Dietary Fiber and Availability of Nutrients: A Case Study on Yoghurt as a Food Model

Abstract

Since the roles of dietary fibers in preventing and treating some diseases have been well documented, the addition of purified dietary fibers to foods has become more popular. Diffe rent types of dietary fibers (soluble and insoluble) and different sources (animal, plant, bacterial or fungi fibers) are now incorporated in purified form into foods for their nutritional or for their technological properties (e.g. gelling or thickening agents) resulting in healthy products. However, the intake of dietary fiber might affect the absorption of nutrients. This can be positive in certain pathologies (diabetes mellitus and cardiovascular diseases) or negative when nutritional deficiencies exist. There is a need to study the interactions between nutrients and dietary fiber and its influenc e on their absorption from f ood. Yogurt fortified with chitosan and different types of plants fibers like wheat, bamboo, apple, psyllium and inulin was used as a food model. The availabilities of glucose and calcium in this model were studied by an in vitro gastrointestinal tract simulation. The gastric environment was simulated with HCl (pH 1.0?2. 0). The duodenal environment was simulated with NaHCO3 (pH 6.8?7.2). Glucose was added to yoghurts with each type of fiber. To investigate the interaction of different fibers with iron from yoghurt, a dialysis tubing cellulose membrane was us ed in the digestive model to reproduce the duodenum wall. Ferrous sulfate was added to yoghurts with each type of fiber. Results showed that chitosan decreased glucose and calcium availabilities (17.7 ± 2.1% and 21.0 ± 2.5% depress respectively) and presented the highest iron retention percentages (53.2% at 30 min; 56.8% at 60 min). The effect of chitosan was higher than plants fibers used in this work.