There is a desire to incorporate high concentrations of whey proteins into nutritional beverages in order to improve the nutritional content and amino acid profile. However, typical thermal treatments for sterility or extended shelf-life cause undesirable aggregation/gelation of whey proteins. To address this instability issue at high protein concentrations, there is a need to develop new protein ingredient technologies that can provide resistance to heat-induced aggregation. Formation of whey protein particles at the size of micro-aggregate was investigated as a means to increase the heat stability of liquid systems at high whey protein concentrations. For this purpose, a micro-particulated WPC containing a combination of soluble and insoluble protein aggregates of controlled size was used.
The heat stability characteristics of model food emulsions containing native or micro-particulated whey protein concentrate (WPC80) were compared. Oil-in-water emulsions [10% (w/w) sunflower oil] containing increasing concentrations of protein (2 to 12 wt%) were prepared at pH 7.0. The effects of retorting at 120 °C for 10 min on particle size distribution, rheological properties, susceptibility to heat-induced coagulation, microstructure, and surface protein concentration were compared for both types of WPCs. Varying levels of NaCl was also added to examine the heat stability of micro-aggregated WPC in the presence of additional salts.
Micro-particulated WPC emulsions showed significantly enhanced heat stability compared to native WPC. Emulsions with up to 11 wt% protein were produced with no visible aggregation or gelation after retorting using the micro-particulated WPC. For native WPC emulsions, formation of large aggregates accompanied with a change in flow behavior to non-Newtonian was observed at 3 wt% protein under same heating conditions. Using this specific technology, high protein whey-based nutritional beverages can be produced using conventional thermal treatments.
Dr. Esra Cakir-Fuller esra.cakir-fuller@fonterra.com
