Impact of heat treatments on the functionalities of milk protein concentrate 80

Abstract Text:

Processing conditions impact the properties and functionality of milk protein concentrate 80 (MPC80).  Nonfat dry milk is categorized according to the processing temperatures (low, medium, high) as these treatments greatly influence its functionality and end use.  It is unknown how MPC80 properties will be affected by increased pasteurization temperatures of skim milk (prior to concentration).  Increased pasteurization temperatures will denature more whey protein, which could impact solubility, foam stability, and viscosity of the reconstituted powder.  Raw skim milk received heat treatments of 72°C for 16 seconds or 77, 82, or 87°C for 1 min, immediately prior to ultra- and diafiltration.  The retentate (23% TS) was spray dried and outlet temperature was  adjusted to maintain consistent moisture content between powders (~4.4%).  The powders had similar composition including fat contents (< 2%). Functionality testing included solubility, foaming, tapped bulk density, and reconstituted viscosity. Tests were conducted within one week of production.  Powders were also stored at 30°C for 6 months with functionality tested every 30 days.  SDS-PAGE results show higher heat treatments produced more di-sulfide linked aggregates.  For all powders, solubility slightly decreased during storage but higher heating temperatures did not have a significant impact on solubility.  Initial foaming experiments indicated that heat treatments of 82°C or 87°C for 1 min produced foams that were stiffer and more stable than samples treated at temperatures of 77°C for 1 min.  Bulk density decreased over storage but was not significantly affected  by heat treatment.  Experiments investigating the viscosity of reconstituted powders are on-going however, initial results indicate that viscosity slightly increased with an increase in heating temperature.  Based on preliminary results, it was concluded that increased heat treatments had the greatest impact on the foaming properties of MPC80 but has less impact on other functional properties. 

 Keywords: milk protein concentrate, processing, functionality