Transformation between 2-Threityl-thiazolidine-4-carboxylic Acid and Xylose-Cysteine Amadori Rearrangement Product Regulated by pH Adjustment during High-Temperature Instantaneous Dehydration.

2-Threityl-thiazolidine-4-carboxylic acid (TTCA) was found to be the predominant product rather than the Amadori rearrangement product (ARP) during the formation of xylose-cysteine-derived (Xyl-Cys-derived) Maillard reaction intermediates (MRIs) through a thermal reaction coupled with vacuum dehydration. To regulate the existence forms of Xyl-Cys-derived MRIs, an effective method carried out by pH adjustment during high-temperature instantaneous dehydration through spray-drying was proposed in this research to promote the conversion from TTCA to ARP. The increased inlet air temperature of spray-drying could properly facilitate the shift of chemical equilibrium between the MRIs and promote the transformation from TTCA to ARP while raising the total yield of TA (TTCA + ARP). The conversion to ARP was increased to 20.83% at 190 °C of hot blast compared to the product without spray-drying (6.03%). The conversion from TTCA to ARP was further facilitated in the pH range of 7.5-9.5. When the pH of the aqueous reactants was adjusted to 9.5, the equilibrium conversion to ARP was improved to 47.23% after spray-drying, which accounted for 59.48% of the TA formation. Accordingly, MRIs with different TTCA/ARP proportions could be selectively obtained by pH adjustment of the stock solution during high-temperature instantaneous dehydration of spray-drying.