Scleroglucan compatibility with thickeners, alcohols and polyalcohols and downstream processing implications

S.C. VIÑARTA; M.M. YOSSEN; J.R. VEGA; L.I.C. FIGUEROA; J.I. FARIÑA

CARBOHYDRATE POLYMERS

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2013 vol. 92 p. 1107 - 1115

0144-8617

Abstract: Hydrocolloid combinations can be industrially used to gain additional advantages aside from the scleroglucan ability to maintain physical and rheological properties in the presence of salts, at high temperatures or extreme pH. The thickening capacity and compatibility of scleroglucan with other commercial thickeners (corn starch, gum arabic, carboxymethylcellulose, gelatin, xanthan and pectin), glycols (ethylene glycol, polyethylene glycol), alcohols (methanol, ethanol, 1-propanol and isopropanol) and polyalcohols (sorbitol, xylitol, manitol) was herein explored. Scleroglucan exopolysaccharides (EPSs) from Sclerotium rolfsii ATCC 201126 and a commercial scleroglucan were comparatively tested. Compatibility and synergism were evaluated taking into account rheology, pH and sensory properties of different thickener/scleroglucan mixtures in comparison with pure solutions. Scleroglucans induced or increased non-Newtonian pseudoplastic behaviour in most of the tested blends resulting compatible and synergistic particularly with corn starch, xanthan, pectin, and carboxymethylcellulose. S. rolfsii ATCC 201126 EPSs showed a better performance than commercial scleroglucan. Scleroglucan combinations showed compatibility and a slight synergistic behaviour with 30% (w/v) ethylene glycol whereas mixtures with polyethylene glycol (PEG) precipitated. Scleroglucan was compatible with polyalcohols, whilst lower alcohols led to scleroglucan precipitation at 20% (v/v) and above. PEG-based scleroglucan recovery and downstream processing was compared to the usual precipitation with alcohols. Downstream processed EPSi (with isopropanol) and EPS-p (with PEG) were evaluated on their yield, purity, rheological properties and final aspect pointing to alcohol downstream processing as the best methodology, whilst PEG recovery would be unsuitable. The highest purified EPSi (EPSi-C) attained a recovery yield of ~23%, similar to ethanol purification, with a high degree of purity (88% w/w vs. EPS-p, 8% w/w) and exhibited optimal rheological properties, solubility in water and appearance. Leading to a narrower molecular weight distribution (Mw, 2*66 × 10^6 g/mol) and a radius of gyration (Rw, 245 nm) slightly lower than ethanol-purified EPSs, isopropanol downstream processing showed to be a suitable methodology for obtaining refined-grade scleroglucan.