The technology of High Hydrostatic Pressure (HHP) is the nonthermal food technology that has been most developed commercially. It has achieved microbial and enzymatic inactivation levels close to thermal pasteurization ones, preserving sensory and nutritional properties of the processed products. To achieve this level of inactivation, a pressure level in the range of [100–800] MPa (megapascals) is used with short treatment times (ranging from a few seconds to several minutes), combined with moderate temperature (20–50 °C). In the present book, the yeast Rhodotorula glutinis and the mold Penicillium aurantiogriseum, spoilage microorganisms responsible for altering the quality of fresh cheese and reducing its shelf life, were treated by HHP at pressure levels of 200, 300, 350, and 400 MPa, with treatment times ranging from 1 to 15 min. The experimental results were fitted to a non-linear model, the Weibull distribution function.