Fortified yogurt with high-quality dietary fiber prepared from the by-products of grapefruit by superfine grinding combined with fermentation treatment

Superfine grinding combined with L. paracasei fermentation was used for soluble dietary fibers (SDFs) modification to produce high quality SDFs. SDFs from the peels of Shatianyou, Dabumiyou, Majiayou and Jinggangmiyou without modification were named S-SDF, D-SDF, M-SDF and J-SDF. SDFs from peels of Shatianyou, Dabumiyou, Majiayou and Jinggangmiyou with combined modification were named FSS-SDF, FSD-SDF, FSM-SDF and FSJ-SDF. Then the structural and functional properties of extracted SDFs were analyzed. It was showed that modification endowed SDFs higher crystallinity, superior thermal stability, smaller molecular weight and irregular microstructure. After modificatifmon, SDFs showed stronger adsorption capacities to water, oil, glucose, cholesterol and nitrite ion molecules. Ultimately, FSS-SDF showed superior functional properties which was evaluated by principal component analysis. Subsequently, FSS-SDF was applied to yogurt (FSSY) which showed lower syneresis, higher gel strength and hardness, stronger odor characteristics compared to blank control yogurt. Therefore, superfine grinding combined with L. paracasei fermentation was an effective approach to producing high quality SDFs from grapefruit peel, meanwhile modified SDFs could be considered as a functional additive for the preparation of functional foods.