Aymeé Michel de Arévalo Phytosterol enrichment in vegetable oil by high pressure processing

Transcription

1 Berichte aus der Verfahrenstechnik Aymeé Michel de Arévalo Phytosterol enrichment in vegetable oil by high pressure processing Shaker Verlag Aachen 2009

2 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 Zugl.: Hamburg-Harburg, Techn. Univ., Diss., 2008 Copyright Shaker Verlag 2009 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publishers. Printed in Germany. ISBN ISSN Shaker Verlag GmbH P.O. BOX D Aachen Phone: 0049/2407/ Telefax: 0049/2407/ Internet: info@shaker.de

3 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.

4 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.

5 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.

6 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.