Japanese Style vs. Cold Brew

Iced coffee has experienced a resurgence of popularity over the last two decades5, a trend marked by the increase in demand for cold brew – a coffee concentrate brewed with cold water over several hours, before being diluted with water of milk. This method produces a mellow, rich cup – but some would argue that the Japanese method of flash-chilling immediately after brewing hot is far superior. Unpacking the reasoning takes some digging into the complex realms of solubility, volatility, and oxidation!


But first – the basics.


Cold brew is made by combining cold water and coarsely ground coffee, typically in a ratio of 4:1 or 4 1/2:1. The mixture is allowed to steep for 6 – 12 hours, then strained through a fine filter. (For our full set of instructions, plus some recipe ideas, check out this post!)


Japanese Style iced coffee is usually made in a Chemex, although any pourover method will work as well. Ice is added to the base, and the standard pourover recipe is tweaked: about 50% more coffee and 50% less water, to compensate for the water added by melting ice. The brewing techniques don’t change, but as the freshly-brewed coffee drips down onto the ice it’s flash-chilled. The end result is a cup (or two) of fresh, cold coffee & ice.


On to Science!



Solubility – the ability of substances to dissolve. Coffee is a solution derived from the interaction of water and beans, specifically, the compounds within beans that can be dissolved into water. This chemical process happens more quickly at higher temperatures, and is affected by factors like: bean freshness, grind size, and agitation2


So how does this play out?


Cold Brew

Cold brew relies on a gentle extraction via cold water, gradually siphoning off flavor compounds over the course of hours3. However, some compounds can only be dissolved with heat, so brighter, fruity notes are left locked within the bean1.

Pros: mellow-sweet flavor, less acidic

Cons: less complex.


Japanese Style

Because Japanese style is brewed with hot water, it contains a wider range of extracted solubles than cold brew2. All of the goodness of a hot cup is present. In fact, the tweaked ratios mean that Japanese style far outstrips simply “pouring hot coffee over ice” or cooling it in a fridge (which results in a dull, bitter cup.)

Pros: fully captures coffee flavors

Cons: more acidic




Volatility – the ability of substances to vaporize. Do you lurve that freshly-brewed coffee smell? Oh gosh, so do we. What we’re smelling is volatile compounds coming in contact with heat (rather, hot water) and transforming into a delicious-smelling vapour4. When water (of any temperature) is added to grounds, trapped carbon dioxide within the beans is released, and pushes the grinds to to the top of the mixture. Typically referred to as “the crust,” the height to which the beans are pushed is representative of how fresh the coffee is: the fresher the bean, the more carbon dioxide, the higher the crust.


Cold Brew

In cold brew, carbon dioxide is released, but just like flavor compounds – some aromatics are simply not tapped into without heat. It’s for this reason that cold brew has very little smell while brewing2.

Pros: none

Cons: Some aromatics not released by cold water, little/no smell


Japanese Style

By contrast, Japanese style brews hot – so aromatics are released – but they are immediately re-captured back into the solution as they come in contact with ice, meaning that you’re now actually tasting what you’re used to smelling4. The effect is subtle, but marvellous.

Pros: volatile substances released and recaptured as flavor

Cons: little/no smell




Oxidation – the effect of oxygen on a substance. Coffee is highly sensitive to oxygen, and the rate of oxidation increases with heat, so freshly-brewed coffee is rapidly staling4. (For the full scoop on freshness, this post has it all.) Staleness tastes dull and bitter, and even perfectly fresh beans will become stale an hour or two after being brewed.


Cold Brew

Since cold brew uses cold water, the rate of oxidation doesn’t increase a great deal, which is why cold brew can be prepared over hours, and stored for days. Some of the smoothness of cold brew is due in part to brighter notes having oxidized, but the strength of the developed flavors compensates for that somewhat.  

Pros: Cold water doesn’t stale coffee nearly as quickly

Cons: It does still stale, and the length of the brew time does make cold brew more vulnerable to the negative effects of oxidation


Japanese Syle

During the brew, Japanese style oxidizes as quickly as hot coffee, but the rate of oxidation dramatically decreases upon contact with ice. While it will stale within a few hours6, it’s more likely that melting ice will dilute the drink before oxidation renders it unpleasant.

Pros: Slower oxidation rate than hot coffee

Cons: hot-water brew oxidizes more quickly than cold brew


While there are always many, many factors that go into the quality of each cup of coffee, the ultimate verdict is on you! What’s your preference? Do some comparisons this week to fully explore the delicious world of iced coffee! Summer is calling, and we must go.


Happy Sipping!




  1. http://www.drinktruenorth.com/blogs/news/15165957-taste-test-japanese-iced-coffee-vs-24-hour-cold-brew
  2. http://www.rohsstreetcafe.com/blog/2014/6/26/cold-brew-vs-japanese-iced-coffee
  3. http://www.clivecoffee.com/learn/2012/05/japanese-iced-coffee/
  4. http://petergiuliano.tumblr.com/post/22177089634/why-you-should-stop-cold-brewing-and-use-the
  5. https://driftaway.coffee/the-history-of-cold-brew/
  6. https://www.reddit.com/r/Coffee/comments/22u6zf/can_you_store_iced_coffee_made_via_the_japanese/


  • http://mimoYmima.com/ Brent Lagerman

    And that’s why we flash brew Keepers Sparkling Coffee – keepers.co