Manufacture of high-protein yogurt without generating acid whey – Impact of the final pH and the application of power ultrasound on texture properties

The fermentation of preconcentrated milk is a challenging method to avoid acid whey during the manufacture of high-protein fermented milks like Greek yogurt. Milk concentrates (10% protein) were fermented to a final pH of 5.0, 4.8, or 4.6 and processed into stirred yogurt. Additionally, the potential of power ultrasound (US) as a post-processing tool was examined by sonicating the stirred yogurt with a sonotrode at 20 kHz. Set gels fermented to pH 4.8 and 5.0 were considerably softer than gels fermented to pH 4.6. Stirred yogurts fermented to pH 4.8 or 5.0 were less grainy and exhibited a reduced apparent viscosity and water-holding capacity. The application of US further decreased the visual graininess and product viscosity whereas the particle size was only slightly affected. The final pH and sonication are two powerful approaches to control the rheological properties of high-protein fermented milks, offering the potential for innovative processes and products.