Re: What makes mature cheese more crumbly than mild cheese

Excellent question. There is a fairly technical paper here that explains it: jds.fass.org/cgi/reprint/70/8/1748.pdf.

The short answer is that as the cheese ages, the proteolytic enzymes in the curd digest the protein in the curd. As the protein (mostly casein) is digested, the cheese becomes more crumbly.

Lawrence RC, Creamer LK, Gilles J (1987) Texture Development During Cheese Ripening J Dairy Sci 70:1748-1760.