Determination of soybean proteins in soybean–wheat and soybean–rice commercial products by perfusion reversed-phase high-performance liquid chromatography

The determination of additions of soybean proteins in commercial bakery products containing soybean–wheat and soybean–rice binary mixtures has been achieved in this work by high-performance liquid chromatography using a perfusive column. Soybean proteins were solubilized in a 25:75 acetonitrile–water mixture containing 0.3% (v/v) acetic acid by ultrasonication for 10 min and centrifugation for 5 min. Soybean proteins were separated from rice and wheat proteins in less than 4 min using a linear binary gradient of acetonitrile–water containing 0.3% (v/v) acetic acid as ion-pairing agent. The proposed method was proved to be specific and sensitive making possible the detection and the quantitation of additions of about 0.10% (w/w) and 0.33% (w/w), respectively, of soybean proteins in soybean–wheat and soybean–rice products (related to 1 g of initial product). Precision and recoveries observed were also acceptable. The method was applied to the determination of soybean proteins in different commercial bakery products.