How to Make The Signature Lactic Acid Brew Recipe - Home Grounds

How to Make The Signature Lactic Acid Brew Recipe

Have you ever wanted to brew coffee like a master barista?

It’s not as easy as it sounds. In fact, brewing the perfect cup of coffee can be compared to an art form – especially when you watch someone do it with ten plus years of experience under their belts.

The truly delectable, yet attainable, cup of coffee that this tutorial focuses on is from Andrea Allen of Onyx Coffee Lab.

Her simple lactic acid brew was showcased as the company’s signature drink when Andrea competed in the United States Barista Championships (USBC) in 2017. 

The history of this simple lactic acid brew is fascinatingly in-depth, carefully thought out, and exquisitely executed.

Andrea was inspired to create something both simple and complex, delicious and coffee-centric.

No covering up the flavor of the espresso with tons of milk and sugar – only ingredients that gently complement the aroma, texture, and taste are added, thereby creating an overall masterful experience.

If this sounds like something you need in your life, read on to learn how to make a lactic acid brew just like Andrea Allen.

The Coffee

The coffee Andrea chose was a lactic washed green tip Geisha, which comes all the way from the La Palma y El Tucan coffee farm in Colombia.

The farm is closely associated with Onyx, and Andrea personally visited it in her search for the exact coffee she wanted to use in this signature drink.

After cupping numerous high-caliber coffees, she finally settled on Geisha (and it’s no wonder – Geisha is consistently ranked as one of the top coffee beans in the world).

Grown at 1900 meters above sea level and picked by a team of women, the coffee is put through a lactic acid washing process in which it is sealed off from any extra oxygen in a cold water tank for 80 hours, during which it produces lactic acid.

This gives a creamier texture and a winey acidity to the excellent taste of these premium beans.

This coffee is complex, clean, and sweet.

The Milk

Andrea clarifies her milk by using a centuries-old method involving limes.

No, that wasn’t a typo... limes!

She adds 120 grams of lime juice to 500 grams of milk and lets it sit. The citric acid in the limes bonds with the fats and solids in the milk, separating it from the rest.

Once separated, she scoops the fats and solids off the top, leaving a “creamy limeade” flavored (as Andrea puts it) clarified milk.

Once this has been done, the milk has literally been adapted to the needs of the coffee. How cool is that?

It’s the perfect complement to the lactic acid-washed coffee.

The Sweetener 

Andrea uses honey “simple syrup,” which she explains is just equal parts honey and water.

Easy enough. Now onto the recipe.

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What You’ll Need


  • 84g lactic washed green tip Geisha espresso
  • 25g clarified milk
  • 6 dashes of rose water
  • 2 dashes of acid phosphate
  • 6g Terroir coffee blossom honey simple syrup

Making the Signature Lactic Acid Brew: Step By Step Instructions

Start by following these steps, and you're on your way to mastering this signature recipe!

  • Step #1. Brew the Coffee 

First things first, you need to brew 84 grams of beautifully pure espresso using the lactic washed green tip Geisha beans.


Don’t rush! Measure carefully. Take a minute to smell the espresso once it’s brewed. The process is part of the experience here!

  • Step #2. Add the Milk 

Next, pour 25 grams of clarified milk into your espresso.

  • Step #2a. Clarifying the Milk 

If you haven’t clarified your milk yet, you can do so here.

Add 120 grams of lime juice to 500 grams of milk and let it sit. Once separated, scoop the fats and solids off the top. This should leave you with more than enough clarified milk at the bottom.

  • Step #3. Add the Rose Water

Add six dashes of rose water.


A dash generally measures between ⅛ and ¼ of a teaspoon. Whenever a “dash” is mentioned, anything between those measurements should yield approximately the same flavor, so don’t sweat the exact amount! 

  • Step #4. Add the Acid Phosphate

Add two dashes of acid phosphate (if you’re interested in learning more, check out how acid phosphate is used in other drinks, too).  

  • Step #5. Add the Simple Syrup

Pour in your 50/50 mixture of “simple syrup” using half water and half Terroir coffee blossom honey.

  • Step #5a. Making the Simple Syrup

If you haven’t made your simple syrup, you can do so here. Simply add 3 grams of Terroir coffee blossom honey to 3 grams of water and mix into a syrup.

  • Step #6. Mix It Up! 

Give the mixture a gentle stir or two.

  • Step #7. Drink It Up!

Pour and enjoy.


Ideally by the time you reach this step the drink is reading at around 100 degrees, the perfect temperature to maximize its sweetness. 

Mastering the Lactic Acid Brew

Remember that in creating this drink you are attempting to mimic a master barista. Andrea is recognized internationally as one of the best baristas in the business.

On a side note, she has also made great headway as an advocate for female coffee competitors, which has been awesome to see!

If you’ve achieved success, you should now be completely consumed by an incredible cup of coffee.

The aroma is amazing on this one, with a strong floral accent from the rose water, that lingering hint of lime, and a perfect sweetness imbibing the air above the cup.

It’s smooth to drink and has a juicy aftertaste.

If you’re drinking your coffee alone, enjoy every last sip. We’re with you in coffee spirit!

However, if you’re drinking with company and you want to follow Andrea’s splendid finish in her performance at the USBC, you can use a bit more rose water to wash the hands of your guests and fellow coffee drinkers, displaying that level of care and hospitality that Andrea excels at as much as she does in brewing coffee.

Whatever your experience (including any other interesting coffee recipes you’ve tried!), please share it with us.

Comment below, and please like or share the post so we can get others in on this utterly fantastic recipe!

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