Every summer we need to prepare several batches of cold brew coffee every day in our coffee shops. Cold brew coffee is one of the most popular coffees of the last period. Everyone has tried to brew their own cold brew once in a while. The thing is: sometimes it can end up with a flavor that is not exactly what we want.
So why does your cold brew taste so sour? If it is sour, it may mean you are not getting enough extraction. A coarser grind will make this worse. Grind finer or let it brew longer. If these changes don't help, you can try a hot cold brew. Use about 25% hot water for 1-2 minutes and then fill as normal with cold and ice. This helps bring out the sweetness and distinctive flavor of the bean (which is often lost during cold brewing).
Why Your Cold Brew Is Acidic And How To Avoid It
The flavor profile of a cup of coffee comes from two main categories: acidity and bitterness. Any parameter change in the processing chain changes the final flavor of your coffee.
Sourness and bitterness are opposite ends of the extraction spectrum – sourness comes from under-extraction and bitterness comes from over-extraction. In your case, perhaps your cold brew needs a little more brewing in water for it to extract properly.
Try to Brew at Room Temperature
Try it on the counter instead of the refrigerator. This will give you more extraction. If better, your problem is insufficient extraction causing sourness. If it's worse, go back to the fridge but try 12 to 18 hours.
Try to Grind Your Coffee Beans Finer
If you have tried the above method and still no results, if incomplete extraction persists, the next thing you can try is to grind the beans finer.
Fine grinding means a quick extraction. But don't overdo it or your coffee will be bitter.
Maybe It's Just Your Beans
Try your coffee beans in hot brew, sometimes it's just the taste of your beans. Generally, the darker the roast, the lower the acid level, and the higher the 'perceived' acidity in light roast coffees.
So you can try the coffee you bought in hot brew to verify if it is suitable for cold brew. Remember, medium to dark roast will be your friend when trying to cold brew.
Solution
The reasons why cold brew tastes acidic is no different than hot brew. Sourness often comes from incomplete extraction.
Therefore, you should monitor the following 4 main factors:
grinding size
brew time
Heat
Coffee bean