Chromatographic and electrophoretic approaches for the analysis of protein quality of soy beverages.

Furosine, generated by acid hydrolysis of fructosyllysine, an early Maillard reaction product, is a highly valuable indicator of food quality and, more specifically, of food protein quality. Ion pair RP-HPLC and CZE techniques were employed to determine furosine content in beverages based on soymilk (n = 15) and cow's milk supplemented with soy isoflavones (n = 1). The levels of furosine found in the samples ranged from 25.55 +/- 0.18 to 170.72 +/- 10.4 mg/100 g of protein by HPLC and from 28.67 +/- 1.84 to 161.25 +/- 5.78 mg/100 g of protein by CZE. Results obtained by both analytical techniques do not differ significantly (p > 0.05), confirming their feasibility for furosine analysis in soy-based products.