Fruit jams are made from crushed fruits with the addition of sugar, acid, and sometimes pectin. These ingredients determine the safety and stability of jams. Acid lowers the pH of the jam, which slows microbial growth. Pectin, a complex starch, helps jam maintain its thick texture without separating. Because fruits have a wide range of pH and pectin content, different fruits may need different amounts of acid and pectin added to the recipe to produce a safe jam that does not separate.