A novel prebiotic enzymatic hydrolysate of citrus pectin during juice processing

Pectinase is used to clarify citrus juice, which it does by destroying the pectin network structure. However, the health-promoting effects of enzymatic hydrolysates of pectin during juice processing are unclear. Here, we investigated the chemical structures and functional properties of citrus pectin after enzymolysis by pectinase. Three main components (SH, S-5, and S-35) were obtained from the supernatant after enzymatic hydrolysis with yields of 16.4%, 4.2%, and 10.3%, respectively; all had a low molecular weight (MW, 0.2-1.5 x 104 g/mol) and were rich in rhamnogalacturonan I (RG-I, 61.8-81.4%). Fermentation experiments showed that the three components increased the concentrations of short-chain fatty acids (SCFAs), which were 1.3-2.9 times higher than those in the original citrus pectin (at 1%), and were used more efficiently by the human gut microbiota. S-5 had the highest use efficiency and caused the greatest enhancement of SCFA levels (1.3-1.4-fold increases in acetate, propionate, and total SCFAs compared with inulin); it also promoted the abundance of beneficial bacterial taxa including Bacteroides, Collinsella, Parabacteroides, and Alistipes. Further ESI-MS and NMR (1D and 2D) analyses showed that S-5 was a novel prebiotic separated from juice processing, containing a & RARR;4)-& alpha;-GalpA-(1 & RARR; 4)& alpha;-GalpA-(1 & RARR; 4)-& alpha;-GalpA-(1 & RARR; 2)-& alpha;-Rhap-(1 & RARR; 4)-3-O-Ac-& alpha;-GalpA-(1 & RARR; 2)-& alpha;-Rhap-(1 & RARR; 4)-& alpha;-GalpA & RARR;2)-& alpha;-Rhap backbone; the O-4 of Rha branches consisted of & beta;-1,3-linked Galp side chains. These results suggest that pectinase treatment of citrus juice generates enzymatic hydrolysates with prebiotic activity, which may exert a healthpromoting effect.