1. Denaturation temperature is formulation-dependent

Heating whey proteins can change their structure and their interactions with other milk proteins. The transition depends not only on temperature but also on protein concentration, pH, ionic strength, buffering capacity, and other ingredients. The cited experiment compared emulsifying salts in concentrated β-lactoglobulin (β-LG) and whey protein isolate (WPI) solutions. It does not establish one denaturation temperature for all whey powders, dairy foods, or industrial recipes.

2. What the concentrated-solution experiment found

In water, reported denaturation temperatures were 73.5°C for 14% β-LG, 71.8°C for 30% β-LG, and 69.9°C for 30% WPI. Increasing salt concentration generally raised WPI denaturation temperature, except with sodium hexametaphosphate, and accelerated gelation. Sodium chloride and tartrate salts showed particularly strong protection against WPI thermal denaturation in the tested system. Buffering salts such as phosphate and citrate could prevent pH decline during heating and, at low concentrations, lower the denaturation temperature. The direction and size of an effect therefore depended on salt chemistry and solution conditions.

3. Protein unfolding and gel formation are distinct events

At low salt concentrations, gelation was the rate-controlling step and could occur up to 10°C above the denaturation temperature. At salt concentrations above 3% by weight, thermal denaturation became the controlling step, with gelation following immediately. These results show why unfolding and network formation should not be treated as a single fixed transition. They also caution against predicting the texture or heat stability of a finished dairy product from a temperature threshold alone.

4. Expert perspective: the yoghurt review addresses a different level of evidence

A review of heat-induced milk-protein interactions describes how denatured whey proteins form covalent and noncovalent complexes with casein and how those complexes influence acid-gel microstructure and yoghurt texture. It provides context for translating molecular behavior into a food structure, but it is not a recipe or a guarantee of a particular texture. Application requires testing the actual milk composition, pH, salts, heating time and temperature, and finished-product texture and syneresis.

Sources: Ionic strength and buffering capacity of emulsifying salts determine denaturation and gelation temperatures of whey proteins / Heat-induced interaction of milk proteins: impact on yoghurt structure