Thermodynamic incompatibility between denatured whey protein and konjac glucomannan |
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Authors: | John T Tobin Sinead M FitzsimonsValérie Chaurin Alan L KellyMark A Fenelon |
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Affiliation: | a Food Chemistry and Technology Department, Teagasc Food Research Centre, Moorepark, Fermoy, Co. Cork, Ireland b School of Food and Nutritional Sciences, University College Cork, Ireland |
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Abstract: | The current study investigated the effect of a neutral polysaccharide, konjac glucomannan, on the heat-induced gelation of whey protein isolate (WPI) at pH 7. Oscillatory rheology (1 rad/s; 0.5% strain), differential scanning calorimetry and confocal laser scanning microscopy were used to investigate the effect of addition of konjac in the range 0-0.5% w/w, on the thermal gelation properties of WPI. The minimum gelling concentration for WPI samples was 11% w/w; the concentration was therefore held constant at this value. Gelation of WPI was induced by heating the samples from 20 to 80 °C, holding at 80 °C for 30 min, cooling to 20 °C, and holding at 20 °C for a further 30 min. On incorporation of increasing concentrations of konjac the gelation time decreased, while the storage modulus (G′) of the mixed gel systems increased to ∼1450 Pa for 11% w/w WPI containing 0.5% w/w konjac gels, compared to 15 Pa for 11% w/w WPI gels (no konjac). This increase in gel strength was attributed to segregative interactions between denatured whey proteins and konjac glucomannan. |
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Keywords: | Rheology Whey protein Phase separation Konjac glucomannan Microstructure |
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