Hello Martha. When coffee tastes sour, it is usually a sign of under-extraction. This happens when water passes through the coffee grounds too quickly, or if the water temperature is too low to properly extract the sweet and bitter compounds, leaving behind the acidic fruit notes. Budget brands often grind their coffee too coarsely for standard drip machines, which accelerates under-extraction.
To fix this, try using slightly hotter water, a finer grind if you can adjust it, or a slightly longer brewing time. If the beans are a light roast, they naturally tend to taste brighter and more acidic anyway.
