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 ripening stages to characterise their microstructure in relation to their composition and water content. The intemalliq- uid phase of the cheeses was extracted by hydraulic pressure and analysed. Non solvent water (NSW) in cheese was calculated according to the method of van Boekel and Walstra from the concentration of sorne completely dissolved components such as potassium (K), sodium (Na) or 13-lactoglobulin (I3-Lg) in the liquid fraction compared to that in the whole cheese. The values obtained for NSW in the 7-d-old cheeses were 1.1, 0.8, 2.1 ss:' casein (CN) for K, Na and I3-Lg, respectively. A reduc- tion in NSW values was observed during ripening, down to 0.6 gg " CN for K and Na and 1.3 ss:' CN for I3-Lg in the 58-d-old cheese. Total water content of cheese decreased during ripening from 4.7 to 1.9 g.g-I CN, so that the relative proportion of NSW to total water increased during ripening. Very different cheese microstructures were observed at the beginning and end of the ripening period. In the early stage of ripening the structure of cheese was loose, characterised by accelerated enzymatic reactions which developed in the aqueous phase as a result of proteolysis. 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 part 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 rates of Iiquid. When cheese total solids reached 600-650 g·kg-1, which occurred after -43 d of ripening, the cheese microstructure became more 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 prote- olytic rate in the cheeses decreased, probably due to the lower content in solvent water. The kinetics of the pressing at this stage was characterised by a low flow rate. © InraJElsevier, Paris. goat cheese 1non solvent water 1hydraulic pressing 1desorption 1structure