Final answer:
Sour taste is linked to the presence of acids, such as citric acid in fruits, and is perceived due to hydrogen ions triggering depolarization in gustatory cells. It is not an indicator of toxicity, calorie content, or mineral or protein levels, but can sometimes indicate spoiled food.
Step-by-step explanation:
The taste of sour is associated with the perception of hydrogen ion (H+) concentration in substances, which is a characteristic of acids. For instance, fruits like lemons and oranges contain citric acid, which results in a sour taste due to their low pH levels. Sour taste is not directly an indicator of toxicity, calories, mineral content, or protein, but it can sometimes suggest that food is spoiled if the sourness is unexpected or out of context for that food item. Additionally, while not mentioned in the provided options, sourness can enhance the enjoyment of certain foods, particularly candies like Sour Patch Kids that are coated with sour sugar, which is a combination of citric or tartaric acid and sugar.