Effect of ultra-high pressure homogenization on viscosity and shear stress of fermented dairy beverage

In this study, dairy base consisting of raw skim milk and reconstituted whey powder were pressurized. The process used ultra-high pressure homogenization (UHPH) at levels of 150, 200 and 250 MPa and inlet temperatures of 15, 20 and 25 °C, following experimental design. Dairy base was inoculated with probiotic lactic culture, incubated, and allowed to ferment. Pineapple juice, previously sweetened with sugar or aspartame, was added, following an experimental design, resulting in dairy beverages. Appropriate formulation, considering the sensory attributes, was identified by Quantitative Descriptive Analysis (QDA) and used for studying rheological parameters. Results disclosed that formulations with higher whey levels had higher average scores for characteristic sensory attributes of products. The aim was to evaluate rheological properties (viscosity and shear stress) of fermented dairy beverages according to inlet temperature and pressure, comparing them to thermally processed samples (90 °C/60s). This evaluation showed that pressurized beverages at 150 MPa/15 °C were similar to controls. These preliminary results obtained in this study suggest that UHPH has the potential to be used to modeling some rheological characteristics of fermented dairy beverages, for example, to favorably modify their consistency. All samples exhibited viscoelastic and thixotropic behaviors.