The Science Behind the Hot Dog: Part 2

The last time I was at my parents’ house, my dad jokingly made a reference to “cow lips” in hot dogs.  I had to cringe.  With labeling requirements that reveal all ingredients in food products, why does the myth of hot dogs being made of "unspeakable" animal parts still exist?  Its longevity may be due to a hot dog’s inner appearance.  The springy, smooth, reddish brown hot dog is a far cry from marbled, fibrous beef chuck.  However, that beef chuck can be turned into a hot dog with the right machinery, ingredients, and cooking process and still deliver the protein, iron, and other nutrients promised by a fresh cut of beef.  In a previous post, I explained the non-meat ingredients of a hot dog.  Today, let’s talk about the meat.

A hot dog is an “emulsified” meat product.  An emulsion is a stabilized mixture of solid particles dispersed throughout a liquid component (Aberle, Forrest, Gerrard & Mills, 2001).  In an emulsified meat product, the particles are fat and the liquid component is water containing salts and proteins (Aberle et al., 2001).  While water and fat would naturally not mix together, proteins with both hydrophobic (“water-fearing”) and hydrophilic (“water-loving”) parts can hold the fat and water together (Figure 1).  Myofibrillar proteins (the stringy, fibrous muscle proteins that allow for movement) hold fat and water together well, but for the myofibrillar proteins to be of use, they must first be extracted from their original positions in skeletal muscle.  A bowl chopper (think of a king-size food processor) will first dice ground lean meat into tiny pieces, thereby increasing the surface area of the meat.  Salt will extract the tightly bound myosin and actin from each other, and these liberated proteins will then interact with the fat and water which are later added to the mix (Aberle et al., 2001). 

Figure 1: Proteins coat fat particles to allow the fat to be held within the water phase of an emulsified product.

If you are unfamiliar with proteins and how they are put together, this might be a little confusing.  The main point, though, is that parts of the animal with LOTS of myofibrillar protein (i.e., skeletal muscle) can interact with water and fat much better than parts of the animal with little myofibrillar protein.  Another type of animal protein is called “stromal protein,” perhaps better known as “connective tissue.”  The main stromal proteins are collagen and elastin.  Collagen is found in skin, lips, ligaments, bones, and blood vessels, and is, in fact, the most abundant protein in an animal’s body (Lodish, Berk, Zipursky, et al., 2000).  However, it is an “insoluble” protein, meaning it is not broken down as myofibrillar proteins are broken down by salt. 

Now, you might be wondering, “What does this have to do with hot dogs?”  Remember that hot dogs are emulsified products, and the emulsion can only be stable if the components bind together well under stress.  Meats that have high binding capabilities are those high in myofibrillar proteins such as bull and cow meat, skinless poultry meat, lean pork trimmings, and beef chucks (Aberle et al., 2001).  Meats with a high percentage of stromal protein include the infamous “filler meats:” lips, stomachs, snouts, skin, and tripe (Aberle et al., 2001).  If hot dogs contain a large percentage of collagen-rich meat, the collagen will melt during heat processing and then congeal as gelatin when the hot dogs are cooled (Aberle et al., 2001).  These hot dogs will undoubtedly not be what the producer or consumer wanted. Since skeletal muscle already contains some collagen due to the presence of blood vessels and connective tissue (Figure 1), deliberately increasing the amount of stromal protein by adding lips or snouts is not greatly practiced. 

Hopefully you now understand why the joke of “cow lips” in hot dogs is not so funny.  Producers want their customers to be happy with tasty, nutritious, good looking products, and this can only happen with the right ingredients.  If you are still curious about what’s in your hot dogs, check the ingredients label.  All filler or “variety meats” must be declared on the label, including the specific meat’s name (e.g. “heart”) (National Hot Dog & Sausage Council, 2013).  So the next time you’re at a weenie roast and someone doesn’t want to eat something made of the “less savory parts of an animal,” show them the ingredient list and enlighten them!  You can even whip out words like "emulsified" or "myofibrillar" to really impress them.

References

Aberle, E.D., Forrest, J.C., Gerrard, D.E. & Mills, E.W.  (2001).  Principles of Meat Science (4^th ed.).  Dubuque, IA: Kendall/Hunt Publishing Company.

Lodish, H., Berk, A., Zipursky, S.L., et al.  (2000).  Molecular Cell Biology (4^th ed.).  New York, NY: W. H. Freeman.

National Hot Dog & Sausage Council (2013).  How hot dogs are made: The real story.  Retrieved from http://www.hot-dog.org/ht/d/sp/i/38597/pid/38597.

hot dog picture: http://www.afdr.org/v2933-HOT-DOG-BEEF-HD-F-DELI-STYLE-BEEF-FRANKS-51.aspx

emulsion diagram: http://lpoli.50webs.com/Tips.htm

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