Phytoestrogens in soy‐based meat substitutes: Comparison of different extraction methods for the subsequent analysis by liquid chromatography‐tandem mass spectrometry

This paper presents the development of an efficient extraction procedure followed by a high performance liquid chromatography‐tandem mass spectrometry (HPLC‐MS/MS) method for the determination of five phytoestrogens (genistein, daidzein, formononetin, biochanin A, and coumestrol) in soy‐based meat substitutes. Phytoestrogens are considered endocrine disrupting compounds, and their quantification is important in soy‐based products, whose diffusion is increasing nowadays. The HPLC‐MS/MS method, with electrospray ionization (ESI) source, was optimized to obtain high specificity and sensitivity, as well as rapidity of the analysis. Three extraction techniques were applied to soy burgers and compared: ultrasound assisted extraction, ultrasound assisted extraction followed by solid phase extraction and the Quick Easy Cheap Effective Rugged and Safe (QuEChERS) methodology. Both ultrasound assisted extraction and QuEChERS proved to be suitable for the determination of phytoestrogens, showing high recoveries, in the range of 86% to 99% and 75% to 105%, respectively. Matrix effect was evaluated, and ion suppression was observed for coumestrol and formononetin, demonstrating the importance of matrix effect assessment when complex samples are analyzed by HPLC‐ESI‐MS. The complete analytical protocols provided limits of detection and quantitation in soy‐burgers at the ng g−1 level for all the considered phytoestrogens. Some soy burger samples were analyzed by both ultrasound assisted extraction and QuEChERS followed by HPLC‐MS/MS. High concentration levels of daidzein and genistein (2‐59 μg g−1 and 2‐72 μg g−1, respectively) were found; formononetin was in the range of 5 to 26 ng g−1, while biochanin A and coumestrol were under the limit of quantitation in all samples. The results obtained with the two different sample treatment were in good agreement, proving the precision and accuracy of the described techniques.