Loss of solubility of alpha-lactalbumin and beta-lactoglobulin during the spray drying of whey proteins

A reversed phase HPLC technique (at pH 4.6) has been developed to measure 10 the loss of solubility of α-lactalbumin and β-lactoglobulin resulting from the 11 spray drying of whey protein isolate solution. Spray drying was performed in a 12 pilot-scale co-current spray dryer with different feed concentrations (20 - 40% 13 w/v) and outlet temperatures (60°C to 120°C). The study reveals that the 14 solubility of both α-lactalbumin and β-lactoglobulin was not significantly affected 15 at low outlet gas temperatures (60-80°C), but was strongly affected (up to 40%) 16 at high temperatures (100-120°C). Significantly higher losses in solubility were 17 observed for β-lactoglobulin compared to α-lactalbumin. Increasing the feed 18 concentration at higher outlet temperatures also caused noticeable increases in 19 insolubility. The reversed phase HPLC results were consistent with those from 20 total protein nitrogen content (Kjeldhal) analysis.