Engineering and Fruitcake
Mark Atwater posted on December 29, 2013 | 6646 views

With the end of the Holiday Season comes a host of unpleasant activities. There’s taking down the decorations, saying goodbye to family and friends and going back to work. There might be some returning of gifts as well. This brings us to the age old question, “What to do with that fruitcake Aunt Rita left behind?”

Regifting is a classic maneuver, and that’s OK. Fruitcake might actually increase in value next time around. We know implicitly that fruitcake is pretty much indestructible, and there is a good body of evidence why.

This is where we can only begin to plumb the depths of wisdom fruitcake has to offer. Engineering courses are jam-packed with boring examples of chemical reactions, mechanical properties and material design. It’s time to bring some holiday spirit into the engineering classroom.

Even if you’re not a teacher, you probably have to describe your job to people that are unaware and uninterested in the wide variety of engineering disciplines (think of Aunt Rita). You have to find some response to the question, “What does an engineer do?”

Unless you drive a locomotive, the explanation will get wordy (and boring) fast. Allow the fruitcake to be your guide.

The connection to fruitcake begins with the macroscale perspective. Students (and family) may appreciate the example more than directly describing enthalpic driving forces and stress gradients. It also gives you a reason to dismantle the fruitcake without actually eating it.

To start, fruitcake is a nice example of a composite material. Being comprised of fruit (reinforcement) and cake (matrix), there is a design factor in achieving the proper mixture of types of fruits and their ratio to the cake. This can be directly tied to concrete, for instance, not only in structure, but in texture and taste as well.

Perhaps some solid mechanics will help emphasize the structural importance. Break a piece off. How does crack propagation occur, and how does the fruit size, shape and percent volume affect that? How about the compressive and tensile properties? Dry fruitcake is brittle while moist fruitcake has a bit more resiliency. (Just don’t admit the cake is dry in front of Aunt Rita, even if it is)

You can reduce the scale and look at the chemistry of it as well. The longevity of a fruitcake is said to be tied to the high sugar content, and the tannins in the dried fruit helps the cake age like wine. A dry fruitcake can be revived by warming it to release the moisture from starch molecules. The high density prevents oxidation and microbial growth (that is for you bioengineers).

This is just the tip of the engineering marvel that a fruitcake is. With such a rich set of engineering practices involved, you might expect fruitcake to have its own research program. And you’d be right.

As described in a 1987 report, “A storage study was conducted at U.S. Army Natick Research, Development, and Engineering Center to determine if fortified, thermoprocessed fruitcake would retain its acceptability and nutritional value in extended storage.”

The goal was to establish whether fortified fruitcake would meet NASA requirements for nutrition after three years in storage at various temperatures. Being an astronaut isn’t looking so glamorous anymore.

The study was a follow-up to a previous one in the 1970s and concluded that certain nutrients were not adequately retained. The recommendations for future work included a call to find “appropriate carriers and adjuncts, such as encapsulation, for ascorbic acid, folacin, and vitamin B12 in fortified products that are thermally processed or are to be stored at nonrefrigerated temperatures.”

That sounds like something we can all get behind. So what do you think? What lessons can we learn from fruitcake? What is your specialty and how does it connect to our mutual friend the fruitcake? Any recommendations for future fruitcake research?

If you’re looking for a solid start to the New Year, try reading the research report, “Effects of storage time and temperature on nutritional content of fortified fruitcake.”

If you’re looking for a more lively way to re-purpose that fruitcake, check out the Manitou Springs Fruit Cake Toss in the video below.


Images adapted from (top) and National Geographic (bottom) 

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