Fortification of goat milk yogurt with goat whey protein concentrate - Effect on rheological, textural, sensory and microstructural properties

Goat milk and its products are valuable sources of nutrients and are good substitutes for cow milk products due to their hypoallergenicity. However, goat milk forms weak gels and it is often difficult to achieve acceptable texture and stability of set-type yogurt. The possibility of using goat milk whey protein concentrate (0.35% w/v and 0.7% w/v, WPC10 and WPC20, respectively) to improve the texture and stability of goat set-type yogurt (control WPC0) was investigated. The rheological properties of the yogurts were analyzed using oscillatory rheometry. The texture, induced syneresis, microstructure and sensory properties of the yogurts were studied after 1 and 21 days of cold storage. Mineral content, starter culture viability, and DPPH* radical scavenging activity of the yogurts were evaluated. The WPC20 yogurt exhibited improved elasticity and consistency, while the WPC10 yogurt was firmer and had a brittle structure but was rated better by the sensory panel after production, indicating preference towards short texture for set-type yogurts. The addition of WPC reduced syneresis and contributed to the viability of starter bacteria during storage but had no effect on the DPPH*- RS activity of the yogurts in the examined range. Fortification of goat milk with goat WPC could be successfully used as a method to improve texture, flavor, and stabilize goat yogurt during storage.