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Determination of the Fat Content Profile of different Chocolate Products using an Automated Workflow for the Generation of Fatty Acid Methyl Esters (FAME)

The composition of the fat in chocolate is an important factor influencing the quality of chocolate. Specifically the replacement of cocoa butter by replacements or CBEs (cocoa butter equivalents) is of interest to food quality laboratories [1]. 

The determination of fat content and composition of food samples via fatty acid methyl esters is a very common task in governmental, quality control (QC) or contract research laboratories (CRO). 

This work presents a fully automated workflow of this procedure using an autosampler with robotic tool change (PAL RTC). The automated workflow improves process safety and minimizes handling errors. The PAL RTC was equipped with (i) an automated dilutor to handle all liquids for the reactions and the extraction and for the cleaning steps, a 25 µL syringe for internal standard addition, (ii) a vortex module to provide fast mixing and extracting and (iii) a normal 10µl syringe tool to inject the sample to the GC. The software of the sampler allows overlapped (prep ahead) sample processing, which increases the efficiency and sample throughput.

The method allows the determination of total fat content, quantitative analysis of saturated and unsaturated cis- and trans- fatty acids. The use of three internal standards allows controlling the yield of extraction, transesterification and undesired saponification [2-4]. Chocolate samples from Japan, Switzerland and the USA were analyzed. The data allowed a clear classification of the chocolates in terms of content of cocoa butter and replacements.

[1] Buchgraber M, Andronis S, J. AOAC 90 (2007) 1326-1339

[2] Arens M. et al., Fat Sci. Technol. 96 (1994) 67-68

[3] Suter B. et al., Z Lebensm. Unters. Forsch. A 204 (1997) 252-258

[4] de Koning S. et al., J. Chromatography A 922 (2001) 391–397