title: Bulk and interfacial behaviour of caseinoglycomacropeptide (GMP).
abstract: Caseinoglycomacropeptide (GMP) is a hydrophilic glycopeptide released from milk kappa-casein by chymosin hydrolysis during cheese making. GMP is thought to be a potential ingredient for specific dietary applications with several health benefits. In this study GMP was characterized at the air-water interface and its behaviour was related with the self-assembly of GMP in solution as affected by pH. This GMP self-assembly was investigated by dynamic light scattering and the interfacial properties were determined by tensiometry and surface dilatational measurements at pH 4, 5 and 7. At pH 5 GMP exhibited higher surface pressure at equilibrium than at pH 7. At pH 4 the behaviour was more complex due to self-assembly close to GMP pI. Dynamic measurement showed that the adsorption/penetration rate constant (K(ads)) is facilitated at higher GMP bulk concentrations, while the rate constant of rearrangement (K(r)) decreased at higher GMP concentrations which could be attributed to the existence of a steric restriction due to the higher GMP load at the interface. K(r) was higher at pH 5 because of lower electrostatic interactions close to the pI. The viscoelastic properties showed a complex behaviour due to the existence of protein-protein interactions depending on the GMP concentration, on the pH of the bulk and on the rates of diffusion, adsorption and rearrangement of GMP at the air-water interface.
authors.affiliation: Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria (1428), Buenos Aires, Argentina.
authors.forename: María J
authors.initials: MJ
authors.lastname: Martinez
authors.forename: Cecilio
authors.initials: C
authors.lastname: Carrera Sánchez
authors.forename: Juan M
authors.initials: JM
authors.lastname: Rodríguez Patino
authors.forename: Ana M R
authors.initials: AM
authors.lastname: Pilosof
mesh_terms: D000327:Adsorption; D000388:Air; D002364:Caseins / Q000737:chemistry*; D004058:Diffusion; D004548:Elasticity; D006020:Glycopeptides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008894:Milk Proteins / Q000737:chemistry; D010316:Particle Size; D011312:Pressure; D012996:Solutions; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D055682:Viscoelastic Substances / Q000737:chemistry; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D002364:Caseins; D006020:Glycopeptides; D008894:Milk Proteins; D012996:Solutions; D055682:Viscoelastic Substances; C020251:kappa-casein glycomacropeptide; D014867:Water