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Phytosterol oxidation products

formation, analysis and occurrence

Johnsson, Lars (2004). Phytosterol oxidation products. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae. Agraria, 1401-6249 ; 490
ISBN 91-576-6770-5
[Doctoral thesis]

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Abstract

The main aim of this thesis was to study the formation of phytosterol oxidation products (POP) and to evaluate and optimize an analytical method for the determination of POP in food products. The cholesterol lowering effect of phytosterols (PS) and phytostanols has been known for more than half a century and many reports in this area have been published. During the last decade the intake of PS has increased and products enriched with PS and phytostanols have been launched on the commercial market. Due to their chemical structure, PS are susceptible to oxidation at various sites in their structure. In the present study, oxidation products from the major phytosterols, sitosterol, campesterol and stigmasterol, were generated through autoxidation at elevated temperature. POP from both the ring-structure and side-chain structure were separated by preparative TLC and characterized using GC, GC-MS and NMR spectroscopy. Chromatographic data for many of the products were reported for the first time. The analytical methodology investigated and optimized in the present study included transesterification of the lipid compounds. The enrichment of POP by amino SPE-technique was reported as efficient and time saving compared with the more commonly used saponification technique. In addition, highly improved separation of a mixture of 29 POP was illustrated when a combination of different polarity GC capillary columns was studied. The optimized methodology was used for the determination of the levels of POP in some food products. The levels increased in olive oil and maize oil after heated at 180 ± 5 °C for 0-2 h from 8 mg/g to 18 mg/g and 4 mg/g to 12 mg/g, respectively. However, the levels of POP were almost unchanged during heating of peanut oil. The total amount of POP in a commercial available PS ester enriched spread was calculated to around 12 mg/g spread. Overall, the findings from this thesis demonstrate that numerous oxidation products from PS are formed during heat-facilitated autoxidation. For quantification of all these POP by GC, very high efficient capillary column/columns are necessary. The development of efficient and reliable analytical methods is urgent for the determination of levels of POP in food products, and possibilities to accurately estimate the daily intake of POP.

Authors/Creators:Johnsson, Lars
Title:Phytosterol oxidation products
Subtitle:formation, analysis and occurrence
Year of publishing :November 2004
Volume:490
Number of Pages:59
Papers/manuscripts:
NumberReferences
ALLI. Johnsson, L. & Dutta, P. C. 2003. Characterization of side-chain oxidation products of sitosterol and campesterol by chromatographic and spectroscopic methods. Journal of the American Oil Chemists' Society. 80(8), 767-776. II. Johnsson, L, Andersson, R. E. & Dutta P. C. 2003. Side-chain autoxidation of stigmasterol and analysis of a mixture of phytosterol oxidation products by chromatographic and spectroscopic methods. Journal of the American Oil Chemists' Society. 80(8), 777-783. III. Johnsson, L. & Dutta, P. C. 2004. Separation of phytosterol oxidation products by combination of different polarity gas chromatography capillary columns. Journal of Chromatography A. (Submitted) IV. Johnsson, L. & Dutta, P. C. 2004. Method optimization and determination of levels of phytosterol oxidation products in some food products. (Manuscript)
Place of Publication:Uppsala
ISBN for printed version:91-576-6770-5
ISSN:1401-6249
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:Q Food science > Q04 Food composition
Subjects:Not in use, please see Agris categories
Agrovoc terms:oxidation, phytosterols, gas chromatography, sterols, plants, foods, sitosterol, stigmasterol, analytical methods
Keywords:autoxidation, campesterol, capillary GC, phytosterols, phytosterol oxidation products, plant sterols, POP, PS, sitosterol, stigmasterol, thermal oxidation
URN:NBN:urn:nbn:se:slu:epsilon-362
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-362
ID Code:706
Department:(NL, NJ) > Dept. of Food Science (until 161231)
Deposited By: Lars Johnsson
Deposited On:23 Nov 2004 00:00
Metadata Last Modified:02 Dec 2014 10:06

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