Improving the Solubility of Yellow Mustard Precipitated Protein Isolate in Acidic Acqueous Solutions

The thesis objective was to investigate methods for improving the solubility of yellow mustard precipitated protein isolate (RTech Laboratories, USA) to allow for its use in protein enhanced acidic beverages along with soluble protein isolate in the pH range of 2 to 4.5. Four treatments were tested: hydrolysis with Alcalase®; cross-linking with transglutaminase; salting in with sodium chloride, sodium tripolyphosphate, and sodium hexametaphosphate; and protective colloid formation with pectin. The effectiveness of each was determined by its ability to improve nitrogen solubility (Nx6.25, AOCS-Ba11-65). The most effective treatments were hydrolysis and pectin stabilization. Pectin (1.5 w/v%) improved solubility from 6% to 29% at pH 4. Alcalase increased solubility from 20% to 70% at pH 3 after 2 h of hydrolysis (0.5AU/5g PPI, pH 8.5, 50-55degC) and eliminated the protein’s isoelectric point in the acidic pH range. Investigating the combined use of both treatments to further increase PPI solubility is recommended.MAS