Peroxidase (POD) and polyphenol oxidase (PPO) photo-inactivation in a coconut water model solution using ultraviolet (UV)

• The POD and PPO photo-inactivation was studied in a coconut water solution model.
• Three different models for describing the phenomenon were evaluated.
• A possible mechanism for the observed photo-inactivation was proposed.
• The absorbed radiation power was modelled.
• The UV processing has been shown to be efficient for the inactivation of the enzymes.

The interest in coconut water as a beverage is increasing due, not only to its sensory properties, but also to its nutritional characteristics. Even so, several challenges limit its processing, the inactivation of the polyphenol oxidase (PPO) and peroxidase (POD) enzymes being the most important. Although the inactivation of these enzymes has been extensively studied in coconut water, both by conventional and emerging technologies, the technologies evaluated so far are either not effective in the inactivation of these enzymes and/or result in undesirable changes. This work evaluated the photo-inactivation of POD and PPO in a coconut water model solution using ultraviolet radiation (UV). Both enzymes showed continuous inactivation behaviour in relation to the processing time, this being described by a two-portion inactivation kinetics. A possible mechanism for the observed photo-inactivation was proposed, involving steps of molecular unfolding and aggregation. The POD activity after 15 min of processing was ~ 5% of its original value, and reduced to ~ 1% after 30 min of UV processing. After 15 min of processing, PPO activity was ~ 8% of its original value, falling to ~ 2% after 30 min of UV processing. The results obtained highlight the potential use of the ultraviolet radiation to inactivate both enzymes in coconut water.