Fluorescence Lifetime pH Measurements in Cheese Matrix

The pH of cheese affects the texture of curd directly by influencing the solubility of the caseins; all else being equal, high pH cheeses are softer than more acid cheeses. pH also affects texture and flavour indirectly by affecting the activity of enzymes important to ripening and, in the case of the coagulant, the retention of enzyme in the curd during manufacture [1]. Since low pH is known to modify the metabolic activity of lactic acid bacteria and to have even more influence when then cells are immobilized it is important to determine local pH in such a complex solid structure such as cheese [2].