Gelation of beta-Lactoglubilin in the Presence of Propylene Glycol Alginate: Kinetics and Gel Properties

BAEZA, R; GUGLIOTTA, L. M.; PILOSOF, A. M. R.

COLLOIDS AND SURFACES B-BIOINTERFACES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2003 vol. 31 p. 81 - 93

0927-7765

The role of the non-gelling polysaccharide, propyleneglycol alginate (PGA), on the dynamics of gelation and gelproperties of b-lactoglobulin (b-lg) under conditions where the protein alone does not gel (6%) was analyzed. To thisend, the kinetics of gelation, aggregation and denaturation of b-lg in the mixed systems (pH 7) were studied at differenttemperatures (64/88 8C). The presence of PGA increased thermal stability of b-lg. The rate of b-lg denaturation wasdecreased and the onset and peak denaturation temperatures increased by 2.2/2.4 8C. PGA promoted the formation oflarger aggregates that continued to grow in time. An average aggregate diameter of approximately 300 nm is reached atthe gel point in the mixed b-lg/PGA systems, irrespective of the heating temperature. Comparing the activationenergies for the aggregation (193 kJ/mol), denaturation (422 kJ/mol) and formation of the primary gel structure (1/tgel)(256 kJ/mol) processes in the mixed protein/polysaccharide system, it can be concluded that the rate determining stepin the formation of the primary gel structure would be the aggregation of protein. Ea values for the processes after thegel point (solid phase gelation) suggest a diffusion limited process because of the high viscosity of the solid gellingmatrix. The characteristics of the mixed b-lg/PGA gels in terms of rheological and textural parameters, water loss andmicrostructure were studied as a function of heating temperature and time. The extent of aggregation and the type ofinteractions involved, prior to denaturation seem to be very important in determining the gel structure and itsproperties.