FREEZING OF WHEY-PROTEIN CONCENTRATE SOLUTIONS AND ITS EFFECT ON PROTEIN FUNCTIONALITY INDICATORS

Solutions (15% protein) of a whey protein concentrate (WPC) at pH 6.8 or 5.0 were subjected to fast, intermediate or slow freezing at -17 de grees C and -30 degrees C, with an unfrozen control held at +4 degrees C for 24 h. After thawing at 20 degrees C, selected physicochemical a nd functional properties were compared; these included solubility inde x, heat stability, viscosity, gel strength, freezing point, as well as observations by cryomicroscopy. It was concluded that there was no ma jor detrimental effect of the freezing process alone on any of the WPC solutions studied at either pH. Minor changes in viscosity, microstru cture and possibly heat gel strength observed at pH 5.0 may indicate t hat long-term storage at this pH could lead to development of quality defects. To assess whether freezing might be a suitable alternative me thod for preservation of concentrated whey protein solutions, the effe cts of frozen storage must be studied further.