This work was designed to study the effect of fibers addition in frankfurters on food bolus characteristics after mastication and on oral release of nutrients. Frankfurters were prepared with addition of fibers (psyllium and tapioca starch) in reduced-fat formulations. Food boluses were prepared during normal mastication programmed on a mastication simulator (AM2). After liquid-solid phase separation, boluses were analyzed for physical (granulometry, rheological behavior) and chemical (protein/lipid oxidation, iron/peptides release in bolus liquid phase) properties. Results showed that physico-chemical characteristics of food bolus after mastication depended on presence and fiber type. Matrix disruption during chewing is more important with fiber addition but significance was observed for psyllium fiber only. The bolus of psyllium-enriched frankfurter was softer, less cohesive than no-fiber and tapioca starch-enriched ones. Iron release from food matrix was significantly lower and peptide release significantly greater in frankfurters containing psyllium fibers compared to no-fibers and tapioca starch-enriched ones. In presence of fibers, liquid part of boluses contained fewer particles, which were of larger diameter with tapioca starch. Fibers used as fat-replacers in frankfurters formulation lead to significant changes in food bolus characteristic after mastication.