Changes on epicuticular waxes and colour induced by ozone in blueberries (Vaccinium corymbosum L. ‘O’ Neal’)

Abstract

The aim of the present work was to assess the effect of ozone in aqueous phase (5.1 mg L−1 of ozone for 10 min) on blueberry surface by analysing the changes in epicuticular waxes (EW) by attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy during storage at 4 °C for 15 d. Besides, colour was studied as a critical quality index for consumers. Ozone treated and controls (untreated fresh fruit and washed fruit without ozone) samples were considered. Among them, three subsets of spectra were acquired: whole fruit, fruit without EW -removed by solvent- and isolated EW. The differences among these sample subsets were much higher than those produced by treatments or storage time as revealed by PCA analysis. Infrared analysis revealed that ozone per se produced chemical modifications on EW of intact fruit, as new bands appeared (such as stretch of C[dbnd]O at 1701 cm-1, from the oxidation of alcohols to carbonyls) and others shifted. However, no significant changes were observed in colour between treatments or time, showing that neither the alterations in EW nor their partial removal or changes in epidermis ultrastructure (evaluated by microscopy) affected this quality parameter. Further studies are needed to deeply understand the extent of the effect of the chemical alterations produced directly by ozone (and not by the process) in line with consumers demands of minimal processed and extended shelf-life products.