WHY DOES FOOD SPOIL? Processing and improper storage practices can expose food items to heat or oxygen, which causes deterioration. In ancient times, salt was used to cure meats and fish to preserve them longer, while sugar was added to fruits to prevent spoilage. Certain herbs, spices and vinegar can also be used as preservatives, along with anti-oxidants, most notably Vitamins C and E. In processed foods, certain FDA-approved chemical additives also help extend shelf life.
WHAT IS HYDROSTATIC PRESSURE? "Hydrostatic" is a word that means stationary (static) water (hydro). Hydrostatic pressure is the force exerted on a surface by a stationary fluid; think of the pressure you feel on your eardrums when you swim to the bottom of a pool. Hydrostatic pressure describes pressure in all stationary fluids, not just water. The air that surrounds us exerts a hydrostatic pressure on our bodies of about 15 pounds per square inch (air, like water, is a fluid that can exert pressure). We don't feel the hydrostatic pressure of the atmosphere because the pressure inside our bodies pushes out and balances the pressure of the air pushing in; which is to say, we are in equilibrium with the pressure of the atmosphere. When you fly in an airplane, the discomfort you feel in your ears is due to the changing hydrostatic pressure in the cabin. Chewing gum, yawning, or swallowing eases the discomfort because it opens airways in your head and lets the pressure inside your ears match the pressure outside. In the deepest parts of the ocean, the hydrostatic pressure reaches about 16,000 pounds per square inch, or roughly 1,000 times the pressure at sea level.