Unmasking synthetic caramel: A fluorescent investigation into the sweet mystery of balsamic vinegar of Modena PGI

Synthetic caramel is one of the most commonly used colorants in the food industry. In the case of Balsamic Vinegar of Modena PGI, its use is regulated by the Consortium of Balsamic Vinegar of Modena. The addition of caramel may be permitted for color stabilization but must be declared on the product label. Among the various coloring agents, the most frequently used is Class IV additive, E-150d, also known as sulphite ammonia caramel. However, caramel can also occur “naturally” in balsamic vinegar due to the cooked must used as a raw material in vinegar production. Currently, no official analytical method exists to differentiate between sulphite ammonia caramel and naturally occurring caramel in Balsamic Vinegar of Modena PGI. To address this issue, an analytical approach based on Fluorescence Spectroscopy was employed. Vinegar samples were analysed both in their original state and after the addition of synthetic caramel. Fluorescence spectroscopy produced three-dimensional Excitation-Emission Matrices (EEMs), which required appropriate data analysis. Specifically, Parallel Factor Analysis (PARAFAC) was applied to identify and quantify fluorophores associated with caramel. Finally, the EEM data were used to quantify the presence of synthetic caramel in Balsamic Vinegar of Modena samples using PLS regression on the PARAFAC loadings. The results were satisfactory, confirming Fluorescence Spectroscopy as an effective analytical method for distinguishing sulphite ammonia caramel from naturally occurring caramel in Balsamic Vinegar of Modena PGI and for quantifying its presence.