The temperature dependent extraction of polysaccharides from eucheuma and the rheological synergistic effect in their mixtures with kappa carrageenan

Water extraction (at 60, 70, 80, and 90 degrees C) was applied to Eucheuma to explore the relationship between the extraction temperature and the structure of the extracted polysaccharides. The extracts mainly comprised iota carrageenan. The extraction temperature affected the compositions and properties of the polysaccharide extract. The yield decreased as the temperature increased (30.33-24.49%). Higher temperature extraction resulted in lower molecular height (60-90 degrees C: 0.57-0.48 nm) and layer height (60-90 degrees C: 0.76-0.58 nm) on atomic force microscopy images, leading to a better gel-forming potential; lower temperature extraction produced more diverse polysaccharides. 60 and 80 degrees C extracts were selected to represent low temperature extract and high temperature extract. Though the extracts had a weakness gelling ability, they cooperated with kappa carrageenan through synergistic effect 80 degrees C extracts provided even higher synergistic effect than commercial IC (iota carrageenan) with stronger gel. It can be due to the amount of crosslink density variation. Possible schematic presentation was shown accordingly to illustrate the synergy.