The Ultrasonic Investigation of Phase Transition in Olive Oil up to 0.7 GPa

Food Bioprocess Technol

et al. 2016

Self Cite

Modeling of high-pressure technological processes in the food industry requires knowledge of thermophysical parameters of processed foodstuffs in a broad range of pressures and temperatures. However, the high-pressure thermophysical parameters of foodstuffs are very rarely published in the literature. Therefore, further research is necessary to achieve a deeper insight into the biophysical and thermophysical phenomena under pressure to provide better control of technological processes and optimize the effects of pressure. The essential goal of this work is to evaluate the impact of high pressure and temperature on the thermophysical parameters of liquid foodstuffs on the example of diacylglycerol (DAG) oil (which attracted recently a considerable attention from research and industrial communities due to its remarkable benefits for health), using ultrasonic wave velocity and density measurements. Isotherms of adiabatic and isothermal compressibility, isobaric thermal expansion coefficient, internal pressure, and thermal pressure coefficient versus pressure were evaluated, based on the measurement of the compressional ultrasonic wave velocity and density of DAG oil at high pressures (up to 500 MPa) and at various temperatures. The adiabatic compressibility is affected mostly by the changes of pressure, i.e., it grows about four times when the pressure increases from the atmospheric pressure (0.1 MPa) to 400 MPa at a temperature of 50°C. By contrast, the internal pressure is a pronounced function of the temperature, i.e., it increases six times when the temperature rises from 20 to 50°C at a pressure of a 200 MPa. To perform numerical calculations, it was convenient to introduce a Tammann-Tait type equation of state to approximate the measured density isotherms of the investigated DAG oil. The results obtained in this paper can be applied in modeling and optimization of high-pressure technological processes and processing of foodstuffs. Evaluation of high-pressure isotherms of the considered thermophysical parameters of the DAG oil is an original authors' contribution to the state-ofthe-art.

Section: Resultsmentioning

confidence: 99%

Evaluation of High-Pressure Thermophysical Parameters of the Diacylglycerol (DAG) Oil Using Ultrasonic Waves

Kiełczyński

Szalewski

Food Bioprocess Technol

et al. 2016

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“…On this basis, knowing the density of the sample measured by pycnometer at atmospheric pressure, we determined the changes in density of the sample as a function of pressure for various temperatures. The measuring set-up and methods have been described in authors' previous works [7][8][9][10]. The expanded relative uncertainty for the sound speed in liquid was equal ± 0.3% at a 95% confidence level.…”

Section: Methodsmentioning

confidence: 99%

Ultrasonic evaluation of thermodynamic parameters of liquids under high pressure

Kiełczyński

Szalewski

2014 IEEE International Ultrasonics Symposium

et al. 2014

In many technological processes (e.g. in chemical, petrochemical, food and plastics industry) liquids are subjected to high pressures and temperatures. Therefore knowledge of their thermodynamic properties is essential for understanding, design and control of the process technology. Direct evaluation of thermodynamic parameters of liquids under high pressure, using conventional methods, is very difficult. Therefore, these methods are useless in industrial conditions, particularly in on-line control of the technological parameters of liquids. Ultrasonic methods (e.g., sound speed measurements) due to their simplicity and accuracy are very suitable for this purpose. The sound velocity is closely related with numerous thermodynamic properties of liquids. In this paper we report ultrasonic velocity and density measurements (performed by the authors) in diacylglycerol (DAG) oil over a range of pressures and temperatures. On the basis of experimental results (the sound velocity and liquid density versus pressure and temperature) the thermal expansion coefficient, specific heat capacity at constant pressure, isothermal and adiabatic compressibility of DAG oil were calculated as a function of pressure and temperature.

“…This olive oil was produced in Spain with a high content of triacylglycerols (97%) of oleic acid mainly (76.8% of all acids)- Table 1 [5]. The remainder (3%) were DAG, MAG, free acids and other compounds.…”

Section: Materials Tag Samplesmentioning

confidence: 99%

Comparison of High‐Pressure Behavior of Physicochemical Properties of the Di‐ and Triacylglycerols Established by Ultrasonic Methods

2017

J Americ Oil Chem Soc

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Two samples of triacylglycerols i.e., olive oil and triolein, and one sample of diacylglycerol were investigated. In the course of compression, the density of the samples was determined by measurements of the change of piston position in a pressure chamber and volume correction due to chamber expansion under pressure. The speed of sound was evaluated from the time of flight of an ultrasonic impulse between emitting and receiving transducers placed in the high pressure chamber. The adiabatic compressibility, the intermolecular free length, the molar volume, the van der Waals’ constant b and the surface tension were evaluated from the density, the speed of sound and the average molecular mass. All tested liquids undergo a high-pressure phase transition. Discontinuities in the measured isotherms of the physicochemical parameters of the investigated oils indicate the presence of high-pressure phase transitions. Moreover the time dependent change of pressure at constant volume during the phase transition was measured. The fundamental difference in the molecular structure of these acylglycerols influences their behavior significantly under high pressure.