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Written by: Alison Kennedy
Written on: May 5th, 2012
Tags: food & drink, health & medicine
Thumbnail by: Roland Zumbuhl/Wikimedia Commons
About the Author
Alison is sugar-loving aerospace engineering major at USC.
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Volume XIV Issue III > Cotton Candy: Carnival Snack to Medical Wonder
Many people know that cotton candy is made from sugar. They may not know, however, this fun carnival treat's colorful history. Cotton candy has been used in many different ways since its properties have become known in greater detail. Melting and spinning sugar, for one, results in a delicious dessert: using chemistry and physics, engineers have created machines that can form the fluffy snack. Nowadays, cotton candy is not only considered for consumption, but also for transplant research.

Introduction

Carnivals, circuses and amusement parks entertain huge crowds of people, but what keeps visitors satisfied in the spare moments among rides, stunts and attractions? One answer is cotton candy.
Cotton candy evolved from a rare and decadent dessert called spun sugar. Spun sugar was an 18th century delicacy, enjoyed mostly by wealthy families due to the high price of sugar. But even as time passed and the price of sugar decreased, very few people had the patience to melt sugar and spin it into a dessert without burning it, so this treat was still a rarity. When sugar spun by machines became available to the public in the early 20th century, however, the dessert took on a new name: cotton candy.
Cotton candy is almost entirely made of sugar. For those who want to manipulate sugar for cooking purposes, an understanding of sugar on a molecular level is vital. Sugar molecules must be manipulated—dyed and arranged in a certain way—in order to produce the commonly pink, fluffy snack we know today (Fig. 1). This manipulation was achieved by the earliest electric cotton candy machines, which were simple to operate and which completed the melting and spinning processes faster than could be accomplished by hand. The spinning motion exhibited by these machines is governed by rotational physics, a topic that the candy machine engineers understood well.
Roland Zumbuhl/Wikimedia Commons
Figure 1: Cotton candy, the sugary carnival treat.
Today, engineers who understand chemistry and biology are using cotton candy to actually improve human health. New research explores the use of small cotton candy threads to create a network of pathways. These pathways would become part of new and complex transplants as a way to imitate vascular networks (i.e. to transport blood).

The History of Spun Sugar

The melt-and-spin technique that transforms hard sugar into threads was known long before cotton candy was sold to the public. In a cookbook published in 1786 "written purely from practice", a housekeeper named Elizabeth Raffald described how to make a dessert of spun sugar. The following instructions for spinning sugar are paraphrased from pages 156 and 157 of the cookbook [1]:
• Set the sugar by the fire until it melts
• Use a clean knife to scoop up the syrup (melted sugar) and be sure not to let it cool
• Move the knife backwards, forwards and in all directions; a thread of syrup will follow
Spinning sugar by hand was time consuming and sugar was expensive in the 18th century. Wealthy families, those who could afford sugar and housekeepers to whom they could assign the tedious task, enjoyed spun sugar both as a dessert and as a preservative.
As a preservative, sugar was spun by knife directly over meat. This created a “silver web” that would keep the meat fresh for a few more days by stopping the growth of bacteria [1]. Bacterial growth is fueled by moisture, and so the reason that sugar can preserve food employs a concept that was developed in the science section of this article: spun sugar absorbs moisture. Not only does spun sugar absorb the moisture produced by the sitting meat, it also takes in the moisture from the bacteria. This kills the existing bacteria in addition to preventing any more growth.

The Chemistry

Sugar, or sucrose, is mostly harvested from sugar cane or sugar beets. Sugar cane produces a pulpy juice that is boiled and strained to remove impurities; after drying into granules, the sugar is ready for distribution [2]. In the early 18th century, however, sugar was often damaged by humidity and water in transport, which required it to be refined after transport and before sale [2]. Raw sugar still goes through the refining process today, and the final product is crystallized sugar, also known as table sugar. This dry, white substance is a collection of sugar crystals, which are formed of neatly organized sucrose molecules that take on a cube-like shape [2]. A sucrose molecule is composed of fructose and glucose, or more specifically, 12 carbon atoms, 22 hydrogen atoms and 11 oxygen atoms (C12H22O11) [3].
The sugar crystal is essentially a neat arrangement of bonded sucrose molecules [4]. The bonds between these molecules are broken at sucrose’s melting point, 190°C [2]. The melted sugar is then cooled before the sucrose molecules can reorganize into crystals. Because the new structure is composed of disordered sucrose molecules, the sugar can be formed into filamentous threads.
Sucrose crystallization, according to an experiment conducted by Dr. Theodore Labuza – awarded professor of Food Science at the University of Minnesota – can be induced by the presence of moisture [5]. This is important in understanding the process of coloring cotton candy. If the infamous pink coloring were added to the spun sugar product, the sugar would soak up the moisture from the dye and crystallize: the customer would be left holding small clumps of colored sugar instead of a collection of airy threads. The trick for coloring while still maintaining a cottony appearance is to add coloring to the table sugar, then melt the mixture. The colored syrup is then spun into threads that cool almost instantly. The sugar does not have a chance to recrystallize, and the result is a colorful, airy treat.

The Cotton Candy Machine at the World’s Fairs

Although the first inventor of the cotton candy machine is unknown, there are two likely candidates. Josef Delarose Lascaux, a dentist, is said to have introduced a cotton candy machine at the 1830 World’s Fair [6]. However, there are no patents or trademarks for a machine in his name.
In 1903, though, William Morrison and John Wharton submitted a patent for their “candy-machine” and used it to sell cotton candy at the 1904 World’s Fair. Their machine was one “in which a revolvable or rotating pan or vessel containing candy or melted sugar causes the said candy or melted sugar to form into masses of thread like or silk like filaments by the centrifugal force due to the rotation of the vessel” [7]. In a method similar to Elizabeth Raffald’s, the sugar is melted and wound into threads. The machine contains a basin that holds the melted sugar and has an array of small holes—each on the order of 50 micrometers in diameter—in the sides [2]. As the machine spins, the syrup is pushed through the holes, creating thin threads that are then spun into the final filamentous product. (A modern cotton candy machine is pictured in Fig. 2.)
Steve Jurvetson/Wikimedia Commons
Figure 2: The inner workings of a cotton candy machine.
Morrison and Wharton noted that centrifugal force was pushing the melted sugar away from the center [7]. A Canadian inventor, Herbert Hurd, even called his own cotton candy machine the “centrifugal machine” [8]. This force manifests itself according to Newton’s Second Law (a force causes an acceleration) and Third Law (every action has an opposite reaction).
The force that causes the melted sugar to accelerate outwards through the small holes is a response to the centripetal force generated by the rotation of the pan. Because the sugar maintains a circular path as it is whirled about inside the pan, the centripetal force is accelerating the sugar toward the pan's center. However, this motion produces a reaction "force"—the centrifugal force—that pushes the sugar radially outward through the holes [9]. As melted sugar reaches the outer bowl, it cools and forms threads, which are then ready to be bundled and consumed.

Medicine

Engineers of the early 20th century designed a machine to melt and spin sugar into a dessert. According to NPR, engineers of the 21st century are investigating the use of cotton candy in medicine (Fig. 3). A reconstructive surgeon and a Cornell graduate student are researching whether cotton candy can be used to create small pathways through which tiny blood vessels can travel. The presence of the cotton candy would allow a mold to be set in place around its pathway, and since the sugar crystals will dissolve when soaked in water, the cotton candy can be subsequently rinsed out. Cotton candy proves to be ideal for this research because it is easy to control the size and shape of the candy, since the molds may need to vary in the number or size of their thread-like tunnels [10].
Alpha/Wikimedia Commons
Figure 3: The thin sugary filaments that may provide vascular pathways for transplanted tissues.
The personalized molds could then be inserted into tissues that are to be used in surgeries on knees, windpipes, and more [9]. These new transplants generally lack functional vascular networks, so blood cannot travel to or throughout them. However, since these transplants are live tissues, they will die after the transplant without an adequate blood supply [11]. The research based on cotton candy is still in the very early stages of development, but in the future it could have a huge impact in the world of transplants.

Conclusion

A wide variety of engineering fields have worked with sugar. Knowing the chemical properties of sucrose allowed people to manipulate its molecules to engineer cotton candy, a delicious treat. This process was simplified, furthermore, by various generations of cotton candy machines, which were invented by mechanical engineers by applying their knowledge of rotational dynamics. Biomedical and chemical engineers, finally, are now using cotton candy in their research on the imitation of vascular tissue in transplants. Cotton candy is a snack that yields many sticky-fingered kids, but it is also a milestone in culinary technology and may soon figure prominently in biomedical engineering.

References

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    • [2] J. H. Galloway. The Sugar Cane Industry: An Historical Geography from Its Origin to 1914. New York: Cambridge University Press, 1989. 13-17, 40.
    • [3] “What is Sugar?” Exploratorium. Internet. Available: http://www.explorato​rium.edu/cooking/can​dy/sugar.html. Accessed Oct. 17, 2013.
    • [4] M. Chiang. “Sugar Load: Unwrap the Secrets Behind Some of the World’s Wackiest Candies.” Internet. Available: http://www.thefreeli​brary.com/Sugar+load​%3A+unwrap+the+secre​ts+behind+some+of+th​e+world's+wackiest..​.-a0127714004 [Nov. 1, 2004]. Accessed Oct. 17, 2013.
    • [5] T. P. Labuza. “Influence of Temperature and Relative Humidity on the Physical States of Cotton Candy.” University of Minnesota and St. Paul Academy, U.S., 2004.
    • [6] “Cotton Candy.” Internet. Available: http://www.candyusa.​com/FunStuff/CandyTy​pe.cfm?ItemNumber=92​6. Accessed Oct. 17, 2013.
    • [7] W. J. Morrison and J. C. Wharton. “Candy-Machine.”​ U.S. Patent 717756, Jan. 6, 1903. Internet. Available: http://www.google.co​m/patents/US717756. Accessed Oct. 17, 2013.
    • [8] H. J. Hurd. “Centrifugal Machine.” U.S. Patent 792899, June 20, 1905. Internet. Available: http://www.google.co​m/patents/US792899. Accessed Oct. 17, 2013.
    • [9] “Centrifugal force.” Internet. Available: http://www.britannic​a.com/EBchecked/topi​c/102839/centrifugal​-force. Accessed Oct. 17, 2013.
    • [10] “Cotton Candy, A Medical Wonder?” National Public Radio. Feb. 2009. Online. Available: http://www.npr.org/t​emplates/story/story​.php?storyId=1007215​00. Accessed Oct. 17, 2013.
    • [11] C. Barras. “Cotton Candy Makes Sweet Blood Vessel Copies.” Internet. Available: http://www.newscient​ist.com/article/dn16​599-cotton-candy-mak​es-sweet-blood-vesse​l-copies.html [Feb. 2009]. Accessed Oct. 17, 2013.