Water holding as determinant for the elastically stored energy in protein-based gels
Pouvreau, L.A.M. ; Wijlen, Emke van; Klok, Jan ; Urbonaite, V. ; Munialo, C.D. ; Jongh, H.H.J. de - \ 2016
Journal of Food Science 81 (2016)4. - ISSN 0022-1147 - p. N982 - N990.
elastically stored energy - predictive values - protein gels - Water holding
To evaluate the importance of the water holding capacity for the elastically stored energy of protein gels, a range of gels were created from proteins from different origin (plant: pea and soy proteins, and animal: whey, blood plasma, egg white proteins, and ovalbumin) varying in network morphology set by the protein concentration, pH, ionic strength, or the presence of specific ions.
The results showed that the observed positive and linear relation between water holding (WH) and elastically stored energy (RE) is generic for globular protein gels studied. The slopes of this relation are comparable for all globular protein gels (except for soy protein gels) whereas the intercept is close to 0 for most of the systems except for ovalbumin and egg white gels. The slope and intercept obtained allows one to predict the impact of tuning WH, by gel morphology or network stiffness, on the mechanical deformation of the protein-based gel. Addition of charged polysaccharides to a protein system leads to a deviation from the linear relation between WH and RE and this deviation coincides with a change in phase behavior.
Modification of Ovalbumin with Fructooligosaccharides: Consequences for Network Morphology and Mechanical Deformation Responses
Munialo, C.D. ; Ortega, R.G. ; Linden, E. van der; Jongh, H.H.J. de - \ 2014
Langmuir 30 (2014)46. - ISSN 0743-7463 - p. 14062 - 14072.
protein gels - rheological properties - beta-lactoglobulin - maillard reaction - pea protein - neutral ph - mixed gels - gelation - aggregation - perception
The Maillardation of proteins has been used as a natural alternative to improve its functionality by covalent coupling of proteins with saccharides. However, the impact of Maillard reaction on the structural aspects of protein networks and, as a consequence, the mechanical breakdown properties of the gel networks has not been reported. The objective of this study was to evaluate how the attachment of linear oligo-sugar moieties onto ovalbumin affects its aggregation, network morphology, and consequently the mechanical deformation properties including the ability of the networks to elastically store energy in this material. To potentially alter the morphology of the network structure, ovalbumin was modified by conjugating some of its amino groups with fructooligosaccharide (FOS) moieties via the Maillard reaction. It was demonstrated that the attachment of FOS to ovalbumin does not affect the integrity of the secondary and tertiary structure as characterized using circular dichroism and tryptophan fluorescence. Differences in the network morphology were observed by scanning electron microscopy for FOS-modified ovalbumin variants. Upon increased modification, the microstructure of the gels had more and larger pores and had thinner strands than nonmodified variants. Evaluation of the large deformation properties of the gels demonstrated that FOS-modified gels were less strong and less brittle and showed lower stiffness than nonmodified variants. The recoverable energy (elastically stored energy) of gels reduced with an increase in the degree of modification. The results show that the attachment of FOS to ovalbumin alters the structural and mechanical (large) breakdown properties of the protein gels. The consequences of the alteration of the network structure and large deformation properties of FOS-modified ovalbumin offer opportunities to efficiently design food materials with desirable techno-functional applications
Rheological properties of acid skim milk gels as affected by the spatial distribution of the structural elements and the interaction forces between them.
Lakemond, C.M.M. ; Vliet, T. van - \ 2008
International Dairy Journal 18 (2008)5. - ISSN 0958-6946 - p. 585 - 593.
protein gels - casein gels - network structure - mixtures - behavior - gelation - ph - permeability - glycinin
The modulus, fracture stress and fracture strain of acid-induced skim milk gels prepared from preheated skim milk that was aged for 1200 min depended strongly on pHheating. The role of gel structure regarding the effect of pHheating on gel modulus and fracture stress and strain is discussed. Milk preheated at pH 6.20 gave finer stranded gels likely containing more curved strands with probably less S-S interactions than gels from pHheating 6.90 milk. The lower stiffness of gels made from pHheating 6.20 milk could be explained by a combined effect of differences in strand curvature, gel coarseness and S-S interactions, and the lower fracture stress by a combined effect of gel coarseness and S-S interactions whereby the first effect is opposite to and overruled by that of the S-S interactions. The lower modulus and fracture stress of gels from unheated milk could be explained by a combination of strand curvature and less S-S interactions, and by less S-S interactions alone, respectively.
Mesostructure of fibrillar bovine serum albumin gels
Veerman, C. ; Heck, J. ; Sagis, L.M.C. ; Linden, E. van der - \ 2003
International Journal of Biological Macromolecules 31 (2003)4-5. - ISSN 0141-8130 - p. 139 - 146.
heat-induced gelation - protein gels - beta-lactoglobulin - globular-proteins - ionic-strength - ph - percolation
The mesostructure of bovine serum albumin (BSA) at low pH was investigated. Rheological measurements were performed to determine the critical percolation concentration (cp). A decreasing cp with increasing ionic strength was found. Fibrils with a contour length of about 100–300 nm were found using transmission electron microscopy. The measured conversion of monomers into fibrils was independent of ionic strength (0.20–0.30 M). Dilution of BSA samples showed that the aggregation process is reversible and that there exists a critical concentration for the self-assembly of BSA. We explain the decreasing cp with increasing ionic strength in terms of an adjusted random contact model.