-Toby’s Estate (Australia)
But first—how to make a good cup of Joe?
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.
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 90°C–96°C / 195–205°F.
A Coffee Recipe
Finally, Coffee 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
- 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
*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.
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.