Thursday, April 26, 2018

Coffee Ice Cream Addendum: Origin Notes and Minutiae

Farmland in Banga, Burundi. Photo by Christine Vaufrey. From

The coffee ice cream method described in the previous post has been so successful at preserving the origin character of excellent coffee that it's turned into a minor fetish. I can't stop making batches with different coffees, and eating them, which is getting me into some trouble with my girlfriend, who turns lycanthropic from caffeine past noon.

A couple of Tuesdays ago, mid-fetish, when she kicked me out of the house suggested that I work remotely, I stopped by our local espresso bar, Coffee Mob. This place just happens to be one the best and most interesting roasters in the city. The barista pulled me a shot of the Burundian natural process they had on tap that day. Holy god was it good—syrupy, sweet, caramely, floral, and then ... an explosion of blackberries. I'd never tasted anything quite like it. I was just picking myself off the floor when the owner, Buck, walked in.

I told him it was the best shot I'd had in the last 6 months—and I'd been to Stumptown and Toby's Estate just in the last week.

"Why don't you come back at 6:30 tonight," He said. "The producer's giving a talk."

So I came back, and listened to Ben from Long Miles Coffee tell the story of his journey into coffee production in Burundi, in the middle of a rising dictatorship, impoverished farmers, and some of the best coffee in the world. His family built a washing station for the farmers on three neighboring hills, and made a commitment to paying the farmers fairly and on-time ... a departure from the status quo in the region.

I brought something for the afterparty—a half-pint of ice cream, made with Stumptown's Ethiopia Duromina, my perennial favorite. This coffee sings through the dairy with notes of cocoa, caramel, and blood oranges. Buck said he tasted the coffee through the ice cream in a way he never had before. Ben just ate the rest of it.

I had a chance to try an espresso made with Long Miles' latest batch of honey-process beans (a hybrid of washed and natural-process), which was delicious and unusual (a dark fruit flavor that was almost familiar), but I couldn't stop thinking about that natural-process blackberry bomb. Buck gave me 100 grams of it try in the next batch of ice cream.

Long Miles Burundi Gishubi Natural Process, roasted to perfection by Coffee Mob.

I was a little concerned that this coffee might be too distinctive—too weird—for ice cream.  Some experienced coffee tasters are wary of dry-process coffees with too strong a fruit flavor. Such coffees can come off as one-note, or even a bit like artificial fruit candy.* And even if the flavor's balanced, sometimes the more distinctive ones aren't appropriate for everything. The first time I tasted Michel Cluizel's Los Ancones single-origin chocolate, I thought: 1. this is one of the best things I've ever had, and 2. I have no idea what to do with it—besides just eat it as it is. Because it tastes like liquorice and olives. It's surprising and wonderful as a self-contained experience, but may make people wince in an ice cream or cake.

This time my worries were unfounded. The ice cream was unique and addictive. Chocolate blackberry, caramel blackberry, blackberry jam. I almost borrowed a Blackberry to write this post. I'm now tempted—and almost dorky enough—to serve multiple regions of coffee ice cream together, maybe each in its own demitasse. I'm thinking Ethiopia, Burundi, and possibly an Indonesian or Sumatran. Like the tired convention of serving something "three ways," but in this case three wheres.

Straight out of the machine. Earth tones belie the blackberry bomb within.
Residence time 7.5 minutes, drawing temperature -6°C. Smoooooth.

Miscellaneous Process Notes

I've never monitored the temperature / time curve of the ice cream mix in the sous-vide bath, because I don't have the kinds of lab equipment that make this easy. I have software for predicting the rate of temperature increase for a steak or fish fillet in a water bath, but doing so for an amorphous bag of viscous fluid is beyond my art.

My wild educated guess was that with a bit of agitation, and with help from convection currents in the ice cream mix, it would take 15 to 20 minutes for the mix to get to 75°C, where it would then remain for a half hour. This last week I decided to test this hypothesis manually, by interrupting the process a few times up until the end and taking a temperature reading.

The hypothesis was way off. The temperature rose much more slowly than I'd expected, was not impressively sped along by my early agitations, and never reached 75°C. This means that at least some portion of the locust bean gum has not been getting hydrated. It also means that the conditions for partial milk protein denaturing have not been what I'd assumed—although the exact expected effects of this are too complex and poorly understood to make any guesses about.

I came up with a quick fix, based on an armchair-understanding of thermodynamics. Knowing that the biggest factor in speed of heating is the temperature difference between the cooking environment and the current food temperature (Delta-T), it made sense to start in a hotter water bath. The trick is to try to heat the mix quickly, but not overshoot by too much. Ideally, you'd let a PID controller take over, like the one that so efficiently gets the water bath to a precise temperature and holds it there. For better or worse, you're not supposed to circulate ice cream mix directly with an immersion circulator. Until someone makes an affordable circulator that works with a probe stuck directly in the food, we're stuck with more primitive methods.**

My first experiment has been to split the cook into two stages. 30 minutes at 85°C, then 30 minutes at 75°C, with the water bath uncovered, so it will cool at a reasonable rate. I haven't charted the temperature / time curve, but the result was clearly different. The ice cream has more body when frozen, and has resisted developing ice crystals in the freezer for two weeks ... several days longer than what I'm used to.

I'd like to do a few more experiments with cooking time and temperatures. This may lead me to updating the sous-vide instructions, and possibly even the stabilizer blends, for all the recipes in this series.

There are all kinds of variables at play here, which will make absolute precision and predictability impossible. This raises the question of why to use an immersion circulator at all. I believe it makes sense, because 1. it's hands-off, and once the temperature stabilizes at or near your target, it will stay there precisely, and 2. cooking in sealed environment is great for preserving aromatic flavors.

Anatomy of a coffee cherry. From

*when you taste odd fruits in coffee or wine—something besides coffee or grapes— you're generally tasting an aromatic compound that also exists in that fruit. But you're not tasting ALL the aromatic compounds from that fruit. If the compound is in the coffee/wine in small quantities, you get a nice hint of blackberries (or whatever) that blends intriguingly with other flavors. But if  there's a ton of that compound, you may be reminded of other foods foods that include a ton of that single flavor compound, isolated from all the fruit's background flavor compounds—think of a Jolly Rancher, or Fruit Roll-Up, or Instant Jell-O. Maybe not what you want in your coffee.

How do these compounds end up in coffee or wine? Usually they're either products of fermentation, maillard reactions from cooking (coffee), or barrel aging (wine). All three of these processes convert simple chemicals into a symphony of complex compounds, with more variables than science has yet been able to wrap its big head around.

**A laboratory hot plate with a magnetic stirrer may end up being the best tool for this. I'm waiting for someone to make one specifically for culinary use. The Breville/PolyScience Control Freak is a nod in the right direction, but it doesn't stir, and it costs $1800.

Part 1 of this series: Introduction
Part 2 of this series: Components
Part 3 of this series: How to Build a Recipe
Part 4 of this series: Basic Recipe Examples
Part 5 of this series: Techniques
Part 6 of this series: Sugars
Part 7 of this series: Stabilizers
Part 8 of this series: Emulsifiers
Part 9 of this series: Booze
Part 10 of this series: Solids, Water, Ice
Part 11 of this series: Introduction to Flavor
Part 12 of this series: Ice Cream Flavor: Coffee

Tuesday, February 27, 2018

Ice Cream Flavor: Coffee

Welcome to the first post that focusses on a single flavor. We’re starting with coffee, not because it’s simple—it’s maybe the most complex flavor we’ll have the pleasure of disecting. We’re going to take on this complexity because coffee flavor illustrates so many principles, and because there’s a mountain of high quality research already available, at least with regards to making a cup of joe. 

To make good coffee ice cream you do have to learn to make good coffee. If this were a simple task, everyone would be doing it. Everyone is not doing it. I lived in New York City for about 15 years before having my first truly good cup. Coffee’s 3rd wave took a couple of decades to make it all the way East from Portland and Seattle, and is only just now gaining traction in a culture that’s been long-steeped in the bitter seas of Starbucks, and before that, street-cart swill and Café Bustello.

Good coffee starts with sourcing high-quality beans that are roasted with precision and that have whatever characteristics you most enjoy. Differences in regional varieties and processing methods are beyond our scope here. See the links at the bottom for suggested reading. 

Roasting, however, is of primary importance and needs to be considered. Roasting coffee well is hard. I’ve bought coffee beans from many local, supposedly artisanal roasters, and have usually been disappointed. Sometimes the roasters just have terrible ideas about coffee. Many of these ideas were propagated by Starbucks and other 2nd wave roasters—like the idea that dark-roasted coffee is somehow “bolder” or more serious than light and medium roasts. Dark-roasted coffee is, more often than not, ruined coffee. Once you inch past a full-city (medium-darkish) roast, the aromatic flavors that distinguish good beans from bad ones, and one region from another, are muted, replaced by generic roasted flavors. Roast  darker still and those origin flavors are demolished entirely, replaced by burnt flavors and bitter non-volatile chemicals. 

Selling us on dark roasts was a cynical ploy by companies like Starbucks, who figured out that 1) if you roast the coffee dark, your customers won’t be able to tell the difference between good beans and bad, from this region or that one, from beans harvested this season or last. So quality and consistency become non-issues. And 2) if you roast the coffee dark, it will be bitter, and people will want to tame it with sugar and milk. Which means that instead of selling $1 coffees or $3 espressos, you can sell $5 lattés and skim-mocha frapuccinos and other coffee-flavored sundaes that can survive bad ingredients and poor technique, and, (bonus!) will let you to mark up milk for a 1000% profit. 

Even roasters who attempt proper degrees of roasting often mess up. Because the process is much more complex and sensitive to precise timing and energy-input modulation than, say, baking bread or popping popcorn. And it's easy to let portions of some of the beans roast more than others. This may lead to coffee that has the overall color and aroma of a proper roast, but upon closer examination will have spots that glisten with oils brought to the surface. The resulting coffee will typically have the basic character of a light or medium roast, but will have burnt / bitter background notes that will always be out of balance. Every attempt at a light or medium-roast coffee I’ve bought from Whole Foods’ in-house roaster has suffered from this. Same with coffee bought from most small shops that roast their own. In the end, looking at the beans only gets you so far. To know for sure you have to taste the coffee.

Not living in the Pacific Northwest, I’ve been limited to a handful 3rd wave companies who have built outposts here, and to a very small number of local roasters who know what they’re doing. 

Some of the nationally-distributed roasters that I like:
-Stumptown (Portland / NYC)
-Intelligentsia (Chicago)
-Toby’s Estate (Australia)

Some NYC roasters that get it right:
-9th St. Espresso
-Joe the Art of Coffee
-Coffee Mob (in my neighborhood. The only mom ’n pop shop I’ve been to that roasts like a boss).

I like to buy single-origin beans, because they're usually the most interesting. Even with espresso (a glorious topic that lies well beyond our scope, because the espresso process doesn’t lend itself to ice cream) baristas have figured out how to work with single origin beans, which were previously believed to be too full of character and fruity acidity to make a balanced shot. Nowadays there’s less reason than in the past to fall back on blends.

I also like to look for direct trade arrangements between the roaster and the plantation. Coffee has historically been rife with colonial exploitation, so it’s gratifying to see roasters working with individual farmers and cooperatives, ocassionally even investing in their operations and helping the farmers achieve prosperity and independence.

My dream coffee is generally from East Africa, especially Ethiopia, where coffees often offer a magical balance of syrupy body, earthy undertones, fruity acidity, and floral or herbal aromas. I like a lot of flavor in my cup. 

People who don’t want so much flavor generally tame their coffee with milk and sugar. I do not, unless the coffee is bad, or I’m enjoying a morning capuccino (which is a whole ‘nuther topic). This introduces the basic problem of coffee ice cream—there’s going to be a lot of milk and sugar. Because it’s ice cream. So if you want those coffee flavors to stand up, you’re going to have to put a lot of them in there to begin with, especially the acidic and aromatic flavors that will be most muted. We’ll get to this.

But first—how to make a good cup of Joe?

Brewing coffee is an extraction process. We’re extracting literally hundreds of compounds from the coffee beans, including the basic sugars, acids, and alkaloids that constitute the heavy molecules detected by our taste buds, and also the myriad volatile organic compounds that we detect with our nose. There are other compounds that we either don’t want, or that we want in minute quantities. And among the ones that we do want, we want them in proportions that taste balanced and satisfying. And we want the overall flavor to be strong enough. But not too strong. 

How do you do all that? Happily, there’s science on the topic. Which means that some very patient men and women with PhDs have done much of the work for us. Here’s a chart from the Specialty Coffee Association of America:

There’s a lot of information here for a 2-dimensional chart. Allow me to summarize. The two axes represent strength (vertical axis) and solubles yield, or extraction (horizontal axis). 

Strength is simply the amount of coffee solids disolved in the brewing water, represented as a percentage of the water weight. More = stronger. 

Solubles yield is what percentage of the available soluble stuff you've drawn out of the beans. Brewing for a longer time, or with a finer grind (which exposes more surface area) gives more extraction.

If you extract too little, you have an “undeveloped” cup, which is typically sour and thin. If you extract too much, the coffee becomes bitter.

The diagonal red lines are each for a brewing ratio, which is the actual ratio of coffee beans to water. The lines are diagonal because as you brew longer, or hotter, both strength and extraction of the coffee increase. You control these variables independently by choosing different brewing ratios.

For both strength and extraction, there’s a sweet spot, represented by the orange square in the middle. According to the chart, you can get into that zone with any brewing ratio between 3.25 and 4.25 oz / half gallon. Or, if you prefer units that aren't preposterous, between 4.8% and 6.3% relative to the weight of the water.

Without a refractometer or hydrometer, it will difficult to follow this chart precisely. And there’s no need to. Use the chart as a model, to help you understand what you’re tasting, and which variables you need to change when trying to adjust the flavors. If your ideal cup doesn't land precisely in that square, who cares.

The chart does not address the specific factors that determine extraction, which are time, temperature, and grind size. Time and grind size are bound together; the coarser the grind, the more time you need to get to a particular level of extraction. Many coffee making methods determine the general grind size. Press pots require a coarse grind (and so a long brew time) otherwise you'll clog the filter. Espresso requires a very fine and consistent grind. Drip and pourover coffees cede the control of time to gravity and physics, so you have to find a grind size that works with the time you're given. See notes on grinding, below.

Temperature is also critical. It affects extraction rate, but does not affect all flavor compounds equally. So brewing temperature is an important variable for adjusting the flavor balance. The generally accepted range of brewing temperatures is  91°C–96°C / 196–205°F. 

Within this range, higher temperatures will give more extraction, more body, more sweetness, more bitterness, and less acidity. Lower temperatures, or course, will give thinner body, more acidity, less bitterness, and less sweetness. Based on my personal experiments, I brew French press coffee at 93°C / 199°F. I use a higher temperature for coffee ice cream. More on that later.

What about cold brew? It's a fad. I believe it’s popular because people are accustomed to bad coffee that tastes burnt and bitter. Cold brew extracts fewer bitter alkaloids from the bean, so without any special skill or even decent quality beans, you can entirely avoid bitterness. But cold brew also results in precious little body or acidity or aromatics—there’s very little there there. Just bass notes and roasted flavors. The coffee shops have turned “low acidity” into a feature, not a bug, because consumers don’t know what acidity is. It sounds scary, and is easy to conflate with bitterness, even though it’s essential to a balanced and lively cup. Acidity and bitterness, in fact, have a reciprocal relationship in hot-brewed coffee. More of one leads to less of the other. 

When making coffee ice cream, we’re interested in increasing acidity and aromatics, not decreasing them. We need to try to punch through the heavy muting tendencies of the dairy and sugar. 

Notes on grinding: If you want good coffee, you need a good burr grinder. This means a grinder with a hopper on top for beans, a set of conical or flat burs to grind the coffee, and a receptacle for grounds on the bottom. A whirly-blade grinder gives no consistency, so you are you are guaranteed some mix of coffee dust in with your grounds, which will over-extract and cause bitterness. If you’re just making brewed coffee and ice cream, any decent burr grinder will do. Entry-level grinders from Baratza will make as good a cup of brewed coffee as anything (if you’re making espresso—again, beyond our scope—you don’t need a good grinder; you need an awesome grinder. You will spend over $700 or you’re wasting your time. More reason to just go to the café). 

Your coffee needs to be fresh, meaning roasted between 4 and 10 days ago, stored in an airtight container at room temperature, and ground right before use. If you’re buying pre-ground coffee and letting it sit around for days, you’re sabotaging the process before you even begin.

A Coffee Recipe

For reference, here’s my idea of good coffee, scaled for a large French press pot:

-1400g filtered water
-80g–90g coffee. A good, fresh, light-to-medium roast. Medium-coarse ground, right before brewing (I don’t know how to measure grind precisely. I go a few clicks finer than the coarsest press pot setting. You’ll have to experiement) Concentration: 5.7%–6.4% by weight.

-preheat the press pot. pour in a few ounces of water just off the boil, swirl around and dump it out.
-put coffee grounds in prewarmed pot
-heat water to  93°C / 199°F  
-fill press pot about 3/4 full. start 4-minute timer.
-after 45 seconds, stir vigorously to break up the foam and raft of grounds on top. chopsticks or a palette knife work well.
-fill the rest of the way. cover.
-brew 4 minutes total. stirr again briefly. press the plunger.
-immediately drink or decant to cups / a prewarmed thermos.

Note on brewing methods: I use a press pot, because I like a lot of body, and because I like the control it gives over every variable. Many other brewing methods are capable of equally good, but different results. Some methods, like percolation, are not capable of good results. 

French press most closely resembles the process I’ll recommend for coffee ice cream, so it offers a good frame of reference.

Finally, Coffee Ice Cream

It took 21 versions to get this right. The goal was to preserve the full spectrum of flavors and aromas I get from a great cup of brewed coffee (like from the above method) or from a great cup of espresso, and to somehow have it complemented by, not demolshed by, the sugar and dairy of the ice cream. 

Some of the challenges:

  • The taste and aroma compounds in coffee have different levels of solubility in fats than in water. So the time / temperature / concentration guidelines that make the best coffee are not identical for ice cream
  • All brewing times / temperatures capable of extracting aromatics, fruity acids, and midrange roasted flavors into milk and cream also extract too much bitterness, possibly because of high carbon dioxide solubility
  • The aromatics in coffee are both muted by dairy and prone to evaporation during brewing and cooking

My solutions:

  • A lowfat base recipe, with milkfat around 10–11%
  • Less than the usual amount of sugar. Also 10–11%
  • A low proportion of eggs (2 yolks per liter), typical of most of my recipes
  • Additional nonfat milk solids, to preserve the full body of the ice cream
  • A high proportion of fresh-ground, high-quality, light-to-medium roast coffee (double the concentration used for brewed coffee in the method above)
  • A higher brew temperature, to increase extraction and help balance flavors
  • A modified brew method, in which the coffee and hot dairy are bloomed, then sealed in a ziploc bag while brewing, and chilled in ice water before straining, in order to preserve the aromatics
  • Added salt, to temper bitterness
  • Added acid, in the form of Pedro Ximenez sherry vinegar, to restore the balance of fruity acidity
  • Additional milk and cream, to compensate for what will be thrown out with the coffee grounds

Recipe: Underbelly Coffee Ice Cream

The recipe is written for cooking in an immersion circulator. It can be adapted to work with other methods, but a circulator is prefered for its ability to cook the mix in a fully sealed container that will preserve the aromatics. This makes about 1L of mix. About 180ml of milk and cream will be lost with the coffee grounds. [instructions edited 5-11-2018 for clarity.]

100g coffee beans (ideally light to medium-light roast, with full body and lots of fruit and acid. East African varieties are often ideal)

580g whole milk* (3.3% fat) divided 320g / 260g
320g  heavy cream* (36% fat) 

65g granulated sugar 
25g dextrose
15g trimoline**
90g nonfat dry milk*

2g salt 
1.4g preblended stabilizers, or: 
0.8g locust bean gum (tested with TIC Gums POR/A, soluble at 74°C)
0.4g guar gum
0.2g lambda carrageenan
2 large egg yolks (36g)
7g sherry vinegar*** (1.5tsp)

*Use the best quality milk and cream you can get. Nothing ultrapasteurized. Low-temperature pasteurized is ideal. Homogenized products will give best texture. Avoid cream with added stabilizer (unknown variables). Dry milk must be 100% skim milk solids, processed without high heat. There should be no off odors either when it's dry or when it's mixed. Store sealed in freezer.

**Or substitute 5g fructose powder, and add an additional 5g dextrose.

***Ideally use a Pedro Ximenez sherry vinegar, which has aged and savory notes that complement the midrange flavors of coffee. The darker the roast, or the lower the acidity of the coffee, the more vinegar will be useful to balance the flavors. adding (or partially substituting) citric acid  can help shift flavor to a brighter / sharper acidity. This may be helfpul if your coffee is lacking in high notes.

-set immersion circulator to 75°C / 167°F

start mixing base
-thoroughly mix powdered ingredients. use a 0.01g scale to measure salt and stabilizers.
-separate eggs and set yolks aside. freeze whites for other use.
-measure smaller portion of milk and trimoline into blender.
-set blender speed to create a vortex; add powdered ingredients. cover and blend on high for 30 seconds to disperse the stabilizers. 

prepare coffee infusion
-measure coffee beans and load burr grinder. set very coarse (like commercial breadcrumbs)
-prepare ice water bath
-prepare 1-gallon ziploc bag, set in a container that can hold it upright
-heat larger portion of milk and all cream on stovetop to 95°C / 203°F.
 (ideally use a relatively narrow vessel that’s easy to pour from and that minimizes evaporation. 
  you can use a metal pitcher set in a pot of boiling water)
-when cream/milk is nearly done heating, grind beans. pour grounds into the ziploc bag
-when milk/cream reaches temperature, pour just enough into bag to saturate the grounds. start timer set for 3 minutes 30 seconds.
-agitatate briefly and let the grounds sit with the bag unsealed.

-after 30 seconds add the remaing hot milk/ cream. push out as much air as possible and seal the bag.

strain coffee infusion and complete base
-set a fine chinois or strainer over the blender jar. cut the zip end off of the ziploc bag of coffee slurry and pour / squeeze it into the chinois
-let it strain for 10 minutes, periodically stirring / pushing on grounds with a rubber spatula to squeeze out as much infused liquid as possible
-add yolks and briefly blend
-add sherry vinegar and briefly blend again

-pour mixture into 1gal ziplock bag.
-add weight (recommended, to keep bag from floating) and evacuate the air.
-cook in water bath for 30 minutes to quickly raise temperature to 75°C / 167°F
-gently agitate bag after 15 minutes and 30 minutes. if you see air accumulated in the bag, release it, and carefully reseal bag.
-Drop circulator temperature to 75°C / 167°F. Uncover the container if was covered.
-cook in water bath an additional 30 minutes to set custard, hydrate stabilizers, denature milk proteins.
-mix will be pasteurized (pasteurization time after reaching this temperature is under 2 minutes).

-remove bag from water bath. open and pour hot mix into clean blender container (or a square container if using a homogenizer or stick blender). remove weight (with tongs). use bag to squeegee off any mix. temporarily seal bag and keep handy. 
-blend on highest speed for 30 seconds to homogenize.
-pour mix back into ziplock bag.

-chill bag in ice water bath (use ice bath to evacuate the air when sealing bag). carefully agitate to cool. Try to cool to refrigerator temperature. 

-refrigerate at least 8 hours, below 38°F / 3°C to age mix / pre-crystalize fat.

-pour into ice cream machine: snip off bottom corner of bag, and squeeze out mix as if using a pastry bag. or squeeze out into an intermediate container that’s easy to pour from.
-spin in the ice cream maker. With a mulitispeed machine, use a slow setting (this recipe works best with a low overrun). Ideal drawing temperature is 23°F / -5°C. Go lower if machine can do so without excessive extra time.
-evaluate when surface texture of ice cream first looks dry. if it needs more overrun, continue on higher speed. if it needs to cool more, continue on lower speed.

-harden for several hours (preferably overnight) in a cold freezer. freezer should be set to -5°F / -20°C or lower. Ice cream will have to warm up several degrees before serving. 20 to 30 minutes in the fridge works well. Ideal serving temperature is 6 to 10° F / -14 to -12°C.


total mass before straining: 1141g
total mass after straining: 983g (assuming 22g / 22% coffee solubles yield)
milk after straining: 490g / 16g fat  / 43g solids nonfat
cream after straining: 230g / 83g fat / 13g soldis nonfat
total milk fat: 99g / 10% 
total fat: 117g / 12%
nonfat milk solids: 146g / 14.8%
total nonfat solids: 291g / 29.6%
total solids (fat + nonfat): 408g / 42%
egg fats: 9g / 1%
egg proteins: 6g / 0.6%
egg lecithin: 2.9g / 0.3%
total egg solids: 18g / 1.8%
sugars (non-lactose): 105g / 10.7%

stabilizers (non-egg): 1.4g / 0.14%

Experiment notes on coffee extraction methods:

-Commercial or homemade coffee extract, made with alcohol: basic coffee, roast, and bitter flavors. Flat. Little fruit or liveliness or lighter aromatics.

-"Instant" infusion into alcohol, made with whipping siphon and nitrous oxide: similar to conventional extract, but more mid-rangey and less bitter.

-Coffee infused into water, brewed as very strong coffee (typically press-pot style) and strained. Extra water compensated for by balancing recipe and adding milk solids: typical ice cream shop coffee ice cream flavors, emphasizing roast and base coffee notes. Brighter flavors and aromas muted.

-Coffee mixed into simmered milk or cream, brewed as it cools, for 10 to 30 minutes: standard coffee ice cream flavor. Fairly flat. Slighty bitter and overextracted tasting when brewed strong. Little fruit or aroma.

-Coffee brewed into ice cream mix in sous-vide bag as mix cooks, at 75°C for 45 minutes: Prominent fruit and aromatic flavors, but a strong, metalic bitter imballance.

-Coffee cold brewed into dairy overnight in fridge: Very weak relative to amount of coffee used. No bitterness, and likewise no acidity or aromatics. All midrange. Similar to instant coffee.

-Coffee brewed with dairy in sealed bag, then chilled in bag before straining (similar to Japanese iced coffee method). 75°C, 4 to 7 minutes: Good aromatics and acidity. Midrange flavors undeveloped. Metalic bitterness present and out of balance.

-Coffee brewed with dairy in sealed bag, then chilled in bag before straining. 93°C to 95°C, 4 to 7 minutes: Fairly well developed coffee flavors, including aromatics and acidity. Metalic bitterness still somewhat present and out of balance.

-Coffee brewed with dairy in sealed bag, then chilled in bag before straining. 96°C, 4 to 5 minutes: Fuller range, 3-dimensional, better balanced flavor. Still too much metalic bitterness.

-Coffee brewed with dairy in sealed bag, then chilled in bag before straining. 96°C, 3 minutes: Full range, 3-dimensional, well balanced. Only slight remaining metalic / bitter notes. Brought mostly into balance by adjusting salt and acidity.

-Coffee brewed with dairy in bag, allowed to bloom before sealing, then chilled in bag before straining. 96°C, 30 second bloom, 3 minutes sealed brew: Full range, 3-dimensional, well balanced. Very slight remaining metalic / bitter notes. Easily brought into balance by adjusting salt and acidity.

Note for making commercial quantities: 
consider preparing the coffee infusion separately, up to a day in advance. Store refrigerated in sealed bags after straining.

For further Reading:

Part 1 of this series: Introduction
Part 2 of this series: Components
Part 3 of this series: How to Build a Recipe
Part 4 of this series: Basic Recipe Examples
Part 5 of this series: Techniques
Part 6 of this series: Sugars
Part 7 of this series: Stabilizers
Part 8 of this series: Emulsifiers
Part 9 of this series: Booze
Part 10 of this series: Solids, Water, Ice
Part 11 of this series: Introduction to Flavor
Part 12 of this series: Ice Cream Flavor: Coffee

Monday, February 26, 2018

Introduction to Flavor


Earlier in this blog series I suggested that good texture was easier for industrial ice cream manufacturers, but that good flavor was easier for the home or pastry cook. This is because some of the tools that promote the finest texture—high-pressure homogenizers, high-end ice cream and gelato machines that can freeze the mix in mere minutes, blast freezers / hardening cabinets—are out of reach for many small shops. 

Meanwhile, good flavor depends, in part, on generous amounts of good flavor ingredients, which are almost always expensive. Premium vanilla beans (around $400 a pound in 2018) are a minor splurge for a pastry chef in a michelin-starred restaurant, or a home cook who doesn’t need to turn a profit. Might as well use the good stuff, and throw in an extra bean if it suits your whims. But for a manufacturer making ice cream by the boxcar, such price premiums are a killer—especially in the context of retail markups and price fluctuations, either seasonal or unpredictable (caused by draught, blight, politics, war, etc.).

But Not Easy

While it's not so challenging to get better flavor than Haagen Dazs or Ben & Jerry, that's not a particularly high standard. Good flavor is easy. Great flavor is hard.

This blog has been silent for many months, in part, because I’ve been researching and experimenting with flavor, and discovering along the way that every answer spawns several new questions. Surprisingly, there’s very little high-quality published science on getting the best flavors into ice cream. The breadth of the topic doesn’t help. A spice like vanilla behaves very differently from an herb like thyme, which behaves differently still from an herb like peppermint. None of these are at all like coffee, and none create the problems you’ll find with ingredients that add water, like fruits, or ones that add fat, like chocolate or nuts. Every flavor is a new adventure, demanding different science, presenting different complications.

When I worked at an ice cream shop way back in the 20th century, our approach to flavors was mostly formulaic. We'd usually use the most concentrated flavor ingredient possible, in the form of commercial extracts, dry spice powders, and cocoa powder. With problem ingredients (fruit, or our house-made, water-based coffee extract) we’d compensate for the extra water by throwing in extra cream. Mix it together, spin it, call it done. This is how most ice cream shops do it. The approach makes decent commercial ice cream, and it lets you use the same base for all your flavors, and gives you a process you can teach someone in a couple of days. But it’s not the path to the best ice cream, and it’s not what we're going to be discussing in the next few posts. 


There are a few basic ways to get flavors into ice cream. I've divided them into the following categories:

Simple recipes (Blend the flavor ingredient into the base)
-Extracts or essences
-Low-bulk spices (cardamom, star anise, peppercorn

Modified recipes (Blend in the flavor ingredient. Compensate by adjusting total fats, sugars, milk solids, etc.)
-alternative sweeteners (honey, molasses, etc.)

Infusions Brew flavor into liquid ingredients at specific temperature and time, strain out)
-high-bulk spices (vanilla)
-aromatic vegetables (ginger)

Recipies with additional processes
-caramelizing sugar
-reducing wine or spirits
-toasting nuts
-browning butter

Compound recipes (Combining two or more of the above)
-dark sugars ice cream (caramelizing sugar, modifying base recipe)
-brown butter cognac ice cream (browning milk solids, reducing spirits, modifying base recipe)
-bourbon smash ice cream (infusion, modifying base recipe)
-coffee (infusion, modifying base recipe)

What is Flavor?

Flavor describes a complex set of physiological-psychological perceptions, based on taste sensations from the tongue, olafactory sensations from the nose, and a whole range of expectations and biases created by what we see, hear, believe, and remember. The science of flavor is young and rapidly expanding. The lore goes back about as far as recorded history.

In this series we're mostly going to be talking about the tongue and nose. The psychological / perceptual sciences are a bit above my pay grade (I happen to get paid nothing for this ... thank you for asking). 

You may have been tought that the tongue perceives just four tastes: sweet, salty, sour, bitter. This is pretty close, but we now believe that in addtion to these four, there is also at least one type of savoriness (umami), which describes our response to glutamic or aspartic acids in meat, seaweed, and aged cheeses; there is a taste for alkalinity (think of soap); there is possibly more than one distinct type of bitterness; and there may be other distinct tastes associated with fat, metals, and calcium.

There are also sensations that are similar to tastes but that are actually physical sensations unrelated to the tongue's taste receptors: pungency (the chemical burn from hot chilis); astringency (the grainy and puckery sensation from tannins in red wine, black tea, and rhubarb); coolness (triggered by mints, ethanol, camphor, and some sugar alcohols); numbness (triggered by some Sichuan chilis and by cloves). 

This describes around a dozen sensations in the mouth. The nose, however, knows no such humble limits. We can detect thousands—possibly tens of thousands—distinct aromatic compounds. And we're discovering new ones all the time. Here's a simplified chart breaking down organic aromatic compounds by family and molecule size. This includes a range of them from herbs to jet fuel, but is far, far from exhaustive:

Table of Aromatic Compounds

Some of this is academic; some may be useful when we have to solve problems. For example, you may find that an herb contains aromatic compounds that you like and ones that you don't. If they are soluble at different temperatures, this will help you decide the temperature of your infusion. Some compounds may be much more soluble in fat than in water. If you want those compounds, then infuse into the cream. If you don't, then infuse into the milk. And so on.

But let's start with something simple. Here's a recipe from the first group, aptly titled Simple Recipes, because you don't have to make any adjustments to the base recipe, and you don't have to use any specieal technique (besides turning the blender on):

Simple Recipe Example: Green Tea Ice Cream  

-12g matcha powder 

-Combine matcha with the other dry ingredients and make as usual. Easy peasy.


Matcha is powder ground from whole green tea leaves. In Japan it's whisked into hot water and enjoyed as a full-bodied tea. Since the powder is expensive, matcha is considered a more special drink than ordinary brewed green tea. Matcha comes in several grades, from "ceremonial" to "premium" to "café" to "culinary" to "classic." The highest grades are distinguished by their delicacy and subtlety, and so are almost always consumed straight without any milk or sweetener. The delicacy does not hold up to the dairy and sugar in ice cream, so it makes the most sense to use a good quality, fresh, culinary grade in this or other green tea ice creams.

For a very intense matcha flavor, increase the quantity to 18g powder. If using 18g and you find you need to decrease bitterness, add  0.4g citric acid and 1.3g additional salt (increase salt in recipe to 2g total)

This is a standard flavor balancing tactic, not just in ice cream but in all cooking, sweet and savory. Some universal guidelines:

-To counteract bitterness, increase salt or acid
-To counteract acid, increase fat or bitterness
-To counteract sweetness, increase acid or bitterness
-Salt will bring forward mid-range, warm, savory flavors
-Metalic flavors are often the product of imbalanced acids

Next post: Coffee Ice Cream (aka Simple Cooking Made Complicated)

For further reading:

How Does Our Sense of Taste Work? [Informed Health Online, via PubMed]

Part 1 of this series: Introduction
Part 2 of this series: Components
Part 3 of this series: How to Build a Recipe
Part 4 of this series: Basic Recipe Examples
Part 5 of this series: Techniques
Part 6 of this series: Sugars
Part 7 of this series: Stabilizers
Part 8 of this series: Emulsifiers
Part 9 of this series: Booze
Part 10 of this series: Solids, Water, Ice
Part 11 of this series: Introduction to Flavor
Part 12 of this series: Ice Cream Flavor: Coffee