EFFECT OF RENNET CONCENTRATION AND METHOD OF COAGULATION ON THE TEXTURE OF FETA CHEESES MADE FROM ULTRAFILTERED BOVINE-MILK

The effects of varying the rennet concentration (by a factor of 216) a nd the coagulation method on the texture of 32 Fete cheeses produced f rom ultrafiltered milk were examined by rheological, sensory and chemi cal methods. Cheeses were obtained that varied greatly in texture but had the same gross chemical composition. All rheological measurements (uniaxial compression, strain sweep and relaxation measurement), senso ry firmness and chemical measures of proteolysis depended significantl y on the rennet concentration used. With increasing rennet addition, t he cheeses became firmer and grittier, and less adhesive and sticky. W ith two of the three coagulation methods, the physicochemical state of the casein micelles at the point of coagulation varied with the renne t level: when less rennet was used, coagulation occurred at a lower pH and after long er contact between milli and NaCl. However, the effect s of increased rennet concentration were also significant with the thi rd method, where there was no effect on the pH or the period with NaCl at coagulation. Probably the primary effect observed was that art inc reased aggregation rate, with increased rennet level, affected the ini tial mode of aggregation of casein particles, leading to a denser netw ork structure and a firmer and grittier texture, The level of micellar disintegration at coagulation (controlled by the coagulation method u sed) had a supplementary effect.