A Mad Scientist’s Dive with Delicious Results
THE GENESIS OF THE IDEA
When I first read the Atlantic Monthly’s article on the perfect cup of coffee, I was enamored by both the science and the art behind it. A deep dive into research from an MIT professor produced a matrix of highly complex simplicity, merging personal taste with a “coffee golden ratio” which I still use today for my morning pour over. https://www.theatlantic.com/health/archive/2013/08/how-to-make-perfect-coffee/278944/
This generated in me a rapacious desire to learn all I could about the science of coffee’s interaction with water. It is an ever-progressing process with each year’s harvest presenting a new profile. Teasing out the terroir for each Som’s Café coffee selection, finding that delicate balance of citrus and sweet, fruits and nuts, earth and floral.
In traditional brewing techniques the heat of the water is central. But what if we remove the heat altogether? Can we achieve the necessary amount of extraction of coffee flavors from room temperature water to make a great cold brew?
A MOLECULAR MASH-UP
The Maillard reaction (add a wiki link) is foundational in coffee roasting by converting amino acids into different phenolic compounds. This conversion and the resulting molecules bonding to aromatic compounds are what give each coffee it’s flavor profile. There are as many compounds as you can imagine, and your mind is particularly good at recalling these memories through smell.
In your water there are compounds that make a big difference in the flavor of your coffee. It bears repeating that you should always use a purified and/or filtered water to make your coffee — hot or cold. Chemicals like fluoride and bleach in municipal water supplies bring their own aromatic compounds that are not necessarily ideal.
Avoid distilled water too. The dissolved solids in your water that make it taste like water are the molecular taxi cabs that your aromatic compounds are going to hop into along the way.
Of course, with every agricultural product that undergoes a process like roasting, other compounds can exist. Included in this is tannin. It’s that feeling in the roof of your mouth when you drink a very dry glass of red wine or (if you dare) taste a dash of straight cinnamon. Tannin can hide those decidedly delicious aromas, especially the sweet ones. By not applying heat, less tannin enters the brew, allowing the sweeter aromatics to shine.
(NOT) BRINGING THE HEAT
To ensure that we have enough of the coffee dissolved solids going into our water we need to increase our surface area. With espresso, the speed and pressure dictate a size of coffee ground that gets the right amount into each shot. With percolator there is repeated and prolonged exposure to the grounds, so they can be more course.
For our cold brew, a fine grind somewhere between pour over and espresso grind is ideal. Experiment with your own grinder to find the size that works best for you.
EASY ON THE TUMMY
One particularly yummy aromatic is what most of us associate with a caramel flavor. With our cold brew method and using our Som’s Cafe Beginnings Blend coffee, we have found that this aroma comes forward in abundance.
We will leave the discussion on pH level and it’s effect on flavor for another post, but it is important to note that this method does produce a product that is more alkaline (less acidic) than coffee made with hot water. This allows the natural sweetness to emerge as it is not buffered by a higher acidity.
It also makes this style of brewing and the result much easier on the stomach for those of us looking to ingest caffeine without soda or hot coffee.
It should be noted that this method requires:
-Sanitary conditions, including the vessel being used, the stirring utensil, the water, and the closure
-Monitoring for any bacterial growth. If you smell it and it smells “off”, DON”T drink it
-Patience. This does take time and the more you open the container to check on it, the higher the risk of spoiling it.
We’ve made large portions for nearly a decade between farmer’s markets and our former café. We use a five gallon Cambro with a spout on the bottom for ease, but you can use any kitchen vessel that can be properly sanitized. Below is a recipe for making one gallon of cold brew coffee.
-A two-gallon container or larger with a tight-fitting lid
-Extra large coffee filters – at least 10 inches. Search for commercial size filters or buy our starter pack
-A large stirring spoon or brewer’s paddle (avoid wood)
-Food safe rubber bands. You can sanitize ones from around your broccoli or asparagus, or buy our starter pack. Remember, you must sanitize every time!
- Pour 5 quarts of room temperature filtered water into your sanitized container
- Add ½ teaspoon of kosher salt (don’t use iodized or sea salt). This acts as a flavor enhancer and as a mild preservative. Skip if you want the second time around, but we recommend trying it the first time.
- Grind 12 ounces of Som’s Café Beginnings Blend coffee, or your favorite local roaster’s selection, to a fine grind.
- Place the coffee in the large filter, fold into a satchel, and loop the food safe rubber band around the top a few times so no grounds can come out. (hint: if your hands are wet or you are too aggressive you will tear your filter)
- Place your satchel into the water and gently use your kitchen tool to ensure it is wet on all sides. Be careful not to puncture the filter.
- Place the lid firmly on your container. You can leave the container on your kitchen counter in a cool dark place or place in the fridge (it will be less concentrated with the fridge method).
- After 24 hours, flip your satchel over with your sanitized kitchen tool and reseal.
- After another 16 hours (40 total), remove the satchel and let it rest in a sanitized colander for 5 minutes over the container. Discard the satchel and save the rubber band if desired.
- Place your finished product in the fridge. Consume within 7 days.
For recipe ideas on how to turn your cold brew into café-level beverages, check out our monthly subscription service coming soon which will come with monthly cold brew, espresso based coffees, and tea latte recipes with demonstrations from our physical café.