How does high-pressure processing (HPP) inactivate microorganisms without relying on thermal energy?

High-pressure processing (HPP), also known as pascalization, inactivates microorganisms by applying intense hydrostatic pressure, typically ranging from 100 to 800 MPa (megapascals), to food products. This pressure disrupts cellular functions without significantly increasing the food's temperature, thus preserving its sensory and nutritional qualities. The primary mechanism involves the denaturation of proteins and enzymes within the microorganisms. Denaturation refers to the unfolding and disorganization of protein structures, rendering them non-functional. HPP also damages microbial cell membranes, causing them to rupture and lose their integrity. Furthermore, HPP affects the ribosomes, cellular structures responsible for protein synthesis, inhibiting their ability to produce essential proteins for microbial survival and replication. The high pressure disrupts non-covalent bonds, such as hydrogen bonds and hydrophobic interactions, which are crucial for maintaining the three-dimensional structure of biomolecules. For instance, HPP can be used to extend the shelf life of guacamole by inactivating spoilage microorganisms and enzymes without affecting the avocado's flavor or texture. Spores, which are dormant and highly resistant microbial forms, are generally more resistant to HPP than vegetative cells, requiring higher pressures or combination with other preservation methods like mild heat to achieve inactivation.