Simultaneous Determination of Protein-bound Maillard Products by Ion Exchange Chromatography and Photodiode Array Detection

Summary Following complete enzymic hydrolysis, simultaneous determination of protein-bound advanced-stage Maillard compounds in addition to the Amadori products lactuloselysine and fructoselysine as well as the common amino acids including tryptophan was achieved by ion-exchange chromatography with photodiode array measurement and subsequent ninhydrin detection. Direct ultraviolet detection at the absorption maximum allowed the quantification of pyrraline (λ max =297 nm), an acid labile lysine derivative with a pyrrole structure, at levels lower than 2 mg/kg protein. Values for pyrraline in a number of commercially available foods (milk products, bakery goods, pasta products) ranged from not detectable up to 3500 mg/kg protein. Pyrraline proved to be a suitable indicator for the advanced stages of the Maillard reaction in foods. In samples of severely heated whey powder, four previously unknown UV-active compounds were detected. Their formation correlated with heating time and temperature. One of these compounds could be identified as maltosine, a pyridone derivative of lysine of the 1-deoxyosone pathway, which up to now has not been described in protein hydrolysates.