Why does jelly not melt at room temperature? Take out a piece of ice from the refrigerator and place it on the table. It will melt quickly at room temperature, but jelly will not melt at room temperature. Why? Jelly still appears semi-solid at room temperature because jelly is made by adding a thickener (a food additive) to a specific liquid whose main components are water, sugar and juice. Thickeners commonly used in the process of making jelly include gelatin, agar, etc. Gelatin is a natural protein product extracted from cooked animal skin and bones. It contains 18 amino acids and can be directly absorbed by the human body and has high nutritional value. Agar is a seaweed extract obtained by heating and condensing a certain seaweed. It is rich in dietary fiber and protein and is recognized as a healthy food by the Food and Agriculture Organization of the United Nations.
So why do these food additives turn liquids into semisolids such as jelly? This is related to the molecular structure of such food additives. The main components of this type of food additive are protein and cellulose, both of which are natural polymer compounds. These compounds have a large molecular weight and a long molecular chain length. They can be dissolved in such liquids to form solutions and make the solution present some novel characteristics. For example, viscosity is one of its novel characteristics. Physicists usually use the viscosity coefficient to describe the strength of viscosity. The larger the viscosity coefficient, the stronger the viscosity, and vice versa. The viscosity coefficient of this kind of solution is related to many factors, the most important of which is the molecular weight and structure of the thickener. The greater the molecular weight, the longer the molecular chain, and the greater the intermolecular force, so the viscosity of the solution The greater the coefficient is.
When people make jelly, they use this principle. Thickening agents are added during the preparation process, which correspondingly increases the viscosity of the jelly, making the jelly form a semi-solid state and will not melt even if it is placed at room temperature. Of course, if the jelly is heated, it will still turn back to liquid when it reaches a certain temperature. This is because the temperature will also affect the viscosity of the jelly. When the temperature increases, its viscosity coefficient will decrease, so it can be transformed from a semi-solid state. It has changed back to liquid state.