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I went into this new specialty coffee shop today, they had a nice place and very informative brochures about the coffee beans they were using that day, happened to be a top quality Brazilian product whose the beans looked nicely roasted, the barista showed expertise in preparing my espresso and answered all my questions with patience. I was savoring my coffee even before it was served, but it was a big disappointment, the brew was extremely acidic (we are talking lemon-juice acid here) and with a such a rough texture that dulled my tongue to other flavors. I did not enjoy my coffee at all. I complained to the barista about the acidity (as we had discussed acidity and he assured me that the coffee was not acidic at all) and he offered to prepare a new coffee with the same result. My question is, given that Brazilian coffee beans are probably the least acidic ones, what could have gone wrong with the brewing to yield such awful tasting product ?

Elfarto
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    This is a super loaded question. I don't have time to write a good answer to this now and likely won't soon, so just know that hard beans (like those typically sourced from Brazil) are plenty acidic when fresh, that water (or more specifically the solutes dissolved in the water) plays an important role in the resulting brew, that coffee roast level affects brew acidity, and that bean preparation method (washed vs unwashed, mainly) affects brew acidity. There are a lot of moving parts that go into that cup of specialty joe. And the why is a trip down Chemistry Lane, too. – R Mac Jul 11 '21 at 03:01
  • Can you briefly explain how washed vs unwashed affects acidity ? I think that washed beans should be less acidic but i'm not sure.. – Elfarto Jul 12 '21 at 15:07
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    Coffee beans are actually seeds plucked from the cherries of coffee trees. Because of this, they are naturally coated with sugary residue when sold in their natural form. Washing removes those sugars, which changes the flavor of the brew eventually made with those beans. The sugar content doesn't reduce acidity actually, but it does curb the tart taste a bit, meaning washed varieties generally taste more acidic than unwashed. – R Mac Jul 12 '21 at 15:31

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While I cannot answer with certainty if the coffee was indeed "awful" because there is no way for me to know, I can answer with a few things that can make espresso more acidic.

  1. Roast level. When coffee is roasted it starts to gain sweetness (it's essentially caramelising) and roasty notes like chocolate and nuts. This happens at the expense of acidity and fruity flavours. Places that sell specialty coffee usually have lighter roasts, so that the origin characteristics of the beans do not get lost. While light roasts can undoubtedly be sweet too, they tend to be more acidic and complex than darker roasts. Because espresso is so concentrated and more intense than filter coffee, many shops even roast their beans differently for filter and espresso, to prevent the exact thing that happened to you.

  2. Variety. Some varieties of Arabica tend to be more acidic than others. For example, the varieties Marsellesa, Starmaya, and SL28 will generally be more acidic and complex than Caturra and Mundo Novo. Of course, the roast level will also impact the acidity that is perceived in the cup.

  3. Processing. In general, simple terms, there are two ways of drying the coffee bean - with its cherry still attached or with the cherry removed and washed away. The former is called natural and the latter method is called washed. Because natural coffee is in contact with the cherry (which is a fruit of course) for a longer time, some of the flavours of the cherry can end up in the bean, which give the coffee a more balanced taste, making it seem less acidic.

  4. (Under)extraction. When extracting coffee with any method, you want to be in the sweet spot for extraction. If you brew it for too long, it will taste bitter, dry, powdery, or dusty. On the other hand, if you brew it too fast it will be underextracted and taste sour, vegetal, or bland. Get it right and the coffee should taste sweet, complex, fruity, and slightly acidic (not like a lemon but think more of a pleasantly juicy green apple).

All of these things considered, it is important to note that for someone who is used to classically roasted coffee, which you can get at most cafes, specialty coffee will definitely be much more acidic than they are used to. It very well may be that the barista was convinced and genuinely thought that the coffee wasn't acidic compared to the other coffees he had.

technical_difficulty
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