**5. Conclusions**

High isostatic pressure and high pressure homogenization can be considered interesting unitary operations to be applied for inducing enzyme changes. Both processes are able to activate and/or stabilize the majority of enzymes when mild process conditions (low pressure and temperature) are applied and this is highly desirable since the use of physical methods are considered cleaner way to change molecules, minimizing the risks of transformed ones. The changes induced by HPH and HIP allow some enzymes overcome usage limitations, as inability to react at desirable process conditions (low or high temperature, pH and salt concentration) and as high costs since the increase of activity induced by the process reduces the amount of required enzyme in industrial reactions and, consequently, the costs of enzyme usage. Considering the multifactorial effects that governed the physical transformations induced by HIP and HPH, it is not possible to predict if is HIP or HPH the better method to obtain the desired activation and, possibly, for several enzymes, different conditions of each process can induce similar activation.

In respect to inactivation, a similar behavior with thermal treatment was observed, being the heat resistant also baroresistant enzymes (e.g. peroxidase, polyphenoloxidase), making necessary the association of pressure and mild temperatures to reach adequate levels of inactivation. In this case, HIP tends to be more effective than HPH to induce irreversible changes on enzymes.

The activation and inactivation effects can be related to the molecular energy input caused by HPH or HIP processing. Differently from the thermal effects, both processes involving pressurization can deliver energy enough to induce changes (enhancement of hydrophobic surface and disulfide bonds formation) that positively affect the enzymes activity due to higher flexibility and exposure sites. However, at extreme conditions, the higher energy delivered induces to drastic changes, with irreversible enzyme changes and consequent permanent activity loss. Therefore, it is concluded that HIP and HPH are versatile technologies to alter enzymes, being possible to reach activation or inactivation, depending on the process conditions chosen.
