Iced coffee taste test
Here in Seattle we’ve been experiencing one of our hottest summers on record, so naturally cold brew has become the go-to method for making coffee. We decided to put various brewing techniques, including the Japanese iced coffee method as well as several traditional 24 hour steep cold brews, to a taste test and find which cold coffee beats the heat.
Traditional “24 Hour Steep” cold brew methods revolve around immersing ground coffee in room temperature or slightly colder water for a span of 12-24 hours. Since the heat of water just off the boil is what normally causes the soluble solids in ground coffee to leave the grounds and move into the water, the added hours give the grounds time to extract without the aid of hot water. This more lengthly method is favored over simply refrigerating hot coffee as the flavors in heated tend to bitter and degrade as the coffee cools.
Unfiltered cold brew coffee
  • UNFILTERED: Our first 24 hour steep trial used a French Press in place of a filter and resulted in cold brew that very full bodied, with a bitter, almost oily texture. While this may be favorable for some palates, it doesn't agree with most drinkers, especially during hot summer afternoons.

  • PRE-INFUSED & UNFILTERED: For the next trial we pre-infused the coffee grounds by boiling about 10% of the total water and pouring it over the grounds for 30 seconds before adding the rest of the room temperature water, again in a French Press. Pre-infusing cut down on a good deal of bitterness and oil (though some still remained) and resulted in very full bodied coffee with a smokiness and light acidity. 

Filtered cold brew coffee
  • FILTERED: The third taste test had us placing ground coffee inside large paper filters which were tied into what looked like a giant Hersey’s Kiss. For this trial we choose to forgo pre-infusing the grounds to see how much of an impact filtration would have on the end result. After 24 hours the end product had much less body, dominated by a stronger acidity.

  • FILTERED & PRE-INFUSED: For our final 24 hour steep test we combined the previous filtered brewing set-up with the pre-infusing technique. This last method was easily the favorite of all the 24 hour steep methods, as it produced a coffee with a full body, lively acidity and retained more of the complex flavor profile of hot coffee. 

 Japanese iced coffee in a chemex
    In spite of all of these findings, our current overall favorite iced coffee technique forgoes 24 hour steep methods entirely. The Japanese method is more of an iced coffee rather than traditional cold brew. Where 24 hour steep methods are known for giving coffees a heavy acidic consistency that can leave your stomach in turmoil during a scorching summer day, the Japanese method produces a coffee with a lighter body and acidity which allows the flavor profile of almost any origin to take center stage. 

    The secret to Japanese iced coffee’s success lies in its combination of hot extraction and quick cooling. In the Japanese method half of the typical water weight for the brew is replaced with ice inside the brewing vessel while the other half is just off the boil and then poured over medium to finely ground coffee and through a filter. 

    One of the primarily limitations of 24 hour steep cold brew methods is that despite the vastly increased brew time, cold water cannot dissolve as much of the ground coffee’s soluble solids as hot. We tried to get around this limitation with the pre-infusing technique mentioned above, but this proved only a partial solution. If we were to try to create iced coffee with the same complexity as hot brewed simply by refrigerating after hot coffee brewing, we run into the same problem with bitterness previously mentioned. However, by having the grounds bloom in water just off the boil, then immediately drip down into ice the Japanese method avoids this problem by quick cooling the coffee and locking in aromatics and flavors so they don’t evaporate into the air. 
    In addition our variation on the Japanese method (which you can find here) only takes about 3-4 minutes to brew, making it the clear winner in flavor, simplicity, and convenience.
    The Verdict: Japanese iced coffee is the clear winner