What characteristic of jelly prevents microbial growth even after extended use?

The characteristic of jelly that prevents microbial growth, even after extended use, is its high osmotic pressure. When jelly is made, it contains a significant amount of sugar, which creates a hypertonic environment. This means that the concentration of solutes (sugar) in the jelly is much higher than that found in microbial cells. As a result, when microbes come into contact with the jelly, water moves out of the microbial cells through osmosis in an attempt to balance the concentration of solutes. This loss of water causes the microbial cells to become dehydrated, effectively inhibiting their growth and reproduction.

While high acidity, low temperature, and high sugar content all play roles in food preservation, the specific mechanism by which jelly's osmotic pressure inhibits microbial growth is particularly influential. The high sugar content leads to the osmotic pressure condition, which is why understanding the principle of osmotic effects is crucial in microbiology and food preservation.