Firm, extra firm tofu is excellent for slicing, marinating, grilling and stir-frying. You can find tofu in most grocery stores in the refrigerated or produce cases. The aseptic packages are airtight and don't need refrigeration until they're opened. If it's not in aseptic packaging or the aseptic package has been opened, handle tofu just like any perishable food and keep it refrigerated. Always check the expiration date.
Fresh tofu has a mild odor.
If it smells sour, return it. This could indicate improper refrigeration during transportation or storage. Try tofu in your next recipe. Chill at least 2 hours. Serve with fresh cut vegetables.