Olfactory indicators change their smell depending on whether they are mixed with an acidic or basic solution. One example is ammonia. In its pure form, ammonia has a strong, pungent odor. When mixed with an acidic solution, the smell of ammonia may become less intense or change altogether, providing an olfactory indication of the acidic nature of the solution.
Citrus fruits, onions, garlic, and vinegar are some of the natural olfactory indicators. They serve a crucial role in cooking and food preparation by improving flavor, balancing acidity, providing scent, hiding odors, tenderizing proteins, and even preserving food.