Grease is the general term for oil and fat. Generally, what is liquid at room temperature is called oil, and what is solid is called fat. The source of fat can be animals or plants. Animal fats are generally solid at room temperature, have good shortening properties, and are more commonly used.
The following is used to understand the saponification value and iodine value of oil and fat:
The mass of potassium hydroxide required for 1g of oil to be completely saponified ( mg) is called the saponification value. The saponification value is related to the molecular weight of the fatty acids contained in the oil. It directly reflects the average molecular weight of various fatty acids, from which the average length of the fatty acid carbon chains in the oil can be inferred. Survey research shows that the saponification value of oils and fats produced from the same oil in different regions does not vary greatly. Therefore, the saponification value can be used to identify the type and quality of oil and grease, and to control the amount of alkali used during saponification. The difference between the saponification value and the acid value is the ester value, which is the number of milligrams of potassium hydroxide required to saponify the ester in 1g of oil. From this, the average molecular weight of the triglycerides in the oil can be calculated.
The iodine value is the mass (g) of iodine that 100g of oil can absorb under certain conditions. It reflects the degree of unsaturation in the oil. Various oils and fats have a certain range of iodine values, and their analysis methods include standard Webster titration, refractive index method, gas chromatography, etc. In domestic and foreign oil standards, saponification value, iodine value, refractive index, relative density and other physical property values are used as indispensable physical and chemical characteristics indicators of oil. With the promotion of gas chromatography, the content of unsaturated fatty acids can be directly measured using gas chromatography, but the iodine value is still a simple method to understand the unsaturation of oils.
微信扫一扫打赏
