The Chemistry of a Latte

Introduction

A latte is a fundamental part of every coffee shop and almost every American’s life. A latte is composed of milk and espresso, which have both been heated separately and brought together. The chemist in charge of this reaction is known as the barista, the barista can change the flavor of the coffee by his method and also the area where the coffee beans are grown.

I did the chemistry of a latte because of its daily affect on me, and also because of the great experience I had with it this past summer. In the year 2015, I traveled the nation for two months with a coffee shop known as Off the Leaf. On this trip, I made coffee everyday, and had an excellent esperience. From this trip, I became curious as to what was in my favorite drink.

Studying coffee has made me love it even more. I still drink it daily, but now have more respect for the exquisite taste. I also understand coffee as more of an art and chemistry now, than ever before. To make good coffee requires more effort than most people know.

Composition of ...

Water: H2O
Caffeine Molecule: C8H10N4O2
Galactose Molecule: C6H12O6
Sucrose: C12H22O11
Chlorogenic acids: C16H18O9
Lignin: C9H10O2, C10H12O3, C11H14O4
Triglycerides: C55H98O6
Trigonelline: C7H7NO2
Quinic Acid: C7H12O6

Main Chemicals, Compounds, Components

Espresso

Espresso is made by ground coffee beans and water. Heated water is forced through the ground coffee beans, which have been pressed into a solid puck. The water which passes through this ground coffee, carries with it micromolecules of the coffee beans with it. On top of the espresso will normally form crema, which is composed of near 1,000 aromatic chemicals. The crema can determine the flavor of the espresso , and also the quality of the barista. The maillard reaction is an important part of this, since the molecules of the coffee are carmelized. Due to the chlorogenic acid lactones, the espresso will normally taste bitter, but it can be sweet, if the reaction is performed correctly. If the water is heated properly, the right amount of water is pushed through, and the correct coffee is being used, the reaction between the amino acids and reducing sugars will create sweet enough molecules to overpowere the chlorogenic acid lactones,.

Milk

Milk is made up of 87% water. the remaining 13% is composed of minerals and vitamins, such as calcium, potassium, and vitamin A. The milk needed for a latte must be heated to a high temperature, to once again cause the maillard reaction. The milk of a latte is normally much sweeter than the espresso. This is due to the lack of chlorogenic acid in milk, and also the easier carmelized milk proteins.If heated correctly, the milk will be very sweet, and pair well with the slightly sweet and strong espresso taste.

Chemistry's Role

Both the milk, and the coffee bean are grown naturally and harvested on farms. The coffee is normally handpicked by workers once or twice a year. The picked coffee cherry is sorted by hand or machine, and only the best is kept. This sorted batch of coffee cherries is then dried, normally in the sun, and cracks to reveal the inside of the coffee cherry. The coffee is bagged, and then sent to the coffee roaster, who cleans, and heats the cherries til they are the wanted flavor and color. The coffee is bagged again, and this time sent to the coffee shop. Many coffee shops grind coffee on site.

The milk is a different process. A cow is milked by vacuum, and the milk is stored in a cooling tank. The milk is taken to a factory, where the bacteria and debris are seperated from the milk. Vitamins A and D are added to the milk, along with other minerals and vitamins. The milk is then superheated and cooled, to kill off all remaining bacteria. The milk is pressurized to homogenize it, and keep all cream off the surface. Finally, the milk is bottled and sent away.

Background Research

Coffee has been drank for centuries by the aztecs and ancient civilizations. The invention of espresso, however, was created in the early European 17th century. Originally, coffee was thought to be rank and bad tasting, but once the process of espresso was created, more people sought after it. Espresso was first enjoyed in countries such as Italy and Turkey. Almost 300 years later, millions enjoy coffee daily. The process has changed throughout the years, but the desire for caffeine has not.

Resources

http://www.chemistryviews.org/details/ezine/694285/Espresso__A_Three-Step_Preparation.html

How to make coffee

http://www.ift.org/~/media/Knowledge%20Center/Publications/Books/Samples/IFTPressBook_Coffee_PreviewChapter.pdf

Chemical components of coffee

http://coffeegeek.com/guides/frothingguide/milk

How to steam milk; lipids and fats in milk

https://scienceandfooducla.wordpress.com/2015/07/21/the-science-of-steamed-milk-understanding-your-latte-art/

Proteins in milk

http://legacy.sweetmarias.com/library/content/espresso-preparing-milk-drinks-espresso-steaming-milk

How to steam milk

http://ansci.illinois.edu/static/ansc438/Milkcompsynth/milkcomp_minerals.html