The invention is a process for preparing a yoghurt with a desired gel strength. It is based on the unexpected observation that gel strength can be varied by varying the pH to an optimum at a given weight ratio of casein to whey protein. Whey protein is added to a milk and the casein:whey protein weight ratio is calculated. The optimum pH for that ratio is determined. The milk solution is then adjusted to that pH, heated to denature the whey protein and formed into yoghurt by known methods. The gel strength of the resulting yoghurt is determined by the optimum pH used in the heating step.