Inactivation of Polyphenoloxidase by Pulsed Light

Abstract

The effect of pulsed light on the inactivation of polyphenoloxidase (PPO) in model solutions was investigated focusing on the effect of enzyme concentration and total energy dose of the treatment. PPO inactivation increased with the dose of the treatment. Complete enzyme inactivation was achieved by pulsed light doses higher than 8.75 J cm(-2) . At low PPO concentrations (4 to 10 U), the enzyme resulted highly inactivated by pulsed light treatment. Further increase in enzyme units determined a progressive decrease in PPO inactivation. The latter was attributed to protein structural modifications including cleavage and unfolding/aggregation phenomena. PPO amounts higher than 10 U probably favoured enzyme conformations that were less prone to intermolecular rearrangements leading to inactivation.

Photo-Induced Modification of Food Protein Structure and Functionality

“…It was also hypothesised that photoinduced protein aggregates could adsorb at the interface to form an ordered network that cross-links the two thin films of adjacent bubbles, thus stabilising the films. This hypothesis was confirmed studying the effect of ultraviolet (0.1-0.6 kJ m -2 ) and PL (0.2-3.1 kJ m -2 ) on egg white [60][61][62]. The higher foam ability and lower tendency to bubble dismutation/coalescence of light-treated egg white were tentatively attributed to the presence of high-size protein aggregates that could behave as surface-active solid particles and beget a Pickering foam [76].…”

“…For instance, when the effects of both UV-C and PL were investigated on polyphenoloxidase and pectin lyase in a wide range of light doses, the same mechanism of structural modification was detected but with different extents depending on light dose [56,63]. Similar results were also observed upon PL treatment of gluten, egg white and polyphenoloxidase [61,62,72]. In the case of polyphenoloxidase, a linear relation was observed between light dose and enzyme inactivation.…”

“…In particular, in highly diluted protein systems, their possibility to interact with each other to form photoinduced aggregates would decrease, as observed in the case of polyphenoloxidase [62]. In this condition, photoreactions would mainly occur via intramolecular rearrangement and only to a minor extent via intermolecular cross-linking.…”

“…Degradation and fragmentation of collagen were presumably attributed to proline oxidation. Protein cleavage has also been observed upon light treatment of egg white proteins and enzymes such as polyphenoloxidase, pectic lyase and lipoxigenase (Manzocco et al [4,56,60,62].…”

UV-A light treatment for controlling enzymatic browning of fresh-cut fruits

“…These emerging strategies can be used not only to control microbiological activity to extend the shelf-life of fresh-cut products (Morris, Brody, & Wicker, 2007;) but also to control enzymatic browning and thus preserve the organoleptic and nutritional qualities of produce better than conventional processes. For example, PPO activity has been shown to be effectively controlled by combined treatment with ultrasound and ascorbic acid Jang & Moon, 2011), pulsed electric fields (Meneses et al, 2013), cold plasma (Surowsky, Fischer, Schlueter, & Knorr, 2013) and pulsed light (Manzocco, Panozzo, & Nicoli, 2013).…”