Blackberries are considered to be an alkaline food because of how they rank on the pH scale. A lot of fruits, vegetables, berries, and dairy products are considered to be alkaline, though that is not true for all of them. Fruits like oranges, lemons, and limes are considered to be acidic because they have a high acid content.
Blackberries are usually categorized at a mild alkaline food. Other foods that are mild alkalines include apples, apricots, avocados, bananas, cherries, and coconuts. Those who have serious problems with acid reflux/heartburn can feel free to eat blackberries because they will not have a negative impact on this condition whatsoever.