73C-6 |
Denaturation-aggregation process of b-lactoglobulin in the presence of non-gelling polysaccharides. |
R. I. BAEZA and A. M. R. Pilosof. Departamento de Industrias, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, 1428, Argentina The study of heat- induced denaturation of proteins in the presence of other biopolymers, is essential for the development of new food ingredients. Previous studies have demonstrated the ability of non-gelling polysaccharides (PS) for promoting the gelation of b-lactoglobulin (b-lg), the main protein in whey. The aim of present study was to obtain more information on the initial stages of denaturation-aggregation of b-lg in mixed biopolymer systems. Pure b-lg and b-lg/PS solutions were heated at constant temperature (68-75°C) for various time periods. The heated samples were analyzed by polyacrilamide gel electrophoresis (PAGE) and dynamic light scattering (DLS). DSC experiments were also performed to obtain the onset and peak temperature of denaturation process. During heating at 68.5°C at neutral pH, the intensity of the b-lg monomer band decreased and coincided with the formation of additional bands of small aggregates that predominated for short heating times. The decrease in native b-lg was delayed by the presence of polysaccharides, probably due to an increase in the onset denaturation temperature. A faster decrease of the small aggregates bands and a subsequent increase in high molecular weight bands observed at the top of separating and stacking gel were promoted by the presence of non-gelling gums. The results coincided with an increase in the scattered intensity and diameter (180 nm) of b-lg aggregates formed in the presence of gums compared with the small aggregates (60 nm) formed in pure b-lg solutions. At pH6 mainly high molecular mass aggregates could be seen in both pure b-lg and mixed systems, and the rate of decrease of native b-lg was lower than at neutral pH. The results allow a better understanding of the nature of b-lg aggregates formed in the presence of gums and may be applied to control the characteristics of food ingredients based on both biopolymers.
Session 73C, Food Engineering: Transport Processes and Kinetics
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