Characterization of the microstructure of Terrincho ewe cheese

The microstructure of Terrincho cheese – a Portuguese traditional cheese bearing a Protected Denomination of Origin, was assessed by scanning electron microscopy (SEM). Terrincho cheese was manufactured according to the traditional protocol using pre-filtered, plain raw ewe’s milk of Churra da Terra Quente breed, without addition of starter of any other type of cultures, and coagulated with animal rennet. The cheeses were salted upon unmoulding, and placed in ripening chambers held at 10–12 °C and 88–89 % relative humidity for a period of 30 days. Cheeses were sampled at 0, 15 and 30 days. Cheese specimens were prepared for SEM by fixing small blocks of cheese (cut from freshly sampled cheeses) in formaldehyde, at room temperature for 1 month, cutting it into 1–2 mm thick slices using sharp razor blades and dehydrating in a graded ethanol series. Slices in absolute ethanol were critical point dried from carbon dioxide, mounted on SEM stubs using adhesive tabs, sputter-coated with gold, and examined using a JEOL scanning electron microscope. The microstructure of the (semi-soft) curd of Terrincho cheese appeared as a continuous casein network possessing a spongy appearance. The various microbial populations present within the cheese were found to grow in the form of colonies, embedded in the casein network and close to the void spaces originally occupied by fat. Microbial colonies were roughly spherical, with bacteria tightly packed in the centre. A similar pattern of microbial growth was observed throughout ripening. Other inclusions were also pinpointed, namely salt crystals.