Carotenoid retention during post-harvest storage of Capsicum annuum: the role of the fruit surface structure.

Degradation of carotenoids in food crops during post-harvest storage results in major economic and nutritional losses. In this study, a pepper (Capsicum annuum) panel for post-harvest carotenoid retention was studied to elucidate underlying mechanisms associated with this commercial trait of interest. Quantitative determination of carotenoid pigments and concurrent cellular analysis indicated that those pepper fruit with thicker lipid exocarp layers and smooth surfaces, following post-harvest drying and storage, possessed increased carotenoid retention. Total cutin monomer content increased in high carotenoid retention fruits and sub-epidermal cutin deposits were responsible for the difference in exocarp thickness. Cutin biosynthesis and cuticle precursor transport genes were differentially expressed between high and low carotenoid retention genotypes, and this supports the finding that fruit cuticle biosynthesis is associated with carotenoid retention. Carotenoids were located within cells embedded within the sub-epidermal cutin layer, and these carotenoids were protected from degradation due to the lack of permeability of the fruit surface to reactive oxygen species, and their precursors. The identification of a novel role for the pepper fruit surface in protecting against carotenoid degradation serves as an important discovery for the function of the fruit cuticle and provides an exploitable resource to enhance fruit quality. Highlight statementCarotenoid pigments in Chilli pepper confer post-harvest colour and nutritional quality. Analysis of diverse commercial genotypes indicates the involvement of the fruit surface in carotenoid retention