Rheological behavior of soluble dietary fiber fractions isolated from artichoke residues

Abstract

Cynara cardunculus var. scolymus agroindustrial by-products (stems, outer bracts, leaves) constitute 80% of the plant. These by-products may be recovered for the extraction of food additives and nutraceuticals. In this research, the rheological behavior of soluble dietary fiber fractions isolated from bracts (B) and stems (S) of artichoke was studied. Fractions were isolated by means of a heat treatment followed by processing with sodium citrate buffer (S1, B1) or buffer/protease (S2, B2) or hemicellulase (S3, B3) or both enzymes (S4, B4). They were composed, mainly, by pectin (degree of methylation, DM ≤ 53%) and inulin. When dissolved in water (2.00% w/v) with Ca2+ (40 mg/g pectin), fractions were sensitive to the ion showing shear thinning flow, with initial yield stress in the case of B2, B3 or S3. Citrate buffer extracted fractions (B1, S1) showed the highest viscosities, whereas extraction with buffer and both enzymes (B4, S4) produced the least viscous fiber fractions. At rest assays revealed the formation of gel-like networks that were stronger, in general, in the presence of higher pectin and inulin content, homogalacturonan proportion, and low methylation degree. Leftovers of artichoke can be used to extract soluble dietary fiber fractions that might be utilized as natural thickeners and gelling agents in foods, pharmaceutical and cosmetics, helping to add value to raw materials and to close the bioeconomy loop in relation to this plant.