Cold Brew Coffee Extraction

This is a little review of the chemistry behind cold brew coffee extraction. This is a bit technical, but if you can read it, it will give you a great perspective on cold brew, and how to tweak your own recipe.

This picture is from a photoshoot for the website That’s Cold Brew – https://thatscoldbrew.com/. The session focused on taking photos of iced coffee made with cold brew coffee or chilled hot brew coffee. The point of the session was to showcase the iced coffee recipe wher the coffee is frozen into coffee ice cubes and milk or water is poured over the coffee ice cubes.

Here are a few

Brewing coffee, (cold or hot), ultimately means dissolving the soluble compounds in coffee grounds, so they flavor and caffeinate our brew.
There are several ways to improve the process of dissolving the soluble solids in coffee grounds. The most popular is heating the solution.
Heating is not the only way to increase extraction. You can also adjust the grind size and agitate the solution.
With cold brew, we need to wait longer for a complete dissolution. We don’t have enough heat is not enough to accelerate it.

Important Tips About Cold Brew and Extraction

Every coffee brewing method is different. Some prefer French press, while others like espresso. Others like paper filtered coffee that is prepared with light-roasted beans.

Regardless of what led you to cold brew, there’s a 50% chance you prefer a stronger cup. In spite of this, most cold brew recipes emphasize caffeine extraction over coffee flavor. As a result, cold brew becomes a wasteful preparation method, which is quite costly.

You need to switch from popular cold brew recipes that use extra-coarse grind sizes and steep for up to 12 hours if you want strong, flavorful coffee. You extract the majority of caffeine with coarse grinding and 12 hours of steeping time, but many other soluble solids remain undissolved. You will have a caffeinated beverage, but it will be very light. If you like this kind of coffee, then follow the trend. If you prefer a stronger cup of coffee, without the bitterness of a hot brew, continue reading.

If you know how to make coffee, many of the concepts we discuss here will be easier to grasp. We explain the concepts as we go, but don’t go too deeply into the details because the article would be too long.

Brew Time

Coffee extraction is a little misunderstood. When we mix hot water and ground coffee, we have to leave them in contact for a predetermined amount of time. Leaving them in contact too long will produce bitter compounds. If we don’t steep long enough, we’ll get a weak brew.

Grind Size

Another factor affecting extraction yield is the grind size. A finer grind leads to better extractions. With finer coffee particles, we must reduce the time grounds and water are in contact. There is another factor that affects extraction, and it has a strong relationship with both brewing time and grind size.

Brew Temperature

At high temperatures, coffee compounds dissolve faster. Low temperatures dissolve bitter compounds in negligible amounts, but high temperatures dissolve them more quickly. Because of this, the SCAA has a standard for filter coffee brewing. When brewing hot coffee, we must be very careful with the grind size and the brewing time. The high brew temperatures can dissolve undesirable compounds very rapidly.

Cold Brew Coffee and Brewing Parameters

Cold brew extraction is a bit misunderstood. The assumption is that if we brew longer, we will risk over-extracting. As a matter of fact, it is an over-extraction since the longer the coffee steeps, the higher the extraction yield. However, due to the low brewing temperature, we extract very little of the undesirable compounds in cold brew. A cold brewed cup of coffee that has been brewed for 36 hours is very strong and needs to be diluted. But so does cold brew steeped for 12 hours. It just requires less diluting.

Caffeine Content

The longer the steeping time, the lower the caffeine per serving. Caffeine is one of the compounds that gets extracted the fastest, so there will be little caffeine difference between a 12 hours brew and a 36 hours brew. Nevertheless, a 36 hours brew will need significantly more diluting.