Phytosterol enrichment in vegetable oil by high pressure processing

Berichte aus der Verfahrenstechnik
Aymeé Michel de Arévalo
Phytosterol enrichment in vegetable oil
by high pressure processing
Shaker Verlag
Aachen 2009
Bibliographic information published by the Deutsche Nationalbibliothek
The Deutsche Nationalbibliothek lists this publication in the Deutsche
Nationalbibliografie; detailed bibliographic data are available in the Internet at
http://dnb.d-nb.de.
Zugl.: Hamburg-Harburg, Techn. Univ., Diss., 2008
Copyright Shaker Verlag 2009
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Printed in Germany.
ISBN 978-3-8322-8236-3
ISSN 0945-1021
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Summary
Phytosterols are cholesterol-like molecules found in plant foods. Their importance
comes from the ability of lowering blood cholesterol and prevention of coronary
heart disease. The highest concentration of phytosterols occurs in vegetable oils
(about 1% in corn germ oil). In this context, the aim of this work was to evaluate
different processing methods to obtain oil enriched in these valuable compounds.
Pressing, supercritical fluid extraction and high pressure crystallization were
investigated and optimised regarding their oil sterol concentration. Supercritical
processing being considered a cleaner technology for food application has been
selected as an alternative to conventional extraction methods.
The influence of temperature and pressure on the kinetics of the supercritical
extraction and on the content of sterols was investigated. The range of pressure
and temperature applied in these experiments were 20MPa – 50 MPa and 20°C –
80°C. The oil obtained by supercritical fluid extraction was compared with the oil
obtained by conventional processes (pressing and solvent extraction). The results
showed that the oil yield of the supercritical fluid extraction (SFE) was similar to
the one of conventional solvent extraction. However, the phytosterols content was
higher using supercritical extraction. Furthermore, it was possible to obtain
enriched fractions of raw oil with 3.56 % sterols through supercritical fluid time
fractionation at 20MPa and 80°C (up to 4.7 times original sterol concentration
present on refined commercial oils).
High pressure crystallization experiments were carried out to the press oil and the
enriched fractions obtained from the supercritical extraction experiments with the
objective of achieving a further increase on the oil’s phytosterol content.
Nevertheless, by means of crystallization merely a small increase of the
phytosterol concentration could be obtained (1.29% sterol).
Different refining steps were applied to the sterol enriched oils obtained by
supercritical fractionated extraction to assess whether or not after refining the
sterols were still concentrated on the refined oil. Approximately 84% of the sterols
present in the extracted oil were retained after the physical refining and 75% after
the chemical refining process. Thus, oils with an enrichment of up to 4 times the
original sterol concentration present on commercial oils could be obtained after
physical refining when extracting the oil with supercritical fluid fractionated
extraction.
A complementary part of this work was the experimentally determination of phase
equilibrium data and physicochemical properties for the system corn germ oil –
sterols – CO2. Two new relationships to calculate the interfacial tension and
density of corn germ oil in contact with carbon dioxide at low temperatures were
developed. Regarding the phase equilibrium of the system, the values obtained for
the distribution coefficient of the sterols are higher than one, what indicates that it
is possible to enrich the sterols using CO2 as solvent. The optimal conditions for a
separation in the gas phase were determined to be at low pressure and high
temperature.
It is demonstrated that SFE is an alternative process to win sterol-enriched oils
and even though after refining the sterol concentration remains higher than the
present one in commercially available oil. With this new process a healthier
product can be obtained avoiding the separation of valuable minor components
during processing and saving the addition of sterols again at the end of the
production chain.
Summary
Phytosterols are cholesterol-like molecules found in plant foods. Their importance
comes from the ability of lowering blood cholesterol and prevention of coronary
heart disease. The highest concentration of phytosterols occurs in vegetable oils.
In this context, the aim of this work was to evaluate different processing methods
to obtain corn germ oil enriched in these valuable compounds. Pressing,
supercritical fluid extraction and high pressure crystallization were investigated
and optimised regarding their oil sterol concentration.
Zusammenfassung
Phytosterine sind cholesterinähnliche Substanzen, die essentielle Bestandteile
von pflanzlichen Zellmembranen sind. Phytosterine werden zur Senkung des
Cholesterinspiegels eingesetzt. In Lebensmitteln liegen sie hauptsächlich in
fettreichen Pflanzenteilen, wie zum Beispiel in Maiskeimen, vor. In diesem Kontext
war das Ziel dieser Arbeit, unterschiedliche Verfahren zu untersuchen, um ein
Phytosterin angereichertes Öl zu erhalten. Pressen, überkritische Extraktion und
Kristallisation unter hohen Drücken wurden untersucht und bezüglich ihrer
Ölsterinkonzentration optimiert.