Pressure Effects on Whey Protein-Pectin Mixtures

A food material science approach using microscopy, rheology and denaturation assessment of proteins was applied to describe the behaviour of mixtures of a whey protein isolate (WPI) and a high methoxy pectin (HM-pectin) upon high-pressure treatment (200 to 800 MPa at 25 or 40 °C and holding time of 10 min). The results of high-pressure treatment were compared to a pure heat treatment at 75 °C (5-20 min) and 85 °C (10 min). Similar textures could be obtained after highpressure treatment of the mix at ambient temperature at all pressure levels tested (200-800 MPa) and after temperature treatments at 75 °C up to 10 min. Significant changes were only obtained in phase separating WPI/HM-pectin mixtures if treated at 40 °C and pressures>400 MPa and after heat-treatment at 85 °C for 10 min, where total WPI denaturation was above 60%. Under such conditions the protein-enriched phase gelled and significantly changed the overall texture as measured by rheology. In the presence of pectin, protein denaturation was decreased in both pressure and temperature treated samples. Microscopic analysis showed that structure formation depends on the processing history. Compared to a pure heat treatment, pressure offers a greater flexibility for fine-tuning the protein denaturation due to an increased freedom in processing parameters (pressure, holding time and temperature).