Allyl Isothiocyanate Reduces Fruit Decay of Blueberries by Paradoxically Generating Reactive Oxygen Species

The effect of allyl isothiocyanate (AITC) on flavonoids, radical scavenging capacity, decay and fruit quality of blueberries var. Duke (Vaccinium corymbosum L.) was evaluated. Results from this study showed that AITC was effective in retarding blueberry decay during storage at 10 °C.  However, AITC decreased the content of total phenolics and anthocyanins, as well as antioxidant capacities. Compared to controls, AITC-treated berries had lower scavenging capacities against free radicals of oxygen radical absorbance capacity (ORAC), hydroxyl radical scavenging capacity (^•OH) and 2, 2-Di (4-tert-octylphenyl)-1-picrylhydrazyl (DPPH), but promoted the accumulation of H₂O₂ radicals. The free radical scavenging properties of blueberry fruit with or without AITC treatment were also evaluated by electron spin resonance (ESR). Results of the ESR measurements confirmed that free radical scavenging capacities against ^•OH, DPPH^• and O₂^•− were lower in treated fruit than in controls.  AITC treatments also reduced the amount of phenolic acids and anthocyanins during storage at 10 °C. The results from this study indicate that AITC does not promote antioxidant properties or scavenging of constitutive reactive oxygen species (ROS), but paradoxically generates additional amounts of ROS to inhibit the growth and proliferation of microbial cells, thereby reducing decay in fruit tissue.