Barley β-glucan cryogels as encapsulation carriers of proteins: Impact of molecular size on thermo-mechanical and release properties

Abstract

Abstract The potential use of barley β-glucan cryogels as encapsulation carriers for delivery-controlled release of proteins was explored. For cryogel preparation, mixed β-glucan (4.2% w/w)/protein (0.8%) aqueous dispersions were subjected to 10 freezing (−23 °C/24 h) and thawing (25 °C/24 h) cycles, using three purified barley β-glucan isolates differing in molecular weight, Mp (55, 140 and 320 kDa) and four proteins, selected as model core constituents; i.e. β-lactoglobulin (18 kDa), ovalbumin (43 kDa), bovine serum albumin (67 kDa), invertase (270 kDa). Dynamic rheometry revealed that the mechanical properties of the composite cryostructurates, were significantly affected ( p G′ ) and the melting enthalpy (Δ Η ) values of the cryogels decreased, while the melting temperature (Tm) of the gels (calorimetry) increased. Incorporation of the highest Mw protein in the β-glucan cryogels also increased ( p G′ . Large deformation mechanical tests have shown an increase of compression modulus ( E ) and true stress ( σ TR ) with increasing Mp of the polysaccharide, whereas the cryogel's swelling capacity, followed the reverse trend. Release kinetics of entrapped proteins was monitored spectrophotometrically in aqueous suspensions of the mixed cryogels at 37 °C. The amount and the apparent diffusion coefficient ( D m ) of proteins released significantly ( p