A while ago, I conducted an experiment where I placed three elodea leaf cells in a 5% salt solution, 20% sugar solution, and distilled water to test the question of salt being a better food preservative than sugar.
Using three elodea leaf cells placed under a microscope, I placed each one in either a 5% salt solution, 20% sugar solution, or distilled water.
There are two types of solutions: A hypertonic and a hypotonic solution. A hypertonic solution means that there would be a higher concentration of solutes located outside the cell, which is what would make water leave the cell. For example, saltwater would be a hypertonic solution because there is a higher concentration of salt in comparison to the inside of the cells. A hypotonic solution is when there is a lower concentration of solutes outside the cell, which would cause water to enter the cell. For example, distilled water has a lower concentration of solutes in comparison to the inside fluid of cells. Osmosis is when the concentration of solutes from one side (higher or lower) travels across the membrane to the other side (higher or lower) in order to reach equilibrium of both inside and outside of a cell.
Salt and sugar were both hypertonic solutions, while distilled water was a hypotonic solution. Therefore, the results of the elodea leaf were quite satisfying.
In the 5% salt solution, the elodea leaf cell's cytoplasm had completely shrunk. The only reason the entire cell did not shrink was because of the cell wall, which was keeping the cell intact. When the water leaves a plant cell, the process is called plasmolysis. When water leaves an animal cell, the process is called crenation. In this scenario, plasmolysis occurred and our evidence is the fact that the cytoplasm had shrunk the most.
In the 20% sugar solution, the cytoplasm had shrunk, but not nearly as much as the 5% salt solution. Because sugar was also hypertonic, water left the cell, letting plasmolysis occur, and the cytoplasm shrank inside the cell wall.
In the distilled water solution, the cytoplasm did not shrink, but it looked a little more full. Since distilled water was a hypotonic solution, water entered the cell and the cell got plumper. This is called turgor pressure. The cell wall was the only thing inside the cell preventing it from bursting. It's the opposite in animal cells because when the water rushes in, the intense pressure can cause the cell to swell and burst. This is known as cytolysis.
Salt had been proved to be the best preservative. The question most people would ask is why? Just because salt created plasmolysis and the cytoplasm shrank the most doesn't mean that it's the best preservative, right? Well, you would be wrong. Let's think back to why the cytoplasm shrinks. It's usually because a large amount of water has left the cell, right? And when our food spoils, microbial cells such as bacteria or fungi tend to grow on it because it is moist and has water in its cells. Well, bacteria cannot survive in dry environments, which is why salt would be considered the best preservative. According to our experiment, salt had the smallest cytoplasm in the end which means the most water had left, therefore it was the driest cell.
Another question may be: How did salt get water to leave the cell? Well, the ions in salt significantly increase solute concentration. In this scenario, the salt ions increased the solute concentration which was outside the cell. This caused a lot of the solutes inside the cell to travel out of the cell and to the external environment to reach an equilibrium through osmosis. Because salt ions attracted more solute than usual, the cell began to dry out and therefore the cytoplasm shrank.
Although there have been many studies going around about whether salt or sugar is the better preservative, I thought it would be fun to see for myself. The results were as predicted as several other studies, but the scientific reason behind why salt is considered the better preservative was interesting to research and learn about.
Stay tuned for more experiments!
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