Effects of added inulin and wheat gluten on structure of rye porridge

The aim was to study the microstructure and distribution of components of rye porridge enriched with different inulin and gluten proportions (0:0, 3:9, 6:6, 9:3), and their relationship with texture. Inulin was labeled with fluorescein isothiocyanate (FITC) prior to its addition to the porridges, and multiple staining was applied to cryosections in order to also observe other components of the porridges. Porridge structure consisted of grain fragments and a continuous phase formed by released amylose, starch granules and protein. Addition of inulin and gluten to rye porridge partly hindered starch gelatinization due to their water binding capacity. The green fluorescence from FITC-labeled inulin was brighter in detached starch granules in the continuous phase, indicating greater interaction of inulin with starch than with protein. Viscosity was lower in those porridges with high inulin content and low gluten content. Solubilized inulin created a protective layer around starch granules limiting their swelling and amylose release, which may explain the differences in viscosity between the porridges and could have further influence in starch digestibility.