17E-8 |
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W. CHANASATTRU, H.-J. Kim, and D. J. McClements. Food Science, University of Massachusetts, Amherst, Chenoweth Lab., Box 31410, Amherst, MA 01003-1410 Cosolvents have previously been shown to have a pronounced influence on the properties and stability of emulsions and gels containing globular proteins. Cosolvents may influence globular protein functionality in a variety of ways, but the molecular and physicochemical origin of these effects is still poorly understood. Our objective was to examine the influence of polyol cosolvents, such as glycerol and sorbitol, on the physical and thermodynamic properties of globular protein solutions. Density and ultrasonic velocity were used to investigate the effect of cosolvents on molecular compressibility of globular proteins. The influence of cosolvents on the thermal denaturation temperature of globular proteins was determined by UV spectrophotometry. Surface tension was used to understand the effect of cosolvents on the lowering of interfacial tension by globular proteins. All investigations were carried out in solutions containing glycerol (0-40 % w/w) or sorbitol (0-35 % w/w) with 0 and 1 % (w/w) b-lactoglobulin in phosphate buffer (pH 7.0) at 30oC. Both glycerol and sorbitol decreased the molecular compressibility of b-lactoglobulin with increasing cosolvent concentration. At the same concentration, sorbitol was more effective at reducing the molecular compressibility than glycerol. Sorbitol was also more effective at increasing the thermal denaturation temperature of b-lactoglobulin with increasing cosolvent concentration. The presence of glycerol and sorbitol had no affect on the surface tension reduction by b-lactoglobulin. These results indicate that cosolvents alter the physical properties of b-lactoglobulin in a manner that depends on their molecular structure. These results might be used to explain the effects of cosolvent on the properties of emulsions and gels containing globular proteins.
Session 17E, Food Chemistry: Proteins
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