Comparison of the Structure and Functional Properties of Soluble Dietary Fiber from Lychee Pomace before and after the Removal of Bound Phenolics
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Abstract:
In this research, soluble dietary fiber (SDF) from litchi pomace was used as the raw material to study the changes in the structure and functional properties of SDF after the removal of the bound phenolics via alkaline hydrolysis. The results showed that the content of bound phenolics in SDF from litchi fruit residue was 4.53 mg GAE/g. The results of SEM examination showed that the structure of SDF became looseer after the removal of bound phenolics; the results of Fourier transform infrared spectroscopy analysis showed that the main components of SDF were pectins and hemicelluloses, and the removal of bound phenolics from SDF did not change the functional groups. The analysis results of monosaccharide composition and rheological properties showed that the monosaccharide compositions of SDF samples before and after the removal of bound phenolics remained the same, and both SDF dispersions were pseudoplastic non-Newtonian fluids; However, at the same shear rate, the apparent viscosity of the SDF sample after the removal of bound phenolics was greatly reduced, which was related to the looser structure of this SDF. At the same SDF concentration, the removal of bound phenolics led to the decreases of DPPH radical scavenging ability by 15.06%~29.02% and ABTS+ radical scavenging ability by 42.06%~78.98%. In addition, the effect of SDF on the in vitro proliferation of three probiotics was also significantly reduced after the removal the bound phenolics. The above results confirmed that the bound phenolics were closely related to the bioactivities of soluble dietary fiber from lychee pomace, and provide a theoretical basis for the exploitation and utilization of litchi pomace.
