The effect of chicken skin gelatin and whey protein interactions on rheological and thermal properties

Physical, thermal and microstructural properties of whey protein isolate (WPI) and unutilized chicken skin gelatin mixtures were investigated for the first time. Small deformation rheology indicated that combinations of gelatin (3, 5 and 10%) and 10% whey protein (WPI) in distilled water produced high elastic modulus (G') values of 1860, 23,914 and 20,145 Pa, respectively, compared with 120 Pa for 10% WPI alone, due to synergistic interaction. Frequency sweeps showed increased strength of networks in gels containing higher gelatin concentrations in WPI/gelatin mixtures. Gelatin gels were more stable and stronger than 10% (w/w) whey protein gels and did not exhibit frequency dependence for G' and G''. Large deformation gel strength values of all samples increased significantly (p < 0.05) with increasing gelatin concentration and were greater at each concentration compared to gelatin alone. Differential scanning calorimetry transition temperature (T-m) and enthalpy change (H) of gelatin and whey protein mixed in the ratios 3:10, 5:10 and 10:10 (w/w) confirmed gelatin reversibility on heating to 90 degrees C and cooling to 10 degrees C and irreversible denaturation of WPI on heating. The addition of 3, 5 or 10% gelatin to whey protein increased whey protein Tm and decreased gelatin Tm. However, the presence of 10% (w/w) WPI significantly increased the Delta H values to 0.62, 1.34 and 2.20 J/g for 3, 5 and 10% (w/w) gelatin solutions respectively, indicating whey-egelatin interaction. Chicken skin gelatin gels exhibited a fine network whereas whey protein gels comprised aggregates and mixtures led to phase separation. This unutilized non-mammalian gelatin may lead to novel industrial applications. (C) 2014 Elsevier Ltd. All rights reserved.