Comparison of structural, functional and in vitro digestion properties of bread incorporated with grapefruit peel soluble dietary fibers prepared by three microwave-assisted modifications.

In our previous study, three kinds of grapefruit peel soluble dietary fibers (SDFs) were prepared by microwave-assisted modifications, including microwave-sodium hydroxide treatment SDF (MST-SDF), microwave-enzymatic treatment SDF (MET-SDF) and microwave-ultrasonic treatment SDF (MUT-SDF). The present study aimed to investigate the structural, functional and in vitro digestion properties of three kinds of bread incorporated with SDFs, named MST-SDF bread (SB), MET-SDF bread (EB), and MUT-SDF bread (UB). Scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and texture profile analysis were used to determine the structural properties. In comparison with the SB and EB, the UB showed an ideal hardness and internal structure, and also significant improvement of the thermal stability. Meanwhile, the UB exhibited the highest overall acceptability in the sensory evaluation. In addition, the water holding capacity (WHC), cholesterol adsorption capacity (CAC) and nitrite ion adsorption capacity (NIAC) of UB were superior to those of the other two samples. Moreover, the in vitro digestive glucose release rates of breads were all significantly reduced by the addition of SDFs, especially that of UB. In summary, the present study showed that UB presented the best performance in terms of structural, functional and in vitro digestion properties, implying that MUT-SDF could be utilized in bread with high quality and low glucose release rate, and developed as a potential ingredient of functional food.