Enhanced microwave-assisted methodology for obtaining cutin monomers from tomato peel

Tomato pomace is an abundant by-product of the agri-food industry with a peel rich in cutin, a plant polyester that can be depolymerized to monomeric building blocks to develop bio-based materials. Because of cutin's crosslinked, three-dimensional structure, alkaline hydrolysis has typically required long reaction times (up to 24 h) to achieve complete depolymerization into its monomers, which hinders the potential development of exploitation processes. In this paper, the effect of temperature and heating mechanism (conventional versus microwave-assisted hydrolysis) on monomer production yield and final product composition of the hydrolysis process were studied. The comparison of the two methods was also based on a detailed kinetic analysis of the hydrolysis processes. The results showed that the usage of microwaves at 120 °C allowed to reduce the reaction time from 24 h at 100 °C to only 1 h, with no significant differences to the conventional hydrolysis method in terms of monomeric composition, but with higher yields. This reduction in processing time promotes the development of new applications from the corresponding monomers and facilitates cutin characterization for analytical purposes.