Marshmallows

The science of toasting marshmallows

The science behind toasting marshmallows

When marshmallows are toasted, a chemical change occurs. The sugar molecules in the marshmallow are being changed into carbon (1). Sugar can be changed into water molecules. When you toast marshmallows, the heat causes a chemical reaction producing water molecules which then evaporate, leaving the carbon behind (4).

A marshmallow undergoes a six-step transformation before it becomes a toasted marshmallow: 

1. The swelling - as you heat the marshmallow, the moisture inside expands, which causes the marshmallow to swell (2).
2. The escape - as the moisture expands, it creates tiny holes in the marshmallow, which allow the moisture to escape as steam (2).
3. The sugar rush - as the marshmallow does not now have moisture, it is a sucrose char. Oxygen in the air rushes to the surface of the marshmallow (2). 
4. The flame on stage - oxygen diffuses to the surface of the marshmallow from the surrounding air. At the surface of the marshmallow, carbon reacts with oxygen, which produces a blue flame (2). 
5. The oxidation stage - carbon atoms combine with oxygen atoms to produce carbon monoxide, and then carbon dioxide (2)
6. The oxyinterruptus stage - as you remove the marshmallow from the fire and blow the marshmallow out, the oxidation process is interrupted, creating soot which is evidence of incomplete combustion: hydrocarbon + oxygen    →    carbon monoxide + carbon + water (2). 

How to cook the perfect marshmallow

You want to put your marshmallow slightly to the side of the flames and in an area of glowing coals. Above the fire, the heat coming up is known as the convective flow (hot gases coming off as flames). If you hold the marshmallow here, the marshmallow can catch on fire if you are not careful. If you want the perfect toasted marshmallow, you need to cook it using radiant energy (heat coming off of the glowing coals). Marshmallows are actually like pieces of fuel as they are made of sugar (carbon, hydrogen and oxygen). Therefore, it is easy to catch marshmallows alight over a fire (3). 

Making marshmallows

Marshmallows are a fun and enjoyable experience when sitting around a campfire. Toasting your marshmallows makes them brown and crispy on the outside, but soft and gooey on the inside! You can even make your own homemade marshmallows as shown in this video: http://www.youtube.com/watch?v=otb9AIGXMaM

For vegans, it is still possible to enjoy this marshmallow experience by following the recipe in this link: http://www.foodmyfriend.com/2012/07/vegetarian-marshmallows/. These marshmallows will still be gooey and soft when heated over the campfire, so vegans are no longer missing out on this tasty treat! 

By Lauren Watmough

(1) http://www.youtube.com/watch?v=mgDFxgtsCHk

(2) http://www.fitnessandfreebies.com/food/toastmarshmallows.html

(3) http://www.npr.org/player/v2/mediaPlayer.html?action=1&t=1&islist=false&id=154781777&m=154828858

(4) http://eatsleepscience.com/ess/index.php?option=com_content&view=article&id=49:marshmallow-science&catid=34:ess-details&Itemid=50