Tomato pomace: a source of the plant polyester cutin to develop bio-based materials

The negative impacts of the fossil fuel industry are driving innovation towards bio-based materials. The valorization of industrial residues to obtain valuable polymers is accelerating the transition to a circular economy with a genuine sustainability potential. In this review, we focus on the plant polyester cutin, primarily obtained from tomato pomace, and/or fractioned tomato peels, as a raw material for creating bio-based materials and coatings. Cutin is most often used in the form of its monomeric building blocks as bio-based additives. These monomers are blended with other polymers and components, mostly through polycondensation reactions and self-assembly, and to a minor extent combining both processes. The cutin monomers contribute a broad range of properties, including hydrophobicity and flexibility, and function as bio-based plasticizers. Direct comparisons between studies are hindered by inconsistent reporting of cutin hydrolysate composition, as the chemistry of monomers and oligomers often remains imprecisely defined. However, our critical analysis of extant literature on the topic reveals a clear opportunity for cutin-derived materials as promising candidates for the rapidly growing bioplastics market. The diversity of cutin-derived biomaterials reported to date, and their potential applications, is discussed in great detail. • The bioeconomy is growing and driving innovation to bio-based materials. • Tomato pomace is the major agro-industrial waste used to recover the polymer cutin. • Cutin-based materials are made via polycondensation, self-assembly, or their combination. • Many of these materials, some with cutin's native functions, still await technological maturity.