How Are Vegetable Oils Produced?

Vegetable oils are the edible oils extracted from seeds, nuts, kernels and other plant tissue. Edible vegetable oils are extracted from plants using solvents such a hexane and/or through mechanical processes such as cold pressing and expelling. Mechanical processing does not involve solvents

and the major difference is the temperature of the extraction processes. Cold pressing involves a hydraulic press between two plates and the temperature tends to stay below 120°F. Meanwhile, expelling involves a screwing mechanism which results in more frictional heat allowing the temperature to reach as high as 185°F.

Why Are Oils Liquid at Room Temperature While Fats Are Solid?

In general, if the majority of fatty acids in a triglyceride source are saturated, then it most likely will be solid at room temperature. Contrarily, if a triglyceride source contains a greater percentage of unsaturated fatty acids, especially PUFA, then this source will most likely be liquid at room temperature. Saturated fatty acids are straighter than unsaturated fatty acid. This allows them to pack closer together and to be more solid. Take a look at Table 5.2 and notice how the oils have a higher percentage of unsaturated fatty acids while the more solid fats (lard, tallow, etc.) have a high percentage of saturated fatty acids. Despite their names, palm oil and palm kernel oil are more solid at room temperature.

What Is the Difference Between Fat, Oils, and Triglycerides?

Fats and oils are terms commonly used to refer to food sources of triglycerides. Often fat and oil are considered to be different based on appearance: fat is solid at room temperature and oil is liquid. However, they are really two of the same thing, generally speaking. They are both collections of triglycerides. For simplicity, we will use “fat” to include all sources of triglycerides.

A triglyceride molecule is a combination of three fatty acids linked to a glycerol molecule backbone (Figure 5.1). Although a triglyceride molecule will always have this general design, there can be great variability in the type and combinations of fatty acids that link to glycerol. Only one glycerol molecule exists, but like monosaccharides there are numerous different types of fatty acids in nature. Furthermore, if a triglyceride involves three fatty acids then monoglycerides and diglycerides will have one and two fatty acids attached to glycerol, respectively. Technically, they can be considered fat as well.