Thermal alteration of the aliphatic biopolymer cutan: implications for composition and degradation

Cutan is the operationally defined residual fraction of cuticles after solvent extraction and hydrolysis. We investigated the thermal behaviour as a consequence of charring experiments of cutan isolated from Agave americana and Clivia miniata . While both cutan fractions exhibited almost identical weight loss patterns as a function of charring temperature, the molecular degradation and transformations differed, mainly reflected by higher carboxylic acid contents released and retained in the cutan residues of C. miniata , whereas cutan of A. americana comprised and released more hydroxy-containing moieties. The extractable fractions after charring yielded initially the building blocks of cutan, but with progressive heating defunctionalisation (removal of hydroxy and carboxylic acid groups) mainly n -1-alkenes and n -alkanes were produced. The lack of polyaromatic condensation products upon charring indicates the highly saturated character of cutan under severe conditions.