The correct answer is:
2. to add tartness
Citric acid is added to food primarily to enhance the tartness or sourness of the product. It is a natural preservative found in citrus fruits like lemons, limes, and oranges. When added to food, citric acid can help balance flavors, especially in products that are too sweet or bland. Additionally, it can act as a preservative, extending the shelf life of certain foods by inhibiting the growth of bacteria and mold. Its tart flavor profile makes it a popular choice in various food and beverage products such as soft drinks, candies, jams, and salad dressings.