Fast determination of the functional peptide soymetide in different soybean derived foods by capillary-high performance liquid chromatography.

The determination of bioactive peptides derived from food sources is gaining special attention in last years, due to their ability to promote health and their potential to reduce the risk of chronic diseases. In this work, a new analytical methodology has been developed enabling for the first time the determination of soymetide, a new immunostimulating peptide derived from soybean, in different soybean derived foodstuffs. Capillary-HPLC was employed for peptide separation after accelerated tryptic digestion of soybean proteins. Two different capillary-HPLC columns were tested and chromatographic separation was optimized in each case. The use of a 300 μm fused-core technology C18 column enabled a suitable separation of soymetide from the other peptides in less than 18 min. Different analytical characteristics of the method were evaluated: selectivity, linearity, accuracy, precision, limit of detection and quantitation, and stability. The developed method was applied to the determination of soymetide content in different soybean dairy-like products for human consumption (powdered milks and infant formulas).