Polysaccharide Composition of Dietary Fiber During Raspberry and Blackberry Juice Production

Fiber is one of the most important ingredients of fruit that has an influence on the gastrointestinal tract and biochemical parameters of blood. Fiber has texturizing functions in food processing. The fiber's properties (water-binding capacity, swelling, and oil-holding capacity) and polysaccharide composition obtained from raspberry and blackberry fruit, juice, and pomace, divided into seed and seedless fractions, were determined. The seedless fraction contains more hemicelluloses and homogalacturonan with higher water-binding capacities, swelling, and oil-holding capacities, and the seeds contain more cellulose, and their physical abilities are much lower. Water-binding capacities were from 2.7 to 14.9 g/g, swelling from 3.3 to 11.1 mL/g, and oil-holding capacities from 8.0 to 16.5 g/g. The sequential extraction of fruit fiber showed that the main fraction was the Residue, followed by the weak alkali extractable pectin (DASP) and the hemicellulose (CASP). Water-extractable pectin (WSP) and chelating-agent extractable pectin (ChSP) both constituted 8-9% of AIS each. In the pomace, the main fraction was the Residue (40% AIS), followed by CASP (16% AIS), DASP and ChSP (6-7% AIS), and WSP and WR (3% AIS). While seeds are composed mostly of Residue (52-57% AIS vs. 24-36% AIS in seedless), the seedless part shares of CASP hemicelluloses were higher (24-28% AIS vs. 12-15% in seeds). In the seedless part, there was also more water-soluble pectin (WSP) (4-5% vs. 2-3% in seeds). Seedless fraction is rich in hemicellulose and has higher water-binding properties and oil-holding capacities compared to seeds, and that is why it could be a source of functional berry polysaccharides.