Question

How does pH and temperature play a role in the formation of a desirable texture in yogurt? In your description mention how the processing methods for making yogurt result in the denaturation of whey and coagulation of casein to form a desirable gel-like structure.

Answer 1

Properties of yoghurt extremely depend on the application of heat treatment to milk prior to manufacture. After heating the milk, denatured whey protein and casein makes complexes which dramatically improve the yoghurt texture such as firmness and water holding capacity etc. The formation of complexes, micelle bound or soluble whey protein/κ-casein complexes, and their localization between casein micelles and serum depends on the physical properties (heat treatment, pH, compositions) of milk. We review the formation of these complexes and their effect on the physical, rheological and microstructural properties of acid milk gels. In order to investigate the interactions of denatured whey protein-casein, the formation of covalent and non-covalent bond namely thiol/disulphide, hydrophobic and electrostatic etc. are reviewed, with the emphasis on acid gelation and final yoghurt texture. This review summarizes the different factors and interactions on the formation of the micelle bound complexes or soluble denatured whey protein/κ-casein complexes in heated milk and how these complexes affect the yoghurt properties. This information could be fundamental knowledge for developing a desirable yoghurt texture, may have potential interest for future research.