Specific heat of vegetable oils as a function of temperature obtained by adiabatic scanning calorimetry

Vegetable oils can undergo changes in their physical and chemical properties when they are subjected to processes such as extraction, purification, cooking, frying, or chemical modifications that are required depending on their application in the food industry. In the present research, different methods were used to determine physical, chemical, and thermal properties of avocado, sesame, extra virgin flaxseed, extra virgin olive, and grape seed oils, in order to evaluate and compare the compositional effects of each vegetable oil. By using an adiabatic scanning calorimeter, an alternative calorimetric method, the specific heat of five vegetable oils was obtained as a function of the temperature, in the range of 25–90 °C. The fatty acid profile was determined via gas chromatography. Monounsaturated acids present in avocado and extra virgin olive oil cause higher specific heat values in these oils, and the presence of polyunsaturated acids, contained mainly in extra virgin flaxseed oil, reduces the specific heat values. We found an almost linear behavior of vegetable oil specific heats, as a function of the temperature, and the slopes of these linear fits depend on the contained percentage of polyunsaturated fatty acids in the vegetable oil. The unsaturated acids are an important factor to analyze the behavior of specific heat of vegetable oils. The obtained specific heat values were compared with the estimation from the Rowlinson–Bondi equation, for specific heat of vegetable oils, giving a very good adjustment, mainly in a temperature range near to the room temperature.