Upgrading of residues of bracts, stems and hearts of Cynara cardunculus L. var. scolymus to functional fractions enriched in soluble fiber

Abstract

Since only the central portion of the immature flowers of artichoke (Cynara cardunculus L. var. scolymus) is consumed (<20%) it is interesting to upgrade its residues to render value added products. In this research, bracts (B), hearts (H) or stems (S) were used to isolate fractions enriched in soluble fiber. Extraction was performed in citrate buffer with or without hemicellulase. Additionally, the effect of preheating (70 °C-5 min) prior to extraction was also tested. Polysaccharides were precipitated with ethanol and the fractions obtained were freeze-dried. The presence of the enzyme increased fiber yields and preheating produced an additional increment, especially from stems (≈21%). Isolated fibers were constituted by 70-84% of carbohydrates and 2-25% of proteins, and contained phenolics (2.1-8.2 g/100 g). Carbohydrates included uronic acids (12-25%) and neutral sugars (NS, 4-55%) of pectins, and inulin (13-55%). The lowest protein and NS contents and the highest inulin content were obtained with the enzyme and preheating. The behavior of fractions isolated with higher yields was characterized, observing a pseudoplastic behavior in water and gelation with Ca2+. They also showed antioxidant activity and an inhibitory effect against herpes simplex virus type 1 without cytotoxicity. The isolated fractions retaining bioactive compounds can be useful as functional food ingredients.