Education Time: Iced Coffee

April 23, 2015

Summer's coming, Spring's already here, so iced coffee is starting to get relevant and vie with the delights of your steamy latte. Here at Gregorys, the brother/sister of sorts to your standard drip is coined as the 'Cold Brew', but why? For good reason. Class in session! Read on to discover the principal brewing methods for an iced cup, while observing the factors that influences that all-important factor: which method makes for great-tasting coffee.

Method #1 - Refrigerated Hot Coffee

Coffee is brewed at regular temperature and then put in the refrigerator to cool. The most straight-forward, but does convenience measure well in this instance?

Method #2 - Cold Brew

A familiar term for any Gregular with a taste for iced coffee. This fellow is brewed overnight using room temperature water; as colder water takes much longer to extract, we let a coarse grind sit in said water for 12 hours.

Emma with Cold Brew

Lovely assistant Emma exhibiting the Cold Brew in all its glory.

Method #3 - Cold Brew with Hot Bloom

'Bloom' refers to what happens when hot water first hits coffee. At this point of contact, gases start escaping from the coffee, which makes it easier for the water to get into the coffee and extract from it. More on the effects of this process later; what's important in sealing the definition is the fact that once bloomed a bit with hot water, ice water is added to continue the trend of a regular cold brew.

Method #4 - Slow Drip (a.k.a. Kyoto Drip)

Ice-cold water is dripped through a chamber of ground coffee and then a (usually ceramic) filter. This method is a bit fiddly, demanding constant attention and adjustment to the nozzle that allows water to pass through to the chamber of coffee - it's to be maintained at, in our recipe, 50 drops per minute. To put it simple, this is like a vertical cold brew that requires a test of patience.

Kyoto Drip

Going Kyoto

Method #5 - Ice-Brew (a.k.a. Japanese method or hot-over-ice brew):

Coffee is brewed directly over ice, usually extra-strong, to allow for immediate melting of the ice. This method can be brewed to order and observed over at our aeropress bar where we serve our single origins.

Gregory showing off the aeropress

Gregory, deep in coffee-brewing mode.

Now for the fun facts to tell your friends as you order the 'Cold Brew' with a pointed wink barista-ward, showing you know exactly what's going down.

What's clearest in the above list of brewing methods is that temperature is an intrinsic factor. The following is a breakdown of the components that make this such a heated issue:

Speaking of breakdown, brewing with cold water doesn't break down all of the same flavor compounds that brewing with hot water does; the outcome generally carries less of that acidity people find so inviting in their hot coffee.

Coffee comes with a make-up of chlorogenic acid. Once brewing begins, this compound degrades into two constituents: quinic and caffeic acids. Sourness, bitterness and astringency ensue over time and the tongue does not register these acids favorably once held to the light of the mind. Time and temperature are partners in this case, as the degradation occurs faster at higher temperature - this explains why we toss out all our hot drip coffee after 30 minutes.

Chlorogenics

Chlorogenics

Oxygen tangos with temperature next in a process known as oxidation: oils exposed to oxygen get rancid and develop off-flavors; once again this happens faster at higher temperatures and accounts for the fact that we toss out hot coffee after that fatal thirty-minute mark.

Volatility: This is the potential for a liquid to turn into a gas. If you follow the link through our archives, you'll note a coffee lecture on smell and its dioramic effect on taste, sending messages to all parts of the brain, sustaining the flavor upon the instant and storing it, via the limbic system, into the deepest reaches and trickster-currents of the brain. Volatility increases with heat, so you're forgiven for not picking up much of a smell from iced coffee - but all's not lost. If you cool the iced coffee quickly, you reduce that volatility, and then you can access some of those sequestered aromatics through the retro-nasal cavity as the coffee heats back up upon hitting the back of your throat.

Hydrolysis: Akin to giving your low-rider a mean hydraulic supplement, this is the process in which hemicellulose (a carbohydrate which is not water-soluble) is broken down into soluble reducing sugars, adding caramel and savory sweetness to the mix. Hydrolysis doesn't happen without both heat and time.

So heat is certainly quite the unstable additive, but it provides a whole delicious mess of flavors for the coffee-drinker to frolic about with; that's one good reason why hot coffee will never go out of fashion, rain or shine. But then again, there's got to be room for iced coffee, especially with an onslaught of summer heat, so what should you be set to order?

Refrigerated coffee comes in last place (sorry) and that's what you may get when you order "iced coffee" somewhere that doesn't preempt the lesser option by omitting it entirely. To be safe, ask if they have "cold brew" - no need to at Gregorys where we've omitted away - and here's why: Because with refrigerated coffee, the coffee isn't cooled immediately; even in the fridge there's a lot of warm time in which acids can break down and those pesky quinic and caffeics come into play. By avoiding this downtime, cold brew avoids the astringent onslaught, producing something much smoother for all interested in a cooling ice coffee nonetheless.

There is still the factor of a loss of acidity in iced coffee, which the cold brew with hot bloom is theoretically supposed to amend; certain flavor compounds should be accessed that give coffee its pleasant acidity and fruitiness. While a shame that this method doesn't support the same accessibility to sustainable quantities (for a sustainable flow of customers with finite patience) as a straight-forward cold brew, the latter option does provide a neutral, smooth, rich flavor not to be missed. The slow drip, while fancy-looking as can be, provides coffee similar to the cold brew, but at much greater inconvenience to whoever has to keep it in check.

But we've saved the best for last: The hot-over-ice brew, staple of the aeropress bar when you're looking for something cooling, presents the best of both worlds. Brewing the coffee immediately over ice slows degradation of acids and oxidation - both of which attract unwelcome flavors - while also capturing all those volatile aromatics that can then reappear as we drink the coffee. Brewing with hot coffee also allows access to that illusive acidity and fruitiness in iced coffee, and the extra suspension provided by hydrolysis.

Emma and the Aeropress

Assistant Emma likes what she sees on the Aeropress front; Sam acts the affectionate dork.

The single origins are our favorite way of presenting the broad and dynamic flavors that coffee offers to a morning routine or daily appreciation of fine drinking. By supporting what these single origins have to offer, the hot-over-ice method is the only way we would have them sold to customers. It's also something that our customers can manage in their own kitchens, provided they carry an aeropress (sold in-store for $24.99), some coffee (also within our domain), and ice. Just check with one of our baristas, or Gregory himself in the following link, and they'll give you a run-down on how to do it best.

Also, pro-tip: Iced Americanos. If you delight in our espresso, you should have no qualms with this - it's hot coffee being cooled immediately, after all.

So whether at home or scurrying through NY streets, iced coffee can be covered for without the need for a refrigerator - except for the whole business of requiring ice. Take that onboard and with that take the summer in a hearty, caffeinated stride!

 


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