Glucosylisomaltol is proposed as a new indicator of the browning reaction in baby cereals and bread. The glucosylisomaltol was synthesized from maltose and proline, purified by semipreparative HPLC, and characterized by NMR, high-resolution mass spectrometry, and GC-MS analysis. Analysis of glucosylisomaltol, previously separated from cereals by centrifugation, was carried out by reversed-phase HPLC with UV detection in isocratic elution with water/acetonitrile (95:5). Mean recovery of glucosylisomaltol by the standard addition method was 96.9%. The relative standard deviation and detection limit were 1.56% and 0.14 mg/kg, respectively. This compound was identified in samples by the similarity of the t(R) and UV spectra to those of synthesized glucosylisomaltol. Moreover, the glucosylisomaltol from samples, previously separated by semipreparative HPLC, was acetylated and then separated and confirmed by GC-MS. Glucosylisomaltol was determined in baby cereals stored at 32 and 55 degrees C for 1 year and at 25 and 55 degrees C for 1 month at a water activity of 0.65. The amount of this indicator increased during storage from 0.48 to 7.7 mg/kg. The glucosylisomaltol was also determined in prebaked bread by heating at 190 degrees C for 30 min. The amount of this compound increased from nondetectable to 20.9 mg/kg after 30 min of baking. Glucosylisomaltol is a useful indicator to control the browning reaction during baby cereal storage and the baking of bread.