By Harold McGee
Both the sensitivity to salt and the preference for saltiness in foods vary a great deal from person to person. They depend on several factors, including inherited differences in the numbers and effectiveness of taste receptors on the tongue, general health, age, and experience. Most young adults can identify as salty a water solution with 0.05% salt, or 1 teaspoon in 10 quarts/liters, while people older than sixty years generally detect saltiness only at double that concentration. Many manufactured soups, which many people experience as moderately to very salty, are around 1% salt (10 grams, or 2 teaspoons per quart/liter), approximately the same concentration as our blood plasma. Some may be 3% salt, which is the average salinity of seawater.