Is Adding Cream To Coffee A Chemical Change

Practice you know what happens when you roast java? What changes take place to brand green beans into the flavorful, aromatic ones we dearest?

In part one of this two-part series, we looked at how the coffee bean'southward beefcake plays an important role and outlined the physical changes that take place during roasting. Now permit's take a wait at some of the chemical changes, including how flavor and aroma develop.

Read part i, What Happens During Coffee Roasting: The Physical Changes

some bags of coffee with green coffee on them

Bags of green java at a roastery. Credit: Ana Valencia

The Main Chemical Reactions

Introducing coffee beans to the rut of the roaster sparks hundreds of different chemic reactions. Roasting degrades some compounds, alters others, and creates new ones.

You may hear people mention a chemic procedure chosen pyrolysis. This is when an organic material is heated above its decomposition temperature, producing volatile compounds and leaving backside a solid residue containing a lot of carbon, or char. In java roasting, we avoid getting the beans hot plenty to cause charring, but they practise undergo chemical changes associated with pyrolysis including the caramelization of sugars and product of volatile compounds.

Hither are the principal chemic reactions that affect your daily loving cup of java.

The Maillard Reaction

This procedure begins at around 150°C/302°F, when the beans are withal absorbing estrus endothermically, and continues in the exothermic role of the roast. Heat causes a reaction between the carbohydrates and amino acids in the beans. This causes changes in color, flavor, and nutritional content.

The modify in color is due to the production of melanoidins. These are large molecules that not merely plow the beans brown, but contribute to mouthfeel and torso.

Small changes in the temperature and length of time spent in the Maillard reaction can have a big bear on on the final profile of a java.

Coffee that has spent longer in the Maillard reaction has been reported to have an increment in viscosity. A shorter Maillard duration can create more perception of sweetness and acidity. This is in part because the acids that produce fruity and sweet notes are destroyed if the coffee remains in the Maillard reaction for too long.

When roasters experiment with roast profiles, it includes varying the length and intensity of Maillard reaction and recording its effects on profile.

Notice out more in The S-Bend Roast Contour: Exploring Roasting Basics

Dark-green java beans. Credit: Ana Valencia

Strecker Degradation

This is a process that depends on the Maillard reaction. Amino acids react with carbonyl-grouped molecules to create compounds such as aldehydes and ketones. Every bit roasters, we don't need to understand exactly what these compounds are – the important thing to recognize is that this reaction is essential for the cosmos of aroma- and flavour-producing compounds.

Caramelization of Sugars

At around 170°C/338°F, heat causes large, complex carbohydrates to break down into smaller carbohydrate molecules that can be dissolved in water. This means that the perceived sweetness level of your finished mash increases. This reaction continues until the finish of the roast and it also contributes to the sweet notes in the java'due south aroma, such as caramel and almond ones.

A coffee roaster. Credit: Miguel Regalado

Volatile & Non-Volatile Compounds

Y'all may hear mention of volatile and not-volatile compounds in roasted coffee. In full general, volatile compounds are responsible for odour and some non-volatile ones contribute to season. But what are they?

Volatile compounds are organic chemicals that have a high vapor pressure at room temperature. Many of them are formed in Strecker degradation, in the development stage of roasting. When aroma-producing volatile compounds disperse, we feel that signature coffee aroma. These include:

Aldehydes, which add fruity, green aromas.
Furans, which contribute caramel odors
Pyrazines, which have an earthy scent.
Sulfur-containing compounds, including ii-furfurylthiol. Some of these have an aroma that is commonly described every bit "roasted java" but at that place are others that don't scent as highly-seasoned in isolation. For example, methanethiol smells like rotten cabbage.
Guaiacol, which has smoky, spicy tones.

Carbon dioxide is a volatile compound that doesn't contribute to smell, but which does have an impact on body.

A roaster at work. Credit: Viktor Nikolaienko

Non-volatile compounds are just substances that are stable at room temperature. That is, they don't vaporize. Some of these compounds are changed during roasting, whereas others remain stable through the process. Many not-volatile compounds contribute to season and contour.

Examples include caffeine, which is responsible for some bitter flavors. Caffeine is naturally occurring in coffee and remains unchanged by the roasting process. Other non-volatile compounds include sucrose, which provides sweetness, and lipids, which provide trunk and mouthfeel. The melanoidins that create color and body are besides non-volatile compounds.

Freshly roasted beans. Credit: Caleb Minear

The Office of Acids

Acids play an important role in creating flavor and are sensitive to heat. Roasting can dethrone some acids and create others.

For example, the citric and tartaric acids that produce fruity and sweet notes are cleaved downward during roasting so a long or overly hot roast can hugely reduce the sugariness of the last profile.

Coffee contains a high amount of chlorogenic acid, which roasting breaks downwards into caffeic and quinic acid. Both chlorogenic acid and the resulting quinic acid are thought to provide bitterness and astringency.

Learn more in Why Are Some Coffees More Acidic Than Others? A Brew & Roast Guide

Freshly roasted beans. Credit: Gregory Hayes

Coffee roasting includes a number of chemical transformations that contribute to the flavor, aroma, and torso of your finished loving cup. Many of these reactions are sensitive to variations in temperature and length of exposure to heat. So a small change in roasting technique can have a profound impact on profile.

Understanding what happens during roasting and knowing why these changes occur can help yous make more informed choices. If y'all have an overview of how chemical compounds are created and inverse during the process, you can improve understand what went wrong, or correct, with your batch and employ the information to brand your next one better.

Y'all might also like A Guide to Achieving Consistency in Coffee Roasting

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