meat – Science and Food

Tag Archive for: meat

Bologna

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

Photo Credit: flickr/Jazz Guy

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

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

Photo Credit: flickr/Anne Mair Valentine

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

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

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

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

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

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

Works Cited

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

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

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

About the author: Elsbeth Sites received her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

Read more by Elsbeth Sites

Meat: where physiology meets flavor

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

A charcuterie board is the perfect accompaniment to any gathering and rivals a cheese plate as a crowd-pleaser. It’s low maintenance, delicious, and will almost certainly have a taste or texture to appeal to the pickiest of palates. Meat comes in an array of textures, fat content, and flavors, which vary species to species and even within the same animal. Flavor profiles of meat can vary wildly and subtleties between different cuts of meat can all be largely explained by chemistry.

Photo credit: willmacdonald18 (Flickr)

What is meat exactly? Meat can loosely mean any type of edible tissue originating from an animal – including everything from chicken feet to cow tongue. The majority of meat we consume, however, is skeletal muscle tissue, comprising roughly 75% water, 20% protein, and 3% fat. While the function of muscle tissue—which is to generate movement—is simple, muscle tissue is a complex system of biochemical machinery.

Muscle tissue consists white and red fibers, which each generate contrasting types of movement. The major differences between the two types of muscle fibers are summarized in the table below.

	red muscle fibers	white muscle fibers
alternate names	slow-twitch fibers	fast-twitch fibers
relative size	thin	thick
movement type	prolonged, deliberate	short, high-powered bursts
fueled by	fat + oxygen	glycogen
Requires oxygen?	absolutely	yes, but can run anaerobically
taste/nutrtion	fattier, more flavorful	higher in protein, relatively bland
appearance	dark/red	white

The main distinction between these types of tissue is in their function and metabolic demands. Red muscle fibers are designed for endurance—think long distance running—or sustained motion. Red tissue runs on fat and oxygen and absolutely requires oxygen to function properly. Since red muscle tissue demands oxygen, it contains an abundance of a pigmented protein called myoglobin. Myoglobin binds and stores oxygen from the then passes it along to a fat-oxidizing cytochrome that generates ATP to fuel the cell. The more exercise a muscle receives, the higher its demand for oxygen, and the more myoglobin and cytochromes it will contain, leading to a darker appearance.

Photo credit: Harlanh (Flickr) Duck breast – an example of dark meat

White muscle fibers, on the other hand, are specialized for more sporadic and brief energetic demands. These tissues use oxygen to burn glycogen, but can also produce energy anaerobically if needed. However, anaerobic metabolism results in the buildup of lactic acid and limits the endurance of these tissues, which is why they can only be used for short periods. White muscle fibers, unsurprisingly, are what comprise white meat—chicken breast, turkey breast, frog legs, and rabbit meat.

Photo credit: allthingschill (Flickr) Turkey breast

The link between structure, function, and taste can be used to answer the question of why chickens and turkeys have a combination of dark and white meat, but why ducks and geese are all dark meat. They’re all birds, after all, so it’s rather surprising that there’s such a drastic difference in their breast meat, until you consider their habits. Chickens and turkeys are relatively flightless birds. They stand, walk, or run, and use their legs to bear their weight. Their constantly used legs are mainly dark meat and their infrequently used breasts are composed of white meat. Duck and geese, however, are migratory birds whose flight patterns enlist the use of breast muscles to help them stay airborne for extended periods. To aid them in sustained flights, their chests muscles require increased stores of oxygen and myoglobin, making their breast meat dark, in stark contrast to a chicken or turkey’s breast.

The dichotomy of metabolic demands between red and white meat clearly impacts their physiology, but how does this translate into taste? The complexity of the biochemical equipment needed to store fat and oxygen and metabolize fat in red muscle tissue equates to a higher number of enzymes present in the cell that can break down and produce more flavorful compounds when cooked. A piece of dark or red meat is fattier, boasts richer and more complex flavors, and retains moisture far better than white meat.

How else can chemistry explain the different tastes of meat, ranging from the beefy flavors of cow to the gamey flavors of duck breast? It’s a common saying in the culinary world that where there’s fat, there’s flavor. While fat serves as storage for energy, it doubles as storage for flavor. With fat distributed throughout the meat, any fat-soluble flavor or aroma compounds can end up in them providing meat with its unique flavor profile. What winds up in the fat is heavily influenced by diet – cows taste “beefy” as a result of flavor compounds metabolized from grass and forage. Lamb and sheep’s distinctive flavors come from compounds produced by the liver, and the gamey flavors of duck meat are likely derived from intestinal microbes.

Examining meat through a scientific lens allows us to relate some common mantras of biology, chemistry, and cooking: structure and function go hand in hand, fat is where the flavor is, and you are (and you also taste like) what you eat. In the context of meat, physiology and flavor are intertwined and whether you’re a fan of dark or white meat, you can surely appreciate the fascinating connection between animal physiology and flavor.

References Cited:

McGee, Harold. On food and cooking: the science and lore of the kitchen. New York: Simon & Schuster, 1997. Print.

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

Freezer Burnt Meat

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

Photo credit: flickr/Steven Depolo

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

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

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

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

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

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

References cited

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

About the author: Elsbeth Sites received her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

Read more by Elsbeth Sites

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.

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

BBQ Physics & Meat Flavors

April 9, 2015/in What We're Reading/by Grant Alkin

Ever put a slab of pork shoulder or beef brisket on the smoker for a BBQ, only to eventually hit “The Plateau”? Physicist Dr. Greg Blonder has the explanation for why the temperature of these meats will rise steadily for a few hours before it inexplicably stops and stalls at several degrees lower than the ideal 190°F. Fortunately, his explanation also comes with a solution. Once that dilemma is solved, check out the science that makes meat so delicious.
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Science of Marinades

March 31, 2015/in Science & Food/by Grant Alkin

Chicken Tikka Masala, Beef Bulgogi, and Ceviche all have one thing in common: each protein is marinated, which contributes to the development of flavors and textures in the final dishes. The use of marinades is common across all cultures, and can provide a unique kick to food when done correctly.

Rostbrätel: marinated cutlet of pig neck. Photocredit: (Sebastian Wallroth/Wikimedia Commons)

What is marination?

Marination is the process of immersing foods in a liquid often made with oil, seasonings, and an acid or enzymatic component, to flavor and tenderize food. This liquid is called a marinade, and the term originally came from the use of seawater to preserve meat. The roots of the word are derived from the Latin word for sea (mare) [1].

Why is marination useful?

To understand the importance of marination, we must first address the components of raw meat. Consider tough, lean cuts of meat such as shank or flank. Meat toughness is related to the collagen and elastin fiber content in its connective tissues. One way to tenderize lean meat is with moist heat, as this breaks down stiff collagen proteins into soft, soluble gelatin [2]. Gelatin is responsible for that silky, falling-apart texture and mouthfeel [3]; this can be achieved with braising and stewing, where meat is simmered in liquid at a low temperature, allowing collagen to dissolve starting at 160º F. However, this conversion process can take some time, even up to 72 hours. Another reason to pre-tenderize meat before cooking is to prevent dried out meat: moisture is lost when heat is applied (despite being cooked in liquid).

This is where marination comes into play, as it provides another opportunity for protein breakdown. This method can thus shorten subsequent cooking time as well as minimize moisture loss as less heat is needed to “cook” the meat. Two types of marination include acidic and enzymatic marination, which both help break down the connective tissue in the meat.

Acidic marination

Acids, such as lemon juice or vinegar, work by denaturing proteins through disruption of hydrogen bonds in the collagen fibrils. Adding alcohol can also supplement the penetration of acid marination since fats present in meat are soluble in alcohol [4]. Beer and wine thus make great marinades, and they also confer their own tenderizing agents (tannins). Be careful not to overmarinate the meat, as prolonged exposure to acid can cause it to become tough. This occurs because after the proteins are denatured, they tighten as water content decreases [5]. Some marinades involve milk or yogurt since they have lower acid content.

Shrimp Ceviche, a dish that uses acidic marination. Photo Credit: Carlos Lopez (cloalpz/Flickr)

Enzymatic marination

Enzymes increase the rate at which cellular reactions occur, and certain enzymes help attack the protein networks of tough meat. Proteolytic enzymes such as fungal amylase (in legume seeds) and protease (in ginger) help break down muscle fiber protein into its constituent amino acids. Enzymes from tropical plants such as bromelain (in pineapple), papain (in papaya) and ficin (in latex of fig tree) break down collagen and elastin [4]. In fact, natives of pre-Columbian Mexico used to wrap their meat in papaya leaves before cooking since they found that it increased tenderness [6]. However, be sure to monitor the time of marination, for the enzymes can completely digest meats if they sit for too long.

Papaya contains papain, a proteolytic enzyme. Photo credit: Tatiana Gerus (Tatters/Flickr)

Adsorption

Another factor to take into account is the amount of contact the meat has with the marinade. Marination is a process of adsorption, where the marinade adheres to the outer surface of the meat rather than absorption, where it would penetrate all the way through [7]. This has resulted in some controversy over whether acidic and enzymatic marinades actually tenderize meat or not, but there are ways to alleviate this problem. It may be helpful to use thinner slices of meat to enhance the marinade penetration and reduce marination time. For thicker cuts, marinades can be injected to increase contact surfaces. Adding salt also helps, as it first draws out liquid by osmosis; then the resultant brine is reabsorbed into the meat while breaking down muscle structure. The brine draws flavors further down below the surface [8]. Fat such as oils are also useful to transfer fat-soluble flavors from the seasonings into the meat.

In general, tender cuts of meat should not require as much marination time as tougher cuts, and fish require even less time. Marinated meats should also be refrigerated to prevent harmful bacterial growth. Although it may seem a hassle to prepare ingredients for a marinade and remember to apply it to the meat for a certain time beforehand, the results can be well worth the wait.

References cited

Some Surprising Facts About Marinades and the Origin of the Word. CulinaryLore.
Collagen. About Food.
Science of Slow Cooking. Science of Cooking.
Juáres, M., Aldai, N., López-Campos, Ó., Dugan, M., Uttaro, B., Aalhus, J. Beef Texture and Juiciness. Handbook of Meat Processing. January 2012.
Marinating Meats. Allrecipies.
Alarcón-Rojo, A. Marination, Cooking, and Curing: Applications. Handbook of Poultry Science and Technology, Secondary Processing. February 2010.
Saucy Science: Exploring the Science of Marinades. Scientific American.
The Food Lab: More Tips For Perfect Steaks. Serious Eats.

Read more by Catherine Hu