Rheological Properties on Acidification of Whey Protein Isolate as Affected by Complex Coacervate Formation with -carrageenan

Protein-polysaccharide mixtures are used to enhance the texture of dairy products. This study was undertaken to examine the aggregation and gelation of 1% (protein basis) preheated (80 C for 30 min) Whey Protein Isolate (WPI) on acidification in the pH range 3.0-7.0 and characterise the acid gelling properties of complex coacervates formed between WPI and 0.5% к-carrageenan. The particle size of preheated WPI increased from 47.7 nm at pH 7 to a peak of 1031 nm at pH 4.75 before decreasing at lower pH values. On acidification using Glucono Delta-Lactone (GDL), preheated WPI commenced gelation at pH 6, had a peak in storage modulus of 71.9 Pa at pH 4.75 before weakening considerably at lower pH values. The zeta potential of the preheated WPI went from -40 mV at pH 7.0 to +35.1mV at pH 3.5. The unheated 1% WPI and 0.5% к-carrageenan mixture formed a gel at pH ~ 6.0, which continued to increase in strength on acidification reaching a G` of 267 Pa at pH 3.5. Results showed the formation of complex coacervates can enhance the acid gelation properties of WPI without the requirement of a preheating step for the WPI.