Cheese making involves concentrating the proteins and fat in milk by removing the aqueous fraction called "whey." This process relies on the enzymatic gelation of milk and the gel's ability to contract and expel its whey after being cut into small pieces. After gel formation, it undergoes a spontaneous maturation process, called "aging," during which its mechanical properties strengthen over time, allowing it to be cut.
Using time-resolved mechanical spectroscopy coupled with structural characterizations (SAXS and confocal) and dynamics (XPCS), we have shown that the aging of enzymatic milk gels involves two sequential stages. First, a particulate network forms at the gelation point, leading to a rapid increase in firmness. Second, the gel's microstructure solidifies, and further aging occurs through the evolution of contacts between the particles constituting the gel as evidence from the gel yielding properties.
Identifying these two aging regimes, separated by a critical time, is crucial for optimizing the early stages of industrial cheese production. It also offers new theoretical perspectives on the aging of colloidal gels composed of "soft" particles.