Heat stability of radio frequency dielectric heat treated low heat and high heat nonfat dry milk

The heat stability of low (LH) and high heat (HH) nonfat dry milk (NDM) that received a radio frequency dielectric heat (RFDH) treatment at 75, 80 or 85 °C for different periods of time (between 43 and 125 min) was assessed. NDM was reconstituted at 3.5% (w/w) protein. Heat stability was assessed at 140 °C by recording the heat coagulation time. Samples were evaluated at native pH, and adjusted pH from 6.4 to 7.2. LH samples heated to 75 °C or 80 °C showed greater heat stability than non-treated LH at pH 6.4 to 6.8. Data suggest that RFDH treatment of LH induced associations between whey proteins and casein micelles, which increased the heat stability in this pH region. The same effect was not observed in the HH samples, suggesting different reactions may be induced. Dry heating NDM may affect protein associations differently from liquid systems, depending upon the conditions.