Why are Coffee Beans Roasted Before Grinding?

It seems that so many good things in this world come through processes that take time. For wine, the best of the best takes years to age, for cheeses, the exact same can be said. With coffee beans, a process that takes time is just as necessary in order to ensure quality. 

Why are coffee beans roasted before grounding? This process takes a green coffee bean from lacking in flavor and richness to a roasted coffee bean that can be turned into an award-worthy cup of joe. If you don’t roast your coffee beans, carbon dioxide cannot be released from the beans- an essential component in the coffee’s final taste.  

Patience is such a difficult virtue to master, especially when you see a shortcut that may get you to your desired destination faster than taking the long way around. In a bind, it may seem like the right move to go ahead and grind your green coffee beans up and get straight to brewing. Although this would end in instant gratification as far as filling your coffee cup up goes, it would be entirely disappointing in the flavor department. 

Do You Need to Roast Coffee Beans Before Grinding? 

Let’s do a bit of at-home imagery really quick: Imagine that you are walking into your most loved coffee shop. It is a crisp fall afternoon, you’re wrapped up with your nose being just a bit chilled and your fingers feel the cool breeze shift between them as you pull the door open. Waves of warm air rush over you and you inhale. Instantly you are met with smells playing different notes of chocolate, deep nutty aromas, and even tinges of citrus all expertly twined together. 

That is the smell of perfectly roasted coffee, the unbelievably rich scents that fill your soul and cleanse your worries away. The keyword here is “roasted” coffee beans. Now, if you open up a fresh sack of green coffee beans, none of these scents would be even remotely present. Instead, you would quickly inhale a scent that is something piney and flat. This is where the necessity of roasting comes in so that a bland green bean can be transformed. 

I realize how painstaking it can be to look at any task and dread the process that helps to lead to completion, after all, patience is difficult. Although this may be true, it does not diminish the fact that grinding green coffee beans would result in nothing but a flat cup of “no thank you.” 

The aroma during brewing would be off, the texture of the coffee would be harsh, and the flavor would be downright offensive. Take my word: you need to roast coffee beans before grinding to achieve a flavor and aroma worthy of consuming.

The Science Behind Roasting 

With that being said, let’s talk about the science behind roasting and the extreme bean makeover that occurs during this process. There are several areas of change that deserve special attention in the science behind roasting your coffee beans: 

  • Color 
  • Moisture and Mass 
  • Volume and Porosity 
  • Oils 


Color has to be the most obvious transformation. Fresh, unroasted coffee beans are a bit of a blue-green color. They look nothing like the beans being ground up for your morning cup. 

When roasting occurs though, the color is changed to either light, medium, or dark brown. This helps to indicate the different levels of roast such as light, medium, or dark roasts. You see the pattern right? This then lets consumers know the coffee’s level of intensity. 

Moisture and Mass 

As you could likely guess due to beans going from a greenish-blue color to a light or dark brown, plenty of moisture is contained within the coffee bean itself. Before roasting, the bean is made up of about 10-12% of water. 

After roasting, this number is greatly reduced and usually lands at around 2.5%. This decrease in moisture thus helps to decrease the overall mass of the bean and helps to determine the impact of the chemical reaction on flavor. 

Volume and Porosity

Since moisture is lost and gases are released, the mass of the bean is decreased and the volume of the bean is expanded. When heat is put to coffee beans the temperature creates a transformation that turns those waters into gases. 

This creates a small pocket of gas within the bean that is later released during the resting period after roasting. Roasting also makes the beans more porous, which helps to create a smoother flavor. 


What you may not know is that, in some way, coffee beans are turned inside out during the roasting process. What I mean by this is that coffee beans contain oils. For a green coffee bean, these oils are contained in the center of the bean. 

When coffee beans are exposed to high heat, however, these oils are brought from the center of the beans to its surface. These oils also help to create those silky flavors within your everyday brew. 

Why Not Grind Coffee Beans Before Roasting? 

Understanding the science behind roasting coffee beans is an essential component to answering why you should not grind coffee beans before roasting. 

Let’s assume that you do not understand this science, though, and begin to think of ways to get around lengthy roasting sessions. It would seem that if you decrease the volume of the beans before roasting that you could save on roasting time while also potentially getting a more well-rounded roast right?

Wrong. The beauty of science is that it is a variable in which methods, patterns, and processes are tried and true. For coffee beans, the scientific process that happens during roasting is an absolutely “do not exclude” type of step. The color change, water loss, volume expansion, mass diminishment, and oil release are all needed, but even more so, can only occur if the coffee bean is fully intact. 

If you were to grind green beans, the structure of the bean itself would be destroyed which would keep the bean from releasing proper amounts of water, would make volume and mass changes impossible, and would keep necessary oils from transferring to the surface of the intact bean. 

By grinding, you mess with the physiology of the bean and therefore mess with its potential to become something great. Skip the pre-grind and put in the roasting work. 

How Soon to Grind Coffee Beans After Roasting? 

All of your dreams have been crushed for skipping around the processes of roasting and grinding in order to speed through to your delicious cup of coffee, but truly, the process is well worth the flavor that is produced through diligence and patience. 

Once your beans have gone from drab to fab, brewing comes next, but take one more tiny note of caution. Your coffee beans may seem ready to go, but they may need a bit more time before their final destination. 

Although it may seem like all your work is done, coffee beans do need some time to rest before they take on their final mission. As discussed earlier, gases are released from the beans during roasting which helps to create all those different coffee flavor profiles that you love. 

Right after roasting though, there is still CO2 present that needs to be released before you get to grinding, This release is necessary in order to keep your coffee from being bitter. 

On average, you need to allow your freshly roasted coffee beans to rest between twelve and twenty-four hours to ensure that enough gas has escaped from them. Once the beans have rested for an ample amount of time, you can either go straight to grinding them or store them for later use. 

It may seem like a complete and utter drag to have to wait yet another amount of time to get to your next cup, but this resting period will take your beans from good to great. 

Tips for Grinding and Storing 

Consider these tips for grinding and storing your beans:


If you choose to grind your beans, consider only grinding a small portion and leaving the rest whole. By grinding only a bit of your beans, you are able to keep the rest of the batch intact which helps to prevent making your beans stale at more accelerated rates. 

After all of your work, you want to make sure that you preserve your beans as long as possible, and keeping the bulk of your batch whole helps to achieve this. 


Storing your coffee, whether grounds or beans, is the same across the board. You want to make sure that both are stored in airtight containers to keep too much CO2 from escaping and to prevent oxygen from getting into your coffee and making it stale. 

You also want to make sure that they are kept in areas that have cooler room temperature and are relatively dark. Too much exposure to heat or direct light can also cause coffee to stale at faster rates. 


As with many things in this world, there is an art to coffee. From the beginning to the end, necessary processes have been put in place to ensure award-worthy brews. Although these processes may seem a bit excessive, they have been proven to work for decades on end and are not to be tampered with. 

Take your time, complete the steps, and you will be on your way to the best brew of your life. Happy sipping! 

Tim S.

Tim loves roasting, brewing, and experimenting with coffee. After years of perfecting this craft, working as a barista, and owning a small coffee service in college, he has decided to share his knowledge with the world.

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