Soft goat cheeses at different ripening stages: cheese structure, composition and non solvent water

Soft goat cheeses of the Sainte-Maure variety were studied at different rip ening stages to characterise their microstructure in relation to their comp osition and water content. The internal liquid phase of the cheeses was ext racted by hydraulic pressure and analysed. Non solvent water (NSW) in chees e was calculated according to the method of van Boekel and Walstra from the concentration of some completely dissolved components such as potassium (K ), sodium (Na) or beta-lactoglobulin (beta-Lg) in the liquid fraction compa red to that in the whole cheese. The values obtained for NSW in the 7-d-old cheeses were 1.1, 0.8, 2.1 g.g(-1) casein (CN) for K, Na and beta-Lg, resp ectively. A reduction in NSW values was observed during ripening, down to 0 .6 g.g(-1) CN for K and Na and 1.3 g.g(-1) CN for beta-Lg in the 58-d-old c heese. Total water content of cheese decreased during ripening from 4.7 to 1.9 g.g(-1) CN, so that the relative proportion of NSW to total water incre ased during ripening. Very different cheese microstructures were observed a t the beginning and end of the ripening period. In the early stage of ripen ing the structure of cheese was loose, characterised by accelerated enzymat ic reactions which developed in the aqueous phase as a result of proteolysi s. A rapid decrease in the water content occurred due to evaporation at the cheese surface, facilitated by the easy movement of water from the inner p art of cheese to the surface through the open and porous structure. During these early stages of ripening, pressing of the cheese led to high flow rat es of liquid. When cheese total solids reached 600-650 g.kg(-1), which occu rred after similar to 43 d of ripening, the cheese microstructure became mo re compact. The residual water had a slower diffusion rate in the structure , as indicated by the lower variation in the cheese water content with time . Residual water was mainly non solvent. The proteolytic rate in the cheese s decreased, probably due to the lower content in solvent water. The kineti cs of the pressing at this stage was characterised by a low flow rate. (C) Inra/Elsevier, Paris.