Kinetics of polyphenol oxidase activity inhibition and browning of avocado purée preserved by combined methods

Abstract

Enzymatic browning reactions limit the commercial shelf life of avocado purée, thus color preservation throughout storage becomes one of the main objectives for fruit processors. The aim of this work was to model the color changes that occurred in avocado purée preserved by combined methods during four months under refrigeration. Changes in polyphenol oxidase (PPO) activity and color were successfully described by first-order models. PPO activity decays could be described by a simple first-order kinetic with rate constants of 4.4×10 −3–40.0×10 −3 day −1. On the other hand, browning ( ΔE *) of purée was due to L * and, in a minor extent, to a * changes, whereas b * did not change significantly throughout time. A fractional conversion kinetic suited color data with high R 2 coefficients and a good fitting to experimental values in the wide range of tried conditions.