Impact of pulsed electric fields on enzymes

Pulsed electric field (PEF) processing has emerged as a promising technology in the development of tailor-made processes to effectively control the enzyme activity. It has been proven as an effective technique for the preservation of food products as it can result in substantial inactivation of most undesirable enzymes. When compared to microbial inactivation, however, large specific energy inputs are required to inactivate enzymes. The existing evidence suggests that PEF can also stimulate the activity of beneficial enzymes at low intense treatments. The PEF affects enzyme activity by changing mainly the secondary (a-helix, ß-sheets, etc.), tertiary (spatial conformation), and quaternary (number and arrangement of protein subunits) structures of the enzyme. There is not yet strong evidence that PEF induce chemical changes in primary structure. Both electrochemical effects and ohmic heating associated with PEF impact contribute to the change in enzyme structure and function. In addition, a number of factors including the physicochemical properties the enzyme, PEF treatment parameters, the processing condition, and the composition of the medium can significantly contribute to the enzyme activity. However, the exact mechanism of PEF action on enzymes at atomic level is not fully understood. In the past 20 years, several studies have confirmed that PEF at high intensity or in combination with mild heat causes substantial inactivation of several food quality-related enzymes such as alkaline phosphatase, peroxidase, proteases, lipase, pectin methylesterase, polyphenol oxidase, etc. Meantime, some reports show that PEF treatment has no effect on inactivation of certain enzymes at a given treatment condition. However, results obtained in different studies cannot be compared as the equipment used, treatment parameters, and medium are inconsistent in these studies. For effective treatment, PEF processing parameters must be optimized depending on the enzyme and target product.