Thermophysical properties of different olive oils: Evaluating density and rheology through a fluid dynamic approach

Abstract

The aim of this study was to investigate the Newtonian viscosity and density of different types of olive oils with the ultimate aim of optimizing the unit operations involved in their production process. A total of 14 oils were selected and tested at a wide range of temperatures. These included ten extra virgin olive oils (EVOOs) and four olive oils (OOs) from five different countries of origin. The oils were analyzed to determine their fatty acid (FA) composition and all were found to contain large amounts of monounsaturated FAs such as oleic acid. FA composition did not appear to influence density, but viscosity demonstrated slight differences in activation energy in accordance with monounsaturated (MUFA) and polyunsaturated fatty acid (PUFA) content. Both viscosity and density were affected by temperature. When the oils were heated, viscosity decreased exponentially following an Arrhenius type equation, while density decreased linearly. Rheological data was fitted well to theoretical results for absolute temperature and FA composition simultaneously, displaying fitting parameters different to those published in literature. A brief study of the fluid dynamics of the oils indicated close agreement between theoretical and experimental friction factor, confirming the accuracy of the prediction models reported in this work. Practical applications: If variations in fatty acid composition are not taken into account during olive oil production processes, problems could be encountered. In other words, over‐ or underestimating the liquid's dynamic properties could have adverse effects on pumping, refining, and other essential operations. This investigation therefore aimed to provide mathematical models to assess the thermophysical properties of various olive oils at a wide range of temperatures. Analyzing changes in density and dynamic viscosity provided valuable data that can be used to ensure equipment and processes are properly designed. The scarcity of fluid dynamic research in this specific area makes this investigation particularly relevant. Not only did it provide information about pressure loss in pipes and other parts of the machinery, it also proved useful in confirming the accuracy of prediction models reported by researching experimental density and rheological parameters. This work evaluated the fluid dynamic as a classical method to confirm the determination of the thermophysical properties of different commercial olive oils.

Quality characteristics and thermal behavior of buriti (<em>Mauritia flexuosa</em> L.) oil

“…Newtonian viscosity presented close values to the ones published by Santos et al (2005) for different vegetable oils. In the same way, the viscosity of buriti oil was comparable to the values found by Ribeiro et al (2017) for different commercial olive oils. These olive oils had a very similar fatty acid composition to buriti oil, which also resulted in close agreement between buriti and olive oil densities.…”

Physical and chemical behaviour of Nabali Mohassan single‐cultivar olive oil during prolonged storage

“…However, it should be highlighted that, particularly for the refractive index and relative density, the observed variations of these physical properties were very low; in some cases, this was in the order of magnitude of the analytical device used, and thus monitoring their decrease is less useful from a practical point of view, if not even misleading. The viscosity values of oil samples stored up to 3 years were similar to those reported in other studies, 21,36,37 although a significant increase of viscosity was observed during storage. Previous studies have shown that olive oil undergoes an increase in viscosity during repeated frying operations 38,39 or after prolonged heating, such as in the case of treatments at 65 ∘ C for 45 days 40 or at 90 ∘ C for 35 days 41 .…”

“…The viscosity values of oil samples stored up to 3 years were similar to those reported in other studies, although a significant increase of viscosity was observed during storage. Previous studies have shown that olive oil undergoes an increase in viscosity during repeated frying operations or after prolonged heating, such as in the case of treatments at 65 °C for 45 days or at 90 °C for 35 days.…”

Physical Properties and Molecular Interactions Applied to Food Processing and Formulation

“…Density also reflects the capacity for thorough homogenization of powder mixtures [15], which is crucial when dealing with milk powder [16], for example. Determining the correlation between density and viscosity can provide ready-to-use data, as well as important information that can be used to assess the quality of vegetable oils [17,18]. When dealing with foams, density is also indicative of air incorporation and, thus, foam stability with the aim of drying, but it can also be used for various other food and culinary applications [19].…”