Salt
Because many germs cannot live in salt, it has been used to preserve food. Its use as a food preservative helped large amounts of food to be stored, sent a long way, and eaten all through the year. This helped populations to grow, cities to develop, and soldiers in wars to be fed. Salt was probably used in Egypt as long ago as 4000 BC. In ancient times, salt was more valuable than it is now, because it was hard to get in many places, and could be used not only to give foods flavor, but also to make them last longer. It allowed food to be kept past its season, and taken on long trips.