Cold plasma interactions with enzymes in foods and model systems

• Cold plasma is an emerging non-thermal food technology.
• Enzymes behaviour under the action of plasma is determined by the plasma chemistry.
• Cold plasma often results in significant levels of enzyme inactivation in foods.
• Inactivation is mainly attributed to the modification of protein secondary structure.

BackgroundThe past decade has seen an increased interest in the application of non-equilibrium plasma for food processing. An important aspect of the interaction of chemical species of plasma with foods is the effect on enzymes, which play an important role in retaining the food quality and often serve as markers for processing efficiency.Scope and approachThe present review covers a critical analysis of the current status of the relationship between plasma parameters and enzyme functionality, with an emphasis on the translation of this knowledge for food applications. The review provides a brief introduction to plasma technology, a summary of the enzyme inactivation studies, followed by a discussion of the mechanism and kinetics of inactivation, and finally, points at the future research needs.Key findings and conclusionCold plasma inactivation of enzymes is primarily dependent on power input of the discharge, degree of exposure to reactive species, the mass transfer between the plasma-liquid phases, structural complexity and stability of the enzymes in their local environment. The mechanism of inactivation is primarily due to the loss of secondary structure due to breakdown of specific bonds or chemical modifications of the side chains by the action of the myriad of chemically active species constituting the plasma. Further research is required to understand the interactions of chemical species in plasma with proteins at a molecular level, coupled with better tools to monitor and control the plasma chemistry.