Emulsifying Properties of Food Proteins Conjugated with Glucose or Lactose by Two Methods (Spray-Drying Or Freeze-Drying)

Emulsifying properties of two commercial food proteins (plasma protein or egg albumen) conjugated with two sugars (glucose or lactose) by spray-drying or lyophylization were studied. Changes in protein structure were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, sulfhydryl group, Fourier transform infrared spectroscopy and differential scanning calorimetry, emulsion properties (emulsion capacity and stability, emulsion work, and emulsifying activity index). Protein conjugation increased proteins molecular weight and decreased sulfhydryl groups, coinciding with lower denaturation enthalpies, corroborating structural changes by conjugation with glucose or lactose by either spray-drying or freeze-drying. Glucose conjugation of the proteins employed at the experimental conditions resulted in structural changes that emulsify more oil with no detrimental effect on emulsion superficial area formation. Although freeze-drying conjugation improved emulsifying properties, spray-drying also enhanced these properties, as compared to non-conjugated proteins. Spray-drying was a faster way to conjugate food proteins via Maillard reaction with improved emulsifying properties.