Effect of Ultrahigh-Pressure on the Physicochemical Properties and Biological Activities of Dietary Fiber From Litchi Pomace

ABSTRACT

This study primarily investigated the effects of ultra-high pressure (UHP) treatment on the physicochemical properties and bioactivities of the soluble dietary fiber (SDF) derived from litchi pomace. Compared to SDF prepared using conventional methods (CSDF), there was minimal difference in monosaccharide composition; however, the molecular weight of SDF obtained through UHP-assisted extraction (PSDF) was lower, resulting in a rougher and looser internal structure. Moreover, PSDF exhibited superior water-holding capacity, swelling capacity, and cation exchange capacity compared to CSDF. These alterations in physicochemical properties contributed to enhanced biological activities of SDF. Specifically, PSDF demonstrated a more pronounced proliferative effect on Lacticaseibacillus rhamnosus and Lactobacillus acidophilus. In addition, PSDF showed greater efficacy in promoting probiotic proliferation and inhibiting the growth of harmful bacteria within the gut microbiota. For example, after 48 h of fermentation, the contents of Bifidobacterium longum, Bacteroides vulgatus, and Bifidobacterium adolescentis in the PSDF group were 1.12, 1.06, and 1.07 times higher than those in the CSDF group, respectively, while the content of Escherichia coli was only 80.94% of that in the CSDF group. This phenomenon was elucidated through the synthesis of short-chain fatty acids (SCFAs), primarily resulting from PSDF's upregulation of key enzyme expressions such as glucose-6-phosphate isomerase, fructose-bisphosphate aldolase, and phosphoglycerate kinase in the SCFAs synthesis pathways. These findings indicated UHP contributed to enhancing biological activities through altering the functional and physicochemical properties.