Quantitation of Three Strecker Aldehydes from Enzymatic Hydrolyzed Rice Bran Protein Concentrates as Prepared by Various Conditions.

The quantitation of three Strecker aldehydes-2-methypropanal (2-MP), 2-methylbutanal (2-MB), and 3-methylbutanal (3-MB)-from rice bran protein hydrolysate (RBPH) prepared under various conditions were investigated. The preparation conditions included hydrolysis time (0, 0.25, 2, 4, or 8 h), pH adjustment (pH 4.0, 7.0, or 10.0), and sugar addition (sucrose, glucose, or fructose). These conditions provide a significant potential for aroma generation from the Strecker degradation and Maillard reaction. The Strecker aldehyde quantitation was performed using gas chromatography (GC) with cryo-focusing technique. These combined techniques encourage the precise 2-MB and 3-MB quantitation. The highest concentrations of three Strecker aldehydes were found in RBPH that was prepared by alcalase hydrolysis at 4 h with fructose addition (RBPH-F) and adjusted to pH 7.0 before spray drying. Thirty-nine aroma-active compounds of RBPH-F were discovered using solid-phase microextraction coupled with GC-olfactometry.