ISO INTERNATIONAL STANDARD 15788-1 First edition 1999-10-15 Animal and vegetable fats and oils - Determination of stigmastadienes in vegetable oils Part 1: Method using capillary-column gas chromatography (Reference method) Corps gras d'origines animale et vegetale - Dosage des stigmastadienes dans les huiles végétales Partie 1: Méthode par chromatographie en phase gazeuse sur colonne capillaire (Méthode de reférence) Tso Reference number ISO 15788-1:1999(E) Not for Resale @ ISO ISO15788-1:1999(E) Foreword committees. Each member body interested in a subject for which a technical committee has been established has liaison with IsO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/lEC Directives, Part 3. International Standard ISO 15788-1 was prepared by Technical Committee ISO/TC 34, Agricultural food products, Subcommittee SC 11, Animal and vegetable fats and oils. Iso 15788 consists of the following parts, under the general title Animal and vegetable fats and oils - Determination of stigmastadienes in vegetable oils: —Part1:Methodusingcapillary-columngas chromatography Part 2: Method using high-performance liquid chromatography Annex A of this part of ISO 15788 is for information only. @ISO1999 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic ormechanical,includingphotocopyingandmicrotilm,withoutpermissioninwritingfromthepublisher nternationalOrganizationforStandardization Casepostale56·CH-1211Geneve20·Switzerland nternet iso@iso.ch Printed in Switzerland tional Organization for Standardizatior @ISO ISO15788-1:1999(E) Introduction Significant amounts of hydrocarbons are formed in vegetable oils as a consequence of thermal treatments during the refining processes [1]. Among these hydrocarbons, 3,5-stigmastadiene, a steroidal compound, is the most is produced together with minor amounts of the 2,4-isomer and both substances give a single well-defined gas- For instance, for virgin olive oils, the usual oil production processes (pressure or centrifuging) do not produce stigmastadienes are found (ranging between 0,2 mg/kg and 3 mg/kg) due to the high temperatures applied during the drying of the raw olive residue. In the refining processes, stigmastadienes are formed in all the steps involving high temperatures, such as bleaching and deodorizing, but more amounts are formed in the first step using acid bleaching earth than in the second [2]. Depending on the conditions applied during the refining process, commercial refined vegetable oils show stigmastadiene concentrations ranging between 1 mg/kg and 120 mg/kg and, therefore, the assessment of stigmastadienes allows not only the identification of thermally treated oils but also the detection of minor amounts of refined vegetable oils in virgin oils. Amethodforthedeterminationof stigmastadienesandtheresultsof acollaborativestudycarriedoutunderthe auspices of the International Olive Oil Council were presented to the International Union of Pure and Applied Chemistry (IUPAC) Commission on Oils, Fats and Derivatives. The stigmastadiene content has been adopted as an identity criterion for virgin olive oils and the resulting analytical method has been adopted as an international standard method. ili