8 May / June 2016
Healthy Fat in Chips and Sausages?
A new Method for Extraction, Digestion and Analysis of Fat in Food Samples
by Marcel Pacheco-Moreno1 1
2 3 , Jürgen Schram1 , Uwe Oppermann2 , Franz Kramp2 , Frank Scholten3
University of Applied Sciences, Frankenring 20, D-47798 Krefeld, Germany Shimadzu Europa GmbH, Albert-Hahn-Str. 6-10, D-47269 Duisburg, Germany CEM GmbH, Carl-Friedrich-Gauß-Str. 9, D-47475 Kamp-Lintfort, Germany
, Ulf Sengutta3 ,
A new method for the determination of saturated and unsaturated fatty acids in food samples such as chocolate, milk powder, sausages, and potato chips has been developed. The method consists of a fast and gentle microwave process in a closed system for sample preparation and the determination of fatty acids using gas chromatography with flame ionisation detection (GC-FID). The analytical data are compared with results of the same food samples generated on the conventional ISO procedures and advantages of the new method are explained.
Introduction
The REGULATION (EU) No 1169/ 2011 OF THE EUROPEAN PARLIAMENT requires the detailed declaration of nutrition values for food as of 2016, especially the differentiation of fat in saturated and unsaturated fatty acids [1]. This differentiation is important in order to protect consumers. For example, the American Dietetic Association (ADA), the European Food Safety Authority (EFSA) and the American ‘Academy of Nutrition and Dietetics’ recommend covering less than 35% of the body’s daily energy requirements by fat; according to ADA, less than 20% should be monounsaturated fatty acids (MUFA).
Determination of total fat content as well as unsaturated and saturated fatty acids in food is performed using methods based on ISO standards. Depending on the type of food, methods like Röse-Gottlieb or Weibull-Stoldt extraction are used for the determination of total fat content [2,3].
The following analysis of saturated and unsaturated fatty acids is done using gas chromatography (GC-FID). This analysis requires the derivatisation of fatty acids in fatty acid methyl esters (FAMEs) based on the ISO norm [4].
Unsaturated fatty acids are sensitive to oxidation processes generated through contact with air and influence of heat. That’s why a gentle microwave process has been developed which is applied
Figure 1: Alkaline Derivatisation of a Triglyceride with methanol to ester [5]5.
Figure 2: Acidic derivatisation of a fatty acid to ester with methanol under formation of water [6].
in a closed system in two steps for various food compartments. This new microwave procedure is faster, cheaper and more environmentally friendly than the conventional ISO procedure.
It is assumed that the oxidation sensitive unsaturated fatty acids are treated more gently in the microwave process and oxidation is thereby minimised, resulting in higher analytical levels of unsaturated fatty acids.
Methods Conventional ISO procedure:
The conventional standard procedure is based on the ISO extraction method (ISO 8262) for total fat determination in milk and milk products according to Weibull-Berntrop and the derivatisation of fatty acids in fatty acid methyl esters (FAMEs) based on the ISO method (DIN EN ISO 12966-2).
The ISO 8262 method serves as a base and
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