Investigation of transformations of aromatic terpenoids in Eureka lemon juice based on simulated systems

This study investigated the transformation reactions and their relationships among aromatic terpenoids in Eureka lemon juice using a simulated system, aiming to elucidate the chemical essence of aroma changes and explore the transformation mechanisms. Sixteen terpenoids underwent transformation reactions mediated by the acids or the enzymes in the juice. Among them, α-pinene, β-pinene, linalool, and nerol were all found to transform to five different terpenoids, and thirteen terpenoids were found to transform to α-terpineol. Six pairs of terpenoids can be interconverted until the equilibrium is reached. Terpinen-4-yl cation and α-terpinyl cation, are the primary active intermediates in these conversions. In both simulated enzyme-free and enzyme-containing lemon juices, the concentrations of d-limonene, α-terpineol, and γ-terpinene always increase, while β-pinene, geraniol, terpinen-4-ol, α-pinene, and nerol are the most reactive compounds for the transformation reactions. The changes in the concentrations of these aromatic terpenoids may alter the aroma of Eureka lemon juice.