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Beverage Strength and “The FIXX”- VST

Beverage Strength and “The FIXX”

I receive a great number of inquiries about final concentration of the beverage when espresso is served as a cappuccino. This is one of the most important observations I’ve learned from using MoJo and the coffee refractometer, and is a great incentive for those looking to truly improve their espresso beverages.

Achieving desired final beverage concentration (% TDS) is up to the barista in order to satisfy the consumer’s request. Depending on the beverage being served, the coffee and its characteristics, there are primarily two ways to move final beverage concentration up/down.  An fundamental goal should be to keep Extraction Yield sweet, in a range of [approximately] 18-21%. This is a guideline, not an absolute, however, at these concentrations espresso served below 17% extraction yield tends to be very sour, and more than 22% will tend toward harsh and bitter.

Milk contains lactose, a sugar, which we perceive about one fifth as sweet as sucrose (table sugar). Keep in mind, however, we use ~4:1 milk to espresso in a traditional cappuccino.  Sweeteners tend to offset sour or bitter flavor defects that can arise in improperly brewed espresso. Conversely you could make the case that sour or bitter flavor defects offset the sweetness of lactose, diminishing the overall beverage sweetness. Either way, in my experience (yours may differ), the sweetest cappuccino is realized when as espresso extraction yield of 18-21% is achieved.

The brewing ratio determines the CONCENTRATION,  which you will set to what ever you need.  For example, many people prefer to drink straight espresso as a Normale (~10%)  or Lungo (~5-7% TDS) when served w/o milk.

However, when served with milk, the espresso beverage is diluted (i.e., making it weaker, but not changing the Ext YLD).   Therefore, when served with milk, many barista will try to increase final beverage strength by a stronger concentration (~ 12-13% TDS) of the same or similar amount of espresso (i.e., a Ristretto)  or

In the process, many times, a barista will tend to go from a sweet normale to a very sour ristretto, by attempting to achieve too high a concentration (i.e., >13%).  This is not necessary, as you will see, below.

The final concentration (Cf) is simply: Cf = (Ci * Wi)  / Wf

Where: Ci = initial concentration

Wi = initial weight

Wf = final weight

Example (Note: all units are expressed in weight, not volume)

Let’s start with a 50% espresso brew ratio in a typical cappuccino, as follows:

Start with 14g Dose/28g Beverage and pull to 20% Ext Yield  =  10.0% TDS

Add 4-oz (weight = 112g) steamed milk (total 140g ~ traditional 5-oz cappuccino)

Final %TDS after milk = (10% * 28g) / (112g + 28g)  =  2.0% TDS

(this is the coffee strength of the final beverage)

If you’re not satisfied with the final coffee strength, and prefer a more dominant coffee taste, you can increase concentration as follows:

22g Dose/34g Beverage and pull to ~19.2% Ext Yield  =  12.4 % TDS (a Ristretto)

Add 106g of steamed milk (total 140g ~ traditional 5-oz cappuccino)

Final %TDS after milk = (12.4% * 34g) / (106g + 34g)  =  3.0% TDS

(this is the coffee strength of the final beverage)

The 50% increase in final strength will result in a significant boost in coffee flavor in the final cappuccino beverage (even though it is only 6-gr of additional espresso, because it is at a higher starting concentration).

Final observation: The [Caffeine] Fixx is in

A typical American cup of [specialty] coffee (in the U.S., a 12 fl-oz cup volume) is served as ~11-oz of coffee by weight (leaving room for milk/cream) and is usually in the range of ~ 1.35% TDS.

The total coffee soluble solids consumed, a.k.a. “the fixx” is about 4.2 grams in this cup of coffee.

A typical cappuccino served at 2% final beverage concentration, as noted above, is only about 2.8 grams, often leaving many wanting for a second serving. However, when served instead with a Ristretto as in (a) or as a double as in (b) above, total coffee soluble solids is…… 4.2 grams, generally a more satisfying beverage in terms of “the fixx”.


A single-serve pour-over Coffee:

22g Dose

340g Water

~300g Beverage @ 1.40% TDS

= 4.2g soluble solids


22g Dose

42g Beverage @ 10.0% TDS

= 4.2g soluble solids