Formation of aroma active volatiles from thermal degradation of 18 amino acids with or without sugars in low-moisture systems and the modulation by sucrose and epigallocatechin gallate

Abstract

This study investigates the thermal degradation of 18 proteinogenic amino acids at 160 °C for 1 h under low-moisture conditions, focusing on the formation of volatile compounds. The structure of amino acid side chains strongly influenced volatile profiles and reaction pathways. Serine and phenylalanine produced the highest levels of volatiles; notably, even in the absence of reducing sugars, amino acids with aliphatic hydroxyl groups (serine and threonine) and with amide groups (glutamine and asparagine) in their side chains generated pyrazines. Significant Strecker aldehyde formation was observed for branched chain amino acids (alanine, isoleucine, and leucine) and valine without sugars. When a sucrose-rich sugar mix, simulating the composition of tea leaves introduced, volatile profiles shifted toward furans, aldehydes, and acids, and modulating pyrazine formation. The presence of epigallocatechin gallate (EGCG) suppressed nitrogen-containing volatiles and dicarbonyls while preserving furans and aldehydes. Aroma impact, assessed by the sum of odor activity values (ΣOAV), suggested potentially significant sensory contributions. While the findings provide general insights into amino acids-derived volatiles relevant to thermal processing, the sugars and EGCG model matrix was based on tea and is primarily applicable to the roasting of baked teas.