Mike Strumpf  |  The Specialty Coffee Chronicle


You are sitting on a patio during a heat wave, knocking back bottle after bottle of fantastic cold brewed coffee in an effort to stay refreshed and also focused on your important task. As a person who drinks coffee daily you can handle your caffeine, but you find yourself over-caffeinated and not able to focus. This is a common situation for industry professionals and coffee drinkers, because little is known or disclosed about the caffeine content of cold brewed coffee. Highly caffeinated cold coffee might be what some people want, but others can be taken by surprise when they drink a cup of cold brew that has 45% more caffeine than their normal cup of hot brewed coffee!

To investigate the caffeine content of cold brewed coffee, Aaron Braun (Cupping Technician at SWISS WATER®) roasted the caffeinated and decaffeinated versions of a coffee from Peru and brewed them hot using a ceramic filter holder and a #2 paper filter (full brewing methodology is shown below). He also brewed up the same coffee in a Toddy® Cold Brew System following the Toddy® brewing instructions. Caffeine testing was done using the High Performance Liquid Chromatography (HPLC) method for caffeine testing, which is the international standard created by the International Organization for Standardization (ISO 20481:2008) in the SWISS WATER® Process laboratory.

Hot Brew Procedure (same for both regular and SWISS WATER® decaf):
1. 45 second bloom with 60g water.
2. Pour remaining water slowly in concentric circles.
3. Total brew time 3:00 min.

Cold Brew Procedure (same for both regular and SWISS WATER® decaf):
1. 250g water poured in bottom of Toddy®.
2. Evenly distribute 125g ground coffee over top of the water.
3. Slowly pour 500g water over the coffee grounds.
4. Wait for 2 minutes.
5. Add remaining 125 g ground coffee, distributing evenly.
6. Gently pour remaining water, saturating all coffee.
7. Use back of spoon to depress any remaining dry grounds.
8. After 16 hours 20 min, pull the plug in the bottom of the Toddy® and drain into carafe.

The hot brewed coffee was made using a ratio of 60g coffee to 1000g water (1:16.67) and resulted in 178 mg of caffeine per 8oz cup of brewed coffee. The cold brew concentrate was made using a ratio of 250g of coffee to 1275g of water (1:4.64). Due to the concentrated nature of this brewing style, a high caffeine content was found of 518 mg/8oz.

Soluble solids extract from ground coffee at a slower extraction rate as brew temperatures go down. This property of extraction efficiency is of why cold brewed coffee requires such a long brew time. Caffeine is a soluble solid, and the same reduction of extraction efficiency holds true for caffeine as brew temperatures go down. To validate the reduced solid extraction efficiency of cold brew water, we diluted the cold brew concentrate with enough water to achieve the same coffee to water ratio as our hot brewed coffee. This ended up being a cold brew concentrate to water ratio of 1:2.268, which had 159 mg/8oz. Compared to hot brewed coffee with 178 mg/8oz, the cold brew had a lower extraction of caffeine- 10.7% less efficient! Since the extraction efficiency of caffeine is slower in cold brew, why do we get over-caffeinated?

The key lies in the dilution factor that each individual uses. The two common approaches when creating cold brew dilution recipes are to dilute to taste or to a targeted TDS. To create a satisfying taste and body, both approaches typically end up with coffee concentrate to water dilution ratios lower than the 1:2.268 ratio we used, and this is where extra caffeine comes in. A coffee concentrate to water dilution ratio of 1:2 will give a cold brew caffeine content of 259 mg/8oz cup, a whopping 45% more caffeine than a hot brewed coffee to which we are accustomed. Many people dilute at even less than 1:2 and create a very highly caffeinated cup of coffee.

What can we as an industry do when we want to create cold-brewed coffee to satisfy and delight our customers? A simple approach is to inform people about an elevated caffeine level. Another approach is to blend your regular coffee with decaffeinated coffee before brewing. The addition of decaffeinated coffee will allow you to achieve a satisfying TDS while also lowering the caffeine content. Our testing showed that decaffeinated cold brew concentrate had only 17 mg of caffeine per 8oz, or 3.3% of the caffeine content of regular cold brew concentrate. Blending even a small amount of decaffeinated coffee before brewing your concentrate is a very effective way to drop your caffeine content to an expected level, and as long as your decaffeinated coffee is delicious you won’t have any negative effects on flavor.

A third approach exists in decaf cold brew. Decaffeinated cold brew is much less prevalent than regular cold brew which is also an easy area for sales growth. One of the difficulties in creating an amazing cup of decaffeinated coffee is that decaf offers you fewer available solids to extract than regular coffee. Creating a cold-brewed concentrate actually lets you make up for this inherent solids deficiency! By using a higher coffee concentrate to water ratio for decaf than for regular, you can create cold brewed decaf with the same TDS as your regular cold-brewed coffee.

Cold-brewed decaf is a great drink so that you can stay refreshed, support your farmer relationships, and keep your head together so that you can finish reading that article on cold fusion.

Photo courtesy of Dennis Tang

Source: www.scaa.org