Fate of Citrus flavonoids during pectin extraction: Distribution between Pectins and biomass residues

Pectin is the main biopolymer in orange peels, consisting of a complex, branched structure with D-galacturonic acid as its primary monomer. Orange peels also contain flavonoids, which can interact with pectin and influence its functional properties. We hypothesized that pectin interacts differently with flavonoids depending on the extraction conditions, which in turn affect their distribution between pectin and the residual biomass. Industrial pectin extraction typically involves inorganic acids followed by alcohol precipitation, and extraction parameters can significantly influence both pectin structure and flavonoid content. While previous studies have focused on pectin characteristics, none have systematically evaluated the impact of extraction conditions on flavonoid profiles in pectin and the corresponding residual biomass. In this study, we investigated five pectin extraction conditions, annotated 33 flavonoids using high-resolution mass spectrometry, and assessed both the pectin and the residual biomass. This is the first study to reveal how pectin extraction conditions influence flavonoid distribution and to evaluate the residual biomass in this context. Our findings provide novel insights for producing pectin enriched with flavonoids, with potential applications in functional foods and human health.