The Chemistry of Reese's


Reese’s Peanut Butter Cups were created in the 1920s by a man

named Harry Burnett Reese. He had many odd jobs during his twenties and thirties (to support his 16 children!), and eventually ended up working at the Hershey chocolate factory in Pennsylvania.

While he was working there, he starting making his own candy creations and selling them. His most popular was the peanut butter cups, and in 1957 he opened his own manufacturing plant, and his candy has been sold ever since! I chose Reese’s Peanut Butter Cups because it is my favorite candy, and I could eat it all day! My life is greatly affected by Reese’s because it brightens my day (and makes me a little hyper). Reese’s is composed of a soft peanut butter filling, and coated with milk chocolate. There are many different kinds of Reese’s, and all are delicious!

Composition of ...

Milk Chocolate:

Sugar- C12H22O11

Milk- H2O (plus fat globules)

Cocoa- C7H8N4O2

Soy Lecithin- C40H80NO8P

Vanillin- C8H8O3

Peanuts Butter Filling:

Peanut- C57H104O6

Sugar- C12H22O11

Dextrose- C6H12O6

Salt- NaCl

Main Chemicals, Compounds, Components

Cocoa → C7H8N4O2

Peanut → C57H104O6

Cocoa is the main ingredient in chocolate, which provides the outer coating of the Reese’s Peanut Butter Cup, and peanuts are the main ingredient found in the creamy peanut butter filling.

Cocoa is a bean that is grown in a pod. When the bean is ripe, the pod is crushed, and the bean is left to dry. The product is roasted, crushed, milled, and then mixed with other substances to create different types of chocolate. Peanuts are grown in small, bushy plants. Once they are harvested, they are left to dry for several days before being packaged.

Chemistry's Role

Milk chocolate is artificially produced by harvesting cocoa beans and allowing them to dry in the sun for seven or more days. The beans are then roasted and liquefied to form cocoa liquor. The cocoa liquor is blended with cocoa butter, sugar, vanillin, and lecithin to create milk chocolate.

Peanuts are naturally grown in the ground, but the process of producing peanut butter is artificial. Similar to cocoa beans, the peanuts are harvested, dried, and roasted. The peanuts are then ground with salt, sweetener, and stabilizer to create peanut butter.

Background Research

There are over 45 different Reese’s, including as Fast Break, Crunchy Cookie Cup, Half Pound Cup, No Bake Bars, and Honey Roasted. Originally, Reese’s were manufactured at the H. B. Reese Candy Co., but shortly after Reese’s death, the company was sold to The Hershey Company. Reese’s are now manufactured in Hershey, Pennsylvania. Peanut Butter Cups are made by putting melted chocolate in the bottom of a muffin tin (making sure to pull the chocolate up the sides with a spoon). They are left to harden and then the peanut butter filling is added. Another layer of chocolate is added to the top, and once it is dry, it is ready to eat!


picture of Reese’s

food label picture and nutrition facts

ingredients in milk chocolate

how milk chocolate is made

history of Henry Burnett Reese

how chocolate is made



soy lecithin





Hershey Company

How Milk Chocolate Is Made

How Peanut Butter Is Made

About the Author

Kelsea Jorden is a senior at Billings Senior High School. After graduating, she will attend Brigham Young University in Provo, UT, where she will earn a degree in Music Education. Kelsea loves to sing, play the piano, knit, run, and collect spoons. She has three piano students, and she also takes voice and piano lessons. Kelsea is currently training for a half marathon this summer.