Journal of Chromatography A, 1131 (2006) 227–234 Authenticity of milk fat by fast analysis of triacylglycerols Application to the detection of partially hydrogenated vegetable oils Fr´ ed´ eric Destaillats a,∗ , Maureen de Wispelaere a , Florent Joffre b , Pierre-Alain Golay a , Bernadette Hug a , Francesca Giuffrida a , Laetitia Fauconnot a , Fabiola Dionisi a a Nestl´ e Research Center, Vers-chez-les-Blanc, Lausanne, Switzerland b Omega 21, 10 route de Flacey, 21380 Marsannay le Bois, France Received 26 June 2006; received in revised form 14 July 2006; accepted 17 July 2006 Available online 7 August 2006 Abstract Detection of foreign fat in milk fat can be performed by analyzing triacylglycerols (TAGs) by gas–liquid chromatography (GLC) using the standardized methodology. The standard methodology recommends the use of a packed column, which allows the separation of milk TAGs according to their chain length (total carbon number). This procedure is not widely applied because these columns are not commercially available. This study describes a fast methodology by using a short apolar open-tubular capillary column. The developed experimental conditions can be used to obtain the chromatographic resolution required in the standardized procedure, and the separation of milk fat TAGs (C24 to C54) is achieved in less than 4 min. As indicated by the standardized method, the quantification was performed by calibration using the certified reference material CRM-519 butterfat as standard substance. The methodology was fully validated and relative repeatability values were compared with the values provided in the standardized procedure. The developed method was applied to detect adulteration of milk fat with partially hydrogenated vegetable oils (PHVOs). PHVOs contain variable amount of trans-18:1 acids and two different PHVOs having different trans-18:1 acid levels (13 and 38%) were added to milk fat at levels ranging from 5 to 30%. The obtained mixtures were analyzed by GLC and formulas established by the European Union were applied. Calculated S values indicated that PHVOs in milk fat could be analyzed at these levels. Approximate amounts of PHVOs added to the composite samples could be calculated using the standardized formula. The impact of adulteration of milk fat with PHVOs, which contains an important amount of trans-9 and trans-10 18:1 acid isomers, was investigated as a complementary analytical criteria. We showed in composite samples, that the trans-18:1 acid isomeric distributions are distinct when referenced to the original milk fat profile and that trans-9 18:1 acid isomer is a good indicator of the occurrence of PHVOs in milk fat. Our results showed clearly that a short apolar capillary column can be used instead of a packed-column and that the mathematical model developed for the detection of foreign fat was suitable to detect adulteration of milk fat with PHVOs. © 2006 Elsevier B.V. All rights reserved. Keywords: Adulteration; Gas–liquid chromatography; Milk fat; Partially hydrogenated vegetable oils; Trans fatty acid; Triacylglycerol 1. Introduction Milk fat is one of the most expensive commodity fats on the market; therefore, the detection of foreign fat in milk fat is a real issue. Milk fat can be adulterated by different ways such as homogenization of skimmed milk with less expensive foreign fat or by direct incorporation of foreign fat in butter or butter fat. An accurate methodology suitable for detection of these frauds ∗ Corresponding author at: Vers-chez-les-Blanc, P.O. Box 44, CH-1000 Lau- sanne 26, Switzerland. Tel.: +41 21 785 8937; fax: +41 21 785 8553. E-mail address: frederic.destaillats@rdls.nestle.com (F. Destaillats). was developed in the eighties [1–6] and was standardized [7]. This methodology consists to separate milk fat triacylglycerols (TAGs) according to their chain length (total carbon number) by gas–liquid chromatography (GLC). TAG analysis is usu- ally achieved either by high-performance liquid chromatography (HPLC), hyphenated with evaporative light-scattering detection or by GLC using both packed and capillary columns. HPLC anal- ysis does not require temperature and prevent, therefore, thermal degradation of lipids. However, the quantification of various TAG species with evaporative light-scattering detector could be challenging due to the limited linearity range of this detector. The standardized method had been developed using packed column. TAG formulas have been developed for both the 0021-9673/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2006.07.040