Abstract
In the production of biopolymers, the processing operations (e.g. extraction and drying) involve some degradation of the polysaccharide-causing structural and functional changes in final products. In this study, short-term heat treatment (75–115 °C, 15 min) influence on commercial carrageenans' — furcellaran, κ-carrageenan, ι-carrageenan and a κ/λ-carrageenan — structure, molecular weight and gel rheology was studied. Compared with other carrageenans, commercial furcellaran that had undergone multiple heatings at high temperatures during production was found to be susceptible to polymer degradation. Heat caused the desulphation and degradation of furcellaran galactans and the molecular weight was significantly decreased, causing a drop in viscosity and gel hardness. The loss of the network cross-linking of furcellaran gels was confirmed by scanning electron microscopy. Carrageenan gel storage modulus values decreased with the increase in the temperature of the treatment. The greatest decrease in storage modulus values occurred with κ/λ-carrageenan gels, followed by ι-carrageenan > furcellaran > κ-carrageenan.
Highlights
Carrageenans are linear sulphated polysaccharides obtained from red algae
The study's objective was to investigate short-term heat treatment effect on the structure and functional properties of drum-dried furcellaran compared with other carrageenans
The molecular weight (Mw) determination was carried out in polysaccharides through size exclusion chromatography (SEC) analysis following the method of Saluri et al [23], using a Shimadzu LC-30AD liquid chromatograph equipped with a RID-10A refractive index detector, a Shimadzu CTO-20AC column oven, an OHpak SB-G guard column, and two Shodex OHpak SB-806MHQ columns in series
Summary
Carrageenans are linear sulphated polysaccharides obtained from red algae Their basic structural units are disaccharides consisting of alternating β-1,3- and α-1,4-linked galactose residues. Robal et al [17] have studied carrageenans' thermal stability in dry and sol states They found that degradation during heat treatment in the dry state depends on the galactan's sulphur content and decomposition begins at lower temperatures for more sulphated preparations. They found that thermal degradation is more intensive in the presence of divalent cations and decreases in the presence of methoxy groups. The study's objective was to investigate short-term heat treatment effect on the structure and functional properties of drum-dried furcellaran compared with other carrageenans. The sample spinning speed was 12.5 kHz, the ramped polarisation transfer pulse duration was 1 ms, and the relaxation delay was 5 s
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