans anymore.

References cited:

How ‘fake meat’ is made. Mother Nature Network.
Riaz, Mian N., Anjum, Faqir M., Khan, Muhammad Issa. “Latest Trends in Food Processing Using Extrusion Technology.” The Pakistan Society of Food Scientists 17.1 (2007): 53-138. Web.
Fake meat: is science fiction on the verge of becoming fact? The Guardian.
The Chemistry of Beef Flavor. BeefResearch.org.
What Foods are Glutamate-Rich? Msgfacts.org.
The Bill Gates-backed company that’s reinventing meat. Fortune.

Read more by Catherine Hu