Effect of high pressure homogenization on microbial and chemico-physical characteristics of goat cheeses

The objective of this work was to compare goat cheeses obtained from milk previously subjected to high pressure homogenization (1000 bar) with those produced from untreated milk and milk subjected to sanitization (61 degrees C; 20 min) or to pasteurization (72 degrees C; 15 s). The pressure homogenization treatment had both direct and indirect effects on cheese characteristics and their evolution during ripening. The direct effects were principally linked to the change in water-binding capacity of proteins as shown also by the lower whey separation. The indirect effects involved the microbial growth or activity and, particularly, modifications of the population of the lactic acid bacteria that occurred naturally and their evolution as well as a more precocious yeast and mold growth with a consequent rapid rise in pH. Although the treatment proved to enhance both proteolytic and lipolytic activities according to Fourier transform infrared analysis, which was used to obtain a rapid description of the biochemical modification, the cheeses homogenized under high pressure showed relevant qualitative differences only in the zone corresponding to amide I and amide II signals of proteins. The activation of these enzymatic activities observed in the homogenized cheeses could be either an indirect effect of the shift of the microbial population or a consequence of a different exposure of the macromolecules to the enzymatic activity. Scanning electron microscopy analyses of goat cheeses revealed that cheeses homogenized under high pressure had a more homogeneous microstructure than did the others.