Rheological Properties of Sodium Caprate-lnduced beta-Lactoglobulin Gel and Changes in Secondary Structure During Gelation

摘要

In this study,we found that transparent gels of p-lactoglobulin (beta-LG) were formed by adding different concentrations of sodium caprate to protein solutions at ambient temperature.We investigated changes in the dynamic viscoelasticity of the mixture with time at 25 deg C and found that more than 12% beta-LC induced the formation of a viscoelastic gel with a suitable amount of sodium caprate (for example,12% beta-LG and 3.6% sodium caprate).Furthermore,we analyzed the changes in the secondary structure of proteins during the gelation step by FTIR spectroscopy.Dissociation of the beta-LG dimer was first observed just after mixing with sodium caprate.Furthermore,in the beta-LG protein in which the original contents were predominantly beta-sheets,intermolecular beta-sheets attributable to aggregation increased with a decrease in the content of intramolecular beta-sheets.Sodium caprate-induced gel was heated at 80 deg C for 30 min after the gel was formed,and a large increase in the inter-molecular beta-sheet bands was observed by heat treatment.These results suggest that the formation of sodium caprate-induced gels of beta-LG was accompanied by less marked changes in the protein conformation than those in heat-induced gels.