As Halloween approaches it seems like an appropriate time to have some fun and celebrate confectionery chemistry. We rarely think about chemical concepts when indulging a sweet tooth, but as chemistry is in everything, it’s time to explore our favorite treats in depth:
Marshmallows: These squishy goods are produced by mixing gelatin, egg white, corn syrup, and sucrose (the common form of sugar, consisting of glucose and fructose) in an aqueous solution, then beating the mixture. To get the cylindrical shape we typically associate with marshmallows, the solution is then poured into a mold and dried.
Chocolates: As many aficionados are aware, chocolate can be found in various forms: bitter, sweet, and milk. The strongest type of chocolate, bitter, is produced when cocoa beans are roasted, then husked, winnowed, de-germed, nibbed, and ground in a heated mill. Once this bitter chocolate is mixed with powdered sugar and refined, sweet chocolate is formed. However cocoa butter must also be added in equal amounts of the sugar; the butter comes from the process of pressing the original bitter chocolate. Then, to get the milk chocolate that fills the majority of Halloween trick-or-treat bags, milk is mixed into the sweet chocolate.
Hard Candy: It is fairly well known that this type of candy consists mainly of plain sucrose and some coloring, but the process of making it can be more complicated. Sucrose is first dissolved into water, then the water is evaporated to produce melted sucrose. Using other methods would result in caramelizing/burning the sugar instead of melting it. This melted sucrose is then either pulled or cooled on a slab without manipulation; it is this pulling process that causes the candy to take on an opacity and lighten any coloring as oxygen is incorporated into the sucrose and the crystallization is affected. To produce the glassy look we typically associate with hard candy, the melted sucrose must remain untouched while it cools.
While briefly summarized here, confectionery manufacturing requires many processes that can be found in a general chemistry laboratory textbook: solution, evaporation, crystallization, dehydration, etc. During production of these candies, there are also several factors that must be carefully regulated. One such is temperature, which is essential for all confectionery as in many processes sucrose is dissolved into water, which is then evaporated. However the sugar-water ratio must be kept precisely for the type of candy being made, which is done by controlling the temperature of both the heating source and the environment. The amount of time the sugar-water mixtures spend boiling to evaporate the water is also extremely important, because after a long period of time aqueous sucrose can decompose to form acid-like products, and eventually change the composition of the solution. And because we can’t talk about chemistry without mentioning structure, we must also factor this in to regulation. To get the proper consistency of a marshmallow, the individual particle size of all the components must be optimized to produce the best possible texture. The crystallization pattern of the sucrose is also very important, as crystal size is often suggestive of the consistency of the product.
And as many a high school chemistry/college general chemistry survivor can attest, color change is also an essential component of chemistry as certain dyes can be indicative of acidity/pH, as well as light exposure and heat. These all must be considered when dying candies, as precise duplication of shades can be difficult without careful protocols. Some shades will change when exposed to light, indigo is especially guilty of this. And because of the variance between local and federal food requirements, some colors must also be reproducible with vegetable coloring. While some states may prohibit the use of certain synthetic food colorings, federal law may allow use. Thus, certain states may require alternate colors. All in all, there is much to candy than meets the eye, and as written in a paper entitled ‘Chemistry and Confectionery’ in Industrial and Engineering Chemistry in 1924, “If one could but realize the history, tradition, and romance that is bound up in a piece of candy, a more appreciative frame of mind would be developed for this growing industry.”