Concentration dependent gamma degradation of inulin in aqueous phase and its impact on antioxidant capacity and probiotic fermentability

Inulin is a water soluble, non-digestible polysaccharide with diverse food and clinical applications depending on its degree of polymerization. This study investigated the effect of inulin concentration on its gamma-induced depolymerization in aqueous phase by analysing changes in relative viscosity ( η r ), solubility (%), total reducing sugar (TRS), free fructose ( F f ) content, and •OH radical scavenging activity. The extent of inulin degradation in aqueous solution was influenced by both irradiation dose and sample concentration. Degradation increased with irradiation dose, while concentration and degree of degradation were in inverse relationship. The level of degradation as a result of molecular fragmentation was confirmed by thin layer chromatography (TLC) and gel permeation chromatography (GPC). FT-IR spectral characterization of unirradiated and irradiated samples revealed no significant changes in peak profiles. Furthermore, concentration-dependent degradation was evaluated for its impact on antioxidant capacity and probiotic fermentability. Inulin irradiated at lower concentrations exhibited significantly higher ( p < 0.05 ) ABTS and DPPH radical scavenging activity and probiotic fermentability than samples irradiated at higher concentrations; specifically, at 25 kGy, inulin irradiated in a 5 % (w/v) aqueous system showed ∼3.5-fold higher antioxidant activity and a ∼2.5-log increase in probiotic fermentability compared to the 60 % (w/v) system. • Gamma-irradiation of inulin caused degradation of the molecule in a dose-dependent manner. • Gamma-induced inulin degradation was also dependent on its concentration in aqueous solution. • Irradiation of dilute aqueous solutions exhibited higher degradation than that of concentrated ones. • Irradiated dilute aqueous solutions showed better antioxidant activity and probiotic fermentability.