Why is my cold brew so sour?
The short answer to this is that it is most likely under extracted. What leads to coffee being under extracted comprises many varying factors that can easily alter how your brew turns out.
When brewing cold brew coffee, or any method of brewing in general, there are a few stages of the brewing process you need to take note of:
Under extraction (sour and oily)
‘Sweet’ spot (sweet and syrupy)
Over extraction (bitter and flat).
Hitting the sweet spot
The compounds in coffee are always extracted in this order with fats and acid being extracted first, sugars next and plant fibres last. The targeted sweet spot is to stop the brewing process once the sugars have been extracted to avoid going into the over extraction stage. In general, a sour cold brew would mean the coffee grounds in your brew is under extracted, whereas a bitter cold brew would mean it is over extracted.
Environmental factors affect the brewing process
There are many factors that affect the speed and duration of reaching that ‘sweet’ spot. Some of these factors include:
Temperature of water
Temperature of your surroundings
For example, brewing your cold brew in the fridge will require a longer brewing time of approximately 16-24h. If you brew your cold brew on your countertop, it can range between 10 hours to 24 hours, depending on the weather.
While there are general guidelines to producing a good brew, the best way to brew a perfect cuppa coffee is through trial and error to find what works for you.
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