Evaluation of volatile characteristics in whey protein isolate–pectin mixed layer emulsions under different environmental conditions

A mixture of whey protein isolate (WPI) and pectin was used to produce mixed layer emulsions, which were taken as delivery systems for volatile compounds. The interaction between WPI and pectin was confirmed by differential scanning calorimetry. At neutral pH (7 or 6) or NaCl ≥ 150 mM, severe droplet aggregation and creaming were observed in the emulsions. The emulsions were stable at pH ≤ 5 or NaCl ≤ 100 mM. When diluted with different artificial salivas containing salts, mucin, and/or α-amylase, the emulsions became phase separated. Volatiles had lower air-emulsion partition coefficients and release rates in mixed layer emulsions than in WPI stabilized emulsions. Change of pH from 5 to 7 did not significantly influence the partition coefficients of most volatiles (p > 0.05), but led to higher release rates of all the volatiles. Increase of NaCl concentration in the emulsions resulted in faster release and higher headspace concentrations of the volatiles. Volatiles had lower partition coefficients and release rates in emulsions treated with artificial salivas containing mucin and/or α-amylase than in emulsion treated with salts alone. These results indicated that WPI–pectin mixed layer emulsions can be potentially used to modulate volatile release by changing the environmental conditions.