Optimizing the Maillard reaction for sweet flavor enhancement in instant tea: Integrating sensory evaluation and metabolomics.

This study aimed to optimize the Maillard reaction (MR) conditions for instant green tea (GT), black tea (BT), and oolong tea (OT) and to characterize the aroma profiles of the resulting MR products (MRPs). Supercritical CO₂ pretreatment reduced tea polyphenols and caffeine in instant teas. Key parameters (time, pH, temperature, exogenous substrate ratio) were optimized for each instant tea. The MRPs developed desirable sweet, roasted, and caramel-like aroma attributes. Volatile analysis revealed that the MR increased the levels of ketones, aldehydes, and esters, while decreasing hydrocarbons in the MRPs. Based on odor activity value and chemometric analysis, key aroma-active compounds such as indole, β-damascone, β-ionone, and dihydroactinidiolide were identified as crucial odorants responsible for the characteristic aroma of the MRPs. This work provides a practical strategy for producing potential aroma-modifying materials with sweet and roasted flavor, and offers insights into the broader utilization of instant tea by-products.